| Objective The study was conducted to determine the drug susceptibility and detect common serotype genes and virulence genes among Streptococcus pneumoniae collected from patients in Tianjin Medical University General Hospital. Explore the mechanism of resistance to macrolide antimicrobial drugs, to provide evidence for clinical medicine, guiding clinical effectively to control the spread of resistant strains in hospitals.Methods A total of 72 non-repetitive Streptococcus pneumoniae were isolated from October 2012 to April 2014 in the General Hospital of Tianjin Medical University. The bacteria identification and antimicrobial susceptibility tests were performed by VITEK-2 compact automatic system and reference broth microdilution methods, respectively. Polymerase chain reaction(PCR) was used to detect antimicrobial-resistant genes of erm B,mef A,mef E,tet M,int Tn; common serotype genes of 3、6A/B、14、15A、19A、19F、23F and virulence genes of lyt A,ply,nan A. The PCR products were purified and following with sequencing. The DNA sequences obtained were compared with those in the National Center Biotechnology Information database.Result All the 72 isolates were susceptible to vancomycin and rifampin.The overall susceptible rates to levofloxacin cefotaxime, chloramphenicol,amoxicillin, penicillin were higher than 76.0%,while to erythromycin, clindamycin, tetracycline were lower than 10.0%.The PCR indicated that 65 strains possessed erm B gene(90.3%),mef E,mef A,tet M,int Tn were detected in 17(23.6%),9(12.5%),63(87.5%)and 62(86.1%), respectively. The most prevalent patterns associated with the five test genes of the strains, were those had erm B,tet M and int Tn(52.8%). The presence of tet M gene in tetracycline–resistant strains was higher(93.8%) than those in tetracycline-susceptible strains(20%).So did the erythromycin and clindamycin resisance rates in tetracycline-resistant strains than those in tetracycline-sensitive strains. The erythromycin, clindamycin and tetracycline resistance rates in int Tn gene-positive strains were higher than int Tn gene-negative strains. The positive ratesof common serotypes were 19F(20.8%),3(16.7%,)23F(12.5%),6A/B(11.1%),14(8.3%),19A(5.6%) and 15A(2.8%). Among the 72 isolates,lyt A was positive in 65(90.3%) and ply,nan A were detected in 67(93.1%) and 52(72.2%),respectively.The coexistence of lyt A、ply and nan A was observed in 51(70.8%) isolates,lyt A and ply in 12(16.7%) isolates and only 1(1.4%)isolates harbored ply and nan A. The result of sequencing confirmed that the PCR products were target genes.Conclusion The susceptible rates of Streptococcus pneumoniae collected from patients to vancomycin and rifampin were 100.0%,and levofloxacin chloramphenicol, cefotaxime exhibited high susceptibility. Nevertheless erythromycin, clindamycin, tetracycline were in low susceptibility. Streptococcus pneumoniae harbored various kinds of antimicrobial-resistant genes and the most common genes combined as erm B+tet M+int Tn. The presence of antimicrobial-resistant genes of erm B and tet M were primarily correlated with Streptococcus pneumoniae resistant to macrolides and tetracycline,respectively.Int Tn genes may play an important role in multi-drug resistance mechanism and clinicians should pay attention to use antibiotics rationally. The proportion of serotypes 19 F,3 and 23 F were high among the Streptococcus pneumoniae,so the population should accept vaccination of PCV13,in which the antibody to capsular polysaccharide of the three serotypes were contained,to protect from Streptococcus pneumoniae infection.Virulence genes lyt A and ply had high detection rate, provide a foundation for further elucidate the mechanism of virulence factors, and for the development of new drugs and anti-streptococcal pneumoniae vaccine. |
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