Phenotypic and Genotypic Characterization of Carbapenem-resistant Enterobacteriaceae: Data From a Longitudinal Large-scale CRE Study in China (2012-2016)

Construction of a Risk Prediction Model for Subsequent Bloodstream Infection in Intestinal Carriers of Carbapenem-Resistant Enterobacteriaceae: A Retrospective Study in Hematology Department and Intensive Care Unit

BACKGROUND

To establish a risk prediction model for carbapenem-resistant Enterobacteriaceae (CRE) bloodstream infection (BSI) in intestinal carriers.

METHODS

CRE screenings were performed every two weeks in hematology department and intensive care unit (ICU). Patients with positive CRE rectal swab screening were identified using electronic medical records from 15 May 2018 to 31 December 2019. Intestinal carriers who developed CRE BSI were compared with those who did not develop CRE infection. A 1:1 matched case-control study was conducted. The control group was selected by stratified random sampling based on the department to ensure that all the departments were represented. Univariate logistic analysis, multivariate logistic analysis and stepwise regression analysis were carried on a variety of patient factors and microbial factors.

RESULTS

A total of 42 cases were included. Multivariate analysis showed that gastrointestinal injury (OR 86.819, 95% CI 2.584-2916.592, P=0.013), tigecycline exposure (OR 14.991, 95% CI 1.816-123.737, P=0.012) and carbapenem resistance score (OR 11.236, 95% CI 1.811-69.700, P=0.009) were independent risk factors for CRE BSI in intestinal carriers (P<0.050). They were included in the Logistic regression model to predict BSI. According to receiver operating characteristic (ROC) curve analysis, the cut-off value of the model was 0.722, and the sensitivity, specificity and area under the curve (AUC) were 90.5%, 85.7% and 0.921, respectively.

CONCLUSION

The risk prediction model based on gastrointestinal injury, tigecycline exposure and carbapenem resistance score of colonizing strain can effectively predict CRE BSI in patients with CRE colonization. Early CRE screening and detection for inpatients in key departments may promote early warning and reduce the risk of nosocomial infection of CRE.

Clinical and microbiological characteristics of nosocomial, healthcare-associated, and community-acquired Klebsiella pneumoniae infections in Guangzhou, China

BACKGROUND

Klebsiella pneumoniae (K. pneumoniae) is a common pathogen associated with hospital and community-onset infections. This study aimed to compare the clinical and microbiological characteristics of nosocomial, healthcare-associated (HCA), and community-acquired (CA) K. pneumoniae infections.

METHODS

Clinical data were extracted from electronic medical records and analyzed retrospectively. Antimicrobial susceptibility and extended-spectrum beta-lactamase (ESBL) production were determined for all identified strains. Carbapenemase and ESBL genes were amplified by PCR. Genotyping of carbapenem-resistant K. pneumoniae (CRKP) and ESBL-producing strains was performed by pulsed-field gel electrophoresis (PFGE).

RESULTS

Of 379 K. pneumoniae infections, 98 (25.9%) were nosocomial, 195 (51.5%) were healthcare-associated, and 86 (22.6%) were community-acquired. Hematological malignancy (OR = 4.467), and hypertension (OR = 2.08) and cerebral vascular disease (OR = 2.486) were associated with nosocomial and HCA infections respectively, when compared to CA infections. Overall, the incidence of antimicrobial resistance for the majority of agents tested was similar between nosocomial and HCA infections (P > 0.05) and both groups had a higher incidence than CA infections (P < 0.05). Moreover, 95.1% (78/82) of CRKP strains were isolated from the nosocomial and HCA groups. The blaKPC was the most prevalent carbapenemase gene among CRKP strains (80.5%, 66/82). ESBL-producing strains were prevalent among nosocomial (40.8%), HCA (35.9%) and CA groups (24.4%). The blaCTX-M-9-group and blaCTX-M-1-group genes were predominant in nosocomial (65.0%) and CA strains (66.7%), respectively. PFGE results showed ESBL-producing and CRKP strains were genetically diverse. Identical PFGE profiles were observed among HCA and nosocomial strains.

CONCLUSIONS

Nosocomial and HCA K. pneumoniae infections presented similar clinical features and antimicrobial resistance, and both two types of infections were different to CA infections. CRKP and ESBL-producing strains were disseminated mainly in HCA and nosocomial groups, and showed a clonal diversity. The cross transmission of CRKP was existed among HCA and nosocomial patients. This finding suggests that similar empirical therapy should be considered for patients with nosocomial and HCA K. pneumoniae infections and bacterial resistance surveillance of these infections is necessary.

Extensive antimicrobial resistance and plasmid-carrying resistance genes in mcr-1-positive E. coli sampled in swine, in Guangxi, South China

Background

The discovery of the superbug mcr-1-positive Escherichia coli (MCRPEC) has drew greet attention. Swine-origin multi-drug resistant MCRPEC has been a potential threat to public health and safety. However, there were few detailed studies have been reported on swine MCRPEC in Guangxi, South China.

Results

In this study, thirty-three MCRPEC strains were detected from 142 E. coli strains from 116 samples in Guangxi in 2018. Which could be classified into eight unique STs and a total of six incompatibility plasmid groups (IncFI, IncHI1, IncY, IncN, IncI1 and IncX1). After that, the susceptibility of MCRPEC isolates to 27 antimicrobial agents belonging to 17 antimicrobial categories was tested. There were nineteen E. coli resistant to 3rd and 4th generation cephalosporins and twelve E. coli resistant to carbapenem resistan. Importantly, the MCRPEC showed high resistance highly resistance for imipenem and meropenem, which were forbidden to use in livestock production. Three MCRPEC strains were further proved to be extensively drug-resistant (XDR), and the other isolates were multi-drug-resistant (MDR). Furthermore, we found that the plasmid-carrying resistance genes coexisted with the mcr-1 gene of the MCRPEC isolates. Which were listed as follows: β-lactamase antimicrobial resistance genes e.g. ESBL genes (bla_CTX-M14, bla_CTX-M24, bla_CTX-M123, bla_OXA-1), plasmid-mediated AmpC (pAmpC) gene (bla_CMY-2), the carbapenem resistance gene (bla_NDM-5), and non-β-lactamase antimicrobial resistance genes (qnrA, qnrB, qnrS, aac (6′)-Ib-cr, tetA, tetB, sul1, sul2, floR, aadA).

Conclusion

Thirty-three mcr-1-positive E. coli isolates in Guangxi displayed a wide profile of antimicrobial resistance. Plasmid-carrying resistance genes might be the main cause of MCRPEC multidrug resistance. This study highlighted the necessity for long-term surveillance of mcr-1-positive E. coli in pigs.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12917-021-02758-4.

Molecular characterization of carbapenem-resistant Enterobacteriaceae and emergence of tigecycline non-susceptible strains in the Henan province in China: a multicentrer study

Introduction

Carbapenem-resistant Enterobacteriaceae (CRE) have been responsible for nosocomial outbreaks worldwide and have become endemic in several countries.

Hypothesis/Gap Statement

To better understand the epidemiological trends and characteristics of CRE in the Henan province.

Aim

We assessed the molecular epidemiological characteristics of 305 CRE strains isolated from patients in 19 secondary or tertiary hospitals in ten areas of the Henan province in China.

Methodology

A total of 305 CRE isolates were subjected to multiple tests, including in vitro antimicrobial susceptibility testing, PCR for carbapenemase genes bla_KPC, bla_NDM, bla_IMP, bla_VIM, bla_OXA-_48-like. Tigecycline-resistant genes ramR, oqxR, acrR, tetA, rpsJ, tetX, tetM, tetL were analysed in five tigecycline non-susceptible carbapenem-resistant Klebsiella pneumoniae isolates (TNSCRKP). Additionally, multilocus sequence typing (MLST) was performed for carbapenem-resistant K. pneumoniae (CRKP).

Results

The most common CRE species were K. pneumoniae (234, 77 %), Escherichia coli (36, 12 %) and Enterobacter cloacae (13, 4 %). All strains exhibited multi-drug resistance. Overall, 97 % (295/305) and 97 % (297/305) of the isolates were susceptible to polymyxin B and tigecycline, respectively. A total of 89 % (271/305) of the CRE isolates were carbapenemase gene-positive, including 70 % bla_KPC, 13 % bla_NDM, 6 % bla_IMP, and 1 % combined bla_KPC/bla_NDM genes. K. pneumoniae carbapenemase (KPC) was the predominant carbapenemase in K. pneumoniae (87 %), whereas NDM and IMP were frequent in E. coli (53 %) and E. cloacae (69 %), respectively. Mutations in the ramR, tetA, and rpsJ genes were detected in five TNSCRKP. Moreover, 15 unique sequence types were detected, with ST11 (74 %), ST15 (9 %) and ST2237 (5 %) being dominant among K. pneumoniae strains.

Conclusion

A high proportion of CRE strains were carbapenemase-positive, and five carbapenem-resistant K. pneumonia isolates were tigecycline non-susceptible, indicating a need for the ongoing surveillance of CRE and effective measures for the prevention of CRE infections.

Co-Production of NDM-1, CTX-M-9 Family and mcr-1 in a Klebsiella pneumoniae ST4564 Strain in China

Purpose

To identify novel sequence types 4564 (ST4564) carbapenem-resistant Klebsiella pneumoniae (CRKP). Characterizing the feature of the clinic, resistance, and virulence of a co-producing NDM-1 and CTX-M-9 family and mcr-1 ST4564 strain.

Methods

A novel ST4564 CRKP was collected from June 2018 to July 2018. We investigated its antimicrobial susceptibility by the microdilution method. Using the modified carbapenem inactivation method (mCIM) to screen phenotype of carbapenemases. Resistance mechanisms, virulence-associated genes, multilocus sequence typing (MLST), and capsular serotypes were characterized by polymerase chain reaction (PCR) and DNA sequencing. Next-generation sequencing (NGS) was carried out to determine the genetic features of carbapenem resistance and virulence.

Results

ST4564, co-carrying NDM-1, CTX-M-9 and mcr-1, was resistant to carbapenems, cephamycin, third- or fourth-generation cephalosporins, β-lactam combination agents, quinolones and tigecycline but remained susceptible to amikacin (AMK) and colistin (COL). Through the NGS analysis with the G+C content of 56.65%, multiple resistance and virulence genomes were detected. The genes encoding the β-lactams, aminoglycosides, quinolones, macrolides, sulfonamide, polysaccharide capsule, type-I fimbriae cluster, siderophore genes, transporter and pumps, T6SS and pullulanase secretion protein. goeBURST analysis showed that ST4564 belonged to the CC1571 and it was not related to the prevalent high-risk clones.

Conclusion

We first identified the novel ST4564 CRKP. Our finding suggested that the urgent need for infection control of the new clone to prevent it from becoming a high-risk clone of CRKP.

Comparing three different phenotypic methods for accurate detection of carbapenemase-producing Enterobacterales

BACKGROUND

Early identification of carbapenemase-producing Enterobacterales (CPE) is highly essential to prevent their dissemination within health care settings.

OBJECTIVE

This study aimed to compare 3 reported phenotypic assays for detecting carbapenemase-producing Enterobacterales (CPE).

