Impact of Multidrug-Resistant Bacterial Colonization on Clinical Characteristics, Antibiotic Treatment, and Clinical Outcomes of Hospital-Acquired Pneumonia.

Purpose: To determine effects of colonization with multidrug-resistant bacteria (MDRB) in general wards on characteristics, treatment, and prognosis of hospital-acquired pneumonia (HAP).

Methods: This was a multicenter retrospective cohort study of patients with HAP admitted to 16 tertiary or university hospitals in Korea from July 2019 to December 2019. From the entire cohort, patients who developed pneumonia in general wards with known colonization status before the onset of pneumonia were included in this study. Patients were categorized into a colonization group and a non-colonization group according to MDRB colonization. Patients of the two groups were then compared.

Results: Among a total of 400 patients, 63 were in the MDRB colonization group. HAP caused by MDR-Staphylococcus aureus or MDR-Pseudomonas aeruginosa was more common in the colonization group than in the non-colonization group (24.4% vs. 8.1%, P = 0.006 or 20.0% vs. 5.4%, P = 0.013, respectively). Colonization with certain bacteria was correlated with subsequent infection with the same bacteria. Carbapenem use (36.5% vs. 24.3%, P = 0.044) and appropriateness of initial antibiotics (50.8% vs. 12.8%) were higher in the colonization group than in the non-colonization group. Although in-hospital mortality was similar in the two groups (34.9% vs. 32.9%, P = 0.759), hospital length of stay was longer (38 days vs. 31 days, P = 0.009) and rate of discharge to home was lower (34.1% vs 59.7%, P = 0.002) in the colonization group.

Conclusions: Colonization with MDRB might influence characteristics and treatment of HAP. However, prognosis of HAP was not associated with MDRB colonization.