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Title: Revision

1
Revision

Term One

2
QA Systems
Quality Assurance measures apply to the
laboratory analytical work overall, which
includes

identifying the person having the
overall responsibility for quality

having laboratory equipment calibrated to
recognised standards

gtUsing only QA.ed materials

Using reference materials ve and -ve

Validating analyses

Internal proficiency testing.

Joining proficiency testing schemes with other
laboratories doing similar tests

gtUsing correct SOP for each method/activity

Using correct record sheets

Traceability of changes to SOPs and records

3
QC systems
Quality control measures apply to each analytical
test in the laboratory by use of
Control chart

reagent blanks
verified standard solutions
check samples (from both within the lab and from
outside)

blind samples
replicate analyses
and control charts
Positive and negative controls
All materials QC ed.

Keeping track of the
samples

Lab. No. F7-002

Sample registration gives each sample a unique
lab number.
The sample register records all the information
about the sample.
Just like a samples passport, you should not
confuse any sample with any other.
The history of the sample should be traceable
throughout.

Sample integrity
Samples recorded on receipt
5
Beta ( ß ) hemolysis (blood agar around bacterial
colonies is completely clear, indicating complete
breakdown and consumption of hemoglobin)
6
Alpha (a) hemolysis (blood agar around bacterial
colonies looks greenish-brown, indicating partial
breakdown and consumption of hemoglobin)
Mixed culture from a throat swab note several
ß-hemolytic colonies
7
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8
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9
Catalase Test
10
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11

Chapter 21 Diseases of Skin and Eyes
1. Staphylococcal Infections
Gram-positive cocci in irregular clusters
Coagulase negative strains make up to 90 of skin
microbiota (S. epidermidis). Only pathogenic
when skin is broken or through invasive entry.
Coagulase positive strains tend to be pathogenic.
Almost all pathogenic S. aureus strains make
coagulase. High correlation between ability to
produce coagulase and production of damaging
toxins
Leukocidin Destroys phagocytic white blood
cells.
Exfoliative toxin Responsible for scalded skin
syndrome.
Enterotoxins Affect gastrointestinal tract.
S. aureus is commonly found in nasal passages.

1. Staphylococcal Infections (Continued)
Common staphylococcal diseases
A. Folliculitis Infection of hair follicles
(pimples).
B. Sty Infected eyelash follicle.
C. Boil (Abscess or Furuncle) More serious
infection of hair follicle in which pus is
surrounded by inflamed tissue. Usually painful
and firm.
D. Carbuncle Aggregate of several infected
follicles (boils). May cause fever, chills,
malaise, and death if not treated.
Forms a round, hard, deep area of inflammation,
typically on neck and back.
Damages surrounding tissue, with extensive
scarring.
May need to lance and drain surgically.

1. Staphylococcal Infections (Continued)
Common staphylococcal diseases
E. Impetigo Problem in hospital nurseries and
day care centers. Thin walled vesicles on skin
rupture and crust over.
Caused by S. aureus, S. pyogenes, or both.
Highly contagious, spread through direct contact
and fomites.
Occurs almost exclusively in children.
Rarely produces fever and easily treated with
penicillin.

Staphylococcal diseases (continued)
6. Scalded skin syndrome Caused by toxemia from
S. aureus strains with two different exfoliative
toxins.
Large sheets of bright red skin peel off.
Usually observed in children under 2, but may
occur in adults.
Bacteremia and septicemia may occur, and can lead
to death within 36 hours.
Require vigorous antibiotic treatment.
Exfoliative toxins are highly antigenic,
preventing recurrence.

Staphylococcal diseases (continued)
7. Toxic shock syndrome (TSS) Fever, vomiting,
and sunburnlike rash, followed by shock. Rash
later peels.
Presently about 25 cases per year reported.
Most cases are associated with use of
superabsorbent tampons.
Males with boils or other staphylococcal
infections are at risk.
A few cases associated with use of contraceptive
sponge.
5-15 of women have S. aureus in vaginal
microflora.
Only a small percentage of these strains produce
TSS.

In addition to skin infections, the staph
bacteria can cause
Bacteremia a blood infection
Deep abscesses an abscess that occurs below the
skin surface
Endocarditis an infection on the valves of the
heart
Food poisoning vomiting or diarrhea caused by a
staph toxin
Lymphadenitis an infection of a lymph gland,
which causes it to be red, swollen and painful

Lymphangitis an infection of the lymph channels
that drain to lymph glands, causing red streaks
in the skin
Osteomyelitis a bone infection
Paronychia an infection of the skin folds of
the nails
Scalded skin syndrome
Septic arthritis an infection of a joint, like
a hip or a knee
Styes an infection of the glands on the eyelid
Toxic shock syndrome

18
MRSA

MRSA stands for Methicillin-Resistant
Staphylococcus aureus
MRSA are Staph aureus bacteria that have become
resistant to this antibiotic.

