Risk factors, antimicrobial susceptibility pattern and patient outcomes of Pseudomonas aeruginosa infection: A matched case-control study

Background Pseudomonas aeruginosa (P.aeruginosa) is a leading nosocomial gram-negative pathogen associated with prolonged hospitalization, morbidity and mortality. Limited data exist regarding P.aeruginosa infection and outcome in patients managed in intensive care units (ICUs). We aimed to determine the risk factors, antimicrobial susceptibility pattern and patient outcomes of P.aeruginosa infection. Methods In this matched case-control study, all P.aeruginosa infections that occurred >48 hours after hospital admission between January 31st 2016 and December 31st 2018 at ICUs affiliated with King Abdulaziz Medical City, Riyadh were included. P.aeruginosa bacilli was confirmed using API 20E test and antimicrobial susceptibility using disk diffusion or Epsilometer test. Results The study included 90 cases and 90 controls. Compared with controls, cases had significantly higher mean ICU stay days, proportions of patients with previous history of antimicrobial therapy, coronary artery disease, malignancy, hemodialysis, previous surgery, use of central line, urethral catheterization, nasogastric tube, and tracheostomy. In a multivariate conditional logistic regression analysis, factors independently associated with P.aeruginosa infection were ICU duration [Odds Ratio (OR)=9.05,95%CI 2.53-32.27, p=.001], previous surgery (OR=7.33,95%CI 1.66-32.36,p=.009), tracheostomy (OR=11.13,95%CI 1.05-118.59,p=.046), urethral catheterization (OR=7.38,95%CI 1.21-45.11,p=.030) and aminoglycoside drug class (OR=10.59,95%CI 1.14-98.13,p=.038). Of antimicrobial drugs used, highest proportion of resistance was calculated for patients receiving tigecycline (93.3%). Mortality was high in both groups but did not differ significantly: 54(60%) cases and 51(56.7%) controls; p=.650. Conclusions: The study identifies several modifiable factors associated with P.aeruginosa infection in ICUs. These factors are of paramount relevance for case identification, control measures, and optimal treatment strategies of P.aeruginosa infection in ICUs.