Abstract
Staphylococcus aureus belongs to one of the most common bacteria causing healthcare and community associated infections in China, but their molecular characterization has not been well studied. From May 2011 to June 2012, a total of 322 non-duplicate S. aureus isolates were consecutively collected from seven tertiary care hospitals in seven cities with distinct geographical locations in China, including 171 methicillin sensitive S. aureus (MSSA) and 151 MRSA isolates. All isolates were characterized by spa typing. The presence of virulence genes was tested by PCR. MRSA were further characterized by SCCmec typing. Seventy four and 16 spa types were identified among 168 MSSA and 150 MRSA, respectively. One spa type t030 accounted for 80.1% of all MRSA isolates, which was higher than previously reported, while spa-t037 accounted for only 4.0% of all MRSA isolates. The first six spa types (t309, t189, t034, t377, t078 and t091) accounted for about one third of all MSSA isolates. 121 of 151 MRSA isolates (80.1%) were identified as SCCmec type III. pvl gene was found in 32 MSSA (18.7%) and 5 MRSA (3.3%) isolates, with ST22-MSSA-t309 as the most commonly identified strain. Compared with non-epidemic MRSA clones, epidemic MRSA clones (corresponding to ST239) exhibited a lower susceptibility to rifampin, ciprofloxacin, gentamicin and trimethoprim-sulfamethoxazole, a higher prevalence of sea gene and a lower prevalence of seb, sec, seg, sei and tst genes. The increasing prevalence of multidrug resistant spa-t030 MRSA represents a major public health problem in China.
Highlights
As one of the most important antibiotic-resistant pathogen in many parts of the world, the rates of methicillin resistant Staphylococcus aureus (MRSA) have been swiftly increasing worldwide over the past decades [1]
Comparison of genome phylogeny with spa typing suggested that t037 represents the ancestral ST239 spa type [11], which is in accordance with the findings that t030 has replaced t037 as the most frequent MRSA type in China, t037 still accounted for a high proportion of MRSA [12]
We mainly used spa typing and multilocus sequence typing (MLST) to illustrate the molecular characterizations of clinical S. aureus isolates in China
Summary
As one of the most important antibiotic-resistant pathogen in many parts of the world, the rates of methicillin resistant Staphylococcus aureus (MRSA) have been swiftly increasing worldwide over the past decades [1]. A review of the data from two main antimicrobial resistance surveillance programs (Mohnarin and CHINET) in China suggested that the proportion of MRSA among clinical S. aureus isolates increased dramatically from 20% in 1980 to 60% in 2008 [2]. Another Gram-Positive Cocci Resistance Surveillance program conducted in 12 teaching hospitals across China showed that the prevalence of MRSA dropped from 53.9% in 2005 to 48.1% in 2010, which might be due to the enhancement of infection control policy recently in. Comparison of genome phylogeny with spa typing suggested that t037 represents the ancestral ST239 spa type [11], which is in accordance with the findings that t030 has replaced t037 as the most frequent MRSA type in China, t037 still accounted for a high proportion of MRSA [12]
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