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Clinical Pathology > Theme 1: Core Microbiology > Flashcards

Theme 1: Core Microbiology Flashcards

1
Q

Staphylococcus aureus is most commonly infects which tissue?

A

Skin and soft tissue

Esp. surgical sites

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2
Q

Which bacteria is most commonly associated with foreign bodies (IV catheters, prosthesis, mechanical valves)?

A

Staphylococcus epidermidis

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3
Q

Which bacteria adheres to metals and plastics using glycocalyx slime to form a biofilm?

A

Staphylococcus epidermidis

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4
Q

Where is staphylococcus epidermidis normally found?

A

On the skin

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5
Q

Group A Strep is also called ____?

A

streptococcus pyogenes

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6
Q

A patient presents with a tongue that is covered in small lesions, making it look a lot like a strawberry. What is the classical diagnosis and which pathogen is responsible?

A

Strawberry tongue is characteristic of scarlet fever, which is caused by streptococcus pyogenes

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7
Q

True or false: Group A Strep can cause skin and soft tissue infections?

A

True.

But it is most commonly associated with scarlet fever and necrotising fasciitis.

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8
Q

What is the most common cause of bacterial pneumonia?

A

Streptococcus pneumoniae

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9
Q

Which gram positive bacterial species looks like bunches of grapes?

A

Staphylococcus spp.

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10
Q

Which gram positive bacterial species forms chains?

A

Streptococcus spp.

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11
Q

Streptococcus pneumoniae is a cause of bacterial meningitis in all age groups EXCEPT ____?

A

neonates

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12
Q

True or false: Streptococcus Pneumoniae can cause otitis media?

A

True

Strep Pneumoniae is the most common cause of bacterial pneumonia, but can also cause other diseases such as meningitis and otitis media.

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13
Q

What is Group B Strep also known as?

A

Streptococcus agalactiae

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14
Q

Which pathogen is the most common cause of bacterial meningitis in neonates?

A

Group B strep/ streptococcus agalactiae

Also the most common cause of neonatal sepsis (neonates = <3 months)

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15
Q

Which gram positive bacterial pathogen is most associated with abscesses?

A

Streptococcus milleri.

This is actually a collective term for a group of three closely-related species of pus-forming streptococci.

The abscesses can be found in diverse places, such as teeth, lung, liver and brain.

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16
Q

Subacute bacterial endocarditis is associated with which group of gram positive bacteria?

A

Viridans streptococci

This group includes strep. oralis and strep. mitis.

They are named after the latin word for ‘green’ (viridis) because they produce a green colouration on agar plates.

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17
Q

Blood cultures for a patient on your ward grow streptococcus gallolyticus. What can this be a red flag symptom for?

A

Colonic malignancy

Strep gallolyticus is an alpha-haemolytic strep species that is found in the normal bowel flora.

Bacteraemia with this organism can be associated with colonic malignancy.

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18
Q

A patient presents with a non-blanching rash and is diagnosed with meningitis. Which organism is most likely responsible for their meningitis?

A

Neisseria meningitidis

This organism is associated with the classic presentation of a non-blanching rash.

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19
Q

Are the neisseria species’ gram negative or gram positive?

A

Gram negative

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20
Q

Which organism is the cause of gonorrhoea?

A

Neisseria gonorrhoeae

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21
Q

Ophthalmia neonatorum is caused by which organism(s)?

A

Neisseria gonorrhoeae and chlamydia trachomatis

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22
Q

How is ophthalmia neonatorum contracted?

A

The baby becomes infected during childbirth as it passes through the vaginal canal of a mother infected with neisseria gonorrhoeae or chlamydia trachomatis.

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23
Q

Which pathogen is associated with consuming cheese from unpasteurised milk?

A

Listeria monocytogenes

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24
Q

Which groups are most at risk of meningitis and sepsis from listeria monocytogenes?

A
  • Pregnant
  • Immunosuppressed
  • Neonates

(PIN)

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25
Q

Is listeria monocytogenes gram negative or gram positive?

A

Gram positive

They would stain dark on a gram film, as their cell wall will retain the dye

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26
Q

Zoonosis most commonly affects animals, but can spread to humans through meat or spreading manure on food products. If a colony of the causative bacteria was to be gram-stained, what colour would it appear?

A

Dark as it would retain lots of the gram stain.

Zoonosis is caused by listeria monocytogenes, which is gram positive. As gram positive bacteria have a thick cell wall, they retain lots of stain and appear dark. Gram negative bacteria appear more reddish, as their thin little cell wall doesn’t retain much stain.

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27
Q

True or false: Listeria monocytogenes can grow in low temperatures.

