Healthcare-associated Pneumonia: The State of Evidence to Date
Purpose of review As evidence about the importance of correct choice of empiric therapy in the setting of pneumonia accumulates, balancing antibiotic spectrum against the risk of selecting for resistant organisms gains importance. Healthcare-associated pneumonia (HCAP) defines a set of risk factors to underscore the probability of a resistant etiologic pathogen, requiring broader spectrum treatment than is generally needed in community-acquired pneumonia (CAP). Controversies persist as to whether HCAP is a useful designation for diagnosis, treatment and outcome prediction.
Recent findings HCAP represents a discrete syndrome, where offending organisms and outcomes differ from those for CAP. However, HCAP designation is neither a sensitive nor a specific system to predict the presence of a resistant organism. Several other instruments have been developed that require prospective validation. Recent findings that CAP guideline-concordant antibiotic treatment among HCAP patients does not alter outcomes is confounded by the emerging understanding that culture-negative HCAP may be successfully treated with therapy targeted at CAP pathogens.
Summary Because HCAP is an important emerging syndrome, a systematic approach to its study is critical. As evidence in this area evolves, it remains important for investigators and clinicians to identify knowledge gaps and to set the research agenda to resolve multiple unanswered questions.
The concept of the healthcare-associated infection (HCAI) continues to gain broad acceptance. The evolution of HCAI as a potentially distinct syndrome attests to the fact that clinicians are frequently encountering traditionally nosocomial pathogens, such as Pseudomonas aeruginosa and methicillin-resistant Staphylococcus aureus (MRSA), in persons presenting to the hospital from the community. Similarly, the development of the HCAI paradigm reflects the need to recognize changes in healthcare delivery and organization, as many traditionally hospital-based interventions now transpire in the ambulatory arena. Thus, HCAI bridges what was thought previously to be a clear divide between community-acquired infection (CAI) and hospital-acquired infection (HAI). HCAI rubric was specifically designed to capture the subgroup of patients with ongoing contact with healthcare which places them at risk for infection with potentially resistant pathogens. Because of the distinct microbiology seen in HCAI and the failure of clinicians to appreciate shifting patterns in epidemiology, patients with HCAI may receive empiric antibiotics not active against the culprit pathogens. This, in turn, results in outcomes that are worse compared to those noted in pure CAIs. Hence, the key usefulness of the HCAI concept lies in its ability to encourage clinicians to differentiate and risk stratify patients for the potential for an infection with a resistant pathogen despite the fact that those with an HCAI present with a syndrome and clinical features comparable to those seen in persons with CAI.
The American Thoracic Society (ATS) and the Infectious Diseases Society of America (IDSA) currently define healthcare-associated pneumonia (HCAP) based on the presence of any one of the following risk factors: hospitalization for 2 days or more in the preceding 90 days; residence in a nursing home (NHR) or extended care facility; home infusion therapy (including antibiotics); chronic dialysis within 30 days; home wound care; and having a family member with a multidrug-resistant pathogen. Based on this profile, the guideline recommends that empiric treatment for a suspected HCAP be different from that for community-acquired pneumonia (CAP) and includes combination therapy with an antipseudomonal cephalosporin or a carbapenem or a β-lactam/β-lactamase inhibitor plus an antipseudomonal fluoroquinolone or an aminoglycoside; linezolid or vancomycin should be added to this combination if the risk of methicillin-resistant Staphylococcus aureus (MRSA) is high. These antibiotic selections are distinctly broader than either a fluoroquinolone or a β-lactam plus a macrolide recommended for treatment of hospitalized patients with CAP. Because of their spectrum of activity, the huge potential size of the HCAP population, and variable ability of physicians to narrow the spectrum of therapy based on cultures, a controversy surrounds the concept of HCAP. The main debate focuses on the ability of the HCAP criteria to identify correctly patients with potentially resistant organisms.
In order to understand the complexities of this ongoing debate, clinicians require an appreciation of recent epidemiologic studies reviewing the prevalence and microbiology of HCAP along with an understanding of other means both to identify better persons presenting to the hospital with resistant pathogens and to facilitate antimicrobial de-escalation.
