Successful treatment of methicillin-resistant Staphylococcus aureus Keratitis with topical ciprofloxacin

Two cases of corneal ulcer due to methicillin-resistant Staphylococcus aureus in high risk groups

Considering the popular use of antibiotic-containing eyedrops in Korea, it is important to know the emerging antibiotic-resistant strains of bacteria before treating infectious eye diseases. This is especially important in high-risk groups because of the high incidence of resistant infections and the subsequent treatment requirements. We report two cases of methicillin-resistant Staphylococcus aureus (MRSA) corneal ulcers in high-risk groups. The first case involved a patient who had keratitis after using antibiotic- and steroid-containing eyedrops to treat a corneal opacity that developed after repeated penetrating keratoplasty. The second case involved a patient who used antibiotic-containing eyedrops and a topical lubricant on a regular basis for >1 month to treat exposure keratitis due to lagophthalmos. The second patient's problems, which included a persistent superficial infiltration, developed after brain tumor surgery. Both cases showed MRSA on corneal culture, and the corneal ulcers improved in both patients after the application of vancomycin-containing eyedrops. In conclusion, MRSA infection should be considered in corneal ulcers that have a round shape, mild superficial infiltration, and slow progression, especially in high-risk groups. This report includes descriptions of the characteristic features, antibiotic sensitivities, prevention, and successful treatment with vancomycin-containing eyedrops for MRSA corneal ulcers.

Effectiveness of Topical TaurolidineversusCiprofloxacin, Ofloxacin, and Fortified Cefazolin in a RabbitStaphylococcusaureusKeratitis Model

PURPOSE

Taurolidine is a broad-spectrum, non antibiotic antimicrobial agent, not previously tested against the common causes of bacterial keratitis. This study, employing an experimental rabbit model of Staphylococcus aureus keratitis, investigated the effectiveness of topical taurolidine in reducing the number of bacteria, and its effectiveness was compared with topical ciprofloxacin, ofloxacin, and 5% cefazolin.

METHODS

The right corneas of all rabbits were intrastromally injected with 100 colony-forming units of Staphylococcus aureus ATCC strain 25923. The animals were divided into the following seven groups: Group 1 (6 rabbits) received taurolidine, group 2 (6 rabbits) received ciprofloxacin, group 3 (6 rabbits) received ofloxacin, group 4 (6 rabbits)received cefazolin, group 5 (5 rabbits) received polyvinylpyrrolidone (vehicle),group 6 (4 rabbits) received sterile water, and group 7 (4 rabbits) was left un-treated (control group). The eyes were topically treated every 30 min with the above-mentioned substances from 4 to 9 h postinjection. One hour after the last drop administration (at 10 h postinjection), signs of inflammation were scored in a masked fashion by slit-lamp examination. Then, their corneas were processed. The number of colony-forming units (cfu) per cornea in all eyes was also determined.

RESULTS

All antimicrobial (taurolidine, ciprofloxacin, ofloxacin, and cefazolin) treatments significantly reduced cfu numbers and slit-lamp examination scores compared with untreated eyes, eyes that received the vehicle, or eyes with sterile water (all p values <0.05). Regarding cfu numbers, although taurolidine therapy was significantly less effective than ciprofloxacin or ofloxacin,there was no significant difference between taurolidine and cefazolin groups.However, taurolidine had similar clinical examination scores with the other antimicrobials, while it had lower scores than the vehicle, sterile water, or un-treated eyes.

CONCLUSIONS

The results obtained in this study suggest that topicaltaurolidine is an effective, novel ocular chemotherapeutic agent for the therapy of rabbit experimental Staphylococcus aureus keratitis. This drug may be a useful and promising ocular antimicrobial.

Methicillin-resistant Staphylococcus aureus infectious keratitis following refractive surgery

PURPOSE

To elucidate risk factors, clinical course, visual outcomes, and treatment of culture-proven methicillin-resistant Staphylococcus aureus (MRSA) infectious keratitis following refractive surgery.

DESIGN

Interventional case series.

METHODS

Multicenter chart review of 13 cases of MRSA keratitis following refractive surgery and literature review.

RESULTS

Thirteen eyes of 12 patients, nine of whom were either healthcare workers or exposed to a hospital surgical setting, developed MRSA keratitis following refractive surgery. All patients presented with a decrease in visual acuity and complaints of pain or irritation in the affected eye. Common signs on slit-lamp biomicroscopy were corneal epithelial defects, focal infiltrates with surrounding edema, conjunctival injection, purulent discharge, and hypopyon. All patients were diagnosed with infectious keratitis on presentation and treated with two antibiotics. All eyes were culture-positive for MRSA.