METHODS

151 Enterobacterales isolates were collected, the sensitivity and specificity of each test was determined, with molecular genotype serving as the gold standard. The phenotypic evaluations were performed using EDTA-synergistic carbapenem inactivation method (esCIM), EDTA-carbapenem inactivation method (eCIM), and enzyme inhibitor enhancement experiment (EIE).

RESULTS

The concordance rate was 98% for the EIE for the detection of KPC producer, and 100% for the esCIM and eCIM. Sensitivity differed among the 3 methods, and all assays had excellent sensitivity exceeding 90% for detecting metallo-β-lactamases (MBLs). The specificity of the eCIM, esCIM and EIE was 100%, 100% and 95%. Both eCIM and esCIM were unsatisfactory in detecting multi-enzyme strains (MBL and class A serine carbapenemase) (0/6). However, EIE increased the positive number to six (6/6).

CONCLUSIONS

The eCIM, esCIM and EIE can be used to accurately detect and distinguish carbapenemase and is suitable for routine use in most clinical microbiology laboratories.

Carriage of Carbapenem-Resistant Enterobacterales in Adult Patients Admitted to a University Hospital in Italy

The emerging spread of carbapenemase-producing Enterobacterales (CPE) strains, in particular, Klebsiella pneumoniae and Escherichia coli, has become a significant threat to hospitalized patients. Carbapenemase genes are frequently located on plasmids than can be exchanged among clonal strains, increasing the antibiotic resistance rate. The aim of this study was to determine the prevalence of CPE in patients upon their admission and to analyze selected associated factors. An investigation of the antibiotic resistance and genetic features of circulating CPE was carried out. Phenotypic tests and molecular typing were performed on 48 carbapenemase-producing strains of K. pneumoniae and E. coli collected from rectal swabs of adult patients. Carbapenem-resistance was confirmed by PCR detection of resistance genes. All strains were analyzed by PCR-based replicon typing (PBRT) and multilocus sequence typing (MLST) was performed on a representative isolate of each PBRT profile. More than 50% of the strains were found to be multidrug-resistant, and the bla_KPC gene was detected in all the isolates with the exception of an E. coli strain. A multireplicon status was observed, and the most prevalent profile was FIIK, FIB KQ (33%). MLST analysis revealed the prevalence of sequence type 512 (ST512). This study highlights the importance of screening patients upon their admission to limit the spread of CRE in hospitals.

Clinical Molecular Epidemiology of Carbapenem-Resistant Klebsiella pneumoniae Among Pediatric Patients in Jiangsu Province, China

PURPOSE

The continuous emergence of carbapenem-resistant Klebsiella pneumoniae (CRKP) has become a serious public health problem globally, especially for children, but data on CRKP infection in pediatric patients are limited. This study aimed to identify epidemiological and molecular patterns of CRKP among pediatric patients in Jiangsu province, China.

PATIENTS AND METHODS

CRKP were consecutively collected from the Children's Hospital of Nanjing Medical University in China from July 2018 to May 2019. Then, CRKP strains were performed for further study: antimicrobial susceptibility testing, drug-resistance determinants screening and homology analysis.

RESULTS

We collected 94 CRKP from 94 children. Overall, bla KPC-2 (79.8%) was the predominant carbapenemase gene, followed by bla NDM-1(14.9%), bla IMP-4 (5.3%) and bla NDM-5(4.3%). Notably, two isolates coharbored bla KPC-2 and bla IMP-4, and two isolates coharbored bla KPC-2 and bla NDM-5. MLST analysis revealed that 14 distinct sequence types (STs) were identified, of which ST11 was the most common sequence type identified. Moreover, two novel STs, ST4854 and ST4855, were detected in this study. PFGE revealed that a predominant cluster consisting of KPC-2-producing CRKP ST11 clone isolates was identified and was distributed mainly in the pediatric intensive care unit (PICU) and cardiac intensive care unit (CCU). Moreover, this is the first report to identify the dissemination of ST716 CRKP coproducing KPC-2 and IMP-4 clones.

CONCLUSION

Clonal dissemination of KPC-2-producing CRKP ST11 was observed in multiple departments. Moreover, two novel STs (ST4854 and ST4855) were identified, which indicates an increased diversity of CRKP strains. To our knowledge, this is the first report that identified the dissemination of Klebsiella pneumoniae coproducing KPC-2 and IMP-4 clones among children, which represents a significant health risk to pediatric patients. Active surveillance and effective control measures are urgently needed to prevent further transmission of these strains among children.

Clinical and Microbiological Characteristics of Invasive and Hypervirulent Klebsiella pneumoniae Infections in a Teaching Hospital in China

Purpose

To investigate the clinical and microbiological characteristics of invasive and hypervirulent Klebsiella pneumoniae (HvKP) in a teaching hospital in Southern China.

Patients and Methods

A total of 495 non-repetitive K. pneumoniae strains were isolated from Dongguan People’s Hospital affiliated to Southern Medical University in 2018. Multivariate analysis was performed using the patients’ clinical data to identify the risk factors for HvKP.

Results

Eighty-one isolates were HvKP (16.4%, 81/495), of which 43 (53.1%) were invasive HvKP, whereas 38 (46.9%) were non-invasive HvKP. The incidence of extended spectrum beta-lactamases (ESBLs) in HvKP and classic K. pneumoniae (cKP) were 7.4% (6/81) and 28.0% (116/414), respectively (p<0.05). Multivariate analysis indicated that diabetes mellitus (odds ratio [OR]=12.849, 95% confidence interval [CI]: 1.494–110.511, P=0.020) was an independent risk factor for invasive HvKP infection. Altogether, 51.2% (22/43) of invasive HvKP infections were treated with antimicrobial therapy combined with surgical drainage, and achieved good prognosis. K1-ST23 HvKP accounted for a higher proportion of invasive infections than non-invasive infections (P<0.05), but there was no statistical difference in the prognosis between the two groups (P>0.05). The most prevalent virulence genes in HvKP were rmpA 98.7% (80/81), followed by rmpA2 (82.7%, 67/81), iroN (98.7%, 80/81), and iutA 90.1% (70/81). There was no significant difference in the distribution of virulence genes between invasive HvKP and non-invasive HvKP isolates (P>0.05).

Conclusion

Invasive HvKP infection in this study was positively associated with diabetes as independent risk factors. Antibiotic therapy combined with surgical drainage is one of the most effective treatment measures of HvKP infection. Adequate attention should be paid to HvKP infection in clinical and microbiological laboratories.

Hypervirulent Klebsiella pneumoniae is emerging as an increasingly prevalent K. pneumoniae pathotype responsible for nosocomial and healthcare-associated infections in Beijing, China

OBJECTIVES

Hypervirulent Klebsiella pneumoniae(hvKp) is an increasingly important pathogen. Tracking its epidemiology and evolving antimicrobial resistance will facilitate care.

METHODS

A retrospective study was conducted in two hospitals. We collected the clinical data. Antimicrobial and virulence-associated phenotype and genotype, sequence type, and whole genome sequencing of selected strains were performed. HvKp was defined by the presence of some combination of prmpA, prmpA2, iucA, iroB, and peg-344, genes shown to accurately identify hvKp.

RESULTS

Of 158 Kp clinical isolates, 79 (50%) were hvKp. Interestingly, 53/79 (67.1%) of hvKp strains were isolated from patients with nosocomial infection and 19/79 (24.1%) from patients with healthcare-associated infection, but only 7/79 (8.8%) from patients with community-acquired infections. Importantly, 27/53 (50.9%) and 4/19 (21.1%) of hvKp nosocomial and healthcare-associated isolates, respectively, were multi-drug-resistant (MDR); 25/53 (47.2%) and 5/19 (26.3%) expressed ESBLs and 14/53 (26.4%) and 2/19 (10.5%) were carbapenem-resistant. Of the hvKp isolates from community-acquired infection, 0/7 (0%) were MDR and 0/7 (0%) were carbapenem-resistant. Additionally, unique characteristics of nosocomial, healthcare-associated, and community-acquired hvKp infection were identified. In summary, 50% of K. pneumoniae infections were caused by hvKp. A concerning, novel finding from this report is a major shift in hvKp epidemiology. Ninety-one percent of hvKp infections were nosocomial or healthcare-associated, and 43.1% of these isolates were MDR.

CONCLUSIONS

These data suggest that hvKp may be replacing classical K. pneumoniae as the dominant nosocomial and healthcare-associated pathotype. Ongoing surveillance is needed to determine if this trend is occurring elsewhere.

Multicenter Evaluation of Xpert Carba-R Assay for Detection and Identification of the Carbapenemase Genes in Rectal Swabs and Clinical Isolates

Rapid detection of carbapenemase-producing organisms is clinically desirable for hospital infection control and antibiotic stewardship. In this multicenter study, the Xpert Carba-R assay was evaluated for detection of the five carbapenemase genes (bla_KPC, bla_NDM, bla_IMP, bla_OXA-48, and bla_VIM) in 2404 nonduplicate rectal swabs of admitted inpatients and 521 Gram-negative isolates from four tertiary hospitals in China, compared with the reference growth-based method with DNA sequence analysis of colonies. All suspected false-positive results in rectal swabs were resolved by supplementary sequencing from broth cultures. A total of 197 bla_KPC, 171 bla_NDM, 142 bla_IMP, 6 bla_VIM, and 5 bla_OXA-48 genes were detected by Xpert Carba-R in 417 rectal swabs, with overall positive and negative percentage agreements ranging from 94.5% to 100% and from 94.8% to 99.9%, respectively. Notably, 17.5% (263/1500) of inpatients had rectal colonization with carbapenem-nonsusceptible organisms detected in intensive care units, and 63.1% (166/263) were Xpert Carba-R positive. Among the 469 carbapenem-nonsusceptible and 52 carbapenem-susceptible isolates examined, 373 were Enterobacteriaceae, 55 were Pseudomonas aeruginosa, and 93 were Acinetobacter baumannii. Compared with the reference isolate sequencing, overall positive and negative percentage agreements were 99.7% and 98.0%, respectively. The intra-assay and interassay coefficient of variability values were both <2%. Thus, we show that Xpert Carba-R assay provides good reproducibility and reliable results for detection and differentiation of five carbapenemase genes in both rectal swabs and clinical isolates.

Klebsiella pneumoniae: Prevalence, Reservoirs, Antimicrobial Resistance, Pathogenicity, and Infection: A Hitherto Unrecognized Zoonotic Bacterium

Klebsiella pneumoniae is considered an opportunistic pathogen, constituting an ongoing health concern for immunocompromised patients, the elderly, and neonates. Reports on the isolation of K. pneumoniae from other sources are increasing, many of which express multidrug-resistant (MDR) phenotypes. Three phylogroups were identified based on nucleotide differences. Niche environments, including plants, animals, and humans appear to be colonized by different phylogroups, among which KpI (K. pneumoniae) is commonly associated with human infection. Infections with K. pneumoniae can be transmitted through contaminated food or water and can be associated with community-acquired infections or between persons and animals involved in hospital-acquired infections. Increasing reports are describing detections along the food chain, suggesting the possibility exists that this could be a hitherto unexplored reservoir for this opportunistic bacterial pathogen. Expression of MDR phenotypes elaborated by these bacteria is due to the nature of various plasmids carrying antimicrobial resistance (AMR)-encoding genes, and is a challenge to animal, environmental, and human health alike. Raman spectroscopy has the potential to provide for the rapid identification and screening of antimicrobial susceptibility of Klebsiella isolates. Moreover, hypervirulent isolates linked with extraintestinal infections express phenotypes that may support their niche adaptation. In this review, the prevalence, reservoirs, AMR, Raman spectroscopy detection, and pathogenicity of K. pneumoniae are summarized and various extraintestinal infection pathways are further narrated to extend our understanding of its adaptation and survival ability in reservoirs, and associated disease risks.

