Download Chapter_020_LO

CHAPTER 20
MEDICAL MICROBIOLOGY
PRETEST
True or False
1.
Microbiology is the scientific study of
microorganisms and their activities.
2.
A disease that can be spread from one person to
another is known as an infectious disease.
3.
Droplet infection is the transfer of pathogens from a
fine spray emitted from a person already infected
with the disease.
4.
Streptococci are round bacteria that grow in pairs.
5.
Chickenpox is caused by a virus.
Elsevier items and derived items © 2008 by Saunders, an imprint of Elsevier Inc.
2
PRETEST, CONT.
True or False
6.
The course adjustment on a microscope is used to
obtain precise focusing of an object.
7.
The purpose of transport media is to provide
nutrients for the multiplication of the specimen.
8.
A throat specimen should be collected from the
tonsillar area and posterior pharynx.
9.
A wet mount is used to examine microorganisms in
the living state.
10. A smear is material spread on a slide for
microscopic examination.
Elsevier items and derived items © 2008 by Saunders, an imprint of Elsevier Inc.
3
Content Outline
Introduction to Microbiology
1. Microbiology: the scientific study of
microorganisms and their activities
a. Microorganisms: Tiny living plants or
animals that cannot be viewed with the
naked eye
2. Anton van Leeuwenhoek (1632-1723)
a. Designed a magnifying glass strong enough
for viewing microorganisms
• Precursor of modern microscope
b. First to observe and describe protozoa and
bacteria
Elsevier items and derived items © 2008 by Saunders, an imprint of Elsevier Inc.
4
Introduction to Microbiology, cont.
3. Microbiology: Deals with unicellular (onecelled) microscopic organisms
4. All life processes of a microorganism are
performed by one cell including:
a. Ingestion of food substances and their use
for energy
b. Growth
c. Reproduction
d. Excretion
Elsevier items and derived items © 2008 by Saunders, an imprint of Elsevier Inc.
5
Introduction to Microbiology, cont.
5. Microorganisms are ubiquitous
a. Means they are found everywhere:
• Air
• Plants
• Food
• Animals
• Water
• Humans
• Soil
Elsevier items and derived items © 2008 by Saunders, an imprint of Elsevier Inc.
6
Introduction to Microbiology, cont.
6. Only a small number of microorganisms
are pathogenic (disease-producing)
7. Pathogen infects host: produces
symptoms of that disease
a. Assists physician in diagnosing that disease
Elsevier items and derived items © 2008 by Saunders, an imprint of Elsevier Inc.
7
Introduction to Microbiology, cont.
8. Microbiologic tests:
a. Also help physician identify pathogen
causing disease
9. Identification of pathogen: leads to
proper treatment
10.Most microbiologic tests: performed at
outside laboratory
a. MA often responsible for collecting the
specimen
Elsevier items and derived items © 2008 by Saunders, an imprint of Elsevier Inc.
8
Normal Flora
1. Every individual has normal flora:
2. Normal flora: Harmless microorganisms that
normally reside in many parts of the body but
do not cause disease
a. Examples of body areas with an abundant
normal flora
• Surface of skin
• Mucous membranes of gastrointestinal (GI) tract
• Respiratory tract
• Genitourinary tract
Elsevier items and derived items © 2008 by Saunders, an imprint of Elsevier Inc.
9
The Normal Flora, cont.
3. Normal flora may be beneficial
a. Example:
•
Normal flora in intestinal tract:
– Feed on potentially harmful microorganisms
– Synthesize vitamin K (needed for blood
clotting)
From Mahon CR, Manuselis G, Jr: Textbook of diagnostic microbiology, ed 2, Philadelphia, 2000, Saunders.
10
Elsevier items and derived items © 2008 by Saunders, an imprint of Elsevier Inc.
The Normal Flora, cont.
4. Sometimes normal flora can become
pathogenic and cause disease
a. May occur during lowered body resistance
Courtesy Cathy Bissonette
Elsevier items and derived items © 2008 by Saunders, an imprint of Elsevier Inc.
11
Infection
1. Infection: invasion of the body by pathogenic
microorganisms
a. If body conditions are favorable
• Pathogen grows and multiplies
• Results in an infectious disease
– Infectious disease: a disease caused by
a pathogen that produces harmful effects on
its host
Elsevier items and derived items © 2008 by Saunders, an imprint of Elsevier Inc.
12
Infection, cont.
2. Not all invading pathogens are able to
cause disease
3. Body attempts to stop invasion
a. Uses second line of defense mechanisms:
• Inflammation: a protective response of the
body to the entrance of foreign matter.
– The purpose of inflammation is to destroy
invading microorganisms and to repair
injured tissue
•
Phagocytosis by white blood cells (WBCs)
•
Production of antibodies
Elsevier items and derived items © 2008 by Saunders, an imprint of Elsevier Inc.
13
Infection, cont.
4. First line of defense: works to prevent
entrance of pathogens into body
a. Examples:
•
Skin
•
Mucous membranes
•
Mucus and cilia in nose
Elsevier items and derived items © 2008 by Saunders, an imprint of Elsevier Inc.
14
Infection, cont.
• Coughing and sneezing
• Tears and sweat
• Acid nature of urine and vaginal secretions
• Hydrochloric acid secreted by stomach
Elsevier items and derived items © 2008 by Saunders, an imprint of Elsevier Inc.
15
Infection, cont.
5. If body defenses are successful:
pathogens are destroyed
a. Individual does not get infectious disease
6. If body defenses are overcome by
pathogen
a. Individual gets infectious disease
Elsevier items and derived items © 2008 by Saunders, an imprint of Elsevier Inc.
16
Infection, cont.
7. Many infectious diseases are contagious
a. Contagious: capable of being transmitted
directly or indirectly from one person to
another
• Droplet infection: inhalation of pathogens
from a fine spray emitted by person infected with
disease
• When infected individual exhales (breathing,
talking, coughing, sneezing)
– Pathogens are dispersed on minute liquid
particles
• Infected individual: should cover mouth when
coughing and sneezing
Elsevier items and derived items © 2008 by Saunders, an imprint of Elsevier Inc.
