Background: Burkholderia pseudomallei are the causative agents of melioidosis, a disease that has a high relapse rate in
endemic areas. The mechanism of relapse is unclear.
Objective: This study aimed to establish relapsed melioidosis in C57BL/6 mice by induction with B. pseudomallei.
Material and Method: Low doses of B. pseudomallei H777 and its biofilm defective mutant (M10) were intra-gastric fed to
C57BL/6 mice. All the infected mice had suppressed immune status by intra-peritoneal injection of hydrocortisone at 2.5 mg
per mouse at day 60 post-infection. Inflammatory response to the infection was investigated by histo-pathological studies and
monitoring bacterial counts in the blood and organs.
Results: All the infected mice were found to have a high infiltration of mononuclear cells at day 60 post-infection. The
results showed high bacterial counts in the blood in both strains post-suppressed immune status after two days. The biofilm
mutant and wild type strains produced relapse in C57BL/6 mice but the latter was responsible for significantly more severe
inflammation than the biofilm mutant.
Conclusion: Low immune status may cause relapsed melioidosis in hosts with chronic inflammation.

Keywords: Burkholderia pseudomallei, Melioidosis, Relapse