Publications by authors named "Ivan Yap"

Klebsiella pneumoniae is a Gram-negative Enterobacteriaceae that is classified by the World Health Organisation (WHO) as a Priority One ESKAPE pathogen. South and Southeast Asian countries are regions where both healthcare associated infections (HAI) and community acquired infections (CAI) due to extended-spectrum β-lactamase (ESBL)-producing and carbapenem-resistant K. pneumoniae (CRKp) are of concern.

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Resistant hypertension is a well-recognised clinical challenge. However, the definition and epidemiology of true resistant hypertension (RH) are less understood, especially in Asia. This cross-sectional study examined the prevalence of RH referred from primary care clinics based on various guidelines.

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Burkholderia pseudomallei (B. pseudomallei) is an intracellular pathogen that causes melioidosis, a life-threatening infection in humans. The bacterium is able to form small colony variants (SCVs) as part of the adaptive features in response to environmental stress.

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Introduction: Pneumonia is a leading cause of death in Malaysia. Whilst many studies have reported the aetiology of pneumonia in Western countries, the epidemiology of pneumonia in Malaysia remains poorly understood. As carriage is a prerequisite for disease, we sought to improve our understanding of the carriage and antimicrobial resistance (AMR) of respiratory tract pathogens in Malaysia.

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Emerging evidence has shown a link between the perturbations and development of the gut microbiota in infants with their immediate and long-term health. To better understand the assembly of the gut microbiota in preterm infants, faecal samples were longitudinally collected from the preterm (n = 19) and term (n = 20) infants from birth until month 12. 16S rRNA gene sequencing (n = 141) and metabolomics profiling (n = 141) using nuclear magnetic resonance spectroscopy identified significant differences between groups in various time points.

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Objective: Gut microbiome alterations in Parkinson disease (PD) have been reported repeatedly, but their functional relevance remains unclear. Fecal metabolomics, which provide a functional readout of microbial activity, have scarcely been investigated. We investigated fecal microbiome and metabolome alterations in PD, and their clinical relevance.

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Coffee is rich in antioxidant and has been shown to confer various health benefits. Here, we investigated the effect of single-dose coffee consumption in healthy human subjects. About 30 healthy volunteers were recruited and given a serving of sugar free black coffee.

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The gastrointestinal tract of humans and swine consist of a wide range of bacteria which interact with hosts metabolism. Due to the differences in co-evolution and co-adaptation, a large fraction of the gut microbiome is host-specific. In this study, we evaluated the effect of close human-animal interaction to the faecal metagenome and metabonome of swine, farmer and human control.

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Background: Resistance to colistin, the last line therapy for infections caused by multidrug-resistant Gram-negative bacteria, represents a major public health threat. Citrobacter freundii B9-C2 which was isolated from the stool of preterm neonate on the first week of life, displayed resistance to almost all major antibiotics, including colistin. Through whole genome sequencing (WGS), we characterised the genome features that underline the antibiotic-resistance phenotype of this isolate.

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Dengue fever is endemic in Malaysia, contributing to significant economic and health burden in the country. Aedes aegypti and Ae. albopictus are the main vectors of the dengue virus (DENV), which circulates in sylvatic and human transmission cycles and has been present in Malaysia for decades.

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Clinical manifestations of leptospirosis range from mild, common cold-like illness, to a life-threatening condition. The host immune response has been hypothesized to play a major role in leptospirosis outcome. Increased levels of inflammatory mediators, such as cytokines, may promote tissue damage that lead to increased disease severity.

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Article Synopsis
  • Cholera is caused by the bacterium Vibrio cholerae, which can form biofilms to protect itself and aid in infection by coaggregating with other bacteria like E. coli and Enterobacter cloacae.
  • A preliminary study showed that this coaggregation leads to significant biofilm formation, prompting further research using mice to examine its effects.
  • Although no major differences in mortality or fluid accumulation were observed, co-infections resulted in higher densities of V. cholerae and increased levels of certain immune responses, indicating that commensal bacteria may play a role in cholera development.
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The increasing prevalence of antibiotic resistant pathogens poses a serious threat to global health. However, less emphasis has been placed to co-relate the gene expression and metabolism of antibiotic resistant pathogens. This study aims to elucidate gene expression and variations in metabolism of multidrug resistant Klebsiella pneumoniae after exposure to antibiotics.

