Pattern of acquisition of hospital-associated pathogens in the ICU of an academic tertiary care hospital.

Background: Among hospitalized patients, a 48-hour window from time of hospitalization defines nosocomial infections and guides empiric antibiotic selection. This time frame may lead to overuse of broad-spectrum antibiotics. Our primary objective was to determine the earliest and median time since hospital admission to acquire antibiotic-resistant pathogens among patients admitted to the intensive care unit (ICU) of an academic, tertiary care hospital.

Methods: Retrospective chart review was conducted for adult patients admitted to the ICU from home or another hospital within the same health authority in 2018, to identify the time to acquisition of hospital-associated pathogens: methicillin-resistant vancomycin-resistant enterococci, extended-spectrum beta-lactamase (ESBL)-producing Enterobacterales, non-ESBL ceftriaxone-resistant Enterobacterales, and . Patients transferred from hospitals outside the health authority, admitted to ICU after 14 days of hospitalization, who were solid organ or bone marrow transplant recipients, or who were otherwise immunocompromised were excluded.

Results: In 2018, 1,343 patients were admitted to this ICU; 820 met the inclusion criteria. Of these, 121 (14.76%) acquired a hospital-associated pathogen in the ICU. The probability of isolating a hospital-associated pathogen by 48 hours of hospital admission was 3%. The earliest time to isolate any of these pathogens was 29 hours, and the median was 9 days (interquartile range [IQR] 3.8-15.6 days).

Conclusions: Most patients (85.3%) in this ICU never acquired a hospital-associated pathogen. The median time to acquire a hospital-associated pathogen among the remaining patients suggests that initiating empiric broad-spectrum antibiotics on the basis of a 48-hour threshold may be premature.