No abstract available.
beta-Lactamases*

No abstract available.
beta-Lactamases*

BACKGROUND: Resistance to beta-lactams in E. coli is mostly via acquisition of plasmid-mediated beta-lactamase gene. Among the plasmid-mediated beta-lactamases, TEM-1 beta-lactamase is by far the most prevalent among ampicillin-resistant E. coli. The prevalence of TEM-1 or TEM-2 ranged from 61% to 98% across the surveys. Klebsiella species generally have class A chromosomal beta-lactamases, which differ greatly from the class C types. Most K. pneumoniae isolates have chromosomally mediated SHV-1 beta-lactamase in most surveys. There has been only one report of prevalence and types of beta-lactamases in E. coli and K. pneumoniae in Korea. We performed this study to determine the prevalence and types of beta-lactamases in E. coli and K. pneumoniae isolated in Korea. METHODS: Ampicillin resistance was determined by disk diffusion test (E. coli) and agar dilution method (K. pneumoniae). Fifty five isolates of E. coli and 92 isolates of K. pneumoniae which were derived from patients in 2 university hospitals in Korea during 1996 were tested by TEM- and SHV-specific PCR. RESULTS: The ampicillin resistance rate in E. coli and K. pneumoniae was 82% and 94.6%, respectively. TEM-type beta-lactamase gene was found in 53% of E. coli isolates. 93.5% of K. pneumoniae isolates was found to have SHV-type beta- lactamase gene. CONCLUSION: In Korea TEM-type beta-lactamase gene was most prevalent in E. coli, but its prevalence rate was relatively low compared with those in other country. For K. pneumoniae, the isolates with SHV type beta-lactamase gene were predominant.
Agar ; Ampicillin Resistance ; beta-Lactamases* ; beta-Lactams ; Diffusion ; Escherichia coli* ; Escherichia* ; Hospitals, University ; Humans ; Klebsiella pneumoniae* ; Klebsiella* ; Korea* ; Penicillinase ; Pneumonia ; Polymerase Chain Reaction ; Prevalence*

BACKGROUND: The prevalence of extended-spectrum beta-lactamase(ESBL)-producing organisms has been increasing in Korea. We performed a study to characterize various TEM derivatives with clinical isolates of Klebsiella pneumoniae collected from 3 hospitals in Korea. METHODS: Fifty-seven isolates of ESBL-producing K. pneumoniae collected from 3 hospitals were screened by TEM-specific PCR for the carriage of TEM genes. Thirteen strains were found to have TEM-related genes. Eleven blaTEM genes were amplifed and sequenced. The transfer of resistance was tested by conjugation and isoelectric points of beta-lactamases were determined. MICs were measured to obtain a resistance pattern for each indivudual wild- type and transconjugant strain. The hydrolysis rate of TEM-52 was measured spectrophotometrically. RESULTS: Ten strains carried plasmid-mediated CTEM-52 gene, which sequence showed the substitution of 3 amino acids compared to that of TEM-1: 104 glutamic acid --> lysine (GAG --> AAG), 182 methionine --> threonine (ATG --> ACG), and 238 glycine --> serine (GGT --> AGT). MIC showed that TEM-52 mediated a resistance to ceftazidime and aztreonam at a lower level than to cefotaxime. TEM-52 enzyme hydrolyzed cefotaxime efficiently (Vmax, 340) and showed fairly weak activity for ceftazidime (Vmax, 15.1), but very weak activity for aztreonam. The gene of TEM-52 beta-lactamases was mediated by approximately 77-kb plasmids. CONCLUSION: From these results, we conclude that the TEM-52 beta-lactamase is a common TEM- type ESBL in K. pneumoniae in Korea.
Amino Acids ; Aztreonam ; beta-Lactamases* ; Cefotaxime ; Ceftazidime ; Glutamic Acid ; Glycine ; Hydrolysis ; Isoelectric Point ; Klebsiella pneumoniae* ; Klebsiella* ; Korea ; Lysine ; Methionine ; Penicillinase ; Plasmids ; Pneumonia ; Polymerase Chain Reaction ; Prevalence ; Serine ; Threonine

