Assessing the national antibiotic surveillance data to identify burden for melioidosis in Malaysia

Objectives

A leading cause of morbidity and mortality in Southeast Asia, the epidemiological data on melioidosis disease occurrence and mortality in Malaysia is not comprehensive. The aim of this study is to determine the burden of melioidosis and assess the National Surveillance for Antibiotic Resistance (NSAR) data as a potential tool melioidosis surveilance in Malaysia.

Methods

We performed a retrospective analysis on the B. pseudomallei reposited data submitted to the NSAR network between January 2014 and December 2020. The data were screened for information on patient demographics and specimen types. Additional patient comorbidities and outcomes were drawn from parallel surveillance for bacteremic melioidosis.

Results

The average annual incidence rate of melioidosis between 2014-2020 was 3.41 per 100,000 population and was significantly different between states (P <0.001). The highest incidence was observed in Pahang at 11.33 per 100,000 population. Individuals of Malay ethnicity, from the states of Pahang, Johor, Perak, and Negeri Sembilan aged 40-49, who were diabetic and working in agriculture-related sectors had a higher risk of succumbing to the infection.

Conclusion

Assessing the NSAR data proved to be a useful tool for the determination of the incidence and socio-demographic risk factors attributed to melioidosis in Malaysia.

Impact of Bacillus species on Fe reduction of kaolin in bioleaching: surface, structural, and chemical studies

Conventional techniques to remove Fe impurities in kaolin typically involve high environmental impact and cost. Alternative methods have been focused on the use of bioleaching where Fe in kaolin is reduced with microorganisms. Early results established a noticeable effect of the bacteria on the redox state of Fe, but knowledge gaps persist such as details on the bacterial-kaolin interactions during attachment of bacteria onto kaolin surface, the metabolites produced by bacteria, and changes in Fe(II)/Fe(III) ion equilibria in solution. To bridge these gaps, this study was conducted to determine the detailed physicochemical changes in bacteria and kaolin during bioleaching through surface, structural, and chemical analysis. Bioleaching experiments were conducted for 10 days where each of the three Bacillus sp. was put in contact (at 9 × 10⁸ CFU) with 20 g of kaolin powder using 200 mL of 10 g/L glucose solution. All samples treated with bacteria showed increasing trends in Fe(III) reduction up until day 6 or 8 followed by a slight decrease towards the end of the ten-day period. Examination of scanning electron microscope (SEM) images suggests that bacterial activity damaged the edges of kaolin particles during bioleaching. Ion chromatography (IC) results showed that during bioleaching, Bacillus sp. produced organic acids such as lactic acid, formic acid, malic acid, acetic acid, and succinic acid. EDS analysis of kaolin before and after bioleaching showed Fe removal efficiencies of up to 65.3%. Analyses of color properties of kaolin before and after bioleaching showed an improvement in whiteness index of up to 13.6%. KEY POINTS: • Dissolution of iron oxides by Bacillus species proven with phenanthroline analysis. • Organic acid type and concentration unique to species detected during bioleaching. • Whiteness index of kaolin is improved after bioleaching.

Perbandingan Penghasilan Siderofor daripada Bacillus aryabhattai, Bacillus megaterium dan Bacillus cereus

Besi merupakan unsur yang penting bagi proses metabolisme organisma seperti kitar asid trikarboksilik, pengangkutan elektron dan fosforilasi oksidatif. Walau bagaimanapun, sumber besi di persekitaran luar sentiasa berada dalam bentuk kompleks yang tidak tersedia untuk pengambilan terus. Bagi mengatasi pengehadan besi, mikroorganisma berupaya untuk menghasilkan siderofor, sejenis pengkelat Fe(III) yang berafinan tinggi. Salah satu genus bakteria yang dapat menghasilkan siderofor adalah Bacillus. Dalam kajian ini, penghasilan dan keupayaan pengkompleksan siderofor Bacillus cereus, Bacillus megaterium dan Bacillus aryabhattai ditentukan melalui asai piring agar dan cecair krom azurol S (CAS). Kesan sumber karbon (glukosa, maltosa dan gliserol) ke atas penghasilan siderofor oleh Bacillus turut dikaji. Hasil kajian telah menunjukkan bahawa B. cereus yang dikulturkan dalam kaldu LB berupaya untuk menghasilkan siderofor yang tertinggi berbanding B. aryabhattai dan B. megaterium. Siderofor yang dihasilkan oleh ketiga-tiga spesies berupaya untuk berkompleks dengan Mn(II), Zn(II) dan Cu(II). Hasil kajian turut menunjukkan pengkulturan dengan maltosa telah memberikan penghasilan siderofor yang paling tinggi bagi B. aryabhattai dan B. megaterium.

