Are omicron infections more frequently associated with bacterial co-infections?

Abstract

Introduction: Clinical observations suggest that Omicron infections may present with different radiographic findings and be more frequently associated with bacterial co-infections, but there is a paucity of published data. This study aimed to compare the clinical and radiographic findings of patients hospitalized with Omicron versus alpha-delta infections.

Materials and methods: Between January 1, 2021 and June 30, 2021 (alpha and delta period) and between January 1, 2022 and July 31, 2022 (Omicron period), respectively 149 and 163 COVID-19 PCR-positive patients who were followed up in the COVID-19 ward and intensive care unit of a tertiary care center were included in the study. Clinical (presence of fever and purulent sputum), laboratory and radiologic findings of the two groups were compared. Sputum culture results and antibiotic use were also evaluated.

Result: In the alpha/delta group, ground glass opacities were seen in 75.2% (112) of the patients, consolidation in 2.7% (4), and both findings together in 6.0% (9). In the Omicron group, ground glass was seen in 40.5% (66), consolidation in 5.5% (9), and both ground glass and consolidation together in 8.7% (13) (p< 0.001). Procalcitonin levels were 0.25 µg/L or higher in 29.6% and 43.9% of the patients in the alpha/delta and Omicron groups, respectively. Mean PCT values were 0.36 µg/L and 1.93 µg/L, respectively (p> 0.05). CRP levels were similar in both groups. Mean LDH level in the Omicron group was 278 U/L and was significantly lower than the alpha/delta group (381 U/L) (p< 0.001). The proportion of patients requiring intensive care during hospitalization was higher in the alpha/delta group (36.2% vs 26.4%) (p= 0.06).

Conclusions: Lower LDH levels, less need for intensive care and less frequent development of ARDS indicate that Omicron causes milder disease, while a higher rate of consolidation and higher procalcitonin levels suggest a higher frequency of bacterial co-infections.