New Delhi metallo-β-lactamase in Klebsiella pneumoniae and Escherichia coli, Canada

Transfer dynamics of antimicrobial resistance among gram-negative bacteria

Antimicrobial resistance (AMR) in gram-negative bacteria (GNBs) is a significant global health concern, exacerbated by mobile genetic elements (MGEs). This review examines the transfer of antibiotic resistance genes (ARGs) within and between different species of GNB facilitated by MGEs, focusing on the roles of plasmids and phages. The impact of non-antibiotic chemicals, environmental factors affecting ARG transfer frequency, and underlying molecular mechanisms of bacterial resistance evolution are also discussed. Additionally, the study critically assesses the impact of fitness costs and compensatory evolution driven by MGEs in host organisms, shedding light on the transfer frequency of ARGs and host evolution within ecosystems. Overall, this comprehensive review highlights the factors and mechanisms influencing ARG movement among diverse GNB species and underscores the importance of implementing holistic One-Health strategies to effectively address the escalating public health challenges associated with AMR.

Aztreonam and avibactam combination therapy for metallo-β-lactamase-producing gram-negative bacteria: a comprehensive review

BACKGROUND

Carbapenem-resistant gram-negative bacteria represent a challenging healthcare threat, accounting for metallo-β-lactamases (MBL) production increase across the world. MBL-producing Enterobacterales and Pseudomonas aeruginosa represent the main target for ultimate antibiotics combinations due to the difficulty to include carbapenems within the antimicrobial treatment.

OBJECTIVES

To provide a comprehensive review of the current knowledge about the aztreonam/avibactam (ATM-AVI) combination, which has emerged as a promising option for treating MBL-producing bacteria.

SOURCES

Relevant in vitro and in vivo studies on ATM-AVI effectiveness.

CONTENT

The review summarizes ATM-AVI characteristics and targets, examining how AVI restores ATM effectiveness against MBLs while protecting it from other β-lactamases. Key in vitro and in vivo studies on ATM-AVI efficacy are presented.

IMPLICATIONS

This review provides insights into the potential clinical management implications of ATM-AVI for treating carbapenem-resistant gram-negative infections, particularly those caused by MBL-producing organisms.

Citrobacter spp. and Enterobacter spp. as reservoirs of carbapenemase blaNDM and blaKPC resistance genes in hospital wastewater

Antibiotic resistance has emerged as a global threat to public health, generating a growing interest in investigating the presence of antibiotic-resistant bacteria in environments influenced by anthropogenic activities. Wastewater treatment plants in hospital serve as significant reservoirs of antimicrobial-resistant bacteria, where a favorable environment is established, promoting the proliferation and transfer of resistance genes among different bacterial species. In our study, we isolated a total of 243 strains from 5 hospital wastewater sites in Mexico, belonging to 21 distinct Gram-negative bacterial species. The presence of β-lactamase was detected in 46.9% (114/243) of the isolates, which belonging to the Enterobacteriaceae family. We identified a total of 169 β-lactamase genes; blaTEM in 33.1%, blaCTX-M in 25.4%, blaKPC in 25.4%, blaNDM 8.8%, blaSHV in 5.3%, and blaOXA-48 in 1.1% distributed in 12 different bacteria species. Among the 114 of the isolates, 50.8% were found to harbor at least one carbapenemase and were discharged into the environment. The carbapenemase blaKPC was found in six Citrobacter spp. and E. coli, while blaNDM was detected in two distinct Enterobacter spp. and E. coli. Notably, blaNDM-1 was identified in a 110 Kb IncFII conjugative plasmid in E. cloacae, E. xiangfangensis, and E. coli within the same hospital wastewater. In conclusion, hospital wastewater showed the presence of Enterobacteriaceae carrying a high frequency of carbapenemase blaKPC and blaNDM. We propose that hospital wastewater serves as reservoirs for resistance mechanism within bacterial communities and creates an optimal environment for the exchange of this resistance mechanism among different bacterial strains.

IMPORTANCE

The significance of this study lies in its findings regarding the prevalence and diversity of antibiotic-resistant bacteria and genes identified in hospital wastewater in Mexico. The research underscores the urgent need for enhanced surveillance and prevention strategies to tackle the escalating challenge of antibiotic resistance, particularly evident through the elevated frequencies of carbapenemase genes such as blaKPC and blaNDM within the Enterobacteriaceae family. Moreover, the identification of these resistance genes on conjugative plasmids highlights the potential for widespread transmission via horizontal gene transfer. Understanding the mechanisms of antibiotic resistance in hospital wastewater is crucial for developing targeted interventions aimed at reducing transmission, thereby safeguarding public health and preserving the efficacy of antimicrobial therapies.

Modified Carbapenem Inactivation Method and Ethylenediaminetetraacetic Acid (EDTA)-Carbapenem Inactivation Method for Detection of Carbapenemase-Producing Enterobacterales and Pseudomonas aeruginosa

INTRODUCTION

The rising incidence of carbapenem resistance in Enterobacterales and Pseudomonas aeruginosa is a concern. Since carbapenemase production is the primary resistance mechanism, detecting and identifying the genes responsible for it is crucial to effectively monitor its spread.

OBJECTIVE

This study aims to detect positivity for the modified carbapenem inactivation method (mCIM) and ethylenediaminetetraacetic acid (EDTA)-carbapenem inactivation method (eCIM) for the detection of carbapenemase-producing Enterobacterales and Pseudomonas aeruginosa.

METHODS

Methods: A cross-sectional study was carried out at a tertiary care hospital, including 250 clinical isolates of Enterobacterales and Pseudomonas aeruginosa. These isolates exhibited resistance to at least one of the carbapenems as determined by the VITEK AST 2 System (bioMérieux, USA). The isolates were subjected to mCIM testing, and those that tested positive were further tested using eCIM. The results were interpreted in accordance with the guidelines provided by the Clinical and Laboratory Standards Institute (CLSI) 2023.

RESULTS

Out of the total 250 carbapenem-resistant Enterobacterales and Pseudomonas aeruginosa isolates, 151 (60.4%) were Klebsiella pneumonia, 44 (17.6%) were Escherichia coli, 10 (4.0%) were Enterobacter cloacae, 6 (2.4%) were Providencia spp., 4 (1.6%) were Serratia marcescens, 4 (1.6%) were Proteus mirabilis and 31 (12.4%) were Pseudomonas aeruginosa. Positivity for the mCIM was observed in 96% (240 out of 250) of the isolates. Of the mCIM-positive isolates, 234 (97.5%) also tested positive for eCIM, indicating metallo-β-Lactamase (MLB) production. A statistically significant association was found between both mCIM and eCIM positivity and the degree of resistance to carbapenem (p<0.05). Conclusion: This study shows that the inexpensive method, a combination of mCIM and eCIM assists in differentiating between serine carbapenemase producers and MLB producers, thereby guiding the selection of appropriate therapy and useful in infection control in resource-limited settings.

Identification of Providencia spp. clinical isolates co-producing carbapenemases IMP-27, OXA-24, and OXA-58 in Mexico

Providencia rettgeri, belonging to the genus Providencia, had gained significant interest due to its increasing prevalence as a common pathogen responsible for healthcare-associated infections in hospitals. P. rettgeri isolates producing carbapenemases have been reported to reduce the efficiency of carbapenems in clinical antimicrobial therapy. However, coexistence with other resistance determinants is rarely reported. The goal of this study was the molecular characterization of carbapenemase-producing Providencia spp. clinical isolates. Among 23 Providencia spp. resistant to imipenem, 21 were positive to blaNDM-1; one positive to blaNDM-1 and blaOXA-58 like; and one isolate co-producing blaIMP-27, blaOXA-24/40 like, and blaOXA-58 like were identified. We observed a low clonal relationship, and the incompatibility groups Col3M and ColRNAI were identified in the plasmid harboring blaNDM-1. We report for the first time a P. rettgeri strain co-producing blaIMP-27, blaOXA-24-like, and blaOXA-58 like. The analysis of these resistance mechanisms in carbapenemase co-producing clinical isolates reflects the increased resistance.

Occurrence and mechanisms of tigecycline resistance in carbapenem- and colistin-resistant Klebsiella pneumoniae in Thailand

Tigecycline has been regarded as one of the most important last-resort antibiotics for the treatment of infections caused by extensively drug-resistant (XDR) bacteria, particularly carbapenem- and colistin-resistant Klebsiella pneumoniae (C-C-RKP). However, reports on tigecycline resistance have been growing. Overall, ~ 4000 K. pneumoniae clinical isolates were collected over a five-year period (2017-2021), in which 240 isolates of C-C-RKP were investigated. Most of these isolates (91.7%) were resistant to tigecycline. Notably, a high-risk clone of ST16 was predominantly identified, which was associated with the co-harboring of blaNDM-1 and blaOXA-232 genes. Their major mechanism of tigecycline resistance was the overexpression of efflux pump acrB gene and its regulator RamA, which was caused by mutations in RamR (M184V, Y59C, I141T, A28T, C99/C100 insertion), in RamR binding site (PI) of ramA gene (C139T), in MarR (S82G), and/or in AcrR (L154R, R13Q). Interestingly, four isolates of ST147 carried the mutated tet(A) efflux pump gene. To our knowledge, this is the first report on the prevalence and mechanisms of tigecycline resistance in C-C-RKP isolated from Thailand. The high incidence of tigecycline resistance observed among C-C-RKP in this study reflects an ongoing evolution of XDR bacteria against the last-resort antibiotics, which demands urgent action.

