Emergence of Unusual Bloodstream Infections Associated with Pig-Borne-Like Staphylococcus aureus ST398 in France

To the Editor—Staphylococcus aureus ST398 is a zoonotic agent primarily described in Europe that is becoming a worldwide threat associated with livestock , their human contacts, and food products. In animals, carriage is frequent , but infections are rare. In humans , infections consist in nosocomial bloodstream and wound infections [1] that are associated with spa types 011 or 034, tetracycline resistance, and the absence of panton-valentine leukocidin (PVL). Recently, a new population of ST398 strains has been isolated in China and from children adopted from China [2] that is responsible for pneumonia and skin and soft-tissue infections in patients without association with animals or animal farming and which is characterized by spa type 571, tetracy-cline susceptibility, and variable presence of PVL [3]. Annual surveys of bloodstream infection are performed in the center region of France [4, 5]. In 2009, we observed the emergence of cases associated with t571, TetS, and PVL-negative ST398 strains. Examination of patient histories revealed exposure to animals in 1 case, a fatal id-iopathic community-acquired bloodstream infection in an 84-year-old man who lived on a farm at which 1 pig was being raised. The remaining cases were hospital-acquired and included 1 case of catheter-associated infection observed in a 58-year-old man with advanced multiple myeloma, 1 case following elective digestive tract surgery in a 69-year-old woman, and 1 case following cardiac surgery in a 68-year-old man. Microarray and MLVA analysis [7] were performed to characterize the strains and compare them with Euro-pean pig-borne methicillin-resistant S. aureus and virulent strains (USA300, MW2, TW20, COL, and Newman). Most characteristics of the present strains were similar to those of the pig-borne strain. All were of accessory gene regulation type I, and none contained the genes encoding the following virulence factors: EsxA and EsxB proteins; leukocidin F; Panton-Valentine Leukocidin; TSST-1; ex-foliatins A and B; and enterotoxins A–E, G–R, and U. None harbored the lantibiotic epidermin/gallidermin genes epiA–epiF typically reported in virulent strains. In addition, similarly to the pig-borne strain, our strains harbored the cna gene, encoding a collagen adhesin associated with colonizing strains and involved in the pathogenesis of osteomyelitis and infectious arthritis [6]; the hyaluronidase gene, involved in the early stages of subcutaneous infections; and a factor SAV2371, associated with bacterial attachment to host cells and virulence. By contrast, unlike the pig-borne strain, the studied strains and the USA300 virulent clone shared cadC–cadM genes, which are responsible for cadmium resistance, …