Colony-forming Units (CFU) in Urine Culture (Nursing)

by Prof. Lawes

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    00:00 Now, you'll see the things about colony-forming units. So I wanted to make sure you and I talked about it. What are colony-forming units? Well, in the urine culture, the number of colony-forming units per mL is an estimate of the number of bacteria in the sample. Okay, cool, that matters, right, because I'm going to have a harder time fighting off an infection that has a high number of colony-forming units versus one that has a lower number of colony-forming units. So we've established that colony-forming units help us estimate how much bacteria there is. Now, we have an actual definition of what infection is or UTI. So, lean in and take a look at that chart. Colony-forming units are on the left-hand side. So, greater than 10 to the 3rd power of the colony-forming units per mL in the urine culture indicates infection. Okay, let's start there. I'm going to give you some other tips after that, but let's just start there.

    01:02 Greater than 10 to the 3rd power which is, right, 1,000 CFUs per mL that means we have infection. So, if it's less than that, can the patient have a UTI? The answer is yes. Now, I'm not trying to confuse you, but what do we always talk about with lab work? You have to compare the number to the actual patient. So the patient may have a UTI if that CFU is less than 10 to the 5th power. What has to be present though is symptoms and urinary leukocytes. So let's move over to the right-hand side of the column and talk about leukocytes. Now, when that's done on a microscopic exam, if you see greater than or equal to 10 leukocytes in the urinalysis, we can diagnose a UTI if they've got those symptoms. Remember this shouldn't be the sole criteria used for diagnosis but you're going to take the numbers that you have, compare them with the patient's symptoms. So, as a general rule, I want you to have greater than 10 to the 3rd power CFUs; however, if the patient has symptoms and greater than or equal to 10 leukocytes, we can still agree the patient likely has a UTI. I've organized this table for you, asymptomatic bacteriuria. Before we leave this section on colony-forming units, I want to give you 2 special notes. One for lower CFUs and one for higher CFUs. So let's start with lower CFUs. Patients with catheter-associated UTIs have lower CFUs. Higher CFU counts happen in the presence of contaminates. So if you see a really high CFU, make sure that sample was collected appropriately because an incorrectly collected specimen could cause contamination and an inappropriately high report of CFUs.

    About the Lecture

    The lecture Colony-forming Units (CFU) in Urine Culture (Nursing) by Prof. Lawes is from the course Interpretation of Renal Lab Values (Nursing).

    Included Quiz Questions

    1. Leukocytes in the urine and the presence of symptoms
    2. Erythrocytes in the urine and the presence of symptoms
    3. Leukocytes and erythrocytes in the urine
    4. Ketones and leukocytes in the urine
    1. Females require two midstream samples for diagnosis
    2. It is the diagnosis that has the most bacteria present in the urine
    3. Symptoms are not present for diagnosis
    4. Males require two midstream samples for diagnosis
    5. Clients with catheters require higher CFUs for diagnosis
    1. An estimate of how much bacteria is in the sample
    2. The type of bacteria in the sample
    3. How sensitive the bacteria is to antibiotics
    4. The rate of growth of bacteria in the sample

    Author of lecture Colony-forming Units (CFU) in Urine Culture (Nursing)

     Prof. Lawes

    Prof. Lawes

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