Integrated analysis of three bacterial conjunctivitis trials of besifloxacin ophthalmic suspension, 0.6%: etiology of bacterial conjunctivitis and antibacterial susceptibility profile

Characterization of Polybacterial versus Monobacterial Conjunctivitis Infections in Pediatric Subjects Across Multiple Studies and Microbiological Outcomes with Besifloxacin Ophthalmic Suspension 0.6

Introduction

The choice of empiric therapy for bacterial conjunctivitis should be guided by an awareness of typical causative pathogen distributions. Bacterial conjunctivitis can be polybacterial, although pediatric-specific data are lacking.

Methods

This was a post-hoc analysis of data in pediatric subjects (1–17 years) from five bacterial conjunctivitis trials evaluating besifloxacin ophthalmic solution 0.6%.

Results

Of the 730 pediatric subjects with culture-confirmed conjunctivitis, nearly one-fourth (23.6%) had polybacterial infections and three-fourths (76.4%) had monobacterial infections at baseline. In both polybacterial and monobacterial infections, the most prevalent organisms were Haemophilus influenzae, Streptococcus pneumoniae, Staphylococcus aureus, and Streptococcus mitis/S. mitis group. In polybacterial versus monobacterial infections, S. mitis/S. mitis group (8.7% vs 4.3%; P=0.032) and Moraxella catarrhalis (4.7% vs 0.5%; P<0.001) were identified more frequently, whereas S. pneumoniae (14.0% vs 28.1%; P<0.001) was identified less frequently, as the dominant infecting species. MICs for individual species were similar for tested antibiotics regardless of polybacterial or monobacterial infection, except Staphylococcus epidermidis for which fluoroquinolone MICs were ≥3 dilutions higher for isolates of this species sourced from polybacterial compared to monobacterial infections. Treatment with besifloxacin resulted in microbial eradication in 79.1% of polybacterial and 92.3% of monobacterial infections (P≤0.005 vs vehicle).

Discussion

One in four pediatric bacterial conjunctivitis infections is polybacterial, highlighting the need for a broad-spectrum antibiotic when choosing empiric therapy.

Characterization of baseline polybacterial versus monobacterial infections in three randomized controlled bacterial conjunctivitis trials and microbial outcomes with besifloxacin ophthalmic suspension 0.6

Background/Purpose

To date, studies examining polymicrobial infections in ocular disease have mostly been limited to keratitis or endophthalmitis. We characterized polybacterial infections compared to monobacterial infections in prior clinical studies evaluating besifloxacin ophthalmic suspension 0.6% for the treatment of bacterial conjunctivitis and report on associated microbiological outcomes.

Methods

In this post-hoc analysis, microbiological data for subjects with conjunctivitis due to one or more than one bacterial species in three previous studies (two vehicle-, one active-controlled) of besifloxacin were extracted. Bacterial species identified at baseline were deemed causative if their colony count equaled or exceeded species-specific prespecified threshold criteria. In subjects with polybacterial infections, the fold-increase over threshold was used to rank order the contribution of individual species. Baseline pathogens and their minimum inhibitory concentrations (MICs) for common ophthalmic antibiotics were compared by infection type, as were microbial eradication rates following treatment with besifloxacin.

Results

Of 1041 subjects with culture-confirmed conjunctivitis, 17% had polybacterial and 83% had monobacterial conjunctivitis at baseline. In polybacterial compared to monobacterial infections, Haemophilus influenzae and Streptococcus pneumoniae were identified less frequently as the dominant infecting species (P = 0.042 and P<0.001, respectively), whereas Streptococcus mitis/S. mitis group was identified more frequently as dominant (P<0.001). Viral coinfection was also identified more frequently in polybacterial infections (P<0.001). Staphylococcus aureus was the most common coinfecting species in polybacterial infections and the second most common dominant species in such infections. With few exceptions, MICs for individual species were comparable regardless of infection type. Clinical microbial eradication rates with besifloxacin were high regardless of infection type (P≤0.016 vs vehicle at follow-up visits).

Conclusions

Approximately one in five subjects with bacterial conjunctivitis are infected with more than one bacterial species underscoring the need for a broad-spectrum antibiotic for such infections. Besifloxacin treatment resulted in robust eradication rates of these infections comparable to monobacterial infections.

Trial registration

NCT000622908, NCT00347932, NCT00348348

Treating with besifloxacin for acute bacterial conjunctivitis: a Meta-analysis

AIM

To evaluate the relative efficacy and safety of besifloxacin for treatment of acute bacterial conjunctivitis.

