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How KY, Hong KW, Sam CK, Koh CL, Yin WF, Chan KG. Unravelling the genome of long chain N-acylhomoserine lactone-producing Acinetobacter sp. strain GG2 and identification of its quorum sensing synthase gene. Front Microbiol 2015; 6:240. [PMID: 25926817 PMCID: PMC4396500 DOI: 10.3389/fmicb.2015.00240] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2014] [Accepted: 03/11/2015] [Indexed: 12/22/2022] Open
Abstract
Myriad proteobacteria use N-acyl homoserine lactone (AHL) molecules as quorum sensing (QS) signals to regulate different physiological functions, including virulence, antibiotic production, and biofilm formation. Many of these proteobacteria possess LuxI/LuxR system as the QS mechanism. Recently, we reported the 3.89 Mb genome of Acinetobacter sp. strain GG2. In this work, the genome of this long chain AHL-producing bacterium was unravelled which led to the molecular characterization of luxI homologue, designated as aciI. This 552 bp gene was cloned and overexpressed in Escherichia coli BL21(DE3). The purified protein was ∼20.5 kDa and is highly similar to several autoinducer proteins of LuxI family among Acinetobacter species. To verify the AHL synthesis activity of this protein, high-resolution liquid chromatography–mass spectrometry analysis revealed the production of 3-oxo-dodecanoyl-homoserine lactone and 3-hydroxy-dodecanoyl-homoserine lactone from induced E. coli harboring the recombinant AciI. Our data show for the first time, the cloning and characterization of the luxI homologue from Acinetobacter sp. strain GG2, and confirmation of its AHLs production. These data are of great significance as the annotated genome of strain GG2 has provided a valuable insight in the study of autoinducer molecules and its roles in QS mechanism of the bacterium.
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Affiliation(s)
- Kah Yan How
- Division of Genetics and Molecular Biology, Institute of Biological Sciences, Faculty of Science, University of Malaya Kuala Lumpur, Malaysia
| | - Kar-Wai Hong
- Division of Genetics and Molecular Biology, Institute of Biological Sciences, Faculty of Science, University of Malaya Kuala Lumpur, Malaysia
| | - Choon-Kook Sam
- Natural Sciences and Science Education Academic Group, National Institute of Education, Nanyang Technological University Singapore, Singapore
| | - Chong-Lek Koh
- Natural Sciences and Science Education Academic Group, National Institute of Education, Nanyang Technological University Singapore, Singapore
| | - Wai-Fong Yin
- Division of Genetics and Molecular Biology, Institute of Biological Sciences, Faculty of Science, University of Malaya Kuala Lumpur, Malaysia
| | - Kok-Gan Chan
- Division of Genetics and Molecular Biology, Institute of Biological Sciences, Faculty of Science, University of Malaya Kuala Lumpur, Malaysia
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Wong CS, Koh CL, Sam CK, Chen JW, Chong YM, Yin WF, Chan KG. Degradation of bacterial quorum sensing signaling molecules by the microscopic yeast Trichosporon loubieri isolated from tropical wetland waters. Sensors (Basel) 2013; 13:12943-57. [PMID: 24072030 PMCID: PMC3859043 DOI: 10.3390/s131012943] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/15/2013] [Revised: 09/08/2013] [Accepted: 09/12/2013] [Indexed: 11/16/2022]
Abstract
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.
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Affiliation(s)
- Cheng-Siang Wong
- Division of Genetics and Molecular Biology, Institute of Biological Sciences, Faculty of Science, University of Malaya, Kuala Lumpur 50603, Malaysia; E-Mails: (C.-S.W.); (J.W.C.); (Y.M.C.); (W.-F.Y.)
| | - Chong-Lek Koh
- Natural Sciences and Science Education AG, National Institute of Education, Nanyang Technological University, 1 Nanyang Walk, Singapore 637616, Singapore; E-Mails: (C.-L.K.); (C.-K.S.)
| | - Choon-Kook Sam
- Natural Sciences and Science Education AG, National Institute of Education, Nanyang Technological University, 1 Nanyang Walk, Singapore 637616, Singapore; E-Mails: (C.-L.K.); (C.-K.S.)
| | - Jian Woon Chen
- Division of Genetics and Molecular Biology, Institute of Biological Sciences, Faculty of Science, University of Malaya, Kuala Lumpur 50603, Malaysia; E-Mails: (C.-S.W.); (J.W.C.); (Y.M.C.); (W.-F.Y.)
| | - Yee Meng Chong
- Division of Genetics and Molecular Biology, Institute of Biological Sciences, Faculty of Science, University of Malaya, Kuala Lumpur 50603, Malaysia; E-Mails: (C.-S.W.); (J.W.C.); (Y.M.C.); (W.-F.Y.)
| | - Wai-Fong Yin
- Division of Genetics and Molecular Biology, Institute of Biological Sciences, Faculty of Science, University of Malaya, Kuala Lumpur 50603, Malaysia; E-Mails: (C.-S.W.); (J.W.C.); (Y.M.C.); (W.-F.Y.)
| | - Kok-Gan Chan
- Division of Genetics and Molecular Biology, Institute of Biological Sciences, Faculty of Science, University of Malaya, Kuala Lumpur 50603, Malaysia; E-Mails: (C.-S.W.); (J.W.C.); (Y.M.C.); (W.-F.Y.)
- Author to whom correspondence should be addressed; E-Mail: ; Tel.: +603-7967-5162; Fax: +603-7967-4509
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Koh CL, Sam CK, Yin WF, Tan LY, Krishnan T, Chong YM, Chan KG. Plant-derived natural products as sources of anti-quorum sensing compounds. Sensors (Basel) 2013; 13:6217-28. [PMID: 23669710 PMCID: PMC3690052 DOI: 10.3390/s130506217] [Citation(s) in RCA: 141] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/22/2013] [Revised: 04/28/2013] [Accepted: 05/02/2013] [Indexed: 01/06/2023]
Abstract
Quorum sensing is a system of stimuli and responses in relation to bacterial cell population density that regulates gene expression, including virulence determinants. Consequently, quorum sensing has been an attractive target for the development of novel anti-infective measures that do not rely on the use of antibiotics. Anti-quorum sensing has been a promising strategy to combat bacterial infections as it is unlikely to develop multidrug resistant pathogens since it does not impose any selection pressure. A number of anti-quorum sensing approaches have been documented and plant-based natural products have been extensively studied in this context. Plant matter is one of the major sources of chemicals in use today in various industries, ranging from the pharmaceutical, cosmetic, and food biotechnology to the textile industries. Just like animals and humans, plants are constantly exposed to bacterial infections, it is therefore logical to expect that plants have developed sophisticated of chemical mechanisms to combat pathogens. In this review, we have surveyed the various types of plant-based natural products that exhibit anti-quorum sensing properties and their anti-quorum sensing mechanisms.
