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Melioidosis : Not Gone, Not Forgotten
Get PDFMELIOIDOSIS: NOT GONE, NOT FORGOTTEN
Podin, Yuwana
Institute of Health and Community Medicine, Universiti Malaysia Sarawak, 94300 Kota Samarahan, Sarawak, Malaysia.
ABSTRACT
Burkholderia pseudomallei, a saprophytic Gram-negative environmental bacteria which causes melioidosis, was first described in what was known then as Burma in 1911. It is able to survive in extreme pH, temperature and even low nutrient conditions, rendering it a hardy environmental bacteria. Ever since it was first reported, melioidosis which was initially only known endemically in the tropical and sub-tropical regions has since been reported in more countries in other regions. Based on a study published in 2014 which collated and analyzed historical data, there is an estimation of 165,000 human melioidosis cases annually worldwide where 89,000 are potentially fatal. Yet, melioidosis remains underreported in the 45 endemic countries in addition to the 34 countries with newly reported cases. In Malaysia, melioidosis is yet to be gazetted as a notifiable disease under the Prevention and Control of Infectious Diseases Act 1988. Hence, despite approximately 1,000 cases reported annually nationwide with mortality rate of up to 55%, the true incidence and burden of disease of melioidosis in the country remains to be determined. In Sarawak of Malaysian Borneo, melioidosis has been recognized as an endemic disease especially in the central regions including Kapit and Bintulu, caused predominantly by the unique B. pseudomallei strain of ST881 which is unconventionally susceptible to aminoglycoside and macrolide. Contrary to what is known thus far, the medical and scientific communities were shocked by the recently reported outbreak of melioidosis in Kota Samarahan; which raises the question of how widespread melioidosis is in Sarawak and the timeliness of environmental investigation for a non-notifiable disease.
Apart from epidemiological perspective, since B. pseudomallei is known to be resistant to a myriad of antibiotics, the biphasic treatment regime of melioidosis is important in preventing recurrent infection. Due to this too that antibiotics susceptibility continues to be monitored in the clinical and laboratory setting.
The aim of this paper is to present the latest research updates on melioidosis which provide new insights into the biogeography of the disease and the antibiotics susceptibility work in Sarawak. It is hoped that this paper is able to inform public health that melioidosis is still and will not be forgotten, or else we will continue to be haunted by the bacteria from the underground.
Keywords Melioidosis, Burkholderia pseudomallei, Sarawak, Malaysian Borneo
Corresponding author
Yuwana Podin (PhD),
Senior Lecturer,
Institute of Health and Community Medicine, Universiti Malaysia Sarawak, 94300 Kota Samarahan, Sarawak, Malaysia.
[email protected]
Studies on the epidemiology of neurotropic viruses in Sarawak : 1998 to 2003
Get PDFHFMD and infection of the CNS were recognized as important diseases to be studied in Sarawak due to the serious health implications they pose. Following the realization, two surveillance programmes were set up in 1998 to monitor these diseases in Sarawak. This study reports the findings of a six-year observation from 1998 to 2003 of the two surveillance programmes, including a case-finding study in Bintulu during an outbreak of HFMD in 2000. HEV71-related HFMD outbreaks were found to occur in three-year interval
The epidemiology and molecular characterization of Burkholderia pseudomallei in Malaysian Borneo
Get PDFMelioidosis is a potentially fatal disease caused by Burkholderia pseudomallei
which is endemic in Malaysian Borneo. The general aim of this study is to
elucidate the molecular epidemiology of B. pseudomallei in Malaysian Borneo.
Consistent with the Wallace line theory of separation, genotyping showed
Malaysian Borneo clinical B. pseudomallei isolates were more related to
Southeast Asian strains than to Australian strains. Whole genome sequencing
demonstrated that B. pseudomallei from Sarawak were very closely related to
each other. Biochemical testing using VITEK 2 revealed that 25% of B.
pseudomallei from Malaysian Borneo were misidentified as B. cepacia,
suggesting that specificity of that identification system is regionally dependent. A
major and unexpected finding was that 88% of Sarawak B. pseudomallei were
gentamicin susceptible, with these B. pseudomallei being restricted to multilocus
sequence type ST881 and its single locus variant ST997. A novel nonsynonymous
mutation was identified within amrB, an essential component of the
AmrAB-OprA multi-drug efflux pump. Reversion of the mutation to the wild-type
sequence confirmed the role of this mutation in conferring aminoglycoside and
macrolide sensitivity. No environmental B. pseudomallei were isolated from
Sarawak but other Burkholderia species were isolated, prompting the formulation
of hypotheses to explain the lack of environmental B. pseudomallei. Although
inconclusive, experiments showed antagonistic activities by other environmental
Burkholderia spp. recovered from environmental sampling studies towards B.
pseudomallei and also that gentamicin susceptible B. pseudomallei were slightly
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less robust than gentamicin resistant strains in competing with other soil
microorganisms. This thesis contributed to the understanding of the population
structure of B. pseudomallei in Malaysian Borneo, Southeast Asia and globally.
The discovery of gentamicin susceptibility in Sarawak B. pseudomallei has
significant implications for laboratory diagnosis and environmental sampling of B.
pseudomallei in Malaysian Borneo and potentially in other melioidosis endemic
regions. Although the exact distributions, quantification and potential
environmental hazards and implications of B. pseudomallei in Malaysian Borneo
remain uncertain, these studies have led to important research questions now to be
explored. Most immediate is further searching for the proposed existence of an as
yet unidentified localized niche of B. pseudomallei in Malaysian Borneo
Chlorine-Based Disinfectant : How Effective Is It Against Burkholderia Species?
Get PDFThe members of the Burkholderia genus are Gram-negative and are mostly environmental bacteria that are either beneficial or pathogenic to humans, animals and plants. Burkholderia pseudomallei is one of the more well-known members of the genus which is pathogenic to humans and animals manifesting as melioidosis. B. pseudomallei possesses two chromosomes where Chromosome 1 holds housekeeping genes whereas Chromosome 2 carries genes for accessory functions such as adaptations to atypical conditions, iron homeostasis, secondary metabolism, regulation and horizontal gene transfer. These genes render the bacteria’s ability to adapt to harsh and nutrient-limited conditions, and to be resistant to a myriad of antibiotics. Due to these characteristics and its potential to be aerolized, B. pseudomallei has been categorized as a Tier 1 select agent in the United States of America by the Center for Disease Control and Prevention. This influences the biosafety considerations including the sterilization methods of B. pseudomallei in laboratories. Chlorine-based disinfectants are commonly used in laboratories and even as drinking-water disinfectants due to its affordability. Previous studies have shown a variation of chlorine efficacies on different microorganisms under various methodologies employed. In this simple study, the effectiveness of chlorine-based disinfectant was evaluated on selected strains of Burkholderia species and B. pseudomallei of Sarawak origin under a range of concentrations, contact time and shelf-lives. Results suggested that minimal inhibitory concentration and shelf-life of chlorine solutions are vital in the inactivation of Burkholderia species and Burkholderia pseudomallei where variations of efficacy for different strains were observed. The findings of this study highlights the importance of the principles of biosafety being applied into daily laboratory practices.
Keywords: Sterilization method, disinfectants, chlorine, Burkholderia pseudomalle
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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