Characterization of some bacterial strains isolated from animal clinical materials and identified as Corynebacterium xerosis by molecular biological techniques

Eighteen Corynebacterium xerosis strains isolated from different animal clinical specimens were subjected to phenotypic and molecular genetic studies. On the basis of the results of the biochemical characterization, the strains were tentatively identified as C. xerosis. Phylogenetic analysis based on comparative analysis of the sequences of 16S rRNA and rpoB genes revealed that the 18 strains were highly related to C. xerosis, C. amycolatum, C. freneyi, and C. hansenii. There was a good concordance between 16S rRNA and partial rpoB gene sequencing results, although partial rpoB gene sequencing allowed better differentiation of C. xerosis. Alternatively, C. xerosis was also differentiated from C. freneyi and C. amycolatum by restriction fragment length polymorphism analysis of the 16S-23S rRNA gene intergenic spacer region. Phenotypic characterization indicated that besides acid production from D-turanose and 5-ketogluconate, 90% of the strains were able to reduce nitrate. The absence of the fatty acids C(14:0), C(15:0), C(16:1)omega 7c, and C(17:1)omega 8c can also facilitate the differentiation of C. xerosis from closely related species. The results of the present investigation demonstrated that for reliable identification of C. xerosis strains from clinical samples, a combination of phenotypic and molecular-biology-based identification techniques is necessary.

Association of extended-spectrum β-lactamase VEB-5 and 16S rRNA methyltransferase armA in Salmonella enterica from the United Kingdom

Aminoglycosides and beta-lactams are used for the treatment of a wide range of infections due to both Gram-negative and Gram-positive. An emerging aminoglycoside resistance mechanism, methylation of the aminoacyl site of the 16S rRNA, confers high-level resistance to clinically important aminoglycosides such as amikacin, tobramycin and gentamicin. Eight 16S rRNA methyltransferase genes, armA, rmtA, rmtB, rmtC, rmtD, rmtE, rmtF and npmA, have been identified in several species of enterobacteria worldwide (2, 6, 7, 9, 11, 13, 14). Resistance to extended spectrum β-lactams remains additionally an important clinical problem. Apart from the large TEM, SHV, and CTX-M families, several other extended-spectrum β-lactamases (ESBLs) have been identified, including VEB enzymes, which confer high-level resistance to cephalosporins and monobactams. Although 16S rRNA methyltransferases have been frequently identified associated with different ESBLs, there has been no report of association of a 16S rRNA methyltransferase with a VEB enzyme, except for the identification of rmtC with blaVEB-6 (14)