Microbiology Flashcards

1
Q

Immediate antibiotic for suspected meningitis?

A

Benzylpenicillin.

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2
Q

Beta-haemolytic gram-positive strep, Lancefield group A?

A

Streptococcus pyogenes

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3
Q

Antibiotic for pregnant woman with UTI?

A

Nitrofurantoin (but not in third trimester).

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4
Q

What nutrient agar is used to grow mycobacterium tuberculosis?

A

Lowenstein-Jensen

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5
Q

C. diff microbiology characteristics?

A
  • anaerobic
  • gram positive
  • rods
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6
Q

Pseudomonas microbiology characteristics?

A
  • aerobic
  • rod
  • non-lactose fermenting
  • positive oxidase test
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7
Q

Proteus microbiology characteristics?

A
  • facultatively anaerobic
  • non-lactose fermenting
  • negative oxidase test
  • gram-negative rod
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8
Q

Salmonella microbiology characteristics?

A
  • gram-negative rod
  • facultatively anaerobic
  • non-lactose fermenting
  • negative oxidase test
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9
Q

Shigella microbiology characteristics?

A
  • gram-negative rod
  • facultatively anaerobic
  • non-lactose fermenting
  • negative oxidase test
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10
Q

Most common cause of infective endocarditis in adults?

A
  1. Staph aureus
  2. Strep viridans
  3. Coagulate negative staph
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11
Q

Strep viridans microbiology?

A

Optochin resistant alpha-haemolytic streptococcus.

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12
Q

Streptococcus pneumoniae microbiology?

A

Optochin sensitive alpha-haemolytic streptococcus.

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13
Q

Test used to distinguish between staphylococcus and streptococcus?

A

Catalase

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14
Q

Gram positive diplococcus causing meningitis?

A

Streptococcus pneumoniae

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15
Q

Gram negative diplococcus causing meningitis?

A

Neisseria meningitidis

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16
Q

Gram negative bacilli?

A
  • E. coli
  • campylobacter
  • pseudomonas
  • salmonella
  • shigella
  • proteus
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17
Q

Gram negative cocci?

A
  • neisseria

- moraxella (catarrhalis)

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18
Q

Gram positive cocci?

A
  • staphylococci
  • streptococci
  • enterococci
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19
Q

Gram positive bacilli?

A
  • bacillus anthracis
  • corynebacterium diphtheriae
  • listeria monocytogenes
  • clostridium
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20
Q

Intracellular bacteria?

A
  • coxiella
  • chlamydia
  • rickettsia
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21
Q

Are the standard staphylococci / streptococci aerobic or anaerobic?

A

Aerobic

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22
Q

Coagulase positive staph?

A

Staph aureus

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23
Q

Coagulase negative staph?

A

Staph epidermidis

Staph saprophyticus

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24
Q

Alpha haemolytic strep?

A
  • s. pneumoniae

- viridans strep

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25
Q

Beta haemolytic strep?

A

s. pyogenes

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26
Q

Group A strep?

A

s. pyogenes

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27
Q

Which gram positive bacilli are aerobic?

A
  • corynebacterium diphtheriae
  • listeria monocytogenes
  • bacillus anthracis
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28
Q

Which gram positive bacilli are anaerobic?

A

Clostridium

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29
Q

How can aerobic gram negative bacilli be sub-classified?

A
  • lactose fermenters

- non-fermenters

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30
Q

Are gram negative bacilli mostly aerobic or anaerobic?

A

Aerobic

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31
Q

Lactose fermenters?

A
  • E. coli

- klebsiella

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32
Q

Non-fermenters?

A
  • salmonella
  • shigella
  • proteus
  • pseudomonas
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33
Q

Other aerobic gram negative bacilli?

A
  • campylobacter
  • helicobacter
  • legionella
  • haemophilus
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34
Q

Stain for mycobacteria?

A

Ziehl-Neelsen

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35
Q

How to distinguish pseudomonas from other gram negative aerobic bacilli (non-lactose fermenting)?

