Since 2004 MRSA emerged in animals, particularly in pigs and veal calves. This new MRSA variant was since its first appearance referred to as Livestock Associated-MRSA (LA-MRSA). In Europe and Northern America, LA-MRSA belongs predominantly to clonal complex (CC) 398 whereas in Asia ST9 seems to be dominant in pigs. Persons in direct contact with LA-MRSA-positive animals have an increased risk of becoming MRSA positive. The risk of carriage is mainly related with the intensity of animal contact and with MRSA prevalence among animals on the farm. In contrast with its success in animals, it seemed that MRSA CC398 is a poor persistent colonizer in humans. MRSA ST398 can, however, cause serious (invasive) infections and outbreaks, although, only incidentally reported so far. Farm hygiene and antimicrobial use contributed to MRSA occurrence in animals. Therefore these two determinants should in principle be incorporated into MRSA-control programmes in animal production. Like any other microorganism, LA-MRSA is expected to be able to adapt to new hosts and may change over time in the potential to colonize and to produce toxins. Also, the current circulating clone CC398 may be replaced by another clone in Western countries or emerge in countries where this clone is currently low-prevalent. Ongoing MRSA surveillance in humans and animals is needed to detect changes in epidemiology and to implement effective control measures.
"Community-associated MRSA (CA-MRSA) strains are genetically distinct from healthcare-associated MRSA (HA- MRSA) strains, but various clones spread between the community and hospitals and the distinction between CA-MRSA and HA-MRSA has become blurred . Recently, another MRSA clone emerged in livestock and humans exposed to livestock    . MRSA sequence type 398 (ST398), also referred to as livestock-associated MRSA (LA-MRSA), isolated from pigs and pig farmers has been reported in European countries and North America     . "
[Show abstract][Hide abstract] ABSTRACT: In addition to being a human pathogen, Staphylococcus aureus causes an array of infections in economically important livestock animals, particularly pigs. In Asia, there have been few reports on livestock-associated meticillin-resistant S. aureus (LA-MRSA), mostly from developed countries, with very few data available from resource-limited countries, not because of low prevalence but probably due to a shortage of diagnostic facilities. Unlike the wide spread of sequence type 398 (ST398) LA-MRSA in European countries and North America, ST9 predominates in most Asian countries. The prevalence of LA-MRSA among pigs in Asian countries varied widely (0.9–42.5%). The prevalence may vary by geographic location, age of pigs and sampling methodologies. Among pig farmers, the prevalence of nasal MRSA colonisation varied from 5.5% in Malaysia to 15% in China and 19.2% in Taiwan. Although most LA-MRSA isolates in Asia are of the same ST, molecular characteristics are not all the same. Dominant isolates in China were characterised as spa type t899-SCCmec III and t899-SCCmec IVb or V for isolates in Hong Kong, and t899-untypeable SCCmec for Taiwan. Dominant isolates in Malaysia were spa type t4358-SCCmec V and t337-SCCmec IX for isolates in Thailand. In addition, MRSA ST221 was reported in Japan and MRSA ST398 was isolated from commercial pigs in South Korea. Attention should be paid because pigs could become an important reservoir for MRSA and spread them to humans, as observed in many countries. There is a potential risk from the livestock reservoir to community and hospitals.
International Journal of Antimicrobial Agents 12/2014; 45(4). DOI:10.1016/j.ijantimicag.2014.12.007 · 4.30 Impact Factor
"Although most S. aureus strains are considered to be host specific (Fitzgerald, 2012), interest in livestock-associated S. aureus was renewed with the discovery of MRSA sequence type (ST) 398, initially in pigs and more recently in calves, chickens, horses, and pets (Armand-Lefevre et al., 2005; Graveland et al., 2011). ST398, as determined by multilocus sequence typing (MLST), is considered a newly emerging, pathogenic and zoonotic strain and the major cause of LA-MRSA in Europe and North America (Smith et al., 2009; Graveland et al., 2010), displaying significant diversity and high content of antimicrobial resistance genes, but so far, no significant virulence genes compared to other ST-lineages have been identified (Jamrozy et al., 2012). "
[Show abstract][Hide abstract] ABSTRACT: TwoTIR-like domain containing proteins in a newly emerging zoonotic Staphylococcus aureus strain sequence type 398 are potential virulence factors by impacting on the host innate immune response Staphylococcus aureus, sequence type (ST) 398, is an emerging pathogen and the leading cause of livestock-associated methicillin-resistant S. aureus infections in Europe and North America. This strain is characterized by high promiscuity in terms of host-species and also lacks several traditional S. aureus virulence factors. This does not, however, explain the apparent ease with which it crosses species-barriers. Recently, TIR-domain containing proteins (Tcps) which inhibit the innate immune response were identified in some Gram-negative bacteria. Here we report the presence of two proteins, S. aureus TIR-like Protein 1 (SaTlp1) and S. aureus TIR-like Protein 2 (SaTlp2), expressed by ST398 which contain domain of unknown function 1863 (DUF1863), similar to the Toll/IL-1 receptor (TIR) domain. In contrast to the Tcps in Gram-negative bacteria, our data suggest that SaTlp1 and SaTlp2 increase activation of the transcription factor NF-κB as well as downstream pro-inflammatory cytokines and immune effectors. To assess the role of both proteins as potential virulence factors knock-out mutants were created. These showed a slightly enhanced survival rate in a murine infectious model compared to the wild-type strain at one dose. Our data suggest that both proteins may act as factors contributing to the enhanced ability of ST398 to cross species-barriers.
Frontiers in Microbiology 12/2014; 5. DOI:10.3389/fmicb.2014.00662 · 3.99 Impact Factor
"For example, methicillin-resistant Staphylococcus aureus (MRSA) is a well-known food-borne pathogen that produces heat-stable enterotoxins during growth on a variety of foods and is an important regional cause of human infection (Doyle et al., 2011). Recently, it has been noted that livestock animals can be reservoirs of MRSA and transmit it to humans that live in close contact with them; MRSA from animals is called livestock-associated MRSA (Graveland et al., 2011). For this reason, it is important to develop new alternative strategies for preventing and treating infectious animal diseases of bacterial origin (Trevisi et al., 2014). "
[Show abstract][Hide abstract] ABSTRACT: Using a combination of molecular modeling and spectroscopic experiments, the naturally occurring, pharmacologically active hypericin compound is shown to form a stable complex with the dimeric form of β-lactoglobulin (β-LG). Binding is predicted to occur at the narrowest cleft found at the interface between monomers in the dimeric β-LG. The complex is able to preserve the fluorescence and singlet oxygen photosensitizing properties of the dye. The equilibrium constant for hypericin binding has been determined as Ka = 1.40 ± 0.07 μM−1, equivalent to a dissociation constant, Kd = 0.71 ± 0.03 μM. The complex is active against Staphylococcus aureus bacteria. Overall, the results are encouraging for pursuing the potential application of the complex between hypericin and β-LG as a nanodevice with bactericidal properties for disinfection.
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