A unique SaeS allele overrides cell-density dependent expression of saeR and lukSF-PV in the ST30-SCCmecIV lineage of CA-MRSA.
ST30 (CC30)-SCCmec IV (USA1100) is one of the most common community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) lineages. ST30 isolates typically carry lukSF-PV genes encoding the Panton-Valentine leukocidin (PVL) and are responsible for outbreaks of invasive infections worldwide. In this study, twenty CC30 isolates were analyzed. All were very susceptible to non-β-lactam antimicrobials, 18/20 harbored the lukSF-PV genes, only 1/20 exhibited agr-rnaIII dysfunction, and the majority was not able to form biofilm on inert surfaces. Analysis of lukSF-PV temporal regulation revealed that opposite to other CA-MRSA isolates, these genes were more highly expressed in early log phase than in stationary phase. This inverted lukSF-PV temporal expression was associated with a similar pattern of saeRS expression in the ST30 isolates, namely high level expression in log phase and reduced expression in stationary phase. Reduced saeRS expression in stationary phase was associated with low expression levels of the sae regulators, agr and agr-upregulator sarA, which activate the stationary phase sae-P1 promoter and overexpression of agr-RNAIII restored the levels of saeR and lukSF-PV trancripts in stationary phase. Altered SaeRS activity in the ST30 isolates was attributed to amino acid substitutions (N227S, E268K and S351T) in the HTPase_c domain of SaeS (termed SaeS(SKT)). Complementation of a USA300 saeS mutant with the saeS(SKT) and saeS alleles under the direction of the log phase sae-P3 promoter revealed that saeR and lukSF-PV transcription levels were more significantly activated by saeS(SKT) than saeS. In summary our data identify a unique saeS allele (saeS(SKT)) which appears to override cell-density dependent SaeR and PVL expression in ST30 CA-MRSA isolates. Further studies to determine the contribution of saeS(SKT) allele to the pathogenesis of infections caused by ST30 isolates are merited.
Universidade Federal do Rio de Janeiro, Instituto de Microbiologia Paulo de Góes, Rio de Janeiro, RJ, Brazil. Electronic address: marianasevero@gmail.com.
Mariana Severo
MS
Ramundo
Universidade Federal do Rio de Janeiro, Instituto de Microbiologia Paulo de Góes, Rio de Janeiro, RJ, Brazil. Electronic address: crisbeltrame85@gmail.com.
Cristiana Ossaille
CO
Beltrame
Universidade Federal do Rio de Janeiro, Instituto de Microbiologia Paulo de Góes, Rio de Janeiro, RJ, Brazil. Electronic address: botelho.amn@micro.ufrj.br.
Ana Maria Nunes
AM
Botelho
Universidade Federal do Rio de Janeiro, Instituto de Microbiologia Paulo de Góes, Rio de Janeiro, RJ, Brazil. Electronic address: coelholr@micro.ufrj.br.
Leonardo Rocchetto
LR
Coelho
Universidade Federal do Rio de Janeiro, Instituto de Microbiologia Paulo de Góes, Rio de Janeiro, RJ, Brazil. Electronic address: cicera@micro.ufrj.br.
Maria Cicera
MC
Silva-Carvalho
Universidade Federal do Rio de Janeiro, Instituto de Microbiologia Paulo de Góes, Rio de Janeiro, RJ, Brazil. Electronic address: bernadetetfcarvalho@gmail.com.
Bernadete Teixeira
BT
Ferreira-Carvalho
Laboratório Nacional de Computação Científica, Petrópolis, RJ, Brazil. Electronic address: marisa@lncc.br.
Marisa Fabiana
MF
Nicolás
Laboratório Nacional de Computação Científica, Petrópolis, RJ, Brazil. Electronic address: isabella@lncc.br.
Isabella Alvim
IA
Guedes
Laboratório Nacional de Computação Científica, Petrópolis, RJ, Brazil. Electronic address: le.dardenne@gmail.com.
Laurent Emmanuel
LE
Dardenne
School of Natural Sciences, Microbiology Department, NUI Galway, Galway, Ireland. Electronic address: james.ogara@nuigalway.ie.
James
J
O'Gara
Universidade Federal do Rio de Janeiro, Instituto de Microbiologia Paulo de Góes, Rio de Janeiro, RJ, Brazil. Electronic address: agnes@micro.ufrj.br.
Agnes Marie Sá
AM
Figueiredo
D000483:Alleles; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D001427:Bacterial Toxins / Q000235:genetics / Q000378:metabolism*; D002452:Cell Count; D005098:Exotoxins / Q000235:genetics / Q000378:metabolism*; D020869:Gene Expression Profiling; D015964:Gene Expression Regulation, Bacterial; D006801:Humans; D007956:Leukocidins / Q000235:genetics / Q000378:metabolism*; D055624:Methicillin-Resistant Staphylococcus aureus / Q000235:genetics* / Q000254:growth & development; D011494:Protein Kinases / Q000235:genetics / Q000378:metabolism*; D014157:Transcription Factors
D001426:Bacterial Proteins; D001427:Bacterial Toxins; D005098:Exotoxins; D007956:Leukocidins; C078284:Panton-Valentine leukocidin; C433805:SaeR protein, Staphylococcus aureus; D014157:Transcription Factors; C108483:leukocidin S-component protein, Staphylococcus; C074300:LukF protein, Staphylococcus aureus; D011494:Protein Kinases; C527351:SaeS protein, Staphylococcus aureus
CA-MRSA; Panton-Valentine leucocidin; ST30-SCCmecIV; USA1100; lukSF-PV; saeRS