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
. In particular, MRSA strains showed high resistance rates to various antibiotics
. 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%
 and rapidly reached 51.7% in 2010
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. Rifampicin resistance emerges easily in S. aureus, in particular in methicillin-resistant Strains
.The prevalence of 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
. 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
. There were two reasons that could explain the difference between the Rif-R rate in China compared to other countries. One possibility was the intensive use of some antimicrobial agents in health care settings in China such as quinolones, which not only could lead to the selection of multi-resistant nosocomial isolates of S. aureus, but also potentially induce endogenous, resistance-conferring mutations in bacterial genes that encode drug targets. A second possibility might be that the prevalence of MRSA clones in China was different from European countries.
For a variety of bacteria, such as E. coli
, Mycobacterium tuberculosis
 and S .aureus, the main mutations responsible for rifampicin resistance were in a particular region encompassing a few hundred nucleotides called the rifampicin resistance-determining region (RRDR). In S. aureus the RRDR was divided into two clusters which were designated cluster I (nucleotides 1384–1464, amino acids 462–488) and cluster II (nucleotides 1543–1590, amino acids 515–530). As described in previous studies, the two clusters were also both closely associated with rifampicin resistance
Here, we have amplified and sequenced portions of rpoB from RIF-R S.aureus isolates. All four amino acid substitutions we identified were present in cluster I. Mutation 481His/Asn was the most prevalent one. The majority (n = 84, 96%) of the 88 RIF-R MRSA isolates harbored the amino acid substitution 481His/Asn, which was in line with previous reports
[3, 19]. Our results further confirm that 481His/Asn has a major impact on the occurrence and development of rifampicin resistance in S. aureus. High-level rifampicin resistance may also be attributed to additional mutations within rpoB, as previously described
. The additional mutations we found were 466Leu/Ser and 477Ala/Asp. Isolates containing multiple mutations, 481His/Asn and 466Leu/Ser,were reported by other studies, which also showed high-level rifampicin resistance
[18, 19]. Mutational changes at amino acid position 477 have also been reported by several groups
[3, 6, 18], but the mutation rate was low and the types of amino acid substitutions which arose were different.
MRSA infections have been caused by a relatively small number of epidemic MRSA clones. As described in previous studies, the two major epidemic MRSA clones identified in China from 2005 to 2006 were ST239-MRSA III and ST5-MRSA II
. A pandemic MRSA clone ST239, which was found to be derived from ST8 and ST30 parental strains through simple chromosome replacement instead of movement of mobile genetic elements, was first found in Brazil and widely spread throughout the world
. In Asia and in China, ST239 accounted for 97% of nosocomial MRSA infections
. ST239-MRSA III was also the major clone found in our study. Staphylococcal protein A (SpA) is a cell wall anchored virulence factor
. Our research shows that most strains with RIF-R S. aureus belong to ST239-MRSAIII-spa t030, a situation in accordance with Chen et al.
. Their research showed t030 was up to 89.6% of MRSA in Peking Union Medical College Hospital (PUMCH) in 2002. In addition, t030 was also found to be rifampicin resistant by Chen et al., which was the main difference with t037. Our results are in line with these reports. These findings indicate that ST239-MRSAIII-spa t030 strains, associated with high-level rifampicin resistance, have spread in Anhui Provincial Hospital. Therefore, bacterial resistance surveillance and the control of hospital infections should take these findings into consideration in order to prevent and limit the spread of high-level rifampicin resistant S. aureus.