Enhancing Phenotypic Detection of ESBL in AmpC co-producers by using Cefepime and Tazobactam

Phenotypic and Genotypic Identification of Four Cases of Plasmid-Mediated AmpC β-Lactamases-Producing Escherichia coli Admitted to a Tertiary Centre

We describe four patients with a positive culture of AmpC β-lactamases-producing Escherichia coli (E. coli), despite the fact that our understanding of plasmid-mediated AmpC β-lactamases (pAmpC) is currently limited. Three out of four cases of AmpC β-lactamases-producing Escherichia coli were isolated from a urine sample, and one was from a peritoneal fluid sample. All four isolates are resistant to cefoxitin disc and were subjected to a confirmatory AmpC phenotypic test (AmpC induction test) and monoplex polymerase chain reaction (PCR) for the determination of six pAmpC genotypes (blaDHA, blaEBC, blaMOX, blaFOX, blaACC, and blaCIT). All four E. coli isolates tested negative for the AmpC induction test, while monoplex PCR analysis was positive only for the blaDHA pAmpC genotype and negative for all five other genotypes (blaEBC, blaMOX, blaFOX, blaACC, and blaCIT). A common clinical characteristic across all patients was fever. One patient was treated for perforated sigmoid diverticulitis, while the other three patients were treated for acute pyelonephritis or urinary tract infections (UTIs). Each patient improved significantly and was successfully discharged.

Prevalence and distribution pattern of AmpC β-lactamases in ESBL producing clinical isolates of Klebsiella spp. in parts of Assam, India

The production of extended-spectrum β-lactamases (ESBLs) and AmpC β-lactamases is the most common explanation of multidrug resistance in clinical isolates of Klebsiella spp. In the present study, a total of 160 isolates of Klebsiella spp. were procured from the DBT-NER project with ethical clearance no. DU/Dib/ECBHR(Human)/2021-22/02). These were collected from various health settings of Assam and identified as drug-resistant. The isolates were screened for antibiotic susceptibility and phenotypic tests were performed on multidrug resistant isolates to confirm ESBL and AmpC β-lactamases production. The distribution pattern of ESBL and AmpC β-lactamase genotype was investigated by polymerase chain reaction (PCR). The results showed that among 107 multidrug-resistant (MDR) isolates of Klebsiella spp., 67.28% of isolates were ESBL producers and 56.07% were potential AmpC producers. The PCR results revealed that blaCTX-M was the most prevalent ESBL genotype. Among the ESBL producers, 11.11% of isolates showed co-occurrence with plasmid-mediated AmpC β lactamases genotype which indicated the high prevalence of ESBL and AmpC co-producers in K. pneumoniae and K. oxytoca, suggesting the possibility of serious public health concerns. Therefore, it is crucial to regularly monitor the spread of multidrug resistance among clinical isolates.

National genomic surveillance integrating standardized quantitative susceptibility testing clarifies antimicrobial resistance in Enterobacterales

Antimicrobial resistance is a global health concern; Enterobacterales resistant to third-generation cephalosporins (3GCs) and carbapenems are of the highest priority. Here, we conducted genome sequencing and standardized quantitative antimicrobial susceptibility testing of 4,195 isolates of Escherichia coli and Klebsiella pneumoniae resistant to 3GCs and Enterobacterales with reduced meropenem susceptibility collected across Japan. Our analyses provided a complete classification of 3GC resistance mechanisms. Analyses with complete reference plasmids revealed that among the blaCTX-M extended-spectrum β-lactamase genes, blaCTX-M-8 was typically encoded in highly similar plasmids. The two major AmpC β-lactamase genes were blaCMY-2 and blaDHA-1. Long-read sequencing of representative plasmids revealed that approximately 60% and 40% of blaCMY-2 and blaDHA-1 were encoded by such plasmids, respectively. Our analyses identified strains positive for carbapenemase genes but phenotypically susceptible to carbapenems and undetectable by standard antimicrobial susceptibility testing. Systematic long-read sequencing enabled reconstruction of 183 complete plasmid sequences encoding three major carbapenemase genes and elucidation of their geographical distribution stratified by replicon types and species carrying the plasmids and potential plasmid transfer events. Overall, we provide a blueprint for a national genomic surveillance study that integrates standardized quantitative antimicrobial susceptibility testing and characterizes resistance determinants.

