Enrofloxacin and macrolides alone or in combination with rifampicin as antimicrobial treatment in a bovine model of acute Chlamydia psittaci infection.

Carola Ostermann,Evelyn Schubert,Petra Reinhold,Wieland Schroedl,Elisabeth Liebler-Tenorio,Michael Rothe,Garry Stewart Anthony Myers,Konrad Sachse,Markus Lohr,Angela Berndt,Annette Prohl

doi:10.1371/journal.pone.0119736

Abstract

Chlamydia psittaci is a zoonotic bacterium with a wide host range that can cause respiratory disease in humans and cattle. In the present study, effects of treatment with macrolides and quinolones applied alone or in combination with rifampicin were tested in a previously established bovine model of respiratory C. psittaci infection. Fifty animals were inoculated intrabronchially at the age of 6–8 weeks. Seven served as untreated controls, the others were assigned to seven treatment groups: (i) rifampicin, (ii) enrofloxacin, (iii) enrofloxacin + rifampicin, (iv) azithromycin, (v) azithromycin + rifampicin, (vi) erythromycin, and (vii) erythromycin + rifampicin. Treatment started 30 hours after inoculation and continued until 14 days after inoculation (dpi), when all animals were necropsied. The infection was successful in all animals and sufficient antibiotic levels were detected in blood plasma and tissue of the treated animals. Reisolation of the pathogen was achieved more often from untreated animals than from other groups. Nevertheless, pathogen detection by PCR was possible to the same extent in all animals and there were no significant differences between treated and untreated animals in terms of local (i.e. cell count and differentiation of BALF-cells) and systemic inflammation (i.e. white blood cells and concentration of acute phase protein LBP), clinical signs, and pathological findings at necropsy. Regardless of the reduced reisolation rate in treated animals, the treatment of experimentally induced respiratory C. psittaci infection with enrofloxacin, azithromycin or erythromycin alone or in combination with rifampicin was without obvious benefit for the host, since no significant differences in clinical and pathological findings or inflammatory parameters were detected and all animals recovered clinically within two weeks.

Highlights

Infections with the zoonotic bacterium Chlamydia (C.) psittaci can cause severe respiratory and systemic disease in humans
Regardless of the reduced reisolation rate in treated animals, the treatment of experimentally induced respiratory C. psittaci infection with enrofloxacin, azithromycin or erythromycin alone or in combination with rifampicin was without obvious benefit for the host, since no significant differences in clinical and pathological findings or inflammatory parameters were detected and all animals recovered clinically within two weeks
No significant levels of azithromycin, erythromycin, rifampicin, enrofloxacin and its active metabolite ciprofloxacin could be detected in blood plasma sampled 1 h prior to inoculation

Summary

Introduction

Infections with the zoonotic bacterium Chlamydia (C.) psittaci can cause severe respiratory and systemic disease in humans. The original hosts of C. psittaci are birds, but it has been detected in several mammalian species, including cattle, horses, sheep, and pigs, where it is often associated with respiratory and reproductive disease [1,2,3,4]. A study detecting DNA of C. psittaci in conjunctival swabs of human and bovine samples from the same farms suggested that transmission from cattle to human or vice versa is possible [8]. The pathogenesis of chlamydiosis has been subject to intense research in the last years (reviewed by Knittler and colleagues [9]), but reasons for the failure of successful treatment of chlamydial infections in both humans and animals are only suspected in most cases

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