The O-antigen negative ∆wbaV mutant of Salmonella enterica serovar Enteritidis shows adaptive resistance to antimicrobial peptides and elicits colitis in streptomycin pretreated mouse model.
BACKGROUND
Salmonella enterica serovar Enteritidis, the most common cause of human gastroenteritis, employs several virulence factors including lipopolysaccharide (LPS) for infection and establishment of disease inside the host. The LPS of S. enterica serovar Enteritidis consists of lipid A, core oligosaccharide and O-antigen (OAg). The OAg consists of repeating units containing different sugars. The sugars of OAg are synthesized and assembled by a set of enzymes encoded by genes organized into clusters. Present study focuses on the effect of deletion of genes involved in biosynthesis of OAg repeating units on resistance to antimicrobial peptides and virulence in mice.


METHODS
In the present study, the OAg biosynthesis was impaired by deleting tyv, prt and wbaV genes involved in tyvelose biosynthesis and its transfer to OAg. The virulence phenotype of resulting mutants was evaluated by assessing resistance to antimicrobial peptides, serum complement, adhesion, invasion and in vivo colonization.


RESULTS
Deletion of the above three genes resulted in the production of OAg-negative LPS. All the OAg-negative mutants showed phenotype reported for rough strains. Interestingly, ΔwbaV mutant showed increased resistance against antimicrobial peptides and normal human serum. In addition, the ΔwbaV mutant also showed increased adhesion and invasion as compared to the other two O-Ag negative mutants Δtyv and Δprt. In vivo experiments also confirmed the increased virulent phenotype of ΔwbaV mutant as compared to Δprt mutant.


CONCLUSIONS
OAg-negative mutants are known to be avirulent; however, this study demonstrates that certain OAg negative mutants e.g. ∆wbaV may also show resistance to antimicrobial peptides and cause colitis in Streptomyces pretreated mouse model.
KIIT School of Biotechnology, KIIT University, Bhubaneswar, Odisha 751024 India.
Sangeeta
S
Jaiswal
KIIT School of Biotechnology, KIIT University, Bhubaneswar, Odisha 751024 India.
Niladri Bhusan
NB
Pati
KIIT School of Biotechnology, KIIT University, Bhubaneswar, Odisha 751024 India.
Manupriyam
M
Dubey
KIIT School of Biotechnology, KIIT University, Bhubaneswar, Odisha 751024 India.
Chandrashekhar
C
Padhi
KIIT School of Biotechnology, KIIT University, Bhubaneswar, Odisha 751024 India.
Prakash Kumar
PK
Sahoo
KIIT School of Biotechnology, KIIT University, Bhubaneswar, Odisha 751024 India.
Shilpa
S
Ray
KIIT School of Biotechnology, KIIT University, Bhubaneswar, Odisha 751024 India.
Aryashree
A
Arunima
Kalinga Institute of Medical Sciences, KIIT University, Bhubaneswar, Odisha 751024 India.
Nirmal Kumar
NK
Mohakud
KIIT School of Biotechnology, KIIT University, Bhubaneswar, Odisha 751024 India.
Mrutyunjay
M
Suar
Antimicrobial peptides; Lipopolysaccharide; OAg biosynthesis; OAg-negative; S. Enteritidis; Virulence; wbaV gene