Search Results (53)

Background: Burkholderia pseudomallei, the causative agent of melioidosis, is intrinsically resistant to multiple antibiotics, posing substantial challenges for treatment. Reports of acquired resistance are increasing, underscoring the need for global surveillance. Objective: This systematic review and meta-analysis aimed to determine the global prevalence of antibiotic-resistant B. pseudomallei isolated from human clinical cases, with a focus on regional differences and variations in antimicrobial susceptibility testing methods. Methods: We systematically searched PubMed, Scopus, and Embase for studies reporting resistance in clinical B. pseudomallei isolates, following PRISMA guidelines. Pooled resistance rates to 11 antibiotics were calculated using a random-effect model. Subgroup analyses were performed based on geographical region and testing methodology (MIC vs. disk diffusion). Results: Twelve studies comprising 10,391 isolates were included. Resistance rates varied across antibiotics, with the highest pooled resistance observed for tigecycline (46.3%) and ciprofloxacin (38.3%). Ceftazidime (CAZ) and trimethoprim–sulfamethoxazole (SXT), commonly used first-line agents, showed resistance rates of 5.3% and 4.2%, respectively. Subgroup analyses of CAZ and SXT revealed significantly higher resistance in studies from Asia compared to Australia and America (p value < 0.0001). Disk diffusion methods tended to overestimate resistance compared to MIC-based approaches, which revealed non-significant differences for CAZ (p value = 0.5343) but significant differences for SXT (p value < 0.0001). Conclusions: Antibiotic resistance in B. pseudomallei exhibits regional variation and is influenced by the susceptibility testing method used. Surveillance programs and standardized antimicrobial susceptibility testing protocols are essential to guide effective treatment strategies and ensure accurate resistance reporting. Full article

Background/Objectives: The pulmonary administration of antibiotics can be advantageous in treating pulmonary infections by promoting high intrapulmonary drug concentrations with reduced systemic exposure. However, limited benefits have been observed for pulmonary administration versus other administration routes due to its rapid clearance from the lung. Here, the effects of structural modifications on the epithelial permeability and antibacterial potency of a third-generation cephalosporin were investigated to improve the understanding of drug properties that promote intrapulmonary retention and how they may impact efficacy. Methods: Ceftazidime was modified by attaching 18 hydrophobic, hydrophilic, and mucus-binding motifs to the carboxylic acid distant from the beta-lactam by amidation. Epithelial permeability was investigated by drug transport assays using human bronchial epithelial air–liquid interface cultures. Antibacterial potency was determined by microtiter MIC assays with B. pseudomallei, P. aeruginosa, E. coli, and S. aureus. Results: A 40–50% reduction in the transepithelial transport rate was exhibited by two PEGylated ceftazidime analogs (mPEG8- and PEG5-pyrimidin-2-amine-ceftazidime) and n-butyl-ceftazidime. An increase in the transport rate was exhibited by four analogs bearing small and hydrophobic or negatively charged motifs (n-heptane-, phenyl ethyl-, glutamic acid-, and 4-propylthiophenyl boronic acid-ceftazidime). The antibacterial potency was reduced by ≥10-fold for most ceftazidime analogs against B. pseudomallei, P. aeruginosa, and E. coli but was retained by seven ceftazidime analogs primarily bearing hydrophobic motifs against S. aureus. Conclusions: The covalent conjugation of PEGs with MW > 300 Da reduced the epithelial permeability of ceftazidime, but these modifications severely reduced antibacterial activity. To improve the pulmonary retention of antibiotics with low membrane permeability, this work suggests future molecular engineering studies to explore high-molecular-weight prodrug strategies. Full article

