Displaying all 12 publications

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  1. Lee SK, Tan KW, Ng SW
    J Inorg Biochem, 2016 06;159:14-21.
    PMID: 26901628 DOI: 10.1016/j.jinorgbio.2016.02.010
    Three transition metal derivatives (Zn, Cu, and Ni) of 2-[2-bromoethyliminomethyl]-4-[ethoxymethyl]phenol (L) were synthesized by the reaction of the metal salts with the Schiff base ligand in one pot. In the crystal structure of [Zn(L)Br], the Schiff base ligand binds to the metal center through its phenolate oxygen and imine nitrogen, and adopts a distorted tetrahedral geometry. These compounds were found to inhibit topoisomerase I (topo I) activity, induce DNA cleavage and show DNA binding activity. Moreover, these compounds were found to be cytotoxic towards several cancer cell lines (A2780, MCF-7, HT29, HepG2, A549, PC3, LNCaP) and prevent metastasis of PC3. Collectively, Cu(II) complex 2 shows superior activity relative to its Zn(II) and Ni(II) analogs.
    Matched MeSH terms: DNA, Bacterial/metabolism*
  2. Chua KH, See KH, Thong KL, Puthucheary SD
    Jpn J Infect Dis, 2011;64(3):228-33.
    PMID: 21617308
    Restriction enzymes SpeI and XbaI were used in a pulsed-field gel electrophoresis (PFGE) study for molecular characterization of 146 clinical Burkholderia pseudomallei isolates. The PFGE parameters were optimized to enable comparable, reproducible, and robust results. The optimized parameters for both SpeI and XbaI restriction enzymes used in this study were 200 V and a pulse time of 5 to 65 s for a 28-h runtime. Using SpeI, 9 different clusters were identified, whereas 6 clusters were identified by XbaI digestion, which exhibited 85% similarity to SpeI. SpeI (discrimination index [D]=0.854) showed higher discriminatory power than XbaI did (D=0.464).
    Matched MeSH terms: DNA, Bacterial/metabolism
  3. Goh HF, Philip K
    J Dairy Sci, 2015 Aug;98(8):5080-90.
    PMID: 26004828 DOI: 10.3168/jds.2014-9240
    Lactic acid bacteria are present in fermented food products and help to improve shelf life and enhance the flavor of the food. They also produce metabolites such as bacteriocins to prevent the growth of undesirable or pathogenic bacteria. In this study, Enterococcus faecium C1 isolated from fermented cow milk was able to produce bacteriocin BacC1 and inhibit the growth of selected food-spoilage bacteria. The bacteriocin was purified through 4 steps: ammonium sulfate precipitation, hydrophobic interaction column, a series of centrifugal steps, and finally reversed-phase HPLC. A membrane permeability test using SYTOX green dye (Invitrogen, Grand Island, NY) showed that the bacteriocin caused significant disruptions to the test bacterial membrane, as shown by transmission electron microscopy. The molecular weight of the BacC1 obtained from SDS-PAGE was around 10kDa, and N-terminal sequencing revealed a partial amino acid sequence of BacC1: GPXGPXGP. The bacterial strain was nonhemolytic and not antibiotic resistant. Therefore, it has high potential for application in the food industry as an antimicrobial agent to extend the shelf life of food products.
    Matched MeSH terms: DNA, Bacterial/metabolism
  4. Ho WS, Ou HY, Yeo CC, Thong KL
    BMC Genomics, 2015;16:199.
    PMID: 25879448 DOI: 10.1186/s12864-015-1421-8
    Strains of Escherichia coli that are non-typeable by pulsed-field gel electrophoresis (PFGE) due to in-gel degradation can influence their molecular epidemiological data. The DNA degradation phenotype (Dnd(+)) is mediated by the dnd operon that encode enzymes catalyzing the phosphorothioation of DNA, rendering the modified DNA susceptible to oxidative cleavage during a PFGE run. In this study, a PCR assay was developed to detect the presence of the dnd operon in Dnd(+) E. coli strains and to improve their typeability. Investigations into the genetic environments of the dnd operon in various E. coli strains led to the discovery that the dnd operon is harboured in various diverse genomic islands.
