Describe bacterial conjunctivitis, including its etiology, clinical presentation, diagnosis, and treatment.

Bacterial Conjunctivitis Overview

Bacterial conjunctivitis is a common, typically self-limited infection characterized by purulent or mucopurulent discharge that mats the eyelids (especially on waking), bilateral bulbar conjunctival injection, and a foreign body sensation, most commonly caused by Staphylococcus aureus, Haemophilus influenzae, Streptococcus pneumoniae, and Moraxella catarrhalis. 1, 2

Etiology

Common Pathogens by Age Group

Adults:

• Staphylococcus aureus (most common) 3, 4
• Staphylococcus epidermidis 3
• Streptococcus pneumoniae 3, 4
• Moraxella species 3

Children:

• Haemophilus influenzae (44.8% of cases, most prevalent) 5, 6, 7
• Streptococcus pneumoniae (30.6% of cases) 5, 6, 7
• Moraxella catarrhalis 5, 6, 7
• Staphylococcus aureus (more prevalent in children aged 7-14 years) 5

Neonates:

• Staphylococcus aureus (most common) 6
• Chlamydia trachomatis (manifests 5-19 days after birth, associated with pneumonia in 50% of cases) 2, 8
• Neisseria gonorrhoeae (manifests within 1-7 days after birth, medical emergency) 1, 2

Special Pathogens Requiring Immediate Recognition

Gonococcal conjunctivitis presents with marked eyelid edema, copious purulent discharge, and preauricular lymphadenopathy—this is a medical emergency that can cause corneal perforation within 24-48 hours and requires immediate systemic antibiotics in addition to topical therapy. 1, 2, 8

Chlamydial conjunctivitis presents with follicular inflammation on the bulbar conjunctiva and semilunar fold, requiring systemic antibiotics because topical agents alone are insufficient. 2, 8

Clinical Presentation

Cardinal Signs

• Discharge: Bilateral green or yellow purulent/mucopurulent discharge that mats eyelids, particularly on waking 2, 6
• Injection: Bulbar conjunctival injection (red eye) 1, 2
• Symptoms: Foreign body sensation, sticky eyes 6
• Laterality: Usually bilateral, though may initially affect one eye before spreading 1, 2

Associated Risk Factors

Children:

• Contact with infected individuals 1
• Concomitant bacterial otitis media, sinusitis, or pharyngitis 1
• Nasopharyngeal bacterial colonization 1
• Oculogenital spread (consider sexual abuse) 1, 8

Adults:

• Contact with infected individuals 1
• Oculogenital spread 1
• Unhygienic living conditions 1
• Infection or abnormality of adnexal structures 1
• Lid malposition 1
• Severe tear deficiency 1
• Immunosuppression 1
• Trauma 1

Diagnosis

Clinical Diagnosis Algorithm

Step 1: Identify purulent discharge pattern

• Bilateral green/yellow discharge matting eyelids on waking strongly suggests bacterial etiology 2, 6

Step 2: Examine for red-flag features requiring immediate referral

• Severe purulent discharge with marked eyelid edema → suspect gonococcal conjunctivitis 2, 8
• Follicles on bulbar conjunctiva and semilunar fold → suspect chlamydial conjunctivitis 2
• Any purulent conjunctivitis in a neonate → emergency until gonococcal/chlamydial causes ruled out 2, 8

Step 3: Perform fluorescein staining

• Always examine the cornea with fluorescein staining in any case of purulent conjunctivitis to detect early corneal involvement 2, 8
• Gonococcal infection often begins with superior corneal infiltration or ulceration 8

Step 4: Determine need for microbiological testing

• Cultures are unnecessary for typical uncomplicated cases in immunocompetent patients 6
• Cultures are indicated for persistent or severe cases, immunocompromised patients, or when gonococcal/chlamydial infection is suspected 4

Laboratory Diagnosis (When Indicated)

Gram stain of conjunctival scrapings:

• Provides rapid prediction of pathogen in 93% of bacterial cases (51 of 55 cases) 7
• Shows neutrophilia in bacterial infections 7

Giemsa stain of conjunctival scrapings:

• Provides etiologic information in 96% of cases (81 of 84 cases) 7
• Neutrophilia indicates bacterial infection 7
• Lymphocytosis indicates viral infection 7
• Eosinophilia indicates allergic disease 7

Culture technique:

• Separately culture specimens from lids and conjunctivae to distinguish normal flora from pathogens 7
• Normal lid flora includes staphylococci, corynebacteria, and alpha-hemolytic streptococci 7

Treatment

First-Line Management for Uncomplicated Cases

Delayed antibiotic prescribing is preferred for most uncomplicated cases because the majority resolve spontaneously within 1-2 weeks—provide a prescription but advise waiting 2-3 days before filling if symptoms do not improve. 2

Immediate topical antibiotic therapy is indicated when rapid resolution is desired to shorten symptom duration and facilitate earlier return to school or work. 2

Topical Antibiotic Options

Recommended agents:

• Fluoroquinolones (e.g., ciprofloxacin) 4, 5
• Azithromycin 4
• Trimethoprim-polymyxin B 2
• Aminoglycosides 2
• Chloramphenicol 5

Evidence for efficacy:

• Topical antibiotics increase the 7-day cure rate by an absolute risk difference of 0.09 compared to placebo 2
• They shorten disease course, reduce discomfort, prevent person-to-person transmission, and reduce reinfection rates 6

Critical Pitfall to Avoid

Do NOT routinely treat the second eye prophylactically in cases of unilateral, uncomplicated bacterial conjunctivitis—instead, educate patients on frequent handwashing to prevent transmission. 8

Special Populations Requiring Systemic Therapy

Gonococcal conjunctivitis:

• Requires immediate systemic antibiotic treatment in addition to topical therapy 2, 8
• Risk of corneal perforation within 24-48 hours 2, 8
• Neonates at risk of septicemia, meningitis, and death 1, 8

Chlamydial conjunctivitis:

• Requires systemic antibiotics because topical agents alone are insufficient 2, 8
• In neonates, up to 50% have concurrent nasopharyngeal, genital, or pulmonary infection 8
• Highly infectious through hand contact, fomites, and flies 8

Natural History and Prognosis

Typical Course

• Mild bacterial conjunctivitis is self-limited in adults, resolving within 1-2 weeks without treatment 1, 2
• With topical antibiotics, symptom duration is shortened and clinical remission is modestly improved 2, 6

Potential Complications

In children:

• Rare but possible complications include corneal infection 1
• May be associated with pharyngitis, otitis media, or meningitis 1

In neonates with gonococcal infection:

• Corneal scarring 1
• Corneal perforation 1
• Septicemia with arthritis 1
• Meningitis 1

In neonates with chlamydial infection:

• Corneal scarring 1
• Pneumonia (in 50% of cases) 2, 8

Prevention and Infection Control

Patient Education

• Frequent handwashing to prevent transmission to the second eye 8
• Avoid sharing towels, bedding, and cosmetics 8
• Maintain proper hygiene, especially after touching eyes or face 9

Screening and Prevention

• Screening and treating pregnant women is an effective prevention strategy by reducing perinatal transmission of gonococcal and chlamydial infections 4

Antibiotic Resistance Considerations

Increasing resistance patterns:

• Streptococcus pneumoniae shows the greatest level of resistance to antibiotics used in eye drops and ophthalmic ointments 5
• Rising antibiotic resistance may necessitate tailored therapy based on antibiotic susceptibility profiles 4
• Widespread antibiotic use and insufficient bactericidal concentrations at the infection site contribute to resistance development 3