17
Stages of an Infectious Disease
1. Infection: invasion and multiplication of
pathogenic microorganisms in the body
2. Incubation period: interval of time between
invasion by a pathogen and appearance of first
symptoms of disease
a. May range from a few days to several
months
b. Pathogen is growing and multiplying during
this time
Elsevier items and derived items © 2008 by Saunders, an imprint of Elsevier Inc.
18
Stages of an Infectious Disease,
cont.
3. Prodromal period: first symptoms appear
a. Examples:
•
Headache
•
Feeling of illness
From Mahon CR, Manuselis G Jr: Textbook of diagnostic microbiology, ed 2, Philadelphia, 2000, Saunders.
Elsevier items and derived items © 2008 by Saunders, an imprint of Elsevier Inc.
19
Stages of an Infectious Disease,
cont.
4. Acute period: disease is at its peak and
symptoms fully developed
a. Example: fever
5. Decline period: symptoms begin to subside
6. Convalescent period: patient regains
strength and returns to good health
Elsevier items and derived items © 2008 by Saunders, an imprint of Elsevier Inc.
20
Microorganisms and Disease
1. Groups of microorganisms known to
contain species capable of causing
human disease:
a. Bacteria
b. Viruses
c. Protozoa
d. Fungi (yeast)
e. Animal parasites
Courtesy Cathy Bissonette.
Elsevier items and derived items © 2008 by Saunders, an imprint of Elsevier Inc.
21
Bacteria
1. Microscopic single-celled organisms
2. Of 1700 species known to dwell in
humans: only about 100 produce human
disease
3. Antibiotics: help in controlling bacterial
infections
a. Not effective against viral infections
4. Classified according to shape
Elsevier items and derived items © 2008 by Saunders, an imprint of Elsevier Inc.
22
Classification of Bacteria by Shape
Elsevier items and derived items © 2008 by Saunders, an imprint of Elsevier Inc.
23
Staphylococci
5. Cocci: round shape
a. Staphylococci
•
Round bacteria that grow in grapelike clusters
From Mahon CR, Manuselis G Jr: Textbook of diagnostic microbiology, ed 2, Philadelphia, 2000, Saunders.
Elsevier items and derived items © 2008 by Saunders, an imprint of Elsevier Inc.
24
Staphylococci, cont.
• S. epidermidis: normally present on skin surface
and mucous membranes of the mouth, nose,
throat, intestines
– Usually nonpathogenic
– Break in the skin can allow invasion
1) Example: cut
2) Results in a mild infection
Elsevier items and derived items © 2008 by Saunders, an imprint of Elsevier Inc.
25
Staphylococci, cont.
• S. aureus: associated with pathologic conditions
-
Boils
-
Abscesses
-
Carbuncles
-
-
Pimples
Staphylococcal food
poisoning
-
Impetigo
-
Wound infections
Elsevier items and derived items © 2008 by Saunders, an imprint of Elsevier Inc.
26
Staphylococci, cont.
• Staphylococcal infections usually cause pus
formation (suppuration)
– Termed: pyogenic infections
From Mahon CR, Manuselis G Jr: Textbook of diagnostic microbiology, ed 2, Philadelphia, 2000, Saunders.
Elsevier items and derived items © 2008 by Saunders, an imprint of Elsevier Inc.
27
Streptococci
b. Streptococci
•
Round bacteria that
grow in chains
From Mahon CR, Manuselis G Jr: Textbook of diagnostic microbiology, ed 2,
Philadelphia, 2000, Saunders.
Elsevier items and derived items © 2008 by Saunders, an imprint of Elsevier Inc.
28
Streptococci, cont.
• Before antibiotics: major cause of human death
• Diseases caused by streptococci:
-
Streptococcal sore
throat
-
Scarlet fever
-
Rheumatic fever
-
Pneumonia
-
Puerperal sepsis
-
Erysipelas
-
Carbuncles
-
Impetigo
From Mahon CR, Manuselis G Jr: Textbook of diagnostic microbiology,
ed 2, Philadelphia, 2000, Saunders.
Elsevier items and derived items © 2008 by Saunders, an imprint of Elsevier Inc.
29
Diplococci
c. Diplococci
•
Round bacteria that grow in pairs
•
Diseases caused by diplococci:
– Pneumonia
– Gonorrhea
– Meningitis
From Mahon CR, Manuselis G Jr: Textbook of diagnostic microbiology, ed 2,
Philadelphia, 2000, Saunders.
Elsevier items and derived items © 2008 by Saunders, an imprint of Elsevier Inc.
30
Bacilli
6. Bacilli: rod shaped bacteria
a. Found in soil and air
Courtesy Cathy Bissonette.
Elsevier items and derived items © 2008 by Saunders, an imprint of Elsevier Inc.
31
Bacilli, cont.
b. Some are able to form spores
• Spore: a hard, thick-walled capsule formed by
some bacteria that contains only the essential
parts of the protoplasms of the bacterial cell
•
Enables them to resist adverse conditions
– Heat
– Disinfectants
Elsevier items and derived items © 2008 by Saunders, an imprint of Elsevier Inc.
32
Bacilli, cont.
• Diseases caused by bacilli:
– Botulism
– Tetanus
– Gas gangrene
– Gastroenteritis caused by
Salmonella food poisoning
– Typhoid fever
– Pertussis
– Bacillary dysentery
– Diphtheria
– Tuberculosis
Courtesy Cathy Bissonette.
Elsevier items and derived items © 2008 by Saunders, an imprint of Elsevier Inc.
33
Bacilli, cont.
c. Escherichia coli (E. coli): a species of
bacillus
•
Normal flora of the large intestine
From Mahon CR, Manuselis G Jr: Textbook of diagnostic microbiology, ed 2, Philadelphia, 2000, Saunders.
Elsevier items and derived items © 2008 by Saunders, an imprint of Elsevier Inc.
34
Bacilli, cont.
• Normally
harmless
• May cause a
urinary tract
infection (UTI) if
enters urinary
tract due to:
– Lowered
resistance
– Poor
hygienic
practices
From Mahon CR, Manuselis G Jr: Textbook of diagnostic microbiology, ed 2,
Philadelphia, 2000, Saunders.