A

True

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28
Q

Many of the corynebacterium species are commensals of the skin and upper respiratory tract. Which of them causes diphtheria?

A

Corynebacterium diphtheriae

gram+ bacilli

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29
Q

____ causes acne and, less commonly, device-associated or post-procedural infections.

A

Propionibacterium acnes

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30
Q

E-coli is most commonly associated with ____.

A

UTIs

E-coli is commensal in the bowel flora but not the urethra.

This species is also associated with

  • Bacteraemia
  • Hospital acquired infections (line infections, pneumonia, wound infections)
  • [toxigenic strains] Severe diarrhoea and haemolytic uraemic syndrome (HUS)
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31
Q

Which pathogen is associated with a 3 day history of bloody diarrhoea, abdominal pain and fever?

A) E-coli
B) Giardia
C) Streptococcus pyogenes
D) Shigella

A

D) Shigella

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32
Q

Which gram negative species is known for its blue-green pigmentation?

A

Pseudomonas aeruginosa

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33
Q

Which of the following is not generally caused by pseudomonas aeruginosa?

A) Respiratory infections
B) SSTIs
C) UTIs
D) These are all caused by pseudomonas aeruginosa

A

D) These are all caused by pseudomonas aeruginosa

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34
Q

True or false: Haemophilus influenzae is commensal to the respiratory tract

A

True

Haemophilus influenzae is found as part of the normal respiratory tract flora

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35
Q

Which gram negative species is associated with pneumonia and infective exacerbation of COPD?

A

Haemophilus influenzae

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36
Q

Which gram negative species is associated with meningitis and epiglottitis?

A

Capsulated strains of haemophilus influenzae (e.g. Type B)

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37
Q

Lyme disease is caused by which organism?

A

Borrielia

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38
Q

Leptospira is associated with what disease?

A

Leptospirosis

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39
Q

Syphilis is caused by which organism?

A

Treponema pallidum

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40
Q

Clostridium spp, bacteroides, fusobacterium and prevotella are all examples of:

A) Anaerobes
B) Aerobes

A

A) Anaerobes

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41
Q

What are the four main subtypes of clostridium species? What condition does each cause?

A
  • Clostridium difficile (diarrhoea/colitis)
  • Clostridium perfringens (gas gangrene)
  • Clostridium tetani (tetanus)
  • Clostridium botulinum (botulism)
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42
Q

True or false: The organism responsible for tuberculosis can be identified with the help of gram staining

A

False

TB is caused by mycobacterium tuberculosis. Mycobacterium do not have a cell wall, so you cannot stain them using conventional gram stain.

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43
Q

Mycobacterium tuberculosis
Mycobacterium pneumoniae
Chlamydia trachomatis

What do these species have in common?

A

None of them have a cell wall

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44
Q

____ often form polybacterial infections; commonly: dental infections, lung abscesses, colonic abscesses, post-trauma SSTIs.

A

Anaerobes

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45
Q

Which species most commonly cause meningitis in these age groups:

a) Neonates (<3 months)
b) Infants
c) Teens/adults
d) Elderly

A

a) Neonates (<3 months): GROUP B STREP (STREP AGALACTIAE)
b) Infants: STREP PNEUMONIAE
c) Teens/adults: NEISSERIA MENINGITIDIS
d) Elderly: STREP PNEUMONIAE

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46
Q

Which of the following are gram negative bacteria?

A) Streptococcus pneumoniae
B) Mycobacterium tuberculosis
C) E-Coli
D) Listeria monocytogenes
E) Neisseria gonorrhoeae
F) Mycoplasma pneumoniae
A

C) E-Coli
E) Neisseria gonorrhoeae

Explanation:
A) Streptococcus pneumoniae (G+)
B) Mycobacterium tuberculosis (no cell wall, no stain)
C) E-Coli (G-)
D) Listeria monocytogenes (G+)
E) Neisseria gonorrhoeae (G-)
F) Mycoplasma pneumoniae (no cell wall, no stain)

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47
Q

Which of these bacteria is common cause of skin infection?

A) Klebsiella pneumoniae
B) Streptococcus pneumoniae
C) Haemophilus influenzae
D) Neisseria meningitidis
E) Staphylococcus aureus
F) Clostridium difficile
A

E) Staphylococcus aureus

Most common infections:
- Klebsiella pneumoniae: pneumonia

  • Streptococcus pneumoniae: pneumonia
  • Haemophilus influenzae: pneumonia
  • Neisseria meningitidis: meningitis
  • Staphylococcus aureus: SSTIs
  • Clostridium difficile: Colitis
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48
Q

Which of the following is the most common sexually transmitted infection?

