Download The Medicines Control Council has recently released a limited list of

The Medicines Control Council has recently released a limited list of medications that it has approved for qualified optometrists to prescribe in the Republic of South Africa. The sole antibiotic chosen for use was chloramphenicol. The short discussion below should provide ample evidence why, if only a single antibiotic is to be permitted for use among optometrists, chloramphenicol is among the worst that could have been selected, if the best interest of patients is to be served through this expanded scope of optometric practice. Chloramphenicol is widely used among general physicians for topical ophthalmic use. Why is it not an equally good choice for optometrists? First, one must note that physicians are not limited in their choice of topical antibiotic and they are free to use their professional judgment in the proper choice of antibiotic for each patient presentation. Optometrists will not be accorded the opportunity to use their training and best clinical judgment in the same way. It appears that they will be limited to the use of a single antibiotic. In such a case, the choice of that one antibiotic becomes very critical. So, why is chloramphenicol not the best choice for both general physicians and optometrists when treating ocular surface disease of bacterial origin? The reason is that optometrists fit contact lenses. Indeed, they fit most of the contact lenses in the country and this one fact changes in a very significant way, the spectrum of pathogens that are of greatest concern when patients present to optometrists with a red eye, compared with those presenting at an emergency clinic or to a general physician. The two main factors pre-­‐disposing to microbial keratitis in the 15-­‐55 age range include: o Ocular trauma o Contact lens wear1,2 In the former category, including minor ocular trauma, the vast majority of bacterial pathogens that produce ocular surface disease are gram positive. These include: o Coagulase-­‐negative Staphylococci (Gram + cocci) o Staphylococcus aureus, (Gram + cocci) o Streptococcus pneumoniae, (Gram + cocci) o Enterobacteriaceae (Gram +, including Klebsiella, Enterobacter and Proteus) But for contact lens wearers, who will most often seek care from their optometrist, an additional pathogen looms large. That pathogen is: o Pseudomonas aeruginosa And Pseudomonas aeruginosa is gram negative. Indeed, gram-­‐negative organisms are isolated far more frequently in contact lens wearers than in minor ocular trauma cases (18.7% vs. 6.5%, p = 0.01). Moreover, the warmer the climate, the more likely it is that Pseudomonas will be the offending agent and certainly compared to Europe, and the UK where use of chloramphenicol is most common, South Africa is a far warmer climate. 2 What does the literature say about the use of topical chloramphenicol to treat ocular surface disease when Pseudomonas looms as a possibility? Reproduced below is a figure taken from a recent study published in the Middle East African J. Ophthalmology3 showing the relative sensitivity and resistance of Pseudomonas to a range of topical ophthalmic antibiotics. It is important to note that in this study, chloramphenicol was among the very least effective agents against Pseudomonas. From: Mehrdad Mohammadpour, Zahra Mohajernezhadfard, Alireza Khodabande, and Payman Vahedi. Antibiotic Susceptibility Patterns of Pseudomonas Corneal Ulcers in Contact Lens Wearers. Middle East Afr J Ophthalmol. 2011 Jul-­‐Sep; 18(3): 228–231. Confirmation that using chloramphenicol when Pseudomonas is a concern is inappropriate comes from an authoritative chapter on “Topical Ophthalmic Antibiotics in the Management of Bacterial Conjunctivitis and Keratitis” published in Duane’s Textbook of Ophthalmology, one of the most comprehensive reference resources in the field of ophthalmology.4 Regarding Chloramphenicol this chapter states that: “chloramphenicol has good antimicrobial activity against most gram-­‐positive ocular isolates and limited gram-­‐negative coverage. Chloramphenicol should not be used to treat infections in which gram-­‐negative bacteria, especially Pseudomonas or Serratia species are suspected5. Because it is usually bacteriostatic, not bacteriocidal, and because of its limited spectrum, chloramphenicol should not be used in vision-­‐threatening circumstances.” And in any ocular surface infection that arises in a contact lens wearer, Pseudomonas must always be suspected and when it occurs, it is vision threatening. Why not leave optometrists to use only chloramphenicol and if the patient is not responding, have them refer the patient? The