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

  • Barry A. Schechter
  • John D. Sheppard
  • Christine M. SanfilippoEmail author
  • Heleen H. DeCory
  • Penny A. Asbell
Open Access
Brief Report

Abstract

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.

Keywords

Antibiotic resistance Besifloxacin Molecular characteristics Ocular surface infections Staphylococci 

Key Summary Points

Why carry out this study?

Few studies have examined antibiotic resistance profiles and genotypic characteristics of staphylococci from ocular infections in association with clinical outcome data, and, to our knowledge, none have reported on how molecular or resistance features of ocular staphylococci might correlate with the clinical efficacy of a specific antibiotic treatment.

This study evaluated in vitro antibiotic resistance patterns and molecular traits of staphylococci isolated from patients with ocular surface infections and evaluated corresponding clinical outcomes following treatment with besifloxacin ophthalmic suspension 0.6%.

What was learned from the study?

We found few toxins among Staphylococcus aureus isolates and a predominance of SCCmec IVa and multidrug resistance among methicillin-resistant Staphylococcus epidermidis isolates from these ocular surface infections, and, despite significant in vitro fluoroquinolone resistance, treatment with topical besifloxacin resulted in clinical resolution in all cases.

Multidrug resistance and SCCmec types IV/V were prevalent among community-acquired ocular methicillin-resistant Staphylococcus epidermidis isolates; however, a clear association between clinical efficacy and in vitro activity of besifloxacin could not be established in this small study.

Introduction

Staphylococci are important causative pathogens of ocular surface infections, including conjunctivitis and keratitis [1]. The prevalence of antibiotic resistance among staphylococci, especially to methicillin, is of clinical concern. Methicillin-resistant Staphylococcus aureus (MRSA) isolates were first reported in 1961 [2] and subsequently spread from hospital environments to the community [3]. Given the rapid development of resistance to multiple additional drug classes among MRSA, several studies have focused on microbiologic characterization of the staphylococcal population with respect to phenotypic and genotypic traits that may contribute to pathogenicity [4, 5, 6]. Molecular typing research, in particular, has proven useful in the understanding of staphylococcal strain epidemiology, virulence, and clonal evolution and could ultimately help design strategies for successful treatment and infection prevention in hospital and community settings [7, 8]. Among isolates of S. aureus and coagulase-negative staphylococci (CoNS, including Staphylococcus epidermidis), one such research method involves characterization of the mecA gene, which confers resistance to beta-lactam antibiotics including methicillin and is harbored within the staphylococcal cassette chromosome mec (SCCmec) element [9, 10, 11].

Historically, hospital-acquired MRSA (HA-MRSA) pathogens have been characterized as having high rates of multidrug resistance (MDR), producing few toxins, and carrying SCCmec variants I–III [12, 13]. In contrast to HA-MRSA, community-acquired MRSA (CA-MRSA) pathogens are typically not MDR, but produce high toxin levels [14] and tend to carry SCCmec variants IV–V [12, 15, 16]. Cytotoxins such as Panton-Valentine leukocidin (PVL) enhance pathogenicity [12, 15, 17], and MRSA isolates carrying SCCmec IV are known to also harbor the PVL gene [18]. Similar studies have begun to evaluate the resistance traits of methicillin-resistant S. epidermidis (MRSE) isolates from ocular infections [19, 20].

Hesje et al. previously reported on traits of 38 ocular MRSA isolates collected between 2006 and 2008 across 14 states. Of these, 22 (58%) carried SCCmec II, while the remaining 16 (42%) carried SCCmec IV [16]. Consistent with previous reports for non-ocular isolates, all SCCmec type II isolates were MDR and lacked PVL genes, traits typical of HA-MRSA, whereas the SCCmec type IV isolates demonstrated greater MDR than expected, and 25% lacked the genes encoding PVL, suggesting the criteria for classifying a MRSA isolate as either CA- or HA-MRSA may be blurring [16]. If confirmed, this trend for CA-MRSA should inform treatment choice in MRSA infections. Further data are thus needed, particularly among staphylococci from ocular surface infections where cultures are not typically collected, to gain insight into the microbiologic and molecular characteristics that contribute to the pathogenesis of these bacteria.

