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14.10: Procedures for Case Study #2

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    Choose unknown #3 as your unknown for Case Study #2.

    A hospitalized 57 year old female with an indwelling urinary catheter and multiple antibiotic therapies presents suprapubic discomfort, lower back pain, and a temperature of 101.1°F. A complete blood count (CBC) shows leukocytosis with a left shift. A urine dipstick shows a positive leukocyte esterase test, a negative nitrite test, 30mg of protein per deciliter, and red blood cells in the urine.


    TREAT EACH UNKNOWN AS A PATHOGEN!. Inform your instructor of any spills or accidents. WASH AND SANITIZE YOUR HANDS WELL before leaving the lab.


    • 1 bile esculin agar slant,
    • 1 tube of SF broth,
    • materials to perform a Gram stain,
    • inoculating loop

    PROCEDURE (to be done in groups of 3)

    [Keep in mind that in a real clinical situation other lab tests and cultures for bacteria other than those upon which this lab is based would also be done.]

    1. Do a Gram stain on the unknown (see Lab 6). Make sure you review the instructions before you do the Gram stain. Because Enterococci and Staphylococci can sometimes look similar in Gram stains done from a plate culture, you may wish to run the catalase test on your unknown (see Lab 8).

    2. Inoculate a Bile Esculin agar slant and a SF broth tube with your unknown. Incubate both tubes in your test tube rack on the shelf of the 37°C incubator corresponding to your lab section until the next lab period.


    Medscape articles on infections associated with organisms mentioned in this Lab Exercise. Registration to access this website is free.


    1. Demonstrations of Pneumococci (Streptococcus pneumoniae)

    Blood agar with Taxo P® (optochin) disc

    description of colony  
    type of hemolysis
    (alpha, beta, or gamma)
    Taxo P® disk (optochin)results
    (inhibition or no inhibition)


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    14.10: Procedures for Case Study #2 is shared under a not declared license and was authored, remixed, and/or curated by LibreTexts.

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