Carbapenem-resistant Klebsiella pneumoniae strains isolated from clinical specimens in Siirt, Türkiye; molecular characterization and antimicrobial resistance genes detection

This study aimed to molecularly identify carbapenem-resistant Klebsiella pneumoniae (CRKP) strains isolated from clinical samples and to determine antibiotic resistance genes. Only carbapenem-resistant strains were included in our study. Of the 35 CRKP strains, 18 (51.4%) were extensive drug, 11 (31.4%) were multi-drug, and 6 (17.1%) were pan-drug resistances. PCR amplification revealed that 25% of the strains carried the OXA-51, 20% the OXA-48, and %5 the OXA23 genes. Multilocus sequence typing (MLST) analysis based on seven house-keeping genes revealed sequence type 39. The capsule and O-antigen types were determined as KL103 and O2a, respectively. WGS analysis revealed the existence of β-lactamase, aminoglycoside, sulfonamide, Phenicol, and Fosfomycin-resistant genes. While the K. pneumoniae OmpK37 gene was detected in all 3 strains, the OmpK36 gene was detected only in the CRSU20 strain. This study is important as it is the first study to perform molecular analysis of CRKP strains from Siirt, Türkiye.

Molecular characterization of hypermucoviscous carbapenemase-encoding Klebsiella pneumoniae isolates from an Egyptian hospital

This study aimed to screen antibiotic resistance and virulence genes in carbapenem-resistant hypermucoviscous Klebsiella pneumoniae isolates from an Egyptian hospital. Among 38 previously confirmed carbapenem-nonsusceptible K. pneumoniae isolates, a string test identified three isolates as positive for hypermucoviscosity. Phenotypic characterization and molecular detection of carbapenemase- and virulence-encoding genes were performed. PCR-based multilocus sequence typing and phylogenetics were used to determine the clonality and global epidemiology of the strains. The coexistence of virulence and resistance genes in the isolates was analyzed statistically using a chi-square test. Three isolates showed the presence of carbapenemase-encoding genes (blaNDM, blaVIM, and blaIMP), adhesion genes (fim-H-1 and mrkD), and siderophore genes (entB); the isolates belonged to sequence types (STs) 101, 1310, and 1626. The relatedness between these sequence types and the sequence types of globally detected hypermucoviscous K. pneumoniae that also harbor carbapenemases was determined. Our analysis showed that the resistance and virulence profiles were not homogenous. Phylogenetically, different clones clustered together. There was no significant association between the presence of resistance and virulence genes in the isolates. There is a need for periodic surveillance of the healthcare settings in Egypt and globally to understand the true epidemiology of carbapenem-resistant, hypermucoviscous K. pneumoniae.

Chasing the landscape for intrahospital transmission and evolution of hypervirulent carbapenem-resistant Klebsiella pneumoniae

The spread of hypervirulent carbapenem-resistant Klebsiella pneumoniae (Hv-CRKP) is a global health concern. Here, we report the intrahospital colonization and spread of Hv-CRKP isolates in a tertiary hospital from 2017 to 2022. Analyses of 90 nonredundant CRKP isolates from 72 patients indicated that Hv-CRKP transferability relies on the dominant ST11-K64 clone. Whole-genome sequencing of 11 representative isolates gave 31 complete plasmid sequences, including 12 KPC-2 resistance carriers and 10 RmpA virulence vehicles. Apart from the binary vehicles, we detected two types of fusion plasmids, favoring the cotransfer of RmpA virulence and KPC-2 resistance. The detection of ancestry/relic plasmids enabled us to establish genetic mechanisms by which rare fusion plasmids form. Unexpectedly, we found a total of five rmpA promoter variants (P9T-P13T) exhibiting distinct activities and varying markedly in their geographic distributions. CRISPR/Cas9 manipulation confirmed that an active PT11-rmpA regulator is a biomarker for the "high-risk" ST11-K64/CRKP clone. These findings suggest clonal spread and clinical evolution of the prevalent ST11-K64/Hv-CRKP clones. Apart from improved public awareness of Hv-CRKP convergence, our findings might benefit the development of surveillance (and/or intervention) strategies for the dominant ST11-K64 lineage of the Hv-CRKP population in healthcare sectors.

Evolution of Beta-Lactamases in Urinary Klebsiella pneumoniae Isolates from Croatia; from Extended-Spectrum Beta-Lactamases to Carbapenemases and Colistin Resistance

K. pneumoniae isolates often harbor various antibiotic resistance determinants including extended-spectrum β-lactamases (ESBLs), plasmid-mediated AmpC β-lactamases (p-Amp-C) and carbapenemases. In this study we analyzed 65 K. pneumoniae isolates obtained from urinary tract infections in the outpatients setting, with regard to antibiotic susceptibility, β-lactamase production, virulence traits and plasmid content.Antibiotic susceptibility was determined by broth microdilution method. PCR was applied to detect genes encoding ESBLs, p-Amp-C and carbapenemases and plasmid incompatibility groups. Phenotypic methods were applied to characterize virulence determinants. Increasing resistance trend was observed for amoxicillin/clavulanate, imipenem, meropenem and ciprofloxacin. The study showed that ESBLs belonging to the CTX-M family, conferring high level of resistance to expanded-spectrum cephalosporins (ESC) were the dominant resistance trait among early isolates (2013 to 2016) whereas OXA-48 carbapenemase, belonging to class D, emerged in significant numbers after 2017. OXA-48 producing organisms coharbored ESBLs. KPC-2 was dominant among isolates from Dubrovnik in the recent years. Colistin resistance was reported in three isolates. Inc L/M was the dominant plasmid in the later period, encoding OXA-48. Hyperviscosity was linked to KPC positivity and emerged in the later period. This report describes evolution of antibiotic resistance in K. pneumoniae from ESBLs to carbapenemases and colistin resistance. The study demonstrated the ability of K. pneumoniae to acquire various resistance determinants, over time. The striking diversity of the UTI isolates could result from introduction of the isolates from the hospitals, transfer of plasmids and multidirectional evolution.

