ACUTE BACTERIAL CONJUNCTIVITIS

Signs and Symptoms

Patients with acute bacterial conjunctivitis present with injection of the bulbar conjunctival and episcleral vessels. In some cases, the palpebral conjunctiva is also affected. Infection typically begins in one eye and subsequently spreads to the other eye within 24 to 48 hours.1 There may be mild photophobia and discomfort, but pain is not typical unless there is concurrent corneal epitheliopathy. There will be mucopurulent discharge, and the patient usually reports that the eyelids and eyelashes are matted shut upon waking.1,2 In fact, a history of the eyelids being “glued shut” in the morning is highly predictive of bacterial infection.2 There frequently is spillover of the discharge onto the patient’s adnexa due to rapid bacterial reproduction with a concomitant, mucopurulent response from the host. While patients of any age can be afflicted with acute bacterial conjunctivitis, it is especially common in children.3-8 Wearing soft contact lenses presents an additional risk factor.9

Visual function typically is normal. However, in that the discharge is often corneotoxic, a coarse punctate epitheliopathy may be present. When this occurs, the condition is better termed acute bacterial keratoconjunctivitis. Significant epitheliopathy may cause vision reduction and discomfort in some cases. Due to drainage of the infection through the nasolacrimal system, there typically is no preauricular node involvement, though some aggressive bacterial strains such as gonococcus can cause lymphadenopathy. A conjunctival papillary or pseudomembranous (composed of coagulated fibrins, bacteria, and leukocytes) response may also be present.2

Pathophysiology

The eye has a series of defense mechanisms to prevent non-native bacterial invasion. These include bacteriostatic factors within the tears, nutrient-poor tears that don’t support bacterial growth, the shearing force of the blink, an intact immune system and a population of normal colonizing non-pathogenic bacteria that competitively prevent invasion by abnormal organisms. When these defenses break down or are overwhelmed by a pathogen that is not sensitive to their mechanisms of action, an infection can occur.

Invading bacteria, along with secreted exotoxins, are foreign antigens that induce an antigen-antibody immune reaction and subsequent inflammation. In a normal, healthy eye, invading pathogenic bacteria will eventually be eradicated as the eye strives to return to homeostasis.5,10-13 However, the external load of organisms can potentiate corneal infection or involvement of other adnexal structures.

The most commonly encountered organisms are Haemophilus influenzae, Streptococcus pneumoniae, Staphylococcus aureus and Pseudomonas aeruginosa.3,4,6,8,9 Several studies have identified H. influenzae and S. pneumoniae as the most prevalent infective bacteria, ranging from 29% to 45% and 20% to 31% of isolates, repectively.4,6 S. viridans, Moraxella catarrhalis, Enterobacteriaceae and Neisseria meningitides are also encountered.6,14

Occasionally, there will be more than one organism in an acute bacterial conjunctivitis.6 Also, otitis media may present concurrent with acute bacterial conjunctivitis, especially in children. This syndrome is highly indicative of H. influenzae infection.4,15 In these cases, the infection often originates in the nasopharynyx.15

Management

In the majority of cases, acute bacterial conjunctivitis is a self-limiting disease requiring no treatment. However, most reports indicate that, despite the benign, self-resolving nature, bacterial conjunctivitis should be treated with topical antimicrobial therapy in order to shorten the disease course and improve the rate of clinical and microbiologic remission.5,10,11,13,16,17 This is especially true early in the clinical course, if sexually transmitted diseases are the suspected etiology, and in contact lens wearing patients.18 However, if the patient presents having had the infection for several days, and is already improving, topical antimicrobial treatment likely will provide only marginal, if any, benefit.11

As in any bacterial infection, a microbiologic study with culturing and sensitivity testing is the optimum means to reach a conclusive diagnosis and treatment plan. However, due to the expense of microbiologic studies and the relatively benign, self-limiting nature of the condition, most clinicians advocate the use of broad-spectrum, empirical topical antibacterial therapy, reserving culturing for hyperacute conditions, concurrent severe nasolacrimal infections, or those that fail to respond to initial therapy.

There are many options for empirical therapy. Excellent initial broad-spectrum topical antibiotics include ciprofloxacin, ofloxacin, levofloxacin, polymyxin B sulfate–trimethoprim, gentamicin and tobramycin.6-8,10,13-19 These will provide good coverage against gram-positive and gram-negative organisms, though the aminoglycosides (gentamicin and tobramycin), through increased resistance, may have weak activity against some Staphylococcal species and some strains of Pseudomonas. Additonally, the generic versions may cause ocular toxicity. A formulation of tobramycin ophthalmic solution with enhanced viscosity showed excellent cure rates, even against tobramycin-resistant pathogens.19 Polyantimicrobial therapy may be necessary to cover all possible organisms in the worst presentations.

