Eye Infections and Microbiota

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Questions and Answers

Which component found in tears has antimicrobial properties?

IgM

Cholesterol

IgA (correct)

Hemoglobin

What is the function of lysozyme in tears?

Acts as an antiviral agent

Neutralizes toxins

Attacks bacterial cell walls by splitting bonds in the peptidoglycan layer (correct)

Inhibits the growth of bacteria by competing for and binding to iron

Which pathogen can penetrate the intact epithelium of the conjunctiva or cornea?

Pseudomonas aeruginosa

Escherichia coli

Neisseria gonorrhoeae (correct)

Bacillus subtilis

Which demographic is more likely to have acute bacterial and viral conjunctivitis?

Children Signup and view all the answers

Which of the following is NOT a risk factor associated with ocular infections?

Educational level Signup and view all the answers

What percentage of indigenous flora from uninflamed eyes is made up of coagulase-negative staphylococci and Corynebacterium spp.?

80% to 90% Signup and view all the answers

Which type of conjunctivitis occurs most frequently in the elderly?

Chronic conjunctivitis Signup and view all the answers

What is the protective role of lactoferrin in tears?

Competes for and binds to iron Signup and view all the answers

Which microorganisms are responsible for a majority of intraocular and corneal infections?

Propionibacterium acnes Signup and view all the answers

What can increase the risk of ocular tissue infection by indigenous flora?

Use of biomaterials, steroids, and antimicrobials Signup and view all the answers

Which of the following has the highest reported incidence in non-inflamed eyes?

Coagulase-negative staphylococci Signup and view all the answers

Where are the sources for ocular resident flora typically found?

Conjunctivae and lids Signup and view all the answers

What protects S. aureus and coagulase-negative staphylococci in ocular tissues?

Biofilm formation Signup and view all the answers

What types of conjunctivitis are listed in the provided content?

Bacterial and viral Signup and view all the answers

Which temperature range is optimal for recovering most bacterial and fungal ocular isolates?

35° to 37° C Signup and view all the answers

Which medium is specifically used for the recovery of fungi in ocular infections?

Sabouraud agar Signup and view all the answers

Which molecular technique has been mentioned as useful in detecting small volumes of ocular pathogens?

PCR Signup and view all the answers

For how many days should all thioglycollate tubes be held if Actinomyces spp. or P. acnes is suspected?

21 days Signup and view all the answers

What is the appropriate transport media for an eye swab specimen?

Amies transport media Signup and view all the answers

Which stain would be used for microexamination in a case of keratitis?

Giemsa stain Signup and view all the answers

Which microorganism is most commonly associated with bacterial conjunctivitis?

Staphylococcus aureus Signup and view all the answers

What type of discharge is associated with viral conjunctivitis?

Watery Signup and view all the answers

What is the recommended treatment for allergic conjunctivitis?

Artificial tears and anti-histamines Signup and view all the answers

Which of the following organisms is associated with both conjunctivitis and blepharitis?

Moraxella spp. Signup and view all the answers

Which symptom is typically unilateral in bacterial conjunctivitis?

Purulent discharge Signup and view all the answers

Which of the following microorganisms is least likely to cause blepharitis?

Adenovirus Signup and view all the answers

What type of inflammation is associated with functional diseases of the seborrheic glands?

Seborrheic blepharitis Signup and view all the answers

Which of the following is rare but can cause blepharitis?

Cryptococcus neoformans Signup and view all the answers

Which condition is considered a true ocular emergency?

Microbial keratitis Signup and view all the answers

What is a predisposing factor for microbial keratitis?

Use of topical steroids Signup and view all the answers

Which of the following is NOT a cause of microbial keratitis?

E. coli Signup and view all the answers

What type of infections usually cause canaliculitis?

Anaerobic Actinomycetes Signup and view all the answers

Which procedure is recommended for diagnosing canaliculitis?

Swabs of the canalicular pus Signup and view all the answers

What could untreated microbial keratitis potentially progress to?

Endophthalmitis Signup and view all the answers

Which microorganism is a Gram-negative bacterium associated with conjunctivitis?

Haemophilus influenza Signup and view all the answers

Which of the following is NOT a symptom of conjunctivitis?

Loss of vision Signup and view all the answers

Which of these viruses is associated with conjunctivitis?

Human coronavirus Signup and view all the answers

Which method is used for collecting conjunctival scrapings?

Spatula Signup and view all the answers

Which of the following is a leading cause of world blindness?

Trachoma Signup and view all the answers

Which Gram-positive bacterium is commonly associated with conjunctivitis?

Staphylococcus aureus Signup and view all the answers

What percentage of office visits to ophthalmologists is due to red eye?

50% Signup and view all the answers

Which diagnosis method can reveal the etiologic agent in most acute cases of conjunctivitis?

Routine stains and culture Signup and view all the answers

Which components of the lacrimal apparatus are responsible for producing the aqueous component of the tear film?

lacrimal glands and accessory glands Signup and view all the answers

What disorder is characterized by the inflammation of the main lacrimal gland?

Dacryoadenitis Signup and view all the answers

Which bacteria is NOT commonly associated with lacrimal apparatus infections?

Escherichia coli Signup and view all the answers

Which virus is known to infect the lacrimal apparatus?

Epstein-Barr virus Signup and view all the answers

What are the primary causes of disorders and infections of the lacrimal apparatus?

Blockage, underproduction, overproduction of tears Signup and view all the answers

Which parasite is associated with infections of the lacrimal apparatus?

Onchocerca volvulus Signup and view all the answers

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.