Intracellular Activity 

Intracellular accumulation and activity of antimicrobials is important not only for obligate or facultative intracellular bacteria (e.g., mycoplasmas, salmonellas) but also for any pathogenic bacteria to be phagocytized by polymorphonuclear leukocytes. Studies of several animal species have shown that intracellular concentrations of Enrofloxacin largely exceed those of the extracellular, interstitial fluids and that such concentrations actively kill intracellular bacteria.

Intraphagozytic killing of A.pleuropneumoniae (APP) was significantly enhanced by Enrofloxacin at 5x the MIC in both polymorphonuclear leukocytes (PMNs) and alveolar macrophages (Ams). AMs are very susceptible to the APP-cytotoxin. This suggests that in serologically naive pigs, the enhancing effect of Enrofloxacin on the bactericidal action of PMNs may have clinical relevance.
(Schoevers et al. 1999. Effects of Enrofloxacin on Porcine Phagocytic Function. Antimicrob. Agents Chemother. 43: 2138 – 2143)

The high concentrations of Enrofloxacin in polymorphonuclear leukocytes support the favourable kinetics by carrying the active ingredient to the site of infection, enhancing intracellular killing of ingested bacteria.

In addition, Enrofloxacin does not impair, but rather it stimulates phagocytic activity ("respiratory burst activity") of polymorphonuclear leukocytes.

Because Baytril shows no adverse effects on the immune system, Baytril can be used simultaneously with vaccines or in combination with vaccination programmes without adversely affecting the immune response.