Evaluation of different phenotypic methods for detection of amp C Beta-lactamase producing bacteria in clinical isolates.

Objective: To compare the sensitivity and specificity of different phenotypic methods for detection of Amp C betalactamase producing bacteria.
Study Design: Analytical study.
Place and Duration of Study: Department of Microbiology, Army Medical College / National University of Sciences and Technology (NUST), Islamabad, Pakistan, from June 2010 to December 2010.
Methodology: A total of 150 clinical isolates were screened for presence of Amp C beta-lactamase by using the cefoxitin disc. The confirmatory methods evaluated were inhibitor based assay (boronic acid), Amp C disc test and Amp C Etest. Three dimensional enzyme extract assay was used as the reference method for determining the sensitivity and specificity.
Results: Among the total isolates tested, 62.8% bacteria showed the presence of Amp C beta-lactamase by standard three dimensional enzyme extract assay. Among the three methods compared, boronic acid disk test found out to be highly sensitive (88%) and specific (92%) for the detection of Amp C beta-lactamase producing bacteria.
Conclusion: Detection of Amp C production is crucial in order to establish the antibiotic therapy and to attain the favourable clinical outcomes. Implementation of simple tests like boronic acid disk tests in the laboratories will help to alleviate the spread of Amp C beta-lactamase harboring organisms.