An observational study on carbapenem-resistant Enterobacterales (CRE) colonisation and subsequent risk of infection in an adult intensive care unit (ICU) at a tertiary care hospital in India

Background

Carbapenem-resistant Enterobacterales (CRE) are a global health problem with a growing prevalence. India has a high prevalence of CRE. CRE infections are difficult to treat, and are associated with significant morbidity and mortality. Colonisation is generally a prerequisite for infection and the prevention of CRE colonisation is key to the prevention of CRE infection.

Objectives

To determine the prevalence of CRE colonisation and subsequent infections in an adult intensive care unit (ICU) in India.

Methods

We conducted a prospective observational study in which perirectal swabs were obtained along with relevant clinical details of consenting adult patients upon ICU admission between January 2019 and August 2020. Rectal screening was performed using MacConkey agar plates with ertapenem disks and further identification was performed using conventional microbiological techniques. Ertapenem minimum inhibitory concentration (MIC) was determined using an epsillometer (E) test. The modified carbapenem inactivation (mCIM) test and EDTA carbapenem inactivation test (eCIM) were performed to confirm carbapenem resistance using the Clinical Laboratory Standards Institute (CLSI) 2020 guidelines.

Results

192 ICU patients were screened for CRE. 37 patients were found to be colonised with CRE. Klebsiella pneumoniae (N=25; 67.6%) was the most frequent CRE isolate, followed by Escherichia coli (N=11; 29.7%) and one Enterobacter species (N=1; 2.7%). 89.2% (33/37) patients developed CRE infection. Pneumonia was the most common CRE infection identified in 12/33 (36.4%) patients.during the hospital stay. The median duration of hospital stay was longer (17 days) for CRE colonised compared to CRE non-colonised patients (9 days) (P<0.001). Death occurred in 27 % (N=10/37) of CRE-colonised patients during the hospital admission.

Conclusion

CRE colonisation is associated with high risk of subsequent CRE infection and longer ICU and hospital admission.

Distribution of Antibiotic Resistance in a Mixed-Use Watershed and the Impact of Wastewater Treatment Plants on Antibiotic Resistance in Surface Water

The aquatic environment has been recognized as a source of antibiotic resistance (AR) that factors into the One Health approach to combat AR. To provide much needed data on AR in the environment, a comprehensive survey of antibiotic-resistant bacteria (ARB), antibiotic resistance genes (ARGs), and antibiotic residues was conducted in a mixed-use watershed and wastewater treatment plants (WWTPs) within the watershed to evaluate these contaminants in surface water. A culture-based approach was used to determine prevalence and diversity of ARB in surface water. Low levels of AR Salmonella (9.6%) and Escherichia coli (6.5%) were detected, while all Enterococcus were resistant to at least one tested antibiotic. Fewer than 20% of extended-spectrum β-lactamase (ESBL)-producing Enterobacteriaceae (17.3%) and carbapenem-resistant Enterobacteriaceae (CRE) (7.7%) were recovered. Six ARGs were detected using qPCR, primarily the erythromycin-resistance gene, ermB. Of the 26 antibiotics measured, almost all water samples (98.7%) had detectable levels of antibiotics. Analysis of wastewater samples from three WWTPs showed that WWTPs did not completely remove AR contaminants. ARGs and antibiotics were detected in all the WWTP effluent discharges, indicating that WWTPs are the source of AR contaminants in receiving water. However, no significant difference in ARGs and antibiotics between the upstream and downstream water suggests that there are other sources of AR contamination. The widespread occurrence and abundance of medically important antibiotics, bacteria resistant to antibiotics used for human and veterinary purposes, and the genes associated with resistance to these antibiotics, may potentially pose risks to the local populations exposed to these water sources.

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%).

Benzoxazine-grafted-chitosan biopolymer films with inherent disulfide linkage: Antimicrobial properties

Synthesis and fabrication of naturally sourced biopolymers, especially chitosan, grafted with renewable small molecules have recently attracted attention as efficient antimicrobial agents and are highly desired for sustainable material development. Advantageous inherent functionalities in biobased benzoxazine extend the possibility of crosslinking with chitosan which holds immense potential. Herein, a low-temperature, greener facile methodology is adopted for the covalent confinement of benzoxazine monomers bearing aldehyde and disulfide linkages within chitosan to form benzoxazine-grafted-chitosan copolymer films. The association of benzoxazine as Schiff base, hydrogen bonding, and ring-opened structures enabled the exfoliation of chitosan galleries, and such host-guest mediated interactions demonstrated outstanding properties like hydrophobicity, good thermal, and solution stability due to the synergistic effects. Furthermore, the structures empowered excellent bactericidal properties against both E. coli and S. aureus as investigated by GSH loss, live/dead fluorescence microscopy, and morphological alteration on the cell surface by SEM. The work provides the benefits of disulfide-linked benzoxazines on chitosan, offering a promising avenue for general and eco-friendly usage in wound-healing and packaging material.

Meropenem MICs at Standard and High Inocula and Mutant Prevention Concentration Inter-Relations: Comparative Study with Non-Carbapenemase-Producing and OXA-48-, KPC- and NDM-Producing Klebsiella pneumoniae

The minimal inhibitory concentration (MIC) is conventionally used to define in vitro levels of susceptibility or resistance of a specific bacterial strain to an antibiotic and to predict its clinical efficacy. Along with MIC, other measures of bacteria resistance exist: the MIC determined at high bacterial inocula (MIC_HI) that allow the estimation of the occurrence of inoculum effect (IE) and the mutant prevention concentration, MPC. Together, MIC, MIC_HI and MPC represent the bacterial "resistance profile". In this paper, we provide a comprehensive analysis of such profiles of K. pneumoniae strains that differ by meropenem susceptibility, ability to produce carbapenemases and specific carbapenemase types. In addition, we have analyzed inter-relations between the MIC, MIC_HI and MPC for each tested K. pneumoniae strain. Low IE probability was detected with carbapenemase-non-producing K. pneumoniae, and high IE probability was detected with those that were carbapenemase-producing. MICs did not correlate with the MPCs; significant correlation was observed between the MIC_HIs and the MPCs, indicating that these bacteria/antibiotic characteristics display similar resistance properties of a given bacterial strain. To determine the possible resistance-related risk due to a given K. pneumoniae strain, we propose determining the MIC_HI. This can more or less predict the MPC value of the particular strain.

Vibrio cholerae O1 associated with recent endemic cholera shows temporal changes in serotype, genotype, and drug-resistance patterns in Bangladesh

BACKGROUND

Despite the advancement in our understanding of cholera and its etiological agent, Vibrio cholerae, the prevention and treatment of the disease are often hindered due to rapid changes in drug response pattern, serotype, and the major genomic islands namely, the CTX-prophage, and related genetic characteristics. In the present study, V. cholerae (n = 172) associated with endemic cholera in Dhaka during the years 2015-2021 were analyzed for major phenotypic and genetic characteristics, including drug resistance patterns.

RESULTS

Results revealed that the V. cholerae strains belonged to serogroup O1 biotype El Tor carrying El Tor -specific genes rtxC, tcpA El Tor, and hlyA El Tor, but possessed classical-biotype cholera toxin. Serotypes of V. cholerae strains differed temporally in predominance with Inaba during 2015-2017, and again in 2020-2021, while Ogawa was the predominant serotype in 2018-2019. Also, ctxB1 was predominant in V. cholerae associated with cholera during 2015-2017, while ctxB7 was predominant in 2018, and in the subsequent years, as observed until 2021. V. cholerae strains differed in their antibiotic resistance pattern with a majority (97%) being multi-drug resistant (MDR) and belonging to six sub-groups. Notably, one of these MDR strains was resistant to eleven of the eighteen antibiotics tested, with resistance to fourth-generation cephalosporin (cefepime), and aztreonam. This extreme drug resistant (XDR) strain carried resistance-related genes namely, extended-spectrum β-lactamases (ESBL), blaOXA-1 and blaPER-3.

CONCLUSION

The observed temporal switching of serotypes, as well as the ctxB genotype, and the emergence of MDR/XDR V. cholerae and their association with endemic cholera in Dhaka underscore the need for routine monitoring of the pathogen for proper patient management.