The current study evaluated in vitro antibiotic resistance patterns and molecular traits of staphylococci isolated from patients presenting with ocular surface infections. We also report on the corresponding clinical outcomes in these patients following empirical treatment with topical BESIVANCE® (besifloxacin ophthalmic suspension) 0.6% (Bausch + Lomb; Bridgewater, NJ, USA).

Methods

This was an observational, retrospective review of longitudinal data gathered during routine treatment of patients with staphylococcal eye infections at three investigational sites, including two community-based ophthalmology practices (Dr. Sheppard [Virginia] and Dr. Schechter [Florida]) and one hospital-based outpatient clinic (Dr. Asbell [New York]). Patients had to be 18 years of age or older and had to have a topical ocular infection with presumed staphylococcal etiology (for example, based on clinician’s observation of purulent discharge) for which besifloxacin was prescribed. Patients with a history of hypersensitivity to besifloxacin or other quinolone antibiotics, patients in an immunocompromised state at the time of initial diagnosis, and those for whom the investigator intended to treat with topical or systemic antimicrobials other than or in addition to besifloxacin were not eligible to participate. The protocol was approved by an institutional review board (Biomedical Research Alliance of New York [BRANY IRB], Lake Success, NY, USA), and the study was conducted in compliance with the Declaration of Helsinki and all of its amendments. All patients provided written informed consent.

Investigators obtained an initial ocular swab (rayon) from the affected eye of patients and submitted the swabs immediately to a central laboratory (International Health Management Associates, Inc.; Schaumburg, IL, USA) for culturing and microbiologic and molecular testing. In cases of bilateral ocular infection, the investigator designated the more severely infected eye as the study eye. If both eyes were of equal severity, the right eye was the study eye.

Immediately upon receipt by the central laboratory, swab samples were cultured on blood agar and chocolate agar plates, and semiquantitative growth ratings (1+ to 4+) were obtained by determining the number of plate quadrants with bacterial growth [21]. Bacterial isolates were identified using matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) mass spectrometry (Bruker Biotyper, Bruker Daltonics, MA, USA). Susceptibility testing was performed on staphylococcal isolates, and minimum inhibitory concentrations (MICs) were determined by broth microdilution [22] for nine classes of antibiotics: fluoroquinolones (besifloxacin, moxifloxacin, gatifloxacin, ciprofloxacin, levofloxacin, and ofloxacin), macrolides (azithromycin), aminoglycosides (tobramycin), lincosamides (clindamycin), penicillins (oxacillin), dihydrofolate reductase inhibitors (trimethoprim), amphenicols (chloramphenicol), tetracyclines (tetracycline), and glycopeptides (vancomycin). Isolates were categorized as susceptible or resistant (intermediate plus full resistance) based on systemic breakpoints, where available [23]; oxacillin was used as a surrogate for methicillin. Multidrug resistance (MDR) was categorized as resistance to ≥ 3 antibiotic classes. Isolates of S. aureus and S. epidermidis underwent DNA extraction (QIAcube, QIAGEN Inc., CA, USA), and any methicillin-resistant strains were examined by PCR for mecA and SCCmec subtype as described previously [24] using S. aureus specific primers. Isolates of S. aureus were also examined for PVL genes [25] as well as the toxic shock syndrome toxin (TSST) gene, 6 staphylococcal enterotoxins (SEs) genes, and 15 SE-like toxin genes [26] as described in the referenced PCR methods.

Demographic and clinical outcome data were obtained retrospectively through review of medical records for those patients with laboratory-confirmed staphylococcal infections. Data collected included demographic data (patient age, gender, initial diagnosis, relevant medical/ocular history), dosage and duration of treatment with besifloxacin, ocular signs and symptoms, visual acuity at baseline and follow-up visits, as well as any adverse events (AEs) during treatment. Clinical resolution of the baseline infection was based on investigator judgment. Before and after ocular photographs were obtained at clinic visits when permitted by patients.

Descriptive statistics were used to summarize demographic variables. Microbiologic results were presented for individual subjects.

