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Approaches vary among practitioners for treating bacterial conjunctivitis, keratitis
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Brett G. Bence, OD, FAAO: Drug selection when treating infectious disease is a balance of choosing an efficacious drug, being mindful of patient cost, steering clear of known allergic and toxic drug reactions and reserving the use of our best antibacterials for vision-threatening disease.
Bacterial conjunctivitis is contagious — so we want to clear up the infection expeditiously — but also essentially self-limited. Most of these infections do not require the biggest hammer in your toolbox. My approach is to treat these patients empirically with either an aminoglycoside (tobramycin) or trimethoprim sulfate/polymyxin B (Polytrim, Allergan). I step up to a third-generation fluoroquinolone, such as Quixin (levofloxacin ophthalmic solution 0.5%, Santen Inc.), if clinical signs strongly suggest a virulent gram-positive organism or poor response to an empirical drug choice. I add a nighttime ointment such as polysporin or erythromycin as adjunct treatment if indicated. I also may culture chronic conjunctivitis if there is poor response to the initial drug.
Bacterial keratitis raises the bar of concern due the risk associated with corneal disease and the potential for compromising corneal integrity and loss of vision. Third-generation fluoroquinolones, with their broad spectrum of effectiveness, are clinically prudent choices. My personal preference resides with Quixin, although Ciloxan (ciprofloxacin, Alcon Laboratories) and Ocuflox (ofloxacin 0.3%, Allergan) are usually sufficient. Combined and judicious use of topical corticosteroids, when appropriate, modulates the stromal cellular immune response.
With the approval of the fourth-generation fluoroquinolones — gatifloxacin and moxifloxacin — we will now have drugs that are more lethal in our battle with increasingly resistant strains of Staphylococcus aureus and Streptococcus. While drug sensitivity is diminished by subtherapeutic and chronic use in ophthalmic practice, we should still reserve these new antibacterials for serious disease (significantly so with oral antibiotic administration). I will consider these topical pharmaceutical agents with bacterial corneal ulcers and fervent bacterial keratitis now that they are FDA approved.
Brett G. Bence, OD, FAAO, is director of optometry for Northwest Eye Surgeons. He can be reached at 10330 Meridian Ave. North, Suite 370, Seattle, WA 98133; (206) 528-6000; fax: (206) 522-1479; e-mail: bbence@nweyes.com. Dr. Bence has no direct financial interest in the products he mentions, nor is he a paid consultant for any of the companies mentioned.
The same
Joseph P. Shovlin, OD, FAAO: The question can only be answered after looking at which antibiotic is most effective and appropriate for each condition and determining whether the broad use of a particular antibiotic, as in bacterial conjunctivitis or antimicrobial prophylaxis, contributes toward the development of increased resistance.
Generally, the most effective and appropriate initial treatment we have available for bacterial conjunctivitis is one of the later generation topical fluoroquinolones. The later generation agents include levofloxacin 1.5%, moxifloxacin 0.5% and gatifloxacin 0.3%. These agents have several advantages over previously used topical antibiotics:
- convenient dosing (amount and duration),
- broad-spectrum bactericidal activity,
- rapid kill rate,
- slow development of and reduced potential for resistance and
- therapeutic levels that are easily obtained in ocular tissues without significant ocular or systemic toxicity.
In addition, we can use these agents on virtually every patient older than 1 year.
Their improved pharmacokinetics and extended spectrum of activity also make them ideal for the single-agent empirical and culture-guided treatment of bacterial keratitis. Arguably, the best feature of the new topical agents is their broad germ-fighting abilities. Later generation fluoroquinolones show a vastly improved gram-positive coverage combined with awesome anaerobic and atypical pathogen efficacy. In addition, they remain, along with the second-generation fluoroquinolones, the most effective antimicrobial agent for gram-negative infections.
The treatment of bacterial keratitis is currently an “off-label” use for these products. Unfortunately, the antibiotic medications already approved by the Food and Drug Administration for bacterial keratitis (such as the aminoglycosides) are toxic, slow to act and do not cover the broad spectrum of bacterial pathogens. This generally requires the need for additional agents primarily for gram-positive coverage.
