Effect of antibiotics on the phagocytotic and respiratory burst activity of bovine granulocytes

The influence of antibiotics on respiratory burst (phorbol-12-myristate-13-acetate (PMA)-stimulated luminol-enhanced chemiluminescence) and phagocytosis (flow cytometry) by bovine granulocytes was studied in vitro. Phagocytosis was impaired by 1000 μg/ml of oxytetracycline, chloramphenicol, erythromycin and spiramycin. All antibiotics, except sulphadiazine, decreased chemiluminescence at 1000 μg/ml or lower concentrations. Enrofloxacin increased chemiluminescence. The inhibition by oxytetracycline and danofloxacin was due to absorption of the light emitted by luminol at 425 nm. Oxytetracycline, ceftiofur, spiramycin and erythromycin affected the myeloperoxidase–H 2O 2–halide system. Ceftiofur, penicillin and danofloxacin showed scavenging effects on H 2O 2 and OCl -. Penicillin and ceftiofur might interfere with luminol. Chloramphenicol, penicillin and ceftiofur affected the production of superoxide radicals. In summary, the observed effects of antibiotics might be of importance during treatment of infectious diseases in normal and immunocompromised animals. However, before classifying a drug as immunosuppressive, attention has to be paid to possible interference with the chemiluminescence assay.