Plasmids -- potential tool for the investigation of gene transfer in Mycobacterium tuberculosis

Phylogeny and Virulence Factors of Escherichia coli Isolated from Dogs with Pyometra

We aimed to investigate the occurrence, phylogeny, and virulence of E. coli in the uterine contents and urine of female dogs with pyometra, through the presence of virulence genes and their genetic similarity. Uterine secretions and urine samples from 52 female dogs with pyometra were collected and cultured. Strains identified as E. coli from 25 uterine and 7 urine samples were tested for virulence genes by PCR. Genetic similarity between the isolates was studied using RAPD-PCR. E. coli was observed in 48.07% uterine samples with pyometra and 20.0% urine samples. The strains showed high percentages for the presence of virulence genes: 96.9% had the gene sfa, 59.4% afa, 46.9% pap, 53.1% hly, and 68.75% cnf. Even with the high prevalence of virulence genes, the samples were not submitted to DNA sequencing to confirm the results. Analysis showed high genetic diversity in E. coli, however, strains isolated from the same animal indicate that cystitis and pyometra could be related. Our study indicated the association between E. coli in dogs with pyometra and cases of urinary tract infection and the pathogenic potential of strains increasing with animal age.

Comparative genomic and phylogenetic approaches to characterize the role of genetic recombination in mycobacterial evolution

The genus Mycobacterium encompasses over one hundred named species of environmental and pathogenic organisms, including the causative agents of devastating human diseases such as tuberculosis and leprosy. The success of these human pathogens is due in part to their ability to rapidly adapt to their changing environment and host. Recombination is the fastest way for bacterial genomes to acquire genetic material, but conflicting results about the extent of recombination in the genus Mycobacterium have been reported. We examined a data set comprising 18 distinct strains from 13 named species for evidence of recombination. Genomic regions common to all strains (accounting for 10% to 22% of the full genomes of all examined species) were aligned and concatenated in the chromosomal order of one mycobacterial reference species. The concatenated sequence was screened for evidence of recombination using a variety of statistical methods, with each proposed event evaluated by comparing maximum-likelihood phylogenies of the recombinant section with the non-recombinant portion of the dataset. Incongruent phylogenies were identified by comparing the site-wise log-likelihoods of each tree using multiple tests. We also used a phylogenomic approach to identify genes that may have been acquired through horizontal transfer from non-mycobacterial sources. The most frequent associated lineages (and potential gene transfer partners) in the Mycobacterium lineage-restricted gene trees are other members of suborder Corynebacterinae, but more-distant partners were identified as well. In two examined cases of potentially frequent and habitat-directed transfer (M. abscessus to Segniliparus and M. smegmatis to Streptomyces), observed sequence distances were small and consistent with a hypothesis of transfer, while in a third case (M. vanbaalenii to Streptomyces) distances were larger. The analyses described here indicate that whereas evidence of recombination in core regions within the genus is relatively sparse, the acquisition of genes from non-mycobacterial lineages is a significant feature of mycobacterial evolution.

Caracterização genotípica dos isolados de Escherichia coli provenientes de frangos de corte

Caracterizaram-se genotipicamente os isolados de Escherichia coli oriundos de fígado de frangos provenientes de dois matadouros avícolas. Foram coletadas 62 amostras de fígados de frangos, sendo 30 macroscopicamente inalterados e 32 com alteração macroscópica e que originaram no descarte da carcaça. Isolaram-se 30 cepas de Escherichia coli pelo método clássico, sendo 21 isoladas de fígados inalterados e nove provenientes de carcaças rejeitadas. Utilizou-se a reação em cadeia de polimerase para verificação de genes de virulência de E. coli, incluindo o gene de resistência sérica (iss) para identificação de E. coli patogênica para aves, o gene para Shiga cytotoxin 1 e 2 (stx) para identificação de E. coli enteroemorrágica, o gene bfpA para identificação de E. coli enteropatogênica e os genes para toxinas LT-I (elt) e ST-I (stI) para identificação de E. coli enterotoxigênica. Identificou-se iss em 83,3% (25/30) dos isolados, sendo 76,2% (16/21) provenientes de fígados de animais hígidos, e detectou-se stx em 13,3% (4/30). Os genes stx e iss foram identificados em três fígados, caracterizando infecção mista. Os genes não foram observados em um isolado de E. coli pelo método clássico. Faz-se necessária a utilização de tecnologias para identificação e prevenção de Escherichia coli nos aviários e matadouros avícolas.