The effect of climate on melioidosis incidence in Townsville, Australia: a dry tropical region.

BACKGROUND: Townsville is in the dry tropics in Northern Australia and an endemic region for melioidosis. Melioidosis is an infectious disease caused by Burkholderia pseudomallei, a soil dwelling organism. The incidence of melioidosis is associated with high levels of rainfall and has been linked to multiple weather variables in other melioidosis endemic regions such as in Darwin. In contrast to Townsville, Darwin is in the wet-dry tropics in Northern Australia and receives 40% more rainfall. We assessed the relationship between melioidosis incidence and weather conditions in Townsville and compared the patterns to the findings in Darwin and other melioidosis endemic regions. METHOD: Performing a time series analysis from 1996 to 2020, we applied a negative binomial regression model to evaluate the link between the incidence of melioidosis in Townsville and various weather variables. Akaike's information criterion was used to assess the most parsimonious model with best predictive performance. Fourier terms and lagged deviance residuals were included to control long term seasonal trends and temporal autocorrelation. RESULTS: Humidity is the strongest predictor for melioidosis incidence in Townsville. Furthermore, the incidence of melioidosis showed a three-times rise in the Townsville region when >200 mm of rain fell within the fortnight. Prolonged rainfall had more impact than a heavy downpour on the overall melioidosis incident rate. There was no statistically significant increase in incidence with cloud cover in the multivariable model. CONCLUSION: Consistent with other reports, melioidosis incidence can be attributed to humidity and rainfall in Townsville. In contrast to Darwin, there was no strong link between melioidosis cases and cloud cover and nor single large rainfall events.

Pulmonary tuberculosis and melioidosis coinfection in Brunei Darussalam: the importance of awareness and screening.

Both tuberculosis (TB) and melioidosis are endemic to certain parts of the world, including Brunei Darussalam, with TB being more widespread. Despite this, coinfection with TB and melioidosis is rarely encountered and reported. Although still uncommon, there has been an increase in the number of cases of this coinfection reported during the past 10 years, all of which have been in India and the World Health Organization's Western Pacific Region. We report a case of coinfection with pulmonary TB and melioidosis in a patient with poorly controlled diabetes mellitus. This 64-year-old man presented with symptoms and radiological features of pulmonary TB, confirmed by sputum smear, but sputum culture also yielded Burkholderia pseudomallei, the pathogen that causes melioidosis. Coinfection was detected due to our practice of routinely screening for other infections in patients suspected or confirmed to have pulmonary TB. This highlights the importance of awareness of melioidosis and the need to consider screening for infection, especially in endemic regions.

Bioinformatics Analysis for Identifying Pertinent Pathways and Genes in Sepsis.

PURPOSE: Sepsis becomes the main death reason in hospitals with rising incidence, causing a growing economic and medical burden. However, the genes related to the pathogenesis and prognosis of sepsis are still unclear, which is a problem that needs to be solved urgently. MATERIALS AND METHODS: Gene expression profiles of GSE69528 were obtained from the National Center for Biotechnology Information. Limma software package got employed to search for differentially expressed genes (DEGs). Kyoto Encyclopedia of Genes and Genomes (KEGG) and Gene Ontology (GO) were used for enrichment analysis. Protein-protein interaction (PPI) network was built by the Search Tool for the Retrieval of Interacting Genes (STRING) database. RESULTS: We screened 101 DEGs, containing 81 upregulated DEGs and 20 downregulated DEGs. GO analysis demonstrated that the upregulated DEGs were chiefly concentrated in negative regulation of response to interferon-gamma and regulation of granulocyte differentiation. KEGG analysis revealed that the pathways of upregulated DEGs were concentrated in prion diseases, complement and coagulation cascades, and Staphylococcus aureus infection. The PPI network constructed by upregulated DEGs contained 67 nodes (proteins) and 110 edges (interactions). Analysis of bioinformatics results showed that CEACAM8, MPO, and RETN were hub genes of sepsis. CONCLUSION: Our analysis reveals a series of signal pathways and key genes related to the mechanism of sepsis, which are promising biotargets and biomarkers of sepsis.

