Microbiology Flashcards
Pathogen
Harmful organism
Commensal
Organism that is part of the normal flora
Opportunistic Pathogen
Probably only cause infection in immunocompromised individuals
Contaminent
Organism that has got into a culture by accident
Pathogenicity
Ability of a microorganism to produce a disease
Virulence
Degree of pathogenicity of an organism
How do bacteria replicate
Binary Fission
3 types of atmosphere
Aerobic- In presence of Oxygen
Anaerobic- No O2 present
Microaerophilic-Reduced O2 concentration and enriched CO2
Microaerophilic
Reduced O2 concentration and enriched CO2
What do Moulds produce?
Produce spores and hyphae
Example of mould
Aspergillus
Yeast
Single cells that reproduce by budding
Example of yeast
Candida
Streptococcus-
Conditions
Shape
Haemolysis
Aerobic
Cocci chains
Alpha (partial) Strep pneumoniae/viridans
Beta (Complete)- Group A &Group B strep
Group A strep?
Throat/skin infection
Group B strep?
Neonatal meningitis
Enterococcus- Conditions Shape Haemolysis Role
Aerobic
Cocci chains
Non-haemolytic
Normal gut commensal and cause of UTIs
Staphylococcus- Shape Test for aureus Antibiotic for aureous Aureus is common cause for
Cocci Clusters
Coagulase positive= staph aureus= wound/skin infections (Golden)
Flucloxacillin
Bacteraemia
Coagulase negative test
Staph epidermis (white)
Normal skin commensal
IV line infections
Mechanism of Fever?
Antigen attacks macrophage
Releases cytokines
They travel to anterior hypothalamus of brain
This stimulates the production of prostoglandin E
Which resets body’s thermal set point
Body percieves it is cold, shivers to conserve heat
Purpose of Fever?
Growth of pathogen is slow if temperature increases
Examples of gram -ve cocci?
Neisseria gonhorrhoea
Neisseria Meningitidis
Gram negative cocci-
Conditions
Aerobic
Diplococci- appear in pairs on Gram Film
Coliforms-
Gram
Shape
Conditions
Negative
Bacilli
Aerobic but can also be anaerobic
Can be part of normal bowel flora
Coliform Gut commensals?
E Coli
Proteus spp.
Klebsiella
Coliform Gut pathogens?
E coli 0157
Salmonella
Shigella
Examples of strict aerobes
Gram Negative Bacilli
Pseudomonas aeruginosa
Legionella pneumophilia
Spiral/curved gram negative bacilli-
Campylobacter- food poisoning
Helicobacter pylori- Gastritis
Common cause of chest infection?
Haemophilus Influenzae
Small gram negative bacillus
Gram positive anaerobic bacilli examples?
Clostridium
Part of normal bowel flora
Produces spores
Produces exotoxin- cause severe tissue damage
Gram negative anaerobic bacilli
Bacteroides spp
Normal Gut commensals, only pathogenic in other sites
What is metrondiazole a first line for?
Infections caused by anaerobes
What cells are prokaryote?
Bacteria
Fungi
Protozoan diseases of man?
Malaria
Gram Negative bacteria examples?
Neisseria Escherichia Klebsiella Enterobachter Proteus Salmonella Shigella Haemophilus Pseudomanas Bacteroides
Gram Positive bacteria?
Streptococcus Staphylococcus Enterococcus Clostridium Fusobacterium
1st antibiotic used for Coliforms?
Gentamicin
Body temp?
37 degrees
Sepsis?
Small blood vessesl become leaky lose fluid into tissues
Lower blood volume requires heart to work harder to maintain oxygenation of tissues
Poor tissue oxygen perfusion means blood supply to less essential organs
Blood clotting system is activated causing blood clotting in tiny blood vessels- using up all blood clotting factors
Genetics of bacteria?
Plasmid and Chromosomes
3 methods of gene transfer?
