Tetracycline Susceptibility in Chlamydia suis Pig Isolates

Area of Science:

• Veterinary Microbiology
• Antimicrobial Resistance
• Bacterial Genetics

Background:

• Chlamydia suis is an important pathogen in swine.
• Tetracycline resistance in bacteria is a growing concern.
• Understanding resistance mechanisms in C. suis is crucial for animal health.

Purpose of the Study:

• To determine the prevalence of Chlamydia suis in an Italian pig herd.
• To assess the tetracycline susceptibility of C. suis isolates.
• To evaluate the expression of tet(C) and tetR(C) genes in C. suis.

Main Methods:

• Real-time PCR was used to detect C. suis in conjunctival swabs.
• C. suis isolates were cultured and tested for tetracycline susceptibility (MIC values).
• Gene expression of tet(C) and tetR(C) was analyzed using transcript analysis.

Main Results:

• Chlamydia suis prevalence was 55% in the studied Italian pig herd.
• All positive samples and isolates harbored the tet(C) resistance gene.
• C. suis isolates exhibited in vitro susceptibility to tetracycline (MIC 0.5-4 μg/mL).
• Tet(C) and tetR(C) transcripts were detected in all isolates, regardless of tetracycline presence, unlike other bacteria.

Conclusions:

• The study highlights the presence and tetracycline resistance gene tet(C) in C. suis within an Italian swine population.
• The constitutive expression of tet(C) and tetR(C) in C. suis warrants further investigation into its regulatory mechanisms.
• Findings suggest potential challenges in managing tetracycline resistance in C. suis infections in pigs.