Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: April 16, 2006
Publication Date: May 16, 2006
Citation: Cray, P.J., Ball, T.A., Rose, M. 2006. In-vitro susceptibility of escherichia coli isolated from feces of us dairy cattle to cephalosporins. Third International Conference on Antimicrobial Agents in Veterinary Medicine. May 16 - 20, 2006. Orlando, FL. Technical Abstract: Background: The objective of this study was to obtain baseline antimicrobial susceptibility data on E. coli isolated from feces of US dairy cows to the 4th generation cephalosporins (4-GC) cefquinome and cefepime. Cefquinome is licensed for therapeutic use in cattle and swine in Europe, and cefepime is a human 4-GC. Methods: Fecal isolates of E. coli (n = 1389) were obtained from a survey of US dairy cows in 2002 and submitted to the animal arm of the National Antimicrobial Resistance Monitoring System - Enteric Bacteria (NARMS) for susceptibility testing to a custom panel of antimicrobials including 1st (cephalothin), 2nd (cefoxitin) and 3rd (3-GC; ceftiofur and ceftriaxone) generation cephalosporins. Using a second panel, the minimum inhibitory concentrations (MICs) of cefquinome and cefepime were determined in 291 randomly selected isolates (CLSI, 2002). Results: The MICs ranged from < 0.015 µg/ml (cefquinome and cefepime) to 16 and > 32 µg/ml (cefoxitin and cephalothin, respectively). The MIC90 of the 4-GCs cefquinome and cefepime were 0.06 µg/ml, and the MIC90 of the 3-GCs ceftriaxone and ceftiofur were 0.25 µg/ml. However, cefoxitin (2-GC) and cephalothin (1-GC) had MIC90 of 8 and 16 µg/ml, respectively. Conclusions: Escherichia coli isolates were highly susceptible to the 4-GCs cefquinome (veterinary) and cefepime (human). Both drugs have a high antimicrobial activity with MICs far below the cefepime resistance breakpoint of > 32 µg/ml (CLSI, 2003). Conversely, the antimicrobial activities of ceftriaxone and ceftiofur (human and veterinary 3-GCs, respectively) were slightly lower, but markedly reduced for cefoxitin (2-GC) and cephalothin (1-GC).