Time kill-assays of antibiotic combinations for multidrug resistant clinical isolates of OXA-48 carbapenemase producing Klebsiella pneumoniae

Treatment of infections caused by OXA-48 carbapenemase producing multidrug-resistant isolates often necessitates combination therapy. In vitro effect of different antibiotic combinations against multidrug-resistant (MDR) Klebsiella pneumoniae isolates were evaluated in this study. Meropenem-tobramycin (MER+TOB), meropenem-ciprofloxacin (MER+CIP), colistin-meropenem (COL+MER), colistin-ciprofloxacin (COL+CIP) and colistin-tobramycin (COL+TOB) combinations were tested by time kill-assays. Each antibiotic alone and in combination at their Cmax values were tested against 4 clinical K. pneumoniae isolates at 1, 2, 4, 6, 8, 12 and 24 h. Effect of colistin and its associations were also assessed at 30 min. Bactericidal activity was defined as ≥3log10 CFU mL-1 decrease compared with initial inoculum. Synergy was defined as ≥2log10CFU mL-1 decrease by the combination compared with the most active single agent. Presence of bla OXA-48, bla NDM, bla VIM, bla IMP, bla KPC and bla CTX-M-1 genes was screened by PCR using specific primers. The bla OXA-48 gene was identified together with bla CTXM-1 group gene in all isolates. COL+MER demonstrated to be synergistic and bactericidal. MER+TOB showed synergistic and bactericidal effect on two strains although, regrowth was seen on other two strains at 24 h. MER+CIP exhibited indifferent effect on the strains. Combination therapy could be a potential alternative to treat MDR K. pneumoniae infections. This combination might prevent resistance development and secondary effects of colistin monotherapy. MER+TOB and MER+CIP might have an isolate-dependent effect, that may not always result in synergism.

Comparative genomic analysis of plasmids encoding metallo-β-lactamase NDM-5 in Enterobacterales Korean isolates from companion dogs

Carbapenems are broad-spectrum antibiotics widely used for the treatment of human infections caused by multidrug-resistant (MDR) Gram-negative bacteria. However, emerging carbapenemase-producing Enterobacterales (CPE) are rising as a public threat to human and animal health. We screened clinical bacterial isolates from 241 dogs and 18 cats hospitalized at Veterinary Medical Teaching Hospital, Seoul National University, from 2018 to 2020 for carbapenemase production. In our study, 5 strains of metallo-β-lactamase NDM-5-producing Escherichia coli and Klebsiella pneumoniae were isolated from 4 different dogs. Multilocus sequence typing (MLST) results showed that all E. coli strains were ST410 and all K. pneumoniae strains were ST378. Whole genome analysis of the plasmid showed that blaNDM-5 is carried on a IncX3 plasmid, showing a high concordance rate with plasmids detected worldwide in human and animal isolates. The blaNDM gene was associated with the bleMBL gene and the ISAba125 element, truncated with the IS5 element. The results of this study show that CPE has already become as a threat to both animals and humans in our society, posing the necessity to solve it in terms of "One Health". Therefore, preventive strategies should be developed to prevent the spread of CPE in animal and human societies.

Phenotypic and Genotypic Features of Klebsiella pneumoniae Harboring Carbapenemases in Egypt: OXA-48-Like Carbapenemases as an Investigated Model

This study aimed at the characterization of carbapenem-resistant Klebsiella pneumoniae isolates focusing on typing of the bla_OXA-48-like genes. Additionally, the correlation between the resistance pattern and biofilm formation capacity of the carbapenem-resistant K. pneumoniae isolates was studied. The collected isolates were assessed for their antimicrobial resistance and carbapenemases production by a modified Hodge test and inhibitor-based tests. The carbapenemases encoding genes (bla_KPC, bla_NDM, bla_VIM, bla_IMP, and bla_OXA-48-like) were detected by PCR. Isolates harboring bla_OXA-48-like genes were genotyped by Enterobacterial Repetitive Intergenic Consensus-Polymerase Chain Reaction (ERIC-PCR) and plasmid profile analysis. The discriminatory power of the three typing methods (antibiogram, ERIC-PCR, and plasmid profile analysis) was compared by calculation of Simpson's Diversity Index (SDI). The transferability of bla_OXA-48 gene was tested by chemical transformation. The biofilm formation capacity and the prevalence of the genes encoding the fimbrial adhesins (fimH-1 and mrkD) were investigated. The isolates showed remarkable resistance to β-lactams and non-β-lactams antimicrobials. The coexistence of the investigated carbapenemases encoding genes was prevalent except for only 15 isolates. The plasmid profile analysis had the highest discriminatory power (SDI = 0.98) in comparison with ERIC-PCR (SDI = 0.89) and antibiogram (SDI = 0.78). The transferability of bla_OXA-48 gene was unsuccessful. All isolates were biofilm formers with the absence of a significant correlation between the biofilm formation capacity and resistance profile. The genes fimH-1 and mrkD were prevalent among the isolates. The prevalence of carbapenemases encoding genes, especially bla_OXA-48-like genes in Egyptian healthcare settings, is worrisome and necessitates further strict dissemination control measures.

Evaluation of two commercial methods for rapid detection of the carbapenemase-producing Klebsiella pneumoniae

In this study, we evaluated the performance of the two commercial methods (Rapidec Carba NP and NG-Test Carba-5) for the rapid detection of carbapenemase-producing Klebsiella pneumoniae. A total of 224 Klebsiella pneumoniae strains previously characterized for carbapenemase genes by polymerase chain reaction were included in the study. The strain collection included 30 non-carbapenemase producers, 85 OXA-48-like, 59 NDM, 14 IMP, 7 KPC, 7 VIM, 19 OXA-48-like plus NDM, and 3 KPC plus NDM producers. Rapidec Carba NP and NG-Test Carba 5 was performed according to the manufacturer's instructions. NG-Test Carba 5 correctly detected all carbapenemase-producing K. pneumoniae, however, Rapidec Carba NP failed to detect 41% of OXA-48-like producers even with extended incubation time. The overall sensitivity and specificity were 81,9% and 100% for Rapidec Carba NP, 100% and 100% for NG-Test Carba 5, respectively. Both tests seem to be fast and reliable for the detection of carbapenemase-producing K. pneumoniae especially for microbiology laboratories where molecular tests cannot be performed. However, Rapidec Carba NP with weak hydrolysis activity for OXA-48 like might be used in regions where OXA-48 is not prevalent. The additional advantage of NG-Test Carba 5 is that it specifically detects carbapenemases giving way to threat-related infections with an effective drug such as ceftazidime-avibactam or meropenem- vaborbactam.

Evaluation of phenotypic tests for detection of carbapenemases: New modifications with new interpretation

INTRODUCTION

The emergence and spread of carbapenemase-producing Enterobacterales (CPE) is a worldwide public health threat. Rapid and accurate detection of CPE is essential to prevent their dissemination within health care settings. The aim of this study was to evaluate the performance of CIM, mCIM and mCIM with ammonium bicarbonate (mCIM-A) methods by using different interpretation criteria for detection of carbapenemases.

METHODS

One hundred and fifty-three Klebsiella pneumoniae isolates previously characterized by molecular tests, including 133 carbapenemase producers and 20 non-carbapenemase producers, were collected in this study. CIM and mCIM tests were performed as described previously. mCIM-A by adding 50 mM ammonium bicarbonate to the bacterial suspension prepared in tryptic soy broth. The inhibition zone diameter of around meropenem disc was measured and interpreted as positive according to i) Pierce and colleagues (<19 mm), ii) EUCAST meropenem susceptibility breakpoint (<22).