A) Chlamydia trachomatis
B) Treponema pallidum
C) Corynebacterium diphtheriae
D) Staphylococcus aureus
E) Neisseria gonorrhoeae
F) Viridans streptococci
A

A) Chlamydia trachomatis

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49
Q

Which of the following can cause meningitis?

A) Neisseria meningitidis
B) Streptococcus pneumoniae
C) Listeria monocytogenes
D) Streptococcus agalactiae
E) Haemophilus influenzae
F) Staphylococcus aureus
A

These can ALL cause meningitis

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50
Q

Albicans, glabrata, parapsilosis and krusei are all subtypes of which species?

A

Candida

Candida spp. are yeasts that can infect any organ, superficially or systemically.

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51
Q

Which organism is responsible for thrush?

A

Candida

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52
Q

Which groups are at greatest risk of developing oral candidosis (thrush)?

A
  • HIV/AIDS
  • Antibiotic use
  • Chemo/radiotherapy for head and neck cancers
  • Hospital inpatients
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53
Q

What should be remembered when prescribing a treatment for candida infection in pregnant women?

A

Oral azoles can cause teratologies in the developing foetus. Therefore, do not prescribe fluconazole or other oral azoles. Use topical preparations instead, such as clotrimazole.

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54
Q

Your patient recently had an in-dwelling catheter fitted. They became unwell and blood cultures have grown a candida spp. What action should be taken?

A
  1. Remove the line
  2. Start antifungal therapy
  3. Investigate the source and spread of candida - especially check heart and eyes
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55
Q

Which groups are at highest risk of candida endocarditis?

A
  • IV drug users

- Patients who have had heart valve surgery

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56
Q

Why is candida UTI hard to treat?

A

Few antifungals are excreted in the urine, therefore it is difficult to get a drug to the infection site.

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57
Q

True or false: You can have a candida UTI but test negative for candiduria.

A

True

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58
Q

Candida oesophagitis is mainly found in patients with __1__. It causes pain/difficulty swallowing and is diagnosed by __2__ and biopsy.

A
  1. HIV

2. endoscopy

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59
Q

Patients undergoing leukaemia treatment are more at risk of which candida infection?

A

Hepatosplenic candidosis

The fungus takes advantage of the neutropenic state of the blood and lodges in the liver, spleen and [occasionally] kidney.

Abscesses, fever and deranged LFT results on presentation.

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60
Q

Fumigatus, niger, flavus and terreus are all subtypes of which species?

A

Aspergillus

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61
Q

A ‘halo’ or ‘air crescent’ sign on CT is indicative of which fungal disease?

A

Invasive pulmonary aspergillosis

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62
Q

Allergic bronchopulmonary aspergillosis is mediated by what? What treatment is effective?

A

IgE and IgG reaction to mould. Responds well to steroid and antifungal treatment.

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63
Q

A patient presents with the following:

  • COPD
  • Consolidation and cavitation seen on CT
  • Sputum culture +ve for aspergillus
  • Blood serum +ve for aspergillus IgG antibody

What is the likely diagnosis?

A

Chronic pulmonary aspergillosis (CPA)

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64
Q

Which class of fungi are slow-growing moulds that live in soils, on animals and on humans? What type of infection are they associated with?

A

Dermatophytes

Skin, nail and hair infections

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65
Q

The following organisms belong to which species?

Trichophyton rubrum
Trichophyton verrucosum
Trichophyton Schoenleinii
Microsporum canis

A

Dermatophytes

A family of slow-growing moulds that live in soil, as well as on animals and humans.

They cause skin, nail and hair infections

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66
Q

Give the main examples of infections caused by dermatophytes.

A 
Tinea pedis (athletes foot)
Tinea unguium (fungal nail)
Tinea cruris (jock itch)
Tinea corporis (ringworm)
Tinea capitis (scalp ringworm)
Tinea barbae (facial hair infection)
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67
Q

What is the cause of pityriasis versicolor?

A

Malassezia - a yeast fungi

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68
Q

Hypo- or hyperpigmented lesions on the upper trunk that are caused by a yeast are most likely to be a case of ____

A

Pityriasis versicolor

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69
Q

How is pityriasis versicolor treated?

A

Treat with topical antifungals (clotrimazole). If this fails, oral antifungals (fluconazole or itraconazole).

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70
Q

What term describes a relationship where two organisms of different species live together closely.

A

Symbiosis

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71
Q

What is the difference between protozoa and helminths?

A

Both are subtypes of parasite:

Protozoa are microscopic; helminths are macroscopic

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72
Q

Define the following:

a) Definitive host
b) Intermediate host
c) Paratenic host?

A

a) Definitive host: Host that harbours adult-stage parasites (i.e. a parasite that can sexually reproduce).
b) Intermediate host: Host that harbours larval or asexual stages of the parasite.
c) Paratenic host: Host which carries a viable parasite, without further development.