Antimicrobial Resistance of Enterobacteriaceae in Bloodstream Infections in Hospitalized Patients in Southern Poland

Aim: The aim of this study was to highlight antimicrobial resistance among Enterobacteriaceae isolated from bloodstream infections in hospitals in southern Poland. Materials and Methods: The present study includes laboratory-confirmed secondary bloodstream infections (LC-BSIs), in the years 2015–2018, in hospitalized adult patients (≥18). Episodes of BSIs were defined according to the strictly described guidelines. Antimicrobial susceptibility testing was performed with the automated system and the disc diffusion method. Extended-spectrum β-lactamases (ESBLs)-producing Enterobacteriaceae were detected using the double-disc synergy test. Results: Between 2015 and 2018, 356 episodes of secondary BSIs in 997 patients aged 21–96 years were documented in a prospective study, including 134 (37.6%) ESBL-producing Enterobacteriaceae. Escherichia coli was the predominant pathogen in internal medicine (37.6%) and surgery units (46.8%); in intensive care units (ICUs), Klebsiella pneumoniae was isolated more frequently (33.3%). Enterobacteriaceae were highly resistant to most antimicrobial agents. K. pneumoniae isolates had a higher level of resistance than E. coli, regardless of the unit. Conclusions: The increase in AMR and the widespread distribution of ESBL-producing Enterobacteriaceae in Polish hospitals can be related to the lack of or inappropriate antibiotic treatment.

Association between Virulence Factors and Antimicrobial Resistance of Klebsiella pneumoniae Clinical Isolates from North Kerala

Klebsiella pneumoniae is a common bacterial pathogen causes wide range of infections all over the world. The antimicrobial resistance of K. pneumoniae is a global concern and expresses several virulence factors contributing to the pathogenesis. The incidences of bacterial co-infection in viral pneumonia are common. Increased risk of K. pneumoniae co-infection in viral respiratory tract infection should be alerted in COVID-19 pandemic period. The study aims to detect the association between antimicrobial resistance and factors causing pathogenicity of K. pneumoniae. For the current study, 108 K. pneumoniae clinical isolates were included. Antimicrobial susceptibility test was done by Kirby-Bauer disc diffusion method according to CLSI guidelines. Virulence factors such as biofilm formation, haemagglutination, haemolysins, hypermucoviscocity, siderophore, amylase, and gelatinase production were determined by phenotypic method. In this study K. pneumoniae showed high level of antimicrobial resistance towards ampicillin (92.59%) followed by amoxicillin-clavulanic acid (67.59%) and cotrimoxazole (47,22%). An important association between biofilm formation and antimicrobial resistance was found to be statistically significant for cotrimoxazole (P-value 0.036) and amoxicillin-clavulanic acid (P-value 0.037). Other virulence factors like hypermucoviscocity, haemagglutination, amylase, and siderophore production were also showed a statistically significant relation (P-value <0.05) with antimicrobial resistance. Further molecular studies are necessary for the identification of virulence and antimicrobial resistance genes, for the effective control of drug-resistant bacteria.

Molecular detection of plasmid-derived AmpC β-lactamase among clinical strains of Enterobacteriaceae in Bahrain

BACKGROUND

Enterobacteriaceae with AmpC β-lactamase are multidrug-resistant organisms and represent a significant challenge to patient care. This study aims to determine the prevalence of plasmid-derived AmpC β-lactamase among extended spectrum β-lactamases (ESBL)-producing Enterobacteriaceae strains in Bahrain.