RESULTS

CIM, although seems to be good for carbapenemases other than OXA-48-like and NDM, is not satisfactory (42.3% and 83.4%, respectively) for those enzymes with any of the interpretation criteria. OXA-48-like and NDM were detected with a better performance (88.7% and 92.8, respectively) with mCIM when results were interpreted according to <22 mm zone diameter for OXA-48-like and NDM. The best results were obtained with mCIM-A using <22 mm criteria without any difference in the results of other enzymes and negative strains.

CONCLUSIONS

mCIM-A method interpreted with <22 mm meropenem zone diameter seems to be preferable compared to CIM and mCIM. mCIM-A is simple and useful tool for identification of CPEs in clinical microbiology laboratories.

Clinical impact of endemic NDM-producing Klebsiella pneumoniae in intensive care units of the national referral hospital in Jakarta, Indonesia

OBJECTIVE

A prospective observational study was performed to assess the epidemiology and clinical impact of carbapenem-non-susceptible Klebsiella pneumoniae (CNKP) in intensive care units (ICUs) of the national referral hospital in Jakarta, Indonesia.

MATERIALS/METHODS

Adult patients consecutively hospitalized for > 48 h in two ICUs of the national referral hospital were included from April until October 2013 and from April until August 2014. K. pneumoniae from clinical cultures and standardized screening of rectum and throat on admission, discharge and weekly if hospitalized > 7 days were collected. Environmental niches and healthcare workers (HCWs) were also screened. Susceptibility was determined phenotypically and the presence of carbapenemase genes by PCR. Raman spectroscopy as well as multiple-locus variable number tandem repeat analysis (MLVA) were used for typing.

RESULTS

Twenty-two out of 412 (5.3%) patients carried CNKP on admission and 37/390 (9.5%) acquired CNKP during ICU stay. The acquisition rate was 24.7/1000 patient-days at risk. One out of 31 (3.2%) environmental isolates was a CNKP. None of the HCWs carried CNKP. Acquisition of CNKP was associated with longer ICU stay (adjusted Hazard Ratio: 2.32 [CI₉₉: 1.35-3.68]). ICU survival was lower among patients with CNKP compared to patients with carbapenem-susceptible K. pneumoniae (aHR 2.57, p = 0.005). Ninety-six of the 100 (96%) CNKP isolates carried a carbapenemase gene, predominantly bla_NDM. Raman typing revealed three major clusters among 48 Raman types identified, whereas MLVA distinguished six major clusters among a total of 30 different genotypes.

CONCLUSIONS

NDM-producing CNKP are introduced into these ICUs and some strains expand clonally among patients and the environment, resulting in endemic CNKP. CNKP acquisition was associated with prolonged ICU stay and may affect ICU survival.

TRIAL REGISTRATION

The study was registered at Netherlands Trial Register http://www.trialregister.nl. Candidate number: 23527, NTR number: NTR5541, NL number: NL5425 (https://www.trialregister.nl/trial/5424), Retrospectively registered: NTR: 22 December 2015.

A review on bacterial resistance to carbapenems: epidemiology, detection and treatment options

Carbapenems are a class of antimicrobial agents reserved for infections caused by multidrug-resistant microorganisms. The emergence of carbapenem resistance has become a serious public health threat. This type of antimicrobial resistance is spreading at an alarming rate, resulting in major outbreaks and treatment failure of community-acquired and nosocomial infections caused by the clinically relevant carbapenem-producing Enterobacteriaceae or carbapenem-resistant Enterobacteriaceae. This review is focused on carbapenem resistance, including mechanisms of resistance, history and epidemiology, phenotypic and genotypic detection in the clinically relevant bacterial pathogens and the possible treatment options available.

Hidden Carbapenem Resistance in OXA-48 and Extended-Spectrum β-Lactamase-Positive Escherichia coli

The purpose of this study was to report the identification OXA-48 carbapenemase in seven extended-spectrum β-lactamase (ESBL)-positive Escherichia coli clinical isolates, fully susceptible to all carbapenems by disk diffusion and E-test methods, but with borderline minimal inhibitory concentration (MIC) values of ertapenem. This report points to the necessity for determination of carbapenem MICs in ESBL-positive E. coli isolates and additional phenotypic testing for carbapenemases in all isolates with borderline ertapenem MIC defined by EUCAST. The isolates showed a high level of resistance to expanded-spectrum cephalosporins because of the production of an additional ESBL belonging to CTX-M family. All isolates and their respective tranconjugants were found to possess L plasmid. Pulsed-field gel electrophoresis analysis revealed two clusters containing highly related isolates. The global spread of multidrug-resistant E. coli should be monitored closely because of the ability of isolates to rapidly obtain additional antibiotic resistance traits such as plasmid-mediated OXA-48 genes.

Characterization of Resistance Genes and Polymerase Chain Reaction-Based Replicon Typing in Carbapenem-Resistant Klebsiella pneumoniae

Background: Fifty isolates of Klebsiella pneumoniae isolated from clinical samples between 2012 and 2016 that were found to be resistant to carbapenems were included in this study. Materials and Methods: Resistance genes were investigated by performing PCR. Plasmid typing was performed using PCR-based replicon typing. The clonal relationships between the strains were investigated using pulsed-field gel electrophoresis (PFGE). Results: OXA-48-type carbapenemase genes were detected in 86% (n = 43/50) of K. pneumoniae isolates, whereas NDM-type carbapenemase genes were detected in 14% (n = 7/50) of the isolates. bla_TEM was detected 60% (n = 30) of the strains, bla_SHV in 78% (n = 39), bla_CTX-M-1 in 48% (n = 24), and bla_CTX-M-2-type β-lactamase in 10% (n = 5). bla_CTX-M-1 and bla_SHV were concomitantly distributed in 40% (n = 20) of the strains, bla_TEM and bla_SHV in 54% (n = 27), bla_TEM, bla_SHV, and bla_CTX-M-1 in 32% (n = 16) and bla_CTX-M-1 and bla_CTX-M-2 in 10% (n = 5). Strain numbers 66, 69, 76, 77, and 78 coproduced carbapenemases, bla_CTX-M-1 and bla_CTX-M-2 in addition to bla_OXA-48 or bla_NDM-1 that were described as hybrid strains. IncR-type replicon was found in 50% (n = 25) of 50 isolates with plasmid typing, whereas IncA/C-type replicon was detected in 40% (n = 20) and IncFIIK-type replicon in 18% (n = 9) of the isolates. Outcomes of the transformation experiments showed that the OXA-48 gene was carried to the receiver cell on FII plasmids. No dominant epidemic clone was detected through PFGE. Conclusion: OXA-48 carbapenemase was found to be the most prevalent type of enzyme in our hospital, and the presence of NDM-1-type carbapenemase-carrying strain and an increase in their rate were detected.

