Burkholderia pseudomallei in water supplies, southern Thailand

A molecular epidemiological analysis of Burkholderia pseudomallei in southern Thailand

Melioidosis, a severe bacterial illness caused by Burkholderia pseudomallei, is prevalent in most parts of Thailand, including its southern region situated within the Malay Peninsula. Despite a lower reported incidence rate of melioidosis in the South compared to the Northeast, the mortality rate remains persistently high. This study aimed to better understand the epidemiology and investigate the presence of B. pseudomallei in the natural environment of southern Thailand. Using multi-locus sequence typing (MLST), we characterized B. pseudomallei isolates derived from human cases and compared them with previously reported sequence types (STs) from the same region. A total of 263 clinical isolates retrieved from 156 melioidosis patients between 2014 and 2020 were analyzed, revealing 72 distinct STs, with 25 (35%) matching STs from Finkelstein's environmental isolates collected in southern Thailand during 1964-1967. Notably, strains bearing STs 288, 84, 54, 289, and 46 were frequently found among patients. Additionally, we observed strain diversity with multiple STs in 13 of 59 patients, indicating exposure to various B. pseudomallei genotypes in the environmental sources of the infection. Environmental surveys were conducted in Songkhla Province to detect B. pseudomallei in soil and water samples where local patients lived. Of the 2737 soil samples from 208 locations and 244 water samples from diverse sources, 52 (25%) soil sampling locations and 63 (26%) water sources were cultured positive for B. pseudomallei. Positive soil samples were predominantly found in animal farming area and non-agricultural zones like mountains and grasslands, while water samples were frequently positive in waterfalls, streams, and surface runoffs, with only 9% of rice paddies testing positive. Collectively, a significant proportion of recent melioidosis cases in Songkhla Province can be attributed to known B. pseudomallei STs persisting in the environment for at least the past six decades. Further characterization of B. pseudomallei isolates from recent environment surveys is warranted. These findings illuminate the contemporary landscape of B. pseudomallei infections and their environmental prevalence in southern Thailand, contributing to the regional threat assessment in Thailand and Southeast Asia.

Seroprevalence of melioidosis and its association with blood profiles and pathogens in sheltered dogs in southern Thailand

Background and Aims

Melioidosis is a notable zoonotic disease in Thailand that can affect both humans and animals. Although dogs are one of the most popular pets worldwide, there is a remarkable lack of information on the prevalence and knowledge of canine melioidosis. This study aimed to estimate the seroprevalence of melioidosis in sheltered dogs and its relationship with the blood profile and blood pathogens.

Materials and Methods

Melioidosis in 156 dogs was analyzed using an indirect hemagglutination assay. Hematology and serum biochemistry tests were performed using an automated system. Blood pathogens (e.g., Ehrlichia, Anaplasma, Hepatozoon, and Babesia) were diagnosed using conventional polymerase chain reaction.

Results

The seroprevalence rates of canine melioidosis and blood pathogen infection were 5.77% (9/156) and 50.64% (79/156), respectively. Seropositive dogs generally have higher lymphocyte counts and aspartate aminotransferase levels but lower total white blood cell, neutrophil, and platelet (PLT) counts than seronegative dogs. No statistically significant difference (p > 0.05) was observed between the seropositive and seronegative dogs' hematology and serum biochemistry findings. Neither the correlation between melioidosis and blood pathogen infection nor the association between melioidosis and thrombocytopenia was statistically significant (p > 0.05). Remarkably, dogs that had coinfections with both melioidosis and blood pathogens demonstrated a significantly reduced PLTcount (49,167 ± 7,167) compared with dogs that tested positive for melioidosis but negative for blood pathogens (139,333 ± 29,913) (p < 0.01).

Conclusion

In southern Thailand, the prevalence of canine melioidosis was low but the prevalence of blood pathogens was high. Coinfection with blood pathogens can significantly reduce PLT counts, which may have a potentially serious impact. Future research should focus on conducting seroprevalence studies in the general dog population.

Burkholderia pseudomallei Bacteria in Ornamental Fish Tanks, Vientiane, Laos, 2023

In 2019, a melioidosis case in Maryland, USA, was shown to have been acquired from an ornamental fish tank contaminated with Burkholderia pseudomallei bacteria, likely derived from Southeast Asia. We investigated the presence of B. pseudomallei in ornamental fish tanks in the endemic area of Vientiane, Laos.