METHODS

It was a cross-sectional study. A total of 185 ESBL-producing Enterobacteriaceae isolates were recovered from clinically significant specimens from January 2018 to December 2019. The samples underwent initial screen for cefoxitin resistance by disc diffusion test and subsequent phenotypic confirmation of AmpC production with phenyl boronic acid assays as well as genotypic analysis by multiplex polymerase chain reactions for AmpC subtypes. Drug-resistant features of these clinical isolates were also examined.

RESULTS

Twenty-nine ESBL-producing Enterobacteriaceae isolates were cefoxitin resistant. Phenotypic and genotypic analyses confirmed that 8 and 12 cefoxitin-resistant isolates are AmpC positive, respectively. These AmpC producers are multidrug resistant, and Escherichia coli is the dominant strain among them.

CONCLUSIONS

Plasmid-mediated spread of AmpC is present in clinically relevant Enterobacteriaceae species in Bahrain. Rational antimicrobial therapy against these multidrug-resistant organisms and continued surveillance of antimicrobial resistance mechanisms among the clinical isolates are recommended for optimal patient care.

CON: Testing for ESBL production is unnecessary for ceftriaxone-resistant Enterobacterales

Phenotypic testing for Enterobacterales that harbour ESBLs is not additive to accurate in vitro β-lactam MICs for clinical decision-making. ESBL testing is an outdated practice established in an era of higher cephalosporin breakpoints to prevent resistant Enterobacterales carrying Ambler class A β-lactamases with affinity for later-generation β-lactams from being reported as susceptible to later-generation cephalosporins, leading to clinical failures. ESBL testing is problematic because of inaccuracies when multiple classes of β-lactamases are produced by the same organism, thus limiting the testing application to specific species and resistance types. Clinical laboratories should instead focus finite resources on accurate susceptibility testing using contemporary interpretative criteria to help guide therapeutic decisions. With continued emergence of antimicrobial resistance and in the setting of accurate susceptibility testing and current breakpoints the use of ESBL phenotypic testing is not helpful in clinical decision-making.

Pet and Stray Dogs as Reservoirs of Antimicrobial-Resistant Escherichia coli

The close contact between dogs and humans creates the best bridge for interspecies transmission of antimicrobial-resistant bacteria. The surveillance of its resistance including the detection of extended-spectrum beta-lactamases (ESBLs) in Escherichia coli as indicator bacteria is an important tool to control the use of antimicrobials. The aim of this research was to evaluate the E. coli resistance in strains by phenotypic methods, isolated from pet and stray dogs of La Plata city, Argentina. Faecal samples were collected using rectal swabs from 50 dogs with owners (home dogs = HD) and 50 homeless dogs (stray dogs = SD). They were cultured in 3 MacConkey agar plates, with and without antibiotics (ciprofloxacin and cefotaxime). 197 strains were isolated, of which only 95 strains were biochemically identified as E. coli, 46 strains were from HD, and 49 were from SD. Antimicrobial susceptibility was evaluated by the Kirby-Bauer disk diffusion method. The most prevalent resistance was for tetracycline, streptomycin, and ampicillin. In both groups, the level of resistance to 3rd generation cephalosporins was high, and there were multiresistant strains. There was a higher level of antimicrobial resistance in strains from SD compared to HD. There were 8% of strains suspected of being ESBLs among samples of HD and 36% of SD. One (2%) of the strains isolated from HD and 11 (22%) from SD were phenotypically confirmed as ESBL. Pets and stray dogs are a potential source of E. coli antibiotic resistance in Argentina; therefore, its surveillance must be guaranteed.

Prevalence and characterization of beta-lactamase-producing Escherichia coli isolates from a tertiary care hospital in India

BACKGROUND:

The purpose of the study was to determine the prevalence and characterize the resistance profiles of Escherichia coli isolated from various clinical specimens by various phenotypic and genotypic methods.