The Impact of Harsh Stratospheric Conditions on Survival and Antibiotic Resistance Profile of Non-Spore Forming Multidrug Resistant Human Pathogenic Bacteria Causing Hospital-Associated Infections

Bacteria are constantly being lifted to the stratosphere due to air movements caused by weather phenomena, volcanic eruptions, or human activity. In the upper parts of the atmosphere, they are exposed to extremely harsh and mutagenic conditions such as UV and space radiation or ozone. Most bacteria cannot withstand that stress, but for a fraction of them, it can act as a trigger for selective pressure and rapid evolution. We assessed the impact of stratospheric conditions on the survival and antibiotic resistance profile of common non-spore-forming human pathogenic bacteria, both sensitive and extremely dangerous multidrug-resistant variants, with plasmid-mediated mechanisms of resistance. Pseudomonas aeruginosa did not survive the exposure. In the case of strains that were recovered alive, the survival was extremely low: From 0.00001% of Klebsiella pneumoniae carrying the ndm-1 gene and methicillin-resistant Staphylococcus aureus mecA-positive with reduced susceptibility to vancomycin (MRSA/VISA), to a maximum of 0.001% of K. pneumoniae sensitive to all common antibiotics and S. aureus sensitive to vancomycin (MRSA/VSSA). We noticed a tendency towards increased antibiotic susceptibility after the stratospheric flight. Antimicrobial resistance is a current real, global, and increasing problem, and our results can inform current understandings of antibiotic resistance mechanisms and development in bacteria.

A Comprehensive Genomic Analysis of the Emergent Klebsiella pneumoniae ST16 Lineage: Virulence, Antimicrobial Resistance and a Comparison with the Clinically Relevant ST11 Strain

Klebsiella pneumoniae is considered an opportunistic pathogen frequently involved with healthcare-associated infections. The genome of K. pneumoniae is versatile, harbors diverse virulence factors and easily acquires and exchanges resistance plasmids, facilitating the emergence of new threatening clones. In the last years, ST16 has been described as an emergent, clinically relevant strain, increasingly associated with outbreaks, and carrying virulence factors (such as ICEKp, iuc, rmpADC/2) and a diversity of resistance genes. However, a far-reaching phylogenetic study of ST16, including geographically, clinically and temporally distributed isolates is not available. In this work, we analyzed all publicly available ST16 K. pneumoniae genomes in terms of virulence factors, including capsular lipopolysaccharide and polysaccharide diversity, plasmids and antimicrobial resistance genes. A core genome SNP analysis shows that less than 1% of studied sites were variant sites, with a median pairwise single nucleotide polymorphism difference of 87 SNPs. The number and diversity of antimicrobial resistance genes, but not of virulence-related genes, increased consistently in ST16 strains during the studied period. A genomic comparison between ST16 and the high-risk clone ST11 K. pneumoniae, showed great similarities in their capacity to acquire resistance and virulence markers, differing mostly in the great diversity of capsular lipopolysaccharide and polysaccharide types in ST11, in comparison with ST16. While virulence and antimicrobial resistance scores indicated that ST11 might still constitute a more difficult-to-manage strain, results presented here demonstrate the great potential of the ST16 clone becoming critical in public health.

Characterisation of Non-Carbapenemase-Producing Carbapenem-Resistant Klebsiella pneumoniae Based on Their Clinical and Molecular Profile in Malaysia

Non-carbapenemase-producing carbapenem-resistant Klebsiella pneumoniae (NC-CRKP) confers carbapenem resistance through a combination of chromosomal mutations and acquired non-carbapenemase resistance mechanisms. In this study, we aimed to evaluate the clinical and molecular profiles of NC-CRKP isolated from patients in a tertiary teaching hospital in Malaysia from January 2013 to October 2019. During the study period, 54 NC-CRKP-infected/colonised patients’ isolates were obtained. Clinical parameters were assessed in 52 patients. The all-cause in-hospital mortality rate among NC-CRKP patients was 46.2% (24/52). Twenty-three (44.2%) patients were infected, while others were colonised. Based on the Charlson Comorbidity Index (CCI) score, 92.3% (48/52) of the infected/colonised patients had a score of ≥ 1. Resistance genes found among the 54 NC-CRKP isolates were bla_TEM, bla_SHV, bla_CTX-M, bla_OXA, and bla_DHA. Porin loss was detected in 25/54 (46.3%) strains. None of the isolated strains conferred carbapenem resistance through the efflux pumps system. In conclusion, only 25/54 (46.3%) NC-CRKP conferred carbapenem resistance through a combination of porin loss and the acquisition of non-carbapenemase resistance mechanisms. The carbapenem resistance mechanisms for the remaining strains (53.7%) should be further investigated as rapid identification and distinction of the NC-CRKP mechanisms enable optimal treatment and infection control efforts.

Tetracycline-Resistant, Third-Generation Cephalosporin-Resistant, and Extended-Spectrum β-Lactamase-Producing Escherichia coli in a Beef Cow-Calf Production System

ABSTRACT

Cow-calf production plays a significant role in the beef production chain. However, bacteria in these systems are not typically monitored for antimicrobial resistance (AMR). We determined the baseline level of AMR in fecal bacteria collected from preweaned calves prior to feedlot entry and evaluated the effects of type of graze and age on AMR occurrence. Two grazing experiments (16 cow-calf pairs each) were conducted on tall fescue or wheat. Fecal samples were cultured for the detection of tetracycline-resistant (TETr), third-generation cephalosporin-resistant (3GCr), and extended-spectrum β-lactamase (ESBL)-producing Escherichia coli. Isolates were characterized for resistance to other antibiotics and resistance mechanisms. Concentrations (P < 0.001) and prevalence (P = 0.007) of TETrE. coli isolates were significantly higher in the calves (5.1 log CFU/g and 93%, respectively) than in the cows (4.4 log CFU/g and 80%, respectively). Wheat grazing did not affect TETr isolates phenotypically; however, it significantly expanded (P = 0.005) the resistant population carrying tet(A) over that carrying tet(B). Fecal prevalence of 3GCr and ESBL-producing isolates was 31.3 and 3.4%, respectively, with no significant effects of age (P = 0.340) or wheat grazing (P = 0.597). All 3GCr and ESBL-producing isolates were multidrug resistant (resistant to at least three antimicrobial classes). 3GCr isolates were positive for blaCMY-2 (73%) or blaCTX-M (27%), and blaCTX-M-15 was the most prevalent gene (94%, n = 17) among the CTX-M-positive isolates. Wheat grazing significantly expanded (P < 0.001) the 3GCr population carrying blaCTX-M and reduced the population carrying blaCMY-2. Five of the seven ESBL-producing isolates were positive for blaCTX-M. Our study revealed age-dependent occurrence of TETrE. coli and that wheat grazing expanded the resistant population carrying certain resistance genes. Cow-calf production is a significant reservoir for antibiotic-resistant bacteria of significant public health importance such as 3GCr and CTX-M ESBL-producing E. coli.

HIGHLIGHTS

Klebsiella pneumoniae ST147: and then there were three carbapenemases

Gram-negative bacteria containing three different carbapenemases are extremely rare. Klebsiella pneumoniae (N22-925) with KPC-2, NDM-1, and OXA-48 was obtained from a Canadian patient with recent hospitalization in Romania. Short and long read whole genome sequencing showed that the bla_KPC-2 was situated on a 214 kb IncFIB(K)/IncFII(K) plasmid, the bla_NDM-1 on a 104 kb IncFIB (pQil)/IncFII(K) plasmid, and the bla_OXA-48 on a 64 kb IncL plasmid. These plasmids were conjugated to Escherichia coli J53. N22-925 belonged to a unique ST147 cluster that is likely endemic in Romania. This case emphasizes the need for rapid carbapenemase screening in patients from endemic regions. We described the first complete genome sequence of a K. pneumoniae isolate with three different carbapenemases, providing a reference for future studies on this rarely reported occurrence.

One Health Genomic Analysis of Extended-Spectrum β-Lactamase‒Producing Salmonella enterica, Canada, 2012‒2016

Extended-spectrum β-lactamases (ESBLs) confer resistance to extended-spectrum cephalosporins, a major class of clinical antimicrobial drugs. We used genomic analysis to investigate whether domestic food animals, retail meat, and pets were reservoirs of ESBL-producing Salmonella for human infection in Canada. Of 30,303 Salmonella isolates tested during 2012–2016, we detected 95 ESBL producers. ESBL serotypes and alleles were mostly different between humans (n = 54) and animals/meat (n = 41). Two exceptions were bla_SHV-2 and bla_CTX-M-1 IncI1 plasmids_, which were found in both sources. A subclade of S. enterica serovar Heidelberg isolates carrying the same IncI1-bla_SHV-2 plasmid differed by only 1–7 single nucleotide variants. The most common ESBL producer in humans was Salmonella Infantis carrying bla_CTX-M-65, which has since emerged in poultry in other countries. There were few instances of similar isolates and plasmids, suggesting that domestic animals and retail meat might have been minor reservoirs of ESBL-producing Salmonella for human infection.

Fate of antibiotic resistant genes in wastewater environments and treatment strategies - A review

Antibiotic-resistant bacteria (ARB) and antibiotic-resistant genes (ARGs) have emerged in aquatic environments through the discharge of large amounts of antibiotics into wastewater. Well-designed wastewater treatment plants (WWTPs) with effective treatment processes are essential to prevent the release of ARGs directly into the environment. Although some systematic sequential treatment methods are used to remove ARGs, considerable gaps in removal mechanisms will be discussed. Therefore, deep analysis and discussion of various treatment methods are required to understand the ARGs removal mechanisms. In this manuscript, the role of antibiotics and the resistance mechanism of ARB are discussed in depth. In addition, the fate of ARGs in an aquatic environment and detection methods are compared comprehensively and discussed. In particular, the advantages and disadvantages of various methods are summarized and reviewed critically. Finally, combined technologies, such as advanced oxidation process (AOP) with biochemical systems, membrane separation with electrochemical AOP, ultrafiltration (UF) membrane coupled with photocatalytic treatment, and UF membrane separation coupled with sonication, are introduced. Overall, low-energy anaerobic treatment reactors with any of the above combined treatments might reduce the discharge of large quantities of ARGs into the environment. Finally, this review provides valuable insights for better ARG removal technologies by introducing combined effective treatment strategies used in real WWTPs.

