Objective—To determine the diversity of Salmonella
serotypes isolated from a large population of cull
(market) dairy cows at slaughter.
Sample Population—Salmonella organisms isolated
from the cecal-colon contents of 5,087 market dairy
Procedure—During winter and summer 1996, cecalcolon
contents of cull dairy cows at slaughter were
obtained from 5 US slaughter establishments.
Specimens were subjected to microbiologic culturing
for Salmonella spp at 1 laboratory. Identified isolates
were compared with Salmonella isolation lists published
by the Centers for Disease Control and
Prevention (CDC) and the National Veterinary Services
Laboratory (NVSL) for approximately the same period.
The Simpson diversity index was used to calculate
the likelihood that Salmonella isolates selected randomly
by establishment were different.
Results—Of 58 Salmonella serotypes identified,
Salmonella ser. Montevideo was the most prevalent. Two
of the top 10 CDC serotypes identified from humans in
1996, Salmonella ser. Typhimurium and S Montevideo,
appeared on our top 10 list; 8 of the top 10 were found
on NVSL listings. Thirty-one of 59 S Typhimurium isolates
were identified as DT104 and found at a west slaughter
establishment, 30 during the winter and 1 during the
summer. The greatest diversity of serotypes was at a
southeast establishment during the summer; the least
diversity was at a central establishment in the winter.
Conclusions and Clinical Relevance—58 Salmonella
serotypes were isolated from market dairy cows at
slaughter and could pose a threat for food-borne illness.
Salmonella Montevideo was the most frequently
isolated serotype and may contribute substantially
to salmonellosis in dairy cattle. (J Am Vet
Med Assoc 2001;219:1216–1220)