Displaying publications 1 - 20 of 114 in total

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  1. Whole-genome sequence analysis and exploration of the zoonotic potential of a rat-borne Bartonella elizabethae
    Tay ST, Kho KL, Wee WY, Choo SW
    Acta Trop, 2016 Mar;155:25-33.
    PMID: 26658020 DOI: 10.1016/j.actatropica.2015.11.019
    Bartonella elizabethae has been known to cause endocarditis and neuroretinitis in humans. The genomic features and virulence profiles of a B. elizabethae strain (designated as BeUM) isolated from the spleen of a wild rat in Kuala Lumpur, Malaysia are described in this study. The BeUM strain has a genome size of 1,932,479bp and GC content of 38.3%. There is a high degree of conservation between the genomes of strain BeUM with B. elizabethae type strains (ATCC 49927 and F9251) and a rat-borne strain, Re6043vi. Of 2137 gene clusters identified from B. elizabethae strains, 2064 (96.6%) are indicated as the core gene clusters. Comparative genome analysis of B. elizabethae strains reveals virulence genes which are known in other pathogenic Bartonella species, including VirB2-11, vbhB2-B11, VirD4, trw, vapA2-5, hbpA-E, bepA-F, bepH, badA/vomp/brp, ialB, omp43/89 and korA-B. A putative intact prophage has been identified in the strain BeUM, in addition to a 8kb pathogenicity island. The whole genome analysis supports the zoonotic potential of the rodent-borne B. elizabethae, and provides basis for future functional and pathogenicity studies of B. elizabethae.
  2. Fulltext Growth inhibition of Candida species by Wickerhamomyces anomalus mycocin and a lactone compound of Aureobasidium pullulans
    Tay ST, Lim SL, Tan HW
    BMC Complement Altern Med, 2014;14:439.
    PMID: 25380692 DOI: 10.1186/1472-6882-14-439
    The increasing resistance of Candida yeasts towards antifungal compounds and the limited choice of therapeutic drugs have spurred great interest amongst the scientific community to search for alternative anti-Candida compounds. Mycocins and fungal metabolites have been reported to have the potential for treatment of fungal infections. In this study, the growth inhibition of Candida species by a mycocin produced by Wickerhamomyces anomalus and a lactone compound from Aureobasidium pullulans were investigated.
  3. Fulltext Lung-infiltrating T helper 17 cells as the major source of interleukin-17A production during pulmonary Cryptococcus neoformans infection
    Movahed E, Cheok YY, Tan GMY, Lee CYQ, Cheong HC, Velayuthan RD, et al.
    BMC Immunol, 2018 Nov 08;19(1):32.
    PMID: 30409128 DOI: 10.1186/s12865-018-0269-5
    BACKGROUND: IL-17A has emerged as a key player in the pathologies of inflammation, autoimmune disease, and immunity to microbes since its discovery two decades ago. In this study, we aim to elucidate the activity of IL-17A in the protection against Cryptococcus neoformans, an opportunistic fungus that causes fatal meningoencephalitis among AIDS patients. For this purpose, we examined if C. neoformans infection triggers IL-17A secretion in vivo using wildtype C57BL/6 mice. In addition, an enhanced green fluorescence protein (EGFP) reporter and a knockout (KO) mouse models were used to track the source of IL-17A secretion and explore the protective function of IL-17A, respectively.

    RESULTS: Our findings showed that in vivo model of C. neoformans infection demonstrated induction of abundant IL-17A secretion. By examining the lung bronchoalveolar lavage fluid (BALF), mediastinal lymph node (mLN) and spleen of the IL-17A-EGFP reporter mice, we showed that intranasal inoculation with C. neoformans promoted leukocytes lung infiltration. A large proportion (~ 50%) of the infiltrated CD4+ helper T cell population secreted EGFP, indicating vigorous TH17 activity in the C. neoformans-infected lung. The infection study in IL-17A-KO mice, on the other hand, revealed that absence of IL-17A marginally boosted fungal burden in the lung and accelerated the mouse death.

    CONCLUSION: Therefore, our data suggest that IL-17A is released predominantly from TH17 cells in vivo, which plays a supporting role in the protective immunity against C. neoformans infection.

