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Microbiology > S2. Pneumococcus & Enterococcus > Flashcards

S2. Pneumococcus & Enterococcus Flashcards

1
Q

Is Streptococcus pneumoniae a human pathogen?

A

Yes, its stricly a human pathogen, doesnt cause diseases in other species.

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2
Q

Streptococcus pneumoniae characteristics?

A
  • gram +ve, non motile, encapsulated, diplococci
  • lancet shaped
  • produces alpha-haemolysis on blood agar
  • autolysis of colonies w/ further incubation
  • some produces mucoid colonies ( excessive production of polysacchride)
  • capsulated (84 serotypes)
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3
Q

Streptococcus pneumoniae clinical infections?

upper resp tract infections:

A
  • otitis media: most common bacterial causative agent in all ages
  • sinusitis: common cause in both children & adults
  • conjunctivitis (or pink eye, is the inflammation of the transparent membrane lining the eyelid/ eyeball)
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4
Q

Streptococcus pneumoniae clinical infections?

lower resp tract infections:

A
  • Pneumonia
  • s.pneumoniae is the commonest cause of community acquired pneumonia
  • a leading cause of death in older adults & immonocomprised patients
  • pneumonia is often proceeded by upper respiratory viral infection which predisposes to S.pneumoniae infection of pulmonary paranchyma
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5
Q

Streptococcus pneumoniae clinical infections?

Meningitis

A
  • most common cause of adult bacterial meningitis
  • bimodal (has 2 peaks) incidence (children < than 3 yrs & adults > 45 yrs)
  • mortality rate ~ 20% even if treated properly
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6
Q

Streptococcus pneumoniae clinical infections?

Arthritis

A
  • infection of the joints

- gram -ve cocci, salmonella can cause arthtitis

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7
Q

Streptococcus pneumoniae clinical infections?

Bacteremia & septicemia

A
  • infections of blood
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8
Q

Streptococcus pneumoniae pathogensis?

A
  • normal oropharyngeal flora (5-70%)

- obligate human pathogen

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9
Q

Streptococcus pneumoniae virulence factors?

A
  • capsular polysaccharides
  • certain serotypes are resposnsible for more than 90% of invasive disease ( bacteremia & meningitis)
  • antigenic & type specific
  • non capsulated strains are avirulent
  • demonstration of the polysacchride capsule by capsular swelling test
  • pneumolysin
  • membrane damaging toxin
  • induces features of lobar pneumonia
  • contributes to mortility
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10
Q

Optochin sensitivity is a feature of?

A

Streptococcus pneumoniae

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11
Q

What’s serogrouping?

A

To know which one of the capsular 84 serotypes causes the infection, esp for vaxxed ppl who still got the infection to know which capsular serotype the vaccine didnt work with, or to know new capsular serotypes that isnt covered by the vaccine causing the infection.

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12
Q

Predisposing factors?

A
  • pre-existing resp diseases e.g. viral infections , COPD ( chronic obstructive pulmonary disease)
  • predisposing diseases e.g. DM (diabetes mellitus), IHD( ischemic heart disease), CRF ( chronic renal failure), malignancy & elderly
  • immune deficiencies eg, sickle cell anemia, asplenia, multiple myeloma, HIV
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13
Q

Labratory diagnosis of streptococcus pneumoniae?

A 
-Culture of the diff specimens:
blood, CSF, sputum, ear pus, sinus fluid 
- alpha- haemolysis on blood agar
- bile soluble 
- optichin sensitive 
- mucoid colonies in capsulated strains
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14
Q

Lab diagnosis of streptococcus pneumoniae?

- rapid direct detection methods

A
  • direct microscopy ( CSF, joint fluid, eye swab)

- direct antigen detection in CSF & urine (latex)

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15
Q

S.pneumoniae differentiation from S.Viridans?

A

S.pneumoniae is Optochin disc (Sensitive)
S.pneumoniae is Bile solubility (Soluble)
S.pneumoniae is Serotyping (latex) (Positive)
-

S.Viridans is Optochin disc (Resistant)
S.Viridans is Bile solubility (Not Soluble)
S.Viridans is Serotyping (latex) (Negative)

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16
Q

Immunoprophylaxis

A
  • killed vaccine —> 2 types
  • polysacchraide vaccine >2 yrs
  • conjugated vaccine —> children < 2 yrs
  • diff serotypes:
    7- valent ( 7 valent meants that the vaccine covers 7 serotypes)
    10- valent
    13- valent
17
Q

Polysacchirde vaccine?

A
  • funtional or anatomical a splenia
  • chronic renal failure
  • chronic heart disease
  • chronic lung disease
  • chronic liver disease
  • DM
  • HIV
18
Q

Conjugate pneumococcal vaccine?

A
  • all children < 2 yrs

- adults > 50 yrs

19
Q

Entrococcus general info:

A
  • GI tract if man & animal is the main habitat
  • catalase negative
  • member of oropharangeal, intestinal, vaginal & skin flora
20
Q

Most common species of Entrococcus associated w human diseases are?

A

E.faecalis —> 80-90%

E.faecium —> 5-10%

21
Q

Pathogensis of Entrococcus?

A
  • intrinsically resistant to many antibiotics

- ability to adhere to heart valve & renal epithelial cells

22
Q

Lab diagnosis of Entrococcus?

A
  • non-hemolytic colonies on blood agar

- esculin positive

23
Q

1) Clinical infections of Entrococcus?

2) what are the risk factors for acquiring nosocomial infections include?

A 
1) Community & nosocomial (in hospitals)
Endogenous (from flora) & Exogenous (from outside)
2) - serious underlying disease 
- length of hospital stay 
- surgery esp abdominal surgery 
- presence of catheters 
- ICU 
- broad spectrum antibiotics eg cephalosporin
24
Q

Clinical infections of Entrococcus?

A

UTI

  • most common type
  • cystitis (lower UTI) & pyelonephritis (upper UTI)
  • nosocomial UTI associated w/ catherization
25
Q

Clinical infections of Entrococcus?

A
  • Bacteraemia ( in elderly )
  • mortality rate is high
  • source —> UTI, wound infection, diabetic foot
  • nosocomial bacteremia not associated w/ endocarditis
  • community bacteraemia may be associated w/ endocarditis
26
Q

Clinical infections of Entrococcus?

A
  • Endocarditis
  • 5-15% of endocarditis
  • elderly w/ underlying valve disease
  • Intra- abdominal - pelvic & wound infections
  • endogenous infection
  • mixed infection

Microbiology (8 decks)

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