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73
Q

Which of the following causes Loeffler’s syndrome?

a) Schistosoma
b) Echinococcus
c) Cryptosporidium
d) Ascaris

A

Ascaris

Loeffler’s syndrome occurs when an increase in eosinophils (in response to a parasitic infection) leads to eosinophil accumulation in the lungs. This results in dry cough, dyspnoea, wheeze, haemoptysis. Eosinophilic pneumonitis can be a sequela.

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74
Q

What type of parasite is ascaris? Protozoa or helminth?

A

Ascaris is an intestinal nematode (worm) which makes it a helminth (i.e. macroscopic parasite).

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75
Q

How is ascariasis acquired?

A

Ingestion of eggs.

Each adult ascaris worm can produce 200,000 eggs per day.

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76
Q

Describe the ascaris life cycle

A

Direct life cycle: Oral-faecal.

Excreted fertilised eggs are ingested and develop in the intestines into larvae. The larvae invade the mucosa and are carried to the lungs by the blood. They then develop further and ascend the respiratory tract into the throat and are swallowed. Back in the intestine, the worms mature to adulthood.

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77
Q

What clinical manifestation might be seen in a patient with ascariasis?

A

Loeffler’s syndrome, malnutrition, malabsorption, bowel obstruction

Loeffler’s syndrome: dry cough, dyspnoea, wheeze, haemoptysis, eosinophilic pneumonitis

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78
Q

How is Loeffler’s syndrome diagnosed?

A

Sample to identify the eggs or worms

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79
Q

What causes schistosomiasis?

A

Infection by schistosoma species

Trematode (fluke) helminth

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80
Q

What causes swimmer’s itch and Katayama fever?

A

Schistosoma infection

Katayama Fever is the acute phase of schistosomiasis. There is also a chronic phase, just called chronic schistosomiasis.

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81
Q

Describe the life cycle of schistosoma

A

Simple indirect life cycle:
Infected person excretes eggs in faeces and urine. Eggs make it to water and hatch. The larvae infect snails (intermediate host) and develop into a swimming bug. Leave snail, penetrate the skin of of a bathing person (definitive host). Migrate to bloodstream, mate and produce eggs.

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82
Q

How might schistosomiasis manifest in the urinary bladder?

A

Haematuria
Fibrosis and dysfunction
Squamous cell carcinoma

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83
Q

How might schistosomiasis manifest in the GI tract?

A

Portal hypertension
Liver cirrhosis
Abdominal pain
Hepatosplenomegaly

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84
Q

How is schistosomiasis diagnosed?

A

Urine:
- Terminal stream microscopy

GI:

  • Stool microscopy
  • Rectal snip microscopy

General:
- Serology (only an aid, as eggs in blood do not indicate active infection)

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85
Q

What controls could be implemented to prevent schistosomiasis?

A
  • Chemical treatment to kill snail intermediates
  • Chemoprophylaxis
  • Avoid snail waters
  • Improve sanitation to prevent faeces and urine reaching water
  • Education
  • Community treatment programme
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86
Q

What disease is caused by echinococcus?

A

Hydatid disease

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87
Q

Hydatid disease is caused by which organism?

A

Echinococcus (tapeworm)

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88
Q

What type of parasite is echinococcus?

A

Helminth (i.e. macroscopic)

Cestode (tapeworm)

89
Q

What are the usual hosts of echinococcus?

A

Sheep and dogs

Echinococcus are found anywhere sheep are farmed. Humans are accidental hosts

90
Q

Describe the life cycle of echinococcus

A

Indirect life cycle.

Eggs pass from faeces of infected dogs, ingested by sheep and other farm animals. Cysts pass from intestine of sheep to their other tissues. Dogs eat these meats/organs and ingest the cysts, which then develop into adulthood.

Sheep are the intermediate host, dogs are the definitive host.

Humans can contract the cysts and would become an intermediate host, in place of the sheep.

91
Q

True or false: Infection of echinococcus is normally asymptomatic.

A

True, infected humans can by asymptomatic for years.

However, mass effect can lead to symptoms. Also associated with secondary bacterial infections and hypersensitivity reactions. Cyst rupture (possibly due to trauma) can cause a mild to severe anaphylactic reaction.

92
Q

How is hydatid disease diagnosed?

A

Imaging

Serology

93
Q

Which site is most commonly affected by hydatid disease?

A

Majority of cysts migrate to liver (70%).

Some also migrate to lungs (20%) and other tissues.

94
Q

What controls can be put in place to manage hydatid disease?

A
  • Regularly worm dogs to reduce egg production
  • Hand hygiene
  • Safe handling and disposal of animal carcasses and products
95
Q

What treatment might be used for hydatid disease?

