Multiplex PCR for rapid detection of genes encoding class A carbapenemases

Whole genome sequence-based molecular characterization of blood isolates of carbapenem-resistant Enterobacter cloacae complex from ICU patients in Kolkata, India, during 2017-2022: emergence of phylogenetically heterogeneous Enterobacter hormaechei subsp. xiangfangensis

Blood-borne infections caused by the carbapenem-resistant Enterobacter cloacae complex (CR-ECC) are major public threats with respect to the challenges encountered during treatment. This study describes the whole genome sequencing-based molecular characteristics of blood isolates (n = 70) of CR-ECC from patients admitted to the intensive care unit of tertiary care hospitals in Kolkata, India, during 2017-2022 with respect to species identification, antimicrobial resistance (AMR) profiling, mechanism of drug resistance, and molecular subtypes. Vitek2 MALDI and species-specific PCR identified Enterobacter hormaechei subsp. xiangfangensis (47.14%) as the emerging CR-ECC subspecies in Kolkata. The predominating carbapenemase and extended-spectrum β-lactamase genes found were blaNDM-1 (51.42%) and blaCTX-M-15 (27%), respectively. Besides, blaNDM-4, blaNDM-5, blaNDM-7, blaCMH-3, blaSFO-1, blaOXA-181, blaOXA-232, blaKPC-3, and blaDHA-7 genes were also detected, which were not previously reported from India. A multitude of Class 1 integrons (including In180, In4874, In4887, and In4888, which were novel) and plasmid replicon types (IncFIB, IncFII, IncX3, IncHI1-HI2, IncC, and IncR) involved in AMR dissemination were identified. Reverse transcription-PCR and western blot revealed that carbapenem resistance in non-carbapenemase-producing CR-ECC isolates was contributed by elevated levels of ampC, overexpression of acrAB, and loss of ompF. A total of 30 distinct sequence types (STs) were ascertained by multi-locus sequence typing; of which, ST2011, ST2018, ST2055, ST2721, and ST2722 were novel STs. Pulsed-field gel electrophoresis analysis showed heterogeneity (69 pulsotypes with a similarity coefficient of 48.40%) among the circulating isolates, suggesting multiple reservoirs of infections in humans. Phylogenetically and genetically diverse CR-ECC with multiple AMR mechanisms mandates close monitoring of nosocomial infections caused by these isolates to forestall the transmission and dissemination of AMR.IMPORTANCEThe emergence and extensive dissemination of the carbapenem-resistant Enterobacter cloacae complex (CR-ECC) have positioned it as a critical nosocomial global pathogen. The dearth of a comprehensive molecular study pertaining to CR-ECC necessitated this study, which is the first of its kind from India. Characterization of blood isolates of CR-ECC over the last 6 years revealed Enterobacter hormaechei subsp. xiangfangensis as the most prevalent subsp., exhibiting resistance to almost all antibiotics currently in use and harboring diverse transmissible carbapenemase genes. Besides the predominating blaNDM-1 and blaCTX-M-15, we document diverse carbapenemase and AmpC genes, such as blaNDM-4, blaNDM-7, blaOXA-181, blaOXA-232, blaKPC-3, blaCMH-3, blaSFO-1, and blaDHA-7, in CR-ECC, which were not previously reported from India. Furthermore, novel integrons and sequence types were identified. Our findings emphasize the need for strengthened vigilance for molecular epidemiological surveillance of CR-ECC due to the presence of epidemic clones with a phylogenetically diverse and wide array of antimicrobial resistance genes in vulnerable populations.

Active Surveillance of Antimicrobial Resistance and Carbapenemase-Encoding Genes According to Sites of Care and Age Groups in Mexico: Results from the INVIFAR Network

We analyzed the antimicrobial resistance (AMR) data of 6519 clinical isolates of Escherichia coli (n = 3985), Klebsiella pneumoniae (n = 775), Acinetobacter baumannii (n = 163), Pseudomonas aeruginosa (n = 781), Enterococcus faecium (n = 124), and Staphylococcus aureus (n = 691) from 43 centers in Mexico. AMR assays were performed using commercial microdilution systems (37/43) and the disk diffusion susceptibility method (6/43). The presence of carbapenemase-encoding genes was assessed using PCR. Data from centers regarding site of care, patient age, and clinical specimen were collected. According to the site of care, the highest AMR was observed in E. coli, K. pneumoniae, and P. aeruginosa isolates from ICU patients. In contrast, in A. baumannii, higher AMR was observed in isolates from hospitalized non-ICU patients. According to age group, the highest AMR was observed in the ≥60 years age group for E. coli, E. faecium, and S. aureus, and in the 19-59 years age group for A. baumannii and P. aeruginosa. According to clinical specimen type, a higher AMR was observed in E. coli, K. pneumoniae, and P. aeruginosa isolates from blood specimens. The most frequently detected carbapenemase-encoding gene in E. coli was blaNDM (84%).

Hospital-acquired infections due to carbapenem-resistant Providencia stuartii

Background & objectives

During the course of a retrospective survey on healthcare associated infections (HAIs) due to carbapenem-resistant organisms, an unusual prevalence of HAIs due to carbapenem-resistant Providencia stuartii (CRPS) was found. Hence this study aimed to conduct the occurrence of P. stuartii associated HAIs with special reference to the drug resistance profiling of these isolates.

Methods

Of the eight total HAI cases (7.5% of total HAIs and 33.3% of HAIs due to Enterobacterales) of CRPS infections included in this study, three were reported from ventilator-associated pneumonia (VAP), three were surgical site infections (SSIs), one was a catheter-associated urinary tract infection (CAUTI) and one was a bloodstream infection. All the eight CRPS isolates were tested for extended-spectrum β-lactamases production, AmpC hyperproduction as well as carbapenem resistance. Typing of the isolates was performed by repetitive extragenic palindromic polymerase chain reaction (REP-PCR).

Results

All the eight isolates of CRPS were found to be AmpC hyperproducers, carbapenemase producers, and harboured chromosomally located blaNDM in seven isolates and blaIMP genes in one. All the cases with CRPS infections had prior history of colistin therapy along with prolonged hospital stay (>20 days). The cases were located in five different wards/intensive care unit (ICU) within the hospital in one year. However, strain typing by REP-PCR revealed 100 per cent similarity and clonal relatedness in all the seven isolates carrying blaNDM genes. Interestingly, routine hospital surveillance revealed a high carriage of P. stuartii in the axilla of patients admitted to the ICU.

Interpretation & conclusions

The study findings suggest CRPS as an important cause of HAIs. This organism often goes unnoticed due to the burden of carbapenem resistance in other Enterobacterales and non-fermenters.

Study of Antimicrobial Resistance, Biofilm Formation, and Motility of Pseudomonas aeruginosa Derived from Urine Samples

Pseudomonas aeruginosa causes urinary tract infections associated with catheters by forming biofilms on the surface of indwelling catheters. Therefore, controlling the spread of the bacteria is crucial to preventing its transmission in hospitals and the environment. Thus, our objective was to determine the antibiotic susceptibility profiles of twenty-five P. aeruginosa isolates from UTIs at the Medical Center of Trás-os-Montes and Alto Douro (CHTMAD). Biofilm formation and motility are also virulence factors studied in this work. Out of the twenty-five P. aeruginosa isolates, 16% exhibited multidrug resistance, being resistant to at least three classes of antibiotics. However, the isolates showed a high prevalence of susceptibility to amikacin and tobramycin. Resistance to carbapenem antibiotics, essential for treating infections when other antibiotics fail, was low in this study, Notably, 92% of the isolates demonstrated intermediate sensitivity to ciprofloxacin, raising concerns about its efficacy in controlling the disease. Genotypic analysis revealed the presence of various β-lactamase genes, with class B metallo-β-lactamases (MBLs) being the most common. The bla_NDM, bla_SPM, and bla_VIM-VIM2 genes were detected in 16%, 60%, and 12% of the strains, respectively. The presence of these genes highlights the emerging threat of MBL-mediated resistance. Additionally, virulence gene analysis showed varying prevalence rates among the strains. The exoU gene, associated with cytotoxicity, was found in only one isolate, while other genes such as exoS, exoA, exoY, and exoT had a high prevalence. The toxA and lasB genes were present in all isolates, whereas the lasA gene was absent. The presence of various virulence genes suggests the potential of these strains to cause severe infections. This pathogen demonstrated proficiency in producing biofilms, as 92% of the isolates were found to be capable of doing so. Currently, antibiotic resistance is one of the most serious public health problems, as options become inadequate with the continued emergence and spread of multidrug-resistant strains, combined with the high rate of biofilm production and the ease of dissemination. In conclusion, this study provides insights into the antibiotic resistance and virulence profiles of P. aeruginosa strains isolated from human urine infections, highlighting the need for continued surveillance and appropriate therapeutic approaches.

