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.

Group G Streptococcus Induces an Autoimmune Carditis Mediated by Interleukin 17A and Interferon γ in the Lewis Rat Model of Rheumatic Heart Disease.

Acute rheumatic fever and rheumatic heart disease (ARF/RHD) have long been described as autoimmune sequelae of Streptococcus pyogenes or group A streptococcal (GAS) infection. Both antibody and T-cell responses against immunodominant GAS virulence factors, including M protein, cross-react with host tissue proteins, triggering an inflammatory response leading to permanent heart damage. However, in some ARF/RHD-endemic regions, throat carriage of GAS is low. Because Streptococcus dysgalactiae subspecies equisimilis organisms, also known as ß-hemolytic group C streptococci and group G streptococci (GGS), also express M protein, we postulated that streptococci other than GAS may have the potential to initiate or exacerbate ARF/RHD. Using a model initially developed to investigate the uniquely human disease of ARF/RHD, we have discovered that GGS causes interleukin 17A/interferon γ-induced myocarditis and valvulitis, hallmarks of ARF/RHD. Remarkably the histological, immunological, and functional changes in the hearts of rats exposed to GGS are identical to those exposed to GAS. Furthermore, antibody cross-reactivity to cardiac myosin was comparable in both GGS- and GAS-exposed animals, providing additional evidence that GGS can induce and/or exacerbate ARF/RHD.

Paediatric thoracic empyema in the tropical North Queensland region of Australia: Epidemiological trends over a decade.

AIM: The Townsville Hospital and Health Service is the regional referral centre for children in the north of Queensland. Aboriginal and Torres Strait Islander (ATSI) people make up 7-10% of the population. Increasing numbers of children with paediatric thoracic empyema (pTE) are being referred to Townsville Hospital and Health Service for management. This study aims to describe the incidence rates, epidemiology, microbiology and trends of this disease in North Queensland over a 10-year period. METHODS: A retrospective chart review of all children (1 month to 16 years), admitted in the years 2007-2016, with community-acquired pTE was conducted. International Classification of Diseases codes were used to identify the patients. Epidemiological and microbiological data were extracted from records. RESULTS: Of the 123 cases identified, incidence rates per 100 000 were 8.5 (95% confidence interval (CI) 8.4-8.6) in all children and much higher at 19.8 (95% CI: 19.5-21.9) in ATSI children. The under 5 years age group had the highest rate (24.5; 95% CI: 24.4-24.6). There was a progressive rise in incidence during the 10-year period, with the highest incidence of 15.2 (95% CI: 15.1-15.2) occurring in 2016. A pathogen was isolated in 76% of cases. Non-multi-resistant methicillin-resistant Staphylococcus aureus was the most common pathogen isolated in 22 of 64 ATSI children (34%), while Streptococcus pneumoniae was the most common pathogen isolated in 27 of 59 non-ATSI children (46%). CONCLUSIONS: A high and increasing incidence of pTE in North Queensland is being observed. ATSI children have higher incidence rates and are more likely to have non-multi-resistant methicillin-resistant Staphylococcus aureus as a causative agent.

Design and Development of an Internationally Applicable Educational Video to Increase Community Awareness in Regions with High Prevalence of Melioidosis and Diabetes.

Melioidosis is a neglected tropical disease that causes high morbidity and mortality. Public health awareness is essential for both prevention and early detection of the infection. This project aimed to develop an internationally applicable educational tool to increase community awareness in regions with high prevalence of diabetes and melioidosis. The animation was created with international collaboration. Sixty-four delegates from different cultural backgrounds participated in the survey to evaluate the animation. Feedback was positive, with 85% agreeing that they would use this video for public education and 82% agreeing that the video was culturally appropriate to them in the context of their region. The animation was refined after feedback. To supplement the 3-minute animation, a 13-minute film footage of interviews with clinicians, researchers and patients was also created. These materials have been made available online through the International Melioidosis Network and can be readily downloaded or subtitled in any language using publicly available software, demonstrating the utility of developing low-cost adaptable health education material targeted for widespread use internationally.

The epidemiology of melioidosis in Townsville, Australia.