CONCLUSIONS

According to a computerized MEDLINE literature search, this is the first case series of MRSA infectious keratitis following refractive surgery, the first reports of MRSA keratitis after refractive surgery in patients with no known exposure to a healthcare facility, the first report of MRSA keratitis after a laser in situ keratomileusis (LASIK) enhancement, and the first reports of MRSA keratitis after prophylaxis with fourth-generation fluoroquinolones. MRSA keratitis is a serious and increasing complication following refractive surgery. Patients with exposure to a healthcare environment should be considered at additional risk for developing MRSA keratitis. However, in addition, surgeons should now be vigilant for community-acquired MRSA. Prompt identification with culturing and appropriate treatment of MRSA keratitis after refractive surgery is important to improve visual rehabilitation.

External ocular infections due to methicillin-resistant Staphylococcus aureus (MRSA)

PURPOSE

To determine the prevalence and clinical characteristics of external ocular infections caused by methicillin-resistant Staphylococcus aureus (MRSA) in an ophthalmic hospital in the UK.

METHODS

A retrospective analysis of the case notes of patients who had culture proven external ocular Staphylococcal infections during a 44-month period was undertaken.

RESULTS

There were a total of 548 external eye infections caused by Staphylococcus aureus. Of these, 17 (3%) were MRSA positive. The most common presentation was conjunctivitis seen in six patients. All MRSA isolates were sensitive to chloramphenicol. Ofloxacin resistance was observed in all isolates from patients over the age of 50 years. All patients had an underlying history of either an ocular surface disease, malignancy, or a debilitating medical illness.

CONCLUSIONS

MRSA is as yet an infrequent cause of external ocular infections. Patients typically have underlying ocular risk factors and/or are medically debilitated. Different strains infect young and old age groups with characteristic antimicrobial sensitivity. This study highlights the need for more work to establish the role of MRSA commensals and ocular infections.

Corneal ciprofloxacin precipitation during bacterial keratitis

PURPOSE

To examine how age affects the risk of developing a white corneal precipitate during ciprofloxacin therapy for bacterial keratitis and to explore the effect of a white precipitate on rates of clinical improvement and cure.

DESIGN

Prospective, multicenter, observational cohort study.

METHODS

Occurrence of a white precipitate of the corneal surface was recorded among 624 patients with presumed bacterial keratitis who were treated with topical ciprofloxacin 0.3% solution or ointment. Relative risks of corneal precipitation were estimated from logistic regression for age categories and other clinical characteristics. The time-dependent effects of precipitate on rates of infection resolution and corneal reepithelialization were estimated by proportional hazards regression.

RESULTS

Ninety-five (15.2%) patients developed a white corneal precipitate during ciprofloxacin therapy; 72 (75.8%) began within the first 3 days of treatment. Compared with those younger than 40 years old, patients aged 60 to 69 years had 2.8 (95% confidence limits [CL], 1.9, 3.9) times the risk of ciprofloxacin precipitation; patients 70 years and older had 3.7 (95% CL, 2.6, 5.0) times the risk. Median duration of the visible corneal precipitate was 8.5 days (90% decile, 32 days). Presence of ciprofloxacin precipitation did not significantly affect the time until therapeutic improvement (P =.09) but slowed the time until reepithelialization by 55% (95% CL 32%, 70%).

CONCLUSIONS

Older patients treated with topical ciprofloxacin for bacterial keratitis have a higher risk of corneal deposition. A white precipitate apparently does not interfere with antibacterial therapeutic response but may delay epithelial healing of ulcerative keratitis.

Effectiveness of mupirocin and polymyxin B in experimental Staphylococcus aureus, Pseudomonas aeruginosa, and Serratia marcescens keratitis

PURPOSE

The purpose of this study was to determine the effectiveness of mupirocin and polymyxin B, alone and in combination, in vitro and in vivo using rabbit models of, and keratitis.

METHODS

Rabbit eyes were intrastromally injected with 1,000 colony-forming units (CFUs) of or or 100 CFUs of Rabbits were then treated with 2.7 mg/mL mupirocin, 10,000 U/mL polymyxin B, a mupirocin:polymyxin B combination, or 0.3% ciprofloxacin. Vehicle and untreated controls were also included. Treatment schedules depended on the strain injected. The number of CFUs was determined for all eyes after treatment.