Melioidosis in Malaysia: Incidence, Clinical Challenges, and Advances in Understanding Pathogenesis

Malaysia is an endemic hot spot for melioidosis; however, a comprehensive picture of the burden of disease, clinical presentations, and challenges faced in diagnosis and treatment of melioidosis is not available. This review provides a nonexhaustive overview of epidemiological data, clinical studies, risk factors, and mortality rates from available literature and case reports. Clinical patterns of melioidosis are generally consistent with those from South and Southeast Asia in terms of common primary presentations with diabetes as a major risk factor. Early diagnosis and appropriate management of Malaysian patients is a key limiting factor, which needs to be addressed to reduce serious complications and high mortality and recurrence rates. Promoting awareness among the local healthcare personnel is crucial to improving diagnostics and early treatment, as well as educating the Malaysian public on disease symptoms and risk factors. A further matter of urgency is the need to make this a notifiable disease and the establishment of a national melioidosis registry. We also highlight local studies on the causative agent, Burkholderia pseudomallei, with regards to bacteriology and identification of virulence factors as well as findings from host⁻pathogen interaction studies. Collectively, these studies have uncovered new correlations and insights for further understanding of the disease.

Transcriptome analysis of Burkholderia pseudomallei T6SS identifies Hcp1 as a potential serodiagnostic marker

Burkholderia pseudomallei, the causative agent of melioidosis, is able to survive extreme environments and utilizes various virulence factors for survival and pathogenicity. To compete and survive within these different ecological niches, B. pseudomallei has evolved specialized pathways, including the Type VI secretion systems (T6SSs), that have a role in pathogenesis as well as interbacterial interactions. We examined the expression profile of B. pseudomallei T6SS six gene clusters during infection of U937 macrophage cells. T6SS-5 was robustly transcribed while the other five clusters were not significantly regulated proposing the utility of T6SS-5 as a potential biomarker of exposure to B. pseudomallei. Transcription of T6SS regulators VirAG and BprB was also not significant during infection when compared to bacteria grown in culture. Guided by these findings, three highly expressed T6SS genes, tssJ-4, hcp1 and tssE-5, were expressed as recombinant proteins and screened against melioidosis patient sera by western analysis and ELISA. Only Hcp1 was reactive by both types of analysis. The recombinant Hcp1 protein was further evaluated against a cohort of melioidosis patients (n = 32) and non-melioidosis individuals (n = 20) sera and the data clearly indicates a higher sensitivity (93.7%) and specificity (100%) for Hcp1 compared to bacterial lysate. The detection of anti-Hcp1 antibodies in patients' sera indicating the presence of B. pseudomallei highlights the potential of Hcp1 to be further developed as a serodiagnostic marker for melioidosis.

Burkholderia pseudomallei transcriptional adaptation in macrophages

Background

Burkholderia pseudomallei is a facultative intracellular pathogen of phagocytic and non-phagocytic cells. How the bacterium interacts with host macrophage cells is still not well understood and is critical to appreciate the strategies used by this bacterium to survive and how intracellular survival leads to disease manifestation.

Results

Here we report the expression profile of intracellular B. pseudomallei following infection of human macrophage-like U937 cells. During intracellular growth over the 6 h infection period, approximately 22 % of the B. pseudomallei genome showed significant transcriptional adaptation. B. pseudomallei adapted rapidly to the intracellular environment by down-regulating numerous genes involved in metabolism, cell envelope, motility, replication, amino acid and ion transport system and regulatory function pathways. Reduced expression in catabolic and housekeeping genes suggested lower energy requirement and growth arrest during macrophage infection, while expression of genes encoding anaerobic metabolism functions were up regulated. However, whilst the type VI secretion system was up regulated, expression of many known virulence factors was not significantly modulated over the 6hours of infection.

Conclusions

The transcriptome profile described here provides the first comprehensive view of how B. pseudomallei survives within host cells and will help identify potential virulence factors and proteins that are important for the survival and growth of B. pseudomallei within human cells.

Cloning, purification and crystallographic analysis of a hypothetical protein, BPSL1549, from Burkholderia pseudomallei

Burkholderia pseudomallei BPSL1549, a putative protein of unknown function, has been overexpressed in Escherichia coli, purified and subsequently crystallized by the hanging-drop vapour-diffusion method using PEG as a precipitant to give crystals with overall dimensions of 0.15 × 0.15 × 0.1 mm. Native data were collected to 1.47 Å resolution at the European Synchrotron Radiation Facility (ESRF). The crystals belonged to space group P2(1)2(1)2(1), with unit-cell parameters a = 37.1, b = 45.4, c = 111.9 Å and with a single polypeptide chain in the asymmetric unit.