Elsevier items and derived items © 2008 by Saunders, an imprint of Elsevier Inc.
35
Spirilla
7. Spirilla: spiral or curved shaped bacteria
a. Treponema pallidum
b. Causative agent of syphilis
c. Cannot be grown in culture media
•
Diagnosis of syphilis made through serologic
tests
Elsevier items and derived items © 2008 by Saunders, an imprint of Elsevier Inc.
36
Spirilla, cont.
b. Vibrio cholerae
•
Causative agent of cholera
– Immunization and proper sanitation: have
eliminated cholera in United States
Elsevier items and derived items © 2008 by Saunders, an imprint of Elsevier Inc.
37
Viruses
1. Smallest living organisms
2. Electron microscope must be used to
view them
3. Can infect: plants, animals, humans
4. Use nutrients inside host cells
a. For metabolic and reproductive needs
Elsevier items and derived items © 2008 by Saunders, an imprint of Elsevier Inc.
38
Viruses, cont.
5. Diseases caused by viruses:
a. Influenza
b. Chickenpox
c. Rubeola (measles)
d. Rubella (German measles)
e. Mumps
Elsevier items and derived items © 2008 by Saunders, an imprint of Elsevier Inc.
39
Viruses, cont.
f. Poliomyelitis
g. Smallpox
h. Rabies
i. Herpes simplex
j. Herpes zoster
Elsevier items and derived items © 2008 by Saunders, an imprint of Elsevier Inc.
40
Viruses, cont.
k. Yellow fever
l. Hepatitis
m. Majority of diseases in upper respiratory
tract
•
Example: Common cold
Elsevier items and derived items © 2008 by Saunders, an imprint of Elsevier Inc.
41
What Would You Do?
What Would You Not Do?
Elsevier items and derived items © 2008 by Saunders, an imprint of Elsevier Inc.
42
What Would You Do?
What Would You Not Do?
Elsevier items and derived items © 2008 by Saunders, an imprint of Elsevier Inc.
43
Microscope
1. Compound microscope: used most often
in medical office
a. Consists of two-lens system
2. Components:
a. Support system
b. Optical system
Elsevier items and derived items © 2008 by Saunders, an imprint of Elsevier Inc.
44
Parts of a Microscope
Elsevier items and derived items © 2008 by Saunders, an imprint of Elsevier Inc.
45
Support System
1. Frame
a. Supports microscope
b. Consists of:
• Base: for support
• Arm:
– For carrying it
– To support magnifying and adjusting
systems
Elsevier items and derived items © 2008 by Saunders, an imprint of Elsevier Inc.
46
Support System, cont.
2. Stage
a. Flat, horizontal
platform
b. Slide is placed on
stage
Elsevier items and derived items © 2008 by Saunders, an imprint of Elsevier Inc.
47
Support System, cont.
c. Has small round opening in center
•
Permits light from below to pass through the
object being viewed and up into lenses
d. Standard microscope: has metal clips to
hold slide in place
•
Slide must be moved by hand
Elsevier items and derived items © 2008 by Saunders, an imprint of Elsevier Inc.
48
Support System, cont.
e. Mechanical stage: allows movement of slide
in vertical or horizontal position using
adjustment knobs
•
Needed for:
– Differential white blood cell count
– Inspection of gram-stained smear
Elsevier items and derived items © 2008 by Saunders, an imprint of Elsevier Inc.
49
Support System, cont.
3. Light source
a. Located at the base
b. Consists of: built-in illuminator
•
Switch for turning on and off
c. Light directed to condenser above
•
Then through object to be viewed
Elsevier items and derived items © 2008 by Saunders, an imprint of Elsevier Inc.
50
Support System, cont.
4. Condenser
a. Compound
microscopes
have lens
system
between light
source and
object
•
Known as
substage
condenser
Elsevier items and derived items © 2008 by Saunders, an imprint of Elsevier Inc.
51
Support System, cont.
b. Popular type: Abbe's condenser
•
Consists of two lenses
•
Collects and concentrates light rays and directs
them up
– Brings light rays to a focus on the object so
it is well-illuminated
Elsevier items and derived items © 2008 by Saunders, an imprint of Elsevier Inc.
52
Support System, cont.
5. Diaphragm
a. Controls the amount of light focused on an
object
b. Amount of light controlled by iris diaphragm
c. Located beneath or inside condenser
d. Consists of:
•
Series of horizontally arranged interlocking
plates
•
With central opening (aperture)
Elsevier items and derived items © 2008 by Saunders, an imprint of Elsevier Inc.
53
Support System, cont.
e. Diaphragm lever:
increases or
decreases aperture
•
Increases or
decreases light
admitted
Elsevier items and derived items © 2008 by Saunders, an imprint of Elsevier Inc.
54
Support System, cont.
f. As magnification increases: more light is
needed
•
Example: Oil immersion requires increased light
intensity
g. Low-power objective
•
Do not need as much light
Elsevier items and derived items © 2008 by Saunders, an imprint of Elsevier Inc.
55
Support System, cont.
h. Degree of illumination: also influenced by
density of the object
•
Stained structures: require more light than
unstained specimens
6. Adjustment knobs
a. Coarse adjustment: to obtain an
approximate focus quickly
b. Fine adjustment: to obtain precise focusing
Elsevier items and derived items © 2008 by Saunders, an imprint of Elsevier Inc.
56
Support System, cont.
c. Adjustment knobs:
-May be mounted as
two separate knobs
-May be placed
together
Elsevier items and derived items © 2008 by Saunders, an imprint of Elsevier Inc.
57
Optical System
1. Compound microscopes have two-lens
magnification system
a. Magnification: The ratio of the apparent
size of an object viewed through the
microscope to the actual size of the object
2. The Eyepiece
a. First lens system
b. Also called ocular lens
Elsevier items and derived items © 2008 by Saunders, an imprint of Elsevier Inc.
58
Optical System, cont.
c. Located at top of body tube
d. Marked 10×(magnifies 10 times)
e. Monocular microscope: has one eyepiece
f. Binocular microscope: has two eyepieces
Elsevier items and derived items © 2008 by Saunders, an imprint of Elsevier Inc.
