Isolation of capsulate anaerobic bacteria from orofacial abscesses

The presence of capsulate Bacteroides spp. and anaerobic gram-positive cocci was investigated in pus specimens from 182 children with chronic orofacial infections or abscesses and in pharyngeal swabs from 26 children without inflammation. Of 216 Bacteroides spp. and anaerobic cocci isolated from clinical infections, 170 (79%) were capsulate, compared with 34 (35%) of 96 isolates from normal pharyngeal flora (p less than 0.001). The commonest organisms found to be capsulate more often from infected patients than from controls belonged to the B. melaninogenicus group. The possible evolution of encapsulation in these organisms and their importance in mixed orofacial infections are discussed.