Analysis of drug-resistance and macrolide-resistant genes of Streptococcus pneumoniae in preschool children

ObjectiveTo understand the drug resistance of Streptococcus pneumoniae (Sp) and the distribution of macrolide-resistant genes in preschool children.

MethodsSixty Sp strains were selected, and the minimum inhibitory concentrations of penicillin, amoxicillin, cefotaxime and ceftriaxone were detected by E-test method; the susceptibility of Sp to erythromycin, clindamycin, cotrimoxazole, tetracycline, chloramphenicol, levofloxacin, vancomycin and linezolid was detected by disk diffusion method; the detection rate of macrolide-resistant genes ermB, mefA and mefE was determined by PCR.The children were divided into 0 to 12-month group, 13 to 36 month group and 37 to 60-month group according to their age.The antimicrobial insensitivity rate and the detection rate of drug resistance genes in the three groups were compared.

ResultsThe results of drug sensitivity test displayed that the 60 strains of Sp showed high drug resistance rate to erythromycin, tetracycline and cotrimoxazole, and the resistance rates were 95.0%, 93.3% and 61.7%, respectively; Sp was sensitive to vancomycin, ertapenem, linezolid and telithromycin, and the sensitivity rate was 100.0%.The insensitivity rates of children to cefotaxime, ceftriaxone, penicillin G, amoxicillin, erythromycin and meropenem in the 0 to 12-month group were higher than those in the 12 to 36-month group and 36 to 60-month group, the difference of insensitivity rates of cefotaxime, ceftriaxone among the three groups was statistically significant (P < 0.05), and the insensitivity rates of children to cotrimoxazole, ofloxacin and tetracycline in the 36 to 60-month group were the highest.The PCR results showed that the detection rate of macrolide-resistant gene ermB was the highest (98.33%), which was 78.33% for mefA and ermB+mefA, 60.00% for mefE and ermB+mefE, and 46.67% for ermB+mefA+mefE.The detection rates of mefE and ermB+mefE gradually decreased in the 0 to 12-month group, 13 to 36-month group and 37 to 60-month group (P < 0.05).

ConclusionsThe resistance rate of Sp to macrolide in preschool children is high, and the resistance gene ermB is the main genotype of Sp to macrolide.