Nasopharyngeal carriage of Streptococcus pneumoniae in healthy children and multidrug resistance

Nasopharyngeal carriage of Streptococcus pneumoniae plays an important role for the development of invasive disease and the spread of resistant strains within the community.. The aims of this study were to determine the carriage rate of nasopharyngeal S.pneumoniae at healthy school children, to search the susceptibility of the strains to various antibiotics and to evaluate the risk factors for nasopharyngeal carriage of penicillin-resistant pneumococci. A total of 1440 healthy children (age range: 6-13 years old) attending to three primary schools Which were chosen randomly in Mersin province (Mediterranean region of Turkey) were included to the study between April 2003 to March 2004. The isolation and identification of S.pneumoniae strains from nasopharyngeal samples were performed by conventional culture methods. Antibiotic sensitivity tests were done according to the Clinical Laboratory Standards Institute directions by disk diffusion method, and penisilin MIC values were detected by E-test (AB Biodisk, Solna, Sweden). S.pneumoniae were isolated from 201 (13.9) of the children. The susceptibility rate of the isolates to penicilin was found as 87.1% (n:175), while 12% (n:24) of the strains yielded intermediate and 1% (n:2) yielded high resistance against penicilin. Overall percentages of resistance to trimethoprim-sulfamethoxazole (TMP-SMX) and macrolides were 30% and 4%, respectively. Two out of eight erythromycin (E) resistant strains showed inducible MLSB (macrolide, lincosamide and streptogramin B) type while six showed M (due to active efflux system) type of resistance. Resistance to meropenem, vancomycin, ceftriaxone and ciprofloxacin were not detected. Of S.pneumoniae isolates, 20% were found resistant to only one antibiotic (two strains to penicilin; 39 strains to TMP-SMX), 8.9% to two antibiotics (16 strains to penicillin +TMP-SMX; two strains to penicillin+E) and 2.9% to three or more antibiotics (five strains to penicillin+ E+TMP-SMX; one strain to TMP-SMX+E+chlaritromycin). Living in a crowded family (p=0.009) and use of antibiotics in the last two months (p=0001) were considered as the risk factors for nasopharyngeal carriage of penicillin-resistant pneumococci. When comparing our data with the results of the other studies reported in Turkey, the nasopharyngeal carriage rate was moderate between healthy children in Mersin, nevertheless the rate of high level penicillin-resistant S.pneumoniae strains was quite low. As a result, improving the living conditions and restriction of antibiotic use could minimize the nasopharyngeal carriage and penicillin-resistant pneumococci.