Methicillin-Susceptible, Vancomycin-Resistant Staphylococcus aureus, Brazil

Abstract

We report characterization of a methicillin-susceptible, vancomycin-resistant bloodstream isolate of Staphylococcus aureus recovered from a patient in Brazil. Emergence of vancomycin resistance in methicillin-susceptible S. aureus would indicate that this resistance trait might be poised to disseminate more rapidly among S. aureus and represents a major public health threat.

Keywords: Brazil; MSSA; Staphylococcus aureus; antimicrobial resistance; bacteremia; bacteria; bacterial infections; gram-positive bacterial infections; methicillin susceptibility; methicillin-susceptible; methicillin-susceptible S. aureus; vancomycin resistance; vancomycin-resistant.

Figure 1

Molecular typing of Staphylococcus aureus strains, Brazil. A) SmaI digestion of total DNA, followed by pulsed-field gel electrophoresis. Lane M, lambda ladder (molecular masses are indicated in kilobases on the left); lane 1, vancomycin-susceptible, methicillin-resistant S. aureus (VS-MRSA) isolated from the blood of a Brazilian patient (1); lane 2, vancomycin-resistant MRSA (VR-MRSA) isolated from the same patient and blood culture (1); lane 3, transconjugant 1 obtained from a mating experiment using vancomycin-resistant MSSA (VR-MSSA) as donor and VS-MRSA as recipient; lane 4, vancomycin-susceptible MSSA (VS-MSSA) isolated from the blood of the same patient 13 days after isolation of VR-MRSA; lane 5, VR-MSSA isolated at the same time as VS-MSSA; lane 6, transconjugant 2 obtained from a mating experiment using VR-MRSA as donor and VS-MSSA as recipient; lane 7, S. aureus RN4220 RF, lane 8, transconjugant 3 obtained using VR-MSSA as donor and RN4220 RF as recipient. B) S1 digestion of total DNA using the same strains shown in panel A. C) Hybridization with vanA probe using the same strains shown in panel A. Arrow indicates a positive signal for the vanA gene.

Figure 2

Phylogenetic analyses of Staphylococcus aureus strains, Brazil. Whole-genome phylogenetic tree (dataset = 325,732 single-nucleotide polymorphisms, gamma-based log likelihood − 1909607.06950) of the S. aureus species showing position of vancomycin-resistant, methicillin-susceptible S. aureus (VR-MSSA) and vancomycin-susceptible MSSA (VS-MSSA) isolates sequenced for this study. Vancomycin-resistant S. aureus (VRSA) strains are shown in red. Numbers on branches are bootstrap values based on 1,000 resampling iterations. All branches without numbers had bootstrap values of 100%. Branch lengths are proportional to number of nucleotide substitutions per site (scale bars). Inset labeled CC5 is expanded to emphasize the polyphyly of VRSA strains. *Genomes sequenced for this study. M1 and M91 are members of the Chilean/Cordobes clone that is widespread in Latin America (Technical Appendix). CC, clonal complex.