Displaying publications 1 - 20 of 24 in total

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  1. A two-step method using air plasma and carbodiimide crosslinking to enhance the biocompatibility of polycaprolactone
    Sahapaibounkit P, Prasertsung I, Mongkolnavin R, Wong CS, Damrongsakkul S
    J Biomed Mater Res B Appl Biomater, 2017 08;105(6):1658-1666.
    PMID: 27177842 DOI: 10.1002/jbm.b.33708
    In this study, polycaprolactone (PCL) film, a high potential material used in biomedical applications, was treated by air plasma prior to a conjugation by carbodiimide cross-linking with various types of proteins, including type A gelatin, type B gelatin, and collagen hydrolysate. The properties of modified PCL films were characterized by X-ray photoelectron spectroscopy (XPS), contact angle measurement, and atomic force microscopy. The XPS results showed that oxygen and nitrogen atoms were successfully introduced on the air plasma-treated PCL surface. Primary amine was found on the air plasma-treated PCL films. All proteins were shown to be successfully cross-linked on air plasma-treated PCL films. The wettability and roughness of protein-conjugated PCL films were significantly increased compared to those of neat PCL film. In vitro biocompatibility test using L929 mouse fibroblast showed that the attachment percentage and spreading area of attached cells on all protein-conjugated PCL films were markedly increased. Comparing among modified PCL films, no significant difference on the attachment of L929 on modified PCL films was noticed. However, the spreading areas of cells after 24 hours of culture on type A gelatin- and type B gelatin-modified PCL surfaces were higher than that on collagen hydrolysate-modified surface, possibly related to the lower percentage of amide bond on collagen hydrolysate-conjugated surface compared to those on both gelatin-conjugated PCL ones. This indicated that the two-step modification of PCL film via air plasma and carbodiimide cross-linking with collagen-derived proteins could enhance the biocompatibility of PCL films. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 1658-1666, 2017.
  2. Fulltext Anatomic considerations for immediate implant placement in the mandibular molar region: a cross-sectional study using cone-beam computed tomography
    Ho JY, Ngeow WC, Lim D, Wong CS
    Folia Morphol (Warsz), 2021 Jun 29.
    PMID: 34184752 DOI: 10.5603/FM.a2021.0060
    BACKGROUND: There is concern regarding immediate implantation in the molar region because of discrepancy between socket size and inserted implant diameter. The purpose of this study was to assess the local anatomy of the posterior mandibular region in relation to immediate implant placement using cone-beam computed tomography (CBCT).

    MATERIALS AND METHODS: Using CBCT imaging data, 204 mandibular first molars and 201 mandibular second molars were assessed for the interradicular and alveolar bone dimensions, tooth sizes and proximity to vital structures. The cross-sectional mandibular shape and root configuration of these molars were determined.

    RESULTS: Distances to the inferior alveolar canal (IAC) from the root apices of the first molar were significantly greater than the second molar. Up to 14.5% of second molars had less than 10mm of vertical bone height between the IAC and furcation bone crest. Interradicular bone width of <3mm was found in 57% of second molars. All first molars in this study had two to three roots while 16% of second molars presented with a single root. The prevalent mandible shape at the first and second molars was the parallel and undercut ridges, respectively.

    CONCLUSIONS: The mandibular second molars from samples of a Southeast Asian population presented with greater anatomical difficulties for immediate implant placement which include absent or inadequate interradicular bone thickness, higher incidence of unfavorable mandible shape and increased proximity to vital structures.