A

If asymptomatic, no treatment required.

Cysts may need to be surgically removed.

96
Q

Which species causes malaria?

A

Plasmodium

Plasmodium falciparum is commonest in the UK

97
Q

What type of parasite causes malaria?

A

Plasmodium spp, which are a family of sporozoa from the protozoa class.

98
Q

Describe the life cycle of the parasite that causes malaria

A

Indirect life cycle.

Female anopheles mosquito picks up plasmodium parasite when feeding and acts as a vector to take it to another host. Injects it into the new host’s blood where it travels to the liver and infects blood cells and grows to adulthood.

99
Q

How does the plasmodium protozoa cause problems?

A

It gets into an erythrocyte and replicates until the cell ruptures.

Ruptured erythrocytes can block vessels and trigger inflammatory reactions.

Symptoms:

  • Fever and rigors
  • Cerebral malaria: confusion, headache, coma
  • Renal failure
  • Hypoglycaemia
  • Pulmonary oedema
  • Circulatory collapse
  • Anaemia, bleeding and DIC (disseminated intravascular coagulation)
100
Q

If your patient has a fever and has recently returned from travelling abroad, what assumption should you make?

A

Malaria

101
Q

How is malaria diagnosed?

A

Thick and thin microscopy

Serology - detect antigen

PCR - detect malarial DNA

102
Q

Which organisms cause cryptosporidiosis?

A

Cryptosporidium parvum and hominis

Protozoa/ Sporozoa

103
Q

Describe the life cycle of cryptosporidium spp.

A

Direct life cycle.
Faecal-oral transmission.

Animal to human
Human to human

Water can be infected and ingested.

104
Q

How does cryptosporidiosis present clinically?

A

7-day incubation followed by watery diarrhoea with mucus (no blood).

Cramps, bloating, fever, nausea, vomiting.

Self-limiting, 2 weeks.

105
Q

How is cryptosporidiosis diagnosed?

A

Stool sample with acid-fast stain

Antigen detection by EIA (enzyme immunoassay)

106
Q

What treatment is given to patients with cryptosporidiosis?

A

Symptomatic relief (rehydration, electrolyte replacement etc)

If immunocompromised:

  • Paromomycin (kills parasite)
  • Octreotide (reduce cramps)
  • HAART activation if HIV+
107
Q

Trichomoniasis is caused by which parasite?

A

Trichomonas vaginalis

108
Q

What type of parasite is trichomonas vaginalis?

A

Flagellated protozoa

109
Q

How is trichomonas vaginalis transmitted?

A

Sexual transmission

110
Q

How does trichomoniasis present clinically?

A

Men: asymptomatic

Women: Smelly vaginal discharge, dyspareunia (painful sex), dysuria, abdominal discomfort, strawberry cervix

111
Q

How is trichomoniasis diagnosed?

A

Microscopy of genital specimens

112
Q

How is transmission of trichomonas prevented?

A

Barrier contraception

113
Q

Giardia causes what symptoms?

A

1 to 3 weeks of:

  • Diarrhoea
  • Abdo pain
  • Bloating
  • Nausea/vomiting
114
Q

How is giardiasis diagnosed?

A

Stool sample microscopy to identify cysts or trophozoites

115
Q

What can be done to control giardia infection?

A
  • Boil/filter water

- Improve hygiene and sanitation

116
Q

How can malaria infection be controlled?

A

Insecticide sprays in homes

Larvacidal spraying on breeding pools

Filling in of breeding pools

Larvivorous species introduced to mosquito breeding areas

Insecticide-impregnated bed nets

Chemoprophylaxis

Vaccine? - possibly in the future.

117
Q

What is the life cycle of a virus?

A 
Attachment
Entry
Uncoating
Synthesis
Assembly
Release
118
Q

What characteristic is distinguishing of the herpes viruses?

A

Their ability to establish latency and then reactivate.

119
Q

Which virus is responsible for the following:

a) Genital herpes
b) Cold sores

A

a) Genital herpes is caused by Herpes Simplex 2 (HSV-2)

b) Cold sores are caused by Herpes Simplex 1 (HSV-1)

120
Q

What is the mode of transmission for herpes simplex 1 and 2?

A

Direct contact with vesicle fluid from HSV lesions (skin, genital, eye)

121
Q

Where does herpes simplex 1 (HSV-1) establish latency?

A

Sensory neurons

122
Q

Where does herpes simplex 2 (HSV-2) establish latency?

A

Sensory neurons

123
Q

What clinical syndromes are associated with herpes simplex 1 and 2?