Results

Ocular cultures were obtained from 43 patients at three investigational sites. Culturing of ocular samples from eight of these patients either produced no growth or were negative for staphylococci. Of 35 patients with suspected staphylococcal infections, 10 were excluded for various reasons including treatment noncompliance (n = 1), no documentation of besifloxacin treatment (n = 1), lack of follow-up (n = 1), or having an infection other than at the ocular surface (i.e., blepharitis, n = 7).

A total of 25 patients (13 men, 12 women) had staphylococci isolated from ocular surface infections, were treated with topical besifloxacin, and subsequently had their medical records reviewed, including 5 patients with conjunctivitis and 20 patients with blepharoconjunctivitis; all 25 were treated at community-based practices. The mean (SD) age of these patients was 80.5 (11.0) years, with ages ranging from 45 to 92 years; all but two patients were between the ages of 72–92 years. Eight patients had relevant comorbid conditions, including diabetes (n = 4), glaucoma (n = 2), glaucoma with hypertension (n = 1), and lymphoma (n = 1), and 19 had previous cataract surgical procedures. At baseline, 24 of the 25 patients had mild-to-moderate bulbar erythema, while severe discharge was noted in eight patients.

Culturing and analysis of ocular swabs from the 25 included patients resulted in the identification of 73 bacterial isolates, 40 of which were unique staphylococci including S. aureus (n = 2), S. epidermidis (n = 27), S. hominis (n = 1), S. warneri (n = 2), S. lugdunensis (n = 2), S. haemolyticus (n = 4), S. caprae (n = 1), and S. schleiferi (n = 1). Table 1 presents the comparative MICs of fluoroquinolones for each isolate by patient. Newer fluoroquinolones (besifloxacin, moxifloxacin, and gatifloxacin) generally had lower MICs compared with older fluoroquinolones (ciprofloxacin, levofloxacin, and ofloxacin). The MIC that inhibited 90% of isolates, or MIC90, was 0.5 µg/ml for besifloxacin, 1 µg/ml for moxifloxacin, 2 µg/ml for gatifloxacin, 4 µg/ml for levofloxacin, and 16 µg/ml for both ciprofloxacin and ofloxacin. For the majority of isolates, besifloxacin had the lowest in vitro MICs among the tested fluoroquinolones, either equal to or often below that of moxifloxacin. With few exceptions, besifloxacin MICs were 2- to 16-fold lower than those for moxifloxacin and up to 128-fold lower for other fluoroquinolones when isolates exhibited resistance to ciprofloxacin (MIC ≥ 2 µg/ml).
Table 1

All isolated staphylococcal organisms and in vitro fluoroquinolone susceptibilities

Swab ID

Pt age

Diagnosis

Staphylococcal organisms present

Growth rating

MIC (µg/ml)

