Microbiology Flashcards
What is the protein that absorbs gram stain?
Peptidoglycan
What type of diseases to prions cause?
Transmissible Spongiform Encephalopathies
eg. CJD
Why does TB not gram stain well?
Has a waxy coat
What is the pathogenicity of a bacteria?
It’s ability to produce disease
What is the virulence of a pathogen?
The degree of pathogenicity - how easily it causes disease
What is the process by which bacteria replicate?
Binary fission
What bacteria produce exotoxins and where is it made?
Gram positive
Inside the cell
What bacteria produce endotoxins and where are they made?
Gram negative
Part of cell wall
What gram positive bacteria produce spores?
Clostridium sp.
Bacillus sp.
What is the most common cause of mould infection?
Aspergillus spp.
What is the most common fungal infection in humans?
Candida spp.
What causative agent of infection is not inactivated by sterilisation?
Prion proteins
What are species of gram positive cocci?
Streptococcus
Enterococcus
Staphylococcus
What environment do Strep and Entero grow in?
Aerobic
What arrangement are strep and enterococcus typically in?
Cocci in chains
What bacteria are classified by haemolysis?
Streptococcus
Which type of haemolysis is partial and why is it partial? What colouration results?
Alpha
Denatures haemoglobin
Greenish
What is beta haemolysis?
Complete haemolysis
Red cells broken down
Most pathogenic
What is gamma haemolysis?
No haemolysis
What are the examples alpha-haemolytic strep?
Strep. pneumoniae
Strep. “viridans”
What is the gram appearance of Strep pneumoniae?
Gram positive cocci in short chains/pairs
What are some examples of Beta haemolytic strep?
Group A - Strep. pyogenes
Group B - cause neonatal meningitis
What infections does Strep. pyogenes cause?
Strep throat (Tonsillitis)
Necrotising fasciitis
Puerperal sepsis
What is Strep. pyogenes sensitive to?
Penicillin and amoxicillin
What group of bacteria commonly cause UTIs?
Enterococcus
Are Enterococcus faecalis sensitive to amoxicillin and penicillin?
No. Just amoxicillin
What is the gram appearance of Staph?
Gram positive cocci in clusters
What is the only coagulase positive Staph?
Staph. aureus (appears golden)
What is Staph epidermidis and what can it cause?
A skin commensal
IV line infections
What are most Staph. aureus strains sensitive to?
Flucloxacillin
What strain of Staph. aureus is resistant to all penicillins and all cephalosporins?
MRSA
What chemical is responsible for the increase in the body’s thermal set point in a fever?
PGE
Where is the body’s thermal control centre?
Anterior hypothalamus
What is the sequence of events in sepsis?
- Capillaries leak into tissues
- Lower blood volume so increased load on heart
- Decreased tissue oxygenation
- Clotting factors used up so increased haemorrhage
What is the main group of gram negative cocci?
Neisseria spp.
What are the two main types of Neisseria and how do they arrange themselves?
Neisseria meningitidis
Neisseria gonorrhoeae
Diplococci
What are the coliforms?
Large Gram negative bacilli that look like E. coli
Examples of gut commensal coliforms?
Most E. coli
Klebsiella spp
Enterobacter spp
Proteus spp
Examples of pathogen coliforms?
Salmonella spp
Shigella spp
Verotoxin-producing E. coli (O157 and O104)
What is the first line treatment for coliform infections?
Gentamicin
What are the two main strict anaerobes?
Clostridium spp
Bacteroides spp
Appearance of Clostridium spp?
Gram positive bacilli (with spores)
What infections do Clostridium spp cause?
Diarrhoea
Gas gangrene
Tetanus
What is the appearance of Bacteroides spp?
Gram negative bacilli
What is the treatment for anaerobe infections?
Metronidazole
What is the staining used for Mycobacteria?
Acid Fast Bacilli
Or
Acid-Alcohol Fact Bacilli
What are the main examples of spirochaetes?
Treponema pallidum (syphilis) Borrelia burgdorferi (Lyme disease)
What are the two methods of genetics varitation in bacteria?
Mutation
Gene transfer
What are the mechanisms for gene transfer in bacteria?
Transformation (DNA taken up by living bacteria)
Conjugation (bacterial sex)
Transduction (viruses transfer DNA between bacteria)
What are the mechanisms of antibiotic resistance?
Production of enzymes
Altered binding sites
Altered cell wall porins
Up-regulation of effluent pumps
What enzymes destroy antibiotics?
Beta-lactamase (early penicillins)
Carbapenemase (all penicillins, all cephalosporins and all carbapenems)
How is MRSA resistance?
Altered penicillin binding site
Which fungi is resistant via up-regulation of efflux?
Candida spp
What is the sequence of events in viral infections?
- Attachment
- Entry (by pinocytosis)
- Uncoating
- Nucleic acid and protein synthesis
- Assembly
- Release (by budding/lysis)
Which viruses show latency?
Herpes simplex
Varicella-zoster
How can viral infections be detected?
PCR
Antigen detection
Methods of antibiotic action
Act on cell wall
Affect ribosomes
Act directly on DNA
What are the groups of antibiotics that act on the cell wall?
Penicillins
Cephalosporins
Glycopeptides
How do penicillins work?
Cross-link peptidoglycan
What are the three forms of penicillin?
Benzylpenicillin (penicillin G, IV)
Phenoxymethylpenicillin (penicillin V, oral)
Benzathine penicillin (long acting, IM)
How do cephalosporins work?
Inhibit cell wall synthesis
Two examples of glycopeptides
Vancomycin
Teicoplanin
What antibiotics inhibit protein synthesis?
Macrolides
Tetracyclines
Aminoglycosides
Others (clindamycin, chloramphenicol)
Examples of macrolides
Erythromycin
Clarythromycin
Azithromycin
What group does gentamicin belong to?
Aminoglycosides
What antibiotics act on bacterial DNA?
Metronidazole
Trimethoprim (+/- sulphonamide)
Fluoroquinolones
Examples of fluoroquinolones
Ciprofloxacin
Levofloxacin
What antibiotics do we try to avoid?
The four Cs
- Cephalosporins
- Co-amoxiclav
- Ciprofloxacin
- Clindamycin