The earlier generations of fluoroquinolones have shown significant emerging patterns of resistance that vary geographically in community- and hospital-acquired infections. In time, the new standards of care for the treatment of bacterial keratitis will likely include the use of these new antibiotics.
Of particular relevance, the new generation agents show no cross-resistance to second-generation fluoroquinolones. They have quorum sensing abilities, possess auto-induction capabilities and block the key enzymes, DNA gyrase and topoisomerase IV. In spite of these wonderful attributes, broad and casual usage for less severe infections and prolonged prophylaxis will likely result in patterns of resistance over time. The two-mutation requirement may mean that it will take longer for resistance to occur. But be assured, it will eventually happen in light of the fact that certain strains have already undergone one of the mutations from prior exposure to earlier generation fluoroquinolones. (All that is needed is one new simultaneous mutation.) The easiest way to drive the development of first step resistance is with the continued use of earlier generation fluoroquniolones.
Resistance from topical usage pales in comparison to what occurs with oral administration of antibiotics. But, once established systemically, the resistant organisms have an opportunity of occurring in the ocular flora as well. Interestingly, fifth-generation systemic fluoroquinolones already exist, and, when needed, topical agents will likely follow.
In the meantime, I plan on using the new antibiotics with confidence for both severe and less troubling ocular infections and prophylaxis. Avoiding the temptation to employ low-dose, chronic therapy is always prudent.
Joseph P. Shovlin, OD, FAAO, is a Primary Care Optometry News Editorial Board member. He can be reached at Northeastern Eye Institute, 200 Mifflin Ave., Scranton, PA 18503; (570) 342-3145; jshovlin@aol.com. Dr. Shovlin has no direct financial interest in the products he mentions, nor is he a paid consultant for any of the companies mentioned.
Different
Ernie Bowling, OD, MS, FAAO: The choice of medications in these conditions depends on the presentation. For conjunctivitis cases that appear to be truly bacterial (noting that the majority of acute conjunctivitis cases are of viral or other origin), I tend to prescribe a broad-spectrum antibiotic such as Polytrim (trimethoprim sulfate/polymyxin B sulfate, Allergan) or Tobrex (tobramycin, Alcon) — TobraDex (tobramycin/dexamethasone, Alcon) if the patient is in pain — four times daily. I also prescribe an antibiotic ointment such as Tobrex for overnight coverage. The patient is typically appointed for follow-up in 1 week. I tend to not use fluoroquinolones in cases of suspected bacterial conjunctivitis, saving them for severe and recalcitrant cases and for corneal infiltrates and ulcers.
Corneal involvement increases the risk of corneal morbidity and calls for more aggressive management. Treatment with a fluoroquinolone such as Ciloxan or Ocuflox up to every hour while awake, Ciloxan ointment at bedtime and a cycloplegic such as scopolamine 0.25% three times daily is common. The patient is followed daily until the condition resolves. The more severe the presentation, the more closely the patient is followed. I refer to these cases as suspected bacterial conjunctivitis because in my primary care practice we do not routinely culture them, with the same being said for small, peripheral corneal infiltrates and ulcers. The commercially available topical fluoroquinolones often provide adequate coverage in most of these presentations.
In cases where the corneal ulcer is central; greater than 2 mm in size; at risk for perforation; in patients in nursing homes and hospitals, where methicillin-resistant Staphylococcus aureus infections are common; or there is a suspicion of another form of infection such as fungal or Acanthamoeba, then corneal scrapings with culture and sensitivity testing are standard. Treatment would consist of fortified antibiotics such as fortified tobramycin or gentamicin with fortified cefazolin or vancomycin. For clinicolegal reasons I prefer to send these cases to our friendly tertiary care center.
Ernie Bowling, OD, MS, FAAO, owns a multi-office primary care optometric practice in northwest Georgia. Dr. Bowling can be reached at 76 Georgia Ave., Summerville, GA 30747; (706) 857-4015; fax: (706) 857-7782; e-mail: bowling@wavegate.com. Dr. Bowling has no direct financial interest in the products he mentions, nor is he a paid consultant for any of the companies mentioned.