Bacteria Flashcards
What is the difference between gram positive and gram negative?
Gram positive has a thick peptidoglycan on the outside
Gramnegative has 2 lipid- membranes with a thin layer of peptidogylcan in between
How to do a gram stain?
Grow bacterial colonies
Smear onto a slide
Apply crystal violet
Add a decolouriser like acetone
Add a different stain
Why is acetone used in staining?
It removes the outer lipid membrane on gram negative so the stain can leak out
How do gram positive bacteria look ?
PURPLE
How does gram negative look?
PINK
Describe the cytoplasmic membrane of bacteria?
More protein than phsopholipids
Because a lot of chemical reactions which normally occur in organelles happen in the mitochondria
Describe the cell wall of bacteria?
Made of peptidoglycan with short peptide cross links
What is endotoxin shock?
Some LPS outer membranes release endotoxins which builds up.
Why are gram negative bacteria scary?
They have an LPS outer membrane
This protects the peptidoglycan but also releases endotoxins
What are the types of capsules?
Slimy and rigid
What is a rigid capsule?
Rigid layer of polysaccharides to prevent phagocytosis
What is a slime capsule?
Slimy layer of polysaccharides which allows the bacteria to stick to surfaces
Why is the flagella important?
Allows for locomotion so the bacteria can have a favourable environment
Also allows for adherence
What is a bacterial conjugation
Donating plasmids between bacteria using receptors and endonuclease enzymes
Describe ribosomes in bacteria
Consist of RNA
Used to make proteins
70s ribosomes
Has 2 subunits
What are fimbriae?
Many tiny filaments that mediate adhesion between the bacteria and host cells
How do bacteria replicate?
Binary Fission
How is there genetic variation in bacteria?
Spontaneous mutation
Transfer of DNA
What is sporulation?
When conditions are not favourable, spore formation is initiated . The DNA divides and is stored in a cortex surrounded by protein .
It gets released when conditions are favourable
What are phenotypic methods of bacteria classification?
Gram stain
Serologic
Mass spec using protein
Growth requirements
What are genotypic bacteria?
Whole gene sequence classification
Why is iodine added to Crystal violet?
It’s fixes the dye so it doesn’t wash with alcohol
What can bacteria be split into?
Aerobic and non aerobic
What can aerobic bacteria be split into?
Cocci or Bacilli
What are chain bacteria called?
Streptococci
What are cluster bacteria called?
Staphylococci
What are cocci split up into?
Chains and clusters
What does streptococci split into?
Alpha haemolytic
Beta haemolytic
Non haemolytic
What is alpha haemolytic?
Partially destroys RBCs using haemolysis
Turns blood agar green
What is beta haemolytic?
Fully destroys RBCs using haemolysis
Turns blood agar clear
What does staphylococci split into?
Coagulase positive
Coagulase negative
What are the different test results for staphylococci ?
Positive would produce the enzyme Coagulase to produce a clot in the serum at the bottom
Or it wouldn’t produce the enzyme and would be fairly liquid
Why is staphylococci Coagulase positive interesting?
It might be staphylococcus aureus then we need to check for antibiotic resistance or MRSA
It produces penicillin ash and is methicillin (synthetic back up penicillin resistant)
What does staphylococci do in our body?
Harmless doesn’t do anything just colonises in our nose
Creates boils on our skin, affects soft tissue and bones and damages heart valves
Puss form infection
Where do we see Coagulase negative staphylococcus
Typically harmless
Can cause UTI in women
Forms biofilms
What are biofilms
Bacteria adheres to a foreign surface and forms a complex microbial community with a slimy matrix that protects bacteria
What does a haemolytic streptococci cause?
Pneumonia
Meningitis
Endocarditis
What is endocarditis?
Infection of the inner lining of the heart
What is group A streptococci?
Viral flesh easing pathogen
What is beta haemolytic streptococci
Further classified based on carbohydrates on outside of pathogen
Can be divided into class A to G
What are group B streptococci?
