Serovars and Drug-Resistance of Salmonella Strains Isolated from Domestic Chicken Meat in Tokyo (1992-2012)

Abstract

A total of 477 Salmonella strains isolated from retail domestic chicken meat during 1992-2012 in Tokyo, were examined regarding their serovars and drug-resistance. These strains were detected in 469 (29.8%) of 1,576 samples. The detection rate in every two years was 10.1% to 46.3% of the range. Serological typing results showed that 477 strains were classified into 22 serovars excepting 2 untypable strains. Among them, S. Infantis (312 strains) was the most prevalent, followed by II O4: b: [e, n, x] (S. II Sofia) (71 strains), S. Hadar (20 strains), S. Typhimurium (20 strains), S. Manhattan (12 strains), S. Schwarzengrund (9 strains), S. Agona (7 strains), and other 15 serovars (24 strains). Results of the antibacterial drug susceptibility test for 477 strains revealed that 89.9% was resistant to some of the 12 drugs tested, and multidrug-resistant strains accounted for 90.2% among them. The frequencies of resistance to each drug were 81.8%; 77.8%, 45.5%, 33.3%, 11.3%, 9.6%, 2.9%, 0.6%, 0.6% and 0.2%, in order with high frequency, for SM, TC, KM, ST, NA, ABPC, CP, FOM, CTX and CAZ, respectively. None of the strains was resistant to NFLX or IPM. Three CTX-resistant strains were CTX-M type extended-spectrum β-lactamase (ESBL) producers, and the group of CTX-M type ESBL genes were CTX-M-2 group (2 strains) and CTX-M-9 group (1 strain). CAZ-resistant 1 strain was an ESBL producer, but the ESBL gene was not determined.