Atypical pneumonia is a term used to distinguish from typi-cal
pneumonia caused by Streptococcus
pneumoniae. Earlier any patient with sudden onset of fever, chills,
pleuritic pain, and expectoration of blood-tinged sputum was believed to
present with typical pneumonia caused by S.
pneumoniae. The patients not showing these characteristic manifestations
were referred to as having atypical pneumonia. M. pneumoniae, Chlamydia
pneumoniae, and Legionella
pneumophila are three importantagents responsible for atypical pneumonia.
In this condition, these pathogens are usually not isolated from sputum by
rou-tine culture methods.
are usually ineffective against Mycoplasma
because of the absence of cell wall, and these anti-biotics usually act by
inhibiting synthesis of cell wall. Penicillin and cephalosporins are
ineffective against all these pathogens because they do not show intracellular
penetration in these pathogens.