Variation in antibiotic susceptibility and presence of type VI secretion system (T6SS) in Campylobacter jejuni isolates from various sources

Abstract

Campylobacter jejuni is a major cause of infectious diarrhea in humans. The bacterium can be transmitted through contaminated poultry meat and waste water. We report the presence of C. jejuni from potential transmission sources including egg shells, poultry waste, waste water and migratory bird droppings with a prevalence rate of 78%, 66%, 86% and 70% respectively. Antibiotic resistance profile showed high number of isolates resistant to multiple antibiotics including 4th generation cephalosporins. C. jejuni isolates were further screened for presence of T6SS, an important virulence factor. None of the C. jejuni isolates from migratory birds carried a T6SS, whereas highest prevalence of T6SS isolates was observed in waste water samples, followed by poultry waste and egg shells. To determine virulence potential of the isolates, hemolytic activity of isolates was compared. Although variation in hemolytic potential between isolates from different sources was noted, higher hemolytic activity was observed for isolates possessing hcp, a T6SS gene. Furthermore, presence of T6SS affords the bacterium some survival advantage when compared to T6SS competent Helicobacter pullorum which occupies the same niche. Taken together our findings indicate that C. jejuni with T6SS have a fitness advantage increasing their isolation frequency from waste water and poultry waste.