Assuntos
Infecções por Bordetella/veterinária , Bordetella avium/crescimento & desenvolvimento , Galinhas , Coturnix , Surtos de Doenças/veterinária , Doenças das Aves Domésticas/epidemiologia , Doenças das Aves Domésticas/microbiologia , Animais , Infecções por Bordetella/epidemiologia , Infecções por Bordetella/microbiologia , Infecções por Bordetella/patologia , Nigéria/epidemiologia , Doenças das Aves Domésticas/patologiaRESUMO
Iron (Fe) is an essential nutrient for most bacterial pathogens. In these organisms, a variety of regulatory systems that respond to specific Fe complexes found within their vertebrate hosts have evolved. In Bordetella avium, the heme utilization locus encoded by rhuIR-bhuRSTUV mediates efficient acquisition of Fe from heme and hemoproteins. Control of bhuRSTUV expression is promulgated at two levels. When Fe is abundant, expression is repressed in a Fur-dependent manner which is partially relieved when Fe is limiting. In the presence of heme or hemoproteins, expression of the bhuRSTUV operon is induced via a three-component signal transduction cascade composed of RhuI, RhuR, and BhuR. Herein, we report the identification of two promoters (PrhuI and PbhuR) that control expression of the rhuIR-bhuRSTUV cluster. Primer extension analysis identified the transcriptional start site of PrhuI within a putative Fur box. Transcriptional initiation of PbhuR mapped within the rhuR-bhuR intergenic region. Maximal transcription from PbhuR required Fe-limiting conditions, the presence of heme (or hemoglobin), and rhuI; however, analysis of transcripts produced from the rhuIR-bhuRSTUV locus revealed a pattern of low-level bhuR transcription in the absence of heme which originated from both PbhuR and PrhuI. Transcription from PrhuI was repressed by Fe in the presence of fur and somewhat enhanced by the addition of hemin to Fe-limited media. The nature of this hemin-associated PrhuI stimulation was rhuI independent and therefore not induced by heme via the BhuR-RhuR-RhuI signal cascade. Fe also repressed transcription from PbhuR in a fur-dependent manner; however, activation from this promoter, in the presence or absence of heme, did not occur without rhuI.
Assuntos
Bordetella avium/metabolismo , Regulação Bacteriana da Expressão Gênica , Heme/metabolismo , Transcrição Gênica , Animais , Proteínas de Bactérias/genética , Proteínas de Bactérias/metabolismo , Bordetella avium/genética , Bordetella avium/crescimento & desenvolvimento , Primers do DNA , Heme/genética , Óperon , Receptores de Superfície Celular/genética , Receptores de Superfície Celular/metabolismo , Proteínas Repressoras/genética , Proteínas Repressoras/metabolismo , Análise de Sequência de DNA , Fator sigma/genética , Fator sigma/metabolismoRESUMO
Left ventricular (LV) outflow tract-right atrial (RA) communication associated with bacterial endocarditis is described in a 6-year-old intact male Great Pyrenees dog with a 4- to 5-day history of fever, lethargy, weight loss, severe regenerative anemia, and asplenia. Typical vegetative mural endocardial lesions were observed grossly. Histologic evaluation revealed small gram-negative coccobacilli that were consistent with Bordetella avium-like organisms. These bacteria were associated with severe endocardial inflammation characterized by neutrophilic infiltration, extensive necrosis of endocardium, and fibrin deposition. LV-RA shunt (Gerbode defect) is a rare cardiac defect in humans that can be either congenital or, more rarely, secondary to septic endocarditis, valve replacement procedures, or thoracic trauma. B. avium-like organisms causing septicemia and endocarditis in immunocompromised and asplenic human patients have been described. To our knowledge, no previous descriptions of Gerbode defect associated with bacterial endocarditis in domestic animals have been reported in veterinary literature.