Melioidosis, an infection with the bacterium Burkholderia pseudomallei, is highly endemic in the Top End of the Northern Territory of Australia. The indirect haemagglutination assay (IHA) is the most widely used serology test globally, but it is not standardised among the limited number of laboratories that perform it. While concerns have been raised about the sensitivity of IHA early in melioidosis infections, the advantage of IHA over more recently developed ELISAs is that testing serial dilutions allows a titre to be recorded. While in Australia a titre of 1:40 or higher is considered positive, the specificity at these low positive titres remains uncertain. However, a high titre is considered to represent recent or past true infection with B. pseudomallei, rather than cross-rection with other environmental Burkholderia species. Also, the natural history of IHA titres over time, in both asymptomatic infection and melioidosis has been little studied. We have assessed the clinical status and serology time courses of all 534 patients who had an IHA titre of 1:640 or higher, over a 20-year period. Of these, 324 (60.7%) were diagnosed with culture-confirmed melioidosis, with varying time courses of diagnosis of melioidosis in relation to the high serology. Of the 210 without confirmed melioidosis, 22 (10.5%) were considered highly likely to be melioidosis despite being culture-negative, and these were all treated as melioidosis. In the remainder, titres mostly gradually decreased over time, but the majority remained seropositive. A small number who had not been treated for melioidosis continued to have high IHA titres over years and activation from latency with a new diagnosis of melioidosis was occasionally documented. This study highlights the importance of a full clinical workup in those found to have high titre melioidosis serology as well as subsequent close clinical surveillance and where resources allow, yearly IHA in those not confirmed or treated as melioidosis. Full article

Introduction: Patients receiving biological and targeted synthetic disease-modifying antirheumatic drugs (b/tsDMARDs) for rheumatological conditions are at an increased risk of serious, potentially life-threatening, infection. However, the incidence, aetiology, and clinical course of serious infection in patients receiving b/tsDMARDs in tropical settings are incompletely defined. Methods: We retrospectively reviewed all patients with rheumatoid arthritis receiving b/tsDMARDs between October 2012 and October 2021, at Cairns Hospital in tropical Australia. The incidence, aetiology, and clinical course of serious infections (those requiring admission to hospital or parenteral antibiotics) were determined. Results: 310 patients had 1468 patient years of b/tsDMARD therapy during the study period; 74/310 (24%) had 147 serious infections translating to an overall risk of 10.0 episodes of serious infection per 100 patient years. The respiratory tract (50/147, 34%) and skin (37/147, 25%) were the most frequently affected sites. A pathogen was identified in 59/147 (40%) episodes and was most commonly Staphylococcus aureus (24/147, 16%). Only 2/147 (1%) were confirmed “tropical infections”: 1 case of Burkholderia pseudomallei and 1 case of mixed B. pseudomallei and community-acquired Acinetobacter baumannii infection. Overall, 13/147 (9%) episodes of serious infection required Intensive Care Unit admission (0.9 per 100-patient years of b/tsDMARD therapy) and 4/147 (3%) died from their infection (0.3 per 100-patient years of b/tsDMARD therapy). The burden of comorbidity and co-administration of prednisone were the strongest predictors of death or a requirement for ICU admission. Conclusions: The risk of serious infection in patients taking b/tsDMARDs in tropical Australia is higher than in temperate settings, but this is not explained by an increased incidence of traditional tropical pathogens. Full article

Background: Burkholderia pseudomallei, the causative agent of melioidosis, is highly genetically recombinant, resulting in significant genomic diversity. Multiple virulence factors have been associated with specific disease presentations. To date, there are limited data relating to genomic diversity and virulence factors associated with melioidosis cases in North Queensland, Australia. Aim: To describe the genetic diversity of B. pseudomallei and identify virulence factors associated with clinical risk factors and patient outcomes. Methods: Whole genome sequencing of clinical isolates was performed and analysed with clinical data obtained from a retrospective melioidosis cohort study. Results: Fifty-nine distinct sequence types (STs) were identified from the 128 clinical isolates. Six STs comprised 64/128 (50%) isolates. Novel STs accounted for 38/59 (64%) STs, with ST TSV-13 as the most prevalent (n = 7), and were less likely to possess an LPS A genotype or YLF gene cluster (p < 0.001). These isolates were most likely to be found outside the inner city (aOR: 4.0, 95% CI: 1.7–9.0, p = 0.001). ST TSV-13 was associated with increased mortality (aOR: 6.1, 95% CI: 1.2–30.9, p = 0.03). Patients with a history of alcohol excess were less likely to be infected by fhaB3 (aOR 0.2, 95% CI: 0.1–0.7, p = 0.01) or YLF (aOR: 0.4, 95% CI: 0.2–0.9, p = 0.04) positive isolates. Conclusions: There are a significant number of novel sequence types in Townsville, Australia. An emerging novel ST appears to have an association with geographic location and mortality. Ongoing investigation is required to further understand the impact of this ST on the Townsville region. Full article

