The recent increase in the incidence of the facultative bacterium Listeria monocytogenes severe infections of human and animals, makes it of significant public health importance. A total of 26 isolates of L. monocytogenes (23 from 23 patient group and 3 from 20 controls) were obtained from pregnant or non- pregnant women with spontaneous abortion and were submitted to serotyping. Only 2 L. monocytogenes serovars (1/2 a and 4b) are isolated in 90% of cases of human listeriosis. Of pregnant women sera , 56% were L. monocytogenes O and H agglutinating antibodies - positive while 100% and 78% of the cerebrospinal fluid (CSF) were L. monocytogenes O and H agglutinating antibodies positive, respectively. In the post-abortive subgroup, 100% and 90%  were sero - and CSF-O and H agglutinins - positive , respectively.
The detection of anti-listeriolysin O ( Anti-LLO) antibodies were done by Indirect Haemagglutination Reaction (IHR) with purified LLO in sera and CSF supernatant of 23 married women with frequent abortion due to L. monocytogenes infection and 20 controls to diagnose human listeriosis. The 23 patients (100%) with listeriosis and 3 (15%) of controls (non healthy subgroup), produced specific Anti-LLO titres ranged from < 100 to > 800.