Microbiology 2 Medically Important Microbes Flashcards
GI microbiome
Bacteroides: phylum bacteroidetes
Oral microbiome
Streptococci: phylum firmicutes
Skin microbiome
Proprionibacterium: phylum actinobacteria
Nasal microbiome
Staphylococci: phylum firmicutes
Urogenital (female) microbiome
Lactobacilli: phylum firmicutes
How do we categorise bacteria?
- staining characteristics
- growth characteristics
- metabolic activities
- antigenic features
- nucleic acid formation
What is gram staining test?
- it tests the ability of the cell wall to retain the stain depending on it’s characteristics
What are the possible results of a gram test?
Negative: rods or cocci
Positive: rods or cocci
Bacterial Growth Characteristics (and examples of each)
- obligate anaerobe: dies when they come in contact with oxygen, i.e. Bacteroides fragilis which lives in the human gut
- obligate aerobe: must have oxygen to survive, i.e. mycobacterium tuberculosis which is the bacteria that causes TB
- facultative anaerobe: can survive in both, but prefers no oxygen, i.e. most medically important bacteria
How do you test bacterial growth characteristics?
- appearance on solid agar
- check for the appearance of haemolysis on a solid red agar
- if the bacteria is eating away at the blood, you will see lighter outlines around the bacteria which with represent growth
Metabolic activity
- checks for the elaboration of various enzymes such as oxidase, catalase and coagulase
- the utilisation of given nutrients or electrolytes, such as iron or lactose
What are metabolic activity tests used for?
- automated multiple test systems for a rapid ‘phenotypic’ identification or specification
What are two examples of gram positive cocci cluster bacteria?
- staphylococcus aureus
- staphylococcus epidermidis
What is the difference between staphylococci epidermidis and aureus?
Of all the staphylococci, aureus is the only one that produces the enzyme coagulase. It is the bacteria that is behind MRSA - very contagious. Bacteria that do not produce coagulase are sometimes called coagulase negative staphylococci
How does categorisation by antigens work?
The antigens on the surface of bacteria bond with the antibody. This causes a reaction which visually presents as clumping.
- An example of this is bacteria colony with specific antigen + latex particles coated with specific antibody = clumping
What is another word for clumping?
Agglutination
What are the Gram positive cocci bacteria clusters and where are they found?
Skin, nasal, desquamated squames - dust: staphylococcus aureus and epidermidis
What are the gram positive chains and where are they found?
Mouth and Upper Resp Tract: beta-haemolytic streptococci: (Lancefield groups A, B and C) - streptococci oralis - streptococci pneumoniae GI tract: - enterococcus faecalis
What is group A haemolytic bacteria most responsible for?
pharyngitis, tonsillitis, necrotising faciitis
What are the gram positive rods and how are they categorized?
Soil, anaerobic, spore forming bacteria: - clostridium difficile - clostridium perfringens - clostridium tetani Food: - bacillus species - listeria monocytogenes Skin: - proprionibacterium acnes Food/Female Urogenital: - lactobacillus lacti
What are the gram negative cocci and how are they categorized?
Upper Respiratory Tract: - Neisseria meningitides Gastro-Urinary Tract: - Neisseria gonorrhea Respiratory Tract: - haemolytic influenzae
What are the gram negative rods and how are they categorised?
GI and enterobacteriaceaes: - Escherichia coli - klebsiella pneumoniae - proteus mirabilis - salmonella enteriditis GI and non-enterobacteriaceae: - bacteriodes fragilis Aquatic and non-enterobacteriaceae: - pseudomonas aeruginosa GI (avian) and non-enterobacteriaceae: - campylobacter jejuni
What are other gram stain bacteria and how are they categorised?
AAFB in the respiratory tract:
- mycobacterium tuberculosis
Cell wall deficient bacteria
- legionella pneumophila (aquatic and resp. tract)
- Chlamydia trachomatis (respiratory and GU tract)
- Mycoplasma pneumoniae (respiratory tract)
Syphillis; spirochaete bacteria of GU tract:
- treponema pallidum
What are acid and alcohol fast bacteria
- bacteria that hold onto the stain even after you squeeze chemicals onto them, wash it off with acetone, and then wash it off with both alcohol and acid
