Bacillus cereus keratitis associated with contact lens wear.
OBJECTIVE
We report the first case of contact lens-related Bacillus cereus keratitis and ulcer associated with B. cereus contamination of the contact lens case. This is also the first study to investigate and establish the genetic identity of an organism isolated from the cornea and contact lens case in a patient with contact lens-associated keratitis.


METHODS
Case report.


METHODS
Conjunctival swabs and corneal scrapings from the left eye were inoculated for culture. The contact lens case was also cultured. Antibiotic susceptibility testing was determined by agar disk diffusion method. Initial treatment with topical ciprofloxacin and fortified tobramycin was given. Genetic analysis of the bacterial isolates was performed using polymerase chain reaction (PCR) with enterobacterial repetitive intergenic consensus primers (ERIC; ERIC-PCR). Susceptibility of B. cereus to heat and contact lens disinfecting solutions containing hydrogen peroxide, hydrogen peroxide-catalase, polyquaternium-1, and polyaminopropyl biguanide (PAPB) was tested.


METHODS
Clinical features, culture results, and antibiotic susceptibility testing were analyzed. The ERIC-PCR amplification products were visualized in ethidium bromide-stained agarose gel. Bacterial growth after exposure to heat and contact lens disinfecting solutions was assessed on blood agar plates.


RESULTS
B. cereus was grown from the conjunctiva, corneal ulcer, and contact lens case. All isolates were sensitive to gentamicin, tobramycin, ciprofloxacin, clindamycin, and vancomycin. The corneal ulcer gradually healed over the next 6 days. Results of ERIC-PCR showed that the isolates from the cornea and contact lens case were indistinguishable, thus demonstrating the source of infecting organism to be the contaminated contact lens case. Exposure to a temperature of 80 degrees C for 20 minutes and incubation with hydrogen peroxide-catalase, polyquaternium-1, and PAPB for the minimum recommended time failed to kill B. cereus. Only exposure to hydrogen peroxide for 4 hours eradicated the organism.


CONCLUSIONS
B. cereus should be considered a possible etiologic agent of contact lens-associated keratitis. Heat and many types of contact lens disinfecting solutions may be ineffective in eradicating B. cereus from contaminated contact lens cases. Only prolonged exposure to hydrogen peroxide appeared to be sporicidal to B. cereus in this study.
Pinna
A
A
Institute of Ophthalmology, University of Sassari, Sassari, Italy. apinna@uniss.it
Sechi
L A
LA
Zanetti
S
S
Usai
D
D
Delogu
G
G
Cappuccinelli
P
P
Carta
F
F
D016863:Bacillaceae Infections / Q000175:diagnosis / Q000188:drug therapy / Q000209:etiology*; D001409:Bacillus cereus / Q000187:drug effects / Q000235:genetics / Q000302:isolation & purification*; D002939:Ciprofloxacin / Q000627:therapeutic use; D003228:Conjunctiva / Q000382:microbiology; D018639:Contact Lens Solutions / Q000494:pharmacology; D003263:Contact Lenses, Hydrophilic / Q000009:adverse effects* / Q000382:microbiology; D003315:Cornea / Q000382:microbiology; D003320:Corneal Ulcer / Q000175:diagnosis / Q000188:drug therapy / Q000209:etiology*; D004269:DNA, Bacterial / Q000032:analysis; D004203:Disinfection / Q000379:methods; D004359:Drug Therapy, Combination / Q000627:therapeutic use; D004866:Equipment Contamination; D015818:Eye Infections, Bacterial / Q000175:diagnosis / Q000188:drug therapy / Q000209:etiology*; D006358:Hot Temperature; D006801:Humans; D007634:Keratitis / Q000175:diagnosis / Q000188:drug therapy / Q000382:microbiology; D008297:Male; D008826:Microbial Sensitivity Tests; D008875:Middle Aged; D016133:Polymerase Chain Reaction; D014031:Tobramycin / Q000627:therapeutic use
D018639:Contact Lens Solutions; D004269:DNA, Bacterial; D002939:Ciprofloxacin; D014031:Tobramycin