Emergence of Staphylococcus aureus carrying multiple drug resistance genes on a plasmid encoding exfoliative toxin B

Antimicrob Agents Chemother. 2013 Dec;57(12):6131-40. doi: 10.1128/AAC.01062-13. Epub 2013 Sep 30.

Abstract

We report the complete nucleotide sequence and analysis of pETBTY825, a Staphylococcus aureus TY825 plasmid encoding exfoliative toxin B (ETB). S. aureus TY825 is a clinical isolate obtained from an impetigo patient in 2002. The size of pETBTY825, 60.6 kbp, was unexpectedly larger than that of the archetype pETBTY4 (∼30 kbp). Genomic comparison of the plasmids shows that pETBTY825 has the archetype pETBTY4 as the backbone and has a single large extra DNA region of 22.4 kbp. The extra DNA region contains genes for resistance to aminoglycoside [aac(6')/aph(2″)], macrolide (msrA), and penicillin (blaZ). A plasmid deletion experiment indicated that these three resistance elements were functionally active. We retrospectively examined the resistance profile of the clinical ETB-producing S. aureus strains isolated in 1977 to 2007 using a MIC determination with gentamicin (GM), arbekacin (ABK), and erythromycin (EM) and by PCR analyses for aac(6')/aph(2″) and msrA using purified plasmid preparations. The ETB-producing S. aureus strains began to display high resistance to GM, which was parallel with the detection of aac(6')/aph(2″) and mecA, after 1990. Conversely, there was no significant change in the ABK MIC during the testing period, although it had a tendency to slightly increase. After 2001, isolates resistant to EM significantly increased; however, msrA was hardly detected in ETB-producing S. aureus strains, and only five isolates were positive for both aac(6')/aph(2″) and msrA. In this study, we report the emergence of a fusion plasmid carrying the toxin gene etb and drug resistance genes. Prevalence of the pETBTY825 carrier may further increase the clinical threat, since ETB-producing S. aureus is closely related to more severe impetigo or staphylococcal scalded-skin syndrome (SSSS), which requires a general antimicrobial treatment.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Anti-Bacterial Agents / pharmacology
  • Base Sequence
  • Dibekacin / analogs & derivatives
  • Dibekacin / pharmacology
  • Drug Resistance, Multiple, Bacterial / genetics*
  • Erythromycin / pharmacology
  • Exfoliatins / biosynthesis
  • Exfoliatins / genetics*
  • Gentamicins / pharmacology
  • Humans
  • Impetigo / drug therapy
  • Impetigo / microbiology
  • Japan
  • Microbial Sensitivity Tests
  • Molecular Sequence Data
  • Plasmids*
  • Retrospective Studies
  • Staphylococcal Scalded Skin Syndrome / drug therapy
  • Staphylococcal Scalded Skin Syndrome / microbiology
  • Staphylococcus aureus / drug effects
  • Staphylococcus aureus / genetics*
  • Staphylococcus aureus / isolation & purification

Substances

  • Anti-Bacterial Agents
  • Exfoliatins
  • Gentamicins
  • Dibekacin
  • Erythromycin
  • arbekacin