    Matched MeSH terms: DNA, Bacterial/metabolism*
  5. Alkotaini B, Anuar N, Kadhum AA
    Appl Biochem Biotechnol, 2015 Feb;175(4):1868-78.
    PMID: 25427593 DOI: 10.1007/s12010-014-1410-4
    The mechanisms of action of AN5-1 against Gram-negative and Gram-positive bacteria were investigated by evaluations of the intracellular content leakage and by microscopic observations of the treated cells. Escherichia coli and Staphylococcus aureus were used for this investigation. Measurements of DNA, RNA, proteins, and β-galactosidase were taken, and the results showed a significant increase in the cultivation media after treatment with AN5-1 compared with the untreated cells. The morphological changes of treated cells were shown using transmission electron microscopy (TEM) and atomic force microscopy (AFM). The observations showed that AN5-1 acts against E. coli and against S. aureus in similar ways, by targeting the cell wall, causing disruptions; at a high concentration (80 AU/ml), these disruptions led to cell lysis. The 3D AFM imaging system showed that at a low concentration of 20 AU/ml, the effect of AN5-1 is restricted to pore formation only. Moreover, a separation between the cell wall and the cytoplasm was observed when Gram-negative bacteria were treated with a low concentration (20 AU/ml) of AN5-1.
    Matched MeSH terms: DNA, Bacterial/metabolism
  6. Lee CM, Sieo CC, Cheah YK, Abdullah N, Ho YW
    J Sci Food Agric, 2012 Feb;92(3):660-6.
    PMID: 21919004 DOI: 10.1002/jsfa.4627
    Four repetitive element sequence-based polymerase chain reaction (rep-PCR) methods, namely repetitive extragenic palindromic PCR (REP-PCR), enterobacterial repetitive intergenic consensus PCR (ERIC-PCR), polytrinucleotide (GTG)₅ -PCR and BOX-PCR, were evaluated for the molecular differentiation of 12 probiotic Lactobacillus strains previously isolated from the gastrointestinal tract of chickens and used as a multistrain probiotic. This study represents the first analysis of the comparative efficacy of these four rep-PCR methods and their combination (composite rep-PCR) in the molecular typing of Lactobacillus strains based on a discriminatory index (D).
    Matched MeSH terms: DNA, Bacterial/metabolism*
  7. Forde BM, Phan MD, Gawthorne JA, Ashcroft MM, Stanton-Cook M, Sarkar S, et al.
    mBio, 2015 Nov 17;6(6):e01602-15.
    PMID: 26578678 DOI: 10.1128/mBio.01602-15
    Escherichia coli sequence type 131 (ST131) is a clone of uropathogenic E. coli that has emerged rapidly and disseminated globally in both clinical and community settings. Members of the ST131 lineage from across the globe have been comprehensively characterized in terms of antibiotic resistance, virulence potential, and pathogenicity, but to date nothing is known about the methylome of these important human pathogens. Here we used single-molecule real-time (SMRT) PacBio sequencing to determine the methylome of E. coli EC958, the most-well-characterized completely sequenced ST131 strain. Our analysis of 52,081 methylated adenines in the genome of EC958 discovered three (m6)A methylation motifs that have not been described previously. Subsequent SMRT sequencing of isogenic knockout mutants identified the two type I methyltransferases (MTases) and one type IIG MTase responsible for (m6)A methylation of novel recognition sites. Although both type I sites were rare, the type IIG sites accounted for more than 12% of all methylated adenines in EC958. Analysis of the distribution of MTase genes across 95 ST131 genomes revealed their prevalence is highly conserved within the ST131 lineage, with most variation due to the presence or absence of mobile genetic elements on which individual MTase genes are located.