Cause neonatal meningitis
Commensal in the genitalia tracts but treated during labour to prevent spread to the child
What are group D streptococci?
Non haemolytic and not as virulent
Found in gut as normal.
What are important bacilli?
C. difficile.
What are C.difficile?
Normal bacteria part of our gut but can become problems when using antibiotics as the flora is affected
Causes diarrhoea associated with toxin production
Spreads via spores
What are C. Perfringens?
Found in soil and commensal in humans
Can form gas garangesor gastroenteritis
What are C. Tetani?
Modified muscle used in vaccine
Affects muscle movement
What is an example of a basic gram negative bacteria?
E.coli
How are bacteria named?
First name is genus and the second is species
They must be in italics
They must be written out in the full at least the first time
What are coliforms?
Large group of organisms in the gram negative Enterobacteriaceae that are mainly found in the gut
What is the major gram negative bacterial group?
Nessaria
What does neissaria cause mainly?
Meningitis
Can identify in blood samples and CSF
What is septicaemia?
Large amounts of bacteria entering the blood also known as blood poisoning
What is E.coli?
Found in humans and animal resevoirs
Has a lot of virulence factors
List and explain all the virulence factors of E. Coli.
Pilli
Capsule
Hide away from immune system
Endotoxin
Exotoxins
How to identify if E.coli is present?
Changes colour of agar as it ferments lactose
Why diseases do E.coli cause?
Enterotoxogenic E.coli can cause diarrhoea sometimes with blood
UTIs
What is another type of gram negative bacteria apart from E.coli?
No lactose
Can be invasive
Common cause of diarrhoea
Some salmonella can cause typhoid
What are campylobacter ?
Look like sea gulls
Found in domestic animals and chickens
Spread via faecal and oral
Cause bloody diarrhoea
What is helicobacter pylori?
Natural habit is the stomach
It damages the mucosa and causes ulcer
Can cause gastric adenocarcinoma
CURVED ROD
What is haemophilia influenza?
Cocco-bacilli
Much reduced due to the hib vaccine
Respiratory tract
What is pseudomonas?
Can affect water and sinks and contaminate medical equipment
Causes a range of sepsis, UTI and pneumonia
Multi drug resistance
And it affects the respiratory pathway
What is an anaerobes? Give an example
Often found in poly microbial infections (many pathogens attacking)
Found in gut and mouth
Most common is bacteriodes in gut
What does bacteriodes?
Colonic flora can cause intra abdominal abscess
What are oral anaerobes?
Peridonteal disease
Dental abscesses
Human and animal infection
What are miscellaneous bacteria?
Minority of bacteria which don’t stain using the grams method
Why would bacteria not stain using the gram’s method?
Gram-staining uses the cell wall but some bacteria have a different wall composition or don’t have acellwall
Give examples of miscellaneous bacteria and the 2 of which have no cell wall
Mycobacterium
No cell wall
- chlamydia
- spirochaetes
Acid and alcohol fast bacilli uses what stain?
ZN or auramine
Resistant to decolpurising by acid or alcohol after staining
What causes TB?
Mycobacterium TB
Also linked with HIV
How is leprosy caused?
Mycobacterium leprae
Attacks peripheral nerves
What are spirochates
Long spiral shape bacteria with no cell wall
Need immunofluorescence
Often done by serology
Can cause syphillis and lyme disease
What is syphillis?
Chancres at infection site so penis or lip
Can be passed from mummy to baby
Systemic illness or rash
Can result in CNS damage
What is a chancre?
Non painful skin lesion
What is lyme disease?
Tranmsitted by ticks
Rash appears and can lead to nerve damage
What is chlamydia?
Diagnosed by serology
Most common STI
And is asymptomatic in woman
Can lead to infertility and pelvic inflammatory disease
Certain chlyamdia bacteria can cause pneumonia
