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Ophthalmology > Microbiology > Flashcards

Microbiology Flashcards

1
Q

Does gram + bacteria have a cell wall? What colour will it stain? What two subtypes does it have?

A

Yes it has a cell wall It will stain purple Can be cocci or bacilli

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2
Q

Gram + cocci can be what?

A

Staph or strep

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3
Q

Does gram - bacteria have a cell wall? What colour will it stain? What three subtypes does it have?

A

No it doesn’t have a cell wall It will stain pink Can be cocci, cocci-bacilli or bacilli

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4
Q

What is Neisseria an example of?

A

Gram - cocci

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5
Q

What is an example of a gram - cocci-bacilli?

A

Haemophilus influenzae

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6
Q

What is an example of a gram - bacilli?

A

Pseudomonas

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7
Q

How can you tell apart bacterial and viral conjunctivitis by clinical presentation?

A

Bacterial- pus Viral- extremely watery

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8
Q

Bacterial conjunctivitis can be an indicator of what?

A

A more severe infection in neonates (always refer to ophthalmology)

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9
Q

Who is bacterial conjunctivitis most common in?

A

Neonates

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10
Q

What organisms can cause bacterial conjunctivitis in neonates?

A
  • Neisseria Gonorrhoeae - Staph Aureus - Chlamydia Trachomatis
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11
Q

What organisms can cause bacterial conjunctivitis in non-neonates?

A
  • Staph Aureus - Haemophilus Influenzae - Strep Pneumoniae
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12
Q

Haemophilis influenzae infection is most common in who?

A

Children

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13
Q

What is the antibiotic of choice for bacterial conjunctivitis? How can this be taken? How often is it taken?

A
  • Chloramphenicol - Topically or as drops - 4 times daily
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14
Q

When should chloramphenicol not be given?

A

If there is any history of aplastic anaemia or allergy

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15
Q

If symptoms of bacterial conjunctivitis worsen after treatment, what could this be suggestive of?

A

Drug allergy

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16
Q

What bacteria does chloramphenicol not treat? If for any reason chloramphenicol cannot be used, what are some other treatment options?

A

It does not treat pseudomonas aeruginosa. Other options are fusidic acid (staph aureus) or gentamicin (gram -‘s)

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17
Q

What is most likely the cause if bacterial conjunctivitis presents with a chronic history and is unresponsive to treatment with chloramphenicol?

A

Chlamydial conjunctivitis

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18
Q

When should chlamydial conjunctivitis be suspected?

A

When there is bilateral conjunctivitis in a young adult (who may or may not have symptoms of urethritis/vaginitis)

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19
Q

Chlamydial conjunctivitis requires contact tracing. It also causes scarring where?

A

Underside of the eyelid

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20
Q

How do you treat chlamydial conjunctivitis?

A

Topical oxytetracycline (adults may also need oral azithromycin for genital chlamydia)

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21
Q

What are 3 organisms causing viral conjunctivitis?

A
  • Adenovirus - Herpes Simplex - Herpes Zoster
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22
Q

What is the general treatment for viral conjunctivitis?

A

Usually self-limiting, use a cold press. Can occasionally give antibiotics to prevent a secondary infection.

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23
Q

What is Hutchinson’s sign? What does it precede?

A

Vesicles on the tip or side of the nose, suggestive of damage to the nasociliary branch of the trigeminal nerve. It precedes Herpes Zoster.

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24
Q

How should Herpes Zoster be treated?

A

Aciclovir (ideally in 72 hours)

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25
Q

What is keratitis?

A

Inflammation of the cornea

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26
Q

Keratitis presents with a very short history and acute onset vision disturbance. What is the most likely cause?

A

Bacterial

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27
Q

Bacterial keratitis often occurs with hypopyon. What is this?

A

Inflammatory cells in the anterior chamber of the eye which causes a characteristic white clouding

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28
Q

Who does bacterial keratitis tend to occur in?

A

Those with other corneal pathology or wear contact lenses

29
Q

Why do patients with bacterial keratitis need hospital admission?

A

Hourly eyedrops and a daily review- this can be sight threatening

30
Q

What is the main treatment for bacterial keratitis? What organism does this NOT target?

A

Oflaxacin- not active against strep pneumoniae

31
Q

What combination treatment can be used in bacterial keratitis?

