MyMedR

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.

Antibiotic resistance and conjugative R plasmids in clinical isolates of Enterobacteriaceae in Peninsular Malaysia

Koh CL

Trans R Soc Trop Med Hyg, 1986;80(1):158-61.

PMID: 3726978

Twenty-five strains of enterobacteria, isolated from man in Peninsular Malaysia and consisting of seven Enterobacter spp., five Escherichia coli, five Salmonella spp., four Klebsiella spp., two Shigella spp., one Proteus sp. and and one Providencia sp., were tested for antibiotic resistance and conjugative R plasmids. They were all sensitive to nalidixic acid and resistant to at least three antibiotics. The number of resistances ranged from 3 to 11 antibiotics, including cefoperazone and sisomicin (two) newly released antibiotics), in addition to common drugs of current use. Of the 25 isolates, 19 (76%) conjugally transferred, at varied frequencies, at least two resistance determinants. Results from equilibrium density gradient centrifugation, agarose gel electrophoresis and transformation experiments provided proof that the transferable resistances were plasmid-mediated. Restriction endonuclease cleavage patterns showed that the plasmids from Proteus strain K005 and Providencia strain K001 may be identical.

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.

Antimicrobial resistance and conjugative R plasmids in Escherichia coli strains isolated from animals in Peninsular Malaysia

Koh CL, Kok CH

Southeast Asian J. Trop. Med. Public Health, 1984 Mar;15(1):37-43.

PMID: 6377513

Fifteen independent E. coli strains of avian, bovine and porcine origin in Peninsular Malaysia were tested for antibiotic resistance and conjugative R plasmids. Eight (53%) isolates were found to be antibiotic resistant. Among them, 37.5% were mono-resistant and 62.5% were resistant to three or more antibiotics, i.e., multi-resistant. All of them were resistant to Tc and sensitive to Gm and Nx. Three of the eight antibiotic resistant strains were able to transfer all or part of their resistance to an E. coli K12 recipient by conjugation. The transfer frequencies of Km, Sm and Tc resistance of the three donors varied between 4.5 X 10(-8) to 6.8 X 10(-7). Analysis of the plasmid profiles of all the three donors and their respective transconjugants after agarose gel electrophoresis provided conclusive evidence that the transferable resistance traits were plasmid-mediated.

Nonconjugative R plasmid-mediated antibiotic resistance in Escherichia coli isolated from animals in Peninsular Malaysia

Koh CL, Kok CH

Southeast Asian J. Trop. Med. Public Health, 1984 Sep;15(3):313-6.

PMID: 6395350

Four of the five veterinary E. coli strains, which were unable to transfer their antibiotic resistance by conjugation, were found to harbour plasmids. Evidence from transformation, agarose gel electrophoresis and curing experiments showed that in strains KE-3, KE-4 and KE-14 a nonconjugative R plasmid carried the gene for resistance to tetracycline. The plasmids in KE-9 were cryptic.

Conjugal transfer of multiple antibiotic resistance from hospital isolates of Klebsiella to Escherichia coli

Koh CL, Lim ME, Wong YH

Southeast Asian J. Trop. Med. Public Health, 1983 Sep;14(3):336-40.

PMID: 6362015

Six independent isolates of Klebsiella from hospital environmental sources in Malaysia were found to be resistant to at least ampicillin, carbenicillin, cefoperazone, chloramphenicol, gentamicin and tetracycline. On the basis of their antibiograms, they were divided into four antibiogroups. They transferred all or part of their multiple antibiotic resistance traits to E. coli by conjugation. The results suggest that these Klebsiella strains harbour self-transmissible R plasmids. The significance of these findings are discussed.

Fulltext Breakpoint cluster region (BCR) gene rearrangement studies in chronic myeloid and acute lymphoblastic leukemias

Chin YM, Bosco JJ, Koh CL

Med J Malaysia, 1992 Jun;47(2):110-3.

PMID: 1494330

Deoxyribonucleic acid (DNA) of twenty chronic myeloid leukemia (CML) and thirty acute lymphoblastic leukemia (ALL) patients were analysed by Southern hybridization. The DNA was digested with BglII and hybridized with a 4.5-kilobase (kb) ph1/bcr-3 DNA probe. All the 20 CML patients showed gene rearrangement within a 5.8-kb segment (the major breakpoint cluster region, M-bcr) of the breakpoint cluster region (bcr) gene of chromosome 22, indicating the presence of the Philadelphia chromosome. M-bcr rearrangement at the bcr gene of chromosome twenty-two was not detected in all the thirty ALL patients (nine adults and twenty-one children) and two normal controls.

