Molecular and epidemiological analysis of IMP-1 metallo-β-lactamase-producing Klebsiella pneumoniae in a tertiary care hospital in Japan

Clinical and genomic characteristics of IMP-producing Enterobacter cloacae complex and Klebsiella pneumoniae

Carbapenemase-producing Enterobacterales (CPEs) are one of the top priority antimicrobial-resistant pathogens. Among CPEs, those producing acquired metallo-β-lactamases (MBLs) are considered particularly problematic as few agents are active against them. Imipenemase (IMP) is the most frequently encountered acquired MBL in Japan, but comprehensive assessment of clinical and microbiological features of IMP-producing Enterobacterales infection remains scarce. Here, we retrospectively evaluated 62 patients who were hospitalized at a university hospital in Japan and had IMP-producing Enterobacterales from a clinical culture. The isolates were either Enterobacter cloacae complex or Klebsiella pneumoniae, and most of them were isolated from sputum. The majority of K. pneumoniae, but not E. cloacae complex isolates, were susceptible to aztreonam. Sequence type (ST) 78 and ST517 were prevalent for E. cloacae complex and K. pneumoniae, respectively, and all isolates carried blaIMP-1. Twenty-four of the patients were deemed infected with IMP-producing Enterobacterales. Among the infected patients, therapy varied and largely consisted of conventional β-lactam agents, fluoroquinolones, or combinations. Three (13%), five (21%), and nine (38%) of them died by days 14, 30, and 90, respectively. While incremental mortality over 90 days was observed in association with underlying comorbidities, active conventional treatment options were available for most patients with IMP-producing Enterobacterales infections, distinguishing them from more multidrug-resistant CPE infections associated with globally common MBLs, such as New Delhi metallo-β-lactamase (NDM) and Verona integron-encoded metallo-β-lactamase (VIM).

Diagnostic Performance of BD Phoenix CPO Detect Panels for Detection and Classification of Carbapenemase-Producing Gram-Negative Bacteria

BD Phoenix CPO Detect panels can identify and classify carbapenemase-producing organisms (CPOs) simultaneously with antimicrobial susceptibility testing (AST) for Gram-negative bacteria. Detection and classification of carbapenemase producers were performed using the BD Phoenix CPO Detect panels NMIC/ID-441 for Enterobacterales, NMIC/ID-442 for nonfermenting bacteria, and NMIC-440 for both. The results were compared with those obtained using comparator methods. A total of 133 strains (32 Klebsiella pneumoniae, 37 Enterobacter cloacae complex, 33 Pseudomonas aeruginosa, and 31 Acinetobacter baumannii complex strains), including 60 carbapenemase producers (54 imipenemases [IMPs] and 6 OXA type), were analyzed. Using panels NMIC-440 and NMIC/ID-441 or NMIC/ID-442, all 54 IMP producers were accurately identified as CPOs (positive percent agreement [PPA], 100.0%; 54/54). Among the 54 IMP producers identified as CPOs using panels NMIC-440 and NMIC/ID-441, 12 and 14 Enterobacterales were not resistant to carbapenem, respectively. Among all 54 IMP producers, 48 (88.9%; 48/54) were correctly classified as Ambler class B using panel NMIC-440. Using panels NMIC-440 and NMIC/ID-442, all four OXA-23-like carbapenemase-producing A. baumannii complex strains (100.0%, 4/4) were correctly identified as CPOs, and three (75.0%, 3/4) were precisely classified as class D using panel NMIC-440. Both carbapenemase producers harboring the blaISAba1-OXA-51-like gene were incorrectly identified as non-CPOs using panels NMIC-440 and NMIC/ID-442. For detecting carbapenemase producers, the overall PPA and negative percent agreement (NPA) between panel NMIC-440 and the comparator methods were 96.7% (58/60) and 71.2% (52/73), respectively, and the PPA and NPA between panels NMIC/ID-441 or NMIC/ID-442 and the comparator methods were 96.7% (58/60) and 74.0% (54/73), respectively. BD Phoenix CPO Detect panels can successfully screen carbapenemase producers, particularly IMP producers, regardless of the presence of carbapenem resistance and can be beneficial in routine AST workflows. IMPORTANCE Simple and efficient screening methods of detecting carbapenemase producers are required. BD Phoenix CPO Detect panels effectively screened carbapenemase producers, particularly IMP producers, with a high overall PPA. As the panels enable automatic screening for carbapenemase producers simultaneously with AST, the workflow from AST to confirmatory testing for carbapenemase production can be shortened. In addition, because carbapenem resistance varies among carbapenemase producers, the BD Phoenix CPO Detect panels, which can screen carbapenemase producers regardless of carbapenem susceptibility, can contribute to the accurate detection of carbapenemase producers. Our results report that these panels can help streamline the AST workflow before confirmatory testing for carbapenemase production in routine microbiological tests.

