Distribution of the novel cell wall anchored protein-encoding gene sasX in Staphylococcus aureus strains / 中华检验医学杂志

ABSTRACT

ObjectiveTo investigate the distribution and effect on antibiotic resistance of the novel cell wall anchored protein-encoding gene sasX.MethodsA total of 300 S.aureus isolates were randomly collected from inpatients with S.aureusinfection in ShanghaiHuashanhospitalin 2004, 2007and 2010.Meanwhile,170 S.aureus isolates from the nasal swabs of healthy people were collected as part of a population-based community prevalence study.Typing of S.aureus isolates were identified by using multilocus sequence typing (MLST) and S.aureus-specific staphylococcal protein A typing (spa typing).Determination of oxacillin MICs was used to screen MRSA.PCR and sequencing were used to analyze sasX gene.The effect on antibiotic resistance of sasX gene was detect by disc agar diffusion drug sensitive test.ResultsThe major clonal types of the 300 S.aureus isolates collected from inpatients with S.aureus infection were ST239 ( 110,36.7％) and ST5 (122,40.7％).From 2004 to 2010,the percentage of isolates from inpatients with S.aureus infection was increased from 17％ to 39％,but sasX was only found in 0.59％ of the S.aureus isolates from the nasal swabs of healthy people.The percentage of sasX positive was increased from 47.2％ to 83.8％ in ST239.The percentage of sasX positive MRSA was increased from 26.4％ to 50.8％,but the percentage of sasX positive MSSA was about 10％.Antibiotic resistance of sasX positive strains were higher than that of sasX negative strains.Conclusions SasX gene is mainly detected in nosocomial pathogenic S.aureus and it is a possible virulence factor of S.aureus in hosptal setting.The presence of sasX gene is related to antibiotic resistance.For better understanding the real function of this novel gene,further studies such as expression of the encoded protein should be carried out.