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Term One
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
>Using 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
>Using correct SOP for each method/activity
•Using correct record sheets
•Traceability of changes to SOPs and records
% Fat
3.30
QC systems
% fa t
Quality control measures
apply to each analytical
test in the laboratory by
use of:
3.25
3.20
3.15
3.10
14/01/02
24/01/02
03/02/02
13/02/02
23/02/02
05/03/02
15/03/02
25/03/02
04/04/02
14/04/02
date
Control chart
• reagent blanks;
• verified standard • blind samples
solutions;
• check samples
• replicate analyses;
• and control charts
(from both within
• Positive and
the lab and from
negative controls
outside);
• All materials QC ed.
24/04/02
Keeping track of the
samples
• Sample registration gives each
sample a unique lab number.
Lab. No. F7-002
Sample integrity
• The sample register records all
the information about the sample.
• Just like a sample’s passport, you
should not confuse any sample
with any other.
• The history of the sample should
be traceable throughout.
Samples recorded on receipt
Beta ( β ) hemolysis (blood agar around bacterial colonies is
completely clear, indicating complete breakdown and consumption
of hemoglobin)
Alpha (α) hemolysis (blood agar
around bacterial colonies looks
greenish-brown, indicating
partial breakdown and
consumption of hemoglobin)
Mixed culture from a throat
swab; note several β-hemolytic
colonies
Optochin (Taxo P) sensitivity
- Results with no zone of inhibition
+ results with a zone of inhibition
P
P
Catalase Test
-
+
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.
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
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
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 bhemolytic streptococci.
– Infections are often localized, but can
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
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
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 bhemolytic streptococci.
– Infections are often localized, but can
Common streptococcal skin diseases
– Erysipelas: From Greek erythos = red, and
pella = skin. Also called St. Anthony’s 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.
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%
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)
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).
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.
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 (Woolsorter‘s 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.
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
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
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
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
Clostridium perfringens
Micro & Macroscopic C. perfringens
NOTE: Large rectangular
NOTE: Double zone of hemolysis
gram-positive bacilli
Inner beta-hemolysis = θ toxin
Outer alpha-hemolysis = α toxin
Clostridial Cellulitis
Clostridium tetani
Clostridium tetani Gram Stain
NOTE:
Round terminal spores give cells a
“drumstick” or “tennis racket” appearance.
Opisthotonos in Tetanus Patient
Mechanism of Action
of Tetanus Toxin
Clostridium botulinum
Mechanism of Action
of Botulinum Toxin
Rates of
Isolation of
C. botulinum
and
Botulinum
Toxin
Tuberculosis
(TB, consumption)
• M. tuberculosis
• major human disease
– healthy people
• problems
– association with AIDS
– multiple drug-resistance
M. avium- M. intracellulare
complex (M. avium)
• non-AIDS
– infection almost never
• AIDS
– major bacterial opportunist
• multiple drug-resistance
M. bovis
• spread from cattle
• infected cattle are culled
– positive skin test
• rarely seen in US
M. leprae
• leprosy
• major disease of third world
• Leprosy rates in Australia are only about
•
•
•
one case per million,
but are higher in Aboriginal Australians
and immigrants from infected areas.
Worldwide, leprosy is still endemic mostly
in Africa and around India.
There is also some leprosy in parts of the
USA
Laboratory diagnosis -
tuberculosis
• skin testing
– delayed hypersensitivity
– tuberculin
– protein purified derivative,
PPD
• X-ray
Laboratory diagnosis
M. tuberculosis
• acid fast bacteria
– sputum
Positive skin test tuberculosis
• indicates exposure to
organism
• does not indicate active
disease
Laboratory diagnosis
M. tuberculosis (culture)
• grows very slowly
– several weeks
– non-pigmented colonies
– niacin production
*differentiates from other mycobacteria
Mycobacterium
leprae
Leprosy (Hansen's Disease)
• M. leprae
– causative agent
• chronic disease
– disfigurement
• rarely seen in the U.S.
• common in third world
• millions of cases
• infects the skin
Leprosy
• tuberculoid
• few organisms
• active cell-mediated immunity
• lepromatous
• immunosuppression
• few organisms
Leprosy
• lepromin
– skin testing
• acid-fast stains
– skin biopsies
• clinical picture
Corynebacterium diphtheriae
Corynebacterium diphtheriae
• Gram positive
• strict aerobe
• pleomorphic (e.g. club-shaped)
Diphtheria
• infection
– upper respiratory tract (pharynx)
– pseudomembrane
– chocking
– bacteria do not spread systemically
.
Diphtheria toxin
• B binds to host cell
• A inhibits protein synthesis
• ADP-ribose moiety (NADH)
attaches
– rare amino acid, diphthamide
– elongation factor 2 inhibited
C. diphtheriae should not be confused with:
• diphtheroids
– other corynebacteria
– propionibacteria
Corynebacterium spp.
Listeria monocytogenes
Listeriosis
(invasive disease & non-invasive
enteritis)
•
The organism – G+ve ovoid to
•
Widespread in environment
rod-shaped bacterium
Listeria monocytogenes
• Characteristics
- grows in wide range of
temperatures (1 to 45o C)
- survives freezing
- aerobic & anaerobic
conditions
Listeria monocytogenes
• The illness – invasive form
- incubation – 30 days
- flu’-like symptoms, diarrhoea,
vomiting, meningitis, septicaemia,
spontaneous abortion
Listeria monocytogenes
• The illness – invasive
form, continued
- infective dose – 100 to 1 000
cells
- pregnant women, newborn
babies, the elderly & AIDS
patients
- Rx – penicillin, ampicillin +/gentamicin
Listeria monocytogenes
• The illness – non-invasive
- incubation – 18 hours
- diarrhoea, fever, muscle pain,
headache, abdominal cramps &
vomiting
Listeria monocytogenes
• The illness – non-invasive
- infective dose – > 100 thou. cells/gm
- all individuals susceptible
- Rx - penicillin, ampicillin +/gentamicin
Listeria monocytogenes
• Sources
- human – person-to-person rare
- animal – diseased animals shed in faeces,
contamination of red meat; silage
- food – ready-to-eat cooked food with long
shelf-life
- raw foods
- environment – widespread in soil, water & sewage
(Hospitals & occupational exposure)
Listeria monocytogenes
Year
2004
2002
2000
1998
1996
1994
1992
1990
1988
1986
1984
1982
40
35
30
25
20
15
10
5
0
1980
Number of cases
Listeriosis cases in NZ from 1980 to 2004