Impact of breastmilk on Campylobacter jejuni survival

PROJECT SUMMARY Campylobacter jejuni is a major cause of bacterial-induced diarrhea worldwide. Infection leads to high rates of morbidity and mortality in low-and-middle income countries (LMICs), particularly in young children where up to 85% of infants are C. jejuni stool positive by one year of age. Also, post-infectious complications such as Guillain- Barré syndrome, irritable bowel syndrome, reactive arthritis, and environmental enteric dysfunction (EED) are increasingly reported. EED is a subclinical chronic disorder resulting from improper nutrient absorption, intestinal injury and prolonged inflammation that leads to growth stunting, impaired cognitive development, and further complications. In parallel, campylobacters continue to show increasing rates of fluoroquinolone resistance, particularly ciprofloxacin, and are thus high priority pathogens for new antimicrobial development. Through genomics studies examining Campylobacter infection profiles in seven sites in sub-Saharan African and South Asia, we discovered that exclusively breastfed infants showed a significantly higher abundance of C. jejuni in their stools compared to non-breastfed infants, and that breastfed infants were predominantly colonized with asaccharolytic (non-carbohydrate metabolizing) strains of C. jejuni while infection with fucose-metabolizing campylobacters was less frequent. While examining the mechanism behind this selection, we discovered that human breastmilk is unexpectedly toxic to C. jejuni. This finding was confirmed using 5 different isolates and 5 independent breastmilk donor samples. Through directed evolution studies, we isolated C. jejuni strains resistant to breastmilk and demonstrated that the milk bioactive agents were derived from proteins and lipids. This study will investigate how components of human breastmilk can suppress the survival of C. jejuni, and in turn will explore how C. jejuni can develop resistance to those components. The specific aims of this project are to identify the bactericidal lipids and antimicrobial peptides within a pooled collection of human breastmilk, then characterize the mechanisms by which C. jejuni can become resistant to these components, and subsequently test how the identified C. jejuni mutations and toxic milk components impact bacterial colonization in a mouse model of C. jejuni-induced EED. Completion of these aims will fill major gaps in our understanding of EED development and how breastmilk components influence C. jejuni colonization. This study may also identify novel treatments to prevent colonization with this pathogen to reduce the burden of disease and mortality.