METHODS

A comprehensive search in PubMed, EMBASE Web of Science, Cochrane Central Database and CNKI was undertaken for randomized controlled trials (RCTs) comparing besifloxacin with other treatments or placebo. The primary outcome measures were clinical resolution, rates of bacterial eradication, individual clinical outcomes, cure rates, and bacterial eradication rates of different kinds of pathogens. Safety outcomes were the number of adverse effects (AEs). The final search was performed on August 2018.

RESULTS

Six RCTs were included. Four studies compared the efficacy and safety of besifloxacin with placebo, 1 study compared besifloxacin with moxifloxacin, and 1 study compared besifloxacin with gatifloxacin. A total of 2780 patients met the inclusion criteria. Besifloxacin presented higher efficacy and safety than did placebo in clinical resolution, rates of bacterial eradication, individual clinical outcomes, cure rates, bacterial eradication rates of different kinds of pathogens and the number of AEs. There was no significant difference between besifloxacin and moxifloxacin or gatifloxacin in the comparison items mentioned above.

CONCLUSION

Besifloxacin is highly effective and safe for treatment of acute bacterial conjunctivitis. Further comparative trials regarding the effect of besifloxacin for treatment of acute bacterial conjunctivitis will aid in treatment decisions.

Pharmacokinetics of Azithromycin, Levofloxacin, and Ofloxacin in Rabbit Extraocular Tissues After Ophthalmic Administration

INTRODUCTION

Azithromycin demonstrates high tissue distribution and prolonged elimination half-life. In this study, we monitored the pharmacokinetics of a single ophthalmic administration of 1% azithromycin ophthalmic solution containing polycarbophil in the extraocular tissues, including the eyelid, and compared it with that of two commercial ophthalmic products, 1.5% levofloxacin ophthalmic solution and 0.3% ofloxacin ophthalmic ointment.

METHODS

Rabbits were treated with either a single topical administration of 1% azithromycin ophthalmic solution, 1.5% levofloxacin ophthalmic solution, or 0.3% ofloxacin ophthalmic ointment. The eyelid, conjunctiva, and cornea were collected at 0.25, 0.5, 1, 2, 4, 8, and 24 h post-administration. Tissue samples were pretreated for drug concentration measurements by ultra-performance liquid chromatography-tandem mass spectrometry. Pharmacokinetic parameters were determined by non-compartmental analysis.

RESULTS

Azithromycin was rapidly absorbed, and its levels remained near the observed maximum concentrations for up to 24 h post-administration in all tissue. In contrast, extraocular tissue concentrations of levofloxacin and ofloxacin decreased with time. The maximum concentrations of azithromycin, levofloxacin, and ofloxacin were 35.6, 34.1, and 55.1 µg/g in the eyelid, 44.2, 46.8, and 20.4 µg/g in the conjunctiva, and 79.9, 18.0, and 2.21 µg/g in the cornea, respectively. The values of the area under the curve from 0 to 24 h after administration of azithromycin, levofloxacin, and ofloxacin were 602, 58.5, and 267 µg·h/g in the eyelid, 837, 43.2, and 51.9 µg·h/g in the conjunctiva, and 1250, 26.4, and 5.46 µg h/g in the cornea, respectively.

CONCLUSION

The drug concentrations of azithromycin and levofloxacin were relatively comparable among the extraocular tissues following topical administration of the respective ophthalmic solutions, whereas the concentrations of ofloxacin varied following dosing of its ophthalmic ointment. The slow elimination profile in any extraocular tissue of rabbits was unique to azithromycin, and led to the demonstration of high exposures of azithromycin in all extraocular tissues after ophthalmic administration.

FUNDING

This research and Rapid Service Fees were supported by Senju Pharmaceutical Co., Ltd.

An Evaluation of Staphylococci from Ocular Surface Infections Treated Empirically with Topical Besifloxacin: Antibiotic Resistance, Molecular Characteristics, and Clinical Outcomes

Introduction

Understanding antibiotic resistance and toxin profiles among staphylococcal isolates in ocular infections can aid in therapeutic management and infection prevention strategies. We evaluated in vitro antibiotic resistance patterns and molecular traits of staphylococci isolated from patients with ocular surface infections. We also report on clinical outcomes for these patients following empirical treatment with topical besifloxacin ophthalmic suspension 0.6%.

