Bacterial superinfection in patients with severe Covid-19 pneumonia

The real incidence and impact of bacterial infectious complications in patients intubated for severe forms of Covid-19 are still uncertain. Still, it is estimated that it should follow the trend of other serious viral infections, such as H1N1, where up to 32% of patients at autopsy revealed the presence of bacterial coinfection as a contributing factor to death (1,2). 

In this scenario, despite recommendations based on weak evidence, several societies recommend the practical use of antimicrobials in severe forms of Covid-19, but with increasing evidence that leads to a change in strategy, since this conduct greatly increases the incidence of infection by resistant germs in patients who did not even have ongoing bacterial coinfection ( 3-5). 

Read also: Anvisa approves the use of baricitinib in patients hospitalized with covid-19.

Within what would be considered more rational today, the best approach would be based on more objective clinical and laboratory criteria before starting a broad empirical antimicrobial regimen, bearing in mind that bronchoalveolar lavage remains the gold standard for microbiological identification, being superior to nasopharyngeal swab and conventional tracheal aspirate (6).

The aim of this study, published in June 2021 in the American Journal of Respiratory and Critical Care Medicine, was to conduct a single-center observational study to determine the prevalence and etiology of bacterial superinfection at the time of initial intubation and the incidence and etiology of VAP ( Subsequent bacterial ventilator-associated pneumonia in patients with severe SARS-CoV-2 pneumonia ( 7 ).

Methodology

This study consisted of a retrospective and observational analysis at Northwestern Memorial Hospital (NMH), an emergency hospital in Chicago. Patients admitted to intensive care units with respiratory failure secondary to SARS-CoV-2 pneumonia confirmed by PCR were intubated and discharged from the hospital or died between March 1 and June 30, 2020. 19 intubated for reasons other than pneumonia (surgical procedures, intoxication, etc.) were excluded after evaluation by at least two intensive care physicians. The study was approved by the ethics and research committee.

Patients had a bronchoalveolar lavage performed within the first 48 hours after intubation and whenever they were suspected of having developed VAP. Cases were defined as bacterial superinfection when isolated either by conventional culture media or by PCR methods, a germ known to cause pulmonary infection.

Results

Three hundred eighty-six lavage samples (BAL) from 179 patients with confirmed and severe forms of Covid-19 who required mechanical ventilation were analyzed. Bacterial superinfection within 48 hours of intubation was confirmed in 21% of patients with Covid-19. During the hospital stay, 72 patients (44.4%) developed at least one episode of VAP (VAP Density 45.2 / 1000 days of ventilation), and 15 (20.8%) of the VAP cases were caused by pathogens. Resistant. 

It was further seen that the isolated use of clinical criteria does not correctly distinguish between patients with and without bacterial superinfection. A rational BAL-based antimicrobial strategy was significantly associated with reduced antibiotic use compared to conventional guideline recommendations.

Conclusion

In patients with severe Covid-19 pneumonia who progress to the need for mechanical ventilation, bacterial superinfection present at the time of intubation occurs in less than 25% of patients. Empirical and early antibiotic management based on weak guideline recommendations at intubation results in antibiotic overuse and a high potential for developing resistant strains. VAP complicated 44% of patients and could not be accurately identified without adequate microbiological analysis by BAL.

Learn more: Case report: Sepsis and septic shock in Covid-19 times

My impression

The use of antibiotics empirically for patients with viral pneumonia is irrational from a therapeutic point of view. This study reinforces the rationale for an adequate strategy for the rational use of antimicrobials and stewardship. Combining clinical data with laboratory parameters such as procalcitonin, CRP, and geometry and adopting an aggressive routine microbiological search seems to be the most suitable for the scenario of viral pneumonia.

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All authors declared that there is no potential conflict of interest regarding.

1. Blair SN, Kampert JB, Kohl III HW, Barlow CE, Macera CA, Paffenbarger RS, et …

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