FREQUENCY AND ANTIMICROBIAL SUSCEPTIBILITY PATTERN OF MRSA IN CLINICAL SAMPLES

Abstract

Background: Methicillin-resistant Staphylococcus aureus (MRSA) is a major cause of healthcare- and community-acquired infections worldwide, posing a significant challenge to effective treatment due to its multidrug-resistant nature. It commonly causes skin, wound, and bloodstream infections, and its rapid spread through direct contact or contaminated surfaces complicates infection control. The increasing antibiotic resistance of MRSA highlights the urgent need for ongoing surveillance and the rational use of effective antimicrobials such as vancomycin to limit morbidity and mortality associated with these infections.

Objective: To determine the frequency and antimicrobial susceptibility pattern of MRSA isolated from various clinical specimens collected in a tertiary care hospital.

Methods: A descriptive cross-sectional study was conducted at the Microbiology Laboratory of Arif Memorial Teaching Hospital, Lahore, from August 2024 to January 2025. A total of 149 clinical samples, including pus, blood, urine, and wound swabs, were collected using a convenient sampling technique after obtaining informed consent. Bacterial identification was performed through standard microbiological techniques, including Gram staining, catalase, and tube coagulase tests. Antimicrobial susceptibility testing was carried out using the Kirby–Bauer disc diffusion method following CLSI 2018 guidelines. MRSA detection was based on cefoxitin (30 µg) disc diffusion, with isolates showing a zone of inhibition ≤21 mm considered resistant. Data were analyzed using SPSS version 25.

Results: Out of 149 patients, 75 (50.3%) were males and 74 (49.7%) were females. Positive bacterial growth was observed in 105 samples, yielding a culture positivity rate of 70.5%. S. aureus was the most frequent isolate (70.5%), predominantly from pus (43%) and blood (28.2%) specimens. All isolates exhibited complete resistance to penicillin (100%), while significant resistance was noted against levofloxacin (54.4%) and septran (53.7%). Conversely, maximum sensitivity was observed to vancomycin (100%), cefoxitin (57.7%), and linezolid (28.2%). The overall frequency of MRSA was recorded as 2.7%.

Conclusion: The study confirms S. aureus as the leading pathogen in clinical infections, exhibiting widespread resistance to commonly used antibiotics but retaining high sensitivity to vancomycin. These findings emphasize the urgent need for rational antibiotic prescribing, regular resistance monitoring, and strict infection control measures to mitigate the rising threat of MRSA in healthcare settings.