Serogroups and antimicrobial susceptibility among Escherichia coli isolated from farmed mink (Mustela vison Schreiber) in Denmark

Escherichia coli is commonly found in outbreaks of diarrhoea in mink during the production season although its role as a primary causal organism remai ns unclear. The present study was undertaken to determine the serogroups an d antimicrobial susceptibility of E. coli isolates from healthy and diarrho eic mink. Rectal swabs were taken from healthy and diseased animals, on six different farms. once at the onset of disease and again approximately 2 we eks later. The swabs were subjected to bacteriological investigation: a tot al of 210 E. coli were isolated, 98 from healthy animals and 112 from disea sed. All isolates were serotyped and MICs were determined for nine antimicr obial compounds. Non-haemolytic isolates numbered 147, whereas 63 were haem olytic. Both haemolytic and non-haemolytic isolates were isolated from both healthy and diseased animals. A wide range of serogroups was detected, the most frequent being O2 (11.0%) . O78 (11.0%), O153 (7.1%). O25 (5.7%). O6 (4.8%). and O15 (4.8%). but diar rhoea was not associated with specific serogroups. All isolates were sensit ive to enrofloxacin, neomycin, gentamicin and colistin. In contrast, consid erable variations in susceptibility were found among the six mink farms, fo r tetracycline (0-16.4%. average 21.9), ampicillin (2.9-50.0%. average 23.3 ), spectinomycin (8.0-35.7%. average 21.9), sulfamethoxazole (8.6-57.7%. av erage 30.0) and trimethoprim (0-35.7%. average 9.5). Resistance to tetracyc line was statistically more prevalent among haemolytic than among non-haemo lytic strains. In conclusion, serogrouping and haemolysin testing failed to identify any a ssociation with diarrhoeal disease and antimicrobial resistance was highly variable between different mink farms. (C): 2001 Elsevier Science B.V. All rights reserved.