Ventilator-associated pneumonia (VAP) is caused by microbial contamination in the lungs. Microbes may enter the lung during intubation or mechanical ventilation. Common species associated with VAP include (most common listed first): Pseudomonas, Staphylococcus aureus, Enterobacteriaceae, Streptococcus, Haemophilus, Acinetobacter, and Neisseria. VAP is commonly polymicrobial. Causative pathogens—and their associated drug resistance rates—vary based on hospital and geography. VAP is not normally due to fungal or virus infections in immunocompetent hosts. VAP-causing pathogens generally remain in the lung, spreading into blood or pleural space in less than 10 percent of cases.
The source of causative pathogens is another matter. Bronchoscopes, tubing, endotracheal cuffs, and other respiratory accessories and instruments can all be colonized by VAP-causing pathogens. Pathogens can also originate in the environment (air, water, fomites) or be transmitted between staff and patients. It is less likely that pathogens are directly inhaled by patients, than they are introduced into the airway by healthcare devices or via aspiration.
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Commonly, VAP can be traced to reusable bronchoscopes. Bronchoscopes are used to perform bronchoalveolar lavages (BALs), collect diagnostic cultures, aid sample collection, and assist intubation. They provide a look inside the airway and an open channel for other instruments to pass into the airway. Contamination can occur during procedures or any time a bronchoscope is handled. Infection from patient flora can be introduced as the bronchoscope passes through the oropharynx and into the airway. Contamination from exogenous bacteria can also occur during reusable bronchoscope cleaning, transport, or storage.
Contaminated, reused bronchoscopes may spread pathogens to subsequent patients and are a noted cause of VAP. Even with properly disinfected bronchoscopes, individual patients may experience “distal spread of organisms” that can lead to pulmonary infection. Bronchoscopes may also cause abrasions in the airway that may increase risk of microbial colonization and VAP.
Outbreaks associated with contaminated bronchoscopes can be deadly. Even the most sophisticated hospitals are not immune. In 2000, P. aeruginosa on bronchoscopes contributed to the deaths of three critically ill patients and caused 48 respiratory and bloodstream infections. An earlier outbreak in South Carolina led to extremely pathogenic, multidrug-resistant Mycobacterium tuberculosis spreading into the community. Respiratory infections like VAP occur worldwide due to contaminated bronchoscope and ventilator equipment, and prevention is a challenge for small and large hospitals alike.