[Evaluation of antigen diagnostic kit in group A streptococcus mass infection]

We report a Food-borne group A streptococcus epidemic at Kitasato University campus on July 30 and 31, 2005, believed caused by lunch. A current mass group A streptococcus infection differing from the food-borne epidemic above occurred at Kitasato University East Hospital, also believed caused by lunch. Group A streptococcus was detected using a prompt diagnostic kit and bacterial culture from 116 clinical specimens taken from 116 patients with group A streptococcus pharyngitis at Kitasato University East Hospital on August 5, 2005. To investigate the utility of immunochromatographic detection of group A streptococcus antigen, 116 clinical specimens obtained from pharyngeal membranes by swab were examined using a prompt diagnostic kit for group A streptococcus (ImmunoCard STAT! STREP A TEST) and conventional bacterial culture. Group A streptococcus positivity differed between the two methods. Fourteen patients were found to be positive by the prompt diagnostic kit and 23 by bacterial culture. Four patients showing 1.0 x 10(6) cfu/mL estimated by the culture were difficult to diagnose with the prompt diagnostic kit,even though the detection sensitivity of this kit was 1.0 x 10(6) cfu/mL or more. Conventional bacterial culture should therefore be used in addition to the prompt diagnostic kit to detect group A streptococcus, especially in pharyngeal samples obtained from patients with pharyngitis.