  3. Bleeding events and associated factors in a cohort of adult patients taking warfarin in Sarawak, Malaysia
    Edwards F, Arkell P, Fong, Roberts LM, Gendy D, Wong CS, et al.
    J Thromb Thrombolysis, 2014;38(2):226-34.
    PMID: 24233388
    Evidence is emerging that rates of adverse events in patients taking warfarin may vary with ethnicity. This study investigated the rates of bleeds and thromboembolic events, the international normalised ratio (INR) status and the relationship between INR and bleeding events in Malaysia. Patients attending INR clinic at the Heart Centre, Sarawak General Hospital were enrolled on an ad hoc basis from May 2010 and followed up for 1 year. At each routine visit, INR was recorded and screening for bleeding or thromboembolism occurred. Variables relating to INR control were used as predictors of bleeds in logistic regression models. 125 patients contributed to 140 person-years of follow-up. The rates of major bleed, thromboembolic event and minor bleed per 100 person-years of follow-up were 1.4, 0.75 and 34.3. The median time at target range calculated using the Rosendaal method was 61.6% (IQR 44.6–74.1%). Of the out-of-range readings, 30.0% were below range and 15.4% were above. INR variability, (standard deviation of individuals’ mean INR), was the best predictor of bleeding events, with an odds ratio of 3.21 (95% CI 1.10–9.38). Low rates of both major bleeds and thromboembolic events were recorded, in addition to a substantial number of INR readings under the recommended target range. This may suggest that the recommended INR ranges may not represent the optimal warfarin intensity for this population and that a lower intensity of therapy, as observed in this cohort, could be beneficial in preventing adverse events.

    Study site: INR clinic at the Heart Centre, Sarawak General Hospital
  4. Cephalhematoma infected by Escherichia coli presenting as an extensive scalp abscess
    Wong CS, Cheah FC
    J Pediatr Surg, 2012 Dec;47(12):2336-40.
    PMID: 23217901 DOI: 10.1016/j.jpedsurg.2012.09.029
    Cephalhematoma is normally a self-limiting condition affecting 1%-2% of live births, especially following instrumental forceps delivery. The sub-periosteal bleed is characteristically limited by the cranial sutures. Although benign in most instances, this condition may, in a small proportion of cases, be complicated by hyperbilirubinemia or scalp infection. We describe a case of cephalhematoma in a newborn infant infected with Escherichia coli resulting in an extensive deep seated scalp abscess. The infection was also systemic causing E. coli septicemia and initial assessment assumed local extension including bone and meningeal to cause skull osteomyelitis and meningitis respectively. Further investigations and multiple-modality imaging with ultrasound, CT scan and bone scintigraphy outlined the involvement as limited to the scalp, resulting in a shorter antibiotic treatment period and earlier discharge from hospital. The infant recovered well with parenteral antibiotics, saucerization of the abscess and a later skin grafting procedure.
  5. Characterization of wetland quorum quenching Pseudomonas aeruginosa strain 2SW8 and its 2-heptyl-3-hydroxy-4-quinolone production
    Wong CS, Yin WF, Sam CK, Koh CL, Chan KG
    New Microbiol., 2012 Jan;35(1):43-51.
    PMID: 22378552
    Most Proteobacteria produce N-acylhomoserine lactones for bacterial cell-to-cell communication, a process called quorum sensing. Interference of quorum sensing, commonly known as quorum quenching, represents an important way to control quorum sensing. This work reports the isolation of quorum quenching bacterium strain 2WS8 from Malaysia tropical wetland water (2°11'8"N, 102°15'2"E, in 2007) by using a modified version of a previously reported KG medium. Strain 2WS8 was isolated based on its ability to utilize N-(3-oxohexanoyl)-L-homoserine lactone (3-oxo-C6-HSL) as the sole source of energy. This bacterium clustered closely to Pseudomonas aeruginosa PAO1. Strain 2SW8 possesses both quiP and pvdQ homologue acylase genes. Rapid Resolution Liquid Chromatography analysis confirmed that strain 2SW8 preferentially degraded N-acylhomoserine lactones with 3-oxo group substitution but not those with unsubstituted groups at C3 position in the acyl side chain. Strain 2SW8 also showed 2-heptyl-3-hydroxy-4-quinolone production.
  6. Fulltext Chemsex among gay, bisexual, and other men who have sex with men in Singapore and the challenges ahead: A qualitative study
    Tan RKJ, Wong CM, Chen MI, Chan YY, Bin Ibrahim MA, Lim OZ, et al.
    Int J Drug Policy, 2018 11;61:31-37.
    PMID: 30388567 DOI: 10.1016/j.drugpo.2018.10.002
    BACKGROUND: Sexualised substance use, or 'chemsex' has been shown to be a major factor driving the syndemic of HIV/AIDS in communities of gay, bisexual, and other men who have sex with men (GBMSM) around the world. However, there is a paucity of research on chemsex among GBMSM in Singapore due to punitive drug laws and the criminalisation of sexual behaviour between men. This qualitative descriptive study is the first to explore perceptions towards, motivators to engaging in, and the barriers to addressing the harms associated with chemsex among GBMSM in Singapore.

