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Kirstys Flashcards > PMB: Steptoccocus 15 > Flashcards

PMB: Steptoccocus 15 Flashcards

1
Q

What are the characterisitics of streptococcus?

A
  • Gram positive
  • Catalase negative (Can’t produce catalase)
  • Non-motile (doesnt move)
  • Non-spore forming
  • Faculative anaerobic (can grow aerobically or anarobically)
  • Growth in pairs or chains
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2
Q

What is classification of species/ chains dependent on?

A
  • Colony morphology
  • Haemolysis
  • Biochemical reactions
  • Serological specificity
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3
Q

What categories of strepptocoi is there dependent on haemolysis?

A

Divided into groups by the type of haemolysis on blood agar

  • a- Haemolysis
  • B- Haemolysis
  • Y- Haemolysis
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4
Q

Describe the effect a-Haemolysis has on blood agar

A
  • Green zone around colonies
  • Complete lysis of RBC
  • Incomplete degradation of Haemoglobin
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5
Q

Describe the effect B-Haemolysis has on Blood agar plates

A
  • Transparent zone around RBC
  • Complete lysis of RBC
  • Complete degradation of haemoglobin
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6
Q

Describe Y-haemolysis on RBC agar plates

A

NO haemolytic activity

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7
Q

Give some examples of a- and y- haemolytic streptococci

A
  • •S. pneumoniae: α-haemolytic, airway infections, sepsis, meningitis
  • •Oral streptococci: α- or g- haemolytic, caries caused by S. mutans and S. sobrinus
    • •S. salivarius
    • •S. sanguis
    • •S. mutans
    • •S. mitis
    • •S. sobrinus
    • •S. constellatus
    • •S. intermedius
    • •etc.
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8
Q

Desribe streptococcus phenomenia

A
  • Also called pneumococcus
  • Cause of pneumonia, meningitis, sepsis, otitis media
  • Diplococcus (pair cells)
  • Surrounded by a dense capsule that makes bacteria resistant to phagocytosis
    • More than 90 diffferent capulse varietnts: Serotypes
    • Encapsulated strains: COlonies with smooth surfaces
    • Non-encapaulsted mutants: colonies with rough surfaces
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9
Q

How severe is steptoccous pneuomiea?

A
  • Commonly occurs after an airway infection e.g. influenza
  • It is common, but life threatening in people with weakened immune systems e.g. Eldery, infants, adults with underlying diseases
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10
Q

What are the symptoms of streptococcus phenumoniea

A
  • Breathing difficulties
  • Chest pains
  • High fever
  • Reusty red sputum colour
  • Can invade blood (sepsis) and meninges (meningitis)
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11
Q

What is the diagnosis of S.Phenuomiea?

A
  • a-haemolysis on blood agar plate
  • Optochin (Antibody) sensitivity test: Zone of inhibitation around disk contain optochin
  • Bile solubility test: Autolysis of bacteria upon addition of deoxycholate
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12
Q

What treatment/ prevention options are available for S.Penumomenia?

A
  • Treatement (After contracting infection)
    • Penicillins
      • Increasing resistance due to altered transpeptidases
    • Macrolides:
      • Used as a reserve
      • Target bacterial ribosomes
  • Prevention:
    • Polycalent polysaccharide vaccine
      • ‘Recomenend in immunocompromised
      • 2-3 valent vaccine for children <2 years and adults
      • 7-calent conjugated vaccine for infants >2months
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13
Q

What are examples of oral streptococcus?

A
  • S. Mutans and S. Sobrinus
  • They attach to the teeth (enamal) and in the presence of sugarsb(Sucrose) form a biofilm which leads to plaqu formation
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14
Q

How is the dental plauqe formed?

A
  • Glycoproteins from saliva form a film on tooth surfaces. ORal streptococci bind to these glycproteins on the enamal and in the presence of sucrose form a biofilm. This leads to plaque formation. In the biofilm sucrose is converted to fructose and glucose.
  • Fructose is fermintated to lactic acid and glucose undergoes polymerisation via glucosyl-transferase to polysaccharide occurs (mutan, glycan, dextran)
  • The lactic acid in the biofilm begins to interact with the enamal which is made up of hydroxyapatite and is sensitive to low pH
  • This leads to regions of the enamal dissolving and generating cavities
  • These cavities colonize with streptococci and other bacteria. Bacteria relese protolytic enxymes whihc destroy the dentin
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15
Q

What is serological classification of B-haemolytic streptococci/

A

Can be grouped based on 2 different methods:

  • Different carbohydrates present on bacterialc cell walls
    • Lancefield serogrouips (A-V)
  • Subtyping based on proteins in cell wall
    • S.Pyrogenes Mtype 1-83
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16
Q

What detectio method can be used for B-haemolytic streptococci?