Carbapenem-resistant Escherichia coli from shrimp and salmon available for purchase by consumers in Canada: a risk profile using the Codex framework

Resistance to carbapenems in human pathogens is a growing clinical and public health concern. The carbapenems are in an antimicrobial class considered last-resort, they are used to treat human infections caused by multidrug-resistant Enterobacterales, and they are classified by the World Health Organization as 'High Priority Critically Important Antimicrobials'. The presence of carbapenem-resistant Enterobacterales (CREs) of animal-origin is of concern because targeted studies of Canadian retail seafood revealed the presence of carbapenem resistance in a small number of Enterobacterales isolates. To further investigate this issue, a risk profile was developed examining shrimp and salmon, the two most important seafood commodities consumed by Canadians and Escherichia coli, a member of the Enterobacterales order. Carbapenem-resistant E. coli (CREc) isolates have been identified in shrimp and other seafood products. Although carbapenem use in aquaculture has not been reported, several classes of antimicrobials are utilised globally and co-selection of antimicrobial-resistant microorganisms in an aquaculture setting is also of concern. CREs have been identified in retail seafood purchased in Canada and are currently thought to be uncommon. However, data concerning CRE or CREc occurrence and distribution in seafood are limited, and argue for implementation of ongoing or periodic surveillance.

Isolating and sequencing vB_Kpn_3, a lytic bacteriophage against multidrug-resistant Klebsiella pneumoniae

Aim: Phage therapy, as an effective and specific method in the treatment of multidrug-resistant (MDR) bacterial infections, has attracted the attention of many researchers. Methods and results: In this study, a double-stranded DNA phage with the ability of lysing some strains of MDR Klebsiella pneumoniae (vB_Kpn_3) was isolated from hospitals' wastewater and then characterized morphologically and genetically. Transmission electron microscopy and genetic analyses have revealed that vB_Kpn_3 is a member of Siphoviridae family. One-step growth curve also showed a burst time of 35 min and a burst size of 31 PFU/ml. The genome of the phage is composed of 112,080 bp with 41.33% G + C content carrying 186 open reading frames. Conclusion: vB_Kpn_3 is a broad host range phage that infects MDR K. pneumoniae and some other species of Enterobacteriaceae such as Escherichia coli and Salmonella typhi. In addition, no antibiotic resistance and toxin genes were detected in its genome.

Colistin Resistance in Monophasic Isolates of Salmonella enterica ST34 Collected From Meat-Derived Products in Spain, With or Without CMY-2 Co-production

Colistin is a last-resort antibiotic in fighting severe infections caused by multidrug resistant Gram negative pathogens in hospitals. Zoonotic bacteria acquire colistin resistance in animal reservoirs and mediate its spread along the food chain. This is the case of non-typhoid serovars of Salmonella enterica. Colistin-resistant S. enterica in foods represents a threat to human health. Here, we assessed the prevalence of colistin-resistance in food-borne isolates of S. enterica (2014–2019; Asturias, Spain), and established the genetic basis and transferability of this resistance. Five out of 231 isolates tested (2.2%) were resistant to colistin. Four of them, belonging to the European monophasic ST34 clone of S. Typhimurium, were characterized in the present study. They were collected from pork or pork and beef meat-derived products, either in 2015 (three isolates) or 2019 (one isolate). Molecular typing with XbaI-PFGE and plasmid profiling revealed distinct patterns for each isolate, even though two of the 2015 isolates derived from the same sample. The MICs of colistin ranged from 8 to 16 mg/L. All isolates carried the mcr-1.1 gene located on conjugative plasmids of the incompatibility groups IncX4 (2015 isolates) or IncHI2 (2019 isolate). Apart from colistin resistance, the four isolates carried chromosomal genes conferring resistance to ampicillin, streptomycin, sulfonamides and tetracycline [bla_TEM–1, strA-strB, sul2, and tet(B)] and heavy metals, including copper and silver (silESRCFBAGP and pcoGE1ABCDRSE2), arsenic (arsRSD2A2BCA1D1) ± mercury (merEDACPTR), which are characteristically associated with the European ST34 monophasic clone. The 2019 isolate was also resistant to other antibiotics, comprising third generation cephalosporins and cephamycins. The latter phenotype was conferred by the bla_CMY–2 gene located on an IncI1-I(α)-ST2 plasmid. Results in the present study identified meat-derived products as a reservoir of a highly successful clone harboring transferable plasmids which confer resistance to colistin and other clinically important antibiotics. An important reduction in the number of food-borne S. enterica detected during the period of the study, together with the low frequency of colistin resistance, underlines the success of One Health initiatives, such as those implemented at the UE, to control zoonotic bacteria along the food chain and to halt the spread of antimicrobial resistance.

β-Lactam Resistance Gene NDM-1 in the Aquatic Environment: A Review

New Delhi Metallo-β-lactamase-1 (NDM-1) offers carbapenem antibiotics resistance that creates an evolving challenge in treating bacterial infections. NDM-1-bearing strains were observed in surface waters around New Delhi in 2010 and after then identified globally. The usage of antibiotics may hasten the growth of the NDM-1-producing bacteria, which pose severe hazards to human and animal health. The emergence of the NDM-1 in the aquatic environment is turning out to be a growing concern worldwide. NDM-1 gene conferring resistance to a widespread class of antibiotics has been observed in bacteria disseminated in animal production wastewaters, hospital sewage, domestic sewage, industrial effluents, wastewater treatment plants, drinking water, surface water, and even in groundwater. This review recapitulates the currently published research studies on the prevalence and geographical distribution of the NDM-1 gene in the aquatic environment, its habitats, and healthcare risk associated with NDM-1-producing bacteria, in addition to molecular techniques employed to reveal the occurrence of the NDM-1 in the aquatic environment, including conventional polymerase chain reaction, real-time qPCR, DNA hybridization, and microarray-based methods.

Virulence characterization and clonal analysis of uropathogenic Escherichia coli metallo-beta-lactamase-producing isolates

Background

Uropathogenic Escherichia coli (UPEC) is a major cause of urinary tract infection (UTI); however, treatment of UTI has been challenging due to increased antimicrobial resistance (AMR). One of the most important types of AMR is carbapenem resistance (CR). CR bacteria are known as an important threat to global public health today. Class B metallo-beta-lactamases (MBLs) are one of the major factors for resistance against carbapenems. We aimed to investigate the characteristics of UPEC isolates producing MBL.

Methods

A cross-sectional study was conducted from October 2018 to December 2019 in Ahvaz; Iran. UPEC isolates were identified by biochemical and molecular methods. Metallo-beta-lactamase-producing isolates were detected using modified carbapenem inactivation method (mCIM) and EDTA-CIM (eCIM) tests. MBL genes, phylogenetic group, and virulence genes profile of carbapenem resistant isolates were determined. Conjugation assay and plasmid profiling were conducted to evaluate the ability of transferring of CR to other E. coli isolates. Clonal similarity of isolates were assessed using Enterobacterial intergenic repetitive element sequence (ERIC)-PCR.

Results

Among 406 UPEC isolates, 12 (2.95%) carbapenem-resistant were detected of which 11 were phenotypically MBL-producing strains. Four isolates were resistant to all investigated antimicrobial agents and were considered possible pandrug-resistant (PDR). bla_NDM, bla_OXA-48, bla_IMP-1, and bla_IMP-2 genes were found in 9, 5, 1, and 1 isolates, respectively. Among 30 virulence genes investigated, the traT, fyuA followed by fimH, and iutA with the frequency of 8 (66.7%), 8 (66.7%), 7 (58.3%), and 7 (58.3%) were the most identified genes, respectively. Siderophore production was the main virulence trait among carbapenem-resistant UPEC isolates. Except for two, all other isolates showed weak to moderate virulence index. In all recovered isolates, CR was readily transmitted via plasmids to other isolates during conjugation experiments.

Conclusion

MBL and carbapenemase genes, especially bla_NDM and bla_OXA-48 are spreading rapidly among bacteria, which can be a threat to global public health. Therefore monitoring the emergence and dissemination of new AMR is necessary to continuously refine guidelines for empiric antimicrobial therapy. Understanding the mechanisms of resistance and virulence in this group of bacteria can play an effective role in providing new therapeutic methods.