Global impact of mcr-1-positive Enterobacteriaceae bacteria on "one health"

Polymyxins, especially polymyxin B and polymyxin E (colistin), are considered to be the last line of defence against infections caused by multi-drug-resistant (MDR) gram-negative bacteria such as carbapenem-resistant Enterobacteriaceae (CRE). However, the recent emergence and dissemination of the plasmid-mediated colistin resistance gene mcr-1 and its variants pose a serious challenge to public health and the livestock industry. This review describes the prevalence and dissemination of mcr-1-positive isolates from different sources, including animals (food animals, pet animals and wildlife), humans (healthy populations and patients) and the environment (farms, urban and rural communities and natural environments) based on existing epidemiological studies of mcr-1 and MCR-1-producing Enterobacteriaceae bacteria around the world. The major mechanisms of mcr-1 transmission across humans, animals and the environment are discussed.

In vitro Activity of Ceftazidime-Avibactam and Aztreonam-Avibactam Against Carbapenem-resistant Enterobacteriaceae Isolates Collected from Three Secondary Hospitals in Southwest China Between 2018 and 2019

Purpose

To assess the antimicrobial activities of ceftazidime/avibactam (CAZ/AVI) and aztreonam/avibactam (ATM/AVI) against carbapenem-resistant Enterobacteriaceae (CRE) isolates collected from three secondary hospitals in Southwest China between 2018 and 2019.

Materials and Methods

A total of 120 unique CRE clinical isolates were collected and carbapenemase genes were detected using PCR. Antimicrobial susceptibility was determined using standard broth microdilution method and the results were interpreted according to CLSI breakpoints.

Results

The 120 carbapenem-resistant strains included 92 Klebsiella pneumoniae, 10 Escherichia coli, 10 Enterobacter cloacae, five Klebsiella aerogenes, and three Klebsiella oxytoca isolates. Seventy-four percent of these 120 CRE isolates were collected from patients located in non-ICUs; 65.0% of these CRE isolates were collected from male patients; and 34.2% of these isolates were isolated from respiratory tracts. Four different carbapenemase genes were identified among 103 carbapenemase-producing Enterobacteriaceae (CPE) isolates, including bla _KPC-2 (n=77), bla _NDM-1 (n=16), bla _NDM-5 (n=12) and bla _IMP-4 (n=2). Overall, 21.7%, 37.5%, 40.8%, 75.0%, and 100% of the CRE strains were susceptible to levofloxacin, trimethoprim/sulfamethoxazole, amikacin, CAZ/AVI, and ATM/AVI, respectively. In addition, antimicrobial susceptibility testing showed that 96.7% isolates (n=116) were resistant to aztreonam, and the addition of avibactam (4 mg/L) significantly reduced the MICs of those aztreonam-resistant isolates by more than 128-fold (range: ≤0.125-4 mg/L), and 90.0% (n=108) of total 120 isolates were inhibited at ATM/AVI concentration ≤1 mg/L.

Conclusion

Our study revealed significant antimicrobial resistance among the CRE isolates against some commonly used antibiotics in three secondary Chinese hospitals. ATM/AVI exhibited potent activity against CRE isolates, including double carbapenemase-producing isolates, whereas CAZ/AVI was active against all KPC producers.

Virulence evolution, molecular mechanisms of resistance and prevalence of ST11 carbapenem-resistant Klebsiella pneumoniae in China: A review over the last 10 years

Sequence type 11 (ST11) carbapenem-resistant Klebsiella pneumoniae (CRKP) has become the dominant clone in China. In this review, we trace the prevalence of ST11 CRKP in the China Antimicrobial Surveillance Network (CHINET), the key antimicrobial resistance mechanisms and virulence evolution. The recent emergence of ST11 carbapenem-resistant hypervirulent K. pneumoniae (CR-hvKP) strains in China due to the acquisition of a pLVPK-like virulence plasmid, which may cause severe infections in relatively healthy individuals that are difficult to treat with current antibiotics, has attracted worldwide attention. There is a very close linkage among IncF plasmids, NTE_KPC and ST11 K. pneumoniae in China. Hybrid conjugative virulence plasmids are demonstrated to readily convert a ST11 CRKP strain to a CR-hvKP strain via conjugation. Understanding the molecular evolutionary mechanisms of resistance and virulence-bearing plasmids as well as the prevalence of ST11 CRKP in China allows improved tracking and control of such organisms.

Emergence of NDM-5-Producing Carbapenem-Resistant Klebsiella pneumoniae and SIM-Producing Hypervirulent Klebsiella pneumoniae Isolated from Aseptic Body Fluid in a Large Tertiary Hospital, 2017-2018: Genetic Traits of blaNDM-Like and blaSIM-Like Genes as Determined by NGS

Purpose

To characterize the clinical, resistance, and virulence features of carbapenem-resistant Klebsiella pneumonaie (CRKP) and hypervirulent Klebsiella pneumoniae (hvKP) and also provide an effective selection of drug in CRKP and hvKP treatment.

Materials and Methods

Twelve strains were collected and investigated these isolates for their antimicrobial susceptibility and molecular features. Resistance mechanisms, virulence-associated genes, multilocus sequence typing (MLST), and serotypes were detected by PCR and sequencing. Next general sequencing (NGS) was carried out to determine the features of carbapenem resistance and virulence. The synergistic activity of tigecycline–imipenem (TGC+IPM), tigecycline–meropenem (TGC+MEM), and tigecycline–aztreonam (TGC+ATM) combinations were performed by microdilution checkerboard method.

Results

Eleven CRKP and one hvKP strains were collected. All strains showed highly sensitive rates to tigecycline (TGC) and amikacin (AMK). NDM (33.3%, 4/12) was the main resistance mechanism and MLST assigned 3 of them to ST11. CTX-M-producing (n = 1) and KPC-2-producing (n = 1) isolates belonged to ST147 and ST11, respectively. The MICs of ATM and quinolones in NDM-1 CRKP and NDM-5 CRKP strains were different. The serotype of the majority strains was KL22KL137 (58.3%, 7/12), hvKP stain belonged to K64. CRKP strains harbored plasmid-mediated quinolone resistance genes (oqxA, oqxB, qnrS, qnrB), β-lactams (bla_CTX-M-3), aminoglycosides, type I and type III fimbriae genes, siderophore genes, and transporter and pumps. SIM-producing ST1764 K64 showed typical features of hvKP, showing hypermucoviscosity phenotype. The virulence genes, including rmpA2, alls and aerobactin genes, linked to hvKP, were found in ST1764 hvKP. hvKP was sensitive to quinolone; also, oqxA gene was detected. All TGC combinations showed highly synergistic effects and TGC+IPM was more effective treatment.

Conclusion

We first identified the NDM-5-producing ST690 CRKP and SIM-producing ST1764 hvKP strains in Shanxi province. Tigecycline-carbapenem combinations were available treatments for CRKP.

Does the presence of multiple β-lactamases in Gram-negative bacilli impact the results of antimicrobial susceptibility tests and extended-spectrum β-lactamase and carbapenemase confirmation methods?

OBJECTIVES

Many multidrug-resistant Gram-negative bacilli (MDR-GNB) harbour multiple β-lactamases. The aim of this study was to assess the impact of multiple β-lactamase carriage on the accuracy of susceptibility tests and extended-spectrum β-lactamase (ESBL) and carbapenemase confirmation methods.

METHODS

A total of 50 MDR-GNB, of which 29 carried multiple β-lactamases, underwent broth microdilution (BMD) and disk diffusion (DD) testing as well as confirmation tests for ESBLs and carbapenemases. Whole-genome sequencing (WGS) was used for β-lactamase gene identification.

RESULTS

Categorical agreement of BMD and DD testing results ranged from 86.5 to 97.7% for 10 β-lactam agents. BMD and DD algorithms for ESBL detection were highly variable; 6 of 8 positive strains carried an ESBL plus a carbapenemase or an AmpC enzyme, which may confound antimicrobial selection. The sensitivity and specificity of the modified carbapenem inactivation method (mCIM) were both 100%, whilst mCIM and EDTA-modified carbapenem inactivation method (eCIM) when used together to differentiate serine from metallo-β-lactamase carriage were both 96%. Xpert® Carba-R results (in vitro diagnostic test) were consistent with WGS results. Predicting phenotypic carbapenem resistance from WGS data overall showed 100% specificity but only 66.7% sensitivity for Enterobacterales isolates that were non-susceptible to imipenem and meropenem.

CONCLUSIONS

Multiple β-lactamases in MDR-GNB does not impact DD results, the utility of mCIM/eCIM tests, or Xpert Carba-R results. However, ESBL algorithms produced inconsistent results and predicting carbapenem resistance from WGS data was problematic in such strains.

Clinical and Genomic Epidemiology of Carbapenem-Nonsusceptible Citrobacter spp. at a Tertiary Health Care Center over 2 Decades

Carbapenem-nonsusceptible Citrobacter spp. (CNSC) are increasingly recognized as health care-associated pathogens. Information regarding their clinical epidemiology, genetic diversity, and mechanisms of carbapenem resistance is lacking. We examined microbiology records of adult patients at the University of Pittsburgh Medical Center (UMPC) Presbyterian Hospital (PUH) from 2000 to 2018 for CNSC, as defined by ertapenem nonsusceptibility. Over this time frame, the proportion of CNSC increased from 4% to 10% (P = 0.03), as did daily defined carbapenem doses/1,000 patient days (6.52 to 34.5; R2 = 0.831; P < 0.001), which correlated with the observed increase in CNSC (lag = 0 years; R2 = 0.660). Twenty CNSC isolates from 19 patients at PUH and other UPMC hospitals were available for further analysis, including whole-genome short-read sequencing and additional antimicrobial susceptibility testing. Of the 19 patients, nearly all acquired CNSC in the health care setting and over half had polymicrobial cultures containing at least one other organism. Among the 20 CNSC isolates, Citrobacter freundii was the predominant species identified (60%). CNSC genomes were compared with genomes of carbapenem-susceptible Citrobacter spp. from UPMC and with other publicly available CNSC genomes. Isolates carrying genes encoding carbapenemases (blaKPC-2,blaKPC-3, and blaNDM-1) were also long-read sequenced, and their carbapenemase-encoding plasmid sequences were compared with one another and with publicly available sequences. Phylogenetic analysis of 102 UPMC Citrobacter genomes showed that CNSC from our setting did not cluster together. Similarly, a global phylogeny of 64 CNSC genomes showed a diverse population structure. Our findings suggest that both local and global CNSC populations are genetically diverse and that CNSC harbor carbapenemase-encoding plasmids found in other Enterobacterales.