RESULTS

The mupirocin:polymyxin B combination was effective for all three genera both in vitro and in vivo. For keratitis, the mupirocin:polymyxin B combination was more effective than either drug alone and significantly reduced the log number of bacteria in the cornea by more than 3 logs compared with the vehicle or untreated controls (p <or= 0.0016). For, the mupirocin:polymyxin B combination treatment significantly reduced the number of CFUs per cornea relative to the individual drugs, vehicle, or untreated controls (p <or= 0.016). For, the mupirocin:polymyxin B combination therapy significantly reduced the number of bacteria in rabbit corneas relative to the individual drugs, vehicle, or untreated groups (p <or= 0.0001). Therapy with the mupirocin:polymyxin B combination was equivalent to ciprofloxacin therapy (p = 0.80).

CONCLUSION

The mupirocin:polymyxin B combination was effective in treating experimental, and keratitis.

Scanning electron microscopic study of a Ciloxan bottle blocked by ciprofloxacin crystals

PURPOSE

To report blockage of a commercially available ciprofloxacin bottle by white crystalline deposits. This study evaluated the ultrastructural features of the ciprofloxacin crystals.

METHODS

A patient underwent intensive topical treatment of an infectious corneal ulcer with commercially available ciprofloxacin 0.3% ophthalmic solution. During treatment, the patient was unable to obtain medication from the ciprofloxacin bottle and required a new prescription. Examination of the bottle revealed that about 50% of the medication remained, but compression of the bottle with any amount of force failed to deliver any medication. On closer examination, a white material partially filled the nozzle track of the bottle and was on the outer bottle near the nozzle and the inner surface of the bottle cap. These white crystalline deposits were evaluated by scanning electron microscopy.

RESULTS

Plate-like, needle, cable and spaghetti-like crystals were found. The needle crystals formed multiple petaloid patterns.

CONCLUSIONS

This is the first report of blockage of a commercially available ciprofloxacin 0.3% bottle by ciprofloxacin crystals and the inability to deliver medication from the bottle. Ultrastructural study of the white crystalline deposits revealed four types of ciprofloxacin crystals.

Bacterial keratitis: a prospective clinical and microbiological study

AIM

To define the clinical and microbiological profile of bacterial keratitis at the Jules Gonin Eye Hospital and to test the in vitro bacterial resistance.

METHODS

Patients presenting with bacterial keratitis were prospectively followed; clinical features (age, risk factors, visual acuity) and response to therapy were analysed. Bacteriological profile was determined and the sensitivity/resistance of isolated strains were tested towards 12 ocular antibiotics (NCCLS disc diffusion test).

RESULTS

85 consecutive patients (mean age 44.3 (SD 20.7) years) were prospectively enrolled from 1 March 1997 to 30 November 1998. The following risk factors were identified: contact lens wear, 36%; blepharitis, 21%; trauma, 20%; xerophthalmia, 15%; keratopathies, 8%; and eyelid abnormalities, 6%. The most commonly isolated bacteria were Staphylococcus epidermidis, 40%; Staphylococcus aureus, 22%; Streptococcus pneumoniae, 8%; others Streptococcus species, 5%; Pseudomonas, 9%; Moraxella and Serratia marcescens, 5% each; Bacillus, Corynebacterium, Alcaligenes xyloxidans, Morganella morganii, and Haemophilus influenza, 1% each. 1-15% of strains were resistant to fluoroquinolones, 13-22% to aminoglycosides, 37% to cefazolin, 18% to chloramphenicol, 54% to polymyxin B, 51% to fusidic acid, and 45% to bacitracin. Five of the 85 patients (5.8%) had a poor clinical outcome with a visual loss of one or more lines of visual acuity.

CONCLUSION

Fluoroquinolones appear to be the therapy of choice for bacterial keratitis, but, based upon these in vitro studies, some strains may be resistant.

The evolution of antibiotic therapy for bacterial conjunctivitis and keratitis: 1970-2000

The editors of this Festschrift asked us to review the use of antibiotics for the treatment of bacterial conjunctivitis and keratitis over the past 25 years, a period coinciding with the life of the Castroviejo Corneal Society. We believe it is more appropriate to begin our review in the late 1960s. about the time that experimental and clinical studies and algorithms for the clinical care derived from these studies helped shape a more rigorous approach to therapy. Those years saw the introduction of antibiotics that were adapted for ophthalmic use, many of which are still being used today. We will give more weight to our review of keratitis than conjunctivitis.

