Microbiology Flashcards

1
Q

What is a coloniser?

A

just present within a host and is sometimes short lived

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2
Q

What is a pathogen?

A

microorganism that has the potential to cause tissue damage and disease

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3
Q

What is virulence?

A

likelihood of the pathogen to cause disease

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4
Q

What are the common infections of the abdomen?

A

peritonitis, liver abscess, cholangitis, perineal abscesses and
gastroenteritis abscesses

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5
Q

What is the structure of a gram positive bacteria?

A

thick peptidoglycan wall

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6
Q

What is the structure of a gram negative bacteria?

A

thin peptidoglycan wall but with many lipopolysaccharides

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7
Q

What is bacteriodes?

A

gram negative bacilli

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8
Q

What are enterobacteriaceae?

A
  • gram negative and don’t form spores
  • pink on agar
  • endotoxins and enterotoxins
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9
Q

What bacteria are in the mouth?

A

strep viridans

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10
Q

What bacteria are in the stomach?

A

candida

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11
Q

What bacteria are in the large bowel?

A
  • enterococcus eg faecalis
  • coliforms
  • strict anaerobes
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12
Q

What are the ways to identify bacteria?

A
  • macroscopic: haemolysis
  • microscopic: gram stain, organism shape and antigenic properties
  • spores
  • respiration
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13
Q

What can microbiology be used to test?

A
blood
stool
urine
wound
tissue culture
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14
Q

What is a test used in tayside for blood cultures?

A

MALDI-TOF

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15
Q

What are the important organisms that can be serotyped?

A

E.coli, salmonella and shigella

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16
Q

What are general risk factors for gastroenteritis?

A
  • malnutrition
  • closed communities
  • exposure to contaminated food and water
  • winter congregating
  • young or older age
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17
Q

What drugs can cause gastroenteritis?

A

PPIs as they suppress acid so can cause C. diff

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18
Q

What can the immunosuppressed get?

A

salmonella

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19
Q

What is inoculum size?

A

different infections require different amount of bug so some diseases only need a small amount of pathogen to cause a problem

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20
Q

What is diarrhoea?

A

more than three unformed stools in one day with no other known cause, the stools will hold the shape of the container and show a departure from normal bowel habits

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21
Q

What can be used to type stool?

A

Bristol stool chart

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22
Q

What is dysentery?

A

diarrhoea with blood and mucus and is associated with fever, abdominal pain and tenesmus eg shigella

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23
Q

What is gastroenteritis?

A

an illness caused by eating food that has been contaminated with microorganisms, toxins, poisons etc

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24
Q

What does gastroenteritis present with?

A

diarrhoea, abdominal pain and vomiting

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25
Q

What are the important history questions in gastroenteritis?

A

food history, medicines, animal contact

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26
Q

What is the bacteria found in reheated rice?

A

Bacillus cereus is in reheated rice which is a gram positive bacillus that causes vomiting

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27
Q

What is the bacteria found in meat, milk and fish at room temperature?

A

Staphylococcus is a gram positive coccus

28
Q

What are the most common invasive pathogens?

A

campylobacter and salmonella

29
Q

What are the features of shigella?

A
  • extremely infectious

- shiga toxin binds to receptors, inhibits protein synthesis and causes cell death

30
Q

What are the features of E.coli?

A
  • shiga-toxin producing
  • mostly caused by 0157
  • low infectious dose is needed for a problem to occur
  • high risk in children and elderly
  • comes from food eg raw milk, water or from animals
31
Q

What is haemolytic uraemia syndrome?

A

comes from E.coli and treating with antibiotics which causes more toxin to be produced and there is a high mortality

32
Q

What is the presentation of HUS and how is it identified and treated?

A
  • low platelets and haemoglobin, high LDH, can develop after the bloody diarrhoea has stopped
  • send a stool culture for all patients with bloody faeces
  • don’t treat with antibiotics, NSAIDS or antimotility agents
  • notify public health
33
Q

Why is PCR not always good?

A

just because bug is present, doesn’t mean it is the one causing the presentation

34
Q

What bug comes from uncooked poultry?

A

campylobacter

35
Q

What bug comes from person to person spread and gives bloody diarrhoea?

A

shigella

36
Q

What bug comes from undercooked meat and unpasteurised milk?

A

E. coli

37
Q

What bug comes from milk, beef or eggs and gives sometimes bloody diarrhoea?

A

salmonella

38
Q

What bug comes from an endemic area and gives diarrhoea?