    METHODS: We conducted 30 semi-structured in-depth interviews with self-identifying GBMSM between the ages of 18-39 in Singapore following a purposive sampling strategy. Interview topics included participants' perceptions of drug use among GBMSM in Singapore, perceptions towards chemsex, reasons for drug use and chemsex, and recommendations to address the harms associated with chemsex in Singapore. Interviews were audio-recorded, transcribed, coded, and analysed using thematic analysis.

    RESULTS: Participants reported that it was common to encounter chemsex among GBMSM in Singapore as it could be easily accessed or initiated using social networking phone apps. Enhancement and prolongation of sexual experiences, fear of rejection from sexual partners and peers, and its use as a means of coping with societal rejection were three main reasons cited for engaging in chemsex. The impact of punitive drug laws on disclosure and stigmatisation of GBMSM who use drugs were reported to be key barriers towards addressing chemsex. Participants suggested using gay-specific commercial venues as avenues for awareness and educational campaigns, and social media to reach out to younger GBMSM.

    CONCLUSIONS: This study highlights the complexities behind chemsex use among GBMSM in Singapore, and the range of individual to institutional factors to be addressed. We recommend that community-based organisations and policy-makers find ways to destigmatise discussion of chemsex and provide safe spaces to seek help for drug use.

  7. Coexistence of quorum-quenching and quorum-sensing in tropical marine Pseudomonas aeruginosa strain MW3A
    Wong CS, Yin WF, Choo YM, Sam CK, Koh CL, Chan KG
    World J Microbiol Biotechnol, 2012 Feb;28(2):453-61.
    PMID: 22806840 DOI: 10.1007/s11274-011-0836-x
    A chemically defined medium called KGm medium was used to isolate from a sample of sea water a bacterial strain, MW3A, capable of using N-3-oxohexanoyl-L: -homoserine lactone as the sole carbon source. MW3A was clustered closely to Pseudomonas aeruginosa by 16S ribosomal DNA sequence analysis. It degraded both N-acylhomoserine lactones (AHLs) with a 3-oxo group substitution and, less preferably, AHLs with unsubstituted groups at C3 position in the acyl side chain, as determined by Rapid Resolution Liquid Chromatography. Its quiP and pvdQ homologue gene sequences showed high similarities to those of known acylases. Spent supernatant of MW3A harvested at 8-h post inoculation was shown to contain long-chain AHLs when assayed with the biosensor Escherichia coli [pSB1075], and specifically N-dodecanoyl-L: -homoserine lactone and N-3-oxotetradecanoyl-L: -homoserine lactone by high resolution mass spectrometry. Hence, we report here a novel marine P. aeruginosa strain MW3A possessing both quorum-quenching and quorum-sensing properties.
  8. Fulltext Degradation of bacterial quorum sensing signaling molecules by the microscopic yeast Trichosporon loubieri isolated from tropical wetland waters
    Wong CS, Koh CL, Sam CK, Chen JW, Chong YM, Yin WF, et al.
    Sensors (Basel), 2013;13(10):12943-57.
    PMID: 24072030 DOI: 10.3390/s131012943
    Proteobacteria produce N-acylhomoserine lactones as signaling molecules, which will bind to their cognate receptor and activate quorum sensing-mediated phenotypes in a population-dependent manner. Although quorum sensing signaling molecules can be degraded by bacteria or fungi, there is no reported work on the degradation of such molecules by basidiomycetous yeast. By using a minimal growth medium containing N-3-oxohexanoylhomoserine lactone as the sole source of carbon, a wetland water sample from Malaysia was enriched for microbial strains that can degrade N-acylhomoserine lactones, and consequently, a basidiomycetous yeast strain WW1C was isolated. Morphological phenotype and molecular analyses confirmed that WW1C was a strain of Trichosporon loubieri. We showed that WW1C degraded AHLs with N-acyl side chains ranging from 4 to 10 carbons in length, with or without oxo group substitutions at the C3 position. Re-lactonisation bioassays revealed that WW1C degraded AHLs via a lactonase activity. To the best of our knowledge, this is the first report of degradation of N-acyl-homoserine lactones and utilization of N-3-oxohexanoylhomoserine as carbon and nitrogen source for growth by basidiomycetous yeast from tropical wetland water; and the degradation of bacterial quorum sensing molecules by an eukaryotic yeast.
  9. Fulltext Draft Genome Sequence of Quorum-Sensing and Quorum-Quenching Pseudomonas aeruginosa Strain MW3a
    Chan KG, Wong CS, Yin WF, Chan XY
    Genome Announc, 2014;2(2).
    PMID: 24744329 DOI: 10.1128/genomeA.00258-14
    Pseudomonas aeruginosa has a broad range of habitation, from aquatic environments to human lungs. The coexistence of quorum-sensing and quorum-quenching activities occurs in P. aeruginosa strain MW3a. In this work, we present the draft genome sequence of P. aeruginosa MW3a, an interesting bacterium isolated from a marine environment.
  10. Engineering pyrolysis biochar via single-step microwave steam activation for hazardous landfill leachate treatment
    Lam SS, Yek PNY, Ok YS, Chong CC, Liew RK, Tsang DCW, et al.
