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Objective: To determine the diagnostic accuracy of Colistin agar for detection of Colistin resistance in clinical isolates of MultiDrug Resistant Gram-Negative Bacilli. Study Design: Cross-sectional validation study. Place and Duration of Study: Department of Microbiology, Armed Forces Institute of Pathology, Rawalpindi Pakistan, from Feb to Aug 2019. Methodology: A total of 100 Multi-Drug Resistant Gram-Negative Bacilli in clinical isolates were included. Isolates were identified using Gram stain, Catalase, Oxidase, API 20E, and API 20NE. After approval from the institutional ethical review committee, Colistin susceptibility was determined simultaneously by Colistin agar and Broth Micro Dilution Minimum Inhibitory Concentration method as per CLSI. For susceptibility criteria, EUCAST guidelines were followed. Results were validated with the gold standard test, i.e., Broth Micro Dilution. Results: Out of 100 Multi-Drug Resistant clinical isolates, the distribution was K. pneumoniae n=60, E.coli n=16, A. baumannii n=11, C. freundii n=8, and E. cloacae n=5. The sensitivity, specificity, positive predictive value, negative predictive value, and diagnostic accuracy of Colistin agar for detection of Colistin resistance, keeping Broth Micro Dilution Minimum Inhibitory Concentration method as the gold standard was 96.67%, 97.14%, 93.55%, 98.55%, and 97%, respectively. Conclusion: Colistin agar has excellent diagnostic accuracy for the detection of colistin resistance with standardized inoculum density. Due to its ease of use, cost-effectiveness, and accurate results, it can be used in lab setups deficient in manpower and advanced equipment for Broth Micro Dilution or genetic sequencing.

Objective: To determine the diagnostic accuracy of CHROMagar MRSA for detecting MRSA from screening swab specimens keeping the Cefoxitin disk diffusion test as the reference method. Study Design: A cross-sectional validation study. Place and duration of study: Department of Microbiology, Armed Forces Institute of Pathology (AFIP), Rawalpindi Pakistan, from Mar to Aug 2019. Methodology: A total of 243 screening swab specimens, e.g., axillary, nasal and web swabs, each of hospitalized patients and healthcare workers (HCW) submitted for MRSA screening were included in the study and were processed simultaneously on blood agar, MacConkey agar and CHROMagar MRSA. The agar plates were incubated at 35°C ± 2°C for 18-24 hours in ambient air. The cefoxitin disk diffusion test followed the isolation and identification of MRSA according to the latest Clinical and Laboratory Standards Institute (CLSI) guidelines. In CHROMagar MRSA screening, after incubation, plates were examined for the presence of mauve colonies (MRSA detected), and the results were obtained and validated against the reference method of Cefoxitin disk diffusion. Results: Overall, the diagnostic accuracy of CHROMagar MRSA for detecting MRSA was 97.53%. Diagnostic accuracy of CHROMagar MRSA was 95.1%, 97.5% and 100% in axillary, nasal and web specimens, respectively. The rate of MRSA detection was maximum in axillary swabs, i.e., 40.7%, followed by 29.6% and 9.8% in nasal and web swabs, respectively. Conclusion: CHROMagar MRSA is found to be accurate for the detection of MRSA. It is reliable, easy to perform, less timeconsuming, and cost-effective. It is an affordable alternative to the conventional..............