BACKGROUND: Accurate detection of organisms producing extended-spectrum beta-lactamase (ESBL) and AmpC beta-lactamase is very important for treatment of patients. However, unlike the ESBL confirmatory test, there are no guidelines for detection of organisms producing AmpC beta-lactamase. We evaluated a detection method using boronic acid (BA) for ESBL and AmpC beta-lactamase. METHODS: Clinical isolates of Escherichia coli, Klebsiella pneumoniae, Klebsiella oxytoca, and Proteus mirabilis showing intermediate resistance or resistance to cefoxitin (FOX) or positive for ESBL were tested. A > or =5 mm increase in zone diameter of ceftazidime/clavulanic acid/BA (CAZ/CA/BA) and/or cefotaxime/clavulanic acid/BA (CTX/CA/BA) versus CAZ/BA and/or CTX /BA was considered positive for ESBL. Likewise, a > or =5 mm increase in zone diameter of FOX/BA and/or cefotetan/BA (CTT/BA) versus FOX and/or CTT alone was considered positive for AmpC beta-lactamase. RESULTS: Among 622 clinical isolates, ESBL positive rates by the CLSI ESBL confirmatory test or by the BA method were 18.1% or 18.4% for E. coli, 38.3% or 40.4% for K. pneumoniae, 8.7% or 8.7% for K. oxytoca, and 14.8% or 14.8% for P. mirabilis, respectively. AmpC beta-lactamase positive rates using the BA method were 3.7% for E. coli, 33.3% for K. pneumoniae, 0% for K. oxytoca, and 7.4% for P. mirabilis. The detection rates of coproducing ESBL and AmpC beta-lactamase were 2.4% in E. coli 27.1% in K. pneumoniae, and 3.7% in P. mirabilis. CONCLUSION: The ESBL confirmatory method using BA was found to enhance the detection of ESBLs, even when potentially masked by AmpC beta-lactamase.
Bacterial Proteins ; beta-Lactamases ; Boron ; Cefoxitin ; Escherichia ; Escherichia coli ; Humans ; Klebsiella ; Klebsiella oxytoca ; Klebsiella pneumoniae ; Masks ; Mirabilis ; Penicillinase ; Pneumonia ; Proteus ; Proteus mirabilis

Background:blaTEM, bla SHV, blaCTX \ufffd?M, blaOXA genes encode for extended spectrum \u03b2 \ufffd?lactamases resistance to broad \ufffd?spectrumcephalosporins. Many species belonging the family Enterobacteriaceae possess these genes. Objectives: To determine the distribution of blaTEM, bla SHV, blaCTX \ufffd?M and blaOXA genes in enteroaggregation E.coli (EAEC) strains. Subjects and method: 67 EAEC strains causing diarrhea and 18 strains isolated from healthy children were screened by PCR with primers specific to blaTEM, bla SHV, blaCTX \ufffd?M \ufffd?1and blaOXA genes. Results: The prevalence of ESBL genes in diarrheagenic EAEC strains and those isolated from healthy children were 83.6 and 72.2 %, respectively. The highest prevalence blaTEM gene (82% in diarrheagenic EAEC strains and 72.2% in isolated from healthy children) was followed by that of blaOXA gene (11.9 and 11.1% in two EAEC groups). Only 2 strains possess blaSHV gene. The blaCTX \ufffd?M \ufffd?1 was not detected in any EAEC strain. Conclusion: our findings have not only provided additional understanding of the distribution of blaTEM, bla SHV, blaCTX \ufffd?M - 1 and blaOXA genes in EAEC strains but also have a given significance in selecting antibiotics for treatment.
beta-Lactamases/ genetics ; Escherichia coli ;

