[Epidemiological study of Streptococcus pneumoniae in the nasopharynx of healthy children under 5 years of age in Wuhan].

Objective: To investigate the population biology of Streptococcus (S.) pneumoniae carried by healthy children under 5 years of age in Wuhan.
Methods: S. pneumoniae was isolated from nasopharyngeal swabs of healthy children under the age of 5 years (under 5) in Wuhan. The susceptibility to 12 antimicrobial agents was tested by agar dilution method. The erythromycin resistant genes were detected by using the technique of polymerase chain reaction. The quellung reaction was used for serotyping.
Results: The carrier rate of S. pneumoniae was 22.31% (135/605) in under 5 children in Wuhan. Among the 133 alive strains, the proportion of penicillin non-susceptible S. pneumoniae (PNSSP) was 45.9% (61/133). The susceptibility of S. pneumoniae to the first (cefalexin), the second (cefaclor) and the third (cefixime, cefpodoxime and cetriaxone) generations of cephalosporins was 6.0%, 45.1%, 54.9%, 56.4%, and 88.7%, respectively. None of the strains were found resistant to fluoroquinolones except for one strain which was resistant to ciprofloxacin at low level. The susceptibility to macrolides was low, 14.3% - 15.8%. Among totally 114 strains resistant to erythromycin, the genes ermB alone, both ermB and mefA, and mefA alone were found in 76 strains (66.7%), 46 strains (40.4%) and 2 strains (1.8%), respectively. Seventeen serotypes were involved and the prevalent serotypes were 19, 23, 6, 15 and 14. Seven strains remained nontypable for serotype. PNSSP strains were found to be distributed in serotypes 19, 23, 6 and nontypable group.
Conclusions: The antibiotic resistance of S. pneumoniae was serious in Wuhan area. The ribosomal modification (ermB gene mediated) was the main mechanism of S. pneumoniae resistant to erythromycin. The major prevalent serotypes were 19, 23 and 6.