Excerpted from the thesis of PhD candidate Nguyen Thi Tham

THESIS ABSTRACT
1. Summary
Full name of Ph.D candidate: NGUYEN THI THAM
Title of thesis: “Study on biological characteristics of Clostridium perfringens causing
diseases in chickens and ostriches, selecting candidate strains for vaccine development”
Major: Veterinary Parasitology and Microbiology
Code number: 964 01 04
Supervisors: 1. VU KHAC HUNG, Ph.D 2. NGUYEN DUC TAN, Ph.D
Educational institution: National Institute of Verterinary Research
2. Objectives and research subjects
Objectives:
– Determine of genotype diversity and virulent factors of Clostridium perfringens
isolated from chickens and ostriches. Selecting candidate strains to develop vaccine
against necrotic enteritis.
Research subjects:
– Clostridium perfringens isolated from chickens and ostriches.
3. Methods
The main methods used in this study including: (1) Isolating and determining the
biochemical properties of C. perfringens (2) Determining toxin types, virulent genes, and
sequencing gene 16S rRNA, gene netB of C. perfringens (3) Determining virulent
factors, virulent stability and NetB toxin purification (4) Detecting specific antibody
NetB toxin (5) Data analysis: EXCELL, DNAstar and BioEdit software.4. Main results and conclusions
Main results
Prevalence of C. perfringens in fecal, intestinal organs samples of enteric
disordered and healthy chickens were 63.69%, 58.82%, 24.06%, respectively. The rates
of isolates from chickens with virulence genes netB, cpe and cpb2 were 39.7%, 1.83%
and 0%, respectively. The prevalences of C. perfringens of fecal, intestinal organs
samples in enteric disordered and healthy ostriches were 29.37%, 34.28%, 20.88%,
respectively. The rates of isolates from ostriches carrying virulence genes netB, cpe and
cpb2 were 13.79%, 0.77% and 4.31%, respectively. All isolated strains belonged to type
A with the same biochemical characteristics of C. perfringes as literature. Sequence of
16S rRNA and netB genes of 8 C. perfringens isolates from chickens and 5 isolates from
ostriches showed 100% identity to each other. Registered netB gene sequences of C.
perfringens isolates from chickens (MT032252 to MT 032259) and C. perfringens
isolates from ostriches (MT032260 to MT 032264) were upload on GenBank.
Selected one strain of C. perfringens (CG69) from chickens and one strain of C.
perfringens (CD115) from ostrich with cpa and netB toxin genes, highly virulent and
stable over generations on Fluid thyoglycolate medium.
NetB toxin was been purified and stimulated specific immunogenicity in mice,
chickens and ostriches.
Conclusion
This study indentified biochemical properties, main toxin types, virulence genes
and genetic relationships of C. perfringens isolates from chickens and ostriches in
Vietnam. The genetic relationships between the Vietnam strains and those in the world
were determined. Selected a highly virulent C. perfringens strain, stable virulent and
stimulated specific immunogenicity. Base on this results for further research on necotic
enteritis vaccine in chickens and ostriches.