Nucleic acid amplification-based microfluidic approaches for antimicrobial susceptibility testing

Because of the global spread of antimicrobials, there is an urgent need to develop rapid and effective tools for antimicrobial susceptibility testing to help clinicians prescribe accurate and appropriate antibiotic doses sooner. The conventional methods for antimicrobial susceptibility testing are usually based on bacterial culture methods, which are time-consuming, complicated, and labor-intensive. Therefore, other approaches are needed to address these issues. Recently, microfluidic technology has gained significant attention in infection management due to its advantages including rapid detection, high sensitivity and specificity, highly automated assay, simplicity, low cost, and potential for point-of-care testing in low-resource areas. Microfluidic advances for antimicrobial susceptibility testing can be classified into phenotypic (usually culture-based) and genotypic tests. Genotypic antimicrobial susceptibility testing is the detection of resistant genes in a microorganism using methods such as nucleic acid amplification. This review (with 107 references) surveys the different forms of nucleic acid amplification-based microdevices used for genotypic antimicrobial susceptibility testing. The first section reviews the serious threat of antimicrobial-resistant microorganisms and the urgent need for fast check-ups. Next, several conventional antimicrobial susceptibility testing methods are discussed, and microfluidic technology as a promising candidate for rapid detection of antimicrobial-resistant microorganisms is briefly introduced. The next section highlights several advancements of microdevices, with an emphasis on their working principles and performance. The review concludes with the importance of fully integrated microdevices and a discussion on future perspectives.

Effect of Synergistic Action of Bovine Lactoferrin with Antibiotics on Drug Resistant Bacterial Pathogens

Background and Objectives: The multidrug resistant (MDR) bacterial pathogenic infection is one of the chief worldwide public health threat to humanity. The development of novel antibiotics against MDR Gram negative bacteria has reduced over the last half century. Research is in progress regarding the treatment strategies that could be engaged in combination with antibiotics to extend the duration of these life-saving antibacterial agents. The current study was therefore planned to assess the synergistic effects of bovine lactoferrin (bLF) in combination with different antibiotics that are conventionally used. This synergism would provide a newer therapeutic choice against MDR pathogens. LF is present in mucosal secretions, vastly in milk. LF is considered an important constituent in host defense. In previous reports, LF has been co-administered as a combination antibiotic therapy. Materials and Methods: This study included synergistic (LF + appropriate antibiotic) exposure against 147 locally encountered bacterial pathogens, which were completely characterized strains. The anti-biofilm effects and the outcome of bLF on minimum inhibitory concentrations (MICs) of antibacterials on clinical MDR bacterial pathogens were determined by standard techniques. Results: In our study, synergism of bLF with antibacterial agents were reproducible and found to be significant. LF on its own had an important effect of inhibiting the biofilm production of some significant bacterial pathogens. Conclusion: The results of this study provides useful data on the antibacterial potential of the combination of LF with antibiotics against drug resistant pathogens.

Resistance determinants and their genetic context in enterobacteria from a longitudinal study of pigs reared under various husbandry conditions

Pigs are major reservoirs of resistant Enterobacteriaceae that can reach humans through consumption of contaminated meat or vegetables grown in manure-fertilized soil. Samples were collected from sows during lactation and their piglets at five time points spanning the production cycle. Cefotaxime-resistant bacteria were quantified and isolated from feed, feces, manures and carcasses of pigs reared with penicillin-using or antibiotic-free husbandries. The isolates were characterized by antibiotic susceptibility testing, whole genome sequencing and conjugation assays. The extended spectrum β-lactamase (ESBL) phenotype was more frequent in isolates originating from antibiotic-free animals, while the bacteria isolated from penicillin-using animals were on average resistant to a greater number of antibiotics. The ESBL-encoding genes identified were bla _CTX-M-1, bla _CTX-M-15 and bla _CMY-2 and they co-localised on plasmids with various genes encoding resistance to ß-lactams, co-trimoxazole, phenicols and tetracycline, all antibiotics used in pig production. Groups of genes conferring the observed resistance and the mobile elements disseminating multidrug resistance were determined. The observed resistance to ß-lactams was mainly due to the complementary actions of penicillin-binding proteins, an efflux pump and ß-lactamases. Most resistance determinants were shared by animals raised with or without antimicrobials. This suggests a key contribution of indigenous enterobacteria maternally transmitted along the sow lineage, regardless of antimicrobial use. It is unclear if the antimicrobial resistance observed in the enterobacteria populations of the commercial pig herds studied were present before the use of antibiotics, or the extent to which historical antimicrobial use exerted a selective pressure defining the resistant bacterial populations in farms using penicillin prophylaxis.Importance: Antimicrobial resistance is a global threat that needs to be fought on numerous fronts along the One Health continuum. Vast quantities of antimicrobials are used in agriculture to ensure animal welfare and productivity, and are arguably a driving force for the persistence of environmental and food-borne resistant bacteria. This study evaluated the impact of conventional, organic and other antibiotic-free husbandry practices on the frequency and nature of antimicrobial resistance genes and multidrug resistant enterobacteria. It provides knowledge about the relative contribution of specific resistance determinants to observed antibiotic resistance. It also showed the clear co-selection of genes coding for extended-spectrum beta-lactamases and genes coding for the resistance to antibiotics commonly used for prophylaxis or in curative treatments in pig operations.

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.

Clonal relatedness in the acquisition of intestinal carriage and transmission of multidrug resistant (MDR) Klebsiella pneumoniae and Escherichia coli and its risk factors among preterm infants admitted to the neonatal intensive care unit (NICU)

BACKGROUND

Gastrointestinal carriage of multidrug resistant (MDR) Gram-negative bacilli, especially Klebsiella pneumoniae and Escherichia coli, was highly associated with severe nosocomial infections. The main objectives of this study were to determine the clonal relatedness of intestinal carriage and transmission risk factors of MDR E. coli and K. pneumoniae amongst preterm infants admitted to the neonatal intensive care unit (NICU).

METHODS

A prospective cohort study of preterm infants with gestational age < 37 weeks was conducted in the NICU of the University of Malaya Medical Centre (UMMC). Infants' stool specimens were collected on day 1 (meconium), week 1, week 2, week 8 and week 10 during their admission (from 1st June to 31st August 2017) until discharge. The presence and antibiotic resistance pattern of MDR E. coli and K. pneumoniae were determined. Strain clonality and relatedness were explored via pulsed-field gel electrophoresis (PFGE) fingerprints. The risk factors for MDR strains acquisition were evaluated using the Cox proportional-hazards model and Firth logistic regression.

RESULTS

A total of 139 stool specimens were obtained from 50 subjects. Twenty-six (52%) infants were colonized with MDR K. pneumoniae and/or E. coli. High clonal dissemination between two clusters of ESBL-producing K. pneumoniae strains was seen from PFGE profile. We detected a persistent, dominant, aminoglycosides-resistant strains cluster (cluster B), which harbored bla_TEM, bla_SHV, bla_OXA-1, bla_CTX-M-1, ompK35 and ompK36 genes. Infants born to women who were anemic in pregnancy [OR = 0.01 (CI = 0.00-0.39), P-value = 0.042] and infants exposed to penicillin/β-lactams group antibiotics during the first week of life [OR = 0.02 (CI = 0.02-0.32), P-value = 0.013] were found to have a lower risk of MDR K. pneumoniae and E. coli colonization.

CONCLUSIONS

The prevalence of dominant aminoglycosides-resistant strains cluster in the NICU is alarming. Awareness of and vigilance for the dominant cluster found will enable the reduction of cross-transmission amongst high-risk infants.

The 'thanato-resistome' - The funeral industry as a potential reservoir of antibiotic resistance: Early insights and perspectives

The funeral industry is a potential reservoir of antibiotic resistance. The occurrence, human exposure and health risks of antibiotic resistance in the funeral industry were examined. The funeral industry harbours antibiotic resistance to multiple common and last-resort antibiotics, hence constitutes the 'thanato-resistome'. Hydrological processes, air-borne particulates and vectors disseminate antibiotic resistance, while horizontal gene transfer circulates antibiotic resistance among resistomes, forming a complex network. Ingestion, inhalation of air-borne particulates, dermal intake and clothes of workers contribute to human exposure. Human health risks include; development of drug resistance in previously susceptible pathogens, and increased morbidity and mortality caused by increased pathogenicity and outbreaks of multi-drug resistant infections. Ecological risks include the proliferation of resistant organisms at the expense of susceptible ones, thereby disrupting ecosystem structure and function, including biogeochemical cycles. Barring inferential data, quantitative evidence linking antibiotic resistance to human infections is weak. This reflects the lack of systematic quantitative studies, rather than the absence of such health risks. Quantitative risk assessment is constrained by lack of quantitative data on antibiotic resistance in various reservoirs and exposure routes. A framework for risk assessment and mitigation is proposed. Finally, ten hypotheses and emerging tools such as genomics, in silico techniques and big data analytics are highlighted.

The present danger of New Delhi metallo-β-lactamase: a threat to public health

The evolution of antimicrobial-resistant Gram-negative pathogens is a substantial menace to public health sectors, notably in developing countries because of the scarcity of healthcare facilities. New Delhi metallo-β-lactamase (NDM) is a potent β-lactam enzyme able to hydrolyze several available antibiotics. NDM was identified from the clinical isolates of Klebsiella pneumoniae and Escherichia coli from a Swedish patient in New Delhi, India. This enzyme horizontally passed on to various Gram-negative bacteria developing resistance against a variety of antibiotics which cause treatment crucial. These bacteria increase fatality rates and play an integral role in the economic burden. The efficient management of NDM-producing isolates requires the coordination between each healthcare setting in a region. In this review, we present the prevalence of NDM in children, fatality and the economic burden of resistant bacteria, the clonal spread of NDM harboring bacteria and modern techniques for the detection of NDM producing pathogens.

