ABSTRACT
Objective To investigate the antimicrobial susceptibility and associated virulence genes of the Staphylococcus aureus?strains?isolated?from?blood,?cerebrospinal?fluid?and?other?sterile?body?fluids?in?Huashan?Hospital?from?year?1999?to?2014.?Methods MIC values of vancomycin and other antibiotics against S. aureus were measured by agar dilution method. Resistant genes mecA and mecC and virulence genes PVL and sasX were detected by PCR in the S. aureus strains. Results The overall prevalence of MRSA in S. aureus was 54.3 % (140 / 258) and 45.7 % (118 / 258) for MSSA. Resistance rates of MRSA to most antimicrobial agents were higher than MSSA. MSSA strains were still sensitive to all the antibiotics tested, resistance rate not higher than 11% except penicillin. MIC90?values?of?β-lactam?antibiotics?(except?penicillin)?to?MSSA?were?lower?than?1?mg?/?L.?No? staphylococcal strains were found resistant to vancomycin, teicoplanin or linezolid. The mecA gene was present in all the 90 MRSA strains, and sasX gene in 46.7% of the strains. The prevalence?of?MRSA?isolated?from?blood,?cerebrospinal?fluid?and?other?sterile?body?fluids?decreased?year?by?year.?No?mecC gene?or?PVL?gene?was?identified?in?these?MRSA?strains.?Both?sasX-positive MRSA and sasX-negative MRSA were resistant to?β-lactam?antibiotics,?fosfomycin?and?levofloxacin.?The?sasX-positive MRSA strains showed higher resistance rates to amikacin and trimethoprim-sulfamethoxazole than sasX-negative MRSA. Conclusions? The?MRSA?strains?isolated?from?blood,?cerebrospinal?fluid?and?other?sterile?body?fluids?in?Huashan?Hospital?were?resistant to most commonly used anbiotics. MRSA surveillance is critical for rational use of antimicrobial agents.
ABSTRACT
Objective To understand fosfomycin resistance and prevalence of fos gene in clinical Staphylococcus aureus strains . Methods A total of 109 clinical strains of S .aureus were isolated from the patients in Huashan Hospital from January to March in 2014 .Antimicrobial susceptibility testing was performed by agar dilution method .The genes related to fosfomycin resistance including fosA ,fosB and fosC were detected by PCR .The flanking sequences of fos gene were determined by primer walking sequencing .The multilocus sequence typing (MLST) was carried out for fos gene positive strains .Results Forty‐four strains were resistant to fosfomycin (MIC> 32 mg/L) ,including 13 positive for fosB gene .Thirteen of the 109 (11 .9% ) strains carried fosB gene .However ,no fosA or fosC gene was identified .ST1 was a dominant MLST type in the strains carrying fosB gene .The three strains positive for fosB gene and associated with high level fosfomycin resistance (MIC> 512 mg/L) belonged to three different ST types . Walking sequencing showed that the fosB gene located on a transferable element containing a transposase gene .Conclusions High prevalence of f osB gene in fosfomycin‐resistant S . aureus strains indicates that f osB gene may mediate or contribute to fosfomycin resistance .