Molecular characterization of rifampicin-resistant Staphylococcus aureus isolates in a Chinese teaching hospital from Anhui, China

Abstract

BackgroundStaphylococcus aureus (S. aureus) is a major nosocomial pathogen that causes a variety of infections and toxicoses. In recent years, the percentage of rifampicin-resistant S. aureus has increased rapidly in China. The aims of this study were to analyze 1) the level of rifampicin resistance in S. aureus and its correlation with mutations in the rpoB gene, and 2) the molecular characterization of rifampicin-resistant S. aureus isolates.Results88 rifampicin-resistant S. aureus isolates were collected for this study. Of the 88 isolates, 83 (94.3%) were high-level rifampicin resistant (MIC≥8 mg/L) while the remaining 5 isolates (5.7%) had a low-level resistance to rifampicin (MIC, 2 to 4 mg/L). Four amino acid substitutions were found in the 88 isolates, which were 481His/Asn (95.5%), 466Leu/Ser (87.5%), 477Ala/Asp (6.8%) and 486Ser/Leu (4.5%) respectively. All mutations were found to be present in cluster I of the rpoB gene. The low-level resistant isolates were found to have only one mutation, while the high-level resistant isolates had at least two or more mutations. The most common multiple mutations were 481His/Asn+466Leu/Ser(92.8%,77/83). The other multiple mutations found were 481His/Asn+477Ala/Asp (6.0%,5/83), and 481His/Asn+466Leu/Ser+477Ala/Asp (1.2%,1/83). Out of 28 high-level rifampicin-resistant S. aureus isolates, three molecular types were found, namely, ST239-MRSA-III-spa t030 (25/28, 89.3%), ST239-MRSA-III-spa t021 (2/28, 7.1%), and ST239-MRSA-III-spa t045 (1/28, 3.6%).ConclusionsRifampicin resistance in S. aureus was closely associated with mutations in the rpoB gene. High-level rifampicin-resistant S. aureus is one of the most important features in Anhui Provincial Hospital, and high-level rifampicin resistance in S. aureus is associated with multiple mutations of rpoB gene. The prevalence of high-level rifampicin-resistant S. aureus in Anhui may be associated with the spread of the ST239-MRSA III-spa t030 clone.

WalK(S221P), a naturally occurring mutation, confers vancomycin resistance in VISA strain XN108

“…L466S double mutations that confer resistance to rifampicin but not vancomycin. 27,28 Since WalK(S221P) appears to be a novel mutation in VISA strain XN108, we focused our efforts on its possible role in vancomycin resistance.…”

Rifampicin resistance among multi-resistant MRSA clinical isolates from Chennai, India, and their molecular characterization

“…The rifampicin minimum inhibitory concentrations (MICs) of all isolates were determined by the agar dilution method. The isolates were interpreted as rifampicinsensitive (MIC ≤ 1 mg/L) or -resistant (MIC ≥ 4 mg/L) as per CLSI criteria ( Zhou et al, 2012).…”

“…Rifampicin resistance in S. aureus, as in other bacteria, is associated with mutations in particular regions (cluster I and II) of rpoB (Zhou et al, 2012). Aiba et al (2013) proposed that a regulatory mutation of rpoB influences the susceptibility of the cell to vancomycin, daptomycin, and linezolid.…”

Identification of a novel tedizolid resistance mutation in rpoB of methicillin-resistant Staphylococcus aureus

“…WGS of the N315-TDZ4 and comparison to the parent strain revealed a single nucleotide variant (SNV) in the rpoB gene (1345 A>G) corresponding to the amino acid substitution Asn449Asp. This mutation lies outside of the rifampin resistance-determining regions, which span from nucleotides 1384 – 1464 (AA 462–488) and 1543 – 1590 (AA 462–488) 8, 9 , and we correspondingly did not observe any change in rifampin susceptibly (Table 1). Previous studies have reported an association between vancomycin and daptomycin susceptibility and certain rpoB mutations including Ala621Glu, and Ala477Asp, and His481Tyr.…”