Under-Reporting Cases and Deaths from Melioidosis: A Retrospective Finding in Songkhla and Phatthalung Province of Southern Thailand, 2014-2020

Melioidosis, caused by Burkholderia pseudomallei, is a notifiable disease associated with a high mortality rate in Thailand. The disease is highly endemic in northeast Thailand, while its prevalence in other parts of the country is poorly documented. This study aimed at improving the surveillance system for melioidosis in southern Thailand, where the disease was believed to be underreported. Two adjacent southern provinces, Songkhla and Phatthalung, were selected as the model provinces to study melioidosis. There were 473 individuals diagnosed with culture-confirmed melioidosis by clinical microbiology laboratories at four tertiary care hospitals in both provinces from January 2014 to December 2020. The median age was 54 years (IQR 41.5-64), 284 (60%) of the patients were adults ≥50 years of age, and 337 (71.2%) were male. We retrospectively analyzed 455 patients treated at either Songklanarind Hospital, Hatyai Hospital, Songkhla Provincial Hospital, or Phatthalung Provincial Hospital, of whom 181 (39.8%) patients died. The median duration from admission to death was five days (IQR 2-17). Of the 455 patients, 272 (57.5%) had at least one clinical risk factor, and 188 (39.8%) had diabetes. Two major clinical manifestations, bacteremia and pneumonia, occurred in 274 (58.1%) and 166 (35.2%) patients, respectively. In most cases, 298 (75%) out of 395 local patients were associated with rainfall. Over the seven years of the study, the average annual incidence was 2.87 cases per 100,000 population (95% CI, 2.10 to 3.64). This study has confirmed that these two provinces of southern Thailand are endemic to melioidosis; even though the incidence rate is much lower than that of the Northeast, the mortality rate is comparably high.

Natural infection of leptospirosis and melioidosis in long-tailed macaques (Macaca fascicularis) in Thailand

This study aimed to determine the incidence of leptospirosis and melioidosis in long-tailed macaques (Macaca fascicularis) in Thailand. Serum samples from 223 monkeys were subjected to the Lepto Latex Test and indirect hemagglutination (IHA) test to detect antibodies against Leptospira spp. and Burkholderia pseudomallei. The microagglutination test (MAT) was used to identify serovars of Leptospira spp. Conventional PCR for the LipL32 gene of L. interogans and the BPSS0120 and btfc-orf18 genes of B. pseudomallei was used for molecular detection. The overall seroprevalence of leptospirosis and melioidosis was 2.69% (95% CI: 0.99-5.76%) and 14.35% (95% CI: 10.03-19.65%), respectively. Six samples that showed positive MAT results were also positive for IHA. The serovars of Leptospira were Ranarum (5/6), Shermani (6/6), and both (5/6). Conventional PCR for the LipL32 gene of Leptospira spp. was positive in 10.31% of the samples (95% CI: 5.56-13.51%). However, there were no positive results for BPSS0120 and btfc-orf18 in B. pseudomallei. Active infection was detected only for leptospirosis; however, it can be assumed that pathogen exposure occurred in this group of animals because immunity could be detected. The routes of infection and elimination pathways of both bacteria remain unclear, and the mechanism of protection in non-human primates needs to be elucidated in further studies. Moreover, this health issue should be considered to prevent human infections in monkeys and their environment.

Modern Analytical Techniques for Detection of Bacteria in Surface and Wastewaters

Contamination of surface waters with pathogens as well as all diseases associated with such events are a significant concern worldwide. In recent decades, there has been a growing interest in developing analytical methods with good performance for the detection of this category of contaminants. The most important analytical methods applied for the determination of bacteria in waters are traditional ones (such as bacterial culturing methods, enzyme-linked immunoassay, polymerase chain reaction, and loop-mediated isothermal amplification) and advanced alternative methods (such as spectrometry, chromatography, capillary electrophoresis, surface-enhanced Raman scattering, and magnetic field-assisted and hyphenated techniques). In addition, optical and electrochemical sensors have gained much attention as essential alternatives for the conventional detection of bacteria. The large number of available methods have been materialized by many publications in this field aimed to ensure the control of water quality in water resources. This study represents a critical synthesis of the literature regarding the latest analytical methods covering comparative aspects of pathogen contamination of water resources. All these aspects are presented as representative examples, focusing on two important bacteria with essential implications on the health of the population, namely Pseudomonas aeruginosa and Escherichia coli.

