Survival and virulence of copper- and chlorine-stressed Yersinia enterocolitica in experimentally infected mice

The effect of gastric pH on the viability and virulence of Yersinia enterocolitica O:8 after exposure to sublethal concentrations of copper and chlorine was determined in mice. Viability and injury were assessed with a nonselective TLY agar (tryptic soy broth containing lactose, yeast extract, and agar) and two selective media, TLYD agar (TLY agar plus sodium deoxycholate) and CIN agar (cefsulodin-Irgasan-novobiocin agar). Both copper and chlorine caused injury which was manifested by the inability of the cells to grow on selective media. CIN agar was more restrictive to the growth of injured cells than TLYD agar. Injury of the exposed cells was further enhanced in the gastric environment of mice. Besides injury, the low gastric pH caused extensive loss of viability in copper-exposed cells. Lethality in the chlorine-exposed cells was less extensive, and a portion of the inoculum (5.2 X 10(5) of 1 X 10(7) inoculated cells) reached the small intestine 5 min postinoculation. No adverse effect on the injured cells was apparent in the small intestine, and a substantial revival (approximately 70%) of the injury occurred in 3 to 4 h after intraluminal inoculation. The virulence of chlorine-stressed Y. enterocolitica in orally inoculated mice was similar to that of the control culture, but copper-stressed cells showed reduced virulence. Virulence was partly restored by oral administration of sodium bicarbonate before the inoculation of copper-exposed cells. Neutralization of gastric acidity had no effect on the virulence of the control or chlorine-stressed cells. The results of this study indicate that the extensive injury caused by the low gastric pH does not affect the virulence potential of chlorine-exposed cells. However, extensive cell death in the mouse stomach is responsible for the reduced virulence of the copper-stressed bacteria.     

Reproductive performance of four aphidophagous ladybirds on cowpea aphid, Aphis craccivora Koch

Abstract:  This study investigated prey consumption, egg production, percent progeny loss, reproductive, pre- and post-reproductive periods, reproductive time ratio, reproductive rate and bioconversion efficiency of four aphidophagous ladybirds, viz. Cheilomenes sexmaculata (Fabricius), Coccinella septempunctata Linnaeus, Coccinella transversalis Fabricius and Propylea dissecta (Mulsant) on Dolichos lablab Linnaeus infested with cowpea aphid, Aphis craccivora Koch. C. sexmaculata had the highest bioconversion efficiency, reproductive rate and reproductive time ratio followed in rank order by P. dissecta , C. transversalis and C. septempunctata . This study indicates that C. sexmaculata has a narrow ecological relationship with A. craccivora . The increased allocation of resources to reproduction as indicated through a high reproductive time ratio and high bioconversion efficiency of C. sexmaculata and P. dissecta suggest that they may be better adapted to compete for this prey with larger species like C. transversalis and C. septempunctata .     

Embryo transfer as a means of controlling the transmission of viral infections. X. The in vivo exposure of zona pellucida-intact porcine embryos to swine vesicular disease virus

Two experiments involving the transfer of embryos from donors infected with swine vesicular disease virus (SVDV) to "clean" recipients were carried out. In Experiment 1, 47 embryos were collected from 4 SVDV-infected donors and transferred to 2 recipients that subsequently produced 10 piglets. All of the recipients and piglets remained seronegative for SVDV. In addition to the transfers, 10 embryos and 58 unfertilized eggs from the infected donors were assayed in vitro and found to be negative for SVDV infectivity. A fifth donor was also inoculated with SVDV in this experiment, but it could not be demonstrated that infection had occurred. This SVDV-exposed donor provided two embryos for transfer and one embryo and two unfertilized eggs for in vitro assay. In Experiment 2, 158 embryos from 9 infected donors were transferred to 7 recipients, resulting in 12 piglets. A total of 7 embryos and 37 unfertilized eggs were assayed in vitro. The recipients, piglets, and embryos/eggs were all negative for SVDV infectivity. Although a final conclusion on the safety of using embryo transfer for the control of swine vesicular disease (SVD) is not possible, the results obtained justify additional studies.     

Embryo transfer as a means of controlling the transmission of viral infections. IX. The in vitro exposure of zona pellucida-intact porcine embryos to swine vesicular disease virus

When zona pellucida-intact porcine embryos were exposed to 10(7) plaque-forming units (pfu)/ml of swine vesicular disease virus (SVDV) and then washed, infectious virus could be isolated from all of the embryos. Culturing the embryos for 24 or 48 h or treating the embryos with pronase, trypsin, or antiserum after virus exposure and washing reduced the number of embryos carrying virus and lessened the amount of virus on each of the embryos. None of the treatments, however, was capable of disinfecting every embryo.