[A single-center study on the distribution and antibiotic resistance of pathogens causing bloodstream infection in adult patients with hematological disease during the period 2014-2018]

Objective: To investigate the distribution of pathogens and the antibiotic resistance profile of bloodstream infections in adult patients with hematological diseases in the period 2014-2018 to provide evidence for the rational use of antibiotics. Methods: We retrospectively analyzed the bloodstream infections in patients with hematological diseases from January 2014 to December 2018 at the institute of Hematology & Blood Diseases Hospital; this included an assessment of the clinical characteristics, distribution of pathogens, and antibiotic resistance data. Results: There were 1935 episodes of BSIs in the 1478 patients who were studied; among these, 1700 episodes occurred in the neutropenic phase. The 7-day and 30-day all-cause mortality rates were 5.5% and 8.2%, respectively. Bloodstream infection was usually accompanied by respiratory tract, perianal zone mucositis, and digestive tract symptoms; the respective proportions were 12.4%, 12.3%, and 9.1%, respectively. Total 2025 strains were isolated; 1551 (76.6%) of the pathogens were gram-negative bacteria, mainly Escherichia coli, Klebsiella pneumonia, and Pseudomonas aeruginosa; 423 (20.9%) were gram-positive bacteria, mainly Staphylococcus spp. and Streptococcus spp. Viridans; 51 (2.5%) were fungi, mainly Candida tropicalis. The resistance rates of Enterobateriaceae to piperacillin/tazobactam, carbapenems, amikacin were <10%. The resistance rates of K. pneumoniae to cefepime, piperacillin/tazobactam and meropenem increased annually. The resistance rates of Pseudomonas aeruginosa to piperacillin/tazobactam, quinolones, Aminoglycosides were <5% even when compared to carbapenems. Eleven stains of methicillin-resistant S. aureus and 1 stain of vancomycin-resistant Enterococcus faecium were detected. Conclusion: The pathogens of bloodstream infection in adult patients with hematological diseases are widely distributed. The resistance rates of different strains vary; the rates in some species had a tendency to increase. Antibiotics should be selected rationally as per the distribution of pathogens and resistance to antibiotics in different patient groups.

Characterization of the IncX3 Plasmid Producing bla NDM-7 From Klebsiella pneumoniae ST34

Carbapenemase-producing Klebsiella pneumoniae has been a major clinical threat worldwide because therapeutic options are limited. Although New Delhi metallo-β-lactamase (NDM) is an important carbapenemase responsible for carbapenem resistance, it is uncommon in carbapenemase-producing K. pneumoniae in China. In this study, we described strain HZW25, an NDM-7-producing K. pneumoniae strain belonging to sequence type 34 (ST34). HZW25 exhibited resistance to all β-lactams tested but was susceptible to aminoglycosides and fluoroquinolones. The whole genome of HZW25 was sequenced with Pacific Biosciences RSII SMRT technology. HZW25 was composed of one chromosomal DNA and four plasmids, and the resistance genes of HZW25 were all located on the chromosome, except bla_NDM–7 was located on a conjugative plasmid belonging to type IncX3 designated P4. The results of conjugation and transformation experiments showed that bla_NDM–7 could be horizontally transferred successfully from the donor strain, HZW25, to the recipient strains, E. coli J53 and E. coli DH5α. The NDM variant transposable elements of the bla_NDM–7-harboring plasmid P4 were the ISL3 and IS3000 families. The upstream region of bla_NDM–7 contained ΔISAba125, which was inserted near the IS5 or ΔIS5 sequence. Our study is the first report of metallo-β-lactamase NDM-7 in a carbapenemase-producing K. pneumoniae strain with ST34 in China. The emergence of NDM-producing K. pneumoniae would be troublesome during treatment using ceftazidime-avibactam. Therefore, the rapid and accurate identification of carbapenemase-producing K. pneumoniae is necessary.

Long-Term Continuous Antimicrobial Resistance Surveillance Among Nosocomial Gram-Negative Bacilli in China from 2010 to 2018 (CMSS)

Purpose

The Chinese Meropenem Surveillance Study (CMSS) was conducted every 2 years from 2010 to 2018 to monitor the antimicrobial activity of commonly used antimicrobial agents against nosocomial gram-negative bacilli in China.

Methods

From 2010 to 2018, 6,537 gram-negative bacilli were collected from 14 teaching hospitals. The minimum inhibitory concentrations (MICs) of meropenem and other antimicrobial agents were determined using the agar dilution and broth microdilution methods.

Results

Continuous surveillance indicated that, except for Klebsiella pneumoniae, the susceptibility of Enterobacterales to carbapenems was relatively stable over time. Carbapenems had the highest activity against the tested isolates, with MIC₉₀ values (MIC for 90% of organisms) ranging from 0.032 mg/L to 8 mg/L. More than 90% of bacteria were susceptible to either meropenem or imipenem; more than 80% were susceptible to ertapenem. The prevalence of extended-spectrum beta-lactamase (ESBL)-producing E. coli, K. pneumoniae, and P. mirabilis each year was 50.4–64.3%, 18–41.2%, and 1.9–33.8%, respectively. The prevalence of carbapenem-resistant K. pneumoniae (CRKP) and carbapenem-resistant Acinetobacter baumannii (CRAB) continued to increase significantly over time, from 7.6% to 21.2% and 64.6% to 69.3%, respectively. The prevalence of CRKP was higher from urinary tract infections (25.4%) than from bloodstream infections (14.2%), intra-abdominal infections (14.5%), and respiratory infections (14.4%). In total, 129 CRKP isolates were evaluated by PCR; of these, 92 (71.3%) carried the bla_KPC-2 gene. Colistin maintained very high in vitro antimicrobial activity against P. aeruginosa and A. baumannii (more than 95% of isolates exhibited susceptibility at all timepoints).

Conclusion

The results indicate an increase in K. pneumoniae resistance to carbapenems over time, mainly owing to KPC-type carbapenemase production. A. baumannii was severely resistant to carbapenems in China. Ongoing MIC-based resistance surveillance, like CMSS, provides additional data for clinical anti-infective treatment.

Clinical and Molecular Epidemiologic Characteristics of Ceftazidime/Avibactam-Resistant Carbapenem-Resistant Klebsiella pneumoniae in a Neonatal Intensive Care Unit in China

Background

Ceftazidime/avibactam (CZA)-resistant carbapenem-resistant Klebsiella pneumoniae (CRKP) infections occur in adults worldwide but are rarely observed in neonates. We evaluated the activities of CZA against CRKP and described the clinical and molecular epidemiology of CZA-resistant CRKP in a NICU prior to CZA approval in China.

Methods

A laboratory-based surveillance of CRKP was conducted from July 2017 to June 2018. Clinical data were initially reviewed. Antimicrobial susceptibility was determined by the broth microdilution method. CZA-resistant CRKP isolates were submitted to carbapenemase types screening and multilocus sequence typing.

Results

Over 23.3% (10/43) of CRKP strains were resistant to CZA, MIC₅₀ and MIC₉₀ values being 0.5 μg/mL and >32μg/mL, respectively. Most neonates shared similar clinical features with cesarean (n=8), preterm birth (n=6), low birth weight (n=5), and exposure to carbapenems/β-lactam (n=8). All CZA-resistant CRKP isolates were highly resistant to most tested drugs except for polymyxin B (POL) and tigecycline (TGC). CZA-resistant CRKP isolates showed greater sensitivity to amikacin (AMK), nitrofurantoin (NIT), levofloxacin (LVX) and ciprofloxacin (CIP), compared with CZA-sensitive CRKP. All CZA-resistant CRKP isolates harbored carbapenemase genes, bla_kpc-2 (n=5) being predominant, followed by bla_NDM-1 (n=4) and bla_NDM-5 (n=2). Among these CZA-resistant CRKP isolates, a total of eight different STs were identified. CRKP harboring KPC belonged to ST1419, ST37 and ST11, while NDM types were assigned to ST784, ST1710, ST37 and ST324. Furthermore, other β-lactamase genes including bla_SHV and bla_CTX-M were also found.

Conclusion

Over 23.3% of CRKP strains isolated from neonates were resistant to CZA. Cesarean, preterm birth, low birth weight, and exposure to carbapenems/β-lactam were similar clinical features of most neonates with CZA-resistant CRKP. The predominant carbapenemases of CZA-resistant CRKP were KPC-2 and NDM-1, and KPC-2 producing K. pneumoniae assigned into 3 STs, which indicate the genetic diversity of clinical CZA-resistant CRKP isolates.

Molecular Characterization of an IncFIIk Plasmid Co-harboring bla IMP-26 and tet(A) Variant in a Clinical Klebsiella pneumoniae Isolate

Carbapenems and tigecycline are two important classes of antimicrobial agents to treat the infections caused by Enterobacterales. Here, we reported a plasmid carrying both bla_IMP–26 and tet(A) variant in clinical Klebsiella pneumoniae KP-1572. MIC results showed that K. pneumonia KP-1572 was resistant to a wide range of antimicrobials. The bla_IMP–26 and tet(A) variant were located on an identical plasmid, which was indicated by S1-PFGE and southern blotting hybridization and can be successfully transferred by electroporation. Whole-plasmid sequencing and analysis revealed that a 142,993-bp-sized plasmid, designated pIMP1572, contains an IncFII_k backbone and a variable region harboring bla_IMP–26 and tet(A) variant. The plasmid pIMP1572 was apparently originated from a tet(A)-carrying IncFII_k plasmid but with a deletion length of 6,216-bp and a multiple drug resistance region (MDRR) insertion of 25,259 bp. The plasmid pIMP1572 in the present study represents the first report of the IncFII_k plasmid co-carrying bla_IMP and tet(A) variant, which should be monitored.

Isolation and Characterization of Novel Lytic Bacteriophages Infecting Epidemic Carbapenem-Resistant Klebsiella pneumoniae Strains

Carbapenem-resistant Klebsiella pneumoniae (CRKP) poses a significant clinical problem given the lack of therapeutic options available. Alternative antibacterial agents, such as bacteriophages, can be used as a valuable tool to treat the infections caused by these highly resistant bacteria. In this study, we isolated 54 phages from medical and domestic sewage wastewater between July and September 2019 and determined their host ranges against 54 clinical CRKP isolates, collected from a tertiary hospital in eastern China. The 54 CRKP isolates were from 7 sequence types (STs) and belonged to 9 capsular K locus types, harboring bla_KPC–2 (n = 49), bla_NDM–1 (n = 5), and bla_IMP–4 (n = 3). Among them, the epidemic KPC-2-producing ST11 strains were most predominant (88.9%). The 54 phages showed different host ranges from 7 to 52 CRKP isolates. The total host ranges of three phages can potentially cover all 54 CRKP isolates. Among the 54 phages, phage P545, classified as a member of Myoviridaes, order Caudovirales, had a relatively wide host range (96.3%), a short latent period of 20 min, and a medium burst size of 82 PFU/cell and was stably maintained at different pH values (4–10) and temperatures (up to 60°C). P545 showed the ability to inhibit biofilm formation and to degrade the mature biofilms. Taken together, the results of our study showed that the newly isolated phage P545 had a relatively wide host range, excellent properties, and antibacterial activity as well as antibiofilm activity against a clinical CRKP ST11 isolate, providing a promising candidate for future phage therapy applications.