A

Oxidase test - pseudomonas is oxidase positive.

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36
Q

Agar for lactose fermentation?

A

MacConkey

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37
Q

Most common pathogens causing CAP?

A
  1. strep pneumoniae

2. haemophilus influenzae

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38
Q

What is chocolate agar?

A

Blood agar with haemolysed RBCs.

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39
Q

How is legionella tested for?

A

Urine antigen test.

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40
Q

What does acid-fast mean?

A

Bacilli are red stained on Ziehl-Neelsen stain, even after washing with acid and alcohol.

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41
Q

Bacterial causes of infection / colonisers in COPD?

A
  • s. pneumoniae
  • h. influenzae
  • moraxella catarrhalis
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42
Q

Viral causes of infection in COPD?

A
  • respiratory syncytial virus
  • influenza
  • rhinovirus
  • seasonal coronaviruses
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43
Q

Cause of bronchiectasis?

A

Severe bacterial infection - whooping cough (bordatella pertussis), TB.

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44
Q

Colonising organisms in bronchiectasis?

A
  • h. influenzae
  • s. pneumoniae
  • m. catarrhalis
  • pseudomonas
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45
Q

Predominant colonising organism in neonates / infants with CF?

A

Staph aureus

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46
Q

Predominant colonising organism in infants / children with CF?

A

Haemophilus influenzae

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47
Q

Predominant colonising organism in older children and adults with CF?

A

Pseudomonas

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48
Q

Bacterial responsible for ‘culture negative’ endocarditis?

A
  • coxiella burnetii

- chlamydia psittaci

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49
Q

Most common cause of IE in IVDU?

A

Staph aureus

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50
Q

Most common organism found in IE blood cultures?

A
  1. Staph aureus
  2. Strep viridans
  3. Staph epidermidis / staph saprophyticus.
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51
Q

Cause of IE found in the oral cavity?

A

Viridans strep

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52
Q

Source of coagulase negative staph in IE?

A

Contamination of IV lines.

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53
Q

Criteria for IE diagnosis?

A

Modified Duke’s criteria

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54
Q

Criteria for ‘definite’ IE?

A
  • 2 major
  • 1 major, 3 minor
  • 5 minor
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55
Q

Major criteria for IE?

A
  • positive blood culture with typical organism

- new valve regurgitation / dehiscence of prosthetic valve

56
Q

Minor criteria for IE?

A
  • fever > 38
  • IVDU
  • prosthetic valve
  • positive blood culture not meeting major criteria
57
Q

Bacterial causes of diarrhoea?

A
  • e. coli
  • vibrio cholerae
  • shigella dysenteriae
  • salmonella
  • campylobacter
  • bacillus cereus
58
Q

Bacterial causes of antibiotic-associated diarrhoea?

A

Clostridium difficile

59
Q

Viral causes of diarrhoea?

A
  • rotavirus

- norovirus

60
Q

Protozoal causes of diarrhoea?

A
  • cryptosporidium

- giardia lamblia

61
Q

Source of salmonella (not typhi)?

A
  • hens’ eggs

- poultry

62
Q

Source of salmonella typhi?

A
  • canned meat
  • shellfish
    Uncommon in the UK.
63
Q

Source of e.coli 0157?

A

Raw or partially cooked ground beef.

64
Q

Source of campylobacter?

A

Undercooked chicken.

65
Q

H. pylori gram stain appearance?

A

Gram negative spiral bacillus.

66
Q

Test for H. pylori?

A

Urea breath test.

67
Q

Source of bacillus cereus?

A

Rice

68
Q

Common infective organisms in cellulitis?

A
  • group A beta haemolytic strep (s. pyogenes)

- staph aureus

69
Q

When are atypical infective organisms seen in cellulitis?

A
  • IVDU

- immunocompromised

70
Q

Microbial cause of skin abscess?

A

Staph aureus

71
Q

Microbial cause of lung abscess?

