Fluoroquinolone therapy in multiple-drug resistant staphylococcal keratitis after lamellar keratectomy in a rabbit model

Levofloxacin in veterinary medicine: a literature review

A potent third-generation antimicrobial fluoroquinolone drug, levofloxacin was introduced into human clinical practice in 1993. Levofloxacin is also used in veterinary medicine, however its use is limited: it is completely banned for veterinary use in the EU, and used extralabel in only companion animals in the USA. Since its introduction to clinical practice, many studies have been published on levofloxacin in animal species, including pharmacokinetic studies, tissue drug depletion, efficacy, and animal microbial isolate susceptibility to levofloxacin. This literature overview highlights the most clinically relevant and scientifically important levofloxacin studies linked to the field of veterinary medicine.

Antimicrobial Efficacy of Gatifloxacin and Moxifloxacin with and without Benzalkonium Chloride Compared with Ciprofloxacin and Levofloxacin Against Methicillin- ResistantStaphylococcus aureus

We compared the antimicrobial activity of gatifloxacin and moxifloxacin with and without benzalkonium chloride (BAK) against clinical isolates of methicillin-resistant Staphylococcus aureus (MRSA). Minimum inhibitory concentrations (MICs) against clinical isolates of MRSA were evaluated. Approximately 10(5 )CFU/ml of methicillinresistant S. aureus was added to Mueller-Hinton broth containing two-fold concentration increments of drug. For the evaluation of gatifloxacin with BAK, 50 microg/ml of BAK were added to the first well of the plate with gatifloxacin or moxifloxacin and then serially diluted. The combination of gatifloxacin or moxifloxacin with BAK was more active than either fluoroquinolone without BAK. The MICs ranged from <or=0.008 microg/ml to 0.125 microg/ml for gatifloxacin plus BAK, from 0.063 microg/ml to (3)8 microg/ml with unpreserved gatifloxacin from <0.004 to 0.25 for moxifloxacin plus BAK, and from <or=0.016 microg/ml to 16.0 microg/ml with unpreserved moxifloxacin. The combinations of gatifloxacin or moxifloxacin and BAK were highly active against MRSA in vitro, providing MICs that were approximately 2- to 500-fold lower than the MICs provided by either gatifloxacin or moxifloxacin without BAK.

Comparison of corneal and aqueous humor penetration of moxifloxacin, gatifloxacin and levofloxacin during keratoplasty

INTRODUCTION

Achieving high antibiotic concentrations is important for preventing and treating postoperative infections. However, no study has simultaneously compared the achieved concentrations of moxifloxacin, gatifloxacin, and levofloxacin in the human cornea and aqueous humor. The authors therefore performed a randomized study to determine the concentrations of 0.5% moxifloxacin, 0.3% gatifloxacin, and 0.5% levofloxacin in the corneal tissue and aqueous humor after topical instillation in patients undergoing penetrating keratoplasty.

METHODS

Patients who required penetrating keratoplasty were eligible for this study. The topical preparations of 0.5% moxifloxacin, 0.3% gatifloxacin, and 0.5% levofloxacin used in the study were preservative free (Japanese formulations). Patients were randomly assigned to one of three sequential drug groups, in which each drug was administered three times before surgery. In each administration cycle, the patients received two drops of each drug at 2-minute intervals. Samples of corneal tissue and aqueous humor were collected during surgery. The concentrations of each drug in the samples were determined by high-performance liquid chromatography.

RESULTS

A total of 63 patients across eight centers in Japan were enrolled in the study. Overall, 61 corneal and 58 aqueous humor samples were evaluated. The concentration (mean±standard deviation) of moxifloxacin in corneal tissues was 12.66±8.93 μg/g, which was significantly higher than that of gatifloxacin (4.71±3.39 μg/g; P<0.0001) and levofloxacin (5.95±4.02 μg/g; P<0.0001). The mean concentration of moxifloxacin in aqueous humor samples was 1.40±1.17 μg/mL, which was significantly higher than that of gatifloxacin (0.65±0.80 μg/mL; P=0.0001) and levofloxacin (0.89±0.86 μg/mL; P<0.05). The sequence of drug administration did not significantly affect the results.

CONCLUSION

These results show that 0.5% moxifloxacin achieved superior ocular concentration than both 0.3% gatifloxacin and 0.5% levofloxacin.

