This document discusses microbiology and the role of the medical assistant. It explains that the medical assistant assists physicians by obtaining specimens, preparing them for examination or transport, and possibly performing microbiology procedures if the office has a point-of-care lab. It also outlines how microorganisms cause disease and the classification, identification, and diagnosis of various microbes like viruses, bacteria, fungi, protozoa and parasites.

1. 46-1
Microbiology
Class II
Dr. Ashish Jawarkar
Consultant Pathologist
Parul Sevashram hospital
© 2009 The McGraw-Hill Companies, Inc. All rights reserved

2. 46-2
Microbiology and the Role of the
Medical Assistant

Microbiology – study of microorganisms
(simple forms of life visible only with a
microscope)
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3. 46-3
Microbiology and the Role of the
Medical Assistant (cont.)

Medical assistant

Assists physician

Obtains specimens

Prepares specimens for direct examination

Prepares specimens for transportation to
reference laboratory

If office has a POL, performs microbiologic
procedures
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4. 46-4
How Microorganisms Cause Disease

Cause disease in variety of ways





Use nutrients needed by cells and tissues
Damage cells directly
Produce toxins
May remain localized or become systemic
Transmission


Direct contact
Indirect contact
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5. 46-5
How Microorganisms Cause
Disease (cont.)

Localized symptoms





Swelling
Pain
Warmth
Redness
Generalized symptoms





Fever
Tiredness
Aches
Weakness
Normal flora


Provides a barrier
Can cause an infection
© 2009 The McGraw-Hill Companies, Inc. All rights reserved

6. 46-6
Apply Your Knowledge
1. What role does the medical assistant play in relation to
microbiology?
ANSWER: The medical assistant may assist the physician in
obtaining specimens, obtain specimens herself, prepare
specimens for direct examination or transport to a reference
laboratory, and possibly perform microbiologic procedures.
2. How do microorganisms cause disease?
ANSWER: Organisms cause disease by
using nutrients needed by cells and
tissues, damaging cells directly, or
producing toxins.
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7. 46-7
Classification of Microorganisms

Structure
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8. 46-8
Classification of Microorganisms

Classification by structure

Subcellular – DNA or RNA surrounded by a
protein coat – viruses

Prokaryotic – simple cell structure with no
nucleus or organelles – bacteria

Eukaryotic – complex cell structure with nucleus
and specialized organelles – protozoans, fungi,
parasites
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9. 46-9



Protozoans – single celled eukaryotes
Fungi – multicelled eukaryotes with cell wall
Parasites – multicelled eukaryotes without
cell wall
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10. 46-10
Naming of microorganisms
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11. 46-11
Naming of Microorganisms (cont.)

Standardized naming

Genus



Category of biologic classification
Example – Staphylococcus
Species of organism


Represents a distinct type of microorganisms
Examples – Staphylococcus aureus and
Staphylococcus epidermidis
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12. 46-12
Apply Your Knowledge
Describe the classifications of microorganisms and give
an example of each.
ANSWER: Microorganisms are classified as:
Subcellular organisms that have DNA or RNA surrounded
by a protein coat – viruses
Prokaryotic organisms have a simple cell structure with no
nucleus or organelles – bacteria
Eukaryotic have a complex cell structure with nucleus and
specialized organelles – protozoans, fungi, parasites
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13. 46-13
Viruses


Smallest known
infectious agents
Subcellular
microorganism


Have only nucleic acid
surrounded by a protein
coat
Must live and grow in
living cells of other
organisms
Hepatitis virus
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14. 46-14
Viruses (cont.)

Illnesses caused by viruses






Colds
Influenza
Croup
Hepatitis
Warts





AIDS
Mumps
Rubella
Measles
Herpes
Vaccines are available for many viruses
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15. 46-15
Bacteria



Single-celled prokaryotic organisms
Reproduce rapidly
Classification



Shape
Ability to retain dyes
Ability to grow
with / without air
Bacillus bacterial
classification
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16. 46-16
Bacteria: Classification and
Identification

Shape

Coccus – spherical, round, or ovoid

Bacillus – rod-shaped

Spirillum – spiral-shaped

Virbrio – comma-shaped
Spirillum bacterial
classification
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17. 46-17
Bacteria: Classification and
Identification

Shape
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18. 46-18
Bacteria: Classification and
Identification (cont.)

