Ocular Infections Flashcards
Staphylococcus aureus
Styes; (can progress to ENDOPHTHALMITIS)
Gram pos cocci, catalase positive
transmossion: respiratory droplet fomites, direct contact
has: capsule; protein A - bound coagulase; leukocidins
Dx: MSA +ve fementer, catalase +ve, coagulase +ve
Propionibacterium acnes
Styes; Keratitis (can progress to ENDOPHTHALMITIS)
Gram Pos rod, non spore forming, pleomorphic
transmission: Normal flora; overgrowth
has pro-inflammatory mediators; proteases, lipases
Dx: culture on agar with Cys; glows orange with fluorescence
Tx: tetracyclines, macrolides
Haemophilus Influenzae (aegyptius)
Purulent Conjunctivitis: dilation and congestion, sticking eyelids from mucopurulent exudative discharge
Gram neg rod, type b has poly ribosyl ribitol phosphate (PRP) capsule - for resistance; fastidious - requires enriched media
transmission: direct contact to mucous membranes; autoinnoculation
has IgA protease to allow carriage and pilli for attachment
Dx: REQUIRES: Hemin (X-factor) and NAD (V-factor) for growth. Culture on Chocolate Agar (heat-lysed blood) or on S. aureus streak (makes NAD which is needed for haemophilus growth)
Tx: topical and/or systemic; augmentin, trimethoprim, sulfonamide; swimming pools contraindicated. Hib vaccine.
Streptococcus pneumoniae
Purulent Conjunctivitis: dilation and congestion, mucopurulent discharge
Gram positive, encapsulated, lancet-shaped paired cocci; catalase negative
transmission: resp droplets, autoinnoculation; mostly children
has capsule, IgA protease, no group-specific carbohydrate
Dx: gram stain confirmed by Neufeld/Quellung reaction; alpha-hemolysis on BAP; catalase negative; bile solubility (ENT)
Tx: penicillin; PCV23 vaccine for high rick ppl between 2 and 65 yo. PCV13 and 7 for children as young as 2mnths.
Neisseria Gonorrhoeae
Purulent Conjunctivitis, Ophthalmia Neonatorum
Gram neg diplococcus, facultative, oxidase & catalase POSITIVE; glucose utilization
transmission: autoinnoculation after infection (STD); neonatal via infected mother
has LOS - infmallatory response from immune complex formation; pili; IgA protease
Dx: social/sexual Hx; culture on Thayer Martin and/or NYC medium (selective for neisseria); glucose utilization; NAAT
Tx: antibiotics against resistant N. gonorrhea; antibiotics against possible coinfection with chlamydia trachomatis; no vaccine
Adenovirus
NON-Purulent Conjunctivitis
- Dilation and congestion of blood vessels and SEROUS EXUDATE; formation of papillae; serosanquineous (fluid w/ no pus)
ds DNA virus, naked
transmission: aerosol, direct contact, fomites, poorly chlorinated pools - WATER; risk to swimmers and water-based construction workers
Dx: clinical presentation; Ag detection
Tx: self-limiting - cleared after 3 weeks
Chlamydia trachomatis
Conjunctivitis –> Keratitis (Keratoconjunctivitis); Ocular Trachoma/Inclusion Conjunctivitis;
pebble formation, entropion (trachomatous trachiasis) –> corneal scarring on tarsal conjunctiva (trachomatous scarring); Corneal opacity
Obligate intracellular bacteria - EB and RB forms in biphasic growth
transmission: hand-eye autoinoculation, neonatal from infected mother; flies; fomites
Dx/Tx: DFA, NAAT, McCoy cell culture; Doxycylcine, erythromycin.
Pseudomonas aeruginosa
Keratitis - RING INFILTRATES; rapidly progressive 12-48 hrs; Keratoconjunctivitis (can progress to ENDOPHTHALMITIS). Hypopyon formation - corneal trauma causes leakage and discharge
Gram neg bacilli; oxidase POSITIVE;
transmission: soil and water; nosocomial; reservoir in URT and GIT
has capsule, biofilm, efflux pumps; pyocyanin and pyochelin (proinflammatory); Endotoxin A - inhibits protein synth via ADP ribosylation of EF-2
Dx: oxidase positive; RING INFILTRATE; strict aerobe; lactose fermenter
Tx: topical antibiotics around the clock for sight-threatening ulcers
Bacillus cereus
Keratitis - rapidly progressive 12-48 hrs after trauma; corneal deterioration; infiltration leading to abscess. (can progress to ENDOPHTHALMITIS)
Gram positive rod; spore forming; aerobe
transmission: from soil and water; direct contact; contaminated blood (intravenous drugs); home-made contact solutions; risk from previous eye trauma
has cereolysin (hemolytic), phospholipase C, necrotic toxin.