Methods

This was a small observational study. Participating investigators from three clinical sites collected an initial ocular culture from the affected eye of patients presenting with ocular surface infections with presumed staphylococcal etiology. Clinical outcome data for patients with confirmed staphylococcal infections were collated later through retrospective review of patient medical records. Staphylococcal species identification in ocular cultures, in vitro antibiotic susceptibility testing, and PCR-based determination of methicillin resistance cassettes and toxin genotypes were conducted at a central laboratory. Isolates were categorized as susceptible or resistant based on systemic breakpoints, where available.

Results

Cultures were collected from 43 patients, and staphylococcal infections were confirmed in 25 patients. Two isolates of Staphylococcus aureus and 27 isolates of Staphylococcus epidermidis were identified. Both S. aureus isolates were methicillin-susceptible, lacked the gene encoding Panton-Valentine leukocidin, and carried few enterotoxin genes. Eight (30%) S. epidermidis were methicillin-resistant (MRSE), and 10 (37%) were ciprofloxacin-resistant. All but two MRSE isolates demonstrated multidrug resistance (MDR), and the staphylococcal cassette chromosome mec (SCCmec) type IVa was detected in five of the eight MRSE isolates. Clinical resolution of the ocular surface infection was reported in all 25 patients following treatment with besifloxacin.

Conclusions

In this study, S. aureus contained few toxins, while SCCmec IVa and MDR was predominant among MRSE from ocular surface infections. Despite significant in vitro fluoroquinolone resistance, there were no cases of treatment failure with topical besifloxacin ophthalmic suspension 0.6%.

Funding

Bausch Health US, LLC.

Defining the core essential genome of Pseudomonas aeruginosa

Genomics offered the promise of transforming antibiotic discovery by revealing many new essential genes as good targets, but the results fell short of the promise. While numerous factors contributed to the disappointing yield, one factor was that essential genes for a bacterial species were often defined based on a single or limited number of strains grown under a single or limited number of in vitro laboratory conditions. In fact, the essentiality of a gene can depend on both the genetic background and growth condition. We thus developed a strategy for more rigorously defining the core essential genome of a bacterial species by studying many pathogen strains and growth conditions. We assessed how many strains must be examined to converge on a set of core essential genes for a species. We used transposon insertion sequencing (Tn-Seq) to define essential genes in nine strains of Pseudomonas aeruginosa on five different media and developed a statistical model, FiTnEss, to classify genes as essential versus nonessential across all strain-medium combinations. We defined a set of 321 core essential genes, representing 6.6% of the genome. We determined that analysis of four strains was typically sufficient in P. aeruginosa to converge on a set of core essential genes likely to be essential across the species across a wide range of conditions relevant to in vivo infection, and thus to represent attractive targets for novel drug discovery.

Infantile Acute Conjunctivitis Induced by β-Lactamase-Positive Amoxicillin-Clavulanate-Resistant Strain of Haemophilus influenzae: A Report of Three Cases

This study is a retrospectively recruited case series. We report three infants with acute conjunctivitis induced by β-lactamase–positive, ampicillin/clavulanic acid-resistant strains of Haemophilus influenzae (BLPACR). Patients with BLPACR-positive cultures were recruited from among 5,107 patients with inflammatory diseases of the ocular surface who underwent examinations, including bacterial culturing of conjunctival sac or corneal scrapings, between 2000 and 2015. Three BLPACR-positive patients were recruited, including a 10-month-old boy, a 4-month-old girl, and a 7-month-old girl. All three demonstrated BLPACR conjunctivitis. The clinical findings in these patients included fever, mucopurulent discharge, lid swelling, and conjunctival hyperemia. Samples of conjunctival swabs were obtained from all three infants, and BLPACR was isolated from all these conjunctival swabs. Antimicrobial susceptibility testing showed sensitivity to levofloxacin and resistance to ampicillin, cefaclor, and clarithromycin. We conclude that in infantile BLPACR conjunctivitis, simultaneous investigation for the determination of causative organism and antibiotic susceptibility testing are crucial aspects of the medical treatment.

Besifloxacin Ophthalmic Suspension 0.6% Compared with Gatifloxacin Ophthalmic Solution 0.3% for the Treatment of Bacterial Conjunctivitis in Neonates

Purpose

The aim of this study was to evaluate the safety and efficacy of topical besifloxacin ophthalmic suspension 0.6% compared with gatifloxacin ophthalmic solution 0.3% in the treatment of bacterial conjunctivitis in neonates.

