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item Gray, Jeffrey
item Turpin, Jennifer
item Minish, Rosetta

Submitted to: American Society of Microbiologists Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 4/23/2004
Publication Date: 5/23/2004
Citation: Gray, J.T., Garland, J.E., Minish, R.C. 2004. The natural transmission of salmonella typhimurium in poultry with and without antimicrobial selective pressure. American Society of Microbiologists Abstracts. Z-040.

Interpretive Summary: N/A

Technical Abstract: Salmonella typhimurium is an economically important pathogen of humans and animals. Recently, Salmonella strains have arisen that are resistant to multiple antimicrobials including third generation cephalosporins. It is unclear whether these multiple resistant isolates have a selective advantage for transmission between hosts and under antimicrobial selective pressure. This experiment was designed to study the transmissibility of a resistant strain (8381r) and a sensitive strain (8382s) of S. typhimurium with and without antimicrobial selective pressure, in a poultry model. The multiple antibiotic resistant phenotype of S. typhimurium 8381r is resistant to 12 of 17 antimicrobials on the NARMS panel. Strain 8382s was pansensitive to all antimicrobials. One bird in each pen of ten was infected with 10E9 CFU of S. typhimurium 8381r or 8382s per os. Treatment groups for each isolate included no antimicrobials and 120 ug/ml chlortetracycline (tet), constant dose in water for a total of 4 treatment groups. Three replicates of each treatment were run. Cloacal swab and liter samples were collected on day (D) 1, 3, 5, and 7 and birds were necropsied on day 10 post inoculation. The percentage of cloacal swabs positive for strain 8381r with and without tet treatment were D3 (10%), D5 (14%), D7 (14%) and D3 (3%), D5 (3%), D7 (6%), respectively. The same samples for strain 8382s were D3 (3%), D5 (7%), D7 (7%) and D3 (6%), D5 (23%), D7 (27%), with and without tet, respectively. Upon necropsy percent positive tissue samples for strain 8381r were ICJ (10%), colon (7%), cec (10%) for tet treated and ICJ (13%), colon (10%), cec (23%) for non-treated birds. Strain 8382s positive tissues were ICJ (31%), colon (24%), cec (69%) for tet treated and ICJ (30%), colon (30%), cec (100%) for non treated birds. These data indicate that multiple antimicrobial resistance in Salmonella isolates does not necessarily lead to increased transmissibility regardless of antimicrobial selective pressure. Additionally, a sensitive Salmonella strain can survive and transmit efficiently between animals even with antimicrobial selective pressure at MIC levels.