The Impact of the Virulence of Pseudomonas aeruginosa Isolated from Dogs

Pseudomonas aeruginosa is a pathogenic bacterium that can cause serious infections in both humans and animals, including dogs. Treatment of this bacterium is challenging because some strains have developed multi-drug resistance. This study aimed to evaluate the antimicrobial resistance patterns and biofilm production of clinical isolates of P. aeruginosa obtained from dogs. The study found that resistance to various β-lactam antimicrobials was widespread, with cefovecin and ceftiofur showing resistance in 74% and 59% of the isolates tested, respectively. Among the aminoglycosides, all strains showed susceptibility to amikacin and tobramycin, while gentamicin resistance was observed in 7% of the tested isolates. Furthermore, all isolates carried the oprD gene, which is essential in governing the entry of antibiotics into bacterial cells. The study also investigated the presence of virulence genes and found that all isolates carried exoS, exoA, exoT, exoY, aprA, algD, and plcH genes. This study compared P. aeruginosa resistance patterns worldwide, emphasizing regional understanding and responsible antibiotic use to prevent multi-drug resistance from emerging. In general, the results of this study emphasize the importance of the continued monitoring of antimicrobial resistance in veterinary medicine.

High Prevalence of blaNDM Among Carbapenem Non-Susceptible Klebsiella pneumoniae in a Tunisian Hospital First Report of blaNDM-9, blaKPC-20, and blaKPC-26 Genes

Fifty-four carbapenem non-susceptible Klebsiella pneumoniae (CNSKP) isolates were collected from a Tunisian hospital over a period of 13 consecutive months. Carbapenemase production and the prevalence of carbapenemase-encoding genes were investigated using combined-disk test (CDT), modified Carba NP (mCarba NP) test, and UV-spectrophotometry method complemented by PCR experiments and sequencing. Carbapenemase production was detected by the mCarba NP test and CDT in 92.59% and 96.29% of the 54 CNSKP isolates, respectively; while imipenem hydrolysis was detected using UV-spectrophotometry in the crude extracts of 44 isolates. bla_NDM, bla_OXA-48-like, and bla_KPC carbapenemase-encoding genes were found in 48, 31, and 22 isolates, respectively. Remarkably, bla_NDM-9, bla_KPC-20, and bla_KPC-26 genes were reported. The co-occurrence of carbapenemase-encoding genes in a single isolate was detected in 62.96% of the isolates. The analysis of clonal relationships between the isolates by pulsed field gel electrophoresis revealed that the majority of them were genetically unrelated. Our investigation provides molecular data on enzymatic mechanism of carbapenem non-susceptibility among 54 CNSKP showing the dominance of bla_NDM, and comprises the first identification of bla_NDM-9, bla_KPC-20, and bla_KPC-26 genes in a Tunisia hospital.

Intra-Abdominal Hypertension Contributes to the Development of Ventilator-Associated Pneumonia from Intestinal Bacteria

Introduction

Ventilator-associated pneumonia (VAP) is an ICU (intensive care unit)-acquired pulmonary parenchymal infection that is complicated by mechanical ventilation and is associated with high morbidity and mortality. Klebsiella pneumoniae (KPN) is known to asymptomatically colonize the gastrointestinal tract and may increase the incidence of corresponding VAP. Our study aims were to investigate the exact origin of the carbapenem-resistant Klebsiella pneumoniae (CRKP) causing VAP in our patient.

Methods

Various environmental samples, including the patient's anal swab, were collected in order to find the source of the bacteria. Minimum inhibitory concentrations (MICs) for antimicrobial agents were determined according to the guidelines of the Clinical and Laboratory Standards Institute (CLSI); resistant genes were detected by using PCR and sequencing; clone relationships were analyzed by using multilocus-sequence typing (MLST) and pulsed field gel electrophoresis (PFGE). The IAP values were obtained via urinary catheter.

Results

One CRKP strain was detected in the patient's anal swab; this strain was confirmed with the same gene type as the strain isolated from the sputum. We found that the patient's intra-abdominal pressure (IAP) was 29.41, 27.06, 24.12, and 22.66 mmHg; the IAP was either equal to or above 12 mmHg, on the operation day and the following three days. Intra-abdominal hypertension (IAH) occurred during the patient's hospitalization and was considered to be caused by the surgical procedure. Meanwhile, we found that there was a correlation between IAH and the detection of CRKP in the sputum. The findings suggested that his VAP was caused by intestinal colonial KPN, and not from the environment.

Discussion

Our research illustrated that the ST11 KPC-2-producing strain colonized the intestinal tract and caused the development of VAP when the IAP was elevated. Routine screening for the intestinal carriage of CRKP, among patients in ICUs, can limit and prevent current and future outbreaks.

Susceptibility profile of bla OXA-23 and metallo-β-lactamases co-harbouring isolates of carbapenem resistant Acinetobacter baumannii (CRAB) against standard drugs and combinations

Background

The rapid emergence of carbapenem resistant Acinetobacter baumannii (CRAB) has resulted in an alarming situation worldwide. Realizing the dearth of literature on susceptibility of CRAB in genetic context in the developing region, this study was performed to determine the susceptibility profile against standard drugs/combinations and the association of in-vitro drug synergy with the prevalent molecular determinants.

Methods and findings

A total of 356 clinical isolates of A. baumannii were studied. Confirmation of the isolates was done by amplifying recA and ITS region genes. Susceptibility against standard drugs was tested by Kirby Bauer disc diffusion. Minimum inhibitory concentration (MIC), MIC50 and MIC90 values against imipenem, meropenem, doripenem, ampicillin/sulbactam, minocycline, amikacin, polymyxin B, colistin and tigecycline was tested as per guidelines. Genes encoding enzymes classes A (bla GES, bla IMI/NMC-A, bla SME, bla KPC), B (bla IMP, bla VIM, bla NDM) and D (bla OXA-51, bla OXA-23 and bla OXA-58) were detected by multiplex polymerase chain reaction. Synergy against meropenem-sulbactam and meropenem-colistin combinations was done by checkerboard MIC method. Correlation of drug synergy and carbapenemase encoding genes was statistically analyzed.

Results

Of the total, resistance above 90% was noted against gentamicin, ciprofloxacin, levofloxacin, ceftazidime, cefepime, ceftriaxone, cotrimoxazole and piperacillin/tazobactam. By MIC, resistance rates from highest to lowest was seen against imipenem 89.04% (n=317), amikacin 80.33% (n=286), meropenem 79.49% (n=283), doripenem 77.80% (n=277), ampicillin/sulbactam 71.62% (n=255), tigecycline 55.61% (n=198), minocycline 14.04% (n=50), polymyxin B 10.11% (n=36), and colistin 2.52% (n=9). CRAB was 317 (89.04%), 81.46% (n=290) were multidrug resistant and 13.48% (n=48) were extensively drug resistant. All the CRAB isolates harboured bla OXA-51 gene (100%) and 94% (n=298) bla OXA-23 gene. The bla IMP gene was most prevalent 70.03% (n=222) followed by bla NDM, 59.62% (n=189). Majority (87.69%, 278) were co-producers of classes D and B carbapenemases, bla OXA-23 with bla IMP and bla NDM being the commonest. Synergy with meropenem-sulbactam and meropenem-colistin was 47% and 57% respectively. Reduced synergy (p= <0.0001) was noted for those harbouring bla OXA-51+blaOXA-23with bla NDM gene alone or co-producers.

Conclusion

Presence of bla NDM gene was a significant cause of synergy loss in meropenem-sulbactam and meropenem-colistin. In bla NDM endemic regions, tigecycline, minocycline and polymyxins could be viable options against CRAB isolates with more than one carbapenemase encoding genes.

High frequency of carbapenem-resistant Enterobacteriaceae fecal carriage among ICU hospitalized patients from Southern Iran

Objectives

The worldwide emergence of carbapenem-resistant Enterobacteriaceae (CRE) has become a major therapeutic concern to medical institutions. To date, no study has determined the frequency and risk factors of inpatients with CRE fecal carriage in Southern Iran. We studied the features of carbapenemase-producing Enterobacteriaceae (CPE) collected from the central ICU of a university hospital.

Materials and Methods

Totally, 173 samples, including 124 stool samples from 46 ICU inpatients on admission and different follow-ups, 9 ICU staff, and 40 environmental samples were included. CRE was identified using microbiological methods. Antimicrobial susceptibility was investigated by using the disk diffusion method and E-test. Carbapenemase producers were detected using the mCIM method. Seven carbapenemase genes were characterized. The genetic relationship among 20 CPE was elucidated by PFGE.

