The molecular epidemiology of the highly virulent ST93 Australian community Staphylococcus aureus strain.
In Australia the PVL-positive ST93-IV [2B], colloquially known as "Queensland CA-MRSA" has become the dominant CA-MRSA clone. First described in the early 2000s, ST93-IV [2B] is associated with skin and severe invasive infections including necrotizing pneumonia. A singleton by multilocus sequence typing (MLST) eBURST analysis ST93 is distinct from other S. aureus clones. To determine if the increased prevalence of ST93-IV [2B] is due to the widespread transmission of a single strain of ST93-IV [2B] the genetic relatedness of 58 S. aureus ST93 isolated throughout Australia over an extended period were studied in detail using a variety of molecular methods including pulsed-field gel electrophoresis, spa typing, MLST, microarray DNA, SCCmec typing and dru typing. Identification of the phage harbouring the lukS-PV/lukF-PV Panton Valentine leucocidin genes, detection of allelic variations in lukS-PV/lukF-PV, and quantification of LukF-PV expression was also performed. Although ST93-IV [2B] is known to have an apparent enhanced clinical virulence, the isolates harboured few known virulence determinants. All PVL-positive isolates carried the PVL-encoding phage ΦSa2USA and the lukS-PV/lukF-PV genes had the same R variant SNP profile. The isolates produced similar expression levels of LukF-PV. Although multiple rearrangements of the spa sequence have occurred, the core genome in ST93 is very stable. The emergence of ST93-MRSA is due to independent acquisitions of different dru-defined type IV and type V SCCmec elements in several spa-defined ST93-MSSA backgrounds. Rearrangement of the spa sequence in ST93-MRSA has subsequently occurred in some of these strains. Although multiple ST93-MRSA strains were characterised, little genetic diversity was identified for most isolates, with PVL-positive ST93-IVa [2B]-t202-dt10 predominant across Australia. Whether ST93-IVa [2B] t202-dt10 arose from one PVL-positive ST93-MSSA-t202, or by independent acquisitions of SCCmec-IVa [2B]-dt10 into multiple PVL-positive ST93-MSSA-t202 strains is not known.
Australian Collaborating Centre for Enterococcus and Sdtaphylococcus Species (ACCESS) Typing and Research, PathWest Laboratory Medicine-Western Australia, Royal Perth Hospital, Western Australia, Australia. Geoffrey.coombs@health.wa.gov.au
Geoffrey W
GW
Coombs
Richard V
RV
Goering
Kyra Y L
KY
Chua
Stefan
S
Monecke
Benjamin P
BP
Howden
Timothy P
TP
Stinear
Ralf
R
Ehricht
Frances G
FG
O'Brien
Keryn J
KJ
Christiansen
D001315:Australia / Q000453:epidemiology; D001427:Bacterial Toxins / Q000235:genetics; D004269:DNA, Bacterial / Q000235:genetics; D005098:Exotoxins / Q000235:genetics; D020869:Gene Expression Profiling; D006801:Humans; D007956:Leukocidins / Q000235:genetics; D055624:Methicillin-Resistant Staphylococcus aureus / Q000145:classification / Q000235:genetics* / Q000302:isolation & purification; D017720:Molecular Epidemiology; D058889:Molecular Typing / Q000379:methods; D010802:Phylogeny; D013203:Staphylococcal Infections / Q000453:epidemiology* / Q000382:microbiology*; D037521:Virulence Factors / Q000235:genetics
D001427:Bacterial Toxins; D004269:DNA, Bacterial; D005098:Exotoxins; D007956:Leukocidins; C078284:Panton-Valentine leukocidin; D037521:Virulence Factors