Fulltext Plasmids in penicillinase-producing Neisseria gonorrhoeae in Peninsular Malaysia

Koh CL, Kalaimathee KK, Ngeow YF

Med J Malaysia, 1984 Dec;39(4):269-71.

PMID: 6443581

The plasmid profiles of 66 strains of penicillinase-producing Neisseria gonorrhoeae (PPNG), isolated in Peninsular Malaysia, were determined by agarose gel electrophoresis. All the isolates harboured two common plasmid species, a 4.4 x 10 6 Far-East type R plasmid associated with beta-lactamase production and a 2.6 x 106 plasmid of unknown function. In addition to these two plasmids, 51 (77%) PPNG isolates also carried a 24.5 x 106 conjugative plasmid.

Fulltext Plasmid-mediated transferable chloramphenicol and tetracycline resistance in Salmonella typhi (Vi phage type 25) isolated in Peninsular Malaysia

Koh CL, Lim ME, Wong YH

Med J Malaysia, 1983 Dec;38(4):320-4.

PMID: 6599991

A clinical isolate of Salmonella typhi (Vi phage type 25), resistant to chloramphenicol, streptomycin and tetracycline, was examined for the presence of R plasmids. Results from conjugation, agarose gel electrophoresis and transformation experiments indicated that it harboured a single large self-transmissible R plasmid which coded for both the chloramphenicol and tetracycline resistance traits.

Complete nucleotide sequences of Nipah virus isolates from Malaysia

Chan YP, Chua KB, Koh CL, Lim ME, Lam SK

J Gen Virol, 2001 Sep;82(Pt 9):2151-5.

PMID: 11514724

We have completely sequenced the genomes of two Nipah virus (NiV) isolates, one from the throat secretion and the other from the cerebrospinal fluid (CSF) of the sole surviving encephalitic patient with positive CSF virus isolation in Malaysia. The two genomes have 18246 nucleotides each and differ by only 4 nucleotides. The NiV genome is 12 nucleotides longer than the Hendra virus (HeV) genome and both genomes have identical leader and trailer sequence lengths and hexamer-phasing positions for all their genes. Both NiV and HeV are also very closely related with respect to their genomic end sequences, gene start and stop signals, P gene-editing signals and deduced amino acid sequences of nucleocapsid protein, phosphoprotein, matrix protein, fusion protein, glycoprotein and RNA polymerase. The existing evidence demonstrates a clear need for the creation of a new genus within the subfamily Paramyxovirinae to accommodate the close similarities between NiV and HeV and their significant differences from other members of the subfamily.

Mapping of domains responsible for nucleocapsid protein-phosphoprotein interaction of Henipaviruses

Chan YP, Koh CL, Lam SK, Wang LF

J Gen Virol, 2004 Jun;85(Pt 6):1675-1684.

PMID: 15166452 DOI: 10.1099/vir.0.19752-0

Hendra virus (HeV) and Nipah virus (NiV) are members of a new genus, Henipavirus, in the family paramyxoviridae. Each virus encodes a phosphoprotein (P) that is significantly larger than its counterparts in other known paramyxoviruses. The interaction of this unusually large P with its nucleocapsid protein (N) was investigated in this study by using recombinant full-length and truncated proteins expressed in bacteria and a modified protein-blotting protein-overlay assay. Results from our group demonstrated that the N and P of both viruses were able to form not only homologous, but also heterologous, N-P complexes, i.e. HeV N was able to interact with NiV P and vice versa. Deletion analysis of the N and P revealed that there were at least two independent N-binding sites on P and they resided at the N and C termini, respectively. Similarly, more than one P-binding site was present on N and one of these was mapped to a 29 amino acid (aa) C-terminal region, which on its own was sufficient to interact with the extreme C-terminal 165 aa region of P.

Efficacy of Motor Interventions on Functional Performance Among Preschool Children With Autism Spectrum Disorder: A Pilot Randomized Controlled Trial

Jin YR, Sung YS, Koh CL, Chu SY, Yang HC, Lin LY

Am J Occup Ther, 2023 Nov 01;77(6).

PMID: 37992052 DOI: 10.5014/ajot.2023.050283

IMPORTANCE: Motor ability plays an important role in overall developmental profiles. Preschool children with autism spectrum disorder (ASD) are at risk of motor skills deficits and delays. However, evidence of the efficacy of different motor interventions for the identification of optimal treatment types is lacking, especially for preschool children with ASD.

