Hospital-acquired pneumonia (HAP) is pneumonia that presents at least 48 hours after admission to the hospital. In contrast, ventilator-associated pneumonia (VAP), is pneumonia that clinically presents 48 hours after endotracheal intubation. Together, these are some of the most common hospital-acquired infections in the United States and pose a considerable burden on hospitals nationwide.
The Infectious Diseases Society of America (IDSA) and the American Thoracic Society (ATS) recently updated their management guidelines for HAP and VAP with a goal of striking a balance between providing appropriate early antibiotic coverage and avoiding unnecessary treatment that can lead to adverse effects such as Clostridium difficile infections and development of antibiotic resistance.1 This update eliminated the concept of Healthcare Associated Pneumonia (HCAP), often used for patients in skilled care facilities, because newer evidence has shown that patients who had met these criteria did not have a higher incidence of multidrug resistant pathogens; rather, they have microbial etiologies and sensitivities that are similar to adults with community acquired pneumonia (CAP).
Hospital-acquired pneumonia
The IDSA recommends that all hospitals create a local antibiogram for their population to facilitate empiric antibiotic choice.2 In all cases, empiric therapy for HAP should have activity against Staphylococcus aureus. The decision to cover against methicillin-resistant S. aureus (MRSA) rather than methicillin-susceptible S. aureus (MSSA) should depend on whether that patient has a risk factor for MRSA infection or is at a high risk of mortality. Once HAP is suspected, antimicrobials should be started immediately.
Reasons to cover for MRSA in HAP:
Risk factors:
• IV antibiotic treatment within 90 days
• Treatment in a unit where the prevalence of MRSA is greater than 20% or unknown
• Prior detection of MRSA by culture or nonculture screening (weaker risk factor)
High risk of mortality: • Septic shock
• Need for ventilator support
MRSA should be covered with use of either vancomycin or linezolid in these cases.
In the absence of risk factors, empiric antibiotic with coverage against MSSA should be used. Piperacillin-tazobactam, cefepime, levofloxacin, imipenem, or meropenem are all acceptable options. If MSSA is isolated as the sole pathogen, then a narrower antibiotic should be used, such as oxacillin, nafcillin, or cefazolin.
In addition, patients with HAP should be covered for Pseudomonas aeruginosa and other gram-negative bacilli. For patients with risk factors for pseudomonas or other gram-negative infection or a high risk for mortality, then two antipseudomonal antibiotics from different classes are recommended, such as piperacillin-tazobactam/tobramycin or cefepime/amikacin.
Use two antipseudomonal antibiotics in HAP if the patient has these risk factors:
Pseudomonas risk factors:
• IV antibiotic treatment within 90 days
• Structural lung disease increasing the risk of gram-negative infection (bronchiectasis, cystic fibrosis)
• High-quality gram stain from respiratory specimen showing predominant and numerous gram-negative bacilli
High risk of mortality:
• Septic shock
• Need for ventilator support
All other patients with HAP can be treated with a single antipseudomonal antibiotic. Of note, an aminoglycoside should not be used as the sole agent with activity against pseudomonas.
Ventilator-associated pneumonia
General management of VAP is similar to HAP in that empiric treatment should be tailored to the local distribution and susceptibilities of pathogens based on each hospital’s antibiogram. All regimens should cover for S. aureus, P. aeruginosa, and other gram-negative bacilli based on the risk of mortality associated with the need for ventilator support. MSSA should be covered for VAP unless the patient has methicillin-resistant risk factors (see below).
MRSA should be covered for VAP if:
• Patient has had IV antibiotic use within past 90 days
• Hospital unit has greater than 10%-20% of S. aureus isolates are MRSA or MRSA prevalence unknown
Only one antipseudomonal agent should be used unless there are one of the following characteristics present, as described below.
Use two antipseudomonal agents in VAP if:
• Prior IV antibiotic use within 90 days
• Septic shock at time of VAP
• Acute respiratory distress syndrome preceding VAP
• 5 or more days of hospitalization prior to the occurrence of VAP
• Acute renal replacement therapy prior to VAP onset
• Greater than 10% of gram-negative isolates are resistant to an agent being considered for monotherapy
• Local antibiotic susceptibility rates unknown
In both HAP and VAP, antibiotics should be de-escalated to those with a narrower spectrum after initial empiric therapy, ideally within 72 hours and based on sputum or blood culture results. The guidelines support obtaining noninvasive sputum cultures in patients with VAP (endotracheal aspirates) and HAP (spontaneous expectoration, induced sputum, or nasotracheal suctioning in a patient who is unable to cooperate to produce a sputum sample). Patients who are improving clinically may be switched to appropriate oral therapy based on the susceptibility of an identified organism. Another key change is that of the standard duration of therapy. Previously, patients were treated for up to 2-3 weeks with antibiotics. The new IDSA/ATS guidelines recommend that patients should be treated with 7 days of antibiotics rather than a longer course.
The bottom line
Empiric therapy for HAP and VAP should be tailored to each hospital’s local pathogen distribution and antimicrobial susceptibilities, as detailed in an antibiogram. In HAP and VAP, empiric antibiotics should cover for S. aureus, but it only needs to target MRSA if risk factors are present, prevalence is greater than 20% or unknown, and – if HAP – a high risk of mortality. P. aeruginosa and other gram-negative bacilli should also be covered in empiric regimens. Dual antipseudomonal antibiotics is only recommended to be used in HAP if there are specific pseudomonal risk factors or a high risk of mortality. They should be used in VAP if there are multidrug-resistant risk factors present or there is a high/unknown prevalence of resistant organisms. All antibiotic regimens should be deescalated rather than maintained, and both HAP and VAP patients ought to be treated for 7 days.
References
1. Kalil AC, Metersky ML, Klompas M, et al. Management of Adults With Hospital-acquired and Ventilator-associated Pneumonia: 2016 Clinical Practice Guidelines by the Infectious Diseases Society of America and the American Thoracic Society. Clin Infect Dis. 2016 Sep 1;63(5):557-82 .
2. Beardsley JR, Williamson JC, Johnson JW, Ohl CA, Karchmer TB, Bowton DL. Using local microbiologic data to develop institution-specific guidelines for the treatment of hospital-acquired pneumonia. Chest. 2006 Sep;130(3):787-93 .
Dr. Botti is a second-year resident in the family medicine residency program department of family and community medicine at Jefferson Medical College, Philadelphia. Dr. Mills is assistant residency program director and assistant professor in the department of family and community medicine and department of physiology at Jefferson Medical College, Philadelphia. Dr. Skolnik is associate director of the family medicine residency program at Abington (Pa.) Memorial Hospital and professor of family and community medicine at Temple University, Philadelphia.
