1990 Volume 53 Issue 2 Pages 143-157
Identification, proportional distribution and antimicrobial susceptibility were examined of Bacteroides forsythus isolated from periodontal pockets, an alveolar abscess and a dentigerous cyst. Non-black pigmented, fastidious Bacteroides with trypsin activity were chosen for this experiment. Clinical isolates were identified by means of an API ZYM system. The DNA-DNA dot hybridization technique was utilized as an additional identification tool. B. forsythus ATCC43037 was labelled by photobiotin for DNA-DNA hybridization.
All strains showed enzymatic activity patterns similar to ATCC type strain. Morphological and SDS-PAGE studies revealed one strain derived from an alveolar abscess case was different from the others. However, DNA of this strain was homologous to the labelled DNA of the B. forsythus type strain. Therefore, all strains tested were identified as B. forsythus. B. forsythus was isolated from 40% of the periodontal pockets of patients with advancing periodontitis. In most cases, the proportional distribution of B. forsythus were approximately 2%, although it was greater than 10% in two cases. Organisms from periapical lesions were more resistant to antibiotics than those from periodontal pockets. Clindamycin was effective against all the bacterial strains tested. Periodontal pocket bacteria were sensitive to metronidazole.
In conclusion, the API ZYM system is useful for identification of B. forsythus. When B. forsythus represents greater than 10% of the organisms in periodontitis, it may exert an important influence on exacerbation due to its ability to produce trypsin.