Additional organisms present

BES

MXF

GAT

CIP

LVX

OFL

15196

74

Conjunctivitis

S. epidermidis

1+

4

64

64

64

256

256

None

S. hominis

1+

0.03

0.015

0.03

0.06

0.06

0.25

15199

81

Conjunctivitis

S. epidermidis (1)

1+

0.25

1

2

8

4

8

Corynebacterium bovis

S. epidermidis (2)

1+

0.03

0.06

0.12

1

0.25

0.5

15200

78

Blepharoconjunctivitis

S. epidermidis

1+

0.03

0.03

0.06

0.5

0.25

0.5

Actinomyces turicensis

Klebsiella oxytoca

Proteus mirabilis

Trueperella bernardiae

15202

78

Acute conjunctivitis

S. epidermidis

1+

0.03

0.008

0.06

0.25

0.12

0.25

Corynebacterium macginleyi

Corynebacterium striatum

Streptococcus oralis

15203

45

Blepharoconjunctivitis

S. epidermidis

1+

0.03

0.03

0.12

0.5

0.25

0.5

Cutibacterium acnes

S. warneri

1+

0.03

0.03

0.06

0.25

0.25

0.25

15204

75

Blepharoconjunctivitis

S. epidermidis

1+

2

32

32

64

128

256

Corynebacterium macginleyi

Pantoea septica

15206

75

Blepharoconjunctivitis

S. epidermidis

2+

0.03

0.06

0.12

1

0.25

0.5

Corynebacterium accolans

S. lugdunensis

1+

0.03

0.06

0.12

0.5

0.25

0.5

15207

91

Blepharoconjunctivitis

S. epidermidis

1+

0.03

0.03

0.06

0.25

0.25

0.25

None

S. haemolyticus

1+

1

4

8

128

32

64

15208

91

Blepharoconjunctivitis

S. epidermidis

1+

0.03

0.06

0.12

0.5

0.25

0.5

Bacillus cereus

Bacillus thuringiensis

Corynebacterium macginleyi

Corynebacterium propinquum

Moraxella catarrhalis

15211

81

Blepharoconjunctivitis

S. epidermidis (1)

2+

0.03

0.03

0.06

0.25

0.25

0.25

None

S. epidermidis (2)

2+

0.03

0.03

0.06

0.25

0.25

0.25

15212

83

Blepharoconjunctivitis

S. haemolyticus

1+

0.03

0.008

0.06

0.25

0.12

0.25

Corynebacterium macginleyi

15596

86

Conjunctivitis

S. warneri

1+

0.06

0.06

0.12

0.25

0.25

0.5

None

S. epidermidis

1+

0.03

0.03

0.06

0.25

0.25

0.25

19313

56

Blepharoconjunctivitis

S. epidermidis

2+

0.06

0.12

0.25

2

1

1

None

19314

78

Blepharoconjunctivitis

S. epidermidis

1+

0.03

0.008

0.06

0.25

0.12

0.25

Acinetobacter pitii

Chryseobacterium gleum

19315

91

Conjunctivitis

S. epidermidis

1+

0.03

0.06

0.12

0.5

0.25

0.5

Rothia (non-speciated)

19316

78

Blepharoconjunctivitis

S. epidermidis (1)

2+

0.25

0.5

2

4

4

8

None

S. epidermidis (2)

1+

0.25

0.5

2

4

4

8

19317

85

Blepharoconjunctivitis

S. epidermidis

1+

0.03

0.03

0.12

0.25

0.25

0.25

Bacillus (non-speciated)

Rothia mucilaginosa

Streptococcus (alpha-hemolytic)

19318

82

Blepharoconjunctivitis

S. haemolyticus

1+

0.03

0.008

0.06

0.25

0.12

0.25

Corynebacterium macginleyi

Corynebacterium pseudodiphtheriticum

S. epidermidis

2+

0.03

0.06

0.06

0.25

0.12

0.25

19319

92

Blepharoconjunctivitis

S. epidermidis

2+

0.5

1

2

16

8

16

Corynebacterium bovis

S. haemolyticus

1+

0.03

0.008

0.06

0.25

0.12

0.25

19320

90

Blepharoconjunctivitis

S. aureus

1+

0.015

0.008

0.06

0.5

0.25

0.25

None

S. lugdunensis

1+

0.06

0.06

0.12

0.25

0.25

0.5

S. epidermidis

1+

0.25

0.25

2

8

4

8

19321

72

Blepharoconjunctivitis

S. epidermidis

1+

0.03

0.03

0.12

0.25

0.25

0.5

Corynebacterium pseudodiphtheriticum

S. caprae

1+

0.5

0.06

2

16

0.25

16

19322

89

Blepharoconjunctivitis

S. epidermidis

1+

0.25

1

2

8

4

8

Corynebacterium amycolatum

S. schleiferi

1+

0.06

0.06

0.12

0.5

0.25

0.5

20032

86

Blepharoconjunctivitis

S. aureus

1+

0.015

0.008

0.06

0.5

0.25

0.25

Corynebacterium macginleyi

20033

91

Blepharoconjunctivitis

S. epidermidis

1+

0.25

1

2

4

4

8

Bacillus cereus

20034

85

Blepharoconjunctivitis

S. epidermidis (1)

1+

0.015

0.008

0.06

0.25

0.12

0.25

Coriobacterium (non-speciated)

Streptococcus (alpha-hemolytic)

S. epidermidis (2)

1+

0.03

0.06

0.12

0.5

0.25

0.5

BES besifloxacin, MXF moxifloxacin, GAT gatifloxacin, CIP ciprofloxacin, LVX levofloxacin, OFL ofloxacin

