NATIONAL ANTIMICROBIAL RESISTANCE MONITORING SYSTEM: MULTIPLE DRUG RESISTANCE IN SALMONELLA FROM ANIMAL SAMPLES FROM 1997 TO 2003

Authors: Bailey, Joseph; Cray, Paula; DARGATZ, D - USDA-APHIS; ANADARAMAN, N - USDA-FSIS; ROSE, B - USDA-FSIS; WINELAND, N - USDA-APHIS; HEADRICK, M - FDA-CVM

Submitted to: Interscience Conference on Antimicrobial Agents & Chemotherapy Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: 6/30/2005
Publication Date: 12/16/2005
Citation: Bailey, J.S., Cray, P.J., Dargatz, D.A., Anadaraman, N., Rose, B., Wineland, N., Headrick, M.L. 2005. National antimicrobial resistance monitoring system: multiple drug resistance in salmonella from animal samples from 1997 to 2003. Interscience Conference on Antimicrobial Agents & Chemotherapy Proceedings. December 17, 2005. Washington, DC.

Interpretive Summary: N/A

Technical Abstract: The National Antimicrobial Resistance Monitoring System – Enteric Bacteria (NARMS) was initiated in 1997 to prospectively monitor changes in antimicrobial susceptibilities of zoonotic pathogens from human and animal origins. From 1997 through 2003, a total of 40,120 Salmonella isolates from animal sources were tested for antimicrobial resistance using custom made plates containing up to 16 antimicrobics in a semi-automated minimal inhibitory concentration format system (SensititerTM, Trek Diagnostic). Isolates were classified as susceptible, intermediate, or resistant based on Clinical Laboratory Standards Institute (CLSI) (formerly National Committee for Clinical Laboratory Standards) established breakpoints, where available. Less resistance was seen in 1997 samples with 65.8% of samples pan-susceptible (resistant to 0 antibiotics) and only 11.1% resistant to 5 or more antibiotics. From 1998 to 2003, pan-susceptibility (48 to 56%) and resistance to 1 antimicrobial (8 to 10%), or 2 to 4 antimicrobials (18 to 22%) was fairly consistent. Multiple drug resistance to 5 to 9 antimicrobials ranged from 13 to 18% and to 10 or more antibiotics increased from 1 to 7.0%. When analyzed by animal source, less resistance was seen in Salmonella from chicken with only 8.3% of isolates exhibiting resistance to 5 or more antimicrobials. Most cattle isolates were pan-susceptible (63.7%), but 20.2% were resistant to 5 or more antibicrobials. Turkey and swine isolates had similar resistance trends with 17 to 20 % of isolates resistant to 5 or more antimicrobials. Diagnostic isolates were 2.5 times more likely to be resistant to 5 or more antimicrobials than slaughter isolates. To interpret changes in antimicrobial resistance patterns, the species of animal and sample type must be clearly identified and similar numbers and types of samples compared to draw meaningful conclusions.