Direct inoculation of food as the cause of an outbreak of group A streptococcal pharyngitis

Abstract

An investigation was conducted of a food-related outbreak of group A streptococcal pharyngitis following an elementary school banquet. Of 166 surveyed banquet attendees, 71 (43%) reported outbreak-associated pharyngitis, and 21 (88%) of 24 tested attendees had evidence of group A streptococcus (GAS) in the throat. Attendees who ate macaroni and cheese were three times more likely to develop pharyngitis than those who did not (66/132 [50%] vs. 5/30 [17%], P = .002). None of the food handlers had GAS recovered by throat culture. However, the cook who prepared the macaroni and cheese had a hand wound; a wound culture grew GAS with the same T agglutination pattern and M- and/or opacity factor type as that of all available GAS strains from ill attendees. Under laboratory conditions, macaroni and cheese supported rapid growth of the outbreak-associated strain of GAS. To the authors' knowledge, this is the first documented foodborne outbreak of GAS pharyngitis in which the only apparent source of contamination was a food handler's skin lesion.