Newer-generation topical fluoroquinolones—moxifloxacin (Moxeza, Alcon) and gatifloxacin (Zymaxid, Allergan)—have gram-negative coverage similar to the existing fluoroquinolones but with enhanced coverage of gram-positive species, with lower incidence of bacterial resistance.20 Research shows they are well tolerated ocularly, with little induced damage to the cornea.21-25 Gatifloxacin administered twice daily for five days is proven effective in treating patients aged one year and older.26 There is some evidence that indicates that moxifloxacin may have a lesser corneotoxic effect due to the lack of the preservative benzalkonium chloride.21

These agents are also more effective than previous fluoroquinolones in resistant bacterial infections.20,27 Moxifloxacin has been shown to be effective at eradicating superficial bacterial infections with excellent tolerability.28 Both moxifloxacin and gatifloxacin have been shown to be clinically equivalent to a fortified cefazolin-tobramycin combination in managing bacterial keratitis.29 For these reasons, newer-generation fluoroquinolones are extremely popular in managing ocular bacterial infection and surgical prophylaxis.17

Newer medications have been shown to be effective in managing patients with acute bacterial conjunctivitis. Besifloxacin ophthalmic suspension 0.6% (Besivance, Bausch + Lomb) has been demonstrated to be effective against susceptible bacteria with an efficacy and tolerability similar to that seen in topical moxifloxacin.30-33 Recently, it has been shown that dosing with besifloxacin as low as twice daily for three days was effective in eradicating bacterial conjunctivitis in adults and children.34,35 Additionally, topical azithromycin 1% (AzaSite, Akorn) has been seen as effective in managing patients with bacterial conjunctivitis.36 Polymyxin B sulfate/trimethoprim solution has been seen as a cost-effective alternative to moxifloxacin with comparable efficacy in children.37

Resistance has become an issue with many antibiotics, even including the newer-generation fluoroquinolones.3,4,7,20,27 Resistance has been noted with all major classes of topical antibiotics including aminoglycosides, polymyxin B combination therapies, macrolides and fluoroquinolones.38 Even so, it appears that the later generation fluoroquinolones still retain excellent efficacy against even methicillin-resistant S. aureus (MRSA).39 There appears to be an increased risk of MRSA infections in patients with giant fornix syndrome (a condition similar to floppy eyelid syndrome) where a capacious upper conjunctival fornix leads to a purulent conjunctivitis and toxic keratopathy. MRSA infection should be considered in patients with this clinical profile.40,41

Although antibiotics will eradicate the antigenic bacteria, they will do little to suppress the concurrent inflammation. If there is no significant corneal disruption, then corticosteroids such as prednisolone acetate 1%, difluprednate 0.05% emulsion (Durezol, Alcon) or loteprednol etabonate 0.5% (Lotemax, Bausch + Lomb) concomitantly with the antibiotics can be used to speed resolution of the inflammation. Steroid-antibiotic combinations such as neomycin-polymixin B sulfate-dexamethasone, (Maxitrol, Alcon), tobramycin-loteprednol (Zylet, Bausch + Lomb), and both tobramycin-dexamethasone and tobramycin-dexamethasone suspension (Tobradex ST, Alcon) are also possible choices for therapy when the cornea is intact.42 In cases where inflammation is problematic, topical steroids can be used, even in the face of a compromised cornea, so long as the topical antibiotic has been adequately loaded and it is clear that the therapy is working. Here, the addition of topical steroids can safely be initiated while the anti-infective coverage is maintained.

Clinical Pearls

While patients with bacterial conjunctivitis will report that their lids are matted shut in the morning with mucopurulent material, patients suffering from viral and allergic conjunctivitis will sometimes report similar experiences.

Patients with viral and allergic conjunctivitis have crusting of the lashes due to drying tears and serous secretions; those with bacterial conjunctivitis will manifest wet, sticky, mucopurulent matting of the lashes. Too often, clinicians consider the dry crusting of the lashes to be the same as the mucopurulent matting and misdiagnose the condition.

Due to the excellent defense systems of the external eye, acute bacterial conjunctivitis is an uncommon condition. Viral and allergic conjunctivitis is more common.

Tapering antibiotics can lead to resistance. Never prescribe below the recommended dosing. Once a condition resolves, discontinue antibiotic therapy abruptly.

Because mucopurulent discharge is corneotoxic, with significant discharge there is often concurrent epitheliopathy. Removal of the discharge with warm saline lavage will benefit patients; they should be instructed to do so frequently.

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