Detection of extended-spectrum beta-lactamases in klebsiellae with the Oxoid combination disk method

Antimicrobial susceptibility testing profiles of ESBL-producing Enterobacterales isolated from hospital and community adult patients in Blantyre, Malawi

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Extended-spectrum β-lactamase (ESBL) strains are an increasingly global health issue

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ESBL-Enterobacteriaceae isolates affected 64% of inpatients and 36% of outpatients

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ESBL-E isolates had high antimicrobial resistance; most were multi-drug resistant

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Surveillance systems are needed to monitor antimicrobial resistance in Malawi

Objective

There is a paucity of data on antimicrobial resistance (AMR) in Malawi. Here we present a study of AMR of extended-spectrum β-lactamases-producing Enterobacterales (ESBL-E) isolated from hospital and community settings in Blantyre, Malawi.

Design and Methods

A cross-sectional study was conducted between March and November 2020, involving 403 adult participants aged ≥18 years. Screening for ESBL-E was performed using CHROMagar ESBL medium. Production of ESBLs was confirmed by a combination disk test method. Antimicrobial susceptibility was tested using the agar disk diffusion method in accordance with the Clinical Laboratory Standards Institute's 2019 guidelines.

Results

The mean resistance rate of ESBL-E to antimicrobial agents tested was 49.2% (range from 1.4%–92%). The highest resistance rates were observed for trimethoprim-sulfamethoxazole (92%), amoxicillin and ceftriaxone (79%), doxycycline (75%) and gentamicin (72%). Carbapenems (meropenem and imipenem) were highly active against isolates. The overall rate of multi-drug resistant (MDR) ESBL-E was 47%. The highest MDR was found in Yersinia enterocolitica (51%) and the least in Serratia spp. (40%).

Conclusions

We found a high resistance rate of ESBL-E isolates to antimicrobial agents; the majority were MDR. Surveillance systems are recommended to monitor AMR in Malawi.

Association between biofilm-production and antibiotic resistance in Escherichia coli isolates: A laboratory-based case study and a literature review

Bacteria can enhance their survival by attaching to inanimate surfaces or tissues, and presenting as multicellular communities encased in a protective extracellular matrix called biofilm. There has been pronounced interest in assessing the relationship between the antibiotic resistant phenotype and biofilm-production in clinically-relevant pathogens. The aim of the present paper was to provide additional experimental results on the topic, testing the biofilm-forming capacity of Escherichia coli isolates using in vitro methods in the context of their antibiotic resistance in the form of a laboratory case study, in addition to provide a comprehensive review of the subject. In our case study, a total of two hundred and fifty (n = 250) E. coli isolates, originating from either clean-catch urine samples (n = 125) or invasive samples (n = 125) were included. The colony morphology of isolates were recorded after 24h, while antimicrobial susceptibility testing was performed using the Kirby-Bauer disk diffusion method. Biofilm-formation of the isolates was assessed with the crystal violet tube-adherence method. Altogether 57 isolates (22.8%) isolates were multidrug resistant (MDR), 89 isolates (35.6%) produced large colonies (>3 mm), mucoid variant colonies were produced in 131 cases (52.4%), and 108 (43.2%) were positive for biofilm formation. Biofilm-producers were less common among isolates resistant to third-generation cephalosporins and trimethoprim-sulfamethoxazole (P = 0.043 and P = 0.023, respectively). Biofilms facilitate a protective growth strategy in bacteria, ensuring safety against environmental stressors, components of the immune system and noxious chemical agents. Being an integral part of bacterial physiology, biofilm-formation is interdependent with the expression of other virulence factors (especially adhesins) and quorum sensing signal molecules. More research is required to allow for the full understanding of the interplay between the MDR phenotype and biofilm-production, which will facilitate the development of novel therapeutic strategies.

Profile and antibiotic-resistance pattern of bacteria isolated from endotracheal secretions of mechanically ventilated patients at a tertiary care hospital

BACKGROUND

Critically ill patients on mechanical-ventilation are always at a higher risk of acquiring ventilator-associated respiratory infections. The current study was intended to determine the antibiotic-resistance pattern of bacteria recovered from the endotracheal (ET) specimens of ventilated patients.

MATERIALS AND METHODS

This was a single-centered, retrospective study carried out in a 400-bed tertiary care hospital in Oman. The data of profile and antibiotic resistance pattern of bacterial isolates recovered from ET aspirates of ventilated patients during the period from January 2017 to August 2019 were retrieved from hospital database. The data were analyzed using the Statistical Package for the Social Sciences (SPSS) software version 22 (IBM, Armonk, New York, USA). Descriptive statistics were applied to find the frequencies and percentages. Charts and tables were constructed.

RESULTS

In total, 201 bacterial isolates recovered from ET secretions of 154 ventilated patients were studied. The rate of isolation was predominant among males (65.6%) and in elderly people (50%). Gram-negative bacilli (GNB) were predominantly (88.6%) isolated. Acinetobacter baumannii (31.3%) was the most common isolate and 86% of them were multidrug-resistant strains. Klebsiella pneumoniae (23.9%) and Pseudomonas aeruginosa (22.9%) were the other common GNB, whereas Staphylococcus aureus was the most frequently isolated Gram-positive bacteria. Gentamicin showed good in vitro activity against S. aureus and all the GNB except A. baumannii reflecting good choice for empirical therapy.

CONCLUSION

Gram-negative bacteria were the predominant isolates in ET secretions of ventilated patients. There was an alarmingly high rate of antimicrobial resistance among GNB. A rational use of antibiotics, regular monitoring of antibiotic resistance and use of right combination of drugs, in addition to refining of existing infection control practices are critical to control the emergence of drug-resistant strains.

In vitro synergistic activity of fosfomycin in combination with other antimicrobial agents against carbapenem-resistant Klebsiella pneumoniae isolated from patients in a hospital in Thailand

INTRODUCTION

Carbapenem-resistant Klebsiella pneumoniae (CRKP) causes high morbidity and mortality worldwide. The purpose of the study was to assess the synergistic activity of fosfomycin in combination with other antimicrobial agents against CRKP isolated from patients in Songklanagarind Hospital, Thailand.

METHODS

A total of 35 K. pneumoniae isolates were obtained from patients in Songklanagarind Hospital. The MICs of imipenem and meropenem were determined in all isolates by broth microdilution. In all CRKP isolates, the presence of carbapenemase and extended-spectrum β-lactamase (ESBL) genes was investigated by PCR, while the production of these enzymes was determined by combined disk test. In the carbapenemase-genes-negative CRKP isolates, the porin loss and efflux pump were characterized by SDS-PAGE and broth microdilution, respectively. Finally, the synergistic effects of fosfomycin and other antimicrobial agents were evaluated by checkerboard analysis.

RESULTS

Twenty-one of 35 K. pneumoniae isolates were classified as CRKP. Most of CRKP isolates carried bla_NDM-1 (n = 18), bla_SHV (n = 21), bla_CTX-M (n = 21), and bla_TEM (n = 16). In fosfomycin-based combination, the result showed that the highest synergistic activity in this study was observed in the combination of fosfomycin and gentamicin (61.9%).

CONCLUSION

These findings suggested that the fosfomycin and gentamicin combination might be useful as a possible treatment option for CRKP infection.