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Affiliation(s)
- Chong-Lek Koh
- Natural Sciences and Science Education AG, National Institute of Education, Nanyang Technological University, 1 Nanyang Walk, 637616, Singapore; E-Mails: (C.-L.K.); (C.-K.S.)
| | - Choon-Kook Sam
- Natural Sciences and Science Education AG, National Institute of Education, Nanyang Technological University, 1 Nanyang Walk, 637616, Singapore; E-Mails: (C.-L.K.); (C.-K.S.)
| | - Wai-Fong Yin
- Division of Genetics and Molecular Biology, Institute of Biological Sciences, Faculty of Science, University of Malaya, Kuala Lumpur 50603, Malaysia; E-Mails: (W.-F.Y.); (L.Y.T.); (T.K.); (Y.M.C.)
| | - Li Ying Tan
- Division of Genetics and Molecular Biology, Institute of Biological Sciences, Faculty of Science, University of Malaya, Kuala Lumpur 50603, Malaysia; E-Mails: (W.-F.Y.); (L.Y.T.); (T.K.); (Y.M.C.)
| | - Thiba Krishnan
- Division of Genetics and Molecular Biology, Institute of Biological Sciences, Faculty of Science, University of Malaya, Kuala Lumpur 50603, Malaysia; E-Mails: (W.-F.Y.); (L.Y.T.); (T.K.); (Y.M.C.)
| | - Yee Meng Chong
- Division of Genetics and Molecular Biology, Institute of Biological Sciences, Faculty of Science, University of Malaya, Kuala Lumpur 50603, Malaysia; E-Mails: (W.-F.Y.); (L.Y.T.); (T.K.); (Y.M.C.)
| | - Kok-Gan Chan
- Division of Genetics and Molecular Biology, Institute of Biological Sciences, Faculty of Science, University of Malaya, Kuala Lumpur 50603, Malaysia; E-Mails: (W.-F.Y.); (L.Y.T.); (T.K.); (Y.M.C.)
- Author to whom correspondence should be addressed; E-Mail: ; Tel.: +603-7967-5162; Fax: +603-7967-4509
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Chang CY, Koh CL, Sam CK, Chan XY, Yin WF, Chan KG. Unusual long-chain N-acyl homoserine lactone production by and presence of quorum quenching activity in bacterial isolates from diseased tilapia fish. PLoS One 2012; 7:e44034. [PMID: 22952864 PMCID: PMC3430623 DOI: 10.1371/journal.pone.0044034] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2012] [Accepted: 08/01/2012] [Indexed: 11/30/2022] Open
Abstract
Growth-dependent cell-cell communication termed quorum sensing is a key regulatory system in bacteria for controlling gene expression including virulence factors. In this study five potential bacterial pathogens including Bacillus sp. W2.2, Klebsiella sp. W4.2, Pseudomonas sp. W3 and W3.1 and Serratia sp. W2.3 were isolated from diseased Tilapia fish in Malaysia, supplied by the leading global fish supplier. Proteolytic activity assays confirmed that with the exception of Klebsiella sp. W4.2, all isolates showed distinct proteolytic activity. Furthermore Bacillus sp. W2.2 and Pseudomonas sp. strains W3 and W3.1 also displayed haemolytic activity. By using high resolution liquid chromatography mass spectrometry, we revealed the presence of unusually long-chain N-(3-oxohexadecanoyl)-homoserine lactone (3-oxo-C16-HSL) from Pseudomonas sp. W3.1 and N-dodecanoyl-homoserine lactone (C12-HSL) from Serratia sp. W2.3, respectively. Interestingly, Pseudomonas sp. W3.1 also produced a wide range of Pseudomonas quinolone signalling (PQS) molecules. Pseudomonas sp. W3 did not show any quorum sensing properties but possessed quorum quenching activity that inactivated AHLs. This study is the first documentation that shows unusual long-chain AHLs production in Serratia sp. and Pseudomonas sp. isolated from diseased fish and the latter also produce a wide range of PQS molecules.
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Affiliation(s)
- Chien-Yi Chang
- School of Molecular Medical Sciences, Centre for Biomolecular Science, University of Nottingham, Nottingham, United Kingdom
| | - Chong-Lek Koh
- Natural Sciences and Science Education AG, National Institute of Education, Nanyang Technological University, Singapore, Singapore
| | - Choon-Kook Sam
- Natural Sciences and Science Education AG, National Institute of Education, Nanyang Technological University, Singapore, Singapore
| | - Xin-Yue Chan
- Division of Genetics and Molecular Biology, Institute of Biological Sciences, Faculty of Science, University of Malaya, Malaysia
| | - Wai Fong Yin
- Division of Genetics and Molecular Biology, Institute of Biological Sciences, Faculty of Science, University of Malaya, Malaysia
| | - Kok Gan Chan
- Division of Genetics and Molecular Biology, Institute of Biological Sciences, Faculty of Science, University of Malaya, Malaysia
- * E-mail:
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Yin WF, Purmal K, Chin S, Chan XY, Koh CL, Sam CK, Chan KG. N-acyl homoserine lactone production by Klebsiella pneumoniae isolated from human tongue surface. Sensors (Basel) 2012; 12:3472-83. [PMID: 22737019 PMCID: PMC3376583 DOI: 10.3390/s120303472] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/12/2012] [Revised: 02/16/2012] [Accepted: 02/23/2012] [Indexed: 11/16/2022]
Abstract
Bacteria communicate by producing quorum sensing molecules called autoinducers, which include autoinducer-1, an N-hexanoyl homoserine lactone (AHL), and autoinducer-2. Bacteria present in the human oral cavity have been shown to produce autoinducer-2, but not AHL. Here, we report the isolation of two AHL-producing Klebsiella pneumoniae strains from the posterior dorsal surface of the tongue of a healthy individual. Spent culture supernatant extracts from K. pneumoniae activated the biosensors Agrobacterium tumefaciens NTL4(pZLR4) and Escherichia coli [pSB401], suggesting the presence of both long and short chain AHLs. High resolution mass spectrometry analyses of these extracts confirmed that both K. pneumoniae isolates produced N-octanoylhomoserine lactone and N-3-dodecanoyl-L-homoserine lactone. To the best of our knowledge, this is the first report of the isolation of K. pneumoniae from the posterior dorsal surface of the human tongue and the production of these AHLs by this bacterium.