Methods

This was a multicenter, randomized, double-masked, parallel group study. Subjects ≤31 days of age with severity grade ≥1 (scale 0–3) for both conjunctival discharge and conjunctival hyperemia were randomized to besifloxacin or gatifloxacin instilled three times daily for 7 days, and completed five study visits (three clinic visits and two phone calls). Primary endpoints included clinical resolution (absence of both conjunctival discharge and conjunctival hyperemia) at visit 5 (day 8 or 9) and ocular and non-ocular treatment-emergent adverse events (AEs). Bacterial eradication was a secondary endpoint.

Results

Thirty-three subjects were included in the intent-to-treat (ITT) population. All were aged <28 days, with a mean (standard deviation) age of 15.5 days (6.0), and 57.6% were female. Twenty-two subjects had culture-confirmed conjunctivitis in at least one eye (modified ITT [mITT] population), most often with Gram-positive bacteria. Visit 5 clinical resolution and bacterial eradication rates were comparable among besifloxacin- and gatifloxacin-treated study eyes (clinical resolution: 12/16 [75.0%] vs. 12/17 [70.6%] for the ITT population, and 11/13 [84.6%] vs. 7/9 [77.8%] for the mITT population; bacterial eradication: 12/13 [92.3%] vs. 8/9 [88.9%] for the mITT population, respectively). No AEs were reported in the besifloxacin treatment group, and AEs reported in the gatifloxacin group were considered not treatment-related.

Conclusions

In this small study in neonates, both besifloxacin and gatifloxacin appeared effective and safe in the treatment of bacterial conjunctivitis. Larger studies are warranted.

Besifloxacin: Efficacy and Safety in Treatment and Prevention of Ocular Bacterial Infections

This comprehensive review summarizes the mechanism of action, pharmacokinetics, efficacy, and safety of besifloxacin ophthalmic suspension, 0.6% and examines its role in the treatment of ocular surface bacterial infections. Besifloxacin possesses balanced activity against bacterial topoisomerase II (also called DNA gyrase) and topoisomerase IV. It has shown a low potential to select for bacterial resistance in vitro and demonstrated strong in vitro activity against many Gram-positive, Gram-negative, and anaerobic organisms, including methicillin-resistant Staphylococcus aureus and Staphylococcus epidermidis (MRSA and MRSE, respectively). Ocular pharmacokinetic studies have shown that besifloxacin achieves high, sustained concentrations in the tear fluid and conjunctiva following topical administration, with negligible systemic exposure. Large randomized, controlled clinical trials have established the efficacy and safety of besifloxacin administered three times daily for 5 days for treatment of acute bacterial conjunctivitis in both adults and children, with high rates of clinical resolution (up to more than 70% by day 5) and bacterial eradication (more than 90% by day 5), and a low incidence of adverse events. Additionally, besifloxacin applied twice daily for 3 days demonstrated greater efficacy than vehicle in treating bacterial conjunctivitis. Case reports, a large retrospective chart review, and animal studies have provided supporting evidence for the efficacy of besifloxacin in the management of acute bacterial keratitis. There is some evidence to suggest that besifloxacin may provide an advantage over other current-generation fluoroquinolones in antimicrobial prophylaxis for ocular surgery. Besifloxacin is an appropriate option for treatment of bacterial conjunctivitis, and its use in the treatment of bacterial keratitis and lid disorders, as well as for surgical prophylaxis, appears promising and warrants further evaluation.

Phenotypic, molecular characterization, antimicrobial susceptibility and draft genome sequence of Corynebacterium argentoratense strains isolated from clinical samples

During a 12-year period we isolated five Corynebacterium argentoratense strains identified by phenotypic methods, including the use of matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF) and 16S rRNA gene sequencing. In addition, antimicrobial susceptibility was determined, and genome sequencing for the detection of antibiotic resistance genes was performed. The organisms were isolated from blood and throat cultures and could be identified by all methods used. All strains were resistant to cotrimoxazole, and resistance to β-lactams was partly present. Two strains were resistant to erythromycin and clindamycin. The draft genome sequences of theses isolates revealed the presence of the erm(X) resistance gene that is embedded in the genetic structure of the transposable element Tn5423. Although rarely reported as a human pathogen, C. argentoratense can be involved in bacteraemia and probably in other infections. Our results also show that horizontal transfer of genes responsible for antibiotic resistance is occurring in this species.

Draft Genome Sequences of the Two Unrelated Macrolide-Resistant Corynebacterium argentoratense Strains CNM 463/05 and CNM 601/08, Isolated from Patients in the University Hospital of León, Spain

Corynebacterium argentoratense has been associated mainly with infections in the human respiratory tract. Genome sequencing of two unrelated clinical macrolide-resistant strains, CNM 463/05 and CNM 601/08, revealed the presence of the antibiotic resistance gene erm(X) allocated to a specific genomic region with 100% similarity to the widely distributed transposable element Tn5432.