Results

The overall fecal carriage rate was 28.2%, while CRE acquisition was 6.1%. CRE were classified as Klebsiella pneumoniae (71.4%), Escherichia coli (23.8%), and Enterobacter aerogenes (4.8%). From 21 CRE, 20 (95.2%) produced carbapenemases, of which 10, 15, 10, 25, 5, and 65% were blaKPC, blaSME, blaIMP, blaVIM, blaNDM and blaOXA-48-positive, respectively. Out of 20 CPE, 14 different PFGE patterns were observed, categorized into six clusters, suggestive of non-clonal spread. No difference between the examined risk factors with CRE carriage was shown.

Conclusion

The data indicate a high CRE fecal carriage rate among inpatients. Our findings implicate the widespread of OXA-48 carbapenemase together with heterogeneity among CRE with great concern for dissemination and therapeutic threat. Early diagnosis and monitoring of CRE among inpatients are urgent.

High Frequency of Antibiotic Resistance Genes (ARGs) in the Lerma River Basin, Mexico

The spread of beta-lactamase-producing bacteria is of great concern and the environment has been found to be a main source of contamination. Herein, it was proposed to determine the frequency of antimicrobial-resistant-Gram-negative bacteria throughout the Lerma River basin using phenotypic and molecular methods. Resistant bacteria were isolated with chromogenic media and antimicrobial susceptibility tests were used to characterize their resistance. ARGs for beta-lactams, aminoglycosides, and quinolones were detected by PCR. Species were identified by Sanger sequencing the 16S rRNA gene and the representative genomes of MDR strains were sequenced by NGS. A high variation in the number of isolates was observed in the 20 sampled sites, while observing a low diversity among the resistant bacteria. Of the 12 identified bacterial groups, C. freundii, E. coli, and S. marcescens were more predominant. A high frequency of resistance to beta-lactams, quinolones, and aminoglycosides was evidenced, where the bla_CTX,qnrB, qnrS y, and aac(6')lb-cr genes were the most prevalent. C. freundii showed the highest frequency of MDR strains. Whole genome sequencing revealed that S. marcescens and K. pneumoniae showed a high number of shared virulence and antimicrobial resistance genes, while E. coli showed the highest number of unique genes. The contamination of the Lerma River with MDR strains carrying various ARGs should raise awareness among environmental authorities to assess the risks and regulations regarding the optimal hygienic and sanitary conditions for this important river that supports economic activities in the different communities in Mexico.

Isolation and characterisation of carbapenem-resistant Pseudomonas aeruginosa from hospital environments in tertiary care hospitals in Dhaka, Bangladesh

OBJECTIVES

Increasing evidence of carbapenem-resistant Pseudomonas aeruginosa (CRPA) infection in healthcare facilities poses an alarming threat to public health. There is little evidence on the occurrence of this organism in Bangladeshi hospitals.

METHODS

We collected 117 environmental swab samples from two tertiary care hospitals in Dhaka, Bangladesh and tested for Pseudomonas species by nonselective enrichment of swabs followed by plating on Cetrimide agar. We confirmed the isolates as P. aeruginosa by API 20NE test and polymerase chain reaction Polymerase Chain Reaction (PCR) for 16S rRNA gene. We analysed P. aeruginosa isolates for susceptibility against 15 clinically important antibiotics and tested the carbapenem-resistant isolates for metallo β-lactamase (MBL). All CRPA isolates were characterised for carbapenem-resistant genes, virulence genes and biofilm formation genes.

RESULTS

Of 117 swab samples, 82 (70%) were tested positive for P. aeruginosa. All P. aeruginosa isolates were multidrug-resistant, and 39% (n = 32) of isolates were CRPA. Around 56% (n = 18) of CRPA were MBL-producing; 22% (n = 7) of isolates were positive for carbapenemase gene bla_NDM followed by 16% (n = 5) for bla_VIM and 13% (n = 4) for bla_IMP. Sequencing identified these genes as bla_NDM-1, bla_IMP-13, bla_VIM-2 variants. Based on optical density values, 94% (n = 30) of CRPA isolates were capable of producing biofilms. All CRPA isolates (n = 32) were positive for at least 1 of 6 biofilm-associated genes and 4 of 12 virulence genes tested in the study.

CONCLUSION

Hospital environments in Bangladesh are contaminated with highly virulent CRPA, which might be a potential source of hospital-acquired infections, accentuating the need for strengthening hospital infection control programs.

Molecular determination of O25b/ST131 clone type among extended spectrum β-lactamases production Escherichia coli recovering from urinary tract infection isolates

Background

Escherichia coli (E. coli) O25b/ST131 clone causes urinary tract infection (UTI) and is associated with a broad spectrum of other infections, such as intra-abdominal and soft tissue infections, that can be affecting bloodstream infections. Therefore, since O25b/ST131 has been reported in several studies from Iran, in the current study, we have investigated the molecular characteristics, typing, and biofilm formation of O25b/ST131 clone type E. coli collected from UTI specimens.

Methods

A total of 173 E. coli isolates from UTI were collected. The susceptibility to all fourth generations of cephalosporins (cefazolin, cefuroxime, ceftriaxone, cefotaxime, ceftazidime, cefepime) and ampicillin, ampicillin-sulbactam and aztreonam was determined. Class A ESBLs, class D ESBL and the presence of pabB gene screenings to detect of O25b/ST131 clone type were performed by using of PCR. Biofilm formation was compared between O25b/ST131 isolates and non-O25b/ST131 isolates. Finally, ERIC-PCR was used for typing of ESBL positive isolates.

Results

Ninety-four ESBL positive were detected of which 79 of them were O25b/ST131. Antimicrobial susceptibility test data showed that most antibiotics had a higher rate of resistance in isolates of the O25b/ST131 clonal type. Biofilm formation showed that there was a weak association between O25b/ST131 clone type isolates and the level of the biofilm formation. ERIC-PCR results showed that E. coli isolates were genetically diverse and classified into 14 groups.

Conclusion

Our results demonstrated the importance and high prevalence of E. coli O25b/ST131 among UTI isolates with the ability to spread fast and disseminate antibiotic resistance genes.

The Role of nmcR, ampR, and ampD in the Regulation of the Class A Carbapenemase NmcA in Enterobacter ludwigii

Various carbapenemases have been identified in the Enterobacteriaceae. However, the induction and corresponding regulator genes of carbapenemase NmcA has rarely been detected in the Enterobacter cloacae complex (ECC). The NmcA-positive isolate ECC NR1491 was first detected in Japan in 2013. It was characterized and its induction system elucidated by evaluating its associated regulator genes nmcR, ampD, and ampR. The isolate was highly resistant to all β-lactams except for third generation cephalosporins (3GC). Whole-genome analysis revealed that bla_NmcA was located on a novel 29-kb putatively mobile element called EludIMEX-1 inserted into the chromosome. The inducibility of β-lactamase activity by various agents was evaluated. Cefoxitin was confirmed as a strong concentration-independent β-lactamase inducer. In contrast, carbapenems induced β-lactamase in a concentration-dependent manner. All selected 3GC-mutants harboring substitutions on ampD (as ampR and nmcR were unchanged) were highly resistant to 3GC. The ampD mutant strain NR3901 presented with a 700 × increase in β-lactamase activity with or without induction. Similar upregulation was also observed for ampC and nmcA. NR1491 (pKU412) was obtained by transforming the ampR mutant (135Asn) clone plasmid whose expression increased by ∼100×. Like NR3901, it was highly resistant to 3GC. Overexpression of ampC, rather than nmcA, may have accounted for the higher MIC in NR1491. The ampR mutant repressed nmcA despite induction and it remains unclear how it stimulates nmcA transcription via induction. Future experiments should analyze the roles of nmcR mutant strains.

Extensive outbreak of colistin resistant, carbapenemase (blaOXA-48, blaNDM) producing Klebsiella pneumoniae in a large tertiary care hospital, India

BACKGROUND

Extensive drug resistance in Klebsiella pneumoniae (K. pneumoniae) causing major outbreaks in large hospitals is an emerging challenge. We describe a near fatal outbreak of colistin resistant, carbapenem resistant K. pneumoniae (CRKp) producing metallo beta-lactamases (blaNDM) and blaOXA-48 in the neonatal intensive care unit (NICU) at the background of a larger outbreak involving multiple parts of the hospital and the challenges in its containment.

METHODS

Following identification of an outbreak due to colistin resistant CRKp between April to June 2017 in the NICU, a thorough surveillance of similar cases and the hospital environment was performed to trace the source. All the isolated K. pneumoniae were tested for susceptibility to standard antibiotics by disc diffusion and microbroth dilution methods. Molecular detection of extended spectrum beta lactamases (ESBLs) and carbapenemases (classes A, B, D) genes was done. Enterobacterial repetitive intergenic consensus (ERIC) PCR and multi-locus sequence typing (MLST) was done to determine the genetic relatedness of the isolates. Characteristics of different sequence types were statistically compared (Student's t-test).

