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Introduction
Microbial keratitis is a potentially sight-threatening, yet treatable ophthalmologic emergency. In the USA, nearly 1million clinical visits for keratitis occur annually with 76.5% resulting in antimicrobial prescriptions. 1 Microbial keratitis has an incidence of 11 per 100000 and is the leading cause of corneal opacity, which is the second most common cause of preventable blindness after cataracts. 2 3 Delayed diagnosis and treatment of microbial keratitis can result in corneal perforation, opacification and even endophthalmitis, which may require a corneal graft or in very rare instances enucleation. 4-6
Common risk factors for microbial keratitis include ocular surface disease, contact lens use, steroid use and history of ocular surgery or trauma. 4 6-10 The most prevalent causative organisms include Pseudomonas aeruginosa, Staphylococcus aureus, coagulase-negative Staphylococci and Streptococcus pneumoniae. 4 6-9
The American Academy of Ophthalmology's preferred practice pattern for empirical treatment of bacterial keratitis recommends cefazolin (50mg/mL) with tobramycin or gentamicin (9-14mg/mL). For the past 10 years, the empirical therapy at our county hospital treating the indigent population in Houston, Texas, has consisted of ceftazidime (50mg/mL) or cefazolin (50mg/mL) with tobramycin (14mg/mL). In most cases, our treatment focused more on the preferred practice pattern of Gram-negative coverage with ceftazidime (50mg/mL) and tobramycin (14mg/mL) to address the presumed prevalence of aggressive Gram-negative organism infections, specifically P. aeruginosa. 11 In 80% of our patients, we started fortified antibiotics while 16% were treated with fourth-generation fluoroquinolone monotherapy. There have been reports of both changes in regional microbial composition and resistance patterns to certain antibiotics such as methicillin-resistant Staphylococcus aureus (MRSA) resistance to fluoroquinolones. 12-16 However, no recent data are available on the risk factors, causative organisms, antibiotic susceptibility and the treatment outcomes of corneal ulcers in Southeast Texas. The purpose of our study is to update the epidemiology, risk factors, microbiological composition, antibiotic susceptibility and treatment outcomes of microbial keratitis in a county hospital in Southeast Texas to better understand and guide future treatment.
Materials and methods
A retrospective case-series study was conducted with the approval of the Institutional Review Board at Ben Taub General Hospital (BTGH) of Harris County Hospital District in Houston, Texas, from January 2011 to May 2015.
The primary ICD-9 (International Classification of Diseases, Ninth Revision) diagnosis codes of 'corneal...