59
Optical System, cont.
3. Objective Lenses
a. Second lens system
b. Three objective lenses: located on a
revolving nosepiece
c. Each objective has a different degree of
magnification: engraved on metal shaft
•
Low-power objective: 10×
•
High-power objective: 40×
•
Oil-immersion objective: 100×
Elsevier items and derived items © 2008 by Saunders, an imprint of Elsevier Inc.
60
Optical System, cont.
d. May have color-coded
rings to identify objective
•
Example:
– Low-power objective:
yellow ring
– High-power
objective: blue ring
– Oil-immersion
objective: white ring
Elsevier items and derived items © 2008 by Saunders, an imprint of Elsevier Inc.
61
Optical System, cont.
e. Metal shafts of objectives: differ in length
• Low-power objective: shortest length
• High-power objective: length between low
and oil objectives
• Oil-immersion objective: longest length
Elsevier items and derived items © 2008 by Saunders, an imprint of Elsevier Inc.
62
Optical System, cont.
f. Total magnification: multiply the ocular
magnification by the objective magnification:
•
Low-power total
magnification:
-100× (10×10)
•
High-power total
magnification:
-400× (10×40)
•
Oil-immersion
magnification:
-1000× (10×100)
Elsevier items and derived items © 2008 by Saunders, an imprint of Elsevier Inc.
63
Optical System, cont.
4. Focus
a. Barrel focus: body tube or barrel moves
while stage remains stationary
b. Stage focus: stage moves while body tube
remains stationary
Elsevier items and derived items © 2008 by Saunders, an imprint of Elsevier Inc.
64
Optical System, cont.
5. Low and High Power
a. Low-power objective used for:
•
Initial focusing and light adjustment
•
Initial observation and scanning requirements
b. High-power objective used for:
•
A more thorough study of the slide
Elsevier items and derived items © 2008 by Saunders, an imprint of Elsevier Inc.
65
Optical System, cont.
c. Working distance: distance between tip of
lens and slide
•
High-power objective: working distance is short
•
Care must be taken when using high-power
objective
– To prevent it from striking and breaking
slide
– To prevent damaging the lens
Elsevier items and derived items © 2008 by Saunders, an imprint of Elsevier Inc.
66
Optical System, cont.
d. Most compound microscopes are parafocal
•
Parafocal: once focused on low power the
nosepiece can be rotated to high power and
focused with fine adjustment
Elsevier items and derived items © 2008 by Saunders, an imprint of Elsevier Inc.
67
Optical System, cont.
6. Oil Immersion
a. Provides highest magnification
b. Used to view very small structures or the
detail of structures
•
Microorganisms
•
Blood cells
Elsevier items and derived items © 2008 by Saunders, an imprint of Elsevier Inc.
68
Optical System, cont.
c. Oil immersion has a
very short working
distance
•
Lens nearly rests on
slide
Elsevier items and derived items © 2008 by Saunders, an imprint of Elsevier Inc.
69
Optical System, cont.
d. Must use immersion
oil
•
Does not dry out when
exposed to air for a
long time
e. Drop of oil placed on
slide
Elsevier items and derived items © 2008 by Saunders, an imprint of Elsevier Inc.
70
Optical System, cont.
• Oil resides between
objective and slide
• Provides path for light to
travel between slide and
lens
• Prevents scattering of
light rays
– Permits clear
viewing of small
structures
Elsevier items and derived items © 2008 by Saunders, an imprint of Elsevier Inc.
71
Optical System, cont.
f. Oil immersion used for:
•
Differential white blood
counts
•
Examination of gramstained smears
Elsevier items and derived items © 2008 by Saunders, an imprint of Elsevier Inc.
72
Care of the Microscope
1. Carry with two hands: one on arm and
one under base
a. Place down gently: prevents jarring it
• Could damage delicate parts
Elsevier items and derived items © 2008 by Saunders, an imprint of Elsevier Inc.
73
Care of the Microscope, cont.
2. Do not touch the lenses: prevents
fingerprints
a. Avoid wearing mascara: difficult to remove
from lens
3. When not in use: keep covered with
plastic dust cover
a. Store in case or cupboard
b. Rotate nosepiece to low objective
•
Position as close as possible to stage
Elsevier items and derived items © 2008 by Saunders, an imprint of Elsevier Inc.
74
Care of the Microscope, cont.
4. Clean by washing enameled surfaces
with soap and water
a. Dry thoroughly with a soft cloth
5. Clean stage after each use:
a. Wipe stage with gauze or tissue
b. If immersion oil gets on stage:
•
Remove with gauze moistened with xylene
Elsevier items and derived items © 2008 by Saunders, an imprint of Elsevier Inc.
75
Care of the Microscope, cont.
6. Ocular, objectives and condenser
a. Consist of hand-ground optical lenses
•
Must keep spotlessly clean
– Use dry lens paper
Elsevier items and derived items © 2008 by Saunders, an imprint of Elsevier Inc.
76
Care of the Microscope, cont.
• Optical glass: softer than ordinary glass
– Do not use tissue or gauze to clean:
scratches the lens
• If lenses are especially dirty
– Clean with commercial lens cleaner or
xylene
– Dry and polish with lens paper
Elsevier items and derived items © 2008 by Saunders, an imprint of Elsevier Inc.
77
Clean with lens paper:
Elsevier items and derived items © 2008 by Saunders, an imprint of Elsevier Inc.
78
Care of the Microscope, cont.
7. Light source: keep free of dust, lint, and
dirt
a. Periodically polish with lens paper
Elsevier items and derived items © 2008 by Saunders, an imprint of Elsevier Inc.
79
Care of the Microscope, cont.
8. Microscope that is malfunctioning
a. Have repaired by qualified service person
•
Do not try to fix yourself
– May result in further damage
Elsevier items and derived items © 2008 by Saunders, an imprint of Elsevier Inc.