    IMPORTANCE: DNA modification plays a crucial role in bacterial regulation. Despite several examples demonstrating the role of methyltransferase (MTase) enzymes in bacterial virulence, investigation of this phenomenon on a whole-genome scale has remained elusive until now. Here we used single-molecule real-time (SMRT) sequencing to determine the first complete methylome of a strain from the multidrug-resistant E. coli sequence type 131 (ST131) lineage. By interrogating the methylome computationally and with further SMRT sequencing of isogenic mutants representing previously uncharacterized MTase genes, we defined the target sequences of three novel ST131-specific MTases and determined the genomic distribution of all MTase target sequences. Using a large collection of 95 previously sequenced ST131 genomes, we identified mobile genetic elements as a major factor driving diversity in DNA methylation patterns. Overall, our analysis highlights the potential for DNA methylation to dramatically influence gene regulation at the transcriptional level within a well-defined E. coli clone.

    Matched MeSH terms: DNA, Bacterial/metabolism*
  8. Loke MF, Ng CG, Vilashni Y, Lim J, Ho B
    Sci Rep, 2016 05 25;6:26784.
    PMID: 27222005 DOI: 10.1038/srep26784
    Helicobacter pylori may reside in the human stomach as two morphological forms: the culturable spiral form and the viable but non-culturable (VBNC) coccoid form. This bacterium transforms from spiral to coccoid under in vitro suboptimal conditions. However, both spiral and coccoid have demonstrated its infectivity in laboratory animals, suggesting that coccoid may potentially be involved in the transmission of H. pylori. To determine the relevance of the coccoid form in viability and infectivity, we compared the protein profiles of H. pylori coccoids obtained from prolonged (3-month-old) culture with that of 3-day-old spirals of two H. pylori standard strains using SWATH (Sequential Window Acquisition of all Theoretical mass spectra)-based approach. The protein profiles reveal that the coccoids retained basal level of metabolic proteins and also high level of proteins that participate in DNA replication, cell division and biosynthesis demonstrating that coccoids are viable. Most interestingly, these data also indicate that the H. pylori coccoids possess higher level of proteins that are involved in virulence and carcinogenesis than their spiral counterparts. Taken together, these findings have important implications in the understanding on the pathogenesis of H. pylori-induced gastroduodenal diseases, as well as the probable transmission mode of this bacterium.
    Matched MeSH terms: DNA, Bacterial/metabolism
  9. Mariappan V, Thavagnanam S, Vellasamy KM, Teh CJS, Atiya N, Ponnampalavanar S, et al.
    BMC Infect Dis, 2018 Sep 05;18(1):455.
    PMID: 30185168 DOI: 10.1186/s12879-018-3371-7
    BACKGROUND: Burkholderia pseudomallei is the causative agent of melioidosis, which is a potentially life threatening disease endemic in Southeast Asian countries. In Malaysia, cystic fibrosis (CF) is an uncommon condition. The association between CF and B.pseudomallei infections has been reported previously. However, this is the first case report of a pediatric melioidosis relapse and co-infection with other Gram-negative bacteria in Malaysia.

    CASE PRESENTATION: A 14-year-old Chinese Malaysian boy presented with a history of recurrent pneumonia, poor growth and steatorrhoea since childhood, and was diagnosed with CF. B. pseudomallei was cultured from his sputum during three different admissions between 2013 and 2016. However, the patient succumbed to end stage of respiratory failure in 2017 despite antibiotics treatment against B.pseudomallei. The isolates were compared using multilocus-sequence typing and repetitive-element polymerase chain reaction (PCR), and confirmed that two of the isolates were of same sequence type, which may indicate relapse.

    CONCLUSIONS: CF patients should be aware of melioidosis in endemic regions, as it is an emerging infectious disease, especially when persistent or recurrent respiratory symptoms and signs of infection occur. The high prevalence rates of melioidosis in Malaysia warrants better management options to improve quality of life, and life expectancy in patients with CF. Travel activities to endemic regions should also be given more consideration, as this would be crucial to identify and initiate appropriate empiric treatment.

    Matched MeSH terms: DNA, Bacterial/metabolism
  10. Hart T, Tang WY, Mansoor SAB, Chio MTW, Barkham T
    BMC Infect Dis, 2020 Apr 28;20(1):314.
    PMID: 32345231 DOI: 10.1186/s12879-020-05019-1
    BACKGROUND: Mycoplasma genitalium is an emerging sexually transmitted infection, with increasing rates of resistance to fluroquinolones and macrolides, the recommended treatments. Despite this, M. genitalium is not part of routine screening for Sexually Transmitted Infections (STIs) in many countries and the prevalence of infection and patterns of disease remain to be determined in many populations. Such data is of particular importance in light of the reported rise in antibiotic resistance in M. genitalium isolates.

    METHODS: Urine and urethral swab samples were collected from the primary public sexual health clinic in Singapore and tested for C. trachomatis (CT) or N. gonorrhoeae (NG) infection and for the presence of M. genitalium. Antibiotic resistance in M. genitalium strains detected was determined by screening for genomic mutations associated with macrolide and fluroquinolone resistance.

    RESULTS: We report the results of a study into M. genitalium prevalence at the national sexual health clinic in Singapore. M. genitalium was heavily associated with CT infection (8.1% of cases), but present in only of 2.4% in CT negative cases and not independently linked to NG infection. Furthermore, we found high rates of resistance mutations to both macrolides (25%) and fluoroquinolones (37.5%) with a majority of resistant strains being dual-resistant. Resistance mutations were only found in strains from patients with CT co-infection.

    CONCLUSIONS: Our results support targeted screening of CT positive patients for M. genitalium as a cost-effective strategy to reduce the incidence of M. genitalium in the absence of comprehensive routine screening. The high rate of dual resistance also highlights the need to ensure the availability of alternative antibiotics for the treatment of multi-drug resistant M. genitalium isolates.

    Matched MeSH terms: DNA, Bacterial/metabolism
  11. 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.
    Matched MeSH terms: DNA, Bacterial/metabolism
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