Antimicrobial Resistance in Clinical Isolates of Streptococcus Pneumoniae: Mechanisms and Association with Serotype Patterns DC17-DC21
Professor and Head of the Department, JIPMER, Dhanvantri Nagar, Gorimedu, Puducherry-605006, India.
Introduction: Serotypes and antimicrobial resistance patterns of pneumococcus are dynamic and need close monitoring. The present study describes serotypes and antimicrobial resistance of pneumococcus from clinical samples and compares them with a study done two decades ago from the same hospital.
Aim: To determine the antimicrobial resistance and its mechanisms among pneumococci and its association with serotypes.
Materials and Methods: Antimicrobial susceptibility was tested according to CLSI-2014 guidelines. Serotyping was performed by multiplex-PCR using primers based on CDC protocols. The macrolide and tetracycline resistance genes were detected using published primers. Appropriate statistical tests were employed to study association between resistance and serotypes.
Results: Of the 134 isolates tested, three isolates were non-typable. Highest resistance rates were found for trimethoprim-sulfamethoxazole (89/134; 66.4%), followed by macrolides (47/134; 35.1%) and tetracycline (46/134; 34.3%). Eight isolates from cerebrospinal fluid (CSF) and one isolate from sputum were resistant to penicillin. Among macrolide resistant isolates, ermB predominated (22/47; 46.8%) and both ermB and mefA/E were found in 17% (8/47), while tetM was the only gene in all tetracycline resistant isolates. Macrolide resistance was significantly associated with serotype/groups 6 and 23 F, and resistance to trimethoprim-sulfamethoxazole with serotypes 23F and 3. There was a significant increase in antibiotic resistance from 1996-2000 to 2014-17.
Conclusion: A marked increase in antimicrobial resistance was observed in the current study. Use of antibiotics need to be closely monitored in India where changes in susceptibility profiles can hamper the treatment of pneumococcal infections.