Clinical and microbiological characteristics of bloodstream infection caused by Klebsiella pneumoniae harboring rmpA in Japanese adults

We investigated the clinical features of bloodstream infections (BSIs) caused by Klebsiella pneumoniae harboring rmpA and molecular characteristics of the bacteria. We retrospectively investigated adult patients with K. pneumoniae BSI from January 2010 to March 2021 at Nagasaki University Hospital. A matched case-control study in a 1:3 ratio was conducted to clarify the clinical and bacterial characteristics of BSI caused by rmpA-positive K. pneumoniae compared with those caused by rmpA-negative isolates. Antimicrobial susceptibility testing and multilocus sequence typing (MLST) were performed for rmpA-positive isolates. The rmpA was detected in 36 (13.4%) of the 268 isolates. Of these 36 isolates, 31 (86.1%) harbored iucA and 35 (97.2%) each possessed peg-344 and iroB; capsular types were identified as K1 in 9 (25.0%) and K2 in 10 isolates (27.8%). Contrarily, of the 108 rmpA-negative isolates, which were matched for case-control studies, 5 isolates (4.6%) harbored iucA and 1 (0.9%) each possessed peg-344 and iroB; 2 (1.9%) and 3 isolates (2.8%) had K1 and K2 capsular types, respectively. Among the rmpA-positive isolates, ST23/K1 (eight isolates) was the most frequent, followed by ST412/non-K1/K2 (seven isolates), ST86/K2 (five isolates), and ST268/non-K1/K2 (four isolates). In a multivariate analysis using clinical factors, liver abscess positively correlated with rmpA-positive isolates, whereas biliary tract infection and use of anticancer drugs negatively correlated with rmpA-positive isolates in patients with K. pneumoniae BSI. Considering the correlation between rmpA-positive isolates and clinical features, rmpA can be used as a marker for understanding the pathophysiology of K. pneumoniae BSI.

Hypervirulent Klebsiella pneumoniae Infections in Pediatric Populations in Beijing (2017-2019): Clinical Characteristics, Molecular Epidemiology and Antimicrobial Susceptibility

BACKGROUND

Hypervirulent variants of Klebsiella pnuemoniae (hvKp) are emerging globally causing life-threatening infectious diseases; however, comprehensive studies on pediatric hvKp strains and related infections are still lacking.

METHODS

Clinical data were collected from medical records. Genotype (multilocus sequence typing), capsular serotype, virulence gene profile and carbapenemase of the isolates were determined by PCR and DNA sequencing. Broth microdilution method was adopted to test the antimicrobial susceptibility. Hypermucoviscosity phenotype and the virulence of the strains were evaluated by string test and Galleria mellonella larvae killing assay.

RESULTS

Among 319 K. pneumoniae strains, 26 (8.2%) hvKp were identified, the detection rates in 2017, 2018 and 2019 were 1.8%, 5.2% and 11.3%. The majority of hvKp infections were found in school-age children and adolescents (57.7%). Pneumonia was the most common diagnosis (38.5%). Single fatal case was hvKp caused liver abscess complicated with bacteremia. hvKp were dominated by ST23 (30.8%) and ST11 (30.8%). Eight carbapenem-resistant hvKp (CR-hvKp) were found, which all belonged to ST11. Virulence gene profile revealed that ST11 hvKp might carry incomplete pLVPK-like plasmids, but they exhibited comparable in vivo virulence to the other hvKp.

CONCLUSIONS

The infections caused by hvKp are not frequent among pediatric populations, but the detection rate of hvKp in pediatric populations is increasing rapidly in recent years. The emerging and dissemination of ST11 CR-hvKp should be monitored continuously.

Rapid detection and surveillance of cfiA-positive Bacteroides fragilis using matrix-assisted laser desorption ionization time-of-flight mass spectrometry

OBJECTIVES

To perform surveillance of cfiA-positive Bacteroides fragilis using new subtyping software module, MALDI Biotyper Subtyping Module (MBT Subtyping Module), on MALDI-TOF MS system, and to evaluate the detection ability of the module.

METHODS

cfiA-positive strains were presumed using the module against B. fragilis isolated between 2006 and 2019. The cfiA gene was confirmed using PCR. In cfiA-positive B. fragilis, the insertion sequence (IS) elements were examined and the MBT STAR-BL assay was performed to examine meropenem hydrolysis activity.