Ability to retain certain dyes



Gram’s stain (Gram +ve, Gram –ve)
Acid-fast stain (AFB+ve, AFB –ve)
Ability to grow in presence or absence of air


Aerobes – grow best in the presence of oxygen
Anaerobes – grow best in the absence of oxygen
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19. 46-19
Bacteria: Classification and
Identification (cont.)

Special groups



Mycobacteria – bacilli
with a cell wall that
differs from most
bacteria


Rickettsiae


Very small
Live and grow within
other living organisms
such as mites and ticks
Chlamydiae

Cell wall structure
differs from other
bacteria
Live and grow within
other living cells
Mycoplasmas –
completely lack the
rigid cell wall
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20. 46-20
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21. 46-21
Protozoans
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22. 46-22
Protozoans

Single-celled eukaryotic organisms, larger than
bacteria

Found in soil and water

Illnesses




Malaria
Amebic dysentery
Trichomoniasis vaginitis
Leading cause of death in developing countries
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23. 46-23
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24. 46-24
Fungi


Eukaryotic organisms with
rigid cell wall
Yeasts


Single-celled
Reproduce by budding

Superficial infections




Molds


Large, fuzzy, multicelled
organisms
Produce spores

Athlete’s foot
Ringworm
Thrush
Can cause systemic
infections
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25. 46-25
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26. 46-26
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27. 46-27
Multicellular Parasites

Organisms that live on or in another organism and
use it for nourishment

Parasitic worms




Usually due to poor
sanitation
Roundworms
Flatworms
Tapeworms

Parasitic insects





Bite or burrow under
the skin
Mosquitoes
Ticks
Lice
mites
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28. 46-28
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29. 46-29
Apply Your Knowledge
Matching: ANSWER:
___ Yeast or mold
D
A. Virus
___ Tapeworm / lice
E
B. Bacteria
___ Classified by shape
B
C. Protozoan
A
___ Subcellular organism
D. Fungus
B
___ May be aerobic or anaerobic
E. Multicellular parasite
Very
Good!
A
___ Smallest known organism
C
___ Found in soil and water
© 2009 The McGraw-Hill Companies, Inc. All rights reserved

30. 46-30
How Infections Are Diagnosed

Steps to diagnosis and treatment
1.
Examine the patient


2.
Presumptive diagnosis
May or may not need additional tests
Obtain specimen(s)


Label properly
Include presumptive diagnosis
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31. 46-31
How Infections Are Diagnosed (cont.)
3.
Examine specimen directly


4.
Wet mount
Smear
Culture specimen


Culture medium – contains nutrients
Examine culture visually and microscopically
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32. 46-32
How Infections Are Diagnosed (cont.)
5.
Determine sensitivity to
antibiotics
6.
Treat the patient as
ordered

Antimicrobial – to kill
pathogen or suppress its
growth
© 2009 The McGraw-Hill Companies, Inc. All rights reserved

33. 46-33
Apply Your Knowledge
What is the process for diagnosing an infection?
ANSWER: There are six steps for diagnosis and treatment of
an infection:
1. Examine the patient
4. Culture the specimen
2. Obtain specimen(s)
5. Determine sensitivity
3. Examine specimen directly
6. Treat patient / appropriate
antimicrobial
Super!
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34. 46-34
Specimen Collection

Must be collected correctly

If not, may not grow in
culture

Contaminants may be
mistakenly identified

Patient may receive
incorrect or harmful therapy
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35. 46-35
Specimen Collection (cont.)

Devices



Use appropriate collection
device or specimen container
Sterile swabs – absorbent
material on the tip
Collection and transporting systems



Sterile, self-contained
Transport medium
Aerobic or anaerobic
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36. 46-36
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37. 46-37
Specimen Collection: Guidelines

Avoid causing harm,
discomfort, or undue
embarrassment

Obtain specimen at
correct time

Obtain sufficient
quantity of specimen

Obtain specimen prior
to the start of
antimicrobial therapy

Label correctly
Collect from
appropriate site


Use appropriate
devices
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38. 46-38
Specimen Collection (cont.)

Throat culture specimens



Swab back of throat in the area
of the tonsils
Avoid touching any structures
in the mouth
Prepare culture plate or
prepare correctly for
transport to laboratory
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39. 46-39
Specimen Collection (cont.)

