Development and Validation of a Real-Time PCR for Chlamydia suis Diagnosis in Swine and Humans

Abstract

Pigs are the natural host for Chlamydia suis, a pathogen which is phylogenetically highly related to the human pathogen C. trachomatis. Chlamydia suis infections are generally treated with tetracyclines. In 1998, tetracyline resistant C. suis strains emerged on U.S. pig farms and they are currently present in the Belgian, Cypriote, German, Israeli, Italian and Swiss pig industry. Infections with tetracycline resistant C. suis strains are mainly associated with severe reproductive failure leading to marked economical loss. We developed a sensitive and specific TaqMan probe-based C. suis real-time PCR for examining clinical samples of both pigs and humans. The analytical sensitivity of the real-time PCR is 10 rDNA copies/reaction without cross-amplifying DNA of other Chlamydia species. The PCR was successfully validated using conjunctival, pharyngeal and stool samples of slaughterhouse employees, as well as porcine samples from two farms with evidence of reproductive failure and one farm without clinical disease. Chlamydia suis was only detected in diseased pigs and in the eyes of humans. Positive humans had no clinical complaints. PCR results were confirmed by culture in McCoy cells. In addition, Chlamydia suis isolates were also examined by the tet(C) PCR, designed for demonstrating the tetracycline resistance gene tet(C). The tet(C) gene was only present in porcine C. suis isolates.

Chronic Chlamydial Diseases: From Atherosclerosis to Urogenital Infections

“…C. pneumoniae, an agent of respiratory infection, is nearly ubiquitous in humans, with seropositivity rates of 70-80% in older populations, suggesting most people experience infection during their lifetime [5]. C. psittaci, a common pathogen of birds, has the best known zoonotic potential of the human pathogenic chlamydiae and causes relatively rare respiratory infections associated with severe clinical manifestations, while several other animal pathogenic chlamydial species, including C. abortus, C. felis, and C. suis, are known, or suspected, to cause infrequent human infections with various clinical presentations [6,7]. Chronic chlamydial infections in animals, particularly ruminants and pigs, are sub-clinical and ubiquitous in nature [8,9].…”

Development of aChlamydia suis-specific antibody enzyme-linked immunosorbent assay based on the use of a B-cell epitope of the polymorphic membrane protein C

“…Group 8 contained sera of 10 clinically affected boars from an Estonian farrowing to slaughter farm dealing with reproductive failure and conjunctivitis in boars and sows (Schautteet, Beeckman, Delava, & Vanrompay, 2010). Rectal swabs of all 10 boars reacted positive in the C. suis-specific real-time PCR (De Puysseleyr et al, 2014).…”

“…Recently, Dean, Rothschild, Ruettger, Kandel, and Sachse () found C. suis mRNA in the eyes of Nepalese trachoma patients. Chlamydia suis DNA and viable organisms were also recovered from the eyes of Belgian slaughterhouse employees (De Puysseleyr, De Puysseleyr, Geldhof, Cox, & Vanrompay, ) and from the eye, nose, throat and stool of Belgian pig farmers (De Puysseleyr, De Puysseleyr, Braeckman, et al, 2017). As far as we know, Tc R C. suis phenotypes have not yet been found in humans.…”

“…Nowadays, C. suis infections are often unnoticed because diagnosis is still not routinely performed in veterinary diagnostic laboratories as follows: (i) tetracycline resistant C. suis strains relatively recently emerged, (ii) C. suis strains are hard to culture (De Puysseleyr, De Puysseleyr, Vanrompay, & De Vos, 2017) and (iii) C. suis ‐specific molecular diagnostic techniques, such as real‐time PCR and DNA micro‐array, only became available in recent years (De Puysseleyr et al., ; Lis, Kumala, Spalinski, & Rypula, ; Pantchev, Sting, Bauerfeind, Tyczka, & Sachse, ; Sachse, Hotzel, Slickers, Ellinger, & Ehricht, ) and are often regarded as too expensive by the pork industry. Moreover, C. suis is sometimes found in association with other pathogens (the usual suspects), which are mostly more easily to detect.…”

“…leyr, De Puysseleyr, Vanrompay, & De Vos, 2017) and (iii) C. suisspecific molecular diagnostic techniques, such as real-time PCR and DNA micro-array, only became available in recent years (De Puysseleyr et al, 2014;Lis, Kumala, Spalinski, & Rypula, 2014;Pantchev, Sting, Bauerfeind, Tyczka, & Sachse, 2010;Sachse, Hotzel, Slickers, Ellinger, & Ehricht, 2005) and are often regarded as too expensive by the pork industry. Moreover, C. suis is sometimes found in association with other pathogens (the usual suspects), which are mostly more easily to detect.…”