Microbial Diversity and Clinical Challenges of Ventilator-Associated Pneumonia in COVID-19 Patients: Epidemiology, Diagnosis, Treatment, and Prevention

Ventilator-associated pneumonia (VAP) is a serious lung infection that develops in patients receiving mechanical ventilation for at least 48 h. Critically ill COVID-19 patients admitted to intensive care units (ICUs) are particularly vulnerable to VAP, which contributes substantially to morbidity and mortality. This review summarizes current knowledge on the epidemiology, microbial diversity, clinical indicators, diagnosis, treatment, and prevention of VAP in COVID-19 patients. The reported incidence of VAP among mechanically ventilated COVID-19 patients ranges widely from 6% to 86%, reflecting differences in diagnostic criteria and study settings. The predominant bacterial pathogens include Staphylococcus aureus, Acinetobacter baumannii, Pseudomonas aeruginosa, Klebsiella pneumoniae, Escherichia coli, and Enterobacter spp., with fungal pathogens such as Candida spp. and Aspergillus fumigatus also implicated. VAP in COVID-19 patients can progress to complications including lung abscess, particularly in severe cases, and is associated with prolonged ICU stays and increased mortality. Diagnosis relies on clinical, radiological, and microbiological criteria, with biomarkers such as procalcitonin showing promise for early detection. Empirical broad-spectrum antibiotic therapy is typically initiated, guided by local resistance patterns and individual risk factors, followed by pathogen-directed treatment when possible. Preventive strategies—including reducing airway colonization, preventing aspiration, and minimizing the duration of mechanical ventilation—are essential to reduce the VAP burden in this population. Given the high prevalence of multidrug-resistant pathogens and the complexity of diagnosis in COVID-19 patients, further research is needed to develop novel antimicrobial strategies and optimize preventive protocols.