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Objective To evaluate the application value of inhibitor enhanced modified carbapenemase inactivation method (imCIM) in the detection of class B carbapenemase.The differences between imCIM and EDTA disc potentiation test (EDPT) were comparatively analyzed.Methods A total of 181 strains of carbapenem insensitive strains were collected,among which there were 44 strains of Klebsiella pneumoniae,44 strains of Escherichia coli,43 strains of Acinetobacter baumannii and 50 strains of Pseudomonas aeruginosa.The 83 strains of carbapenem-sensitive strains were composed of 25 strains of Klebsiella pneumoniae,16 strains of Escherichia coli,25 strains of Acinetobacter baumannii and 17 strains of Pseudomonas aeruginosa.The class B carbapenemase in the 264 strains of pathogenic bacteria was screened by imCIM and EDPT,and PCR results were used as gold standard.The statistical analysis wasperformed with consistency check,related-sample Wilcoxon signed rank sum test,independent samples Kruskal-Wallis H test and ROC curve.Results Among the 181 strains of carbapenem insensitive strains,PCR results of 144 strains were positive for drug resistance gene.The samples of class A,B and D of carbapenemase were 39,77 and 28 strains respectively.The results of imCIM showed that 70 strains were positive,and the other 111 strains were negative.The imCIM results of 166 strains were consistent with those of PCR.The results of EDPT showed that 72 strains were positive,and the other 109 strains were negative.The EDPT results of 134 strains were consistent with those of PCR.The results of PCR,EDPT and imCIM of 83 carbapenem sensitive strains were negative.The sensitivity and specificity of imCIM were 85.71％ (66/77) and 97.86％ (183/187),and the value of Kappa was 0.859.The sensitivity and specificity of EDPT were 66.23 ％ (51/77) and 88.77 ％ (166/187),and the value of Kappa was 0.561.The difference of inhibition zone of imCIM (AdimCIM) was different from EDPT(AdEDPr) and the difference was statistically significant (Z =-6.941,P ＜ 0.05).In the imCIM detection,the AdimciM level of class B carbapenemase showed different population distribution position from class A and D carbapenemase with the statistically significant difference (x2 =108.887,P ＜ 0.05).The areas under the ROC curve of imCIM and EDPTwere 0.988 (95％CI:0.977 to0.999) and0.936 (95％CI:0.909 to0.963),respectively.Conclusion imCIM should be accurate,efficient and convenient for screening of carbapenem phenotype for its high sensitivity and specificity,and suitable for epidemiological monitoring.
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Background: Acquired drug resistance is reported in Pseudomonas spp by production of plasmid mediated AmpC beta (β)-lactamase, Extended Spectrum (β)-lactamase (ESBL) and Metallo beta (β)-lactamase (MBL) enzymes. Nosocomial infections by Pseudomonas aeruginosa are escalating and importantly the production of MBL is a matter of concern. Carbapenems, being the most potent and reserved drug for treating the infections cause by multi-drug resistant bacteria especially Pseudomonas spp is under threat due to the emergence of MBL producing Pseudomonas aeruginosa. Thus, the present study was undertaken to detect MBL producing Psedumonas aeruginosa isolated from different clinical samples of hospitalized patient. Methods: Psedumonas aeruginosa strains were obtained by standard isolation and identification techniques from various clinical samples of hospital. Strains were then subjected to susceptibility testing for anti-pseudomonas drugs as per Clinical and Laboratory Standards Institute (CLSI) guidelines (year 2011). Carbapenems resistant strains were selected for the detection of MBL enzyme production by disc potentiation test. Production of MBL was confirmed by enhancement of inhibition zone around imipenem and meropenem discs impregnated with EDTA, as compared to discs without EDTA. Results: Amongst the 135 strains of P. aeruginosa isolated, 26 (19.26%) were found to be carbapenem resistant and 15 (11.11%) were found to be MBL producers. There was high prevalence of MBL enzyme amongst multidrug resistant P. aeruginosa. Conclusion: Study indicates that, surveillance for the detection of MBL is necessary. The rapid dissemination of MBL producers is worrisome and necessitates the implementation of proper and judicious selection of antibiotics especially carbapenem.
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Purpose: The present study was undertaken to evaluate the screening antibiotic, confirmatory phenotypic test and agent against PCR as gold standard and to detect the prevalent MBL gene. Materials and Methods: Three hundred and twenty-six Pseudomonas aeruginosa isolates were screened for resistance to Imipenem (IPM), Meropemem (MEM) and Ceftazidime (CAZ) by disc diffusion. Isolates resistant to any of these were considered screen test-positive for MBL and were subjected to Double disc synergy test (DDST) and Disc potentiation test (DPT: Using IPM, MEM and CAZ alone and with EDTA), Minimum inhibitory concentration (MIC) reduction [four-fold or more reduction in MIC of IPM and MEM in presence of chelators: EDTA and 1,10-phenanthroline (EPI/EPM: EDTA-phenanthroline- Imipenem/Meropenem Broth Microdilution method)] and polymerase chain reaction (PCR) for blaIMP and blaVIM . Results: Screen test-positives by MEM and CAZ were 19.3% as against 17.8% by IPM. MEMDDST, DPT and EPM confirmed 100% screen-test positives as against 93.7% by CAZ DDST and DPT-2, 76.2% by CAZ DPT-1, 88.9% by IPM DDST, 85.7% by IPM DPT-1 and 92.1% by EPI. IPMand CAZ DDST together confirmed 100% while IPM and CAZ DPT-2 confirmed 96.8%. All 63 screen-test positives showed the presence of blaVIM . Conclusions: MEM was found to be the best screening and confirmatory agent for MBL detection and blaVIM was found to be the prevalent MBL gene in this part of the country.