Inducible clindamycin resistance in β-hemolytic streptococci and Streptococcus pneumoniae.
Introduction: Hemolytic streptococci are one of the most frequent human pathogens capable of producing a variety of diseases ranging from pharyngitis, impetigo, to more severe and life threatening diseases like Toxic Shock Syndrome, neonatal sepsis, pneumonia and meningitis. Though they are still susceptible to commonly used antibiotics, resistance is increasingly reported. Materials and Methods: This was a hospital based prospective study conducted to characterize the beta hemolytic streptococci prevalent in a tertiary care centre in North-east India. All the catalase negative, beta hemolytic gram positive cocci were subjected to phenotypic tests for presumptive identification and Lancefield antigen grouping was performed using Latex agglutination kit test. Antimicrobial sensitivity testing by Kirby-Bauer disk diffusion method and broth macrodilution method were performed. Results: A total of 91 non-duplicate, consecutive patient-specific clinical isolates of β-hemolytic streptococci were obtained. No gender predilection was noted except for Group B Streptococcus. More than half the isolates were obtained during winter months. GAS was the most common group isolated in our hospital followed by GBS, GGS, GCS and GFS. All the isolates were sensitive to beta lactams. Though disk diffusion method showed 100% sensitivity for penicillin, 3 GBS isolates showed increased MIC for penicillin. Of the isolates, 94.5% and 84.61% were sensitive to erythromycin and tetracycline respectively. Conclusion: Invasive streptococcal infections have increased worldwide in the recent past, despite the organism’s susceptibility to commonly used antibiotics. Large scale surveillance programmes like LEADER, SENTRY surveillance etc., had reported increasing resistance among beta hemolytic streptococci. Further evaluation of the strains and continued monitoring of the antimicrobial sensitivity pattern will help in better understanding of these bacterial infections.