CGMBS ch. 11 Detection and Identification of Microorganisms Questions and Answers 2024/2025
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CGMBS
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CGMBS
Salmonella typhi specimen collection
→ initially present in peripheral bloo but not in urine or stool util at least 2 weeks after
infection
Smallpox must be handled only in approved laboratories
→ level 4 containment
When processing whole blood, why is it important to remove homoglobin
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→ B-actin, glyceraldehyde-3-phosphate, interferon-y, extrinsic homologous control, human
mitochondril DNA, peptidylprolyl isomerase A
Homologous extrinsic control
→ target-derived control with a non-target-derived sequence insert; control is added to
every sample after nucleic acid extraction and before amplification
Heterologous extrinsic controls
→ non-target-derived controls that are added to every sample before nucleic acid
extraction; second set of primers must also be added to the reaction for the conrol to
be amplified
Heterologous intrinsic ontrols
→ nontarget sequences natrually present in the sample, such as eukaryotic genes in a test
for microorganisms
Reasons for false-negative results on a sample
→ 1. organism may be present, but nucleic acid was degraded during collection,
transport, and or extraction
→ 2. amplification procedures may be inhibited by substances present in the specimen
Sequencing of the DNA region encoding 16S rRNA is performed to determine
→ the evolutionary and genetic relatedness of microorganisms and has driven changes in
microorganism nomenclature