2. Streptococcal Infections
Gram-positive cocci in chains.
Cause many disease including meningitis,
pneumonia, sore throat, otitis media,
endocarditis childbirth fever, and dental caries.
Produce multiple toxins and virulence factors.
Stretokinases Dissolve blood clots.
Proteases Destroy proteins.
Hyaluronidase Breaks down connective tissue.
Hemolysins Lyse red blood cells. Alpha, beta,
and gamma hemolysis.
Beta hemolytic streptococci are often associated
with human disease.
Streptococcus pyogenes Group A b-hemolytic
streptococci.
Infections are often localized, but can produce
great damage when they reach deeper tissue.

Chapter 21 Diseases of Skin and Eyes
1. Staphylococcal Infections
Gram-positive cocci in irregular clusters
Coagulase negative strains make up to 90 of skin
microbiota (S. epidermidis). Only pathogenic
when skin is broken or through invasive entry.
Coagulase positive strains tend to be pathogenic.
Almost all pathogenic S. aureus strains make
coagulase. High correlation between ability to
produce coagulase and production of damaging
toxins
Leukocidin Destroys phagocytic white blood
cells.
Exfoliative toxin Responsible for scalded skin
syndrome.
Enterotoxins Affect gastrointestinal tract.
S. aureus is commonly found in nasal passages.

1. Staphylococcal Infections (Continued)
Common staphylococcal diseases
A. Folliculitis Infection of hair follicles
(pimples).
B. Sty Infected eyelash follicle.
C. Boil (Abscess or Furuncle) More serious
infection of hair follicle in which pus is
surrounded by inflamed tissue. Usually painful
and firm.
D. Carbuncle Aggregate of several infected
follicles (boils). May cause fever, chills,
malaise, and death if not treated.
Forms a round, hard, deep area of inflammation,
typically on neck and back.
Damages surrounding tissue, with extensive
scarring.
May need to lance and drain surgically.

1. Staphylococcal Infections (Continued)
Common staphylococcal diseases
E. Impetigo Problem in hospital nurseries and
day care centers. Thin walled vesicles on skin
rupture and crust over.
Caused by S. aureus, S. pyogenes, or both.
Highly contagious, spread through direct contact
and fomites.
Occurs almost exclusively in children.
Rarely produces fever and easily treated with
penicillin.

Staphylococcal diseases (continued)
6. Scalded skin syndrome Caused by toxemia from
S. aureus strains with two different exfoliative
toxins.
Large sheets of bright red skin peel off.
Usually observed in children under 2, but may
occur in adults.
Bacteremia and septicemia may occur, and can lead
to death within 36 hours.
Require vigorous antibiotic treatment.
Exfoliative toxins are highly antigenic,
preventing recurrence.

Staphylococcal diseases (continued)
7. Toxic shock syndrome (TSS) Fever, vomiting,
and sunburnlike rash, followed by shock. Rash
later peels.
Presently about 25 cases per year reported.
Most cases are associated with use of
superabsorbent tampons.
Males with boils or other staphylococcal
infections are at risk.
A few cases associated with use of contraceptive
sponge.
5-15 of women have S. aureus in vaginal
microflora.
Only a small percentage of these strains produce
TSS.

In addition to skin infections, the staph
bacteria can cause
Bacteremia a blood infection
Deep abscesses an abscess that occurs below the
skin surface
Endocarditis an infection on the valves of the
heart
Food poisoning vomiting or diarrhea caused by a
staph toxin
Lymphadenitis an infection of a lymph gland,
which causes it to be red, swollen and painful

26
MRSA

MRSA stands for Methicillin-Resistant
Staphylococcus aureus
MRSA are Staph aureus bacteria that have become
resistant to this antibiotic.

2. Streptococcal Infections
Gram-positive cocci in chains.
Cause many disease including meningitis,
pneumonia, sore throat, otitis media,
endocarditis childbirth fever, and dental caries.
Produce multiple toxins and virulence factors.
Stretokinases Dissolve blood clots.
Proteases Destroy proteins.
Hyaluronidase Breaks down connective tissue.
Hemolysins Lyse red blood cells. Alpha, beta,
and gamma hemolysis.
Beta hemolytic streptococci are often associated
with human disease.
Streptococcus pyogenes Group A b-hemolytic
streptococci.
Infections are often localized, but can produce
great damage when they reach deeper tissue.

Common streptococcal skin diseases
Erysipelas From Greek erythos red, and pella
skin. Also called St. Anthonys fire. Common
skin infection associated with S. pyogenes.
Spread through contact or insect bites.
Skin erupts into reddish patches with raised
margins.
High fever is common.
Organisms can spread through lymphatics and cause
septicemia, abscesses, pneumonia, endocarditis,
arthritis, and even death if untreated.
Mortality was high before use of antibiotics.
Responds well to antibiotic (b-lactams) treatment.

