Hello sugar! Campylobacter just can’t resist

Scientists at the University of Nottingham hope their findings could lead to better understanding of the host-bacterial interaction, prevention and treatment of Campylobacter jejuni infections.

Professor Ala’Aldeen, Dr Jafar Mahdavi and their team discovered the bacteria piggy-back on a set of blood-group antigens (BgAgs) triggered by the host’s cells and use these to colonise and spread.

Dr Ala’Aldeen told FoodQualityNews.com that Campylobacter is the most common cause of food poisoning in the UK and worldwide.

“The disease burden is massive in terms of the economic impact and on the chicken industry it is considerable,” ​he said.

“Normal cooking is enough to prevent infection if it is handled well and well separated but if it is with ready to eat foods and salads people are not always mindful of streamlining when they are cooking in the home.”​

Helping molecular hand​

The team identified the bacterial molecules that facilitate the host-bacterial cell binding and the sugar coated carbohydrates used to attract the bacteria.

They are the flagellar protein (FlaA) and the major outer membrane protein (MOMP).

Identification of FlaA and MOMP as BgAg-binding adhesins was surprising as the proteins have little in common in primary sequence, predicted structure or known functions, said the study.

The MOMP is ‘sugar coated’ and it is these ‘glycan decorations’ that are critical for binding BgAgs and the binding to human and chicken intestine.

Deletion of flaA led to reduced binding of Camylobacter strain NCTC11168 to all examined BgAgs.

One step further​

“We are one step further to identifying the precise molecules responsible for the affinity between the two,” ​said Dr Ala’Aldeen.

“The hope is to design strategies, economically and to make a healthcare difference. At the moment the investment by industry in cleaning and decontamination in chickens is expensive and they need ways to minimise it.”​

Prevention and treatment of the consequences of Campylobacter infection are hampered by a poor understanding of the molecular interplay between cells of the gastrointestinal lining and the pathogen.

Changing organism​

Dr Ala’Aldeen said this was because the organism is a complex agent and the human gut is complex which leads to sophisticated methods of interaction.

“The organism has evolved clever strategies to change its code through outside layers so it takes a long time to characterize and to know what is made of," ​he said.

“The bacterium has very flexible genetics, its DNA is made in a way to reshuffle itself and change behaviour and the external protein structure protects against attacks we might mount against it.​

“In humans it has also evolved efficient means to colonize and go on to cause disease which is not the case in chickens.”​

The discovery should help the development of products to block the binding between Campylobacter and BgAgs, and prevent chicken or human colonisation or reduce the burden of raw meat contamination, said the researchers.

Dr Mahdavi said: “We found that removing a single molecule (Threonine-268) from MOMP significantly reduced the protein’s sugar coating and radically reduced the bacterial ability to bind host cells, cause biofilms in the lab or colonise chickens in broilers​.”

Source: Royal Society Journal Open Biology

Online ahead of print, DOI: 10.1098/rsob.130202​

“A novel ​O​-linked glycan modulates Campylobacter​​ jejuni​ major outer membrane protein-mediated adhesion to human histo-blood group antigens and chicken colonization​”

Authors: Jafar Mahdavi, Necmettin Pirinccioglu, Neil J. Oldfield, Elisabet Carlsohn, Jeroen Stoof, Akhmed Aslam, Tim Self, Shaun A. Cawthraw, Liljana Petrovska, Natalie Colborne, Carina Sihlbom, Thomas Borén, Karl G. Wooldridge and Dlawer A. A. Ala'Aldeen