[Characteristics and related factors related to the resistance on antibiotics among group A streptococcus strains isolated from children in Beijing, during May and July 2011].

OBJECTIVE: To analyze the characteristics of antibiotic resistance on group A streptococcus isolated from pediatrics in Beijing in 2011, to provide reference for clinical drug administration.

METHODS: Strains of group A streptococcus were collected from the Departments of Pediatrics in 36 hospitals at different Districts of Beijing, from May to July 2011. Minimal inhibitory concentrations (MIC) with ten antibiotics of these isolates were tested by VITEK 2 Compact method. All the Susceptibility rate (S%), Intermediate rate (I%) and Resistance rate (R%) were calculated according to their MIC values. The macrolides resistant phenotype of group A streptococcus was detected by D-test.

RESULTS: A total of 633 (19.1%) group A streptococcus strains were cultured from 3315 throat swabs. All the isolates were susceptible to penicillin, ampicillin, streptogramin, linezolid, tigecycline, vancomycin, while 96.5% (611/633) of the isolates were susceptible to levofloxacin. A total of the 96.1% (608/633) isolates exhibited resistance to erythromycin. The resistance rates to clindamycin and tetracycline were 79.3% (502/633) and 93.7% (593/633), respectively. A total of 9 different resistant patterns were observed, with the dominant patterns as:concomitant resistance to erythromycin, clindamycin and tetracycline (72.7%, 460/633), followed by combined resistance to erythromycin and tetracycline (18.0%, 114/633). The most commonly seen macrolide resistant phenotype was cMLS type (83.2%). In total, 97 strains belonged to iMLS type and 5 strains to M type. Data through multivariate logistic regression analysis showed that factors as occupation and samples being collected from the sub-urban areas etc. were significantly associated with the resistance rates to tetracycline and the odds ratio (95%CI) as 2.43 (1.16 - 5.09) and 2.35 (1.47 - 3.73). Isolates collected from the sub-urban areas were significantly associated with resistance rates to clindamycin, with the odds ratio (95%CI) being 0.48 (0.25 - 0.92).

CONCLUSION: All the isolates acquired from the Pediatrics Departments in Beijing were susceptible to penicillin and ampicillin. The high resistance rates of erythromycin, clindamycin and tetracycline resistance to group A streptococcus were observed, with the major resistant phenotype as cMLS. Factors as occupation and the collection site of samples were significantly associated with the resistance rates to tetracycline while the sites of sample collection were significantly associated with the resistance rates to clindamycin.