BACKGROUND: Melioidosis in an infection caused by Burkholderia pseudomallei, an organism endemic to tropical and subtropical regions. METHODS: This study describes the epidemiology of melioidosis in Townsville, QLD, Australia, as well as clinical features, risk factors associated with the disease, the burden of infection on the Aboriginal and Torres Strait Islander (ATSI) community and patient outcomes over time. RESULTS: From 1997 to 2020, 128 patients were admitted to Townsville University Hospital. The total annual incidence of infection was 3.2 cases per 100 000 compared with 15.3 per 100 000 in the ATSI population. The majority of cases (n=82 [64%]) were male. Alcohol excess (55%) and diabetes mellitus (48%) were the most common risk factors. Bacteraemia occurred in 87 (70%) patients and pneumonia was the most common focus of infection in 84 (69%). The case fatality rate was 23%, with no difference for the ATSI population (6/32 [19%]). The presence of malignancy was the risk factor most associated with mortality (relative risk 2.7 [95% confidence interval 1.4-5.1], p=0.005). CONCLUSIONS: The ATSI community was overrepresented in this study, however, there was no significant difference in adverse outcomes. The case fatality rate was higher than in other regions in Australia. This discrepancy may relate in part to the different risk groups seen in these settings coupled with potential organism variability.

Clinical Burkholderia pseudomallei isolates from north Queensland carry diverse bimABm genes that are associated with central nervous system disease and are phylogenomically distinct from other Australian strains.

BACKGROUND: Burkholderia pseudomallei is an environmental gram-negative bacterium that causes the disease melioidosis and is endemic in many countries of the Asia-Pacific region. In Australia, the mortality rate remains high at approximately 10%, despite curative antibiotic treatment being available. The bacterium is almost exclusively found in the endemic region, which spans the tropical Northern Territory and North Queensland, with clusters occasionally present in more temperate climates. Despite being endemic to North Queensland, these infections remain understudied compared to those of the Northern Territory. METHODOLOGY/PRINCIPAL FINDINGS: This study aimed to assess the prevalence of central nervous system (CNS) disease associated variant bimABm, identify circulating antimicrobial resistance mutations and genetically distinct strains from Queensland, via comparative genomics. From 76 clinical isolates, we identified the bimABm variant in 20 (26.3%) isolates and in 9 (45%) of the isolates with documented CNS infection (n = 18). Explorative analysis suggests a significant association between isolates carrying the bimABm variant and CNS disease (OR 2.8, 95% CI 1.3-6.0, P = 0.009) compared with isolates carrying the wildtype bimABp. Furthermore, 50% of isolates were identified as novel multi-locus sequence types, while the bimABm variant was more commonly identified in isolates with novel sequence types, compared to those with previously described. Additionally, mutations associated with acquired antimicrobial resistance were only identified in 14.5% of all genomes. CONCLUSIONS/SIGNIFICANCE: The findings of this research have provided clinically relevant genomic data of B. pseudomallei in Queensland and suggest that the bimABm variant may enable risk stratification for the development CNS complications and be a potential therapeutic target.

Melioidosis: Laboratory Investigations and Association with Patient Outcomes.

Melioidosis is an infection caused by the bacterium Burkholderia pseudomallei. The most common presentation is bacteremia occurring in 38-73% of all patients, and the mortality rate ranges from 9% to 42%. Although there is abundant data representing risk factors for infection and patient outcomes, there is limited information regarding laboratory investigations associated with bacteremia and mortality. We assessed a range of baseline and diagnostic investigations and their association with patient outcomes in a retrospective cohort study in Townsville, Australia. 124 patients' medical and laboratory records were reviewed between January 1, 1997 and December 31, 2020. Twenty-seven patients died and 87 patients were bacteremic. The presence of lymphopenia (< 1.5 × 109 cells/L) was the highest risk for bacteremia (relative risk [RR] 2.2; 95% CI: 1.3-3.7, P < 0.001). Factors associated with mortality included lymphopenia, (RR: 1.4; 95% CI: 1.2-1.6, P = 0.004); uremia (RR: 1.7; 95% CI: 1.1-2.5, P = 0.03); and an elevated international normalized ratio (RR: 1.5; 95% CI: 1.2-2.0, P = 0.006). Median incubation to positive blood culture result was 28 hours with 15/82 (18%) positive in ≤ 24 hours. For serological testing during admission only 53/121 (44%) were indirect hemagglutination assay positive, 67/120 (56%) enzyme immunoassay IgG positive, and 23/89 (26%) IgM positive. Simple baseline investigations at time of presentation may be used to stratify patients at high risk for both bacteremia and mortality. This information can be used as a decision aid for early intensive management.

