Isolation, serotyping and drug resistance of salmonellae in scouring pigs in Taiwan

Abstract

The incidence of salmonellae in scouring pigs (from 6 to 16 weeks of age) in Taiwan was investigated by means of rectal swab survey and a study of necropsy pigs. The rectal swab survey revealed salmonellae in 62 (9.5%) of 655 scouring feeder pigs. Salmonellae isolates belonged to 10 different serotypes. Of these, S. typhimurium was the serotype most frequently isolated (41.5%) and the second one was S. panama (10.8). Of 69 samples of internal organs from the feeder pigs died of scouring and septicemia examined, 33 (47.8%) yielded salmonellae which belonged to 6 different serotypes. Of these, S. choleraesuis was the most common serotype (42.4%) and S. typhimurium appeared to be the second (36.4%). However, salmonellae were not isolated from the rectal swabs of suckling pigs and the sows nursing those baby pigs. Of 98 salmonellae isolates examined for drug susceptibility, 94 (95.5%) were resistant to two or more drugs, and 50 (53.2%) were resistant to more than five drugs. The percentage of isolates (all serotypes) resistant to the individual drugs was as follows: 95.9% to sulfathiazole (1.0 mg), 89.8% to tetracycline (30 ug), 76.5% to streptomycin (10 ug), 56.1% to kanamycin (30 ug), 53.1% to chloramphenicol (30 ug), and 45.9% to ampicillin (10 ug). However, all of the salmonellae isolates were sensitive to colistin, gentamicin and nalidixic acid. Results pertaining to the resistance of S. typhimurium and other serotypes to the six individual drugs are given separately.