Assessment of ceftiofur residues in cow milk using commercial screening test kits

Abstract

Ceftiofur, a third-generation cephalosporin, is one of the most used antibiotics in dairy industry. Intramuscular injection of 1 mg/kgBW ceftiofur hydrochloride (HCl) generally results in 0 hour withdrawal time for the milk in dairy cows. Nevertheless, farmers and dairy processors occasionally complain about ceftiofur-based products in case of positive result to a commercial rapid screening test for the presence of violative residues of antimicrobials (inhibitors) in the bulk milk tank. Six lactating cows were injected with a 50 mg/ml ceftiofur HCl-based product at the dosage regimen of 1 mg/kg, intramuscularly, once a day, for five consecutive days, as per label. Milk samples were then collected just before the very last injection (T0) and then at 12, 24, 36, 48, 60, 72, 84 and 96 hours after the last injection. Individual milk samples were tested using three commercial screening test kits for inhibitor residues: DelvotestSP NT, SNAP Beta-Lactam ST Plus and ROSA MRL Beta-Lactam Test. Since bulk tank is screened in real operating conditions, samples were also diluted to 1:4, 1:10 and tested again. For the Delvotest SP NT, which lowest detected concentration is close the MRL of the ceftiofur (100 µg/kg), all results were negative. For the ROSA MRL Beta-Lactam Test and the SNAP Beta-Lactam ST Plus, several samples yielded positive and doubtful results at T0 and T12. However, after dilution to 1:10, all results were negative. Consequently, when used as officially instructed, the tested 50 mg/ml ceftiofur HCl-based injectable veterinary products are safe, and milk should be free of violative residues of ceftiofur. With consideration to the low specificity and the low positive predictive value of commercial screening tests, positive reactions of the bulk milk should be interpreted as false positive or another risky usage of β-lactam-based medicines in the farm must be investigated.

A Focus Group Study of Canadian Dairy Farmers' Attitudes and Social Referents on Antimicrobial Use and Antimicrobial Resistance

“…When treating cows, participants often preferred to use ceftiofur-based products, which is the only antimicrobial with a zero-day milk withdrawal time, in order to avoid milk withholding periods. Third and higher generation cephalosporins, such as ceftiofur are considered critically important antimicrobials (CIAs) in human medicine ( 36 ), yet ceftiofur has been reported as one of the most commonly used antimicrobials in dairy cows around the world, presumably due to the zero-day withdrawal period for milk ( 37 ). High priority CIA represented a median of 17% of AMU on dairy farms in Quebec ( 23 ).…”

Evaluation of four commercial tests for detecting ceftiofur in waste milk bulk tank samples

“…As an example, the Council Directive 96/23/EC document includes the use of different approaches for test validation, including the use of detection capability (CCβ), which is the smallest content of the substance that may be detected, identified and/or quantified in a sample with an error probability of β, and decision limit (CCα), which is the limit at and above which it can be concluded with an error probability of α that a sample is non-compliant. As outlined in a recently published study conducted in France assessing the risk of positive reaction to widely used rapid screening test for inhibitors in milk from cows treated with a new ceftiofur formulations, CCβ and CCα are not usually clearly indicated by manufacturers of rapid drug residues tests, and because of that the lowest detected concentrations was estimated to be an appropriate threshold for the interpretation of test results [33].…”

Enhancing Drug Efficacy against Mastitis Pathogens—An In Vitro Pilot Study in Staphylococcus aureus and Staphylococcus epidermidis

“…Ceftiofur is a third-generation cephalosporin and is one of the most used antibiotics in dairy industry. Ceftiofur is labeled for veterinary use in the USA and Europe and is the drug of choice for the treatment of mastitis in the majority of dairy farms [ 7 , 8 ]. Ceftiofur inhibits bacterial cell wall synthesis.…”