reason is that Pseudomonas is renowned for having the ability to give rise to corneal ulceration that can lead to perforation of the cornea and penetration of the eye in less than 48 hours.2 In such cases, there is not time to get results on cultures or antibiotic sensitivities. And by the time one knows that a more effective antibiotic should have been chosen, the case has often advanced to require hospitalization and intensive medical treatment, and/or surgical treatment to transplant the destroyed cornea, adding immeasurably to the cost of care, with a poorer outcome. That is why it is critical that the first antibiotic chosen when contact lens wearers present with a red eye be one that has a broad spectrum of coverage, but also has proven efficacy against Pseudomonas. We would therefore urge the Medicines Control Council, in the interest of public health and safety, to reconsider its position regarding limiting optometrists to the use of chloramphenicol. It is reasonable to project that addition of at least one agent effective against gram negative microbes and specifically Pseudomonas, will mitigate against the far greater costs that are likely to result from anyone (optometrist or ophthalmologist) being limited to treating those at high risk of Pseudomonas infection, solely with a medication known to be ineffective against that microbe. REFERENCES 1. O’Brien TP. Management of bacterial keratitis: Beyond exorcism towards consideration of organism and host factors. Eye 2003;17:957-­‐74. 2. Winning the Battle Against Corneal Ulcers Christopher Kent, Senior Editor 9/5/2013 Review of Ophthalmology Online versions at http://www.reviewofophthalmology.com/content/i/2548/c/42796/ 3. Mehrdad Mohammadpour, Zahra Mohajernezhadfard, Alireza Khodabande, and Payman Vahedi. Antibiotic Susceptibility Patterns of Pseudomonas Corneal Ulcers in Contact Lens Wearers. Middle East Afr J Ophthalmol. 2011 Jul-­‐Sep; 18(3): 228–231. 4. Chapter 39 Topical Ophthalmic Antibiotics in the Management of Bacterial Conjunctivitis and Keratitis RENÉE SOLOMON and ERIC DONNENFELD Duane’s Textbook of Ophthalmology , Foundations, vol 3, Cptr 39. (2006) Edition, Lippincott, Williams and Wilkins. 5. Jensen HG, Felix C: In vitro antibiotic susceptibilities of ocular isolates in North and South America. In Vitro Antibiotic Testing Group. Cornea 17:79, 1998. 6. Gardner S: Treatment of bacterial keratitis. Ocular Ther Management 3:1, 1990. 7. Abrams SM, Degnan TJ, Vinviguerra V: Marrow aplasia following topical application of chloramphenicol eye ointment. Arch Intern Med 140:576, 1980. 8. Carpenter G: Chloramphenicol eye drops and marrow aplasia. Lancet 2:326, 1975. 9. Fraunfelder FT, Bagby GC, Kelly DJ: Fatal aplastic anemia following topical application of ophthalmic chloramphenicol. Am J Ophthalmol 93:356, 1982. 10. Brodsky E, Biger Y, Zeidan Z, Schneider M: Topical application of chloramphenicol eye ointment followed by fatal bone marrow aplasia. Isr J Med Sci 25:5, 1989. 11. Fraunfelder FT, Morgan RL, Yunis AA: Blood dyscrasias and topical ophthalmic chloramphenicol. Am J Ophthalmol 115:812, 1993. 12. Scott JL, Finegold SM, Belkin GA et al: A controlled double-­‐blind study of the hematologic toxicity of chloramphenicol. N Engl J Med 272:1137, 1965. 13. Rosenthal RL, Blackman A: Bone-­‐marrow hypoplasia following use of chloramphenicol eye drops. JAMA 191:136, 1965. 14. Trobe GE, Lawrence JR, Hind VM, Bunney J: Systemic absorption of topically applied chloramphenicol eyedrops. Br J Ophthalmol 163:690, 1970. 15. Apt L, Gaffney WL: Toxic effects of topical eye medication in infants and children. In: Tasman W, Jaeger EA, eds. Duane's Foundations of Clinical Ophthalmology, vol 3. Philadelphia: JB Lippincott, 1990. 16 Cagle G, Davis S, Rosenthal A et al: Topical tobramycin and gentamicin sulfate in the treatment of ocular infections: multicenter study. Current Eye Res 1:523, 1982. 17. Lass JH, Mack RJ, Imperia PS et al: An in vitro analysis of aminoglycoside corneal epithelial toxicity. Curr Eye Res 8:299, 1989. X Abdullah Al-­‐Mujaini,* Nadia Al-­‐Kharusi, Archana Thakral, and Upender K Wali Sultan Qaboos Univ Med J. 2009 Aug; 9(2): 184–195. Published online 2009 Jun 30. PMCID: PMC3074777 Bacterial Keratitis: Perspective on Epidemiology, Clinico-­‐
Pathogenesis, Diagnosis and Treatment ******************************************************************************* Prepared by: Thomas F. Freddo, O.D., Ph.D, Visiting Scholar, Graduate Institute of Optometry, East London, South Africa and Professor of Ophthalmology and Pathology (Retired) Senior Consultant in Diagnostic Ophthalmic Pathology (Retired) Boston University Medical Center, Boston, MA.