Successful de-escalation antibiotic therapy using cephamycins for sepsis caused by extended-spectrum beta-lactamase-producing Enterobacteriaceae bacteremia: A sequential 25-case series

Carbapenems are frequently used to treat infections caused by extended-spectrum beta-lactamase-producing Enterobacteriaceae (ESBL-E), but carbapenem-resistant Enterobacteriaceae bacteria are a clinical concern. Although cephamycins (cefmetazole; CMZ) have been shown to be effective against mild cases of ESBL-E infection, data on their use for severe ESBL-E infections with sepsis or septic shock remain scarce. Herein, we discuss a de-escalation therapy to CMZ that could be used after empiric antibiotic therapy in ICU patients with sepsis or septic shock caused by ESBL-E bacteremia. A sequence of 25 cases diagnosed with sepsis or septic shock caused by ESBL-E bacteria was evaluated. The attending infectious disease specialist physicians selected the antibiotics and decided the de-escalation timing. The median SOFA (Sequential Organ Failure Assessment) and APACHE II (Acute Physiology and Chronic Health Evaluation II) severity scores were 8 and 30; the rate of septic shock was 60%. Infections originated most frequently with urinary tract infection (UTI) (56%) and Escherichia coli (85%). Eleven patients were de-escalated to CMZ after vital signs were stable, and all survived. No patients died of UTI regardless of with or without de-escalation. The median timing of de-escalation antibiotic therapy after admission was 4 days (range, 3–6 days). At the time of de-escalation, the median SOFA score fell from 8 to 5, the median APACHE II score from 28 to 22, and the rate of septic shock from 55% to 0%. We conclude that for sepsis in UTI caused by ESBL-E bacteremia, de-escalation therapy from broad-spectrum antibiotics to CMZ is a potential treatment option when vital signs are stable.

Characterization of extended-spectrum-β-lactamase producing Klebsiella pneumoniae phage KP1801 and evaluation of therapeutic efficacy in vitro and in vivo

Extended spectrum β lactamase-producing Klebsiella pneumoniae (ESBL-KP) is being reported with high morbidity and mortality rates and is considered as the highest priority for new antimicrobial strategies. To develop an alternative antimicrobial agent, phage KP1801 with broad lytic activity was isolated. The genome of phage KP1801 was double stranded DNA of 49,835 base pairs, with a GC content of 50.26%. There were 75 putative open reading frames. Phage KP1801 was classified as being in the order Caudovirales, belonging to the Siphoviridae family. About 323 proteins were detected by shotgun proteome analysis. The phage inhibited biofilm formation and reduced pre-formed biofilm in a dose dependent manner. Scanning electron microscopic studies demonstrated a membrane damage of bacterial cells treated with phage, resulting in cell death. Prophylactic and therapeutic efficacies of the phage were evaluated in Galleria mellonella. Administration of ESBL-KP infection with phage significantly improved the survival of G. mellonella. The number of intracellular bacteria in larvae showed a significant decrease compared with untreated control while the number of phage increased. These studies suggested that phage KP1801 has the potential for development as an alternative for antibiotics and biocontrol agents against ESBL-KP infection.

Association between Biofilm-Production and Antibiotic Resistance in Uropathogenic Escherichia coli (UPEC): An In Vitro Study

Urinary tract infections (UTIs) are among the most common infections requiring medical attention worldwide. The production of biofilms is an important step in UTIs, not only from a mechanistic point of view, but this may also confer additional resistance, distinct from other aspects of multidrug resistance (MDR). A total of two hundred and fifty (n = 250) Escherichia coli isolates, originating from clean-catch urine samples, were included in this study. The isolates were classified into five groups: wild-type, ciprofloxacin-resistant, fosfomycin-resistant, trimethoprim-sulfamethoxazole-resistant and extended spectrum β-lactamase (ESBL)-producing strains. The bacterial specimens were cultured using eosine methylene blue agar and the colony morphology of isolates were recorded. Antimicrobial susceptibility testing was performed using the Kirby-Bauer disk diffusion method and E-tests. Biofilm-formation of the isolates was carried out with the crystal violet tube-adherence method. n = 76 isolates (30.4%) produced large colonies (>3 mm), mucoid variant colonies were produced in n = 135 cases (54.0%), and n = 119 (47.6%) were positive for biofilm formation. The agreement (i.e., predictive value) of mucoid variant colonies in regard to biofilm production in the tube-adherence assay was 0.881 overall. Significant variation was seen in the case of the group of ESBL-producers in the ratio of biofilm-producing isolates. The relationship between biofilm-production and other resistance determinants has been extensively studied. However, no definite conclusion can be reached from the currently available data.

Occurrence of Multidrug-resistant Uropathogens Implicated in Asymptomatic Bacteriuria in Adults with Sickle Cell Disease in Ile-Ife, Southwest Nigeria

OBJECTIVES

We sought to determine the prevalence of asymptomatic bacteriuria (ASB) in patients with sickle cell disease (SCD), the susceptibility profile of its agents and their extended-spectrum β-lactamase (ESBL) production.

METHODS

Fifty-nine patients with SCD and 116 healthy controls were investigated. Urine samples were collected and cultured by standard techniques. We used the disc diffusion technique to determine antibiotic susceptibility. ESBL was detected by the combination disc method and detection of bla SHV, bla TEM, and bla CTX-M genes by multiplex-polymerase chain reaction.

RESULTS

The prevalence of ASB was higher among patients with SCD (8.6%) than controls (0.9%) (p = 0.016), predominantly among females. Coagulase-negative staphylococci (n = 2; 33.3%) predominated among the isolates. Other uropathogens included Stenotrophomonas maltophilia, Acinetobacter baumannii, and Enterobacter cloacae. All isolates were sensitive to meropenem but were resistant to ceftazidime, ampicillin, and tetracycline. bla SHV, bla TEM, and bla CTX-M-15 were detected in Enterobacter cloacae.

CONCLUSIONS

The prevalence of ASB is high in patients with SCD predominantly among females. Rare multidrug-resistant uropathogens were implicated. We posit a need for resistance surveillance programs and antibiotic stewardship to prevent treatment failure and reduce drug resistance.

Is whole genome sequencing the answer for identifying Shigella bacteraemia?

We present a rare case of Shigella flexneri bacteraemia and the challenges of differentiating Escherichia coli and Shigella spp using conventional and newer laboratory techniques in diagnostic laboratories. The organism was identified only after whole genomic sequencing .

Prevalence and risk factors for multi-drug resistant Escherichia coli among poultry workers in the Federal Capital Territory, Abuja, Nigeria

Background

Antimicrobial resistance has emerged as a global health threat. Antimicrobial resistant Escherichia coli infections are associated with high morbidity and expenditure when compared with infections caused by susceptible strains. In Nigeria, antimicrobial drugs are readily available over-the-counter with potential for indiscriminate use by poultry farmers and eventual development of drug resistance. The objective of this study was to investigate prevalence and risk factors for multi-drug resistant E. coli among poultry workers (PW) in Abuja, Nigeria.

Materials and methods

A cross-sectional study was conducted among 122 randomly selected apparently healthy poultry workers (poultry-farmers/ sellers) in Municipal and Kuje Area Councils from December 2018 to April 2019. Data was collected on socio-demographics and exposure factors using a structured interviewer-administered questionnaire. E. coli was isolated and identified from stool samples of poultry workers. Antibiotic susceptibility testing was done using Kirby-Bauer disk diffusion method. Multidrug resistance (MDR) was defined as resistance to three or more classes of antimicrobials. Data was analyzed by computing proportions, prevalence odds-ratios (POR) and logistic regression at 5% significance level.

