Fluoroquinolones are a synthetic class of antibiotics, which have found wide application in both human and veterinary clinical practice. These antibiotics have bactericide effects and all act by inhibition of DNA gyrase, abolishing its activity by interfering with the DNA-rejoining reaction. Since gyrase is an essential enzyme in prokaryotes but is not found in eukaryotes, bacteria are an ideal target for these antibiotics. Use of fluoroquinolones in animals used for meat production and its use in aquaculture, however, has generated concern, as fluoroquinolones have contributed to an increasing bacterial resistance for these antibiotics in man. Bacterial resistance has been demonstrated for Staphylococcus aureus (MRSA, MRSE), Campylobacter jejuni, Neisseria gonorrheae, Escherichia coli and Pseudomonas aeruginosa. For this reason, effective screening methods for the presence of fluoroquinolones in animal products as well as in food products are needed.

Euro-Diagnostica B.V. has developed specific ELISA kits for enrofloxacin and flumequine. Furthermore, a generic ELISA kit for screening for a broad group of fluoroquinolones is available.

Enrofloxacin (1-cyclopropyl-7-(4-ethyl-1-piperazinyl)-6 fluoro-1,
4- dihydro-4-oxo-3-quinolone carboxylic acid) is a synthetic 6-fluoroquinolone which acts by inhibition of bacterial DNA-gyrase. In veterinary medicine it is administrated by subcutaneous injection to cattle, intramuscularly to pigs, and orally to cattle, pigs, turkeys and chickens for the treatment of infections of the respiratory and alimentary tract. In Europe, the European Commission, Council Regulation No. 2377/90 and its successive regulations has established the Maximum Residue Limits (MRLs) for drugs employed in veterinary medicine. The MRLs for the sum of enrofloxacin and its active metabolite ciprofloxacin have been stated at 100 µg/kg for muscle tissue and fat (bovine, ovine, caprine, porcine, rabbits, poultry), 200 µg/kg for kidney and 300 µg/kg for liver (bovine, ovine, caprine), 300 µg/kg for kidney and 200 µg/kg for liver (porcine, rabbits, poultry) and 100 µg/kg for milk (bovine, ovine, caprine). The antibody used in the EIA test is specific for enrofloxacin and does not cross-react with any of the other fluoroquinolones tested.

Fluoroquinolones are a synthetic class of antibiotics, which all act by inhibition of DNA gyrase, abolishing its activity by interfering with the DNA-rejoining reaction. Since gyrase is an essential enzyme in prokaryotes but is not found in eukaryotes, bacteria are an ideal target for these antibiotics. In the generic Fluoroquinolones EIA an antiserum is used that shows high cross-reactivities towards enrofloxacin (92%), ciprofloxacin (124%), norfloxacin (100%), nadifloxacin (85%) pefloxacin (70%), enoxacin (57%), piromidic acid (62%),  lomefloxacin (40%), ofloxacin (18%), danofloxacin (89%), fleroxacin (40%),  oxolinic acid (57%), marbofloxacin (16%), sarafloxacin (4%), pipemidic acid (5%), difloxacin (1%), levofloxacin (3%), gatifloxacin (5%), flumequine (2%), pazufloxacin (1%). The limit of detection of the generic Fluoroquinolone EIA (expressed as norfloxacin-equivalents) was found to be as follows: Shrimp, meat, egg and milk < 0.3 ppb (results of blank samples were equal to a B/Bo of approximately 100%); serum 2.5 ppb and urine 7 ppb.