Displaying publications 1 - 20 of 47 in total

Abstract:
Sort:
  1. Tan LT, Lee LH, Yin WF, Chan CK, Abdul Kadir H, Chan KG, et al.
    PMID: 26294929 DOI: 10.1155/2015/896314
    Ylang-ylang (Cananga odorata Hook. F. & Thomson) is one of the plants that are exploited at a large scale for its essential oil which is an important raw material for the fragrance industry. The essential oils extracted via steam distillation from the plant have been used mainly in cosmetic industry but also in food industry. Traditionally, C. odorata is used to treat malaria, stomach ailments, asthma, gout, and rheumatism. The essential oils or ylang-ylang oil is used in aromatherapy and is believed to be effective in treating depression, high blood pressure, and anxiety. Many phytochemical studies have identified the constituents present in the essential oils of C. odorata. A wide range of chemical compounds including monoterpene, sesquiterpenes, and phenylpropanoids have been isolated from this plant. Recent studies have shown a wide variety of bioactivities exhibited by the essential oils and the extracts of C. odorata including antimicrobial, antibiofilm, anti-inflammatory, antivector, insect-repellent, antidiabetic, antifertility and antimelanogenesis activities. Thus, the present review summarizes the information concerning the traditional uses, phytochemistry, and biological activities of C. odorata. This review is aimed at demonstrating that C. odorata not only is an important raw material for perfume industry but also considered as a prospective useful plant to agriculture and medicine.
  2. Isa H, Luthert P, Rose G, Verity D, Pusey C, Tomkins-Netzer O, et al.
    Ophthalmology, 2015 Oct;122(10):2140-2.
    PMID: 26116342 DOI: 10.1016/j.ophtha.2015.04.016
  3. Lin B, Ser HL, Wang L, Li J, Chan KG, Lee LH, et al.
    Int J Mol Sci, 2023 Feb 28;24(5).
    PMID: 36902078 DOI: 10.3390/ijms24054648
    Matrix metalloproteinase-12 (MMP12), or macrophage metalloelastase, plays important roles in extracellular matrix (ECM) component degradation. Recent reports show MMP12 has been implicated in the pathogenesis of periodontal diseases. To date, this review represents the latest comprehensive overview of MMP12 in various oral diseases, such as periodontitis, temporomandibular joint dysfunction (TMD), orthodontic tooth movement (OTM), and oral squamous cell carcinoma (OSCC). Furthermore, the current knowledge regarding the distribution of MMP12 in different tissues is also illustrated in this review. Studies have implicated the association of MMP12 expression with the pathogenesis of several representative oral diseases, including periodontitis, TMD, OSCC, OTM, and bone remodelling. Although there may be a potential role of MMP12 in oral diseases, the exact pathophysiological role of MMP12 remains to be elucidated. Understanding the cellular and molecular biology of MMP12 is essential, as MMP12 could be a potential target for developing therapeutic strategies targeting inflammatory and immunologically related oral diseases.
  4. Yong YL, Tan LT, Ming LC, Chan KG, Lee LH, Goh BH, et al.
    Front Pharmacol, 2016;7:538.
    PMID: 28119613 DOI: 10.3389/fphar.2016.00538
    In particular, neuropathic pain is a major form of chronic pain. This type of pain results from dysfunction or lesions in the central and peripheral nervous system. Capsaicin has been traditionally utilized as a medicine to remedy pain. However, the effectiveness and safety of this practice is still elusive. Therefore, this systematic review aimed to investigate the effect of topical capsaicin as a pain-relieving agent that is frequently used in pain management. In brief, all the double-blinded, randomized placebo- or vehicle-controlled trials that were published in English addressing postherpetic neuralgia were included. Meta-analysis was performed using Revman(®) version 5.3. Upon application of the inclusion and exclusion criteria, only six trials fulfilled all the criteria and were included in the review for qualitative analysis. The difference in mean percentage change in numeric pain rating scale score ranges from -31 to -4.3. This demonstrated high efficacy of topical capsaicin application and implies that capsaicin could result in pain reduction. Furthermore, meta-analysis was performed on five of the included studies. All the results of studies are in favor of the treatment using capsaicin. The incidence of side effects from using topical capsaicin is consistently higher in all included studies, but the significance of safety data cannot be quantified due to a lack of p-values in the original studies. Nevertheless, topical capsaicin is a promising treatment option for specific patient groups or certain neuropathic pain conditions such as postherpetic neuralgia.