Identification of an extensively drug-resistant Escherichia coli clinical strain harboring mcr-1 and blaNDM-1 in Korea

The development of colistin resistance in carbapenem-resistant strains poses a serious public health problem. In this study, we collected 249 carbapenem-resistant Escherichia coli isolates from patients in Seoul in 2018, and screened all isolates for colistin resistance and for the presence of mobile colistin resistance (mcr) genes. Colistin-resistant strains were further analyzed using multilocus sequence typing, antimicrobial susceptibility testing, detection of antibiotic resistance determinants, plasmid transconjugation, and whole-genome sequencing. Three of the 249 carbapenem-resistant isolates were resistant to colistin, and mcr-1 was detected in one isolate (SECR18-0888), which belonged to sequence type 156 and was resistant to all antibiotics tested except tigecycline. The mcr-1.1 gene was located on an ~62 kb self-transferable IncI2 plasmid along with the bla_CTX-M-55 gene, and the bla_NDM-1, bla_TEM, qepA1, and rmtB genes were additionally detected in SECR18-0888. As an extensively drug-resistant E. coli strain producing MCR-1 and NDM-1 was identified in Korea for the first time, continued monitoring of colistin resistance in carbapenem-resistant Enterobacteriaceae should be reinforced.

Dissemination of Carbapenemases (KPC, NDM, OXA-48, IMP, and VIM) Among Carbapenem-Resistant Enterobacteriaceae Isolated From Adult and Children Patients in China

This study aimed to investigate the dissemination and characteristics of bla_KPC, bla_NDM, bla_OXA-48-like , bla_IMP, and bla_VIM among the carbapenem-resistant Enterobacteriaceae (CRE) strains isolated from adult and children patients. A total of 935 non-duplicate CRE strains were collected from 36 hospitals in 24 provinces or cities across China from 2016 to 2018. Antimicrobial susceptibility testing was performed by broth microdilution method and carbapenemase genes bla_KPC, bla_NDM, bla_OXA-48-like , bla_IMP, and bla_VIM were screened by PCR and confirmed by DNA sequencing. Overall, carbapenemases were produced in 97.4% (911/935) of CRE strains, including KPC-2 (51.6%, 482/935), NDM (35.7%, 334/935), and OXA-48-like carbapenemases (7.3%, 68/935). Overall, the most prevalent carbapenemase gene was bla_KPC-2 among Klebsiella pneumoniae (64.6%, 457/709) and the CRE strains isolated from adult patients (70.3%, 307/437), and bla_NDM among Escherichia coli (96.0%, 143/149) and the CRE strains from children (49.0%, 247/498). The bla_OXA-232-positive carbapenem-resistant K. pneumoniae (9.3%, 66/709) were all isolated from children. Sixteen strains were positive for bla_IMP and 9 strains produced multiple carbapenemases. No strain was positive for bla_VIM. Most of the CRE strains (>90%) were resistant to cephalosporins and carbapenems, more than half (>50%) were resistant to aminoglycosides and fluoroquinolones, but the majority (95.8 and 98.4%) were susceptible to polymyxin B and tigecycline. Ceftazidime-avibactam showed excellent in vitro activity against bla_KPC-2 and bla_OXA-48-like positive strains (100% susceptible). In China, KPC-2, NDM, and OXA-48-like carbapenemases were predominant among CRE clinical isolates. The most prevalent carbapenemase gene was bla_KPC-2 among K. pneumoniae isolates from adult patients, and bla_NDM among E. coli isolates from children.

Evaluation of the Etest and disk diffusion method for detection of the activity of ceftazidime-avibactam against Enterobacterales and Pseudomonas aeruginosa in China

Background

Ceftazidime-avibactam was approved in China in 2019 for treating complicated intra-abdominal infections, hospital-acquired pneumonia, ventilator-associated pneumonia, and infections caused by Enterobacterales and Pseudomonas aeruginosa for which treatment options are limited. However, no currently available commercial systems have been approved for antimicrobial susceptibility testing of ceftazidime-avibactam in China. Here, we evaluated the Etest and disk diffusion method for detecting the activity of ceftazidime-avibactam against Enterobacterales and P. aeruginosa in China.

Results

In total, 194 Enterobacterales and 77 P. aeruginosa isolates, which were divided into a random selection group (140 Enterobacterales and 46 P. aeruginosa isolates) and stock group (54 Enterobacterales and 31 P. aeruginosa isolates), were assessed by the Etest, disk diffusion and broth microdilution methods. Minimum inhibitory concentrations and zone diameters were interpreted according to the CLSI supplement M100 30th edition. For all 271 tested isolates, no very major errors were found by using Etest, whereas the overall major error rate was 2.0% (4/203). The overall categorical agreement rates of Etest for Enterobacterales and P. aeruginosa were 99.5% (193/194) and 96.1% (74/77), respectively, and the essential agreement rates were 95.9% (186/194) and 94.8% (73/77), respectively. The disk diffusion method showed that the very major error and major error rates were 1.5% (3/204) and 2.5% (5/203), respectively. Overall categorical agreement rates values of the disk diffusion method for Enterobacterales and P. aeruginosa were 98.5% (191/194) and 93.5% (72/77) compared with broth microdilution, respectively.

Conclusions

For Enterobacterales and P. aeruginosa, both the Etest and disk diffusion method showed acceptable performance as alternatives to the standard broth microdilution method for clinical treatment interpretation. Application of the disk diffusion method in Enterobacterales was slightly better than that in P. aeruginosa.

Bloodstream Infections due to Carbapenem-Resistant Klebsiella pneumoniae: A Single-Center Retrospective Study on Risk Factors and Therapy Options

We aimed to compare efficacy of different patterns of antibiotics and explore the risk factors related to mortality in patients with bloodstream infections (BSIs) due to carbapenem-resistant Klebsiella pneumoniae (CRKP). This study retrospectively included 89 patients with BSIs due to CRKP with complete data during the year of 2018 in the First Affiliated Hospital of Zhejiang University School of Medicine. Overall, the 28-day mortality was 47.2% (42/89). Multivariate analysis of Cox regression revealed that hematological malignancy (hazard ratio [HR] 5.698; 95% confidence interval [CI], 2.405-13.504; p < 0.001) and Pitt bacteremia score (HR per unit increase, 1.303; 95% CI, 1.109-1.532; p = 0.001) were identified as independent predictors for 28-day mortality. Among 70 patients with appropriate therapy, 35 received tigecycline (TGC)-based therapy, 20 received polymyxin B (PMB)-based therapy, 9 received ceftazidime/avibactam-based therapy, and 6 patients had other kinds of antibiotics, including ciprofloxacin, amikacin, and cotrimoxazole. By adjusting variables selected by crude analysis, it showed that receiving PMB-based therapy provided a survival benefit comparing with TGC-based therapy (HR, 0.068; 95% CI, 0.018-0.260; p < 0.001). Hematological malignancy and Pitt bacteremia score were independent risk factors of death in patients with BSIs due to CRKP and PMB-based therapy improved survival rate compared with TGC-based therapy.

Evaluation of Modified Rapid Carbapenem Inactivation Method (mrCIM) Combined with Rapid EDTA-Modified Carbapenem Inactivation Method (reCIM) to Detect Carbapenemase and Distinguish Metallo-Carbapenemase in Enterobacteriaceae Within Four Hours

Purpose

To develop a rapid EDTA-modified carbapenem inactivation method (reCIM) combined with modified rapid carbapenem inactivation method (mrCIM) to detect carbapenemase and distinguish metallo-β-lactamases from carbapenemases in Enterobacteriaceae in 4 hrs.

Materials and Methods

The sensitivities and specificities of mrCIM and reCIM were retrospectively evaluated in 247 carbapenem-resistant Enterobacteriaceae of which 107 were carbapenemase producers confirmed by PCR and sequencing. In addition, mrCIM and reCIM were prospectively evaluated with 47 carbapenem-resistant enterobacterial isolates.

Results

The sensitivity and specificity of mrCIM were 96.3% and 97.1% at 2.5 hrs post incubation, and the specificity increased to 98.6% at 3 hrs. The combined mrCIM and reCIM showed a sensitivity of 95.4% and a specificity of 100% at 2.5 hrs post incubation in identifying metallo-β-lactamases, and the sensitivity increased to 97.0% at 3 hrs. These performance characteristics are comparable to mCIM and eCIM; however, compared with mCIM and reCIM tests which need at least 24 hrs to detect results, the mrCIM and reCIM required less than 4 hrs of total work time.

Conclusion

The combined mrCIM and reCIM can be used to accurately and quickly detect carbapenemase and metallo-β-lactamases in Enterobacteriaceae in 4 hrs and are suitable for routine use in most clinical microbiology laboratories.

Successful control of the first carbapenem-resistant Klebsiella pneumoniae outbreak in a Chinese hospital 2017-2019

Background

Carbapenem-resistant Klebsiella pneumoniae (CRKP) is considered as a serious global threat. CRKPs occurred only sporadically in the Second Hospital of Shanxi Medical University. Our study aimed to investigate and control the first outbreak of CRKP in our hospital occurred between October 2017 and August 2019.

Methods

The antimicrobial stewardship (AMS) workers have been implemented control measures properly. Clinical and epidemiological data were retrospectively collected from medical records. Carbapenemase genes were detected by modified carbapenem inactivation method (mCIM) test and the EDTA-modified carbapenem inactivation method (eCIM) test. Resistance genes were identified by polymerase chain reaction (PCR) and sequencing. Genetic relatedness was studied by multilocus sequence typing (MLST).

Results

During the outbreak, 31 patients were infected with CRKP isolates. 20 (64.5%) patients were infected with KPC-2 and/or NDM-1 producing K. pneumoniae. Mostly MLST-sequence types belonged to ST11 (21/31). The outbreak was two major K. pneumoniae clusters present in epidemiologically linked patients.

Conclusions

Setting up AMS workers is potentially a highly efficient strategy for the successful control of the outbreak. A multimodal and multidisciplinary infection control strategy proved to be crucial. The emergence of CRKP in our hospital emphasizes the importance of continuous monitoring of these isolates, which helps to limit the spread of CRKPs and improve the level of management.

Molecular Characteristics of Carbapenem-Resistant Enterobacter cloacae in a Tertiary Hospital in China

Background

Infections caused by the carbapenem-resistant Enterobacter cloacae (CREC) bring great challenges to the clinical treatment and pose a serious threat to public health. In this study, we investigated the molecular characteristics of CREC in a tertiary hospital.

Materials and Methods

A total of 12 non-duplicate CREC strains isolated during the period of November 2016 to July 2019 were subjected to automated microbial identification and antimicrobial susceptibility testing (AST) using the BD Phoenix-100 identification and antimicrobial susceptibility testing (ID/AST) system. The strains were also subjected to phenotypic screening for the detection of antibiotic resistance genes such as the carbapenemase and other β-lactamase genes, with the use of the polymerase chain reaction assay (PCR). Finally, multi-locus sequence typing (MLST) and pulsed-field gel electrophoresis (PFGE)-based homology analysis were applied.

Results

Four types of carbapenemases namely IMP-26, NDM-5, NDM-1, and KPC-2 were identified in 12 CREC strains. IMP-26 was the most prevalent type (6/12 strains, 50 %), followed by NDM-5 (3/12 strains, 25 %). The results of MLST revealed that these 12 strains could be divided into five sequence types (STs) among which ST544 was the dominant type (6/12 strains, 50 %). The PFGE results divided the 12 strains into four clusters.