Gram-negative bacteria as causative agents of ventilator-associated pneumonia and their respective resistance mechanisms

Ventilator-associated pneumonia (VAP) is a serious and common complication in patients admitted to intensive care unit (ICU) and contributes to mortality. Multidrug Gram-negative bacteria such as Acinetobacter baumannii, Pseudomonas aeruginosa, and Klebsiella pneumoniae are frequently associated with VAP in ICU. A prospective study was set up in three ICUs of the University Hospital Center Zagreb and one ICU in General Hospital Pula from September 2017 to March 2018. Antibiotic susceptibility was determined by broth microdilution method. Production of extended-spectrum β-lactamases (ESBLs) was determined by double-disk synergy test and carbapenemases by Hodge and carbapenem inactivation method (CIM). The genes encoding ESBLs, carbapenemases of class A, B and D and qnr genes were determined by PCR. In total 97 Gram-negative bacteria isolates were analyzed. P. aeruginosa demonstrated high resistance rates for imipenem and meropenem with 74% and 68% of resistant strains, respectively. Moderate resistance rates were observed for ceftazidime andpiperacillin/tazobactam, ciprofloxacin and gentamicin (44%). All except three A. baumannii isolates, were resistant to carbapenems and to all other antibiotics apart from colistin and amikacin. Eight A. baumannii isolates were positive for bla_OXA-23 and 12 for bla_OXA-24 genes. Four K. pneumoniae and two E. cloacae strains were ESBL positive and harboured group 1 of CTX-M β-lactamases. Three P. mirabilis strains were positive for plasmid-mediated ampC β-lactamase of CMY family. Two carbapenem-resistant K. pneumoniae harboured OXA-48 and one carbapenem-resistant E. cloacae VIM-1. A high proportion of multidrug-resistant P. aeruginosa, K. pneumoniae and extensively resistant A. baumannii was reported. Acquired resistance mechanisms, mainly production of carbapenemases and ESBLs were dominant in A. baumannii and K. pneumoniae, respectively. Resistance of P. aeruginosa isolates was more likely due to upregulation of efflux pumps or porin loss. A marked diversity of β-lactamases was identified in Enterobacteriaceae.

Comparison of Genotypic and Phenotypic Methods of Metallo-β- lactamase Detection in Acinetobacter spp

INTRODUCTION

MBL containing genes have been reported in all GNBs including Acinetobacter spp since 1990s which are worrisome as they are transmitted by mobile genetic elements. Thus, early detection of MBL encoding organisms is necessary. The current study was designed to identify the most sensitive cost-effective test which could be used as a screening test for detection of cabapenamase producing Acinetobacter isolates.

METHODOLOGY

All consecutive strains of Acinetobacter spp isolated from various clinical samples were included. All isolates found resistant to any of the carbapenems were tested for MBL production using MHT (on MacConkey Agar and Mueller Hinton Agar), Etest (using Imipenem/Meropenem-EDTA) and Combined Disc Test (using EDTA and 2 MPA as inhibitors and Ceftazidime/Imipenem/Meropenem as substrate discs). PCR was performed for representative strains for IMP, VIM, KPC, OXA and NDM-1 gene.

RESULTS

Total of 154 non-duplicate strains of Acinetobacter spp were isolated and identified, of which, 134 (88%) and 126 (82%) were resistant to meropenem and imipenem respectively. All 134 meropenem resistant strains were tested for MBL production and PCR was performed on 100 strains. 3(3%), 5(5%), 7(7%), 26(26%), and 51(51%) strains had IMP gene, VIM gene, KPC gene, OXA gene and NDM-1 gene. MHT on MAC had better performance than on MHA and dilution to 0.05 McFarland was not required.

CONCLUSION

MHT on MAC had best sensitivity when compared with gold standard PCR and was also cost effective. With ROC curve, we found that 2MPA was not a good MBL inhibitor when compared with EDTA..

Alarming emergence, molecular characterization, and outcome of blaNDM-1 in patients infected with multidrug-resistant Gram-negative bacilli in a tertiary care hospital

INTRODUCTION:

This study was conducted to assess the prevalence of metallo-beta-lactamases (MBLs) in general and blaNDM-1 in particular. It also aimed at evaluating clinical characteristics and outcome in patients infected with MBLs.

MATERIALS AND METHODS:

A total of 116 carbapenem-resistant Gram-negative bacilli (CRGNB) were evaluated in the study. These CRGNB were tested for MBL production both phenotypically for MBLs and genotypically for blaNDM-1 gene by polymerase chain reaction (PCR). Representative stains of NDM-1 isolates were further sequenced by Triyat Scientific Co., (Nagpur, India).

RESULTS:

Among 116 CRGNB Citrobacter species 28 (24.13%) was the most common pathogen. Phenotypically, MHT, imipenem-EDTA (IPM-EDTA) double-disk synergy test and IPM-EDTA combined disk synergy test (CDST) detected MBL production in 105 (90.51%), 96 (81.03%), and 87 (75%) CRGNB, respectively. However, blaNDM-1 genes were detected in 66 (56.89%) isolates. The prevalence of blaNDM-1 gene was highest among Escherichia coli 26 (100%). Considering PCR as gold standard, it was observed that IMP-EDTA CDST was most specific (78.38%) while MHT was most sensitive (97.47%). Results of blaNDM-1 gene by PCR were further confirmed by sequencing (Triyat genomics, Nagpur). All the 11 representative strains were confirmed to be an NDM-1 gene. The presence of MBLs in our group of patients (non-Intensive Care Unit patients) is a cause for concern. However, on tracing their outcome, it was interesting to note that while the duration of stay lengthened in a large number of patients 112 (96.5%), mortality was relatively low 5 (4.31%).

CONCLUSION:

The results of this study provide insight into the prevalence of MBLs, including blaNDM-1, in a tertiary care hospital. Antibiotic stewardship implemented in all seriousness may to a great extent stave off the impending pan-drug resistance. The surprising outcome of our patients suggests either that the bacteria trade off virulence for drug resistance or the relatively robust immune response of non ICU patients fights back.

Circulation of emerging NDM-5-producing Escherichia coli among humans and dogs in Egypt

The emergence of NDM-producing Escherichia coli has considerably threatened human and animal health worldwide. This study describes for the first time in Egypt, the draft genome sequences of emerging NDM-5-producing E. coli from humans and dogs, and investigates genetic relatedness between isolates from both sources. Two E. coli from human urine and seven from environmental clinical samples of dogs exhibited resistance to carbapenems and harbouring bla_NDM were subjected to Illumina Miseq whole-genome sequencing (WGS). Assembly and analysis of the reads were performed to identify resistance genes, multilocus sequence types (MLST), plasmid replicon types (Inc) and insertion sequences (IS) of the bla_NDM region; core genome MLST (cgMLST) analysis was also performed. Two different NDM alleles were identified; bla_NDM-5 in E. coli HR119 from the urine of a healthy person and environmental samples of dogs, and bla_NDM-1 in E. coli HR135 from a human patient's urine. Multiple mobilizable resistance genes to different antimicrobial classes were identified except the colistin resistance gene, mcr. E. coli isolates from humans and dogs were assigned to different sequence types (STs). Using cgMLST, dog isolates clustered together with only 1-2 allellic differences; however, human E. coli showed 1,978 different allelles compared with dog isolates. Plasmidfinder results indicated the presence of an IncX3 replicon in bla_NDM-5 -producing E. coli; however, bla_NDM-1 was linked to IncCoIKP3. Notably, the NDM region (3 Kb) in all isolates from humans and dogs was highly similar with variable flanking sequences that represented different IS elements. This study reports the first emergence of NDM-5-producing E. coli from dogs in Egypt that shared some genetic features with human isolates and could be considered potential public health threats.

Plasmid Replicons and β-Lactamase-Encoding Genes of Multidrug-Resistant Escherichia coli Isolated from Humans and Food Animals in Lagos, Southwest Nigeria

As resistance to the β-lactam class of antibiotics has become a worldwide problem, multidrug-resistant (MDR) human (n = 243) and food animal (n = 211) isolates from Lagos, Nigeria were further tested to characterize β-lactamase-encoding genes and plasmid replicons. Four β-lactamase-encoding genes (bla_CMY, bla_CTX-M, bla_OXA, and bla_TEM) were detected using PCR-based replicon typing, 13 and 17 different replicons were identified using a subset of MDR E. coli from humans (n = 48) and animals (n = 96), respectively. Replicon types FIB and X2 were detected in equal numbers (2/48; 4.2% each) from human isolates, while type Y (16/96; 16.7%) was the most common type from animals. Only two replicon types, FIB and Y, were detected in both groups; all other types were confined to one group or the other, but not both. Using conjugation, replicon type Y, present in three donors, transferred in all three instances, whereas FIA transferred in 75% (3/4) of the matings. This study showed that β-lactamase genes were prevalent in MDR E. coli from both humans and animals in Nigeria and also contained diverse plasmid replicons. As the replicon-associated genes were mobile, they are likely to continue disseminating among E. coli and facilitating transfer of associated β-lactamase genes in this region.