  4. Fulltext Prevalence and molecular heterogeneity of Bartonella bovis in cattle and Haemaphysalis bispinosa ticks in Peninsular Malaysia
    Kho KL, Koh FX, Jaafar T, Nizam QN, Tay ST
    BMC Vet Res, 2015;11:153.
    PMID: 26179499 DOI: 10.1186/s12917-015-0470-1
    Bartonellosis is an emerging zoonotic infection responsible for a variety of clinical syndromes in humans and animals. Members of the genus Bartonella exhibit high degrees of genetic diversity and ecologic plasticity. The infection is usually transmitted to animals and humans through blood-feeding arthropod vectors such as fleas, lice, ticks and sandflies. This study was conducted to investigate the prevalence of Bartonella species in 184 beef cattle, 40 dairy cattle, 40 sheep and 40 goats in eight animal farms across Peninsular Malaysia. Bartonella-specific PCR assays and sequence analysis of partial fragments of the citrate synthase gene were used for detection and identification of B. bovis. Isolation of B. bovis was attempted from PCR-positive blood samples. Molecular heterogeneity of the isolates was investigated based on sequence analysis of gltA, ITS, rpoB genes, ERIC-PCR, as well as using an established multilocus sequence typing (MLST) method. The carriage rate of B. bovis in ticks was also determined in this study.
  5. Fulltext Molecular analysis of ciprofloxacin resistance mechanisms in Malaysian ESBL-producing Klebsiella pneumoniae isolates and development of mismatch amplification mutation assays (MAMA) for rapid detection of gyrA and parC mutations
    Al-Marzooq F, Mohd Yusof MY, Tay ST
    Biomed Res Int, 2014;2014:601630.
    PMID: 24860827 DOI: 10.1155/2014/601630
    Ninety-three Malaysian extended-spectrum β-lactamase (ESBL)-producing Klebsiella pneumoniae isolates were investigated for ciprofloxacin resistance. Two mismatch amplification mutation (MAMA) assays were developed and used to facilitate rapid detection of gyrA and parC mutations. The isolates were also screened for plasmid-mediated quinolone resistance (PMQR) genes including aac(6')-Ib-cr, qepA, and qnr. Ciprofloxacin resistance (MICs 4- ≥ 32  μ g/mL) was noted in 34 (37%) isolates, of which 33 isolates had multiple mutations either in gyrA alone (n = 1) or in both gyrA and parC regions (n = 32). aac(6')-Ib-cr was the most common PMQR gene detected in this study (n = 61), followed by qnrB and qnrS (n = 55 and 1, resp.). Low-level ciprofloxacin resistance (MICs 1-2  μ g/mL) was noted in 40 (43%) isolates carrying qnrB accompanied by either aac(6')-Ib-cr (n = 34) or a single gyrA 83 mutation (n = 6). Ciprofloxacin resistance was significantly associated with the presence of multiple mutations in gyrA and parC regions. While the isolates harbouring gyrA and/or parC alteration were distributed into 11 PFGE clusters, no specific clusters were associated with isolates carrying PMQR genes. The high prevalence of ciprofloxacin resistance amongst the Malaysian ESBL-producing K. pneumoniae isolates suggests the need for more effective infection control measures to limit the spread of these resistant organisms in the hospital.
  6. Synthesis and Staphylococcus aureus biofilm inhibitory activity of indolenine-substituted pyrazole and pyrimido[1,2-b]indazole derivatives
    Yap CH, Ramle AQ, Lim SK, Rames A, Tay ST, Chin SP, et al.
    Bioorg Med Chem, 2023 Nov 15;95:117485.
