[Antimicrobial resistance in Streptococcus pneumoniae in Beijing and molecular typing of penicillin-resistant...

To investigate antimicrobial resistance of Streptococcus pneumoniae in Beijing and molecular epidemiology of penicillin-resistant pneumococci strains.

The resistance to beta-lactam and non-beta-lactam antibiotics of 244 nasopharyngeal isolates of Streptococcus pneumoniae collected from September to November 1997 in 8 day-care centers in Beijing was studied by Etest and agar dilution method. Serotyping was done by "capsular swelling" technique. BOX-PCR technique was used to detect the DNA of resistant strains.

24.8% (244/985) of the children carried Streptococcus pneumoniae. The agreement between the MICs obtained by Etest and agar dilution for penicillin and ceftriaxone was > 93.7%. By Etest, 3/244 (1.3%) strains were resistant to penicillin(MICs, 3 micrograms/ml) and 32/244(13.1%) strains in termedinte (MICs, 0.094-0.25 microgram/ml). Penicillin-susceptible strains were also susceptible to the other 4 tested beta-lactams. In penicillin non-susceptible strains, 11.4% (4/35) isolates were resistant to the other beta-lactams. The resistant rates of erythromycin, tetracycline, chloramphenicol and trimethoprim-sulfamethoxazole (TMP-SMZ) were 74.0%, 87.6%, 47.8%, 63.3%, respectively. All of the strains were susceptible to vancomycin and rifampin. 119/244(48.7%) strains isolated were multiresistant to tetracycline, erythromycin and TMP/SMZ. Serotype 6A(33.6%), 19F(16.8%), 23F(15.1%), 15(11.2%), 6B(4.3%) were most common. 57.1% (20/35) penicillin non-susceptible strains were of serotype 23F and had similar or identical multiresistance and BOX patterns.

In Beijing, the prevalence of penicillin-resistant pneumococci was obviously lower than that of neighboring countries, but resistant rate to non-beta-lactams was high. The epidemic multiresistant 23F clone found in day-care centers was different from the Spanish clone.