One new LEN enzyme and two new OKP enzymes in Klebsiella pneumoniae clinical isolates and proposed nomenclature for chromosomal beta-lactamases of this species.
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ABSTRACT:
SUBMITTER: Siebor E
PROVIDER: S-EPMC1168668 | biostudies-literature | 2005 Jul
REPOSITORIES: biostudies-literature
Publications
One new LEN enzyme and two new OKP enzymes in Klebsiella pneumoniae clinical isolates and proposed nomenclature for chromosomal beta-lactamases of this species.
Siebor Eliane E Péchinot André A Duez Jean-Marie JM Neuwirth Catherine C
Antimicrobial agents and chemotherapy 20050701 7
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Project description:Despite the discovery of novel beta-lactamases such as extended-spectrum beta-lactamases (ESBLs), imported AmpC, and carbapenem-hydrolyzing beta-lactamases at least a decade ago, there remains a low level of awareness of their importance and how to detect them. There is a need to increase the levels of awareness of clinical laboratories about the detection of newer beta-lactamases. Therefore, a study was conducted in 2000 to investigate the occurrence of these beta-lactamases in Klebsiella pneumoniae isolates at 24 U.S. medical centers. To enhance the likelihood of detecting imported AmpC and carbapenem-hydrolyzing beta-lactamases, participating laboratories were permitted to include archived strains (1996 to 2000) that were intermediate or resistant to either cefoxitin or imipenem. The beta-lactamase production of 408 isolates positive by screening of 1,123 isolates was investigated by ESBL phenotypic confirmation tests; and for AmpC and carbapenem-hydrolyzing beta-lactamases, three-dimensional tests, isoelectric focusing, beta-lactamase inhibitor studies, spectrophotometric assays, induction assays, and molecular tests were used. ESBL-producing isolates were detected at 18 of the 24 sites (75%), imported AmpC-producing isolates were detected at 10 sites (42%), inducible imported AmpC-producing isolates were detected at 3 sites (12.5%), and a molecular class A carbapenem-hydrolyzing enzyme was detected at 1 site (4%). No class B or D carbapenem-hydrolyzing enzymes were detected. ESBLs and imported AmpC beta-lactamases were detected at a significant number of sites, indicating widespread penetration of these enzymes into U.S. medical institutions. Because these enzymes may significantly affect therapeutic outcomes, it is vital that clinical laboratories be aware of them and be able to detect their occurrence.
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Project description:Nosocomial infections caused by Klebsiella pneumoniae are primarily characterized by a high prevalence of extended-spectrum β-lactamases (ESBL's) and a soaring pace of carbapenemase dissemination. Availability of limited antimicrobial agents as a therapeutic option for multidrug-resistant bacteria raises an alarming concern. This study aimed at the molecular characterization of multidrug-resistant K. pneumoniae clinical isolates and studied the role of efflux pumps in β-lactam resistance. Thirty-three isolates confirmed as ESBL-positive K. pneumoniae that harbored resistance genes to major classes of antibiotics. The results showed that CTX-M15 was the preeminent β-lactamase along with carbapenemases in ESBL-positive isolates. However, the efficacy of different antibiotics varied in the presence of lactamase inhibitors and efflux pump inhibitors (EPIs). Those showing increased efficacy of antibiotics with EPI were further explored for the expression of efflux pump genes and expressed a significantly different level of efflux pumps. We found that an isolate had higher expression of kpnF (SMR family) and kdeA (MATE family) pump genes relative to RND family pump genes. No mutations were observed in the genes for porins. Together, the findings suggest that β-lactamases are not the only single factor responsible for providing resistance against the existing β-lactam drugs. Resistance may increase many folds by simultaneous expression of RND family (the most prominent family in Gram-negative bacteria) and other efflux pump family.
