Question

Streptococcus Case Study A 75-year-old man, Tony G., presented to the emergency room with fever, shortness of breath, chest pain, and severe, extremely productive cough. Tony had been a heavy smoker for almost 50 years before he quit 7 years ago, when he was diagnosed with emphysema. Tony occasionally used oxygen at home when he had difficulty breathing, and on presentation he was using portable oxygen because of his severe respiratory distress. A chest x-ray revealed a right lower lobe infiltrate, and Tony was admitted to the hospital. Sputum, urine, and blood cultures were collected. The direct Gram's stain of the sputum specimen revealed the following: Many neutrophils (>25 per low-power field) Rare squamous epithelial cells (<1 per-low-power field) Many gram-positive lancet-shaped diplococci and cocci in short chains (>25 per oil immersion field) Few gram-negative diplococci (<10 per oil immersion field) Few gram-positive bacilli (<10 per oil immersion field) After overnight incubation at 35C in 5% to 7% co, a blood-agar plate inoculated with the specimen revealed a mixture of two colony type. Rare, non-hemolytic, tiny, white, dry-looking colonies were present. A predominance of small, wet-looking, convex (crater-form), entire-edged colonies were also seen, with a greening of the medium around them. The urine culture showed no growth at 24 hours. All blood cultures were negative after 5 days incubation. Questions: 1. Based on the direct Gram's stain, what is the quality of this sputum specimen? Is this specimen of acceptable quality to provide clinically relevant information? 2. Based on the colony morphology and the Gram's stain, what organism is suspect as the cause of Tony's pneumonia? 3. What other (nonpathogenic) organisms commonly found in this type of specimen this type of hemolysis? 4. What laboratory tests are useful in differentiating these organisms and identifying the pathogen? List at least two tests, and be sure to include expected reactions for each organism 5. Organisms other than the predominant organism were seen in the Gram's stain and culture. Does this mean that the patient has polymicrobial pneumonia? Why are those other organisms present.

Answer 1

1. The sputum is considered as an acceptable quality. It is determined by two criteria, If neutrophils is more than 25 per low power field and squamous epithelial cells less than 10 per low power field.In the above case the neutrophils are more than 25 and the squamous epithelial cells are rare and less than 1 indicates that it is in acceptable quality.

2. The organism is streptococcus pneumoniae. These are the organisms are lancet shape diplococci, gram positive organism and are in short chains.

3. Other organisms found are gram negative diplococci and gram positive bacilli. It can be any organism under the category. They are less in number hence they are non pathogenic. It can be viridens streptococci it cause green coloration around colonies.

4. Coagulase test is used to differentiate streptococcus aureus from the other organisms. Coagulase is the enzyme produced by this organism.In Coagulase test the organism present in the specimen will produce the enzyme. The reaction if clumping occurs test is positive. Thus it differ from other organisms. By the gram staining can differentiate the other two gram negative organisms. In gram staining when the dye is added the negative organism vanish its color but the gram positive organism retain its crystal violet color. This is the reaction of the gram negative organisms.Optochin sensitivity can be check these viridians are non sensitive while s. auerus are sensitive. These two test helps to identify the organisms.

5. Predominant organism is streptococcus aureus.It is not the polymicrobial pneumonia. The other are normal flora thats why it is present there. The others are low in number hence not to include with polymicrobial pneumonia.