What are the causes of endophthalmitis in a patient post cataract surgery?

Causes of Post-Cataract Surgery Endophthalmitis

Post-cataract surgery endophthalmitis is primarily caused by bacterial contamination during or immediately after surgery, with coagulase-negative staphylococci being the most common pathogen, followed by other gram-positive organisms, gram-negative bacteria, and rarely fungi. 1

Primary Causative Organisms

Bacterial Pathogens (Most Common)

• Coagulase-negative staphylococci are the predominant causative organisms in postoperative endophthalmitis, representing the majority of culture-positive cases 1
• Staphylococcus aureus is another significant gram-positive pathogen in post-surgical infections 1
• Propionibacterium acnes (P. acnes) causes chronic postoperative endophthalmitis and should never be dismissed as a contaminant in this clinical context 1
• Streptococcus species can cause acute, aggressive postoperative infections 2
• Gram-negative organisms including Pseudomonas aeruginosa, Enterobacteriaceae (especially Klebsiella pneumoniae), and other glucose-fermenting gram-negative rods are less common but associated with worse visual outcomes 1, 3, 4
• Enterobacter species have been reported in outbreak situations following cataract surgery 5

Fungal Pathogens (Rare)

• Candida albicans and related species can cause postoperative endophthalmitis, particularly in immunocompromised patients 1
• Aspergillus species may cause infection through direct inoculation during surgery 1
• Fusarium species are environmental organisms that can contaminate surgical equipment or solutions 1

Sources and Routes of Infection

Exogenous Introduction (Most Common Route)

• Patient's own ocular surface flora is the primary source, with organisms from the conjunctiva, eyelid margins, and tear film gaining access during surgery 1
• Contaminated surgical instruments or solutions can introduce pathogens directly into the eye 3
• Breach in sterile technique during the surgical procedure allows bacterial entry 3
• Inadequate preoperative antisepsis with povidone-iodine increases infection risk 1

Environmental Contamination

• Operating room air and surfaces can harbor organisms that contaminate the surgical field 3
• Contaminated intraocular lenses or viscoelastic materials may serve as vectors for infection 3
• Healthcare worker contamination through improper hand hygiene or technique 3

Risk Factors That Increase Susceptibility

Patient-Related Factors

• Pre-existing blepharitis significantly increases the risk of postoperative endophthalmitis and should be treated before surgery 6
• Advanced age is associated with worse visual outcomes when endophthalmitis occurs 4
• Immunocompromised status increases susceptibility to both bacterial and fungal pathogens 1
• Poor ocular surface health including dry eye disease and meibomian gland dysfunction 6

Surgical Factors

• Extracapsular extraction with secondary implantation carries higher infection risk than standard phacoemulsification 1
• Prolonged surgical duration increases exposure time for contamination 3
• Posterior capsule rupture or vitreous loss during surgery provides additional routes for infection 2
• Inadequate wound construction allowing postoperative wound leak 2

Postoperative Factors

• Failure to use appropriate antibiotic prophylaxis (intracameral cefuroxime 1 mg is standard) 1
• Contamination of postoperative eye drops by the patient 2
• Poor compliance with postoperative care instructions 2

Clinical Timing Patterns

Acute-Onset Endophthalmitis (Most Common)

• Presents within 1-7 days post-surgery, typically on day 2-3 with severe pain, decreased vision, and hypopyon 3, 4
• Earlier onset (1-2 days) is associated with more virulent organisms like gram-negative bacteria and worse prognosis 4
• Gram-negative infections particularly present early and aggressively 4

Chronic Endophthalmitis

• Presents weeks to months after surgery with indolent course 1
• P. acnes is the classic causative organism in delayed-onset cases 1
• Fungal infections may also present in a delayed, chronic pattern 1

Important Clinical Pitfalls

• Never dismiss coagulase-negative staphylococci or P. acnes as contaminants in the context of post-cataract surgery endophthalmitis—these are true pathogens in this setting 1
• Gram-negative bacterial infections carry significantly worse prognosis and require aggressive early intervention 4
• Outbreak situations should trigger immediate investigation of surgical technique, sterilization procedures, and environmental contamination 3, 5
• Patients with blepharitis must receive preoperative treatment to reduce the bacterial load on ocular surfaces before surgery 6