Diagnosis of melioidosis: the role of molecular techniques.

Melioidosis is an emerging infectious disease with an estimated global burden of 4.64 million disability-adjusted life years per year. A major determinant related to poor disease outcomes is delay to diagnosis due to the fact that identification of the causative agent Burkholderia pseudomallei may be challenging. Over the last 25 years, advances in molecular diagnostic techniques have resulted in the potential for rapid and accurate organism detection and identification direct from clinical samples. While these methods are not yet routine in clinical practice, laboratory diagnosis of infectious diseases is transitioning to culture-independent techniques. This review article aims to evaluate molecular methods for melioidosis diagnosis direct from clinical samples and discuss current and future utility and limitations.

In Search of the Holy Grail: A Specific Diagnostic Test for Rheumatic Fever.

Current diagnosis of Acute Rheumatic Fever and Rheumatic Heart Disease (ARF/RHD) relies on a battery of clinical observations aided by technologically advanced diagnostic tools and non-specific laboratory tests. The laboratory-based assays fall into two categories: those that (1) detect "evidence of preceding streptococcal infections" (ASOT, anti-DNAse B, isolation of the Group A Streptococcus from a throat swab) and (2) those that detect an ongoing inflammatory process (ESR and CRP). These laboratory tests are positive during any streptococcal infection and are non-specific for the diagnosis of ARF/RHD. Over the last few decades, we have accumulated considerable knowledge about streptococcal biology and the immunopathological mechanisms that contribute to the development, progression and exacerbation of ARF/RHD. Although our knowledge is incomplete and many more years will be devoted to understanding the exact molecular and cellular mechanisms involved in the spectrum of clinical manifestations of ARF/RHD, in this commentary we contend that there is sufficient understanding of the disease process that using currently available technologies it is possible to identify pathogen associated peptides and develop a specific test for ARF/RHD. It is our view that with collaboration and sharing of well-characterised serial blood samples from patients with ARF/RHD from different regions, antibody array technology and/or T-cell tetramers could be used to identify streptococcal peptides specific to ARF/RHD. The availability of an appropriate animal model for this uniquely human disease can further facilitate the determination as to whether these peptides are pathognomonic. Identification of such peptides will also facilitate testing of potential anti-streptococcal vaccines for safety and avoid potential candidates that may pre-dispose potential vaccine recipients to adverse outcomes. Such peptides can also be readily incorporated into a universally affordable point of care device for both primary and tertiary care.

The Burkholderia pseudomallei intracellular 'TRANSITome'.

Prokaryotic cell transcriptomics has been limited to mixed or sub-population dynamics and individual cells within heterogeneous populations, which has hampered further understanding of spatiotemporal and stage-specific processes of prokaryotic cells within complex environments. Here we develop a 'TRANSITomic' approach to profile transcriptomes of single Burkholderia pseudomallei cells as they transit through host cell infection at defined stages, yielding pathophysiological insights. We find that B. pseudomallei transits through host cells during infection in three observable stages: vacuole entry; cytoplasmic escape and replication; and membrane protrusion, promoting cell-to-cell spread. The B. pseudomallei 'TRANSITome' reveals dynamic gene-expression flux during transit in host cells and identifies genes that are required for pathogenesis. We find several hypothetical proteins and assign them to virulence mechanisms, including attachment, cytoskeletal modulation, and autophagy evasion. The B. pseudomallei 'TRANSITome' provides prokaryotic single-cell transcriptomics information enabling high-resolution understanding of host-pathogen interactions.

Evaluation of recombinant antigens for diagnosis of melioidosis.