80
Microbiologic Specimen Collection
1. Purpose:
a. To identify pathogen causing the disease
• Assists in the diagnosis
– Example: Obtaining a urine specimen to
assist in diagnosis of a urinary tract infection
2. Specimen: a small sample or part taken from
the body to show the nature of the whole
Elsevier items and derived items © 2008 by Saunders, an imprint of Elsevier Inc.
81
Microbiologic Specimen Collection,
cont.
3. MA often responsible for collecting
microbiologic specimens
a. Examples: throat, nose, and wound
specimens
4. MA may assists physician in collecting
specimens
a. Examples: vagina, cervix, urethra, rectum
Elsevier items and derived items © 2008 by Saunders, an imprint of Elsevier Inc.
82
Microbiologic Specimen Collection,
cont.
5. Sterile swab used to collect specimen
a. Swab: small piece of cotton wrapped
around the end of a slender wooden or
plastic stick
•
Passed across body surface or opening
– To obtain a specimen for microbiologic
analysis
Elsevier items and derived items © 2008 by Saunders, an imprint of Elsevier Inc.
83
Sterile Swab
Elsevier items and derived items © 2008 by Saunders, an imprint of Elsevier Inc.
84
Microbiologic Specimen Collection,
cont.
6. To prevent inaccurate test results:
a. Use good techniques of medical and
surgical asepsis
b. Do not contaminate with extraneous
microorganisms
•
Extraneous microorganisms: undesirable
microorganisms that can enter the specimen in
various ways.
–
They grow and multiply
–
Can obscure and prevent identification of
pathogens that might be present
Elsevier items and derived items © 2008 by Saunders, an imprint of Elsevier Inc.
85
Microbiologic Specimen Collection,
cont.
c. To prevent contamination of a specimen
with extraneous microorganisms:
•
Supplies used to collect specimen must be
sterile
– Examples: Swabs and specimen containers
Elsevier items and derived items © 2008 by Saunders, an imprint of Elsevier Inc.
86
Microbiologic Specimen Collection,
cont.
• Do not allow swab to touch areas surrounding
collection site
– Example: Throat specimen: Do not allow
swab to touch inside of mouth
Elsevier items and derived items © 2008 by Saunders, an imprint of Elsevier Inc.
87
Microbiologic Specimen Collection,
cont.
7. Follow OSHA Bloodborne Pathogens
Standard when performing
microbiologic procedures:
a. Wear gloves
b. No eating, drinking, smoking, or applying
makeup
•
Pathogens can be transmitted through hand-tomouth contact
c. Do not lick labels for specimen containers
d. Cover breaks in skin with a bandage
Elsevier items and derived items © 2008 by Saunders, an imprint of Elsevier Inc.
88
Microbiologic Specimen Collection,
cont.
e. If accidentally touch specimen:
•
Wash area immediately with soap and water
f. If specimen comes in contact with
worktable:
•
Immediately clean with soap and water followed
by disinfectant (e.g., phenol)
g. At end of day:
•
Clean worktable with disinfectant
Elsevier items and derived items © 2008 by Saunders, an imprint of Elsevier Inc.
89
Microbiologic Specimen Collection,
cont.
8. After collection: place specimen in
proper container
a. Securely fasten lid
b. Label with:
•
Patient's name
•
Date
•
Source of specimen
•
Initials
Elsevier items and derived items © 2008 by Saunders, an imprint of Elsevier Inc.
90
Handling and Transporting
Microbiologic Specimens
1. Delay in processing specimen:
a. May cause death of pathogens
b. Overgrowth of specimen by normal flora
(usually collected along with pathogen)
2. If specimen analyzed in office:
a. Examine under microscope or culture
immediately
Elsevier items and derived items © 2008 by Saunders, an imprint of Elsevier Inc.
91
Handling and Transporting
Microbiologic Specimens, cont.
3. If specimen transported to outside
laboratory by courier
a. Place in transport medium
(e.g., Starswab II, Culturette)
•
Prevents drying of specimen
•
Preserves specimen in its original state
b. Outside laboratory: provides instructions
on care and handling of specimen
Elsevier items and derived items © 2008 by Saunders, an imprint of Elsevier Inc.
92
Handling and Transporting
Microbiologic Specimens, cont.
c. Specimen must be accompanied by
laboratory request which includes:
•
Physician's name and address
•
Patient's name, age, and gender
•
Date and time of collection
•
Type of microbiologic examination requested
Elsevier items and derived items © 2008 by Saunders, an imprint of Elsevier Inc.
93
Handling and Transporting
Microbiologic Specimens, cont.
• Source of specimen
– Examples: throat, wound, urine
• Physician's clinical diagnosis
– Clinical diagnosis: a tentative diagnosis
of a patient's condition obtained through the
evaluation of the health history and the
physical examination without the benefit of
laboratory or diagnostic tests
Elsevier items and derived items © 2008 by Saunders, an imprint of Elsevier Inc.
94
Handling and Transporting
Microbiologic Specimens, cont.
• If patient is receiving antibiotic treatment
– Antibiotics suppress growth of bacteria
– Could cause false-negative results
Elsevier items and derived items © 2008 by Saunders, an imprint of Elsevier Inc.
95
Handling and Transporting
Microbiologic Specimens, cont.
4. Wound Specimens
a. Must be collected from within wound
(rather than from surface of wound)
•
To obtain accurate and reliable test results
b. Usually two swabs used
Elsevier items and derived items © 2008 by Saunders, an imprint of Elsevier Inc.
96
Handling and Transporting
Microbiologic Specimens, cont.
c. Swab inserted into area of wound that
contains the most drainage
d. Swab gently rotated from side to side
•
To completely absorb microorganisms present
e. Swab placed in specimen container
f. Process repeated with second swab
Elsevier items and derived items © 2008 by Saunders, an imprint of Elsevier Inc.
97
Collection and Transport System
1. Types available
a. Culturette
b. Starswab II
Elsevier items and derived items © 2008 by Saunders, an imprint of Elsevier Inc.
98
Collection and Transport System,
cont.
2. Consist of sterile swab and plastic tube
that contains a transport medium
a. Comes packaged in peel-apart envelope
b. Should be stored at room temperature
Elsevier items and derived items © 2008 by Saunders, an imprint of Elsevier Inc.
