RESUMO
BACKGROUND: The bacterial biothreat agents Burkholderia mallei and Burkholderia pseudomallei are the cause of glanders and melioidosis, respectively. Genomic and epidemiological studies have shown that B. mallei is a recently emerged, host restricted clone of B. pseudomallei. RESULTS: Using bacteriophage-mediated immunoscreening we identified genes expressed in vivo during experimental equine glanders infection. A family of immunodominant antigens were identified that share protein domain architectures with hemagglutinins and invasins. These have been designated Burkholderia Hep_Hag autotransporter (BuHA) proteins. A total of 110/207 positive clones (53%) of a B. mallei expression library screened with sera from two infected horses belonged to this family. This contrasted with 6/189 positive clones (3%) of a B. pseudomallei expression library screened with serum from 21 patients with culture-proven melioidosis. CONCLUSION: Members of the BuHA proteins are found in other Gram-negative bacteria and have been shown to have important roles related to virulence. Compared with other bacterial species, the genomes of both B. mallei and B. pseudomallei contain a relative abundance of this family of proteins. The domain structures of these proteins suggest that they function as multimeric surface proteins that modulate interactions of the cell with the host and environment. Their effect on the cellular immune response to B. mallei and their potential as diagnostics for glanders requires further study.
Assuntos
Anticorpos Antibacterianos/biossíntese , Proteínas de Bactérias/imunologia , Burkholderia mallei/imunologia , Burkholderia pseudomallei/imunologia , Mormo/imunologia , Melioidose/imunologia , Adolescente , Adulto , Idoso , Animais , Anticorpos Antibacterianos/imunologia , Antígenos de Bactérias/biossíntese , Antígenos de Bactérias/genética , Antígenos de Bactérias/imunologia , Proteínas da Membrana Bacteriana Externa/biossíntese , Proteínas da Membrana Bacteriana Externa/genética , Proteínas da Membrana Bacteriana Externa/imunologia , Proteínas de Bactérias/biossíntese , Proteínas de Bactérias/genética , Sequência de Bases , Burkholderia mallei/genética , Burkholderia pseudomallei/genética , Criança , Feminino , Biblioteca Gênica , Mormo/diagnóstico , Mormo/microbiologia , Hemaglutininas/imunologia , Cavalos , Humanos , Masculino , Melioidose/sangue , Melioidose/microbiologia , Pessoa de Meia-Idade , Dados de Sequência Molecular , Fatores de Virulência/biossíntese , Fatores de Virulência/genética , Fatores de Virulência/imunologiaRESUMO
Melioidosis is a notoriously protracted illness and is difficult to cure. We hypothesize that the causative organism, Burkholderia pseudomallei, undergoes a process of adaptation involving altered expression of surface determinants which facilitates persistence in vivo and that this is reflected by changes in colony morphology. A colony morphotyping scheme and typing algorithm were developed using clinical B. pseudomallei isolates. Morphotypes were divided into seven types (denoted I to VII). Type I gave rise to other morphotypes (most commonly type II or III) by a process of switching in response to environmental stress, including starvation, iron limitation, and growth at 42 degrees C. Switching was associated with complex shifts in phenotype, one of which (type I to type II) was associated with a marked increase in production of factors putatively associated with in vivo concealment. Isogenic types II and III, derived from type I, were examined using several experimental models. Switching between isogenic morphotypes occurred in a mouse model, where type II appeared to become adapted for persistence in a low-virulence state. Isogenic type II demonstrated a significant increase in intracellular replication fitness compared with parental type I after uptake by epithelial cells in vitro. Isogenic type III demonstrated a higher replication fitness following uptake by macrophages in vitro, which was associated with a switch to type II. Mixed B. pseudomallei morphologies were common in individual clinical specimens and were significantly more frequent in samples of blood, pus, and respiratory secretions than in urine and surface swabs. These findings have major implications for therapeutics and vaccine development.
Assuntos
Burkholderia pseudomallei/genética , Burkholderia pseudomallei/patogenicidade , Animais , Aderência Bacteriana/genética , Aderência Bacteriana/fisiologia , Burkholderia pseudomallei/citologia , Células Epiteliais/microbiologia , Genótipo , Humanos , Macrófagos/microbiologia , Melioidose/microbiologia , Melioidose/mortalidade , Camundongos , Fenótipo , Taxa de Sobrevida , Virulência/genéticaRESUMO
Pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing (MLST) was used to type 21 laboratory strains of Burkholderia mallei. We demonstrated good resolution by PFGE together with clustering of some geographically related isolates, and confirmed previous observations that B. mallei is clonal as defined by MLST.
Assuntos
Burkholderia mallei/classificação , Eletroforese em Gel de Campo Pulsado/métodos , Mormo/microbiologia , Alelos , Animais , Bioterrorismo , Burkholderia mallei/genética , Burkholderia mallei/isolamento & purificação , Análise por Conglomerados , DNA Bacteriano/química , DNA Bacteriano/genética , Cavalos , Humanos , Reação em Cadeia da Polimerase/veterinária , SorotipagemRESUMO
The indirect hemagglutination assay routinely used to detect antibodies to Burkholderia pseudomallei was modified to detect cross-reactivity of antibodies to B. pseudomallei, B. mallei, and B. thailandensis antigens. We demonstrate a lack of cross-reactivity between B. pseudomallei and B. thailandensis but marked cross-reactivity between B. pseudomallei and B. mallei.
