Foodborne outbreak of group G streptococcal pharyngitis

An outbreak of pharyngitis associated with beta-hemolytic streptococci of Lancefield group G occurred among persons who had attended a convention that was held June 21-24, 1979, in a Florida hotel. Seventy-two (31 per cent) of 231 interviewed conventioneers were ill. Group G streptococci were isolated from the throats of 10 (63 per cent) of 16 persons with pharyngitis and 1 (2 per cent) of 41 persons without pharyngitis (p less than 10(-5)). Antistreptolysin O titers in convalescent-phase serum samples from persons with pharyngitis were significantly higher than those from age-matched controls. Fifty-seven (51 per cent) of 111 conventioneers who had attended a convention luncheon developed pharyngitis compared with 12 (10 per cent) of 117 persons who did not (p less than 10(-9)). All persons who had attended the luncheon and had become ill had eaten a chicken salad served at the luncheon. Their median incubation period was two days. The cook who had prepared this chicken salad developed pharyngitis after the luncheon and had a throat culture positive for group G streptococci. No instances of rheumatic fever were identified and secondary illness in household contracts was rare. This outbreak indicates that group G streptococci can cause outbreaks of pharyngitis similar to those caused by group A streptococci and suggests that penicillin therapy and prophylaxis may not be needed.