RESULTS

A total of 45 K. pneumoniae isolates were studied from NICU (14 cases of neonatal sepsis), ICU (18 cases), other wards (7 cases) along with 6 isolates from hospital environment and human colonizers. The primary case was identified in the ICU. All the K. pneumoniae from NICU and 94.4% from the ICU were colistin resistant CRKp. Majority (59.37% and 56.25%) harbored blaSHV/blaCTXM and blaOXA-48 genes, respectively. Two distinct sequence types ST5235 and ST5313 were noted with colistin resistance, distribution within the NICU and mortality as significant attributes of ST5235 (p < 0.05). The outbreak was contained with strengthening of the infection control practices and unintended short duration closure of the hospital.

CONCLUSION

Large hospital outbreaks with considerable mortality can be caused by non-dominant clones of colistin resistant CRKp harboring blaOXA-48 and blaNDM carbapenemases in endemic regions. The exact global impact of these sequence types should be further studied to prevent future fatal outbreaks.

The Antimicrobial Resistance Characteristics of Imipenem-Non-Susceptible, Imipenemase-6-Producing Escherichia coli

Imipenemase-6 (IMP-6) type carbapenemase-producing Enterobacteriaceae is regarded as dangerous due to its unique lack of antimicrobial susceptibility. It is resistant to meropenem (MEPM) but susceptible to imipenem (IPM). In addition to carbapenemase, outer membrane porins and efflux pumps also play roles in carbapenem resistance by reducing the antimicrobial concentration inside cells. Extended-spectrum β-lactamase (ESBL) is transmitted with IMP-6 by the plasmid and broadens the spectrum of antimicrobial resistance. We collected 42 strains of IMP-6-producing Escherichia coli and conducted a molecular analysis of carbapenemase, ESBL, porin, efflux, and epidemiological characteristics using plasmid replicon typing. Among the 42 isolates, 21 strains were susceptible to IPM (50.0%) and 1 (2.4%) to MEPM. Seventeen strains (40.5%) co-produced CTX-M-2 type ESBL. We found that the relative expression of ompC and ompF significantly correlated with the MIC of IPM (p = 0.01 and p = 0.03, respectively). Sixty-eight% of CTX-M-2-non-producing strains had IncI1, which was significantly different from CTX-M-2-producing strains (p < 0.001). In conclusion, 50.0% of our IMP-6-producing strains were non-susceptible to IPM, which is different from the typical pattern and can be attributed to decreased porin expression. Further studies investigating other types of carbapenemase are warranted.

Characterization and Comparative Genomics Analysis of lncFII Multi-Resistance Plasmids Carrying bla CTX - M and Type1 Integrons From Escherichia coli

This research aimed to investigate the presence and transferability of the extended-spectrum β-lactamase resistance genes to identify the genetic context of multi-drug resistant (MDR) loci in two Escherichia coli plasmids from livestock and poultry breeding environment. MICs were determined by broth microdilution. A total of 137 E. coli resistant to extended-spectrum β-lactam antibiotics were screened for the presence of the ESBL genes by PCR. Only two E. coli out of 206 strains produced carbapenemases, including strain 11011 that produced enzyme A, and strain 417957 that produced enzyme B. The genes were bla_KPC and bla_NDM, respectively. The plasmids containing bla_CTX–M were conjugatable, and the plasmids containing carbapenem resistance gene were not conjugatable. Six extended-spectrum β-lactamase resistance genes were detected in this research, including bla_TEM, bla_CTX–M, bla_SHV, bla_OAX–1, bla_KPC, and bla_NDM, and the detection rates were 94.89% (130/137), 92.7% (127/137), 24.81% (34/137), 20.43% (28/137), 0.72% (1/137), and 0.72% (1/137), respectively. Two conjugative lncFII multi-resistance plasmids carrying bla_CTX–M, p11011-fosA and p417957-CTXM, were sequenced and analyzed. Both conjugative plasmids were larger than 100 kb and contained three accessory modules, including MDR region. The MDR region of the two plasmids contained many antibiotic resistance genes, including bla_CTX–M, mph (A), dfrA17, aadA5, sul1, etc. After transfer, both the transconjugants displayed elevated MICs of the respective antimicrobial agents. A large number of resistance genes clusters in specific regions may contribute to the MDR profile of the strains. The presence of mobile genetic elements at the boundaries can possibly facilitate transfer among Enterobacteriaceae through inter-replicon gene transfer. Our study provides beta-lactam resistance profile of bacteria, reveals the prevalence of β-lactamase resistance genes in livestock and poultry breeding environment in Zhejiang Province, and enriches the research on IncFII plasmids containing bla_CTX–M.

High occurrence of carbapenem-resistant Escherichia coli isolates from healthy rabbits (Oryctolagus cuniculus): first report of blaIMI and blaVIM type genes from livestock in Tunisia

We aimed to study the antibiotic susceptibility and possible occurrence of extended-spectrum beta-lactamases (ESBL)/carbapenemase-producing Escherichia coli isolates collected from rabbits in Tunisia. In all, 35 faecal samples from healthy rabbits were collected from one farm and E. coli were isolated from three media: antibiotic-free TBX agar, TBX+2 mg l^-1 cefotaxime and TBX+1 mg l^-1 imipenem. In total, 39 E. coli isolates were recovered; the majority showed resistance to at least one antibiotic and none was ESBL producer. Carbapenem resistance was detected in 16 isolates from either selective or un-selective media. Phenotypic methods used to detect carbapenemase production showed two positive isolates by Modified Hodge Test, six metallo-carbapenemase producers (Imipenem disc+EDTA) and all were temocillin resistant (possible OXA-48 carbapenemase). bla_VIM and bla_IMP type genes were detected in two and one isolates, respectively; one of them harboured both genes. Isolates contained common genes encoding resistance to sulphonamides (sul1, sul2), tetracycline (tetA, tetB, tetC) and fluoroquinolones (qnrS, aac(6')-Ib-cr). Class 1 and 2 integrons were detected in five and four isolates, respectively. These findings highlight the importance of rabbit production as reservoir of carbapenem-resistant E. coli and argument the first report of bla_VIM and bla_IMP genes in livestock in Tunisia.

Role of early foldscopy (microscopy) of endotracheal tube aspirates in deciding restricted empirical therapy in ventilated patients

PURPOSE

Prevention of healthcare-associated infections (HAI) like ventilator associated pneumonia (VAP) is particularly challenging especially in resource limited settings. Complex microbial interactions between patients and health care workers (HCWs) further complicate the situation, requiring a holistic approach for successful management. To bridge the gap between laboratory and intensive care unit (ICU) this study was conducted to find the role of hand-held microscope 'Foldscope' in restricting empirical therapy in intubated patients.

METHODS

A total of 75 endotracheal aspirates (ETA) were collected from intubated patients in the ICU with (group 1) and without (group 2) VAP. For group 2, those with less than 48 ​h ventilation and with endotracheal tube (ETT) in situ were considered. Presence of biomass was detected through foldscope and ETA samples were processed for quantitative gram staining (QGS), semi-quantitative and quantitative culture. Phenotypic and genotypic characterization of Acinetobacter baumannii, the commonest isolate, was done and findings were statistically analysed.

RESULTS

Biomass was present as seen through a foldscope in 45 cases (90%) in group 1 and 17 cases (68%) in group 2. In both the groups, A. baumannii was the most common isolate. Biomass production, significant QGS and culture was significantly more in group 1 (p ​< ​0.05). However, carbapenem resistant A. baumannii (CRAB) was comparably present in both the groups thus showing limited role of empirical carbapenem therapy.

CONCLUSIONS

Early assessment of biomass in mechanically ventilated patients could provide guidance for empirical antibiotic therapy. Foldscope proved to be an excellent tool for restricting empirical therapy and driving antimicrobial stewardship in low resource settings.

