Volume 17, Number 6—June 2011
Lethal Necrotizing Pneumonia Caused by an ST398 Staphylococcus aureus Strain
To the Editor: The prevalent colonization of livestock with methicillin-resistant Staphylococcus aureus (MRSA) sequence type (ST) 398 in many countries is a cause for consternation. However, understanding of the emergence of these organisms and their public health implications is embryonic. The perceptions that all MRSA found in livestock are of ST398 lineage or that livestock are the only reservoirs of ST398 oversimplify a complex epidemiology, therefore, prudence is required when attributing human infections with S. aureus ST398 to livestock reservoirs. The fatal infection of a young girl with ST398 methicillin-susceptible S. aureus (MSSA) is tragic (1). However, the conclusion by the authors that “the spread of S. aureus ST398 among livestock is a matter of increasing concern because strains of this sequence type were able to acquire PVL [Panton-Valentine leukocidin] genes” is misleading.
The authors report no history of livestock exposure and the spa type reported (t571) is relatively rare among livestock isolates (2,3). The isolate from the fatal case was tetracycline-susceptible and positive for PVL toxin, while livestock ST398 isolates have been almost uniformly tetracycline resistant and PVL negative. Notably, spa type t571 ST398 MSSA was detected in 9 families from the Dominican Republic living in Manhattan, New York, without contact with livestock (4). Furthermore, t571 was the only spa type of MSSA identified in a study in the Netherlands of ST398 isolates, including 3 independent cases of nosocomial bacteremia in Rotterdam with no apparent livestock contact (5). spa type t571 was the predominant (11%) MSSA type in patients at a Beijing, China, hospital (6). More recently, a study of t571 MSSA strains from cases of bloodstream infections in France determined that the isolates differed from pig-borne strains and shared similarities with strains from humans in China and virulent USA300 strains (7). These observations concur with a hypothesis that ST398 strains of diverse genotype and geographic origin may also be epidemiologically distinct (8), and livestock contact is a notably inconsistent feature of invasive ST398 infections (5,7–10).
The possibility that variants of the ST398 lineage may persist in human populations without livestock contact should not be dismissed. The incidence and severity of clinical infections with ST398 S. aureus in livestock workers as yet have been minimal. Understanding the public health implications of ST398 S. aureus requires systematic investigation of their epidemiology in animals and humans. Human clinical cases of ST398 S. aureus infection should not be indiscriminately attributed to livestock, particularly if isolates are genotypically dissimilar to those occurring commonly in animals.
- Rasigade J-P, Laurent F, Hubert P, Vandenesch F, Etienne J. Lethal necrotizing pneumonia caused by an ST398 Staphylococcus aureus strain. Emerg Infect Dis. 2010;16:1330.
- de Neeling AJ, van den Broek MJ, Spalburg EC, van Santen-Verheuvel MG, Dam-Deisz WD, Boshuizen HC, High prevalence of methicillin resistant Staphylococcus aureus in pigs. Vet Microbiol. 2007;122:366–72.
- Graveland H, Wagenaar JA, Heesterbeek H, Mevius D, van Duikeren E, Heedrik D. Methicillin resistant Staphylococcus aureus ST398 in veal calf farming: human MRSA carriage related with animal antimicrobial usage and farm hygiene. PLoS ONE. 2010;5:e10990.
- Bhat M, Dumortier C, Taylor B, Miller M, Vasquez G, Yunen J, Staphylococcus aureus ST398, New York City and Dominican Republic. Emerg Infect Dis. 2009;15:285–7.
- van Belkum A, Melles DC, Peeters JK, van Leeuwen WB, van Duijkeren E, Huijsdens XW, Methicillin-resistant and -susceptible Staphylococcus aureus sequence type 398 in pigs and humans. Emerg Infect Dis. 2008;14:479–83.
- Chen H, Liu Y, Jiang X, Chen M, Wang H. Rapid change of methicillin-resistant Staphylococcus aureus clones in a Chinese tertiary care hospital over a 15-year period. Antimicrob Agents Chemother. 2010;54:1842–7.
- van der Mee-Marquet N, François P, Domelier-Valentin AS, Coulomb F, Decreux C, Hombrock-Allet C, Emergence of unusual bloodstream infections associated with pig-borne-like Staphylococcus aureus ST398 in France. Clin Infect Dis. 2011;52:152–3.
- Stegger M, Lindsay JA, Sørum M, Gould KA, Skov R. Genetic diversity in CC398 methicillin-resistant Staphylococcus aureus isolates of different geographical origin. Clin Microbiol Infect. 2010;16:1017–9.
- Ekkelenkamp MB, Sekkat M, Carpaij N, Troelstra A, Bonten MJ. Endocarditis due to methicillin-resistant Staphylococcus aureus originating from pigs. Ned Tijdschr Geneeskd. 2006;150:2442–7.
- Welinder-Olsson C, Florén-Johansson K, Larsson L, Öberg S, Karlsson L, Åhrén C. Infection with Panton-Valentine leukocidin–positive methicillin-resistant Staphylococcus aureus t034. Emerg Infect Dis. 2008;14:1271–2.