Community-Acquired Pneumonia

Joseph P. Lynch, III, M.D., Thomas M. File, Jr., M.D.

Despite advances in the development of new and more potent antibiotics, community-acquired pneumonia (CAP) continues to be a leading cause of illness for the world's population. CAP is one of the leading causes of death in the United States, accounting for ~65,000 deaths in 2002,[1] and is responsible for more than 10 million physician visits a year and ~1.4 million hospital discharges.[2] The emergence of newly recognized pathogens and drug-resistant bacteria, particularly Streptococcus pneumoniae, increases the challenge to effectively treat this infection. Practicing physicians need to be aware of new information, which impacts the management needed to provide optimal care for patients. This issue of Seminars in Respiratory and Critical Care Medicine includes contributions from world-renowned experts in the field of CAP who have provided state-of-the-art information on important aspects of the clinical management of CAP.

In the first article, Ramírez describes an international network of investigators, the Community-Acquired Pneumonia Organization (CAPO), which collects extensive information concerning the care of patients with CAP from many international locations. Ramírez evaluates various processes of care provided to hospitalized patients and finds the greatest opportunities for improvement in prevention of CAP, initial empirical therapy, and switch from intravenous to oral antibiotics. He also indicates that care recommended by national guidelines is not being appropriately delivered to adults in all regions of the world, and suggests that new interventions are necessary to improve clinical and economic outcomes in CAP.

In the second article, Wunderink and Waterer describe variable clinical presentations of CAP that may be related to specific genetic predispositions, and review genetic studies evaluating host response to infection. They review the potential value of the findings of genetic studies in CAP and suggest the management of an individual patient may be optimized by therapy based on the individual's genotype for molecules important in outcome.

Several articles in this issue provide up-to-date information concerning specific pathogens that cause CAP, including a newly recognized one, community-onset methicillin-resistant Staphylococcus aureus (MRSA). In the first of these, Örtqvist et al provide a comprehensive review of the most common cause of CAP, Streptococcus pneumoniae, and they include information regarding the epidemiology, diagnosis, treatment, and prevention. Concerning appropriate treatment of pneumococcal pneumonia, Lynch and Zhanel review the issue of drug-resistant strains and discuss the clinical relevance of these strains to clinical outcome. As they note, clinical failures often reflect factors other than antimicrobial susceptibility of the infecting organisms. They review new studies evaluating optimal antimicrobial therapy of severe pneumococcal pneumonia.

Blasi et al discuss the importance of Mycoplasma and Chlamydophila as causes of CAP, including appropriate methods of diagnosis and treatment. They conclude that the current opinion supports antibiotics that include activity against atypicals whenever they are suspected. In the subsequent article, Pedro-Botet and Sabrià review Legionella pneumonia and indicate that community-acquired legionnaires' disease has dramatically increased in the Legionella urinary (LUA) antigen era. Appropriate therapy is necessary to reduce the morbidity and mortality of this serious infection. Finally, concerning specific pathogens, Bradley describes the characteristics of a newly described pathogen, community-associated (also referred to as community-acquired or community-onset) methicillin-resistant S. aureus (CA-MRSA), which has recently emerged as a cause of serious CAP. CA-MRSA strains are distinct from hospital-acquired strains from an epidemiological, genotypic, and phenotypic perspective. They tend to be less resistant to antimicrobials than hospital-acquired MRSA strains and almost always contain a novel type IV Staphylococcus cassette chromosome (SCC) mec gene. In addition, many of these strains have been found to contain the gene for Panton-Valentine leukocidin (PVL), a toxin that has been associated with clinical features of serious disease.

In the seventh article Dubois et al discuss an interesting concept-the use of antibody-mediated therapies as treatment options for respiratory viruses. They speculate that the use of new vaccination strategies which induce high titers of virus-specific immunoglobulin (Ig)G and IgA as well as development of passive monoclonal and polyclonal antibody therapies may provide more effective protection against many important respiratory viral illnesses.

In the final article, Loeb reviews the epidemiology of pneumonia in residents of nursing homes and other long-term care facilities (LTCFs). The clinical diagnosis of pneumonia among long-term care facility residents is often challenging because the clinical manifestations may be altered and patients tend to be more debilitated than their elderly community-dwelling counterparts. Functional status is an important predictor of outcome in this population. Immunization with influenza and pneumococcal vaccines remains a mainstay of prevention.

This issue of Seminars should be a valuable resource for clinicians providing care for patients with CAP. We believe the information presented here will be instructive and of practical value to our readers.

REFERENCES

• 1 National Vital Statistics Report .Death and percentage of total deaths for the 10 leading causes of death, by race: United States, 2002. Centers for Disease Control and Prevention 2005 53: 9
• 2 DeFrances C J, Hall M J, Podgornik M N. 2003 National Hospital Discharge Survey.  Advance data from vital and health statistics. 2005;  359 1-20