Adaptations of carbapenem resistant Acinetobacter baumannii (CRAB) in the hospital environment causing sustained outbreak

Introduction. Carbapenem resistance in Acinetobacter baumannii (A. baumannii) is an emerging global threat.Gap statement. The adaptation strategies of A. baumannii for this emergence as a nosocomial pathogen has been less studied.Aim. This prospective study analysed a sustained outbreak of carbapenem resistant Acinetobacter baumannii (CRAB) in the intensive care unit (ICU) with reference to antimicrobial resistance and virulence in the colonizing and pathogenic isolates under carbapenem stress.Results. The CRAB isolates from initial and sustained outbreak were found harbouring multiple carbapenemase genes. These genes included bla _OXA-23 ,bla _IMP, bla _VIM and bla _NDM. From NICU environment three phenotypically carbapenem susceptible isolates were found carrying bla _OXA-23, bla _IMP, bla _VIM genes. Prior imipenem therapy was one of the risk factors (P=0.0016). The outbreak was polyclonal. Under imipenem stress, outbreak isolates showed no loss of carbapenemase genes against stress free conditions (23.7±1.33 days). Biofilm formation increased with imipenem concentration, with outbreak isolates producing highest biomass. While the pathogens showed a slow growth rate on imipenem exposure, the colonisers grew rapidly (P <0.0001).Methods. Sustained outbreak of CRAB was identified in the ICU (July 2015 to December 2017). Risk factors for acquisition of CRAB was studied. A. baumannii isolates were also collected from the environments of ICU and neonatal ICU (NICU) and blood cultures of septic neonates. Isolates were characterized based on antimicrobial susceptibility, genetic profile, integrons carriage and clonality. Biofilm formation and growth kinetics were studied under varying carbapenem stress.Conclusion. Intense carbapenem exposure in the ICU facilitates persistence of CRAB by several adaptations causing sustained outbreaks.

Drug resistance phenotypes and genotypes in Mexico in representative gram-negative species: Results from the infivar network

Aim

This report presents phenotypic and genetic data on the prevalence and characteristics of extended-spectrum β-lactamases (ESBLs) and representative carbapenemases-producing Gram-negative species in Mexico.

Material and methods

A total of 52 centers participated, 43 hospital-based laboratories and 9 external laboratories. The distribution of antimicrobial resistance data for Escherichia coli, Klebsiella pneumoniae, Enterobacter cloacae complex, Acinetobacter baumannii complex, and Pseudomonas aeruginosa in selected clinical specimens from January 1 to March 31, 2020 was analyzed using the WHONET 5.6 platform. The following clinical isolates recovered from selected specimens were included: carbapenem-resistant Enterobacteriaceae, ESBL or carbapenem-resistant E. coli, and K. pneumoniae, carbapenem-resistant A. baumannii complex, and P. aeruginosa. Strains were genotyped to detect ESBL and/or carbapenemase-encoding genes.

Results

Among blood isolates, A. baumannii complex showed more than 68% resistance for all antibiotics tested, and among Enterobacteria, E. cloacae complex showed higher resistance to carbapenems. A. baumannii complex showed a higher resistance pattern for respiratory specimens, with only amikacin having a resistance lower than 70%. Among K. pneumoniae isolates, bla_TEM, bla_SHV, and bla_CTX were detected in 68.79%, 72.3%, and 91.9% of isolates, respectively. Among E. coli isolates, bla_TEM, bla_SHV, and bla_CTX were detected in 20.8%, 4.53%, and 85.7% isolates, respectively. For both species, the most frequent genotype was bla_CTX-M-15. Among Enterobacteriaceae, the most frequently detected carbapenemase-encoding gene was bla_NDM-1 (81.5%), followed by bla_OXA-232 (14.8%) and bla_oxa-181(7.4%), in A. baumannii was bla_OXA-24 (76%) and in P. aeruginosa, was bla_IMP (25.3%), followed by bla_GES and bla_VIM (13.1% each).

Conclusion

Our study reports that NDM-1 is the most frequent carbapenemase-encoding gene in Mexico in Enterobacteriaceae with the circulation of the oxacillinase genes 181 and 232. KPC, in contrast to other countries in Latin America and the USA, is a rare occurrence. Additionally, a high circulation of ESBL bla_CTX-M-15 exists in both E. coli and K. pneumoniae.

Extensively Drug-Resistant Hypervirulent Klebsiella pneumoniae From a Series of Neonatal Sepsis in a Tertiary Care Hospital, India

The recent emergence of multidrug-resistant (MDR) Klebsiella pneumoniae with hypervirulent traits causing severe infections and considerable mortality is a global cause for concern. The challenges posed by these hypermucoviscous strains of K. pneumoniae with regard to their optimal treatment, management, and control policies are yet to be answered. We studied a series of extensively drug-resistant (XDR) and hypervirulent K. pneumoniae ST5235 isolates with resistance to carbapenems and polymyxins causing neonatal sepsis in a tertiary care hospital in India. A total of 9 K. pneumoniae isolates from 9 cases of neonatal sepsis were studied with respect to their clinical relevance, antimicrobial susceptibility profile, presence of extended spectrum β lactamase (ESBL) production, and responsible genes, carbapenemases (classes A, B, and D), and aminoglycoside-resistant genes. Hypervirulence genes encoding hypermucoid nature, iron uptake, and siderophores were detected by multiplex PCR. The plasmid profile was studied by replicon typing. Isolates were typed by multilocus sequence typing (MLST) and enterobacterial repetitive intergenic consensus (ERIC) PCR to study the sequence types (STs) and clonal relation, respectively. The neonates in the studied cases had history of pre-maturity or low birth weight with maternal complications. All the cases were empirically treated with piperacillin-tazobactam and amikacin followed by imipenem/meropenem and vancomycin and polymyxin B as a last resort. However, all the neonates finally succumbed to the condition (100%). The studied isolates were XDR including resistance to polymyxins harboring multiple ESBL genes and carbapenemase genes (bla _NDM and bla _OXA-48). Hypervirulence genes were present in various combinations with rmpA/A2 genes present in all the isolates. IncFI plasmids were detected in these isolates. All belonged to ST5235. In ERIC PCR, 6 different clusters were seen. The study highlighted the emergence and burden of XDR hypervirulent isolates of K. pneumoniae causing neonatal sepsis in a tertiary care hospital.

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.

Antibiogram and Genetic Characterization of Carbapenem-Resistant Gram-Negative Pathogens Incriminated in Healthcare-Associated Infections

Purpose

Carbapenems are considered the most efficient antibiotic used in the treatment of nosocomial infections. Carbapenem-resistant Gram-negative rods are becoming a serious hazard in hospitals threatening public health. The aim of the current study was to investigate the prevalence of carbapenem-resistant Gram-negative pathogens incriminated in healthcare-associated infections, along with antimicrobial resistance profiles, carbapenemase and metallo-β-lactamase production, and their molecular characterization.

Methods

A total of 186 clinical specimens were collected from 133 patients at various hospitals in Cairo, Egypt. The obtained specimens were subjected to bacteriological examination, antimicrobial susceptibility testing, detection of carbapenemase production using the modified Hodge test (MHT), the metallo-β-lactamase production using the EDTA combined disc test (CDT), and PCR-based detection of the bla _KPC and bla _GES resistance genes. The identification of the highly resistant retrieved isolates was then confirmed by 16S rRNA gene sequencing.

Results

The most common isolated Gram-negative species was Klebsiella pneumoniae (40.9%), followed by Acinetobacter baumannii (18.8%), Pseudomonas aeruginosa (17.3%), Escherichia coli (15.4%), Enterobacter aerogenes (5.3%), and Proteus mirabilis (2.4%). The prevalence of carbapenem-resistant isolates was 36.1% (n=75). However, 86.5% of the recovered clinical isolates were susceptible to colistin. The MHT revealed that 33.6% (n=70) of the tested strains were positive for carbapenemase production, while the CDT showed that 33.17% (n=69) of the examined strains were metallo-β-lactamase producers. The PCR revealed that 98.6% (74/75) of the tested strains possessed the bla _KPC gene; moreover, 97.3% (73/75) of the examined strains harbored the bla _GES gene.

Conclusion

This study displayed the emergence of carbapenem-resistant Gram-negative pathogens incriminated in healthcare-associated infections. The accurate identification of carbapenem-resistant bacterial pathogens is pivotal for the treatment of patients, in addition to propelling appropriate contamination control measures to restrain the fast spread of such pathogens. Colistin showed a potent in vitro antimicrobial activity against the carbapenem-resistant strains.

Molecular Relatedness of Salmonella enterica Typhimurium Isolates from Feces and an Infected Surgical Wound

Purpose

Salmonella enterica serovar Typhimurium infection is common in foodborne diseases, but its isolation from surgical incisions is rare. Our aim in this study was to trace the transmission source of a surgical incision infected with S. Typhimurium in a Yunnan Province hospital patient and elucidate the underlying molecular mechanisms of antibiotic resistance.

Methods

Primers were designed to amplify the drug-resistance genes using polymerase chain reaction (PCR). Susceptibility to antibiotics was determined using Etest strips. Macrorestriction profiles were analyzed using pulsed-field gel electrophoresis (PFGE) and XbaI. The two isolates were characterized using agglutination tests and multilocus sequence typing (MLST).

