Complete genome sequence of methicillin-sensitive Staphylococcus aureus containing a heterogeneic staphylococcal cassette chromosome element

Staphylococcus aureus is a common human bacterium that sometimes becomes pathogenic,causing serious infections.A key feature of S.aureus is its ability to acquire resistance to antibiotics.The presence of the staphylococcal cassette chromosome(SCC) element in serotypes of S.aureus has been confirmed using multiplex PCR assays.The SCC element is the only vector known to carry the mecA gene,which encodes methicillin resistance in S.aureus infections.Here,we report the genome sequence of a novel methicillin-sensitive S.aureus(MSSA) strain:SCC-like MSSA463.This strain was originally erroneously serotyped as methicillin-resistant S.aureus in a clinical laboratory using multiplex PCR methods.We sequenced the genome of SCC-like MSSA463 using pyrosequencing techniques and compared it with known genome sequences of other S.aureus isolates.An open reading frame(CZ049;AB037671) was identified downstream of attL and attR inverted repeat sequences.Our results suggest that a lateral gene transfer occurred between S.aureus and other organisms,partially changing S.aureus infectivity.We propose that attL and attR inverted repeats in S.aureus serve as frequent insertion sites for exogenous genes.

Preliminary molecular epidemiology of the Staphylococcus aureus in lower respiratory tract infections： a multicenter study in China

Background Staphylococcus aureus （S. aureus） remains as an important microbial pathogen resulting in community and nosocomial acquired infections with significant morbidity and mortality. Few reports for S. aureus in lower respiratory tract infections （LRTIs） have been documented. The aim of this study was to explore the molecular epidemiology of S. aureus in LRTIs in China.Methods A multicenter study of the molecular epidemiology of S. aureus in LRTIs was conducted in 21 hospitals in Beijing, Shanghai and twelve other provinces from November 2007 to February 2009. All the collected S. aureus strains were classified as minimum inhibitory concentration （MIC）, mecA gene, virulence genes Panton-Valentine Leukocidin （PVL） and y-hemolysin （hlg）, staphylococcal cassette chromosome mec （SCCmec） type, agr type, and Multilocus Sequence Typinq （MLST）.Results Totally, nine methicillin-sensitive S. aureus （MSSA） and 29 methicillin-resistant S. aureus （MRSA） strains were isolated after culture from a total of 2829 sputums or bronchoalveolar lavages. The majority of MRSA strains （22/29） had a MIC value of 〉512 μg/ml for cefoxitin. The mecA gene acting as the conservative gene was carried by all MRSA strains. PVL genes were detected in only one S. aureus strain （2.63%, 1/38）. The hlg gene was detected in almost the all S. aureus （100% in MSSA and 96.56% in MRSA strains）. About 75.86% of MRSA strains carried SCCmec Ⅲ. Agr type 1 was predominant （78.95%） among the identified three agr types （agr types 1,2, and 3）. Totally, ten sequence type （ST） of S. aureus strains were detected. A new sequence type （ST1445） was found besides confirming ST239 as the major sequence type （60.53%）. A dendrogram generated from our own MLST database showed all the bootstrap values 〈50%. Conclusion Our preliminary epidemiology data show SCCmec Ⅲ, ST239 and agr type 1 of S. aureus as the predominant strains in LRTIs in Mainland of China.

Investigation of the prevalence of patients co-colonized or infected with methiclllin-resistant Staphylococcus aureus and vancomycin- resistant enterococci in China： a hospital-based study

Background Nosocomial infection caused by methicillin-resistant Staphylococcus aureus （MRSA） and vancomycin-resistant enterococci （VRE） could lead to increased morbidity and mortality. In 2006, VRE nosocomial spread became a reality in our hospital since the first VRE nosocomial infection in 2003. Little is known about the prevalence of coexistence with VRE and MRSA in the patients. The primary objective of the study was to identify the molecular characteristics of epidemic MRSA clones in our hospital and the prevalence of the coexistence with MRSA and VRE in same patients during the 2-year period, 2006-2007. Methods The clinical features, laboratory test results, and therapeutic outcomes of 129 cases who isolated MRSA collected from January 2006 to December 2007 were retrospectively analyzed. Polymerase chain reaction （PCR） was used to determine mecA-femB type and staphylococcal cassette chromosome mec （SCCmec） type. All the participants were screened for clinical and microbiological data to identify the coexistence of VRE strains with MRSA. Results One hundred and twenty-nine MRSA isolates were included in the study： 71 （55%） from the intensive care unit, 35 （27.2%） from the surgical wards and 23 （17.8%） from the medical wards. The most frequent source of isolation of MRSA was sputum （76.7%）. From seven patients we isolated MRSA and VRE （E. faecium） simultaneously during their inpatient stay. One hundred and twenty-seven （127/129, 98.4%） MRSA isolates harboured SCCmec type Ⅲ, only 2 MRSA strains contained SCCmec type Ⅱ. All of the 129 MRSA isolates remained sensitive to vancomycin, teicoplanin and linezolid. Higher sensitivity rates were noted for chloramphenicol 99.2% （128/129）. Only 20.2% （26/129） of the MRSA isolates were sensitive to rifampin. All isolates presented resistance to multiple antimicrobial agents with high minimum inhibitory concentrations （MICs）, including： β-Iactams （penicillin, oxacillin, cefoxitin, and cefazolin）, tetracycline, erythromycin, gentamicin, and quinolones （ciprofloxacin, levofloxacin, and moxifloxacin）. Conclusions The predominant MRSA clone at Beijing Chaoyang Hospital from 2006 to 2007 had the type Ⅲ SCCmec element. All of the MRSA isolates were multiresistant to antimicrobial agents. Emergence of coexistence of MRSA and VRE in the same patient was not rare. Physicians should pay more attention to infections resulting from MRSA and VRE. Aggressive infection control measures should be taken to prevent the transmission of the multidrug resistance organism.