Results

Among PW, there were 121 males (99.2%). Mean age of the male workers was 30.6 ± 9.7years, 54.6% (n = 66) married, 57.9% (n = 70) had secondary education and 62.0% (n = 75) were farm-workers. Prevalence of E. coli was 39.7% (n = 48), highest among farm-workers (POR = 2.7, 95% Confidence Interval [CI] = 1.3–5.7; p = 0.01) compared to poultry-sellers. Of the 48 E. coli isolates, 16.7% (n = 8) were extended spectrum beta lactamase (ESBL) producers and 79.2% (n = 38) were MDR. We detected resistance against Tetracycline: (83.3%, n = 40), Sulfamethoxazole-Trimethoprim: (79.2%, n = 38), Ampicillin: (77.1%, n = 37), Streptomycin: (72.9%, n = 35), Nalidixic acid: (50%, n = 24), Gentamicin: (41.7%, n = 20), Chloramphenicol: (31.3%, n = 15), Cephalothin: (27.1%, n = 13), Nitrofurantoin: (10.4%, n = 5) and Imipenem: (6.3%, n = 3). Absence of lavatory (POR = 2.7, 95% CI = 1.1–6.7); existence of farm/market for >10years (POR = 2.5, 95% CI = 1.1–5.4) and PW’s history of diarrhea in last three months (POR = 2.8, CI = 1.2–6.3) were associated with MDR. Controlling for age, absence of lavatory (adjusted OR [aOR] = 4.31, 95% CI = 1.6–11.9); PW’s history of diarrhea in last three months (aOR = 3.3,95%CI = 1.3–8.5) and work exposure >10years (aOR = 0.3, 95%CI = 0.1–0.9) remained independent risk factors for MDR.

Conclusion

Prevalence of resistant E. coli was highest among farm-workers and associated with older farms/markets, occupational exposure of over 10 years and poor hygienic measures. The management of Municipal and Kuje Area Councils were recommended to provide lavatories for public use in farm-settlements/markets. The importance of hand-hygiene and responsible use of antimicrobials in poultry production was emphasized.

Rapid Increase in Carriage Rates of Enterobacteriaceae Producing Extended-Spectrum β-Lactamases in Healthy Preschool Children, Sweden

By collecting and analyzing diapers, we identified a >6-fold increase in carriage of extended-spectrum β-lactamase (ESBL)–producing Enterobacteriaceae for healthy preschool children in Sweden (p<0.0001). For 6 of the 50 participating preschools, the carriage rate was >40%. We analyzed samples from 334 children and found 56 containing >1 ESBL producer. The prevalence in the study population increased from 2.6% in 2010 to 16.8% in 2016 (p<0.0001), and for 6 of the 50 participating preschools, the carriage rate was >40%. Furthermore, 58% of the ESBL producers were multidrug resistant, and transmission of ESBL-producing and non–ESBL-producing strains was observed at several of the preschools. Toddlers appear to be major carriers of ESBL producers in Sweden.

Co-production of AmpC and extended spectrum beta-lactamases in cephalosporin-resistant Acinetobacter baumannii in Egypt

Acinetobacter baumannii is an opportunistic pathogen that has been held responsible for a lot of infections worldwide. Infections caused by this pathogen are difficult to control because of the widespread of antimicrobial resistance mechanisms. The aim of the present study is to assess the prevalence of extended spectrum β-lactamases (ESBLs) and AmpC β-lactamases among isolates of A. baumannii collected from different clinical sources in Mansoura University Hospitals, Egypt. Antimicrobial susceptibility testing has demonstrated elevated resistance level to β-lactams, quinolones and aminoglycosides. All isolates were sensitive to colistin and polymyxin B. ESBL activity was detected in 86% of the isolates. Among the tested ESBL encoding genes, bla_TEM gene was the most prevalent gene as it was detected in 52% of the isolates. While bla_PER, bla_SHV and bla_VEB were detected in 12%, 4%, and 2%, respectively. AmpC activity and bla_ADC gene were detected in 90% of the tested isolates. Insertion sequence ISAba1 was located 9 bp upstream of bla_ADC gene in 88.9% of the ADC-expressing isolates providing a potent promoter activity for its expression. To our knowledge this is the first report of loss of intrinsic ADC activity, in 10% of the tested isolates, as a result of insertional inactivation by an element belonging to IS5 family transposase. Co-expression of both ESBLs and AmpC β-lactamases was detected in 78% of the isolates. The study demonstrates high prevalence of resistance to β-lactam antibiotics through ESBLs and AmpC β-lactamases production among A. baumannii clinical isolates. Prevalence of β-lactamases should be detected routinely and reported in hospitals to avoid inappropriate use of antibiotics and therapeutic failure.

High Prevalence and Temporal Variation of Extended Spectrum β-Lactamase-Producing Bacteria in Urban Swedish Mallards

Antibiotic resistant bacteria present a growing global healthcare challenge. Previous research demonstrates that wild birds harbor extended spectrum β-lactamase (ESBL)-producing Enterobacteriaceae and may contribute to their dissemination. We aimed to assess prevalence and temporal variation in the detection rate of ESBL-producing bacteria in urban wild birds and to evaluate methods regarding sample handling. Monthly fecal sampling was performed in 2013 at an urban pond in Sweden. ESBL-producing Escherichia coli and Klebsiella pneumoniae were analyzed by polymerase chain reaction targeting bla_CTX-M. Subsets of samples were analyzed in multiple replicates and without previous freezing. Pond water samples were screened for 12 antibiotics. Out of 813 fecal samples, 47% grew ESBL-producing E. coli, a higher prevalence than in similar studies. Detection rate varied considerably between months, ranging from 4.2% in May to 84% in July, and was significantly higher during warm months. A majority of isolates harbored CTX-M-15 type ESBL. Detection rates were increased by duplicating samples and by avoiding freezing. No antibiotics were detected in pond water. This study demonstrates high prevalence and a previously undescribed temporal variation in detection rate of ESBL-producing Enterobacteriaceae in wild birds. The distribution of CTX-M genes corresponds well with Swedish human isolates, indicating communication between the genetic pools of ESBLs in humans and wild birds. Urban ponds may serve as important natural reservoirs for antimicrobial resistance.

Synthesis, spectral and extended spectrum beta-lactamase studies of transition metal tetraaza macrocyclic complexes

Urinary tract infections commonly occur in humans due to microbial pathogens invading the urinary tract, which can bring about a range of clinical symptoms and potentially fatal sequelae. The present study is aimed at addressing the development of a new antimicrobial agent against extended spectrum beta lactamase (ESBL) producing E. coli bacteria. We have synthesised some biologically potent (NNNN) donor macrocycles (L ₁  = dibenzo[f,n]dipyrido[3,4-b:4',3'-j][1,4,9,12]tetraazacyclohexadecine-6,11,18,23(5H,12H, 7H, 24H)-tetraone, and L ₂  = 6,12,19,25-tetraoxo-4,6,11,12,16,18,23,24-octahydrotetrabenzo [b,g,k,p][1,5,10,14]tetra azacyclooctadecine-2,13-dicarboxylic acid) and their Ti and Zr metal complexes in alcoholic media using microwave protocol. Macrocyclic ligands were synthesised by incorporating of 3,5-diaminobenzoic acid, phthalic acid and 3,4-diaminopyridine in 1:1:1 molar ratio. The macrocyclic ligands and their metal complexes have been characterised by elemental analysis, conductance measurement, magnetic measurement and their structure configurations have been determined by various spectroscopic (FTIR, ¹H/¹³C NMR, UV-Vis, LC-MS mass, XRD and TGA) techniques. [ZrL₂Cl₂]Cl₂ metal complex shows excellent antibacterial activity against ESBLs. A zone of inhibition and minimum inhibitory concentration was determined by McFarland and the dilution method, respectively. The spectral studies confirm the binding sites of the nitrogen atom of the macrocycles. An octahedral geometry has been assigned to the metal complexes based on the findings.

