Physiology, pathogenicity and immunogenicity of lon and/or cpxR deleted mutants of Salmonella Gallinarum as vaccine candidates for fowl typhoid

To construct a novel live vaccine candidate for fowl typhoid (FT) caused by Salmonella Gallinarum (SG), the lon and cpxR genes that are related to host-pathogen interaction were deleted from a wild type SG using the allelic exchange method. The mutants were grown normally, as was the wild type. The biochemical properties of the mutants remained very similar to those of the wild-type, while JOL914 (Δlon) and JOL916 (ΔlonΔcpxR) were mucoid. Extracellular polysaccharide increased 30.6-, 1.3-, and 46.2-fold in JOL914, JOL915 (ΔcpxR), and JOL916, respectively. Dot-blot analysis demonstrated significant increases of FimA expression at 6.77-, 2.33-, and 3.90-fold for JOL914, JOL915, and JOL916, respectively. Internalizations of JOL914, JOL915, and JOL916, in chicken abdominal macrophages, were increased at 4.65-, 0.50-, and 2.72-fold, respectively. Virulences of JOL914, JOL915 and JOL916, analyzed by LD50 using 1-week-old chickens, were attenuated approximately at 101-, 101-, and > 103-fold, respectively. The oral inoculations of 2 × 107 cfu of the wild type, JOL914, JOL915 and JOL916 caused 55.6, 16.7, 22.2, and 0.0% mortality, respectively. Significantly moderate gross lesions of the liver and spleen were observed in the JOL916 group compared to the other groups. An induced immune response and significant peripheral mononuclear proliferation reaction were observed in the JOL916 group. At the protection against the wild type challenge, JOL916 offered 100% protection. Thus, the results of this study suggest that JOL916 among the mutants studied represented the safest and most effective live vaccine candidate against FT

Effects of in vitro culture methods on morphological development and infectivity of Strongyloides venezuelensis filariform larvae

The effects of in vitro culture methods on morphological development and infectivity of Strongyloides venezuelensis filariform larvae (L3) to rats were investigated. A significantly higher body length was observed in L3 from filter paper culture (597.3 ± 32.2 µm) than those in fecal (509.9 ± 35.0 µm) and nutrient broth culture (503.3 ± 31.0 µm) (P<0.05). Larval infectivity was assessed by exposing rats to 1,000 L3 from each culture and worms were recovered from the lungs and small intestines. Recovery rate of these worms did not show any significant difference. A significantly greater body length of adults was recorded in those corresponding to the L3 harvested from filter paper (2,777.5 ± 204.4 µm) and nutrient broth culture (2,732.5 ± 169.8 µm) than those corresponding to the L3 obtained from fecal culture (2,600.5 ± 172.4 µm) (P<0.05). Although worm fecundity and EPG counts differed among culture methods but worm burdens and course of infection did not. These findings suggest that the methods of cultures have a significant effect on the morphological development of the larvae to the L3 stage, but do not influence the infectivity to rats

Profiles of Virulence-associated Genes of Avian Pathogenic Escherichia coli Isolates from Chickens with Colibacillosis

The colibacillosis caused by avian pathogenic E. coli (APEC) is responsible for a significant loss of productivity and mortality in the poultry industry. The pathogenicity of these bacteria is based on the presence and expression of various virulence factors. In this study, the presence of the 19 virulence-associated genes in APEC was determined using PCR. Among the 118 E. coli isolates from the chickens with colibacillosis, all contained at least one of the 19 genes as approximately 95% of the isolates contained fimC. Interestingly, the clpG gene, which has not been detected in APEC previously, was detected in half of the isolates. The ColV plasmid-associated genes such as colV, tsh, iucC, iucD and iss genes were also detected in 57.6, 55.9, 50.0, 47.5, 47.5 and 41.5% of isolates, respectively. With regard to the fimbrial genes, the papA (14.4%), papC (14.4%) and papG genes (15.2%) were identified at relatively low rates, none of the isolates harbored afa8D, f17A or facA, and only 3 of the isolates (2.5%) contained eaeA. In this study, 94 isolates harbored two or more of the genes, and there were 43 different patterns of gene combination in the isolates. The most common pattern, which was found in 14.4% (17 isolates), was clpG-fimC-iutA-colV-tsh-iucC-iucD-irp2-fyuA-vat-iss. Overall, these results suggest that APEC strains in this area commonly contain multiple virulence factors and approximately half of the APEC strains contained the ColV plasmid-associated genes. Especially, colV and tsh were detected more than half of the isoaltes