Growth and development of tetracycline-resistant Chlamydia suis

Area of Science:

• Microbiology
• Bacteriology
• Antimicrobial Resistance

Background:

• Tetracycline (TET) is a crucial antibiotic for treating chlamydial infections.
• The emergence of TET-resistant (Tet(r)) Chlamydia poses a significant clinical challenge.
• Recent isolation of Tet(r) Chlamydia strains from swine highlights the need for further characterization.

Purpose of the Study:

• To characterize the intracellular development of two Tet(r) Chlamydia suis strains (R19 and R27) from swine.
• To compare the growth of Tet(r) strains with TET-sensitive strains in varying TET concentrations.
• To investigate the effect of TET removal on the developmental cycle of Tet(r) Chlamydia.

Main Methods:

• Tissue culture and immunofluorescence techniques were employed.
• Growth curves and inclusion morphology were analyzed under different TET concentrations.
• Sequential infection experiments were conducted to assess co-infection dynamics.

Main Results:

• Tet(r) strains R19 and R27 grew in up to 4 microg/ml TET, while sensitive strains grew in up to 0.1 microg/ml.
• TET exposure led to aberrant reticulate bodies (RBs) that failed to differentiate into elementary bodies.
• Removal of TET allowed aberrant RBs to revert to typical RBs and complete the developmental cycle.
• Co-infection demonstrated the ability of two distinct chlamydial strains to develop within a single inclusion.

Conclusions:

• Tetracycline resistance in Chlamydia suis impacts intracellular development, leading to aberrant forms.
• Reversibility of aberrant forms upon TET removal suggests potential therapeutic strategies.
• Chlamydia strains can co-exist and develop within the same host cell inclusion.