  5. Tan LT, Chan KG, Pusparajah P, Lee WL, Chuah LH, Khan TM, et al.
    Front Pharmacol, 2017;8:12.
    PMID: 28167913 DOI: 10.3389/fphar.2017.00012
    Cancer mortality and morbidity is projected to increase significantly over the next few decades. Current chemotherapeutic strategies have significant limitations, and there is great interest in seeking novel therapies which are capable of specifically targeting cancer cells. Given that fundamental differences exist between the cellular membranes of healthy cells and tumor cells, novel therapies based on targeting membrane lipids in cancer cells is a promising approach that deserves attention in the field of anticancer drug development. Phosphatidylethanolamine (PE), a lipid membrane component which exists only in the inner leaflet of cell membrane under normal circumstances, has increased surface representation on the outer membrane of tumor cells with disrupted membrane asymmetry. PE thus represents a potential chemotherapeutic target as the higher exposure of PE on the membrane surface of cancer cells. This feature as well as a high degree of expression of PE on endothelial cells in tumor vasculature, makes PE an attractive molecular target for future cancer interventions. There have already been several small molecules and membrane-active peptides identified which bind specifically to the PE molecules on the cancer cell membrane, subsequently inducing membrane disruption leading to cell lysis. This approach opens up a new front in the battle against cancer, and is of particular interest as it may be a strategy that may be prove effective against tumors that respond poorly to current chemotherapeutic agents. We aim to highlight the evidence suggesting that PE is a strong candidate to be explored as a potential molecular target for membrane targeted novel anticancer therapy.
  6. Chew SS, Tan LT, Law JW, Pusparajah P, Goh BH, Ab Mutalib NS, et al.
    Cancers (Basel), 2020 Aug 13;12(8).
    PMID: 32823729 DOI: 10.3390/cancers12082272
    Colorectal cancer (CRC) is a global public health issue which poses a substantial humanistic and economic burden on patients, healthcare systems and society. In recent years, intestinal dysbiosis has been suggested to be involved in the pathogenesis of CRC, with specific pathogens exhibiting oncogenic potentials such as Fusobacterium nucleatum, Escherichia coli and enterotoxigenic Bacteroides fragilis having been found to contribute to CRC development. More recently, it has been shown that initiation of CRC development by these microorganisms requires the formation of biofilms. Gut microbial biofilm forms in the inner colonic mucus layer and is composed of polymicrobial communities. Biofilm results in the redistribution of colonic epithelial cell E-cadherin, increases permeability of the gut and causes a loss of function of the intestinal barrier, all of which enhance intestinal dysbiosis. This literature review aims to compile the various strategies that target these pathogenic biofilms and could potentially play a role in the prevention of CRC. We explore the potential use of natural products, silver nanoparticles, upconverting nanoparticles, thiosalicylate complexes, anti-rheumatic agent (Auranofin), probiotics and quorum-sensing inhibitors as strategies to hinder colon carcinogenesis via targeting colon-associated biofilms.
  7. Pusparajah P, Letchumanan V, Law JW, Ab Mutalib NS, Ong YS, Goh BH, et al.
    Int J Mol Sci, 2021 Aug 28;22(17).
    PMID: 34502269 DOI: 10.3390/ijms22179360
    Biofilms formed by methicillin-resistant S. aureus (MRSA) are among the most frequent causes of biomedical device-related infection, which are difficult to treat and are often persistent and recurrent. Thus, new and effective antibiofilm agents are urgently needed. In this article, we review the most relevant literature of the recent years reporting on promising anti-MRSA biofilm agents derived from the genus Streptomyces bacteria, and discuss the potential contribution of these newly reported antibiofilm compounds to the current strategies in preventing biofilm formation and eradicating pre-existing biofilms of the clinically important pathogen MRSA. Many efforts are evidenced to address biofilm-related infections, and some novel strategies have been developed and demonstrated encouraging results in preclinical studies. Nevertheless, more in vivo studies with appropriate biofilm models and well-designed multicenter clinical trials are needed to assess the prospects of these strategies.
