Microbiology E-Learning Compilation
CVR
Table of Content
Streptococci
Staphylococci
Neisseria
Corynebacteria/Listeria/Brucella
Cardiovascular Infections
Mycobacteria
Gram Negative Bacilli
Chlamydia/Mycoplasma/Rikesttsia
Respiratory Tract Infections
Measles, Mumps, Rubella
Respiratory viruses
Contributors:
Noor Khairiah Kamaludin
Abdul Rasyid Nasir
Ahmad Zafrullah Afham Ahmad Fikri
Nur Hamizah Che Hashim
Muhammad Iqbal A Ghani
Editor:
Muhammad Iqbal A Ghani
Disclaimer
All the materials belong and copyrighted to Microbiology Department of RCSI. The compilation only meant to be helping the student
studying throughout the haunting IC1 Microbiology Module. We, the contributors do not held any responsibility regarding the material.
This copy cans freely circulating for student by no business means – if you pay for this, ask your money back-. Specially for RCSI Buddies
2008-2013. The Editor would like to thank the contributors for the effort and everything and those who involve directly or indirectly.
Credit to Microsoft Word 2007 and Adobe Acrobat Pro Extended.
,STREPTOCOCCI
What is the microscopic appearance of streptococci on Gram staining?
They appear as Gram-positive oval cocci, usually in chains
How are streptococci classified?
This is done based on the presence or absence of haemolysis around colonies growing on
blood agar.
1. Haemolytic
o alpha, greenish-hue on blood agar - represents incomplete haemolysis.
o beta, complete haemolysis - the agar is cleared of blood.
2. Non-haemolytic - no haemolysis
List the most important streptococci that cause human infections .
The following are the most important streptococci:
Streptococcus pyogenes (Group A beta-haemolytic).
Streptococcus agalactiae (Group B beta-haemolytic).
Viridans streptococci (alpha-haemolytic).
Streptococcus pneumoniae (alpha-haemolytic).
Enterococci (beta-haemolytic or non-haemolytic).
Peptostreptococci (anaerobic, non-haemolytic)
,Group A streptococci (GAS) i.e. Streptococcus pyogenes
What is the natural habitat of GAS?
May be carried in the upper respiratory tract, usually the tonsillar area.
What contributes to the pathogenicity of GAS or Str. pyogenes ?
The virulence (and pathogenicity) of GAS is due to the production of the following:
- M Protein
- Streptokinase (or fibrinolysin).
- Hyaluronidase
- Erythrogenic/pyrogenic Toxin
- Leucocidin
- Haemolysins - 2 are produced
- DNAases A, B and C
Group A streptococci (GAS) i.e. Streptococcus pyogenes
1. M Protein
Located as fimbrial projections which cover the entire coccus. Antibodies to it are formed in
the body in response to infection and these will protect from future infection with that
particular M type.
M protein mediates attachment to epithelial cells and is anti-phagocytic and there are different
types. M types 1, 3 12 and 28 are the most common isolates from patients with shock and
multi organ failure.
2. Streptokinase (or fibrinolysin).
Acts on plasminogen and converts it to Plasmin which is an enzyme capable of breaking
down fibrin and other proteins. Has been given intravenously to patients with myocardial
infarction, pulmonary emboli and venous thrombosis as an anti-thrombotic agent.
3. Hyaluronidase
An enzyme that splits hyaluronic acid, part of the cementing substance of tissues.
These two substances (2 & 3) allow the streptococcal infection to spread along lymphatics
leading to "cellulitis." From the lymphatics, infection may spread into the bloodstream,
resulting in bloodstream infection or bacteraemia.
4. Erythrogenic/pyrogenic Toxin
This is an exotoxin and produces the rash of Scarlet Fever, i.e. tonsillitis with rash. This
toxin is only produced in Group A cells which are lysogenic, i.e. contain a temperate phage
(virus).
This toxin is antigenic and those infected produce antibodies (antitoxins) to the toxin. Such
people are immune to development of rash, but are not immune to other infections with GAS.
, Some of these toxins, most notably SPE A and SPE B, are superantigens, and are responsible
for streptococcal toxic shock syndrome, which is a multi-system condition arising from the
release of cytokines.
5. Leucocidin
An enzyme that can kill leucocytes.
6. Haemolysins
2 are produced.
Streptolysin O and Streptolysin S; ASO titre used to retrospectively diagnose infection such
as with acute rheumatic fever (see later).
7. DNAases A, B and C
Antibody to C appears in most infections with Group A streptococcus. Antibody levels rise
more slowly than ASO antibodies but they remain raised for a longer period of time.
Infections
What are the important infections caused by GAS and outline the main features of
each?
These include:
1. Acute Tonsillitis
2. Scarlet Fever
3. Skin infections
4. Puerpural Sepsis
5. Sepsis in Burns
6. Bloodstream Infection/Bacteraemia
7. Necrotizing Fasciitis
8. Post-streptococcal infections:
9. Toxic shock syndrome
Infections
1. Acute Tonsillitis
In young children this may spread to middle ear (otitis media), or to the mastoid (acute
mastoiditis).
In older children and adults, it is usually accompanied by a higher temperature than that seen
in the very young, and enlarged cervical glands are usually present.
Differential Diagnosis: Must be distinguished from infection caused by:
Adenoviruses, most important cause of moderate to severe tonsillitis.
Epstein-Barr virus (EBV), i.e. infectious mononucelosis.
