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BMS212 - Bacteriology > Purulent and bacteraemic infections > Flashcards

Purulent and bacteraemic infections Flashcards

1
Q

Purulent Infections

  • what are they
  • 3 main culprits
A

-Purulent = pus forming

Main culprits;

  • Staphylococci
  • Streptococci
  • Corynebacteria and others
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2
Q

Staphylococcus

  • what are they
  • what they cause (and due to what)
A
  • commersals of skin and mucous membranes
    • also important pathogens
  • are opportunists
  • cause suppurative (pus forming) inflammation due to the production of leukotoxins
  • can lead to septicaemia (potentially fatal whole body inflammation)
  • Also can cause food poisoning, toxic shock
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3
Q

Isolation & identification of Straphylococcus

  • gram & morphology
  • what it can tolerate

-3 features

A

-Gram positive cocci in clusters
-tolerates high salt concentration (mannitol salt agar useful)
-also grow readily on blood agar
Identification;
-pigmented
-haemolytic
-catalase positive (hydrogen peroxide into gas bubbles)

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4
Q

Staphylococcus aureus (“Golden Staph”)

Staphylococcus albus (“white Staph”)

-features

A

S. aureus

  • not necessarily golden (can be white or grey)
  • are a coagulase positive species
  • carried on skin and nose by many, can be pathogenic

S. albus

  • now called S. epidermidis
  • coagulase negative
  • skin commensals/opportunists
  • less pathogenic, but can form biofilms in catheters, joints etc & may be resistant to antibiotics
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5
Q

Properties of Pathogenic Straphylococcus species

A
  • Often resistant to penicillins
  • mecA gene causes changes in penicillin binding proteins in peptidoglycan layer (transmissible - horizontally)
  • Produce range of tissue-damaging enzymes
  • produce leukotoxins - pus
  • strains vary greatly - some can be highly aggressive
  • Vaccines generally not available due to strain differences
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6
Q

Staph aureus -> major human pathogen

  • Localised skin infections it can cause
  • MRSA
    • what is it
    • reservoir
    • where can it come from & what can it cause
A

Causes various localised skin infections;
-impetigo
-boils (infected hair follicle)
-furunculosis (recurring crops of boils in an area)
-Staph scalded skin syndrome (SSSS) - skin blisters and sheds
MRSA (Methicillin resistant S. aureus)
-reservoir in pigs, horses, dogs
-nosocomial (from hospitals) , also emerging in community, transmitted by contact
-toxic shock syndrome
-food poisoning

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7
Q

Streptococci

  • where found
  • what they are
  • what they usually cause
A
  • Widespread - skin, nose, throat
  • Commensals/opportunists (many species/strains of varying pathogenic potential
  • usually localised purulent lesions - but can spread in bloodstream
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8
Q

Streptococci vs Staphococci

A

Strept - Staph

Chains - clusters
small colonies on plates - large colonies
enriched media - basal media
catalase negative - catalase positive

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9
Q

Enterococcus

  • problem with them
  • Avoparcin in pigs
  • 2 e.g.
A
  • not very virulent, but highly resistant to antimicrobials & readily become bacteraemic from the gut
  • Vancomycin resistant enterococci (VRE) in hospitals = major problem
  • Avoparcin (antibiotic/growth promoter) banned from vet use because of fears of inducing cross-resistance w/ vancomycin in enterococci in poultry and pigs
    - then fear of subsequent spread to humans

e.g. E. faecium & E. faecalis

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10
Q

Lancefield Grouping of Pathogenic Streptococci

  • What is it, what is it based on
  • Types & Species
  • Virulence factors of different strains (6)
A

-based on antigenicity of cell wall polysaccharides
-further typing uses M proteins
Types: based on antisera to surface proteins
Species: Based on biochemical reactivity etc. within groups
Virulence factors of different strains;
-Haemolysins
-Sreptokinase
-Hyaluronidase
-DNases
-Erthyrogenic toxin
-Capsules

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11
Q

Streptococcal haemolysis (3 types)

A 
alpha = partial
beta = complete haemolysis
gamma = no haemolysis
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12
Q

Human Diseases associated with groups a and b of streptococcus

-e.g. of bacterial species

A 
Group A - e.g. Strep pyogenes
-Tonsilitis
-Erysipelas
-scarlet fever
-septicaemia
-rheumatic fever
-Glomerulonephritis (inflammation of kidney)
-Necrotising faciitis
Group B -
e.g. strep agalactiae - neonatal bacteraemia
strep mutans - tooth decay
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13
Q

Streptococcus pneumoniae

  • what organ they affect
  • Difficulties in vaccination
  • resistance
  • what it is also involved in
A