Transduction
Transformation
Conjugation
Transformation
DNA from dead bacteria is taken up by living bacteria and incorperated into plasmids or chromsomes
Conjugation
Sex pillus formed by one bacteria through which plasmid DNA can be transferred
Transduction
Virus infecting bacteria can transfer bits of DNA from one bacterium to another
Standard infection precautions
For all patients all the time eg hand washing, PPE etc
Transmission based infection control
For patients with suspected known infections
Antibiotics?
Drugs used to treat or prevent infection caused by microorganisms
Bactericidal
Kill antibodies
Bacteriostatic
Inhibit bacterial growth
Which antibiotics work on the cell wall?
Penicillin, cephalosporins, glycopeptides (vancomycin)
Gram positive Phospholipid bilayer?
1
Gram negative phospholipid bilayer?
2
How do penicillins inhibit cell wall synthesis?
Prevent cross-linking of peptidoglycan sub-units
What method are penicillins?
Bactericidal
What coulf flucoxacillin treat?
Cellulitis
Wound infection
Skin/soft tissue infection
What method are cephalosporins?
Bactericidal
Beta lactam antibiotics?
Cephalosporins
Penicillins
How are cephalosporins excreted?
Kidneys
How glycopeptides work?
Bind to end of growing chain and prevent cross-linking and weakens bacterial cell wall
Glycopeptides method?
Bactericidal
What are glycopeptides only active against?
Gram positive cell walls
How are glycopeptides excreted?
Urine
Exampple of glycopeptide
Vancomycin
Antibiotics that inhibit protein synthesis?
Macrolides
Tetracyclines
Aminoglycosides
Method of tetracyclines and macrolides?
Bacteriostatic
Aminoglycosides method?
Bactericidal
example of tetracyclines?
Doxycycline
What are aminoglycosides mainly effective against?
Gram negative aerobic organisms
Macrolides-
excreted?
Useful because?
Biliary tract
Lipophilic so pass through cell membranes easily- good for infections where bacteria hides from Immune system
Tetracyclines?
Range
Excreted
Broad spectrum (can destruct intestinal flora= secondary infections) Biliary tract
How are aminoglycosides excreted and what is there problem?
Urine
Toxic to kidneys
How metrondiazole acts?
Causes strand breakage of bacterial DNA
How trimethoprim works?
Inhibits bacterial folic acid synthesis
What trimethoprim works on
Some gram negative and some gram positive
How fluoroquionolones work?
Prevents supercoiling of bacteria
Side effects of fluoroquinolones?
How it’s excreted?
Weakens Tendons
Causes seizures
Excreted in urine
General antibiotics side effects?
Nausea
Vomiting
Diarrhoea
Antibiotics to avoid in pregnancy?
Gentamicin
Fluoroquinolones
Tetracyclines
Antibiotics to avoid first 3 months of pregnancy?
Trimethoprim
Metrondiazole
MRSA resistance?
Change in bacterial DNA can cause change in gene product which is the target of antibiotic
Resistance mechanism 2?
Destruction of antibiotic-
bacteria can code for enzymes that chemically degrade/ inactivate antibiotic
Resistance mechanism 3?
Increases Efflux-
Efflux pumps actively export amtibiotics out of bacterial cell; genetic change may result in increased rate of efflux
6 stages of virus replication?
Attachment Entry Uncoating Nucleic acid and protein synthesis Assembly Release
Attachment
Interact with specific receptors in target cells
Entry of virus replication
Endocytosis
Uncoating in viral replication
Nucleic acid and proteins unpacked together
Nucelic acid and protein synthesis is viral replication
Host ribsomes used (or sometimes host polymerases)
Assembly in viral replication
Nucleic acids and proteins packed back together
Release in viral replication?
Budding-Virus released with envelope developed from host cell membrane. Doesn’t kill cell
Lysis- Virus accumulates until cell bursts. Kills cell
What do cytoxic T lymphocytes do?
Recognise proteins on cell surface as being foreign and will signal infected cells to commit suicide in order to prevent formation of new viruses
Examples of neutralizing antibodies?
IgM, IgG
Neutralizing antibodies function?
Prevent viruses binding to cellular receptors