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ARS Home » Research » Publications at this Location » Publication #158735
Title: TETRACYCLINE RESISTANCE IN CHLAMYDIA SUIS MEDIATED BY GENOMIC ISLANDS INSERTED INTO THE CHLAMYDIAL INV-LIKE GENE

Author
item DUGAN, JAE - OREGON STATE UNIVERSITY
item ROCKEY, DANIEL - OREGON STATE UNIVERSITY
item JONES, LOREN
item ANDERSEN, ARTHUR

Submitted to: Antimicrobial Agents and Chemotherapy
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/11/2004
Publication Date: 10/6/2004
Citation: Dugan, J., Rockey, D.D., Jones, L.K., Andersen, A.A. 2004. Tetracycline resistance in Chlamydia suis mediated by genomic islands inserted into the chlamydial inv-like gene. Antimicrobial Agents and Chemotherapy. 48(10):3989-3995.

Interpretive Summary: Chlamydia suis strains recently isolated from swine are resistant to tetracycline. Tetracycline has been the antibiotic of choice for control of chlamydiae. The swine strains are the only chlamydiae known to have a stable resistance to tetracycline. Molecular studies were done to determine why the swine strains were resistant and why the resistance was stable. It was found that the swine strains had integrated the tet(C) resistance gene into the chlamydial chromosome. The tet(C) resistance gene was found in four different arrangements, but was always integrated in the same location in the chromosome. The tet(C) resistance gene was acquired from other bacteria as it was identical to the tet(C) resistance gene seen in other enteric bacteria. The identification of the tet(C) resistance gene in chlamydiae is the first example of any horizontally acquired genes into chlamydia or any other obliqate intracellular bacteria. Information on the type of gene incorporated and the location it was incorporated in the chromosome should aid in developing methods to incorporate other genes into chlamydiae for molecular studies.

Technical Abstract: Tetracycline (TET) and its derivatives are successful and inexpensive frontline antibiotics of choice against chlamydial infection in humans and other animals. Although there are no reports of stable TET-resistance in Chlamydiae pathogenic to humans, Chlamydia suis, a pathogen of pigs, expresses a stable TET-resistance phenotype. In this report we demonstrate that this resistance pattern is manifested through a tet(C) resistance allele integrated into the chlamydial chromosome. Four related genomic islands were identified in seven TET-resistant C. suis strains. In each strain, the island is recombined into an identical position in the chlamydial invasin gene. All isolates encode the tet(C) structural gene, TET repressor, and most carry a novel homolog to the IS605 family of insertion sequences located at one or the other ends of the island. Each island also carries genes found in resistance plasmids from a variety of species. These genetic islands represent the first examples of horizontally acquired DNA integrated into a natural isolate of chlamydiae, or within any other obligate intracellular bacterium.