  8. Mangzira Kemung H, Tan LT, Chan KG, Ser HL, Law JW, Lee LH, et al.
    Molecules, 2020 Aug 03;25(15).
    PMID: 32756432 DOI: 10.3390/molecules25153545
    There is an urgent need to search for new antibiotics to counter the growing number of antibiotic-resistant bacterial strains, one of which is methicillin-resistant Staphylococcus aureus (MRSA). Herein, we report a Streptomyces sp. strain MUSC 125 from mangrove soil in Malaysia which was identified using 16S rRNA phylogenetic and phenotypic analysis. The methanolic extract of strain MUSC 125 showed anti-MRSA, anti-biofilm and antioxidant activities. Strain MUSC 125 was further screened for the presence of secondary metabolite biosynthetic genes. Our results indicated that both polyketide synthase (pks) gene clusters, pksI and pksII, were detected in strain MUSC 125 by PCR amplification. In addition, gas chromatography-mass spectroscopy (GC-MS) detected the presence of different chemicals in the methanolic extract. Based on the GC-MS analysis, eight known compounds were detected suggesting their contribution towards the anti-MRSA and anti-biofilm activities observed. Overall, the study bolsters the potential of strain MUSC 125 as a promising source of anti-MRSA and antibiofilm compounds and warrants further investigation.
  9. Tan LT, Mahendra CK, Yow YY, Chan KG, Khan TM, Lee LH, et al.
    Microbiologyopen, 2019 10;8(10):e859.
    PMID: 31199601 DOI: 10.1002/mbo3.859
    Microbial natural products serve as a good source for antioxidants. The mangrove-derived Streptomyces bacteria have been evidenced to produce antioxidative compounds. This study reports the isolation of Streptomyces sp. MUM273b from mangrove soil that may serve as a promising source of antioxidants and UV-protective agents. Identification and characterization methods determine that strain MUM273b belongs to the genus Streptomyces. The MUM273b extract exhibits antioxidant activities, including DPPH, ABTS, and superoxide radical scavenging activities and also metal-chelating activity. The MUM273b extract was also shown to inhibit the production of malondialdehyde in metal-induced lipid peroxidation. Strong correlation between the antioxidant activities and the total phenolic content of MUM273b extract was shown. In addition, MUM273b extract exhibited cytoprotective effect on the UVB-induced cell death in HaCaT keratinocytes. Gas chromatography-mass spectrometry analysis detected phenolics, pyrrole, pyrazine, ester, and cyclic dipeptides in MUM273b extract. In summary, Streptomyces MUM273b extract portrays an exciting avenue for future antioxidative drugs and cosmeceuticals development.
  10. Tan LT, Chan CK, Chan KG, Pusparajah P, Khan TM, Ser HL, et al.
    Cancers (Basel), 2019 Nov 06;11(11).
    PMID: 31698795 DOI: 10.3390/cancers11111742
    New and effective anticancer compounds are much needed as the incidence of cancer continues to rise. Microorganisms from a variety of environments are promising sources of new drugs; Streptomyces sp. MUM256, which was isolated from mangrove soil in Malaysia as part of our ongoing efforts to study mangrove resources, was shown to produce bioactive metabolites with chemopreventive potential. This present study is a continuation of our previous efforts and aimed to investigate the underlying mechanisms of the ethyl acetate fraction of MUM256 crude extract (MUM256 EA) in inhibiting the proliferation of HCT116 cells. Our data showed that MUM256 EA reduced proliferation of HCT116 cells via induction of cell-cycle arrest. Molecular studies revealed that MUM256 EA regulated the expression level of several important cell-cycle regulatory proteins. The results also demonstrated that MUM256 EA induced apoptosis in HCT116 cells mediated through the intrinsic pathway. Gas chromatography-mass spectrometry (GC-MS) analysis detected several chemical compounds present in MUM256 EA, including cyclic dipeptides which previous literature has reported to demonstrate various pharmacological properties. The cyclic dipeptides were further shown to inhibit HCT116 cells while exerting little to no toxicity on normal colon cells in this study. Taken together, the findings of this project highlight the important role of exploring the mangrove microorganisms as a bioresource which hold tremendous promise for the development of chemopreventive drugs against colorectal cancer.
