Prevalence of Listeria monocytogenes in municipal and industrial sewage

An overall number of sixty samples of treated and untreated sewage was tested in our studies. The samples represented both municipal and industrial sewage (30 samples each type) and were collected respectively at the point of sewage discharge to a river, and at a poultry processing plant, namely from a secondary settler and an aeration chamber, as well as at the discharge of the treated sewage to the environment. Industrial sewage was tested with both chemically treated and untreated samples. The samples were analysed microbiologically for the presence of Listeria sp with a modified MPN method using membrane filtration, fecal coliforms by means of MPN method based on the PN-77 C-04615 standard, including the ISO 7251:1993 standard, and tested for the total microbial count on agar plates at 20°C.