Antimicrobial susceptibility pattern of β-haemolytic group A, C and G streptococci isolated from North India.

The objective of this study was to determine the antibiotic resistance amongst beta-haemolytic streptococci (BHS) from North India. A total of 155 BHS isolates, comprising group A streptococci (GAS) (102), group C streptococci (GCS) (25) and group G streptococci (GGS) (28), collected from patients with pharyngitis, rheumatic fever, skin disease and invasive disease were analysed for their antimicrobial susceptibility to 20 antibiotics using the Kirby-Bauer disc diffusion method. The MICs of penicillin, tetracycline, clarithromycin, azithromycin and erythromycin were also determined using the HiComb test, following the Clinical and Laboratory Standards Institute guidelines. The results showed that 37.4% of BHS isolates were susceptible to all antibiotics and 19.4% were highly resistant to tetracycline; however, only 2.6-5.2% were resistant to macrolides. The tetracycline resistance (P<0.05) of BHS was found to be statistically significant. GAS isolates from different sources of infection also showed statistically significant antibiotic resistance to azithromycin (P=0.029). Multi-drug resistance was found irrespective of streptococcal emm types. No association between GAS emm types and drug resistance was seen. MIC determination showed all isolates to be susceptible to the five antibiotics tested, except for two GAS and one GGS isolates that were resistant to clarithromycin, and one GAS skin isolate that was resistant to tetracycline. This study suggests that the variation in antibiotic resistance amongst BHS isolates from North India is independent of the isolation source and emm type distribution, hence emphasizing the need for a longitudinal surveillance in different regions of India.