Burkholderia pseudomallei peri-prosthetic infection following medial malleolar internal fixation: a case report.

BACKGROUND: Melioidosis-associated peri-prosthetic infection is extremely rare. To date, melioidosis associated septic arthritis of the ankle joint following a medial malleolar internal fixation has not been reported. CASE PRESENTATION: We describe a 49-year-old male with a history of long standing diabetes who presented with fever, constitutional symptoms and right ankle pain for 1 week. Ten years ago, he underwent a medial malleolar screw fixation following a traumatic closed fracture. His initial right ankle radiographs showed no evidence of osteomyelitis. He underwent a wound debridement and washout of the right ankle joint. The peripheral blood and pus from the ankle joint was culture positive for Burkholderia pseudomallei with very high antibody titres. His subsequent radiographs showed features of chronic osteomyelitis. He was treated with a prolonged course of antibiotics and repeated wound debridement. At follow up after 6 months, he had no clinical features of recurrent infection. CONCLUSIONS: Melioidosis should be entertained in the differential diagnosis of peri-prosthetic infections in high risk patients.

Quantitative Proteomics Reveals Differences in the Response of Neutrophils Isolated from Healthy or Diabetic Subjects to Infection with Capsule-Variant Burkholderia thailandensis.

In Thailand, diabetes mellitus is the most significant risk factor for melioidosis, a severe disease caused by Burkholderia pseudomallei. In this study, neutrophils isolated from healthy or diabetic subjects were infected with B. thailandensis E555, a variant strain with a B. pseudomallei-like capsular polysaccharide used here as a surrogate micro-organism for B. pseudomallei. At 2 h post-infection, neutrophil proteins were subjected to 4-plex iTRAQ-based comparative proteomic analysis. A total of 341 proteins were identified in two or more samples, of which several proteins involved in oxidative stress and inflammation were enriched in infected diabetic neutrophils. We validated this finding by demonstrating that infected diabetic neutrophils generated significantly elevated levels of pro-inflammatory cytokines TNFα, IL-6, IL-1ß, and IL-17 compared to healthy neutrophils. Our data also revealed that infected neutrophils from healthy or diabetic individuals undergo apoptotic cell death at distinctly different rates, with infected diabetic neutrophils showing a diminished ability to delay apoptosis and an increased likelihood of undergoing a lytic form of cell death, compared to infected neutrophils from healthy individuals. Increased expression of inflammatory proteins by infected neutrophils could contribute to the increased susceptibility to infection and inflammation in diabetic patients in melioidosis-endemic areas.

Role of Toll-Like Receptor 5 (TLR5) in Experimental Melioidosis.

The Gram-negative intracellular pathogen Burkholderia pseudomallei is the causative agent of melioidosis, an important cause of sepsis in Southeast Asia. Recognition of pathogen-associated molecular patterns by Toll-like receptors (TLRs) is essential for an appropriate immune response during pathogen invasion. In patients with melioidosis, TLR5 is the most abundantly expressed TLR, and a hypofunctional TLR5 variant has been associated with improved survival. Here, we studied the functional role of TLR5 and its ligand flagellin in experimental melioidosis. First, we observed differential TLR5 expression in the pulmonary and hepatic compartments upon infection with B. pseudomallei Next, we found that B. pseudomallei-challenged TLR5-deficient (Tlr5-/- ) mice were more susceptible to infection than wild-type (WT) mice, as demonstrated by higher systemic bacterial loads, increased organ injury, and impaired survival. Lung bacterial loads were not different between the two groups. The phenotype was flagellin independent; no difference in in vivo virulence was observed for the flagellin-lacking mutant MM36 compared to the wild-type B. pseudomallei strain 1026b. Tlr5-/- mice showed a similar impaired antibacterial defense when infected with MM36 or 1026b. Ex vivo experiments showed that TLR5-deficient macrophages display markedly impaired phagocytosis of B. pseudomallei In conclusion, these data suggest that TLR5 deficiency has a detrimental flagellin-independent effect on the host response against pulmonary B. pseudomallei infection.

