Antigenic Relationships among Bacteriodes Species Studied by Rocket-Line Immunoelectrophoresis

Tessier, F; Quentin, Claudine; Capdepuy, M.; Guinet, R

doi:10.1099/00207713-43-2-191

Cited by 2 publications

(1 citation statement)

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“…1 and 2). This result is in agreement with rDNA-DNA hybridization data (12) and with the relatedness of these species as reflected by their shared antigenicity (36). All B. fragilis strains formed a homogeneous taxon that comprised two robust monophyletic units.…”

Section: Resultssupporting

confidence: 80%

A recent fixation of cfiA genes in a monophyletic cluster of Bacteroides fragilis is correlated with the presence of multiple insertion elements

et al. 1996

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Small-subunit ribosomal DNA sequences of 16 strains of Bacteroides fragilis were determined and compared with previously published sequences. Three phylogenetic methods (the neighbor-joining, maximum-likelihood, and maximum-parsimony methods) as well as a bootstrap analysis were used to assess the robustness of each topology. All phylogenetic analyses demonstrated that the B. fragilis strains were clearly divided into two robust monophyletic units which corresponded to the cfiA-negative and cfiA-positive groups. Strains of two previously identified DNA homology groups separated similarly into these two monophyletic units. According to the intensity of the hybridization signal with a cfiA probe, the cfiA-positive cluster could be further divided into two groups. This difference might reflect the existence of two, probably closely related cfiA-type genes. In the strongly hybridizing cfiA-positive strains, the gene is capable of conferring high-level resistance to the carbapenems and to most ␤-lactamase inhibitors as well, while in the weakly hybridizing cfiA-positive strains, only the latter type of resistance is known to occur. The presence of the cfiA-type genes within a monophyletic cluster of B. fragilis that apparently represents only a minority of the species B. fragilis is suggestive of a recent acquisition. The fact that this cluster is also the predominant pool of all known B. fragilis insertion elements, which have been found to play an important role in the expression of carbapenem resistance, raises the possibility that both genetic determinants, i.e., the resistance gene(s) and insertion elements, may have coevolved.Bacteroides fragilis, the anaerobic bacterial species most frequently isolated from human infections (3, 4), shows little phenotypic variability but can nevertheless be assigned to different genotypic groups (11,22). DNA homology studies led to the distinction of two homology groups, called I and II (11). DNA relatedness between B. fragilis ATCC 25285 T , representative of homology group I, and strains of homology group II ranged from 64 to 72%, while intragroup relatedness ranged from 80 to 90% (11). About 80% of B. fragilis strains isolated in clinical studies can be assigned to homology group I (11). Although strains from homology groups I and II are phenotypically indistinguishable (12), strains of homology group II lack susceptibility to the synergistic effect of such ␤-lactamase inhibitors as clavulanic acid, sulbactam, and tazobactam (2, 40), which are potent inhibitors of the vast majority of the ␤-lactamases produced by clinical isolates of B. fragilis (3,4,10,20,40). These are active-site serine enzymes, loosely related to those of Ambler's class A (1, 17, 28). Probing with cfiA gene sequences led to the distinction within B. fragilis of the cfiAnegative and cfiA-positive groups, representing ca. 3 and 97%, respectively, of the clinical B. fragilis isolates (22, 23). The cfiA gene, which has been searched for only in B. fragilis, encodes a metallo-␤-lactamase (5, 21, 25, 37), i.e...

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Section: Resultssupporting

confidence: 80%