Dx: culture on chromogenic bacillus cereus agar; beta-hemolytic on BAP; spores
Tx: antibiotics - clindamycin, gentamycin
Aspergillus spp.
Fungal Keratitis - central corneal ulceration sounded by grey-white, dry-appearing keratitic infiltrates (precipitates) with fuzzy/feathery borders.
Monomorphic fungus w/ Septate Hyphae
transmission: soil and decaying vegetation; traumatic implantation of spores; risk from ocular trauma, corticosteroids, surgery, immunosuppression, contact lenses/solution;
has Phospholipase and Phialides
Dx: SDA agar; confocal microscopy; KOH wet prep
Tx: topical anti-fungals; mechanical debridement of cornea
Fusarium spp.
Fungal Keratitis - central corneal ulceration sounded by grey-white, dry-appearing keratitic infiltrates (precipitates) with fuzzy/feathery borders; satellite infiltrates
Monomorphic mold w/ slender septate hyphae
transmission: soil and decaying vegetation; traumatic implantation of spores; risk from ocular trauma, corticosteroids, surgery immunosuppression, contact lenses/solution;
has fruiting structure (bunch of grapes); Phospholipase
Dx: SDA agar; confocal microscopy; KOH wet prep
Tx: topical anti-fungals; mechanical debridement of cornea
Acanthamoeba castellani
Keratitis - RING INFILTRATES; late-stage complete opacity; slowly progressive weeks to months); [may have early dendritic infiltrate w/o unceration]
Amoeba - Protozoan; trophozoites
transmission: ubiquitous; WARM Waters (eg, hot tubs): direct contact; risk from contact lenses/solution
Dx: microscopy, biopsy
Tx: ineffective due to resistance and long progression; debridement at minimum
Herpes Simplex Viruses
Dendritic Keratitis - dendritic vesicles leading to corneal ulceration; first, clear vesicles (BULLAE) form which coalesce within hours into dendritic vesicles, with further disease progression into dendeitic ulcer after central epithelial defect; swollen epithelial borders, ulceration thru basement membrane.
ds DNA linear, enveloped; nuclear replication; live-long infection
transmission: direct/indirect contact w/ skin/mucosa; STD; transplacental; life-long infection latent in ganglia (trigeminal); risk to everyone, sexually active, immunosuppressed;
Dx: ELISA, PCR, Tzanck smear rare; Impression Cytology - glass slide pressed against conjunctiva then analysed for multinucleated giant cells
Tx: Acyclovir
Loa Loa
Loiasis; Keratitis - NO LOSS OF VISION; painful cutaneous swellings as larvae migrate: Calabar swellings; painful and pruritic (allergic rxn to worms themselves or by-products)
Filarial nematode - helminthic
transmission: Deer or Mango Fly; risk from travel to equatorial rainforests of Africa
Dx: microfilariae in blood smear (migrate through blood, CSF, lungs); EOSINOPHILIA and IgE
Tx: Anti-parasitic drugs (rapid destruction of worms can cause severe allergic rxns tho); surgical removal of eye
Onchocerca volvulus
Onchoceriasis; Keratitis - Punctate lesions progressing to sclerosing keratitis: BLINDNESS as area becomes opague; Loss of skin elastin (atrophy) and melanocytes in skin resulting in thin, depigmented areas: Lizard Skin, Leopard Skin; Painful pruritic cutaneous swellings as larvae migrate – Calabar swellings;
Filarial nematode; migrates through tissues, seen in blood; releases bacterial symbionts
transmission: Black Flies; risk from travel to African Congo and Central/South America;
Dx: microfilariae on skin snips from swellings
Tx: surgical removal of nodes; antiparasitic drugs - ivermectin; doxycycline (targets endosymbiotic bacteria)