    PMID: 37812886 DOI: 10.1016/j.bmc.2023.117485
    Staphylococcus aureus is a highly adaptable opportunistic pathogen that can form biofilms and generate persister cells, leading to life-threatening infections that are difficult to treat with antibiotics alone. Therefore, there is a need for an effective S. aureus biofilm inhibitor to combat this public health threat. In this study, a small library of indolenine-substituted pyrazoles and pyrimido[1,2-b]indazole derivatives were synthesised, of which the hit compound exhibited promising antibiofilm activities against methicillin-susceptible S. aureus (MSSA ATCC 29213) and methicillin-resistant S. aureus (MRSA ATCC 33591) at concentrations significantly lower than the planktonic growth inhibition. The hit compound could prevent biofilm formation and eradicate mature biofilms of MSSA and MRSA, with a minimum biofilm inhibitory concentration (MBIC50) value as low as 1.56 µg/mL and a minimum biofilm eradication concentration (MBEC50) value as low as 6.25 µg/mL. The minimum inhibitory concentration (MIC) values of the hit compound against MSSA and MRSA were 50 µg/mL and 25 µg/mL, respectively, while the minimum bactericidal concentration (MBC) values against MSSA and MRSA were > 100 µg/mL. Preliminary structure-activity relationship analysis reveals that the fused benzene ring and COOH group of the hit compound are crucial for the antibiofilm activity. Additionally, the compound was not cytotoxic to human alveolar A549 cells, thus highlighting its potential as a suitable candidate for further development as a S. aureus biofilm inhibitor.
  7. Expression of recombinant proteins of Orientia tsutsugamushi and their applications in the serodiagnosis of scrub typhus
    Tay ST, Rohani MY, Ho TM, Devi S
    Diagn Microbiol Infect Dis, 2002 Oct;44(2):137-42.
    PMID: 12458119
    In this study, recombinant proteins that encompassed the AD I-AD III regions of 56 kDa immunodominant gene of 2 Orientia tsutsugamushi (OT) serotypes; Gilliam and TA763 were expressed in Escherichia coli. Both recombinant proteins exhibited serologic cross-reactivity with the rabbit antisera against various OT serotypes, as evaluated by enzyme-linked immunosorbent assay (ELISA), but not against other rickettsial species, including Rickettsia typhi, R. prowazekii and TT118 SFG rickettsiae. The feasibility of using the recombinant proteins as a diagnostic reagent was further evaluated by ELISA using sera from blood donors and scrub typhus patients. The results suggested a higher affinity of the antihuman IgM than IgG with both recombinant proteins. The IgM ELISA findings were agreeable with the results of indirect immunoperoxidase (IIP) assay especially with sera of high antibody (1:1600). However, more than one antigen are probably needed for development of an effective assay for serodiagnosis of scrub typhus in endemic areas.
  8. Fulltext Rickettsial infections in monkeys, Malaysia
    Tay ST, Koh FX, Kho KL, Sitam FT
    Emerg Infect Dis, 2015 Mar;21(3):545-7.
    PMID: 25695615 DOI: 10.3201/eid2103.141457
  9. Fulltext Rickettsial seropositivity in the indigenous community and animal farm workers, and vector surveillance in Peninsular Malaysia
    Kho KL, Koh FX, Hasan LI, Wong LP, Kisomi MG, Bulgiba A, et al.
    Emerg Microbes Infect, 2017 Apr 12;6(4):e18.
    PMID: 28400593 DOI: 10.1038/emi.2017.4
    Rickettsioses are emerging zoonotic diseases that are often neglected in many countries in Southeast Asia. Rickettsial agents are transmitted to humans through exposure to infected arthropods. Limited data are available on the exposure of indigenous community and animal farm workers to the aetiological agents and arthropod vectors of rickettsioses in Peninsular Malaysia. Serological analysis of Rickettsia conorii and Rickettsia felis was performed for 102 individuals from the indigenous community at six rural villages and 87 workers from eight animal farms in Peninsular Malaysia in a cross-sectional study. The indigenous community had significantly higher seropositivity rates for R. conorii (P<0.001) and R. felis (P<0.001), as compared to blood donors from urban (n=61). Similarly, higher seropositivity rates for R. conorii (P=0.046) and R. felis (P<0.001) were noted for animal farm workers, as compared to urban blood donors. On the basis of the sequence analysis of gltA, ompA and ompB, various spotted fever group rickettsiae closely related to R. raoultii, R. heilongjiangensis, R. felis-like organisms, R. tamurae, Rickettsia sp. TCM1, R. felis, Rickettsia sp. LON13 and R. hulinensis were identified from tick/flea samples in animal farms, indigenous villages and urban areas. This study describes rickettsial seropositivity of the Malaysian indigenous community and animal farm workers, and provides molecular evidence regarding the presence of rickettsial agents in ticks/fleas infesting domestic animals in Peninsular Malaysia.