Conclusion

Our study indicated that the epidemics of the IMP-26-producing E. cloacae ST544 strain did occur in the intensive care unit (ICU) of a tertiary hospital. Therefore, early surveillance and strict implementation of control measures are crucial for the prevention of nosocomial infections and transmissions in hospitals.

Phenotypic and Genomic Characterization of Virulence Heterogeneity in Multidrug-Resistant ST11 Klebsiella pneumoniae During Inter-Host Transmission and Evolution

Background

Multidrug-resistant (MDR) ST11 hypervirulent Klebsiella pneumoniae (hvKp) is emerging in China.

Purpose

The aim of this study was to track the transmission and evolution of hvKp.

Materials and Methods

A retrospective study focused on Kp infection was conducted. Clinical data were collected from electronic medical records. Whole-genome sequencing of Kp strains was performed. Single-nucleotide polymorphisms (SNPs) were analyzed and a transmission map was constructed. Sequence type, and antimicrobial and virulence-associated genes were characterized. Strains with some combination of the virulence genes, _prmpA, _prmpA2, iucA, iroB, and peg-344, were defined as hvKp. Kp virulence phenotypes were evaluated using the Galleria mellonella model.

Results

All 33 Kp strains were MDR-Kp and 13 (39.4%) were hvKp. Most hvKp strains (84.6%, 11/13) were hospital-acquired infections (HAIs). Two unique combinations of virulence-associated genes were detected among hvKp strains. Eleven cases were associated with _prmpA2+iucA and two strains presented with peg-344+_prmpA+_prmpA2+iucA. Surprisingly, two community-acquired MDR-hvKp infection cases were identified. Eight hvKp strains (61.5%, 8/13) exhibited a hypervirulent phenotype in the G. mellonella model. Five MDR-hvKp strains with the hypervirulence phenotype originated from a single cluster. Additionally, nine clones were identified among the two clades, six of which were hvKp. Moreover, the hvKp in clade 1 carried the IncHI1B plasmid replicon, whereas none of the hvKp strains in clade 2 harbored IncHI1B. These data, showing that different hvKp clones distributed into separate clades, indicate that transmission and evolution occurred within the hospital.

Conclusion

During inter-host evolution and transmission, various virulence clusters of the epidemic clone, MDR-ST11, converged, conferring phenotypic virulence heterogeneity and spread within the hospital and possibly the community. Mobile/conjugative genetic elements associated with virulence-encoding gene clusters might emerge and have been transmitted within the hospital, suggesting that enhanced ongoing surveillance is essential.

Contaminated in-house environment contributes to the persistence and transmission of NDM-producing bacteria in a Chinese poultry farm

While carbapenem use is prohibited in the poultry production chain and carbapenem-resistant Enterobacteriaceae (CRE) are absent from hatchery farms, New Delhi metallo-β-lactamase-producing CRE contamination of commercial broiler chicken farms (grow-out farms) can occur via living hosts such as flies. However, it is not known whether the inanimate factors from in-house environment play a role in the persistence of CRE on commercial farms. Herein, we monitored one typical broiler house in Hebei Province, China, from January 2017 to April 2018. We collected 350 cloacal samples from four broiler batches along with 582 environmental samples (194 in the raising period and 388 in the vacancy period) from sites including the surfaces of drooping boards, feeding troughs, nipple drinkers, corridor floors, sewage trenches, and air. All samples were screened for bla_NDM and cultured for NDM-producing isolates. The resistance profiles, genotypes, and genetic context of bla_NDM in CRE isolates were further characterized. Results showed that 1-day-old broilers, which were transferred from a hatchery farm and negative for CRE, acquired bla_NDM within 24 h of transfer (2 days of age), with a detection rate of up to 18.6%. High bla_NDM detection rates (26.8%-31.4%) were obtained among all environmental samples except air after standard cleaning and disinfection during the vacancy period. bla_NDM carriage rates (52.9%-72.9%) within the flocks remain stable and high across the next three broiler batches. Overall, 279 NDM-producing bacteria, including 259 Enterobacteriaceae (8 species), 14 Morganellaceae (3 species), three Alcaligenes faecalis and three Pseudomonas putida isolates, were recovered from 85 (24.3%) cloacal and 101 (17.4%) environmental samples. Three NDM variants, including NDM-5 (n = 181), NDM-1 (n = 92), and NDM-9 (n = 3), and a novel NDM-like-metallo-β-lactamase (NLM, n = 3) were identified among the samples. The predominant NDM-producing CRE species among the samples were Klebsiella pneumoniae (CRKP; 32.6%, n = 91) and Escherichia coli (CREC; 27.2%, n = 76). Both clonal and horizontal transmission of bla_NDM and an overlap of sequence types (STs) were observed in both CREC and CRKP from chicken and environmental samples. Notably, ST6751 CREC and ST37 CRKP persisted throughout the 16-month surveillance period. IncX3 (n = 197, 7 species), IncA/C₂ (n = 41, 5 species), and IncFII (n = 8, E. coli) were the three major bla_NDM-carrying plasmid types among the isolates. Although routine cleaning and disinfection procedures and "all-in/all-out" management were performed, once introduced to the farm environment, a diverse range of NDM-positive isolates may survive and persist, becoming an important reservoir of NDM-positive CRE for broiler chickens. Therefore, cleaning and disinfection procedures should be improved on poultry farms to avoid cross-contamination of NDM-producing bacteria between different batches of chickens, as well as further downstream in the poultry production chain.

Prevalence and characteristics of surgical site hypervirulent Klebsiella pneumoniae isolates

BACKGROUND

We aim to determine the prevalence of hypervirulent Klebsiella pneumoniae (hvKp), which causes surgical site infections (SSIs), and describe the microbiological and molecular characteristics of hvKp isolates.

METHODS

Non-duplicate K. pneumoniae strains were isolated from wound drainage specimens of postoperative patients at the Chinese PLA General Hospital between September 2008 and July 2017. Antimicrobial susceptibility, string test, pulsed-field gel electrophoresis (PFGE), and genome sequencing analyses were performed.

RESULTS

Fifty-one K. pneumoniae strains were isolated from wound drainage specimens collected from postoperative patients. Twenty-six hvKp strains, including 17 (17/37, 46.0%) and 9 (9/14, 64.3%) hvKp strains, were isolated from 37 and 14 patients with SSIs and community-acquired infections (CAIs), respectively. Notably, 4 extended-spectrum beta-lactamase (ESBL)-producing hvKp strains (4/26, 15.4%) and 2 carbapenem-resistant hvKp strains (2/26, 7.7%) were found. Thirteen K1 serotype (13/26, 50.0%) and 7 K2 serotype (7/26, 26.9%) strains were identified. Phylogenetic analysis results showed that 13 K1 serotype isolates exhibited a high degree of clonality, while 7 K2 serotype strains were genetically unrelated. MLST analysis indicated that there was a strong correlation between ST23 and the K1 serotype. ST65, ST86, and ST375 were prevalent in K2 serotype strains. Almost all hvKp strains (24/26, 92.3%) harbored large virulence plasmids with a high degree of homology to pNTUH-K2044 and sizes ranging from 140 to 220 kbp.

CONCLUSIONS

HvKp strains were prevalent in SSIs. Effective surveillance and control measures should be implemented to prevent the dissemination of such organisms, including the ESBL-producing and carbapenem-resistant hvKp strains.

Epidemic Characteristics of Carbapenem-Resistant Klebsiella pneumoniae in the Pediatric Intensive Care Unit of Yanbian University Hospital, China

Introduction

Carbapenem-resistant Enterobacteriaceae (CRE) pose a serious threat to clinical patient management and public health, as they are generally resistant to most antibiotics and cause infections with high mortality rates. Klebsiella pneumoniae ranks second among Enterobacteriaceae species that cause nosocomial infections. In this study, we investigated the epidemic characteristics of carbapenem-resistant K. pneumoniae (CRKP) in the pediatric intensive care unit (PICU) of Yanbian University Hospital.

Materials and Methods

A total of 14 non-duplicate CRKP strains, collected from March 2015 to November 2019, were subjected to automated microbial identification and antimicrobial susceptibility tests using the Phoenix-100 ID/AST system. The strains were also subjected to genotypic resistance testing, polymerase chain reaction assays to detect genes encoding carbapenemases and other β-lactamases, multi-locus sequence typing (MLST), and pulsed-field gel electrophoresis (PFGE)-based homology analysis.

Results

Two carbapenemase genes, KPC-2 and NDM-1 (in eight and six strains, respectively), were detected. MLST enabled the division of the strains into two sequence types, ST11 and ST1224 (containing eight and six strains, respectively). PFGE results classified the 14 strains into clonotypes A–D, of which clonotypes A and B belonged to ST11, while clonotypes C and D belonged to ST1224.

Conclusion

Our study reveals that epidemics of the KPC-2-ST11 and NDM-1-ST1224 strains occurred in the PICU of Yanbian University Hospital. Surveillance and strict implementation of prevention and control measures are crucial to prevent the occurrence and rapid spread of nosocomial infections.

Genetic diversity and in vitro activity of ceftazidime/avibactam and aztreonam/avibactam against imipenem-resistant Enterobacteriaceae isolates in Southwest China: A single-centre study

OBJECTIVES

The aim of this study was to investigate the molecular mechanisms of imipenem resistance in Enterobacteriaceae and to assess the antimicrobial activities of ceftazidime/avibactam (CAZ/AVI) and aztreonam/avibactam (ATM/AVI) against imipenem-resistant clinical isolates in a tertiary hospital in China.

METHODS

A total of 91 imipenem-resistant Enterobacteriaceae were collected and genes encoding carbapenemases, ESBLs, AmpC β-lactamases and porins were detected using PCR. MICs and susceptibility were determined using in-house-prepared broth microdilution panels and were interpreted according to CLSI breakpoints.

RESULTS

Imipenem-resistant isolates comprising 54 Klebsiella pneumoniae, 18 Escherichia coli, 8 Enterobacter cloacae, 6 Serratia marcescens, 3 Klebsiella oxytoca and 2 Klebsiella aerogenes were collected independently. Five different carbapenemase genes were identified, namely bla_KPC-2 (n = 60), bla_NDM-5 (n = 14), bla_NDM-1 (n = 11), bla_KPC-3 (n = 4) and bla_IMP-4 (n = 1). Among the 91 carbapenem-resistant Enterobacteriaceae (CRE), 85 isolates harboured at least one ESBL and/or AmpC gene, including 5 strains without carbapenemase-encoding genes. Moreover, 31 K. pneumoniae carried ompK35 and/or ompK36 mutations. MLST results showed that the K. pneumoniae belonged to 12 different STs, with ST11 being predominant (29/54; 53.7%). Overall, 17.6%, 25.3%, 41.8%, 65.9% and 100% of the CRE strains were susceptible to amikacin, trimethoprim/sulfamethoxazole, tetracycline, CAZ/AVI and ATM/AVI, respectively.

CONCLUSION

This study revealed that CRE isolates differ significantly in their species, STs, porins and carbapenemase genes in a single Chinese hospital. ATM/AVI exhibited potent activity against CRE isolates, even for the most notorious double-carbapenemase-producers with porin defects, whereas CAZ/AVI was active against all the non-metallo-β-lactamase-producing isolates.

