Melioidosis is a disease of humans caused by opportunistic infection with the 
soil and water bacterium Burkholderia pseudomallei. Melioidosis can manifest as 
an acute, overwhelming infection or as a chronic, recurrent infection. At 
present, it is not clear where B. pseudomallei resides in the mammalian host 
during the chronic, recurrent phase of infection. To address this question, we 
developed a mouse low-dose mucosal challenge model of chronic B. pseudomallei 
infection and investigated sites of bacterial persistence over 60 days. 
Sensitive culture techniques and selective media were used to quantitate 
bacterial burden in major organs, including the gastrointestinal (GI) tract. We 
found that the GI tract was the primary site of bacterial persistence during the 
chronic infection phase, and was the only site from which the organism could be 
consistently cultured during a 60-day infection period. The organism could be 
repeatedly recovered from all levels of the GI tract, and chronic infection was 
accompanied by sustained low-level fecal shedding. The stomach was identified as 
the primary site of GI colonization as determined by fluorescent in situ 
hybridization. Organisms in the stomach were associated with the gastric mucosal 
surface, and the propensity to colonize the gastric mucosa was observed with 4 
different B. pseudomallei isolates. In contrast, B. pseudomallei organisms were 
present at low numbers within luminal contents in the small and large intestine 
and cecum relative to the stomach. Notably, inflammatory lesions were not 
detected in any GI tissue examined in chronically-infected mice. Only low-dose 
oral or intranasal inoculation led to GI colonization and development of chronic 
infection of the spleen and liver. Thus, we concluded that in a mouse model of 
melioidosis B. pseudomallei preferentially colonizes the stomach following oral 
inoculation, and that the chronically colonized GI tract likely serves as a 
reservoir for dissemination of infection to extra-intestinal sites.