Incidence and risk factors for secondary pulmonary infections in patients hospitalized with coronavirus disease 2019 pneumonia

Abstract

Background: Secondary pulmonary infections (SPI) have not been well described in COVID-19 patients. Our study aims to examine the incidence and risk factors of SPI in hospitalized COVID-19 patients with pneumonia.

Methods: This was a retrospective, single-center study of adult COVID-19 patients with radiographic evidence of pneumonia admitted to a regional tertiary care hospital. SPI was defined as microorganisms identified on the respiratory tract with or without concurrent positive blood culture results for the same microorganism obtained at least 48 h after admission.

Results: Thirteen out of 244 (5%) had developed SPI during hospitalization. The median of the nadir lymphocyte count during hospitalization was significantly lower in patients with SPI as compared to those without SPI [0.4 K/uL (IQR 0.3-0.5) versus 0.6 K/uL (IQR 0.3-0.9)]. Patients with lower nadir lymphocyte had an increased risk of developing SPI with odds ratio (OR) of 1.21 (95% CI: 1.00 to 1.47, p = 0.04) per 0.1 K/uL decrement in nadir lymphocyte. The baseline median inflammatory markers of CRP [166.4 mg/L vs. 100.0 mg/L, p = 0.01] and d-dimer (18.5 mg/L vs. 1.4 mg/L, p<0.01), and peak procalcitonin (1.4 ng/mL vs. 0.3 ng/mL, p<0.01) and CRP (273.5 mg/L vs. 153.7 mg/L, p<0.01) during hospitalization were significantly higher in SPI group.

Conclusions: The incidence of SPI in hospitalized COVID-19 patients was 5%. Lower nadir median lymphocyte count during hospitalization was associated with an increased OR of developing SPI. The CRP and d-dimer levels on admission, and peak procalcitonin and CRP levels during hospitalization were higher in patients with SPI.

Keywords: COVID-19; Coronavirus disease 2019; SARS-CoV-2; Secondary bacterial infections; Secondary pulmonary infections; Severe acute respiratory syndrome coronavirus 2.

FIGURE 1

Flowchart for hospitalized COVID-19 patients enrolled in the study.

FIGURE 2

Lymphocyte nadir was significantly less (Mann-Whitney, p = 0.03) in patients with secondary pulmonary infections (SPI). Data points were plotted on the left. In the box plots, the central rectangle spans the first quartile to the third quartile (the interquartile range or IQR) with the horizontal line within the rectangle marking the median. The square symbol marks the mean. The “whiskers” above and below the box are drawn to the furthest point within 1.5 x IQR from the box (the non-outlier range) with “X” marking outliers.