Extended-spectrum β-lactamase-producing and carbapenemase-producing Enterobacteriaceae

Antimicrobial resistance (AMR) is a global public-health emergency, which threatens the advances made by modern medical care over the past century. The World Health Organization has recently published a global priority list of antibiotic-resistant bacteria, which includes extended-spectrum β-lactamase-producing Enterobacteriaceae and carbapenemase-producing Enterobacteriaceae. In this review, we highlight the mechanisms of resistance and the genomic epidemiology of these organisms, and the impact of AMR.

Epidemic spread of OXA-48 beta-lactamase in Croatia

PURPOSE

A dramatic increase in OXA-48 β-lactamase was observed recently not only in large hospital centres, but also in smaller suburban hospital centres in geographic areas bordering Croatia. The aim of the study was to analyse the epidemiology, the mechanisms of antibiotic resistance and the routes of spread of OXA-48 carbapenemase in Croatia.

METHODS

Carbapenemase and other β-lactamase and fluoroquinolone resistance genes were detected by PCR and sequencing. Whole-genome sequencing (WGS) was performed on five representative isolates. The isolates were genotyped by PFGE.

RESULTS

Forty-eight isolates positive for OXA-48, collected from seven hospital centres in Croatia from May 2016 to May 2017, were analysed (40 Klebsiella pneumoniae, 5 Enterobacter cloacae, 2 Escherichia coli and one Citrobacter freundii). Thirty-three isolates were ESBL positive and harboured group 1 CTX-M 1 β-lactamases. In addition to the β-lactam resistance genes detected by PCR (blaSHV-1, blaOXA-48 and blaOXA-1), WGS of five representative isolates revealed the presence of genes encoding aminoglycoside resistance, aadA2 and aph3-Ia, fluoroquinolone resistance determinants aac(6)Ib-c, oqxA and oqxB, the sulfonamide resistance gene sul1, and fosA (fosfomycin resistance). IncL plasmid was found in all isolates. Two K. pneumoniae isolates belonged to ST16, two E. cloacae to ST66 and E. coli to ST354. K. pneumoniae isolates were allocated to five clusters by PFGE which occured in different hospitals, indicating epidemic spread.

CONCLUSIONS

The OXA-48-positive organisms found in this study showed wide variability in antibiotic susceptibility, β-lactamase content and PFGE banding patterns. This study revealed a switch from the predominance of VIM-1 in 2012-2013 to that of OXA-48 in the 2015 to 2017.

Performance of "RESIST-3 O.K.N. K-SeT" immunochromatographic assay for the detection of OXA-48 like, KPC, and NDM carbapenemases in Klebsiella pneumoniae in Turkey

In this study, the performance of the “RESIST-3 O.K.N. K-SeT” (Coris BioConcept, Gembloux, Belgium) immunochromatographic assay was evaluated in 132 Klebsiella pneumoniae comprising 102 carbapenem resistant and 30 carbapenem susceptible isolates. Genotypically known isolates of Gram negative bacteria (n = 22) including various species were also tested by the assay as controls. The isolates tested by the immunochromatographic assay and also were run PCR for bla_KPC, bla_IMP, bla_VIM, bla_NDM, and bla_OXA-48. The rates of bla_NDM, bla_OXA-48, and bla_KPC in carbapenem resistant isolates were found at 52.9%, 39.2%, and 2.0%, respectively. Both bla_NDM and bla_OXA-48 were found in six (5.9%) isolates. The results of the assay showed 100% concordance with those obtained by PCR in 132 K. pneumoniae. The agreement between the two methods was found to be identical at the isolate level. The assay also correctly detected all genotypically known isolates of Escherichia coli, Serratia marcescens, Citrobacter freundii, Enterobacter cloacae, K. pneumoniae carrying bla_KPC, bla_NDM, and/or bla_OXA-48. On the other hand, the assay did not exhibit any cross-reaction in control isolates harboring bla_IMP and bla_VIM. We conclude that the RESIST-3 O.K.N. K-SeT is a reliable, rapid, and user friendly test and we recommend it for routine diagnostic laboratories.

OXA-48-like carbapenemases producing Enterobacteriaceae in different niches

The emergence of carbapenem-resistant enterobacterial species poses a serious threat to public health worldwide. OXA-48-type carbapenem-hydrolyzing class D β-lactamases are widely distributed among Enterobacteriaceae, with significant geographical differences. To date, 11 OXA-48-like variants have been identified, with classical OXA-48 being the most widespread. These enzymes show high-level hydrolytic activity against penicillins and low-level hydrolysis towards carbapenems. Since the first description of the OXA-48 carbapenemase in Turkey, bacterial strains producing the enzyme have been extensively reported in nosocomial and community outbreaks in many parts of the word, particularly in the Mediterranean area and European countries. The rapid spread of Enterobacteriaceae producing OXA-48-like enzymes in different ecosystems has become a serious issue recently. The number of reservoirs for such organisms is increasing, not only in hospitals, but also in the community, among animals (e.g., livestock, companion animals, and wildlife) and in the environment. This review aims to summarize the main characteristics of the OXA-48-type carbapenemases, covering genetic and enzymatic traits, their epidemiology, clonality and associated genes, correlation with extended-spectrum β-lactamases (ESBLs) or plasmidic AmpC (pAmpC) in different bacterial species worldwide.

Distribution of β-lactamase genes among carbapenem-resistant Klebsiella pneumoniae strains isolated from patients in Turkey

Background

The emergence of carbapenem-resistant Klebsiella pneumoniae poses a serious problem to antibiotic management. We investigated the β-lactamases in a group of carbapenem-resistant K. pneumoniae clinical isolates from Turkey.

Methods

Thirty-seven strains of K. pneumoniae isolated from various clinical specimens were analyzed by antimicrobial susceptibility testing, PCR for the detection of β-lactamase genes, DNA sequencing, and repetitive extragenic palindronic (REP)-PCR analysis.

Results

All 37 isolates were resistant to ampicillin, ampicillin/sulbactam, piperacillin, piperacillin/tazobactam, ceftazidime, cefoperazone/sulbactam, cefepime, imipenem, and meropenem. The lowest resistance rates were observed for colistin (2.7%), tigecycline (11%), and amikacin (19%). According to PCR and sequencing results, 98% (36/37) of strains carried at least one carbapenemase gene, with 32 (86%) carrying OXA-48 and 7 (19%) carrying NDM-1. No other carbapenemase genes were identified. All strains carried a CTX-M-2-like β-lactamase, and some carried SHV- (97%), TEM- (9%), and CTX-M-1-like (62%) β-lactamases. Sequence analysis of bla_TEM genes identified a bla_TEM-166 with an amino acid change at position 53 (Arg53Gly) from bla_TEM-1b, the first report of a mutation in this region. REP-PCR analysis revealed that there were seven different clonal groups, and temporo-spatial links were identified within these groups.

