Doxycycline Coverage for Pseudomonas aeruginosa
Doxycycline is not reliable for treatment of Pseudomonas aeruginosa because P. aeruginosa has intrinsic resistance to tetracyclines. [1]
Antimicrobial Activity Profile
Tetracyclines act by inhibiting bacterial protein synthesis at the 30S ribosome. [1] P. aeruginosa is intrinsically resistant to tetracyclines due to constitutively overexpressed efflux systems (MexAB/MexXY). [1] Most strains of P. aeruginosa show significantly increased resistance to tetracycline-class agents compared with many other gram-negative rods. [2]
Clinical Implication for Empiric or Definitive Therapy
Doxycycline should not be selected as an antipseudomonal agent for P. aeruginosa infections based on intrinsic resistance. [1] Appropriate antipseudomonal therapy should be selected based on organism identification and susceptibility testing. [1]
Susceptibility Testing Nuance
In vitro susceptibility testing is required to confirm activity for any specific isolate. [1] Mechanisms of intrinsic resistance can make susceptibility uncommon. [1]
Treatment Selection Framework for Suspected or Confirmed Infection
Antipseudomonal agents should be selected from classes with demonstrated activity against P. aeruginosa (for example, antipseudomonal β-lactams, fluoroquinolones, or aminoglycosides) based on susceptibility results and infection site. [1]
Key Evidence Supporting This Recommendation
Intrinsic tetracycline resistance in P. aeruginosa is attributed to MexAB/MexXY efflux systems. [1] Efflux-pump–mediated intrinsic resistance to tetracycline-class drugs in P. aeruginosa has been demonstrated experimentally. [2]
Bottom-Line Clinical Point
Doxycycline should not be considered coverage for Pseudomonas aeruginosa due to intrinsic tetracycline resistance. [1]