Abstract
Diabetic foot ulcers (DFUs) represent a major complication of diabetes mellitus, often leading to prolonged morbidity, limb amputation, and increased healthcare burden. The present study aimed to investigate the prevalence, antimicrobial susceptibility patterns, and methicillin-resistance status of Staphylococcus aureus isolated from DFUs in patients attending a tertiary care hospital. A total of 120 tissue samples were collected from patients with clinically diagnosed DFUs. Standard microbiological techniques were employed for bacterial isolation, presumptive identification, and biochemical characterization, including Gram staining, catalase, coagulase, oxidase tests, and growth on selective media such as Mannitol Salt Agar and Blood Agar.Out of 120 samples, 90 (75%) were culture-positive, indicating a high burden of bacterial colonization in DFUs. Among the culture-positive samples, S. aurous was isolated from 56 samples (46.7%), establishing it as a predominant pathogen in this patient population. Phenotypic characterization of S. aureus isolates confirmed Grampositive cocci arranged in clusters, β-hemolysis on blood agar, and mannitol
fermentation on selective media. Catalase and coagulase positivity, along with oxidase negativity, were consistent across all isolates, aligning with standard microbiological criteria.Antibiotic susceptibility testing using the Kirby–Bauer disc diffusion method revealed variable responses among isolates. Highest sensitivity was observed to Vancomycin (31.9%) and Linezolid (31.1%), while increased resistance was noted against Erythromycin (27.5%), Penicillin (21%), and Ciprofloxacin (19.3%). Methicillinresistant S. aureus (MRSA) accounted for 24.2% of isolates, whereas methicillinsensitive S. aureus (MSSA) represented 20.8%, highlighting the clinical significance of methicillin resistance in DFUs. Internal comparisons demonstrated that MRSA isolates exhibited consistently higher resistance across most tested antibiotics, whereas MSSA isolates retained partial susceptibility, particularly to beta-lactams and
glycopeptides. Intermediate susceptibility was observed for Cefoxitin, Oxacillin, Tetracycline, and Clindamycin (15–18%), and approximately 55% of isolates were categorized as non-tested or NA for certain antibiotics. These findings emphasize the 2importance of antibiotic susceptibility testing and guided therapy to manage infections effectively and prevent the spread of resistant strains.Overall, the study establishes a clear link between DFUs and bacterial colonization, particularly by S. aureus, and underscores the high prevalence of MRSA in this clinical setting. The data highlight the preserved efficacy of last-line agents such as Vancomycin and Linezolid, while revealing concerning resistance trends toward commonly used antibiotics. These results reinforce the need for continuous antimicrobial surveillance, rational antibiotic stewardship, and regular monitoring of resistance patterns in DFU management.