Conclusions

Combinations of β-lactamases were found in all strains, with the most common being OXA-48, SHV, TEM, and CTX-M-type (76% of strains). We have reported, for the first time, a high prevalence of the NDM-1 (19%) carbapenemase in carbapenem-resistant K. pneumoniae from Turkey. These enzymes often co-exist with other β-lactamases, such as TEM, SHV, and CTX-M β-lactamases.

Epidemiology of Carbapenem Resistant Klebsiella pneumoniae Infections in Mediterranean Countries

Infections by Carbapenem-Resistant Enterobacteriaceae (CRE), in particular, carbapenem-resistant Klebsiella pneumoniae (CRKp), are a significant public health challenge worldwide. Resistance to carbapenems in enterobacteriaceae is linked to different mechanisms, including the production of the various types of enzymes like KPC, VIM, IMP, NDM, and OXA-48. Despite several attempts to control the spread of these infections at the local and national level, the epidemiological situation for CRKp had worsened in the last years in the Mediterranean area. The rate and types of CRKp isolates greatly differ in the various Mediterranean countries. KPC-producing K. pneumoniae is diffused particularly in the European countries bordering the Mediterranean Sea and is endemic in Greece and Italy. On the contrary, OXA-48-producing K. pneumoniae is endemic in Turkey and Malta and diffused at inter-regional level particularly in some

North African and Middle East countries. The spread of these multiresistant pathogens in the world and the Mediterranean countries has been related to various epidemiological factors including the international transfer of patients coming from endemic areas.

Boronic acid disk diffusion for the phenotypic detection of polymerase chain reaction-confirmed, carbapenem-resistant, gram-negative bacilli isolates

Background

The Middle East is regarded as a secondary reservoir for OXA-48 and New Delhi metallo-β-lactamase (NDM) carbapenemases. One of the main challenges in clinical microbiology diagnostics is the detection of carbapenemases. For this reason simple screening methods have been sought to detect carbapenemase producers to determine appropriate therapeutic measures and implement infection control interventions. The present study aimed to evaluate the efficacy of the modified Hodge test (MHT) and a boronic acid-based combined disk test using carbapenems as substrates for the phenotypic determination of OXA-48 and NDM type carbapenemases in 45 epidemiologically unrelated carbapenem-resistant clinical isolates of Klebsiella pneumoniae (13 isolates), Acinetobacter baumanii (20 isolates), and Pseudomonas aeruginosa (12 isolates).

Results

Boronic acid disk test using meropenem as substrate and 600 µg of 3- aminophenylboronic acid (APB) was the most sensitive method (83.33 %) for detection of OXA-48, while the most specific method was MHT (100 %). As regards NDM carbapenemase, boronic acid disk tests using imipenem and 600 µg of APB per disk, and meropenem with 300 or 600 µg of APB were the most  sensitive methods (87.50 %), while the most specific method was the MHT (100 %).

Conclusions

The results of the present study indicate that phenotypic screening with the MHT and the boronic acid disk test may be used to detect OXA-48 and NDM carbapenemases in Gram-negative bacilli clinical isolates, and that these tests can be easily applied in tertiary care settings with minimal infrastructure.

Epidemiology of carbapenem-resistant Klebsiella pneumoniae colonization: a surveillance study at a Turkish university hospital from 2009 to 2013

Between June 2009 and December 2013, 4105 patients were screened for carbapenem-resistant Klebsiella pneumoniae (CR-Kp) colonization in a tertiary care university hospital. The antimicrobial susceptibility and resistance determinants of 279 (6.8%) CR-Kp isolates from single patients were investigated. Additional analysis was performed to evaluate the characteristics and various risk factors for infection in patients with colonization. Of the 279 isolates, 270 harboured OXA-48-like enzymes, and a single isolate harboured IMP-type carbapenemase. A high proportion of isolates were susceptible to carbapenems - except ertapenem. All isolates were susceptible to amikacin and most (94%) were susceptible to colistin and fosfomycin. There was consistent high-level resistance for all isolates to temocillin, piperacillin-tazobactam, amoxicillin-clavulanate and ticarcillin-clavulanate. When colonized and infected patients were compared, only prior carbapenem administration (P = 0.003), was found to be significantly associated with patients with CR-Kp infection.

Epidemiology of antimicrobial resistance in bloodstream infections

Antimicrobial resistance in bacterial pathogens is a worldwide challenge leading high morbidity and mortality in clinical settings. Multidrug resistant patterns in gram-positive and -negative bacteria have resulted in difficult-to-treat or even untreatable infections with conventional antimicrobials. Since the early identification of causative microorganisms and their antimicrobial susceptibility patterns in patients with bacteremia and other serious infections is lacking in many healthcare institutions, broad spectrum antibiotics are liberally and mostly unnecessarily used. Such practice has, in turn, caused dramatic increases in emerging resistance and when coupled with poor practice of infection control, resistant bacteria can easily be disseminated to the other patients and the environment. Thus, availability of updated epidemiological data on antimicrobial resistance in frequently encountered bacterial pathogens will be useful not only for deciding on empirical treatment strategies, but also devising an effective antimicrobial stewardship program in hospitals.

Laboratory Detection and Clinical Implication of Oxacillinase-48 like Carbapenemase: The Hidden Threat

Carbapenemase producing Gram-negative pathogen is of great concern for physician. The challenging aspects are treatment option and infection control. Monitoring of respective carbapenemase resistance mechanism is necessary to prevent the outbreaks. Currently, the rapid emergence of oxacillinase (OXA-48) like is alarming. Increasing frequency of OXA-48 is seen than the classical carbapenemase (KPC, NDM, IMP, and VIM) across the world. The bla OXA-48 gene is commonly identified in Escherichia coli and Klebsiella pneumoniae. The transferrable plasmid of OXA-48 is associated with rapid spread and inter-species dissemination. In general, OXA-48-like enzymes weakly hydrolyzes both carbapenem and broad spectrum cephalosporins. Except OXA-163, which effectively hydrolyze cephalosporin. This poor hydrolytic profile obscures the detection of OXA-48-like. It may go undetected in routine diagnosis and complicates the treatment option. Co-production of OXA-48-like with CTX-M-15 and other carbapenemase (NDM, VIM) leads to the emergence of multidrug resistant strains.

First Detection of OXA-10 Extended-Spectrum Beta-Lactamases and the Occurrence of mexR and nfxB in Clinical Isolates of Pseudomonas aeruginosa from Nigeria

BACKGROUND

The characterization of β-lactamase production in Pseudomonasaeruginosa is rarely reported in Nigeria. The objective of this study was to investigate the occurrence and characterize the different β-lactamases as well as mechanisms of fluoroquinolones resistance among P. aeruginosa isolated from various clinical sources from Nigeria.

MATERIALS AND METHOD

Isolates were investigated using PCR, RFLP and sequencing for the detection of various β-lactamases and efflux pump regulator genes.