Growing Menace of Antibacterial Resistance in Clinical Isolates of Pseudomonas aeruginosa in Nepal: An Insight of Beta-Lactamase Production

Introduction. Pseudomonas aeruginosa is the most frequently isolated organism as it acts as the opportunistic pathogen and can cause infections in immunosuppressed patients. The production of different types of beta-lactamases renders this organism resistant to many commonly used antimicrobials. Therefore, the aim of this study was to document the antibiotic resistance rate in Pseudomonas aeruginosa isolated from different clinical specimens. Methods. Pseudomonas aeruginosa recovered was identified by standard microbiological methods. Antibiotic susceptibility testing was performed by modified Kirby-Bauer disc diffusion method following Clinical and Laboratory Standard Institute (CLSI) guidelines and all the suspected isolates were tested for the production of ESBLs, MBLs, and AmpC. Results. Out of total (178) isolates, 83.1% were recovered from the inpatient department (IPD). Majority of the isolates mediated resistance towards the beta-lactam antibiotics, while nearly half of the isolates were resistant to ciprofloxacin. Most of the aminoglycosides used showed resistance rate up to 75% but amikacin proved to be better option. No resistance to polymyxin was observed. ESBLs, MBLs, and AmpC mediated resistance was seen in 33.1%, 30.9%, and 15.7% isolates, respectively. Conclusions. Antibiotic resistance rate and beta-lactamase mediated resistance were high. Thus, regular surveillance of drug resistance is of utmost importance.

Multidrug Resistant and Extensively Drug Resistant Bacteria: A Study

Background and Objective. Antimicrobial resistance is now a major challenge to clinicians for treating patients. Hence, this short term study was undertaken to detect the incidence of multidrug-resistant (MDR), extensively drug-resistant (XDR), and pandrug-resistant (PDR) bacterial isolates in a tertiary care hospital. Material and Methods. The clinical samples were cultured and bacterial strains were identified in the department of microbiology. The antibiotic susceptibility profile of different bacterial isolates was studied to detect MDR, XDR, and PDR bacteria. Results. The antibiotic susceptibility profile of 1060 bacterial strains was studied. 393 (37.1%) bacterial strains were MDR, 146 (13.8%) strains were XDR, and no PDR was isolated. All (100%) Gram negative bacterial strains were sensitive to colistin whereas all (100%) Gram positive bacterial strains were sensitive to vancomycin. Conclusion. Close monitoring of MDR, XDR, or even PDR must be done by all clinical microbiology laboratories to implement effective measures to reduce the menace of antimicrobial resistance.

A qPCR and multiplex pyrosequencing assay combined with automated data processing for rapid and unambiguous detection of ESBL-producers Enterobacteriaceae

Rapid and specific detection of extended-spectrum β-lactamase-producing (ESBL) bacteria is crucial both for timely antibiotic therapy when treating infected patients as well as for appropriate infection control measures aimed at curbing the spread of ESBL-producing isolates. Whereas a variety of phenotypic methods are currently available for ESBL detection, they remain time consuming and sometimes difficult to interpret while being also affected by a lack of sensitivity and specificity. Considering the longer turnaround time (TAT) of susceptibility testing and culture results, DNA-based ESBL identification would be a valuable surrogate for phenotypic-based methods. Putative ESBL-positive Enterobacteriaceae isolates (n = 330) from clinical specimen were prospectively collected in Bulgaria, Romania and Democratic Republic of Congo and tested in this study. All isolates were assessed for ESBL-production by the E-test method and those giving undetermined ESBL status were re-tested using the combination disk test. A genotypic assay successively combining qPCR detection of blaCTX-M, blaTEM and blaSHV genes with a multiplex pyrosequencing of blaTEM and blaSHV genes was developed in order to detect the most common ESBL-associated TEM and SHV single nucleotides polymorphisms, irrespective of their plasmid and/or chromosomal location. This assay was applied on all Enterobacteriaceae isolates (n = 330). Phenotypic and genotypic results matched in 324/330 (98.2%). Accordingly, real-time PCR combined with multiplex pyrosequencing appears to be a reliable and easy-to-perform assay with high-throughput identification and fast TAT (~5 h).

Community acquired multi-drug resistant clinical isolates of Escherichia coli in a tertiary care center of Nepal

BACKGROUND

Multi-drug resistance (MDR) in Gram-negative organisms is an alarming problem in the world. MDR and extensively-drug resistance (XDR) is in increasing trend due to the production of different types of beta (β)-lactamases. Thus the aim of this study was to document the incidence of MDR and XDR in clinical isolates of Escherichia coli and also to find out the enzymatic mechanisms of β-lactam antibiotics resistance.

METHODS

Two hundred clinical isolates of Escherichia coli (E. coli) identified by standard laboratory methods were studied. Antibiotic susceptibility profile was performed for all the isolates and the suspected isolates were phenotypically tested for the production of extended spectrum β-lactamase (ESBL), metallo β-lactamase (MBL) and AmpC β-lactamase (AmpC) by recommended methods.

RESULTS

Around three-fourth (78%) of the total isolates were multi-drug resistant. ESBL, MBL and AmpC production was found in 24%, 15% and 9% of isolates respectively. Amikacin, chloramphenicol and colistin were found to be the most effective antibiotics.

CONCLUSIONS

High percentage of MDR was observed. β-lactamase mediated resistance was also high. Thus, regular surveillance of drug resistance due to β-lactamases production and infection control policy are of utmost importance to minimize the spread of resistant strains.

Prospective Evaluation of Colonization with Extended-Spectrum β-Lactamase (ESBL)–Producing Enterobacteriaceae Among Patients at Hospital Admission and of Subsequent Colonization with ESBL-Producing Enterobacteriaceae Among Patients During Hospitalization

Objective.

To determine the rates of and risk factors for carriage and acquisition of extended-spectrum (β-lactamase (ESBL)-producing Enterobacteriaceae during hospitalization.

Design.

Cohort study.

Setting.

Shaare Zedek Medical Center, a 550-bed teaching hospital.

Methods.

During a 5-month period (February 1-June 30, 2004), 167 (8%) of 1,985 newly admitted general medical patients were enrolled in our study. Nasal, oropharyngeal, and rectal swab specimens were obtained at admission and every 2-3 days until hospital discharge or death. Enterobacteriaceae isolates were tested for ESBL, andStaphylococcus aureusisolates were tested for methicillin resistance.

Results.

