The current guidelines do not specifically comment on the optimal duration of HCAP therapy or the assessment of HCAP patients not responding to therapy, likely because these areas have not been studied. Regardless, there is ever increasing support for shortening the duration of antibiotic therapies in clinically responding patients regardless of the subset of nosocomial pneumonia. As such, the duration of therapy should likely be closer to seven days than the conventional 14- to 21-day courses of therapy. In the absence of evidence to the contrary, the 2005 guidelines imply that the evaluation of HCAP patients who are not responding to therapy should be the same as for patients with other nosocomial pneumonias not responding to antibiotic therapy.

Although only briefly addressed in the guidelines, the importance of incorporating local microbiologic data cannot be overemphasized. Just as antimicrobial sensitivities vary within institutions, there is likely to be comparable variability between settings in which each subset of HCAP patients comes into contact with the healthcare system.27,28 Although, ideally, every long-term care facility would have its own, frequently updated, antibiogram, this is not feasible either logistically or financially. Due to these limitations, hospital antibiograms are typically employed as a surrogate whenever these patients are hospitalized. Given the similarity of HCAP pathogens to nosocomial organisms, individualized intensive care unit-specific antibiograms will likely better reflect the resistant pathogens of highest concern when prescribing empiric therapy.22,27,28

The implication of the severity of illness in prescribing initial antibiotic therapy is another poorly studied and controversial topic. Because HCAP likely includes a broad spectrum of potential pathogens—both community-acquired and nosocomial—it has been proposed that the presenting severity of illness may be a surrogate marker for the etiologic organisms. This philosophy proposes that less severely ill patients are more likely to have community-acquired organisms that may be successfully treated with more narrow spectrum agents, while those with a higher severity of illness are more likely to have nosocomial pathogens that should be empirically given broad spectrum agents. This topic is not addressed by the current ATS-IDSA guidelines.

Conclusions

The ATS-IDSA nosocomial pneumonia guidelines’ recent definition of HCAP and the attendant recommendations regarding therapies are welcome additions for clinicians who have long struggled with how best to treat these patients. It is important to realize the limitations behind the assertions made in this important document, however. First and foremost, the knowledge base on this topic is limited, and many conclusions are based on expert opinion or extrapolation of concepts relating to other nosocomial infections. What little knowledge is available comes almost exclusively from nursing-home-acquired pneumonia. This is problematic because these studies are plagued with issues regarding their limited or poor-quality microbiologic data.

In several areas, including the need for Legionella therapy, the implications of severity of illness, and the assessment of response to therapy, the data are entirely lacking. As a result, the recommendations for hospital-acquired pneumonia are generally followed in these instances. These facts highlight the need for increased epidemiologic HCAP data to optimize antibiograms, to promote adequate empiric antibiotic therapy, to assess the obsolescence of older trials, and to investigate the similarities and differences among the heterogeneous groups of patients included in the present definition. TH

Drs. Morrow and Malesker both work at Creighton University Medical Center, Omaha, Neb.

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