RESULT

The prevalence of OXA-10, AmpC, CTX-M and SHV in P. aeruginosa was 80, 70, 5 and 5%, respectively. The coexistence of blaOXA-10 with blaAmpC, blaSHV and blaCTX-M was reported in 40, 5 and 5% of isolates, respectively. The efflux pump regulator genes mexR and nfxB were both amplified in 45% of the OXA-10-positive isolates.

CONCLUSION

This is the first report of the characterization of OXA-10 extended-spectrum β-lactamases and occurrence of mexR and nfxB efflux regulator genes in clinical isolates of P. aeruginosa in Nigeria.

Molecular characterization and risk factors for carbapenem-resistant Gram-negative bacilli colonization in children: emergence of NDM-producing Acinetobacter baumannii in a newborn intensive care unit in Turkey

BACKGROUND

Multidrug-resistant Gram-negative bacilli are responsible for more than 50% of healthcare-associated infections. Colonization dynamics, characteristics, and risk factor data for CR-GNB are scarce in children.

AIM

To examine the molecular characteristics of, and risk factors for nosocomial colonization with, carbapenem-resistant Gram-negative bacilli (CR-GNB) in hospitalized paediatric patients in a tertiary university hospital's paediatric units in Turkey.

METHODS

A prospective case-control study was performed at a university hospital in Istanbul, Turkey.

FINDINGS

A total of 1840 rectal swab specimens were collected from all 762 hospitalized children between March 2013 and October 2013. Among them, 176 (23%) patients were colonized with CR-GNB. Of these, 72 (9%) patients were colonized with carbapenem-resistant Enterobacteriaceae, 138 (18%) with CR-non-fermenter Gram-negative bacilli (CR-NF) and 34 (4%) with both. The median CR-GNB colonization time was 10 days (range: 1-116). The median duration of rectal colonization with CR-GNB was 8 days (range: 1-160). NDM (31%) was the second most frequent carbapenemase identified in Acinetobacter baumannii isolates, and has not previously been detected in Turkey. All of the 17 patients colonized with NDM-producing A. baumannii were newborns in the neonatal intensive care unit. Independent risk factors for CR-GNB colonization were: age <1 year, nasogastric tube placement, presence of underlying chronic diseases, ampicillin usage, surgical intervention, and carbapenem use.

CONCLUSION

This is the first description of NDM in A. baumannii in newborn units in Turkey. Carbapenem usage is a common independent risk factor for both CRE and CR-NF colonization, which underscores the importance of antibiotic stewardship programmes.

Evaluation of carbapenem resistance using phenotypic and genotypic techniques in Enterobacteriaceae isolates

BACKGROUND

Bacterial resistance to antibiotics is increasing worldwide. Antibiotic-resistant strains can lead to serious problems regarding treatment of infection. Carbapenem antibiotics are the final treatment option for infections caused by serious and life-threatening multidrug-resistant gram-negative bacteria. Therefore, an understanding of carbapenem resistance is important for infection control. In the study described herein, the phenotypic and genotypic features of carbapenem-resistant Enterobacteriaceae strains isolated in our hospital were evaluated.

METHODS

In total, 43 carbapenem-resistant strains were included in this study. Sensitivity to antibiotics was determined using the VITEK(®)2 system. The modified Hodge test (MHT) and metallo-β-lactamase (MBL) antimicrobial gradient test were performed for phenotypic identification. Resistance genes IMP, VIM, KPC, NDM-1, and OXA-48 were amplified by multiplex PCR.

RESULTS

The OXA-48 gene was detected in seven strains, and the NDM-1 gene in one strain. No resistance genes were detected in the remainder of strains. A significant correlation was observed between the MHT test and OXA-48 positivity, and between the MBL antimicrobial gradient test and positivity for resistance genes (p < 0.05).

CONCLUSION

The finding of one NDM-1-positive isolate in this study indicates that carbapenem resistance is spreading in Turkey. Carbapenem resistance spreads rapidly and causes challenges in treatment, and results in high mortality/morbidity rates. Therefore, is necessary to determine carbapenem resistance in Enterobacteriaceae isolates and to take essential infection control precautions to avoid spread of this resistance.

First Report of Klebsiella pneumoniae-Carbapenemase-3-Producing Escherichia coli ST479 in Poland

An increase in the antibiotic resistance among members of the Enterobacteriaceae family has been observed worldwide. Multidrug-resistant Gram-negative rods are increasingly reported. The treatment of infections caused by Escherichia coli and other Enterobacteriaceae has become an important clinical problem associated with reduced therapeutic possibilities. Antimicrobial carbapenems are considered the last line of defense against multidrug-resistant Gram-negative bacteria. Unfortunately, an increase of carbapenem resistance due to the production of Klebsiella pneumoniae carbapenemase (KPC) enzymes has been observed. In this study we describe the ability of E. coli to produce carbapenemase enzymes based on the results of the combination disc assay with boronic acid performed according to guidelines established by the European Community on Antimicrobial Susceptibility Testing (EUCAST) and the biochemical Carba NP test. Moreover, we evaluated the presence of genes responsible for the production of carbapenemases (bla_KPC, bla_VIM, bla_IMP, bla_OXA-48) and genes encoding other β-lactamases (bla_SHV, bla_TEM, bla_CTX-M) among E. coli isolate. The tested isolate of E. coli that possessed the bla_KPC-3 and bla_TEM-34 genes was identified. The tested strain exhibited susceptibility to colistin (0.38 μg/mL) and tigecycline (1 μg/mL). This is the first detection of bla_KPC-3 in an E. coli ST479 in Poland.

The difficult-to-control spread of carbapenemase producers among Enterobacteriaceae worldwide

The spread of carbapenemase producers in Enterobacteriaceae has now been identified worldwide. Three main carbapenemases have been reported; they belong to three classes of β-lactamases, which are KPC, NDM, and OXA-48. The main reservoirs of KPC are Klebsiella pneumoniae in the USA, Israel, Greece, and Italy, those of NDM are K. pneumoniae and Escherichia coli in the Indian subcontinent, and those of OXA-48 are K. pneumoniae and Escherichia coli in North Africa and Turkey. KPC producers have been mostly identified among nosocomial isolates, whereas NDM and OXA-48 producers are both nosocomial and community-acquired pathogens. Control of their spread is still possible in hospital settings, and relies on the use of rapid diagnostic techniques and the strict implemention of hygiene measures.

Retrospective identification of a previously undetected clinical case of OXA-48-producing K. pneumoniae and E. coli: the importance of adequate detection guidelines

INTRODUCTION

The laboratory detection of OXA-48-carbapenemase-producing Enterobacteriaceae is difficult, as minimum inhibition concentrations for carbapenems are often below the clinical breakpoint. In 2011, the Dutch national guideline for the detection of highly resistant micro-organisms was issued, which includes recommendations on the use of carbapenem screening breakpoints for the detection of carbapenemase-producing Enterobacteriaceae.