A

Gentamycin and cefuroxime

32
Q

Keratitis associated with contact lenses is most often caused by what organism?

A

Pseudomonas aeruginosa

33
Q

What are the 2 causes of viral keratitis?

A

Adenovirus and herpes

34
Q

What condition cannot be treated with steroids? Why?

A

Herpetic keratitis- can cause a corneal melt and perforation

35
Q

How does adenoviral keratitis usually present?

A

Bilaterally after an URTI

36
Q

Is adenoviral keratitis infectious? How is it treated?

A

Yes it is infectious. You can give topical antibiotics to prevent secondary infections or steroids to speed up recovery.

37
Q

Keratitis presents with a long history of slow onset with an eye which is not as red as would be expected and is not particularly sore. What is the most likely cause?

A

Fungi from a history of trauma from vegetation

38
Q

What is orbital cellulitis often preceded by?

A

Paranasal sinusitis, or an operation (common post-operative complication)

39
Q

What are some complications of orbital cellulitis?

A
  • Compartment syndrome - Compromised optic nerve - Infection passing to the cranial fossa - Compromised medial rectus muscle
40
Q

What are some organisms which can cause orbital cellulitis?

A

Staph, strep, coliforms, HI, anaerobes

41
Q

What test is used to detect orbital abscesses? When else are these used?

A

CT scans, also used if there are suggestions of muscle restriction or optic nerve dysfunction

42
Q

What is endopthalmitis? What can cause it?

A

Devastating infection causing inflammation of the entire eye- can be caused post-surgery or by a dormant organism

43
Q

What is the most common organism causing endopthalmitis?

A

Staph epidermidis

44
Q

How is endopthalmitis treated?

A

Intra-vitreous amikacin/caftazidime/vancomycin and topical antibiotics

45
Q

What is chorioretinitis?

A

Infection at the back of the eye

46
Q

CMV in AIDS, toxoplasma gondii and toxocara canis are causes of what?

A

Chorioretinitis

47
Q

Where does toxoplasma gondii come from? What type of organism is it?What happens if it is present in immunocompromised? When does it require treatment?

A

Cats and raw meat- it is a protozoa. In immunocompromised it forms cysts and can reactivate. It only requires treatment if sight threatening.

48
Q

What is toxocara canis? What happens when it is in humans?

A

A parasitic nematode. In humans it forms granulomas though is unable to replicate.

49
Q

What is the diagnostic test for conjunctivitis?

A

Swabs

50
Q

What is the test for bacterial keratitis?

A

Corneal scrapes

51
Q

What is the best test for endophthalmitis?

A

Aqueous/vitreous humour culture

52
Q

What is the best test for toxoplasma and toxocara?

A

Serology

53
Q

What are the 3 broad categories of antibiotic and give examples?

A
  • Inhibit protein synthesis (chloramphenicol) - Inhibit cell wall synthesis (penicillins and cephalosporins) - Inhibit nucleic acid synthesis (quinolones)
54
Q

How does chloramphenicol work? It is bactericidal for what? It is bacteriostatic for what?

A

Inhibits the peptide transferase enzyme to stop bacterial protein being made. Bactericidal for strep and haemophilus and bacteriostatic for staph.

55
Q

What are the side effects of chloramphenicol?

A
  • Allergy - Irreversible aplastic anaemia - Grey baby syndrome
56
Q

What organism is a common contaminant of old eyedrop bottles?

A

Pseudomonas

57
Q

What % acyclovir should be used in the eye?

A

3%

58
Q

What is this?

A

Bacterial conjunctivitis

59
Q

What is this?

A

Adenoviral conjunctivitis

60
Q

What is this?

A

Herpes Simplex conjunctivitis

61
Q

What is this?

A

Herpes Zoster conjunctivitis

62
Q

What condition causes this scarring?

A

Chlamydial conjunctivitis

63
Q

What is this?

A

Bacterial keratitis with hypopyon

64
Q

What is this?

A

Dendritic ulcer from herpetic keratitis

65
Q

What is this?

A

Orbital cellulitis

66
Q

What is this?

A

Endophthalmitis

67
Q

What antibiotics should be given for orbital cellulitis?

A

IV ceftriaxone, flucloxacillin and metronidazole

68
Q

What complication should you be most worried about with regards to orbital cellulitis?

A

Cavernous sinus thrombosis

Ophthalmology (12 decks)

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