Results

MLST analysis revealed that S. Typhimurium isolates SM043 and SM080 belonged to the same genotype, ST34, and PFGE revealed that SM043 and SM080 had high similarity. The isolates were both resistant to third-generation cephalosporins. SM043 harbored the antibiotic resistance genes blaCTX-M-15, blaTEM-1, qnrS-1, qnrB, and acc-3, whereas blaCTX-M-15, blaTEM-1, blaCMY-2, qnrS-1, and acc-3 were detected in SM080.

Conclusion

The surgical incision infection by S. Typhimurium may have been hospital-acquired. Thus, it is critical to strengthen hospital sanitation by addressing hand hygiene and sterilization of the operational environment to avoid outbreaks of nosocomial Salmonella infections.

Comparative Evaluation of Five Assays for Detection of Carbapenemases with a Proposed Scheme for Their Precise Application

The escalating problem of the dissemination of carbapenemase-producing bacteria (CPB) has gained worldwide attention. The prompt diagnosis of CPB and precise identification of carbapenemases are imperative to enable specific antibiotic therapy and control the spread of these bacteria. The present study was designed to assess the performance of five important assays for the detection of carbapenemases. The modified carbapenem inactivation method (mCIM), CARBA-5, GeneXpert Carba-R, BD MAX Check-Points CPO, and GeneFields CPE assays were evaluated with an international collection of 159 bacterial isolates, including 93 CPB and 66 non-CPB isolates. The overall accuracy/sensitivity/specificity for carbapenemase detection were 100% (95% CI, 97.7%-100%)/100% (95% CI, 96.1%-100%)/100% (95% CI, 94.6%-100%) for mCIM, 98.7% (95% CI, 95.5%-99.9%)/97.9% (95% CI, 92.5%-99.7%)/100% (95% CI, 94.6%-100%) for CARBA-5, 96.9% (95% CI, 92.8%-99%)/95.7% (95% CI, 89.4%-98.8%)/98.5% (95% CI, 91.8%-99.9%) for GeneXpert Carba-R, 94.3% (95% CI, 89.5%-97.4%)/90.3% (95% CI, 82.4%-95.5%)/100% (95% CI, 94.6%-100%) for BD MAX Check-Points CPO, and 86.2% (95% CI, 79.8%-91.1%)/77.4% (95% CI, 67.6%-85.5%)/98.5% (95% CI, 91.8%-100%) for GeneFields CPE. Interestingly, mCIM and CARBA-5 assays showed 100% accuracy/sensitivity/specificity for detection of the target genes. Furthermore, all the other assays showed comparable high accuracy (96.9% to 100%), sensitivity (100%), and specificity (96.4% to 100%) for the detection of the target genes. On the basis of these results, a new scheme was proposed for their efficient application. These results confirmed the high sensitivity of the evaluated assays, and the proposed scheme is reliable and improves the overall sensitivity and specificity of the assays.

Antimicrobial Resistance of Serial Isolates of Acinetobacter baumannii Colonizing the Rectum of Adult Intensive Care Unit Patients in a Teaching Hospital in Kuwait

Objectives: Outbreak and endemic isolates of Acinetobacter baumannii are known to be polyclonal. In an ongoing study, we hypothesized that the patient gut was the source of the polyclonality where genetic exchanges take place. To test the hypothesis, we collected 270 serial rectal isolates from 32 adult intensive care unit patients over 16 months and investigated their drug resistance profiles. Methods: Antimicrobial susceptibility was determined according to recommended methods. The bla_IMP, bla_VIM, bla_SIM, bla_OXA-23, bla_OXA-24/40, bla_OXA-51, bla_OXA-48, bla_KPC, bla_GES, bla_NDM and bla_OXA-58 were sought by PCR. A subset of 42 isolates were studied for plasmid-mediated resistance. Results: Most of the 270 isolates were multidrug resistant (MDR; with resistances to meropenem of 85.18% and imipenem of 87.04%), but susceptible to colistin and trimethoprim/sulfamethoxazole. There was no correlation between the pattern of resistance and antibiotics administered to treat infections. There was no consistent pattern of resistance or content of carbapenemase genes in serial rectal isolates suggesting polyclonality of the isolates. Genes mediating production of OXA-23, OXA-24/40, IMP, and GES enzymes were carried on plasmids and they mediated resistance to all carbapenems in conjugation studies. Conclusion: A. baumannii colonizing the rectum were polyclonal, MDR, and carbapenem resistance genes were found on plasmids and some plasmids were transferable.

Comparison between IMP carbapenemase-producing Enterobacteriaceae and non-carbapenemase-producing Enterobacteriaceae: a multicentre prospective study of the clinical and molecular epidemiology of carbapenem-resistant Enterobacteriaceae

BACKGROUND

Carbapenem-resistant Enterobacteriaceae (CRE) are classified as carbapenemase-producing Enterobacteriaceae (CPE) and non-CPE; the majority of CPE in Japan produce IMP carbapenemase.

OBJECTIVES

We evaluated the clinico-epidemiological and microbiological information and effects of IMP-type carbapenemase production in CRE.

METHODS

Patients with isolations of CRE (MICs of meropenem ≥2 mg/L, imipenem ≥2 mg/L or cefmetazole ≥64 mg/L) from August 2016 to March 2018 were included. Microbiological analyses and WGS were conducted and clinical parameters were compared between groups. Independent predictors for the isolation of CPE from patients were identified by logistic regression. For comparing clinical outcomes, a stabilized inverse probability weighting method was used to conduct propensity score-adjusted analysis.

RESULTS

Ninety isolates (27 CPE and 63 non-CPE) were collected from 88 patients (25 CPE and 63 non-CPE). All CPE tested positive for IMP carbapenemase. Antibiotic resistance (and the presence of resistance genes) was more frequent in the CPE group than in the non-CPE group. Independent predictors for CPE isolation were residence in a nursing home or long-term care facility, longer prior length of hospital stay (LOS), use of a urinary catheter and/or nasogastric tube, dependent functional status and exposure to carbapenem. Although in-hospital and 30 day mortality rates were similar between the two groups, LOS after CRE isolation was longer in the CPE group.

CONCLUSIONS

IMP-CPE were associated with prolonged hospital stays and had different clinical and microbiological characteristics compared with non-CPE. Tailored approaches are necessary for the investigational and public health reporting, and clinical and infection prevention perspectives for IMP-CPE and non-CPE.

Environmental Presence and Genetic Characteristics of Carbapenemase-Producing Enterobacteriaceae from Hospital Sewage and River Water in the Philippines

Carbapenemase-producing Enterobacteriaceae (CPE) cause severe health care-associated infections, and their increasing prevalence is a serious concern. Recently, natural ecosystems have been recognized as important reservoirs of antibiotic resistance genes. We investigated the prevalence and genetic characteristics of CPE isolated from the environment (hospital sewage and river water) in the Philippines and found several CPE, including Escherichia coli and other species, with different carbapenemases. The most prevalent carbapenemase gene type was NDM, which is endemic in clinical settings. This study revealed that isolates belonging to carbapenemase-producing E. coli CC10 and K. pneumoniae sequence type 147 (ST147), which are often detected in clinical settings, were dominant in the natural environment. Our work here provides a report on the presence and characteristics of CPE in the environment in the Philippines and demonstrates that both hospital sewage and river water are contaminated by CPE strains belonging to clinically important clonal groups.

This study aimed to evaluate the prevalence and genetic characteristics of carbapenemase-producing Enterobacteriaceae (CPE) in hospital sewage and river water in the Philippines, which has a typical tropical maritime climate. We collected 83 water samples from 7 hospital sewage and 10 river water sites. CPE were identified using CHROMagar mSuperCARBA, and Gram-negative strains were identified using matrix-assisted laser desorption ionization–time of flight mass spectrometry (MALDI-TOF MS) or 16S rRNA gene sequencing. Resistance genes in Enterobacteriaceae strains were identified using PCR and DNA sequencing, and transferability of carbapenemase genes from the CPE was investigated with conjugation experiments. Genotyping was performed using multilocus sequence typing (MLST) for Escherichia coli and Klebsiella pneumoniae. Out of 124 Enterobacteriaceae isolates, we identified 51 strains as CPE and divided these into 7 species, 11 E. coli, 14 Klebsiella spp., 15 Enterobacter spp., and 11 others, including 4 additional species. Conjugation experiments via broth mating and using E. coli J53 revealed that 24 isolates can transfer carbapenemase-encoding plasmids. MLST analysis showed that 6 of 11 E. coli isolates belonged to clonal complex 10 (CC10). Of 11 K. pneumoniae strains, 9 unique sequence types (STs) were identified, including ST147. Five types of carbapenemase genes were identified, with the most prevalent being NDM (n = 39), which is epidemic in clinical settings in the Philippines. E. coli CC10 and K. pneumoniae ST147, which are often detected in clinical settings, were the dominant strains. In summary, our results indicate that hospital sewage and river water are contaminated by CPE strains belonging to clinically important clonal groups.

