| Streptococcus pneumoniae ( S. pneumoniae) is one of the most significant pathogens which is responsible for a variety of infections in children. For many years, pneumococci were uniformly susceptible to penicillin, until the first clinical isolate resistant to penicillin was reported in 1967. The extensive use of large numbers of antimicrobial agents, however, has fueled the crisis of antibiotic resistance in the era of modern chemotherapy. During the past one or two decades , the resistance of S. pneumoniae to penicillin , other β-lactam agents has been rapidly increasing in many countries and it is now a worldwide problem. The penicillin resistant S. pneumoniae, which were also frequently resistant to other antibiotic classes, covered almost the whole globe; on the other hand , they constituted proportions of isolates ranged from 0% to 92.9% in different countries. Data on the prevalence of pneumococcal resistance to antibiotics have given rise to global concern and many national multi-centure surveillance studies conducted all over the world, while little was down in China except in Beijing, Shanghai and Guangzhou. As a country with huge population, which covered a vast geographic areas under different selection effect of antimicrobial usage, it is possible that the resistance of pneumococci in different provinces is different. The project is to investigate the prevalence of antibiotic-resistant types and molecular epidemiology of S. pneumoniae isolated from children in Hangzhou, and provide an etiological basis for diagnosis or the clinical antibiotic selection of S. pneumoniae.Methods 323 S. pneumoniae strains, including 243 from patients with active infections and 80 from carriers, were collected during the period from August 2001 to July 2002. (1) The sensitivities to penicillin, erythromycine , tetracycline, trimethoprim-sulfamethoxazole, chloromycetin, rifampin, ofloxacin and vacomycine were determined in vitro with Kirby-Bauer diffuse methods , while MICs of penicillin, cefotaxime and erythromycine were determined with E-test methods. Antibiotic susceptibility tests were performed and interpreted according to NCCLS standards and breakpoints(M100-S9). E-test was performed according to the manufacturer's instruction with strips from a single lot, on Mueller-Hinton agar with 5% blood. Penicillin susceptibility was determined using both oxacillin disk(1μg) and penicillin G E-test strip. In all assays, the S. pneumoniae reference strain ATCC 49619 was included as a quality control. (2) The DNA sequence of primers was designed according to the stem-loop structure of the consensus BOX-A sequence. Selected penicillin-resistant isolates and the strains from the same patient at different time or from the same specimen with nonidentical phenotype, were characterized further by BOX-PCR methods. The amplified products were subjected to electrophoresis in a 2% agarose gel and DNA banding patterns were analyzed. The clone relation was performed according to BOX patterns.Results Of 323 strains, 136 (42.1%) were sensitive to penicillin , while 57 (17.7%) were penicillin-resistant. Penicillin MICs arranged from 0.012 μg/ml to 4.0 μg/ml, including 317 (98.1%) strains MICs ≤ 1. 5μg/ml and 6(1.9%)strains MIC ≥ 3. 0μg/ml. 316 (97.8%) isolates were sensitive (MICs ≤ 0. 5μg/ml ) to cefotaxime while no resistant isolates was found. The most inactive antibiotic was erythromycine and 90.7% of the pneumococci were resistant strains (including 73.9% high level resistant ones with MIC≥ 256μg/ml), followed by tetracycline(87.6%) , Trimethoprim-sulfamethoxazole (48.6%) and chloromycetin(14.9%). 197 strains (61.0%) were multi-resistant pneumococci and most of them were resistant to Trimethoprim-sulfamethoxazole, erythromycine and tetracycline. Two strains (0.6%) were resistant to rifampin and none was resistant to vacomycine or ofloxacin. BOX PCR typing were carried out and the types or the subtypes of A. B, B1,B2, C1, C2, C3, D, D1, D2, D3, D4, E, E1, E2, E3, F, F2, F3, G, H, I, J, Lwere defined... |
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