OUTBREAK OF SCARLET FEVER AT A HOSPITAL DAY-CARE-CENTER - ANALYSIS OFSTRAIN RELATEDNESS WITH PHENOTYPIC AND GENOTYPIC CHARACTERISTICS

An outbreak of scarlet fever involving 12 children occurred at a hospi tal day care centre from February to March 1996. Twenty-five throat is olates of Streptococcus pyogenes (GAS, group A streptococcus) availabl e from 24 children, including 10 children with scarlet fever and 14 as ymptomatic carriers, and one asymptomatic staff member were studied fo r the presence of genes encoding streptococcal pyrogenic exotoxin type s A (speA), B (speB), and C (speC) and for protease activity. Antimicr obial susceptibilities using the E-test, cluster analysis by cellular fatty acid composition and random amplified polymorphic DNA (RAPD) pat terns by means of arbitrarily-primed polymerase chain reaction (APPCR) of the isolates were performed to investigate the outbreak. Only one isolate from an asymptomatic child possessed the speA gene. All isolat es possessed the speB gene and 24 (96%) isolates were positive for the speC gene. There was no difference in protease activity between isola tes from children with scarlet fever and from asymptomatic carriers. T hirteen isolates (10 recovered from children with scarlet fever, two f rom asymptomatic children, and one from the staff member) were conside red to be the same strain according to the identical antimicrobial sus ceptibility profile and RAPD patterns and were also considered to be s imilar by cluster analysis of fatty acid composition. These findings s uggest that the outbreak was caused by a unique clone of GAS. We concl ude that RAPD typing and cluster analysis by cellular fatty acids comp osition both provide a powerful tool for epidemiological investigation of GAS infections.