Prevalence of SCCmec type IV in nosocomial bloodstream isolates of methicillin-resistant Staphylococcus aureus

Abstract

Over a period of 7 months, 151 consecutive methicillin-resistant Staphylococcus aureus blood isolates were evaluated. None was community acquired. Twenty (13%) were susceptible to four or more antimicrobials, and 95% of these isolates were identified as SCCmec type IV. Molecular typing demonstrated four patterns, with one predominant pattern. Although usually community acquired, SCCmec type IV in our setting is clearly nosocomial.

FIG. 1.

(a) Distribution of 17 MRSA isolates in the hospital's main building (the other 3 isolates were from three different buildings). The numbers correspond to the isolates. *, nosocomial infection; #, healthcare-associated infection. Colored circles indicate different PFGE patterns as follows: pink, pattern A; blue, pattern B; yellow, pattern B1; green, pattern C. Colored squares indicate SCCmec types as follows: yellow, type IV; red, type IV variant. Colored triangles indicate diagnosis of infection as follows: pink, endocarditis; red, primary bloodstream infection; green, omphalitis; yellow, urinary tract infection; blue, surgical site infection. (b) Molecular typing results with pulsed-field gel electrophoresis identified the following patterns and strains: pattern A (lanes 2 to 11 and 13 to 15), pattern B (lanes 16 to 19), pattern C (lane 21), pattern B1 (lane 22), pattern D (lane 23), Brazilian endemic clone (lane 24), strain NCTC 10442 (lane 25), strain N315 (lane 26), strain 85/2082 (lane 27), strain JSCS1968 (lane 28), and strain JSCS1978 (lane 29). Molecular weight markers (48.5 kb) are in lanes 1, 12, 20, and 30. (c) Results of SCCmec typing identified the following types and strains: type IV variant (lanes 2, 4, 20, and 21), type IV (lanes 3, 5 to 13, 16 to 19, and 23), type IIIA (lane 22), strain NCTC 10442 (SCCmec type I; lane 24), strain N315 (SCCmec type II; lane 25), strain 85/2082 (SCCmec type III; lane 25), and strain JSCS 1968 (SCCmec type IV; lane 27). Lanes 1, 14, and 15 are DNA molecular size markers (1-kb DNA ladder; Invitrogen); lane 28 is a negative control (water).