Animal models of bacterial keratitis

Bacterial keratitis is a disease of the cornea characterized by pain, redness, inflammation, and opacity. Common causes of this disease are Pseudomonas aeruginosa and Staphylococcus aureus. Animal models of keratitis have been used to elucidate both the bacterial factors and the host inflammatory response involved in the disease. Reviewed herein are animal models of bacterial keratitis and some of the key findings in the last several decades.

Scanning electron microscopy visualization of methicillin-resistant Staphylococcus aureus after contact with gatifloxacin with and without preservative

PURPOSE

To test a visual model by looking at the differences in effect of Zymar((R)) (gatifloxacin plus benzalkonium chloride [BAK]) when compared to gatifloxacin and a normal saline (NS) control upon a methicillin and gatifloxacin-resistant Staphylococcus aureus (MRSA) species.

METHODS

An ocular isolate of gatifloxacin-resistant (minimal inhibitory concentration >2 to 4 microg/mL) MRSA was grown to confluency. Chambered slides were prepared with bacterial culture smears, and then incubated with either gatifloxacin at the concentrations of 1 and 10 microg/mL, Zymar containing equivalent concentrations of gatifloxacin, or NS. Bacterial cultures were fixed after 10, 30, and 60 min. Fixed slides were coated in gold sputter for examination. Bacteria were visually evaluated with scanning electron microscopy (SEM) at 50,000x. Blinded review of SEM images compared structural changes and mitotic activity across samples.

RESULTS

MRSA exposed to 10 microg Zymar for 60 min showed significantly greater pleomorphism and cell wall surface changes when compared to gatifloxacin (P < 0.0001) and NS (P = 0.001), and significantly less mitotic activity than NS (P = 0.002).

CONCLUSION

Using SEM, the topical formulation of gatifloxacin 0.3% (Zymar), which contains BAK, had greater antibacterial activity than did gatifloxacin alone in gatifloxacin and methicillin-resistant S. aureus, thereby illustrating potential advantages of the preservative in the commercial formulation. We further show that these effects can be visualized and quantified.

Kill rates of preserved and preservative-free topical 8-methoxy fluoroquinolones against various strains of Staphylococcus

PURPOSE

To assess the kill rates of preserved and preservative-free 8-methoxy fluoroquinolones and benzalkonium chloride (BAC) against isolates of Staphylococcus aureus and coagulase-negative Staphylococcus (CNS) species.

SETTING

Bascom Palmer Eye Institute, Miami, Florida, USA.

METHODS

Ocular and standard isolates of S aureus and CNS were inoculated with saline, 0.005% BAC, gatifloxacin 0.3% containing 0.005% BAC (Zymar), or BAC-free moxifloxacin 0.5% (Vigamox) at 37 degrees C. Bacterial viability was assessed after 15 minutes, 30 minutes, and 60 minutes.

RESULTS

Thirteen isolates of S. aureus and 5 isolates of CNS were used. The mean initial load of bacterial inoculum was 5.45 log colony-forming units (CFU)/mL +/- 0.37 (SD). Saline did not affect the density of staphylococci; BAC significantly decreased the staphylococci count to a mean of 3.80 +/- 0.32 log CFU/mL at 60 minutes (P<.05). Gatifloxacin 0.3% reduced the number of staphylococci significantly more than moxifloxacin 0.5% at 15 minutes (mean 0.47 +/- 1.12 log CFU/mL versus 4.55 +/- 0.60 log CFU/mL), 30 minutes (mean 0.07 +/- 0.31 log CFU/mL versus 3.82 +/- 1.07 log CFU/mL), and 60 minutes (mean 0.00 +/- 0.00 log CFU/mL versus 2.75 +/- 1.29 log CFU/mL) (P<.005). Gatifloxacin 0.3% completely eradicated most S. aureus (10/13) and CNS (3/5) isolates at 15 minutes; moxifloxacin 0.5% did not achieve complete kill in any S. aureus isolate (13/13) or in most CNS isolates (4/5) at 60 minutes.

CONCLUSION

The commercial formulation of gatifloxacin 0.3% containing BAC 0.005% completely eradicated staphylococcal isolates more rapidly than the BAC-free formulation of moxifloxacin 0.5% or BAC 0.005% alone.

