Identification and Antibiogram of Presumptive Methicillin- and Vancomycin-Resistant Staphylococcus aureus Isolated from Untrimmed Fingernails: A Cross-Sectional Study from Peshawar, Pakistan
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Background: Staphylococcus aureus is a clinically important pathogen with a rising prevalence of methicillin-resistant (MRSA) and, less commonly, vancomycin-resistant (VRSA) phenotypes. The sub-ungual space of the human fingernail offers a favourable niche for staphylococcal carriage, but community-level data on S. aureus recovered from untrimmed fingernails in Pakistan remain limited. Objective: To isolate presumptive S. aureus from sub-ungual swabs of untrimmed fingernails in community participants in Peshawar and to determine the in-vitro phenotypic susceptibility of the recovered isolates to methicillin, vancomycin, teicoplanin, and linezolid. Methods: A descriptive cross-sectional, laboratory-based study was conducted at the Medical Laboratory Technology research laboratory of the City University of Science and Information Technology, Peshawar, between March and June 2025. Fifty community-residing adults whose fingernails had not been trimmed for at least two weeks were enrolled by convenience sampling after written informed consent. Sub-ungual swabs were inoculated onto Mannitol Salt Agar and Nutrient Agar and incubated aerobically at 37 °C. Isolates were identified by Gram stain and a standard biochemical panel comprising oxidase, catalase, slide coagulase, and DNase tests. Antimicrobial susceptibility was determined by the Kirby–Bauer disc-diffusion method on Mueller–Hinton agar and interpreted using Clinical and Laboratory Standards Institute (CLSI) M100 breakpoints, with S. aureus ATCC 25923 as the quality-control strain. Frequencies were summarised with 95% confidence intervals using the Wilson score method. Results: All fifty swabs (100%) yielded bacterial growth, with isolates demonstrating Gram-positive cocci in clusters and a biochemical profile of oxidase-negative, catalase-positive, coagulase-positive, and DNase-positive in every case. On disc-diffusion testing, 45/50 isolates (90.0%, 95% CI 78.6–95.7) were resistant to methicillin and 39/50 (78.0%, 95% CI 64.8–87.2) showed reduced vancomycin-disc susceptibility on screening, while 44/50 (88.0%, 95% CI 76.0–94.4) remained sensitive to teicoplanin and 48/50 (96.0%, 95% CI 86.5–98.9) to linezolid. Conclusion: Untrimmed fingernails of community participants in Peshawar harboured presumptive S. aureus with high phenotypic resistance to methicillin and reduced vancomycin-disc susceptibility, alongside retained sensitivity to teicoplanin and linezolid. Findings underline the public-health value of routine nail hygiene but should be interpreted as phenotypic screening observations, pending confirmation by cefoxitin-disc testing, minimum inhibitory concentration determination, and molecular detection of mecA and vanA.
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