Abstract
Panton-Valentine leukocidin (PVL, encoded by lukSF-PV genes), a bi-component and pore-forming toxin, is carried by different staphylococcal bacteriophages. The prevalence of PVL in Staphylococcus aureus has been reported around the globe. However, the data on PVL-encoding phage types, lukSF-PV gene variation and chromosomal phage insertion sites for PVL-positive S. aureus are limited, especially in China. In order to obtain a more complete understanding of the molecular epidemiology of PVL-positive S. aureus, an integrated and modified PCR-based scheme was applied to detect the PVL-encoding phage types. Phage insertion locus and the lukSF-PV variant were determined by PCR and sequencing. Meanwhile, the genetic background was characterized by staphylococcal cassette chromosome mec (SCCmec) typing, staphylococcal protein A (spa) gene polymorphisms typing, pulsed-field gel electrophoresis (PFGE) typing, accessory gene regulator (agr) locus typing and multilocus sequence typing (MLST). Seventy eight (78/1175, 6.6%) isolates possessed the lukSF-PV genes and 59.0% (46/78) of PVL-positive strains belonged to CC59 lineage. Eight known different PVL-encoding phage types were detected, and Φ7247PVL/ΦST5967PVL (n = 13) and ΦPVL (n = 12) were the most prevalent among them. While 25 (25/78, 32.1%) isolates, belonging to ST30, and ST59 clones, were unable to be typed by the modified PCR-based scheme. Single nucleotide polymorphisms (SNPs) were identified at five locations in the lukSF-PV genes, two of which were non-synonymous. Maximum-likelihood tree analysis of attachment sites sequences detected six SNP profiles for attR and eight for attL, respectively. In conclusion, the PVL-positive S. aureus mainly harbored Φ7247PVL/ΦST5967PVL and ΦPVL in the regions studied. lukSF-PV gene sequences, PVL-encoding phages, and phage insertion locus generally varied with lineages. Moreover, PVL-positive clones that have emerged worldwide likely carry distinct phages.
Highlights
Staphylococcus aureus causes a spectrum of diseases from minor skin and soft tissue infections (SSTIs) to life-threatening conditions due to its potential to produce many toxins and efficiency at overcoming antibiotics (David and Daum, 2010; Uhlemann et al, 2014)
multilocus sequence typing (MLST) results showed 15 Sequence types (STs) types were produced in isolates studied, namely ST1 (CC1), ST9 (CC9), ST22 (CC22), ST25 (CC25), ST30 (CC30), ST59 (CC59), ST88 (CC88), ST188 (CC1), ST149 (CC5), ST217 (CC22), ST338 (CC59), ST398 (CC398), ST1301 (CC121), ST160 (CC121), and ST172
Two STs identified in this study have not found matching profiles in the MLST database, and subsequently were designated ST160 and ST172 after we uploaded the data to the website
Summary
Staphylococcus aureus causes a spectrum of diseases from minor skin and soft tissue infections (SSTIs) to life-threatening conditions due to its potential to produce many toxins and efficiency at overcoming antibiotics (David and Daum, 2010; Uhlemann et al, 2014). All known S. aureus phages belong to the order Caudovirales, which can be separated into three major families (Podoviridae, Siphoviridae, and Myoviridae) depending on the tail morphology (Xia and Wolz, 2014). At least 10 PVL phages have been described and sequenced, and all of them belong to the Siphoviridae family characterized by double-stranded DNA and a long non-contractile tail (Zhang et al, 2011; Xia and Wolz, 2014). To identify as many PVL-encoding phages as possible, this article summarized a strategy by integrating and modifying the expanded PCR-based scheme described previously (Ma et al, 2008; Boakes et al, 2011; Chen et al, 2013; Sanchini et al, 2014). By the usage of this strategy, fifteen-reaction PCR assay was carried out to detect 10 of the PVL-encoding phages ( PVL, 108PVL, tp310, Sa2958, Sa2mw, SLT, Sa2USA, TCH60, 7247PVL/ ST5967PVL, and Sa119) in S. aureus from China
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