ListeriaandErysipelothrix

Abstract

The majority of cases of listeriosis occur in individuals who have an underlying condition that leads to suppression of their cell-mediated immunity. Among veterinarians and abattoir workers, primary cutaneous listeriosis with or without bacteremia has been reported. Transient bacteremia can result in placentitis and/or amnionitis, and since Listeria is able to cross the placenta, it can infect the fetus, causing abortion, stillbirth, or, most commonly, preterm labor. In general, specimens for detection of Listeria do not need special handling during collection. Listeria colonies appear blue, and colonies of other bacteria appear yellowish or orange. The CAMP (Christie, Atkins, Munch-Petersen) test can be used to differentiate among hemolytic Listeria species. Commercially available miniaturized tests considerably speed up biochemical identification of Listeria spp. The matrix-assisted laser desorption ionization-time of flight (mass spectrometry) (MALDI-TOF [MS]) technique has recently been introduced and allows discrimination of the Listeria species by use of the respective software. Treatment with an aminopenicillin (ampicillin or amoxicillin) plus gentamicin is still regarded as the most effective therapeutic regimen for listeriosis. Listeria species are catalase positive, motile, esculin positive, and not alpha-hemolytic. The genus Erysipelothrix has three validly published species, Erysipelothrix rhusiopathiae, Erysipelothrix tonsillarum, and the more recently described Erysipelothrix inopinata. E. rhusiopathiae has been recognized for more than 100 years as the agent of swine erysipelas, an acute or chronic disease. Occurrence of this species in wound or tissue specimen indicates erysipeloid rather than contamination. Species identification is essential in order to ensure adequate antimicrobial therapy.