MATERIALS AND METHODS

During a validation study of the Check-MDR CT103 microarray (Check-Points, Wageningen, The Netherlands) in 2013, an OXA-48-like carbapenemase gen was identified in two isolates that were previously obtained from a patient with non-Hodgkin lymphoma in 2007. Whole-genome sequencing (WGS) and subsequent BLAST Ringe Image Generator (BRIG) analysis were performed to establish the presence of OXA-48 carbapenemase encoding plasmids and their similarity.

RESULTS

This case report describes the first documented OXA-48-producing Klebsiella pneumonia (ST648) and Escherichia coli (ST866) in the Netherlands. A similar IncL/M plasmid was identified in both strains, suggesting within-patient horizontal transfer.

CONCLUSION

This case illustrates that OXA-48-carbapenemase-producing Enterobacteriaceae can be unnoticed without adequate laboratory detection procedures. Our observation stresses the importance of uniform and adequate laboratory methods for the timely and accurate detection of important antimicrobial resistance.

Detection of blaIMP4 and blaNDM1 harboring Klebsiella pneumoniae isolates in a university hospital in Malaysia

Background

Antibiotic resistance among Enterobacteriaceae posts a great challenge to the health care service. The emergence of carbapenem-resistant Klebsiella pneumoniae (CRKP) is attracting significant attention due to its rapid and global dissemination. The infection is associated with significant morbidity and mortality, thus creating challenges for infection control and managing teams to curb the infection. In Southeast Asia, there have been limited reports and subsequent research regarding CRKP infections. Thus, the study was conducted to characterize CRKP that has been isolated in our setting.

Methods

A total of 321 K. pneumoniae were included in the study. Each isolate went through an identification process using an automated identification system. Phenotypic characterization was determined using disk diffusion, modified Hodge test, Epsilometer test, and inhibitor combined disk test. Further detection of carbapenemase genes was carried out using polymerase chain reaction and confirmed by gene sequence analysis.

Results

All together, 13 isolates (4.05%) were CRKP and the majority of them were resistant to tested antibiotics except colistin and tigercycline. Among seven different carbapenemase genes studied (bla_KPC, bla_IMP, bla_SME, bla_NDM, bla_IMI, bla_VIM, and bla_OXA), only two, bla_IMP4 (1.87%) and bla_NDM1 (2.18%), were detected in our setting.

Conclusion

Evidence suggests that the prevalence of CRKP in our setting is low, and knowledge of Carbapenem-resistant Enterobacteriaceae and CRKP has improved and become available among clinicians.

Antibiotic resistance and extended spectrum beta-lactamases: Types, epidemiology and treatment

Antibiotic resistance is a problem of deep scientific concern both in hospital and community settings. Rapid detection in clinical laboratories is essential for the judicious recognition of antimicrobial resistant organisms. Production of extended-spectrum β-lactamases (ESBLs) is a significant resistance-mechanism that impedes the antimicrobial treatment of infections caused by Enterobacteriaceae and is a serious threat to the currently available antibiotic armory. ESBLs are classified into several groups according to their amino acid sequence homology. Proper infection control practices and barriers are essential to prevent spread and outbreaks of ESBL producing bacteria. As bacteria have developed different strategies to counter the effects of antibiotics, the identification of the resistance mechanism may help in the discovery and design of new antimicrobial agents. The carbapenems are widely regarded as the drugs of choice for the treatment of severe infections caused by ESBL-producing Enterobacteriaceae, although comparative clinical trials are scarce. Hence, more expeditious diagnostic testing of ESBL-producing bacteria and the feasible modification of guidelines for community-onset bacteremia associated with different infections are prescribed.

Carbapenem-resistant Klebsiella pneumoniae sepsis in corticosteroid receipt mice: tigecycline or colistin monotherapy versus tigecycline/colistin combination

This study compared the effect of monotherapy of colistin, tigecycline, and their combination in sepsis model of mice. OXA-48 producing Carbapenem-resistant Klebsiella pneumoniae (CRKP) strain was used in Balb/c mice. The mice were divided into competent and Methylprednisolone acetate (MPA)-treated groups. Each group was sub-divided into (1) colistin or (2) tigecycline monotherapy and (3) colistin/tigecycline combination therapy. After 3 hours of intraperitoneal bacterial inoculation, antimicrobials were administered, and mice were sacrificed at 24 and 48 hours Time-kill curve study demonstrated that colistin sulphate had early bactericidal activity following re-growth. In competent and MPA-treated groups of mice at 24 hours, bacterial counts in liver samples significantly lowered compared to control, however, there were no statistically differences between monotherapy and combination therapy subgroup. Bacterial count in lung samples of competent group was significantly lesser than control for all three antimicrobial subgroups at 24 hours Colistin plus tigecycline combination therapy was not superior against colistin or tigecycline monotherapy.

First report of KPC-producing Klebsiella pneumoniae in Croatia

In February 2011, a 78-year-old male patient was admitted to Clinical Hospital Center Zagreb with subdural haematoma. Klebsiella pneumoniae with reduced susceptibility to carbapenems was isolated. PCR revealed the presence of bla(KPC), bla(TEM), and bla(SHV) genes. Sequencing of bla(KPC) gene identified K. pneumoniae carbapenemase (KPC)-2 beta-lactamase. The strain belonged to ST37 clone by multilocus sequence typing. Infection control efforts limited the spread of KPC-producing clone of K. pneumoniae in our hospital so far. To our knowledge, this is the first report of a KPC-producing K. pneumoniae in Croatia.

Bloodstream infections caused by IMP-8-producing Enterobacteriaceae isolates: the need for clinical laboratory detection of metallo-β-lactamases?

A retrospective study was conducted at a Taiwanese medical center to characterize bloodstream infections caused by IMP-8 metallo-β-lactamase (MBL)-producing Enterobacteriaceae isolates and to assess the need for laboratory detection of IMP producers. We analyzed 37 patients infected with IMP-8 producers (two Escherichia coli, nine Klebsiella pneumoniae, 25 Enterobacter cloacae, and one Citrobacter freundii) and 107 patients infected with non-IMP-8 producers (eight E. coli, 26 K. pneumoniae, 70 E. cloacae, and three C. freundii) that were interpreted as carbapenem-nonsusceptible based on the updated Clinical and Laboratory Standards Institute (CLSI) 2010 guidelines. Only 18 (48.6 %) of the IMP-8 producers were regarded as potential carbapenemase producers based on the CLSI 2012 guidelines. The production of extended-spectrum β-lactamases (ESBLs) was more common in the MBL group (73.0 %) than in the non-MBL group (41.1 %). There were no significant differences in carbapenem susceptibilities, clinical characteristics, carbapenem use for empirical and definitive treatment, and mortality rates between the two groups. Eighteen IMP-8 producers could be deemed as resistant to all carbapenems [minimum inhibitory concentration (MIC) of any carbapenem ≥2 μg/mL]; patients with these isolates had a lower, but non-significant, 28-day mortality rate (27.8 %) than patients infected with non-MBL producers having similar carbapenem MICs (39.0 %) (p = 0.41). A multivariate analysis revealed severity of acute illness as the single independent variable associated with both 7-day and 28-day mortality rates (p < 0.01) for infections caused by Enterobacteriaceae with decreased carbapenem susceptibilities. Our findings suggest that the clinical detection of IMP-producing Enterobacteriaceae is not required even when the "old" CLSI criteria are used.

