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Query: UMLS:C0519030 (Klebsiella)
 21,988 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Six Escherichia coli and 12 Klebsiella pneumoniae isolates from a single hospital expressed a common beta-lactamase with a pI of approximately 9.0 and were resistant to cefoxitin and cefotetan (MIC ranges, 64 to > 128 and 16 to > 128 micrograms/ml, respectively). Seventeen of the 18 strains produced multiple beta-lactamases. Most significantly, three K. pneumoniae strains were also resistant to imipenem (MICs, 8 to 32 micrograms/ml). Spectrophotometric beta-lactamase assays with purified enzyme indicated hydrolysis of cephamycins, in addition to cephaloridine and benzylpenicillin. The 4ene encoding the pI 9.0 beta-lactamase (designated ACT-1 for AmpC type) was cloned and sequenced, which revealed an ampC-type beta-lactamase gene that originated from Enterobacter cloacae and that had 86% sequence homology to the P99 beta-lactamase and 94% homology to the partial sequence of MIR-1. Southern blotting revealed that the gene encoding ACT-1 was on a large plasmid in some of the K. pneumoniae strains as well as on the chromosomes of all of the strains, suggesting that the gene is located on an easily mobilized element. Outer membrane protein profiles of the K. pneumoniae strains revealed that the three imipenem-resistant strains were lacking a major outer membrane protein of approximately 42 kDa which was present in the imipenem-susceptible strains. ACT-1 is the first plasmid-mediated AmpC-type beta-lactamase derived from Enterobacter which has been completely sequenced. This work demonstrates that in addition to resistance to cephamycins, imipenem resistance can occur in K. pneumoniae when a high level of the ACT-1 beta-lactamase is produced in combination with the loss of a major outer membrane protein.
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PMID:Imipenem resistance in Klebsiella pneumoniae is associated with the combination of ACT-1, a plasmid-mediated AmpC beta-lactamase, and the foss of an outer membrane protein. 905 93

The purpose of this study was to identify the genetic organization and inducibility of bla(ACT-1) in a clinical isolate of Klebsiella pneumoniae possessing at least five different beta-lactamases. The genetic organization of the bla(ACT-1)/ampR region is identical to those of inducible chromosomal ampC genes. RNA analysis using primer extension demonstrated a five-fold increase in bla(ACT-1) transcript production on exposure to cefoxitin. These findings are significant because induction was detected in a complicated beta-lactamase background. In addition, this report is the first to describe an inducible plasmid-encoded AmpC beta-lactamase of Enterobacter cloacae origin.
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PMID:The ACT-1 plasmid-encoded AmpC beta-lactamase is inducible: detection in a complex beta-lactamase background. 1186 60

Polyclonal rabbit antibodies against SHV-1 and CMY-2 beta-lactamases were produced and characterized, and enzyme-linked immunosorbent assays (ELISAs) were developed. Immunoblots revealed that the anti-SHV-1 antibody recognized SHV-1 but did not recognize TEM-1, K-1, OXA-1, or any AmpC beta-lactamase tested. The anti-CMY-2 antibody detected Escherichia coli CMY-2, Enterobacter cloacae P99, Klebsiella pneumoniae ACT-1, and the AmpC beta-lactamases of Enterobacter aerogenes, Morganella morganii, and Citrobacter freundii. No cross-reactivity of the anti-CMY-2 antibody was seen against laboratory strains of E. coli possessing TEM-1, SHV-1, K-1, or OXA-1 beta-lactamases. Operating conditions for performing ELISAs were optimized. Both anti-CMY-2 and anti-SHV-1 antibodies detected picogram quantities of purified protein in ELISAs. The reactivity of the anti-CMY-2 antibody was tested against a number of AmpC beta-lactamases by assaying known quantities of purified enzymes in ELISAs (AmpC beta-lactamases of M. morganii, C. freundii, E. coli, and E. cloacae). As the homology to CMY-2 beta-lactamase decreased, the minimum level needed for detection increased (e.g., 94% homology recognized at 1 ng/ml and 71% homology recognized at 10 ng/ml). The ELISAs were used to assay unknown clinical isolates for AmpC and SHV beta-lactamases, and the results were confirmed with PCR amplification of bla(AmpC) and bla(SHV) genes. Overall, we found that our ELISAs were at least 95% sensitive and specific for detecting SHV and AmpC beta-lactamases. The ELISA format can facilitate the identification of AmpC and SHV beta-lactamases and can be used to quantify relative amounts of beta-lactamase enzymes in clinical and laboratory isolates.
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PMID:Development of a sensitive and specific enzyme-linked immunosorbent assay for detecting and quantifying CMY-2 and SHV beta-lactamases. 1203 47

