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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.

4
  • 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.

12
  • 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.

13
  • 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.

14
  • 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.

15
  • 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.

16
  • 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

17
  • 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.

19
  • 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.

20
  • 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.

21
  • 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.

22
  • 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.

23
  • 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.

24
  • 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.

25
  • 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.

27
  • 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.

28
  • 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.

29
  • 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)
  • M. tuberculosis
  • major human disease
  • healthy people
  • problems
  • association with AIDS
  • multiple drug-resistance

50
  • M. avium- M. intracellulare complex (M. avium)
  • non-AIDS
  • infection almost never
  • AIDS
  • major bacterial opportunist
  • multiple drug-resistance

51
M. bovis
  • spread from cattle
  • infected cattle are culled
  • positive skin test
  • rarely seen in US

52
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

53
Laboratory diagnosis - tuberculosis
  • skin testing
  • delayed hypersensitivity
  • tuberculin
  • protein purified derivative, PPD
  • X-ray

54
Laboratory diagnosis M. tuberculosis
  • acid fast bacteria
  • sputum

55
Positive skin test -tuberculosis
  • indicates exposure to organism
  • does not indicate active disease

56
Laboratory diagnosis M. tuberculosis (culture)
  • grows very slowly
  • several weeks
  • non-pigmented colonies
  • niacin production
  • differentiates from other mycobacteria

57
Mycobacterium leprae
58
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
  • low temperature

59
Leprosy
  • tuberculoid
  • few organisms
  • active cell-mediated immunity
  • lepromatous
  • immunosuppression
  • few organisms

60
Leprosy
  • lepromin
  • skin testing
  • acid-fast stains
  • skin biopsies
  • clinical picture

61
Corynebacterium diphtheriae
62
Corynebacterium diphtheriae
  • Gram positive
  • strict aerobe
  • pleomorphic (e.g. club-shaped)

63
Diphtheria
  • infection
  • upper respiratory tract (pharynx)
  • pseudomembrane
  • chocking
  • bacteria do not spread systemically
  • .

64
Diphtheria toxin
  • B binds to host cell
  • A inhibits protein synthesis
  • ADP-ribose moiety (NADH) attaches
  • rare amino acid, diphthamide
  • elongation factor 2 inhibited

65
  • C. diphtheriae should not be confused with
  • diphtheroids
  • other corynebacteria
  • propionibacteria

66
Corynebacterium spp.
67
Listeria monocytogenes
  • Listeriosis
  • (invasive disease non-invasive enteritis)
  • The organism Gve ovoid to rod-shaped bacterium
  • Widespread in environment

68
Listeria monocytogenes
  • Characteristics
  • - grows in wide range of temperatures (1 to
    45o C)
  • - survives freezing
  • - aerobic anaerobic
  • conditions

69
Listeria monocytogenes
  • The illness invasive form
  • - incubation 30 days
  • - flu-like symptoms, diarrhoea,
  • vomiting, meningitis, septicaemia,
  • spontaneous abortion

70
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

71
Listeria monocytogenes
  • The illness non-invasive
  • - incubation 18 hours
  • - diarrhoea, fever, muscle pain,
  • headache, abdominal cramps
  • vomiting

72
Listeria monocytogenes
  • The illness non-invasive
  • - infective dose gt 100 thou. cells/gm
  • - all individuals susceptible
  • - Rx - penicillin, ampicillin /-
  • gentamicin

73
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)

74
Listeria monocytogenes
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