A
  • staph aureus
  • klebsiella pneumoniae
  • mycobacterium tuberculosis
72
Q

Microbial cause of liver abscess?

A
  • e. coli
73
Q

Microbial cause of kidney abscess?

A
  • e. coli

- klebsiella

74
Q

Common organisms causing UTI?

A
  • e. coli
  • proteus mirabilis
  • klebsiella
  • staphylococcus saprophyticus
  • staphylococcus epidermidis
  • enterococci
75
Q

Causes of UTI?

A
  • sexual intercourse
  • catheterisation
  • enlarged prostate
  • renal tract tumours
  • renal stones
76
Q

Investigations for UTI?

A

Mid stream urine - microscopy, sensitivity and culture.

77
Q

Bacterial causes of meningitis in neonates?

A
  • e. coli
  • group B strep (strep agalactiae)
  • listeria monocytogenes
78
Q

Bacterial causes of meningitis in infants?

A
  • neisseria meningitidis
  • haemophilus influenzae
  • strep pneumoniae
79
Q

Bacterial causes of meningitis in young adults?

A
  • neisseria meningitidis

- strep pneumoniae

80
Q

Bacterial causes of meningitis in the elderly?

A
  • strep pneumoniae
  • neisseria meningitidis
  • listeria monocytogenes
81
Q

Viral causes of meningitis?

A
  • enteroviruses (Coxsackie virus)
  • herpes simplex virus
  • mumps virus
82
Q

Is encephalitis normally viral or bacterial?

A

Viral

83
Q

Organisms causing encephalitis?

A
  • herpes simplex virus
  • varicella zoster virus
  • HIV
  • mumps virus
  • measles virus
84
Q

What agar does neisseria meningitidis grow on?

A

Chocolate agar

85
Q

Macroscopic appearance of staph aureus?

A

Gold, round colonies

86
Q

What grows on blood agar?

A

Streptococcus

87
Q

What is CLED agar used for?

A
  • proteus (stops motile proteus swarming)

- lactose status

88
Q

What is XLD agar used for?

A

Salmonella and shigella.

89
Q

Atypical causes of CAP?

A
  • mycoplasma pneumoniae
  • chlamydophila pneumoniae
  • legionella pneumophila
90
Q

Treatment of CAP?

A
  • oral amoxicillin

- IV co-amoxiclav (if unwell)

91
Q

Treatment of HAP?

A

Guided by microbiology - often IV co-amoxiclav and gentamicin.

92
Q

What are the 4 Cs associated with C. diff infection?

A
  • clindamycin
  • cephalosporins
  • co-amoxiclav
  • ciprofloxacin
93
Q

What does C. diff infection lead to?

A
  • pseudomembranous colitis
  • toxic megacolon
  • perforation and death
94
Q

Treatment of C. diff infection?

A

Discontinue inciting antibiotic, and start vancomycin.

95
Q

Which gram negative rods are oxidase positive?

A
  • pseudomonas aeruginosa

- haemophilus influenzae

96
Q

Most common organism causing UTI?

A

E. coli

97
Q

Common cause of UTI in young women?

A

Staphylococcus saprophyticus

98
Q

Treatment of UTI in pregnant women at term?

A
  • amoxicillin (if culture results available and sensitive)

- cefalexin

99
Q

Which two classes of antibiotics inhibit cell wall synthesis?

A
  • glycopeptides

- beta lactams

100
Q

Examples of glycopeptide antibiotics?

A
  • vancomycin

- teicoplanin

101
Q

Sub-categories of beta lactam antibiotics?

A
  • penicillins
  • cephalosporins
  • carbapenems
102
Q

Examples of penicillins?

A
  • benzylpenicillin
  • amoxicillin
  • flucloxacillin
103
Q

Examples of cephalosporins?

A
  • cefotaxime

- ceftriaxone

104
Q

Examples of carbapenems?

A
  • meropenem
105
Q

Which antibiotic classes inhibit protein synthesis?