Multilocus sequence types of clinical Burkholderia pseudomallei isolates from peninsular Malaysia and their associations with disease outcomes.

BACKGROUND: Previous studies on the Burkholderia pseudomallei genetic diversity among clinical isolates from melioidosis-endemic areas have identified genetic factors contributing to differential virulence. Although it has been ruled out in Australian and Thai B. pseudomallei populations, it remains unclear whether B. pseudomallei sequence types (STs) correlate with disease in Malaysian patients with melioidosis. METHODS: In this study, multi-locus sequence typing (MLST) was performed on clinical B. pseudomallei isolates collected from Kelantan state of Malaysia, patients' clinical data were reviewed and then genotype-risk correlations were investigated. RESULTS: Genotyping of 83 B. pseudomallei isolates revealed 32 different STs, of which 13(40%) were novel. The frequencies of the STs among the 83 isolates ranged from 1 to 12 observations, and ST54, ST371 and ST289 were predominant. All non-novel STs reported in this study have also been identified in other Asian countries. Based on the MLST data analysis, the phylogenetic tree showed clustering of the STs with each other, as well as with the STs from Southeast Asia and China. No evidence for associations between any of B. pseudomallei STs and clinical melioidosis presentation was detected. In addition, the bacterial genotype clusters in relation with each clinical outcome were statistically insignificant, and no risk estimate was reported. This study has expanded the data for B. pseudomallei on MLST database map and provided insights into the molecular epidemiology of melioidosis in Peninsular Malaysia. CONCLUSION: This study concurs with previous reports concluding that infecting strain type plays no role in determining disease presentation.

A case report of co-infection of Melioidosis and cutaneous Leishmaniasis.

BACKGROUND: Leishmaniasis and melioidosis are frequently reported from the North Central Province of Sri Lanka. However, only one case of co-infection of the two diseases has been reported to date over the world. This is a case report of a patient who had co-infection with cutaneous leishmaniasis and melioidosis and was successfully treated and recovered from the illness. CASE PRESENTATION: A 61 year old female patient with diabetes mellitus presented with fever for one month's duration and was found to have hepatosplenomegaly and an ulcer over the left arm. She had elevated inflammatory markers and blood culture grew Burkholderia pseudomallei and serum was highly positive for melioidosis antibodies. A slit skin smear of the ulcer showed Leishmania amastigotes. CONCLUSION: Melioidosis and leishmaniasis are emerging infectious diseases in endemic countries and can be severe. The high prevalence rates in Sri Lanka should keep the treating physicians' threshold for suspicion low for these two diseases.

Peritoneal Dialysis-Related Peritonitis Due to Melioidosis: A Potentially Devastating Condition.

♦ BACKGROUND: Melioidosis, an infectious disease caused by Burkholderia pseudomallei, is endemic in Southeast Asia and Northern Australia. Although a wide range of clinical manifestations from this organism are known, peritonitis associated with peritoneal dialysis (PD) has rarely been reported. ♦ PATIENTS AND METHODS: Peritoneal dialysis patients from all regions in Thailand were eligible for the study if they had peritonitis and either peritoneal fluid or effluent culture positive for B. pseudomallei. Patient data obtained included baseline characteristics, laboratory investigations, treatments, and clinical outcomes. When possible, PD fluid and removed Tenckhoff (TK) catheters were submitted for analyses of minimal inhibitory concentration (MIC) and microbial biofilm, respectively. ♦ RESULTS: Twenty-six patients were identified who were positive for peritoneal B. pseudomallei infection. The recorded mean age was 50 ± 15 (24 - 75) years, and the majority (58%) were female. Most of the cases were farmers living in Northeastern and Northern Thailand. Almost half of the cases had diabetes. Infections were reported commonly during the monsoon season and winter. The clinical presentations of peritonitis were similar to the manifestations from other microorganisms. Nine patients (41%) died (7 from sepsis), 6 fully recovered, and 7 switched to permanent hemodialysis. The mortality was potentially associated with sepsis (p = 0.007), infection during the monsoon season (p = 0.017), high initial dialysate neutrophils (p = 0.045), and high hematocrit (p = 0.045). Although no antibiotic resistance to ceftazidime and carbapenems was detected, approximately 50% of patients died with this treatment. Microbial biofilms were identified on the luminal surface of 4 out of 5 TK catheters, but the removal of the catheter did not alter the outcomes. ♦ CONCLUSION: Peritoneal dialysis-related peritonitis due to melioidosis is uncommon but highly fatal. Increased awareness, early diagnosis, and optimal management are mandatory.