RESULTS

Of the 396 B. fragilis strains included, the MBT Subtyping Module detected 33 presumptive cfiA-positive strains (8.3%), of which 32 harbored the cfiA gene. The sensitivity and specificity of the MBT Subtyping Module for detecting cfiA-positive B. fragilis were 100.0% and 99.7%, respectively. Of the 32 strains harboring the cfiA gene, seven strains possessed IS elements, which were thought to induce high cfiA expression. Meropenem hydrolysis was detected in all seven strains that were positive for both cfiA and IS elements, and they exhibited resistance to meropenem and imipenem. The overall non-susceptibility rates to meropenem and imipenem were 84.8% and 36.4%, respectively, in the 33 presumptive cfiA-positive strains.

CONCLUSION

The MBT Subtyping Module can detect cfiA-positive B. fragilis rapidly and accurately, supporting its use for surveillance of cfiA-positive B. fragilis in clinical settings.

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.

A Matched Case-Case-Control Study of the Impact of Clinical Outcomes and Risk Factors of Patients with IMP-Type Carbapenemase-Producing Carbapenem-Resistant Enterobacteriaceae in Japan

IMP-type carbapenemase, found in various Gram-negative bacteria, has been increasingly detected worldwide. We aimed to study the outcomes and risk factors for acquisition of IMP-type carbapenemase-producing carbapenem-resistant Enterobacteriaceae (IMP-CRE), as this has not been evaluated in detail. We conducted a matched case-case-control study of patients from whom IMP-CRE isolates were obtained. All patients who tested positive for IMP-CRE were included; they were matched with patients with carbapenem-susceptible Enterobacteriaceae (CSE) and with controls at a ratio of 1:1:2. The risk factors for acquisition for the CRE and CSE groups and mortality rates, which were calculated using multivariate logistic regression models with weighting according to the inverse probability of propensity scores, were compared. In total, 192 patients (96 patients each in the CRE and CSE groups, with 130 Enterobacter cloacae isolates and 62 Klebsiella sp. isolates) were included. The IMP-11 type was present in 43 patients, IMP-1 in 33, and IMP-60 and IMP-66 in 1 each; 31 patients with CRE (32.3%) and 34 with CSE (35.4%) developed infections. Multivariate analysis identified the following independent risk factors: gastrostomy, history of intravenous therapy or hemodialysis, and previous exposure to broad-spectrum β-lactam antibiotics, including penicillin with β-lactamase inhibitors, cephalosporins, and carbapenems. In propensity score-adjusted analysis, mortality rates for the CRE and CSE groups were similar (15.0% and 19.5%, respectively). We found that IMP-CRE may not contribute to worsened clinical outcomes, compared to CSE, and gastrostomy, previous intravenous therapy, hemodialysis, and broad-spectrum antimicrobial exposure were identified as risk factors for CRE isolation. Fluoroquinolone and aminoglycosides are potentially useful antibiotics for IMP-CRE infections.

Efficacy of meropenem and amikacin combination therapy against carbapenemase-producing Klebsiella pneumoniae mouse model of pneumonia

BACKGROUND

The emergence and spread of carbapenem-resistant Enterobacteriaceae (CRE) is a global health problem due to its high mortality and limited treatment options. Combination antimicrobial therapy is reported to be effective against CRE in vitro; however, its efficacy in vivo has not been thoroughly evaluated. Thus, this study assessed the efficacy of combination therapy of meropenem (MEPM) and amikacin (AMK) in a carbapenem-resistant Klebsiella pneumoniae (CR-Kp) mouse model of pneumonia.

MATERIALS AND METHODS

Agar-based bacterial suspension of CR-Kp clinical isolates was inoculated into the trachea of BALB/c mice. Treatment was initiated 6 h post infection, with 100 mg/kg MEPM every 6 h, 100 mg/kg AMK every 12 h, or in combination; survival was evaluated for 7 days. The number of viable bacteria in the lungs, lung histopathology, and neutrophil counts in broncho-alveolar lavage fluid (BALF) were evaluated 42 h after infection.

RESULTS

All mice in the untreated control group died in 48 h, while all the mice in treatment groups survived past 7 days following infection. The bacterial count in the lungs (log₁₀ CFU/mL, mean ± SEM) in the combination group (2.00 ± 0.00) decreased significantly compared to that in control (10.19 ± 0.11, p < 0.0001), MEPM (6.38 ± 0.17, p < 0.0001), and AMK (6.17 ± 0.16, p < 0.0001) groups. BALF neutrophil count reduced only in the combination therapy group. Combination therapy prevented the progression of lung inflammation, including alveolar neutrophil infiltration and hemorrhage.

CONCLUSIONS

This study demonstrates in vivo efficacy of MEPM and AMK combination therapy against CR-Kp pneumonia.

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.