Early diagnosis is essential for the successful management of Burkholderia pseudomallei infection, but it cannot be achieved by the current gold standard culture technique. Therefore, this study aimed to develop a lateral flow immunoassay (LFIA) targeting B. pseudomallei capsular polysaccharide. The development was performed by varying nitrocellulose membrane reaction pads and chase buffers. The prototype LFIA is composed of Unisart CN95 and chase buffer containing tris-base, casein, and Surfactant 10G. The assay showed no cross-reactivity with E. coli, S. aureus, P. aeruginosa, and P. acne. The limit of detections (LODs) of the prototype LFIA was 10⁷ and 10⁶ CFU/mL B. pseudomallei in hemoculture medium and artificial urine, respectively. These LODs suggest that this prototype can detect melioidosis from positive hemoculture bottles but not straight from urine. Additionally, these LODs are still inferior compared to Active Melioidosis Detect (AMD^TM). Overall, this prototype holds the potential to be used clinically with hemoculture bottles. However, further improvements should be considered, especially for use with urine samples. Full article

Background and Objectives: Melioidosis is an infectious disease caused by Burkholderia pseudomallei, and it has a wide range of clinical symptoms. It is endemic in tropical areas, including Southeast Asia. Despite the availability of effective treatment, the mortality rate is still high, especially in patients presenting with septic shock. The aim of this study was to determine and explore clinical characteristics, microbiology, treatment outcomes, and factors associated with in-hospital mortality which could predict prognosis and provide a guide for future treatment. Materials and Methods: The population in this retrospective cohort study included all 262 patients with a diagnosis of melioidosis who were hospitalized at Surin Hospital, Surin, Thailand, from April 2014 to March 2017. We included patients older than 15 years with a positive culture for B. pseudomallei. Data regarding the clinical characteristics, microbiology, and treatment outcomes of the patients were collected and analyzed. The patients were divided into two groups dependent on outcome, specifically non-survival and survival. Logistic regression was performed to determine the risk factors associated with in-hospital mortality. Results: Out of the 262 patients with melioidosis during the study period, 117 (44.7%) patients died. The mean age was 57.2 ± 14.4 years, and 193 (73.7%) patients were male. The most common comorbidity was diabetes (123, 46.9%), followed by chronic kidney disease (35, 13.4%) and chronic liver disease (31, 11.8%). Four risk factors were found to be associated with in-hospital mortality, including age (adjusted odds ratio (aOR) 1.04, 95%CI: 1.01–1.07), respiration rate (aOR 1.18, 95%CI: 1.06–1.32), abnormal chest X-ray finding (aOR 4.79, 95%CI: 1.98–11.59), and bicarbonate levels (CO₂) (aOR 0.92, 95%CI: 0.85–0.99). Conclusions: Our study identified age, respiration rate, abnormal chest X-ray finding, and CO₂ levels are predictive factors associated with in-hospital mortality in melioidosis patients. Physicians should be aware of these factors, have access to aggressive treatment options, and closely monitor patients with these risk factors. Full article

Burkholderia are a group of Gram-negative bacteria that can cause a variety of diseases in at-risk populations. B. pseudomallei and B. mallei, the etiological agents of melioidosis and glanders, respectively, are the two clinically relevant members of the B. pseudomallei complex (Bpc). The development of vaccines against Bpc species has been accelerated in recent years, resulting in numerous promising subunits and glycoconjugate vaccines incorporating a variety of antigens. However, a second group of pathogenic Burkholderia species exists known as the Burkholderia cepacia complex (Bcc), a group of opportunistic bacteria which tend to affect individuals with weakened immunity or cystic fibrosis. To date, there have been few attempts to develop vaccines to Bcc species. Therefore, the primary goal of this review is to provide a broad overview of the various subunit antigens that have been tested in Bpc species, their protective efficacy, study limitations, and known or suspected mechanisms of protection. Then, we assess the reviewed Bpc antigens for their amino acid sequence conservation to homologous proteins found in Bcc species. We propose that protective Bpc antigens with a high degree of Bpc-to-Bcc sequence conservation could serve as components of a pan-Burkholderia vaccine capable of protecting against both disease-causing groups. Full article

