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Take a systematic approach when treating ocular infection
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By and large, optometrists are a relatively prudent group. Perhaps nowhere is this more evident than in prescribing antibiotics.
We are careful not to over treat, prescribing antibiotics only when true bacterial infection is suspected. We are never cavalier, often asking for consultation in cases of hyperinfection or first-line therapy failure. And we always select drugs judiciously, staging therapy according to the clinical presentation.
We adhere to this paradigm with one simple goal in mind. Treat first with time-honored antibiotics and reserve the “big guns” for more severe clinical presentations. Arguably, a very noble approach. But is it the right thing to do?
Microbial resistance
We’ve embraced this strategy in an effort to mitigate against microbial resistance, and for good reason. Recent in vitro and clinical studies have concluded that a fair number of Pseudomonas, staphylococcal and streptococcal strains are resistant to current-generation fluoroquinolone antibiotics. How did this happen?
The reality is that bacterial mutations (and subsequent resistance patterns) are the result of years of sub-lethal dosing orally as well as use in livestock feed. In fact, topical ocular applications have probably contributed minimally to the overall resistance issue.
Unfortunately, even though topical use isn’t the culprit, we must still contend with the consequences of resistance — for sure, not a reassuring feeling when reaching for an antibiotic for infectious keratitis or surgical prophylaxis. The good news is that the next-generation fluoroquinolone antibiotics provide us with much-needed relief. Both moxifloxacin and gatifloxacin boast a greater spectrum of activity, potency, solubility and exposure duration than their predecessors. As a result, we can prescribe with greater confidence.
Staging treatment
While the next-generation fluoroquinolone antibiotics are a great addition, the same clinical dilemma remains. How do we position these agents when staging treatment? It is here where the paradigm shift ultimately occurs. On one hand, conventional wisdom would have us reserve these newer drugs for the most severe infections. However, in doing so, we might actually facilitate resistance.
Granted, the likelihood of next-generation fluoroquinolone antibiotic resistance is infinitely small — requiring a spontaneous mutation at both the DNA-gyrase and topoisomerase IV sites. But the ongoing use of older fluoroquinolone antibiotics will undoubtedly contribute to further DNA-gyrase mutations, putting us just one step away from the next generation of bacterial resistance. Couple this with the fact that both moxifloxacin and gatifloxacin have been available in oral forms, and we’ve got the real potential for eventual resistance.
Assess, treat, never taper
So, what should we do? The answer lies in a systematic approach. First, assess the infection. If the signs and symptoms are significant, reach for the next-generation fluoroquinolone antibiotics. Second, treat aggressively. Dosing frequently for a defined period enhances antibiotic effectiveness. And third, never taper to sub-lethal doses, as this practice only increases the likelihood of bacterial mutation.
Certainly, incorporating the next-generation fluoroquinolone antibiotics is dependent upon many variables, including availability, insurance formulary inclusion and cost. However, I’m confident these agents will quickly become first-line therapy in primary eye care practice for a variety of reasons — the primary of which being that they are most often the best drug for the job.