Bacterial endophthalmitis: Difference between revisions
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==Overview== | ==Overview== | ||
Bacterial endophthalmitis means bacterial infection inside the eye, involving the vitreous and/or aqueous | Bacterial endophthalmitis means bacterial infection inside the eye, involving the [[vitreous]] and/or [[aqueous humor]]s. 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== | ==Historical Perspective== | ||
==Classification== | ==Classification== | ||
Based on how Infectious agents generally gain access to the posterior segment of the eye, bacterial endophthalmitis may be classified into: | Based on how Infectious agents generally gain access to the posterior segment of the eye, bacterial endophthalmitis may be classified into: | ||
*Exogenous bacterial endophthalmitis | *Exogenous bacterial endophthalmitis | ||
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==Pathophysiology== | ==Pathophysiology== | ||
===Exogenous bacterial endophthalmitis=== | ===Exogenous bacterial endophthalmitis=== | ||
'''Postoperative endophthalmitis''' has been reported following nearly every type of ocular surgery, such as | '''Postoperative endophthalmitis''' has been reported following nearly every type of ocular surgery, such as [[cataract]], [[glaucoma]], [[retinal]], [[radial keratotomy]], and [[intravitreal injections]]. | ||
Following surgical procedure, the eye globe integrity disturbed. As a result | Following surgical procedure, the eye globe integrity disturbed. As a result ocular surface bacteria, most commonly [[Coagulase-negative Staphylococcus|coagulase-negative staphylococci]], may contaminate the [[aqueous humor]]. | ||
Preoperative topical antimicrobial agents can decrease colony counts in the tear film, but they do not | 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 immune system|innate ocular defenses]] against infection. | ||
Postoperative bacterial endophthalmitis may also occur weeks to years following surgery. | Postoperative 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 postoperative 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 | The exact pathogenesis of '''delayed postoperative bacterial endophthalmitis''' is not fully understood. It is thought that delayed postoperative 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 postoperative bacterial endophthalmitis. It may occur weeks to months after surgery. | ''[[Propionibacterium acnes]]'' is the most common microorganism encountered in delayed postoperative bacterial endophthalmitis. It may occur weeks to months after surgery. | ||
'''Posttraumatic bacterial endophthalmitis''' occurs following penetrating ocular injuries. | '''Posttraumatic 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 | Following penetrating injury, the eye globe integrity disturbed. Penetrating ocular injuries are accompanied by infection at a much higher rate compere to postoperative endophthalmitis. | ||
The broad prevalence range is due to factors such as: | The broad prevalence range is due to factors such as: | ||
*Presence of an intraocular foreign body | *Presence of an intraocular foreign body | ||
*Delay | *Delay primary globe repair | ||
*Location and extent of laceration of the globe | *Location and extent of laceration of the globe | ||
Posttraumatic endophthalmitis associated with a greater variety of organisms. The most common isolated organisms include Gram-positive | Posttraumatic endophthalmitis associated with a greater variety of organisms. The most common isolated organisms include Gram-positive ''[[Staphylococcus epidermidis]]'' and ''[[Streptococcus|Streptococcus species]]'' (as a part of the normal skin flora and regularly contaminate open wounds). ''[[Bacillus cereus]]'' is ranked second and some cases are polymicrobial. | ||
===Endogenous bacterial endophthalmitis=== | ===Endogenous bacterial endophthalmitis=== | ||
Endogenous bacterial endophthalmitis, is often seen in patients who are [[|bacteremia|bacteremic]] in situations such as [[endocarditis]]. | Endogenous bacterial endophthalmitis, is often seen in patients who are [[|bacteremia|bacteremic]] in situations such as [[endocarditis]]. | ||
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 | Following [[bacteremia]], the blood-borne organisms permeate the [[blood-ocular barrier]] by: | ||
*Direct invasion ([[septic emboli]]) | *Direct invasion ([[septic emboli]]) | ||
*Change in vascular endothelium (caused by [[inflammatory mediators]] released during infection) | *Change in vascular endothelium (caused by [[inflammatory mediators]] released during infection) | ||
==Causes== | ==Causes== | ||
===Postoperative Bacterial Endophthalmitis=== | |||
*[[Gram-positive bacteria]] (95%) | |||
**[[Coagulase-negative Staphylococcus|coagulase-negative staphylococci]] (70%) | |||
**''[[Staphylococcus aureus]]'' (10%) | |||
**[[Streptococci]] (9%) | |||
**[[Enterococci]] and mixed bacteria (5%) | |||
*[[Gram-negative bacilli]] (6%) | |||
==Differentiating Bacterial Endophthalmitis from Other Diseases== | ==Differentiating Bacterial Endophthalmitis from Other Diseases== | ||
Revision as of 18:33, 19 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 of the eye, bacterial endophthalmitis may be classified into:
- Exogenous bacterial endophthalmitis
- Postoperative bacterial endophthalmitis (consequence of intraocular surgery)
- Delayed postoperative bacterial endophthalmitis
- Posttraumatic bacterial endophthalmitis (following a penetrating injury of the globe)
- Endogenous bacterial endophthalmitis (hematogenous spread of bacteria to the eye from a distant anatomical site)
Pathophysiology
Exogenous bacterial endophthalmitis
Postoperative endophthalmitis has been reported following nearly every type of ocular surgery, such as cataract, glaucoma, retinal, radial keratotomy, and intravitreal injections. Following surgical procedure, the eye globe integrity disturbed. As a result ocular surface bacteria, most commonly coagulase-negative staphylococci, may 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.
Postoperative 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 postoperative 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 postoperative bacterial endophthalmitis. It may occur weeks to months after surgery.
Posttraumatic 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 postoperative endophthalmitis. 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
Posttraumatic endophthalmitis associated with a greater variety of organisms. The most common isolated organisms include Gram-positive Staphylococcus epidermidis and Streptococcus species (as a part of the normal skin flora and regularly contaminate open wounds). Bacillus cereus is ranked second and some cases are polymicrobial.
Endogenous bacterial endophthalmitis
Endogenous bacterial endophthalmitis, is often seen in patients who are [[|bacteremia|bacteremic]] in situations such as endocarditis. 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)
Causes
Postoperative Bacterial Endophthalmitis
- Gram-positive bacteria (95%)
- coagulase-negative staphylococci (70%)
- Staphylococcus aureus (10%)
- Streptococci (9%)
- Enterococci and mixed bacteria (5%)
- Gram-negative bacilli (6%)