Benzalkonium chloride enhances antibacterial activity of gatifloxacin and reduces its propensity to select for fluoroquinolone-resistant strains

PURPOSE

To assess the impact of benzalkonium chloride (BAK) on the minimum inhibitory concentration (MIC) and mutant prevention concentration (MPC) of gatifloxacin against Gram-positive pathogens in comparison to gatifloxacin and moxifloxacin alone, moxifloxacin plus BAK, and/or levofloxacin.

METHODS

The MIC was measured following incubation of 10(5) colony-forming units (CFU)/mL of coagulase-negative staphylococci (CNS; n = 20), methicillin-susceptible Staphylococcus aureus (MSSA; n = 20), and methicillin-resistant S. aureus (MRSA; n = 20) with gatifloxacin, levofloxacin, or moxifloxacin. When present, BAK was added from 3.125 microg/mL to 6.25 microg/mL. The MPC was measured following incubation of 10(10) CFU/mL of MRSA (n = 9) and a commercially available MSSA strain with gatifloxacin or moxifloxacin in the absence and presence of BAK at concentrations from 7 microg/mL to 10 microg/mL.

RESULTS

CNS was more susceptible to gatifloxacin (MIC(90) = 2 microg/mL) than levofloxacin (MIC(90) = 8 microg/mL) or moxifloxacin (MIC(90) = 4 microg/mL). MSSA was more susceptible to moxifloxacin (MIC(90) = 1 microg/mL) than gatifloxacin (MIC(90) = 4 microg/mL) or levofloxacin (MIC(90) = 4 microg/mL). MRSA were resistant to gatifloxacin, levofloxacin, and moxifloxacin. In the presence of BAK, however, the MIC(90) of gatifloxacin and moxifloxacin against CNS, MSSA, and MRSA was < or =0.008 microg/mL. Gatifloxacin and moxifloxacin had similar MPCs against MRSA (> or =4 microg/mL). In the presence of BAK, the MPC of gatifloxacin and moxifloxacin against MRSA ranged from < or =0.004 microg/mL to 0.125 microg/mL.

CONCLUSIONS

BAK substantially lowered the MIC and MPC of gatifloxacin and moxifloxacin against Gram-positive staphylococci compared to gatifloxacin alone, moxifloxacin alone, and/or levofloxacin. These findings suggest that the presence of BAK in the ophthalmic formulation of gatifloxacin (Zymar) may serve to enhance the potency of gatifloxacin and decrease its propensity to select for fluoroquinolone-resistant S. aureus strains.

Rate of bacterial eradication by ophthalmic solutions of fourth-generation fluoroquinolones

INTRODUCTION

Antibacterial activity of ophthalmic fourth-generation fluoroquinolones has traditionally been evaluated by comparing only their active ingredients, gatifloxacin and moxifloxacin. However, ophthalmic formulations of fourth-generation fluoroquinolones differ in terms of the inclusion of preservatives. While gatifloxacin ophthalmic solution 0.3% (Zymar; Allergan, Inc., Irvine, CA, USA) contains 0.005% benzalkonium chloride (BAK), moxifloxacin ophthalmic solution 0.5% (Vigamox; Alcon Laboratories, Inc., Fort Worth, TX, USA) is preservative-free. Recent studies have demonstrated that the presence of BAK dramatically affects the antibacterial activity of the ophthalmic formulation of gatifloxacin. This study was designed to compare the kill rates of ophthalmic solutions of fourth-generation fluoroquinolones against isolates of common ocular bacterial pathogens.

METHODS

Approximately 5.6 log(10) colony-forming units (CFU)/mL of Haemophilus influenzae (n=1), Streptococcus pneumoniae (n=1), Staphylococcus aureus (n=2), methicillin-resistant Staphylococcus aureus (MRSA) (n=4), methicillinresistant Staphylococcus epidermidis (MRSE) (n=4), and fluoroquinolone-resistant S. epidermidis (n=1) were incubated with ophthalmic solutions of either gatifloxacin or moxifloxacin. Viable bacteria were quantified at specific time points up to 60 minutes.

RESULTS

Gatifloxacin 0.3% completely eradicated H. influenzae and Strep. pneumoniae in 5 minutes, one of two S. aureus isolates in 15 minutes, and the other S. aureus isolate in 60 minutes. Gatifloxacin 0.3% completely killed all MRSA, MRSE, and fluoroquinolone-resistant S. epidermidis isolates in 15 minutes. Moxifloxacin 0.5% completely eradicated Strep. pneumoniae and one of four MRSA isolates in 60 minutes. All other isolates incubated with moxifloxacin 0.5% retained viable bacteria ranging from 1.8 to 4.4 log(10) CFU/mL.