  10. Fulltext Correction: First isolation and identification of Cystobasidium calyptogenae from the oral samples of an elderly patient presenting with angular cheilitis
    Karajacob AS, Goh JPE, Kallarakkal TG, Tay ST
    Eur J Med Res, 2022 Dec 06;27(1):277.
    PMID: 36471451 DOI: 10.1186/s40001-022-00884-9
  11. Prevalence of plasmid-mediated qnr determinants and gyrase alteration in Klebsiella pneumoniae isolated from a university teaching hospital in Malaysia
    Saiful Anuar AS, Mohd Yusof MY, Tay ST
    Eur Rev Med Pharmacol Sci, 2013 Jul;17(13):1744-7.
    PMID: 23852897
    The ciprofloxacin resistance of Klebsiella (K.) pneumoniae is mediated primarily through alterations in type II topoisomerase (gyrA) gene and plasmid-mediated quinolone resistance-conferring genes (qnr). This study aimed to define the prevalence of plasmid-mediated quinolone resistance-conferring genes (qnr) and type II topoisomerase (gyrA) alterations of a population of ciprofloxacin-resistant (n = 21), intermediate (n = 8), and sensitive (n = 18) K. pneumoniae isolates obtained from a teaching hospital at Kuala Lumpur, Malaysia.
  12. First characterization of bla(VIM-11) cassette-containing integron in metallo-beta-lactamase producing Pseudomonas aeruginosa in Malaysia
    Khosravi Y, Tay ST, Vadivelu J
    Eur Rev Med Pharmacol Sci, 2010 Nov;14(11):999-1000.
    PMID: 21284350
  13. Fulltext Nocardia kroppenstedtii: a rare pathogen isolated from the spinal vertebral abscess of a patient on long-term immunosuppressive therapy
    Tay ST, Wong PL, Chiu CK, Tang SN, Lee JL, Hamdan NW, et al.
    Eur Rev Med Pharmacol Sci, 2021 01;25(2):605-608.
    PMID: 33577013 DOI: 10.26355/eurrev_202101_24618
    OBJECTIVE: Nocardia kroppenstedtii was isolated from the spinal vertebral abscess of a 78-year-old patient presenting with mid-thoracic pain and bilateral lower limb weakness and numbness. The patient was on long-term immunosuppressive therapy with steroids for underlying autoimmune hemolytic anemia. Investigations showed a T5 pathological fracture and vertebra plana with the erosion of the superior and inferior endplates. There was evidence of paraspinal collection from the T4-T6 vertebrae with an extension into the spinal canal. Analysis of Nocardia 16S rRNA (99.9%, 1395/1396 nt) and secA1 gene (99.5%, 429/431 nt) fragments showed the highest sequence similarity with Nocardia kroppenstedtii type strain (DQ157924), and next with Nocardia farcinica (Z36936). The patient was treated with intravenous carbapenem and oral trimethoprim-sulfamethoxazole for four weeks, followed by another six months of oral trimethoprim-sulfamethoxazole. Despite the improvement of neurological deficits, the patient required assistive devices to ambulate at discharge. This study reports the first isolation of N. kroppenstedtii from the spinal vertebral abscess of a patient from Asia. Infections caused by N. kroppenstedtii may be underdiagnosed as the bacterium can be misidentified as N. farcinica in the absence of molecular tests in the clinical laboratory.
  14. Surgical site infection and development of antimicrobial sutures: a review
    Chua RAHW, Lim SK, Chee CF, Chin SP, Kiew LV, Sim KS, et al.
    Eur Rev Med Pharmacol Sci, 2022 Feb;26(3):828-845.