  11. Tan LT, Chan KG, Khan TM, Bukhari SI, Saokaew S, Duangjai A, et al.
    Front Pharmacol, 2017;8:276.
    PMID: 28567016 DOI: 10.3389/fphar.2017.00276
    Reactive oxygen species and other radicals potentially cause oxidative damage to proteins, lipids, and DNA which may ultimately lead to various complications including mutations, carcinogenesis, neurodegeneration, cardiovascular disease, aging, and inflammatory disease. Recent reports demonstrate that Streptomyces bacteria produce metabolites with potent antioxidant activity that may be developed into therapeutic drugs to combat oxidative stress. This study shows that Streptomyces sp. MUM212 which was isolated from mangrove soil in Kuala Selangor, Malaysia, could be a potential source of antioxidants. Strain MUM212 was characterized and determined as belonging to the genus Streptomyces using 16S rRNA gene phylogenetic analysis. The MUM212 extract demonstrated significant antioxidant activity through DPPH, ABTS and superoxide radical scavenging assays and also metal-chelating activity of 22.03 ± 3.01%, 61.52 ± 3.13%, 37.47 ± 1.79%, and 41.98 ± 0.73% at 4 mg/mL, respectively. Moreover, MUM212 extract was demonstrated to inhibit lipid peroxidation up to 16.72 ± 2.64% at 4 mg/mL and restore survival of Vero cells from H2O2-induced oxidative damages. The antioxidant activities from the MUM212 extract correlated well with its total phenolic contents; and this in turn was in keeping with the gas chromatography-mass spectrometry analysis which revealed the presence of phenolic compounds that could be responsible for the antioxidant properties of the extract. Other chemical constituents detected included hydrocarbons, alcohols and cyclic dipeptides which may have contributed to the overall antioxidant capacity of MUM212 extract. As a whole, strain MUM212 seems to have potential as a promising source of novel molecules for future development of antioxidative therapeutic agents against oxidative stress-related diseases.
  12. Kemung HM, Tan LT, Khan TM, Chan KG, Pusparajah P, Goh BH, et al.
    Front Microbiol, 2018;9:2221.
    PMID: 30319563 DOI: 10.3389/fmicb.2018.02221
    Methicillin-resistant Staphylococcus aureus (MRSA) pose a significant health threat as they tend to cause severe infections in vulnerable populations and are difficult to treat due to a limited range of effective antibiotics and also their ability to form biofilm. These organisms were once limited to hospital acquired infections but are now widely present in the community and even in animals. Furthermore, these organisms are constantly evolving to develop resistance to more antibiotics. This results in a need for new clinically useful antibiotics and one potential source are the Streptomyces which have already been the source of several anti-MRSA drugs including vancomycin. There remain large numbers of Streptomyces potentially undiscovered in underexplored regions such as mangrove, deserts, marine, and freshwater environments as well as endophytes. Organisms from these regions also face significant challenges to survival which often result in the production of novel bioactive compounds, several of which have already shown promise in drug development. We review the various mechanisms of antibiotic resistance in MRSA and all the known compounds isolated from Streptomyces with anti-MRSA activity with a focus on those from underexplored regions. The isolation of the full array of compounds Streptomyces are potentially capable of producing in the laboratory has proven a challenge, we also review techniques that have been used to overcome this obstacle including genetic cluster analysis. Additionally, we review the in vivo work done thus far with promising compounds of Streptomyces origin as well as the animal models that could be used for this work.
  13. Ser HL, Tan LT, Palanisamy UD, Abd Malek SN, Yin WF, Chan KG, et al.
    Front Microbiol, 2016;7:899.