    J Hazard Mater, 2020 05 15;390:121649.
    PMID: 31753673 DOI: 10.1016/j.jhazmat.2019.121649
    Improving the sustainability and cost-effectiveness of biochar production is crucial to meet increased global market demand. Here, we developed a single-step microwave steam activation (STMSA) as a simplified yet efficient method to produce microwave activated biochar (MAB) from waste palm shell (WPS). The STMSA recorded a higher heating rate (70 °C/min) and higher conversion (45 wt%) of WPS into highly microporous MAB (micropore surface area of 679.22 m2/g) in contrast with the conventional heating approach (≤ 12-17 wt%). The MAB was then applied as biosorbent for hazardous landfill leachate (LL) treatment and the adsorption performance was compared with commercial activated carbon under different pH, adsorbent quantity, adsorbate concentrations, and contact times. The MAB demonstrated high adsorption capacity, achieving maximum adsorption efficiency at 595 mg/g and 65 % removal of chemical oxygen demand (COD) with 0.4 g/L of adsorbent amount under optimal acidic conditions (pH ≈ 2-3) after 24 h of contact time. The Freundlich isotherm and pseudo second-order kinetic models were well-fitted to explain the equilibrium adsorption and kinetics. The results indicate the viability of STMSA as a fast and efficient approach to produce activated biochar as a biosorbent for the treatment of hazardous landfill leachate.
  11. Evaluating the quality of images produced by soft X-ray units
    Bradley DA, Wong CS, Ng KH
    Appl Radiat Isot, 2000 9 26;53(4-5):691-7.
    PMID: 11003508
    For broad-beam soft X-ray sources, assessment of the quality of image produced by such units is made complex by the low penetration capabilities of the radiation. In the present study we have tested the utility of several types of test tool, some of which have been fabricated by us, as part of an effort to evaluate several key image defining parameters. These include the film characteristic, focal-spot size, image resolution and detail detectability. The two sources of X-rays used in present studies were the University of Malaya flash X-ray device (UMFX1) and a more conventional soft X-ray tube (Softex, Tokyo), the latter operating at peak accelerating potentials of 20 kVp. We have established, for thin objects, that both systems produce images of comparable quality and, in particular, objects can be resolved down to better than 45 microm.
  12. Improvement of early cell adhesion on Thai silk fibroin surface by low energy plasma
    Amornsudthiwat P, Mongkolnavin R, Kanokpanont S, Panpranot J, Wong CS, Damrongsakkul S
    Colloids Surf B Biointerfaces, 2013 Nov 1;111:579-86.
    PMID: 23893032 DOI: 10.1016/j.colsurfb.2013.07.009
    Low energy plasma has been introduced to treat the surface of Thai silk fibroin which should be enhanced for cell adhesion due to its native hydrophobic surface. Plasma surface treatment could introduce desirable hydrophilic functionalities on the surface without using any chemicals. In this work, nitrogen glow discharge plasma was generated by a low energy AC50Hz power supply system. The plasma operating conditions were optimized to reach the highest nitrogen active species by using optical emission spectroscopy. X-ray photoelectron spectroscopy (XPS) revealed that amine, hydroxyl, ether, and carboxyl groups were induced on Thai silk fibroin surface after plasma treatment. The results on Fourier transform infrared attenuated total reflection (FTIR-ATR) spectroscopy confirmed that the plasma treated effects were only on the outermost layer since there was no change in the bulk chemistry. The surface topography was insignificantly changed from the detection with atomic force microscopy (AFM). The plasma-treated effects were the improved surface wettability and cell adhesion. After a 90-s treatment, the water contact angle was at 20°, while the untreated surface was at 70°. The early cell adhesion of L929 mouse fibroblast was accelerated. L929 cells only took 3h to reach 100% cell adhesion on 90 s N2 plasma-treated surface, while there was less than 50% cell adhesion on the untreated Thai silk fibroin surface after 6h of culture. The cell adhesion results were in agreement with the cytoskeleton development. L929 F-actin was more evident on 90 s N2 plasma-treated surface than others. It could be concluded that a lower energy AC50Hz plasma system enhanced early L929 mouse fibroblast adhesion on Thai silk fibroin surface without any significant change in surface topography and bulk chemistry.
  13. Fulltext Knowledge, attitudes and practices towards antibiotic use in upper respiratory tract infections among patients seeking primary health care in Singapore
    Pan DS, Huang JH, Lee MH, Yu Y, Chen MI, Goh EH, et al.
    BMC Fam Pract, 2016 11 03;17(1):148.
    PMID: 27809770 DOI: 10.1186/s12875-016-0547-3
    BACKGROUND: Patients' expectations can influence antibiotic prescription by primary healthcare physicians. We assessed knowledge, attitude and practices towards antibiotic use for upper respiratory tract infections (URTIs), and whether knowledge is associated with increased expectations for antibiotics among patients visiting primary healthcare services in Singapore.

