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Mineola, NY
Dr. Hiramatsu is Visiting Scholar, Division of Pulmonary and Critical Care Medicine, Winthrop-University Hospital, and is affiliated with the Fourth Department of Internal Medicine, Nippon Medical School, Tokyo, Japan. Dr. Niederman is affiliated with the Department of Medicine, Division of Pulmonary and Critical Care Medicine, Winthrop-University Hospital.
Correspondence to: Michael S. Niederman, MD, Chairman, Department of Medicine, Winthrop-University Hospital, 222 Station Plaza N, Suite 509, Mineola, NY 11501; e-mail: mniederman{at}winthrop.org
Patients residing in long-term care facilities, and individuals who have recently been hospitalized or who have come in contact with the health-care environment (eg, therapy in a dialysis center) are an expanding part of our population. In 1990, approximately 1.6 million people resided in nursing homes, but this number is expected to reach 5.3 million in 2030.12 In this population, infection is more common than in individuals residing in the community, and lower respiratory tract infection, including pneumonia, is the second most common infection.34 In the nursing home population, the median rate of pneumonia is 365 per 1,000 persons, compared to 34 per 1,000 persons in those over 75 years of age who live in the community.4 When a resident of a long-term care facility requires transfer to the hospital for the treatment of infection, pneumonia is the most common cause, and 10 to 18% of all admissions to the hospital for pneumonia are among nursing home residents.4
Over the last several years, a number of investigators567 have documented that the pathogens infecting patients coming from the health-care associated (HCA) environment may be different from the pathogens seen in patients from other populations who have been admitted to the hospital from the community. In fact, because of their contact with the health-care environment, these patients may already be colonized with drug-resistant pathogens, importing these organisms at the time of admission to the hospital. For example, in one study of 383 patients with methicillin-resistant Staphylococcus aureus (MRSA) infections, 123 organisms were isolated from patients who had been in the hospital < 48 h, and only 1 of these was a true community-acquired isolate.5 The remainder of patients were from long-term care facilities (21 patients) or had been recently hospitalized or treated in an outpatient facility (94 patients), while the rest had received dialysis or visiting nurse care, or had undergone day surgery. In another study of 1,100 MRSA infections, 85% were health-care–related.6 In this study, the definition of HCA infection was a history of hospitalization, surgery, dialysis, or residence in a long-term care facility within a year of contracting the infection, or the presence of a permanent indwelling catheter or percutaneous medical device (eg, gastrostomy, tracheostomy, or Foley catheter). This pattern of patients with HCA infection bringing multidrug-resistant (MDR) pathogens with them to the hospital, also applies to enteric Gram-negative organisms. In a 6-year study7 of patients who harbored MDR Gram-negative organisms in clinical cultures collected within the first 48 h of hospital admission, the prevalence of isolates rose for Escherichia coli, Klebsiella species, and Enterobacter cloacae, but not for Pseudomonas aeruginosa, which remained a common pathogen during the entire period. Fifty-three percent of these isolates were resistant to three antimicrobial groups, and 12% were resistant to five antibiotic classes. The risk factors associated with infection with these pathogens were as follows: prior exposure to antibiotics; prior residence in a long-term care facility; and age 
65 years.
While most of the epidemiology of HCA infections has not been focused strictly on pneumonia, the same trends also apply to pneumonia arising in residents of long-term care facilities. For example, in a study of 95 elderly pneumonia patients, those admitted from a nursing home, compared to those admitted from the community, had a higher frequency of enteric Gram-negative organisms and S aureus, and a lower frequency of pneumococcus.8 In another study9 of patients with severe pneumonia who had been admitted from a nursing home, the frequency of MDR pathogens was increased in those who had recently received antibiotics and in those who also had a worse functional status (defined by the performance of activities of daily living).