Fatal bacteremic melioidosis in patients with prolonged neutropenia.

Melioidosis, an infection with an expanding geographic range, is extremely rare in neutropenic patients. We report bacteremic melioidosis (ST-70 and ST-660) in 2 patients with prolonged neutropenia, who succumbed despite appropriate antibiotics. Clinicians should be aware of this emerging infection in neutropenic patients residing in or returning from endemic areas.

Use of Whole-Genome Sequencing to Link Burkholderia pseudomallei from Air Sampling to Mediastinal Melioidosis, Australia.

The frequency with which melioidosis results from inhalation rather than percutaneous inoculation or ingestion is unknown. We recovered Burkholderia pseudomallei from air samples at the residence of a patient with presumptive inhalational melioidosis and used whole-genome sequencing to link the environmental bacteria to B. pseudomallei recovered from the patient.

Melioidosis: evolving concepts in epidemiology, pathogenesis, and treatment.

Infection with Burkholderia pseudomallei can result in asymptomatic seroconversion, a single skin lesion that may or may not heal spontaneously, a pneumonia which can be subacute or chronic and mimic tuberculosis or rapidly progressive resulting in fatal overwhelming sepsis. Latency with subsequent activation of disease is well recognized, but very uncommon. Melioidosis also has a myriad of other clinical presentations and diagnosis is often delayed because of this and because of difficulties with laboratory diagnosis and lack of recognition outside melioidosis-endemic regions. The perception of B. pseudomallei as a top tier biothreat agent has driven large funding for research, yet resources for diagnosis and therapy of melioidosis in many endemic locations remain extremely limited, with mortality as high as 50% in comparison to around 10% in regions where state-of-the-art intensive care therapy for sepsis is available. Fatal melioidosis is extremely unlikely from natural infection in a healthy person, provided the diagnosis is made early, ceftazidime or meropenem is commenced and intensive care therapy is available. While biothreat research is directed toward potential aerosol exposure to B. pseudomallei, the overall proportion of melioidosis cases resulting from inhalation rather than from percutaneous inoculation remains entirely uncertain, although the epidemiology supports a shift to inhalation during severe weather events such as cyclones and typhoons. What makes B. pseudomallei such a dangerous organism for patients with diabetes and other selective risk factors remains unclear, but microbial genome-wide association studies linking clinical aspects of melioidosis cases to nonubiquitous or polymorphic B. pseudomallei genes or genomic islands are beginning to uncover specific virulence signatures. Finally, what also remains uncertain is the global phylogeography of B. pseudomallei and whether melioidosis is spreading beyond historical locations or is just being unmasked in Africa and the Americas by better recognition and increased surveillance.

The coagulation system in melioidosis: from pathogenesis to new treatment strategies.

