Microbiology

Question 1

Common causes of Bacterial Conjunctivitis

Answer 1

Staph Aureus
Strep Pneumoniae
Haemophilus Influenzae (children esp.)

Question 2

Treatment of Bacterial Conjunctivitis

Answer 2

Topical Chloramphenicol (ointment or drops)

NB - avoid in aplastic anaemia and allergy

Question 3

Common causes of Viral Conjunctivitis

Answer 3

Adenovirus
Herpes Simplex
Herpes Zoster

Question 4

Treatment of Viral Conjunctivitis

Answer 4

Nil, supportive where required

Education on hygiene as highly contagious

Question 5

Features of Chlamydial Conjunctivitis

Answer 5

Follicular conjunctivitis - rice grains
Often chronic history, unresponsive to Tx
May or may not have associated symptoms e.g. urethritis, vaginitis

Question 6

Treatment of Chlamydial Conjunctivitis

Answer 6

Topical oxytetracycline
May require oral azithromycin/Tx of genital disease
Contact tracing

Question 7

Complication of Chlamydial Conjunctivitis

Answer 7

Subtarsal scarring

Question 8

What is keratitis?

Answer 8

Infection of the cornea results in a white area in the cornea and a white level of pus at the bottom.
Most frequently with other eye pathology or contact lens wearing.

Question 9

Suspect bacterial keratitis - what next?

Answer 9

Refer
Take scraping for culture
Daily review

Question 10

Complications of bacterial keratitis

Answer 10

Scarring

Perforation

Question 11

Causes of Viral Keratitis

Answer 11

Herpes

Adenovirus

Question 12

Features of Herpetic Keratitis

Answer 12

Dendritic ulcer - branching

Pain

Question 13

Ix for Herpetic Keratitis

Answer 13

Fluorescein dye to show missing epithelium

Question 14

What is important to avoid in viral keratitis?

Answer 14

Steroids - can cause corneal melt and perforation

Question 15

Features of adenoviral keratitis

Answer 15

Subepithelial infiltrates
Bilateral
Following on from URTI
Blurred vision

Question 16

Tx adenoviral keratitis

Answer 16

topical steroids if chronic

Can give topical ABs to prevent secondary infection

Question 17

Common presentation of Acanthamoeba Keratitis?

Answer 17

Contact lens wearer
Non-responsive to treatment for bacterial keratitis
Painful

Question 18

Common presentation of Fungal Keratitis?

Answer 18

Chronic history
Outdoor workers - farmers, landscapers, or those with ocular disease
Defined corneal lesion +/- hypopyon

Question 19

Tx of Fungal Keratitis?

Answer 19

Topical antifungals and admission

Natamycin/Amphotericin

Question 20

Red swollen eye, pain on movement, proptosis, pyrexial, and may be associated with paranasal sinusitis - diagnosis?

Answer 20

Orbital Cellulitis

Question 21

Causes of Orbital Cellulitis

Answer 21

Staph 
Strep 
Coliforms 
H. Influenzae 
Anaerobes 

From sinus, focal orbital infection, or post-op

Question 22

Ix for orbital cellulitis

Answer 22

CT to identify orbital abscesses
Differentiate between preseptal and orbital
If evidence of muscle restriction or optic nerve dysfunction - scan

Question 23

Tx of Orbital Cellulitis

Answer 23

Broad Spec AB, drain abscess if indicated

Question 24

Most common cause of Endophthalmitis

Answer 24

Staph Epidermidis

Almost always commensals post-op

Question 25

Features of Endophthlamitis

Answer 25

very painful Decreased vision very red eye systemic upset

Question 26

Tx of Endophthalmitis

Answer 26

intravitreal amikacin/ceftazidime/vancomycin and topical ABs - give general anaesthetic

Question 27

Causes of Chrioretinitis

Answer 27

Haemorrhagic CMV retinitis in those with AIDS HSV in immunosuppresse (rare) Parasitic - toxoplasmosis gondii and toxocara

Question 28

Common presentation of Toxoplasmosis

Answer 28

Exposure - cats, undercooked meat | Flu like symptoms

Question 29

Tx of toxoplasmosis

Answer 29

Systemic clindamycin/azithromycin +/- steroids if sight threatening (check fundoscopy in relation to macula)

Question 30

Toxoplasmosis in immunosuppressed patient

Answer 30

May recur due to formation of latent cysts

Question 31

How does Toxocara cause vision loss?

Answer 31

Granuloma formation --> scarring --> irreversible vision loss

Question 32

Ix for bacterial keratitis?

Answer 32

Corneal scrape

Question 33

Ix for endophthalmitis?

Answer 33

aqueous/vitreous culture

Question 34

Ix for parasitic choroiretinitis?

Answer 34

Serology

Question 35

What is the mechanism of action of Chloramphenicol?

Answer 35

Inhibition of peptidyl transferase - prevents bacterial protein synthesis Bacteriocidal - Strep and H. influenzae Bacteriostatic - Staph

Question 36

Side Effects of Chloramphenicol?

Answer 36

Allergy Irreversible aplastic anaemia (rare) Grey baby syndrome

Question 37

Mechanism of action of penicillins and cephalosporins?

Answer 37

B lactam ring inhibits enzyme for bacterial cell wall synthesis

Question 38

ABs used in cellulitis and dacryocystitis?

Answer 38

Penicillins and Cephalosporins

Question 39

Mechanism of action of Quinolones?

Answer 39

Inhibit DNA gyrase (which is needed for supercoiling of bacterial DNA) - cell death

Question 40

Example of Quinolone and it's indications

Answer 40

``` Ofloxacin (aka 4-quinolone) - used sparingly due to resistance Corneal ulcers (bacterial keratitis) ```

Question 41

Tx of Bacterial Keratitis

Answer 41

Ofloxacin Gentamicin Cefurozime

Question 42

What is the most common contaminant in eyedrops?

Answer 42

Pseudomonas - only keep for 28 days max