ABSTRACT
The frequency and mechanisms of resistance to macrolides in Streptococcus.pyogenes isolated within 3 periods: 2011-2012 (246 strains), 2013-2014 (273 strains) and from January to November of 2015 (120 strains) were studied. The strains of S.pyogenes (639) were isolated from 17107 nasopharyngeal, vaginal and middle ear discharge smears of children on their visits to physiciants or hospitalization at somatic hospital departments. The susceptibility was tested by the disk diffusion method and E-test strips. Identification of the mechanisms of resistance to macrolides and lincosamides included phenotypic and molecular genetic methods. PCR was used to determine ermB and mef genes in 23 erythromycin resistant isolates. As compared to 2011-2012, resistance of S.pyogenes to macrolides increased from 5 to 16% in 2015 and that to clindamycin from 2 to 10%. Among 23 erythromycin resistant strains 6 (26.1%) belonged to the M phenotype, 3 (13.0%) belonged to the iMLS(b) phenotype and 14 (60.9%) belonged to the cMLS(b) pheno-type. The results of detecting the macrolide resistance genes in S.pyogenes showed that only 26.1% of the isolates expressed the mefA gene. The predominant share (65.2%) of the erythromycin resistant isolates possesed the ermB gene as a determinant and in 4.3% of the isolates the ermB gene was associatied with the mefgene. No resistance genes were detected 1 isolate. Therefore, the main mech- anism that determined resistance of S.pyogenes to macrolides was methylation of ribosomes mediated by the ermB gene.
Subject(s)
Anti-Bacterial Agents/pharmacology , Bacterial Proteins/genetics , Drug Resistance, Multiple, Bacterial/genetics , Streptococcal Infections/microbiology , Streptococcus pyogenes/genetics , Azithromycin/pharmacology , Bacterial Proteins/metabolism , Child , Clarithromycin/pharmacology , Clindamycin/pharmacology , Ear, Middle/microbiology , Ear, Middle/pathology , Erythromycin/pharmacology , Female , Gene Expression , Genotype , Humans , Male , Membrane Proteins/genetics , Membrane Proteins/metabolism , Methylation/drug effects , Microbial Sensitivity Tests , Nasopharynx/microbiology , Nasopharynx/pathology , Phenotype , Ribosomes/drug effects , Ribosomes/genetics , Ribosomes/metabolism , Streptococcal Infections/drug therapy , Streptococcal Infections/pathology , Streptococcus pyogenes/classification , Streptococcus pyogenes/drug effects , Streptococcus pyogenes/isolation & purification , Vagina/microbiology , Vagina/pathologyABSTRACT
Nosocomial infections and their rational antibiotic treatment represent a major challenge for the healthcare nowadays. In this context, gramnegative bacteria including Pseudomonas aeruginosa, Acinetobacter baumanii and Enterobacteriaceae spp. are etiologically important and characterized by a significant level of antibiotic resistance. To examine dynamics of the respiratory tract colonization by hospital flora, tracheal aspirates obtained at three time points from 69 children with severe craniocerebral trauma during their stay in ICU were analysed. Colonization was observed on the 4th day of the ICU stay with predomination of K. pneumoniae (45%) and A. baumanii (27-37%). P. aeruginosa was detected after the 8th day of the ICU stay with the isolation rate of 33%. Substantial proportions of P. aeruginosa (61%), A. baumanii (78%) and K. pneumoniae (25%) were resistant to carbapenems. In 65 carbapemen resistant isolates, the presence of carbapenemases was examined using PCRs. OXA-48 carbapenemase was detected in 11 out of 14 (78%) K. pneumoniae isolates. Among the A. baumanii isolates, 30/31 (97%) carried OXA-40 and 1/31 (3%) had OXA-23 carbapenemases. None of the examined A. baumanii and K. pneumoniae isolates produced metallo-betalactamases (MBL). In contrast, all 20 carbapenem resistant P. aeruginosa isolates produced a MBL, and in 12 out of 20 (60%) of theme VIM-2 was detected. Thus, gramnegative nosocomial microflora rapidly colonizes ICU patients and has a high level of resistance to antibiotics, including carbapenems.
