Route of Infection in Melioidosis

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Incidence, risk factors and clinical epidemiology of melioidosis: a complex socio-ecological emerging infectious disease in the Alor Setar region of Kedah, Malaysia

<p>Abstract</p> <p>Background</p> <p>Melioidosis, a severe and fatal infectious disease caused by <it>Burkholderia pseudomallei</it>, is believed to an emerging global threat. However, data on the natural history, risk factors, and geographic epidemiology of the disease are still limited.</p> <p>Methods</p> <p>We undertook a retrospective analysis of 145 confirmed cases extracted from a hospital-based Melioidosis Registry set up from 2005 in Hospital Sultanah Bahiyah, Alor Setar, Kedah state, Malaysia, in order to provide a first description of the contemporary incidence, risk factors, and clinical epidemiology of the disease in this putatively high risk region of the country.</p> <p>Results</p> <p>The incidence of melioidosis in Alor Setar is remarkably high at 16.35 per 100,000 population per year. The mean age of patients was 50.40 years, with infection varying nonlinearly with age. Males (75.2%; <it>P </it>< 0.0001) predominated and the majority of cases were Malays (88.9%). The overall, crude mortality rate among the study patients was 33.8%. The proportions of cases and deaths were significantly greater among patients involved in farming, forestry and fishing and the unemployed (χ²= 30.57, <it>P </it>< 0.0001). A majority of cases (62.75%) were culture positive, with mortality in these patients being 45.05%. A large proportion (83.0%) of culture positives was also bacteremic. Pneumonia accounted for 42.06% of primary diagnoses followed in importance by soft tissue abscess. In patients with pneumonia and who were culture positive, the mortality rate was as high as 65.00%. Diabetes mellitus constituted the major underlying risk factor for developing and dying from melioidosis, occurring in 57% of all diagnosed cases. The age distribution of diabetes paralleled that of melioidosis cases. There were linear associations between cases and deaths with monthly rainfall.</p> <p>Conclusions</p> <p>Melioidosis represents a complex socio-ecological public health problem in Kedah, being strongly related with age, occupation, rainfall and predisposing chronic diseases, such as diabetes mellitus. Among cases, bacteremic patients were associated with significantly high mortality despite provision of the recommended antibacterial therapy. The burden of this disease is likely to grow in this region unless better informed interventions targeted at high-risk groups and associated diseases are urgently implemented.</p

Identification of a predicted trimeric autotransporter adhesin required for biofilm formation of Burkholderia pseudomallei.

The autotransporters are a large and diverse family of bacterial secreted and outer membrane proteins, which are present in many Gram-negative bacterial pathogens and play a role in numerous environmental and virulence-associated interactions. As part of a larger systematic study on the autotransporters of Burkholderia pseudomallei, the causative agent of the severe tropical disease melioidosis, we have constructed an insertion mutant in the bpss1439 gene encoding an unstudied predicted trimeric autotransporter adhesin. The bpss1439 mutant demonstrated a significant reduction in biofilm formation at 48 hours in comparison to its parent 10276 wild-type strain. This phenotype was complemented to wild-type levels by the introduction of a full-length copy of the bpss1439 gene in trans. Examination of the wild-type and bpss1439 mutant strains under biofilm-inducing conditions by microscopy after 48 hours confirmed that the bpss1439 mutant produced less biofilm compared to wild-type. Additionally, it was observed that this phenotype was due to low levels of bacterial adhesion to the abiotic surface as well as reduced microcolony formation. In a murine melioidosis model, the bpss1439 mutant strain demonstrated a moderate attenuation for virulence compared to the wild-type strain. This attenuation was abrogated by in trans complementation, suggesting that bpss1439 plays a subtle role in the pathogenesis of B. pseudomallei. Taken together, these studies indicate that BPSS1439 is a novel predicted autotransporter involved in biofilm formation of B. pseudomallei; hence, this factor was named BbfA, Burkholderia biofilm factor A

Dimerisation induced formation of the active site and the identification of three metal sites in EAL-phosphodiesterases