    PMID: 27379040 DOI: 10.3389/fmicb.2016.00899
    A novel strain, Streptomyces antioxidans MUSC 164(T) was recovered from mangrove forest soil located at Tanjung Lumpur, Malaysia. The Gram-positive bacterium forms yellowish-white aerial and brilliant greenish yellow substrate mycelium on ISP 2 agar. A polyphasic approach was used to determine the taxonomy status of strain MUSC 164(T). The strain showed a spectrum of phylogenetic and chemotaxonomic properties consistent with those of the members of the genus Streptomyces. The cell wall peptidoglycan was determined to contain LL-diaminopimelic acid. The predominant menaquinones were identified as MK-9(H6) and MK-9(H8), while the identified polar lipids consisted of aminolipid, diphosphatidylglycerol, glycolipid, hydroxyphosphatidylethanolamine, phospholipid, phosphatidylinositol, phosphatidylethanolamine, phosphatidylglycerol and lipid. The cell wall sugars consist of galactose, glucose and ribose. The predominant cellular fatty acids (>10.0%) were identified as iso-C15: 0 (34.8%) and anteiso-C15: 0(14.0%). Phylogenetic analysis identified that closely related strains for MUSC 164(T) as Streptomyces javensis NBRC 100777(T) (99.6% sequence similarity), Streptomyces yogyakartensis NBRC 100779(T) (99.6%) and Streptomyces violaceusniger NBRC 13459(T) (99.6%). The DNA-DNA relatedness values between MUSC 164(T) and closely related type strains ranged from 23.8 ± 0.3% to 53.1 ± 4.3%. BOX-PCR fingerprints comparison showed that MUSC 164(T) exhibits a unique DNA profile, with DNA G + C content determined to be 71.6 mol%. Based on the polyphasic study of MUSC 164(T), it is concluded that this strain represents a novel species, for which the name Streptomyces antioxidans sp. nov. is proposed. The type strain is MUSC 164(T) (=DSM 101523(T) = MCCC 1K01590(T)). The extract of MUSC 164(T) showed potent antioxidative and neuroprotective activities against hydrogen peroxide. The chemical analysis of the extract revealed that the strain produces pyrazines and phenolic-related compounds that could explain for the observed bioactivities.
  14. Tan LT, Chan KG, Lee LH, Goh BH
    Front Microbiol, 2016;7:79.
    PMID: 26903962 DOI: 10.3389/fmicb.2016.00079
    In response to the increased seafood demand from the ever-going human population, aquaculture has become the fastest growing animal food-producing sector. However, the indiscriminate use of antibiotics as a biological control agents for fish pathogens has led to the emergence of antibiotic resistance bacteria. Probiotics are defined as living microbial supplement that exert beneficial effects on hosts as well as improvement of environmental parameters. Probiotics have been proven to be effective in improving the growth, survival and health status of the aquatic livestock. This review aims to highlight the genus Streptomyces can be a good candidate for probiotics in aquaculture. Studies showed that the feed supplemented with Streptomyces could protect fish and shrimp from pathogens as well as increase the growth of the aquatic organisms. Furthermore, the limitations of Streptomyces as probiotics in aquaculture is also highlighted and solutions are discussed to these limitations.
  15. Tan CS, Bandak DB, Habeebur-Rahman SP, Tan LT, Lim LLA
    Virol J, 2023 Aug 07;20(1):176.
    PMID: 37550752 DOI: 10.1186/s12985-023-02133-9
    SARS-CoV-2 is a zoonotic betacoronavirus that was first reported at the dawn of 2019 in Wuhan, China and has since spread globally, causing an ongoing pandemic. Anthroponotic transmission was reported early, with confirmed infections reported in 26 species to date, including dogs and cats. However, there is a paucity of reports on the transmission of SARS-CoV-2 to companion animals, and thus, we aimed to estimate the seroprevalence of SARS-CoV-2 in dogs and cats in Sarawak, Malaysia. From August 2022 to 2023, we screened plasma samples of 172 companion animals in Sarawak, Malaysia, using a species-independent surrogate virus neutralization test. Our findings revealed the presence of neutralizing antibodies of SARS-CoV-2 in 24.5% (27/110) of dogs and 24.2% (15/62) of cats. To the best of our knowledge, this is the first report of the seroprevalence of SARS-CoV-2 in companion animals in Malaysia. Our findings emphasize the need for pet owners to distance themselves from their pets when unwell, and a strategy must be in place to monitor SARS-CoV-2 in companion animals to assess the potential impact of the virus on companion animals.