A
  • macrolides
  • tetracyclines
  • aminoglycosides
    Also chloramphenicol (not a class).
106
Q

Examples of macrolides?

A
  • clarithromycin

- erythromycin

107
Q

Examples of tetracyclines?

A

Doxycycline

108
Q

Examples of aminoglycosides?

A
  • gentamicin

- streptomycin

109
Q

Which antibiotics inhibit nucleic acid synthesis?

A
  • trimethoprim
  • ciprofloxacin (fluoroquinolone)
  • rifampicin
  • metronidazole
110
Q

Agar used for sensitivity testing?

A

Mueller-Hinton agar.

111
Q

Common antibiotic resistance mechanisms?

A
  • beta-lactamase

- efflux pumps (pseudomonas aeruginosa)

112
Q

Why is MRSA resistant to flucloxacillin?

A
  • mecA gene
  • encodes a unique transpeptidase not inhibited by beta lactam antibiotics
  • can continue peptidoglycan crosslinking
113
Q

Fungi cell wall composition?

A

Chitin and glucan.

114
Q

How do treatments for fungal infections work?

A
  • target cell wall / plasma membrane

- not very effective

115
Q

Example of antifungals?

A
  • fluconazole
  • ketoconazole
  • clotrimazole
  • terbinafine
116
Q

What does candida albicans cause?

A
  • vaginal infections
  • oral infections
  • sepsis
  • line / catheter infections
117
Q

What does aspergillus fumigatus cause?

A

Lung infections

118
Q

Two examples of pathogenic fungi?

A
  • candida albicans

- aspergillus fumigatus

119
Q

Definition of a virus?

A

Infectious, obligate intracellular parasite.

Comprises genetic material surrounded by a protein coat or membrane.

120
Q

Example of dsDNA virus?

A
  • herpes viruses

- adenovirus

121
Q

Example of ssDNA virus?

A
  • HPV

- parvovirus

122
Q

Example of dsRNA virus?

A

Rotavirus

123
Q

Example of ssRNA positive sense virus?

A
  • hep A, C, E

- polio

124
Q

Example of ssRNA negative sense virus?

A
  • hep D
  • influenza
  • measles
  • rabies
125
Q

Example of ssRNA virus with reverse transcriptase?

A

HIV

126
Q

Example of dsDNA virus with reverse transcriptase?

A

Hepatitis B

127
Q

Which hepatitis viruses can lead to chronic infection?

A
  • hep B
  • hep C
  • hep D (only with hep B)
128
Q

Vector for malaria?

A

Anopheles mosquito

129
Q

Clinical implication of the distinguishing gram positive and gram negative bacteria?

A

Affects choice of antibiotics. Gram positive bacteria cell wall is easier to penetrate so they are susceptible to more antibiotics than gram negative bacteria.

130
Q

What is MRSA resistant to?

A
  • beta lactams
  • gentamicin
  • tetracycline
  • erythromycin
131
Q

Treatment for thread worms?

A

Mebendazole

132
Q

Five properties of a virus?

A
  • genetic material is DNA or RNA
  • attachment proteins
  • intracellular parasite, require host cell for survival & replication
  • carry enzymes that function within host cells
  • viruses have a protein coat surrounding their genetic material, and may also have a lipid envelope (no cell wall)
133
Q

How can viruses cause disease?

A
  • trigger an overactive immune response resulting in inflammation
  • directly kill host cells
  • cause abnormal host cell functioning
  • evade intra- and extra-cellular immune system
  • viral proliferation
134
Q

Most common cause of fungal nail infection?

A

Trichophyton species

135
Q

How do antibiotics work?

A

Binding to a specific target site, crucial to bacteria survival (site varies between classes).

136
Q

Clinical situations requiring HIV test?

A
  • recurrent candida infection
  • recurrent infection
  • atypical pneumonia (pneumocystis jiroveci)
  • suspected Kaposi sarcoma (abnormal skin lesions)