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COMMUNITY ACQUIRED PNEUMONIA - TYPICAL OR ATYPICAL ? Rajinder Singh Bedi Lung India 2006; 23: 130-131
A number of studies have concluded that there is little use of classifying CAP into atypical or typical one, on the basis of clinical features of radiology, as this classification often can not predict microbial aetiology and thus help in planning the management. In one study, clinical features were only 40 percent accurate in telling the difference between pneumococcal, mycoplasma and other pneumonic infections 2. Similarly, in a study of 196 patients with CAP, multilobar disease, pleural effusion, lobar collapse and cavitations were suf ficient common in patients with pneumococcal pneumonia, Legionnaires disease, mycoplasma and psittacosis so that the radiology could not be used to determine bacterial aetiology 3.
Pneumonia continues to play an important role in medicine. It denotes in flammation of the lung parenchyma caused by a microbial agent. Community acquired pneumonia (CAP) is the most important infection in clinical medicine world wide. Clinically, CAP is often classi fied as “typical” or “atypical.” In typical pneumonia. There is sudden onset of fever, chills, pleuritic chest pain and productive cough. Typical pneumonia is usually caused by bacterial pathogens like Streptococcus pneumoniae, Staphylococcus aureus. Klebsiella pneumoniae, Haemophilus in fluenzae etc. In contrast, atypical CAP is characterized by preceeding upper airway symptoms, myalgias, fever without chills, headache and unproductive cough. The causative organisms responsible for atypical pneumonia include Viruses, Mycoplasma pneumoniae, Legionella pneumophilia, Chlamydia psittaci and Coxiella burnetli etc.
There are two main reasons why clinical features correlate poorly with the microbial aetiology. Certain pathogens such as legionella and C psittacci often produce clinical picture that mimics both typical and atypical syndromes. Secondly, if the host’s immune response is impaired because of comorbid illness or advanced age, even then the clinical features may be changed. Here even bacterial pathogens can produce atypical clinical or radiological features.
In typical pneumonia total leucocyte counts, ESR and CRP are mostly raised ; in contrast to atypical pneumonia, where these parameters are usually normal or only slightly raised. Radiologically, chest radiograph will show lobar or segmental homogeneous homogeneou s opacity in over 80% of typical bacterial pneumonias. But this finding can also be seen in nearly half the cases of atypical aty pical infection. In atypical pneumonias, diffuse patchy or ground glass shadows are more commonly observed.
For guiding therapy for CAP, knowledge of the potential pathogen is very important. As discussed above, in clinical practice it is often dif ficult to predict the microbial aetiology on the basis of clinico-radiological picture. The typical pneumonias often respond well to β lactam antibiotics where as atypical pathogens, being intracellular, do not respond to β lactams but respond to antibiotic such as macrolides, tetracyclines and some quinolones.
In Western countries, nearly 60 - 80% of CAP are caused by bacteria, 10 - 20-% by atypical organisms and a similar proportion by viruses. Over the past few years, several studies have shown that atypical organisms are common, being present in upto 40% of all CAP patients, often as copathogens along with bacterial organisms 1. From India, atypical organisms have rarely been isolated from patients with CAP, mainly due to lack of facilities for culture/serology of these organisms.
In view of these observations, it seems that classifying CAP into typical and atypical may not be very helpful in planning the effective management of CAP. A judicious use of epidemiology, laboratory data and clinical findings is needed to achieve this target.
Sher-e-Punjab unjab Market, Patiala - 147001 (Pb.), , E-mail : rsbedi@sancharne
[email protected], t.in, Correspondence: Dr. Rajinder Singh Bedi, Bedi Clinic & Nursing Home, Sher-e-P Recieved : December 2004 Accepted : March March 2005 130
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Community Acquired Pneumonia - Typical Or Atypical ?
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Nominations Invited For Indian Chest Society Orations/Awards Nominations are invited from members of the Indian Chest Society for the following Orations and Awards for the year 2006 for excellence in scienti fic and meritorius contributions in the field of pulmonary sciences. 1. ICS Oration 2. Silver Jubilee ICS Oration 3. O.A. Sarma Oration (for TB), Both the Indian Chest Society Orations (1 and 2) are awarded for any subject related to respiratory medicine and are open only for members of the Indian Chest Society. The OA Sarma Oration is meant for distinguished contribution in tuberculosis made by any eminent person. Each nomination must include the consent letter of the nominee along with 5 copies of his/her brief curriculum vitae and a summary of the contributions for which the nomination is being made. A nominee (for Oration 1 and 2) must be a member of the ICS at least for the preceding 3 years. All nominations should reach the of fice of the Secretary of Indian Chest Society at following address on before 31 August, 2006. st
Dr. J. K. Samaria Hon. Secretary
Indian Chest Society Plot No. 36-A, Kabir Nagar Durgakund, Varanasi - 221 005 Tel : (0542) 2310333, E-mail :
[email protected]
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