Genetic Study of Extended Spectrum Beta-Lactamase and Carbapenemase Producing Escherichia Coli Causing Sepsis among Egyptian Children

Background:

Treatment failure of sepsis caused by Escherichia coli (E. Coli) is a leading cause of death of infants and children in intensive care units.

Objective:

To detect the prevalence of Extended-Spectrum Beta-Lactamase (ESBL) and carbapenemase-genes between E. coli isolates from infants and children with septicemia and to identify their antibiotic sensitivity pattern.

Methods:

This is a cross-sectional study performed on 88 patients with sepsis. The isolated E. coli were identified by Gram stain and biochemically by the Microscan automated system. ESBL and carbapenemase producing E. coli were isolated on double disk diffusion and EDTA double disk, respectively. Polymerase chain reaction for ESBL and carbapenemase producing E. coli genes were performed. Bacterial susceptibility to antibiotics was tested. The initial results were measured through the 30-days of hospital admission. IRB approved the study.

Results:

Of 88 patients with sepsis, 49 and 30 strains were ESBL producing and carbapenemase producing E. coli; respectively. Neither risk factors for infection nor clinical picture can differentiate between ESBL and carbapenemase producing E. coli. The most frequently detected gene of ESBL producing E. coli was SHV, it was more sensitive to Piperacillin/Tazobactam (90%) and cefepime (86.7%) while for carbapenemase-producing E. coli; IMP was the most frequent, its sensitivity was high to Piperacillin/Tazobactam and Ciprofloxacin (52.6% each).

Conclusion:

The commonest gene of ESBL producing E. coli is SHV whereas for carbapenemase-producing E. coli is IMP. Piperacillin/Tazobactam is the candidate drug to start in children with septicemia and suspected ESBL or carbapenemase-producing E. coli infection.

Molecular and genetic characterization of carbapenemase-producing bacteria in Venezuela

Carbapenem-resistant Gram-negative bacteria isolated in Venezuela have been poorly characterized. The present study characterized a total of 34 isolates obtained from 27 patients; five of these patients were multi-infected. The bacterial species identified were Klebsiella pneumoniae (17), Pseudomonas aeruginosa (9), and Acinetobacter baumannii (8). From these isolates, 85% were identified as carbapenemase-producing bacteria, and the identified carbapenemase genes were bla_KPC-2 (10/29 [34.4%]), bla_VIM-type (7/29 [24.1%]), bla_OXA-23 (7/29 [24.1%]), bla_NDM-1 (8/29 [27.5%]), and the coexistence of bla_OXA-23/bla_NDM-1 (2/29 [6.8%]). Patient 1 was multi-infected by K. pneumoniae ST11 and ST2413 isolates harbouring the bla_NDM-1 and bla_KPC-2 genes, respectively. The other patients were multi-infected by two or three different bacterial species such as ESBL-producing K. pneumoniae isolates, P. aeruginosa harbouring the bla_VIM-type gene, K. pneumoniae ST147 harbouring the bla_KPC-2 gene and by A. baumannii harbouring the bla_OXA-23 gene. The bla_NDM-1 gene in A. baumannii is flanked by an uncommon genetic structure, whereas bla_NDM-1 gene in K. pneumoniae revealed a common structure described in different plasmids from Enterobacteriaceae isolates. This study provides new information about the epidemiology of carbapenemase-producing bacteria in clinical setting in Venezuela.

Molecular Characterization of Multidrug-Resistant and Extended-Spectrum Beta-Lactamase-Producing Klebsiella pneumoniae Isolated from Swine Farms in Malaysia

Aims: The high prevalence of multidrug resistance (MDR) and extended-spectrum β-lactamase (ESBL)-producing Klebsiella pneumoniae associated with nosocomial infections has caused serious therapeutic challenges. The objectives of this study were to determine the genotypic and phenotypic characteristics of K. pneumoniae strains isolated from Malaysian swine farms and the transferability of ESBL genes by plasmids. Results: A total of 50 K. pneumoniae strains were isolated from 389 samples, which were collected from healthy and unhealthy pigs (swine rectum and oral cavities), healthy farmers (human rectum, urine, and nasal cavities), farm's environment, and animal feeds from seven Malaysian swine farms. Antimicrobial susceptibility analysis of these 50 K. pneumoniae strains showed that the majority (86%) were resistant to tetracycline, while 44% and 36% of these strains were MDR and ESBL producers, respectively. PCR and DNA sequencing of the amplicons showed the occurrence of bla_TEM (15/18), bla_SHV (15/18), bla_CTX-M-1 group (7/18), and bla_CTX-M-2 group (2/18), while only class 1 integron-encoded integrase was detected. Conjugation experiments and plasmid analysis indicated that the majority of the ESBL genes were plasmid encoded and the plasmids in 11 strains were conjugative. Genotyping by pulsed-field gel electrophoresis and repetitive extragenic palindrome-polymerase chain reaction (REP-PCR) showed that these 50 strains were genetically diverse with 44 pulsotypes and 43 REP-PCR subtypes. Conclusions: ESBL-producing K. pneumoniae strains showed high resistance to tetracycline as this antibiotic is used for prophylaxis and therapeutic purposes at the swine farms. The findings in this study have drawn attention to the issue of increasing MDR in animal husbandry and it should be taken seriously to prevent the spread and treatment failure due to antimicrobial resistance.

Multicentre investigation of carbapenemase-producing Klebsiella pneumoniae and Escherichia coli in Bulgarian hospitals - Interregional spread of ST11 NDM-1-producing K. pneumoniae

AIM

The aim of this study was to investigate the mechanisms of beta-lactam-resistance and the clonal relatedness of carbapenem-nonsusceptible Klebsiella pneumoniae and Escherichia coli isolates, collected consecutively in eight centers in five Bulgarian cities from November 2014 to March 2018. Carbapenemase-producing enterobacteria were detected in all but one centers. Overall, 104 K. pneumoniae and one E. coli were analysed.

MATERIALS AND METHODS

Antimicrobial susceptibility and beta-lactamases were analysed. Conjugation experiments, plasmid fingerprinting and replicon typing, as well as MLST and ERIC-PCR were carried out.

RESULTS

KPC-2 (51%) and NDM-1 (47%) were the main carbapenemases identified. KPC-2 producing K. pneumoniae were classified into 10 MLST-types. The four dominating MLST-types ST29, ST15, ST336 and ST902 comprised 79% of the KPC-2 producers. All but one of the NDM-1 producing isolates belonged to the MLST-type ST11 and were found in seven centers. Furthermore, single K. pneumoniae isolates producing VIM-1 (ST147) and OXA-48 (ST15) were identified. In addition to the carbapenemases, the ESBLs CTX-M-15, CTX-M-3, and SHV-12 as well as AmpC enzyme CMY-4 were found. The FIIAs-replicon-type was found in all KPC-2 producers while the A/C-replicons dominated in NDM-1 producing isolates. The single NDM-1 producing E. coli was determined as MLST-Type ST10 (Warwick scheme).

CONCLUSION

The interregional clonal expansion of NDM-1 producing ST11 K. pneumoniae and the dissemination of bla_KPC-2 carrying plasmids were responsible for the spread of carbapenemase-producing K. pneumoniae in Bulgaria. Our findings highlight the urgency to prevent dissemination of these highly transmissible and dangerous lineages.

Significance of Screening Tests and the Incidence of New Delhi Metallo-beta-lactamase-Producing Gram-negative Bacilli in the Surgery and Transplantation Wards of a Warsaw Medical Center During the Period From April 2014 to May 2017

BACKGROUND

The first New Delhi metallo-beta-lactamase (NDM)-producing bacteria were isolated in 2008 in the world, and in 2011 in Poland. Due to the high clonal diversity (17 types) of their blaNDM gene, encoded on (Tn125-like) mobile genetic elements, these strains usually exhibit resistance to nearly all available antibiotics, which is particularly dangerous for organ transplant recipients.

PURPOSE

To assess of the prevalence of Gram-negative NDM-positive bacilli in surgery/transplantation wards of a teaching hospital in Warsaw and to ascertain the significance of screening tests on the rates and nature of colonization.

MATERIALS AND METHODS

The evaluated strains were isolated from 30 patients (between April 2014 and May 2017). The species were identified with VITEK-MS, antibiotic susceptibility was determined with VITEK 2, disk-diffusion, and/or E-test methods, according to EUCAST guidelines. The presence of the blaNDM-1 gene was confirmed using the polymerase chain reaction technique.

