The clinical significance of pneumonia in patients with respiratory specimens harbouring multidrug-resistant Pseudomonas aeruginosa: a 5-year retrospective study following 5667 patients in four general ICUs.

Pseudomonas aeruginosa is the leading cause of pneumonia in intensive care units (ICUs), with multidrug-resistant (MDR) strains posing a serious threat. The aim of this study was to assess the clinical relevance of MDR Pseudomonas isolates in respiratory clinical specimens. A 5-year retrospective observational study in four medical-surgical ICUs from a referral hospital was carried out. Of 5667 adults admitted to the ICU, 69 had MDR-PA in respiratory samples: 31 were identified as having pneumonia (HAP/VAP): 21 ventilator-associated pneumonia (VAP) and ten hospital-acquired pneumonia (HAP). Twenty-one (67.7%) adults with MDR-PA HAP/VAP died after a median of 4 days (18 of the 21 deaths within 8 days), compared with one (2.6%) without pneumonia at day 8. In a Cox proportional regression model, MDR-PA pneumonia was an independent variable [adjusted hazard ratio (aHR) 5.92] associated with 30-day ICU mortality. Most strains (85.1%) were susceptible to amikacin and colistin. Resistance to beta-lactams (third-generation cephalosporins and piperacillin-tazobactam) ranged from 44.1% to 45.3%. Meropenem showed poor overall activity (MIC[50/90] 16/32 mg/dL), with 47.0% having a minimum inhibitory concentration (MIC) breakpoint >8 mg/L. Twenty-four (77.4%) HAP/VAP episodes received inappropriate empirical therapy. Although empirical combination therapy was associated with less inappropriate therapy than monotherapy (16.7% vs. 88.3%, p < 0.01), there was no difference in survival (30% vs. 33.3%, p = 0.8). Pneumonia was identified in one-third of adult ICU patients harbouring MDR-PA in respiratory clinical specimens. These patients have a 6-fold risk of (early) death compared to ventilator-associated tracheobronchitis (VAT) and respiratory colonisation. New antibiotics and adjuvant therapies are urgently needed to prevent and treat MDR-PA HAP/VAP.

Infections in intensive care unit adult patients harboring multidrug-resistant Pseudomonas aeruginosa: implications for prevention and therapy.

The purpose of this paper was to report the burden and characteristics of infection by multidrug-resistant Pseudomonas aeruginosa (MDR-PA) in clinical samples from intensive care unit (ICU) adults, and to identify predictors. This was a retrospective observational study at four medical-surgical ICUs. The case cohort comprised adults with documented isolation of an MDR-PA strain from a clinical specimen during ICU stay. Multivariate analysis was performed to identify predictors for MDR-PA infection. During the study period, 5667 patients were admitted to the ICU and P. aeruginosa was isolated in 504 (8.8%). MDR-PA was identified in 142 clinical samples from 104 patients (20.6%); 62 (43.6%) of these samples appeared to be true infections. One hundred and eighteen (83.1%) isolates were susceptible only to amikacin and colistin, and 13 (9.2%) were susceptible only to colistin. Overall, the MIC50 to meropenem was 16 µg/mL and the MIC90 was >32 µg/mL, with 60.4% of respiratory samples being MIC >32 µg/mL to meropenem. Independent predictors for MDR-PA infection were fever/hypothermia [odds ratio (OR) 9.09], recent antipseudomonal cephalosporin therapy (OR 6.31), vasopressors at infection onset (OR 4.40), and PIRO (predisposition, infection, response, and organ dysfunction) score >2 (OR 2.06). This study provides novel information that may be of use for the clinical management of patients harboring MDR-PA and for the control of the spread of this organism.