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Project description:The increase in the prevalence of infections caused by certain bacteria, such as Klebsiella pneumonia (K. pneumoniae), is a global health concern. Bacterial production of an enzyme called extended-spectrum beta-lactamase (ESBL) can generate resistance to antimicrobial therapeutics. Therefore, between 2012 and 2013, we investigated K. pneumoniae that produce ESBLs with the prevalence of individual genes including blaSHV, blaCTX-M, blaTEM, and blaOXA isolated from clinical samples. A total of 99 variable diagnostic samples including blood from hematological malignancies (n = 14) or other clinical sources including sputum, pus, urine, and wound (n = 85) were analyzed. All samples' bacterial type was confirmed and their susceptibility to antimicrobial agents was established. Polymerase chain reaction (PCR) amplification was carried out to ascertain presence of specific genes that included blaSHV, blaCTX-M, blaTEM, and blaOXA. Plasmid DNA profiles were determined to assess significance between resistance to antimicrobial agents and plasmid number. It was found that among non-hematologic malignancy isolates, the highest rate of resistance was 87.9% to imipenem, with lowest rate being 2% to ampicillin. However, in hematologic malignancy isolates, the highest microbial resistance was 92.9% to ampicillin with the lowest rate of resistance at 28.6% to imipenem. Among collected isolates, 45% were ESBL-producers with 50% occurrence in hematologic malignancy individuals that were ESBL-producers. Within ESBL-producing isolates from hematologic malignancy individuals, blaSHV was detected in 100%, blaCTX-M in 85.7%, and blaTEM and blaOXA-1 at 57.1% and 27.1%, respectively. In addition, blaSHV, blaCTX-M, and blaOXA were found in all non-hematological malignancy individuals with blaTEM detected in 55.5% of samples. Our findings indicate that ESBLs expressing blaSHV and blaCTX-M genes are significantly prevalent in K. pneumoniae isolates from hematologic malignancy individuals. Plasmid analysis indicated plasmids in isolates collected from hematological malignancy individuals. Furthermore, there was a correlation between resistance to antimicrobial agents and plasmids within two groups analyzed. This study indicates an increase in incidence of K. pneumoniae infections displaying ESBL phenotypes in Jordan.
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Project description:We tested 190 Klebsiella pneumoniae bloodstream isolates recovered from 189 patients in 30 U.S. hospitals in 23 states to determine the occurrence of extended-spectrum beta-lactamase (ESBL) and AmpC beta-lactamase producers. Based on growth inhibition by clavulanic acid by disk and MIC test methods, 18 (9.5%) of the isolates produced ESBLs. Although the disk diffusion method with standard breakpoints identified 28 cefoxitin-nonsusceptible isolates, only 5 (18%) of these were confirmed as AmpC producers. Of two AmpC confirmatory tests, the three-dimensional extract test was easier to perform than was the double-disk approximation test using a novel inhibitor, Syn2190. Three of the five AmpC producers carried the bla(FOX-5) gene, while the other two isolates harbored the bla(ACT-1) gene. All AmpC genes were transferable. In vitro susceptibility testing with standard inocula showed that all five AmpC-producing strains were susceptible to cefepime, imipenem, and ertapenem but that with a high inoculum, more of these strains were susceptible to the carbapenems than to cefepime. All but 1 of 14 screen-positive AmpC nonproducers (and ESBL nonproducers) were susceptible to ceftriaxone and cefepime at the standard inoculum as were 6 of 6 isolates that were randomly selected and tested with a high inoculum. These results indicate that (i). a significant number of K. pneumoniae bloodstream isolates harbor ESBL or AmpC beta-lactamases, (ii). confirmatory tests are necessary to identify true AmpC producers, and (iii). in vitro, carbapenems are active against AmpC-producing strains of K. pneumoniae.
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Project description:Background and objectivesPlasmid-mediated AmpC producers are considered an increasing concern. The aim of this study was to investigate the prevalence of plasmid-mediated AmpC β-lactamases (pAmpCs) in Klebsiella pneumoniae isolates.Materials and methodsA total of 228 clinical isolates of K. pneumoniae were collected in Bushehr province, Iran, from December 2017 to February 2019. Cefoxitin disks were applied for screening AmpC-producing isolates. Furthermore, 3 phenotypic confirmatory tests including combine disk test (CDT), double disk synergy test (DDST) and modified three dimensional test (M3DT) were used. Finally, the presence of pAmpC genes was tested by multiplex PCR.ResultsWe identified 18 pAmpC-KP isolates among the 228 isolates (7.9%): 12 DHA (66.6%) and 6 CMY (33.3%). In the present study only 47% of cefoxitin-resistant isolates were pAmpC producers. The sensitivity of CDT, DDST, and M3DT was 89%, 67% and 100% and the specificity was 90%, 90% and 85%, respectively. In addition, M3DT displayed a higher rate of efficiency (92%) than CDT (89%) and DDST (79%) in detecting plasmid-meditated AmpC producers.ConclusionDHA was the most prevalent pAmpC beta-lactamase in this study. DDST and CDT tests proved inefficient to detect two and six pAmpC producers, respectively, while M3DT represented the best overall performance.
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