Antigenic Studies of Oral and Nonoral Black-Pigmented Bacteroides Strains

Abstract

Antigens of several oral and nonoral strains of B. asaccharolyticus (proposed classification of oral B. asaccharolyticus, B. gingivalis), B. melaninogenicus ssp. intermedius, B. melaninogenicus ssp. melaninogenicus, and B. melaninogenicus ssp. levii were identified in soluble preparations obtained by sonication, autoclaving and NaOH treatment of whole bacterial cells. The sonicate preparations contained the most complete representation of soluble antigens using antisera to the whole organism in gel precipitation tests. Among strains of B. melaninogenicus ssp. intermedius many common antigens were detected and no consistent antigenic differences were seen between strains from oral and nonoral sites. None of the antigens of B. melaninogenicus ssp. intermedius reacted with sera raised to several strains of oral or nonoral B. asaccharolyticus, nor did antigens prepared from the latter strains react with antisera to B. melaninogenicus ssp. intermedius. At least 1 common antigen was shared by strains of B. melaninogenicus ssp. intermedius and strains of B. melaninogenicus ssp. melaninogenicus; subspecies-specific antigens were also found. Antigens from and antisera to oral and nonoral strains of B. asaccharolyticus did not react with sera to and antigens from B. melaninogenicus ssp. melaninogenicus. Strains of B. asaccharolyticus isolated from the oral cavity were antigenically distinct from strains of B. asaccharolyticus obtained from nonoral sites and lesions. This lack of cross-reactivity between the oral and nonoral strains of B. asaccharolyticus together with recent fingins of marked genetic differences between oral and nonoral strains of B. asaccharolyticus suggest that these groups of organisms may represent different species.