Article in Japanese

A bacterial study of 32 children with clinical symptoms typical of group A β -hemolytic streptococcal pharyngitis showing negative rapid antigen detection tests

Hideaki KIKUTA¹⁾, Mutsuo SHIBATA²⁾, Shuji NAKATA³⁾, Tatsuru YAMANAKA⁴⁾, Hiroshi SAKATA⁵⁾, Kunihiko KOBAYASHI⁶⁾, The research group for prophylaxis of group A β-hemolytic streptococcal pharyngitis in Hokkaido

Most of the rapid antigen detection tests (RADTs) for group A β-hemolytic streptococci (GABHS) that are currently in use have a high specificity (i. e., 95% or greater) and a sensitivity of approximately 90% when compared with blood agar plate (BAP) culture. The necessity for a backup BAP culture for negative RADTs is a controversial issue. This study was conducted to determine whether culture confirmation is needed for a negative RADT. Backup BAP cultures were performed for 32 children aged 2-10 years who were negative for RADTs but strongly suspected as having streptococcal pharyngitis by experienced pediatricians. Streptococcus pyogenes (GABHS) was detected in cultures of throat swabs from seven children, indicating a 22% false negative rate of RADT. Nine cultures (28%) were negative for bacterial pathogens. Probable bacterial pathogens detected in cultures of throat swabs from the remaining 16 children (50%) were as follows: six cases of Staphylococcus aureus, five cases of Haemophilus influenzae, three cases of Haemophilus parainfluenzae, two cases of Klebsiella pneumoniae, one case of Streptococcus dysgalactiae subsp. equisimilis, one case of Streptococcus constellatus subsp. constellatus, and 1 case of Streptococcus agalactiae. Three cases involved two pathogens. Probable bacterial pathogens resistant to penicillin were relatively prevalent and showed a high sensitivity to a third-generation cephalosporin. This study showed a high false-negative rate of RADTs and also a high detection rate of probable bacterial pathogens in cases of strongly suspected GABHS pharyngitis. Therefore, we recommend culture confirmation in such patients with negative RADTs.

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1) Pediatric Clinic, Touei Hospital
2) Department of Pediatrics, Health Sciences University of Hokkaido
3) Nakata Pediatric Clinic
4) Yamanaka Tatsuru Pediatrics
5) Department of Pediatrics, Asahikawa Kosei Hospital
6) Department of Pediatrics, Sapporo Hokuyu Hospital

Key words
Received	February 17, 2011
Accepted	April 21, 2011

23 (3)：233─239,2011