Burkholderia pseudomallei, the causative agent of melioidosis, is endemic to Southeast Asia and northern Australia. Clinical manifestations of the disease are diverse, ranging from chronic localized infection to acute septicaemia, with death occurring within 24-48 h after the onset of symptoms. Definitive diagnosis of melioidosis involves bacterial culture and identification, with results obtained within 3-4 days. This delayed diagnosis is a major contributing factor to high mortality rates. Rapid diagnosis is vital for successful management of the disease. This study describes the purification and evaluation of three recombinant antigenic proteins, BPSL0972, BipD and OmpA from B. pseudomallei 08, for their potential in the serodiagnosis of melioidosis using an indirect enzyme-linked immunosorbent assay (ELISA) method. The recombinant proteins were evaluated using 74 serum samples from culture-confirmed melioidosis patients from Malaysia, Thailand and Australia. In addition, 62 nonmelioidosis controls consisting of serum samples from clinically suspected melioidosis patients (n=20) and from healthy blood donors from an endemic region (n=18) and a nonendemic region (n=24) were included. The indirect ELISAs using BipD and BPSL0972 as antigens demonstrated poor to moderate sensitivities (42% and 51%, respectively) but good specificity (both 100%). In contrast, the indirect ELISA using OmpA as an antigen achieved 95% sensitivity and 98% specificity. These results highlight the potential for OmpA to be used in the serodiagnosis of melioidosis in an endemic area.

Evaluating Burkholderia pseudomallei Bip proteins as vaccines and Bip antibodies as detection agents.

Burkholderia pseudomallei is a biothreat agent and an important natural pathogen, causing melioidosis in humans and animals. A type III secretion system (TTSS-3) has been shown to be critical for virulence. Because TTSS components from other pathogens have been used successfully as diagnostic agents and as experimental vaccines, it was investigated whether this was the case for BipB, BipC and BipD, components of B. pseudomallei's TTSS-3. The sequences of BipB, BipC and BipD were found to be highly conserved among B. pseudomallei and B. mallei isolates. A collection of monoclonal antibodies (mAbs) specific for each Bip protein was obtained. Most recognized both native and denatured Bip protein. Burkholderia pseudomallei or B. mallei did not express detectable BipB or BipD under the growth conditions used. However, anti-BipD mAbs did recognize the TTSS needle structures of a Shigella strain engineered to express BipD. The authors did not find that BipB, BipC or BipD are protective antigens because vaccination of mice with any single protein did not result in protection against experimental melioidosis. Enzyme-linked immunosorbent assay (ELISA) studies showed that human melioidosis patients had antibodies to BipB and BipD. However, these ELISAs had low diagnostic accuracy in endemic regions, possibly due to previous patient exposure to B. pseudomallei.

Correlation between serum cryptococcal antigen titre and meningitis in immunocompetent patients.

The aim of this paper was to determine the correlation between serum cryptococcal antigen and a diagnosis of cryptococcal meningitis in the immunocompetent cohort. A retrospective multicentre analysis of immunocompetent patients diagnosed and treated for cryptococcal meningitis between January 2000 and December 2017 was performed. Sixty-seven of the 143 cases of cryptococcosis occurred in immunocompetent patients. The serum cryptococcal antigen titre was significantly higher in the meningitis group [1 : 256 (IQR: 64-1024)] compared with that for non-meningitis patients [1 : 64 (IQR: 8-256)], P=0.012. The relative risk of meningitis with a serum cryptococcal antigen (CRAG) >1 : 64 was 1.8 (95 % CI: 1.15-2.82). This study demonstrates a clear correlation between serum cryptococcal antigen titre and meningitis. While the serum titre is not definitive for meningitis, in resource-limited settings or cases where lumbar puncture may be contraindicated, this evidence may aid diagnosis and subsequent therapeutic decisions.

A survey of the antibiotic prescribing practices of doctors in an Australian Emergency Department.

BACKGROUND: Appropriate antibiotic prescribing is important for good patient care and reducing the development of resistance. There has been limited research into doctors' prescribing practices. The aim of this study is to evaluate antibiotic prescribing practices in an Australian emergency department compared with the Therapeutic Guidelines. METHODS: A case vignette survey was sent to emergency department doctors at The Townsville Hospital between February and May 2016. Antibiotic choices were assessed for appropriateness using the National Antimicrobial Prescribing Survey guidelines. Factors associated with antibiotic choice were assessed according to case, clinician experience and rationale. Data was analysed using a non-parametric Kruskal-Wallis test. Post-hoc analysis of variance was performed using Dunn test with Bonferroni correction for multiple simultaneous comparisons, with p < 0.05 considered significant. RESULTS: 197 of 274 antibiotic choices (72%) were appropriate with 149 (54%) optimal. Antibiotic choice was more likely to be appropriate for a urinary tract infection (UTI) compared with severe pyelonephritis (p < 0.01), severe cellulitis (p < 0.01), moderate community-acquired pneumonia (CAP) (p < 0.01) and sepsis (p < 0.01), and was more likely to be appropriate for cellulitis than CAP (p = 0.03) and sepsis (p = 0.02). Antibiotic choices were more likely to be appropriate when doctors reported basing antibiotic choice on the Therapeutic Guidelines compared with current hospital practice (p = 0.02). No significant difference was found in antibiotic appropriateness in relation to grade of doctor (p = 0.34). CONCLUSION: This study demonstrates generally poor antibiotic prescribing compliance with the Therapeutic Guidelines across all grades of clinician. Antibiotic prescribing was more likely to be appropriate if based on the Therapeutic Guidelines and in less severe infection.