A
  • Latex Agglutination tesr
  • POstive response - clumping
  • Negative response - no clumping
17
Q
  1. What group does Streptococcus pyrogens belong too?
  2. What does it cause
  3. What is the treatment?
A
  1. Only species in group A of lancefield serogroup A
  2. Causes:
    • Skin infections e.g. Necrotizinf fasciitis
    • Sore throat
    • Toxigenic infections
    • Immunological diseases
18
Q

What is the treatment for streptococcus Pyrogenes?

A

B-lactams ABs

19
Q

Describe skin infections caused by streptococcus pyrogenes

A
  • Necrotizing Fascitis
  • Agressive skin infection
  • Multiple pathogenic factors involved e.g. proteases, toxins, super antigens.
  • Bacterial toxins interfere with blood flow to tissues - this can lead to infection in these tissues
  • Digestion of tissue proteins by proteases - allows spread of bacteria
  • Can cause systemic effects like septic shock
20
Q

What are other disease caused by S.Pyrogenes?

A
  1. Pyrogenic infections of throat: tonsilitis
  2. Toxinogenic fevers: scarlet fever
  3. Immunological diseases: Rheumatic fever a post-streptococcal disease
21
Q

What is tonsilitis

A
  • Severe sore throat
  • sore or difficulty swallowing
  • headache
  • fever and chills
  • changes or loss in ones voice
22
Q

What are your tonsils and what happens to them during tonisilits?

A
  • pair of speicalised lymph nodes behind the tounge
  • Store white blood cells to engulf bacteria and viruses which enter the nose or mouth
  • When overwhelmed by bacteria, they becoe swollen and inflammed
23
Q

What is scarlet fever cause by and what are the symptoms?

A
  • Cause: Rare form of S.Pyrogenes infection. Caused by a lysogenized strain of S.Pyrogenes: a phage codes for an erythrogenic toxin
  • Symptoms:
    • Red rash on body that feels like sand paper
    • Strawberry tougne: Red tounge with prominant piapillae
    • Sore throat
    • fatigue
24
Q

What are the complicaitons of scarlet fever for children?

A
  • Serious complicatinose.g. rheumatic fever and acute glomerulonephritis
25
Q

What is rheuam

A
  • Occurs after a streptococcus pyrogene infection e.g. strept throat or scarlrt fever
  • It is an immune response which causes inflammation and damge to certain organs, particularly the heart.
  • The ABs prodcues by the body against the intital streptococcus (M protein) infection cross-react with the heart and attack the bodies own cells
26
Q

Rheumatic fever symptoms

A
  • Fever
  • Wekaness
  • Abdominal pain
27
Q

What is glomerulonephritis?

Symptoms

A
  • •Acute glomerulonephritis:
    • •blockage of glomeruli by streptococcal immuno-complexes
  • •Symptoms of the disease:
    • •blood in the urine
    • •high blood pressure
    • •decreased or increased urine output
28
Q

What makes combating S.Pyrogenes difficult?

A
  • M protein receptors on bacterial cell wall bind to fibrinogen and prevent acess for ABs to bind
  • S.Pyrogenes produces peptidase C5a peptidase which cleaves immune component C5a. This prevents the migration and movement of macrophages which would normally attack S.pyrogenes
  • The capsule surface of S.Pyrogenes contains Hyaluronic acid. This is specific to eukaroytes and can mean immune cells don’t recoginize the bacteria as forgin and produce ABs
  • May over stimulate T cells and AB by B lymphocytes. This can lead to toxic shock and organ failure (more info next slide)
29
Q

Superanitgen notes

A
  • Uptake of antigen by antigen presenting cell; processing and presentation in major histocompatibility complex (MHC II)
  • Recognition of antigen by T helper cell with suitable receptor (0.01%)
  • Cytokine production; antibody production by B lymphocytes
  • Superantigen links MHC II receptor to any T helper cell
  • overstimulation of T helper cells; overproduction of cytokines
  • may result in toxic shock: organ failure
30
Q

Describe adhesion an dinvasion

A
  • Adhesion mediated by protein F
  • isolated protein in the bacterial cell wall binding to fibronection on host cell surface
  • Invasion of the body mediated by
  • Streptolysin, a hemolysin
  • Streptokinase and Hyaluronidase,

spreading factors

Kirstys Flashcards (116 decks)

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