    METHODS: Data was collected through a cross-sectional interviewer-assisted survey of patients aged ≥21 years waiting to see primary healthcare practitioners for one or more symptoms suggestive of URTI (cough, sore throat, runny nose or blocked nose) for 7 days or less, covering the demographics, presenting symptoms, knowledge, attitudes, beliefs and practices of URTI and associated antibiotic use. Univariate and multivariate logistic regression was used to assess independent factors associated with patients' expectations for antibiotics.

    RESULTS: Nine hundred fourteen out of 987 eligible patients consulting 35 doctors were recruited from 24 private sector primary care clinics in Singapore. A third (307/907) expected antibiotics, of which a substantial proportion would ask the doctor for antibiotics (121/304, 40 %) and/or see another doctor (31/304, 10 %) if antibiotics were not prescribed. The majority agreed "antibiotics are effective against viruses" (715/914, 78 %) and that "antibiotics cure URTI faster" (594/912, 65 %). Inappropriate antibiotic practices include "keeping antibiotics stock at home" (125/913, 12 %), "taking leftover antibiotics" (114/913, 14 %) and giving antibiotics to family members (62/913, 7 %). On multivariate regression, the following factors were independently associated with wanting antibiotics (odds ratio; 95 % confidence interval): Malay ethnicity (1.67; 1.00-2.79), living in private housing (1.69; 1.13-2.51), presence of sore throat (1.50; 1.07-2.10) or fever (1.46; 1.01-2.12), perception that illness is serious (1.70; 1.27-2.27), belief that antibiotics cure URTI faster (5.35; 3.76-7.62) and not knowing URTI resolves on its own (2.18; 1.08-2.06), while post-secondary education (0.67; 0.48-0.94) was inversely associated. Those with lower educational levels were significantly more likely to have multiple misconceptions about antibiotics.