Molecular and clinical epidemiology of carbapenem-resistant Enterobacterales in the USA (CRACKLE-2): a prospective cohort study

BACKGROUND

Carbapenem-resistant Enterobacterales (CRE) are a global threat. We aimed to describe the clinical and molecular characteristics of Centers for Disease Control and Prevention (CDC)-defined CRE in the USA.

METHODS

CRACKLE-2 is a prospective, multicentre, cohort study. Patients hospitalised in 49 US hospitals, with clinical cultures positive for CDC-defined CRE between April 30, 2016, and Aug 31, 2017, were included. There was no age exclusion. The primary outcome was desirability of outcome ranking (DOOR) at 30 days after index culture. Clinical data and bacteria were collected, and whole genome sequencing was done. This trial is registered with ClinicalTrials.gov, number NCT03646227.

FINDINGS

1040 patients with unique isolates were included, 449 (43%) with infection and 591 (57%) with colonisation. The CDC-defined CRE admission rate was 57 per 100 000 admissions (95% CI 45-71). Three subsets of CDC-defined CRE were identified: carbapenemase-producing Enterobacterales (618 [59%] of 1040), non-carbapenemase-producing Enterobacterales (194 [19%]), and unconfirmed CRE (228 [22%]; initially reported as CRE, but susceptible to carbapenems in two central laboratories). Klebsiella pneumoniae carbapenemase-producing clonal group 258 K pneumoniae was the most common carbapenemase-producing Enterobacterales. In 449 patients with CDC-defined CRE infections, DOOR outcomes were not significantly different in patients with carbapenemase-producing Enterobacterales, non-carbapenemase-producing Enterobacterales, and unconfirmed CRE. At 30 days 107 (24%, 95% CI 20-28) of these patients had died.

INTERPRETATION

Among patients with CDC-defined CRE, similar outcomes were observed among three subgroups, including the novel unconfirmed CRE group. CDC-defined CRE represent diverse bacteria, whose spread might not respond to interventions directed to carbapenemase-producing Enterobacterales.

FUNDING

National Institutes of Health.

Is There a Role for the Therapeutic Drug Monitoring of Colistin? An Overview

Colistin is used as a last-line antibiotic for the treatment of Gram-negative multiresistant bacteria. Due to its high nephrotoxicity, Therapeutic Drug Monitoring (TDM) is recommended for dose adjustment. We aimed to evaluate the available evidence of TDM in patients given colistin to treat Gram-negative infections. In this paper, we offer an overview, using an electronic search of the literature (published up to June 2019, without language restrictions) that compares the clinical outcomes and measurements of colistin TDM. Ultimately, the Therapeutic Drug Monitoring (TDM) of colistin in Plasma could prevent nephrotoxicity risk.

Emergence of a Plasmid-Encoded Resistance-Nodulation-Division Efflux Pump Conferring Resistance to Multiple Drugs, Including Tigecycline, in Klebsiella pneumoniae

In an era of increasing concerns about antimicrobial resistance, tigecycline is likely to have a critically important role in the treatment of carbapenem-resistant Enterobacteriaceae, the most problematic pathogens in human clinical settings—especially carbapenem-resistant K.pneumoniae. Here, we identified a new plasmid-borne RND-type tigecycline resistance determinant, TMexCD1-TOprJ1, which is widespread among K. pneumoniae isolates from food animals. tmexCD1-toprJ1 appears to have originated from the chromosome of a Pseudomonas species and may have been transferred onto plasmids by adjacent site-specific integrases. Although tmexCD1-toprJ1 still appears to be rare in human clinical isolates, considering the transferability of the tmexCD1-toprJ1 gene cluster and the broad substrate spectrum of TMexCD1-TOprJ1, further dissemination of this mobile tigecycline resistance determinant is possible. Therefore, from a “One Health” perspective, measures are urgently needed to monitor and control its further spread. The current low prevalence in human clinical isolates provides a precious time window to design and implement measures to tackle this.

Transporters belonging to the chromosomally encoded resistance-nodulation-division (RND) superfamily mediate multidrug resistance in Gram-negative bacteria. However, the cotransfer of large gene clusters encoding RND-type pumps from the chromosome to a plasmid appears infrequent, and no plasmid-mediated RND efflux pump gene cluster has yet been found to confer resistance to tigecycline. Here, we identified a novel RND efflux pump gene cluster, designated tmexCD1-toprJ1, on plasmids from five pandrug-resistant Klebsiella pneumoniae isolates of animal origin. TMexCD1-TOprJ1 increased (by 4- to 32-fold) the MICs of tetracyclines (including tigecycline and eravacycline), quinolones, cephalosporins, and aminoglycosides for K.pneumoniae, Escherichia coli, and Salmonella. TMexCD1-TOprJ1 is closely related (64.5% to 77.8% amino acid identity) to the MexCD-OprJ efflux pump encoded on the chromosome of Pseudomonas aeruginosa. In an IncFIA plasmid, pHNAH8I, the tmexCD1-toprJ1 gene cluster lies adjacent to two genes encoding site-specific integrases, which may have been responsible for its acquisition. Expression of TMexCD1-TOprJ1 in E. coli resulted in increased tigecycline efflux and in K. pneumoniae negated the efficacy of tigecycline in an in vivo infection model. Expression of TMexCD1-TOprJ1 reduced the growth of E. coli and Salmonella but not K. pneumoniae. tmexCD1-toprJ1-positive Enterobacteriaceae isolates were rare in humans (0.08%) but more common in chicken fecal (14.3%) and retail meat (3.4%) samples. Plasmid-borne tmexCD1-toprJ1-like gene clusters were identified in sequences in GenBank from Enterobacteriaceae and Pseudomonas strains from multiple continents. The possibility of further global dissemination of the tmexCD1-toprJ1 gene cluster and its analogues in Enterobacteriaceae via plasmids may be an important consideration for public health planning.

Molecular epidemiology of Carbapenem-resistant Klebsiella pneumoniae in a paediatric hospital in China

OBJECTIVE

We investigated the epidemiological characteristics of drug resistance and virulence factors of carbapenem-resistant Klebsiella pneumoniae (CRKP) isolates from paediatric patients in Shanghai.

METHODS

CRKP strains were consecutively collected between January and December in 2018. Antimicrobial susceptibility was determined by VITEK 2 compact. Polymerase chain reaction (PCR) was used to analyse drug resistance determinants, virulence genes and plasmid types. wzi sequencing and multilocus sequence typing was used to determine clonal relatedness.

RESULTS

Among 172 CRKP strains, bla_KPC-2 and bla_NDM-5 were the predominant carbapenemase genes. Compared with NDM-5, KPC-2 producers showed higher resistance rates to fluoroquinolones and aminoglycosides. The majority of KPC-2 producers belonged to KL64-ST11 background, while NDM-5 producers were mainly identified as KL62-ST48. Plasmid typing shown that IncF and IncFIB were the most prevalent plasmids in KPC-2 producers and IncX3 was widely spread in NDM-5-KP. Thirty-seven isolates carried various hypervirulence genes and the profiles of these genes showed high diversity.

CONCLUSIONS

The predominant carbapenemase of CRKP strains from paediatric patients in Shanghai were KPC-2 and NDM-5. KL47-ST11 KPC-2-KP and KL62-ST48 NDM-5-KP were representative clonal lineages. Although not prevalent, hypervirulence associated genes have begun to spread. Active long-term surveillance should be performed in both drug resistance characteristics and virulence factors.

Analysis of the Drug Resistance of Carbapenem-Resistant Klebsiella pneumoniae in the China Antimicrobial Resistance Surveillance Trial Program, 2007-2018

Objective: To analyze the drug resistance data of carbapenem-resistant Klebsiella pneumoniae (CRKP) collected in 19 tertiary hospitals in the China Antimicrobial Resistance Surveillance Trial Program from 2007 to 2018. Methods: According to the unified plan, clinical isolates of Klebsiella pneumoniae were collected from 19 tertiary hospitals in 19 cities in mainland China. The minimum inhibitory concentrations (MIC) were determined by a twofold agar dilution method, and antimicrobial susceptibility was established. The isolates were characterized by antimicrobial susceptibility testing, and their drug resistance data were analyzed. Results: In total, 302 strains of CRKP were screened from 3,671 strains of K. pneumoniae. The clinical isolation rate of CRKP increased from 0.9% to 19.9% in the past 12 years, and the isolation rate of CRKP in pediatric patients increased the fastest, to 24.7%. Along this period, the isolation rate in the intensive care unit was higher than that in other settings. The number of CRKP strains with imipenem and meropenem MIC ≤8 mg/L decreased from 63.6% to 11.7% and from 72.7% to 14.2%, respectively. Resistance to drugs that may be used to treat drug-resistant bacterial infections has increased to varying degrees, and CRKP has the lowest resistance rate to polymyxin B (<19.0%). Conclusion: Because the MIC of CRKP is increasing each year in China, carbapenems are less likely to be used as part of combined therapy to treat CRKP infections. It is difficult to obtain good therapeutic effects against CRKP infections with MICs that are too high. CRKP is still the most sensitive to polymyxin B in vitro, followed by tigecycline. Combination therapy may be the most effective current treatment for CRKP infection.

Clinical outcomes of ceftazidime-avibactam in lung transplant recipients with infections caused by extensively drug-resistant gram-negative bacilli

Background

Infections produced by extensively drug-resistant (XDR) gram-negative bacilli (GNB) in solid organ transplant (SOT) are an important cause of morbidity and mortality. Ceftazidime/avibactam (CAZ-AVI) is a novel β-lactam/β-lactamase combination antibiotic with anti-GNB activity, but experience in real clinical practice with CAZ-AVI in lung transplant (LT) recipients is limited.

Methods

We conducted a retrospective study of patients with XDR-GNB infection who received at least 3 days of CAZ-AVI in the Department of Lung Transplantation Between December 2017 and December 2018 at China-Japan friendship hospital (CJFH). The general information, clinical manifestations, laboratory examinations, treatment course, and outcomes were summarized.

Results

A total of 10 patients who underwent LT at our center were included. They were all males with a mean age 51 years. Infections after LT included pneumonia and/or tracheobronchitis [n=9; 90% (9/10)], cholecystitis and blood stream infection (BSI) (n=1, patient 8). In these 10 LT recipients, the incidence of various airway complications was 70% (7/10). Carbapenem-resistant Klebsialla pneumoniae (CRKP) was the predominant pathogen, being detected in 9 patients. Multilocus sequence typing (MLST) analysis showed that all 9 CRKP isolates belonged to ST11. Six patients (6/10, 60%) started CAZ-AVI as salvage therapy after a first-line treatment with other antimicrobials. CAZ-AVI was administered as monotherapy or in combination regimens in 20% (2/10) and 80% (8/10) of patients respectively. There were no difference in temperature before and after CAZ-AVI treatment (P>0.05). White blood cell (WBC) at 7 days, and procalcitonin (PCT) at 7 days and 14 days significantly dropped (P<0.05). After 7-14 days of CAZ-AVI treatment, the PaO₂/FiO₂ratio (P/F ratio) significantly improved (P<0.05). Nine patients (9/10, 90%) obtained negative microbiologic culture of CRKP/CRPA, with a median time to was 6.7 days (range, 1-15 days). However, 5 patients (5/10, 50%) had relapse of CRKP/CRPA infections in the respiratory tract regardless of whether negative microbiologic culture was obtained or not. The 30-day survival rate was 100%, and the 90-day survival rate was 90% (1/10). No severe adverse events related to CAZ-AVI occurred.

