Eye Infections: Conjunctivitis

Infections of the Conjunctiva (Conjunctivitis)

• Conjunctivitis is the most common ocular complaint, affecting all age groups worldwide.
• Symptoms include itching, tearing, foreign body sensation, discharge, and hyperemia (red or pink eye).
• Red eye constitutes more than 50% of office visits to ophthalmologists and is the most common ocular source for microbiologic evaluation.

Microorganisms Associated with Conjunctivitis

• Gram-negative bacteria:
  • Acinetobacter spp., Borrelia burgdorferi, Enterobacteriaceae (e.g., Escherichia coli, Proteus mirabilis, Shigella spp.)
  • Haemophilus influenza, Haemophilus ducreyi, Moraxella catarrhalis, Moraxella lacunata, Neisseria gonorrhoeae, Neisseria meningitides, Pseudomonas aeruginosa
• Gram-positive bacteria:
  • β-Hemolytic streptococci (A, B, C, G), Corynebacterium diphtheriae, Corynebacterium spp., Staphylococcus aureus, Staphylococcus epidermidis, Streptococcus pneumoniae, Viridans Streptococci
• Viruses:
  • Human coronavirus, Herpesviruses (1 to 8), Chlamydia and related spp. (Chlamydophila pneumoniae, Chlamydia psittaci, Chlamydia trachomatis)
• Fungi (rare):
  • Candida spp.
• Parasites (rare):
  • Ascaris lumbricoides

Laboratory Diagnosis

• Laboratory tests help differentiate acute, allergic, and chronic conjunctivitis.
• Conjunctival scrapings are collected using a spatula, blade, or sterile swabs.
• Samples are plated directly onto slides and culture media.
• Routine stains (Gram, Giemsa) and culture should reveal the etiologic agent in most acute cases.

Infections of the Lids (Blepharitis)

• Blepharitis is the inflammation of the lid margins.
• It is not mutually exclusive with conjunctivitis, and any organism that causes conjunctivitis can affect the lids.
• The skin covering the lids is among the thinnest on the body, making it susceptible to skin infections.
• Staphylococcus aureus and coagulase-negative staphylococci are the most frequently isolated bacteria from the lid margins.

Microorganisms Associated with Blepharitis

• Bacteria:
  • Common isolates: Staphylococcus aureus, Staphylococcus epidermidis, and other coagulase-negative staphylococci
  • Less common isolates: Group A and other ß-streptococci, Moraxella lacunata, Moraxella spp.
• Fungi (rare):
  • Candida spp., Cryptococcus neoformans
• Viruses:
  • Herpes simplex virus types 1 and 2

Infections of the Cornea (Keratitis)

• Microbial keratitis is an infection of the cornea and is considered a true ocular emergency.
• Few organisms can invade the intact cornea, but if the cornea epithelium is breached, organisms can enter and cause infections.
• Predisposing factors include contact lens wear, pre-existing ocular disease, ocular trauma, ocular surgery, and laser refractive surgery.

Microorganisms Associated with Keratitis

• Bacteria:
  • Staphylococci, Streptococci, Pseudomonads, Enterobacteriaceae, Corynebacterium species, Moraxella species, Serratia species, Haemophilus
• Fungi:
  • Aspergillus species, Candida species
• Parasites:
  • Propionbacterium species

Canaliculitis (TEHAB ALQNIAT ALDMUEIA)

• Canaliculitis is a rare infection of the lacrimal canaliculus.
• Infections are usually chronic and caused by anaerobic Actinomycetes such as Actinomyces israelii or by Propionibacterium propionicum.
• Swabs of samples of the canalicular pus are preferable.

Infections of the Lacrimal Apparatus

• The lacrimal glands, accessory glands, puncta, canaliculi, tear sac, and nasolacrimal duct together are known as the lacrimal apparatus.
• Disorders and infections of the lacrimal apparatus are caused by blockage, underproduction, or overproduction of tears.
• Organisms are seeded into the gland via the bloodstream.

Microorganisms Associated with Lacrimal Apparatus Infections

• Bacteria:
  • Staphylococcus aureus, Streptococcus pneumonia, Streptococcus pyogenes, Haemophilus influenzae, Pseudomonas aeruginosa, Proteus mirabilis, Chlamydia trachomatis, Treponema pallidum
• Viruses:
  • Coxsackie A virus, Cytomegalovirus, Echovirus, Epstein-Barr virus, Herpes simplex virus types 1 and 2
• Fungi:
  • Aspergillus spp., Candida albicans, Rhizopus spp., Mucor
• Parasites:
  • Cysticercus cellulosae, Onchocerca volvulus, Schistosoma haematobium