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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PMID:Occurrence of extended-spectrum and AmpC beta-lactamases in bloodstream isolates of Klebsiella pneumoniae: isolates harbor plasmid-mediated FOX-5 and ACT-1 AmpC beta-lactamases. 1257 81

A sample of 752 resistant Klebsiella pneumoniae, Klebsiella oxytoca, and Escherichia coli strains from 70 sites in 25 U.S. states and the District of Columbia was examined for transmissibility of resistance to ceftazidime and the nature of the plasmid-mediated beta-lactamase involved. Fifty-nine percent of the K. pneumoniae, 24% of the K. oxytoca, and 44% of the E. coli isolates transferred resistance to ceftazidime. Plasmids encoding AmpC-type beta-lactamase were found in 8.5% of the K. pneumoniae samples, 6.9% of the K. oxytoca samples, and 4% of the E. coli samples, at 20 of the 70 sites and in 10 of the 25 states. ACT-1 beta-lactamase was found at eight sites, four of which were near New York City, where the ACT-1 enzyme was first discovered; ACT-1 beta-lactamase was also found in Massachusetts, Pennsylvania, and Virginia. FOX-5 beta-lactamase was also found at eight sites, mainly in southeastern states but also in New York. Two E. coli strains produced CMY-2, and one K. pneumoniae strain produced DHA-1 beta-lactamase. Pulsed-field gel electrophoresis and plasmid analysis suggested that AmpC-mediated resistance spread both by strain and plasmid dissemination. All AmpC beta-lactamase-containing isolates were resistant to cefoxitin, but so were 11% of strains containing transmissible SHV- and TEM-type extended-spectrum beta-lactamases. A beta-lactamase inhibitor test was helpful in distinguishing the two types of resistance but was not definitive since 24% of clinical isolates producing AmpC beta-lactamase had a positive response to clavulanic acid. Coexistence of AmpC and extended-spectrum beta-lactamases was the main reason for these discrepancies. Plasmid-mediated AmpC-type enzymes are thus responsible for an appreciable fraction of resistance in clinical isolates of Klebsiella spp. and E. coli, are disseminated around the United States, and are not so easily distinguished from other enzymes that mediate resistance to oxyimino-beta-lactams.
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PMID:Epidemiology of conjugative plasmid-mediated AmpC beta-lactamases in the United States. 1474 6

High-level resistance to ertapenem was produced by beta-lactamases of groups 1, 2f, and 3 in a strain of Klebsiella pneumoniae deficient in Omp35 and Omp36. From a wild-type strain producing ACT-1 beta-lactamase, ertapenem-resistant mutants for which the ertapenem MICs were up to 128 microg/ml and expression of outer membrane proteins was diminished could be selected.
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PMID:Role of beta-lactamases and porins in resistance to ertapenem and other beta-lactams in Klebsiella pneumoniae. 1527 52

Extended spectrum beta lactamase genes were detected by the PCR in 87.6% of 231 Enterobacteriaceae strains isolated in medical institutions of Moscow, St. Petersburg, Tomsk and Nazran that showed a decrease in their susceptibility to 3rd generation cephalosporins. Alone or in various combinations TEM type beta lactamases were detected in 43.3% of the isolates, 46.8 and 51.2% of the isolates produced SHV type and CTX type beta lactamases respectively. Combinations of 2 and 3 different determinants were detected in 40 and 14% of the isolates respectively. Production of class C beta lactamases was suspected in 28% of the isolates by their resistance to cefoxitin. The gene of ACT type beta lactamase was detected in 1 strain of Klebsiella pneumoniae and the gene of CMY type beta lactamase was detected in 1 strain of Proteus mirabilis. By the NCCLS 100% of the isolates was susceptible to meropenem, 14% was susceptible to cefotaxime, 64% was susceptible to cefepime, 81% was susceptible to cefoperazone/sulbactam, 47% was susceptible to gentamicin, 57% was susceptible to amikacin and 36% was susceptible to ciprofloxacin.
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PMID:[Molecular mechanisms of cephalosporin resistance in Gram-negative bacteria of the Enterobacteriaceae family]. 1534 91

