1. UKM Learning and Research Repository
2. PHD Thesis / Tesis PHD
3. Faculty of Science and Technology / Fakulti Sains dan Teknologi

Title:	Characterisation Of Burkholderia Cepacia Complex (BCC) Soil Isolates From Malaysia
Authors:	Mohsen Arefnejad (P38424)
Supervisor:	Rahmah Mohamed, Prof. Dr.
Keywords:	Characterisation Of Burkholderia Cepacia Complex Soil Isolates Burkholderia Cepacia Complex (BCC) Pathogenic bacteria
Issue Date:	7-Oct-2013
Description:	Many bacterial pathogens capable of infecting vulnerable individuals exist in the soil. These include the Burkholderia cepacia complex (Bcc), a closely related group of gram-negative non-fermentative bacteria found in both natural and clinical environmental niches. Currently, the diversity and prevalence of Bcc species in Malaysia is poorly understood. Thus, this study was initiated to characterize environmental Bcc isolates from Malaysia using conventional phenotypic and genotypic methods. Out of a total of 137 heterotrophic bacterial isolates recovered from soil samples, 44 isolates were positively identified as Bcc by various phenotypic and genotypic methods. Subsequently, Bcc species-specific primers were used for amplification of the recA and gyrB genes. This secondary genotyping analysis confirmed 30 (recA) and 14 (gyrB) isolates as Bcc, respectively. A phylogenetic tree based on recA gene sequences clearly indicated that these isolates were closely related to clinical and environmental Bcc strains across different geographical origins. Four Bcc isolates i.e. two strains of B. cepacia, a strain of B. cenocepacia and B. multivorans, demonstrated resistance to cephalosporin (ceftazidime). To determine the virulence of these Bcc isolates towards plant and animal models, a maceration assay and a Caenorhabditis elegans killing assay were performed. The polygalacturonase (PGase)-based maceration enzyme assay demonstrated plant pathogenic characteristics of the Bcc phenotypes tested. In the C. elegans killing assay, cephalosporin-resistant Bcc isolates were used to infect the animals. Survival data obtained showed that these isolates could kill the animals at rates comparable to those of the established Bcc clinical strain H111 and Pseudomonas aeruginosa PA14, with the mean time to death (TDmean) ranging from 24 to 60 hr. C. elegans immune response pathway mutants, pmk-1, sma-6 and daf-2, were used to understand how the host conserved innate immune system responded to infection. Based on the observed TDmean, the sma-6 and pmk-1 mutants exhibit increased susceptibility to infection by the isolated Bcc strains, implicating the importance of both the MAP Kinase and TGF-β pathways in mounting an antibacterial response towards Bcc. The delayed mean time to death of daf-2 loss-of-function C. elegans animals suggests that Bcc bind to the DAF-2 receptor thus favouring the activation of DAF16, a forkhead transcription factor which regulates targets that promote increased resistance and longevity. Hence, this study has demonstrated that Bcc soil isolates are comparable to clinical Bcc and virulent P. aeruginosa PA14 in overcoming host innate immunity and protective responses.,PhD
Pages:	179
Call Number:	QR201.B34 .A734 2013
Publisher:	UKM, Bangi
Appears in Collections:	Faculty of Science and Technology / Fakulti Sains dan Teknologi

Items in DSpace are protected by copyright, with all rights reserved, unless otherwise indicated.