Fecal shedding of, antimicrobial resistance in, and serologic response to Salmonella Typhimurium in dairy calves.
OBJECTIVE
To determine the duration of fecal shedding of and serologic response to Salmonella spp after natural infection in dairy calves and characterize Salmonella organisms recovered from these herds.


METHODS
Longitudinal study.


METHODS
Calves from 2 dairy herds (A and B) in the northeast United States that were identified at the beginning of a Salmonella outbreak.


METHODS
Fecal samples were collected twice per week (herd A) or once per week (herd B); blood samples were collected for serologic testing once per week in both herds. Bacteriologic culture of fecal samples was performed, and Salmonella isolates were characterized by serotype, pulsed-field gel electrophoresis (PFGE) pattern, and antimicrobial resistance profile.


RESULTS
All Salmonella isolates from herd A were serovar Typhimurium var Copenhagen, had the same PFGE pattern, and were resistant to at least 9 antimicrobials. All isolates from herd B were Salmonella Typhimurium, represented 2 PFGE patterns, and were susceptible to all antimicrobials evaluated. The estimated duration of fecal shedding was 14 days in herd A and 9 days in herd B. Few calves were seropositive for antibody against Salmonella lipopolysaccharide within the first week after birth (0 of 20 in herd A and 13 of 79 in herd B) or seroconverted (6 in herd A and 4 in herd B). Fecal shedding was more common in calves that seroconverted, but overall, there was not a strong association between seropositivity and fecal shedding of Salmonella organisms.


CONCLUSIONS
Although the herds differed in serologic response and Salmonella subtype, the duration of fecal shedding among calves was similar between herds.
Alexander
Kimberly A
KA
Department of Population Medicine and Diagnostic Sciences, College of Veterinary Medicine, Cornell University, Ithaca, NY 14853, USA.
Warnick
Lorin D
LD
Cripps
Chris J
CJ
McDonough
Patrick L
PL
Grohn
Yrjo T
YT
Wiedmann
Martin
M
Reed
Kelly E
KE
James
Karen L
KL
Soyer
Yesim
Y
Ivanek
Renata
R
D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D002417:Cattle; D003612:Dairying; D024901:Drug Resistance, Multiple, Bacterial; D005243:Feces / Q000382:microbiology*; D012481:Salmonella Infections, Animal / Q000382:microbiology*; D012486:Salmonella typhimurium; D013997:Time Factors
D000900:Anti-Bacterial Agents