Abstract
Background & objectives: Extended-Spectrum Beta-Lactamases (ESBLs) is an important resistance mechanism in Enterobacteriaceae infections. Lack of standard guidelines from Clinical Laboratory Standards Institute (CLSI) for Amp C beta-lactamase detection poses a problem. This study was undertaken to detect ESBLs by phenotypic tests and Amp C beta-lactamase by inhibitor based method. Material and Methods: 200 consecutive non-repetitive isolates of E.coli, Klebsiella and Proteus from clinical samples were screened for ESBLs as per CLSI guidelines and confirmed by PCDT, DDST and E-tests (AB Biodisk, Biomerieux). Amp C beta lactamases were screened by cefoxitin resistance and confirmed by inhibitor (Cloxacillin) based method. Simultaneous occurrence of Amp C and ESBLs was detected by combined disk test (Neo-Sensitabs and Diatabs). Descriptive and Kappa statistics were used. Results: Out of 200 isolates studied, 131 were initially screened as ESBL producers and later 114 (57%) were confirmed by phenotypic methods. E-Test was found most sensitive phenotypic test as compared to PCDT and DDST. 13 strains resistant to cefoxitin (30?g) were found to be pure Amp C producers. Combined disk test detected 36 to be ESBL and Amp C co-producers. Surprisingly, six isolates found sensitive to cefoxitin disk were confirmed as Amp C producers by cloxacillin disk inhibition test. Conclusion: 57% ESBLs and 27.5% Amp C producers were isolated from nosocomial pathogens showing significant resistance to 3rd generation cephalosporins. Phenotypic confirmation by E-test, PCDT & DDST were useful for ESBL identification and for detection of Amp C, cloxacillin was found to be an effective inhibitor. DOI: http://dx.doi.org/10.3329/bjms.v12i4.13309 Bangladesh Journal of Medical Science Vol. 12 No. 04 October 13 Page 378-384
Highlights
Background & objectivesExtended-Spectrum Beta-Lactamases (ESBLs) is an important resistance mechanism in Enterobacteriaceae infections
Pneumonia and Proteus (Table 4). 131 ESBL producers found initially positive by and Non ESBL isolates screening test (CLSI 2010) were further subjected to confirmatory tests such as E-Test, Phenotypic confirmatory disk diffusion test (PCDT) and Double Disk Synergy test (DDST). 114 isolates were found as confirmed positive by these tests (Table 5)
Strength of agreement was perfect between PCDT and E-test and substantial between DDST and E-test
Summary
Background & objectivesExtended-Spectrum Beta-Lactamases (ESBLs) is an important resistance mechanism in Enterobacteriaceae infections. This study was undertaken to detect ESBLs by phenotypic tests and Amp C beta-lactamase by inhibitor based method. Material and Methods: 200 consecutive non-repetitive isolates of E.coli, Klebsiella and Proteus from clinical samples were screened for ESBLs as per CLSI guidelines and confirmed by PCDT, DDST and E-tests (AB Biodisk, Biomerieux). Amp C beta lactamases were screened by cefoxitin resistance and confirmed by inhibitor (Cloxacillin) based method. Results: Out of 200 isolates studied, 131 were initially screened as ESBL producers and later 114 (57%) were confirmed by phenotypic methods. Six isolates found sensitive to cefoxitin disk were confirmed as Amp C producers by cloxacillin disk inhibition test. Phenotypic confirmation by E-test, PCDT & DDST were useful for ESBL identification and for detection of Amp C, cloxacillin was found to be an effective inhibitor
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