High Prevalence of Mrsa and Resistance to Quinolones and Lincosamides in Community-Acquired Skin, Soft Tissue and Musculoskeletal Infections: Implications for Empirical Treatment

Skin, soft tissue and musculoskeletal infections (SSTMMIs) have increased in recent decades and represent a clinical challenge due to disease severity, high rates of therapeutic failure and associated complications. Knowledge of local microbiology is essential to guide appropriate clinical management. A total of 118 patients with community acquired SSTMMIs were included, and samples were obtained via skin, soft tissue or bone biopsy or joint aspiration. Microbiological and phenotypic identification was performed using BD PHOENIX™ and MALDI-TOF MS. The susceptibility profile of MRSA isolates was determined by disk diffusion (Kirby-Bauer), and vancomycin MICs were assessed by broth microdilution according to BrCAST criteria. A total of 145 microorganisms were isolated, including 138 bacteria (95.2%), with predominance of Gram-positive cocci (122; 84.6%). Staphylococcus spp. was the most prevalent genus (110 isolates), of which 89 were S. aureus (35 MRSA 39.3% and 54 MSSA 60.7%). Coagulase-negative staphylococci were identified in 21 cases (14.5%), mainly S. epidermidis (16; 11.3%). Gram-negative bacilli (GNB) were isolated in 16 samples (11%), particularly Klebsiella pneumoniae (4; 2.8%). Candida spp. (3; 2.1%) and Mycobacterium tuberculosis (3; 2.1%) were also isolated. Among the 138 bacterial isolates, 26.8% (n=37) were multidrug-resistant (MDR), including 26 MRSA, 3 MSSA, 6 S. epidermidis and 2 S. haemolyticus . No GNB were MDR. Among MSSA isolates, the highest resistance rates were to ciprofloxacin (30; 55.5%) and clindamycin (16; 29.6%). MRSA isolates showed resistance to ciprofloxacin (13; 37.1%) and clindamycin (16; 45.7%) and were 100% susceptible to vancomycin (MICs 0.5–2 μg/mL). S. aureus remains the main etiologic agent of community acquired SSTMMIs, with a high rate of MRSA and significant resistance to quinolones and lincosamides. These findings underscore the need to revise initial empirical therapy to avoid therapeutic failures, increased healthcare costs and worse clinical outcomes.