Glyburide Reduces Bacterial Dissemination in a Mouse Model of Melioidosis

Abstract

Background

Burkholderia pseudomallei infection (melioidosis) is an important cause of community-acquired Gram-negative sepsis in Northeast Thailand, where it is associated with a ∼40% mortality rate despite antimicrobial chemotherapy. We showed in a previous cohort study that patients taking glyburide ( = glibenclamide) prior to admission have lower mortality and attenuated inflammatory responses compared to patients not taking glyburide. We sought to define the mechanism underlying this observation in a murine model of melioidosis.

Methods

Mice (C57BL/6) with streptozocin-induced diabetes were inoculated with ∼6×10 ² cfu B. pseudomallei intranasally, then treated with therapeutic ceftazidime (600 mg/kg intraperitoneally twice daily starting 24 h after inoculation) in order to mimic the clinical scenario. Glyburide (50 mg/kg) or vehicle was started 7 d before inoculation and continued until sacrifice. The minimum inhibitory concentration of glyburide for B. pseudomallei was determined by broth microdilution. We also examined the effect of glyburide on interleukin (IL) 1β by bone-marrow-derived macrophages (BMDM).

Results

Diabetic mice had increased susceptibility to melioidosis, with increased bacterial dissemination but no effect was seen of diabetes on inflammation compared to non-diabetic controls. Glyburide treatment did not affect glucose levels but was associated with reduced pulmonary cellular influx, reduced bacterial dissemination to both liver and spleen and reduced IL1β production when compared to untreated controls. Other cytokines were not different in glyburide-treated animals. There was no direct effect of glyburide on B. pseudomallei growth in vitro or in vivo. Glyburide directly reduced the secretion of IL1β by BMDMs in a dose-dependent fashion.

Conclusions

Diabetes increases the susceptibility to melioidosis. We further show, for the first time in any model of sepsis, that glyburide acts as an anti-inflammatory agent by reducing IL1β secretion accompanied by diminished cellular influx and reduced bacterial dissemination to distant organs. We found no evidence for a direct effect of glyburide on the bacterium.

Author Summary

Burkholderia pseudomallei infection (also called melioidosis) is a common cause of bacterial infection in Northeast Thailand, where the mortality rate is 43% despite appropriate antibiotic treatment. We showed previously that patients taking glyburide ( = glibenclamide) prior to admission have lower mortality rates and lower levels of inflammation in the blood. In this study, we used a mouse model to better understand the mechanism underlying this observation. In this study, we used a mouse model of diabetes and infected the mice with B. pseudomallei. Half the mice were treated with glyburide and half were not. We also performed in vitro experiments to find the minimum concentration of glyburide that would inhibit the growth of B. pseudomallei. We found that glyburide treatment was associated with reduced inflammation (as measured by the flow of cells into the lungs and by interleukin-1β production) and reduced spread of the bacterium to liver and spleen when compared to untreated controls. There was no direct effect of glyburide on B. pseudomallei growth in vitro or in vivo. Because the effect of glyburide is on the host and not on the bacterium, it is possible that this effect will be seen in other causes of sepsis, not just melioidosis.