Healthcare Associated Pneumonia 101

Below is a quick review on Healthcare Associated Pneumonia. Big thanks to Mo, Sam, and Kendrick from UT Southwestern Medical School for this post!

Definition

The 2005 American Thoracic Society/Infectious Disease Society of America (ATS/IDSA) guidelines distinguish the following types of pneumonia [1]:

  • Hospital-acquired pneumonia (HAP), or nosocomial pneumonia is pneumonia that occurs 48 hours or more after admission and did not appear to be incubating at the time of admission.
  • Ventilator-associated pneumonia (VAP) is a type of HAP that develops more than 48 to 72 hours after endotracheal intubation.
  • Healthcare-associated pneumonia (HCAP) includes any patient who is either within 90 days of hospitalization at an acute care facility, resided in a long term care facility, within 30 days of intravenous antimicrobial therapy, chemotherapy, or wound care treatment or attends a hospital or hemodialysis clinic.

Epidemiology

Type and prevalence of healthcare acquired infections (HAI) depend on the location of care. Estimated prevalence of acute care HAI is 721,800 or 4% of all inpatients [2]. Hospital acquired pneumonia accounts for roughly 20% of these infections. The prevalence of healthcare acquired infections in long term care facilities (LTC) is less well studied. Total infection prevalence of patients in LTC’s has been estimated to be 12% with UTI, pneumonia and cellulitis being the most prevalent types of infections [3]. Furthermore rates of device associated infections in LTCs are similar to infection rates in ICU’s [4].

Similar rates of HAI appear in Europe as well. European countries reports HAI rates of 6% and 3.4% in acute care hospitals and LTC’s respectively [5,6].

Risk factors

The strongest associated risk factor for HAI’s is length of hospital admission. This by far outweighs other risk factors such as age, hospital size, CCU setting, presence of a central line or presence of a ventilator.

Etiology

Hospitalized patients often become colonized as early as 48 hours after admission. Mechanically ventilated patients can acquire infection through direct contact with environmental reservoirs, such as respiratory devices, and contaminated water reservoirs. In addition, ulcer prophylaxis regimens and enteric feeding can alter gastric pH to disrupt sterility of the stomach and upper GI tract increasing the risk for pneumonia. Common microbes for HCAP include aerobic gram-negative bacilli (eg, Escherichia coli, Klebsiella pneumoniae, Enterobacter spp, Pseudomonas aeruginosa, Acinetobacter spp) and gram-positive cocci (eg, Staphylococcus aureus, including methicillin-resistant S. aureus [MRSA], Streptococcus spp).

The microorganisms that cause HAI’s differ in both species and drug sensitivity compared to community acquired infections. For instance, although the most common microbe in both HCAP and CAP is S. pneumonia, the drug resistant strains of S. pneumonia are more common in HCAP. MRSA is more prevalent in HCAP/HAP patients compared to CAP patients. In ventilator-associated pneumonia (VAP), P.aeruginosa and MRSA infection are often the cause. Patients at risk of harboring multiple drug resistant organisms are those who are hospitalized for more than 2 days, with severe illness, antibiotic therapy within 6months, poor functional status by ADLS and immune compromised. Nosocomial pneumonia due to viruses or fungi is significantly less common, except in the immune-compromised patient.

Diagnosis

HAP, VAP, or HCAP should be suspected in patients with clinical signs of fever, cough, shortness of breath and purulent sputum along with new or progressive infiltrate on chest x-ray and leukocytosis. Empiric antimicrobial therapy is usually started with new infiltrate on chest x-ray and at least two out of three of the following criteria: fever >38ºC, leukocytosis or leukopenia, and purulent secretions. Molecular tests for detection of respiratory pathogens offer more rapid identification of microorganisms but have limited specificity and do not obviate the need for culture. Sputum culture with gram stain should be obtained for all patients with HCAP, VAP and HAP. Specimen likely will be rejected if more than 10 squamous cells per LPF are present as this is a poor sample. Positive sputum cultures should be interpreted within clinical context due to colonization of several bacteria in upper and lower respiratory tract. The following microorganisms are more likely to be normal flora and less likely pathogenic: Candida spp, coagulase-negative staphylococci, enterococci, gram-positive bacilli (other than Nocardia), H. parainfluenzae, and streptococci (other than S. pneumoniae, S. pyogenes, S. agalactiae, and S. anginosus). If sputum samples cannot be obtained by expectoration, bronchoscopy should be considered. Bronchoscopy is particularly useful to diagnose mycobacterium tuberculosis, P. jirovecii (formerly P. carinii) or fungal pathogens.

Prevention

The World Health Organization’s Guide for Prevention of Hospital-Acquired Infections lists the following key components as cornerstones of the prevention of general nosocomial infections [7]:

  • Limiting transmission of organisms between patients in direct patient care through adequate hand-washing and glove use, and appropriate aseptic practice , isolation strategies, sterilization and disinfection practices, and laundry
  • Controlling environmental risks for infection
  • Protecting patients with appropriate use of prophylactic antimicrobials, nutrition, and vaccinations
  • Limiting the risk of endogenous infections by minimizing invasive procedures , and promoting optimal antimicrobial use
  • Surveillance of infections, identifying and controlling outbreaks
  • Prevention of infection in staff members
  • Enhancing staff patient care practices, and continuing staff education.

