Download 250ch22 study guide

CHAPTER 22
STUDY GUIDE
What system is based on infrared spectrophotometry?
Automated Blood Culture Systems such as NR-660, NR-730 and the NR-860
What system is based on an internal colorimetric sensor?
BacT/Alert Microbial Detection System
Some important parameters in selection of automated methods include:
Easy to use, cost effective, accurate. Electronic monitoring and audible alarms to alert the
operator.
Which systems produce same day results?
Identification and susceptibility instruments, totally automated systems will produce
same day results
How does bioluminescence detect the presence of bacteria?
By detecting the presence of bacterial adenosine triphosphate (ATP) in urine
What does the Bac-t screen detect the presence of?
Pyuria and bacteriuria
How are AMS Vitek test cards filled?
Using a vacuum chamber
Define:
Off-line incubation- 5 hour or overnight incubation at a standard temperature of 35 to
37° C, takes place after inoculation,
Nephelometer- specially designed spectrophotometer with a fixed or variable angle of
detection for measuring light scattered by particles, used to adjust the density of the test
inoculum
Growth index- the measurement of microbial metabolism given a numeric value.
Reflectometer- is an instrument that measures the amount of light
Luciferin/luciferase- chemical used to detect any microbial ATP present, detectable
light is emitted as a by-product
Colorometric sensor- a sensor that is sensitive to carbon dioxide and is able to change
color with increasing levels produced.
Fluorogenic substrate- nonfluorescent molecule that becomes fluorescent when
modified by an enzymatic process.
Minimal inhibitory concentration- compared with the growth rate in the positive
control well to determine the minimal inhibitory concentration (MIC), shows the rate at
which an antimicrobial agent inhibits the growth of bacteria. This is calculated from the
composite slope and the coefficients for that particular organism/drug combination
One of the last laboratory disciplines to become automated- Clinical microbiology
labs have been on of the last disciplines in the lab to become automated
What methods are traditionally growth dependent?
Conventional testing methods in microbiology were traditionally growth dependent. This
method called for overnight incubation times and wasn’t compatible with rapid testing.
What type of instruments are used to screen urine for the presence of bacteriuria
and pyuria?
Urine Screen Instruments
Why was automation developed?
To streamline procedures and to increase productivity, overnight incubation times
weren’t compatible with rapid testing.
What are the three types of instruments covered in this chapter?
 Automated blood culture
 Urine screen
 Identification and susceptibility