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AY Principles > Microbiology > Flashcards

Microbiology Flashcards

1
Q

Diagnostic methods for microbiology

A

Cel culture
Antigen or antibody detection
PCR

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2
Q

3 bacterial shapes

A

Cocci (round)
Bacillus (rod-shaped)
Spirochaetes (spirals)

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3
Q

What colour are gram stains?

A

Purple - positive

Pink - negative

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4
Q

Organisms that don’t stain well with gram stain

A

TB (waxy coat)

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5
Q

Factors required for bacterial growth

A

Food
Moisture
Correct temperature
Correct pH

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6
Q

3 types of atmosphere bacteria can grow in

A

Aerobic
Microaerophikic
Anaerobic

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7
Q

What is an exotoxin?

A

Produced inside cell and then exported from it

Mainly gram positive

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8
Q

What is an endotoxin?

A

Part of cell wall

Mainly gram negative

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9
Q

Role of toxins in sepsis

A

Cause damage to red and white blood cells causing them to become leaky. This causes BP drop affects blood clotting which can lead to sepsis

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10
Q

Gram positive bacilli that can form spores

A

Clostridium (e.g. C. diff)

Bacillus sp. (e.g. anthrax)

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11
Q

What are spores?

A

Inactive hardy forms of bacteria that cannot replicate but can survive adverse conditions

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12
Q

Which organism is haemolysis used to classify?

A

Streptococcus

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13
Q

What is alpha haemolysis?

A

Partial haemolysis

Enzymes denature haemoglobin side red blood cells causing greenish discolouration round the colony

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14
Q

What is beta haemolysis?

A

Complete haemolysis

Enzymes breakdown red blood cell causing complete clearing round the colony - most pathogenic

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15
Q

What is gamma haemolysis?

A

No haemolysis

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16
Q

What is strep pneumonia?

A

Gram positive cocci
Commonest cause of pneumonia, also causes meningitis
Part of normal upper respiratory tract flora in many people
Majority of UK strains are still sensitive to penicillin

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17
Q

What is streptococcus viridans?

A

Gram positive cocci
Group of species which are common come sales
Can cause endocarditis (infection of heart valves)

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18
Q

What is group A strep (strep pyogenes)?

A

Most pathogenic of all strep.
Cause tonsillitis, necrotising fasciitis, puerperal sepsi
All strains are still sensitive to penicillin

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19
Q

What are group B strep (strep. Agalactiae)?

A

Most common cause of newborn infections

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20
Q

Examples of non-haemolytic strains?

A

Enterococcus
Not particularly pathogenic
Common cause of UTI
Most sensitive to amoxicillin (but not penicillin)

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21
Q

What are prion proteins?

A

Infectious protein that have no DNA or RNA

Cannot be sterilised or cleaned off

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22
Q

What test distinguishes staph aureus from other staph organisms?

A

Coagulase test

Staph aureus - positive - golden

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23
Q

What are coagulate negative staphylococci?

A

Common skin commensals
Do not produce toxins
Common causes of prosthetic joint and prosthetic heart valve infection and catheter infection - difficult to treat with antibiotics

24
Q

What is staph aureus?

A

Produces both exotoxins (enzymes that damage cells) and endotoxins (toxins that act on the gut - food poisoning)
Strains sensitive to flucloxacillin - MSSA
Strains resistant to flucloxacillin - MRSA (also resistant to penicillins +!cephlaosporins)

25
Q

Infections caused by staph aureus

A

Commonest cause of skin, soft tissue and wound infection
Commonest causes of bone and joint infection
Food poisoning (enterotoxjn producing strains)
Flucloxacillin is treatment of choice for MSSA

26
Q

What is Staph. aureus bacteraemia?

A

Infection in the blood stream
Leads to sepsis
Can spread to other sites in the body
Many are hospital acquired

27
Q

Examples of gram positive strict anaerobes

A

Clostridium

28
Q

What is clostridium?

