Results are shown in Table 2. The majority (n =25, 89.3%) belonged to a common molecular type, Selleckchem STA-9090 ST239-MRSAIII-spa t030. The
remaining molecular types were identified as KU-57788 clinical trial ST239-MRSA-III-spa t021 (2/28, 7.1%) and ST239-MRSA-III-spa t045 (1/28, 3.6%). Table 2 Molecular features of 28 high-level rifampicin-resistant S. aureus isolates MLST (ST) SCCmec type spa-type Number of isolates Nucleotide mutation Amino acid substitution Resistance pattern ST239 III t030 24 CAT/AAT+TTA/TCA 481His/Asn+466Leu/Ser CIP+E+GEN+TET(1) CIP+E+GEN+TET+CC(23) 1 CAT/AAT+GCT/GAT 481His/Asn+477Ala/Asp CIP+E+GEN+TET+CC (1) ST239 III t021 2 CAT/AAT+TTA/TCA 481His/Asn+466Leu/Ser CIP+E+GEN+TET+CC(2) ST239 III t045 1 CAT/AAT+TTA/TCA 481His/Asn+466Leu/Ser CIP+E+GEN+TET+CC+SXT(1) CIP, ciprofloxacin; E, erythromycin; CC, clindamycin; TET, tetracycline; SXT, sulfamethoxazole/trimethoprim; GEN, gentamycin; QD, quinupristin/dalfopristin.
Discussion p38 MAPK phosphorylation Multiresistance and high infection rates are common features of S .aureus and are growing problems in hospital settings. The high prevalence of antibiotic resistance in S. aureus nosocomial isolates is currently explained by intensive use of topical and systemic antimicrobial agents in health care settings, which represents a highly selective pressure for antibiotic-resistant bacterial clones [12]. In particular, MRSA strains showed high resistance rates to various antibiotics [13]. The proportion of MRSA isolates has increased in recent years. In China, surveillance data of bacterial resistance in 1998–1999 showed that the percentage of MRSA was 37.4% [14] and rapidly reached 51.7% in 2010 [4]. Rifampicin is an antibiotic of significant interest in the rise of MRSA infections. A
combination therapy, with an antibiotic such as vancomycin often is required to reach deep-seated infections effectively. Rifampicin acts by interacting specifically with bacterial RNA polymerase encoded by the gene rpoB[15]. Rifampicin resistance emerges easily in S. aureus, in particular in methicillin-resistant Strains [3].The prevalence of O-methylated flavonoid RIF-R MRSA has risen rapidly in the past few years and remains at a high resistance rate. In China, the data obtained from the surveillance of bacterial resistance showed that the percentage of RIF-R MRSA was 15.5% in 2004 and rapidly reached 49.6% by 2006. The percentage remained high from 2006 to 2009 [4]. Obviously, the nature of RIF-R MRSA isolates represents a therapeutic challenge for treating serious MRSA infections. Most RIF-R MRSA isolates were high-level resistant in our study and the percentage was found to be 94.3%. In fact, it was higher than the rate reported in some European countries, such as Spain, which had a rate of 3.7% (4/108) in 2010 [6]. There were two reasons that could explain the difference between the Rif-R rate in China compared to other countries.