›› 2013, Vol. 28 ›› Issue (3): 189-193.DOI: 10.3969/j.issn.1673-8640.2013.03.005

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Detection of erm genes and epidemiology research of Staphylococcus aureus in patients with bloodstream infection

  

  1. 1 .Department of Clinical Laboratory,Tianjin Medical University General Hospital,Tianjin 300052,China; 2.School of Medical Laboratory,Tianjin Medical University,Tianjin 300203,China
  • Received:2012-04-17 Revised:2012-06-29 Online:2013-03-30 Published:2013-03-14

Abstract: Objective To investigate the distribution and epidemic situation of erythromycin ribosome methylase(erm)genes in erythromycin-resistant Staphylococcus aureus in patients with bloodstream infection from January 2006 to August 2011. Methods A total of 39 isolates of erythromycin-resistant Staphylococcus aureus were collected from January 2006 to August 2011 among patients with bloodstream infection. The bacterium identification and antimicrobial susceptibility test were conducted by VITEK 2 Compact automatic system,matched identification card and antimicrobial susceptibility card. Methicillin-resistant Staphylococcus aureus (MRSA) was identified by disk diffusion method with cefoxitin. Phenotypic expression of inducible resistance was assessed by D test. Polymerase chain reaction (PCR) was used to detect ermA,ermB and ermC genes. The epidemic situation of ermA-producing Staphylococcus aureus was analyzed by pulsed-field gel electrophoresis (PFGE) and Staphylococcal cassette chromosome mec(SCCmec)typing. Results The resistant rates of 39 erythromycin-resistant Staphylococcus aureus to clindamycin,penicillin and gentamicin were high,and were 100.0%,92.3% and 53.8%,respectively. A total of 8(20.5%) isolates of Staphylococcus aureus with discordant resistance pattern (erythromycin resistant and clindamycin sensitive) were all positive in D test. The positive rates of ermA,ermB and ermC were 25.6%(10/39),46.2%(18/39) and 46.2%(18/39),respectively. A total of 75.0% (6/8) and 25.0% (2/8) isolates with phenotypic expression of inducible resistance by D test harbored ermC and ermA genes. PFGE analysis of the all 10 MRSA isolates harboring ermA gene produced 6 distinct pulsotypes,8 MRSA isolates were SCCmecⅢ genotype,and 2 MRSA isolates could not be determined by SCCmec typing. Conclusions The positive rate of erm genes in erythromycin-resistant Staphylococcus aureus in patients with bloodstream infection is relatively high. The ermA and ermB genes are mainly harbored by MRSA and methicillin-sensitive Staphylococcus aureus(MSSA),respectively. The isolates with erythromycin inducible to clindamycin resistance mainly harbored ermC gene. A total of 10 isolates harboring ermA gene are all MRSA ,and are multidrug-resistant .There is scattered cloning spread of MRSA belonging to SCCmecⅢ genotype with ermA gene.

Key words: Erythromycin ribosome methylase gene, Staphylococcus aureus, Bloodstream infection, Erythromycin, Clindamycin