Of the 167 patients enrolled in our study, 15 (9%) were identified as nasal carriers of methicillin-resistantS. aureus(MRSA) at admission, and 13 (8%) were rectal carriers of ESBL-producing Enterobacteriaceae at admission. Univariate risk factors for rectal carriage of ESBL-producing Enterobacteriaceae included female sex (odds ratio [OR], 11 [95% confidence interval {CI}, 1.4—238];P< .05), nursing home residence (OR, 6.9 [95% CI, 1.8-27];P< .01), recent antibiotic treatment (OR, 9.8 [95% CI, 1.7-74];P< .05), and concomitant nasal carriage of MRSA and/or ESBL-producing Enterobacteriaceae (OR, 5.8 [95% CI, 1.2-26];P< .01). Multivariate risk factors were female sex and recent antibiotic treatment. During hospitalization, 35 (21%) of 167 patients had acquired rectal carriage of ESBL-producing Enterobacteriaceae (P= .002, for trend analysis). Of the 12 patients who were still in the hospital 2 weeks after admission, 4 (33%) were carriers of ESBL-producing Enterobacteriaceae. Univariate risk factors for acquisition included an age of older than 65 years (P< .005), nursing home residence (OR 2.6, [95% CI, 0.98-2.6]), impaired cognition (OR, 4.8 [95% CI, 1.9-12]), recent antibiotic treatment (OR, 2.7 [95% CI, 0.9-8.3]), respiratory assistance (OR, 4.2 [95% CI, 1.2-14]), and prolonged hospitalization. Multivariate risk factors were an age of older than 65 years and broad-spectrum antibiotic therapy.

Conclusions.

Rectal carriage of ESBL-producing Enterobacteriaceae occurred in 13 (8%) of 167 patients at admission to the medical departments of our hospital and in 4 (33%) of 12 patients still remaining in our hospital after 2 weeks.

Phenotypic and genetic features of enteropathogenic Escherichia coli isolates from diarrheal children in the Ribeirão Preto metropolitan area, São Paulo State, Brazil

This study was designed to characterize a collection of 60 enteropathogenic Escherichia coli (EPEC) isolates from diarrheic feces of patients in the Ribeirão Preto metropolitan area regarding different phenotypic and molecular features. We examined antibiotic resistance profiles, occurrence of virulence factors-encoding genes, intimin subtypes and the correlation of serotypes among typical (tEPEC) and atypical (aEPEC) EPEC isolates. The results demonstrated that atypical EPEC was more heterogeneous than typical EPEC concerning the characteristics investigated and 45.2% do not belong to classical EPEC serogroups. Intimin subtype β was the most frequent among the EPEC isolates (46.7%), being detected in both tEPEC and aEPEC. The majority of aEPEC isolates presented localized adherence-like (LAL) pattern to HEp-2 cells, although aEPEC isolates displaying diffuse adherence (DA) or non-adherent were also detected. High prevalence of antimicrobial resistance was found for ampicillin, cephalothin, sulfonamide and tetracycline. In general, tEPEC isolates were more resistant to the antimicrobials tested than aEPEC isolates.

Prevalence of extended-spectrum beta-lactamase-producing Enterobacteriaceae in healthy Swedish preschool children

AIM

The objective was to determine the prevalence of extended-spectrum beta-lactamase (ESBL)-producing Enterobacteriaceae in faeces from healthy Swedish preschool children and to establish whether transmission took place between children in preschools.

METHODS

Diapers from children attending preschools in Uppsala city were collected during September to October 2010, and the faeces was cultured. Antibiotic profiles and carriage of CTX-M, TEM, SHV and AmpC type enzymes were determined. PCR-positive isolates were further characterized by sequencing and epidemiological typing. Statistics on antibiotic use and ESBL producers in paediatric patients at Uppsala University Hospital were extracted for comparison.

RESULTS

A total of 313 stool specimens were obtained, representing 24.5% of all preschool children in Uppsala city. The carriage rate of ESBL-producing Enterobacteriaceae was 2.9% among these healthy children. The corresponding figure for patients in the same age group was 8.4%. Escherichia coli with CTX-M type enzymes predominated, and only one E. coli isolate carried genes-encoding CMY. CTX-M-producing E. coli isolates with identical genotypes were found in children with no familial relation at two different preschools.

CONCLUSIONS

Using diapers, the prevalence of ESBL-producing Enterobacteriaceae in children was quickly established, and, most likely, a transmission of ESBL-producing E. coli was for the first time documented between children at the same preschool.

CTX-M-producing Escherichia coli and Klebsiella pneumoniae isolated from community-acquired urinary tract infections in Valledupar, Colombia

OBJECTIVE

Describe the presence of CTX-M-1 phylogenetic subgroup extended-spectrum β-lactamases (ESBL), associated with TEM and SHV genes, and the gene encoding cephalosporinase, CMY-2 in Escherichia coli and Klebsiella pneumoniae isolates from community-acquired urinary tract infections.

METHODS

102 E. coli and 21K. pneumoniae were collected from patients with culture-proven urinary tract infection (UTI), during February and March, 2011. Antimicrobial susceptibility test was performed by disk diffusion according to the standards of the Clinical Laboratory Standard Institute. Screening for cephalosporins-resistant E. coli and K. pneumoniae was performed by PCR assay for bla(TEM), bla(SHV), bla(CTX-M-1),(-2),(-8),(-9), bla(PER-2) and bla(CMY-2) genes. Statistical analysis was performed by chi-squared test and multivariate logistic regression analysis.

RESULTS

ESBL production was detected in 12 (11.7%) E. coli and four (19%) K. pneumoniae isolates. TEM ESBLs were detected in seven E. coli and three K. pneumoniae isolates. SHV ESBLs were found in four K. pneumoniae isolates. CTX-M-1 phylogenetic subgroup was positive in seven E. coli and three K. pneumoniae isolates. CMY-2 β-lactamase gene was detected in nine E. coli and one K. pneumoniae isolates. A significant association of ESBL expression in E. coli was observed with resistance to tobramycin (p≤0.001), tetracycline (p=0.043), and ciprofloxacin (p≤0.001). In K. pneumoniae isolates, significant association was found with resistance to tobramycin and ciprofloxacin (p=0.006), and trimethoprim-sulfamethoxazole (p=0.043). Multivariate analyses did not show association between ESBL production in E. coli and K. pneumoniae, and resistance to non-β-lactams drugs.

CONCLUSIONS

CTX-M ESBL in uropathogens isolated from the community is cause for concern due to the enormous potential for multidrug resistance from strains that produce these enzymes, which could lead to failure of empirically-administered therapies and development of complicated UTIs.

Rapid molecular detection of extended-spectrum β-lactamase gene variants with a novel ligation-mediated real-time PCR

Extended-spectrum β-lactamases (ESBLs) are emerging worldwide, making rapid and adequate ESBL detection crucial for infection control measures as well as for the choice of correct antimicrobial therapy. The aim of this study was to compare the performance of a novel rapid ligation-mediated real-time PCR (LM-PCR) with a combination disc test (CDT). In total, 172 prospective putative ESBL-positive Enterobacteriaceae isolates from clinical specimens based on VITEK2 results were included in this study and tested with the phenotypic CDT and the LM-PCR. Positive ESBL results were obtained in 100 and 95 isolates using CDT and LM-PCR, respectively. The sensitivity, specificity, negative predictive value and positive predictive value of the LM-PCR were 99.0, 92.2, 98.6 and 94.0 %, respectively, compared with the CDT. The LM-PCR technique provides an important reduction in turnaround time (~4.5 h versus overnight incubation using CDT) for ESBL confirmation. As a consequence, all ESBL results are available within the same day, making this assay an important tool for rapid and accurate ESBL detection.

