Campylobacter jejuni resistance to human milk involves the acyl carrier protein AcpP

Authors: ZHOU, BIBI - University Of Georgia; GARBER, JOLENE - University Of Georgia; BUTCHER, JAMES - University Of Georgia; MUSZYNSKI, ARTUR - University Of Georgia; CASEY, REBEKAH - University Of Georgia; Huynh, Steven; ARCHER-HARTMANN, STEPHANIE - University Of Georgia; PORFIRIO, SARA - University Of Georgia; ROGERS, ASHLEY - University Of Georgia; AZADI, PARASTOO - University Of Georgia; Parker, Craig; NG, KENNETH - University Of Windsor; HINES, KELLY - University Of Georgia; STINTZI, ALAIN - University Of Ottawa; SZYMANSKI, CHRISTINE - University Of Georgia

Submitted to: mBio
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/28/2025
Publication Date: 2/25/2025
Citation: Zhou, B., Garber, J.M., Butcher, J., Muszynski, A., Casey, R.L., Huynh, S., Archer-Hartmann, S., Porfirio, S., Rogers, A.M., Azadi, P., Parker, C.T., Ng, K.K., Hines, K.M., Stintzi, A., Szymanski, C.M. 2025. Campylobacter jejuni resistance to human milk involves the acyl carrier protein AcpP. mBio. 16(4). Article e03997-24. https://doi.org/10.1128/mbio.03997-24.
DOI: https://doi.org/10.1128/mbio.03997-24

Interpretive Summary: The foodborne pathogen, Campylobacter jejuni, is linked to high rates of morbidity and mortality among infants from low-to-middle income countries (LMICs). Human breastmilk is an important source of nutrients for infants, that also contains antimicrobial components for protection against infection. However, recent studies, including our own, have indicated that in breastfed infants with diarrhea from LMICs, the Campylobacter levels in their feces are significantly higher than non-breastfed infants. We hypothesized that C. jejuni may have unique strategies to resist the antimicrobial compounds in human breastmilk and even grow in this medium. In this study, we evolved C. jejuni strains that can grow in the presence of human breastmilk. After evolving two model C. jejuni strains in human breastmilk, we performed genomic sequencing to compare the evolved isolates to the original strains. We found that mutations in the gene encoding acyl carrier protein, AcpP, are important for growth in human breastmilk. The acpP mutations in the evolved isolates altered the cell membrane and resulted in increased antimicrobial resistance. This study provides some insights into possible strategies of how C. jejuni can survive and propagate in the gut of breastfed infants from LMICs.

Technical Abstract: Campylobacter jejuni is a common foodborne pathogen and linked to high rates of morbidity and mortality among infants from low-to-middle income countries (LMICs). Human breastmilk is an important source of nutrients for infants, that also contains antimicrobial components for protection against infection. However, recent studies, including our own, have indicated that in breastfed infants with diarrhea from LMICs, the Campylobacter levels in their feces are significantly higher than non-breastfed infants. We hypothesized that C. jejuni may have unique strategies to resist the antimicrobial compounds in human breastmilk and even grow in this medium. In this study, we found that exposure of C. jejuni to 100% human breastmilk results in increased expression of ribosomal proteins, receptors and transporters for iron, and proteins for amino acid utilization. However, the C. jejuni strains were unexpectedly unable to grow in these breastmilk samples. After evolving two model C. jejuni strains in human breastmilk, followed by genomic sequence comparisons of those isolates compared to the original strains, we found that mutations in the gene encoding acyl carrier protein, AcpP, are important for growth in human breastmilk, and that the acpP mutations lead to cell membrane changes. The evolved strains showed increased resistance to polymyxin. Furthermore, proteinaceous compounds in human breastmilk are involved in the C. jejuni growth inhibition phenotype and lipids may play synergistic roles. Taken together, this study provides insights into how C. jejuni may survive in human breastmilk.