“the pneumococcus” -> infects lungs

  • No groups but over 90 capsular serotypes (therefore polyvalent vaccines)
    • hard to do
  • multi drug resistant strains emerging
  • middle ear infection
  • sinuses
  • lungs
  • joints/meninges
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14
Q

Corynebacterium

  • features
  • Clinical disease
    • animal forms
    • C. ulcerans
    • C. diptheriae
A

-Pleomorphic
-gram positive rods and opportunists
-stain irregularly
-many species
Clinical disease
-Occasional infection w/ “animal coryneforms (e.g. C. equi in AIDS patient)
-C. ulcerans: pharangitis
-C. diptheriae: localised pharangitis, generalised toxaemia (tho not all strains are toxaemic - can carry w/out disease - esp so in developing countries)

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15
Q

Erysipelothrix

-features

  • E. rhusiopathiae
    • where it multiples in cells
    • 2 sources
A
  • Small, gram positive rods
  • resistant
  • facultative intracellular pathogens (need to invade cell)
  • Have rough filamentous forms (allows adhesion)

E. rhusiopathiae
-multiples in and kills neutrophils -> bacteraemia
Sources: soil, carriers

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16
Q

Erysipeloid in humans

  • what it causes
  • where commonly found (what type of workers)
  • features of bacteria (Hint; it is caused by Erysipelothrix)
  • what it is resistant to
A
  • Raised purple skin lesion (e.g. crayfish handlers)
  • Often found in butchers, fishmonger and abbatoir workers
  • Gram positive bacillus
  • catalase negative
  • Intrinsically Vancomycin resistant
17
Q

Listeriosis

  • Symptoms
  • Common sources
A 
Symptoms;
-high fever
-severe headaches
-nausea
-abdominal pain
-diarrhea
Common sources;
-Washing salad w/ unclean water
-uncooked fish
-cheese
-processed meats
18
Q

Listeria monocytogenes

  • features of disease/bacteria
    • where it multiplies
    • ideal temperatures
  • where found
  • why is it an important foodborne zoonosis?
    • what can it cause
A

-Sporadic disease
-Reduced host resistance
-multiplies in macrophages (intracellular pathogen)
-High case fatality
-‘Cold enrichment”
Found in soil, faecs, silage etc.
*in humans, is an important foodborne zoonosis esp. in pregnant individuals
Can cause;
-abortions, high mortality and epidemics/endemic

19
Q

Bacillus -features

-why are they significant medically?

  • Bacillus cereus
    • features
    • what mainly involved in?
      • illness & what specifically causes it
A
  • Large Gram positive Rods
  • Spore formers
  • Very Resistant (antibiotically & environmentally)

Bacillus cereus

  • no bacteraemia
  • occasionally bovine mastitis
  • Human food poisoning (esp. in reheated rice)
    • nausea, vomiting, diahorrea
  • toxin is in spore coat (is what causes illness)
20
Q

Anthrax

  • Pulmonary, Gastrointestinal and Cutaneous symptoms
    • name for skin lesions
A
  • Pulmonary: Flu-like symptoms, pneumonia, severe respiratory collapse
  • Gastrointestinal: Vomiting blood, severe diarrhea, loss of appetite, acute inflammation of GI tract
  • Cutaneous: Boil-like skin lesions, painless necrotic ulcer w/ black centre (ESCHAR)
21
Q

Anthrax Letters (9/11/01)

A
  • Letters addressed to certain senators had anthrax in them
  • was the Ames strain that had 2 virulence plasmids;
    - anthrax toxin, polyglutamic acid capsule
  • Vollum strain is more dangerous
22
Q

Bacillus antrhracis

  • how it grows
  • vaccine
  • Use in war/terrorism
  • What it is a clone of (difference between them)
  • spores (features and how reactivated)
A
  • grows in chains (rods)
  • notifiable: humans and animals
  • Pasteur’s vaccine 1881 = 5 dose series
  • Has been used in germ warfare & bio-terrisim
  • is a virulent clone of B. cereus (just has an extra plasmid!)
  • spores can survive for centuries
    • are reactivated when inhaled, ingested or come in contact with skin
    • soil borne spores present globally
23
Q

3 features that make anthrax dangerous

  • Where found in Australia -> what is most susceptible
    • what infection causes
A
  1. Endospores: prolonged survival
  2. Capsule: hard for them to be engulfed or for antibodies to bind to them
  3. Produce powerful toxins (all 3 needed to produce anthrax toxin)
    • oedema factor
    • protective factor
    • lethal factor
      • all three cause tissue degradation, swelling, bleeding and death
  • is an anthrax belt in central NSW - spores in soil
    • Ruminants most susceptible as they may inhale/ingest spores
      • spores germinate, local lesion
      • lymphatics - spleen - spill out: causes septicaemia/toxaemia – peracute death

BMS212 - Bacteriology (15 decks)

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