Overall, 2 isolates of S. aureus and 27 isolates of S. epidermidis were identified from 24 patients. Both isolates of S. aureus were methicillin-susceptible Staphylococcus aureus (MSSA) and susceptible to all antibiotic classes tested (Table 2). The 2 MSSA isolates lacked the PVL gene and carried at maximum only 2 of the 22 tested enterotoxin genes. Of the 27 S. epidermidis isolates, 10 (37%), 13 (48%), and 8 (30%) were resistant to ciprofloxacin, azithromycin, and oxacillin/methicillin, respectively; resistance to trimethoprim and tobramycin was also noted (19% for each). All isolates were susceptible to vancomycin, with MICs of either 1 µg/ml or 2 µg/ml. Of the eight MRSE, five carried SCCmec type IVa, one carried SCCmec type V, and two isolates contained un-typeable SCCmec variants. Multidrug resistance was observed in eight S. epidermidis isolates (30%), whereas six of eight (75%) MRSE demonstrated MDR.
Table 2

In vitro susceptibility profiles and molecular characteristics of Staphylococcus aureus and Staphylococcus epidermidis isolates

Swab ID

Resistance profile

Molecular characteristics

CIP

AZI

CHL

CLI

TET

TOB

TMP

VAN

OXA

MDR

mecA

SCCmec type

PVL

Toxins

S. aureus

19320

S

S

S

S

S

S

S

S

S

No

Neg

 

Neg

SE-like L

20032

S

S

S

S

S

S

S

S

S

No

Neg

 

Neg

SEA, SE-like X

S. epidermidis

15196

R

R

S

R

S

R

R

S

R

Yes

Pos

IVa

  

15199

R

S

S

I

S

S

S

S

R

Yes

Pos

IVa

  

15199

S

S

S

S

S

S

S

S

S

No

    

15200

S

S

S

S

S

R

S

S

S

No

    

15202

S

S

S

S

S

S

S

S

S

No

    

15203

S

R

S

S

I

S

S

S

S

No

    

15204

R

R

S

R

S

S

S

S

S

Yes

    

15206

S

S

S

S

S

S

S

S

S

No

    

15207

S

R

S

S

S

S

R

S

R

Yes

Pos

Un-typeable

  

15208

S

S

S

S

S

S

S

S

S

No

    

15211

S

S

S

I

S

S

R

S

S

No

    

15211

S

S

S

S

S

S

S

S

S

No

    

15596

S

S

S

S

S

S

S

S

S

No

    

19313

I

R

S

S

R

R

S

S

R

Yes

Pos

IVa

  

19314

S

S

S

S

S

S

S

S

S

No

    

19315

S

R

S

S

S

S

S

S

S

No

    

19316

R

S

S

S

S

S

S

S

R

No

Pos

IVa

  

19316

R

R

S

S

S

R

S

S

R

Yes

Pos

IVa

  

19317

S

R

S

I

S

S

S

S

S

No

    

19318

S

R

S

S

S

S

S

S

S

No

    

19319

R

R

S

S

S

S

R

S

S

Yes

    

19320

R

R

S

S

S

S

S

S

S

No

    

19321

S

R

S

S

S

S

S

S

S

No

    

19322

R

S

S

S

R

R

R

S

R

Yes

Pos

V

  

20033

R

S

S

S

S

S

S

S

R

No

Pos

Un-typeable

  

20034

S

S

S

S

S

S

S

S

S

No

    

20034

S

R

S

R

S

S

S

S

S

No

    

CIP ciprofloxacin, AZI azithromycin, CHL chloramphenicol, CLI clindamycin, TET tetracycline, TOB tobramycin, TMP trimethoprim, VAN vancomycin, OXA oxacillin, MDR multidrug resistance (to ≥ 3 antibiotic classes), S susceptible, I intermediate, R resistant, Pos positive, Neg negative

