Methicillin-resistant Staphylococcus aureus: microbiologic characteristics, antimicrobial susceptibilities, and assessment of virulence of an epidemic strain.
An epidemic strain of methicillin-resistant Staphylococcus aureus (MRSA) isolated from patients at the University of Virginia Hospital in Charlottesville (MRSA-Va) was characterized, and virulence properties were compared with those of three clinically significant strains of methicillin-sensitive S. aureus. Unlike most known strains of MRSA, MRSA-Va was sensitive to tetracycline and streptomycin and exhibited high-level homogeneous methicillin resistance (minimal inhibitory concentration, greater than 128 microgram/ml). The expression of resistance was not influenced by incubation temperature. MRSA-Va contained significantly more catalase (P less than 0.05) than methicillin-sensitive strains but about the same amount of protein A. Phagocytosis and killing of MRSA-Va by normal polymorphonuclear leukocytes were not significantly different from that of the Wood-46 strain of S. aureus. In mouse virulence studies using both intraperitoneal and intravenous modes of infection, 50% lethal doses for MRSA-Va were comparable with those of the three methicillin-sensitive strains. This epidemic strain of MRSA appears to be fully virulent.
D000818:Animals; D002374:Catalase / Q000096:biosynthesis; D006801:Humans; D007928:Lethal Dose 50; D008297:Male; D008712:Methicillin / Q000494:pharmacology*; D051379:Mice; D010403:Penicillin Resistance; D010405:Penicillinase; D010587:Phagocytosis; D012293:Rifampin / Q000494:pharmacology; D013205:Staphylococcal Protein A; D013211:Staphylococcus aureus / Q000254:growth & development / Q000302:isolation & purification / Q000472:pathogenicity*; D013696:Temperature; D014640:Vancomycin / Q000494:pharmacology; D014774:Virulence
D013205:Staphylococcal Protein A; D014640:Vancomycin; D002374:Catalase; D010405:Penicillinase; D008712:Methicillin; D012293:Rifampin