Differentiation of Bacteroides ovatus and Bacteroides thetaiotaomicron by means of bacteriophage

Abstract

Two members of the Bacteroidesfragilis group, B. ovatus and B. thetaiotaomicron, are difficult to distinguish by biochemical methods. They are currently identified on the basis of their variable ability to ferment salicin. We studied a method of identification for these two species by using cell lysis by bacteriophages. A total of 38 bacteriophages were used to distinguish the two species. Identification by bacteriophages was compared with species identification by prereduced anaerobically sterilized biochemical testing with salicin as the differentiating test. A total of 215 clinical isolates biochemically identified as B. ovatus or B. thetaiotaomicron were tested. A total of 100% of the strains identified as B. ovatus by bacteriophages produced strong acid in salicin (pH s 5.4). However, 40% of the strains identified as B. thetaiotaomicron by bacteriophages also produced strong acid in salicin, and an additional 39% produced weak acid (pH 5.5 to 5.7). This study demonstrates that salicin fermentation is an inadequate test for the differentiation of B. ovatus and B. thetaiotaomicron.

Bacteriophages active against Bacteroides fragilis in sewage-polluted waters

“…This high specificity of bacteriophages infecting Bacteroides spp. has already been observed by other investigators (8,15,33,40). No polyvalent phages active against B. fragilis, which are so frequently observed with coliphages (17, 18, 43, 53), seemed to occur in Bacteroides spp.…”

“…One of the problems in detecting bacteriophages in the environment is the lack of an universal plating indicator for particular bacterial species. Moreover, some strains consistently give higher counts than others (15,27). Our results are in good agreement with those of previous reports because B. fragilis HSP 40 consistently gave higher counts than the other Bacteriodes strains tested.…”

“…Although the recovery of Bacteroides phages from raw sewage has already been reported (8,15,40), no data have aSamples from areas with sewage pollution. b Water and sediments from areas without known sewage pollution.…”

Human origin of Bacteroides fragilis bacteriophages present in the environment

“…These data are in agreement with some preliminary results (data not shown). Published data (3,9,10,20) show that the host range of phages infecting B. fragilis strains is very restricted. This could explain the ability of strain HSP40 to discriminate between human and nonhuman contamination.…”

General and host-associated bacteriophage indicators of faecal pollution

“…Phages infecting Bacteroides seem to infect the host through the cell wall and therefore are somatic phages (Puig et al, 2001) yet most phages infecting Bacteroideshave a quite narrow host range (Cooper et al, 1984;Kory and Booth, 1986;Tartera and Jofre, 1987).…”