Isolation of Tetracycline-Resistant Chlamydia suis from a Pig Herd Affected by Reproductive Disorders and Conjunctivitis

Abstract

Due to various challenges in diagnosing chlamydiosis in pigs, antibiotic treatment is usually performed before any molecular or antibiotic susceptibility testing. This could increase the occurrence of tetracycline-resistant Chlamydia (C.) suis isolates in the affected pig population and potentiate the reoccurrence of clinical signs. Here, we present a case of an Austrian pig farm, where tetracycline resistant and sensitive C. suis isolates were isolated from four finishers with conjunctivitis. On herd-level, 10% of the finishers suffered from severe conjunctivitis and sows showed a high percentage of irregular return to estrus. Subsequent treatment of whole-herd using oxytetracycline led to a significant reduction of clinical signs. Retrospective antibiotic susceptibility testing revealed tetracycline resistance and decreased susceptibility to doxycycline in half of the ocular C. suis isolates, and all isolates were able to partially recover following a single-dose tetracycline treatment in vitro. These findings were later confirmed in vivo, when all former clinical signs recurred three months later. This case report raises awareness of tetracycline resistance in C. suis and emphasizes the importance of preventative selection of tetracycline resistant C. suis isolates.

Transferrins Reduce Replication of Chlamydia suis in McCoy Cells

“…Currently, the anti-chlamydial effect of transferrins has only been demonstrated for the avian pathogen C. psittaci [ 38 , 39 , 40 ] and, more recently, for the human pathogen C. trachomatis [ 43 ]. Emerging tetracycline resistance in C. suis strains in the domestic pig population worldwide [ 8 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 ] requires the development of alternative preventive strategies or therapeutics. Therefore, we examined the effect of transferrins towards the C. suis reference strain S45.…”

“…Tetracycline is the main antibiotic used in the treatment of chlamydial infections. However, since 1998, tetracycline-resistant C. suis strains have been emerging worldwide [ 8 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 ]. Alternatives to antibiotics are urgently needed, as antimicrobial resistance is an increasingly important concern for both human and animal health [ 18 ].…”

A comprehensive review on avian chlamydiosis: a neglected zoonotic disease

“…Resistance to antibiotics by C. psittaci was not reported, but some in vivo studies suggested the possibility of drug resistance strains (Prohl et al 2015 ). In the Chlamydiae family, C. suis (recently identified as a zoonotic pathogen) is the only bacteria that showed the homotypic antibiotic resistance against tetracycline conferred by acquired resistance gene ( tet A) through horizontal gene transfer (Joseph et al 2016 ; Seth-Smith et al 2017 ; Marti et al 2018 ; Unterweger et al 2020 ). The entry of persistence state by bacterium could be possible by treating the infection with Penicillin G, azithromycin which leads to chronic infections and antibiotic failure (Goellner et al 2006 ; Zheng et al 2015 ; Leonard et al 2017 ; Xue et al 2017 ).…”

Generation of Tetracycline and Rifamycin Resistant Chlamydia Suis Recombinants

“…There have been multiple reports about the presence of tetracycline-resistant (TetR) strains in pigs worldwide, including China (Li et al, 2017 ), Israel, Cyprus, and Western European countries such as Switzerland, Austria, Germany, Italy, and Belgium (Di Francesco et al, 2008 ; Borel et al, 2012 ; Schautteet et al, 2013 ; Wanninger et al, 2016 ; Peisker et al, 2018 ; Unterweger et al, 2020 ), as well as the USA (Dugan et al, 2004 ). However, to date, none of the zoonotically transmitted C. suis infections screened for tetracycline resistance (De Puysseleyr et al, 2014 , 2017 ; Kieckens et al, 2018 ) have tested positive.…”