Podcast
Questions and Answers
Which component found in tears has antimicrobial properties?
Which component found in tears has antimicrobial properties?
What is the function of lysozyme in tears?
What is the function of lysozyme in tears?
Which pathogen can penetrate the intact epithelium of the conjunctiva or cornea?
Which pathogen can penetrate the intact epithelium of the conjunctiva or cornea?
Which demographic is more likely to have acute bacterial and viral conjunctivitis?
Which demographic is more likely to have acute bacterial and viral conjunctivitis?
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Which of the following is NOT a risk factor associated with ocular infections?
Which of the following is NOT a risk factor associated with ocular infections?
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What percentage of indigenous flora from uninflamed eyes is made up of coagulase-negative staphylococci and Corynebacterium spp.?
What percentage of indigenous flora from uninflamed eyes is made up of coagulase-negative staphylococci and Corynebacterium spp.?
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Which type of conjunctivitis occurs most frequently in the elderly?
Which type of conjunctivitis occurs most frequently in the elderly?
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What is the protective role of lactoferrin in tears?
What is the protective role of lactoferrin in tears?
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Which microorganisms are responsible for a majority of intraocular and corneal infections?
Which microorganisms are responsible for a majority of intraocular and corneal infections?
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What can increase the risk of ocular tissue infection by indigenous flora?
What can increase the risk of ocular tissue infection by indigenous flora?
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Which of the following has the highest reported incidence in non-inflamed eyes?
Which of the following has the highest reported incidence in non-inflamed eyes?
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Where are the sources for ocular resident flora typically found?
Where are the sources for ocular resident flora typically found?
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What protects S. aureus and coagulase-negative staphylococci in ocular tissues?
What protects S. aureus and coagulase-negative staphylococci in ocular tissues?
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What types of conjunctivitis are listed in the provided content?
What types of conjunctivitis are listed in the provided content?
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Which temperature range is optimal for recovering most bacterial and fungal ocular isolates?
Which temperature range is optimal for recovering most bacterial and fungal ocular isolates?
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Which medium is specifically used for the recovery of fungi in ocular infections?
Which medium is specifically used for the recovery of fungi in ocular infections?
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Which molecular technique has been mentioned as useful in detecting small volumes of ocular pathogens?
Which molecular technique has been mentioned as useful in detecting small volumes of ocular pathogens?
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For how many days should all thioglycollate tubes be held if Actinomyces spp. or P. acnes is suspected?
For how many days should all thioglycollate tubes be held if Actinomyces spp. or P. acnes is suspected?
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What is the appropriate transport media for an eye swab specimen?
What is the appropriate transport media for an eye swab specimen?
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Which stain would be used for microexamination in a case of keratitis?
Which stain would be used for microexamination in a case of keratitis?
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Which microorganism is most commonly associated with bacterial conjunctivitis?
Which microorganism is most commonly associated with bacterial conjunctivitis?
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What type of discharge is associated with viral conjunctivitis?
What type of discharge is associated with viral conjunctivitis?
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What is the recommended treatment for allergic conjunctivitis?
What is the recommended treatment for allergic conjunctivitis?
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Which of the following organisms is associated with both conjunctivitis and blepharitis?
Which of the following organisms is associated with both conjunctivitis and blepharitis?
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Which symptom is typically unilateral in bacterial conjunctivitis?
Which symptom is typically unilateral in bacterial conjunctivitis?
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Which of the following microorganisms is least likely to cause blepharitis?
Which of the following microorganisms is least likely to cause blepharitis?
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What type of inflammation is associated with functional diseases of the seborrheic glands?
What type of inflammation is associated with functional diseases of the seborrheic glands?
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Which of the following is rare but can cause blepharitis?
Which of the following is rare but can cause blepharitis?
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Which condition is considered a true ocular emergency?
Which condition is considered a true ocular emergency?
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What is a predisposing factor for microbial keratitis?
What is a predisposing factor for microbial keratitis?
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Which of the following is NOT a cause of microbial keratitis?
Which of the following is NOT a cause of microbial keratitis?
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What type of infections usually cause canaliculitis?
What type of infections usually cause canaliculitis?
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Which procedure is recommended for diagnosing canaliculitis?
Which procedure is recommended for diagnosing canaliculitis?
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What could untreated microbial keratitis potentially progress to?
What could untreated microbial keratitis potentially progress to?
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Which microorganism is a Gram-negative bacterium associated with conjunctivitis?
Which microorganism is a Gram-negative bacterium associated with conjunctivitis?
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Which of the following is NOT a symptom of conjunctivitis?
Which of the following is NOT a symptom of conjunctivitis?
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Which of these viruses is associated with conjunctivitis?
Which of these viruses is associated with conjunctivitis?
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Which method is used for collecting conjunctival scrapings?
Which method is used for collecting conjunctival scrapings?
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Which of the following is a leading cause of world blindness?
Which of the following is a leading cause of world blindness?
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Which Gram-positive bacterium is commonly associated with conjunctivitis?
Which Gram-positive bacterium is commonly associated with conjunctivitis?
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What percentage of office visits to ophthalmologists is due to red eye?
What percentage of office visits to ophthalmologists is due to red eye?
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Which diagnosis method can reveal the etiologic agent in most acute cases of conjunctivitis?
Which diagnosis method can reveal the etiologic agent in most acute cases of conjunctivitis?
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Which components of the lacrimal apparatus are responsible for producing the aqueous component of the tear film?
Which components of the lacrimal apparatus are responsible for producing the aqueous component of the tear film?
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What disorder is characterized by the inflammation of the main lacrimal gland?