Antibacterial efficacy of prophylactic besifloxacin 0.6% and moxifloxacin 0.5% in patients undergoing cataract surgery

Background

The purpose of this study was to investigate the ocular bacterial flora in patients scheduled to undergo cataract surgery and compare the antibacterial effects of besifloxacin ophthalmic suspension 0.6% and moxifloxacin ophthalmic solution 0.5% in these patients.

Methods

This was a prospective, randomized, laboratory-masked clinical trial. Patients received besifloxacin or moxifloxacin “quater in die” or QID (four times a day) for 3 days before cataract surgery in the surgical eye and 1 hour before surgery in the nonsurgical fellow eye. Conjunctival and eyelid swabs were obtained from both eyes at baseline and after treatment, on the day of surgery (Visit 2). Swabs were processed for bacterial colony counts (in terms of colony-forming units) and species identification. In vitro antibiotic susceptibilities of isolates were determined using Clinical and Laboratory Standards Institute breakpoints.

Results

Fifty-nine patients (n=28 besifloxacin, n=31 moxifloxacin) completed the study. The majority (73%) of conjunctival samples were culture negative at baseline. The most frequent isolates were coagulase-negative staphylococci (CoNS, 89%), specifically Staphylococcus epidermidis (72%). Both fluoroquinolones reduced the lid CFU values when administered QID for 3 days (P≤0.019), but only besifloxacin reduced the lid CFU estimate 1 hour following instillation of a single drop (P=0.039). Fewer besifloxacin-treated eyes had lids that were culture positive for CoNS at Visit 2 compared with moxifloxacin-treated eyes regardless of dosing regimen (P≤0.03). The minimum inhibitory concentration (MIC₉₀) of besifloxacin against methicillin-resistant S. epidermidis (MRSE) was eightfold lower than that of moxifloxacin.

Conclusion

Besifloxacin appeared more effective in reducing bacterial counts on eyelids of patients undergoing cataract surgery, with significant reductions as early as 1 hour postdose, compared with moxifloxacin. Besifloxacin was more active in vitro against MRSE.

The safety of besifloxacin ophthalmic suspension 0.6 % used three times daily for 7 days in the treatment of bacterial conjunctivitis

BACKGROUND

Besifloxacin ophthalmic suspension 0.6 % (Besivance(®); Bausch & Lomb, Rochester, NY, USA) was approved by the FDA in 2009 for the treatment of bacterial conjunctivitis, with a recommended 7-day dosing regimen.

OBJECTIVE

The objective of this study was to compare the safety of besifloxacin ophthalmic suspension 0.6 %, administered three times a day for 7 days, with that of its vehicle.

METHODS

This randomized, multicenter, double-masked, vehicle-controlled, parallel-group study involved 518 patients ≥1 year of age with a clinical diagnosis of bacterial conjunctivitis. Patients were randomized 2:1 to treatment with besifloxacin 0.6 % ophthalmic suspension or vehicle, one drop in the infected eye(s) TID for 7 days. Main outcomes included the incidence and types of adverse events reported by the subject or observed by the investigator at each study visit.

RESULTS

Thirty-one ocular treatment-emergent adverse events (TEAEs) were reported by 28 subjects in the study eye; 19 occurred in 17/344 (4.9 %) besifloxacin patients, and 12 occurred in 11/170 (6.5 %) vehicle patients (p = 0.5362). Only two ocular events (mild instillation site reaction, one case in each group) were considered "definitely related" to study treatment. One event of self-limited dysgeusia in the besifloxacin group was considered definitely related to treatment; there were no other nonocular TEAEs considered related to treatment. There were no serious adverse events, and other safety outcomes (visual acuity, biomicroscopy, ophthalmoscopy) were unremarkable.

CONCLUSION

These findings indicate that besifloxacin ophthalmic suspension 0.6 % is safe in patients aged 1 year and older when used TID for 7 days.

Besifloxacin ophthalmic suspension 0.6% administered twice daily for 3 days in the treatment of bacterial conjunctivitis in adults and children

BACKGROUND AND OBJECTIVE

Besifloxacin ophthalmic suspension 0.6% given thrice daily for 5 days is safe and effective in the treatment of patients with bacterial conjunctivitis. This study evaluated the safety and efficacy of besifloxacin ophthalmic suspension 0.6% administered twice daily for 3 days compared with vehicle in the treatment of bacterial conjunctivitis.