    CONCLUSION: Majority of patients seeking primary health care in Singapore are misinformed about the role of antibiotics in URTI. Agreeing with the statement that antibiotics cure URTI faster was most strongly associated with wanting antibiotics. Those with higher educational levels were less likely to want antibiotics, while those with lower educational levels more likely to have incorrect knowledge.
  14. Fulltext Lesbian, gay, bisexual, transgender, queer and intersex (LGBTQI+) healthcare in Singapore: perspectives of non-governmental organisations and clinical year medical students
    O'Hara CA, Foon XL, Ng JC, Wong CS, Wang FY, Tan CY, et al.
    Med Educ Online, 2023 Dec;28(1):2172744.
    PMID: 36744296 DOI: 10.1080/10872981.2023.2172744
    PURPOSE: International studies document that lesbian, gay, bisexual, transgender, queer and intersex (LGBTQI+) patients face significant health disparities. Studies exploring the attitudes, knowledge, preparedness and comfort levels of healthcare students towards LGBTQI+ health have been conducted in the United States, United Kingdom and Malaysia. This study aims to investigate stigma in healthcare for LGBTQI+ patients in Singapore, and possible upstream factors within medical education.

    METHODS: This mixed-methods study adopts a convergent parallel design. The Health Stigma and Discrimination Framework was referenced to devise in-depth interviews with representatives from 13 LGBTQI-affirming non-governmental organisations, analysed through thematic analysis. 320 clinical medical students were surveyed about attitudes, knowledge, comfort, preparedness, and perceived importance of/towards LGBTQI+ health, analysed via descriptive statistics and multivariate regression.

    RESULTS: Prevailing stigma in Singaporean society against LGBTQI+ individuals is exacerbated in healthcare settings. Doctors were cited as unfamiliar or uncomfortable with LGBTQI+ health, possibly from lack of training. Among medical students surveyed, the median composite attitudes, comfort and preparedness index was 3.30 (Interquartile Range (IQR) = 0.50), 3.17 (IQR = 0.83), 2.50 (IQR = 1.00) respectively. Only 12.19% of students answered all 11 true-false questions about LGBTQI+ health correctly.

    CONCLUSION: Medical students in Singapore have scored sub-optimally in their knowledge and preparedness towards LGBTQI+ health, while interpersonal and structural stigma in healthcare towards LGBTQI+ people in Singapore negatively affects health and wellbeing. These findings are an impetus to improve medical training in this area. High scores among medical students in attitudes, comfort and perceived importance of LGBTQI+ topics demonstrate that there is space for LGBTQI+ health in the local medical education curriculum. Curricular interventions can prioritise content knowledge, communication skills and sensitivity.