OBJECTIVE: To examine the efficacy of the Motor Skill Occupational Therapy Intervention ON ASD (MOTION-ASD) and Cognitive Orientation Exercise (CO-EXC) programs to improve motor skills performance, self-care performance, and adaptive behaviors among preschool children with ASD.

DESIGN: Randomized controlled trial, two-group, triple-blinded, repeated-measures design Setting: University laboratory.

PARTICIPANTS: Thirteen preschool children with ASD (M age = 4.91 yr).

OUTCOMES AND MEASURES: The Bruininks-Oseretsky Test of Motor Proficiency-Second Edition, Brief Form, Assessment of Motor and Process Skills, and Vineland Adaptive Behavior Scales-Third Edition.

RESULTS: Children in the MOTION-ASD group showed significantly greater improvements in manual coordination and overall gross and fine manual skills than those in the CO-EXC group immediately after the intervention. Significant improvements in fine manual control, body coordination, overall motor skills, and self-care performance were made throughout both interventions and were retained at the posttest and the 4-wk follow-up.

CONCLUSIONS AND RELEVANCE: These findings provide supporting evidence that motor skills interventions involving fundamental skills and cognitive training may be a viable therapeutic option for treating children with ASD. The results also suggest that practitioners may consider providing structured and strategic motor skills interventions for preschool children with ASD. What This Article Adds: This study's rigorous tests of motor skills interventions support ways to manage motor difficulties in children with autism spectrum disorder (ASD). An intervention based on motor learning theory could benefit preschool children with ASD, especially in terms of manual coordination ability and overall gross and fine motor skills.

Fulltext Analysis of ras gene mutations in acute myeloid leukemia by the polymerase chain reaction and oligonucleotide probes

Chin YM, Bosco JJ, Koh CL

Singapore Med J, 1992 Feb;33(1):48-50.

PMID: 1598607

In vitro deoxyribonucleic acid (DNA) amplification by the polymerase chain reaction (PCR) followed by hybridization with oligonucleotide probes were used to study ras gene mutations in acute myeloid leukemia (AML). The DNA of 30 AML patients at presentation of the disease at the University of Malaya Hospital, Kuala Lumpur were screened for ras gene mutations in codons 12, 13 and 61 of the N-ras, K-ras and H-ras genes. Four patients (13.3%) had ras gene mutations. They were all below their early thirties in age. Of the four patients with ras gene mutations, three were M3 and one was M4 according to the French American British (FAB) classification of AML.

Fulltext R plasmid-borne transferable multiple antibiotic resistance in a clinical isolate of Proteus sp in Peninsular Malaysia

Koh CL, Tay SH

Singapore Med J, 1984 Oct;25(5):300-3.

PMID: 6523137

A clinical isolate of Proteus sp., resistant to ampicillin, carbenicillin, cephaloridine, chloramphenicol, cotrimoxazole, gentamicin,
kanamycin and tetracycline, was examined for the presence of conjugative R plasmids. Results from conjugation, agarose gel
electrophoresis and transformation experiments showed that it harboured a large self-transmissible R plasmid which coded for all
the resistance traits.

Fulltext Pseudomonas cremoricolorata strain ND07 produces N-acyl homoserine lactones as quorum sensing molecules

Yunos NY, Tan WS, Koh CL, Sam CK, Mohamad NI, Tan PW, et al.

Sensors (Basel), 2014;14(7):11595-604.

PMID: 24984061 DOI: 10.3390/s140711595

Quorum sensing (QS) is a bacterial cell-to-cell communication system controlling QS-mediated genes which is synchronized with the population density. The regulation of specific gene activity is dependent on the signaling molecules produced, namely N-acyl homoserine lactones (AHLs). We report here the identification and characterization of AHLs produced by bacterial strain ND07 isolated from a Malaysian fresh water sample. Molecular identification showed that strain ND07 is clustered closely to Pseudomonas cremoricolorata. Spent culture supernatant extract of P. cremoricolorata strain ND07 activated the AHL biosensor Chromobacterium violaceum CV026. Using high resolution triple quadrupole liquid chromatography-mass spectrometry, it was confirmed that P. cremoricolorata strain ND07 produced N-octanoyl-L-homoserine lactone (C8-HSL) and N-decanoyl-L-homoserine lactone (C10-HSL). To the best of our knowledge, this is the first documentation on the production of C10-HSL in P. cremoricolorata strain ND07.

Fulltext Short chain N-acyl homoserine lactone production by soil isolate Burkholderia sp. strain A9

Chen JW, Koh CL, Sam CK, Yin WF, Chan KG

Sensors (Basel), 2013;13(10):13217-27.