99
Collection and Transport System,
cont.
3. Procedure for use
a. Complete laboratory request form
b. Sanitize hands
c. Apply gloves
Elsevier items and derived items © 2008 by Saunders, an imprint of Elsevier Inc.
100
Collection and Transport System,
cont.
d. Check expiration date
e. Peel open envelope
f. Remove cap from the collection tube
g. Remove cap/swab unit from envelope
h. Collect specimen using aseptic technique
•
Do not allow swab to touch any other area
Elsevier items and derived items © 2008 by Saunders, an imprint of Elsevier Inc.
101
Collection and Transport System,
cont.
i. Insert swab into collection tube
j. Push cap/swab as far as it will go to
completely immerse in transport medium
k. Remove gloves and sanitize hands
Elsevier items and derived items © 2008 by Saunders, an imprint of Elsevier Inc.
102
Collection and Transport System,
cont.
l.
Label tube
m. Place in biohazard specimen transport bag
•
Place laboratory request in outside pocket
n. Chart procedure
o. Transport to laboratory to laboratory within
24 hours
Elsevier items and derived items © 2008 by Saunders, an imprint of Elsevier Inc.
103
What Would You Do?
What Would You Not Do?
Elsevier items and derived items © 2008 by Saunders, an imprint of Elsevier Inc.
104
What Would You Do?
What Would You Not Do?
Elsevier items and derived items © 2008 by Saunders, an imprint of Elsevier Inc.
105
Cultures
1. Once a microbiologic specimen is
collected
a. Examined to determine type of
microorganisms present
2. Most specimens: only contain a small
number of pathogens
a. Must induce pathogens to grow and multiply
Elsevier items and derived items © 2008 by Saunders, an imprint of Elsevier Inc.
106
Cultures, cont.
3. Culture medium: a mixture of nutrients on
which microorganisms are grown in the
laboratory
a. Must contain growth requirements:
•
Presence or absence of oxygen
•
Proper nutrition
•
Temperature
•
pH
•
Moisture
Elsevier items and derived items © 2008 by Saunders, an imprint of Elsevier Inc.
107
Cultures, cont.
b. Solid culture medium
•
Blood agar most commonly used
– Sheep's blood added to agar
1) Contains nutrients to grow bacteria
From Mahon CR, Manuselis G Jr: Textbook of diagnostic microbiology, ed 2, Philadelphia, 2000, Saunders.
Elsevier items and derived items © 2008 by Saunders, an imprint of Elsevier Inc.
108
Cultures, cont.
c. Liquid culture medium
•
Referred to as broth
•
Usually contained in a tube
•
Example: nutrient broth
Elsevier items and derived items © 2008 by Saunders, an imprint of Elsevier Inc.
109
Cultures, cont.
4. Culture media: must be stored in
refrigerator
a. Warm to room temperature before use
b. Do not use cold culture medium
•
Results in death of microorganisms
Elsevier items and derived items © 2008 by Saunders, an imprint of Elsevier Inc.
110
Cultures, cont.
5. Petri plate: frequently used to hold solid
culture medium
a. Consists of shallow circular dish with a
cover (made of glass or clear plastic)
b. Microorganisms cultured on surface of
medium in plate
c. Allows examination of culture
•
Prevents microorganisms from entering or
escaping
Elsevier items and derived items © 2008 by Saunders, an imprint of Elsevier Inc.
111
Cultures, cont.
d. Culture: a mass of microorganisms
growing in a laboratory culture medium
From Mahon CR, Manuselis G Jr: Textbook of diagnostic microbiology, ed 2, Philadelphia, 2000, Saunders.
Elsevier items and derived items © 2008 by Saunders, an imprint of Elsevier Inc.
112
Cultures, cont.
6. Most offices use commercially prepared
culture media in disposable plastic Petri
plates
a. Plates are packaged in plastic bag
•
Prevents medium from drying out
b. Stored in refrigerator with medium side
facing up
•
Prevents condensation on surface of medium
Elsevier items and derived items © 2008 by Saunders, an imprint of Elsevier Inc.
113
Cultures, cont.
c. Expiration date: check before using
•
Do not use plates that are:
– Expired
– Dried out
– Contaminated
Elsevier items and derived items © 2008 by Saunders, an imprint of Elsevier Inc.
114
Cultures, cont.
7. Inoculation of solid culture medium in
Petri plate
a. Specimen swab is lightly rolled across
surface of medium (streaking)
•
Only remove Petri plate cover during streaking
of specimen
– Prevents contamination with extraneous
microorganisms
b. Culture is incubated for 24 to 48 hours
Elsevier items and derived items © 2008 by Saunders, an imprint of Elsevier Inc.
115
Cultures, cont.
8. Most specimens for analysis contain a
mixture of microorganisms
a. Mixed culture: contains two or more types
of microorganisms
•
Suspected pathogen must be separated to
analyze
b. Pure culture: contains only one type of
microorganism
•
Tests to identify pathogen are performed on
pure culture
Elsevier items and derived items © 2008 by Saunders, an imprint of Elsevier Inc.
116
Cultures, cont.
9. Viruses cannot be grown by the above
method
a. Are identified by:
•
Culturing on living tissue
•
Serologic tests
Elsevier items and derived items © 2008 by Saunders, an imprint of Elsevier Inc.
117
Streptococcus Testing
1. Streptococcal sore throat
(streptococcal pharyngitis)
a. Primarily affects children and young adults
b. Causative agent: group A beta-hemolytic
streptococcus
Elsevier items and derived items © 2008 by Saunders, an imprint of Elsevier Inc.
118
Streptococcus Testing, cont.
2. Potentially serious condition
a. Small percentage of patients develop a
poststreptococcal sequela
• Sequela: a morbid secondary condition that
occurs as a result of a less serious primary
infection
– Example: rheumatic fever
b. Early diagnosis and treatment of “strep
throat” with antibiotics is important
Elsevier items and derived items © 2008 by Saunders, an imprint of Elsevier Inc.
119
Rapid Streptococcus Tests
1. Detects group A streptrococci from a
throat swab
Elsevier items and derived items © 2008 by Saunders, an imprint of Elsevier Inc.