Among the 443 clinical isolates of Escherichia coli and Klebsiella spp. collected between June and November 2003 from 3 university hospitals in Korea, 62 isolates were confirmed as extended-spectrum beta-lactamase (ESBL)- or plasmid-mediated AmpC beta-lactamase-producers by double disk synergy test, PCR and sequencing for beta-lactamase genes. The most frequently identified ESBL gene among E. coli and K. pneumoniae isolates was bla(SHV-12) and bla(CTX-M) (bla(CTX-M-9), bla(CTX-M-14), bla(CTX-M-3), and bla(CTX-M-15)). Four kinds of plasmid-mediated AmpC beta-lactamases, ACT-1, CMY-1, CMY-2, and DHA-1, were detected. ESBL production was associated with high levels of resistance to tetracycline, sulfisoxazole, streptomycin, kanamycin, gentamicin and tobramycin when compared to non-ESBL producing isolates. Conclusively, this study suggests that the CTX-M beta-lactamases are prevalent and various kinds of plasmid-mediated AmpC enzymes are distributed in clinical isolates of E. coli and Klebsiella spp. in Korea.
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PMID:CTX-M and SHV-12 beta-lactamases are the most common extended-spectrum enzymes in clinical isolates of Escherichia coli and Klebsiella pneumoniae collected from 3 university hospitals within Korea. 1579 85

Detection of the resistance mediated by class C beta-lactamases remains a challenging issue, considering that transferable plasmid-mediated class C beta-lactamases are of worldwide concern. Methods for the identification of strains that produce extended-spectrum beta-lactamases (ESBLs) or metallo-beta-lactamases (MBLs) have been developed and applied for routine use in clinical microbiology laboratories, but no practical methods for identification of plasmid-mediated class C producers have been established to date. We therefore developed three simple methods for clinical microbiology laboratories that allow identification of plasmid-mediated class C beta-lactamase-producing bacteria using a boronic acid derivative, 3-aminophenylboronic acid (APB), one of the specific inhibitors of class C beta-lactamases. Detection by the disk potentiation test was based on the enlargement of the growth-inhibitory zone diameter (by greater than or equal to 5 mm) around a Kirby-Bauer disk containing a ceftazidime (CAZ) or a cefotaxime (CTX) disk in combination with APB. In a double-disk synergy test, the discernible expansion of the growth-inhibitory zone around the CAZ or the CTX disk toward a disk containing APB was indicative of class C beta-lactamase production. A greater than or equal to eightfold decrease in the MIC of CAZ or CTX in the presence of APB was the criterion for detection in the microdilution test. By using these methods, Escherichia coli and Klebsiella pneumoniae isolates producing plasmid-mediated class C beta-lactamases, ACT-1, CMY-2, CMY-9, FOX-5, LAT-1, and MOX-1, were successfully distinguished from those producing other classes of beta-lactamases, such as ESBLs and MBLs. These methods will provide useful information needed for targeted antimicrobial therapy and better infection control.
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PMID:Practical methods using boronic acid compounds for identification of class C beta-lactamase-producing Klebsiella pneumoniae and Escherichia coli. 1595 62

The aim of the study is to investigate the prevalence of plasmid-mediated AmpC beta-lactamases in Enterobacteriaceae naturally lacking chromosomal AmpC beta-lactamases. A total of 1860 clinical isolates of Klebsiella spp., Salmonella spp., and Proteus mirabilis were collected from a Korean hospital between January 2002 and December 2004. For the isolates that are nonsusceptible to cefoxitin, polymerase chain reaction amplification of the bla(SHV), bla(TEM), and bla(AmpC) genes and sequencing were performed. Plasmid-mediated AmpC beta-lactamases were found in 2.9% (37 isolates of DHA-1, 1 isolate of CMY-1, 1 isolate of CMY-2, and 1 isolate of ACT-1) of Klebsiella pneumoniae, 2.5% (5 isolates of DHA-1) of Klebsiella oxytoca, 0.8% (1 isolate of DHA-1) of Salmonella spp., and none of P. mirabilis isolates. The DHA-1-producing K. pneumoniae was only 2 isolates (0.6%) in 2002, but the rate and the number significantly increased to 2.4% (13 of 538 isolates) in 2003 and to 4.3% (22 of 512) in 2004. In conclusion, DHA-1 is the most prevalent plasmid-mediated AmpC beta-lactamase in Enterobacteriaceae lacking chromosomal ampC gene, and the DHA-1-producing K. pneumoniae isolates have rapidly increased since 2003 in a Korean hospital. In addition, this is the first report of the appearance of a K. pneumoniae isolate producing ACT-1 beta-lactamase in Korea.
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PMID:Increasing trend in the prevalence of plasmid-mediated AmpC beta-lactamases in Enterobacteriaceae lacking chromosomal ampC gene at a Korean university hospital from 2002 to 2004. 1654 35


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