Bacterial endophthalmitis: Difference between revisions
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===Endogenous bacterial endophthalmitis=== | ===Endogenous bacterial endophthalmitis=== | ||
====Pathogenesis==== | ====Pathogenesis==== | ||
Endogenous endophthalmitis is typically the result of hematogenous spread from a distant infective source within the body. Endogenous endophthalmitis is associated with [[chronic | Endogenous endophthalmitis is typically the result of hematogenous spread from a distant infective source within the body. Endogenous endophthalmitis is associated with [[chronic conditions]], such as [[diabetes]], [[HIV]], [[malignancy]], [[intravenous drug use]], [[transplantation]], [[immunosuppressive therapy]], and [[catheterization]]. | ||
Under normal circumstances, the [[blood-ocular barrier]] provides a natural resistance against invading organisms. | Under normal circumstances, the [[blood-ocular barrier]] provides a natural resistance against invading organisms. | ||
Following [[bacteremia]], the blood-borne organisms permeate the [[blood-ocular barrier]] by: | Following [[bacteremia]], the blood-borne organisms permeate the [[blood-ocular barrier]] by: | ||
Revision as of 12:32, 20 July 2016
Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Sara Mehrsefat, M.D. [2]
Overview
Bacterial endophthalmitis means bacterial infection inside the eye, involving the vitreous and/or aqueous humors. Most cases of endophthalmitis are exogenous, and organisms are introduced into the eye via trauma, surgery, or an infected cornea. Endogenous endophthalmitis occurs when the eye is seeded via the bloodstream. Patients usually have symptoms from their underlying systemic infection, but sometimes present only with eye symptom
Historical Perspective
Classification
Based on how infectious agents generally gain access to the posterior segment posterior segment of the eye, bacterial endophthalmitis may be classified into:
- Exogenous bacterial endophthalmitis
- Post-operative bacterial endophthalmitis
- Delayed post-operative bacterial endophthalmitis
- Post-traumatic bacterial endophthalmitis (following a penetrating injury of the globe)
- Endogenous bacterial endophthalmitis
Pathophysiology
Exogenous bacterial endophthalmitis
Pathogenesis
Post-operative endophthalmitis is an ocular inflammation resulting from the introduction of an infectious agent, most commonly coagulase-negative staphylococci, into the posterior segment of the eye.
Nearly every type of ocular surgery, such as cataract, glaucoma, retinal, radial keratotomy, and intravitreal injections, may be able to disturb the eye globe integrity and contaminate the aqueous humor. Preoperative topical antimicrobial agents can decrease colony counts in the tear film, but they do not sterilize the area. The exact low rate of clinical infection following eye surgery (despite the relatively high prevalence of microorganisms in the eye) is not fully understood. It is thought that low rate of clinical infection following surgical procedure is explained by combination of low inoculum levels, low pathogenicity, and the innate ocular defenses against infection.
Post-operative bacterial endophthalmitis may also occur weeks to years following surgery. The exact pathogenesis of delayed postoperative bacterial endophthalmitis is not fully understood. It is thought that delayed pos-toperative bacterial endophthalmitis is caused by either sequestration of low-virulence organisms introduced at the time of surgery or delayed inoculation of organisms to the eye through wound abnormalities, suture tracks, or filtering blebs. Propionibacterium acnes is the most common microorganism encountered in delayed post-operative bacterial endophthalmitis. It may occur weeks to months after surgery.
Post-traumatic bacterial endophthalmitis occurs following penetrating ocular injuries. Following penetrating injury, the eye globe integrity disturbed. Penetrating ocular injuries are accompanied by infection at a much higher rate compere to ocular surgery. The broad prevalence range is due to factors such as:
- Presence of an intraocular foreign body
- Delay primary globe repair
- Location and extent of laceration of the globe
Post-traumatic endophthalmitis associated with a greater variety of organisms. The most common isolated organisms include Gram-positive Staphylococcus epidermidis and Streptococcus (as a part of the normal skin flora and regularly contaminate open wounds). Bacillus cereus is ranked second and some cases are polymicrobial.
Gross Pathology
On gross pathology, eyelid swelling, eyelid erythema, injected conjunctiva and sclera, hypopyon, chemosis, and mucoprulunt dischage are characteristic findings of exogenous bacterial endophthalmitis.
Endogenous bacterial endophthalmitis
Pathogenesis
Endogenous endophthalmitis is typically the result of hematogenous spread from a distant infective source within the body. Endogenous endophthalmitis is associated with chronic conditions, such as diabetes, HIV, malignancy, intravenous drug use, transplantation, immunosuppressive therapy, and catheterization. Under normal circumstances, the blood-ocular barrier provides a natural resistance against invading organisms. Following bacteremia, the blood-borne organisms permeate the blood-ocular barrier by:
- Direct invasion (septic emboli)
- Change in vascular endothelium (caused by inflammatory mediators released during infection)
Gross Pathology
On gross pathology, eyelid swelling, eyelid erythema, injected conjunctiva and sclera, hypopyon, chemosis, and mucoprulunt dischage are characteristic findings of endogenous endophthalmitis.
Causes
Post-operative Bacterial Endophthalmitis
Post-operative endophthalmitis has been reported following nearly every type of ocular surgery. Common causes of post-operative bacterial endophthalmitis include:
- Gram-positive bacteria (95%)
- coagulase-negative staphylococci (70%)
- Staphylococcus aureus (10%)
- Streptococcus (9%)
- Enterococcus and mixed bacteria (5%)
- Gram-negative bacilli (6%)
Delayed Post-operative Bacterial Endophthalmitis
Common causes of delayed post-operative bacterial endophthalmitis include:
- Propionibacterium acnes (most common)
- Streptococcus species
Post-traumatic Bacterial Endophthalmitis
Common causes of post-traumatic bacterial endophthalmitis include:
- Streptococcus
- Bacillus cereus
- Polymicrobial
Endogenous bacterial endophthalmitis
Common causes of endogenous bacterial endophthalmitis include:
- Gram-positive bacteria
- Staphylococcus aureus
- Bacillus cereus (primary bacterial cause in intravenous drug abusers and are most likely seeded from contaminated injection paraphernalia and drug solutions)
- Gram-negative bacteria