A

Ulcers: skin or mucous membranes - typically mouth (HSV-1) and genitals (HSV-2)

Encephalitis: majority HSV-1

Meningitis: majority HSV-2, often follows genital lesions

Neonatal herpes: contracted from mother’s genital tract at delivery

124
Q

The primary infection of varicella zoster virus is known as __1__; the reactivation is known as __2__.

A

1) ‘chicken pox’

2) ‘herpes zoster’ or ‘shingles’

125
Q

How is varicella zoster transmitted?

A

Respiratory droplets or contact with vesicle fluid

126
Q

Where does varicella zoster establish latency?

A

Dorsal root ganglion

127
Q

Which of the following is not associated with chicken pox?

a) Complications can include pneumonitis, encephalitis and acute cerebellar ataxia
b) Unilateral vesicles in a dermatomal distribution
c) Febrile illness with vesicular rash
d) Usually uncomplicated in children

A

b) Unilateral vesicles in a dermatomal distribution

Chicken pox presents as a febrile illness with a widespread vesicular rash.

Though it is usually uncomplicated (esp. children), it can result in pneumonitis, encephalitis and acute cerebellar ataxia.

A unilateral distribution of vesicles in a single dermatome is characteristic of the reactivated form, shingles (or herpes zoster).

128
Q

What causes glandular fever?

A

Epstein Barr virus (80-90%)

Cytomegalovirus (10-20%)

These names are all synonyms of the same disease:

  • glandular fever
  • infectious mononucleosis
  • epstein barr virus
129
Q

How is epstein barr virus transmitted?

A

Saliva and genital secretions

“Kissing disease”

Also known as mono (infectious mononucleosis) and glandular fever

130
Q

What is the usual clinical presentation of the primary disease caused by the Epstein Barr virus?

A

Causes infectious mononucleosis (glandular fever/EBV)

Sore throat, fever, lymphadenopathy, hepatosplenomegaly

Atypical lymphocytes on blood film (look like monocytes - mononucleosis)

131
Q

Where does Epstein Barr virus establish latency?

A

In B cells

132
Q

Turn over for a cool fact.

A

You are awesome. And you’re doing great. Keep going!

133
Q

True or false: In the UK, % prevalence ~ age (e.g. 20% of 20 year olds, 50% of 50 year olds)

A

True

134
Q

How is CMV transmitted?

A

Saliva/genital secretions

Donated blood, stem cells, organs

135
Q

Where does cytomegalovirus establish latency?

A

In monocytes, dendritic cells, myeloid progenitors

i.e. the immune system

136
Q

What is the most common primary condition associated with CMV?

A

Infectious mononucleosis

80-90% of cases are caused by EBV, the rest are CMV.

137
Q

What symptoms might you expect a baby to born with if their mother contracted CMV while pregnant?

A

Congenital CMV infection:

Retinitis, deafness, microcephaly, hepatosplenomegaly

138
Q

Which pathogen causes the common cold?

A

Rhinovirus

‘rhino’ = nose

139
Q

Which common virus can infect animals as well as humans, and can spread between species?

A

Influenza

140
Q

Which influenza strain mutates regularly?

A

Influenza A

141
Q

What are the two important viral markers on influenza, variants of which are used to identify different strains?

A

H and N

e.g. H1N1 is swine flu, H3N2 is seasonal

142
Q

Which virus infects 70% of children within their first year of life?

A

Respiratory syncytial virus (RSV)

143
Q

What virus causes bronchiolitis? Describe the condition.

A

Bronchiolitis is caused by respiratory syncytial virus (RSV). It affects children under 2 years, due to their small lungs.

Bronchiolitis is inflammation of the smallest airways: the bronchioles.

Symptoms: cough, wheeze, hypoxia, fever.

144
Q

What is the target for the HIV virus?

A

Helper T cells (CD4)

145
Q

What symptoms commonly affect people who have recently contracted HIV (2-6 weeks ago)?

A

Acute seroconversion illness:

  • fever
  • sore throat
  • lymphadenopathy
146
Q

How long can the asymptomatic chronic phase of HIV last?

A

Usually 5-15 years

147
Q

When does HIV become classified as AIDS?

A

AIDS

Increase in viral load and fall in CD4 count, infection by one of the AIDS-defining illnesses:

TB, pneumocystis pneumonia, cryptococcal meningitis, cerebral toxoplasmosis, Kaposi’s sarcoma.

148
Q

What are the AIDS-defining illnesses?

A
  • TB
  • Pneumocystis pneumonia
  • Cryptococcal meningitis
  • Cerebral toxoplasmosis
  • Kaposi’s sarcoma.
149
Q

What are the 5 primary hepatotropic viruses?

A

Hep A, B, C, D and E

Hepatitis D is defective and can only survive with hep B.

