Streptococci Flashcards
Name 3 species of the mutans streptococcus group
- S. mutans 2. S. sobrinus 3. S. cricetus
Mode of action of mutans streptococcus
They bind to and colonise the tooth surface by producing extracellular polysaccharides (sucrose)
Name 3 virulence factors of streptococcus pyogenes required for adherence
- M protein 2. Fibronectin binding protein (Protein F) 3. Lipoteichoic acid
Major causes of infective endocarditis
- S. sanguinis (32%) 2. S. oralis (30%) 3. S. gordonii (13%)
Name some members of the viridans group streptococci Describe their appearance on a CBA.
Streptococcus mutans Streptococcus salivarius Streptococcus sanguinis Streptococcus mitis Green colonies Alpha-haemolytic
What does pyrogenic exotoxins cause?
- Scarlet fever - Toxic shock like syndrome (TSLS)
Which bacteria is the leading cause of dental caries?
Streptococcus mutans
What does GAS bacteria cause? Name one bacteria
Streptococcus pyogenes “Strep” throat Scarlet fever Rheumatic fever Post-streptococcal glomerulonephritis (PSGN) Necrotising fasciitis
Antibiotic treatment for GAS?
- Penicillin (10 day course) 2. Amoxicillin (but narrow spectrum acceptable for children) 3. Erythromycin (for patients sensitive to penicillin) 4. CoAmoxy-Clav Clindamycin (for repeated infections)
Where would one expect to find Streptococcus salivarius?
Saliva and tongue; (keratinised surfaces of mouth) Upper respiratory tract; GI tract
Name 2 properties of mutans streptococcus
- Acidogenic - produce acid at a high rate from sugar 2. Aciduric - tolerate high concentrations of acid
Where would one expect to find Streptococcus mutans?
On tooth surfaces/fissures
Name the group of bacteria that appears to have a “greening” effect on CHOC
Viridans group of streptococcus
What test can be carried out to differentiate streptococcus from staphylococcus?
- Gram stain –> Streptococcus appear as chains; Staphylococcus appear as grape-like clusters 2. Catalase test –> Streptococcus - catalase negative Staphylococcus - catalase positive
What can streptococcus anginosus lead to?
Nasty infections: - oral abscesses & brain, liver - bacteraemia & endocarditis - appendicitis & peritontitis
Name the bacteria that have ‘beta’ haemolytic activity on CBA
Streptococcus Pyogenes; Streptococcus Anginosus
Name a bacteria sensitive to bacitracin
Streptococcus Pyogenes
What does M protein serve as?
Major virulence factor for the group A streptococcus. It inhibits the activation of complement and protects the organism from phagocytosis. However, plasma (B) cells generate antibodies against the M protein, which bind to the M protein (opsonization), aiding in the destruction of the organism by macrophages and neutrophils.
Name a bacteria sensitive to optochin
Streptococcus Pneumonia
Viral pharyngitis VS “Strep Throat”?
Absence of fever and presence of cough in viral pharyngitis
Name 5 members of the oralis group of streptococci
- Streptococcus oralis 2. Streptococcus sanguinis 3. Streptococcus gordonii 4. Streptococcus mitis 5. Streptococcus crista
Where would one expect to find Streptococcus anguinosis?
On dental plaque and abscesses
Name the bacteria with ‘alpha’ haemolytic activity on CBA
Viridans group of streptococcus; Streptococcus pneumonia
Where would one expect to find Streptococcus oralis?
On tooth, forming biofilms
Name 3 main types of infections caused by the viridans group of streptococcus
- Dental infections - caries 2. Endocarditis 3. Abscesses
Function of hyaluronic acid capsule in S. pyogenes
Serve as a virulence factor - 1. Evasion of host defences: function as an immunological disguise as it produces hyaluronic acid which is similar to human produced ones, hence reducing phagocytosis 2. Functions in tissue penetration/spread
Type of vaccine used against Strep. Pneumonia
Inactivated (Killed) vaccine
