However, MSSA st398 in a childcare worker cannot be dismissed easily, especially when it occurs in pig farming country.
The connection of MSSA st398 and MRSA st398 to pigs may be becoming less noticeable as it moves into the community undetected through lack of adequate surveillance, not least in Britain.
No doubt some of our less scrupulous veterinarians are working, hoping and praying for just that.
They doubtless will get their chance to explain their actions and inaction over the past years before the international courts.
The title and content of this particular comment has been amended after publication to reflect that the strain found was S. aureus susceptible to methicillin and was therefore MSSA. Not all ST398 strains are MRSA. More information is now available from one of the authors of the study - Tara C. Smith here
Full US government report here
Volume 17, Number 4–April 2011
Livestock-associated Staphylococcus aureus in Childcare Worker
Erin D. Moritz and Tara C. Smith
Author affiliation: University of Iowa, Iowa City, Iowa, USA
To the Editor:
Carriage of Staphylococcus aureus sequence type (ST) 398 has primarily been reported as occurring among persons in contact with livestock, including swine and cattle (1,2). This association has given rise to the characterization of this strain as livestock associated (3). However, ST398 colonization or infection in persons lacking identified livestock-associated risk factors have been reported (4,5). We report ST398 colonization in a childcare worker in Iowa, USA...
...The colonized employee was a 24-year-old woman who had worked at the facility for ≈5 years. She reported a history of melanoma but was not currently taking any chemotherapy drugs and had not been hospitalized in the previous 12 months. She reported having a family member who worked in a hospital and had direct contact with patients, but the employee lived alone and responded negatively to questions about whether she or immediate family members had had contact with animals or worked in a processing plant.
ST398 may be transmitted from livestock to community members and then from person to person. It can potentially be transmitted in food; several studies have documented ST398 in raw meats (7,8), and we identified this strain in retail meat products in Iowa (T.C. Smith et al., unpub. data). Secondary transmission of ST398 from colonized persons to contacts has also been suggested, but the few publications reporting this suggest that ST398 seems to be less transmissible by this route than are common human strains (9).
We cannot be sure whether either of these routes played a role in acquisition of ST398 by this employee. Although no other tested persons in this childcare facility were found to carry ST398, only 24 (40%) of the 60 employees and 8 (4.8%) of the 168 children participated, suggesting the possibility of a reservoir in the facility among those who were not tested. Of the 24 employees who participated, 2 reported occupational contact with any animals, 2 reported contact with swine, and 3 reported contact with cattle. However, no participant reported having animals other than cats or dogs on their property. It is possible that >1 sampled employee may have been a transient ST398 carrier but negative at the time of our sampling.
Reports of ST398 in persons who had no direct contact with livestock in the United States are rare (10). To provide a better understanding of the epidemiology of this novel strain, further examination of the emergence of this isolate in community settings and on farms is needed.