a 70-year - old male presented to our hospital ( department of ophthalmology , sahm yook medical center , seoul , korea ) with a three - day history of left eye pain and decreased vision . he had a long history of diabetes mellitus that was controlled with oral anti - hyperglycemic agents . the patient suffered from bilateral proliferative diabetic retinopathy and had undergone pan retinal photocoagulation several times since march 1995 . at age 60 he had undergone phacoemulsifications with intraocular lens implantation for the treatment of senile cataracts in both eyes . on presentation , the patient 's visual acuity was hand motion in the left eye . slit lamp examination revealed a heavily edematous cornea and a round 3.7  5.0 mm dense central stromal infiltrate with an overlying epithelial defect ( fig . after scrapings were collected from the lesion for smears and cultures , the patient was treated hourly with 0.5% moxifloxacin and 0.5% tobramycin . four days after the initiation of treatment , heavy growth of s. maltophilia was observed in culture . the isolated bacteria were sensitive to ciprofloxacin , sulfamethoxazole - trimethoprim , levofloxacin , and moxifloxacin , but were resistant to all aminoglycosides and b - lactams ( table 1 ) . according to the results of susceptibility tests , topical 0.5% moxifloxacin was given every hour and 0.5% tobramycin was stopped . the patient 's best corrected visual acuity improved from hand motion to 20 / 25 . his infectious keratitis was controlled and had not recurred at the one - year follow - up examination . s. maltophilia is a motile , non - fermentative , oxidase - negative , aerobic , gram - negative bacillus that is widespread in the environment . it is an opportunistic pathogen believed to have limited pathogenicity unless it is associated with nosocomial infections of immune compromised patients . s. maltophilia is a seldom - reported pathogen in lens care systems or ocular infections . however , reports of postoperative and post - traumatic s. maltophilia ocular infections are increasing . the reasons underlying this emergence are complex , but may be related to the improved laboratory isolation techniques and enhanced reporting . treatment of s. maltophilia infections is complicated by the fact that isolates are often resistant to many broad - spectrum antibiotic agents . reported the treatment results and prognoses of 10 cases of s. maltophilia keratitis in 2007 after one time applications of levofloxacin ophthalmic solution as a first line treatment of choice before culture results . they then added fortified tobramycin and cefazolin if corneal ulcers were large and centrally located of the cornea . the final visual acuity in three cases that had no co - infections was worse than hand motion . fourth - generation fluoroquinolones ( moxifloxacin and gatifloxacin ) show an enhanced spectrum of activity against gram - positive bacteria and comparable activity to second- and third - generation fluoroquinolones ( ciprofloxacin and levofloxacin ) against gram - negative bacteria . new ocular antibiotic formulations with improved potency , such as moxifloxacin ophthalmic solution 0.5% ( vigamox ; alcon laboratories , fort worth , tx , usa ) or gatifloxacin ophthalmic solution 0.3% ( zymar ; allergan , irvine , ca , usa ) are currently available and have been shown to inhibit growth of organisms resistant to second- and third - generation fluoroquinolones . several in vitro susceptibility studies , demonstrate that moxifloxacin is more active than earlier generation fluoroquinolones ( ciprofloxacin , ofloxacin , and levofloxacin ) , especially against s. maltophilia . for these reasons , we chose moxifloxacin monotherapy for treatment of s. maltophilia keratitis , even though antibiotic sensitivity was equal for both levofloxacin and moxifloxacin . in conclusion , we report the case of a patient who was diagnosed with s. maltophilia keratitis and effectively treated with moxifloxacin monotherapy . unlike most previously - reported cases , which had poor prognoses , in our patient moxifloxacin monotherapy led to a good visual outcome .
a 70-year - old man with a long history of diabetes mellitus presented to our hospital ( department of ophthalmology , sahm yook medical center , seoul , korea ) complaining of severe ocular pain and visual disturbance in his left eye that had started three days prior to admission . a round 3.7  5.0 mm dense central stromal infiltrate with an overlying epithelial defect was noted on slit - lamp examination . following corneal scrapings and culture , topical 0.5% moxifloxacin and 0.5% tobramycin 
 were administered hourly . 
 a few days later , stenotrophomonas maltophilia was isolated in a bacterial culture from a corneal specimen . according to the results of susceptibility tests , 
 topical 0.5% moxifloxacin was given every hour and 0.5% tobramycin was stopped . 
 the patient 's clinical features improved steadily with treatment . 
 the corneal epithelium healed rapidly , and the infiltrate resolved within four weeks of the initiation of treatment . 
 the patient 's best corrected visual acuity improved from hand motion to 20 / 25 .