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Based on the results of GC content determination and 16S rRNA sequence analysis among the type strains of Achromobacter xylosoxidans, 4 Alcaligenes species, 5 Bordetella species, and 12 species of 4 other genera, the separation of genus Achromobacter Yabuuchi and Yano 1981, with the type species Achromobacter xylosoxidans, is confirmed. Alcaligenes ruhlandii (Packer and Vishniac) Aragno and Schlegel 1992 is a distinct species and not a senior synonym of Achromobacter xylosoxidans. Alcaligenes ruhlandii and Alcaligenes piechaudii Kiredjian et al 1986 are transferred to genus Achromobacter. Thus 2 new combinations, Achromobacter ruhlandii (Packer and Vishniac) and Achromobacter piechaudii (Kiredjian et al) are proposed; their type strains are ATCC 15749 and ATCC 43552, respectively. Alcaligenes denitrificans Rüger and Tan 1983 is also transferred to genus Achromobacter and ranked down to the subspecies of Achromobacter xylosoxidans. Thus a new subspecies name, Achromobacter xylosoxidans subsp. denitrificans (Rüger and Tan) is proposed. The type strain of the subspecies is ATCC 15173. This proposal automatically creates type subspecies, Achromobacter xylosoxidans subsp. xylosoxidans, with type strain ATCC 27061. An emended description of genus Achromobacter and of type species Achromobacter xylosoxidans are given.

Based on the results of phenotypic characterization, cellular lipid and fatty acid analysis, phylogenetic analysis of 16S rDNA nucleotide sequences and rNA-DNA hybrization, Burkholderia pickettii, Burkholderia solanacearum and Alcaligenes eutrophus are transferred to the new genus Ralstonia, and Ralstonia pickettii (Ralston, Palleroni and Doudoroff 1973) comb. nov., Ralstonia solanacearum (Smith 1896) comb. nov., and R. eutropha (Davis 1969) comb. nov. are proposed. The type species of the new genus is R. pickettii. Type strain of R. pickettii is ATCC 27511T, of R. solanacearum is ATCC 10696T, and of R. eutropha is ATCC 17697T.

Adult rabbits were immunized with nine Achromobacter xylosoxidans strains by intravenous injection of Formalin-killed organisms. Antisera thus obtained were reciprocally titrated with the nine A. xylosoxidans strains, and seven sera were defined as serologically distinct. Three of nine antisera possessed one common antibody while also each having their own specific antibody. Ninety-five strains of A. xylosoxidans were examined for serotyping by a microtiter agglutination test with the nine antisera, and the strains were divided into seven serogroups. The distribution of the 95 strains among the serogroups was as follows: serogroup A, 15 strains; B, 17 strains; C, 43 strains; D, 2 strains; E, 4 strains; G, 8 strains; F, 2 strains. Four strains were not agglutinated with any of the antisera. Serogroups A, B, and F had the ability to reduce nitrate to nitrogen gas and to grow in heart infusion broth at 41 degrees C, although there were some exceptions. In contrast, most strains of serogroups C, D, and E could not produce nitrogen gas from nitrate, although they did produce nitrite. The strains of serogroup C could not grow at 41 degrees C, whereas those of serogroups D and E could. Thus, we concluded that serogroups A, B, and F referred to biotype IIIb described by Tatum, and serogroups C, D, and E referred to biotype IIIa. The serotyping of A. xylosoxidans may be useful for the analysis of nosocomial infections caused by these organisms.