Horizontal Transfer of Tetracycline Resistance among Chlamydia spp. In Vitro

Abstract

There are no examples of stable tetracycline resistance in clinical strains of Chlamydia trachomatis. However, the swine pathogen Chlamydia suis is commonly tetracycline resistant, both in America and in Europe. In tested U.S. strains, this resistance is mediated by a genomic island carrying a tet(C) allele. In the present study, the ability of C. suis to mobilize tet(C) into other chlamydial species was examined. Differently antibiotic resistant strains of C. suis, C. trachomatis, and Chlamydia muridarum were used in coculture experiments to select for multiply antibiotic resistant progeny. Coinfection of mammalian cells with a naturally occurring tetracyclineresistant strain of C. suis and a C. muridarum or C. trachomatis strain containing selected mutations encoding rifampin (rifampicin) or ofloxacin resistance readily produced doubly resistant recombinant clones that demonstrated the acquisition of tetracycline resistance. The resistance phenotype in the progeny from a C. trachomatis L2/ofl R -C. suis R19/tet R cross resulted from integration of a 40-kb fragment into a single ribosomal operon of a recipient, leading to a merodiploid structure containing three rRNA operons. In contrast, a cross between C. suis R19/tet R and C. muridarum MoPn/ofl R led to a classical double-crossover event transferring 99 kb of DNA from C. suis R19/tet R into C. muridarum MoPn/ofl R . Tetracycline resistance was also transferred to recent clinical strains of C. trachomatis. Successful crosses were not obtained when a rifampin-resistant Chlamydophila caviae strain was used as a recipient for crosses with C. suis or C. trachomatis. These findings provide a platform for further exploration of the biology of horizontal gene transfer in Chlamydia while bringing to light potential public health concerns generated by the possibility of acquisition of tetracycline resistance by human chlamydial pathogens.

Water-filtered infrared A reduces chlamydial infectivity in vitro without causing ex vivo eye damage in pig and mouse models

“…Together with C. trachomatis, C. suis belongs to the obligate intracellular and Gram-negative bacterial family Chlamydiaceae, which is characterized by a unique biphasic lifecycle consisting of infectious elementary bodies (EBs) and intracellular, dividing reticulate bodies (RBs) (12,13). Alarmingly, mixed infections with C. trachomatis and C. suis have been reported in Nepalese trachoma patients, while co-infection of the two closely related species generated tetracycline resistant C. trachomatis strains in vitro (14,15). Taking these findings together, mixed infection with tetracycline resistant C. suis and ocular C. trachomatis strains may amplify the emergence of therapy-resistant trachoma strains.…”

Chlamydial Intracellular Survival Strategies

“…In cells coinfected with C. trachomatis serovars that were naturally resistant to ofloxacin or to rifampin, doubly drug-resistant recombinant Chlamydia arose at 10 4 times higher frequency than that of spontaneous mutations, and the genomes of these recombinants were chimeric recombinants of the parental strains. Whole genome sequencing of recombinants from additional crosses provided evidence that recombination events ranged from 40 kb to 790 kb and that the sizes of recombination sites range from a short 11-bp sequence to a 366-bp stretch (Suchland et al 2009). The mechanisms underlying the release of DNA, uptake, and recombination are largely unknown.…”

Generation of targeted Chlamydia trachomatis null mutants

“…The development of genetic systems has been hampered by the organism's obligate intracellular lifestyle and complex biphasic developmental biology (4). C. trachomatis genomes are amenable to manipulation as shown by naturally occurring recombination (5) and by the moderate frequency of in vitro lateral gene transfer (6,7). Chlamydiae have also been successfully transformed to antibiotic resistance by electroporation, but transformants either were unstable or successful transformation was limited to replacing the 16S rRNA with its antibiotic-resistant allele (8,9).…”