Food-borne intoxication, caused by heat-stable enterotoxins produced by Staphylococcus aureus, causes over 240,000 cases of food-borne illness in the United States annually. Other staphylococci commonly associated with animals may also produce these enterotoxins. Foods may be contaminated by infected food handlers during slaughter and processing of livestock or by cross-contamination during food preparation. S. aureus also causes a variety of mild to severe skin and soft tissue infections in humans and other animals. Antibiotic resistance is common in staphylococci. Hospital-associated (HA) S. aureus are resistant to numerous antibiotics, with methicillin-resistant S. aureus (MRSA) presenting significant challenges in health care facilities for over 40 years. During the mid-1990s new human MRSA strains developed outside of hospitals and were termed community-associated (CA). A few years later, MRSA was isolated from horses and methicillin resistance was detected in Staphylococcus intermedius/pseudintermedius from dogs and cats. In 2003, a livestock-associated (LA) MRSA strain was first detected in swine. These methicillin-resistant staphylococci pose additional food safety and occupational health concerns. MRSA has been detected in a small percentage of retail meat and raw milk samples indicating a potential risk for food-borne transmission of MRSA. Persons working with animals or handling meat products may be at increased risk for antibiotic-resistant infections. This review discusses the scope of the problem of methicillin-resistant staphylococci and some strategies for control of these bacteria and prevention of illness.

Background: Community-acquired methicillin-resistant Staphylococcusaureus (CA-MRSA), a novel strain of MRSA, has recently emerged and rapidlyspread in the community. Invasion into the hospital setting with replacement of thehospital-acquired MRSA (HA-MRSA) has also been documented. Co-colonization with bothCA-MRSA and HA-MRSA would have important clinical implications given differences inantimicrobial susceptibility profiles and the potential for exchange of geneticinformation.

Methods: A deterministic mathematical model was developed to characterizethe transmission dynamics of HA-MRSA and CA-MRSA in the hospital setting and to quantifythe emergence of co-colonization with both strains

Results: The model analysis shows that the state of co-colonization becomesendemic over time and that typically there is no competitive exclusion of either strain.Increasing the length of stay or rate of hospital entry among patients colonized withCA-MRSA leads to a rapid increase in the co-colonized state. Compared to MRSAdecolonization strategy, improving hand hygiene compliance has the greatest impact ondecreasing the prevalence of HA-MRSA, CA-MRSA and the co-colonized state.

Conclusions: The model predicts that with the expanding community reservoirof CA-MRSA, the majority of hospitalized patients will become colonized with both CA-MRSAand HA-MRSA.