Pathogenicity of MRSA for humans and animals

The first meticillin-resistant strains of Staphylococcus aureus (MRSA) emerged in the early 1960s after the introduction beta-lactamases, semi-synthetic penicillins, such as methicillin. For nearly 30 years the incidence was confined to the hospital environment (hospital-associated MRSA, HA-MRSA), which have a selective advantage over strains of S. aureus sensitive to methicillin (meticillin-susceptible Staphylococcus aureus, MSSA). CA-MRSA strains, as well as hospital strains, are capable of inducing a variety of infections; they are frequently responsible for the initial infection of the skin and soft tissues as well as necrotizing pneumonia. The factors that predispose the occurrence of MRSA are: diabetes mellitus, intravenous drug abuse, chronic hemodialysis, the colonization of the skin lesions, specific immunotherapy, neutropenia, increased IgE level, hemodialysis, surgical wound infections, stays in hospitals and nursing homes. The first reports of MRSA occurring in cattle took place in Belgium in 1972. MRSA strains have also been identified in horses, pigs, dogs, poultry and turtles. The common coexistence of VRE and MRSA can lead to the formation of MDR (multidrug resistant) strains of S. aureus. The emergence of multidrug-resistant strains is a major problem for MRSA eradication, and therefore it is necessary to discover antibacterial substances reducing the activity of the pathogens.