CONCLUSIONS

The ophthalmic solution of gatifloxacin 0.3% eradicated bacteria that frequently cause postoperative ocular infections substantially faster than did the ophthalmic solution of moxifloxacin 0.5%.

The effects of moxifloxacin ophthalmic solution 0.5% or gatifloxacin ophthalmic solution 0.3% treatment on corneal wound healing in pigmented rabbits following anterior keratectomy

PURPOSE

These studies examined corneal healing rates, Type-IV collagen and zonula occludens membrane-associated protein (ZO-1) expression, as well as aqueous PGE(2) and IL-1 beta concentrations in pigmented rabbits treated with either moxifloxacin 0.5%, gatifloxacin 0.3% or BSS following anterior keratectomy.

METHODS

Anterior keratectomy surgery was followed by topical administration with commercial ophthalmic formulations of either moxifloxacin or gatifloxacin or BSS (TID for 96 h). Images of the fluorescein-stained healing corneas were analyzed for wound area. At 48 or 96 h following surgery, aqueous humor samples were collected and analyzed for the inflammatory mediators PGE(2) and IL-1 beta using an ELISA. The corneas were subsequently evaluated using both scanning and transmission electron microscopy. In a second parallel study, corneas were evaluated at both 48 and 96 h for Type-IV collagen and ZO-1 expression using immunohistochemistry.

RESULTS

Fluorescein-stained corneal images at 96 h postsurgery demonstrated that 90% +/- 8% re-epithelialization for moxifloxacin, 81% +/- 14% for gatifloxacin, and 88 +/- 6% for BSS((R)) (P > 0.05). PGE(2 )levels in the aqueous humor of fluoroquinolone treated eyes were reduced at 48 h compared to BSS treated eyes. IL-1 beta was undetectable in all samples. No differences in Type-IV collagen or ZO-1 expression were observed between any treatment groups. There were no differences between groups in histological appearance or in ultrastructural healing processes.

CONCLUSIONS

These studies demonstrated that the commercial ophthalmic formulations of moxifloxacin and gatifloxacin were similar to each other in their effects on the levels of aqueous humor PGE(2) and rates of corneal wound re-epithelialization.

Review of third-and fourth-generation fluoroquinolones in ophthalmology: in-vitro and in-vivo efficacy

INTRODUCTION

Beginning with second-generation ciprofloxacin 0.3% and ofloxacin 0.3%, fluoroquinolones have been widely used in the treatment and prophylaxis of ocular infections. However, their in-vitro potencies have been decreasing steadily since their introduction. Third-generation levofloxacin 0.5% produces higher ocular tissue penetration, thereby reducing the risk of selecting for decreased fluoroquinolone potency. Fourth-generation gatifloxacin 0.3% and moxifloxacin 0.5% have structural modifications that both reduce risk of resistance and improve potency against Gram-positive bacteria. A new third-generation formulation, levofloxacin 1.5%, was recently introduced, demonstrating increased ocular penetration compared with gatifloxacin 0.3% but clinical equivalence to its second-generation parent, ofloxacin 0.3%, in two randomized trials.

METHODS

We investigated the therapeutic potential of levofloxacin 1.5% and compared it to that of existing fourth-generation fluoroquinolones. A MEDLINE search was conducted using the following search terms: moxifloxacin or gatifloxacin; levofloxacin; minimum inhibitory concentration or prevention or prophylaxis; keratitis or endophthalmitis.

RESULTS

Nine eligible studies published between 2002 and 2008 were identified, eight of which are presented. The five in-vitro studies demonstrated that moxifloxacin and gatifloxacin are statistically more potent than levofloxacin against Gram-positive organisms and similar in potency in most cases of Gram-negative bacteria. In-vivo animal models testing moxifloxacin or gatifloxacin against levofloxacin 0.5% (no clinical trials testing the efficacy of levofloxacin 1.5% have yet been published) demonstrated that fourth-generation agents were superior to third-generation levofloxacin 0.5% for prophylaxis of Gram-positive bacteria-induced infections and were equal to, or better than, levofloxacin 0.5% for the treatment of Gram-negative infections.