150
Q

Of the 5 hepatotropic viruses, which are:

a) blood borne
b) faeco-oral spread

A

a) blood borne: hep B, C, D

b) faeco-oral spread: hep A and E

151
Q

Which age group is most affected by Hep A in endemic countries?

A

Children.

Hep A is an infection of childhood, more than 90% of children under the age of 5yrs have been exposed in endemic countries.

152
Q

How is Hep A transmitted?

A

Faeco-oral

153
Q

How does Hepatitis A present clinically?

A

Nausea, myalgia, arthralgia and fevers
then jaundice and right upper quadrant pain

Self limiting

154
Q

How do different age groups present when infected with Hep A?

A

Children under 5 usually asymptomatic.

50% of infected adults are symptomatic

155
Q

Which groups are at highest risk of contracting Hep A?

A
  • Lower socio-economic groups
  • Returning travellers
  • MSM
156
Q

Which hepatitis virus is associated with undercooked pork?

A

Hepatitis E

157
Q

How is Hep E transmitted?

A

Faeco-oral

158
Q

True or false: vast majority of patients with Hep E are symptomatic.

A

False. Vast majority are asymptomatic. Clinical symptoms occur in 2-5% of patients with acute HEV.

Nausea, myalgia, arthralgia and fevers
then jaundice and right upper quadrant pain – self limiting

159
Q

Which groups are at high risk of severe condition if infected with hepatitis E?

A

Pregnant women at high risk of fulminant hepatitis, with high mortality (25%)

Also more severe in older males and those with chronic liver disease.

160
Q

How is Hepatitis B transmitted?

A

Blood borne

Vertical, sexual and parenteral

(parenteral = blood products, organ transplant etc.)

161
Q

Following infection of HBV, acute clinical hepatitis may occur.

This acute infection is either cleared, or develops into chronic infection.

How does chronic hepatitis develop further?

A

Chronic hepatitis –> cirrhosis –> hepatocellular carcinoma

HBV = hepatitis B virus

162
Q

How is risk of developing chronic hep B related to age at infection?

A

Risk of chronicity is inversely related to age at infection

163
Q

In the UK, 50% of IVDUs have evidence of hepatitis ____

A

c

164
Q

How is hepatitis C transmitted?

A

Blood borne.

IVDU, needlestick injury, transfusion of contaminated products.

Vertical and sexual transmission are less common.

165
Q

Vertical and sexual transmission is common in hepatitis ____

A

B

166
Q

Following infection by hepatitis __?__, approximately 25% will develop acute acute clinical hepatitis. 15% will then clear the virus, but 85% will become chronically infected.

A

C

167
Q

Which diarrhoea and vomiting virus is associated with point-source outbreaks (e.g. hospitals, cruise ships, military)?

A

Norovirus

168
Q

True or false: Norovirus is a single-strand RNA virus

A

True

169
Q

What is the dominant clinical symptom associated with norovirus?

A

Vomiting

The virus is transmitted in aerosolised vomit particles.

170
Q

True or false: Rotavirus infects about 50% of children in the first 3 years of life.

A

False.

Rotavirus infects 80-100% in first 3 years of life.

171
Q

True or false: Rotavirus is a major cause of infant mortality in the developing world?

A

True

172
Q

Which pathogen is most commonly responsible for causing viral meningitis?

A

Enteroviruses

More than 50% of viral meningitis cases are enteroviruses.

173
Q

True or false: Enteroviruses replicate in the gut and lead to GI symptoms.

A

False.

Enteroviruses replicate in the gut, but do not cause GI symptoms.

From the gut they migrate to the lymph nodes and then the blood (viraemia).

174
Q

The following syndromes are common to which family of virus?

  • Fever-rash syndromes (e.g. hand, foot and mouth)
  • Common cold
  • Meningitis
  • Encephalitis
A

Enteroviruses

175
Q

Which virus causes herpangina?

A

Coxsackie A (enterovirus)

176
Q

Which virus causes pericarditis?

A

Coxsackie B (enterovirus)

177
Q

By what medium is mumps transmitted?

A

Saliva and respiratory secretions.

178
Q

Acute parotitis, orchitis and meningitis are all associated with which viral infection?

A

Mumps

179
Q

In mumps, is acute parotitis unilateral or bilateral?

A

Can be both

180
Q

20-30% of males with mumps will develop __1__.

This typically develops 4-5 days after __2__.

A

1) orchitis

2) parotitis

181
Q

Which of these diseases is not associated with sensorineural deafness?

a) Mumps
b) Measles
c) Rubella

A

b) Measles

182
Q

__?__ is highly infectious - the environment is still infectious 2 hours later.

A

Measles

183
Q

What are the symptoms associated with primary measles infection?

