Clifford W Houston, PhD
Herman Barnett Distinguished Professor, Microbiology & Immunology
Associate Vice President for Educational Outreach and Diversity
Phone: (409) 772-4987
Phone: (409) 772-4777
Fax: (409) 747-6869
Education: PhD, 1979, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma
MS, 1974, Oklahoma State University, Stillwater, Oklahoma
BS, 1972, Oklahoma State University, Stillwater, Oklahoma
hydrophila, cytotoxic enterotoxin.
My doctoral graduate research activities involved studies on type A streptococcal exotoxin produced by group A streptococci. I was able to purify the type A toxin and to develop the ELISA technique for the detection of the toxin. This technique was
used to monitor the kinetics of toxin synthesis in strains of streptococci. In addition, several biochemical and biological studies were conducted on the toxin.
As a postgraduate, my research has included the development of a very sensitive
antigenic assay for the detection of Salmonella toxin (ELISA). This assay was employed as a probe to determine the effect of heating on the antigenic structure of Salmonella toxin as well as the isoelectric point and molecular weight of the toxin.
Data were obtained which suggested that mitomycin C (MTC) caused cell lysis, resulting in the release of intracellular Salmonella toxin rather than an increase in toxin synthesis. The mechanism of this phenomenon was substantiated by the appearance
of bacteriophage concomitantly with the detection of Salmonella toxin subsequent to the addition of MTC to Salmonella broth cultures. Experiments were conducted which indicated that the gene which codes for Salmonella toxin synthesis was not associated
with a bacteriophage.
Presently, the long term objective of our laboratory is to determine the role of Aeromonas hydrophila virulence factors in the pathogenesis of disease in man. The virulence factors presently reported in the literature associated with
A. hydrophila have not been defined clearly. A. hydrophila, a member of the family Vibrionaceae, is considered to be a significant human pathogen. This microorganism is responsible for a variety of diseases including acute bacterial diarrhea,
septicemia, meningitis, endocarditis, corneal ulcers, peritonitis, and wound infections. These diseases have occurred in immunocompetent and well as immunocompromised individuals. A. hydrophila produce as well as possess a number of factors which
contribute to the overall virulence of the organism. We have characterized two enterotoxins biochemically, biologically and antigenically. We have identified the genes for both enterotoxins and have cloned them. A complete nucleotide sequence
analysis of the cytolytic enterotoxin gene has been accomplished. Our preliminary results regarding the mechanism of action of our cytotonic enterotoxin as been published. Our goals for the future will be to define the domains on the cytolytic
enterotoxin that are responsible for various biological activities associated with this toxin molecule as well as to locate the binding region on the cytolytic enterotoxin which interacts with the host eukaryotic cell membrane; to study the regulation
of expression of the cytolytic enterotoxin gene; to define the area in a cloned DNA fragment that codes for a cytotonic enterotoxin gene and subject it to nucleotide sequence analysis; to overexpress both the cytolytic and cytotonic enterotoxins
using several expression vector systems i.e., pET, pGEX or pTRXFUS; and, to initiate studies to establish the precise role of these enterotoxins in the pathogenesis of Aeromonas-mediated diseases.
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