CONCLUSION

Fourth-generation agents have increased potency against Gram-positive bacteria compared with levofloxacin, while maintaining similar potency against Gram-negative bacteria. Although levofloxacin 1.5% has demonstrated superior ocular penetration relative to gatifloxacin, the limited available data do not suggest this translates into superior clinical activity compared with moxifloxacin, which has significantly greater ocular penetration and better Gram-positive potency than gatifloxacin.

Fluoroquinolone therapy in a rabbit model of post-LASIK methicillin-resistant Staphylococcus aureus keratitis

PURPOSE

To develop a rabbit model of post-laser in situ keratomileusis (LASIK) methicillin-resistant Staphylococcus aureus (MRSA) keratitis for studying fluoroquinolone prophylaxis and treatment.

SETTING

Department of Microbiology, University of Mississippi Medical Center, Jackson, Mississippi, USA.

METHODS

An MRSA keratitis isolate (5 microL, 500 colony forming units [CFU]) was inoculated underneath a corneal flap. Bacterial growth and pathology were determined by quantitative cultures (CFU) and slitlamp examination, respectively. The effectiveness of commercial moxifloxacin and gatifloxacin formulations was compared in 3 regimens: prophylaxis (4 drops before inoculation), early therapy (single drop hourly from 4 to 9 hours postinfection), and late therapy (single drop hourly from 10 to 15 hours postinfection). Zones of bacterial inhibition to known in vivo antibiotic concentrations were determined.

RESULTS

Bacteria grew to a maximum of approximately 10(6) CFU/cornea within 10 hours postinfection. The slitlamp examination scores showed pathologic changes beginning 10 hours postinfection and progressed throughout the infection. For prophylaxis, eyes treated with moxifloxacin had significantly fewer CFU than gatifloxacin-treated eyes or untreated controls (both P < or = .0001). During early treatment, the antibiotics were equally effective in reducing CFU relative to untreated controls (P < or = .0001). In late treatment, gatifloxacin and moxifloxacin caused significant reductions in CFU relative to untreated controls (P < or = .0007 and P < or = .0001, respectively). Moxifloxacin produced zones of bacterial inhibition significantly larger than those produced by gatifloxacin.

CONCLUSIONS

Methicillin-resistant S aureus inoculation beneath a rabbit corneal flap produced an infection that was useful for quantitative microbiological studies. A significant advantage in using moxifloxacin relative to gatifloxacin was observed in prophylaxis of keratitis (P = .0001).

Prophylactic gatifloxacin therapy in prevention of bacterial keratitis in a rabbit laser in situ keratomileusis model

PURPOSE

Use the ID(50) (infectious dose to 50% of experimental animals) to quantify the most effective prophylactic dosing regimen to use with gatifloxacin 0.3% (Zymar) for the prevention of keratitis in a rabbit laser in situ keratomileusis model of Staphylococcus epidermidis infection.

SETTING

University Laboratory, University of Arizona, Tucson, Arizona, USA.

METHODS

Two groups of rabbits were compared in each of 2 experiments that were separated by 12 months. In the first experiment, rabbits receiving no postoperative antibiotic therapy (Group 1) were compared with rabbits receiving postoperative antibiotic therapy (Group 2). In the second experiment, postoperative antibiotic therapy (Group 3) was compared with preoperative and postoperative antibiotic therapy (Group 4). All antibiotic regimens used gatifloxacin 0.3%. Before antibiotic therapy began, corneal pockets were created in the right eye of each rabbit and all rabbits received balanced salt solution (BSS) only or BSS and S epidermidis inoculations in the corneal pocket. Rabbits were monitored for corneal infiltrates after surgery.

RESULTS

The ID(50) of the first, second, third, and fourth groups of rabbits was 10(2), 10(4), 10(5), and 10(7) organisms, respectively. The data showed a statistically significant difference between rabbits receiving BSS only and most rabbits receiving BSS plus inoculate at each postoperative measurement (P<.05).

CONCLUSIONS

The findings suggest that the use of both preoperative and postoperative antibiotic therapy may be most effective in preventing infection. Postoperative antibiotic therapy increased the number of S epidermidis necessary to cause infection by at least 100-fold over no antibiotic intervention. Preoperative plus postoperative antibiotic therapy increased the number of bacteria necessary to cause infection by at least 100-fold over postoperative therapy alone and by more than 10000-fold over no antibiotic intervention.

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.