Daily dosing with topical besifloxacin ranged from 2 to 4 doses per day (1 drop per dose), while besifloxacin treatment duration ranged from 7 to 14 days. The follow-up clinic visit occurred 6–21 days (mean of 11) after initiation of besifloxacin therapy. Clinical resolution of the ocular surface infections was reported for all 25 patients at follow-up. All signs/symptoms were absent at follow-up with few exceptions (mild discharge in one patient; superficial punctate keratitis in another). Visual acuity findings were unremarkable at either baseline or follow-up, and there were no AEs reported for any patient during besifloxacin treatment. Notably, eight patients reported relief of ocular signs/symptoms as early as 1–2 days and 14 as early as 3–4 days, following treatment initiation. Representative photographs of patient eyes prior to and following treatment with besifloxacin are shown in Fig. 1.
Fig. 1

Photographs from representative eyes with staphylococcal ocular surface infections before (a, c) and after (b, d) besifloxacin treatment

Discussion

The current study was undertaken to evaluate in vitro antibiotic resistance patterns and molecular traits of staphylococci isolated from patients presenting with ocular surface infections and to report on clinical outcomes following treatment with besifloxacin ophthalmic suspension 0.6%. Pending results, a secondary objective was to begin to formulate an ocular breakpoint for this fluoroquinolone. To date, few studies have examined antibiotic resistance profiles and genotypic characteristics of staphylococci from ocular infections in association with clinical outcome data [27, 28, 29], and to our knowledge, none have reported on how molecular or resistance features of ocular staphylococci might correlate with the clinical efficacy of a specific antibiotic treatment.

Of the 40 staphylococci collected at baseline from 25 patients with either conjunctivitis or blepharoconjunctivitis, only 2 were identified as S. aureus. The low number of S. aureus isolates was surprising but probably a consequence of the small sample size. Neither of the isolates was methicillin-resistant, and both produced few toxins, which is encouraging. In contrast, approximately one-third of S. epidermidis isolates were MRSE, and all but two MRSE were also MDR. This finding is consistent with data obtained in the Antibiotic Resistance Monitoring in Ocular micRoorganisms (ARMOR) study, an ongoing surveillance program specific to ocular bacterial pathogens, which reported that approximately three-quarters of MRSA and methicillin-resistant CoNS (MRCoNS) isolates were MDR whether considering all ocular isolates regardless of anatomical source [30] or conjunctival isolates [31]. Similarly, in vitro fluoroquinolone (ciprofloxacin) resistance rates observed among S. epidermidis isolates in the current study (37%) are also consistent with those reported in ARMOR (~ 30%), with newer fluoroquinolones having lower MICs within the class [30, 31].

Despite evidence of in vitro fluoroquinolone resistance, treatment of patients with topical besifloxacin resulted in clinical resolution of the baseline infection in all 25 patients by the follow-up visit. While these results were welcomed, they, however, precluded the possibility of defining an ocular breakpoint for this drug. Besifloxacin is a fluoroquinolone with structural modifications intended to increase its inhibition of bacterial DNA gyrase and topoisomerase IV [32] and has been reported to be highly bactericidal with broad-spectrum activity against a range of bacterial pathogens, including drug-resistant pathogens [33, 34, 35, 36]. The clinical outcomes in this study attest to the efficacy of this chlorinated fluoroquinolone necessary for empiric use and confirm findings from prospective studies specific to bacterial conjunctivitis [37, 38, 39]. Importantly, this is the first report of besifloxacin efficacy in blepharoconjunctivitis, although randomized, vehicle-controlled, clinical trials are needed to confirm these observations. More than half of patients were infected with two or more species or strains of staphylococcal species in this study, and other bacterial species in addition to staphylococcal species were recovered from nearly three quarters of patients (18/25). Thus, in this study besifloxacin also demonstrated efficacy in mixed pathogen or polybacterial infections.

Recent publications suggest that resistance and virulence may be converging and that SCCmec types associated with community-acquired staphylococci are now exhibiting increased antibiotic resistance [16, 19, 20, 28, 40, 41, 42]. Despite the predominance of SCCmec types IV/V among MRSE in the current study (n = 6), nearly all (83%) showed MDR. These findings are consistent with those from an analysis of 30 MRSE isolates from ocular infections in Sao Paulo, Brazil, which found that of 17 isolates containing SCCmec IV/V, at least 70% were MDR [19]. Similarly, Jena et al. examined the molecular traits of 52 ocular Sepidermidis isolates (23 from infections and 29 from asymptomatic healthy conjunctiva) in India and determined that all isolates containing SCCmec IV/V (10 from infections; 11 from healthy conjunctiva) were MDR [20]. Consistent with results reported from health-care settings, an analysis of 643 staphylococci isolated from environmental samples in a community in the UK found that of 46 CoNS isolates for which SCCmec types were determined, 18 were type IV/V, and 16 of these demonstrated resistance to 3 or more antibiotics [40].

