Mini ReviewLivestock-associated methicillin-resistant Staphylococcus aureus in animals and humans
Introduction
Staphylococcus aureus (S. aureus) is a Gram-positive bacterium which belongs to the commensal flora of humans and various animal species (Vanderhaeghen et al., 2010b). Multiple body sites can be colonized in humans, but the anterior nares are the most frequent colonized sites (Wertheim et al., 2005). Approximately 20% of healthy human individuals are persistent S. aureus carriers, about 30% are intermittent carriers and around 50% are never colonized with S. aureus (Kluytmans and Struelens, 2009). In humans, S. aureus is regarded the most important cause of nosocomial infections with clinical conditions ranging from minor skin infections to severe, life-threatening infections (Lowy, 1998, Kluytmans and Struelens, 2009).
In animals, S. aureus is one of the three major pathogenic Staphylococcus species, together with S. hyicus and the Staphylococcus intermedius group – SIG (S. pseudintermedius, S. intermedius, and S. delphini) with S. hyicus and SIG more restricted in host species compared to S. aureus. S. aureus can cause intramammary infections in cattle and small ruminants (Vanderhaeghen et al., 2010b). It can also cause joint problems in chickens (Butterworth et al., 2001) and it is increasingly reported in surgical site infections in small companion animals and horses (Catry et al., 2010).
Section snippets
Methicillin-resistant Staphylococcus aureus (MRSA)
Soon after the introduction of penicillin, around 1945, the majority of the S. aureus population had become resistant to penicillin through the production of beta-lactamase, an enzyme that hydrolyzes penicillin. In the late 1950s, the beta-lactamase-resistant methicillin was introduced in human medicine. However, soon after introduction, the first methicillin-resistant isolates of S. aureus were reported (Robinson and Enright, 2003).
Methicillin resistance is caused by the acquisition of the mecA
MRSA control in humans
The large MRSA prevalence differences between countries can partly be explained by differences in level of screening, isolation and treatment of patients and staff in hospitals. For example, in the Netherlands and Scandinavian countries a pro-active system has been applied, called the “search and destroy” policy. This strategy consists of active screening of high-risk patients and exposed healthcare workers for MRSA carriage. Risk patients involved hospitalized patients who are repatriated from
Emergence of LA-MRSA in livestock and other animals
From 1970 to 2000, MRSA was rarely isolated from animals, and if so, these strains were generally supposed to be of human origin, as shown by bio-typing. Therefore, it was thought that until the end of the 20th century, the animal husbandry reservoir was of little relevance to MRSA causing diseases in humans. It was assumed that MRSA was a problem caused by antimicrobial use in human medicine (Catry et al., 2010).
In 1975 the first report on MRSA isolated from cows with mastitis was published (
Molecular aspects of MRSA ST398
MRSA isolates of ST398 possess some typical features. As aforementioned, the strains are non-typeable with standard PFGE using SmaI digestion. This is due to the presence of a restriction/methylation system leading to protection from SmaI digestion (Bens et al., 2006). The strains carry SCCmec element IV or V (Smith and Pearson, 2010). SCCmec cassette types II and III have also been reported but this may be the result of misidentification (Jansen et al., 2009). Many different spa-types have
Public health consequences of LA-MRSA
Persons in direct contact with MRSA-positive animals have an increased risk of becoming MRSA positive. This has been documented for individuals working in companion animal and equine clinics, and livestock production environments (Morgan, 2008). It has been shown that MRSA ST398 has limited host specificity; it is able to colonize and to cause infections in various hosts. So far, the mechanisms of host adaptation are poorly understood (Cuny et al., 2010). However, incidentally reported so far,
Risk factors for animal and human LA-MRSA carriage
Few studies investigated risk factors for the occurrence of ST398 in animals and humans. A high risk of animal to human transmission of ST398 has been reported in pig farming (Lewis et al., 2008, Smith et al., 2009, van den Broek et al., 2009). A direct association between MRSA carriage in animals and MRSA carriage in humans was observed in veal calf farming (Graveland et al., 2010). It was demonstrated that LA-MRSA carriage among veal farmers and their family members and employees was strongly
Human to human transmission of MRSA ST398
Few studies have examined transmissibility, and from these it appears that in hospital settings, ST398 transmits less frequently than most HA-MRSA strains (van Rijen et al., 2008, van Rijen et al., 2009, Wassenberg and Bonten, 2010, Wassenberg et al., 2011). A large Dutch multi-center study in hospital settings has shown that the relative risk on transmission of MRSA ST398, as compared to HA-MRSA, was 0.28 (Wassenberg et al., 2011). Based on these data, the genotype-specific single admission
Conclusions
LA-MRSA seems to be recently introduced into production animals and is predominantly present in pigs and veal calves. However other animals can be MRSA carrier as well due to overflow towards other species.
It has been shown that persons in direct (occupational) contact to LA-MRSA-positive animals have an increased risk for LA-MRSA carriage. The risk for LA-MRSA carriage in humans is mainly related to exposure to MRSA-positive animals. However, the positive association between MRSA carrier
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2022, Saudi Journal of Biological SciencesCitation Excerpt :MRSA isolates have also been found in a wide range of animal species, including various livestock species (Aires-de-Sousa, 2017; Alzohairy, 2011). These MRSA strains have evolved into three types: healthcare-associated MRSA (HA-MRSA) since the 1960 s; community-acquired MRSA (CA-MRSA) since the 1990 s; and new strains that have been associated with livestock since the 2000 s, so-called live-stock-associated MRSA (LA-MRSA) (Graveland et al., 2011; Li et al., 2017). The emergence of the latest MRSA strains in cattle is of great concern for livestock and public health (Haran et al., 2012; Wang et al., 2015; Weese, 2010).