MATERIALS AND METHODS:

A total of 196 consecutive, nonduplicate strains of clinically significant E. coli isolated from various clinical specimens were included in the study. Identification and antimicrobial susceptibility testing was performed by using Vitek-2 system (Biomerieux, France). Phenotypic detection of extended spectrum beta-lactamase (ESBLs), Amp-C-β lactamase (Amp C), and carbapenemase production was done by various combination of disc diffusion methods, minimum inhibitory concentration determination by E-test, followed by polymerase-chain-reaction for the detection of β-lactamase-encoding genes.

RESULTS:

Overall prevalence of ESBLs, Amp C, and carbapenemase production was found to be 88.3%, 42.2%, and 65.1% by the phenotypic detection methods. Our study also revealed high resistance rates against other antibiotics such as cefepime (89%), cefotaxime (95.4%), ceftazidime (85.4%), ceftriaxone (91.8%), cefpodoxime (92.7%), aztreonam (56.3%), piperacillin/tazobactam (89.2%), and ticarcillin/clavulanic acid (76.3%). The most prevalent ESBL gene was bla_TEM (67.30%), and least prevalent ESBL gene was bla_VEB (2.61%). In case of Amp C, bla_FOX gene (21.9%) was predominant. Among the genes encoding for carbapenemases, the most common gene was bla_NDM (61.7%) followed by bla_VIM (30.8%), bla_KPC (10.6%), bla_OXA-48 (5.3%), and bla_IMP (2.1%).

CONCLUSION:

Our findings suggest a high rate of ESBLs, Amp C, and carbapenemase production among the E. coli isolates. A combination of both phenotypic and genotypic methods would be ideal for better characterization of resistance patterns among the E. coli isolates.

Co-Occurrence of Plasmid-Mediated AmpC β-Lactamase Activity Among Klebsiella pneumoniae and Escherichia Coli

Introduction:

Extended-spectrum β-lactamases (ESBLs), including the AmpC type, are important mechanisms of resistance among Klebsiella pneumoniae and Escherichia coli isolates.

Objective:

The aim of the study was to investigate the occurrence of AmpC-type β-lactamase producers isolated from two hospitals in Tripoli, Libya.

Methods:

All clinical isolates (76 K. pneumoniae and 75 E. coli) collected over two years (2013-2014) were evaluated for susceptibility to a panel of antimicrobials and were analyzed phenotypically for the ESBL and AmpC phenotype using E-test and ESBL and AmpC screen disc test. Both ESBL and AmpC-positive isolates were then screened for the presence of genes encoding plasmid-mediated AmpC β-lactamases by polymerase chain reaction (PCR).

Results:

Of the K. pneumoniae and E. coli tested, 75% and 16% were resistant to gentamicin, 74% and 1.3% to imipenem, 71% and 12% to cefoxitin, 80% and 12% to cefepime, 69% and 22.6% to ciprofloxacin, respectively. None of the E. coli isolates were multidrug resistant compared with K. pneumoniae (65.8%). K. pneumoniae ESBL producers were significantly higher (85.5%) compared with (17.3%) E. coli isolates (P <0.0001, OR=4.93). Plasmid-mediated AmpC genes were detected in 7.9% of K. pneumoniae, and 4% E. coli isolates. There was low agreement between phenotypic and genotypic methods, phenotypic testing underestimated detection of AmpC enzyme and did not correlate well with molecular results. The gene encoding CMY enzyme was the most prevalent (66.6%) of AmpC positive isolates followed by MOX, DHA and EBC. Only one AmpC gene was detected in 5/9 isolates, i.e, bla_CMY (n=3), bla_MOX (n=1), bla_DHA (n=1). However, co-occurrence of AmpC genes were evident in 3/9 isolates with the following distribution: bla_CMY and bla_EBC (n=1), and bla_CMY and bla_MOX (n=2). Neither bla_FOX nor bla_ACC was detected in all tested isolates. All AmpC positive strains were resistant to cefoxitin and isolated from patients admitted to intensive care units.

Conclusion:

Further studies are needed for detection of other AmpC variant enzyme production among such isolates. Continued surveillance and judicious antibiotic usage together with the implementation of efficient infection control measures are absolutely required.