Bacteriophage-encoded shiga toxin gene in atypical bacterial host

• Main Authors: Casas Veronica, Sobrepeña Gerico, Rodriguez-Mueller Beltran, AhTye Justine, Maloy Stanley R
• Format: Article
• Language: English
• Published: BMC 2011-07-01
• Series: Gut Pathogens
• Online Access: http://www.gutpathogens.com/content/3/1/10

<p>Abstract</p> <p>Background</p> <p>Contamination from fecal bacteria in recreational waters is a major health concern since bacteria capable of causing human disease can be found in animal feces. The Dog Beach area of Ocean Beach in San Diego, California is a beach prone to closures due to high levels of fecal indicator bacteria (FIB). A potential source of these FIB could be the canine feces left behind by owners who do not clean up after their pets. We tested this hypothesis by screening the DNA isolated from canine feces for the bacteriophage-encoded <it>stx </it>gene normally found in the virulent strains of the fecal bacterium <it>Escherichia coli</it>.</p> <p>Results</p> <p>Twenty canine fecal samples were collected, processed for total and bacterial fraction DNA, and screened by PCR for the <it>stx </it>gene. The <it>stx </it>gene was detected in the total and bacterial fraction DNA of one fecal sample. Bacterial isolates were then cultivated from the <it>stx</it>-positive fecal sample. Eighty nine of these canine fecal bacterial isolates were screened by PCR for the <it>stx </it>gene. The <it>stx </it>gene was detected in five of these isolates. Sequencing and phylogenetic analyses of 16S rRNA gene PCR products from the canine fecal bacterial isolates indicated that they were <it>Enterococcus </it>and not <it>E. coli</it>.</p> <p>Conclusions</p> <p>The bacteriophage-encoded <it>stx </it>gene was found in multiple species of bacteria cultivated from canine fecal samples gathered at the shoreline of the Dog Beach area of Ocean Beach in San Diego, California. The canine fecal bacteria carrying the <it>stx </it>gene were not the typical <it>E. coli </it>host and were instead identified through phylogenetic analyses as <it>Enterococcus</it>. This suggests a large degree of horizontal gene transfer of exotoxin genes in recreational waters.</p>