Epetraborole (EBO) is a boron-containing inhibitor of bacterial leucyl-tRNA synthetase, with potent activity against nontuberculous mycobacteria (NTM) and Gram-negative bacteria, including Burkholderia pseudomallei. EBO is being developed for the treatment of NTM lung disease and melioidosis, administered in combination with other therapeutic agents in both diseases. Therefore, EBO and its major circulating metabolite M3 were evaluated in comprehensive drug–drug interaction (DDI) in vitro studies. The CYP inhibitory and substrate potential of EBO and M3 were assessed using hepatic microsomes. Stably transfected cells that expressed individual efflux or uptake transporters were used to determine whether EBO or M3 were substrates or inhibitors for these receptors. Stability studies indicated that EBO is a poor substrate for major CYP enzymes. Neither EBO nor M3 was a potent reversible or time-dependent inhibitor of major CYP enzymes. EBO was not an inducer of CYP1A2 mRNA, while it was a weak inducer of CYP2B6 and CYP3A4. EBO was a substrate only for OCT2. At clinically relevant concentrations, neither EBO nor M3 inhibited major human efflux or uptake transporters. Based on these data, at clinically relevant concentrations of EBO and M3, there is a low risk of victim or perpetrator DDI. Full article

Melioidosis, a severe tropical illness caused by Burkholderia pseudomallei, poses significant treatment challenges due to limited therapeutic options and the absence of effective vaccines. The pathogen’s intrinsic resistance to numerous antibiotics and propensity to induce sepsis during acute infections further complicate management strategies. Thus, exploring alternative methods for prevention and treatment is crucial. Monoclonal antibodies (mAbs) have emerged as a promising strategy for the prevention and treatment of infectious diseases. This study focused on generating three mAbs (13F1, 14G11, and 15D9) targeting hemolysin-coregulated protein 1 (Hcp1), a protein involved in the type VI secretion system cluster 1 (T6SS1) of B. pseudomallei. Notably, pretreatment with 13F1 mAb significantly reduced the intracellular survival of B. pseudomallei and inhibited the formation of macrophage-derived multinucleated giant cells (MNGCs). This protective effect was also observed in vivo. We identified a sequence of amino acids (Asp95-Leu114) within Hcp1 as the likely binding site for 13F1 mAb. In summary, our findings reveal that 13F1 mAb counteracts infection by targeting Hcp1, offering potential new targets and insights for melioidosis prevention. Full article

Central nervous system (CNS) melioidosis caused by Burkholderia pseudomallei is being increasingly reported. Because of the high mortality associated with CNS melioidosis, understanding the underlying mechanism of B. pseudomallei pathogenesis in the CNS needs to be intensively investigated to develop better therapeutic strategies against this deadly disease. The type VI secretion system (T6SS) is a multiprotein machine that uses a spring-like mechanism to inject effectors into target cells to benefit the infection process. In this study, the role of the T6SS accessory protein TagAB-5 in B. pseudomallei pathogenicity was examined using the human microglial cell line HCM3, a unique resident immune cell of the CNS acting as a primary mediator of inflammation. We constructed B. pseudomallei tagAB-5 mutant and complementary strains by the markerless allele replacement method. The effects of tagAB-5 deletion on the pathogenicity of B. pseudomallei were studied by bacterial infection assays of HCM3 cells. Compared with the wild type, the tagAB-5 mutant exhibited defective pathogenic abilities in intracellular replication, multinucleated giant cell formation, and induction of cell damage. Additionally, infection by the tagAB-5 mutant elicited a decreased production of interleukin 8 (IL-8) in HCM3, suggesting that efficient pathogenicity of B. pseudomallei is required for IL-8 production in microglia. However, no significant differences in virulence in the Galleria mellonella model were observed between the tagAB-5 mutant and the wild type. Taken together, this study indicated that microglia might be an important intracellular niche for B. pseudomallei, particularly in CNS infection, and TagAB-5 confers B. pseudomallei pathogenicity in these cells. Full article