    PMID: 35179749 DOI: 10.26355/eurrev_202202_27991
    Sutures are used to facilitate wound healing and play an important role in ensuring the success of surgical interventions in healthcare facilities. Suture-associated surgical site infection (SSI) may develop when bacterial contaminants colonize the suture surface and establish biofilms that are highly resistant to antibiotic treatment. The outcome of SSI affects postoperative care, leading to high rates of morbidity and mortality, prolonged hospitalization, and increased financial burden. Antimicrobial sutures coated with antiseptics such as triclosan and chlorhexidine have been used to minimize the occurrence of SSI. However, as the efficacy of antiseptic-based sutures may be affected due to the emergence of resistant strains, new approaches for the development of alternative antimicrobial sutures are necessary. This review provides an update and outlook of various approaches in the design and development of antimicrobial sutures. Attaining a zero SSI rate will be possible with the advancement in suturing technology and implementation of good infection control practice in clinical settings.
  15. Review: antimicrobial properties of allicin used alone or in combination with other medications
    Choo S, Chin VK, Wong EH, Madhavan P, Tay ST, Yong PVC, et al.
    Folia Microbiol (Praha), 2020 Jun;65(3):451-465.
    PMID: 32207097 DOI: 10.1007/s12223-020-00786-5
    Garlic (Allium sativum L.) is a well-known spice widely utilised for its medicinal properties. There is an extensive record of the many beneficial health effects of garlic which can be traced back to as early as the ancient Egyptian era. One of the most studied properties of garlic is its ability to cure certain ailments caused by infections. In the 1940s, the antimicrobial activities exhibited by garlic were first reported to be due to allicin, a volatile compound extracted from raw garlic. Since then, allicin has been widely investigated for its putative inhibitory activities against a wide range of microorganisms. Allicin has demonstrated a preference for targeting the thiol-containing proteins and/or enzymes in microorganisms. It has also demonstrated the ability to regulate several genes essential for the virulence of microorganisms. Recently, it was reported that allicin may function better in combination with other antimicrobials compared to when used alone. When used in combination with antibiotics or antifungals, allicin enhanced the antimicrobial activities of these substances and improved the antimicrobial efficacy. Hence, it is likely that combination therapy of allicin with additional antimicrobial drug(s) could serve as a viable alternative for combating rising antimicrobial resistance. This review focuses on the antimicrobial activities exhibited by allicin alone as well as in combination with other substances. The mechanisms of action of allicin elucidated by some of the studies are also highlighted in the present review in order to provide a comprehensive overview of this versatile bioactive compound and the mechanistic evidence supporting its potential use in antimicrobial therapy.
  16. Fulltext Triclosan Demonstrates Synergic Effect with Amphotericin B and Fluconazole and Induces Apoptosis-Like Cell Death in Cryptococcus neoformans
    Movahed E, Tan GM, Munusamy K, Yeow TC, Tay ST, Wong WF, et al.
    Front Microbiol, 2016;7:360.
    PMID: 27047474 DOI: 10.3389/fmicb.2016.00360
    Cryptococcus neoformans is an opportunistic fungus that causes fatal meningoencephalitis especially in AIDS patients. There is an increasing need for discovery of new anti-cryptococcal drugs due to emergence of resistance cases in recent years. In this study, we aim to elucidate the antifungal effect of triclosan against C. neoformans.
  17. Transcriptome analysis of Burkholderia pseudomallei SCV reveals an association with virulence, stress resistance and intracellular persistence
    Al-Maleki AR, Vellasamy KM, Mariappan V, Venkatraman G, Tay ST, Vadivelu J
    Genomics, 2020 01;112(1):501-512.
    PMID: 30980902 DOI: 10.1016/j.ygeno.2019.04.002
    Differences in expression of potential virulence and survival genes were associated with B. pseudomallei colony morphology variants. Microarray was used to investigate B. pseudomallei transcriptome alterations among the wild type and small colony variant (SCV) pre- and post-exposed to A549 cells. SCV pre- and post-exposed have lower metabolic requirements and consume lesser energy than the wild type pre- and post-exposed to A549. However, both the wild type and SCV limit their metabolic activities post- infection of A549 cells and this is indicated by the down-regulation of genes implicated in the metabolism of amino acids, carbohydrate, lipid, and other amino acids. Many well-known virulence and survival factors, including T3SS, fimbriae, capsular polysaccharides and stress response were up-regulated in both the wild type and SCV pre- and post-exposed to A549 cells. Microarray analysis demonstrated essential differences in bacterial response associated with virulence and survival pre- and post-exposed to A549 cells.