IMPORTANCE Carbapenemase-producing Enterobacteriaceae (CPE) cause severe health care-associated infections, and their increasing prevalence is a serious concern. Recently, natural ecosystems have been recognized as important reservoirs of antibiotic resistance genes. We investigated the prevalence and genetic characteristics of CPE isolated from the environment (hospital sewage and river water) in the Philippines and found several CPE, including Escherichia coli and other species, with different carbapenemases. The most prevalent carbapenemase gene type was NDM, which is endemic in clinical settings. This study revealed that isolates belonging to carbapenemase-producing E. coli CC10 and K. pneumoniae sequence type 147 (ST147), which are often detected in clinical settings, were dominant in the natural environment. Our work here provides a report on the presence and characteristics of CPE in the environment in the Philippines and demonstrates that both hospital sewage and river water are contaminated by CPE strains belonging to clinically important clonal groups.

Phenotypic and genotypic characterization of carbapenem-resistant Acinetobacter baumannii isolates from Egypt

Background

Antibiotic use is largely under-regulated in Egypt leading to the emergence of resistant isolates. Carbapenems are last resort agents to treat Acinetobacter baumannii infections resistant to other classes of antibiotics. However, carbapenem-resistant isolates are emerging at an alarming rate. This study aimed at phenotypically and molecularly characterizing seventy four carbapenem-unsusceptible A. baumannii isolates from Egypt to detect the different enzymes responsible for carbapenem resistance.

Methods

Carbapenemase production was assessed by a number of phenotypic methods: modified Hodge test (MHT), carbapenem inactivation method (CIM), combined disc test (CDT), CarbAcineto NP test and boronic acid disc test. Polymerase chain reaction (PCR) was used to screen the isolates for the presence of some genes responsible for resistance to carbapenems, as well as some insertion sequences.

Results

PCR amplification of class D carbapenemases revealed the prevalence of bla_OXA-51 and bla_OXA-23 in 100% of the isolates and of bla_OXA-58 in only one isolate (1.4%). bla_VIM and bla_NDM-1 belonging to class B metallo-β-lactamases were present in 100 and 12.1% of the isolates, respectively. The prevalence of ISAba1, ISAba2 and ISAba3 was 100, 2.7 and 4.1%, respectively. None of the tested isolates carried bla_OXA-40, bla_IMP, bla_SIM, bla_SPM, bla_GIM or the class A bla_KPC. Taking PCR as the gold standard method for the detection of different carbapenemases, the sensitivities of the MHT, CIM, CDT, CarbAcineto NP test and boronic acid disc/imipenem or meropenem test for this particular collection of isolates were 78.4, 68.9, 79.7, 95.9, and 56.8% or 70.3%, respectively.

Conclusions

The widespread detection of carbapenem-resistant A. baumannii (CR-AB) has become a real threat to the efficacy of treatment regimens. Among the studied cohort of CR-AB clinical isolates, bla_OXA-51, bla_OXA-23 and bla_VIM were the most prevalent, followed by bla_NDM-1 and bla_OXA-58. The genotypic detection of carbapenemases among CR-AB clinical isolates using PCR was most conclusive, followed closely by the phenotypic testing using CarbAcineto NP test.

Emergence and transmission of New Delhi metallo-beta-lactamase-5-producing Escherichia coli Sequence Type 361 in a Tertiary Hospital in South Korea

Background

The emergence of carbapenem‐resistant Escherichia coli (E coli) is a serious global health threat, but little is known about carbapenemase‐producing E coli in Daejeon, South Korea. The aim of this study was to investigate characteristics of thirteen carbapenem‐resistant E coli isolates in a tertiary hospital.

Methods

Thirteen non‐duplicate carbapenem‐resistant E coli strains were collected from October 2017 to January 2018. Antimicrobial susceptibility was determined with the E test or disk diffusion method. The carbapenem minimum inhibitory concentrations (MICs) were determined by the agar dilution method. The colistin and tigecycline MICs were determined by broth microdilution. The resistance genes, including carbapenemase genes, were evaluated by polymerase chain reaction, and DNA sequencing was performed to characterize the genes. Pulsed‐field gel electrophoresis and multilocus sequence typing (MLST) were performed to evaluate the clonal relatedness of isolates. The clinical data of patients were retrospectively reviewed.

Results

All the E coli isolates harbored bla_NDM‐5 gene and were resistant to most of the antimicrobial agents, such as carbapenem, cephalosporins, ciprofloxacin, and chloramphenicol, excluding amikacin and colistin. Other resistant genes, such as bla_TEM‐1, bla_CTX‐M‐15, bla_CMY‐2, aac(6')‐Ib‐cr, and qepA, were detected. The E coli isolates harboring bla_NDM‐5 belonged to ST361 (n = 11), ST12 (n = 1), ST410 (n = 1), and PFGE types A (n = 11), B (n = 1), and C (n = 1).

Conclusions

This study reports on an outbreak of a predominant epidemic clone, the NDM‐5 producing, multidrug‐resistant E coli ST361 isolate. These findings suggest that we should pay attention to infection control measures to limit the spread of NDM‐5‐producing pathogens.

Molecular Characterization of Chryseobacterium indologenes with Multidrug Resistance in the Brazilian Amazon Region

Chryseobacterium indologenes is an emerging nosocomial pathogen that produces IND-type chromosomal metallo-beta-lactamase. The phenotype and molecular aspects of two multidrug resistant C. indologenes strains and the analysis of the tertiary structure of the IND enzyme were studied. Identification of species and susceptibility tests were performed using the Vitek-2 compact. Chromosomal and plasmid DNA were extracted using PureLink™ Genomic DNA Mini Kit and PureLink Quick Plasmid Miniprep Kit, and the sequencing was performed using ABI 3130 genetic analyzer. Two strains were isolated and are registered as P-23 and P-113. Of the two, P-113 was sensitive to ciprofloxacin and cefepime only, whereas the P-23 showed reduced sensitivity to ceftazidime, ciprofloxacin, and tigecycline. The genetic analysis of both isolates identified the presence of the bla_IND-like gene, with similarity to IND-3 and IND-8 alleles. The IND-3 identified in the P-133 sample presented a single mutation at position T355G, which corresponds to a nonsynonymous substitution of the amino acid at position 119 (Ser→Ala). The phylogenetic analysis of INDs showed lineages that are circulating in Asian and European countries. These results emphasize the need for effective preventive actions to avoid the dissemination of this type of pathogen in the hospital environment.

High Prevalence and Endemicity of Multidrug Resistant Acinetobacter spp. in Intensive Care Unit of a Tertiary Care Hospital, Varanasi, India

The increasing emergence of Acinetobacter spp. with healthcare associated infections (HCAI) in intensive care units (ICU) is alarming. This study was a laboratory-based audit to determine the prevalence of Acinetobacter spp. associated with HCAI in the adult ICU of a tertiary care hospital in Varanasi, north India, with special reference to antimicrobial resistance and resistance determinants over a period of 5 years. A total of 993 cases of HCAI were analyzed. Isolates were characterized as multidrug resistance and extended drug resistance (MDR/XDR) based on antimicrobial susceptibility records. Few (100) randomly selected isolates of Acinetobacter baumannii (A. baumannii) were tested for imipenem, meropenem, and polymyxin B susceptibility by minimum inhibitory concentration (MIC) and for the presence of class A and B carbapenemases by multiplex PCR. Active surveillance of ICU environment was also performed. High prevalence of Acinetobacter related hospital acquired pneumonia (HAP) with significant resistance to imipenem (p<0.05) and 88.02% MDR and 61.97% XDR was detected along with persistence in the ICU environment. The isolates harbored bla_IMP (89%), bla_VIM (51%), bla_NDM-1 (34%), and bla_OXA-23-like (93%) genes. Specific interventional measures should be adopted to control these imipenem resistant Acinetobacter spp. which have attained the level of endemicity in our ICU setup.

Clonal replacement of epidemic KPC-producing Klebsiella pneumoniae in a hospital in China

BACKGROUND

Klebsiella pneumoniae is a frequent nosocomial pathogen causing difficult-to-treat infections worldwide. The prevalence of Klebsiella pneumoniae carbapenemase (KPC)-producing Klebsiella pneumoniae (KPC-KP) is increasing in China. The aim of this study was to investigate the molecular epidemiology of KPC-KP in a nosocomial outbreak.

METHODS

Fifty-four KPC-KP isolates were consecutively collected between November 2013 and August 2014 during a KPC-KP outbreak in a tertiary care hospital in Beijing, China. Antimicrobial susceptibility was determined by agar dilution. Carbapenemase, extended-spectrum β-lactamase, 16S rRNA methylase, AmpC β-lactamase, and plasmid-mediated quinolone resistance determinants were detected by PCR amplification. The genetic relatedness of isolates was analyzed by pulsed-field gel electrophoresis and multi-locus sequence typing.

