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Context: Carbapenemase production is an important mechanism responsible for carbapenem resistance. Aims: Phenotypic detection and differentiation of types of carbapenemase in carbapenem resistant Enterobacteriaceae is important for proper infection control and appropriate patient management. Settings and Design: We planned a study to determine the occurrence of Class A Klebsiella pneumoniae carbapenemase (KPC type) and Class B Metallo-β-lactamase (MBL type) carbapenemase in hospital and community. Materials and Methods: Clinical isolates of Escherichia coli and Klebsiella species and simultaneously evaluate different phenotypic methods for detection of carbapenemases. Results: It was observed that 20.72% clinical isolates of E. coli and Klebsiella spp. were resistant to carbapenem on screening of which, 14.64% were E. coli and 29.69% were Klebsiella spp. Using phenotypic confirmatory tests the occurrence of carbapenemase production was found to be 87.01% in E. coli and 91.51% in Klebsiella spp. using both modified Hodge test (MHT) and combined disk test (CDT) using imipenem-ethylenediaminetetraacetic acid. Conclusions: Both MBL and KPC type carbapenemases were seen among clinical isolates of E. coli and Klebsiella spp. CDT is simple, rapid and technically less demanding procedure, which can be used in all clinical laboratories. Supplementing MHT with CDT is reliable phenotypic tests to identify the class A and class B carbapenemase producers.
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Background and objectives: Acinetobacter baumannii is emerging as an important pathogen causing hospital acquired infections. The present study was directed to find out the incidence, antibiotic susceptibility and metallo β lactamases production of Acinetobacter baumannii isolated from various clinical samples, in an intensive care unit. Methods: Isolation of Acinetobacter baumannii from various clinical samples was done. The isolates were tested for antibiotic sensitivity as per conventional methods. Imipenem resistant isolates were further tested for MBL production by double disk synergy test and MBL E test. Results: Total number of Acinetobacter baumannii isolates from clinical samples was 48. Maximum number of isolates were from blood (31.25%) followed by endotracheal aspiration (25%). Total 10 (20.83%) isolates were imipenem resistant, among which, 9(18.75%) were metallo β lactamases producers. MBL producers were more resistant to commonly used antibiotics than its non MBL producing counter parts. All isolates were susceptible to colistin (10 μg), polymyxin B (300 μg) and tigecycline (15μg).Conclusions: Multidrug resistant, metallo β lactamases producing Acinetobacter baumannii infection was not uncommon in our intensive care unit. Colistin, polymyxin B and tigecycline were very effective against such isolates.
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Background: One leading factor responsible for resistance in Acinetobacter baumannii, an important opportunist in health care institutions globally, is the production of carbapenamases like metallo-β-lactamases (MBLs), which hydrolyze a variety of β-lactams including penicillin, cephalosporins and carbapenems. However, neither any standard guidelines are available nor any method has been found to be perfect for their detection. Various methods have shown discordant results, depending upon the employed methodology, β-lactamase substrate and MBL inhibitor used. This study aims to evaluate two phenotypic methods against PCR as gold standard among carbapenem resistant A. baumannii for identifying MBL producers. Materials and Methods: A total of 130 A. baumannii were screened for imipenem and meropenem resistance by Kirby-Bauer disc diffusion method. Phenotypic expression of MBL was detected by EDTA-imipenem-microbiological (EIM) assay and extended EDTA disc synergy (eEDS) test and presence of bla-IMP and bla-VIM was detected by PCR in all the carbapenem resistant isolates. Results: Of the 43 imipenem and/or meropenem resistant A. baumannii isolates, 4 (9.3%) were found to be MBL producers by EIM and 3 (6.97%) by eEDS. Only bla-VIM gene was detected in 7 (16.28%) by PCR. In addition EIM detected 14 (32.56%) carbapenem resistant non-metallo enzyme producers. Conclusion: Of the two MBL genes targeted, bla-VIM was only detected and that too in isolates resistant to both imipenem and meropenem. Further, EIM was useful in differentiating MBL from non-metalloenzymes producers.