Comparison of topical gatifloxacin 0.3% and ciprofloxacin 0.3% for the treatment of bacterial keratitis

PURPOSE

To compare the bacteriologic and clinical efficacy of gatifloxacin and ciprofloxacin for the treatment of bacterial keratitis.

DESIGN

Prospective, randomized clinical trial.

METHODS

A total of 104 eyes of 104 patients with bacterial keratitis seen at a tertiary eye-care center were randomized to treatment with gatifloxacin 0.3% eyedrops (GAT group, 50 eyes) or ciprofloxacin 0.3% eyedrops (CIP group, 54 eyes). Patients and the treating physician were masked to the antibiotic being used. Main outcome measure studied was healing of the ulcer. Patients lost to follow-up before complete healing were excluded from further analysis.

RESULTS

A significantly higher proportion of ulcers in the GAT group exhibited complete healing compared with those in the CIP group (39 eyes [95.1%] vs 38 [80.9%]; P=.042). Gatifloxacin demonstrated a significantly better action than ciprofloxacin against gram-positive cocci in vitro (P<.001), and the percentage of ulcers caused by these pathogens that healed in the GAT group was significantly better than in the CIP group (P=.009). Mean time taken for healing of ulcer and the efficacy against gram-negative bacteria did not significantly differ between the two groups.

CONCLUSIONS

Gatifloxacin had a significantly better action against gram-positive cocci both in vitro and in vivo when compared with ciprofloxacin. In view of these organisms being the leading cause of keratitis worldwide, gatifloxacin may be a preferred alternative to ciprofloxacin as the first-line monotherapy in bacterial keratitis.

In vitro and in vivo potency of moxifloxacin and moxifloxacin ophthalmic solution 0.5%, a new topical fluoroquinolone

Fluoroquinolones are a class of synthetic antibacterial agents that were approved for ocular therapy in 1991 and have become popular therapy for the treatment and prevention of various ocular infections. These agents are synthetic, broad-spectrum, rapidly bactericidal, and have good penetration into ocular tissues. Their main mechanism of action is the inhibition of bacterial enzymes needed for bacterial DNA synthesis. However, antibiotic resistance occurred swiftly to the earlier fluoroquinolones and better fluoroquinolones were needed. The fourth-generation fluoroquinolones, such as moxifloxacin and gatifloxacin, have enhanced activity against gram-positive bacteria while retaining potent activity against most gram-negative bacteria. These fourth-generation fluoroquinolones have improved penetration into the anterior chamber and have also demonstrated increased in vivo efficacy in several animal models of ocular infections. In addition, topical ophthalmic antibiotic products can deliver antibiotic concentrations directly to the eye that are thousands of times higher than their MICs. This article reviews published data describing the in vitro potency of moxifloxacin and its in vivo activity for treating and preventing experimental ocular infections.

Dacryocystitis Caused by Community-Onset Methicillin-Resistant Staphylococcus Aureus

PURPOSE

To describe the occurrence of community-onset methicillin-resistant Staphylococcus aureus (MRSA) infections of the lacrimal system and their treatment.

METHODS

This cases series consisted of data obtained from seven clinical cases of acute or subacute MRSA dacryocystitis, with or without concurrent conjunctivitis, occurring in nonhospitalized individuals presenting between December 2001 and July 2003. Clinical presentations, microbial culture results, treatment modalities, and outcomes were retrospectively reviewed.

RESULTS

Three patients were successfully treated with antibiotics and lacrimal surgery with no recurrence of symptoms after surgery for 6 months or longer. Four patients had temporary relief of symptoms with antibiotic therapy, but surgery was not performed for non-ophthalmologic reasons, and recurrence occurred.

CONCLUSIONS

The treatment of MRSA dacryocystitis can be challenging. Microbiologic cultures should be performed in all patients with dacryocystitis that is unresponsive to conventional first-line antibiotic treatment and in patients at risk for acquisition of MRSA. Appropriate antibiotic therapy in combination with dacryocystorhinostomy appears to be the optimal treatment.

Penetration of topically applied gatifloxacin 0.3%, moxifloxacin 0.5%, and ciprofloxacin 0.3% into the aqueous humor

PURPOSE

To investigate the aqueous penetration of 3 commercially available ophthalmic fluoroquinolones.

DESIGN

Prospective, double-masked, clinical study.

PARTICIPANTS

Fifty-two eyes of 52 patients.