What disorder is characterized by the inflammation of the main lacrimal gland?
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Which bacteria is NOT commonly associated with lacrimal apparatus infections?
Which bacteria is NOT commonly associated with lacrimal apparatus infections?
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Which virus is known to infect the lacrimal apparatus?
Which virus is known to infect the lacrimal apparatus?
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What are the primary causes of disorders and infections of the lacrimal apparatus?
What are the primary causes of disorders and infections of the lacrimal apparatus?
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Which parasite is associated with infections of the lacrimal apparatus?
Which parasite is associated with infections of the lacrimal apparatus?
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Study Notes
Eye Infections
Normal Ocular Microbiota
- The normal resident conjunctival and lid microbiota changes with age
- The intact epithelia of the lid, conjunctiva, and cornea provide a protective barrier against invasion by most microorganisms
- Tears contain high concentrations of IgA, lysozyme, and lactoferrin, which have antimicrobial properties
- Lysozyme attacks bacterial cell walls by splitting bonds in the peptidoglycan layer
- Lactoferrin inhibits the growth of bacteria by competing for and binding to iron
- The flow of tears protects the eye from infection by removing bacteria and debris from the ocular surface
Risk Factors for Ocular Infections
- Age
- Sex
- Race
- Socioeconomic status
- Behavior
- Geographic location
- Occupation
- Underlying disease
Conjunctivitis
- Acute bacterial and viral conjunctivitis occurs more frequently in childhood, whereas chronic conjunctivitis and varicella-zoster virus (VZV) conjunctivitis occurs most frequently in the elderly
- Women are more likely than men to be associated with Trachoma, a disease caused by Chlamydia (C.trachomatis)
- Several pathogens can penetrate the intact epithelium of the conjunctiva or cornea, including Neisseria gonorrhoeae, Neisseria meningitidis, S.pneumoniae, Listeria monocytogenes, and Corynebacterium diphtheriae
Microorganisms Associated with Conjunctivitis
- Gram-negative: Acinetobacter spp., Borrelia burgdorferi, Enterobacteriaceae, Haemophilus influenza, Moraxella catarrhalis, Neisseria gonorrhoeae, Neisseria meningitidis, Pseudomonas aeruginosa
- Gram-positive: B-Hemolytic streptococci, Corynebacterium diphtheriae, Staphylococcus aureus, Staphylococcus epidermidis, Streptococcus pneumoniae, Viridans Streptococci
- Viruses: Human coronavirus, Herpesviruses, Chlamydia and related spp.
- Fungi (rare): Candida spp.
- Parasites (rare): Ascaris lumbricoides
Laboratory Diagnosis
- Laboratory tests can be of assistance in differentiating acute, allergic, and chronic conjunctivitis
- Conjunctival scrapings are collected using a spatula, blade, or sterile swabs
- Plated directly onto slides and culture media
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
- Inflammation of the main lacrimal gland, known as dacryoadenitis, may be infectious or noninfectious
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, Influenza, Measles, Varicella-zoster virus
- Fungi: Aspergillus spp., Candida albicans, Rhizopus spp., Mucor
- Parasites: Cysticercus cellulosae, Onchocerca volvulus, Schistosoma haematobium
Discriminating Between Indigenous Microbiota and Pathogens
- The distinction between indigenous microbiota and ocular pathogens is blurred
- Coagulase-negative staphylococci, Propionibacterium acnes, and S.aureus are responsible for a majority of intraocular and corneal infections
- The presence of biomaterials, use of steroids, and antimicrobials can predispose ocular tissues to infection with indigenous flora
Infections of the Conjunctiva
- Viral Conjunctivitis
- Bacteria Conjunctivitis
Anatomy of the Eye
- Sclera
- Vitreous
- Iris
- Choroid
- Cornea
- Optic nerve
- Pupil
- Macula
- Lens
- Retina
- Conjunctiva
Culture and Identification
- Most of the bacterial and fungal ocular isolates may be recovered on chocolate and blood agar when they are incubated under the proper conditions of temperature and atmosphere
- The addition of thioglycollate broth, Thayer-Martin agar, Sabouraud agar with gentamicin, viral and chlamydial transport media, Löwenstein-Jensen slants allows for the recovery of most pathogens involved in ocular disease
Molecular Techniques
- DNA probes and PCR help in confirming clinical diagnosis for difficult or unusual ocular pathogens
- This method may be ideal for detecting microbes in ocular samples because of the small volume
Lab Diagnosis of Eye Infection
- Specimen: Eye swab (2), and scraping in case of keratitis
- Transportation: Stuart or Amies transport media
- Microexamination: Gram stain, Direct immunofluorescence stain, Geimsa stain, Iodine preparation
- Culture: Routine, Additive media, and Liquid media
Infections of the Lids (Blepharitis)
- Blepharitis (inflammation of the lid margins) and inflammation of the conjunctivae are not mutually exclusive
- Any organism that causes conjunctivitis can affect the lids
- Staphylococcus aureus and members of the coagulase-negative staphylococcal family are the most frequently isolated bacteria from the lid margins
- Blepharitis involving these organisms is a low-grade inflammation associated with functional diseases of the seborrheic glands (seborrheic blepharitis)
Microorganisms Associated with Blepharitis
- Bacteria: Staphylococcus aureus, Staphylococcus epidermidis, Group A and other β-streptococci, Moraxella lacunata, Moraxella spp.
- Fungi (rare): Candida spp., Cryptococcus neoformans
- Viruses: Herpes simplex virus types 1 and 2
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Description
Learn about the changes in conjunctival and lid microbiota with age and the defense mechanisms that protect ocular structures from microorganisms.
