Influence of pCP1NetB ancillary genes on the virulence of Clostridium perfringens poultry necrotic enteritis strain CP1
Zhou, H., Lepp, D., Pei, Y., Liu, M., Yin, X., Ma, R., Prescott, J.F., Gong, J. (2017). Influence of pCP1NetB ancillary genes on the virulence of Clostridium perfringens poultry necrotic enteritis strain CP1. Gut Pathogens, [online] 9(1), http://dx.doi.org/10.1186/s13099-016-0152-y
Plain language summary
Necrotic enteritis (NE) is an economically important disease of poultry caused by certain strains of bacterial pathogen, Clostridium perfringens. The NetB toxin is a critical virulent factor for the disease and located in a transferrable DNA plasmid vector that also harbors a number of other genes. To determine the role of these ancillary genes in the disease development, the present study has characterized a mutant strain without the DNA vector and compared the virulence of this mutant to the parent strain by both in vitro and in vivo studies. The results demonstrate that the mutant strain of C. perfringens lost its virulence and was unable to induce cell lysis in vitro and NE disease in chickens. When the netB gene was introduced back to the mutant strain, it fully restored the virulence in vitro, but partially induced NE disease in chickens. These results suggest that other ancillary genes within the same transferrable DNA vector also play a role in the development of NE disease.
Background: Necrotic enteritis (NE) is an economically important disease of poultry caused by certain Clostridium perfringens type A strains. The NetB toxin plays a critical role in the pathogenesis of NE. We previously demonstrated that netB is located within a 42 kb plasmid-encoded pathogenicity locus (NELoc-1), which also encodes 36 additional genes. Although NetB clearly plays a role in pathogenesis, the involvement of the other NELoc-1 genes has not yet been established. The current study was to provide experimental evidence to confirm the involvement of these genes in NE pathogenesis. Results: The present study has characterized a virulent C. perfringens strain (CP1) that has spontaneously lost the NELoc-1-encoding plasmid, pCP1netB. When assessed for cytotoxicity on Leghorn Male Hepatoma (LMH) cells, the culture supernatant of the pCP1netB-deficient CP1 variant (CP1ΔpCP1netB) demonstrated significantly reduced cytotoxicity compared to the wild-type. In addition, CP1ΔpCP1netB was unable to cause intestinal lesions in chickens in a NE disease model. When netB alone was introduced into CP1ΔpCP1netB, in vitro cytotoxicity was restored to the wild-type level; however, it did not completely restore virulence when used to challenge broiler chickens [mean lesion score of 0.71 compared to 3.23 in the wild type control group (n = 14)]. Conclusions: The results of this study suggest that other genes present in NELoc-1, in addition to netB, are required for full virulence in the chicken challenge model.