Microbiology Flashcards
What part of “Herpes simplex” is the species name?
simplex
What are the names of infectious proteins that have no DNA or RNA?
Prion proteins
What are responsible for transmissible spongiform encephalopathies such as Creutzfeldt-Jakob Disease (CJD)?
Prion proteins
What is the name of the protein coat that viruses have?
Capsomere
What can be described as obligate intracellular parasites?
Viruses
What three methods can be used to diagnose viruses?
Cell culture
Antigen or antibody detection in blood (serology)
Polymerase chain reaction to detect DNA or RNA
What shape are coccus bacteria?
Round
What shape are bacillus bacteria?
Rod-shaped
What shape are spirochaetes?
Spirals
What part of bacteria do Gram stains stain?
The bacterial cell wall
What colour will Gram positive bacteria stain?
Purple
What colour will Gram negative stain?
Pink
Which two organisms do not stain well with Gram stain?
- Mycobacterium tuberculosis (waxy coat)
2. Treponema pallidum (a spirochaete organism that causes syphilis)
What has the definition of a harmful organism?
A pathogen
What is an organism that is part of the normal flora?c
Commensal
What is an opportunistic pathogen?
An organisms that will likely only cause infection in an immunocompromised individual.
What is the ability of a microorganism to produce disease?
Pathogenicity
What is the word for the degree of pathogenicity of an organism?
Virulence
In what way do bacteria replicate?
Binary fission
How often can bacteria replicate their numbers?
Every 20 minutes
What are the 4 phases of bacterial growth?
Lag phase
Log phase
Stationary phase
Death phase
What 3 types of atmosphere for bacterial growth are there?
Aerobic
Microaerophilic
Anaerobic
What atmosphere has a reduced concentration of oxygen and enriched with CO2?
Microaerophilic
Which type of bacteria produce exotoxins?
Gram positive bacteria
What are usually produced inside a Gram positive cell and then exported from it?
Exotoxin
What toxin do Gram negative bacteria produce?
Endotoxin
What toxin is part of the Gram negative bacterial cell wall?
Endotoxin
What, released from bacteria, interact with cells of the immune system causing release of cytokines?
Toxins
What 3 effects do some toxins have on the body?
Damage white and red blood cells
Make small blood vessels leaky causing decreased BP
Affect blood clotting
All can lead to sepsis
What endotoxin is found in Gram-negative bacterial cell walls?
LPS
What can some Gram positive bacilli form?
Spores
What are the 5 methods for diagnosing bacteria?
- Microscopy - Gram stained film
- Culture
- Detection of antigen (e.g. in urine)
- Detection of antibodies in blood (serology)
- Molecular methods such as PCR
How long does a TB culture take?
4 - 12 weeks
What two things do moulds produce?
Spores - spread in air currents
Hyphae - invade organic tissue
What is single celled and reproduces by budding?
Yeasts
Name a mould of fungi?
Aspergillus
Do Gram stains stain Aspergillus spp.?
No
Name a common yeast fungus?
Candida spp.
How do yeasts Gram stain?
As large positive oval structures
What is the term for the dstruction nad removal of 99.9% of micro-organisms and spores?
Sterilisation
What is sterilisation used for?
Dressings, surgical instruments
What are the 4 methods of sterilisation?
- Autoclave
- Dry heat in oven at 160
- Exposure to ethylene oxoid gas
- Irradiation (gamma-irradiation)
What is the term for the removal or destruction of pathogenic micro-organisms enough to make an item safe?
Disinfection
What 3 chemicals are used for disinfection?
- Hypochlorite - bleach
- Chlorohexidine - handwash
- Povidone iodine - skin antiseptic
What does the “us” mean at the end of “Staphylococcus”?
Singular term i.e. one organism
What does “i” at the end of “Staphylococci” mean?
The plural term, more than one
What does the “sp.” at the end of Staphylococcus sp. mean?
1 species of Staph
What does the “spp.” at the end of Staphylococcus spp. mean?
More than one species of Staph.
How do streptococcus and enterococcus grow best?
Aerobically (also can facultatively anaerobically grow)
How would Streptococcus and Enterococcus be described?
As Gram positive cocci in chains (streptococci come in strips)
How are streptococcus and enterococcus differentiated initially?
By the type of haemolysis seen on growth on blood agar
What is another term for alpha haemolysis?
Partial haemolysis
What is another term for beta haemolysis?
Complete haemolysis
Haemolysis is only important for the classification of what?
Streptococci
What is caused by enzymes that denature the haemoglobin inside red blood cells causing greenish discolouration round the colony?
Alpha haemolysis
What is caused by enzymes that lyse red blood cells causing complete clearing round the colony?
Beta-haemolysis
What occurs in gamma-haemolysis?
No haemolysis
What colouration does denaturised haemoglobin go, and what is this as a result of?
Green discolouration as a result of alpha haemolysis
What two can alpha-haemolytic streptococci be differentiated into?
Streptococcus pneumoniae
Streptococcus “viridans” group
How would you describe Streptococcus pneumoniae?
Gram positive cocci in short chains or pairs
How would you describe Streptococcus viridans?
Gram positive cocci in chains on microscopy
What heart condition may be caused by Streptococcus “viridans” group?
Infective endocarditis
What are the most pathogenic Streptococci?
Beta-haemolytic
What do Beta-haemolytic streptococci produce which lyse red blood cells?
Exotoxins
How are the beta-haemolytic streptococci further classified?
Into group A strep and group B strep
What two infections can Streptococcus group A cause?
Streptococcal sore throat (tonsilitis) - if rash present = scarlet fever
Necrotising fasciitis - skin and soft tissue infection
Puerperal sepsis - infection in pregnant women
What are all strains of group A streptococcus still sensitive to?
Penicillin
What is the most important group of non-haemolytic streptococci?
Enterococci
Name a common cause of urinary tract infection?
Enterococci
What are most strains of E. faecalis sensitive to?
Amoxicillin (not penicillin)
Name a very resistant type of Enterocci? (vancomycin resistant enterococci)
E. faecium
How would you describe Staphylococci?
Gram positive cocci in grape-like clusters
How do we distinguish Staph. aureus from all other Staphylococci?
We use the coagulase test
What would the result of a Staph. aureus positive coagulase test show?
Golden