Morphology of Vibrio cholerae during enterotoxin production under anaerobic conditions

The Impact of Oxygen on Bacterial Enteric Pathogens

Bacterial enteric pathogens are responsible for a tremendous amount of foodborne illnesses every year through the consumption of contaminated food products. During their transit from contaminated food sources to the host gastrointestinal tract, these pathogens are exposed and must adapt to fluctuating oxygen levels to successfully colonize the host and cause diseases. However, the majority of enteric infection research has been conducted under aerobic conditions. To raise awareness of the importance in understanding the impact of oxygen, or lack of oxygen, on enteric pathogenesis, we describe in this review the metabolic and physiological responses of nine bacterial enteric pathogens exposed to environments with different oxygen levels. We further discuss the effects of oxygen levels on virulence regulation to establish potential connections between metabolic adaptations and bacterial pathogenesis. While not providing an exhaustive list of all bacterial pathogens, we highlight key differences and similarities among nine facultative anaerobic and microaerobic pathogens in this review to argue for a more in-depth understanding of the diverse impact oxygen levels have on enteric pathogenesis.

New medium for the production of cholera toxin by Vibrio cholerae O1 biotype El Tor

A new medium that stimulates in vitro production of cholera toxin by Vibrio cholerae O1 El Tor (El Tor vibrios) was developed. The medium contains 0.5% NaCl, 0.3% NaHCO3, 0.4% yeast extract, and 1.5% Bacto-Peptone. El Tor vibrios were cultured in a stationary test tube at 37 degrees C for 20 h. The culture supernatant was assayed for cholera toxin by a reversed passive latex agglutination method. Most vibrios grown in this medium produced 10 to 20 times more toxin than in traditional syncase medium. The number of live vibrios at the end of culture was about 10(8)/ml in the new medium (AKI medium) and about 10(10)/ml in the syncase medium. As a result, each individual organism in the new medium should have produced as much as 1,000 times more toxin than in syncase medium. Sodium bicarbonate was found to be the most important factor in toxin production by El Tor vibrios in the new medium. We recommend this new medium because of its high yield of cholera toxin and its technical simplicity.