Streptococci

1
Streptococci

• Gehan J. Panagoda
• Division of Microbiology

2
Morphology

• Gram ve, chains, diplo, initially from
  erysipelas, divisions one plane, mention about
  Staph, length of chains varies on culture
  conditions. No relationship between length and
  virulence

3
? haemolysis
Strep and pus
Cervical lymph adenitis
Tonsilitis
4
Culture

• Aerobes, facultatively anerobic, pathgenic Strep
  require exacting nutrients. Therefore, grow well
  in BA. 10 CO2 promotes growth and haemolysis.

5

• Haemolysis Alpha, partial with greenish
  discolouration (unidentified reductant
  haemoglobin - viridans strep and pneumococcus
  (NO SUCH THING CALLED STREP. VIRIDANS). Beta, a
  wide clear zone, beta haemolysins - Streptolysin
  O and S - S. pyogenes. Gamma - non-haemolytic
  (commonly used term) - S. faecalis.

6
Classification

• For aerobic and facultative anaerobic
• .Haemolytic classification
• I have already mentioned about this. Most of the
  pathogenic Strep causing primary infections fall
  into beta. Alpha Strep is generally remains as
  commensals.

7

• .Serological classification - For beta haemolytic
  Strep
• 1. Based on the group specific polysaccharide (c)
  antigen of the cell wall - Lancefield
  classification, 20 A-V, No I and J. THE MOST
  IMPORTANT GROUP IS A - S. pyogenes.

8

• 1.1 Based on the type specific antigen (M, T, R
  most important is A - Mass Transit Railway) - for
  S. pyogenes serotyping - Grifith classification -
  80 serotypes. M is on the cell, resists
  phagocytosis, promotes adherence to the host.
  WITHOUT M IS AVIRULENT.

9

• .Classification based on Schleifer and
  Kilpper-Balz (1987) -Based on the structure of
  the cell wall and G C composition (NOT
  IMPORTANT FOR YOU).

10
S. pyogenes

• PATHOGENIC FEATURES -
• 1. M that is the type specific antigen
• 2. Capsular hyaluronic acid - capsule also in gp
  C during the logrithmic phase. ANTIBODIES
  PRODUCED AGAINST THE CAPSULE IS NOT PROTECTICE.

11

• MEANS THE CAPSULE IS A VIRULENT FACTOR, SIMILAR
  TO THAT OF PNEUMOCOCCUS, INHIBITS PHAGOCYTOSIS

12

• 3. Toxins and enzymes
• Toxins - Streptolysin S and O - have already
  mentioned. Streptolysin O acts not only against
  red cells but also cytotoxic to neutrophils and
  platelets and cardiac tissue. An ASO titre of
  160-200 units - suggests a recent infection.
  Erythrogenic toxin - the rash of scarlet fever.

13

• Enzymes
• Streptokinase - lyse RBC, prevents a fibrin
  barrier around the leision thus spread
• Nicotinamide adenine dinucleotidase (NADase)

14

• Hyaluronidase - acts on hyaluronic acid -
  antibodies against this is diagnostic. THEREFORE,
  ASO AND THIS IS IMPORTANT IN DIAGNOSIS OF S.
  PYOGENES INFECTIONS

15
.Suppurative infections

• Acute infections of the respiratory tract. Sore
  throat-(acute tosillitis/and or pharyngitis -
  organisms are at the site - can spread and cause
  cervical adenitis, otitis media, meningitis.
  Scarlet fever- a complication of sore throat,
  rash is due to erythrogenic toxin, organism is
  not at the site.

16

• Skin infections - Impetigo - among children,
  discrete infections, highly communicable, common
  in countries like Sri lanka (Why ? hot and
  humid). Organism is at the site. Can cause also
  by Staph. aureus Erysipelas mainly among elderly
  - acutely spreading infection. Some time is
  associated with sore throat. Organism is present
  at the site. Believed to be a hypersensitivity
  reaction.

17
Erysipelas - Butterfly-wing rash

• Followed by upper
• respiratory tract infection
• On the face or leg
• Transferred by fingers

18
Scarlet fever
Caused by an erythrogenuc strain Portal of
entry is the throat May followed by infection of
wound/burn
19
(No Transcript)
20

• Pathogenesis
• (Immune mechanism) Ab produced against protein
  and polysaccharide of orga cross react with
  myocardial and heart valve tissue Not clear.
• Immune response Marked ASO titre ? 200 Moderate
  to low
• Course Progressive Spontaneous resolution
• Penicillin
• Prophylaxis Because of repeated attacks,
  Penicillin
• Prophylaxis is Essential Not indicative

21

• .Laboratory diagnosis
• .Acute suppurative infections
• Smear - Strep and pus Culture - in a transport
  medium, on BA 370C , ? haemolysis, overnight,
  better under anaerobic with 5-10 CO2, ELISA to
  detect Strep antigens, Serological tests - not
  useful

22

• .Non-suppurative complication
• Culture - useful for the presence of Strep/
  serological test to check the level of ASO titre
  ? 200 for rheumatic fever, DNAase-B test for
  acute nephritis

23
(No Transcript)
24
(No Transcript)
25

• .Other haemolytic Streptococci
• Group B -S. agalactiae - bovine mastitis,
  neonatal septicaemia and meningitis
• Group C and G
• ENTEROCOCCI - Group D
• STREPTOCOCCUS MILLERI (UK term) in USA (S.
  intermedius) (Group F) alpha, beta of gamma,
  present in the mouth, throat GI tract, infect
  internal organs, brain liver,

26
(No Transcript)
27
Suacute bacterial endocarditis

• Splinter haemorrhages
• Lodging of emboli under finger nails
• other than kidneys and brain

28
(No Transcript)
29
(No Transcript)
30
(No Transcript)
31
(No Transcript)
32
(No Transcript)