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1
Q

How does C. diphtheriae cause damage, which organs are most badly affected?

A

It releases an AB exotoxin that prevents protein synthesis within cells. Intoxication of the heart and kidneys is fatal.

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2
Q

Describe the structure of the influenza virus

A

It is a RNA virus consisting of 8 weakly linked RNA segments, surrounded by a capsule with spike proteins (haemagglutinin and neuraminidase)

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3
Q

How does bordetella pertussis cause disease

A

Releases tracheal cytotoxin which incapacitates ciliated cells, resulting in buildup of mucus and bacteria in the lower RT

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4
Q

Why does the convalescence period in pertussis take months following treatment?

A

Erythromycin eliminates the bacteria, but ciliated cells must also be replenished

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5
Q

What are the differences between pneumococcal pneumonia and H. pneumoniae pneumonia? (3)

A

S. pneumoniae is gram positive whereas H. pneumoniae is gram negative.
Strep occurs due to lowered immunity in a healthy carrier, while H occurs in those who are immunocompromised (alcoholic, diabetic, cancer, poor nutrition)
Strep can be treated with penicillin/optichin while H is resistant to penicillin so penicillinase resistant 2nd gen cephalosporins are used

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6
Q

What are two similarities of Q fever and chlamydial pneumonia/ ornithosis

A

Both are obligate intracellular and cause atypical pneumonia

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7
Q

What is a major complication of Q fever

A

Endocarditis

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8
Q

Where does blastomycosis begin and where does it spread?

A

Begins with infection of the lungs and spreads to skin to cause cutaneous ulcers

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9
Q

How is leptospirosis transmitted

A

Dogs and cats shed the bacteria in their urine, which contaminates water. It can then enter the body through damaged skin or the digestive tract.

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10
Q

What are two complications of leptospirosis

A

Severe liver and kidney disease

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11
Q

How much more likely are females to develop gonorrhoea after a single exposure than males

A

Thrice (60-90% compared to 20-35%)

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12
Q

Gonorrhoea symptoms

A

Pus and painful urination

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13
Q

What part of the female body is infected and why- gonorrhoea

A

Cervix (columnar epithelium) and not vagina (stratified squamous)

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14
Q

How is the causative agent of syphilis cultured

A

Treponema pallidum can be grown in cell cultures only

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15
Q

Are antibodies effective against treponema pallidum? Why/ why not?

A

No, CMI only due to lipid outer layer of the bacteria ‘teflon coated’

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16
Q

Which 3 factors may contribute to increased risk of vaginitis and why

A

Pregnancy, oral contraceptives and use of broad spectrum antibiotics. Suppress the growth of lactobacilli (normal flora) which obtain energy from sexual hormones, leading to opportunistic infection

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17
Q

What treatments can be used to restore acidity of the vagina

A

Acetic acid gels and replacement lactobacilli

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18
Q

What symptoms are the same vs different for males v females with genital herpes

A

Vesicles appear on external genitals (female) vs base of penis (male)
Both have dysuria (painful urination) and trouble walking

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19
Q

How is genital herpes cured

A

It is not curable, antivirals like acyclovir could possibly be used

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20
Q

Why is topical podofilax/ podophyllum used to treat genital warts

A

Caused by human papillomavirus
Podofilax contains zinc which inhibits viral replication

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21
Q

What major condition is genital warts associated with

A

Cervical cancer

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22
Q

How is lymphogranuloma venereum diagnosed

A

Iodine staining of pus from lymph nodes

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23
Q

Common feature between 3 common causes of bacterial meningitis. How does this relate to type of vaccine used?

A

All capsulated. All vaccines are based on the capsular antigens

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24
Q

Haemophilus influenza vaccine is based on

A

Hib capsular antigen

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25
Q

Meningococcal vaccine is based on

A

Capsular antigens of A or C serotypes

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26
Q

Meningococcal A is most prevalent in

A

Africa and middle east

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27
Q

Meningococcal C is most prevalent in

A

North America

28
Q

How is N. meningitidis cultured

A

Chocolate agar = heated blood agar kills RBCs, releasing haem

29
Q

N. meningitidis treatments

A

Doxycycline, ofloxacin, erythromycin

30
Q

How does C. tetani cause disease

A

It is an anaerobic bacteria. When it is in an aerobic environment such as the blood, the bacteria dies, releasing tetanospasmin a potent neurotoxin. The toxin inhibits the relaxation pathway in the CNS, resulting in rigid paralysis and pain

31
Q

Which serological type of C. botulinum has an exotoxin that is the most resistant to heat

A

Type A

32
Q

Under what conditions is C. botulinum exotoxin released, how does this differ to that of C. tetani

