Pseudomonas aeruginosa is a gram-negative bacillus found in moist environments. Together with Serratia marcescens, P aeruginosa is 1 of the 2 most consistently antimicrobial-resistant pathogenic bacteria. The virulence of pseudomonas is related to extracellular toxins, endotoxin, and a polysaccharide protection from phagocytosis. Usual sites of infection include the respiratory system, skin, eyes, urinary tract, bone, and wounds. Systemic infections caused by a resistant organism carry a high mortality rate and are usually associated with depressed immunity, often in a hospital setting.
More than half of P aeruginosa isolates are now resistant to aminoglycosides. Ceftazidime has been the most effective cephalosporin for treatment of pseudomonal infections. Piperacillin-tazobactam, imipenem, and meropenem also remain highly effective against most isolates, but resistance to the carbapenems and fluoroquinolones has been increasing gradually. The initial choice of antimicrobials depends on local susceptibility prevalence and should be guided by susceptibility testing.
The use of vaccines incorporating multiple P aeruginosa serotypes is under investigation for the treatment of patients with severe burns, cystic fibrosis, or immunosuppression.
Excerpted from BCSC 2020-2021 series: Section 1 - Update on General Medicine. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.