CVR
Table of Content
Streptococci
Staphylococci
Neisseria
Corynebacteria/Listeria/Brucella
Cardiovascular Infections
Mycobacteria
Gram Negative Bacilli
Chlamydia/Mycoplasma/Rikesttsia
Respiratory Tract Infections
Measles, Mumps, Rubella
Respiratory viruses
Contributors:
Noor Khairiah Kamaludin
Abdul Rasyid Nasir
Ahmad Zafrullah Afham Ahmad Fikri
Nur Hamizah Che Hashim
Muhammad Iqbal A Ghani
Editor:
Muhammad Iqbal A Ghani
Disclaimer
All the materials belong and copyrighted to Microbiology Department of RCSI. The compilation only meant to be helping the student
studying throughout the haunting IC1 Microbiology Module. We, the contributors do not held any responsibility regarding the material.
This copy cans freely circulating for student by no business means – if you pay for this, ask your money back-. Specially for RCSI Buddies
2008-2013. The Editor would like to thank the contributors for the effort and everything and those who involve directly or indirectly.
Credit to Microsoft Word 2007 and Adobe Acrobat Pro Extended.
,STREPTOCOCCI
What is the microscopic appearance of streptococci on Gram staining?
They appear as Gram-positive oval cocci, usually in chains
How are streptococci classified?
This is done based on the presence or absence of haemolysis around colonies growing on
blood agar.
1. Haemolytic
o alpha, greenish-hue on blood agar - represents incomplete haemolysis.
o beta, complete haemolysis - the agar is cleared of blood.
2. Non-haemolytic - no haemolysis
List the most important streptococci that cause human infections .
The following are the most important streptococci:
Streptococcus pyogenes (Group A beta-haemolytic).
Streptococcus agalactiae (Group B beta-haemolytic).
Viridans streptococci (alpha-haemolytic).
Streptococcus pneumoniae (alpha-haemolytic).
Enterococci (beta-haemolytic or non-haemolytic).
Peptostreptococci (anaerobic, non-haemolytic)
,Group A streptococci (GAS) i.e. Streptococcus pyogenes
What is the natural habitat of GAS?
May be carried in the upper respiratory tract, usually the tonsillar area.
What contributes to the pathogenicity of GAS or Str. pyogenes ?
The virulence (and pathogenicity) of GAS is due to the production of the following:
- M Protein
- Streptokinase (or fibrinolysin).
- Hyaluronidase
- Erythrogenic/pyrogenic Toxin
- Leucocidin
- Haemolysins - 2 are produced
- DNAases A, B and C
Group A streptococci (GAS) i.e. Streptococcus pyogenes
1. M Protein
Located as fimbrial projections which cover the entire coccus. Antibodies to it are formed in
the body in response to infection and these will protect from future infection with that
particular M type.
M protein mediates attachment to epithelial cells and is anti-phagocytic and there are different
types. M types 1, 3 12 and 28 are the most common isolates from patients with shock and
multi organ failure.
2. Streptokinase (or fibrinolysin).
Acts on plasminogen and converts it to Plasmin which is an enzyme capable of breaking
down fibrin and other proteins. Has been given intravenously to patients with myocardial
infarction, pulmonary emboli and venous thrombosis as an anti-thrombotic agent.
3. Hyaluronidase
An enzyme that splits hyaluronic acid, part of the cementing substance of tissues.
These two substances (2 & 3) allow the streptococcal infection to spread along lymphatics
leading to "cellulitis." From the lymphatics, infection may spread into the bloodstream,
resulting in bloodstream infection or bacteraemia.
4. Erythrogenic/pyrogenic Toxin
This is an exotoxin and produces the rash of Scarlet Fever, i.e. tonsillitis with rash. This
toxin is only produced in Group A cells which are lysogenic, i.e. contain a temperate phage
(virus).
This toxin is antigenic and those infected produce antibodies (antitoxins) to the toxin. Such
people are immune to development of rash, but are not immune to other infections with GAS.
, Some of these toxins, most notably SPE A and SPE B, are superantigens, and are responsible
for streptococcal toxic shock syndrome, which is a multi-system condition arising from the
release of cytokines.
5. Leucocidin
An enzyme that can kill leucocytes.
6. Haemolysins
2 are produced.
Streptolysin O and Streptolysin S; ASO titre used to retrospectively diagnose infection such
as with acute rheumatic fever (see later).
7. DNAases A, B and C
Antibody to C appears in most infections with Group A streptococcus. Antibody levels rise
more slowly than ASO antibodies but they remain raised for a longer period of time.
Infections
What are the important infections caused by GAS and outline the main features of
each?
These include:
1. Acute Tonsillitis
2. Scarlet Fever
3. Skin infections
4. Puerpural Sepsis
5. Sepsis in Burns
6. Bloodstream Infection/Bacteraemia
7. Necrotizing Fasciitis
8. Post-streptococcal infections:
9. Toxic shock syndrome
Infections
1. Acute Tonsillitis
In young children this may spread to middle ear (otitis media), or to the mastoid (acute
mastoiditis).
In older children and adults, it is usually accompanied by a higher temperature than that seen
in the very young, and enlarged cervical glands are usually present.
Differential Diagnosis: Must be distinguished from infection caused by:
Adenoviruses, most important cause of moderate to severe tonsillitis.
Epstein-Barr virus (EBV), i.e. infectious mononucelosis.