A

vibrio cholerae

39
Q

What virus comes from person to person spread and mostly in kids?

A

rotavirus

40
Q

What virus comes from person to person spread and outbreaks in dense populations?

A

norovirus

41
Q

What are the four types of E.coli?

A
  • enterotoxigenic (makes heat stable toxin and is travel related)
  • enteropathogenic (can be asymptomatic)
  • enteroinvasive (watery diarrhoea)
  • enteroaggregative (travellers diarrhoea)
42
Q

What are the main features of E.coli 0157?

A
  • blood diarrhoea
  • children
  • elderly
43
Q

What are the features of campylobacter?

A
  • poultry and raw milk
  • treat with supportive or maybe macrolide
  • very common
44
Q

What are the features of salmonella?

A
  • poultry, meat and raw eggs
  • non-typhoidal
  • D and V, blood and fever
  • different antigens called O-antigens
  • B,C and D are common locally
45
Q

What are the features of listeria monocytogenes?

A
  • grows in fridge
  • causes fever, muscle aches and diarrhoea
  • from unpasteurised milk, deli counter and soft cheese
  • gram positive rod
46
Q

What are the features of viral gastroenteritis?

A
  • Rotavirus: vaccine, winter with kids, low infectious dose and rehydration treatment
  • Norovirus: winter vomiting bug, all ages, explosive and sudden diarrhoea, closed communities
47
Q

What does C diff produce?

A

toxin A and B

48
Q

What causes C diff and why?

A

antibiotics kill off the normal gut flora and C diff will begin to proliferate

49
Q

What are the symptoms of C diff infection?

A
  • diarrhoea (sometimes bloody)
  • abdominal pain
  • severe cases have pseudomembranous colitis or bowel perforation
50
Q

What is the C diff treatment?

A

less severe = oral metronidazole

severe = oral vancomycin (only time this is given orally and not IV)

51
Q

What is c diff microbiologically?

A

gram positive
spore-bearing
bacillus
resistant to disinfectants

52
Q

How is c diff diagnosed?

A

look for GDH
look for toxin A and B
no culture

53
Q

What are the features of rotavirus?

A
  • diarrhoea in the winter
  • no blood
  • treatment is supportive rehydration
  • low infectious dose
  • diagnosis is PCR on faeces
  • vaccine in UK
54
Q

What are the features of the noravirus?

A
  • winter vomiting bug
  • sudden explosive diarrhoea and vomiting for 2-4 days
  • PCR diagnosis
  • supportive treatment for dehydration
  • still infectious after recovery
  • outbreaks are common on cruises and in schools and hospitals
55
Q

How do you tell if diarrhoea is infectious?

A

fever?

length of onset

56
Q

What other infectious apart from diarrhoea diseases are spread by the faecal-oral route?

A

hepatitis A and E

57
Q

What are antimicrobials?

A

all agents that act against all microorganisms so bacteria, fungi, viruses and protozoa

58
Q

What are antibacterials?

A

only act on bacteria which includes antibiotics

59
Q

What are antibiotics?

A

produced naturally by microorganisms and kill or inhibit growth of other microorganisms

60
Q

What are the two ways in which antibiotic resistance can be acquired?

A
  • vertical transmission (accumulation of mutations which are then passed on by replication)
  • horizontal transmission (resistance genes are swapped from one microbe to another)
61
Q

What are the main contributors to drug resistance?

A

prior antibiotic exposure
invasive procedures
prior hospitalization
underlying disease

62
Q

What are the main areas of impact of antibiotic resistance?

A

health impact (morbidity and mortality)

economic impact (more treatment costs)

societal impact (lack of trust in healthcare)

63
Q

Why do we see more resistance recently?

A
  • More sick and chronically ill patients
  • More immunocompromised
  • More procedures and devices
  • More pathogens
  • Complacent antibiotic prescribing and increased use of broad-spectrum antibiotics
  • Poor infection control
  • Lots of patients in small areas
  • International travel
64
Q

What are the main parts of antimicrobial stewardship?

A

right drug
right dose
right duration
right de-escalation

65
Q

What are the main rules for prescribing antibiotics?

A
  • Use narrow spectrum
  • Follow guidance
  • Respond to positive microbiology
  • Switch to oral if possible
  • Do as short a course as possible
  • Don’t give multiple courses if possible
  • De-escalate the broad therapy quickly
  • Only give surgical prophylaxis for 24 hours