STUDY DESIGN

This was a multicenter, double-masked, randomized, vehicle-controlled, parallel-group study.

METHODS

A total of 474 patients aged ≥1 year with bacterial conjunctivitis were randomized in a 1 : 1 ratio to receive either besifloxacin ophthalmic suspension 0.6% or vehicle administered twice daily for 3 days. There were three study visits: day 1 (the baseline visit), day 4/5 (visit 2), and day 7 ± 1 (visit 3). The co-primary efficacy endpoints were bacterial eradication and clinical resolution at day 4/5 in designated study eyes of patients with culture-confirmed bacterial conjunctivitis. Secondary efficacy endpoints were bacterial eradication and clinical resolution at day 7 ± 1, individual clinical outcomes of ocular discharge and bulbar conjunctival injection at all visits; and microbial and clinical outcomes for overall bacterial species and individual Gram-positive and Gram-negative bacterial species at each follow-up visit. Safety endpoints included adverse events (AEs), changes in visual acuity and biomicroscopy findings at each visit, and changes in ophthalmoscopy findings at day 7 ± 1.

RESULTS

Bacterial eradication and clinical resolution rates were significantly higher in the besifloxacin group than in the vehicle group (115/135 [85.2%] vs 77/141 [54.6%], p < 0.001, and 89/135 [65.9%] vs 62/141 [44.0%], p < 0.001, respectively) at day 4/5. Rates of bacterial eradication continued to be significantly greater in the besifloxacin group (115/135 [85.2%] vs 91/141 [64.5%], respectively; p < 0.001) at day 7 ± 1; however, the rates of clinical resolution did not differ significantly between the groups (103/135 [76.3%] and 94/141 [66.7%], p = 0.209) at this visit. Ocular discharge and bulbar conjunctival injection at each visit were consistent with the primary outcomes. Clinical resolution and bacterial eradication with Gram-positive or Gram-negative organisms were consistent with the overall findings. All AEs in both groups were of mild or moderate severity and were considered unrelated to the treatment.

CONCLUSION

Treatment with besifloxacin ophthalmic suspension 0.6% administered twice daily for 3 days was effective and safe in adults and children with bacterial conjunctivitis.

CLINICAL TRIAL REGISTRATION

Registered at ClinicalTrials.gov as NCT00972777.

Integrated analysis of three bacterial conjunctivitis trials of besifloxacin ophthalmic suspension, 0.6%: microbiological eradication outcomes

Purpose

To assess clinical antimicrobial efficacy results obtained with besifloxacin ophthalmic suspension, 0.6%, administered three times a day (TID) for 5 days, integrated across three clinical trials of bacterial conjunctivitis and to investigate any microbiological eradication failures.

Methods

Clinical microbiological eradication data from three randomized, double-masked, parallel group studies of patients with bacterial conjunctivitis (two vehicle controlled; one active controlled with moxifloxacin ophthalmic solution, 0.5%) were integrated. All bacterial samples isolated at baseline above the species-specific threshold value were subjected to antimicrobial susceptibility testing. Samples isolated at subsequent visits were subjected to susceptibility testing and pulsed-field gel electrophoresis (PFGE) to investigate the cause of eradication failures and the potential for drug resistance development.

Results

Visit 2 (day 4 or 5) and visit 3 (day 8) overall microbiological eradication rates were 92.2% and 88.4% for besifloxacin ophthalmic suspension compared with 61.4% and 72.5% for vehicle and 91.6% and 85.7% for moxifloxacin ophthalmic solution. Visit 2 and visit 3 microbiological eradication rates for Gram-positive and Gram-negative isolates and for individual species were consistent with the overall eradication rates. The majority of observed eradication failures in any treatment group were due to the persistence of the pathogen isolated at baseline. Eradication failures in the besifloxacin treatment group were not associated with lower antimicrobial susceptibility at baseline. PFGE data showed that the majority of bacterial strains in eyes with eradication failures were identical to the strain isolated at baseline; these eradication failures were not associated with a lower antimicrobial susceptibility at the follow-up visit.

Conclusion

Treatment with besifloxacin ophthalmic suspension, 0.6%, administered TID for 5 days resulted in microbiological eradication rates that were ≥ 90% across the three clinical studies for the common pathogens of bacterial conjunctivitis. The few eradication failures were not due to fluoroquinolone resistance at baseline and/or resistance development during treatment.