PMID: 24084115 DOI: 10.3390/s131013217

In the bacteria kingdom, quorum sensing (QS) is a cell-to-cell communication that relies on the production of and response to specific signaling molecules. In proteobacteria, N-acylhomoserine lactones (AHLs) are the well-studied signaling molecules. The present study aimed to characterize the production of AHL of a bacterial strain A9 isolated from a Malaysian tropical soil. Strain A9 was identified as Burkholderia sp. using matrix-assisted laser desorption ionization-time-of-flight mass spectrometry and 16S rDNA nucleotide sequence analysis. AHL production by A9 was detected with two biosensors, namely Chromobacterium violaceum CV026 and Escherichia coli [pSB401]. Thin layer chromatography results showed N-hexanoylhomoserine lactone (C6-HSL) and N-octanoylhomoserine lactone (C8-HSL) production. Unequivocal identification of C6-HSL and C8-HSL was achieved by high resolution triple quadrupole liquid chromatography-mass spectrometry analysis. We have demonstrated that Burkholderia sp. strain A9 produces AHLs that are known to be produced by other Burkholderia spp. with CepI/CepR homologs.

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.

Fulltext Characterization of quorum sensing and quorum quenching soil bacteria isolated from Malaysian tropical montane forest

Chong TM, Koh CL, Sam CK, Choo YM, Yin WF, Chan KG

Sensors (Basel), 2012;12(4):4846-59.

PMID: 22666062 DOI: 10.3390/s120404846

We report the production and degradation of quorum sensing N-acyl-homoserine lactones by bacteria isolated from Malaysian montane forest soil. Phylogenetic analysis indicated that these isolates clustered closely to the genera of Arthrobacter, Bacillus and Pseudomonas. Quorum quenching activity was detected in six isolates of these three genera by using a series of bioassays and rapid resolution liquid chromatography analysis. Biosensor screening and high resolution liquid chromatography-mass spectrometry analysis revealed the production of N-dodecanoyl-L-homoserine lactone (C12-HSL) by Pseudomonas frederiksbergensis (isolate BT9). In addition to degradation of a wide range of N-acyl-homoserine lactones, Arthrobacter and Pseudomonas spp. also degraded p-coumaroyl-homoserine lactone. To the best of our knowledge, this is the first documentation of Arthrobacter and Pseudomonas spp. capable of degrading p-coumaroyl-homoserine lactone and the production of C12-HSL by P. frederiksbergensis.

Fulltext Quorum quenching revisited--from signal decays to signalling confusion

Hong KW, Koh CL, Sam CK, Yin WF, Chan KG

Sensors (Basel), 2012;12(4):4661-96.

PMID: 22666051 DOI: 10.3390/s120404661

In a polymicrobial community, while some bacteria are communicating with neighboring cells (quorum sensing), others are interrupting the communication (quorum quenching), thus creating a constant arms race between intercellular communication. In the past decade, numerous quorum quenching enzymes have been found and initially thought to inactivate the signalling molecules. Though this is widely accepted, the actual roles of these quorum quenching enzymes are now being uncovered. Recent evidence extends the role of quorum quenching to detoxification or metabolism of signalling molecules as food and energy source; this includes "signalling confusion", a term coined in this paper to refer to the phenomenon of non-destructive modification of signalling molecules. While quorum quenching has been explored as a novel anti-infective therapy targeting, quorum sensing evidence begins to show the development of resistance against quorum quenching.

Fulltext Quorum quenching Bacillus sonorensis isolated from soya sauce fermentation brine

Yin WF, Tung HJ, Sam CK, Koh CL, Chan KG

Sensors (Basel), 2012;12(4):4065-73.

PMID: 22666018 DOI: 10.3390/s120404065

An N-acylhomoserine lactone (AHL)-degrading bacterial strain, L62, was isolated from a sample of fermentation brine of Chinese soya sauce by using rich medium agar supplemented with soya sauce (10% v/v). L62, a rod-shaped Gram positive bacterium with amylolytic activity, was phylogentically related to Bacillus sonorensis by 16S ribosomal DNA and rpoB sequence analyses. B. sonorensis L62 efficiently degraded N-3-oxohexanoyl homoserine lactone and N-octanoylhomoserine lactone. However, the aiiA homologue, encoding an autoinducer inactivation enzyme catalyzing the degradation of AHLs, was not detected in L62, suggesting the presence of a different AHL-degrading gene in L62. To the best of our knowledge, this is the first report of AHL-degrading B. sonorensis from soya sauce liquid state fermentation.

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