[Emergence of Salmonella Typhimurium monophasic serovar: determinants of antimicrobial resistance in porcine and human strains].
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.
Barone
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Dipartimento di Sanità Pubblica-Microbiologia-Virologia, Università degli Studi di Milano, Milano.
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VA
Pellissier
N
N
Viganò
A
A
Romani
C
C
Pontello
M
M
D000818:Animals; D024881:Drug Resistance, Bacterial; D006801:Humans; D008826:Microbial Sensitivity Tests; D012486:Salmonella typhimurium / Q000145:classification* / Q000187:drug effects* / Q000302:isolation & purification; D013552:Swine / Q000382:microbiology