Discipline: Ecology Environmental and Earth Sciences
Mahaa M. Ahmed - Rowan University
Co-Author(s): Erica Fuhrmeister, University of California, Berkeley, Berkeley, CA; Kara Nelson, University of California, Berkeley, Berkeley, CA
Diarrhea is the second leading cause of death among under-five children in developing countries such as Bangladesh. One of the primary causes of diarrheal illness in developing countries is Pathogenic E. coli (PEC). Pathotypes of E. coli that cause gastroenteritis include enterotoxigenic E. coli (ETEC), enteropathogenic E. coli (EPEC), enteroinvasive E. coli (EIEC), enterohemorrhagic E. coli (EHEC), and enteroaggregative E. coli (EAEC).
The WASH Benefits trial is a multi-institutional public health study aiming to measure the effects of various interventions on child health. The cluster-randomized control trial started in 2012 near Mymensingh, Bangladesh. Six intervention arms were implemented. Participating households of the sanitation arm received a dual-pit latrine, child potty, and sani-scoop used to remove animal feces. The research objective is to detect PEC genes in a subset of environmental samples from the control and sanitation arms to assess the impact of the sanitation intervention.
Samples collected from households include hand-rinse samples from children (N=104), hand-rinse samples from mothers (N=105), stored water samples (N=127), and soil samples (N=110). The IDEXX-Colilert test was used to quantify total coliforms and E. coli. DNA was extracted from the cultured E. coli pellet from the positive wells of the IDEXX tray using the Qiagen DNeasy Blood and Tissue Kit. One extraction blank was prepared for each set of extractions. A multiplex polymerase chain reaction assay was used. Gene targets of this assay included st1b and lt1 (ETEC), eae (EPEC), ipah (EIEC), stx1 and stx2 (EHEC), and aggR (EAEC). A 2% agarose gel was used for gel electrophoresis. Positive and no-template controls were run on each gel.
PEC was detected in all samples types in both the control and sanitation arms. EAEC was detected most often in soil samples in the control and sanitation arms. 36% of hand-rinse samples from mothers in the sanitation arm were positive for EHEC and 21% were positive in the control. 25% of hand-rinse samples from children in the sanitation arm were positive for EHEC and 32% were positive in the control. 37% of stored water samples in the sanitation arm were positive for EHEC and 34% were positive in the control. 22% of stored water samples were positive for ETEC and 33% were positive in the control.
Hands, soil, and water can all be key sources of exposure to PEC. Further analysis is needed to determine which source contributes most to diarrheal disease transmission in children. The most important reservoirs of pathogens are the ones that children come in contact with most often. Overall, the WASH Benefits sanitation intervention seems to have a limited effect on the presence of PEC in hands, soil, and water.
Future work includes analyzing remaining hand-rise, soil, and stored water samples, determining if fecal contamination is of human or animal sources, and modeling the source of exposure children have most contact with.
Funder Acknowledgement(s): This study is funded by the National Institute of Health, ReNUWIt, and the NSF-REU Program.
Faculty Advisor: Kara Nelson, firstname.lastname@example.org
Role: I looked at a subset of environmental samples (approximately 100 of each sample type of approximately 700 total samples collected) from the WASH Benefits Trial's sanitation intervention arm. I was responsible for detecting pathogenic E. coli in the four environmental sample types from the WASH Benefits Trial. I extracted DNA from the cultured E. coli pellet from the positive wells of the IDEXX tray using the Qiagen DNeasy Blood and Tissue Kit, conducted the multiplex polymerase chain reaction assay, and gel electrophoresis as well as data analyses.