Melioidosis, caused by the Gram-negative bacterium Burkholderia pseudomallei, is a dreadful disease common in South-East Asia and Northern Australia and is characterized by chronic suppurative lesions and pneumonia. Melioidosis may evolve into severe sepsis with multi-organ failure with high mortalities, despite proper antibiotic therapy. Besides activation of a strong pro-inflammatory host response, the coagulation system plays an important role during melioidosis, which is thought to be host-protective. In particular, a procoagulant state together with downregulation of anticoagulant pathways and activation of fibrinolysis are present, all closely interrelated with parameters of inflammation. This review presents an overview of recent studies in which the role of coagulation, anti-coagulation and fibrinolysis during melioidosis was investigated both in patients and in experimental settings.

Melioidosis from contaminated bore water and successful UV sterilization.

Two cases of melioidosis at a residence in rural northern Australia were linked to the unchlorinated domestic bore (automated well) water supply, which was found to have a high concentration of Burkholderia pseudomallei. Using multilocus sequence typing, clinical B. pseudomallei isolates from both cases were identical to an isolate from the bore water supply. A simple UV sterilizer reduced B. pseudomallei from the domestic water supply to undetectable levels. We have shown that UV treatment is highly effective for remediation of water contaminated with B. pseudomallei and recommend its consideration in households where individuals may be at heightened risk of contracting melioidosis.

Melioidosis as a consequence of sporting activity.

In the tropical city of Darwin, Northern Territory, Australia, dry season soil sampling cultured Burkholderia pseudomallei from 7 (70%) of 10 sports fields. However, during the 23 years of the Darwin Prospective Melioidosis Study, only 5 (0.6%) of 785 melioidosis cases have been attributed to infection from sports fields. In one soccer player with cutaneous melioidosis, B. pseudomallei cultured from the player was identical by multilocus sequence typing and multilocus variable-number tandem repeat analysis with an isolate recovered from soil at the location on the sports field where he was injured. Melioidosis is uncommon in otherwise healthy sports persons in melioidosis-endemic regions but still needs consideration in persons with abrasion injuries that involve contact with soil.

Glutathione deficiency in type 2 diabetes impairs cytokine responses and control of intracellular bacteria.

Individuals with type 2 diabetes are at increased risk of acquiring melioidosis, a disease caused by Burkholderia pseudomallei infection. Although up to half of melioidosis patients have underlying diabetes, the mechanisms involved in this increased susceptibility are unknown. We found that B. pseudomallei-infected PBMCs from diabetic patients were impaired in IL-12p70 production, which resulted in decreased IFN-γ induction and poor bacterial killing. The defect was specific to the IL-12-IFN-γ axis. Defective IL-12 production was also observed during Mycobacterium tuberculosis infection, in which diabetes is likewise known to be a strong risk factor. In contrast, IL-12 production in diabetic cells was not affected upon Salmonella enterica infection or in response to TLR2, -3, -4, and -5 ligands. Poor IL-12 production correlated with a deficiency in intracellular reduced glutathione (GSH) concentrations in diabetic patients. Addition of GSH or N-acetylcysteine to PBMCs selectively restored IL-12 and IFN-γ production and improved bacterial killing. Furthermore, the depletion of GSH in mice led to increased susceptibility to melioidosis, reduced production of IL-12p70, and poorer disease outcome. Our data thus establish a link between GSH deficiency in diabetes and increased susceptibility to melioidosis that may open up new therapeutic avenues to protect diabetic patients against some intracellular bacterial pathogens.

Emerging clinico-epidemiological trends in melioidosis: analysis of 95 cases from western coastal India.

