Classification of bacteria Flashcards
What shape are bacilli ?
Rod shaped
What shape are cocci ?
Round/Spherical
What are the two structural types of cocci and what are their structures ?
Staphylococci and Streptococci.
Staphylococci are clusters
Streptococci are chains.
Name the three sub categories of Streptococci and give examples for each.
Alpha haemolytic - Streptococci Pneumoniae
- Streptococci Viridans
Beta haemolytic - Streptococci Pyogenes
- Streptococci Agalactiae
Non haemolytic - Enterococci
What does alpha haemolytic streptococci do to blood agar ?
Turns it green
What does beta haemolytic streptococci do to blood agar ?
Turns it clear
What test is used to distinguish Staphylococci ?
Coagulase test
What strain of bacteria is coagulase positive ?
Staphylococci Aureus
What are the three gram positive anaerobic bacilli ?
Clostridium tetani
Clostridium perfringens
Clostridium difficile
Name the strict aerobic gram negative bacilli
Pseudomonas aeruginosa
Name the gram negative diplococci
Neisseria meningitidis
Neisseria gonorrhoeae
Name the small bacilli which is gram negative
Haemophilus influenzae
There are two categories of large aerobic bacilli. What are they and give examples of each.
Gut commensals:
E.Coli
Proteus
Klebsiella
Gut pathogens:
E.coli 0157
Shigella
Salmonella
What are the two microaerophilic bacteria ? Mention their shape too.
Campylobacter - small curved bacilli
Helicobacter - spiral bacilli
Name the strict anaerobic gram negative bacilli
Bacteriodes
Explain what colour gram positive bacteria are under the gram stain and why this is the case.
Gram positive bacteria take up the crystal violet stain, which appears purple when seen under the microscope. They have a thick peptidoglycan layer in the cell wall which retains the stain even after washing.
Explain what colour gram negative bacteria are under the gram stain and why this is the case.
Gram negative bacteria take up the crystal violet stain. However they do not retain this stain after washing, because they have liposaccharides in their cell wall which dissolve from the alcohol used in the washing. Thus they don’t retain the stain and appear red/pink in colour.
What are the three pathogens which cant be cultured well nor can be stained using the gram stain technique ?
Mycobacterium
Spirochaetes
Chlamydia
What stain is used to see mycobacterium
ZN stain
What causes TB and what causes leprosy ?
TB - mycobacterium tuberculosis
Leprosy - mycobacterium leprae
What is the shape of spirochaetes and how are they diagnosed ?
They are long and spiral shaped bacteria.
They are diagnosed using serology
How is Chlamydia diagnosed and why only that method ?
Using serology because they don’t grow in cell lines
What are the groups of beta haemolytic bacteria, and which are the important ones ?
Groups A-G
Groups A, B and D are the important ones
