Downloaded from www.microbiologyresearch.org by IP: 54.70.40.11 On: Mon, 05 Nov 2018 13:45:20 Exotoxin gene backgrounds in bloodstream and wound Staphylococcus aureus isolates from geriatric patients attending a long-term care Spanish hospital M. A ´ ngeles Argudı ´n, 1 M. Carmen Mendoza, 1 Fernando Va ´ zquez 1,2 and M. Rosario Rodicio 1 Correspondence M. Rosario Rodicio rrodicio@fq.uniovi.es Received 24 May 2011 Accepted 12 July 2011 1 Department of Functional Biology, Laboratory of Microbiology, University of Oviedo, Oviedo, Spain 2 Monte Naranco Hospital, Oviedo, Spain The exotoxin gene content was established for 62 Staphylococcus aureus isolates causing bloodstream (n531) and wound (n531) infections in geriatric patients attending a long-term care Spanish hospital from 1996 to 2006. Content was determined based on PCR screening of genes encoding five haemolysins, three exfoliatins, three leukotoxins and 21 pyrogenic toxin superantigens (PTSAgs), in addition to markers of genomic (nSab) and pathogenicity (SaPIs) islands. Exotoxin genes were abundant in both bloodstream (11–23 genes) and wound (8–19 genes) isolates, and they were arranged in 55 combinations with only two represented in both groups. All isolates were positive for genes encoding haemolysins (hl; 3–5) and PTSAgs (tst, se and sel; 5–14), whereas exfoliatin (et) and leukotoxin (luk) genes appeared in 98.4 and 51.6 % of isolates, respectively. The hlg, lukPV, tst, sec and selu genes were found significantly more frequently in bloodstream than in wound isolates, whereas hlg-variant, sea, seb, see and selk-selq were more frequent in wound isolates (P,0.05). Distinctive exotoxin gene combinations could potentially be associated with specific mobile genetic elements, including genomic islands [lukED, egc1 (seg, seln, sei, selm, selo) and egc2(seg, seln, selu, sei, selm, selo)]; pathogenicity islands (etd, seb, sec, sell, selq, selk and tst); bacteriophages (eta, lukPV, sea, selp, selk, selq and see); and plasmids (sed, selj, ser, ses and set). The abundance of exotoxin genes and variety of arrangements shown by S. aureus from geriatric patients could play a role in the adaptation of the pathogen. INTRODUCTION Staphylococcus aureus has long been recognized as an important human pathogen causing disease in both hospitals and the community. The relative importance of host factors versus bacterial virulence determinants in the outcome of the disease is not well known, but it is accepted that bacterial components and products, including the capsule, surface-associated adhesins, secreted proteins and exotoxins, play a role in the process (Ferry et al., 2005). The vast majority of S. aureus isolates produce cytotoxins, such as haemolysins (encoded by hl genes), as well as enzymes, whose main function is to convert local host tissues into nutrients required for bacterial growth and to promote the spread of the pathogen through the human body. Some isolates also secrete other toxins, like bicomponent leukotoxins (LukS–LukF, encoded by luk genes) (Kaneko & Kamio, 2004), exfoliatins (ET, et genes) (Nishifuji et al., 2008), toxic shock syndrome toxin (TSST-1, tst gene), enterotoxins (SEs, se genes) and enterotoxin-like toxins (SEls, sel genes), with TSST-1, SEs and SEls belonging to the pyrogenic toxin superantigens (PTSAgs) (Larkin et al., 2009; Argudı ´n et al., 2010). Exotoxin-encoding genes are variably represented in S. aureus isolates and most are carried by mobile genetic elements (MGEs), including genomic islands (nSa), pathogenicity islands (SaPIs), prophages and plasmids (Novick & Subedi, 2007; Baba et al., 2008; Ono et al., 2008; Goerke et al., 2009). Specific exotoxins appear to be responsible for some syndromes caused by S. aureus. For instance, scalded skin syndrome has been associated with ETA and ETB (Nishifuji et al., 2008), toxic shock syndrome with TSST-1, SEB and SEC (Dinges et al., 2000), food poisoning with SEA (Dinges et al., 2000), haemolytic pneumonia and skin and soft tissue infections with LukPV (Lina et al., 1999) and allergic Abbreviations: CC, clonal complex; DI, discrimination index; MGE, mobile genetic element; MLST, multilocus sequencing typing; MNH, Monte Naranco Hospital; MRSA, meticillin-resistant S. aureus; MSSA, meticillin- sensitive S. aureus; PTSAg, pyrogenic toxin superantigen. Journal of Medical Microbiology (2011), 60, 1605–1612 DOI 10.1099/jmm.0.034611-0 034611 G 2011 SGM Printed in Great Britain 1605