  15. Fulltext Leucostasis: an uncommon cause of respiratory distress
    Goh KL, Bosco J, Wong CS
    Med J Malaysia, 1983 Sep;38(3):194-6.
    PMID: 6584709
  16. Non-thermal plasma for air and water remediation
    Hashim SA, Samsudin FN, Wong CS, Abu Bakar K, Yap SL, Mohd Zin MF
    Arch Biochem Biophys, 2016 09 01;605:34-40.
    PMID: 27056469 DOI: 10.1016/j.abb.2016.03.032
    A modular typed dielectric barrier discharge (DBD) device is designed and tested for air and water remediation. The module is made of a number of DBD tubes that can be arranged in series or parallel. Each of the DBD tubes comprises inner electrode enclosed with dielectric barrier and arranged as such to provide a gap for the passage of gases. Non-thermal plasma generated in the gap effectively creates gaseous chemical reactions. Its efficacy in the remediation of gas stream containing high NOx, similar to diesel emission and wastewater containing latex, are presented. A six tubes DBD module has successfully removed more than 80% of nitric oxide from the gas stream. In another arrangement, oxygen was fed into a two tubes DBD to generate ozone for treatment of wastewater. Samples of wastewater were collected from a treatment pond of a rubber vulcanization pilot plant. The water pollution load was evaluated by the chemical oxygen demand (COD) and biological oxygen demand (BOD5) values. Preliminary results showed some improvement (about 13%) on the COD after treatment and at the same time had increased the BOD5 by 42%. This results in higher BOD5/COD ratio after ozonation which indicate better biodegradability of the wastewater.
  17. Quorum sensing in Aeromonas species isolated from patients in Malaysia
    Chan KG, Puthucheary SD, Chan XY, Yin WF, Wong CS, Too WS, et al.
    Curr Microbiol, 2011 Jan;62(1):167-72.
    PMID: 20544198 DOI: 10.1007/s00284-010-9689-z
    Bacterial quorum sensing signal molecules called N-acylhomoserine lactone (AHL) controls the expression of virulence determinants in many Gram-negative bacteria. We determined AHL production in 22 Aeromonas strains isolated from various infected sites from patients (bile, blood, peritoneal fluid, pus, stool and urine). All isolates produced the two principal AHLs, N-butanoylhomoserine lactone (C4-HSL) and N-hexanoyl homoserine lactone (C6-HSL). Ten isolates also produced additional AHLs. This report is the first documentation of Aeromonas sobria producing C6-HSL and two additional AHLs with N-acyl side chain longer than C(6). Our data provides a better understanding of the mechanism(s) of this environmental bacterium emerging as a human pathogen.
  18. Rapid degradation of N-3-oxo-acylhomoserine lactones by a Bacillus cereus isolate from Malaysian rainforest soil
    Chan KG, Wong CS, Yin WF, Sam CK, Koh CL
    Antonie Van Leeuwenhoek, 2010 Oct;98(3):299-305.
    PMID: 20376561 DOI: 10.1007/s10482-010-9438-0
    A bacterial strain, KM1S, was isolated from a Malaysian rainforest soil sample by using a defined enrichment medium that specifically facilitates selection of quorum quenching bacteria. KM1S was clustered closely to Bacillus cereus by 16S ribosomal DNA sequence analysis. It degraded N-3-oxo-hexanoyl homoserine lactone and N-3-oxo-octanoyl homoserine lactone in vitro rapidly at 4.98 and 6.56 microg AHL h(-1) per 10(9) CFU/ml, respectively, as determined by the Rapid Resolution Liquid Chromatography. The aiiA homologue, encoding an autoinducer inactivation enzyme catalyzing the degradation of N-acylhomoserine lactones, of KM1S was amplified and cloned. Sequence analysis indicated the presence of the motif (106)HXDH-59 amino acids-H(169)-21 amino acids-D(191) for N-acylhomoserine lactone lactonases.
  19. Socioecological differences in factors associated with inconsistent condom use with female sex workers and casual partners: an observational study of heterosexual men attending an anonymous HIV testing clinic in Singapore
    Takashima K, Yeoh GWJ, Chua HE, Ting PLM, Chong JY, Tan RKJ, et al.
    Sex Health, 2019 11;16(6):593-595.
    PMID: 31615617 DOI: 10.1071/SH18230
    Sexual practices among heterosexual men may differ between female sex workers (FSWs) and casual partners. We surveyed 203 heterosexual men and investigated the attributes associated with inconsistent condom use among them. Lower educational attainment was positively associated with inconsistent condom use with FSWs (adjusted prevalence ratio (aPR) 2.63; P = 0.018) and casual partners (aPR 1.55; P = 0.022), whereas early age of sexual debut (aPR 3.00; P = 0.012) and alcohol use during sex (aPR 7.95; P < 0.001) were positively associated with inconsistent condom use with FSWs. Socioecological factors may explain such differences.
  20. Sound production in the tiger-tail seahorse Hippocampus comes: Insights into the sound producing mechanisms
    Lim AC, Chong VC, Chew WX, Muniandy SV, Wong CS, Ong ZC
    J Acoust Soc Am, 2015 Jul;138(1):404-12.
    PMID: 26233039 DOI: 10.1121/1.4923153
    Acoustic signals of the tiger-tail seahorse (Hippocampus comes) during feeding were studied using wavelet transform analysis. The seahorse "click" appears to be a compounded sound, comprising three acoustic components that likely come from two sound producing mechanisms. The click sound begins with a low-frequency precursor signal, followed by a sudden high-frequency spike that decays quickly, and a final, low-frequency sinusoidal component. The first two components can, respectively, be traced to the sliding movement and forceful knock between the supraorbital bone and coronet bone of the cranium, while the third one (purr) although appearing to be initiated here is produced elsewhere. The seahorse also produces a growling sound when under duress. Growling is accompanied by the highest recorded vibration at the cheek indicating another sound producing mechanism here. The purr has the same low frequency as the growl; both are likely produced by the same structural mechanism. However, growl and purr are triggered and produced under different conditions, suggesting that such "vocalization" may have significance in communication between seahorses.
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