  16. Goonewardene ST, Tang C, Tan LT, Chan KG, Lingham P, Lee LH, et al.
    Front Pediatr, 2019;7:339.
    PMID: 31456997 DOI: 10.3389/fped.2019.00339
    Nephrotic syndrome affects both children and adults. Idiopathic nephrotic syndrome is reported to be one of the most frequent renal pathologies in childhood. Nephrotic children are at high risk for severe pneumococcal infections as one of the life-threatening complications of nephrotic syndrome due to involvement of the immunosuppressive regimen and the acquired immune deficiency induced by nephrotic syndrome including decreased plasma IgG and low complement system components. Aiming to prevent pneumococcal infection is of paramount importance especially in this era of ever-increasing pneumococcal resistance to penicillins and cephalosporins. The pneumococcal vaccines currently available are inactivated vaccines-the two main forms in use are polysaccharide vaccines and conjugated vaccines. However, the data supporting the use of these vaccines and to guide the timing and dosage recommendations is still limited for nephrotic children. Thus, this review discusses the evidences of immunogenicity and safety profile of both vaccinations on nephrotic patients as well as the effect of nephrotic syndrome treatment on vaccine seroresponses.
  17. Ma DSL, Tan LT, Chan KG, Yap WH, Pusparajah P, Chuah LH, et al.
    Front Pharmacol, 2018;9:102.
    PMID: 29515440 DOI: 10.3389/fphar.2018.00102
    Bacterial foodborne pathogens are a significant health burden and the recent emergence of pathogenic resistant strains due to the excessive use of antibiotics makes it more difficult to effectively treat infections as a result of contaminated food. Awareness of this impending health crisis has spurred the search for alternative antimicrobials with natural plant antimicrobials being among the more promising candidates as these substances have good acceptability and likely low toxicity levels as they have long been used in traditional medicines. Resveratrol (3,5,4'-trihydroxystilbene) is a naturally occurring stilbenoid which has been gaining considerable attention in medical field due to its diverse biological activities - it has been reported to exhibit antioxidant, cardioprotective, anti-diabetic, anticancer, and antiaging properties. Given that resveratrol is phytoalexin, with increased synthesis in response to infection by phytopathogens, there has been interest in exploring its antimicrobial activity. This review aims to provide an overview of the published data on the antibacterial activity of resveratrol against foodborne pathogens, its mechanisms of action as well as its possible applications in food packing and processing; in addition we also summarize the current data on its potential synergism with known antibacterials and future research and applications.
  18. Thye AY, Law JW, Tan LT, Pusparajah P, Ser HL, Thurairajasingam S, et al.
    Biology (Basel), 2022 Jan 02;11(1).
    PMID: 35053059 DOI: 10.3390/biology11010061
    There is growing evidence of studies associating COVID-19 survivors with increased mental health consequences. Mental health implications related to a COVID-19 infection include both acute and long-term consequences. Here we discuss COVID-19-associated psychiatric sequelae, particularly anxiety, depression, and post-traumatic stress disorder (PTSD), drawing parallels to past coronavirus outbreaks. A literature search was completed across three databases, using keywords to search for relevant articles. The cause may directly correlate to the infection through both direct and indirect mechanisms, but the underlying etiology appears more complex and multifactorial, involving environmental, psychological, and biological factors. Although most risk factors and prevalence rates vary across various studies, being of the female gender and having a history of psychiatric disorders seem consistent. Several studies will be presented, demonstrating COVID-19 survivors presenting higher rates of mental health consequences than the general population. The possible mechanisms by which the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) enters the brain, affecting the central nervous system (CNS) and causing these psychiatric sequelae, will be discussed, particularly concerning the SARS-CoV-2 entry via the angiotensin-converting enzyme 2 (ACE-2) receptors and the implications of the immune inflammatory signaling on neuropsychiatric disorders. Some possible therapeutic options will also be considered.
  19. Sun S, Tan LT, Fang YL, Jin ZJ, Zhou L, Goh BH, et al.
    Mol Plant Microbe Interact, 2020 Mar;33(3):488-498.
