Community-acquired pneumonia (CAP) refers to a lower respiratory tract infection, primarily involving the lungs, that is acquired outside the hospital. The usual organisms associated with CAP are respiratory tract pathogens, i.e., Streptococcus pneumoniae, Haemophilus influenzae, Moraxella catarrhalis.<sup>3 Bartlett J.G., Mundy L.M. Community-acquired pneumonia N Engl J Med 1995 ;  333 : 1618-1624  [cross-ref]

Cliccare qui per andare alla sezione Riferimenti, 21 Garibaldi R.A. Epidemiology of community-acquired respiratory tract infections in adults: Incidence, etiology, and impact Am J Med 1985 ;  78 : 32-37  [cross-ref]

Cliccare qui per andare alla sezione Riferimenti, 24 Hirschmann J.V., Everett E.D. Haemophilus influenzae infections in adults: Report of nine cases and review of the literature Medicine 1979 ;  58 : 80-94  [cross-ref]

Cliccare qui per andare alla sezione Riferimenti, 46 Wallace R.J., Musher D.M., Martin R.R. Hemophilus influenzae pneumonia in adults Am J Med 1978 ;  64 : 87-93

Cliccare qui per andare alla sezione Riferimenti, 47 Wallace R.J., Musher D.M. In honor of Dr. Sarah Branham. A star is born: The realization of Branhamella catarrhalis as a respiratory pathogen Chest 1986 ;  90 : 447-450  [cross-ref]

Cliccare qui per andare alla sezione Riferimenti, 48 Woodhead M.A., Radvan J., Macfarlane J.T. Adult community-acquired staphylococcal pneumonia in the antibiotic era: A review of 61 cases Q J Med 1987 ;  64 : 783-790

Cliccare qui per andare alla sezione Riferimenti</sup> Less commonly, other organisms may cause CAP under special circumstances. These include Staphylococcus aureus pneumonia following viral influenza pneumonia, Klebsiella pneumonia in alcoholics, and only rarely other aerobic gram-negative pathogens. Aspiration pneumonia is also included under the broad general category of CAP. Community-acquired aspiration pneumonia is caused by the aspirated polymicrobial oropharyngeal flora, which are primarily anaerobic.<sup>2 Bartlett J.G. Anaerobic bacterial pneumonitis Am Rev Resp Dis 1979 ;  119 : 19-23

Cliccare qui per andare alla sezione Riferimenti</sup> The most common anaerobic organisms associated with community acquired aspiration pneumonia include anaerobic streptococci and the so-called oral-pigmented Bacteroides, i.e., B. melaninogenicus as well as Peptococcus vianella, etc.<sup>14 Fang G.D., Fine M., Orloff J. , e al. New and emerging etiologies for community-acquired pneumonia with implication for therapy: A prospective multicenter study of 359 cases Medicine 1990 ;  69 : 307-316

Cliccare qui per andare alla sezione Riferimenti, 16 Fekety F.R., Caldwell J., Grump D. , e al. Bacteria, viruses, and mycoplasmas in acute pneumonia in adults Am Rev Resp Dis 1971 ;  104 : 499-507

Cliccare qui per andare alla sezione Riferimenti, 22 Gleckman R., DeVita J., Hibert D. , e al. Sputum Gram's stain assessment in community-acquired bacteremic pneumonia J Clin Microbiol 1988 ;  26 : 846-849

Cliccare qui per andare alla sezione Riferimenti, 25 Holmberg H. Aetiology of community-acquired pneumonia in hospital-treated patients Scand J Infect Dis 1987 ;  19 : 491-501  [cross-ref]

Cliccare qui per andare alla sezione Riferimenti, 37 MacFarlane J.T., Finch R.G., Ward M.J. , e al. Hospital study of adult community-acquired pneumonia Lancet 1982 ;  2 : 255-258  [cross-ref]

Cliccare qui per andare alla sezione Riferimenti, 39 Moine P., Vercken J.-P., Chevret S. , e al. Severe community-acquired pneumonia Chest 1994 ;  105 : 1487-1495  [cross-ref]

Cliccare qui per andare alla sezione Riferimenti, 49 Woodhead M.A., Arrowsmith J., Chamberlain-Webber R. , e al. The value of routine microbial investigation in community-acquired pneumonia Respir Med 1991 ;  85 : 313-317  [cross-ref]

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Atypical pneumonias are caused by atypical rather than unusual pathogens. Depending on geographical factors, the organisms responsible for atypical pneumonia are quite varied. Community-acquired atypical pneumonias may be viewed as consisting of two groups of organisms, primarily nonzoonotic or zoonotic in their mode of transmission.<sup>13 Cunha B.A. Atypical pneumonias Current Diagnosis 9 Philadelphia: WB Saunders (1997).  311-312

Cliccare qui per andare alla sezione Riferimenti</sup> Zoonotic atypical pneumonias include psittacosis, Q fever, and tularemia; the nonzoonotic atypical pneumonias consist of Mycoplasma pneumoniae, Chlamydia pneumoniae, and Legionnaires' disease. It is important to appreciate that coinfections with one or more atypical pathogens, or an atypical pathogen and a bacterial pathogen are rare.<sup>5 Cunha B.A. Legionnaires' disease Infect Dis Pract 1994 ;  18 : 72

Cliccare qui per andare alla sezione Riferimenti, 11 Cunha B.A., Ortega A.M. Atypical pneumonias Postgrad Med 1996 ;  99 : 123-132

Cliccare qui per andare alla sezione Riferimenti, 23 Heath C.H., Grove D.I., Looke D.F. Delay in appropriate therapy of Legionella pneumonia associated with increased mortality Eur J Clin Microbiol Infect Dis 1996 ;  5 : 286-290  [cross-ref]

