Ear and Eye infections; Drugs! Flashcards
Conjunctivitis
conjunctiva- thin membrane
discharge, red eye, irritation, and sensitivity to palpitation; caused by dilation and congestion of subepithelial vessels
Could be viral, bacterial, or allergic
Viral conjunctivitis
Neonatal – HSV-1 (acute)
Post-natal – Adenovirus (most common)
recent upper respiratory tract infection, preauricular adenopathy benign and self limited in immunecompetent treat with cold compress and topical vasoconstrictors
Adenovirus
non-enveloped, double-stranded DNA virusLytic in epithelial cells and latent in lymphoid highly contagious spread through fomites like swimming pools
Acute bacterial conjunctivitis
Children- Staphylococcus aureus, Streptococcus pneumoniae, Haemophilus influenzae
Adults- Staphylococcus aureus
Self-limited but treating decreases patient morbidity and transmission
Empiric treatment with both Gram positive and negative coverage
Moxifloxacin solution (best coverage, expensive, >3 yr)
trimethoprim-polymyxin B
Neisseria gonorrhoeae
Copious yellow-green discharge (purulent)
Preauricular adenopathy
Gram stain for gram-negative intracellular diplococci and growth on chocolate agar supplemented with vancomycin, colistin, nystatin, and trimethoprim (nonsterile site)
Treat promptly with systemic ceftriaxone otherwise can quickly progress to corneal ulceration and perforation, can augment with topical antibiotics and irrigation
Ophthalmia neonatorum
conjunctivitis or keratoconjunctivitis occurring within first four weeks of birth
Timing of infection can help predict etiology
N. gonorrhoeae, C. trachomatis, Staphylococcus, Streptococcus, E. coli, H. influenzae or H. simplex
Prophylaxis with erythromycin ointment
Treat with appropriate antimicrobial often erythromycin
Cultures and smears for diagnosis
Macrolides
erythromycin, azithromycin
Mechanism:
Inhibits translation by binding 23S rRNA of the 50S subunit
Spectrum: Broad coverage of respiratory pathogens, Chlamydia
Resistance: Increased efflux, hydrolysis of drug by esterases, methylation of drug binding site
Adverse effects:
GI discomfort, Hepatic failure, and Prolonged QT interval
Inhibitors of cytochrome P450 enzymes (check with other medications)
Chlamydia trachomatis
Inclusion conjunctivitis (serotypes D-K)
Trachoma (serotypes A-C), leading cause of blindness worldwide due to multiple infections since no long lasting immunity
Diagnosis: direct fluorescent antibody
Coinfections should be considered, most often N. gonorhoaea
Treat with systemic azithromycin and improve hygiene
Treat sexual partner(s) and widespread prophylaxis is being used to try to eliminate Trachoma by 2020.
Elementary body is taken up by mucosal epithelial cells of uterus and eye converts to metabolically active reticulate body which divides by binary fission. Converts back and then is released to infect neighboring cells. Interferon-gamma can create persistent form which is reactivated when the drug is removed.
Herpes simplex virus
Similar presentation to adenovirus although lesions can be painful especially if scarring of the cornea occurs and often only one eye
Avoid corticosteroids since can facilitate corneal penetration
If corneal involvement treat with topical trifluridine and systemic acyclovir and consider prophylactic treatment with erythromycin to prevent bacterial superinfection
often affects neonates
Trifluridine
pyrimidine analog effective against acyclovir resistant virus because it can be phosphorylated by host kinases also making it much more toxic and should only be used topically
Keratitis
cornea
vision defects, photophobia, pain (cornea has lots of nerve endings), and foreign body sensation
Trauma, drying of the epithelia, and hypoxia increase susceptibility.
Viral keratitis is caused by HSV-1, adenovirus, and VZV.
Bacterial keratitis Staph. aureus and epidermidis, Pseudomonas aerugrinosa, and Bacillus cereus.
Fungal infection in warm, humid climate
Acanthamoeba, a free-living ameba, frequently resides in improperly stored contact lens cleaning fluids and initiates eye infections.
Treatment- for bacteria Moxifloxacin eye drops
for HSV-1 trifluridine + acyclovir
Pseudomonas aeroginsoa
Gram negative, aerobic rod, flagella
Free living found in water and soil with minimal nutrition requirements and can use 75 different organic compounds for growth
Plant and nosocomial pathogen
Contact lens wearers are at greater risk
Opportunistic infection- if decrease in host defense (trauma) can infect most tissues
Naturally resistant to many antibiotics and disinfectants partly due to its ability to form biofilms
Bacterial cell surface adherence factors and secreted cytotoxins like elastase and alkaline protease destroy corneal epithelium.
The host immune response damages the cornea leading to scarring and loss of visual acuity
Uveitis
iris, ciliary body, and choroid
inflammation of uveal tract can leading to blurred vision permanent vision loss
Iritis (anterior uveitis)- often not infectious, photophobia, pain, and decreased visual acuitiy
Treponema pallidum, Herpes simplex, varicella-zoster
Chorioretinitis (poster uveitis)- most common, floaters, no pain
Chorioretinitis
choroid and retinal layers
blurred vision and visual field defects
Blood borne route via retinal arteries, frequently manifestation of systemic disease
Congenital Toxoplasma and CMV (ganciclovir implant) are most common especially in HIV positive individuals and neonates
Two parasitic worm infections (Toxocara canis and Onchocerca volvulus) cause eye infections; the latter causes “river blindness” and is transmitted by sand flies.
Endophthalmitis
vitreous and/or aqueous humors
Rare
Pain, redness, and decreased vision
Bacteria/ fungi
Exogenous- Recent intraocular surgery esp. cataract
with agent coming from normal flora: Pseudomonas, Staphylococci or Candida
Endogenous- hematogenous spread
Fluoroquinolone or vancomycin injected into eye
