Why Do Culture Results Take So Long (About 5+ Days)

Why Do Culture Results Take So Long (About 5+ Days)


With an infection, it is not unusual to
obtain a culture in order to determine what germs are present as well as what
antibiotic will work best to get rid of it. Regardless of how and where the
culture is obtained, the same basic steps are followed. In this example, we have a
patient with a severe ear infection with pus that has been coming out of her
right ear for the past few weeks that has not responded to antibiotics. A
culture is obtained of the pus that is coming out of the ear with a q-tip swab.
This is placed in a tube for transport. In this second example, we have a patient
that has been suffering from high spiking fevers. Blood is drawn from the
patient and into a blood culture bottle. Once the blood cultures have been
obtained, they are placed into a bag for transport. Both these culture samples are
delivered to the microbiology lab where a technician logs the samples into a
computer. The blood cultures are placed inside an
incubator to allow any infection present to grow further before processing. The
ear culture is placed in a holding bucket along with other samples that has
been collected from other patients. The ear culture swab is moved under a
special ventilated hood to prevent contamination. After labeling, the swab is
streaked onto four different algar plates as well as a slide. Each plate
contains a different type of medium or food which allows for differentiation of
what germ may be present as it grows. A loop further streaks out the specimen
on the agar plates. The plates are inserted into an incubator to allow any
germ to grow. Sometime within the next five days. blood
cultures which have been allowed to incubate are now removed and placed
under the hood. Just as with the ear culture swabs, the blood cultures are
applied onto agar plates streaked with a loop and placed in an incubator to
allow for further differentiated growth. The slides which have been set aside are
now brought over to a sink for further processing. The slides are stained and
fixed with special chemicals followed by rinses. This process is used to Gram
stain any organisms present for rough classification of the infectious
organism. Once the slides have been air-dried, the
slides are then examined under the microscope to visualize any germs
present and classified as either gram positive or gram negative. In this case,
gram positive cocci are identified that resemble Staphylococcus. However to
determine whether MRSA is present or not
takes more testing. The next day, the ear culture and blood culture agar
plates which have been placed in the incubator are removed and carefully
examined by a microbiologist. By seeing within which plates growth has occurred,
identification of the infecting organism can be made and reported. For the ear
culture, a diagnosis of Staphylococcus aureus is made. However the next question
is whether this infection is resistant to any antibiotics or not. The main
concern is whether MRSA is present otherwise known as M R S A.
As such, sensitivities will be performed on the ear culture. The agar plates are
taken to a station where a swab of the organism is diluted inside a test tube. A detector ensures the proper amount of
dilution has occurred. A cartridge containing a panel of different
antibiotics for the germ to be tested against is then placed with the test
tube inside a machine that will then process the sample. The next day, the machine will provide a
report of what antibiotics the infection is sensitive and resistant to allowing a
physician to provide the best antibiotic that will kill the germ. For the ear
culture, it was found to be MRSA. The blood culture obtained from our second
example did not end up revealing any infection in the blood. This culture and
sensitivity process applies to any culture obtained from anywhere else in
the body.

Author: Kennedi Daugherty

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