RESULTS AND CONCLUSIONS

There were 77 blaNDM-1-positive Klebsiella pneumoniae strains isolated from 30 patients. Cultures from individual patients, mainly from rectal swabs (53.9%) and urine samples (39.8%), yielded 1-11 isolates. Fifteen patients were already colonized on admission, and the other 15 developed a symptomatic infection. In total, 24 (80%) patients were carriers, and their colonizations persisted for <1-20 months. Most isolates were susceptible only to colistin, gentamicin, amikacin, tigecycline, and/or sulfamethoxazole/trimethoprim. Gastrointestinal-tract-colonizing K pneumoniae are the main reservoir of the blaNDM-1 gene. Following the introduction of on-admission mandatory screening for carbapenem-resistant strains, the rates of NDM-producing K pneumoniae isolation increased (7.5-fold), while the rates of isolation from patients with symptomatic infections considerably decreased (2.8-fold).

Fecal carriage of carbapenem-resistant Enterobacteriaceae and risk factor analysis in hospitalised patients: A single centre study from India

PURPOSE

Carbapenem-resistant Enterobacteriaceae (CRE) have emerged and disseminated widely causing a variety of infections. In India, the carriage of CRE in hospitalised patients has not been well-studied. Therefore, we conducted the present study to observe gut carriage rate of CRE in patients admitted to our tertiary care hospital.

METHODS

A total of 232 faecal swabs collected from consecutive stool samples from admitted patients were inoculated on ChromID extended spectrum β-lactamase plates and members of Enterobacteriaceae family were subjected to antibiotic susceptibility as per the Clinical Laboratory Standards Institute guidelines. Polymerase chain reaction for blaVIM, blaKPC, blaIMPand blaNDM-1 genes was performed. CRE was identified if the isolates showed resistance to either imipenem or meropenem or showed the presence of resistant genes. Risk factors of patients with or without CRE colonisation were also analysed.

RESULTS

A total of 232 faecal swabs yielded 252 Enterobacteriaceae isolates, of which 49 isolates from 42 patients showed the presence of CRE (occurrence 42/232; 18.1%); 27 isolates from 22 patients carried blaNDM-1, whereas 20 isolates from 17 patients possessed blaVIMgene. No isolate was positive for blaKPCand blaIMPgenes. The CRE was common in both intensive care units (38.4%) and wards (46%) which may reflect the excessive use of broad-spectrum antibiotics in both these settings. The CRE was also found to have a significantly higher antimicrobial resistance as compared to non-CRE isolates. The logistic regression analysis of significance showed the presence of any indwelling device (P = 0.049) and nasogastric tube (P = 0.043) as independent risk factors for acquiring gut colonisation.

CONCLUSIONS

The study is the first from India to show high CRE carriage in patients admitted to a tertiary care centre and emphasises the need of strict antimicrobial stewardship implementation in hospitals to prevent dissemination of multidrug-resistant CRE.

Evolution and typing of IncC plasmids contributing to antibiotic resistance in Gram-negative bacteria

The large, broad host range IncC plasmids are important contributors to the spread of key antibiotic resistance genes and over 200 complete sequences of IncC plasmids have been reported. To track the spread of these plasmids accurate typing to identify the closest relatives is needed. However, typing can be complicated by the high variability in resistance gene content and various typing methods that rely on features of the conserved backbone have been developed. Plasmids can be broadly typed into two groups, type 1 and type 2, using four features that differentiate the otherwise closely related backbones. These types are found in many different countries in bacteria from humans and animals. However, hybrids of type 1 and type 2 are also occasionally seen, and two further types, each represented by a single plasmid, were distinguished. Generally, the antibiotic resistance genes are located within a small number of resistance islands, only one of which, ARI-B, is found in both type 1 and type 2. The introduction of each resistance island generates a new lineage and, though they are continuously evolving via the loss of resistance genes or introduction of new ones, the island positions serve as valuable lineage-specific markers. A current type 2 lineage of plasmids is derived from an early type 2 plasmid but the sequences of early type 1 plasmids include features not seen in more recent type 1 plasmids, indicating a shared ancestor rather than a direct lineal relationship. Some features, including ones essential for maintenance or for conjugation, have been examined experimentally.

Failure of a multiplex polymerase chain reaction assay to detect IMP-27 in a clinical isolate of Morganella morganii

A case of an IMP-27-positive Morganella morganii isolate is reported, where the carbapenemase enzyme was demonstrated by whole genome sequencing. Carbapenemase detection using a multiplex PCR assay was negative due to mutations in the primer binding site. This case serves to illustrate the limitations of multiplex PCR for carbapenemase detection.

Synthesis and structure-activity relationship of novel bisindole amidines active against MDR Gram-positive and Gram-negative bacteria

A series of novel diamidines with N-substituents on an amidine N-atom were synthesized and evaluated for their cytotoxicity and in vitro antibacterial activity against a range of Gram-positive and Gram-negative bacterial strains. Based on structure-activity relationship, N-substituents with a branched chain and a shorter carbon chain on the amidine N-atom exhibited more promising activity against Gram-negative and MDR-Gram-positive bacteria; compounds 5c and 5i were the most powerful candidate compounds. Compound 5c showed greater efficacy than levofloxacin against most drug-resistant Gram-positive bacteria and exhibited broad-spectrum antibacterial activity against Gram-negative bacteria, with MIC values in the range of 2-16 μg/mL. Slightly more potent antibacterial activity against Klebsiella pneumoniae, Acinetobacter calcoaceticus, Enterobacter cloacae, and Proteus mirabilis was observed for 5i in comparison with 5c. Compound 5i also showed remarkable antibacterial activity against NDM-1-producing Gram-negative bacteria, with MIC values in the range of 2-4 μg/mL, and was superior to the reference drugs meropenem and levofloxacin. Effective antibacterial activity of 5i was also shown in vivo in a mouse model of Staphylococcus aureus MRSA strain, with an ED₅₀values of 2.62 mg/kg.

Evolution in situ of ARI-A in pB2-1, a type 1 IncC plasmid recovered from Klebsiella pneumoniae, and stability of Tn4352B

The IncC plasmid pB2-1, from a Klebsiella pneumoniae isolate recovered in Brisbane prior to 1995, belongs to a subtype of type 1 IncC plasmids, here designated type 1a, that includes those carrying carbapenem resistance genes such as bla_NDM and bla_KPC. pB2-1 carries a 2358bp deletion in the rhs1 gene found in four other type 1a IncC plasmids. pB2-1 confers resistance to ampicillin, gentamicin, kanamycin, neomycin, tobramycin, sulfamethoxazole, tetracycline and trimethoprim. It transferred at a frequency of 4.7×10^-3 transconjugants per donor, similar to that of another type 1a plasmid pDGO100 but ten-fold lower than for its closest relative pRMH760. This difference may be due to a single amino acid substitution in TraL. pB2-1 has an ISEc52 insertion in the dsbC gene, demonstrating that dsbC is not essential for transfer. pB2-1 lacks the ARI-B insertion and hence the sul2 gene. The resistance genes sul1, dfrA10, aphA1a, bla_TEM, aadB, and tetA(B) are all in the ARI-A island, in a configuration that has evolved from ARI-A of pRMH760 in two steps. A 10.3kb segment extending from the catA1 gene to the end of pDUmer module was lost via homologous recombination between two copies of IS4321. In addition, a 5.3kb segment extending from IS1326 to the left end of Tn4352B was replaced with an 18.7kb tet(B)-containing segment bounded on one end by IS1 and on the other by IS26. The IS26-bounded transposon Tn4352B was shown to be stable in K. pneumoniae in contrast to the high instability observed in E. coli.

Molecular epidemiology of beta-lactamase producing nosocomial Gram-negative pathogens from North and South Indian hospitals

PURPOSE

Resistant Gram-negative bacterial (GNB) infections, apart from tremendously escalating the cost of treatment, are a cause for substantial morbidity and mortality among hospitalized patients. Such bacteria are rapidly acquiring resistance to many antimicrobial agents, especially the beta-lactams which are the most frequently prescribed antimicrobials in hospital and community patient care settings, and now also to colistin; a last-line drug to treat infections with such bacteria. The greatest threat to antimicrobial treatment is the production of metallo beta-lactamases, and plasmid-mediated serine carbapenemases.

METHODOLOGY

We conducted a two-year study to observe the pattern of beta-lactamase enzyme production (extended spectrum beta-lactamases (ESBLs), AmpC and carbapenemases) among the nosocomial GNB isolated from intensive care units (ICUs) of North and South Indian hospitals. A total of 761 non-duplicate GNB were included in the study from North (554; 73 %) and South India (207; 27 %). All strains were subjected to Clinical and Laboratory Standards Institute (CLSI) recommended screening tests for detection of beta-lactamase production, followed by polymerase chain reaction (PCR)-based detection of clinically important beta-lactamase genes mediating resistant phenotypes among these isolates.

RESULTS

Out of the 761 GNB, Acinetobacter spp., Klebsiella spp., Pseudomonas spp., Enterobacter spp. and others were 27, 23 , 21 , 17 , 5  and 7 % respectively. A high prevalence of ESBL was found across all genera in these strains. The carbapenem resistance was higher in North than in South Indian GNB. The level of AmpC production was comparatively lower in both North and South Indian strains.

CONCLUSION

Beta-lactamases showed tremendous variation in geographic distribution. Thus, their detection and characterization is important from a clinical-epidemiological, laboratory and infection control point of view. Knowledge of this epidemiology can predict the empiric antimicrobial treatment.