Urine specimen


Clean-catch
midstream to
minimize
contaminants
Process within 60
minutes or
refrigerate

Sputum specimen


Specimen from
lungs
Avoid
contaminating
specimen with
saliva
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40. 46-40
Specimen Collection (cont.)

Wound specimen


Swab wound or
lesion
Do not touch
outside of wound

Stool Specimens

Technique varies



Bacterial infection
Protozoal or
parasitic infection
Instruct patient in
correct collection
procedure
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41. 46-41
© 2009 The McGraw-Hill Companies, Inc. All rights reserved

42. 46-42
Apply Your Knowledge
What are the general guidelines for specimen collection?
ANSWER: They are to avoid causing harm, discomfort, or
undue embarrassment; collect from appropriate site; obtain
specimen at correct time; use appropriate collection devices;
obtain sufficient quantity of specimen; obtain specimen prior
to the start of antimicrobial therapy; and label specimen
correctly.
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43. 46-43
Transporting Specimens to an
Outside Laboratory

Many offices send cultures to an outside lab

Three main objectives



Follow proper collection
procedures and proper
collection device
Prevent deterioration of
specimen
Protect anyone handling
specimen
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44. 46-44
Direct Examination of Specimens

Enables physician to initiate treatment immediately

Wet mounts


NaCl mixed with
specimen of glass slide
Presence of pathogen
and movement of
microorganism

Potassium hydroxide
(KOH) mounts


Used if a fungal
infection of the skin,
nails, or hair is
suspected
KOH dissolves keratin
that can mask presence
of a fungus
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45. 46-45
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46. 46-46
Preparation and Examination of
Stained Specimens


Quick, tentative
diagnosis
Differentiation
between types of
infections

Gram’s stain


Moderatecomplexity test
Bacteria either
retain or lose purple
color


Gram-positive
bacteria
Gram-negative
bacteria
© 2009 The McGraw-Hill Companies, Inc. All rights reserved

47. 46-47
Apply Your Knowledge
1. What are the methods for preparing a slide for direct
examination by the physician?
ANSWER: They are wet mount and KOH mount.
2. How does the examination of stained specimens
facilitate patient care?
ANSWER: Stained specimens enable the physician
to provide a quick, tentative diagnosis and
differentiate between types of infections.
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48. 46-48
Culturing Specimens

Inoculating a culture plate




Transfer some of the specimen onto a culture
plate
Label the plate correctly
Qualitative analysis – determination of type of
pathogen
Quantitative analysis – number of bacteria
present in sample
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49. 46-49
Culturing Specimens (cont.)

Incubating culture plates



35 to 37º C for 24 to 78 hours
Agar side up
Interpreting cultures




Requires skill and practice
Characteristics of colonies
Relative number
Changes to media around colonies
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50. 46-50
Culturing Specimens (cont.)

Culture media




Liquid, semisolid, or
solid forms
Contains agar
Selective or nonselective
Special culture units


Rapid urine culture – Uricult
Also available for throat, vaginal, and blood
specimens
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51. 46-51
Apply Your Knowledge
3. What is the process for culturing a specimen?
ANSWER: The culture medium is inoculated with
the specimen and placed in an incubator to
promote growth of the organism on the culture
medium.
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52. 46-52
Determining Antimicrobial Sensitivity
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53. 46-53
Determining Antimicrobial Sensitivity

An outside lab
reports



Sensitive – no
growth
Intermediate – little
growth
Resistant –
overgrown

Procedure



Filter paper containing
antimicrobial agents
placed on inoculated
agar plate
Incubated for 24 hours
Evaluate effectiveness
of agent
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54. 46-54
Apply Your Knowledge
1. What is the difference between selective and
nonselective culture media?
ANSWER: Selective culture media allows the growth of only
certain kinds of bacteria. Unselective culture media support
the growth of most organisms.
2. The office received a culture sensitivity report on a
bacteria that said it was resistant to an antimicrobial.
What does this mean?
ANSWER: It means that the bacteria was not killed by the
antimicrobial and that there was an overgrowth of the bacteria.
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55. 46-55
In summary






Types of microorganisms
Nomenclature
Structure
Specimen collection
Techniques
Antibiotic resistance
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56. 46-56
Thank You
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