OBJECTIVES: To study the clinico-epidemiological trends in melioidosis, an emerging disease in the western coastal region of India. METHODS: Data of 95 patients with melioidosis in the western coastal region of India were retrospectively analyzed with respect to monthly rainfall, risk factors, clinical presentations, and outcome. RESULTS: A strong linear correlation was seen between average monthly rainfall and the occurrence of cases (p=0.002). Mortality was seen only in patients with bacteremia (p<0.001). Nine (40.9%) patients with septic shock died (p<0.001). Age ≥ 40 years and diabetes mellitus were seen in 75.8% of cases, each. Pneumonia was the most common clinical presentation (32.6%), followed by musculoskeletal disease (20%), melioidotic lymphadenopathy (7.4%), and dental abscess (6.3%). Only 36.8% of patients had exposure to wet soil/surface water. CONCLUSIONS: Melioidosis is quite prevalent in the western coastal region of India, and is strongly associated with rainfall, age, and diabetes mellitus. Higher proportions of musculoskeletal, dental, and lymph node melioidosis were seen in this region as compared to endemic areas. Bacteremic melioidosis has a poorer prognosis than non-bacteremic melioidosis. The presence of septic shock is a strong predictor of mortality. Percutaneous inoculation may not be the main portal of entry for Burkholderia pseudomallei in this region.

Melioidosis at Royal Darwin Hospital in the big 2009-2010 wet season: comparison with the preceding 20 years.

OBJECTIVE: To compare the unprecedented 91 cases of melioidosis in the Top End of the Northern Territory of Australia from 1 October 2009 to 30 September 2010 with the 540 cases in the preceding 20 years and postulate reasons for this year of very high melioidosis incidence. DESIGN, SETTING AND PARTICIPANTS: Review of prospectively collected data on all patients with culture-confirmed melioidosis at Royal Darwin Hospital, the Top End's tertiary referral centre, since 1 October 1989. MAIN OUTCOME MEASURES: Population-based annual incidence of melioidosis; differences in epidemiology, clinical presentations and outcomes for 2009-2010 compared with the preceding 20 years. RESULTS: In 2009-2010, the estimated population-based incidence of melioidosis was 50.2 cases per 100 000 in the Top End population overall, and 102.4 cases per 100 000 in the Top End Indigenous population. The proportion of patients acquiring melioidosis in the Darwin urban area increased from 49% in 1989-2009 to 65% in 2009-2010 (OR, 1.96; 95% CI, 1.20-3.19). Among the 49 Indigenous Australian patients with melioidosis in 2009-2010, 63% acquired the infection in Darwin, compared with 35% of Indigenous patients in the previous 20 years (OR, 3.17; 95% CI, 1.62-6.24). CONCLUSIONS: In 2009-2010, the Top End had the highest annual incidence of melioidosis documented from anywhere to date. The prominent increase in cases in Darwin was associated with above average rainfall in Darwin during December 2009 to February 2010. The increase in the proportion of Indigenous Australians who acquired melioidosis in Darwin may reflect movement of some Indigenous people into Darwin from remote communities.

Melioidosis of the extremities in Brunei Darussalam.

INTRODUCTION: Melioidosis caused by Burkholderia pseudomallei is an infectious disease endemic to Southeast Asia and northern Australia. It has a broad spectrum of clinical manifestations and high mortality, and can mimic other infectious diseases. The aim of this study was to review cases of melioidosis of the extremities in Brunei Darussalam. METHODS: Culture-positive cases for Burkholderia pseudomallei in Raja Isteri Pengiran Anak Saleha Hospital were identified from records in the Microbiology Department. The case notes were reviewed to identify patients who were treated for problems affecting the extremities. 14 (13 males and one female) out of 48 patients were identified. RESULTS: The median age of the patients was 45 (range 14-55) years. Septicaemia was the most common presenting feature in 11 patients. Multisystem involvement was noted in eight patients, diabetes mellitus in nine patients and other risk factors in two patients. Blood culture was positive in ten patients and pus culture in 11 patients. The presentations noted were cellulitis of the limbs, abscess, osteomyelitis (three patients each) and septic arthritis (five patients). Orthopaedic intervention (joint washout/incision and drainage/curettage) was required in 11 patients. The median hospital stay was 27.5 (range 13-63) days; two patients required admission to intensive care. No mortality was reported. CONCLUSION: Melioidosis of the extremities is not uncommon in Brunei Darussalam. It is associated with significant morbidity, and a large number of patients require surgical intervention. Thus, a high index of suspicion is required for early diagnosis and institution of appropriate antibiotic therapy.