[Effect of Listeria on contractibility of human uterine muscle]

In Austria the prevalence of listeriosis is 2.6 cases per million inhabitants yearly, hence rather rarely the cause of spontaneous abortion or premature birth. On the other hand, Listeria monocytogenes is found in 1% of the asymptomatic population as a component of stool flora. Since the cause of premature labour contractions remains unclear in about half of all cases, we examined 29 listeria strains for their ability to cause myometrial contraction by direct contact using an in-vitro uterine strip-model. Seven of nine L. monocytogenes strains were able to cause contractions; contractions were not inducible by an nonhaemolytic mutane (SLCC 53, avirulent) nor by a rough strain (SLCC 5779, only slightly virulent). Three of six L. ivanovii isolates also exhibited the ability to induce contractions. None of the apathogenic species (L. innocua, L. seeligeri, L. welshimeri, L. grayi and L. murrayi) was capable of activating contractions in our in-vitro model. Only L. monocytogenes and L. ivanovii cause conjunctivitis after being dropped in rabbit's eyes (positive Anton Test). The influence of listeria on uterine activity as found in our in-vitro model thus correlates with the classical pathogenicity test. We consider these in-vitro results as an additional argument to oppose the presence of L. monocytogenes in ready-to-eat foods.