Streptococcus pneumoniae is a common commensal of the respiratory tract of healthy children and adults(1). It is responsible for severe invasive infections such as meningitis and septicemia resulting in high mortality rates especially in developing countries. Worldwide, pneumococcal infections are estimated to cause 1.2 million pneumonia deaths per year, i.e., nearly 40% of all pneumonia deaths in children aged less than 5 years(2). Antibiotics resistance among strains of Streptococcus pneumoniae has become a worldwide problem and is a major source of concern.

We evaluated the antibiotic sensitivity pattern of Streptococcus pneumoniae isolated from invasive infections in children for a period of 2 years, at our institution. The organism was cultured from CSF, blood and pleural fluid. All the strains were screened for penicillin susceptibility using 1 µg oxacillin disc by Kirby Bauer method. Strains showing a zone diameter of ³20 mm were considered sensitive to pencillin and strains showing zone diameter £19 mm were considered resistant or intermediately susceptible. Other antibiotics tested were cefotaxime, vancomycin, erythromycin, and chloramphenicol. MIC was done using Episilometery test (E-test strips obtained from Genetix). Streptococcus pneumoniae having MIC of 0.12 to 1 µg/mL are relatively resistant or intermediately susceptible to penicillin and those with MIC >2 µg/mL are resistant(3).

A total of 37 isolates of Streptococcus pneumoniae were obtained from CSF, (n = 13) blood (n = 20) and pleural fluid (n = 4). Of these, 35 isolates were sensitive to penicillin. Among the 2 isolates with reduced suscepti-bility one was from CSF with meningitis and the other from the blood culture of a patient having bronchopneumonia. The strains from nasopharynx of these 2 patients also showed reduced susceptibility to penicillin. The CSF isolate showed MIC of 0.5 µg/mL and the blood culture isolate 1 µg/mL. These strains were sensitive to the third generation cephalosporins and vancomycin but resistant to erythromycin. The relative resistance or intermediate sensitivity to penicillin is clinically significant in meningitis as it is seen that such strains are responsible for prolonged illness or treatment failure(4).

The nasopharynx as a source of Strepto-coccus pneumoniae has predictive potential for emergence of resistance in clinically signi-ficant isolates(5). Nasopharyngeal carriage of Streptococcus pneumoniae is common among children especially in the age group of 0-5 years. In our study too, the nasopharynx in both patients (from whom the relatively resistant pneumococci were isolated) were colonized with relatively resistant pneumo-cocci.

Penicillin is the drug of choice in the treatment of pneumococcal infections; reports of occurrence of penicillin resistance are on the rise. Routine screening for antibiotic susceptibility is advocated for clinical isolates of pneumococci. Strains with reduced susceptibility should be subjected to MIC determination to detect relative resistance or true resistance as such strains are associated with increased virulence. If the strain is relatively resistant to penicillin, a third generation cephalosporin should be used, and when true resistant strains are isolated, vancomycin is the antimicrobial agent of choice. The choice of antibiotics should be guided by the prevalence of local resistance patterns of pneumococci.

Shalini Shenoy,
Vandana K.E.,
Department of Microbiology,
Kasturba Medical College,
Mangalore 575 001, India.
E-mail: [email protected]

1. Gray BM, Converse GM, Dillon HC. Epidemiologic studies of Streptococcus pneumoniae in infants: acquisition, carriage and infection during the first 24 months of life. J Infect Dis 1980; 142: 923-933.

2. Mulholland EK. A report prepared for the scientific advisory group of experts, Global programme for vaccine and immunization, Geneva. World Health Organization 1997.

3. National Committe for Clinical Laboratory Standards. Performance standards for antimicrobial susceptibility testing. Sixth informational supplement M1150-56. Wayne (PA): Naltional Committee for Clincial Laboratroy standards, 1995.

4. Saah AJ, Mallonee JP, Tarpay M, Thornsberry CT, Roberts MA, Rhoades ER. Relative resistance of penicillin in pneumococcus. JAMA 1980; 243: 1824-1827.

5. Malik AS, Ismail A, Pennie RA, Naidu JV. Susceptibility pattern of Streptococcus pneumoniae among pre-school children in Kota Bhan, Malaysia. J Trop Pediatr 1998; 44: 10-13.