RESUMO
Brucella ovis is a veterinary pathogen associated with epididymitis in sheep. Despite its genetic similarity to the zoonotic pathogens B. abortus, B. melitensis and B. suis, B. ovis does not cause zoonotic disease. Genomic analysis of the type strain ATCC25840 revealed a high percentage of pseudogenes and increased numbers of transposable elements compared to the zoonotic Brucella species, suggesting that genome degradation has occurred concomitant with narrowing of the host range of B. ovis. The absence of genomic island 2, encoding functions required for lipopolysaccharide biosynthesis, as well as inactivation of genes encoding urease, nutrient uptake and utilization, and outer membrane proteins may be factors contributing to the avirulence of B. ovis for humans. A 26.5 kb region of B. ovis ATCC25840 Chromosome II was absent from all the sequenced human pathogenic Brucella genomes, but was present in all of 17 B. ovis isolates tested and in three B. ceti isolates, suggesting that this DNA region may be of use for differentiating B. ovis from other Brucella spp. This is the first genomic analysis of a non-zoonotic Brucella species. The results suggest that inactivation of genes involved in nutrient acquisition and utilization, cell envelope structure and urease may have played a role in narrowing of the tissue tropism and host range of B. ovis.
Assuntos
Brucella ovis/genética , Genoma Bacteriano , Interações Hospedeiro-Patógeno/genética , Animais , Proteínas de Bactérias/genética , Proteínas de Bactérias/metabolismo , Brucella ovis/patogenicidade , Elementos de DNA Transponíveis , Deleção de Genes , Ovinos/microbiologiaRESUMO
OBJECTIVES: To study at the molecular level the heterogeneity of expression of the two chromosomal beta-lactamases, BlaA and BlaB, in Yersinia enterocolitica strains isolated from clinical samples. METHODS: MIC determination by the agar dilution method and beta-lactamase assays was performed to determine the resistance level conferred by these enzymes. DNA cloning, PCR and direct sequencing were used to detect the presence of mutations. RESULTS: The blaA allele from strain IP97 (blaA97) was found to carry a deletion of 51 bp which entirely abolished its beta-lactamase activity. Both the ampR gene and the promoter region of strain Y56 were shown to be functional by a gene swapping experiment. The blaB allele from strain Y56 was found to carry two point mutations, only one of them resulting in a change in the amino acid sequence of the protein. This single amino acid change created a practically inactive BlaB or AmpC cephalosporinase in Y. enterocolitica Y56. CONCLUSIONS: The lack of activity observed in the beta-lactamases of some Y. enterocolitica isolates was due to the presence of point mutations or small deletions in the corresponding genes.
Assuntos
Deleção de Genes , Genes Bacterianos , Mutação Puntual , Yersinia enterocolitica/enzimologia , beta-Lactamases/genética , Alelos , Antibacterianos/farmacologia , Sequência de Bases , Cromossomos Bacterianos/genética , Clonagem Molecular , DNA Bacteriano/genética , Testes de Sensibilidade Microbiana , Dados de Sequência Molecular , Reação em Cadeia da Polimerase , Regiões Promotoras Genéticas , Yersinia enterocolitica/efeitos dos fármacos , Yersinia enterocolitica/genética , Yersinia enterocolitica/isolamento & purificação , Resistência beta-Lactâmica , beta-Lactamases/metabolismoAssuntos
Antibacterianos/farmacologia , Elementos de DNA Transponíveis , DNA Bacteriano/genética , Farmacorresistência Bacteriana , Fosfomicina/farmacologia , Análise de Sequência de DNA , Serratia marcescens/efeitos dos fármacos , Sequência de Bases , DNA Bacteriano/química , Humanos , Dados de Sequência Molecular , Infecções por Serratia/microbiologia , Serratia marcescens/genética , Serratia marcescens/isolamento & purificação , EspanhaRESUMO
The hexanucleotide CCAGCA was found repeated 15 times in tandem on the 5' side of the virginiamycin acetyl transferase gene of Yersinia enterocolitica strain Y56. The corresponding region was analysed by PCR from 54 clinical strains belonging to the same biotype and serotype, and others from this laboratory collection belonging to different biotypes and serotypes. Each strain produced a single amplification product whose size was variable among strains, revealing that the locus was polymorphic. Nucleotide sequence determination of selected PCR products showed that the polymorphism was due to the precise expansion or reduction in the number of hexanucleotide repeats. Analysis of this locus in a few strains showing the same PFGE pattern showed that it was also polymorphic. These results suggest that this method could be valuable to increase the discriminatory power of current Y. enterocolitica typing schemes.