RESULTS

All isolates belonged to ST11 except one isolate which was identified as a new sequence type (ST2040). PFGE profile of genomic DNA revealed seven clusters, of which cluster A and C dominated the KPC-KP outbreak and cluster A was replaced by cluster C during the outbreak. PFGE of genomic DNA, S1-PFGE of plasmids, replicon typing, and drug resistant characteristics showed that clonal spread occurred during the outbreak. When compared with isolates within cluster A, all isolates in cluster C harbored rmtB and showed higher level of resistance to cefepime, amikacin, tobramycin, and tigecycline.

CONCLUSION

We reported a nosocomial outbreak of KPC-KP with clonal replacement and a new sequence type (ST2040) of KP. High degree of awareness and surveillance of KPC-KP should be given to avoid potential outbreaks, especially in ICU wards.

Disk Carbapenemase Test for the Rapid Detection of KPC-, NDM-, and Other Metallo-β-Lactamase-Producing Gram-Negative Bacilli

Background

Rapid detection of carbapenemase-producing gram-negative bacilli (GNB) is required for optimal treatment of infected patients. We developed and assessed a new disk carbapenemase test (DCT).

Methods

Paper disks containing 0.3 mg of imipenem and bromothymol blue indicator were developed, and the performance of the DCT were evaluated by using 742 strains of GNB with or without carbapenemases.

Results

The paper disks were simple to prepare, and the dried disks were stable at -20℃ and at 4℃. The DCT detected 212 of 215 strains (98.6% sensitivity with 95% confidence interval [CI] 96.0-99.5%) of GNB with known class A (KPC and Sme) and class B (NDM, IMP, VIM, and SIM) carbapenemases within 60 min, but failed to detect GES-5 carbapenemase. The DCT also detected all two Escherichia coli isolates with OXA-48, but failed to detect GNB with OXA-232, and other OXA carbapenemases. The DCT showed 100% specificity (95% CI, 99.2-100%) in the test of 448 imipenem-nonsusceptible, but carbapenemase genes not tested, clinical isolates of GNB.

Conclusions

The DCT is simple and can be easily performed, even in small laboratories, for the rapid detection of GNB with KPC, NDM and the majority of IMP, VIM, and SIM carbapenemases.

Current methods for the identification of carbapenemases

Detection of carbapenemases in clinical microbiology labs is a challenging issue. Comparison of the results of susceptibility testing with the breakpoint values of carbapenems is the first step in the screening of carbapenemase producers. To date, screening of carbapenemase-producing (CP) bacteria has been mostly performed by a selective medium. Although these media are practical for the detection of most CP isolates, the inoculated plates have to be incubated overnight. Subsequently, we need the confirmation of the carbapenemase producers present in the culture medium by additional testing [e.g. inhibition studies with liquid or solid media, modified Hodge test (MHT), or gradient strips], which can take up to another 48 hours. Despite the lack of discrimination between the three different classes of carbapenemases (KPC, MBL and OXA) and difficulties in the interpretation of the results, the MHT is usually deemed as the phenotypic reference method for the confirmation of carbapenemase production. Molecular techniques, such as real-time polymerase chain reaction (PCR) assays, in contrast to phenotypic methods that are very time consuming, are faster and allow for the quick identification of carbapenemase genes. These techniques can detect and characterize carbapenemases, including NDM- and KPC-mediated resistance, which is critical for epidemiological investigations. The aim of this review is to gather a summary of the available methods for carbapenemase detection and describe the strengths and weaknesses of each method.

Phenotypic detection and molecular characterization of beta-lactamase genes among Citrobacter species in a tertiary care hospital

Objective:

To examine the distribution, emergence, and spread of genes encoding beta-lactamase resistance in Citrobacter species isolated from hospitalized patients in a tertiary care hospital.

Methods:

A prospective study was conducted in a 1000-bed tertiary care center in Pune, India from October 2010 to October 2013. A total of 221 Citrobacter spp. isolates were recovered from clinical specimens from different patients (one isolate per patient) admitted to the surgical ward, medical ward and medical and surgical Intensive Care Units. Polymerase chain reaction (PCR) assays and sequencing were used to determine the presence of beta-lactamase encoding genes. Conjugation experiments were performed to determine their transferability. Isolate relatedness were determined by repetitive element based-PCR, enterobacterial repetitive intergenic consensus-PCR and randomly amplified polymorphic DNA.

Results:

Among 221 tested isolates of Citrobacter spp. recovered from various clinical specimens, 179 (80.9%) isolates showed minimum inhibitory concentration (MIC) >4 μg/ml against meropenem and imipenem. One hundred and forty-five isolates with increased MICs value against carbapenems were further processed for molecular characterization of beta-lactamase genes. Susceptibility profiling of the isolates indicated that 100% retained susceptibility to colistin. Conjugation experiments indicated that bla_NDM-1 was transferable via a plasmid.

Conclusion:

The ease of NDM-1 plasmid transmissibility may help their dissemination among the Citrobacter species as well as to others in Enterobacteriaceae. Early detection, antimicrobial stewardship and adequate infection control measures will help in limiting the spread of these organisms.

Molecular epidemiology of Acinetobacter baumannii in different hospitals in Tripoli, Lebanon using bla(OXA-51-like) sequence based typing

Background

A. baumannii has emerged as an important nosocomial pathogen with an outstanding ability to acquire multidrug resistant mechanisms. In this study, we investigate the molecular epidemiology and carbapenem resistance mechanisms of A. baumannii in Tripoli, Northern Lebanon.

Methods

One hundred sixteen non-duplicate isolates isolated between 2011 and 2013 in different hospitals in Tripoli, Lebanon from Lebanese patients and wounded Syrian patients during Syrian war were studied. Antibiotic susceptibility testing was determined by agar disc diffusion and Etest. Carbapenemase-encoding genes were investigated by PCR. All isolates were typed by bla_OXA-51-like sequence based typing (SBT) and 57 isolates were also analysed by MLST using Pasteur’s scheme followed by eBURST analysis.

Results

Of the 116 isolates, 70 (60 %) showed a carbapenem resistance phenotype. The bla_OXA-23 with an upstream insertion of ISAba1 was the major carbapenem resistance mechanism and detected in 65 isolates. Five isolates, including four from wounded Syrian patients and one from a Lebanese patient, were positive for bla_NDM-1. bla_OXA-51-like SBT revealed the presence of 14 variants, where bla_OXA-66 was the most common and present in 73 isolates, followed by bla_OXA-69 in 20 isolates. MLST analysis identified 17 sequence types (ST) and showed a concordance with bla_OXA-51-like SBT. Each clonal complex (CC) had a specific bla_OXA-51-like sequence such as CC2, which harboured bla_OXA-66 variant, and CC1 harbouring bla_OXA-69 variant. NDM-1 producing isolates belonged to ST85 (4 Syrian isolates) and ST25 (1 Lebanese isolate).

Conclusions

Our results showed a successful predominance of international clone 2 with a widespread occurrence of OXA-23 carbapenemase in Lebanese hospitals. These findings emphasise the urgent need of effective measures to control the spread of A. baumannii in this country.

Carbapenem Resistance among Enterobacter Species in a Tertiary Care Hospital in Central India

Objective. To detect genes encoding carbapenem resistance among Enterobacter species in a tertiary care hospital in central India. Methods. Bacterial identification of Enterobacter spp. isolates from various clinical specimens in patients admitted to intensive care units was performed by routine conventional microbial culture and biochemical tests using standard recommended techniques. Antibiotic sensitivity test was performed by standard Kirby Bauer disc diffusion technique. PCR amplification and automated sequencing was carried out. Transfer of resistance genes was determined by conjugation. Results. A total of 70/130 (53.84%) isolates of Enterobacter spp. were found to exhibit reduced susceptibility to imipenem (diameter of zones of inhibition ≤13 mm) by disc diffusion method. Among 70 isolates tested, 48 (68.57%) isolates showed MIC values for imipenem and meropenem ranging from 32 to 64 mg/L as per CLSI breakpoints. All of these 70 isolates were found susceptible to colistin in vitro as per MIC breakpoints (<0.5 mg/L). PCR carried out on these 48 MBL (IP/IPI) E-test positive isolates (12 Enterobacter aerogenes, 31 Enterobacter cloacae, and 05 Enterobacter cloacae complex) was validated by sequencing for beta-lactam resistance genes and result was interpreted accordingly. Conclusion. The study showed MBL production as an important mechanism in carbapenem resistance in Enterobacter spp. and interspecies transfer of these genes through plasmids suggesting early detection by molecular methods.