A 
Fever
Coryza
Cough
Conjunctivitis
Koplik's spots inside cheek
Maculopapular rash
184
Q

__1__ can occur 7-10 days after acute measles infection. It has a __2__ mortality rate and is __3__ mediated.

A

1) Acute post-infectious measles encephalitis
2) high mortality
3) immune mediated

185
Q

__1__ can occur 7-10 years after primary measles infection. It is a progressive, degenerative and fatal disease of __2__

A

1) Subacute sclerosing panencephalitis (SSPE)

2) CNS

186
Q

__?__ is also known as German measles.

A

Rubella

187
Q

What symptoms are associated with primary postnatal rubella?

A

Mild illness with fever and maculopapular rash.

In 30% of adults: arthralgia and arthritis also occur

188
Q

What symptoms are associated with congenital rubella?

A

Classic triad:

1) Bilateral cataracts
2) Sensorineural deafness
3) Microcephaly

Risk of malformation is highest in first 12 weeks of pregnancy.

189
Q

Which is the more severe rubella syndrome?

A

Congenital rubella is more severe than primary postnatal rubella.

190
Q

__?__ is also known as ‘slapped cheek syndrome’ or ‘Fifth disease’.

A

Parvovirus

191
Q

How does parvovirus cause transient anaemia?

A

Parvovirus infects and destroys erythrocyte progenitor cells, causing transient anaemia.

192
Q

What pathogen and symptoms are associated with erythema infectiosum?

A

Parvovirus

Fever, coryza, fiery red rash to cheeks

193
Q

Parvovirus can cause dyspnoea, confusion and cardiac failure in which group of patients?

A

Those with high erythrocyte turnover

e.g. sickle cell, thalassemia

194
Q

Parvovirus is most likely to lead to miscarriage in which stage of pregnancy?

a) last trimester
b) first 20 weeks
c) first 20 days
d) after 30 weeks

A

b) first 20 weeks

There is a 7-10% chance of foetal loss if mother contracts parvovirus in first 20 weeks.

195
Q

What virus causes severe anaemia, oedema, ascites and heart failure in developing fetus?

A

Parvovirus

2-3% chance of developing hydrops fetalis:

severe fetal anaemia → oedema, ascites, heart failure

196
Q

Which pathogen type contains no nucleic acid?

A

Prions

197
Q

How do prions occur?

A

Gene mutation leads to changes in folding pattern of prion protein. If they become resistant to protease enzyme, the prion accumulates in cells and becomes pathogenic.

198
Q

True or false: Abnormal prions can be inherited but never transmitted.

A

False. Prions can be inherited or transmitted.

Transmission usually occurs via consumption of infected meat products.

199
Q

Which system is almost always affected by prions?

A

CNS

200
Q

Prions lead to __?__ changes in brain tissue on histology.

A

spongiform

201
Q

Do prion diseases have long or short incubation periods?

A

Long: up to 30 years

202
Q

Sporadic Creutzfeldt-Jakob disease is rare. It is cause by a gene mutation and results in what symptoms?

A

Progressive ataxia
Depression
Dementia
Death

203
Q

New variant CJD is linked to which prion disease?

A

Bovine spongiform encephalopathy (BSE)

204
Q

nvCJD is associated with consumption of which product?

A

Infected beef.

205
Q

Which drug is used in the treatment of giardiasis?

A

Metronidazole

206
Q

What is the commonest cause of bacterial pneumonia?

A

Streptococcus pneumoniae

207
Q

What is the commonest cause of bacterial meningitis and sepsis in neonates?

A

Streptococcus agalactiae (group B strep)

208
Q

What disease is caused by treponema pallidum?

A

Syphilis

209
Q

Which virus can trigger transient aplastic crisis in patient with haemoglobinopathies?

A

Parvovirus

210
Q

What is the commonest cause of STIIs?

A

Staphylococcus Aureus

211
Q

Which clostridium species is a classic cause of gas gangrene?

A

Clostridium perfringens

212
Q

__?__ is a clinical syndrome produced by respiratory syncytial virus in children, characterised by wheeze and hypoxia

A

Bronchiolitis

213
Q

Which organ is most commonly affected by hydatid cyst?

A

Liver

214
Q

An infection of the heart valves often caused by viridans streptococci

A

Endocarditis

215
Q

The type of histological change produced in the brain by prion disease

A

Spongiform

216
Q

The cause of scalp ringworm

A

Tinea capitis

217
Q

A sexually transmitted parasitic disease

A

Trichomoniasis

218
Q

The virus that causes 80-90% of clinical infectious mononucleosis

A

Epstein Barr Virus

Clinical Pathology (11 decks)

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