ABSTRACT
Context: The management of Group A β‑haemolytic Streptococci (Streptococcus pyogenes or GAS) infection include the use of penicillins, cephalosporins or macrolides for treatment. A general increase in macrolides resistance in GAS has been observed in recent years. Differences in rates of resistance to these agents have existed according to geographical location and investigators. Aims: To investigate the antibiotic pattern and erythromycin‑resistant genes of GAS isolates associated with acute tonsillitis and scarlet fever in Chengdu, southwestern China. Settings and Design: To assess the macrolide resistance, phenotype, and genotypic characterization of GAS isolated from throat swabs of children suffering from different acute tonsillitis or scarlet fever between 2004 and 2011 in the city of Chengdu, located in the southwestern region of China. Materials and Methods: Minimal inhibitory concentration with seven antibiotics was performed on 127 GAS isolates. Resistance phenotypes of erythromycin‑resistant GAS isolates were determined by the double‑disk test. Their macrolide‑resistant genes (mefA, ermB and ermTR) were amplified by PCR. Results: A total of 98.4% (125/127) of the isolates exhibited resistance to erythromycin, clindamycin and tetracycline. All isolates were sensitive to penicillin G and cefotaxime. Moreover, 113 ermB‑positive isolates demonstrating the cMLS phenotype of erythromycin resistance were predominant (90.4%) and these isolates showed high‑level resistance to both erythromycin and clindamycin (MIC90 > 256 μg/ml); 12 (9.6%) isolates demonstrating the MLS phenotype of erythromycin resistance carried the mefA gene, which showed low‑level resistance to both erythromycin (MIC90 = 8 μg/ml) and clindamycin (MIC90 = 0.5 μg/ml); and none of the isolates exhibited the M phenotype. Conclusions: The main phenotype is cMLS, and the ermB gene code is the main resistance mechanism against macrolides in GAS. Penicillin is the most beneficial for treating GAS infection, and is still used as first‑line treatment. And macrolide antibiotics are not recommended for treatment of GAS infection in children because of the high rates of antimicrobial resistance in mainland China.
ABSTRACT
Objective: To describe the clinical features of infection, and the antibiotic susceptibility of epidemic strains, and investigate plasmid maps and integrons of the isolates from an outbreak of Shigella sonnei infection at an elementary school in southwest China. Study design: Cross-sectional study. Setting: An elementary school and five hospitals in Chengdu in southwest China. Results: There were 1,134 students in the school. 937 (82.6%) students had signs and symptoms. Of the 568 (60.6%, 568/937) hospitalized students, 93.3% 86.8%, 72.4%, and 28.9% of the hospitalized patients had diarrhea, fever, abdominal pain, and vomiting, respectively. S. sonnei strains were isolated from the stool samples of 36.0% (337/937) students. All of the outbreak isolates had the same high-level antimicrobial resistance and plasmid profiles, which were different from that of sporadic strains. All the outbreak S. sonnei isolates were positive for the integrin gene and contained class 2 integron; however, two outbreak isolates contained class 1 and class 2 integrons. Conclusions: Diarrhea, fever, and abdominal pain were the three most common clinical manifestations observed in patients infected with S. sonnei. High-level antibiotic resistance was observed among Shigella species.