Mycobacterial soft tissue infections in North Queensland.

BACKGROUND: Mycobacterial soft tissue infections are a heterogeneous group of infections that usually require a variety of therapeutic methods for cure. North Queensland has an environment, which predisposes to several such infections. The aim of this study was to assess the incidence and epidemiology of mycobacterial soft tissue infections in North Queensland and to review surgical and non-surgical interventions in these conditions. METHODS: This study was a retrospective review of all patients with a proven mycobacterial soft tissue infection, seen between 1997 and 2005 in a tertiary referral centre in North Queensland. RESULTS: In total, 34 patients were identified. The most common causative organisms were Mycobacterium fortuitum (44%), M. ulcerans (17.6%) and M. abscessus (11.8%). The risk factors identified were the male sex, lower-limb involvement and preceding trauma including surgery. Twenty-four (70.6%) patients had surgical excision or debridement with a variety of adjuvant antimicrobial therapies. There were eight (23.5%) local recurrences. CONCLUSION: The optimal management of soft tissue mycobacterial infections includes early microbiological identification based on tissue biopsy, appropriate combination antimicrobial therapy and early wide surgical excision where appropriate. North Queensland has a unique environment, which may predispose to these infections. An awareness of this is essential to surgical practice in the region.

Clinical presentation of melioidosis in Queensland, Australia.

A retrospective study was performed on culture-positive patients (n = 57) with melioidosis presenting to the Townsville Hospital to define the epidemiology of the disease in Queensland, Australia. Mortality was 25% (n = 14) with a 9% (n = 5) relapse rate. At presentation, primary organs involved included the lungs (58%; n = 33), genitourinary system (11%; n = 6), skin and soft tissue (9%; n = 5), bone and joints (4%; n = 2), central nervous system (4%; n = 2), mycotic aneurysm (2%; n = 1) and peritonitis (2%; n = 1). No focus of infection could be identified in 12% of cases (n = 7). There was no significant difference in the clinical presentation of melioidosis in Queensland compared with the Northern Territory. Regional trends in the clinical presentation of melioidosis in Australia compared with Southeast Asia were confirmed. Risk factors for disease included diabetes (42%), excess alcohol consumption (42%), chronic lung disease (26%), immunosuppressive drug use (12%), renal disease (11%), malignancy (7%) and autoimmune disease (5%). No risk factors were identifiable in 18% of cases. The presence of multiple risk factors for melioidosis was not significantly associated with increased mortality (P > 0.05).

Rapid serological diagnosis of melioidosis: an evaluation of a prototype immunochromatographic test.

AIMS: To evaluate the Panbio melioidosis prototype (ICT) IgG and IgM test kits in detecting antibodies to Burkholderia pseudomallei from an endemic region of Australia. This would be of particular importance in high prevalence, low resource regions. METHODS: Seventy-five culture-confirmed sera for melioidosis and 158 negative control sera from subjects in North Queensland were tested. All sera samples were also tested with an in-house indirect haemagglutination assay (IHA). Seventy-three of the positive sera were further tested using an in-house EIA IgG and IgM assay. RESULTS: The Panbio IgG kits had a sensitivity of 50.6% (95%CL 38.9-62.4) and a specificity of 97.4% (95%CL 93.7-99.3). The Panbio IgM kits had a sensitivity and specificity, respectively, of 72.0% (95%CL 60.4-81.8) and 71.5% (95%CL 63.8-78.4). CONCLUSIONS: The ICT kits were found to be rapid and easier to use than current serological methods. In particular, the IgG ICT kit would have a potential role in determining existing disease in low resource regions.