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Affiliation(s)
- Wai-Fong Yin
- Division of Genetics and Molecular Biology, Institute of Biological Sciences, Faculty of Science, University of Malaya, 50603 Kuala Lumpur, Malaysia; E-Mails: (W.-F.Y.); (S.C.); (X.-Y.C.)
| | - Kathiravan Purmal
- School of Dental Sciences, Universiti Sains Malaysia, 16150 Kubang Kerian, Kelantan, Malaysia; E-Mail:
| | - Shenyang Chin
- Division of Genetics and Molecular Biology, Institute of Biological Sciences, Faculty of Science, University of Malaya, 50603 Kuala Lumpur, Malaysia; E-Mails: (W.-F.Y.); (S.C.); (X.-Y.C.)
| | - Xin-Yue Chan
- Division of Genetics and Molecular Biology, Institute of Biological Sciences, Faculty of Science, University of Malaya, 50603 Kuala Lumpur, Malaysia; E-Mails: (W.-F.Y.); (S.C.); (X.-Y.C.)
| | - Chong-Lek Koh
- Natural Sciences and Science Education AG, National Institute of Education, Nanyang Technological University, 1 Nanyang Walk, 637616, Singapore; E-Mails: (C.-L.K.); (C.-K.S.)
| | - Choon-Kook Sam
- Natural Sciences and Science Education AG, National Institute of Education, Nanyang Technological University, 1 Nanyang Walk, 637616, Singapore; E-Mails: (C.-L.K.); (C.-K.S.)
| | - Kok-Gan Chan
- Division of Genetics and Molecular Biology, Institute of Biological Sciences, Faculty of Science, University of Malaya, 50603 Kuala Lumpur, Malaysia; E-Mails: (W.-F.Y.); (S.C.); (X.-Y.C.)
- Author to whom correspondence should be addressed; E-Mail: ; Tel.: +603-7967-5162; Fax: +603-7967-4509
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Wong CS, Yin WF, Sam CK, Koh CL, Chan KG. Characterization of wetland quorum quenching Pseudomonas aeruginosa strain 2SW8 and its 2-heptyl-3-hydroxy-4-quinolone production. New Microbiol 2012; 35:43-51. [PMID: 22378552] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Received: 04/01/2011] [Accepted: 09/02/2011] [Indexed: 05/31/2023]
Abstract
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.
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Affiliation(s)
- Cheng-Siang Wong
- Division of Genetics and Molecular Biology, University of Malaya, Kuala Lumpur, Malaysia
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Sautter R, Ramos D, Schneper L, Ciofu O, Wassermann T, Koh CL, Heydorn A, Hentzer M, Høiby N, Kharazmi A, Molin S, Devries CA, Ohman DE, Mathee K. A complex multilevel attack on Pseudomonas aeruginosa algT/U expression and algT/U activity results in the loss of alginate production. Gene 2011; 498:242-53. [PMID: 22088575 DOI: 10.1016/j.gene.2011.11.005] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2011] [Revised: 09/27/2011] [Accepted: 11/01/2011] [Indexed: 11/18/2022]
Abstract
Infection by the opportunistic pathogen Pseudomonas aeruginosa is a leading cause of morbidity and mortality seen in cystic fibrosis (CF) patients. This is mainly due to the genotypic and phenotypic changes of the bacteria that cause conversion from a typical nonmucoid to a mucoid form in the CF lung. Mucoid conversion is indicative of overproduction of a capsule-like polysaccharide called alginate. The alginate-overproducing (Alg(+)) mucoid phenotype seen in the CF isolates is extremely unstable. Low oxygen tension growth of mucoid variants readily selects for nonmucoid variants. The switching off mechanism has been mapped to the algT/U locus, and the molecular basis for this conversion was partially attributed to mutations in the algT/U gene itself. To further characterize molecular changes resulting in the unstable phenotype, an isogenic PAO1 derivative that is constitutively Alg(+) due to the replacement of the mucA with mucA22 (PDO300) was used. The mucA22 allele is common in mucoid CF isolates. Thirty-four spontaneous nonmucoid variants, or sap (suppressor of alginate production) mutants, of PDO300 were isolated under low oxygen tension. About 40% of the sap mutants were rescued by a plasmid carrying algT/U (Group A). The remaining sap mutants were not (Group B). The members of Group B fall into two subsets: one similar to PAO1, and another comparable to PDO300. Sequence analysis of the algT/U and mucA genes in Group A shows that mucA22 is intact, whereas algT/U contains mutations. Genetic complementation and sequencing of one Group B sap mutant, sap22, revealed that the nonmucoid phenotype was due to the presence of a mutation in PA3257. PA3257 encodes a putative periplasmic protease. Mutation of PA3257 resulted in decreased algT/U expression. Thus, inhibition of algT/U is a primary mechanism for alginate synthesis suppression.
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Affiliation(s)
- Robert Sautter
- Department of Biological Sciences, College of Arts and Sciences, Florida International University, Miami, FL 33199, USA
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Chong YM, Yin WF, Ho CY, Mustafa MR, Hadi AHA, Awang K, Narrima P, Koh CL, Appleton DR, Chan KG. Malabaricone C from Myristica cinnamomea exhibits anti-quorum sensing activity. J Nat Prod 2011; 74:2261-2264. [PMID: 21910441 DOI: 10.1021/np100872k] [Citation(s) in RCA: 98] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
A methanol-soluble extract of the bark of Myristica cinnamomea was found to exhibit anti-quorum sensing activity, and subsequent bioassay-guided isolation led to the identification of the active compound malabaricone C (1). Compound 1 inhibited violacein production by Chromobacterium violaceum CV026 when grown in the presence of a cognate signaling molecule, N-3-oxohexanoyl-homoserine lactone. Furthermore, 1 inhibited the quorum sensing-regulated pyocyanin production and biofilm formation in Pseudomonas aeruginosa PAO1. These results suggest that the anti-quorum sensing activity of 1 and related molecules should be investigated further.
