The study aimed to show bacterial overgrowth was linked with intestinal inflammation and growth delay. In addition, the study also wanted to examine why children from developing countries, with no known gastrointestinal dysfunction, went on to develop bacterial overgrowth.
Stunting has been attributed to the presence of environmental enteropathy (EE), a poorly understood condition leading to chronic intestinal inflammation. It is thought small intestine bacterial overgrowth (SIBO) contributes to the development of EE as overgrowth has been associated with intestinal inflammation and micronutrient malabsorption.
Around 165 million children worldwide are considered stunted, which is associated with increased risk of cognitive disability and infant mortality.
SIBO prevalent in the slum
Recent studies have suggested children in the developing world may develop SIBO at significantly higher rates than their more privileged counterparts, with a prevalence of up to 30% in slum-dwelling children.
SIBO in children from low-income countries has been associated with poor carbohydrate absorption and underperformance of an oral cholera vaccine. Yet it is unclear what role SIBO plays in EE.
To further explore SIBO, the researchers from Virginia and Bangladesh examined 103 two-year-old children tracked from birth in an urban slum in Mirpur, Dhaka.
Despite vaccination, medical care, nutritional counselling and care, stunting increased in these infants from 9.5% at birth to 27.6% at the age on one.
Notably, one in six children aged two showed signs of SIBO, as revealed by the presence of hydrogen on their breath, a result of bacterial metabolism of sugar to hydrogen in the small intestine.
The study noted that its findings differed from other research, which found an increase in intestinal permeability in adults with SIBO in the developed world. However, these subjects had underlying gastrointestinal disease that may have predisposed them to increased intestinal permeability.
Other results in this study led the researchers to believe that SIBO and EE were separate but associated conditions. Another explanation described EE as a syndrome consisting of a group of intestinal inflammatory conditions with common outcomes.
Environmental enteropathy common in kids
The results also noticed SIBO-negative children featured in this study had faecal calprotectin levels higher than those reported in asymptomatic children in the developed world, suggesting the majority of children in the study population had some degree of EE.
“One of the things we are working on now is to see when small intestine bacterial overgrowth occurs as children grow up in urban slums and understand its contribution,” said Dr Jeff Donowitz, lead author on the study and paediatric infectious disease specialist at Virginia Commonwealth University.
Given the known nutritional consequences of SIBO in other settings, it is biologically plausible that SIBO plays a causative role in growth stunting.
However, the study was quick to point out that the pathogenesis and pathophysiology of SIBO in developing world children with no underlying gastrointestinal disease may be different from those of patients in industrialised countries.
“Future study is needed to prospectively determine whether SIBO itself has a detrimental impact on growth of developing world children. Based on this study, these efforts should focus on the role of environmental contamination’s ability to cause a functional intestinal disorder that may predispose to SIBO and the development of EE.”
Published online ahead of print, doi: 10.1128/mBio.02102-15
“Small Intestine Bacterial Overgrowth and Environmental Enteropathy in Bangladeshi Children.”
Authors: Jeffrey R. Donowitz, Rashidul Haque, Beth D. Kirkpatrick, Masud Alam, Miao Lu, Mamun Kabir, Shahria Hafiz Kakon, Bushra Zarin Islam, Sajia Afreen, Abu Musa, Shaila Sharmeen Khan, E. Ross Colgate, Marya P. Carmolli, Jennie Z. Mae, William A. Petri Jr.