Chlamydial Antibiotic Resistance and Treatment Failure in Veterinary and Human Medicine

Abstract

The Chlamydiaceae are widespread pathogens of both humans and animals. Chlamydia trachomatis infection causes blinding trachoma and reproductive complications in humans. Chlamydia pneumoniae causes human respiratory tract infections and atypical pneumonia. Chlamydia suis infection is associated with conjunctivitis, diarrhea, and failure to gain weight in domestic swine. Chlamydial infections in humans and domesticated animals are generally controlled by antibiotic treatment—particularly macrolides (usually azithromycin) and tetracyclines (tetracycline and doxycycline). Tetracycline-containing feed has also been used to limit infections and promote growth in livestock populations, although its use has decreased because of growing concerns about antimicrobial resistance development. Because Sandoz and Rockey published an elegant review of chlamydial anti-microbial resistance in 2010, we will review the following: (i) antibiotic resistance in C. suis, (ii) recent evidence for acquired resistance in human chlamydial infections, and (iii) recent non-genetic mechanisms of antibiotic resistance that may contribute to treatment failure.

Selective Pressure Promotes Tetracycline Resistance of Chlamydia Suis in Fattening Pigs

“…C . suis strains carrying the tet (C) gene have been identified in several pig farms in the USA, Italy, Switzerland, Belgium, Cyprus and Israel in recent years [7, 12–14, 15]. Moreover, there has been preliminary evidence for selective pressure as a result of antibiotic treatment in C .…”

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

“…Of particular interest is the emergence of tetracycline resistance in C. suis, a growing problem in the pig rearing industry and probably the result of excessive tetracycline use for therapeutic purposes and as growth promoters in livestock since the 1950s (7)(8)(9)(10)(11). C. suis is primarily known to inapparently infect the porcine gastrointestinal tract with a prevalence of up to 90 % in fattening pigs (12).…”

Novel Detection Strategy To Rapidly Evaluate the Efficacy of Antichlamydial Agents

“…Although both EBs and RBs have a metabolic capacity (36,37), rapidly replicating RBs are more responsive to antimicrobials than EBs (38,39). Alternatively, a small number of bacteria may have adapted to a viable, nondividing persistent form (9,26,39,40) that was less susceptible to antimicrobials in vitro. Suchland et al (11) reported that the survival rate of Chlamydia exposed to an effective antimicrobial is approximately one bacterium per 5,000 infected cells.…”

“…We consider this cell-based method to have significant potential to be an efficient tool in screening new antimicrobial agents and measuring neutralizing antibody. The versatility of P ompA -GFP also opens numerous possibilities to monitor the dynamic behavior of C. trachomatis, in particular, in scenarios of persistence induced by stressors and reactivation upon removal of the stressors, as well as the host adaptation of C. trachomatis and its related heterotypic resistance (5,(7)(8)(9)(10). Such studies will provide new insights into the intracellular survival mechanism of C. trachomatis contributing to C. trachomatis pathogenesis.…”

“…It is unclear what causes treatment failure. Although true antimicrobial resistance by genetic mutation has not emerged in human strains, C. trachomatis has the ability to build up a heterotypic resistance, which refers to the replication of a heterogeneous population of resistant and susceptible bacteria from a subculture of a single resistant organism without genetic changes (5,(7)(8)(9)(10). The potential role of such nongenetic resistance in the failure of treatment of C. trachomatis infection has been debated and has increasingly drawn a great deal of attention (5,(7)(8)(9)(10).…”