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Affiliation(s)
- Yee Meng Chong
- Division of Genetics and Molecular Biology, Institute of Biological Sciences, Faculty of Science, University of Malaya, 50603 Kuala Lumpur, Malaysia
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Abstract
T cells undergo a series of complex phenotypic changes before achieving maturation. Discrete stages of T-cell differentiation are simplified to four stages (pro-, pre-, cortical and mature-T cell) and used in the classification of T-cell leukaemia. HLA-DR has been reported to be expressed in immature T-cell acute lymphoblastic leukemia (ALL) and also confer a poorer treatment outcome. Simultaneously, the genotype goes through distinct pattern changes due to rearrangement of T-cell receptor (TCR) genes. TCR gene rearrangement is important in the diagnosis of clonality and used as markers to detect minimal residual disease in lymphoproliferative disorders. We identified a subset within Pro-T and Pre-T cell cases distinguished by the expression of HLA-DR. These subgroups appeared to be more immature as rearrangement of the TCR-gamma gene was either at germline or involved only the first constant region (C1) unlike a more rearranged pattern in the HLA-DR-subgroups. We also observed a higher incidence of mediastinal mass (67%) in the HLA-DR-subgroup in the Pre-T stage. These characteristics may be useful as markers to further refine staging of T-cell ALL and determine prognosis.
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Affiliation(s)
- Abdullah Maha
- Department of Pathology, Faculty of Medicine and Health Sciences, Universiti Putra Malaysia, Serdang, Selangor, Malaysia.
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Chan KG, Atkinson S, Mathee K, Sam CK, Chhabra SR, Cámara M, Koh CL, Williams P. Characterization of N-acylhomoserine lactone-degrading bacteria associated with the Zingiber officinale (ginger) rhizosphere: co-existence of quorum quenching and quorum sensing in Acinetobacter and Burkholderia. BMC Microbiol 2011; 11:51. [PMID: 21385437 PMCID: PMC3062576 DOI: 10.1186/1471-2180-11-51] [Citation(s) in RCA: 126] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2010] [Accepted: 03/08/2011] [Indexed: 11/30/2022] Open
Abstract
BACKGROUND Cell-to-cell communication (quorum sensing (QS)) co-ordinates bacterial behaviour at a population level. Consequently the behaviour of a natural multi-species community is likely to depend at least in part on co-existing QS and quorum quenching (QQ) activities. Here we sought to discover novel N-acylhomoserine lactone (AHL)-dependent QS and QQ strains by investigating a bacterial community associated with the rhizosphere of ginger (Zingiber officinale) growing in the Malaysian rainforest. RESULTS By using a basal growth medium containing N-(3-oxohexanoyl)homoserine lactone (3-oxo-C6-HSL) as the sole source of carbon and nitrogen, the ginger rhizosphere associated bacteria were enriched for strains with AHL-degrading capabilities. Three isolates belonging to the genera Acinetobacter (GG2), Burkholderia (GG4) and Klebsiella (Se14) were identified and selected for further study. Strains GG2 and Se14 exhibited the broadest spectrum of AHL-degrading activities via lactonolysis while GG4 reduced 3-oxo-AHLs to the corresponding 3-hydroxy compounds. In GG2 and GG4, QQ was found to co-exist with AHL-dependent QS and GG2 was shown to inactivate both self-generated and exogenously supplied AHLs. GG2, GG4 and Se14 were each able to attenuate virulence factor production in both human and plant pathogens. CONCLUSIONS Collectively our data show that ginger rhizosphere bacteria which make and degrade a wide range of AHLs are likely to play a collective role in determining the QS-dependent phenotype of a polymicrobial community.
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Affiliation(s)
- Kok-Gan Chan
- Division of Genetics and Molecular Biology, Institute of Biological Sciences, Faculty of Science, University of Malaya, 50603 Kuala Lumpur, Malaysia
- School of Molecular Medical Sciences, Centre for Biomolecular Sciences, University of Nottingham, Nottingham, NG7 2RD, UK
- Institute of Biological Sciences (Division of Genetics and Molecular Biology), Faculty of Science, University of Malaya, 50603 Malaysia
| | - Steve Atkinson
- School of Molecular Medical Sciences, Centre for Biomolecular Sciences, University of Nottingham, Nottingham, NG7 2RD, UK
| | - Kalai Mathee
- Department of Molecular Microbiology and Infectious Diseases, Herbert Wertheim College of Medicine, Florida International University, Miami, FL 33199, USA
| | - Choon-Kook Sam
- Natural Sciences and Science Education AG, National Institute of Education, Nanyang Technological University, 1 Nanyang Walk, Singapore 637616, Singapore
| | - Siri Ram Chhabra
- School of Molecular Medical Sciences, Centre for Biomolecular Sciences, University of Nottingham, Nottingham, NG7 2RD, UK
| | - Miguel Cámara
- School of Molecular Medical Sciences, Centre for Biomolecular Sciences, University of Nottingham, Nottingham, NG7 2RD, UK
| | - Chong-Lek Koh
- Natural Sciences and Science Education AG, National Institute of Education, Nanyang Technological University, 1 Nanyang Walk, Singapore 637616, Singapore
| | - Paul Williams
- School of Molecular Medical Sciences, Centre for Biomolecular Sciences, University of Nottingham, Nottingham, NG7 2RD, UK
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Chan KG, Yin WF, Sam CK, Koh CL. A novel medium for the isolation of N-acylhomoserine lactone-degrading bacteria. J Ind Microbiol Biotechnol 2008; 36:247-51. [DOI: 10.1007/s10295-008-0491-x] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2008] [Accepted: 10/07/2008] [Indexed: 10/21/2022]
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Kong KF, Jayawardena SR, Indulkar SD, Del Puerto A, Koh CL, Høiby N, Mathee K. Pseudomonas aeruginosa AmpR is a global transcriptional factor that regulates expression of AmpC and PoxB beta-lactamases, proteases, quorum sensing, and other virulence factors. Antimicrob Agents Chemother 2006; 49:4567-75. [PMID: 16251297 PMCID: PMC1280116 DOI: 10.1128/aac.49.11.4567-4575.2005] [Citation(s) in RCA: 125] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
In members of the family Enterobacteriaceae, ampC, which encodes a beta-lactamase, is regulated by an upstream, divergently transcribed gene, ampR. However, in Pseudomonas aeruginosa, the regulation of ampC is not understood. In this study, we compared the characteristics of a P. aeruginosa ampR mutant, PAOampR, with that of an isogenic ampR+ parent. The ampR mutation greatly altered AmpC production. In the absence of antibiotic, PAOampR expressed increased basal beta-lactamase levels. However, this increase was not followed by a concomitant increase in the P(ampC) promoter activity. The discrepancy in protein and transcription analyses led us to discover the presence of another chromosomal AmpR-regulated beta-lactamase, PoxB. We found that the expression of P. aeruginosa ampR greatly altered the beta-lactamase production from ampC and poxB in Escherichia coli: it up-regulated AmpC but down-regulated PoxB activities. In addition, the constitutive P(ampR) promoter activity in PAOampR indicated that AmpR did not autoregulate in the absence or presence of inducers. We further demonstrated that AmpR is a global regulator because the strain carrying the ampR mutation produced higher levels of pyocyanin and LasA protease and lower levels of LasB elastase than the wild-type strain. The increase in LasA levels was positively correlated with the P(lasA), P(lasI), and P(lasR) expression. The reduction in the LasB activity was positively correlated with the P(rhlR) expression. Thus, AmpR plays a dual role, positively regulating the ampC, lasB, and rhlR expression levels and negatively regulating the poxB, lasA, lasI, and lasR expression levels.
