In: Biology
You have isolated an organism from the urine of Patient X, a 24 year old female. It is showing gamma hemolysis on blood agar and the colonies are large with an entire margin and are white in color. You perform a gram stain with the results pictured below.
You perform a catalase test and it produces bubbles. You next perform an oxidase test and it is oxidase negative.
1. What is the next step to take in identifying the organism?
2. If your test is positive, what is the genus and species of the organism?
3. If the test is negative, what further test needs to be done to further confirm the negative result?
4. If the result is truly negative, what further testing needs to be run on this particular specimen? In other words, what organism of this type can cause urinary tract infections in sexually active females and how is it tested? (You will need to do some research to find out these results.)
Oxidase negative normally means the bacterium does not contain cytochrome c oxidase and, therefore, either cannot use oxygen for energy production with an electron transfer chain or employs a different cytochrome for transferring electrons to oxygen.
Enterococci are typically Oxidase negative.
Species identification:
16s rRNA sequencing can be done. Acid production from 1% (w/v)
mannitol, sorbitol, sorbose, L-arabinose, D-ribose, sucrose and
raffinose can be tested in basal M17 broth (Terzaghi and Sandine
1975) (lacking lactose), using bromocresol purple as pH indicator.
Deamination of arginine can be tested in Thornley's semi-solid
arginine medium (Smibert and Krieg 1981). Motility can be using
phase contrast microscopy (Smibert and Krieg 1981). Pigment
production on tryptic soy agar. Tolerance to tellurite can be
tested on GM17 agar containing 0á04% (w/v) potassium tellurite.
Utilization of pyruvate tested using pyruvate broth (Facklam and
Sahm 1995).