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Ramundo MS, Beltrame CO, Botelho AMN, Coelho LR, Silva-Carvalho MC, Ferreira-Carvalho BT, Nicolás MF, Guedes IA, Dardenne LE, O'Gara J, Figueiredo AMS. A unique SaeS allele overrides cell-density dependent expression of saeR and lukSF-PV in the ST30-SCCmecIV lineage of CA-MRSA. Int J Med Microbiol 2016; 306:367-80. [PMID: 27265234 DOI: 10.1016/j.ijmm.2016.05.001] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2015] [Revised: 05/06/2016] [Accepted: 05/08/2016] [Indexed: 12/11/2022] Open
Abstract
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.
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Affiliation(s)
- Mariana Severo Ramundo
- Universidade Federal do Rio de Janeiro, Instituto de Microbiologia Paulo de Góes, Rio de Janeiro, RJ, Brazil.
| | - Cristiana Ossaille Beltrame
- Universidade Federal do Rio de Janeiro, Instituto de Microbiologia Paulo de Góes, Rio de Janeiro, RJ, Brazil.
| | - Ana Maria Nunes Botelho
- Universidade Federal do Rio de Janeiro, Instituto de Microbiologia Paulo de Góes, Rio de Janeiro, RJ, Brazil.
| | - Leonardo Rocchetto Coelho
- Universidade Federal do Rio de Janeiro, Instituto de Microbiologia Paulo de Góes, Rio de Janeiro, RJ, Brazil.
| | - Maria Cicera Silva-Carvalho
- Universidade Federal do Rio de Janeiro, Instituto de Microbiologia Paulo de Góes, Rio de Janeiro, RJ, Brazil.
| | | | | | | | | | - James O'Gara
- School of Natural Sciences, Microbiology Department, NUI Galway, Galway, Ireland.
| | - Agnes Marie Sá Figueiredo
- Universidade Federal do Rio de Janeiro, Instituto de Microbiologia Paulo de Góes, Rio de Janeiro, RJ, Brazil.
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