Subject(s)
Acinetobacter baumannii/metabolism , Acinetobacter baumannii/physiology , Biological Assay/methods , Microbial Sensitivity Tests/methods , Polymerase Chain Reaction/methods , beta-Lactamases/analysis , beta-Lactamases/classification , beta-Lactamases/genetics , beta-Lactams/physiologyABSTRACT
Objective To analyze the antibiotic resistance of the carbapenem no-susceptibility Enterobacteriaceae isolated from pediatric patients and the resistant genes of carbapenemase-producing.Methods In all,46 carbapenem no-susceptibility Enterobacteriaceae strains were isolated from patients at Beijing Children's Hospital between January 2008 and December 2010.Agar dilution method recommended by the Clinical and Laboratory Standards Institute was used to examine the minimum inhibitory concentrations (MICs) of 14 antimicrobial agents.Phenotypic testing for carbapenemase-producing was conducted using Hodge test and double-disk synergy test.PCR was used to detect the expression of the carbapenemase-related genes KPC,GES,IMI/NMC-A,SME,IMP,VIM,GIM,SPM,SIM and OXA.WHONET5.6 was used to perform resistance analysis.Results Among 46 carbapenem no-susceptibility Enterobacteriaceae strains,26 (56.5％) were Klebsiella pneumoniae strains,13(28.3％ ) were Enterobacter cloacae and 7( 15.2％ ) were Escherichia coli.The rates of imipenem and meropenem no-susceptibility Klebsiella pneumoniae were 69.2％ and 80.8％,Enterobacter cloacae were 76.9％ and 100％ and Escherichia coli were 85.7％ and 100％,respectively.40(87.0％ ) strains were positive of Hodge test.41 (89.1％) strains were positive of doubledisk synergy test.38 (82.6％) were positive for the IMP genotype.The carbapenemase-related genes were not found in other 8 strains.Conclusion The prevalence of carbapenem no-susceptibility Enterobacteriaceae strains in Klebsiella pneumoniae isolates is relatively high in children.Resistance to imipenem was lower than that to meropenem from Klebsiella pneumoniae,Enterobacter cloacae and Escherichia coli strains.Many carbapenem no-susceptibility Enterobacteriaceae isolated from pediatric patients carry the blaIMP gene.No the KPC gene was found.
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Background & objectives: The production of carbapenemases is an important mechanism responsible for the carbapenem resistance. A simple and inexpensive testing method for screening of carbapenemase producers is essential. A prospective study was undertaken to detect metallo-β-lactamases (MBLs) and AmpC β-lactamases in nonfermentative Gram negative bacteria and to evaluate the various methods for detection of carbapenemases and MBLs. Methods: A total of 100 Acinetobacter spp. (78 A. baumannii and 22 A. lwoffi i) and 140 Pseudomonas spp. (103 P. aeruginosa and 37 other Pseudomonas spp.) were screened for meropenem resistance by Kirby- Bauer disc diffusion method. Modifi ed Hodge test, EDTA disk synergy (EDS) test and AmpC disk test were used for the detection of carbapenemases, MBLs and AmpC β-lactamases, respectively. Results: Forty six (59.0%) A. baumannii, 7 (31.8%) A. lwoffi i, 32 (31.1%) P. aeruginosa and 7 (18.9%) Pseudomonas spp. were resistant to meropenem. Among the 32 meropenem resistant P. aeruginosa, 15 (46.9%) were AmpC β-lactamase producers, 16 (50.0%) MBL producers by EDS test, but only 9 (28.1%) found positive for carbapenemases by modifi ed Hodge test. Among the 46 meropenem resistant A. baumannii, 31 (67.4%) were AmpC β-lactamase producers, 3 (6.5%) MBL producers, but only 1 (14.3%) was positive for carbapenemases by modifi ed Hodge test. One P. aeruginosa was positive for carbapenemase by modifi ed Hodge test, but was negative for MBL and AmpC β-lactamase. Interpretation & conclusions: MBL production is an important mechanism of carbapenem resistance among Pseudomonas species but not among Acinetobacter species. EDS is more sensitive for detection of MBLs than modifi ed Hodge test. Both EDTA-meropenem and EDTA-ceftazidime combination must be used to detect all the MBL producers. Carbapenemases other than MBL may also be responsible for carbapenem resistance. AmpC β-lactamase is also a contributory factor for carbapenem resistance among the isolates in the hospital.
Subject(s)
Acinetobacter/enzymology , Bacterial Proteins/metabolism , Drug Resistance, Multiple, Bacterial/genetics , Humans , Microbial Sensitivity Tests/methods , Prospective Studies , Pseudomonas/enzymology , beta-Lactamases/metabolismABSTRACT
To investigate the distribution of the genes of two major metallo-β-lactamases (MBL; i.e., IMP and VIM) and class 1 integrons (intI) in the clinical imipenem-resistant Pseudomonas aeruginosa, a total of 65 isolates, from a university hospital in Sichuan between December 2004 and April 2005 were screened for MBL genes by PCR using primers specific for blaIMP-1, blaVIM and blaVIM-2 genes. The MBL-positive isolates were further assessed for class 1 integrons by PCR using specific primers. The nucleotide sequences of several PCR products were also determined. The results revealed that the blaVIM gene was found in 81.5% (53/65) of all isolates, bla<VIM-2> gene was found in only 1 isolate and the intI gene was observed in 45.3% (24/53) of blaVIM-positive isolates. One isolate carried simultaneously both blaIMP-1 and intI genes, and to the best of our knowledge this is the first report of such isolate in southwest China. These observations highlight that the genes for VIM β-lactamase and class 1 integrons were predominantly present among the imipenem-resistant P. aeruginosa tested, confirming the current widespread threat of imipenem-resistant, integron-borne P. aeruginosa.