Hospital-acquired pneumonia (HAP) is defined as pneumonia that develops 48 hours or more after admission that was not present on admission; and ventilator-associated pneumonia (VAP) is pneumonia that develops 48 hours or more after endotracheal intubation.
HAP and VAP are common afflictions in hospitalized patients, accounting for nearly one-quarter of all hospital-acquired infections. They confer mortality rates of 24%-50%, increasing to nearly 75% if caused by resistant organisms.1,2 Given the high prevalence and significant mortality associated with these types of pneumonia, diagnosis and treatment are essential. Treatment must be balanced against potential unintended consequences of antibiotic use including Clostridium difficile infections and the promotion of resistant bacteria caused by poor antibiotic stewardship.
Given the frequency with which HAP and VAP occur, and the need for equipoise with antibiotic use, it is essential that all practicing clinicians have an evidence-based construct for the diagnosis and treatment of HAP and VAP.
In 2016, the Infectious Diseases Society of America (IDSA) and the American Thoracic Society (ATS) reconvened after 11 years to update their recommendations for the treatment of HAP and VAP.2 The decision to update their recommendations was based on the availability of new evidence regarding the diagnosis and treatment of these conditions.
Notably, these new guidelines have completely removed the entity of health care–associated pneumonia (HCAP), as these patients are not necessarily at high risk for resistant organisms, and most will present with their illness directly from the community. This update alone significantly changes the scope of these guidelines. HCAP likely will be addressed in future guidelines for community-acquired pneumonia.
Included in this review are guideline updates on methods for diagnosis, initial antibiotic choice, pathogen-specific therapy, and duration of therapy. The guidelines also have recommendations for the role of inhaled antibiotics and pharmacokinetic optimization of antibiotic dosing, which will not be reviewed here.
Methods for Diagnosis: The use of semi-quantitative, noninvasive sampling of respiratory cultures is preferred for HAP and VAP, rather than empiric treatment or quantitative cultures (i.e., bronchoalveolar lavage, protected-specimen brush and blind bronchial sampling).
Initial antibiotic choice: For HAP and VAP, clinicians should include therapy targeting S. aureus, Pseudomonas aeruginosa, and other gram-negative bacilli. Therapy for methicillin-resistant S. aureus should be included if patients are at high risk for death (i.e., septic shock or ventilated patients) or if local drug-resistant prevalence is greater than 10%-20%. Similarly, two antipseudomonal antibiotics should be used only with empiric therapy if the patient is at high risk for mortality or local drug-resistant prevalence is greater than 10%.
Duration of therapy: HAP and VAP should be treated for 7 days with regimens that are tailored to culture data when available, assuming there has been appropriate clinical response. Procalcitonin may be paired with clinical judgment when considering antibiotic discontinuation.
There are several notable differences between the 2016 IDSA/ATS guidelines and the 2005 guidelines.3 The earlier guidelines recommended strong consideration of invasive respiratory cultures such as bronchoalveolar lavage or protected-specimen brush sampling for HAP/VAP. It is now recommended that only noninvasive cultures be performed in most clinical scenarios.
Regarding Pseudomonas infections, the previous guidelines recommended consideration of an aminoglycoside combined with a beta-lactam antibiotic. The new guidelines recommend against the use of aminoglycosides because of their poor lung penetration, risk of oto- and nephrotoxicity, and potential clinical inferiority when compared to nonaminoglycoside-containing regimens. In addition, a 14-day course of antibiotics had been recommended for the treatment of pseudomonal pneumonia, which has been changed to 7 days in the most recent guidelines.
Last, the updated guidelines recommend dual therapy for potential or documented Pseudomonas infection only for patients at high risk for mortality or in hospitals with a high prevalence of antibiotic resistance; previously, dual antipseudomonal therapy was recommended for all cases of HAP and VAP, based upon the risk of developing resistant strains with monotherapy.3
Since 2005, several organizations have released guidelines addressing the management of HAP and VAP.1,4,5,6 These are largely in keeping with the current version released by the IDSA/ATS. Across all guidelines, there is a focus on the importance of local antibiograms for appropriate and effective treatment, and the use of noninvasive culture data to guide therapy. Also, all groups recommend a short-course (7-8 days) of antibiotics for both HAP and VAP, assuming there has been an appropriate clinical response. The recent Canadian guidelines have one unique recommendation, which is to avoid the use of ceftazidime for suspected Pseudomonas pneumonia, based upon inferior outcomes when compared to alternative regimens.5