Question

Is a Gram stain of a throat swab useful for making a rapid, presumptive diagnosis of strep throat? Why? Is a Gram stain of a sputum specimen useful in making a rapid, presumptive diagnosis of pneumonia? How is a Gram-stained smear of spectrum useful for evaluating the quality of the specimen? What is the clinical significance of staphylococci isolated from throat specimens? What is the clinical significance of staphylococci isolated from sputum specimens?

Answer 1

1.No a gram stain of a throat swab is not useful for making a rapid presumptive diagnosis of strep throat.This is becauses gram stain shows only presence of gram positive and gram negative bacteria.Strep throat is caused by Streptococcus pyogenes( a gram positive bacteria) but special tests have to be carried out to confirm its presence. Strep throat can can be identified only on blood agar plates.On blood agar plates these colonies appear as small, white colonies that are translucent and convex in shape showing a clear zone of beta hemolysis due to release of toxins that are possess beta hemolytic properties.

2.Yes a Gram stain of sputum specimen can be useful in presumptive diagnosis of pneumonia.It will help to find out the cause of pnemonia as to what type of bacteria are present i.e gram negative or gram positive bacteria.If gram stain is positive it is an indication of presence of streptococcus and staphylococcus bacteria that cause pneumonia.

3.A gram satined smear of sputum is useful in evaluating the quality of the specimen as it reveals if the specimen is can be accepted or not for further evaluation.The quality is determined by the minimum number of squamous epithelial cells and polymorphonucleocytes that are present per power field of microscope at lower magnification..A normal acceptable specimen should display presence of more than 25 leukocytes and less than 10 epithelial cells per power field of microscope at lower magnification.Specimens other than thes ecounts are rejected.

4.The clinical significance of isoltion of staphylococci from throat specimen is that it is an indication of respiratory tract infection such as sinusitis.

5.Sputum specimen is used to diagonise diseases associated with respiratory infections as pneumonia, bronchitis etc.Isolation of staphylococci from sputum specimen is an indication of respiratory tract infection such as pneumonia.