Bacterial and Viral Co-Infections in COVID-19 Patients: Etiology and Clinical Impact

Mixed infections can worsen disease symptoms. This study investigated the impact of mixed infections with viral and bacterial pathogens in patients positive for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2).

Using the in-house multiplex PCR method, we tested 337 SARS-CoV-2 positive samples for co-infections with three bacterial and 14 other viral pathogens.

Between August 2021 and May 2022, 8% of 337 SARS-CoV-2-positive patients had bacterial co-infections, 5.6% had viral co-infections, and 1.4% had triple mixed infections. The most common causes of mixed infections were Haemophilus influenzae (5.93%) and respiratory syncytial virus (RSV) (1.18%). Children < 5 years old had more frequent co-infections than adults < 65 years old (20.8% vs. 16.4%), while adults showed a more severe clinical picture with a higher C-reactive protein (CRP) level (78.1 vs.16.2 mg/L; p = 0.033), a lower oxygen saturation (SpO2) (89.5 vs. 93.2%), and a longer hospital stay (8.1 vs. 3.1 days; p = 0.025) (mean levels). The risk of a fatal outcome was 41% in unvaccinated patients (p = 0.713), which increased by 2.66% with co-infection with two pathogens (p = 0.342) and by 26% with three pathogens (p = 0.005). Additionally, 50% of intensive care unit (ICU) patients had a triple infection, compared with only 1.3% in the inpatient unit (p = 0.0029). The risk of death and/or ICU admission was 12 times higher (p = 0.042) with an additional pathogen and increased by 95% (p = 0.003) with a third concomitant pathogen.

Regular multiplex testing is important for prompt treatment and targeted antibiotic use.