Matrix-assisted laser desorption ionization-time of flight mass spectrometry-based functional assay for rapid detection of resistance against β-lactam antibiotics

Resistance against β-lactam antibiotics is a growing challenge for managing severe bacterial infections. The rapid and cost-efficient determination of β-lactam resistance is an important prerequisite for the choice of an adequate antibiotic therapy. β-Lactam resistance is based mainly on the expression/overexpression of β-lactamases, which destroy the central β-lactam ring of these drugs by hydrolysis. Hydrolysis corresponds to a mass shift of +18 Da, which can be easily detected by matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS). Therefore, a MALDI-TOF MS-based assay was set up to investigate different enterobacteria for resistance against different β-lactam antibiotics: ampicillin, piperacillin, cefotaxime, ceftazidime, ertapenem, imipenem, and meropenem. β-Lactamases are enzymes that have a high turnover rate. Therefore, hydrolysis can be detected by MALDI-TOF MS already after a few hours of incubation of the bacteria to be tested with the given antibiotic. The comparison of the MS-derived data with the data from the routine procedure revealed identical classification of the bacteria according to sensitivity and resistance. The MALDI-TOF MS-based assay delivers the results on the same day. The approved routine procedures require at least an additional overnight incubation.

Nursing and physician attire as possible source of nosocomial infections

BACKGROUND

Uniforms worn by medical and nursing staff are not usually considered important in the transmission of microorganisms. We investigated the rate of potentially pathogenic bacteria present on uniforms worn by hospital staff, as well as the bacterial load of these microorganisms.

METHODS

Cultures were obtained from uniforms of nurses and physicians by pressing standard blood agar plates at the abdominal zone, sleeve ends, and pockets. Each participant completed a questionnaire.

RESULTS

A total of 238 samples were collected from 135 personnel, including 75 nurses (55%) and 60 physicians (45%). Of these, 79 (58%) claimed to change their uniform every day, and 104 (77%) defined the level of hygiene of their attire as fair to excellent. Potentially pathogenic bacteria were isolated from at least one site of the uniforms of 85 participants (63%) and were isolated from 119 samples (50%); 21 (14%) of the samples from nurses' gowns and 6 (6%) of the samples from physicians' gowns (P = NS) included of antibiotic-resistant bacteria.

CONCLUSION

Up to 60% of hospital staff's uniforms are colonized with potentially pathogenic bacteria, including drug-resistant organisms. It remains to be determined whether these bacteria can be transferred to patients and cause clinically relevant infection.

Comparison of nine phenotypic methods for detection of extended-spectrum beta-lactamase production by Enterobacteriaceae

The detection of extended-spectrum β-lactamase-producing (ESBL) bacteria is of importance for infection control and epidemiological surveillance. We aimed to compare phenotypic methods available in the routine laboratory and to evaluate two-step strategies using these methods for the detection of ESBL-positive Enterobacteriaceae. Two methods used for routine susceptibility testing (Vitek2 and disk diffusion methods) and seven methods designed for the detection of ESBL production (ESBL Etests, combination disks, double-disk synergy [DDS] methods on Mueller-Hinton [MH] agar and cloxacillin-containing MH agar, and the Cica-Beta test) were tested against 107 strains of Enterobacteriaceae not susceptible to extended-spectrum cephalosporins. All strains were screened for the presence of acquired ESBL-encoding genes by PCR, and the PCR result was considered the gold standard for evaluation of the other test methods. Among the 107 strains, 52 (49%) were ESBL positive. With Vitek2, sensitivities were the highest when using extended cards (73% to 79%), but 25% to 31% of the strains yielded indeterminate results. For the disk diffusion method, sensitivities were the highest (96%) when testing at least cefotaxime, cefepime, and a third compound (ceftazidime, cefpodoxime, or aztreonam). For the specific methods, specificities ranged from 62% (ceftazidime ESBL Etest) to 100% (DDS using a disk spacing of 20 mm). When a method designed for ESBL detection was used on strains considered ESBL negative or with an indeterminate result by a first routine susceptibility method, sensitivities reached 100% for a majority of combinations. In conclusion, two-step strategies using phenotypic methods available in most clinical laboratories may reach a sensitivity of 100% for ESBL detection among a large panel of species, including AmpC producers, providing a sensible choice of tests.

Determinants of beta-lactam resistance in meningitis-causing Enterobacteriaceae in Brazil

This study analyzed resistance determinants in extended-spectrum beta-lactamase (ESBL)-producing enterobacteria and the epidemiology of 11 Escherichia coli isolates obtained from meningitis patients in a region of Brazil from 2000 to 2005. ESBL-encoding genes and their genetic environment were investigated by PCR and sequencing. The gene blaCTX-M-2 was identified in 3 different enterobacteria (E. coli, Serratia marcescens, and Proteus mirabilis) downstream of the insertion sequence ISCR1 (localized in class 1 integrons), but not as part of the resistance cassettes region. Multilocus sequence typing (MLST) was used to investigate genetic relationships between the 11 E. coli isolates in this study and strains associated with meningitis in the E. coli MLST database. MLST analysis indicated high genetic diversity among isolates, and no significant genetic relationship was identified with meningitis-causing E. coli in the database. The results in this report reinforce the need to be attentive to meningitis suspected to be due to ESBL-producing enterobacterial isolates, especially where ESBL epidemiology is well known.

Prevalence, molecular characterization, and phenotypic confirmation of extended-spectrum beta-lactamases in Escherichia coli, Klebsiella pneumoniae, and Klebsiella oxytoca at the Radboud University Nijmegen Medical Centre in The Netherlands

The prevalence and molecular types of extended-spectrum beta-lactamases (ESBLs) were determined during a 1-year period in unselected clinical nonduplicate isolates of Escherichia coli (n = 1,738), Klebsiella pneumoniae (n = 436), and Klebsiella oxytoca (n = 208), cultured at the University Medical Centre Nijmegen, The Netherlands. Isolates identified as ESBL producer by the Phoenix automated system were collected prospectively and subjected to molecular analysis for the most common ESBLs TEM, SHV, and CTX-M, as well as OXA and GES. Both the Etest ESBL and double-disk synergy test were performed as confirmatory tests. The estimated prevalence of ESBLs was 2.1% in E. coli, 5.2% in K. pneumoniae, and 2.4% in K. oxytoca. TEM-12 and -26, SHV-5 and -12, and CTX-M groups 1 and 9 were the most frequent ESBLs found. Isolates identified as ESBLs by the Phoenix were confirmed by polymerase chain reaction (PCR) in only 42%. In ESBL PCR-positive E. coli and K. pneumoniae, both confirmatory tests were positive in 95% of the isolates. In 28% of the Etest and 13% of the double-disk synergy test-positive isolates, PCR could not detect any ESBL gene. In these cases, other resistance mechanisms may play a role. Confirmatory tests were unreliable for K. oxytoca. A previously described mutation in the K1 enzyme was detected in one ceftazidime-resistant K. oxytoca. The prevalence of ESBLs in The Netherlands is increasing. The predominant molecular types of ESBLs detected were comparable to other studies. Phoenix ESBL results need to be confirmed as advocated by ESBL detection guidelines.