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Affiliation(s)
- Kok-Fai Kong
- Department of Biological Sciences, Florida International University, University Park, Miami, Florida 33199, USA
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13
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Cha PC, Yamada R, Sekine A, Nakamura Y, Koh CL. Inference from the relationships between linkage disequilibrium and allele frequency distributions of 240 candidate SNPs in 109 drug-related genes in four Asian populations. J Hum Genet 2004; 49:558-572. [PMID: 15372322 DOI: 10.1007/s10038-004-0190-z] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2004] [Accepted: 07/23/2004] [Indexed: 10/26/2022]
Abstract
The extensive nucleotide diversity in drug-related genes predisposes individuals to different drug responses and is a major problem in current clinical practice and drug development. Striking allelic frequency differences exist in these genes between populations. In this study, we genotyped 240 sites known to be polymorphic in the Japanese population in each of 270 unrelated healthy individuals comprising 90 each of Malaysian Malays, Indians, and Chinese. These sites are distributed in 109 genes that are drug related, such as genes encoding drug-metabolizing enzymes and drug transporters. Allele frequency and linkage disequilibrium distributions of these sites were determined and compared. They were also compared with similar data of 752 Japanese. Extensive similarities in allele frequency and linkage disequilibrium distributions were observed among Japanese, Malaysian Chinese, and Malays. However, significant differences were observed between Japanese and Malaysian Chinese with Malaysian Indians. These four populations were grouped into two genetic clusters of different ancestries. However, a higher correlation was found between Malaysian Malays and Indians, indicating the existence of extensive admixture between them. The results also imply the possible and rational use of existing single nucleotide polymorphism databases as references to assist future pharmacogenetic studies involving populations of similar ancestry.
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Affiliation(s)
- Pei-Chieng Cha
- Institute of Biological Sciences (Genetics and Molecular Biology), Faculty of Science, University of Malaya, 50603, Lembah Pantai, Kuala Lumpur, Malaysia.
| | - Ryo Yamada
- Laboratory for Rheumatic Diseases, SNP Research Center (SRC), Institute of Physical and Chemical Research (RIKEN), Yokohama, Japan
| | | | - Yusuke Nakamura
- Research Group for Personalized Medicine, SRC, RIKEN, Yokohama, Japan
- Laboratory of Molecular Medicine, Human Genome Center, Institute of Medical Science, University of Tokyo, Tokyo, Japan
| | - Chong-Lek Koh
- Institute of Biological Sciences (Genetics and Molecular Biology), Faculty of Science, University of Malaya, 50603, Lembah Pantai, Kuala Lumpur, Malaysia
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14
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Abstract
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.
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Affiliation(s)
- Y P Chan
- Institute of Biological Sciences (Genetics), University of Malaya, 50603 Kuala Lumpur, Malaysia
| | - C L Koh
- Institute of Biological Sciences (Genetics), University of Malaya, 50603 Kuala Lumpur, Malaysia
| | - S K Lam
- Department of Medical Microbiology, University of Malaya, 50603 Kuala Lumpur, Malaysia
| | - L-F Wang
- CSIRO Livestock Industries, Australian Animal Health Laboratory, PO Bag 24, Geelong, Victoria 3220, Australia
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15
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Koh CL, Viegas OA, Yuen R, Chua SE, Ng BL, Ratnam SS. Plasminogen activators and inhibitors in normal late pregnancy, postpartum and in the postnatal period. Int J Gynaecol Obstet 2004; 38:9-18. [PMID: 1348996 DOI: 10.1016/0020-7292(92)90723-v] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
Tissue plasminogen activator (t-PA), urokinase plasminogen activator (u-PA) and plasminogen activator inhibitors (PAI) are elevated in late pregnancy with t-PA and u-PA remaining so at 6 weeks postnatal. PAI-2 remains at postpartum but was absent by 6 weeks postnatal unlike PAI activity which was absent at postpartum and returned to nonpregnant level at postnatal. The potential fibrinolytic response to stress is much reduced in pregnancy thus increasing the risk of thromboembolism.
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Affiliation(s)
- C L Koh
- Department of Obstetrics and Gynaecology, National University of Singapore, National University Hospital
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16
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Abstract
Analyses of the spatial distribution pattern, spatial genetic structure and of genetic diversity were carried out in two tropical tree species with contrasting breeding systems and different ploidy levels using a 50-ha demographic plot in a lowland dipterocarp forest in Peninsular Malaysia. Shorea leprosula is a diploid and predominantly outcrossed species, whereas S. ovalis ssp. sericea is an autotetraploid species with apomictic mode of reproduction. Genetic diversity parameters estimated for S. leprosula using microsatellite were consistently higher than using allozyme. In comparisons with S. leprosula and other tropical tree species, S. ovalis ssp. sericea also displayed relatively high levels of genetic diversity. This might be explained by the lower pressure of genetic drift due to tetrasomic inheritance, and for autotetraploids each locus can accommodate up to four different alleles and this allows maintenance of more alleles at individual loci. The observed high levels of genetic diversity in S. ovalis ssp. sericea can also be due to a random retention of more heterogeneous individuals in the past, and the apomictic mode of reproduction might be an evolutionary strategy, which allows the species to maintain high levels of genetic diversity. The spatial distribution pattern analyses of both species showed significant levels of aggregation at small and medium but random distribution at the big diameter-class. The decrease in magnitude of spatial aggregation from small- to large-diameter classes might be due to compensatory mortality during recruitment and survival under competitive thinning process. Spatial genetic structure analyses for both species revealed significant spatial genetic structure for short distances in all the three diameter-classes. The magnitude of spatial genetic structure in both species was observed to be decreasing from smaller- to larger-diameter classes. The high spatial genetic structuring observed in S. ovalis ssp. sericea at the small-diameter class is due primarily to limited seed dispersal and apomictic mode of reproduction. The similar observation in S. leprosula, however, can be explained by limited seed and pollen dispersal, which supports further the fact that the species is pollinated by weak fliers, mainly of Thrips and Megalurothrips in the lowland dipterocarp forest.
