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Copyright © 2007 by Saunders, Inc., an imprint of Elsevier Inc.
Assisting in Microbiology and Immunology
Chapter 54
Copyright © 2007 by Saunders, Inc., an imprint of Elsevier Inc. Slide 2
Microbiology
The medical assistant needs to understand the role of microorganisms.
The main objective of microbiology procedures is to identify the organisms responsible for illness so that the physician can properly treat the patient.
Microbiology procedures may be performed in the POL or in the microbiology department of a medical referral laboratory.
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Specimen Collection and Transport
“In what ways can I prevent extraneous microorganisms from contaminating this sample?”
“What can I do to prevent myself from becoming infected while I collect this sample?”
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Specimen Collection and Transport
Transport media– Stuart medium or Amies medium
The medical assistant must strictly follow the directions.
Transport specimen directly after collection or by courier.
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Classification of Microorganisms
Bacteria, fungi, protozoa
Parasitic worms
Viruses
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Naming of Microorganisms
Binomial system of nomenclature– Assigns two names: the first is the genus, and the
second is the species
– Neisseria gonorrhoeae
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Typical Pathogenic Bacteria
Bacteria are single-celled prokaryote organisms that reproduce by binary fission.
Often classified by their shape, staining characteristics, and the environmental conditions.
Three types of cell wall structures: gram positive, gram negative, acid fast.
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Bacterial Oxygen Requirements
Aerobes
Anaerobes
Facultative anaerobes
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Bacterial Physical Structures
Flagella
Capsules
Endospores
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Unusual Pathogenic Bacteria
Chlamydia
Mycoplasmic
Rickettsiae
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Fungi
Mycology
Fungi are eukaryotes, larger than bacteria
Present in soil, air, and water
Few cause disease
Transmission
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Parasites
Parasitology
Transmitted by ingestion during the infective stage, direct penetration of the skin, inoculation by a vector
Identified in urine, sputum, or tissue fluid or through tissue biopsy
Helminths
Protozoa
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The Microbiology Laboratory
Most laboratories have:
– Refrigerator, autoclave, safety cabinet, microscope, and incubator
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Inoculating Equipment
Inoculating loops and needles
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Incineration Equipment
Fastest way to sterilize reusable equipment
Used to heat-fix smears
Bunsen burner
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Incineration Equipment (cont’d)
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Culture Media
Solid, liquid, or semisolid
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Inoculation of Media
Quadrant streak
Lawn or spread streak
After inoculation, plate is inverted
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Identification of Pathogens in the Microbiology Laboratory
Assessing a culture– Throat culture
– Urine culture
Staining– Gram’s stain
– Acid-fast stain
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Identification of Pathogens in the Microbiology Laboratory (cont’d)
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Identification of Pathogens in the Microbiology Laboratory
Gram stain
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Identification of Pathogens in the Microbiology Laboratory
Biochemical testing– Performed to identify the
genus and species
Rapid identification methods– Designed to give the physician a positive indication of
the problem
– Rapid strep testing
– Influenza A and B testing
– RSV testing
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Identification of Pathogens in the Microbiology Laboratory (cont’d)
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Antimicrobial Susceptibility Testing
“Culture and sensitivity” test.
The physician’s decision for antimicrobial agents is based on numerous factors.– Test results, physical examination, and the knowledge
of the patient
Kirby-Bauer Antimicrobial Susceptibility Test.
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Antimicrobial Susceptibility Testing (cont’d)
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Miscellaneous Microbiology Testing
Testing for pinworms– Specimens best collected at night or early before bowel
movement, urination, or bathing.
– Petroleum jelly paraffin swabs used to collect eggs.
– Parent may also be instructed to bring child to office.
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Immunology Testing
Provides information about past or present infections with bacteria or viruses and certain cancers
Demonstrates the reaction between antigen and antibody– Agglutination, precipitation, immunochromatographic
assay
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Immunology Testing
The medical assistant may perform CLIA-waived tests for infectious mononucleosis, H. pylori, HIV, and Lyme disease.
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Patient Education
List of teaching topics to help educate patients– An explanation of patient’s type of infection
– How infection spreads
– Normal barriers to infection
– Risk factor
– Patient preparations, collection
– Hand washing, proper storage and cleaning