    PMID: 31710580 DOI: 10.1094/MPMI-09-19-0264-R
    Phenazine-1-carboxylic acid (PCA) is the primary active component in the newly registered, commercial biopesticide Shenqinmycin and is produced during fermentation by the engineered rhizobacterium strain Pseudomonas PA1201. Both phz1 and phz2 gene clusters contribute to PCA biosynthesis. In this study, we evaluated the role of OxyR in the regulation of PCA biosynthesis in PA1201. We first showed a functional link between oxyR expression and PCA biosynthesis. Deletion of oxyR and overexpression of oxyR both increase PCA biosynthesis. The molecular mechanisms underlying OxyR regulation of PCA production were investigated using several approaches. OxyR acts divergently in phz1 and phz2. Overexpression of oxyR activated the expression of phz1 and phz1-dependent PCA production. However, overexpression of oxyR had little effect on phz2-dependent PCA biosynthesis, while deletion of oxyR promoted phz2-dependent PCA production and exerted a negative effect on phz2 expression. Further, OxyR directly bound to the phz2 promoter region. In addition, the regulation of PCA biosynthesis by OxyR was associated with quorum sensing (QS) systems. Overexpression of OxyR positively regulated pqs QS system. Finally, transcriptomic analysis and subsequent genetic analysis revealed the small RNA phrS plays a key role in OxyR-dependent PCA accumulation. Specifically, OxyR directly binds to the phrS promoter region to positively regulate phrS expression wherein PhrS regulates the PCA positive regulator MvfR in order to control PCA biosynthesis.
  20. Letchumanan V, Pusparajah P, Tan LT, Yin WF, Lee LH, Chan KG
    Front Microbiol, 2015;6:1417.
    PMID: 26697003 DOI: 10.3389/fmicb.2015.01417
    High consumer demand for shellfish has led to the need for large-scale, reliable shellfish supply through aquaculture or shellfish farming. However, bacterial infections which can spread rapidly among shellfish poses a major threat to this industry. Shellfish farmers therefore often resort to extensive use of antibiotics, both prophylactically and therapeutically, in order to protect their stocks. The extensive use of antibiotics in aquaculture has been postulated to represent a major contributing factor in the rising incidence of antimicrobial resistant pathogenic bacteria in shellfish. This study aimed to investigate the incidence of pathogenic Vibrio parahaemolyticus and determine the antibiotic resistance profile as well as to perform plasmid curing in order to determine the antibiotic resistance mediation. Based on colony morphology, all 450 samples tested were positive for Vibrio sp; however, tox-R assay showed that only 44.4% (200/450) of these were V. parahaemolyticus. Out of these 200 samples, 6.5% (13/200) were trh-positive while none were tdh-positive. Antibiotic resistance was determined for all V. parahaemolyticus identified against 14 commonly used antibiotics and the multiple antibiotic resistance index (MAR) was calculated. The isolates demonstrated high resistance to several antibiotics tested- including second and third-line antibiotics- with 88% resistant to ampicillin, 81% to amikacin,70.5% to kanamycin, 73% to cefotaxime, and 51.5% to ceftazidime. The MAR index ranged from 0.00 to 0.79 with the majority of samples having an index of 0.36 (resistant to five antibiotics). Among the 13 trh-positive strains, almost 70% (9/13) demonstrated resistance to 4 or more antibiotics. Plasmid profiling for all V. parahaemolyticus isolates revealed that 86.5% (173/200) contained plasmids - ranging from 1 to 7 plasmids with DNA band sizes ranging from 1.2 kb to greater than 10 kb. 6/13 of the pathogenic V. pathogenic strains contained plasmid. After plasmid curing, the plasmid containing pathogenic strains isolated in our study have chromosomally mediated ampicillin resistance while the remaining resistance phenotypes are plasmid mediated. Overall, our results indicate that while the incidence of pathogenic V. parahaemolyticus in shellfish in Selangor still appears to be at relatively reassuring levels, antibiotic resistance is a real concern and warrants ongoing surveillance.
Filters
Contact Us

Please provide feedback to Administrator (afdal@afpm.org.my)

External Links