Sam W. Joseph

Emeritus Professor

Research Interests: Bacterial Pathogenesis.

The numbers of recognized organisms, originating from the aquatic environment and causing disease in humans, has been increasing in recent years. For example, there are now 12 species of pathogenic Vibrios and seven pathogenic Aeromonas species. Our studies are centered on studying the classification of these organisms and the mechanisms by which they cause disease in humans. We are interested not only in the anthropocentric nature of these diseases, but in studying the causative organisms in their native ecologic niches, as well. With these studies we can better decipher the differences between those aquatic organisms which are capable of causing human disease versus those which constitute a relatively benign subset.

Thus far we have developed a further understanding of adhesion, flagellation and iron requirements as enhancing features in the virulence of vibrios. Our study of over 700 strains of vibrios has now revealed the probability of at least two more species of vibrios. We have confirmed the existence of the new species, Aeromonas schubertii, in the Chesapeake Bay area, named three other new species A. jandae, A. trota and A. bestiarum and are developing new methodologies to phenotypically discriminate among the fourteen different genotypes of Aeromonas. We are identifying markers based on their different epitopes and their role as possible major virulence features of the aeromonads.

In collaboration with others, we have studied various features of the Salmonella on-farm contamination problem in poultry houses and transportation. Thus far, we have developed an agarless medium, a quantitative culture method (non-MPN), a prototype model for disinfecting poultry crates, and a hypothesis for using water activity (Aw) as a predictor for the presence of Salmonella. We have further developed the quantitative filter monitor method and immunological colony filter transfer method to also allow detection and quantitation in a rapid, accurate identification package for Salmonella enteriditis. We are presently developing the quantitative filter monitor method and colony lift immunoassay (CLI) as a SELeCT system to detect and quantify the major foodborne pathogens, Salmonella, Campylobacter, E. coli 0157:H7 and Listera.

Courses Taught

Graduate Students

M.S. Thesis
1994-97-David Ingram, "Development and Evaluation of Rapid, Diagnostic Methodologies for the Isolation, Quantification and Identification of Escherichia coli 0157:H7 in Redmeat and Poultry Products.

Undergraduate Students

Rhonda Foard
Christian deRezende

Representative Publications

Rollins, D.M., L.H. Lee, B.E. Rice, C. Lamichhane, S.W. Joseph. 1997. Development of a quantitative methodology to estimate the number of enteropathogenic Campylobacter on fresh poultry products. In Campylobacter VIII. Proceedings of the Eighth International Workshop on Campylobacters, Helicobacters and Related Organisms. Plenum Publ. Corp., N.Y., N.Y.

Ali, A., A.M. Carnahan, M. Altwegg, J. Luthy-Hottenstein, and S.W. Joseph. 1996. Aeromonas bestiarum sp. nov. (Formerly genomospecies DNA Group 2 A. hydrophila) a new species isolated from non-human sources. Med. Microbiol. Lett. 5:156-165.

Joseph, S.W. 1996. Aeromonas - A case study for causality? in The Genus Aeromonas, ed. M. Altwegg, B. Austin, P. Gosling and S. Joseph. Pub. John Wiley and Sons, Ltd., London, England.

Rice, B.E., C. Lamichhane, S.W. Joseph, and D.M. Rollins. 1996. Development of a rapid and specific colony - lift immunoassay for detection and enumeration of Campylobacter jejuni, C. coli and C. lari. Clin. Diag. Lab. Immunol. 3:669-677.

Carr, L.E., E.T. Mallinson, C. Tate, R. Neely, E. Russek-Cohen, L.E. Stewart, O. Opara, C.A. White, and S.W. Joseph. 1995. Prevalence of Salmonella in broiler flocks: effect of litter water activity, house construction and watering devices. Avian Dis. 39:39-44.

El-Assaad, F.G., L.E. Stewart, E.T. Mallinson, L.E. Carr, S.W. Joseph and G. Berney. 1995. Decontamination of poultry transport cages. Trans. Amer. Soc. Agric. Engineer. 38:1213-1220.

Turbyfill, K.R., S.W. Joseph, and E.V. Oaks. 1995. Recognition of three epitopic regions on invasion plasmid antigen C by immune sera of Rhesus monkeys infected with Shigella flexneri 2a. Infect. Immun. 63:3927- 3935.

Carr, L.E., E.T. Mallinson, L.E. Stewart and S.W. Joseph. 1994. The influence of water activity on Salmonella presence in broiler operations. Appl. Engineer. Agric. 10:403-405.

Joseph, S.W. and A.M. Carnahan. 1994. The isolation, identification and systematics of the motile Aeromonas species. Ann. Rev. Fish Dis. 4:315-343.

Guerry, P., P.M. Pope, D.H. Burr, J. Leifer, S.W. Joseph, and A.L. Bourgeois. 1994. Development and characterization of recA mutants of Campylobacter jejuni for inclusion into attenuated vaccines. Infec. Immun.62:426-432.