Streptococcus and enterococcus

Question 1

Streptococcus meaning

Answer 1

Streptos = chainm coccus = grain or berry

Question 2

Obligate anearobe

Answer 2

Killed by atmospheric oxygen

Question 3

Streptococcus metabolism

Answer 3

General strong fermenters of carbohydrates (makes lactic acid and changes pH)

Question 4

Name the six clusters of the streptococcus genus:

Answer 4

1) Pyogenic (pus generating) includesmost of the pathogens
2) Mitis (pneumonia) - oral commensals
3) Anginosus (commensal oral)
4) Salivarius (commensal oral)
5) Bovis (colon)
6) Mutans (colonises tooth surfaces - some are dental caries)

Almost all are opportunistic pathogens if they gain acces to blood stream.

Question 5

Haemolytic activity in streptococci

Answer 5

Investigations have shown that the pyogenic strains posses bacterial haemolysins that can break of red blood cells (this process is called beta haemolysis) - this gives clear area around pyogenic strains grown on blood agar.

Commensal streptococci don’thave this but causes oxidation of haemoglobin by hydrogen peroxide (alpha hemolysis). This is green (viridis in latin - viridans streptococci)

Question 6

Lancefield grouping

Answer 6

The different species of the pyogenic streptococci has been shown to have different cell wall components called lancefield grouping. (see images).

Question 7

Streptococcus Pyogenes

Answer 7

Lancefield group A. Respiratory tract, skin and soft tissue infections.

Question 8

Virulence factors of streptococcus pyogenes:

Answer 8

1) F-protein interacts with fibronectin in connective tissue and on cells mediating cell internalisation.
2) M-protein - binds host protein and thereby masks the bacterialo cell from phagocytosis.
3) Some strains produce hualrounic acid capsule that disguises the bacterium
4) C5a peptidase
5) Streptolysin O (oxygen) and S (serum soluble) - lysis of blood cells.
6) pyrogenic exotoxins (generates fever) -SPE-A to C
7) Hyaluronidase - degrades connective tissue
8) Streptokinase - Plasmin activating (breaks down fibrin) which makes invasion easier.

Question 9

Most normal non-invasive strep. pyogenes infections:

Answer 9

1) Pharyngitis (inflammation in the pharynx, enlarged tonsils, sore throat) - strep throat
2) Scarlet fever - after pharyngitis a red rash is seen usually in chest region and the mucuos membrane of tongue and mouth
3) Skin infections - makes pus filled regions - enters through small craks in skin

Question 10

Most normal invasive strep. pyogenes infections:

Answer 10

1) Necrotising fascitis - enters through skin but colonises fat or fascia (bindevæv) and kills it
2) Streptococcal toxic shock syndrome - fever diarrhea etc from toxins produced by strep. pyogenes.
3) Bacteraemia - bacteria in blood

Question 11

Sequalae from pyogenes:

Answer 11

1) Rheumatic fever - inflammtion of joints, heart mm. Autoimmune from cross reactive antibodies.
2) Acute poststreptococcal glomerulonephritis - coffee coulered urine and edema.

Question 12

Streptococcus agalactiae

Answer 12

Group B lancefield and beta-hemolysis - exists in the colon and sometimesin the vagina.

Question 13

2 different neonatal agalactiae infections:

Answer 13

1) Early onset - 12 hours after birth - from vagina into amniotic fluid - initially causes tiredness, low blood oxygen and apnoea - then septicimea (bloodstream infection)follws which can lead to meningitis or other stuff.
2) late onset 7 days to 3 months after birth. - purulent meningitis

Can alsoinfect non-pregnant people.

Question 14

Streptococcus pneumoniae

Answer 14

Diplococcus (two) In the respiratory microbiota.

Question 15

Strep. pneu. virulence factors

Answer 15

1) Anti-phagocytotic capsule
2) IgA1 protease

3) Pneumolysis - autolysid toxin that damges membranes and through that
- Neutrophil chemotaxis
- Phagocytosis
- lymphocyte proliferation

4) autolysin - cuts up own cell wall and causes massive reaction.

Question 16

When do you get pneumonia infection?

Answer 16

1) Disease or operations disturb normal respiratory mucus flow etc.
2) diabetes and all those things
3) Immunocompromised people

Question 17

Most common clinical manifestations of streptococcus pneumoniae:

Answer 17

1) pneumonia - Infection following aspiration and migration of bacteria - causes inflammation.
2) Middle ear infection
3) Meningitis
4) Conjuncitivitis

Question 18

Where are enterococcus?

Answer 18

In the gut

Question 19

Most common diseases caused by enterococcus

Answer 19

1) UTI
2) Infective endocarditis
3) Biliary tract infections
4) peritonitis
5) suppurative abdominal lesions

Question 20

Most common enterococcus species:

Answer 20

E. faecalis and E. faecium

Question 21

Detection pf streptococcal infection

Answer 21

Show the bacterium in:

• Throat swap
• CSF sample
• Blood
• pus etc

Question 22

Big difference between staph and streph:

Answer 22

Streph lacks catalase. Streph colonies are without color.

Question 23

Primary cultivation for strep:

Answer 23

Blood agar

Question 24

Typing of streptococci:

Answer 24

Usually done on the M-protein (very variable)

Question 25

Treatment of streptococcus:

Answer 25

Pyogenes = Penicillin (no resistance)

Agalactiae = Penicillin (or other beta lactam)

pneumococci and viridans = can have penicillin resistance (some can be susceptible to high doses) - erythromycin.