A

Anaerobic whereas tetanospasmin is released upon death in aerobic conditions

33
Q

What kind of contact is required to contract leprosy

A

Prolonged intimate contact

34
Q

How is polio virus dangerous

A

Kills motor nerve cells leading to paralysis and can enter CNS

35
Q

Why is post-exposure prophylaxis effective for rabies

A

The virus has a long incubation period so there is time for a vaccine to be administered and stimulate the immune system

36
Q

How do arboviruses survive between transmission periods

A

Hibernation and transovarian transmission

37
Q

How do arboviruses cause harm

A

The virus multiplies in the reticuloendothelial system and becomes localised in target organs, causing necrosis, inflammation and fever. It then enters nervous pathways and then the CNS

38
Q

How is yellow fever linked to dengue haemorrhagic fever

A

The arbovirus localises in the liver, killing liver cells and impairing clotting factor production. Reduced clotting factor results in haemorrhage

39
Q

What causes symptoms in BSE

A

The prion causes mass accumulation of misfolded proteins (beta sheets instead of alpha) in the CNS leading to neurological symptoms

40
Q

How is S. mutans cariogenic

A

Salivary amylase converts sucrose to glucose and fructose. The bacteria converts glucose to dextran, a gummy polysaccharide which forms plaque, and breaks fructose to lactic acid which breaks down tooth enamel.

41
Q

How does staphylococcal intoxication occur, which species is involved

A

S. aureus. Cooked food (bacteria destroyed) is contaminated by unclean hands. Staph is transferred. When the food is reheated, the bacteria are killed but the enterotoxins remain

42
Q

How can shigella be identified in the lab?

A

Does not produce colour on MacConkey agar.

43
Q

Describe the antigens on salmonella

A

O antigen = LPS
H antigen = flagella
Virulent (Vi) = surrounds O

44
Q

What differentiates S. typhi from other salmonella

A

It multiplies in macrophages rather than epithelial cells

45
Q

How does v. cholerae cause rice water diarrhoea

A

LT toxin causes cells to secrete potassium ions and water, leading to rice water diarrhoea

46
Q

Which serotype of V. cholerae is responsible for pandemic cholera

A

O139

47
Q

What toxin is produced by yersinia enterocolitica

A

Similar to stable toxin (ST) of enterotoxigenic E coli

48
Q

What enzyme is produced by yersinia, how does this inform antibiotic choice

A

Produces beta lactamase so cannot be treated with penicillin or cephalosporins

49
Q

Which exotoxins are produced by C. difficile and which is an enterotoxin

A

A (enterotoxin) and B

50
Q

True or false: Bacillus cereus produces spores and toxins

A

True

51
Q

What coinfection is common with rotavirus and why

A

Rota exposes receptors for ETEC, leading to more severe diarrhoea

52
Q

Who is rotavirus most common in and when

A

Infants and children in winter

53
Q

What type of vaccine is the mumps vaccine

A

MMR is live attenuated

54
Q

How does cytomegalovirus cause owl eye appearance

A

Incorporates into nucleus of epithelial cells. Viral inclusion body causes enlarged nucleus and cytomegaly.

55
Q

Symptoms of ergotism

A

Hallucinogenic symptoms, nausea and vomiting

56
Q

What are two severe complications of aflatoxin poisoning

A

Cirrhosis of liver and cancer (carcinogen)

57
Q

What toxin of S. pyogenes causes puerperal fever

A

Superantigen (exotoxin)

58
Q

How does s. pyogenes cause rheumatic fever and endocardial damage

A

Misdirected immune response to cardiac myosin which resembles M protein on streptococci (antigenic mimicry)

59
Q

Major symptom of tularaemia

A

Ulceroglandular tularaemia = swollen lymph nodes

60
Q

What two toxins are produced by bacillus anthracis

A

Oedema factor (causes oedema) and lethal toxin (kills macrophages)

61
Q

How does C. perfringens cause ischaemia in gas gangrene

A

Alpha toxin destroys RBCs (it is a membrane disrupting toxin), reducing oxygen carrying capacity of blood -> ischaemia and necrosis

62
Q

How does plague caused by Y. pestis progress

A

Bubonic plague (lymph nodes) -> septicaemic plague -> pneumonic plague (haemorrhage from lungs- necrotising haemorrhagic pneumonia)

63
Q

Why do relapses occur in relapsing fever

A

Due to infection by antigenically different serotypes of the borrelia species

64
Q

Visceral leishmaniasis is caused by

A

Leishmania donovani

65
Q

Cutaneous leishmaniasis is caused by

A

Leishmania tropicalis and braziliensis

66
Q

Urinary schistosomiasis is caused by

A

Schistosoma haematobium

67
Q

Intestinal inflammation in schistosomiasis is caused by

A

Schistosoma mansoni and schistosoma japonicum

USC Microbiology 1 (9 decks)

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