Evaluation of antimicrobial treatment in a bovine model of acuteChlamydia psittaciinfection: tetracycline versus tetracycline plus rifampicin

Abstract

Antimicrobial treatment of chlamydial infections is known to be of limited efficacy. In this study, effects of doxycycline (D), usually the drug of choice, were compared with the combined therapy of doxycycline and rifampicin (R) in a bovine model of respiratory Chlamydia psittaci infection. After intrabronchial inoculation of the pathogen, 30 animals were assigned to five groups (n = 6 per group): untreated controls, monotherapy with D (5 mg kg(-1)day(-1) or 10 mg kg(-1)day(-1)), and combination therapy of D and R (600 mg day(-1)). Treatment continued until day 14 post inoculation (d.p.i.). Clinical signs, inflammatory markers, and pathological findings confirmed successful infection in all animals. Reisolation of the pathogen was possible in 4/6 untreated animals and in 4/12 animals treated with D alone until 4 d.p.i., but in none of the calves of the two D + R groups. Pathogen detection was possible in all animals without significant differences among groups. Severity of disease and time course of its resolution, assessed by clinical and pathological findings as well as inflammatory parameters, were not significantly different between untreated controls and calves receiving D alone or in combination with R. Regardless of the treatment regimen, all groups recovered clinically and cleared the infection within 2 weeks.

Acute phase proteins as local biomarkers of respiratory infection in calves

“…Exclusion of co-infections and standard antibiotic treatment after purchase, i.e. about 3 weeks before challenge, was performed as described previously [ 31 , 34 ]. Briefly, the presence of Mycoplasma , Pasteurella , or Mannheimia spp.…”

“…The 13 infected animals in the present study had served as untreated controls in previous studies [ 31 , 34 ].…”

“…1 ). All animals were euthanized 14 dpi and BALF was sampled from the exenterated lung in 6 fractions of 20 mL as described [ 31 ]. Sterile, isotonic, body warm saline was always used as flushing liquid.…”

“…-7 d: 7 days before inoculation; −4 d: 4 days before inoculation; dpi: days past inoculation; grey: animals prior to inoculation with C. psittaci; white: animals after inoculation with C. psittaci ( n = 13). The 13 calves served as untreated controls in two previous treatment studies where the general clinical scores and concentrations of LBP in blood sera have been published separately [ 31 , 34 ] …”

Regeneration of Pulmonary Tissue in a Calf Model of Fibrinonecrotic Bronchopneumonia Induced by Experimental Infection with Chlamydia psittaci

“…The infection model was very efficient, since all calves inoculated with the pathogen developed pneumonia, but none of the controls. The model was highly reproducible, and therefore repeatedly used to examine outcomes of different treatment regimens [23,24]. The localization of lesions corresponded to the inoculation sites and was distinct from field infections that have a cranioventral distribution [25].…”