Prevalence of extended-spectrum beta-lactamases-producing microorganisms in nosocomial patients and molecular characterization of the shv type isolates

The emergence of Extended-Spectrum Beta-Lactamase (ESBL)-producing microorganisms in Brazilian hospitals is a challenge that concerns scientists, clinicians and healthcare institutions due to the serious risk they pose to confined patients. The goal of this study was the detection of ESBL production by clinical strains of Escherichia coli and Klebsiella sp. isolated from pus, urine and blood of patients at Hospital Universitário Santa Maria, Rio Grande Sul, RS, Brazil and the genotyping of the isolates based on bla SHV genes. The ESBL study was carried out using the Combined Disc Method, while Polymerase Chain Reaction (PCR) was used to study the bla SHV genes. Of the 90 tested isolates, 55 (61.1%) were identified as ESBL-producing by the combined disk method. The bla SHV genes were found in 67.8% of these microorganisms. K. pneumoniae predominated in the samples, presenting the highest frequency of positive results from the combined disk and PCR.

High prevalence of extended-spectrum beta-lactamase-producing enterobacteriaceae in bacteremia after transrectal ultrasound-guided prostate biopsy: a need for changing preventive protocol

OBJECTIVES

To determine whether the incidence of bacteremia after transrectal ultrasound-guided prostate biopsy (TRUSGPB) significantly diminishes with the setting up of a new preventive protocol. This protocol was set up after detecting an augmented incidence of bacteremia after TRUSGPB with a high prevalence of antibiotic-resistant microorganisms.

METHODS

Retrospective descriptive and prospective intervention study performed at a University Hospital.

PARTICIPANTS

Patients undergoing TRUSGPB under the old preventive protocol (January 2006-February 2007), that is, amoxicillin-clavulanate 500 mg tid the day before, the day of the procedure, and 1 day after the procedure, and after setting up a new protocol (March 2007-April 2008), that is, 2 g cefoxitin 1 hour before the procedure and ciprofloxacin 750 mg p.o. bid the day before, the day of the procedure, and 3 days after the procedure; dipstick urinalysis was performed before the procedure, and patients with positive results were not biopsied.

RESULTS

Incidence of bacteremia with old and new protocols: 9 of 204 procedures (4.4%) vs 2 of 207 (0.9%), (P = .03). Four isolates (44.4%) under the old protocol produced extended-spectrum beta-lactamase (ESBL). With the new protocol, 2 (0.9%) cases of non-ESBL Escherichia coli bacteremia were observed. Sixty-five (23.8%) cases were not biopsied because of positive result of dipstick urinalysis, lack of antibiotic prophylaxis adherence, or altered coagulation parameters.

CONCLUSIONS

Antibiotic prophylaxis for TRUSGPB should take into account local resistance patterns. Cefoxitin could be used as prophylaxis in centers with high prevalence of ESBL enterobacteriaceae. Before TRUSGPB, excluding patients with positive results of dipstick urinalysis is an advisable practice.

Prevalência das famílias TEM, SHV e CTX-M de β-lactamases de espectro estendido em Escherichia coli e Klebsiella spp no Hospital Universitário de Santa Maria, Estado do Rio Grande do Sul

Neste estudo estimou-se a distribuição e prevalência de β-lactamases de espectro estendido pertencentes às famílias TEM, SHV e CTX-M entre amostras de Escherichia coli e Klebsiella spp. no Hospital Universitário de Santa Maria, Rio Grande do Sul. Durante 14 meses, 90 microrganismos foram selecionados como prováveis produtores de ESBL. Os isolados foram submetidos a testes fenotípicos confirmatórios para a presença de ESBL. A seguir, os tipos de ESBLs presentes em cada microrganismo foram determinados através da pesquisa dos respectivos genes através da reação em cadeia da polimerase. Empregando-se o método do disco combinado, a presença de ESBLs foi confirmada em 55 (61,1%) amostras; quando o método do duplo disco foi utilizado, 57 (63,3%) amostras foramprodutoras de ESBLs. Com base na PCR, as ESBLs do tipo TEM e SHV foram mais presentes em Klebsiella pneumoniae enquanto que ESBL do tipo CTX-M foram mais presentes em Klebsiella oxytoca.

Prevalence and genetic characterization of blaCTX-M among Klebsiella pneumoniae isolates collected in an intensive care unit in Brazil

Thirteen (44.8%) CTX-M-2-producing K. pneumoniae clinical isolates were identified among 29 strains collected from single patients with serious infection hospitalized in an intensive care unit of a tertiary hospital located in São Paulo, Brazil. These isolates belonged to 9 different typing clusters and showed great diversity of plasmid content. Their bla(CTX-M-2)was carried in an ISCR1/sul1-type integron structure located in transferable plasmids of different sizes or in the chromosome.

Extended-spectrum β-lactamase (ESBL) in Omani Children: Study of prevalence, risk factors and clinical outcomes at Sultan Qaboos University Hospital, Sultanate of Oman

OBJECTIVES

Antimicrobial resistance is a growing problem worldwide, which imposes difficulties in the selection of appropriate empirical antimicrobial therapy. This study evaluated extended-spectrum β-lactamase (ESBL) isolates in 2005 in The Department of Child Health at Sultan Qaboos University Hospital (SQUH), Oman.

METHODS

During the 12 month period from January 2005 to December 2005, ESBL isolates from paediatrics inpatients were identified and analysed. Risk factors for the patients who grew ESBLs were analysed.

RESULTS

13.3% of E. coli and 16.6% of Klebsiella pneumoniae isolated were ESBL producers. Most of the ESBLs were from urine (46.2%) and blood (42.6%). The main risk factors for ESBL in these children were previous exposure to antimicrobials (100%), prolonged hospital stay, severe illness (92.3%) and female gender (84.6%). Sensitivity of 100% was observed to carbapenems whereas 92% of the isolates were susceptible to amikacin. The oximino-cephalosporins were 100% resistant. Klebsiella pneumoniae were 100% resistant to piperacillin-tazobactam and nitrofurantoin. E. coli was 100% resistant to trimethoprim-sulfamethoxazole and ciprofloxacin. No resistance was recorded for the following combinations: amikacin plus piperacillin-tazobactam, amikacin plus nitrofurantoin and gentamicin plus nitrofurantoin.

CONCLUSION

ESBL-producing organisms are becoming a major problem in Omani children. Exposure to antimicrobials and long admissions are modifiable risk factors that should be targeted for better control. Carbapenems are the most sensitive and reliable treatment options for infections caused by ESBLs. Amikacin plus piperacillin-tazobactam or nitrofurantoin are good alternatives.

Antibiotic combination as empirical therapy for extended spectrum Beta-lactamase

BACKGROUND

extended spectrum β-lactamase (ESBL) producing gram negative bacilli are becoming a growing problem worldwide with difficulties in designing a national formulary for empirical treatment of gram negative sepsis.

OBJECTIVES

In this study, we investigated the in vitro activity of Carbapenems, Pipracillin-Tazobactam, Ciprofloxacin alone or in combination with aminoglycosides against ESBL-producing strains isolated from clinical samples.

METHODS

Three hundred and one ESBL-producing Escherichia coli and K. pneumoniae strains isolated from clinical samples were investigated. Isolates were screened initially for ESBL production using an automated system. All ESBL isolates were further confirmed using the double-disk diffusion method.