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Affiliation(s)
- Kevin K S Ng
- Genetic Laboratory, Forest Research Institute Malaysia, 52109 Kuala Lumpur, Malaysia
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17
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Abstract
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.
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Affiliation(s)
- Y P Chan
- Institute of Biological Sciences, Faculty of Science1, Department of Medical Microbiology, Faculty of Medicine2 and Institute of Postgraduate Studies and Research3, University of Malaya, 50603 Kuala Lumpur, Malaysia
| | - K B Chua
- Institute of Biological Sciences, Faculty of Science1, Department of Medical Microbiology, Faculty of Medicine2 and Institute of Postgraduate Studies and Research3, University of Malaya, 50603 Kuala Lumpur, Malaysia
| | - C L Koh
- Institute of Biological Sciences, Faculty of Science1, Department of Medical Microbiology, Faculty of Medicine2 and Institute of Postgraduate Studies and Research3, University of Malaya, 50603 Kuala Lumpur, Malaysia
| | - M E Lim
- Institute of Biological Sciences, Faculty of Science1, Department of Medical Microbiology, Faculty of Medicine2 and Institute of Postgraduate Studies and Research3, University of Malaya, 50603 Kuala Lumpur, Malaysia
| | - S K Lam
- Institute of Biological Sciences, Faculty of Science1, Department of Medical Microbiology, Faculty of Medicine2 and Institute of Postgraduate Studies and Research3, University of Malaya, 50603 Kuala Lumpur, Malaysia
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18
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Abstract
The limited sequencing approach was used to study the molecular epidemiology of 24 Malaysian dengue 2 viruses which were isolated between 1968 and 1993. The sequences of a 240-nucleotide-long region across the envelope/non-structural 1 protein (E/NS1) gene junction of the isolates were determined and analysed. Alignment and comparison of the nucleotide and deduced amino acid sequences of the isolates revealed that nucleotide changes occurred mostly at the third position of a particular codon and were of the transition (A<-->G, C<-->U) type. Five nucleotide changes resulted in amino acid substitutions. Pairwise comparisons of the nucleotide sequences gave divergence values ranging from 0 to 9.2%. At the amino acid level, the divergence ranged between 0 and 3.8%. Based on the 6% divergence as the cut-off point for genotypic classification, the isolates were grouped into two genotypes, I and II. Comparison of the nucleotide sequences of the Malaysian dengue isolates with those of the dengue viruses of other regions of the world revealed that members of genotypes I and II were closely related to viruses from the Indian Ocean and Western Pacific regions, respectively.
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Affiliation(s)
- M Y Fong
- Department of Parasitology, University of Malaya, Kuala Lumpur, Malaysia
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19
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Abstract
The D1S80 allele frequencies in 124 unrelated Malays from the Malaysian population were determined and 51 genotypes and 19 alleles were encountered. The D1S80 frequency distribution met Hardy-Weinberg expectations. The observed heterozygosity was 0.80 and the power of discrimination was 0.96.
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Affiliation(s)
- C L Koh
- Department of Genetics and Cellular Biology, University of Malaya, Kuala Lumpur, Malaysia
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20
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Abstract
The HLA-DQ alpha genotype and allele frequencies in 130 Malays, 125 Chinese, and 137 Indians in the Malaysian population were determined using a commercial HLA-DQ alpha DNA amplification and typing kit which distinguishes 6 alleles (DQA1.1, DQA1.2, DQA1.3, DQA2, DQA3, and DQA4) and 21 possible genotypes at this locus. All 21 genotypes were encountered in the Malay and Indian samples, but DQA1.1,DQA1.3 and DQA2,DQA2 genotypes were absent in the Chinese sample. In all three ethnic groups, the numbers observed for the various DQ alpha genotypes were in accordance with those expected from Hardy-Weinberg equilibrium. The allele frequencies observed in these three groups were significantly different to allow them to be distinguished as distinct populations. For the Malays, Chinese, and Indians, heterozygosity values at this locus were 0.77, 0.77, and 0.83, respectively, and values of the power of discrimination were 0.91, 0.90, and 0.94, respectively. These population data will enable the HLA-DQ alpha locus to be used as a marker in forensic identity testing in Malaysia.
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Affiliation(s)
- C L Koh
- Department of Genetics and Cellular Biology, University of Malaya, Kuala Lumpur, Malaysia
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21
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Thong KL, Cheong YM, Puthucheary S, Koh CL, Pang T. Epidemiologic analysis of sporadic Salmonella typhi isolates and those from outbreaks by pulsed-field gel electrophoresis. J Clin Microbiol 1994; 32:1135-41. [PMID: 7914202 PMCID: PMC263623 DOI: 10.1128/jcm.32.5.1135-1141.1994] [Citation(s) in RCA: 95] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
Pulsed-field gel electrophoresis (PFGE) was used to compare and analyze 158 isolates of Salmonella typhi from five well-defined outbreaks of typhoid fever in Malaysia and also isolates involved in sporadic cases of typhoid fever occurring during the same period. Digestion of chromosomal DNAs from these S. typhi isolates with the restriction endonucleases XbaI (5'-TCTAGA-3'), SpeI (5'-ACTAGT-3'), and AvrII (5'-CCTAGG-3') and then PFGE produced restriction endonuclease analysis (REA) patterns consisting of 11 to 24 DNA fragments ranging in size from 20 to 630 kbp. Analysis of the REA patterns generated by PFGE after digestion with XbaI and SpeI indicated that the S. typhi isolates obtained from sporadic cases of infection were much more heterogeneous (at least 13 different REA patterns were detected; Dice coefficient, between 0.73 and 1.0) than those obtained during outbreaks of typhoid fever. The clonal nature and the close genetic identities of isolates from outbreaks in Alor Setar, Penang, Kota Kinabalu, Johor Bahru, and Kota Bahru were suggested by the fact that only a limited number of REA patterns, which mostly differed by only a single band, were detected (one to four patterns; Dice coefficient, between 0.82 and 1.0), although a different pattern was associated with each of these outbreaks. Comparison of REA patterns with ribotyping for 18 S. typhi isolates involved in sporadic cases of infection showed a good correlation, in that 72% of the isolates were in the same group. There was no clear correlation of phage types with a specific REA pattern. We conclude that PFGE of s. typhi chromosomal DNA digested with infrequently cutting restriction endonucleases is a useful method for comparing and differentiating S. typhi isolates for epidemiological purposes.