Additionally, the Infectious Disease Society of America released new guidelines in 2014 for strategies to prevent ventilator associated pneumonia [8].   Interventions backed with high quality evidence include use of non-invasive positive pressure ventilation, interrupting sedation daily, assessing readiness to extubate daily and change of ventilator circuit only if visibly soiled.

Management

Antimicrobial selection is based on risk factors for infection with multi-drug resistant bacteria, presence of underlying diseases or conditions, and available culture data and susceptibilities. When healthcare associated pneumonia is first suspected, it is imperative to start therapy early even before cultures and sensitivity information is available. Thus, empiric broad spectrum, multidrug therapy is usually recommended initially until speciation and susceptibility patterns are identified and antibiotic therapy can be narrowed. Information on pathogens frequently encountered in specific healthcare institutions and the associated susceptibilities of those pathogens can help guide proper antibiotic coverage. A common guide for empiric therapy selection adapted from the American Thoracic Society, Infectious Diseases Society of America is given below [1].

Empiric Therapy:

For empiric coverage of HAP and VAP in patients with no known risk factors for multidrug-resistant (MDR) pathogens one of the following agents is usually sufficient to treat the patient.

For patients with known MDR risk factors, the recommended empiric therapy combination includes:

ONE of the following:

  • An antipseudomonal cephalosporin such as cefepime (2 g intravenously every eight hours) or ceftazidime (2 g intravenously every eight hours)
  • An antipseudomonal carbapenem such as imipenem (500 mg to 1 g intravenously every six hours) or meropenem (1 g intravenously every eight hours)
  • Piperacillin-tazobactam (4.5 g intravenously every six hours)

PLUS consider adding one of the following 

  • Antipseudomonal fluoroquinolone, preferred regimen ifLegionellais likely, such as ciprofloxacin (400 mg intravenously every eight hours) or levofloxacin (750 mg intravenously daily).
  • Aminoglycoside such as gentamicinor tobramycin (7 mg/kg intravenously once daily) or amikacin (20 mg/kg intravenously once daily); once-daily dosing is only appropriate for patients with normal renal function.

PLUS ONE of the following if MRSA is suspected, there are MRSA risk factors, or there is a high incidence of MRSA locally:

  • Linezolid (600 mg intravenously every 12 hours; may be administered orally when the patient is able to take oral medications).
  • Vancomycin (15 to 20mg/kg [based on actual body weight] intravenously every 8 to 12 hours for patients with normal renal function, with a target serum trough concentration of 15 to 20 mg/L.)

References

  1. American Thoracic Society, Infectious Diseases Society of America. Guidelines for the management of adults with hospital-acquired, ventilator-associated, and healthcare-associated pneumonia. Am J Respir Crit Care Med 2005; 171:388.
  2. Magill SS, Edwards JR, Bamberg W, et al. Multistate Point-Prevalence Survey of Health Care–Associated Infections. N Engl J Med 2014;370:1198-208.
  3. Dwyer, L. L., Harris-Kojetin, L. D., Valverde, R. H., Frazier, J. M., Simon, A. E., Stone, N. D. and Thompson, N. D. Infections in Long-Term Care Populations in the United States. Journal of the American Geriatrics Society 2013, 61: 341–349. doi: 10.1111/jgs.12153
  4. Chitnis, A. Edwards, J. Ricks, P., et al. Device-Associated Infection Rates, Device Utilization, and Antimicrobial Resistance in Long-Term Acute Care Hospitals Reporting to the National Healthcare Safety Network, 2010. Infection Control and Hospital Epidemiology, 33(10) (2012), pp. 993-1000
  5. European Centre for Disease Prevention and Control. Point prevalence survey of healthcare-associated infections and antimicrobial use in European acute care hospitals – Protocol version 4.3. Stockholm: ECDC; 2012. http://www.ecdc.europa.eu/en/publications/Publications/0512-TED-PPS-HAI-antimicrobial-use-protocol.pdf
  6. European Centre for Disease Prevention and Control. Point prevalence survey of healthcare-associated infections and antimicrobial use in European long-term care facilities. April-May 2013. Stockholm: ECDC; 2014. http://www.ecdc.europa.eu/en/publications/Publications/healthcare-associated-infections-point-prevalence-survey-long-term-care-facilities-2013.pdf
  7. World Health Organization, Department of Communicable Disease. Prevention of hospital-acquired infections. 2nd WHO/CDS/CSR/EPH/2002.12
  8. Klompas M, Branson R, Eichenwald EC, et al. Strategies to prevent ventilator-associated pneumonia in acute care hospitals: 2014 update. Infect Control Hosp Epidemiol 2014; 35:915.