120
Rapid Streptococcus Tests, cont.
a. Requires only 4 to 10 minutes to process
• Diagnosis can be made while patient is at office
– If streptococci present: antibiotics
prescribed
Elsevier items and derived items © 2008 by Saunders, an imprint of Elsevier Inc.
121
Rapid Streptococcus Tests, cont.
2. Direct antigen identification test: most
frequently used
a. Particles sensitized to streptococcal
antibody are combined with specimen
(antigen)
b. Produces a color change if streptococcal is
present (through antigen-antibody
reaction)
c. Test includes a control
•
To ensure results are accurate and reliable
Elsevier items and derived items © 2008 by Saunders, an imprint of Elsevier Inc.
122
Rapid Streptococcus Tests, cont.
3. Includes a control to verify the results
are accurate and reliable
4. Advantage
a. Provides physician with immediate results
Elsevier items and derived items © 2008 by Saunders, an imprint of Elsevier Inc.
123
Rapid Streptococcus Tests, cont.
5. Examples of tests
a. Q Test Strep
b. Clearview Strep A
c. Quick Vue In-Line Strep A
Elsevier items and derived items © 2008 by Saunders, an imprint of Elsevier Inc.
124
Hemolytic Reaction and Bacitracin
Susceptibility
1. Streptococci classified into three types
based on their hemolytic properties:
a. Alpha
b. Beta: produces streptolysin (exotoxin) that
hemolyzes red blood cells (RBCs)
c. Gamma
Elsevier items and derived items © 2008 by Saunders, an imprint of Elsevier Inc.
125
Hemolytic Reaction and Bacitracin
Susceptibility, cont.
2. Further divided according to their
antigenic properties
a. Into 15 subgroups designated by letters A
through O
•
Group A streptococci: susceptible to the
antibiotic bacitracin
– Are destroyed by it
Elsevier items and derived items © 2008 by Saunders, an imprint of Elsevier Inc.
126
Hemolytic Reaction and Bacitracin
Susceptibility, cont.
3. Test uses these hemolytic and antigenic
properties to interpret test results
a. Causative agent of strep throat:
•
Group A beta-hemolytic streptococcus
Elsevier items and derived items © 2008 by Saunders, an imprint of Elsevier Inc.
127
Hemolytic Reaction and Bacitracin
Susceptibility, cont.
4. Testing procedure:
a. Throat specimen inoculated on blood agar
medium
b. Bacitracin disc placed on surface of
medium
c. Medium incubated for 18 to 24 hours
Elsevier items and derived items © 2008 by Saunders, an imprint of Elsevier Inc.
128
Hemolytic Reaction and Bacitracin
Susceptibility, cont.
c. Plate examined for hemolytic and antigenic
reactions
d. Positive reaction for Group A betahemolytic streptococcus
• Hemolytic reaction: clear wide colorless
zone around bacterial colonies
– Streptolysin from beta streptococci has
hemolyzed RBCs
• Antigenic reaction: clear zone of inhibition
around the bacitracin disk
– Group A streptococci are susceptible to and
destroyed by bacitracin
Elsevier items and derived items © 2008 by Saunders, an imprint of Elsevier Inc.
129
Bacitracin Susceptibility Test
From Mahon CR, Manuselis G Jr: Textbook of diagnostic microbiology, ed 2, Philadelphia, 2000, Saunders.
Elsevier items and derived items © 2008 by Saunders, an imprint of Elsevier Inc.
130
Sensitivity Testing
1. Determines susceptibility of pathogenic
bacteria to antibiotics
a. Allows physician to determine best
antibiotic to use to treat patient's condition
2. Must be performed on a pure culture
Elsevier items and derived items © 2008 by Saunders, an imprint of Elsevier Inc.
131
Sensitivity Testing, cont.
3. Disk-diffusion method
a. Most common method
b. Use disks impregnated with various
antibiotics
•
Dropped on surface of solid culture medium in
Petri plate inoculated with pathogen
Elsevier items and derived items © 2008 by Saunders, an imprint of Elsevier Inc.
132
Sensitivity Testing, cont.
c. Culture is incubated
•
Allows antibiotics to diffuse into culture medium
d. If pathogen is susceptible to an antibiotic:
e. Clear zone without bacterial growth around
disk
•
Indicates antibiotic is effective against pathogen
Elsevier items and derived items © 2008 by Saunders, an imprint of Elsevier Inc.
133
Sensitivity Testing, cont.
e. If pathogen is resistant to an antibiotic
•
No clear zone around disk
– Indicates antibiotic was unable to kill
pathogen
Elsevier items and derived items © 2008 by Saunders, an imprint of Elsevier Inc.
134
Sensitivity Testing
From Mahon CR, Manuselis G Jr: Textbook of diagnostic microbiology, ed 2, Philadelphia, 2000, Saunders.
Elsevier items and derived items © 2008 by Saunders, an imprint of Elsevier Inc.
135
What Would You Do?
What Would You Not Do?
Elsevier items and derived items © 2008 by Saunders, an imprint of Elsevier Inc.
136
What Would You Do?
What Would You Not Do?
Elsevier items and derived items © 2008 by Saunders, an imprint of Elsevier Inc.
137
Microscopic Examination of
Microorganisms
1. Can be examined in fixed or in living
state
2. Examining microorganisms in a fixed
state
a. Most microorganisms are examined this
way
b. Preparation of a smear through heat
fixation: followed by staining
• Example: Gram staining
• Easier to examine when stained
Elsevier items and derived items © 2008 by Saunders, an imprint of Elsevier Inc.
138
Microscopic Examination of
Microorganisms, cont.
3. Examining microorganisms in a living
state
a. Allows visualization of movement
b. Helpful in identification of certain motile
microorganisms
•
Example: Trichomonas vaginalis
Elsevier items and derived items © 2008 by Saunders, an imprint of Elsevier Inc.
139
Microscopic Examination of
Microorganisms, cont.
c. Microorganisms suspended in liquid
medium
•
Microorganisms are free to move about
d. Wet mount: most common method used
Elsevier items and derived items © 2008 by Saunders, an imprint of Elsevier Inc.
