Minimal Inhibitory Concentrations Of Azithromycin In Typhoidal Salmonella Isolated In Tertiary Care Setting

Objective: To determine the variations in minimal inhibitory concentrations (MIC) of Azithromycin amongst Salmonella typhi isolates. Study Design: Cross-sectional study. Place and Duration of Study: Department of Microbiology, Combined Military Hospital, Lahore Pakistan, from Jan to Dec 2020. Methodology: Three hundred and eighty-four samples yielding the growth of Salmonella typhi were processed. Antibiotic susceptibility testing was done using the Kirby-Bauer Disk Diffusion technique, and the MIC of Azithromycin was determined using the E-strip method. Clinical and Laboratory Standards Institute (CLSI) recommended that MIC breakpoints be used for susceptibility testing of Azithromycin. Results: Of 384 tested isolates, 103(26.8%) were multidrug-resistant (MDR). Resistance to Ciprofloxacin was as high as 367(95.6%) isolates, whereas extensively drug-resistant (XDR) isolates were calculated to be 204(53.1%). No resistance against Azithromycin was observed. All the isolates were in the susceptible MIC range of 0.5 and 8 μg/ml. The lowest MIC observed was 0.5 μg/ml by 12(5%) of the isolates. The highest MIC value of 8 μg/ml was observed in 6(1.5%) isolates, all of which were XDR. 231(60.2%) isolates had one μg/ml MIC, followed by MIC 4 μg/ml of 72(18.8%) isolates. The mean MIC value of all the isolates was calculated to be 1.82±1.3μg/ml. Conclusion: The rise in XDR Salmonella typhi could lead to Azithromycin resistance. Antimicrobial stewardship is of prime importance, and Azithromycin MICs should be reported to keep the trends in check.