The role of colonization pressure in the dissemination of colistin or tigecycline resistant KPC-producing Klebsiella pneumoniae in critically ill patients

To identify the risk factors for incident enteric colonization by KPC-producing Klebsiella pneumoniae (KPC-Kp) resistant to colistin or tigecycline during Intensive Care Unit (ICU) stay. A prospective observational study of patients admitted to the ICU was conducted during a 27-month period. Rectal samples taken upon admission and weekly afterwards were inoculated on selective chromogenic agar. K. pneumoniae isolates were characterized by standard methodology. Mean inhibitory concentration (MIC) to colistin and tigecycline were determined by E-test. The presence of bla (KPC) gene was confirmed by PCR. Among 254 patients, 62 (24.4 %) became colonized by colistin- resistant KPC-Kp during their stay. Multivariate analysis revealed that corticosteroid, colistin administration and number of colonized patients in nearby beds per day were significantly associated with colonization. Among 257 patients, 39 (17.9 %) became colonized by tigecycline resistant KPC-Kp during their stay. Risk factors identified by multivariate analysis were: days at risk, obesity, number of colonized patients treated in nearby beds per day and administration of tigecycline. The high prevalence of colistin or tigecycline resistant KPC-Kp enteric carriage in ICU patients indicate that dissemination is due to their transfer from patient to patient via the personnel and indicates the importance of strict infection control protocols.