Treatment-Resistant Bacterial Keratitis: Challenges and Solutions

Bacterial keratitis is an important ophthalmic emergency and one of the most common causes of corneal blindness. The main causes of treatment resistance in bacterial keratitis are failure to eliminate predisposing factors, misdiagnosis and mistreatment. At first, exogenous, local and systemic predisposing factors that disturbing ocular surface must be eliminated to improve corneal ulcers and to prevent recurrences. Smears and scrapings for staining and culture are indispensable diagnostic tools for cases of sight-threatening keratitis (centrally located, multifocal, characterized by melting, painful). Main treatment agents in bacterial keratitis treatment are topical antibiotics. Until the results of culture antibiograms reach the ophthalmologist, empirical antibiotic selections based on direct microscopic examination and gram stain findings are the most appropriate initial treatment approach currently. S. aureus and coagulase-negative staphylococci (CoNS), the most common gram-positive agents, have resistance rates of more than 30% for fluoroquinolone and methicillin. Multidrug resistance rates are similarly high in these microorganisms. P. aeruginosa is the most common gram-negative micro-organism, in case of multidrug-resistant isolates, both functional and anatomical prognosis of the eyes are very poor. In cases of sight-threatening and resistant keratitis, antibiotic susceptibility testing containing imipenem, colistin, and linezolid is seeming to be an important requirement. Despite its efficiency limited to superficial cases, a nonpharmaceutical anti-infective treatment option such as corneal crosslinking for bacterial keratitis is an emerging hope, while antibiotic resistance increases.