RESULTS

The overall Piperacillin-Tazobactam susceptibility was 57.9 (64.4% E. coli and 43.6% Klebsiella pneumoniae). Only 29.6% of ESBLs (24.9% E. coli and 39.6% Klebsiella pneumoniae) were ciprofloxacin susceptible. 98.1% E. coli and 93.1% of Klebsiella pneumoniae were susceptible to Piperacillin-Tazobactam plus Amikacin combination. 73.7% E. coli and 61.4% of Klebsiella pneumoniae were susceptible to Piperacillin-Tazobactam plus Gentamicin combination. 96.7% E. coli and 91.1% of Klebsiella pneumoniae were susceptible to Ciprofloxacin plus Amikacin combination. 41.2% E. coli and 51.5% of Klebsiella pneumoniae were susceptible to Ciprofloxacin plus Gentamicin combination.

CONCLUSION

ESBLs have high resistance profile against Piperacillin/Tazobactam and Ciprofloxacin. The ESBLs from Oman have similar resistantce pattern as those reported from UK and USA. This resistance decreases when these drugs are combined with Amikacin. All ESBLs are susceptible to Carbapenems. However, carbepenam overuse can lead to emergence of carbapenems resistant gram negative bacilli and ESBLs. Combination of Amikacin plus Piperacillin/Tazobactam is a feasible empirical therapy for ESBLs.

Clonal transmission of ESBL-producing Klebsiella spp. at a university hospital in Brazil

The present study was designed to determine the prevalence and extended-spectrum beta-lactamase (ESBL) types in clinical isolates of Klebsiella spp. at a university hospital located in the Brazilian southern region (Ribeirão Preto, São Paulo) as well as their antibiotic susceptibility and genetic profiles. This study included 147 non-repeat Klebsiella spp. isolates collected from January to June 2000, of which 23 K. pneumoniae and 8 K. oxytoca were selected as ESBL producers by using the Oxoid combination disk method and Etest ESBL strip. beta-lactamases were characterized by IEF, PCR and sequencing assays using primers for ESBL genes. Antibiotic susceptibility was evaluated by MicroScan system. Dissemination of two major clones of ESBL-producing Klebsiella spp. occurred in the hospital. According to the results obtained in this study there was a clonal spread of CTX-M-producing K. oxytoca in five clinics and dissemination of ESBL-producing K. pneumoniae in the nursery and pediatrics wards.

The continuing challenge of ESBLs

Since their first description more than 20 years ago, Escherichia coli and Klebsiella pneumoniae possessing extended-spectrum class A beta-lactamases (ESBLs) continue to thwart our best clinical efforts. In the 'early years' the most common beta-lactamases were of the TEM and SHV varieties. Now, CTX-M enzymes are being discovered throughout the world and are becoming the most prevalent beta-lactamases found in clinical isolates. The K. pneumoniae carbapenemases (KPC) (ESBL-type enzymes that confer resistance to extended-spectrum cephalosporins and carbapenems) present the most significant challenge to date. Structural studies of ESBLs indicate that active site expansion and remodeling are responsible for this extended hydrolytic activity. Continuing questions still exist regarding the optimal detection method for ESBLs. Most relevant are the increasing concerns regarding the status of carbapenems as 'best therapy' for ESBL-producing bacteria in light of the emergence of carbapenemases.

Multilocus Sequence Typing of Uropathogenic ESBL-Producing Escherichia coli Isolated in a Brazilian Community

In the present study, multilocus sequence typing (MLST), pulsed-field gel electrophoresis (PFGE) and polymerase chain reaction detection of three resistance genes were combined to characterize seven uropathogenic E. coli isolated from outpatients. Selected portions of seven housekeeping and three antibiotic-resistance genes of the isolates were sequenced. The seven isolates were classified into four different sequence types (STs) by MLST and five PGFE types. Three isolates had a novel allelic profile representing a new ST designated as ST528 and showed the same PFGE and resistance genes. Two isolates, both characterized as ST359, were differentiated by PFGE and shared only one of the antibiotic-resistance genes studied. Comparison of MLST results with those of PFGE and resistance genes demonstrated that Escherichia coli had acquired different antibiotic-resistance genes and DNA rearrangements, causing alterations in PFGE patterns but maintaining the same ST. Furthermore, this article also reports the first detection of a CTX-M-2 ESBL E. coli and SHV-5 in a Brazilian community.

Sensitivity and specificity of various beta-lactam antibiotics and phenotypical methods for detection of TEM, SHV and CTX-M extended-spectrum beta-lactamases

The aim of this study was to compare the sensitivity and specificity of six different beta-lactam antibiotics using five phenotypical tests for detection of extended spectrum beta-lactamases (ESBLs) based on synergism of beta-lactam antibiotics and clavulanate. Experiments were performed on a set of 80 Klebsiella pneumoniae strains and 105 Escherichia coli strains with previously characterized ESBLs (SHV, TEM and CTX-M). ESBLs were detected by five different phenotypical methods: MIC (minimum inhibitory concentration) determination of beta-lactam antibiotics with and without clavulanate, double-disk synergy test (DDST), inhibitor-potentiated disk-diffusion test (IPDDT), CLSI-Clinical and Laboratory Standard Institution (former NCCLS) combined-disk-test, and modified MAST-disk-diffusion test (MAST-DD-test). Seven antibiotics were tested as indicators of ESBL production: ceftazidime, cefotaxime, ceftriaxone, aztreonam, ceftibuten, cefpodoxime and cefepime. Ceftazidime and aztreonam were the best indicators for SHV-5, SHV-12 and TEM beta-lactamases whereas cefotaxime and ceftriaxone were the most sensitive in detection of SHV-2 and CTX-M beta-lactamases in DDST, IPDDT and CLSI test. MIC determination of beta-lactam antibiotics with and without clavulanate was the most sensitive method. DDST was the least sensitive test. Double-disk synergy test, which is the most frequently used test for detection of ESBLs in routine laboratories, was the least sensitive independently of the indicator antibiotic. Since MIC determination is a very laborious and time consuming method, we would recommend the NCCLS combined disk test or IPDD test for detection of ESBLs in routine laboratories with 5 mm zone augmentation breakpoint.

Prevalence of community-occurring extended spectrum beta-lactamase-producing Enterobacteriaceae in Brazil

The occurrence of extended-spectrum-beta-lactamase (ESBL)-producing strains in the community was investigated in a private laboratory located in Juiz de Fora, Brazil. All enterobacterial isolates analysed were collected from urine of human patients between the years 2000 and 2002. ESBL production was confirmed by double disk screening, combination disk method, and Etest ESBL strip. The isoelectric point of each beta-lactamase was determined in the crude extracts from each isolate. Detection of ESBL genes was performed by polymerase chain reaction and the genetic relatedness of the isolates determined by pulsed-field gel electrophoresis (PFGE). Of the 1,481 isolates, 22 (12 Klebsiella pneumoniae, 7 Escherichia coli, 1 Providencia stuartii, 1 Citrobacter freundii, and 1 Serratia marcescens) were identified as ESBL producers. The frequency of ESBL producers in the community was 1.48%. TEM-type enzymes were identified in 95.4% of the isolates, followed by the SHV type. Seven strains produced CTX-M-type enzymes. This study showed that strains producing multiple beta-lactamases are also present in community-acquired bacterial isolates. Multiple strains exhibiting identical PFGE genotypes were found in individual patients indicating a common source of acquisition.