|Lactobacillus acidophilus, Numbered ticks are 11 μm|
(Moro 1900) Hansen & 1970
Lactobacillus acidophilus (New Latin 'acid-loving milk-bacillus') is a species of gram positive bacteria in the genus Lactobacillus. L. acidophilus is a homofermentative, microaerophilic species, fermenting sugars into lactic acid, and grows readily at rather low pH values (below pH 5.0) and has an optimum growth temperature of around 37 °C (99 °F). L. acidophilus occurs naturally in the human and animal gastrointestinal tract and mouth. Some strains of L. acidophilus may be considered to have probiotic characteristics. These strains are commercially used in many dairy products, sometimes together with Streptococcus thermophilus and Lactobacillus delbrueckii subsp. bulgaricus in the production of acidophilus-type yogurt, or acidophiline. Its genome has been sequenced. Lactobacillus acidophilus was found, when fed to pigs, to lower serum cholesterol and raise the amount of cholesterol present in fecal matter. 
Lactobacillus acidophilus is part of the vaginal microbiota along with other species in the genus including Lactobacillus crispatus, Lactobacillus gasseri, Lactobacillus jensenii, and Lactobacillus iners. In lab experiments, L. acidophilus seemed to decrease Candida albicans’ ability to adhere to vaginal epithelial cells; however, L. acidophilus’ role in preventing yeast infections is unclear because this species of Lactobacilli has also been found not to have a very strong ability to adhere to (and thereby colonize) the vaginal cells.
Although probiotics are generally safe, when they are used by oral administration there is a small risk of passage of viable bacteria from the gastrointestinal tract to the blood stream (bacteremia), which can cause adverse health consequences. Some people, such as those with a compromised immune system, short bowel syndrome, central venous catheters, cardiac valve disease and premature infants, may be at higher risk for adverse events. In children with lowered immune systems or who are already critically ill, consumption of probiotics may rarely cause bacteremia or fungemia, leading to sepsis, which is a potentially fatal disease. Scant complaints of mild gastrointestinal discomfort or gas have been noted.
Lactobacillus acidophilus is a constituent in VSL#3. This proprietary, standardized, formulation of live bacteria may be used in combination with conventional therapies to treat ulcerative colitis.
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- Lactobacillus at MedlinePlus
- Lactobacillus acidophilus at University of Maryland Medical Center
- Lactobacillus acidophilus from the U. of Wisconsin
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- Pictures and research on Lactobacillus acidophilus
- Type strain of Lactobacillus acidophilus at BacDive – the Bacterial Diversity Metadatabase
- Lactobacillus acidophilus - Benefits & Probiotic Uses at Pocket Reviewer