Conclusions

CAZ-AVI treatment of CRKP/ CRPA infection in LT recipients was associated with high rates of clinical success, survival, and safety, but recurrent CRKP/CRPA infections in the respiratory tract did occur.

Epidemiological characteristics of carbapenem-resistant Enterobacteriaceae collected from 17 hospitals in Nanjing district of China

Objective

In total, 97 carbapenem-resistant Enterobacteriaceae (CRE) were collected from 17 hospitals located in Nanjing, Southeast China, and analyzed for epidemiological characteristics.

Methods

Antimicrobial susceptibility was determined; followed by determination of the prevalence of resistance determinants, including extended-spectrum β-lactamase (ESBLs), plasmid-mediated AmpC enzyme (pAmpCs), plasmid-mediated quinolone resistance genes (PMQRs), fosfomycin resistance gene and exogenously acquired 16S rRNA methyltransferase (16S-RMTase) using PCR and DNA sequencing. The sequence types (STs) of CRE were determined by multi-locus sequence typing (MLST). The plasmid profiles were detected by PCR-based replicon typing (PBRT).

Results

All the CRE strains displayed high MIC₅₀ and MIC₉₀ for nearly all clinical available antibiotics, except for aztreonam/avibactam, minocycline, ceftazidime/avibactam, tigecycline, and colistin. KPC-2 (79.4%) and NDM (19.6%) were the main carbapenemases, CTX-M (76.3%) and SHV (60.8%) were the predominant ESBLs. In addition, oqxAB (70.1%) and qnr (63.9%) were the major PMQRs; rmtB (47.4%) was the main 16S-RMTase; fosA (76.3%) and fosA3 (37.1%) were the fosfomycin resistance gene. PBRT analysis showed presence of IncR (66.0%) and IncFII (64.9%) replicon types in the majority of the isolates, followed by IncFIB (46.4%) and IncX3 (16.5%). The IncFII and IncR replicon-types were found mainly in K. pneumoniae (68.8%), whereas the IncX3 replicons dominated in E. coli isolates (100.0%). The three dominating MLST-types ST11, ST15 and ST268 comprised 68.0% of the 77 K. pneumoniae. Seven distinct STs were identified among 8 E. coli.

Conclusions

The treatment for infections caused by CRE isolates is challenged by the presence of multiple resistance determinants and plasmid replicons. Our results highlighted the expansion of blaKPC-2 carrying K. pneumoniae ST11, the new emergency of single blaNDM-5 carrying K. oxytoca ST36, as well as blaIMP-4 and blaNDM-1 co-carrying E. cloacae ST418, which alert us on the urgency for antimicrobial resistant surveillance, to prevent dissemination of these highly transmissible and dangerous lineages.

Carbapenem-Resistant Enterobacter cloacae Causing Nosocomial Infections in Southwestern China: Molecular Epidemiology, Risk Factors, and Predictors of Mortality

Background

The emergence and spread of carbapenem-resistant Enterobacter cloacae (CR-ECL) have posed a serious threat to clinical management. This retrospective study assessed the epidemiological characteristics of CR-ECL to explore the risk factors and predictors of mortality in patients with CR-ECL infection.

Methods

We performed a retrospective 1:2 case-control study of hospitalized patients from January 2014 to December 2017. A total of 85 consecutive unique CR-ECL strains comprised the case group, and 170 matched patients with carbapenem-susceptible Enterobacter cloacae (CS-ECL) infection at the same period as the control group. Isolates were screened for potential resistance genes by polymerase chain reaction (PCR) and molecular typing was performed by multilocus sequence typing (MLST).

Results

The results of drug resistance gene detection showed that blaNDM-1 was the most common carbapenem resistance gene. The MLST results showed that ST51 was the predominant epidemic type, followed by ST88. ICU admission (P<0.001), drainage tube (P=0.002), central venous catheter (P=0.005), and carbapenem exposure (P=0.003) were independent risk factors for CR-ECL infection. Significant predictors for 28-day mortality included solid tumours (P=0.005), septic shock (P=0.019), and mechanical ventilation (P=0.027).

Conclusion

Our study indicated that ST51 and ST88, which are closely related, were the predominant epidemic types of CR-ECL producing blaNDM-1 in southwestern China. Strengthening the surveillance of patients with solid tumours, septic shock and mechanical ventilation is an urgent need.

The transferability and evolution of NDM-1 and KPC-2 co-producing Klebsiella pneumoniae from clinical settings

BACKGROUND

Emergence of KPC-2 and NDM-1-coproducing carbapenem-resistant Klebsiella pneumoniae (KPC-2-NDM-1-CRKP) has escalated threat of CRKP to healthcare. Currently, only 4 isolates had been reported sporadically. It remains unclear how KPC-2-NDM-1-CRKPs emerged, and whether they are stable and have transmission capacity.

METHODS

PCR and Sanger sequencing was used to screen carbapenemase genes for 2057 CRKP isolates, to identify KPC-2-NDM-1-CRKPs. The clinical information of the patients was collected from medical records. Antimicrobial susceptibility, plasmid stability, plasmid conjugation and growth curve were measured. The whole genomes were sequenced on PacBio and Illumina platforms. Similar plasmids were searched against public database. Phylogenetic tree was built based on related genomes which carried similar plasmids, to infer the evolutionary history of KPC-2-NDM-1-CRKP.

FINDINGS

We identified to date the largest cohort of 7 KPC-2-NDM-1-CRKPs. An increased incidence rate was observed. Plasmid transferability assay and phylogenic analysis suggested an evolutionary pathway that KPC-2-NDM-1-CRKP emerged from a KPC-2-CRKP progenitor which acquired another highly transferable blaNDM-1 plasmid later. Further, demographics and stability test revealed that these isolates were stable and had the potential for transmission among patients.

INTERPRETATION

Our study extends our concern on KPC-2-NDM-1-CRKP about its high stability and non-inferior fitness, sheds light on the evolution of KPC-2-NDM-1-CRKP, strengthens the importance of continued surveillance on these isolates, and would improve clinical treatment and management.

FUNDING

This work was supported by National Natural Science Foundation for Distinguished Young Scholars of China (81625014) and NSFC-RCUK-MRC (81661138006).

Fecal Carriage and Epidemiology of Carbapenem-Resistant Enterobacteriaceae Among Hospitalized Patients in a University Hospital

Purpose

To determine the prevalence and epidemiology of fecal carriage of carbapenem-resistant Enterobacteriaceae (CRE), antimicrobial susceptibility, carbapenemase phenotype/genotype, and the colistin-resistance gene mcr-1 in a university hospital in China.

Methods

A comprehensive study of the fecal carriage of CRE in 704 patients was performed. Multilocus sequence typing (MLST) and pulsed-field gel electrophoresis (PFGE) were applied to elucidate the molecular epidemiology of the isolates.

Results

In total, 60 CRE were detected in the 704 stool samples (8.5%), including 42 Klebsiella pneumoniae, 7 Escherichia coli, 3 Citrobacter freundii, 3 Klebsiella oxytoca, 3 Enterobacter cloacae, 1 Enterobacter aerogenes, and 1 Raoultella planticola. Fifty-five CRE isolates were positive for the carbapenemase phenotype, of which 39 were Klebsiella pneumoniae carbapenemase (KPC) producers. Thirty KPC-producing K. pneumoniae sequence type (ST) 11 isolates were identified and 28 were grouped into one cluster with a similarity of ≥85%, of predominately intensive care unit (ICU) strains. Three KPC-producing ST1889 strains were isolated from the pediatric ward, all indistinguishable and resistant to tigecycline. All CRE were susceptible to colistin and negative for mcr-1.

Conclusion

This study revealed a predominant fecal carriage of the KPC-producing K. pneumoniae ST11 clone, with several indistinguishable strain clusters, and the emergence of ST1889 in a Chinese university hospital. This evidence of cross-infection supports the urgent need for the implementation of infection control measures to prevent CRE dissemination.

Performance of modified carbapenem inactivation method and inhibitor-based combined disk test in the detection and distinguishing of carbapenemase producing Enterobacteriaceae

Background

This study aimed to evaluate the performance of modified carbapenem inactivation method (mCIM) combined EDTA-carbapenem inactivation method (eCIM), and inhibitor-based combined disk test (CDT) in the detection and distinguishing of carbapenemase production in Enterobacteriaceae.

Methods

A total of 101 nonrepetitive carbapenem insensitive Enterobacteriaceae [minimal inhibitory concentration (MIC) ≥2 µg/mL] were tested by mCIM, eCIM and CDT respectively, and the major carbapenemase genes including blaKPC, blaNDM, blaIMP, blaVIM and blaOXA-48-like genes were detected by polymerase chain reaction (PCR) as control.

Results

Seventy-nine (78.2%) of isolates were found to harbour one or more carbapenemase genes by PCR, with blaKPC and blaNDM being the most common genes. OXA-48-like genes were undetectable. The coincidence rate of mCIM combined eCIM and CDT was 97.5% (77/79) and 96.2% (76/79) respectively, compared with gene detection. Both assays had a misclassification in two bla_KPC+NDM-producing isolates of Klebsiella oxytoca. The sensitivity and specificity of two assays above were 100.0% vs. 95.0% and 98.4% vs. 98.4%, respectively in distinguishing serine-carbapenemase, while they were 95.1% vs. 97.6% and 100% vs. 100.0%, respectively in distinguishing metallo-carbapenemase.

Conclusions

mCIM combined eCIM and the CDT are both useful tools for the reliable detection and distinguishing single serine-carbapenemase or metallo-carbapenemase, but not for mixed types.

Coexistence Of Plasmid-Mediated mcr-1 And bla NDM-4 Genes In A Klebsiella pneumoniae Clinical Strain In Vietnam

In this study, we characterized the first clinical Klebsiella pneumoniae strain co- harboring mcr-1 and bla_NDM-4 genes in Vietnam, which was recovered from a patient admitted to hospital in 2015. This strain demonstrated nonsusceptible to all tested antibiotics, including last-line antibiotics such as carbapenems (MICs ≥128 μg/mL) and colistin (MIC =32 μg/mL), except tigecycline (MIC =1 μg/mL). Whole-genome analysis using both MinION and MiSeq data revealed that the strain carried 29 resistance genes. Particularly, mcr-1 and bla_NDM-4 genes were carried by different self-conjugative plasmids and able to be transferred to a recipient by conjugation. The colistin resistance of this strain was conferred by mcr-1 and additional chromosomal resistance determinants. Eight amino acid substitutions found in PmrA, PmrB, PmrC, PmrI, and PmrJ, all proteins that are involved in lipopolysaccharide modifications, may be associated with chromosomal colistin resistance. The accumulation of multiple antibiotic resistance mechanisms in this clinical isolate raises alarm on potential spread of extensively drug-resistant K. pneumoniae in healthcare settings.