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Affiliation(s)
- K L Thong
- Department of Medical Microbiology, University of Malaya, Kuala Lumpur, Malaysia
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22
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Yang PY, Kautner I, Koh CL, Lam SK. Nucleotide and deduced amino acid sequences of genes encoding the structural and nonstructural NS1 proteins of a dengue-2 virus isolated in China. Virus Genes 1994; 8:71-4. [PMID: 7911607 DOI: 10.1007/bf01703603] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
We have determined the nucleotide and encoded amino acid sequences of the capsid, membrane precursor, membrane, envelope, and nonstructural NS1 protein genes of a dengue-2 virus (D2-04) isolated from a patient in Hainan, China. The sequenced region contains a gene organization similar to that of other flaviviruses. The overall amino acid sequence similarity between D2-04 and other dengue-2 viruses is greater than 92%, whereas that between D2-04 and members of the other dengue serotypes is about 65%.
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Affiliation(s)
- P Y Yang
- Department of Virology, Institute of Microbiology and Epidemiology, Beijing, People's Republic of China
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23
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Abstract
Human mononuclear cells pre-labeled with [3H]arachidonic acid were shown to release metabolites following in vitro addition of heat-killed Salmonella typhi (HKST). The amount of label released was significantly higher than that seen with live S. typhi (LST). Addition of increasing amounts of HKST resulted in an increased release of metabolites. Enzyme immunoassay of the culture supernatants revealed that the bulk of the metabolite released was prostaglandin E2 (PGE2). Leukotriene B4 (LTB4) and leukotriene C4 (LTC4) were not detectable in the culture supernatants. The significance and implications of these results are discussed.
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Affiliation(s)
- W N Yusof
- Institute of Advanced Studies, University of Malaya, Kuala Lumpur
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24
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Verdugo-Rodriguez A, Gam LH, Devi S, Koh CL, Puthucheary SD, Calva E, Pang T. Detection of antibodies against Salmonella typhi outer membrane protein (OMP) preparation in typhoid fever patients. Asian Pac J Allergy Immunol 1993; 11:45-52. [PMID: 8216558] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
An indirect ELISA was used to detect antibodies against outer membrane protein preparations (OMPs) from Salmonella typhi. Sera from patients with a definitive diagnosis of typhoid fever (TF) gave a mean absorbance reading, at 414 nm, of 1.52 +/- 0.23 as compared to 0.30 +/- 0.11 for sera from healthy individuals. This gave a positive to negative ratio of absorbance readings of approximately 5.1. Suspected TF patients (no isolation of S. typhi), with positive and negative Widal titers had mean absorbance readings of 1.282 +/00.46 and 0.25 +/- 0.19, respectively. Sera from patients with leptospirosis, rickettsial typhus, dengue fever, and other infections gave mean absorbances of 0.20 +/- 0.08, 0.24 +/- 0.08, 0.27 +/- 0.08, and 0.31 +/- 0.16, respectively. The sensitivity, specificity, positive and negative predictive values were 100%, 94%, 80% and 100%, respectively. The antibody response detected in the definitive TF cases was predominantly IgG in nature and no cross-reactivity was seen with OMP preparations extracted from E. coli. Variable reactivity was noted with OMP preparations obtained from other Salmonella spp. Three major OMPs are presented in the antigen preparation and strong binding of positive sera was detected to all three bands.
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Chin YM, Bosco JJ, Koh CL. Breakpoint cluster region (BCR) gene rearrangement studies in chronic myeloid and acute lymphoblastic leukemias. Med J Malaysia 1992; 47:110-3. [PMID: 1494330] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
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.
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Affiliation(s)
- Y M Chin
- Hematology Division, Institute for Medical Research, Jalan Pahang, Kuala Lumpur
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26
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Pang T, Altwegg M, Martinetti G, Koh CL, Puthucheary S. Genetic variation among Malaysian isolates of Salmonella typhi as detected by ribosomal RNA gene restriction patterns. Microbiol Immunol 1992; 36:539-43. [PMID: 1513268 DOI: 10.1111/j.1348-0421.1992.tb02053.x] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Genetic variation among Malaysian isolates of Salmonella typhi was determined by analysis of ribosomal RNA gene restriction patterns. Of the 20 isolates analyzed, eight different pattern combinations were detected. The amount of variation observed was also dependent upon the restriction endonuclease used; PstI produced more different patterns than did SmaI. The results suggested that disease activity was due to a number of different clones circulating simultaneously rather than a single strain. Further implications of the data are discussed.
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Affiliation(s)
- T Pang
- Institute for Advanced Studies, University of Malaya, Kuala Lumpur, Malaysia
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27
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Chin YM, Bosco JJ, Koh CL. Analysis of ras gene mutations in acute myeloid leukemia by the polymerase chain reaction and oligonucleotide probes. Singapore Med J 1992; 33:48-50. [PMID: 1598607] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
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.
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Affiliation(s)
- Y M Chin
- Haematology Division, Institute for Medical Research, Jalan Pahang, Kuala Lumpur, Malaysia
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Phipps M, Pang T, Koh CL, Puthucheary S. Plasmid incidence rate and conjugative chloramphenicol and tetracycline resistance plasmids in Malaysian isolates of Salmonella typhi. Microbiol Immunol 1991; 35:157-61. [PMID: 1886492 DOI: 10.1111/j.1348-0421.1991.tb01543.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Seven (6.1%) of 115 strains of Salmonella typhi isolated from Malaysian patients harbored a single large plasmid of 71 to 166 mD. Two of the seven plasmid-bearing strains were resistant to chloramphenicol (Cm) and tetracycline (Tc) and they transferred Cm and Tc resistance traits to Escherichia coli K12 at frequencies from 1.6 x 10(-7) to 1.9 x 10(-6). Agarose gel electrophoresis provided evidence that the resistance traits were cotransferred on a conjugative plasmid. The significance and importance of these results are discussed.
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Affiliation(s)
- M Phipps
- Institute for Advanced Studies, University of Malaya, Kuala Lumpur
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30
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Préhaud C, Harris RD, Fulop V, Koh CL, Wong J, Flamand A, Bishop DH. Expression, characterization, and purification of a phosphorylated rabies nucleoprotein synthesized in insect cells by baculovirus vectors. Virology 1990; 178:486-97. [PMID: 2219704 DOI: 10.1016/0042-6822(90)90346-s] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
A baculovirus expression vector (AcNPV3) derived from the nuclear polyhedrosis virus of Autographa californica (AcNPV) was prepared containing the complete coding region of the nucleoprotein (N) gene of rabies virus (Gif-sur-Yvette clone of the CVS strain). The gene was placed under the control of the AcNPV polyhedrin promoter and was expressed to high levels (66 mg N protein/liter of 2 x 10(9) cells) by the derived recombinant virus using a Spodoptera frugiperda cell line. Using available antisera, it was established that the antigenic characteristics of the N protein were similar by comparison with those of the native N protein of rabies virus. Characterization of the expressed protein established that, like the N protein of mammalian cell-grown CVS virus, the N protein was phosphorylated. The expressed rabies N protein induced antibodies in mice that reacted strongly with the rabies viral protein. The expressed nucleoprotein was recovered from the insect cells by differential centrifugation followed by ion exchange chromatography. The expressed rabies N protein represents a source of authentic protein suitable for virus diagnosis as well as structural studies.
