Gram Negative Coccobacilli
M. pneumoniae induced pneumonia may be rapidly identified by which of the following procedures?
|A||Cold agglutinin test|
|B||Culture of respiratory secretions in HeLa cells after centrifugation of the inoculated tubes|
|C||Culture of respiratory secretions on monkey kidney cells|
|D||Detection of specific antigen in urine|
a. “Atypical pneumonia” is an old classification used for respiratory disease that is not lobar and is not “typical.” That is, it does not include pneumonia caused by pneumococcus, Klebsiella, Haemophilus, or 13- hemolytic streptococci that results in a typical lobular infiltrate.
b. In recent years, the atypical pneumonias have become much more frequent than pneumococcal pneumonia. They are characterized by a slower onset with headache, joint pain, fever, and signs of an acute upper respiratory infection.
c. There are usually no signs of acute respiratory distress, but patients report malaise and fatigue. The most common cause of atypical pneumonia is M. pneumoniae. A quick test for M. pneumoniae infection is cold agglutinins. The test may lack both sensitivity and specificity, but it is rapid and readily available compared with culture of M. pneulnoniae or specific anti body formation.
d. Particularly in the winter months, influenza must be ruled out. In the early stages of an epidemic, viral isolation in primary monkey cells is used. However, as the epidemic proceeds, diagnosis is usually made clinically or by an increase in antibody titer.
e. In certain age groups (men over 55 years old), Legionnaires’ disease must be ruled out. While direct microscopy, culture, and serology are available, the detection of Legionella antigen in respiratory secretions is the most sensitive test available.
f. Pneumoniae may also cause respiratory infection particularly in, but not limited to, children. Diagnosis is best made by growing these energy- defective bacteria in tissue culture such as HeLa cells. Serology is usually not helpful.
g. During the winter months, Bordetella infection may be quite prevalent, particularly in those patients whose immunizations are not current. Adult Bordetella infection may not present with typical whooping cough symptoms and must be differentiated from other forms of acute bronchitis by culture on specific media or direct fluorescent microscopy