A

Part of normal bowel flora
Produces spores
Produces exotoxins

29
Q

First line treatment for clostridium

A

Metronidazole (first line treatment for infections caused by anaerobes)

30
Q

What does C. diff cause?

A

Antibiotic associated diarrhoea esp. in the elderly

31
Q

What is C. perfrigens?

A

Gas gangrene
Severe soft tissue infection following wound contamination
(e.g. Gunshot wound)

32
Q

What is C. tetani?

A

Causes tetanus, usually fatal paralytic illness

33
Q

Examples of gram negative strict anaerobes

A

Legionella

Pseudomonas

34
Q

Examples of aerobic gram negative cocci?

A

Neisseria meningitides & Neisseria gonorrhoeae

35
Q

Examples of small gram negative aerobic bacilli?

A

Bordetella pertussis & Haemophilis influenzae

36
Q

What are coliforms?

A

Species of gram negative bacilli that look like E. coli

37
Q

2 main subtypes of aerobic gram-negative coliforms?

A

Gut commensals

Gut pathogens

38
Q

Examples of gut commensals?

A

Most strains of E. coli
Klabsiella spp.
Enteronacter spp.
Proteus spp.

39
Q

Examples of gut pathogen commensals

A

Salmonella spp.
Shigella spp.
Verotoxin
E. coli 0157 (outbreaks in nurseries & care homes)

40
Q

First line treatment for coliforms?

A

Gentamicin

41
Q

Examples of gram-negative microacrophilic bacilli (spiral)?

A

Vibrio cholerae, Campylobacter sp. & Heliconacter sp.

42
Q

What does Helicobacter pylori cause?

A

Gastritis & duodenal ulcers

43
Q

Examples of gram-negative strict anaerobes?

A

Bacteroides spp.

44
Q

First line treatment for anaerobes?

A

Metronidazole

45
Q

What are mycobacteria?

A

Thick waxy coat doesn’t gram stain

Acid fast bacilli or acid-alcohol fast bacilli

46
Q

Examples of Spirochaetes?

A 
Treponema pallidum (causes syphilis) 
Borrelianburgdorferi (causes Lyme disease)
47
Q

Methods of gene transfer in bacteria

A

Transformation (dead bacteria DNA taken up by living bacteria)
Conjugation (bacteria sex)
Transduction (viruses transfer DNA from one bacteria to another)

48
Q

General signs of infection

A

Local symptoms - pain, redness, swelling, heat, loss of function
Systemic symptoms - fever, sweats rigors

49
Q

Investigations for infection

A 
WCC (non-specific) 
Culture 
- blood
- urine
- stool
- psoutum 
PCR
Blood for serology (antibodies/antigen)
50
Q

What causes sepsis?

A

Cytokines cause blood vessels to become leaky
Lower blood volume requires heart to work harder to maintain oxygenation a of tissues
Blood supply to less essential organs (skin, kidneys liver) is hut down to try maintain blood supply to brain
Blood clotting system is activated causing blood clotting in tiny vessels -> uses up clotting factors -> increased risk of haemorrhage

51
Q

Difference between bactericidal & bacteriostatic?

A

Bactericidal - kill bacteria

Bacteriostatic - inhibit bacterial growth

52
Q

Where in bacteria can antibiotics act?

A

Bacteria wall
Bacterial ribosome
Bacterial DNA

53
Q

Examples of antibiotics that act on bacterial cell walls?

A

Penicillins
Cephalosporins
Glycopeptides

54
Q

Examples of glycopeptides

A

Vancomycin, teicoplanin

Need to be administered IV

55
Q

Types of antibiotics that inhibit protein synthesis

A 
Macrolides (erthromycin' clarythromycin & azithromycin) 
Amino glycosides (Gentamicin IV) 
Tetracyclines (doxycycline)
56
Q

Types of antibiotics that act on bacterial DNA

A

Metronidazole
Trimethoprin
Fluroquinolones (Ciprofloxacin)

AY Principles (11 decks)

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