[Emergence of Salmonella Typhimurium monophasic serovar: determinants of antimicrobial resistance in porcine and human strains]. / Emergenza di una variante monofasica di Salmonella Typhi- murium: caratteri di antibiotico-resistenza in stipiti isolati dalla filiera suinicola e da casi di infezione nell'uomo.

Salmonella enterica serovar Typhimurium (S. Typhimurium) is a common cause of non-typhoideal salmonellosis in humans and animals; since the end of '90 a monophasic serovar defined by the antigenic formula 4,5:i:- has been emerged. This study shows occurrence of monophasic serovar in Italy (Lombardia Region) and analyses antimicrobial resistance of 147 S. Typhimurium and 45 monophasic strains. Multiple drug resistance (MDR) has been detected in 94,5% and 76,6% of 55 porcine and 137 human isolates, respectively; tetra-resistance pattern AmSSuTe is the most common among in both sources (55 out of 116 strains of MDR S. Typhimurium and 16 out of 41 strains of MDR monophasic variant). Transfer of resistance determinants has been investigated by plasmid conjugation for all the 157MDR strains: only 16 isolates (10,2%) gave positive results, and transfer has almost been partial. Data from our investigation and data reported by other studies show a wide difference in the circulating phenotypes and in polymorphism of S. Typhimurium, confirmed also by the emergence of the monophasic serovar.

Prevalence of E. coli, thermotolerant coliforms, Salmonella spp. and Vibrio spp. in ready-to-eat foods: Pemba Island, United Republic of Tanzania.

This study is aimed to evaluate the microbiological quality of ready-to-eat foods in Pemba island. A total of 300 food samples have been analysed: 66 household preparations, 115 samples of raw cow milk, and 119 fried sea-foods. The thermotolerant coliforms have been detected in 34% sea-foods, 58% household meals, and 98% milk samples; the coliforms count is 5 x 10(2), 10(3), and 3 x 10(4) cfu/g, respectively. E. coli is the species most frequently isolated: 60 on 100 strains agglutinate one of the tested polyvalent antisera. Salmonella spp. have been found exclusively in cow milk (11%); in 15% sea-foods V. alginolyticus has been isolated. The prevalence of faecal contamination is extremely high in cow milk, a critical vehicle for the transmission of pathogens, probably for a lacking thermal treatment (pasteurization). Salmonella spp., V. cholerae, and V. parahaemolyticus have not been isolated from boiled or fried foodstuffs, but in any case the cooked foods are faecally contaminated: their contamination occurs likely after preparation and before consumption. The identification of risk factors for the faecal contamination could be helpful to plan educational programmes involving food operators and may be an effective preventive measure, especially in settings where financial resources are lacking for the construction of adequate infrastructures.