INTERVENTION

Fifty-two patients undergoing cataract surgery were given preoperative topical gatifloxacin 0.3% (Zymar), moxifloxacin 0.5% (Vigamox), or ciprofloxacin 0.3% (Ciloxan). The patients were instructed to use their antibiotic drops 4 times a day for 3 days before surgery. On the day of surgery, patients were given their assigned antibiotic every 15 minutes for 3 doses, 1 hour before their procedure. At the time of surgery, 0.1 ml of aqueous fluid was aspirated from the anterior chamber with an air cannula needle attached to a tuberculin syringe. The aspirate was immediately stored at -70 degrees C.

MAIN OUTCOME MEASURE

Fluoroquinolone concentrations were determined by reverse-phase high-pressure liquid chromatography assay technique with ultraviolet detection at a wavelength of 275 nm.

RESULTS

Mean aqueous concentration of gatifloxacin in 16 eyes was 0.63 microg/ml (standard deviation [SD], 0.30), moxifloxacin in 14 eyes was 1.31 microg/ml (SD, 0.46), and the mean concentration of ciprofloxacin in 22 eyes was 0.15 microg/ml (SD, 0.11).

CONCLUSIONS

Both moxifloxacin (P<0.001) and gatifloxacin (P<0.005) penetrated the aqueous humor at significantly higher levels than ciprofloxacin. Moxifloxacin penetrated into the aqueous humor at significantly higher levels than gatifloxacin (P<0.05). The anterior chamber levels of moxifloxacin and gatifloxacin may be due to the difference in antibiotic concentration.

Fourth-generation fluoroquinolones: new topical agents in the war on ocular bacterial infections

PURPOSE OF REVIEW

The fourth-generation fluoroquinolones, moxifloxacin and gatifloxacin, were introduced in 2003 promising improved spectrum of activity and delayed development of resistance. Although these topical agents have recently been introduced in commercial form, there is already a growing body of evidence showing excellent potency in the war on ocular infections. The purpose of this review is to discuss the literature to date regarding these two agents.

RECENT FINDINGS

Since their introduction in 1990 in the United States, fluoroquinolones have rapidly become the standard of care in the topical antibiotic arena. Unfortunately, recent evidence has shown the widespread use of fluoroquinolones, not only in eye care, but also in agriculture, and general medical and surgical use, has lead to decreasing susceptibilities of important ocular bacterial pathogens. Moxifloxacin and gatifloxacin have improved potency and are able to overcome resistant isolates. These agents also provide improved penetration into ocular tissues.

SUMMARY

Moxifloxacin and gatifloxacin offer improved spectrum of activity, increased penetration into ocular tissues, and delayed propensity to the development of bacterial antibiotic resistance.

Treatment of rabbit corneal infections with ophthalmic gatifloxacin: a concentration dependence study

This study was designed to determine the most effective dose of gatifloxacin in ophthalmic solution for control of methicillin-resistant Staphylococcus aureus (MRSA) corneal infections in rabbits. Rabbits were inoculated by injecting 9300 colony-forming units of MRSA into the corneal stroma of the eye (n=43). They were then randomly assigned to topical administration of saline, ofloxacin 0.3%, or gatifloxacin 0.02%, 0.1%, 0.3%, or 0.5% ophthalmic solutions. Infection severity 48 hours postinoculation was assessed by masked observers using standard scales. After treatment completion, viable MRSA in corneal tissue were counted, and pathologic examinations of ocular tissues were conducted. Relative to saline, treatment with gatifloxacin 0.3% or 0.5% decreased mean infection scores at every time point from 16 to 48 hours after inoculation (P < or = .012) and reduced area-under-the-curve values for infection scores by 50.3% and 54.2%, respectively (P = .00005). Rabbits treated with gatifloxacin 0.3% and 0.5% had lower area-under-the-curve values than those treated with ofloxacin 0.3% (P < or = .039). Viable MRSA in corneal tissue after gatifloxacin 0.3% or 0.5% treatment were decreased to less than 1% of those found after ofloxacin 0.3% treatment. Gram-positive colony formation and abscesses found in saline-treated corneas were distinctly alleviated by treatment with gatifloxacin 0.3% or 0.5%. No significant differences were observed between treatments with gatifloxacin 0.3% or 0.5% ophthalmic formulations and they were equally effective. Topical administration of gatifloxacin 0.3% or 0.5% ophthalmic solutions controlled MRSA corneal infections in rabbits significantly better than saline or ofloxacin 0.3%.