Background:Resistance to antibiotics due to extended \ufffd?spectrum \ufffd?Lactamase (ESBL) which increased quickly, made treatment much more difficult. However, this matter was not enough to be concerned in our country. Objectives: To investigate the prevalence of ESBL producing among clinical isolates of E.coli, K.pneumoniae and Enterobacter spp and the classification of ESBLs gene by PCR. Subjects and method: 663 strains, including 248 E.coli, 393 K.pneumoniae, 22 Enterobacter spp, isolated from patients in Viet Tiep hospital (Hai Phong), Bach Mai and Pediatric hospital (Ha Noi). ESBLs were detected using modified double \ufffd?disc method. The classification of ESBLs producing strains was implemented by PCR. Results:the percentage of ESBL producing in E.coli, K.pneumoniae and Enterobacter spp is 20.2; 18.3 and 36.4%, respectively. The ESBLs producing strains were co \ufffd?resistant to most of the tested antibiotics. These strains were prevalent in intensive care units (sputum or respiratory fluid samples). TEM, SHV, CTX \ufffd?M, OXA were 87.7; 62.3; 24.6 and 12.3%, respectively. They were detected alone or in combination in the same strain. Conclusion: The rate of ESBLs producing strains is high. ESBLs were marker for multi \ufffd?drug resistance. TEM and SHV type ESBLs are most prevalent in the tested strains.
beta-Lactamases ; Klebsiella pneumoniae ; Enterobacter ; Escherichia coli ;

Extended-spectrum beta-lactamases (ESBLs), mediated by plasmids, can hydrolyze and cause resistance to penicillins, broad spectrum-cephalosporins, and monobactams. Most ESBLs are derived from the widespread broad-spectrum beta-lactamases TEM-1 and SHV-1. There are also other families of ESBLs, including CTX-M and OXA-type enzymes as well as novel unrelated beta-lactamases. This article reviews recent advances in the classification, characteristics, and other molecular biological aspects of ESBLs.
Molecular Biology ; beta-Lactamases ; classification ; genetics

Aims: The detection of the metallo-beta-lactamase (MBL) producing Pseudomonas aeruginosa isolates is crucial for infection control and public health. The present study aimed to investigate the MBL production in carbapenem-resistant P. aeruginosa isolated from various clinical samples in Kastamonu Training and Research Hospital, Turkey. Methodology and results: Seventy-three carbapenem-resistant P. aeruginosa isolates were recovered from different patients between April 2018 and November 2020. Identification of the isolates was performed by conventional methods (culture examination, determination of Gram reaction, and oxidase test) and an automated system (Vitek 2). Antibiotic susceptibility patterns were determined using the Vitek 2 and the results were interpreted based on the European Committee on Antimicrobial Susceptibility Testing (EUCAST) standards. The MBL production was phenotypically investigated using the imipenem-EDTA combined disk test. The presence of beta-lactamase IMP (blaIMP), beta-lactamase VIM (blaVIM) and beta-lactamase GIM (blaGIM) genes were determined using PCR to confirm the MBL production. Seventy-one isolates (97%, n=71/73) were resistant to imipenem, sixty-four isolates (88%, n=64/73) to meropenem and sixty-two isolates (85%, n=62/73) to both imipenem and meropenem. Sixty-five isolates (89%, n=65/73) were defined as multidrug-resistant. The MBL production was detected in 57 isolates (78%, n=57/73) phenotypically. However, the blaIMP, blaVIM and blaGIM genes were not detected in all the isolates. Conclusion, significance and impact of study It was determined that there were no imipenemase (IMP), Verona integron-encoded metallo-beta-lactamase (VIM) and German imipenemase (GIM) type MBLs in carbapenem-resistant P. aeruginosa isolated from Kastamonu Training and Research Hospital. MBL production in carbapenem-resistant P. aeruginosa strains can be investigated phenotypically. However, confirmation of results with molecular tests is especially significant for epidemiological studies.
beta-Lactamases ; Carbapenem-Resistant Enterobacteriaceae ; Pseudomonas aeruginosa

The dogma that ampC genes are located exclusively on the chromosome was dominant until about 10 years ago. Since 1989 over 15 different plasmid-encoded AmpC beta-lactamases have been reported from several countries. Most of these enzymes evolved in two clusters. The major cluster includes several enzymes with a high similarity to CMY-2, which is the closest related chromosomal AmpC enzyme of Citrobacter freundii. A second cluster centers around CMY-1. It is less homogeneous and not closely related chromosomal AmpC enzymes. Molecular diversification by amino acid substitutions does not usually translate into a change in the resistance phenotype. At this time, CMY-2 appears to be the most prevalent and widely distributed. Further global increase of prevalence and diversity of plasmidic AmpC beta-lactamases have to be anticipated in the next millenium.
Microbiology/trends ; Plasmids/genetics* ; Structure-Activity Relationship ; Tissue Distribution ; beta-Lactamases/metabolism ; beta-Lactamases/genetics*