Pediococcus species

Pediococci are gram-positive cocci that grow in pairs and tetrads and belong to the lactic acid bacteria group. Normal inhabitants of the gastrointestinal tract, they are used extensively in industry to ferment cheese and other dairy products, soy products, and alcoholic beverages. Thirteen species of pediococci are recognized today, but only Pediococcus acidilactici and Pediococcus pentosaceus, typically found in sugar-rich foods, have been identified as human pathogens. In recent years, these organisms have been increasingly recognized as a cause of bacteremia, endocarditis, and pneumonitis in the immunocompromised host. These organisms have also been isolated from intra-abdominal infections such as peritonitis and hepatic abscesses. Risk factors for Pediococcus infections include prior antibiotic therapy, abdominal surgery, and gastric feeding.

Diagnosis is made by isolation and identification of the organism from cultures of blood or other body fluids. Pediococcus species may be difficult to distinguish from enterococci and Leuconostoc species given its association with food. Approximately 95% of clinical isolates will cross-react with group D streptococcal antisera. Tests that aid in distinguishing pediococci from other organisms include a negative pyrrolidonyl arylamidase (PYRase) test and the absence of gas production from glucose. With newer application of molecular genetic techniques to determine relatedness of food-associated lactic acid bacteria, reorganization of the genus with novel morphologic or phenotypic differentiation of Leuconostoc species from Pediococcus species is being studied.