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Affiliation(s)
- C Préhaud
- NERC Institute of Virology and Environmental Microbiology, Oxford, United Kingdom
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31
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Samuel S, Koh CL, Pang T, Lam SK. Nucleotide and encoded amino acid sequences of the membrane protein precursor and the membrane protein genes of three dengue-2 viruses isolated in Malaysia from patients with dengue haemorrhagic fever, dengue shock syndrome or dengue fever. Nucleic Acids Res 1990; 18:1905. [PMID: 2336374 PMCID: PMC330628 DOI: 10.1093/nar/18.7.1905] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Affiliation(s)
- S Samuel
- Department of Medical Microbiology, University of Malaya, Kuala Lumpur
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32
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Samuel S, Koh CL, Pang T, Lam SK. Nucleotide and encoded amino acid sequences of the capsid protein gene of three dengue-2 viruses isolated in Malaysia from patients with dengue haemorrhagic fever, dengue shock syndrome or dengue fever. Nucleic Acids Res 1990; 18:1904. [PMID: 2336373 PMCID: PMC330627 DOI: 10.1093/nar/18.7.1904] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Affiliation(s)
- S Samuel
- Department of Medical Microbiology, University of Malaya, Kuala Lumpur
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33
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Fong MY, Koh CL, Samuel S, Pang T, Lam SK. Nucleotide sequences of the nonstructural protein NS1 gene of three dengue-2 viruses, M1, M2 and M3, isolated in Malaysia from patients with dengue haemorrhagic fever, dengue shock syndrome and dengue fever, respectively. Nucleic Acids Res 1990; 18:1642. [PMID: 2139210 PMCID: PMC330548 DOI: 10.1093/nar/18.6.1642] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Affiliation(s)
- M Y Fong
- Department of Medical Microbiology, University of Malaya Kuala Lumpur, Malaysia
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Samuel S, Koh CL, Blok J, Pang T, Lam SK. Nucleotide sequence of the envelope protein gene of a Malaysian dengue-2 virus isolated from a patient with dengue shock syndrome. Nucleic Acids Res 1989; 17:8888. [PMID: 2587243 PMCID: PMC335080 DOI: 10.1093/nar/17.21.8888] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Affiliation(s)
- S Samuel
- Department of Medical Microbiology, University of Malaya, Kuala Lumpur
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Samuel S, Koh CL, Blok J, Pang T, Lam SK. Nucleotide sequence of the envelope protein gene of a Malaysian dengue-2 virus isolated from a patient with dengue fever. Nucleic Acids Res 1989; 17:8887. [PMID: 2587242 PMCID: PMC335079 DOI: 10.1093/nar/17.21.8887] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Affiliation(s)
- S Samuel
- Department of Medical Microbiology, University of Malaya, Kuala Lumpur
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Samuel S, Koh CL, Blok J, Pang T, Lam SK. Nucleotide sequence of the envelope protein gene of a Malaysian dengue-2 virus isolated from a patient with dengue haemorrhagic fever. Nucleic Acids Res 1989; 17:8875. [PMID: 2587234 PMCID: PMC335068 DOI: 10.1093/nar/17.21.8875] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Affiliation(s)
- S Samuel
- Department of Medical Microbiology, University of Malaya, Kuala Lumpur
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Koh CL. Antibiotic resistance and conjugative R plasmids in clinical isolates of Enterobacteriaceae in Peninsular Malaysia. Trans R Soc Trop Med Hyg 1986; 80:158-61. [PMID: 3726978 DOI: 10.1016/0035-9203(86)90221-x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
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.
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Kalaimathee KK, Koh CL, Ngeow YF. Plasmid profiles of Neisseria gonorrhoeae in Peninsular Malaysia. Microbiol Immunol 1985; 29:921-6. [PMID: 3935906 DOI: 10.1111/j.1348-0421.1985.tb02957.x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
The plasmid profiles of 160 strains of Neisseria gonorrhoeae isolated in Peninsular Malaysia, comprising 80 penicillinase-producing (PPNG) and 80 non-penicillinase-producing (non-PPNG) isolates, were determined. The 80 PPNG isolates were divided into two plasmid groups. All of them harbored two common plasmid species, a 4.4 megadalton (Md) R plasmid previously associated with beta-lactamase production in PPNG strains from the Far East and a 2.6 Md multicopy plasmid of unknown function. In addition to these two plasmids, 60 (75%) PPNG isolates also carried a large 24.5 Md conjugative plasmid. In contrast, the 80 non-PPNG strains were divided into three plasmid groups. All of them possessed the 2.6 Md cryptic plasmid, and 35 (44%) isolates also harbored the 24.5 Md transfer plasmid. Besides these two plasmids, one non-PPNG isolate carried an additional 7.8 Md cryptic plasmid.
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Koh CL, Kalaimathee KK, Ngeow YF. Plasmids in penicillinase-producing Neisseria gonorrhoeae in Peninsular Malaysia. Med J Malaysia 1984; 39:269-71. [PMID: 6443581] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
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Koh CL, Tay SH. R plasmid-borne transferable multiple antibiotic resistance in a clinical isolate of Proteus sp in Peninsular Malaysia. Singapore Med J 1984; 25:300-3. [PMID: 6523137] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
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Koh CL, Kok CH. Nonconjugative R plasmid-mediated antibiotic resistance in Escherichia coli isolated from animals in Peninsular Malaysia. Southeast Asian J Trop Med Public Health 1984; 15:313-6. [PMID: 6395350] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
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.
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Koh CL, Kok CH. Antimicrobial resistance and conjugative R plasmids in Escherichia coli strains isolated from animals in Peninsular Malaysia. Southeast Asian J Trop Med Public Health 1984; 15:37-43. [PMID: 6377513] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
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.
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Koh CL, Lim ME, Wong YH. Conjugal transfer of multiple antibiotic resistance from hospital isolates of Klebsiella to Escherichia coli. Southeast Asian J Trop Med Public Health 1983; 14:336-40. [PMID: 6362015] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
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.
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