140
Wet Mount Method
1. MA prepare slide
2. Drop of fluid containing organism:
placed on glass slide
a. Covered with coverslip
b. Coverslip ringed with petroleum jelly
• Provides seal
– Reduces rate of evaporation
– Evaporation could lead to drying out of slide
and death of specimen
Elsevier items and derived items © 2008 by Saunders, an imprint of Elsevier Inc.
141
Wet Mount Method, cont.
1. Slide placed under microscope
2. Examined under high power by
physician
3. Slide discarded in biohazard sharps
container
Elsevier items and derived items © 2008 by Saunders, an imprint of Elsevier Inc.
142
Wet Mount Method
Elsevier items and derived items © 2008 by Saunders, an imprint of Elsevier Inc.
143
Smears
1. Smear: material spread on a slide for
microscopic examination
Elsevier items and derived items © 2008 by Saunders, an imprint of Elsevier Inc.
144
Smears, cont.
2. Prepared:
a. Directly from specimen swab
b. Specimen first grown on culture medium
3. Most smears must be stained before
viewing under microscope
Elsevier items and derived items © 2008 by Saunders, an imprint of Elsevier Inc.
145
Smears, cont.
4. Smears can be prepared and examined
immediately
a. Helpful when time is a factor
5. Provides a preliminary clue
a. While more time-consuming tests are being
performed
Elsevier items and derived items © 2008 by Saunders, an imprint of Elsevier Inc.
146
Gram Stain
1. Used in combination with other tests: to
diagnose and treat infectious diseases
2. Bacteria in a smear are colorless
a. Makes them difficult to identify
b. Staining allows for direct viewing of
bacteria
• Size
• Shape
• Growth patterns
Elsevier items and derived items © 2008 by Saunders, an imprint of Elsevier Inc.
147
Gram Stain, cont.
3. Discovered by Christian Gram in 1883
a. Differentiates bacteria on basis of their
color reactions to various stains
Elsevier items and derived items © 2008 by Saunders, an imprint of Elsevier Inc.
148
Gram Stain, cont.
4. Gram-positive
bacteria: exhibit a
purple color
a. When treated with
purple crystal violet
dye: gram-positive
bacteria
permanently retain
this dye
Courtesy Cathy Bissonette.
Elsevier items and derived items © 2008 by Saunders, an imprint of Elsevier Inc.
149
Gram Stain, cont.
5. Gram-negative bacteria:
exhibit pink or red color
a. Gram-negative bacteria
are unable to retain
purple dye: are
counterstained with a
red dye
6. Staining characteristics
of bacteria:
From Mahon CR, Manuselis G Jr: Textbook of diagnostic microbiology, ed 2,
Philadelphia, 2000, Saunders.
a. Caused by differences in
the chemical
composition of bacterial
cell walls
Elsevier items and derived items © 2008 by Saunders, an imprint of Elsevier Inc.
150
Gram Stain, cont.
7. Infectious diseases caused by grampositive bacteria:
a. Streptococcal sore throat
b. Scarlet fever
c. Rheumatic fever
d. Diphtheria
Elsevier items and derived items © 2008 by Saunders, an imprint of Elsevier Inc.
151
Gram Stain, cont.
e. Lobar pneumonia
f. Tetanus
g. Botulism
Courtesy Cathy Bissonette.
Elsevier items and derived items © 2008 by Saunders, an imprint of Elsevier Inc.
152
Gram Stain, cont.
8. Infectious diseases caused by gramnegative bacteria:
a. Whooping cough
b. Gonorrhea
c. Meningitis
From Mahon CR, Manuselis G Jr: Textbook of diagnostic microbiology, ed 2,
Philadelphia, 2000, Saunders.
Elsevier items and derived items © 2008 by Saunders, an imprint of Elsevier Inc.
153
Gram Stain, cont.
d. Bacillary dysentery
e. Cholera
f. Typhoid fever
g. Plague
From Mahon CR, Manuselis G Jr: Textbook of diagnostic microbiology, ed 2,
Philadelphia, 2000, Saunders.
Elsevier items and derived items © 2008 by Saunders, an imprint of Elsevier Inc.
154
Gram Stain, cont.
9. Categories of gram stained bacteria:
a. Gram-positive rods
b. Gram-negative rods
c. Gram-positive cocci
d. Gram-negative cocci
•
Example: gonorrhea caused by a gram-negative
diplococcus
Elsevier items and derived items © 2008 by Saunders, an imprint of Elsevier Inc.
155
Prevention and Control of Infectious
Diseases
1. Practice good techniques of medical
asepsis.
2. Obtain proper nutrition and rest.
3. Use good hygienic measures.
Elsevier items and derived items © 2008 by Saunders, an imprint of Elsevier Inc.
156
Prevention and Control of Infectious
Diseases, cont.
4. Infected individuals should contact their
physicians to ensure early diagnosis and
treatment.
5. MA responsible for educating community
members
a. Practices that reduce transmission of
pathogens
b. Practices that control and prevent
infectious diseases
Elsevier items and derived items © 2008 by Saunders, an imprint of Elsevier Inc.
157
POSTTEST
True or False
1.
Microorganisms that reside in the body but do not
cause disease are known as transient flora.
2.
The invasion of the body by a pathogenic
microorganism is known as infection.
3.
The interval of time between the invasion by a
pathogen and the first symptoms of disease is known
as the prodromal period.
4.
Staphylococcal infections usually result in pus
formation.
5.
E. coli normally reside in the urinary tract.
Elsevier items and derived items © 2008 by Saunders, an imprint of Elsevier Inc.
158
POSTTEST, CONT.
True or False
6.
The high-power objective has a magnification of 40x.
7.
Examination of urine sediment requires the use of
the oil immersion objective.
8.
A mixed culture contains two or more types of
microorganisms.
9.
The purpose of sensitivity testing is to identify the
type of microorganism present.
10. When viewed under a microscope gram-positive
bacteria appear pink or red.
Elsevier items and derived items © 2008 by Saunders, an imprint of Elsevier Inc.
159