الكاتب: Multiple References

Trimethoprim/sulfonamide combinations (TMPS) are often used for antibacterial treatment in horses because of their broad spectrum of activity and the convenience of oral administration (van Duijkeren et al., 1994). Many bacteria are susceptible to TMPS in vitro and this includes Streptococcus equi subsp. zooepidemicus (S. zooepidemicus), a major pathogen in horses (Ensink et al., 1993). The mechanism of action of sulfonamides is inhibited by an excess of p-aminobenzoic acid (PABA), such as found in tissue exudates (Prescott & Baggot, 1993). Thymidine is known to diminish the susceptibility of bacteria to trimethoprim (TMP) in vitro (Prescott & Baggot, 1993), and Greko et al. have shown that thymidine may also play a role in antagonizing the effect of TMPS in vivo (Greko et al., 2002). To determine whether TMPS is effective against S. zooepidemicus in vivo would require a study in patients. In horses this poses a problem, because it is rare to have a sufficient number of naturally infected animals available for these studies. Therefore, most studies are performed with standardized experimental infections. For this purpose the tissue chamber (TC) infection model has proved very useful (Beadle et al., 1989; Ensink et al., 1996a)