Klebsiella pneumoniae is the second most important bacterial cause of lobar pneumonia. It may have a role in the causation of bronchitis, bronchopneumonia, sinusitis and otitis media. Since it is virtually always resistant to beta-lactam antibiotics and often to other antimicrobials too, prior use of antibiotics tends to select the organisms into a numerically prominent position in the oral flora. Staphylococcus aureus An aerobic Gram-positive coccus, part of the aerobic flora of the nose and throat, it grows readily on usual culture media. It can produce bronchopneumonia or lung abscess following influenza, may give rise to lung abscesses in intravenous drug abusers and is an important cause of nosocomial pneumonia.
Most strains are penicillinase producers and some are methicillin resistant.
Such strains are commonly resistant to many other antibiotics. Mycoplasma pneumoniae Mycoplasmas are bacteria which lack rigid cell walls. They can be grown in the laboratory on special culture media but will not be grown on routine examination of samples. Diagnosis is clinical, radiological and by serological blood tests. Mycoplasma years , where many cases are seen, occur every three to four years, alternating with periods when few, if any, such infections occur.