Salmonella and Listeria spp. carriage by gulls (larids)

Abstract

As in other countries, the population of gulls (Laridae) has been increased exponentially in Portugal. To evaluate the public health implications of this development, two hundred and eighty-five samples of gulls’ faeces were investigated for two bacteria species of zoonotic importance, Salmonella spp. and Listeria sp. Thirty-seven (13.0 %) samples were positive for Salmonella spp. Amongst these, teh most common serovars were Salmonella Typhimurium (37.8%) and Salmonella Derby (18.9%). Simultaneously presence of two different serovars was detected in six samples. Twenty four different antibioresistance profiles were detected in Salmonella sp. isolates (68.7%).Phage-types found for Salmonella Typhimurium 5+ were PT 12 and U302. Listeria spp. were present in twenty-eight (9.8%) samples, seventeen of which had Listeria monocytogenes (6.0%). Other species isolated were Listeria seeligeri (0.7%), L. innocua (5.3%), and L.welshimeri (0.7%). Seven samples were co-contaminated with two or more species. A combination of serotyping, phage-typing, cadmium and arsenic sensitivities were used to subtype 18 of the L. monocytogenes isolates recognising at least 10 different strains. Both bacterial genera were simultaneously isolated from twelve samples (4.2%). Several epidemiological explantion and the possible significance as markers waste management in the geographical area studied are discussed.