OXA-48-like carbapenemases: the phantom menace

OXA-48-type carbapenem-hydrolysing class D β-lactamases are increasingly reported in enterobacterial species. To date, six OXA-48-like variants have been identified, with OXA-48 being the most widespread. They differ by a few amino acid substitutions or deletions (one to five amino acids). The enzymes hydrolyse penicillins at a high level and carbapenems at a low level, sparing broad-spectrum cephalosporins, and are not susceptible to β-lactamase inhibitors. When combining permeability defects, OXA-48-like producers may exhibit a high level of resistance to carbapenems. OXA-163 is an exception, hydrolysing broad-spectrum cephalosporins but carbapenems at a very low level, and being susceptible to β-lactamase inhibitors. The bla(OXA-48)-type genes are always plasmid-borne and have been identified in association with insertion sequences involved in their acquisition and expression. The current spread of the bla(OXA-48) gene is mostly linked to the dissemination of a single IncL/M-type self-transferable plasmid of 62 kb that does not carry any additional resistance gene. OXA-48-type carbapenemases have been identified mainly from North African countries, the Middle East, Turkey and India, those areas constituting the most important reservoirs; however, occurrence of OXA-48 producers in European countries is now well documented, with some reported hospital outbreaks. Since many OXA-48-like producers do not exhibit resistance to broad-spectrum cephalosporins, or only decreased susceptibility to carbapenems, their recognition and detection can be challenging. Adequate screening and detection methods are therefore required to prevent and control their dissemination.

The threat of carbapenem-resistant Enterobacteriaceae in Lebanon: an update on the regional and local epidemiology

Bacterial resistance to antimicrobial agents is increasing. Complex resistant mechanisms have resulted in a wide spectrum of species and strains with multidrug-resistant patterns. In addition to the production of extended-spectrum-β-lactamases (ESBLs), Gram-negative rods have acquired the capacity to hydrolyze carbapenem antibiotics by means of carbapenemases. The enzyme that has gained the most publicity recently is the New Delhi metallo-β-lactamase (NDM-1). This enzyme and others are now spreading from their homeland on the Indian subcontinent to other continents, primarily via medical tourists. This spread contributes to be a global threat in an era when no potent antibiotics are expected to be developed. Patients coming from countries where antimicrobial use is not restricted, such as Iraq, may harbor similar organisms. Reports from the Middle East and Arabian countries describing the occurrence of carbapenem-resistant Enterobacteriaceae are rare. In this communication, an update on the epidemiology, prevalence and mechanisms of carbapenem-resistant Enterobacteriaceae in Lebanon and the surrounding region will be addressed in addition to the detection methods and required infection control practices.

In vitro activity of avibactam (NXL104) in combination with β-lactams against Gram-negative bacteria, including OXA-48 β-lactamase-producing Klebsiella pneumoniae

The objective of this study was to investigate the in vitro antibacterial activity of avibactam (formerly NXL104) in combination with imipenem, cefepime or ceftazidime against Gram-negative bacteria. Bacterial isolates included: Pseudomonas aeruginosa harbouring PER-1 β-lactamase (n=14); Acinetobacter baumannii harbouring PER-1, OXA-51 and OXA-58 (n=20); carbapenem-non-susceptible Klebsiella pneumoniae (n=25) and Escherichia coli (n=1) harbouring OXA-48; carbapenem-non-susceptible E. coli (n=1) harbouring both IMP-1 metallo-β-lactamase and extended-spectrum β-lactamase (ESBL); carbapenem-non-susceptible Serratia marcescens (n=1); and carbapenem-susceptible E. coli (n=20) and K. pneumoniae isolates (n=12) with CTX-M-15 ESBL. Minimum inhibitory concentrations (MICs) of imipenem, cefepime and ceftazidime were determined in combination with 4 mg/L avibactam by the Clinical and Laboratory Standards Institute (CLSI) method on Mueller-Hinton agar. Imipenem/avibactam and ceftazidime/avibactam displayed limited potency against A. baumannii isolates, whereas cefepime/avibactam and ceftazidime/avibactam were active against P. aeruginosa. Klebsiella pneumoniae isolates with OXA-48 β-lactamase were resistant to imipenem [MIC for 90% of the organisms (MIC(90)) ≥4 mg/L]. MIC(90) values for the combination of avibactam 4 mg/L with imipenem, cefepime and ceftazidime were in the susceptible range for all strains (MIC(90)≤0.5mg/L). All E. coli and K. pneumoniae isolates with CTX-M-15 β-lactamase were inhibited at ≤1 mg/L for combinations with avibactam and 100% were susceptible by CLSI breakpoint criteria to imipenem, cefepime and ceftazidime. In conclusion, combinations of imipenem, cefepime and ceftazidime with avibactam may present a promising therapeutic strategy to treat infections due to K. pneumoniae with OXA-48 enzyme as well as K. pneumoniae and E. coli with CTX-M-15 enzyme.

Coexistence of blaOXA48 and aac(6′)-Ib-cr Genes in Klebsiella Pneumoniae Isolates from Istanbul, Turkey

This study evaluated the presence of carbapenem hydrolysing β-lactamase genes and plasmid-mediated quinolone resistance (PMQR) determinants in 22 Klebsiella pneumoniae isolates collected from the Istanbul Medical Faculty, Turkey, which reduced the susceptibility or resistance to carbapenem. The VITEK® 2 system and E-tests were used to determine the minimum inhibitory concentrations needed to inhibit bacterial growth. Genes were screened by polymerase chain reaction, and gene transferability was evaluated by transconjugation. Strain clonality was investigated by pulsed-field gel electrophoresis (PFGE). All strains were OXA-48 β-lactamase producers and three (13.6%) were also positive for the aac(6′)-Ib-cr gene. Most of the strains harboured other b-lactamase (bla) genes such as blaTEM, blaSHV, blaCTX-M and blaVEB-1. The transconjugants mostly harboured blaOXA-48 and other β-lactamases separately. PFGE revealed eight pulsotypes among the isolates. The coexistence of blaOXA-48 and PMQR in K. pneumoniae isolates may present a significant threat to health, especially in the nosocomial setting.