Abstract and Introduction
Abstract
Purpose of review As evidence about the importance of correct choice of empiric therapy in the setting of pneumonia accumulates, balancing antibiotic spectrum against the risk of selecting for resistant organisms gains importance. Healthcare-associated pneumonia (HCAP) defines a set of risk factors to underscore the probability of a resistant etiologic pathogen, requiring broader spectrum treatment than is generally needed in community-acquired pneumonia (CAP). Controversies persist as to whether HCAP is a useful designation for diagnosis, treatment and outcome prediction.
Recent findings HCAP represents a discrete syndrome, where offending organisms and outcomes differ from those for CAP. However, HCAP designation is neither a sensitive nor a specific system to predict the presence of a resistant organism. Several other instruments have been developed that require prospective validation. Recent findings that CAP guideline-concordant antibiotic treatment among HCAP patients does not alter outcomes is confounded by the emerging understanding that culture-negative HCAP may be successfully treated with therapy targeted at CAP pathogens.
Summary Because HCAP is an important emerging syndrome, a systematic approach to its study is critical. As evidence in this area evolves, it remains important for investigators and clinicians to identify knowledge gaps and to set the research agenda to resolve multiple unanswered questions.
Introduction
The concept of the healthcare-associated infection (HCAI) continues to gain broad acceptance. The evolution of HCAI as a potentially distinct syndrome attests to the fact that clinicians are frequently encountering traditionally nosocomial pathogens, such as Pseudomonas aeruginosa and methicillin-resistant Staphylococcus aureus (MRSA), in persons presenting to the hospital from the community. Similarly, the development of the HCAI paradigm reflects the need to recognize changes in healthcare delivery and organization, as many traditionally hospital-based interventions now transpire in the ambulatory arena. Thus, HCAI bridges what was thought previously to be a clear divide between community-acquired infection (CAI) and hospital-acquired infection (HAI). HCAI rubric was specifically designed to capture the subgroup of patients with ongoing contact with healthcare which places them at risk for infection with potentially resistant pathogens. Because of the distinct microbiology seen in HCAI and the failure of clinicians to appreciate shifting patterns in epidemiology, patients with HCAI may receive empiric antibiotics not active against the culprit pathogens. This, in turn, results in outcomes that are worse compared to those noted in pure CAIs. Hence, the key usefulness of the HCAI concept lies in its ability to encourage clinicians to differentiate and risk stratify patients for the potential for an infection with a resistant pathogen despite the fact that those with an HCAI present with a syndrome and clinical features comparable to those seen in persons with CAI.
The American Thoracic Society (ATS) and the Infectious Diseases Society of America (IDSA) currently define healthcare-associated pneumonia (HCAP) based on the presence of any one of the following risk factors: hospitalization for 2 days or more in the preceding 90 days; residence in a nursing home (NHR) or extended care facility; home infusion therapy (including antibiotics); chronic dialysis within 30 days; home wound care; and having a family member with a multidrug-resistant pathogen. Based on this profile, the guideline recommends that empiric treatment for a suspected HCAP be different from that for community-acquired pneumonia (CAP) and includes combination therapy with an antipseudomonal cephalosporin or a carbapenem or a β-lactam/β-lactamase inhibitor plus an antipseudomonal fluoroquinolone or an aminoglycoside; linezolid or vancomycin should be added to this combination if the risk of methicillin-resistant Staphylococcus aureus (MRSA) is high. These antibiotic selections are distinctly broader than either a fluoroquinolone or a β-lactam plus a macrolide recommended for treatment of hospitalized patients with CAP. Because of their spectrum of activity, the huge potential size of the HCAP population, and variable ability of physicians to narrow the spectrum of therapy based on cultures, a controversy surrounds the concept of HCAP. The main debate focuses on the ability of the HCAP criteria to identify correctly patients with potentially resistant organisms.
In order to understand the complexities of this ongoing debate, clinicians require an appreciation of recent epidemiologic studies reviewing the prevalence and microbiology of HCAP along with an understanding of other means both to identify better persons presenting to the hospital with resistant pathogens and to facilitate antimicrobial de-escalation.
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