Comparison of ciprofloxacin ophthalmic solution 0.3% to fortified tobramycin-cefazolin in treating bacterial corneal ulcers. Ciprofloxacin Bacterial Keratitis Study Group

PURPOSE

The purpose of the study is to compare the clinical efficacy and safety of ciprofloxacin ophthalmic solution 0.3% (Ciloxan) with a standard therapy regimen (fortified tobramycin, 1.3%-cefazolin, 5.0%) for treating bacterial corneal ulcers.

METHODS

This randomized, parallel group, double-masked, multicenter study was conducted in 324 patients at 28 centers in the United States, Europe, and India. Patients were randomized into 2 treatment groups: 160 to ciprofloxacin and 164 to fortified tobramycin-cefazolin. Positive microbiologic cultures were obtained in 188 (58%) of 324 patients. Of these, 176 patients met protocol criteria and were evaluated for treatment efficacy: 82 in the ciprofloxacin group and 94 in the standard therapy group. The dosing schedule for both treatment groups was 1 to 2 drops of the first study medication (ciprofloxacin or fortified tobramycin) every 30 minutes for 6 hours, then hourly for the remainder of day 1; 1 to 2 drops every hour on days 2 and 3; 1 to 2 drops every 2 hours on days 4 and 5, followed by 1 to 2 drops every 4 hours on days 6 to 14. The second medication (ciprofloxacin or cefazolin) was instilled 5 to 15 minutes after the first drug, following the same dosing frequency. Physician's judgment of clinical success, cure rate, changes in ocular sings, and symptoms and the rate of treatment failures were the primary efficacy criteria.

RESULTS

Topical ciprofloxacin monotherapy is equivalent clinically and statistically to the standard therapy regimen of fortified antibiotics. No statistically significant treatment differences were found between ciprofloxacin (91.5%) and standard therapy (86.2%) in terms of overall clinical efficacy (P = 0.34). Similarly, no differences were noted in resolution of the clinical signs and symptoms (P > 0.08) or the time to cure (P = 0.55). The incidence of treatment failures was less in the ciprofloxacin group (8.5%) compared with the standard therapy group (13.8%). Significantly fewer patients treated with ciprofloxacin reported discomfort than did patients treated with the standard therapy regimen (P = 0.01).

CONCLUSION

Ciprofloxacin ophthalmic solution 0.3% monotherapy is equivalent clinically and statistically to standard therapy (fortified tobramycin-cefazolin) for the treatment of bacterial corneal ulcers and produces significantly less discomfort.

Pharmacokinetic considerations in the treatment of bacterial keratitis

The eye is relatively impermeable to micro-organisms and other environmental elements. However, if corneal integrity is breached by trauma, a sight-threatening bacterial infection can result. Staphylococcus aureus, Pseudomonas aeruginosa, and Streptococcus pneumoniae are the most common bacterial pathogens associated with infection of compromised corneas. Bacterial enzymes and toxins, as well as factors associated with the host immune response, can lead to tissue destruction during corneal infection. For successful therapy, an antibacterial agent must be active against the pathogen and must be able to overcome the permeability barrier of the cornea. Topical application of antibacterial agents adequately delivers drugs to the cornea and aqueous humour. However, drug concentrations at the site of infection are not always sufficient to rapidly kill infective organisms. Infections with antibiotic-resistant strains present an even greater therapeutic challenge. In addition, sterilisation of the cornea by antibacterial agents does not eliminate inflammation and corneal scarring that accompany infection. Steroidal and non-steroidal antiinflammatory agents limit corneal scarring during experimentally induced bacterial keratitis. However, although promising, concomitant use of these drugs with antibacterial agents remains controversial. Two ocular drug delivery systems that provide high and sustained concentrations of drug to ocular tissues are corneal collagen shields and transcorneal iontophoresis. The collagen shield, originally designed as a bandage lens, prolongs drug contact with the cornea. Chemotherapeutic studies of experimental bacterial keratitis demonstrate that shields hydrated with antibacterial agents reduce bacteria in the cornea as well as or better than frequent applications of fortified antibacterial drops. Transcorneal iontophoresis uses an electric current to drive charged drugs into the cornea. In experimentally induced bacterial keratitis, transcorneal iontophoresis of antibacterial agents is superior to topically administered ocular drops for reducing the numbers of bacteria in the cornea. Although both drug delivery systems appear to be well tolerated and nontoxic in animal models, clinical trials in patients are required to determine the usefulness of these drug delivery systems in clinical trials. Based on present experimental results, future therapy of bacterial keratitis will involve efficient drug delivery devices, the use of new antibacterial agents or combinations of presently available antibacterial agents, and careful use of adjuvant anti-inflammatory agents.

