[A new butyric acid-producing bacteroides species: B. splanchnicus n. sp. (author's transl)].

Three butyric acid-producing saccharolytic Bacteroides cultures (1651/6, BM 158, and IPP 3751) were described by WERNER and REICHERTZ in 1971 (Zbl.Bakt.Hyg., I. Abt. Orig. A 217,206-216). Since then, 6 strains closely resembling 1651/6 were isolated from stool specimens and surgically removed appendices. In the present communication, strains 1651/6, S2/34, S3/38, S4/28, S6/6, A5/2 are described as members of a new species, Bacteroides splanchnicus n.sp. The strains were morphologically very similar (Gram negative non-sporing non-motile rods, 1-2.5 mu in length and 0.7 mu in width) and fermented glucose, fructose, galactose, mannose, lactose, and arabinose (pH values of 4.6-5.4, moderate gas formation). Negative reactions (pH values of 5.8-7.2) were observed with 20 other carbohydrates. The strains were positive in the glutamic acid decarboxylase test and formed indole and H2S. In peptone-yeast extract broth and peptone-yeast extract-glucose broth acetic, propionic, isobutyric, butyric, and isovaleric acids were produced. Washed cells of strains 1651/6 and S4/28 incubated anaerobically in sterile solutions of single amino acids produced butyrate from lysine only. Abundant butyric acid was also produced from glucose. The in vitro activity of 15 antibiotics on 5 strains was studied by broth dilution tests. Uniformly, the strains showed resistance to aminoglycosides and polymyxins (MIC values, 60-500 mug/ml) and susceptibility to tetracyclines, lincomycin, clindamycin, rifampicin, and erythromycin (MIC values, 0.05-0.5 mug/ml). Chloramphenicol, penicillins, and cephalosporins showed bacteriostatic activity at concentrations of 5-40 mug/ml. The serological behaviour of 5 strains was studied in cross-agglutination and gel-diffusion experiments. Cross-reactivity was pronounced in gel-diffusion tests using rabbit antisera and autoclaved extracts and extracts prepared by repeated deep-freezing and thawing of whole cell suspensions as antigens. However, antisera against the B. splanchnicus strains did not react with antigens of B. fragilis 6869, B. thetaiotaomicron AS 126, B. vulgatus AM 45 a, B. distasonis AII 104 and butyric acid-producing strains BM 158 and IPP 3751 in agglutination and gel-diffusion experiments, and there were no cross-reactions between B. splanchnicus antigens and antisera against B. fragilis 6869 and the other aforementioned strains. The new species has been confirmed by members of the ICSB Taxonomic Subcommittee for Gram negative anaerobic rods. Strains 1651/6 and S4/28 have been deposited in The National Collection of Type Cultures, London (NCTC numbers 10825 and 10826). Strain NCTC 10825 (= 1651/6) is the type of the species, B. splanchnicus.