The in vitro Antibacterial Activity of Florfenicol in Combination with Amoxicillin or Cefuroxime against Pathogenic Bacteria of Animal Origin

Myung-Jin Choi, Eun-Mi Lee, Seung-Jin Lee, Joong-Su Reza, Elias Lee, Man-Hee Gebru, Seung-Chun Rhee, Park
Pakistan Veterinary Journal   unpublished
This study evaluated the in vitro activity of florfenicol (F) in combination with amoxicillin (AM) or cefuroxime (CRM) against pathogenic bacteria of animal origin, including E. coli, S. aureus, S. cholerasuis and P. mirabilis. The MIC of AM ranged from 16 to 256 µg/ml. The MBC of AM (64 µg/ml) was four-fold higher than its MIC value (16 µg/ml) for E. coli, and similar to the MIC for the other three species. The MIC of F ranged from 8 to 16 µg/ml. The MBC values of F for E. coli, S. aureus, and
more » ... S. cholerasuis were eight-fold higher than the respective MIC values, and 32-fold higher than the MIC of P. mirabilis. The MIC of CRM ranged from 8 to 128 µg/ml. The MBC of CRM was the highest (≥ 256 µg/ml), except for E. coli. The F/AM combination resulted in synergism (FIC index ≤ 0.5) for E. coli, S. aureus, and P. mirabilis and indifference (FIC index >1) for S. cholerasuis. For F/CRM combination, synergism (E. coli and S. cholerasuis) and indifference (S. aureus and P. mirabilis) were observed. Killing rate study showed a 1.5-> 3 log 10 cfu/ml reduction of E. coli with F/AM compared to AM or F alone. The highest activity of the combinations was observed when F comprised at least 50% of the combination. Further studies using many bacterial isolates and various proportion of each drug would reveal the potential of a combination product containing F and AM/CRM for use in veterinary practice.