Comparison of topical ciprofloxacin to conventional antibiotic therapy in the treatment of ulcerative keratitis

We evaluated the efficacy of ciprofloxacin (3 mg/ml) as the sole topical antibiotic used to treat infectious keratitis in 14 patients. We compared the ciprofloxacin-treated group to a retrospective control group of 30 consecutive culture-positive patients treated with conventional therapy in which cefazolin (50 mg/ml) and fortified gentamicin sulfate (9.1 mg/ml) solutions were used. We found no remarkable difference between the control group and the ciprofloxacin-treated group regarding patient age, risk factors, need for hospitalization, and virulence of organism isolated. The average time to healing in culture-positive ciprofloxacin-treated patients was 34 +/- 33 days vs 45 +/- 71 days in the control group and this difference was not statistically significant. The duration of antibiotic therapy in the culture-positive ciprofloxacin-treated group was 27 +/- 15 days vs 33 +/- 50 days in the control group. Four of the 30 control patients required modification of their antibiotic regimen, whereas no ciprofloxacin-treated patient required a change. Ciprofloxacin appears to be an effective single agent in the treatment of ulcerative keratitis.

Bioassays for quantitating ciprofloxacin and tobramycin in aqueous humor

Development of new therapies for bacterial keratitis requires assays of antibiotics in infected ocular tissues; however, methods for such drug quantitation can be expensive and can lack precision and sensitivity. To develop a more suitable assay for quantitating tobramycin and ciprofloxacin in the aqueous humor, sixteen bioassays were compared. Variables assessed included: the strain of bacteria used as indicator (Staphylococcus aureus ATCC 25923 versus Klebsiella pneumoniae ATCC 10031), the application of bacteria to the agar surface versus inclusion in molten agar, the volume of the agar, and the application of antibiotic on paper discs versus instillation into agar wells. The best results were obtained when the appropriate indicator organism (S. aureus for tobramycin and K. pneumoniae for ciprofloxacin) was applied to the surface of the agar, antibiotic solution was put into agar wells, and the volume of agar was 30 ml per plate. The best sensitivity for assays of tobramycin and ciprofloxacin diluted in water were 0.98 and 0.12 micrograms/ml, respectively. These sensitivities improved as much as fourfold when antibiotics were diluted in aqueous humor or normal saline. The precision of all assays tested was high as determined by regression coefficients (r > 0.90). The sensitivity and precision of these assays indicate their utility for quantitating fluoroquinolones and aminoglycosides in aqueous humor.

Methicillin-resistant Staphylococcus aureus keratitis in the rabbit: therapy with ciprofloxacin, vancomycin and cefazolin

To determine the efficacy of a fluoroquinolone antibiotic in the treatment of methicillin-resistant Staphylococcus aureus (MRSA) keratitis, topical administration of 0.3% ciprofloxacin was compared with topical 5.0% vancomycin or 5.0% cefazolin in experimental infections in the rabbit eye. The infections were established by intrastromal injection of 100 colony forming units (CFU) of MRSA, which resulted in greater than 10(6) CFU per cornea by 12 hr postinfection. Chemotherapy (one drop every 15 min) was given from 4-9, 10-15, or 10-20 hr postinfection. Early therapy (4-9 hr postinfection) with ciprofloxacin rendered all eyes free of bacteria; ciprofloxacin was significantly more effective than vancomycin or cefazolin. When treatment was initiated 6 hr later (10-15 hr postinfection), no corneas became free of bacteria, but ciprofloxacin was again more effective than vancomycin or cefazolin. Bacterial killing by ciprofloxacin after treatment from 10-20 hr postinfection was also significantly greater than that of vancomycin. Overall, the results show that ciprofloxacin is effective in killing methicillin-resistant staphylococcus aureus, and is most effective when applied during the very early stages of infection.

Ciprofloxacin-resistant bacterial keratitis

Ciprofloxacin, a new broad-spectrum antibiotic effective against a variety of gram-positive and gram-negative bacteria, has recently become available in topical ophthalmic solution (3 mg/ml) for the treatment of bacterial keratitis. It has rapidly become the drug of choice in treating bacterial keratitis. We treated three patients with bacterial corneal ulcers that were resistant to ciprofloxacin, yet were effectively treated with other topical antimicrobial agents. The initial culture results are important in the therapy of corneal ulcers.