Opportunistic pathogens and large microbial diversity detected in source-to-distribution drinking water of three remote communities in Northern Australia

In the wet-dry tropics of Northern Australia, drinking water in remote communities is mostly sourced from bores accessing groundwater. Many aquifers contain naturally high levels of iron and some are shallow with surface water intrusion in the wet season. Therefore, environmental bacteria such as iron-cycling bacteria promoting biofilm formation in pipes or opportunistic pathogens can occur in these waters. An opportunistic pathogen endemic to northern Australia and Southeast Asia and emerging worldwide is Burkholderia pseudomallei. It causes the frequently fatal disease melioidosis in humans and animals. As we know very little about the microbial composition of drinking water in remote communities, this study aimed to provide a first snapshot of the microbiota and occurrence of opportunistic pathogens in bulk water and biofilms from the source and through the distribution system of three remote water supplies with varying iron levels. Using 16s-rRNA gene sequencing, we found that the geochemistry of the groundwater had a substantial impact on the untreated microbiota. Different iron-cycling bacteria reflected differences in redox status and nutrients. We cultured and sequenced B. pseudomallei from bores with elevated iron and from a multi-species biofilm which also contained iron-oxidizing Gallionella, nitrifying Nitrospira and amoebae. Gallionella are increasingly used in iron-removal filters in water supplies and more research is needed to examine these interactions. Similar to other opportunistic pathogens, B. pseudomallei occurred in water with low organic carbon levels and with low heterotrophic microbial growth. No B. pseudomallei were detected in treated water; however, abundant DNA of another opportunistic pathogen group, non-tuberculous mycobacteria was recovered from treated parts of one supply. Results from this study will inform future studies to ultimately improve management guidelines for water supplies in the wet-dry tropics.

Prevalence and genetic diversity of Burkholderia pseudomallei isolates in the environment near a patient's residence in Northeast Thailand

BACKGROUND

Burkholderia pseudomallei is the causative agent of melioidosis, a severe infectious disease in tropical regions. It is necessary to understand the risk of acquiring this infection from the environment.

METHODOLOGY /PRINCIPAL FINDINGS

The prevalence, concentration and genetic diversity of B. pseudomallei isolates collected from two sites in Buriram, Northeast Thailand were investigated. Forty-four environmental samples (18 from soil, 14 from rice rhizosphere, and 12 from water) were collected; of those 44 samples, 19 were collected from near a patient's residence and 25 from suspected exposure sites and compared with 10 clinical isolates of the patient. Quantitative culture was performed, and B. pseudomallei was identified using the latex agglutination test and matrix-laser absorption ionisation mass spectrometry. Genotyping was performed in 162 colonies from clinical (N = 10) and environmental samples (N = 152) using pulse-field gel electrophoresis (PFGE) followed by multi-locus sequence typing (MLST) of the clinical strain. B. pseudomallei was detected in 11 of the 44 environmental samples (1 from soil, 4 from rice rhizosphere, and 6 from water). The bacterial count in the positive soil sample was 115 CFU/g. The mean concentrations ± SDs of B. pseudomallei in the positive water and rhizosphere samples were 5.1 ± 5.5 CFU/ml and 80 ± 49 CFU/g, respectively. Six water samples with positive results were collected from a pond and water sources for drinking and daily use. All colonies isolated from the patient shared the same PFGE type (PT) indicating monoclonal infection of ST99. Although the 152 colonies from environmental isolates exhibited 25 PTs, none were identical to the patient's isolates. PT5 and PT7 were most common genotype among the environmental samples.

CONCLUSIONS/SIGNIFICANCE

Diverse genotypes of B. pseudomallei were prevalent in the environment. However, the patient may have been infected with a low-density genotype. Intervention strategies for preventing B. pseudomallei infection are required.

Melioidosis in Thailand: Present and Future

A recent modelling study estimated that there are 2800 deaths due to melioidosis in Thailand yearly. The Thailand Melioidosis Network (formed in 2012) has been working closely with the Ministry of Public Health (MoPH) to investigate and reduce the burden of this disease. Based on updated data, the incidence of melioidosis is still high in Northeast Thailand. More than 2000 culture-confirmed cases of melioidosis are diagnosed in general hospitals with microbiology laboratories in this region each year. The mortality rate is around 35%. Melioidosis is endemic throughout Thailand, but it is still not uncommon that microbiological facilities misidentify Burkholderia pseudomallei as a contaminant or another organism. Disease awareness is low, and people in rural areas neither wear boots nor boil water before drinking to protect themselves from acquiring B. pseudomallei. Previously, about 10 melioidosis deaths were formally reported to the National Notifiable Disease Surveillance System (Report 506) each year, thus limiting priority setting by the MoPH. In 2015, the formally reported number of melioidosis deaths rose to 112, solely because Sunpasithiprasong Hospital, Ubon Ratchathani province, reported its own data (n = 107). Melioidosis is truly an important cause of death in Thailand, and currently reported cases (Report 506) and cases diagnosed at research centers reflect the tip of the iceberg. Laboratory training and communication between clinicians and laboratory personnel are required to improve diagnosis and treatment of melioidosis countrywide. Implementation of rapid diagnostic tests, such as a lateral flow antigen detection assay, with high accuracy even in melioidosis-endemic countries such as Thailand, is critically needed. Reporting of all culture-confirmed melioidosis cases from every hospital with a microbiology laboratory, together with final outcome data, is mandated under the Communicable Diseases Act B.E.2558. By enforcing this legislation, the MoPH could raise the priority of this disease, and should consider implementing a campaign to raise awareness and melioidosis prevention countrywide.

Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry for the identification of Burkholderia pseudomallei from Asia and Australia and differentiation between Burkholderia species

Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) is increasingly used for rapid bacterial identification. Studies of Burkholderia pseudomallei identification have involved small isolate numbers drawn from a restricted geographic region. There is a need to expand the reference database and evaluate B. pseudomallei from a wider geographic distribution that more fully captures the extensive genetic diversity of this species. Here, we describe the evaluation of over 650 isolates. Main spectral profiles (MSP) for 26 isolates of B. pseudomallei (N = 5) and other Burkholderia species (N = 21) were added to the Biotyper database. MALDI-TOF MS was then performed on 581 B. pseudomallei, 19 B. mallei, 6 B. thailandensis and 23 isolates representing a range of other bacterial species. B. pseudomallei originated from northeast and east Thailand (N = 524), Laos (N = 12), Cambodia (N = 14), Hong Kong (N = 4) and Australia (N = 27). All 581 B. pseudomallei were correctly identified, with 100% sensitivity and specificity. Accurate identification required a minimum inoculum of 5 x 107 CFU/ml, and identification could be performed on spiked blood cultures after 24 hours of incubation. Comparison between a dendrogram constructed from MALDI-TOF MS main spectrum profiles and a phylogenetic tree based on recA gene sequencing demonstrated that MALDI-TOF MS distinguished between B. pseudomallei and B. mallei, while the recA tree did not. MALDI-TOF MS is an accurate method for the identification of B. pseudomallei, and discriminates between this and other related Burkholderia species.

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.

The epidemiology and clinical spectrum of melioidosis in a teaching hospital in a North-Eastern state of Malaysia: a fifteen-year review

Background

Over the last two decades, many epidemiological studies were performed to describe risks and clinical presentations of melioidosis in endemic countries.

Methods

We performed a retrospective analysis of 158 confirmed cases of melioidosis collected from medical records from 2001 to 2015 in Hospital Universiti Sains Malaysia, Kubang Kerian, Kelantan, Malaysia, in order to update the current status of melioidosis clinical epidemiology in this putatively high risk region of the country.

Results

Principal presentations in patients were lung infection in 65 (41.1 %), skin infection in 44 (27.8 %), septic arthritis/osteomyelitis in 20 (12.7 %) and liver infection in 19 (12.0 %). Bacteremic melioidosis was seen in most of patients (n = 121, 76.6 %). Focal melioidosis was seen in 124 (78.5 %) of patients and multi-focal melioidosis was reported in 45 (28.5 %) cases. Melioidosis with no evident focus was in 34 (21.5 %) patients. Fifty-four (34.2 %) patients developed septic shock. Internal organ abscesses and secondary foci in lungs and/or soft tissue were common. A total of 67 (41 %) cases presented during the monsoonal wet season. Death due to melioidosis was reported in 52 (32.9 %) patients, while relapses were occurred in 11 (7.0 %). Twelve fatal melioidosis cases seen in this study were directly attributed to the absence of prompt acute-phase treatment. Predisposing risk factors were reported in most of patients (n = 133, 84.2 %) and included diabetes (74.7 %), immune disturbances (9.5 %), cancer (4.4 %) and chronic kidney disease (11.4 %). On multivariate analysis, the only independent predictors of mortality were the presence of at least one co-morbid factor (OR 3.0; 95 % CI 1.1–8.4), the happening of septic shock (OR 16.5; 95 % CI 6.1–44.9) and age > 40 years (OR 6.47; 95 % CI 1.7–23.8).

Conclusions

Melioidosis should be recognized as an opportunistic nonfatal infection for healthy person. Prompt early diagnosis and appropriate antibiotics administration and critical care help in improved management and minimizing risks for death.