  18. Fulltext Physician's Perspectives on Factors Influencing Antibiotic Resistance: A Qualitative Study in Vietnam
    Di KN, Tay ST, Sri La Sri Ponnampalavanar S, Pham DT, Wong LP
    Healthcare (Basel), 2022 Dec 31;11(1).
    PMID: 36611587 DOI: 10.3390/healthcare11010126
    (1) Background: The antibiotic resistance (ABR) rates are escalating to seriously high levels worldwide. This study was conducted to determine physicians' perspectives on factors influencing ABR in Vietnam. (2) Methods: Focus group discussion (FGD) was conducted through in-depth interviews on ABR perspectives with 5-6 physicians from different geographical locations and hospitals in Vietnam between March and June 2020. The research questions were focused on three main themes of (a) knowledge deficiency on ABR and hospital-acquired infection, (b) antibiotic prescribing practice among clinicians in the healthcare setting, and (c) regulations and hospital policies on antibiotic use. The descriptive analysis was performed using QRS NVivo software. (3) Results: A total of six FGDs were conducted among 34 physicians (18 males, 16 females) aged 26-53 years old from six public and six private hospitals in Vietnam. Most of the participants were attending physicians (85.3%) and had 5-10 years of experience in surgical wards (55.9%). For theme (a), a majority of participants agreed that they had adequate information updates on how ABR develops in their clinical setting; and were well aware of hospital-acquired infections. For theme (b), the participants agreed that WHO guidelines and Vietnam national guidelines were two important reference documents in guiding physicians in antibiotic use. For theme (c), the FGD study revealed awareness of ABR, hospital antibiotic policies, and procedures for administrators on antibiotic use that were updated and complied with. (4) Conclusions: While different levels of control measures against ABR are ongoing in Vietnam, several weaknesses in the current antibiotic prescribing strategies in the hospital and clinical setting management policies have been identified in the healthcare system. The research findings will be helpful for policymakers to have better plans of action against ABR in Vietnam.
  19. Emergence of Klebsiella pneumoniae producing dual carbapenemases (NDM-1 and OXA-232) and 16S rRNA methylase (armA) isolated from a Malaysian patient returning from India
    Al-Marzooq F, Ngeow YF, Tay ST
    Int J Antimicrob Agents, 2015 Apr;45(4):445-6.
    PMID: 25631676 DOI: 10.1016/j.ijantimicag.2014.12.013
  20. Fulltext Falsarthrobacter nasiphocae periprosthetic joint infection
    Tay ST, Merican AM, Abdul Jabar K, Velayuthan RD, Ayob KA, Lee JL, et al.
    Int J Infect Dis, 2023 Nov;136:77-80.
    PMID: 37660726 DOI: 10.1016/j.ijid.2023.08.025
    We report the isolation of a rare Gram-positive coccobacillary bacterium from synovial fluids of a patient with periprosthetic joint infection on three occasions over an 8-month period. As routine microbiological methods were not able to identify the isolate definitely, sequence analyses of the bacterial 16S ribosomal RNA gene and whole genome were performed. Analysis of the bacterial 16S ribosomal RNA gene showed the highest similarity (98.1%) with that of Falsarthrobacter (previously known as Arthrobacter) nasiphocae, which was first isolated from the nasal cavities of common seals (Phoca vitulina). The genome size of the strain (designated as UM1) is 2.4 Mb. With a high G+C content (70.4 mol%), strain UM1 is phylogenetically most closely related to F. nasiphocae based on whole genome analysis. Strain UM1 was susceptible to vancomycin, linezolid, trimethoprim-sulfamethoxazole, doxycycline, and intermediate to penicillin and ciprofloxacin. Ceftriaxone resistance was noted. The patient who was also on hemodialysis for his end stage kidney disease died approximately 3 weeks following implant removal and fusion with an external fixator. This study describes the first isolation of F. nasiphocae from human clinical samples. The use of emerging technologies has supported more definitive etiological diagnosis associated with rarely encountered organisms in periprosthetic joint infection.
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