Changing trend in susceptibility pattern of Streptococcus pneumoniae to penicillin in India

Prior to 1995 all strains of Streptococcus pneumoniae isolated at a tertiar y care hospital in south India were uniformly susceptible to penicillin. Ho wever, since late 1995 strains of S. pneumoniae with intermediate resistanc e to penicillin have been observed. Altogether there were 25 such isolates, 9 from invasive (5 from CSF as well as blood, 1 from pleural fluid and 3 f rom CSF alone) and 16 from noninvasive sites (6 from throat, 6 from sputum, 3 from eye and 1 from ear) respectively, thus 4.6 per cent of S. pneumonia e showed intermediate resistance of a total of 535 strains studied so far. The minimum inhibitory concentration (MIC) values of penicillin, erythromyc in, chloramphenicol and cefotaxime were determined by agar dilution method and for confirmation, E test was carried out for penicillin alone, The MIC range obtained for penicillin was between 0.125-1.0 mu g/ml, Kirby-Bauer di sc diffusion method was adopted for testing of erythromycin, chloramphenico l, co-trimoxazole, cefotaxime, tetracycline and vancomycin. We observed tha t none of the strains with intermediate resistance to penicillin were multi drug resistant. These strains belonged predominantly ta serotype 14 (n=10) , 7B (n=9), 19A (n=3), 7P (n=2) and 23F (n=1). Clonality was not observed i n the 5 representative strains subjected to Box A finger printing method.