The bacterial second messenger cyclic di-3′,5′-guanosine monophosphate (c-di-GMP) is a key regulator of bacterial motility and virulence. As high levels of c-di-GMP are associated with the biofilm lifestyle, c-di-GMP hydrolysing phosphodiesterases (PDEs) have been identified as key targets to aid development of novel strategies to treat chronic infection by exploiting biofilm dispersal. We have studied the EAL signature motif-containing phosphodiesterase domains from the Pseudomonas aeruginosa proteins PA3825 (PA3825EAL) and PA1727 (MucREAL). Different dimerisation interfaces allow us to identify interface independent principles of enzyme regulation. Unlike previously characterised two-metal binding EAL-phosphodiesterases, PA3825EAL in complex with pGpG provides a model for a third metal site. The third metal is positioned to stabilise the negative charge of the 5′-phosphate, and thus three metals could be required for catalysis in analogy to other nucleases. This newly uncovered variation in metal coordination may provide a further level of bacterial PDE regulation

Biofilm Induced Tolerance towards Antimicrobial Peptides

Increased tolerance to antimicrobial agents is thought to be an important feature of microbes growing in biofilms. We address the question of how biofilm organization affects antibiotic susceptibility. We established Escherichia coli biofilms with differential structural organization due to the presence of IncF plasmids expressing altered forms of the transfer pili in two different biofilm model systems. The mature biofilms were subsequently treated with two antibiotics with different molecular targets, the peptide antibiotic colistin and the fluoroquinolone ciprofloxacin. The dynamics of microbial killing were monitored by viable count determination, and confocal laser microscopy. Strains forming structurally organized biofilms show an increased bacterial survival when challenged with colistin, compared to strains forming unstructured biofilms. The increased survival is due to genetically regulated tolerant subpopulation formation and not caused by a general biofilm property. No significant difference in survival was detected when the strains were challenged with ciprofloxacin. Our data show that biofilm formation confers increased colistin tolerance to cells within the biofilm structure, but the protection is conditional being dependent on the structural organization of the biofilm, and the induction of specific tolerance mechanisms

Burkholderia pseudomallei: abscess in an unusual site.

Melioidosis is an infection caused by Burkholderia pseudomallei. It is an important human pathogen in tropical area. The clinical manifestations are protean and multisystem involvement. We report an unusual case of melioidosis with abscess at root of mesentery in an elderly, non-insulin dependent diabetic Thai women. She presented with prolonged fever and chronic abdominal pain. The early clinical diagnosis was carcinomatous mass with peritonitis. Diagnosis of melioidosis arose from the surgical finding and pus culture. Treatment with surgical drainage and ceftazidime followed by co-trimoxazole plus doxycycline had a good clinical outcome

Burkholderia pseudomallei: abscess in an unusual site

Melioidosis is an infection caused by Burkholderia pseudomallei   . It is an important human pathogen in tropical area. The clinical manifestations are protean and multisystem involvement. We report an unusual case of melioidosis with abscess at root of mesentery in an elderly, non-insulin dependent diabetes Thai women. She presented with prolonged fever and chronic abdominal pain. The early clinical diagnosis was carcinomatous mass with peritonitis. Diagnosis of melioidosis arose from the surgical finding and pus culture. Treatment with surgical drainage and ceftazidime followed by co-trimoxazole plus doxycycline had a good clinical outcome

Case Report - Burkholderia pseudomallei : Abscess in an Unusual Site

Melioidosis is an infection caused by Burkholderia pseudomallei . It is an important human pathogen in tropical area. The clinical manifestations are protean and multisystem involvement. We report an unusual case of melioidosis with abscess at root of mesentery in an elderly, non-insulin dependent diabetes Thai women. She presented with prolonged fever and chronic abdominal pain. The early clinical diagnosis was carcinomatous mass with peritonitis. Diagnosis of melioidosis arose from the surgical finding and pus culture. Treatment with surgical drainage and ceftazidime followed by co-trimoxazole plus doxycycline had a good clinical outcome