Prevalence and Molecular Determinants of Antimicrobial Resistance in Clinical Isolates of <i>Staphylococcus haemolyticus</i> from India
Meerabai Manoharan, Sujatha Sistla, Pallab Ray
Abstract
Aims: Although Staphylococcus haemolyticus is considered as a part of normal skin flora, infections associated with them are increasing. Irrespective of the low virulence profile it poses a severe threat to patients with indwelling devices due to its multidrug-resistant nature. The aim of this study was to determine antibiotic resistance patterns and to detect the genes responsible in clinical isolates of S. haemolyticus . Results: All the 356 S. haemolyticus isolates were susceptible to glycopeptides. 91.3% were resistant to cefoxitin, 85.4% to erythromycin, 57.3% to co-trimoxazole, 52.8% to clindamycin, whereas only 3.7% of isolates were resistant to linezolid. Tetracycline resistance was found in 16.6% of isolates with tet K as the major genetic determinant. Most of the cefoxitin-resistant isolates carried mec A gene (99.4%), whereas dfr G gene was found only in 57.3% of co-trimoxazole-resistant isolates. Macrolides resistance was seen in 85.4% of isolates with cMLS B (constitutive macrolide, lincosamide, and streptogramin B) (42.5%) as the major phenotype with erm C and msr AB genes as the predominant genetic determinants. Among linezolid-resistant isolates all except one showed higher minimum inhibitory concentration (MIC) (>256 μg/mL) with chloramphenicol–florfenicol resistance ( cfr) gene as the genetic determinant, whereas one isolate had a lower MIC (16 μg/mL) and was negative for cfr gene. Conclusion: Emerging resistance to linezolid is a cause for concern. Strategies to prevent the spread of antibiotic resistance require continuous surveillance of these multidrug-resistant strains.