This manuscript elucidates the occurrence of glanders in an asymptomatic mare from Brazil presenting positive Burkholderia mallei antibody titers. The diagnosis was established through a multi-pronged approach encompassing microbiological culture, mass spectrometry, and genome sequencing. The outbreak occurred in 2019 in Tatuí, São Paulo, Brazil, and the infected mare, despite displaying no clinical symptoms, had multiple miliary lesions in the liver, as well as intense catarrhal discharge in the trachea. Samples were collected from various organs and subjected to bacterial isolation, molecular detection, and identification. The strain was identified as B. mallei using PCR and confirmed by MALDI-TOF mass spectrometry. Whole-genome sequencing revealed a genome size of 5.51 Mb with a GC content of 65.8%, 5871 genes (including 4 rRNA and 53 tRNA genes), and 5583 coding DNA sequences (CDSs). Additionally, 227 predicted pseudogenes were detected. In silico analysis of different genomic loci that allow for differentiation with Burkholderia pseudomallei confirmed the identity of the isolate as B. mallei, in addition to the characteristic genome size. The BAC 86/19 strain was identified as lineage 3, sublineage 2, which includes other strains from Brazil, India, and Iran. The genome sequencing of this strain provides valuable information that can be used to better understand the pathogen and its epidemiology, as well as to develop diagnostic tools for glanders. Full article

Burkholderia pseudomallei, the causative agent of the disease melioidosis, has been isolated from the environment in 45 countries. The treatment of melioidosis is complex, requiring lengthy antibiotic regimens, which can result in the relapse of the disease following treatment cessation. It is important that novel therapies to treat infections with B. pseudomallei be assessed in appropriate animal models, and discussions regarding the different protocols used between laboratories are critical. A ‘deep dive’ was held in October 2020 focusing on the use of the BALB/c mouse model and the inhalational route of infection to evaluate new antibiotic therapies. Full article

The microbial pathogens Burkholderia pseudomallei and Bacillus anthracis are unrelated bacteria, yet both are the etiologic agents of naturally occurring diseases in animals and humans and are classified as Tier 1 potential biothreat agents. B. pseudomallei is the gram-negative bacterial agent of melioidosis, a major cause of sepsis and mortality globally in endemic tropical and subtropical regions. B. anthracis is the gram-positive spore-forming bacterium that causes anthrax. Infections acquired by inhalation of these pathogens are challenging to detect early while the prognosis is best; and they possess innate multiple antibiotic resistance or are amenable to engineered resistance. Previous studies showed that the early generation, rarely used aminocoumarin novobiocin was very effective in vitro against a range of highly disparate biothreat agents. The objective of the current research was to begin to characterize the therapeutic efficacy of novobiocin in mouse models of anthrax and melioidosis. The antibiotic was highly efficacious against infections by both pathogens, especially B. pseudomallei. Our results supported the concept that specific older generation antimicrobials can be effective countermeasures against infection by bacterial biothreat agents. Finally, novobiocin was shown to be a potential candidate for inclusion in a combined pre-exposure vaccination and post-exposure treatment strategy designed to target bacterial pathogens refractory to a single medical countermeasure. Full article

Burkholderia pseudomallei is a Gram-negative bacterium that causes melioidosis, a disease of humans and animals. It is primarily transmitted through direct contact with contaminated soil and surface water. The epidemiology of this pathogen in Africa, including Uganda, is largely unknown. The objectives of this study were to estimate the seroprevalence of B. pseudomallei in pigs slaughtered in central Uganda and to identify potential hotspots for this pathogen in the country. A total of 1035 pig sera were analyzed for serological responses to B. pseudomallei with type A and type B LPS using OPS type A and OPS type B ELISAs. Of the 1035 samples, 75 (7.25%, 95% CI: 5.8–9%) were seropositive to the OPS-A ELISA using a two standard deviations (SD) cutoff and 19 (1.84%, 95% CI: 1.2–2.9%) at 3 SD. For the OPS-B ELISA, 93/1035 (8.99%, 95% CI: 7.4–10.9%) were seropositive at the 2 SD cutoff, and 28/1035 (2.71%, 95% CI: 1.9–3.9%) at the 3 SD cutoff. Pigs slaughtered in central Uganda were exposed to B. pseudomallei, and there is a higher seroprevalence in the rainy months. Public health awareness campaigns about melioidosis may be needed. Full article