Cliccare qui per andare alla sezione Riferimenti, 35 Lieberman D., Porath A., Schlaeffer F. , e al. Legionella species community-acquired pneumonia: A review of 56 hospitalized adult patients Chest 1996 ;  109 : 1243-1249  [cross-ref]

Cliccare qui per andare alla sezione Riferimenti, 40 Plouffe J.F., Herbert M.T., File T.M. , e al. Ofloxacin versus standard therapy in treatment of community-acquired pneumonia requiring hospitalization Antimicrob Agents Chemother 1996 ;  40 : 1175-1179

Cliccare qui per andare alla sezione Riferimenti, 45 van Riemsdijk, van Overbeeke I.C., van den Berg B. Severe legionnaire's disease requiring intensive care treatment Neth J Med 1996 ;  49 : 185-188

Cliccare qui per andare alla sezione Riferimenti</sup>

All typical and atypical pathogens causing CAP may present clinically with varying severity, depending on the pathogen, host defense status, underlying lung disease, associated systemic illnesses, and the size of the infecting inoculum.<sup>17 Fine M.J., Orloff J.J., Arisumi D. , e al. Prognosis of patients hospitalized with community-acquired pneumonia Am J Med 1990 ;  88 : 5

Cliccare qui per andare alla sezione Riferimenti, 18 Fine M.J., Hanusa B.H., Lave J.R. , e al. Comparison of medis groups admission severity groups and a pneumonia-specific severity index for patients hospitalized with community-acquired pneumonia J Gen Intern Med 1995 ;  10 : 359-368  [cross-ref]

Cliccare qui per andare alla sezione Riferimenti, 19 Fine M.J., Smith M.A., Carson C.A. , e al. Prognosis and outcomes of patients with community-acquired pneumonia JAMA 1996 ;  274 : 134-141

Cliccare qui per andare alla sezione Riferimenti, 20 Fine M.J., Hough L.J., Medsger A.R. , e al. The hospital admission decision for patients with community-acquired pneumonia Arch Intern Med 1997 ;  157 : 36-44

Cliccare qui per andare alla sezione Riferimenti, 38 Marrie T.J., Durant H., Yates L. Community-acquired pneumonia requiring hospitalization: Five year prospective Rev Infect Dis 1989 ;  11 : 586-599  [cross-ref]

Cliccare qui per andare alla sezione Riferimenti</sup> Although each of these pathogens can cause death under certain circumstances, fulminant disease is more frequently associated with some of these organisms, all other factors being equal.<sup>15 Farr B.M., Sloman A.J., Fisch M.J. Predicting death in patients hospitalized for community-acquired pneumonia Ann Intern Med 1991 ;  115 : 428-436

Cliccare qui per andare alla sezione Riferimenti, 34 Leroy O., Santré C., Beuscart C. , e al. A five-year study of severe community-acquired pneumonia with emphasis on prognosis in patients admitted to an intensive care unit Intensive Care Med 1995 ;  21 : 24-31  [cross-ref]

Cliccare qui per andare alla sezione Riferimenti</sup> Acute fulminating CAP is more associated with pneumococci than with H. influenzae, for example.<sup>46 Wallace R.J., Musher D.M., Martin R.R. Hemophilus influenzae pneumonia in adults Am J Med 1978 ;  64 : 87-93

Cliccare qui per andare alla sezione Riferimenti</sup> Except when it occurs in patients with a severe underlying cardiac, pulmonary, or systemic illness, M. catarrhalis pneumonia is rarely severe.<sup>47 Wallace R.J., Musher D.M. In honor of Dr. Sarah Branham. A star is born: The realization of Branhamella catarrhalis as a respiratory pathogen Chest 1986 ;  90 : 447-450  [cross-ref]

Cliccare qui per andare alla sezione Riferimenti</sup> Group A streptococcal pneumonia, S. aureus pneumonia, and Klebsiella pneumonia usually result in clinically severe pneu-monias.<sup>29 Jong G.M., Hsiue T.R., Chen C.R. , e al. Rapidly fatal outcome of bacteremic Klebsiella pneumonia in alcoholics Chest 1995 ;  107 : 214-217  [cross-ref]

Cliccare qui per andare alla sezione Riferimenti, 30 Karalus N.C., Cursons R.T., Leng R.A. , e al. Community-acquired pneumonia: Etiology and prognostic index evaluation Thorax 1991 ;  46 : 413-418  [cross-ref]

Cliccare qui per andare alla sezione Riferimenti</sup> Among the atypical pathogens, Legionella is most likely to present as a severe CAP, but M. pneumoniae pneumonia in compromised hosts may be a life-threatening illness.<sup>23 Heath C.H., Grove D.I., Looke D.F. Delay in appropriate therapy of Legionella pneumonia associated with increased mortality Eur J Clin Microbiol Infect Dis 1996 ;  5 : 286-290  [cross-ref]

Cliccare qui per andare alla sezione Riferimenti, 45 van Riemsdijk, van Overbeeke I.C., van den Berg B. Severe legionnaire's disease requiring intensive care treatment Neth J Med 1996 ;  49 : 185-188

Cliccare qui per andare alla sezione Riferimenti</sup> Usually, C. pneumoniae is a relatively mild and benign illness. Psittacosis, Q fever, and tularemia are serious problems, but usually do not present as acute fulminating CAPs (Table 1).<sup>35 Lieberman D., Porath A., Schlaeffer F. , e al. Legionella species community-acquired pneumonia: A review of 56 hospitalized adult patients Chest 1996 ;  109 : 1243-1249  [cross-ref]

Cliccare qui per andare alla sezione Riferimenti</sup>