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Background: The giant amoebal viruses of Mimivirus and Marseillevirus are large DNA viruses and have been documented in water, soil, and sewage samples. The trend of discovering these giant amoebal viruses has been increasing throughout Asia with Japan, India, and Saudi Arabia being the latest countries to document the presence of these viruses. To date, there have been no reports of large amoebal viruses being isolated in South East Asia.

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Article Synopsis
  • The adoption of pneumococcal conjugate vaccines (PCVs) has significantly improved pneumonia prevention, but middle-income countries (MICs) are falling behind due to limited financial support and implementation issues.* -
  • A systematic review of 21 eligible studies found that lower middle-income countries (LMICs) have a notably higher PCV uptake (71%) compared to upper middle-income countries (UMICs) (48%), largely due to challenges following their graduation from GAVI support.* -
  • Key barriers identified include lack of data on disease burden, insufficient local expertise in economic evaluation, and costs associated with PCVs, with suggested solutions involving cost-effectiveness analyses, better disease evaluation, and ongoing vaccine impact monitoring.*
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The prevalence and antibiotic susceptibility of intestinal carriage of Gram-negative bacteria among preterm infants admitted to the neonatal intensive care unit (NICU) in a tertiary teaching hospital in Malaysia were determined. A total of 34 stool specimens were obtained from preterm infants upon admission and once weekly up to two weeks during hospitalization. The presumptive colonies of Escherichia coli and Klebsiella pneumoniae were selected for identification, antibiotic susceptibility testing, and subtyping by using pulsed-field gel electrophoresis (PFGE).

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Article Synopsis
  • The study investigates the prevalence of intestinal parasitic infections (IPIs) in two indigenous sub-ethnic groups in Malaysia (Temuan and Mah Meri), highlighting that previous research often overlooked polyparasitism and the diversity of cultural practices among different groups.
  • Conducted as a cross-sectional study, it involved collecting and analyzing faecal samples from 186 participants to identify infections and assessing risk factors through questionnaires regarding demographics and behaviors.
  • Results showed that trichuriasis was the most common infection in both groups, with the Temuan community presenting a prevalence of 64.2%, while Mah Meri had an even higher rate of 77.5%, indicating significant variations in infection rates between the two sub-eth
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Cryptococcus neoformans is an encapsulated basidiomycetous yeast commonly associated with pigeon droppings and soil. The opportunistic pathogen infects humans through the respiratory system and the metabolic implications of C. neoformans infection have yet to be explored.

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Heat shock proteins (Hsps) 60 and 70 are postulated as a potential drug target for toxoplasmosis due to its importance in the developmental and survival of Toxoplasma gondii (T. gondii). As of today, there have been no reports on three-dimensional (3D) structure of Hsp60 and Hsp70 deposited in the Brookhaven Protein Data Bank.

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Gut microbiota plays an important role in mammalian host metabolism and physiological functions. The functions are particularly important in young children where rapid mental and physical developments are taking place. Nevertheless, little is known about the gut microbiome and the factors that contribute to microbial variation in the gut of South East Asian children.

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Understanding the basal gut bacterial community structure and the host metabolic composition is pivotal for the interpretation of laboratory treatments designed to answer questions pertinent to host-microbe interactions. In this study, we report for the first time the underlying gut microbiota and systemic metabolic composition in BALB/c mice during the acclimatisation period. Our results showed that stress levels were reduced in the first three days of the study when the animals were subjected to repetitive handling daily but the stress levels were increased when handling was carried out at lower frequencies (weekly).

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In Malaysia, homosexuality is illegal; little is known about access to HIV prevention services among Malaysian men who have sex with men (MSM). We analysed PT Foundation outreach data to describe the profiles among MSM who accessed PT Foundation services and to examine factors associated with being aware of PT Foundation and having visited the organization. A survey was administered during weekly outreach throughout Kuala Lumpur from March-December 2012.

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The NMRI outbred mouse model is widely used for studying metabolic disease, toxicity, and infection, yet information regarding baseline metabolism of this murine strain is relatively sparse. Using different batches of female NMRI mice, we assessed the stability of the metabolic phenotype with increasing age and weight, and determined the influence of acclimatization on the metabolic profile of biofluids (urine, plasma, and faecal water). Differences in urinary concentrations of 3-ureidopropionate, 2-oxoisocaproate, trimethylamine, and glycine were detected between three batches of 9-week-old female NMRI mice using proton nuclear magnetic resonance ((1)H NMR) spectroscopy coupled with multivariate statistical analysis.

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