How to diagnose bacterial co-infection in COVID-19?

Diagnosing Bacterial Co-infection in COVID-19 Patients

A comprehensive microbiologic workup should be performed before administering empirical antibiotics in COVID-19 patients to facilitate appropriate antibiotic management. 1

Clinical Indicators of Bacterial Co-infection

• Critically ill COVID-19 patients, especially those requiring ICU admission or mechanical ventilation, have a higher risk of bacterial co-infection and may require antibiotic therapy 1

• Laboratory findings suggestive of bacterial co-infection include:

  • Elevated white blood cell (WBC) count 1
  • Elevated C-reactive protein (CRP) levels 1
  • Procalcitonin (PCT) level >0.5 ng/mL (stronger indicator) 1

• However, serum biomarkers alone should not determine when to start antibiotics, especially in non-critically ill patients 1

• Among these biomarkers, C-reactive protein has shown the best diagnostic accuracy for documented bacterial infections (AUC of 0.822), though sensitivity and specificity remain below 90% 2

Diagnostic Testing Approach

• Syndromic diagnostic testing (multiplex PCR) should be performed using specimens from:

  • Endotracheal tube samples or bronchoalveolar lavage (BAL) 1
  • Conventional cultures should always be performed in parallel with PCR testing 1

• Nasopharyngeal swabs are not recommended for guiding antimicrobial treatment during early COVID-19 1

• Blood cultures and respiratory cultures should be obtained before starting antibiotics 3, 4

• The most common bacterial pathogens identified in COVID-19 patients include:

  • Klebsiella species 4, 5
  • Staphylococcus aureus (both MRSA and MSSA) 4
  • Escherichia coli 4
  • Haemophilus influenzae 5
  • Streptococcus pneumoniae 4, 5
  • Pseudomonas aeruginosa 4, 5

Antibiotic Management Guidelines

• Restrict antibiotic use in mild-to-moderately ill COVID-19 patients, especially those with low initial PCT levels (<0.25 ng/mL) 1

• For non-critically ill patients with suspected bacterial co-infection:

  • Use empirical antibiotics covering both typical and atypical pathogens of community-acquired pneumonia 1
  • A single anti-pseudomonal antibiotic is recommended for secondary bacterial infections 1

• For critically ill patients with suspected bacterial co-infection:

  • Consider empirical anti-MRSA antibiotics 1
  • Double antipseudomonal antibiotics and/or anti-MRSA antibiotics may be prescribed based on local epidemiology 1

• Serial PCT measurements should be performed in all hospitalized patients, especially critically ill or mechanically ventilated patients 1

• Early de-escalation or discontinuation of antibiotics is recommended in patients with low PCT levels (<0.25 ng/mL) 1

Important Considerations and Pitfalls

• Bacterial co-infection is relatively infrequent in COVID-19 patients (5.5-12.5% at admission) 3, 4, 5

• Empirical antibiotic use in COVID-19 pneumonia has not been shown to prevent clinical deterioration or reduce mortality 2

• Risk factors for bacterial co-infection include:

  • Previous positive respiratory cultures in the past year 5
  • Underlying conditions like COPD with inhaled corticosteroids, heart failure, and dyslipidemia 5
  • Prolonged ICU stay and intubation 3

• Overuse of antibiotics can lead to increased antimicrobial resistance, particularly in ICU settings 6

• Patients with bacterial co-infections tend to have worse outcomes and higher mortality rates 6, 5