Optimal site of throat swab for the isolation of beta-hemolytic streptococci.

The optimal site for the isolation of beta-hemolytic streptococci (BHS) from throat cultures was investigated in 164 healthy elementary school children. All throat cultures were streaked onto duplicate blood agar plates (BAP), one of which was taken from the tonsillar fossae and the other from the posterior pharynx. BHS were isolated in cultures from 56 (34.2%) of the children. BHS were more frequently recovered from the tonsillar fossae than from the posterior pharynx (54 vs. 47; both sites, 45; tonsillar fossae only, 9; posterior pharynx only, 2; P < 0.0001). There were significantly more numerous colonies in the tonsillar fossae than in the posterior pharynx (p < 0.01). To conclude, the tonsillar fossae are more optimal sites of throat cultures to isolate BHS than the posterior pharynx.