Prevalence and Molecular Determinants of Antimicrobial Resistance in Clinical Isolates of Staphylococcus haemolyticus from India.

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 tetK as the major genetic determinant. Most of the cefoxitin-resistant isolates carried mecA gene (99.4%), whereas dfrG gene was found only in 57.3% of co-trimoxazole-resistant isolates. Macrolides resistance was seen in 85.4% of isolates with cMLSB (constitutive macrolide, lincosamide, and streptogramin B) (42.5%) as the major phenotype with ermC and msrAB 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.