Common streptococcal skin diseases
Flesh eating bacterial infections
Caused by invasive group A streptococci.
15,000 cases per year in U.S.
Exotoxin A acts as superantigen causing damage by
the immune system.
Attacks and destroys muscle (myositis), muscle
covering (fasciitis), and solid tissue
(cellulitis).
Can destroy several inches of tissue per hour.
Antibiotics are not effective because dead tissue
has no circulation.
Requires amputation or surgical removal of
tissue.
Mortality rate up to 40
Impetigo Refer to previous description.

30
Flesh eating bacterial infections

Caused by invasive group A streptococci.
15,000 cases per year in U.S.
Exotoxin A acts as superantigen causing damage by
the immune system.
Attacks and destroys muscle (myositis), muscle
covering (fasciitis), and solid tissue
(cellulitis).
Can destroy several inches of tissue per hour.
Antibiotics are not effective because dead tissue
has no circulation.
Requires amputation or surgical removal of
tissue.
Mortality rate up to 40

31
Bacillus

Classification
All are large Gram-positive bacilli
Are aerobic
Form endospores
Most are found in dust and soil
Bacillus anthracis is the major pathogen in the
group
Morphology and Cultural Characteristics
(Bacillus anthracis)

32
Bacillus

Grow well on ordinary lab media producing large
granular colonies with a coarse texture.
Virulence factors
Capsule helps organism to resist phagocytosis
but antibodies are not protective.
Exotoxin is very complex and is produced only
when the bacteria is growing in animal tissues.
Toxin production is mediated by a temperature
sensitive plasmid.
The toxin consists of three protein components
(maximum toxicity occurs when all three
components are present).

33
Bacillus

Clinical significance
Anthrax which is the disease caused by B.
anthracis is essentially a disease of animals
who acquire the organism by ingestion or
inhalation of spores.
The spores are extremely resistant to adverse
chemicals and physical environments.
They may remain a source of infection in soil
for 2-3 years.
Man acquires anthrax usually from contact
with animal products less commonly from
working in an agricultural setting with
infected animals.

34
Bacillus

Man may acquire the organism through skin
abrasions, by inhalation of spores, or by
ingestion. The disease that develops depends
upon the mode of transmission
Pulmonary (Woolsorters disease) Spores are
inhaled and germinate in the lungs where they
multiply and spread to cause a fatal
septicemia or meningitis.
This is the most serious form of the disease.
Intestinal anthrax results from ingestion of
spores.

35
Bacillus

Antibiotic susceptibility and treatment
Penicillin or tetracycline
A short-term PA vaccine is available for
industrial workers and others at high risk.
Other Bacillus species
Bacillus subtilis, and occasional other
species may occasionally cause opportunistic
infections.
Bacillus cereus is a major cause of
enterotoxin food poisoning
The toxin is protein in nature and can be
destroyed by heating
Food poisoning occurs after ingestion of
pre-formed toxin
Vomiting occurs 1-5 hours after ingestion

36
Bacillus

B. cereus is also an opportunistic pathogen that
has been cultured from cases of
septicemia, endocarditis, meningitis, wound
infections, pneumonia, and fulminant eye
infections
In addition to the enterotoxin that bacteria may
produce, a dermonecrotic and a lethal
toxin, hemolysins, lecithinase, proteases, and
nucleases may be involved in its pathogenesis
Clindamycin with or without gentamycin may be
used for treatment of infections

37
Clostridium

Clostridium form endospores under adverse
environmental conditions
Spores are a survival mechanism
Spores are characterized on the basis of
position, size and shape
Most Clostridium spp., including C. perfringens
and C. botulinum, have ovoid subterminal (OST)
spores
C. tetani have round terminal (RT) spores

38
Clostridium

Clostridium form endospores under adverse
environmental conditions
Spores are a survival mechanism
Spores are characterized on the basis of
position, size and shape
Most Clostridium spp., including C. perfringens
and C. botulinum, have ovoid subterminal (OST)
spores
C. tetani have round terminal (RT) spores

39
Clostridium perfringens
40
Micro Macroscopic C. perfringens
41
Clostridial Cellulitis
42
Clostridium tetani
43
Clostridium tetani Gram Stain
NOTE Round terminal spores give cells a
drumstick or tennis racket appearance.
44
Opisthotonos in Tetanus Patient
45
Mechanism of Action of Tetanus Toxin
46
Clostridium botulinum
47
Mechanism of Action of Botulinum Toxin
48
Rates of Isolation of C. botulinum and
Botulinum Toxin
49
Tuberculosis (TB, consumption)