Despite this information, we have few studies that have used the same methodology to compare the bacteriology and outcomes of those persons with pneumonia arising in the community (ie, community-acquired pneumonia [CAP]) with those having health-care–associated pneumonia (HCAP), those nonintubated patients with hospital-acquired pneumonia (HAP), and those with ventilator-associated pneumonia (VAP). In the current issue of CHEST (see page 3854), Kollef and colleagues10 have tackled this problem by retrospectively analyzing a large inpatient database. The study defined 4,543 culture-positive pneumonia patients, of whom 2,221 had CAP (48.9%), 988 had HCAP (21.7%), 835 had HAP (18.4%), and 499 had VAP (11%) The definition of HCAP required the patient to have the first positive bacterial respiratory tract culture within 2 days of hospital admission, and to have come from a health-care facility, be receiving hemodialysis, or have been hospitalized within the past 30 days. Although the database could not necessarily allow the investigators to separate colonization from infection, or to tell whether the isolated pathogen was actually causing the respiratory infection, the epidemiologic, bacteriologic, and outcomes data were interesting, and help to better define the entity of HCAP.
In the study, HCAP patients were significantly older than CAP patients (77 vs 65 years), but were similar to those with HAP. Half of the HCAP patients came from nursing homes, which was a far higher percentage than the percent residing in long-term care facilities among patients with HAP and VAP. Illness severity was similar in both HCAP and VAP patients, but was higher than that seen in those patients with CAP and HAP. The bacteriologic data were unusual, since S aureus was the most common pathogen in patients with all four types of pneumonia, including CAP. This may have been an artifact of the inclusion criteria for the study, but even in CAP patients, pneumococcus was seen in only 16.6%, compared to 25.5% of patients with S aureus. In the HCAP population, the bacteriology was very similar to the HAP and VAP populations, with 46.7% having S aureus (MRSA, 56.8%), 25.3% harboring P aeruginosa, while other Gram-negative organisms were also common. The mortality rate of HCAP patients (19.8%) was similar to that of HAP patients, but was higher than that of CAP patients (10%) and lower than that of VAP patients (29.3%). In addition, the length of hospital stay increased progressively for CAP, HCAP, HAP, and VAP patients, and, in parallel with this, hospital costs increased for each of the four groups in the same order.
The findings in this study establish very clearly that HCAP is a unique entity and one that differs from CAP, and in many ways is similar to nosocomial pneumonia, either HAP or VAP. HCAP differs from CAP in both its bacteriology and outcomes, and thus therapy for these two groups should probably be approached differently. This conclusion fits very well with the recently published American Thoracic Society/Infectious Disease Society of America guidelines11 for the treatment of nosocomial pneumonia, which included patients with HCAP, and suggested that these individuals be treated differently from CAP patients, but similarly to those with HAP and VAP. The guideline definition for HCAP included the following: hospitalization for 2 days in the preceding 90 days; residence in a nursing home or extended care facility; home infusion therapy; long-term dialysis within 30 days; home wound care; and exposure to family members infected with MDR pathogens. In the guideline, which was corroborated by the current study, patients with HCAP were recommended to be treated for potential MDR pathogens, including resistant Gram-negative organisms and MRSA.
The publication of these recommendations has been recognized by the Centers for Medicare and Medicaid Services (CMS) in their application of "core measures" for the treatment of CAP. Since July 2005, CMS has decided to exclude HCAP patients from adherence to the CAP antibiotic therapy recommendations. Thus, if a clinician chooses to treat a nursing home pneumonia patient with an anti-pseudomonal ß-lactam antibiotic (eg, cefepime, imipenem, meropenem, or piperacillin/tazobactam) or an MRSA drug (eg, vancomycin or linezolid), that clinician will not be out of compliance with the core measure recommended therapy. The current study adds further justification to this decision. It is, however, important to realize that the inclusion of HCAP in the nosocomial pneumonia guidelines and algorithms means that empiric therapy for HCAP patients will not routinely include atypical pathogens, as is the case in CAP patients; this requires vigilance, since outbreaks of atypical pathogen pneumonia can occur among nursing home residents. In addition, there may be some patients with HCAP (such as those with a risk factor only of recent antibiotic therapy for a short time or dialysis) who may not be at high risk for infection with MDR pathogens, and they may be treated too broadly if the nosocomial pneumonia approach is used. Clearly, we need more data on this subject, but the current study by Kollef and colleagues10 goes a long way to helping sort out this important issue.
References
This article has been cited by other articles:
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  Healthcare-Associated Pneumonia -- An Important New Entity Journal Watch Infectious Diseases, January 27, 2006; 2006(127): 8 - 8. [Full Text]
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