Antimicrobial Resistance Types and Genes in Salmonella enterica Infantis Isolates from Retail Raw Chicken Meat and Broiler Chickens on Farms

Abstract

Salmonella enterica subsp. enterica serotype Infantis isolates from retail raw chicken meat (n = 98) and broiler chickens on farms (n = 70) were examined for antimicrobial susceptibility and antimicrobial resistance genes. A total of 15 antimicrobial resistance types, 14 in meat and 10 in broiler isolates, were identified, and 9 of the 15 types were indistinguishable between meat and broiler isolates. Resistance to both oxytetracycline and dihydrostreptomycin accounted for 94.0% of the resistance types in meat and broiler isolates, and each type harbored aadA1 within 1.0 kb of class 1 integron and tetA. Of nalidixic acid resistance types, point mutations at 87Asp (GAC) to Tyr (TAC) in the quinolone resistance-determining region of gyrA was detected in 10 of 13 meat isolates and at 87Asp to Asn (AAC) in four of seven broiler isolates. These findings suggest that the antimicrobial resistance of Salmonella Infantis in retail chicken meat predominantly originates from broiler chickens.

Antimicrobial Resistance in Salmonella Isolates from Apparently Healthy Food-Producing Animal from 2000 to 2003: the First Stage of Japanese Veterinary Antimicrobial Resistance Monitoring (JVARM)

“…The present study showed that 131 (71.6%) isolates were resistant to two or more of the antimicrobials tested ( [2]. b) Data from our previous report [6] were interrupted according to resistant breakpoint in this study.…”

“…Salmonella [2], 104 isolates were subjected to antimicrobial susceptibility testing. The MICs of each antimicrobial were interpreted using the NCCLS criteria [12].…”

“…In Japan, S. Typhimurium DT104 was first isolated in the late 1980s and has spread widely among domestic animals in Japan in the past decade [15]. S. Infantis from retail broiler meats increased in 1997 [10], and the isolates from broiler meats harbored antimicrobial-resistant types similar to those of broiler isolates [2]. The prevalence of MAR S. Infantis is much higher in broilers in Japan than in other countries [8,14].…”

Long‐Term Prevalence of Antimicrobial‐ResistantSalmonella entericaSubspeciesentericaSerovar Infantis in the Broiler Chicken Industry in Japan

“…Eight KM-resistant strains were PCR-positive for the aphA1 gene. Thus, 7 strains of S. Infantis isolated after 1993 harbored similar antimicrobial susceptibilities and resistance genes of the recent isolates from retail raw chicken meat and broiler chickens (3).…”

“…In the later 1990's, S. Infantis became a predominant serovar of Salmonella isolated from broiler chicken meat (11). The isolates from broiler chicken meat exhibited resistance to both tetracycline and streptomycin w/wo kanamycin and/or trimethoprim (11) as well as recent isolates from feces and meat of broiler chickens (2,3). Therefore, antimicrobial-resistant strains of S. Infantis may have disseminated in the broiler industry in Japan in the late 1990's, and may continue to be isolated for a long time.…”