It has been challenging trying to awaken my recollections of all of the information I learned in microbiology. Although it seems like yesterday, a year is just about enough time to forget all those little details. It's coming back to me now though. There were lots of bells ringing in lab this week.
It started yesterday when I received a blood culture bottle and case history for a 70 year old woman with multiple myeloma who was experiencing classic signs of a respiratory infection. I started off my investigation with a Gram Stain, but unfortunately nothing showed up. The only thing left to do was plate the blood culture out on chocolate agar and wait until the following day.
The following day and saw this!!!
Then I did a gram stain and saw this!!!
The presence of raised, umbilicate or flattened, gray colonies on the chocolate agar and gram positive lancet shaped diplococci on the gram stain directed my efforts to finding a confirmatory method for the identification of Streptococcus pneumoniae. I performed a bile solubility test on two of the colonies. Bile solubility is performed to differentiate Streptococcus pneumoniae from other alpha-hemolytic species of streptococcus. S. pneumoniae undergoes autolysis when exposed to bile salts by lowering the surface tension between the medium and the bacterial cell membrane. After the addition of bile salts my colony had diminished, which is a positive finding for bile solubility and the identification of S. pneumoniae. That is when I did some additional research on S. pneumoniae to determine the clinical significance and happened upon the battle between S. pneumoniae and Haemophilus influenzae.
Streptococcus pneumoniae vs. Haemophilus influenzae:
IN VITRO: S. pneumoniae overpowers H. influenzae by attacking it with hydrogen peroxide.
IN VIVO: H. influenzae is the only bacteria that survives when both are placed into the nasal cavity. That begs the question..."Why doesn't the hydrogen peroxide work for S. pneumoniae in vivo?" One of two hypotheses...The individuals immune system is triggered to attack S. pneumoniae when it attacks H. influenzae, or the presence of both species triggers a response that is not triggered by one species alone.
Interesting...for more information check out this link:
http://www.phschool.com/science/science_news/articles/bacterial_snitch.html
This "streptococcus" posting, completely useful..
ReplyDelete