Partial characterization of bacteriocin-like compound (BLIS) produced by Burkholderia stagnalis strain K23/3 against Burkholderia pseudomallei

Aims@#Burkholderia pseudomallei, the human pathogen that causes melioidosis, is intrinsically resistant towards a wide range of antibiotics and there have been reports of acquired resistance towards antibiotics used for melioidosis treatments. Antimicrobial peptides (AMP) such as bacteriocins are gaining the interests of researchers as alternative for treating infections caused by multidrug resistant bacteria. In this study, we aimed to identify Burkholderia spp. isolated from soil in Sarawak that possess the potential in inhibiting the growth of B. pseudomallei and to further characterize the antagonistic compound produced.@*Methodology and results@#A total of 50 Burkholderia spp. isolates of environmental origin and two isolates of Ralstonia solanacearum were screened against five clinical isolates of B. pseudomallei using spot-on-lawn assay and flip streak method. Burkholderia stagnalis isolate K23/3 showed clear zones of inhibition (ZOI) in both preliminary tests. Cell-free supernatant (CFS) was obtained from B. stagnalis K23/3 broth culture and was tested via agar well diffusion assay (AWDA). The antagonistic compound secreted at the early log phase of the bacterial growth was shown to be stable in a wide range of temperatures and pH. Treatment with different enzymes revealed that it was sensitive towards proteinase K, suggesting that it is proteinaceous. The bacteriocin-like-substance (BLIS) was subjected to ammonium sulfate precipitation and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). The SDS-PAGE gel was overlaid with indicator B. pseudomallei isolates where the active protein was shown to be less than 7.1 kDa.@*Conclusion, significance and impact of study@#Burkholderia stagnalis isolate K23/3 was able to secrete bacteriocin-like-substance (BLIS) that has the potential in biocontrol of B. pseudomallei in the environment or as potential treatment for melioidosis.

Antibiotics susceptibility of Burkholderia species of Sarawak origin

Aims@#The Burkholderia species is comprised of more than 70 members which co-exist in the same ecological niche including Burkholderia pseudomallei, which causes fatal melioidosis infections in humans and animals. Many of the members of the Burkholderia species share similarities in their biochemical and morphological profiles. B. pseudomallei is intrinsically resistant to a myriad of antibiotics and hence, the treatment of melioidosis involves various types of antibiotics with prolonged prescription. Apart from B. pseudomallei which has been widely described due to its clinical importance, little is known about the antibiotics mechanisms and susceptibility profile of Burkholderia species. This leads to the question of whether the antibiotics susceptibility profile of the Burkholderia species is similar to that of B. pseudomallei. @*Methodology and results@#In this study, Burkholderia species isolated from environmental samples were tested for their susceptibility against gentamicin, ceftazidime, cotrimoxazole (trimethoprim/sulfamethoxazole) and azithromycin using the disk diffusion test method. The antibiogram profiles Burkholderia species isolates tested in this study suggested that the antibiogram profile of Burkholderia spp. resembles that of B. pseudomallei for some antibiotics while totally different for other antibiotics.@*Conclusion, significance and impact of study@#The actual mechanisms which render these observations and whether the interaction of these subspecies within the same ecological niche attribute to these observations warrant further investigation.