Prolonged use of carbapenems and colistin predisposes to ventilator-associated pneumonia by pandrug-resistant Pseudomonas aeruginosa

Objective: We present our experience with five cases of pandrug- resistant Pseudomonas aeruginosa ventilator- associated pneumonia ( VAP) and analysis of risk factors. Design and setting: Case- control study in a 15- bed intensive care unit ( ICU). Patients and participants: The study included 5 cases and 20 controls. Each case patient was matched to four contemporary controls according to gender, prior hospital admissions, hospitalization duration, ICU admission cause, Acute Physiology and Chronic Health Evaluation ( APACHE) II and Sequential Organ Function Assessment ( SOFA) scores on ICU admission, and length of ICU stay, and mechanical ventilation duration until first VAP episode by a multidrug- resistant bacterium. Measurements and results: Recorded variables included age, gender, daily APACHE II and SOFA scores, patient medication, treatment interventions, positive cultures and corresponding antibiograms, occurrence of infection, sepsis, and septic shock, other ICU- associated morbidity, length of ICU stay and mechanical ventilation, and patient outcome. Healthcare worker and environmental cultures, and a hand-disinfection survey were performed. Pandrug- resistant P. aeruginosa isolates belonged to the same genotype and were bla(VIM-1)- like gene positive. The outbreak resolved following reinforcement of infection- control measures ( September 27). The sole independent predictor for pandrug-resistant P. aeruginosa VAP was combined use of carbapenem for more than 20 days and colistin use for and more than 13 days ( odds ratio 76.0; 95% confidence interval 3.7 - 1487.6). An additional risk factor was more than 78 open suctioning procedures during 6 - 26 September ( odds ratio 16.0; 95% confidence interval 1.4 - 185.4). Conclusions: Prolonged carbapenem-colistin use predisposes to VAP by pandrug- resistant P. aeruginosa. Cross- transmission may be facilitated by open suctioning.