While findings for MRSE do not inform on convergence of virulence and resistance in MRSA, there is an increasing recognition that MRCoNS may play a role in the pathogenesis of community-acquired infections [40, 43] since it is thought that CoNS may be an important reservoir of resistance genes for S. aureus [10, 42, 44]. This hypothesis is based in part on the greater prevalence of methicillin resistance among S. epidermidis relative to S. aureus isolates [30, 42, 44] and the reporting of in vivo transfer of SCCmec from S. epidermidis to S. aureus [45], notwithstanding that CoNS and S. aureus co-colonize and/or commonly coinfect the ocular surface [46, 47, 48]. The transfer of antimicrobial resistance genes across staphylococcal species [11, 44] represents one potential mechanism underlying the rapid spread of antimicrobial resistance into the community and may be a factor contributing to the high proportion of MDR observed among SCCmec type IV MRCoNS in the current study. To what degree polymicrobial infections contribute to or result from this phenomenon is another interesting area of research.

Our study is limited by the small sample size and the very few S. aureus isolates obtained, thereby limiting any inferences as to whether resistance and virulence may be converging among ocular MRSA. While there was some geographic diversity among the three study sites, all were in the eastern part of the US, and only two of the sites had patients with confirmed staphylococcal ocular surface infections. Furthermore, since almost all patients were 72 years of age or older, the results may simply reflect real-world pathology of ocular surface infections in this age group. Systemic breakpoints were used to interpret in vitro susceptibility/resistance of antibiotics other than besifloxacin, which is of limited value for determining clinical antibiotic resistance given the expected achievable drug concentrations in the eye. Finally, there were no cases of treatment failure with besifloxacin precluding the possibility of beginning to formulate an ocular breakpoint for this drug.

Conclusions

The findings of this small observational study found few toxins among S. aureus isolates and a predominance of SCCmec IVa and MDR among MRSE isolates from ocular surface infections obtained at community-based practices. Future studies with larger numbers of S. aureus and MRSA isolates from a more diverse patient population, including from patients with hospital-acquired infections, could further our knowledge of the comparative molecular traits of MRSA and MRCoNS from ocular surface infections and inform on any potential convergence of resistance and virulence among MRSA. Finally, besifloxacin appeared effective in this study of staphylococcal infections with no cases of treatment failure and no AEs.

Notes

Acknowledgements

The authors thank the study participant(s) for their involvement in the study.

Funding

This study and the journal’s Rapid Services and Fees was funded by Bausch Health US, LLC.

Medical Editing/Writing Assistance

The authors acknowledge the writing assistance of Sandra Westra, PharmD, of Churchill Communications (Maplewood, NJ), funded by Bausch Health US, LLC.

Authorship

All named authors meet the International Committee of Medical Journal Editors (ICMJE) criteria for authorship for this article, take responsibility for the integrity of the work as a whole, and have given their approval for this version to be published.

Disclosures

All investigators (Barry Schechter, John D. Sheppard, and Penny A. Asbell) received honoraria (funded by Bausch Health US, LLC) for participation in the current study. Barry Schechter has received speaker fees from Bausch Health US, LLC. John D. Sheppard has received grants and advisory board/consultancy fees from Bausch Health US, LLC. Penny A. Asbell has received grants and advisory board/consultancy fees from Bausch Health US, LLC. Heleen H. DeCory is an employee of Bausch Health US, LLC. Christine M. Sanfilippo is an employee of Bausch Health US, LLC. The authors report no other conflicts of interest in this work.

Compliance with Ethics Guidelines

The protocol was approved by an institutional review board (Biomedical Research Alliance of New York [BRANY IRB], Lake Success, NY), and the study was conducted in compliance with the Declaration of Helsinki and all of its amendments. All patients provided written informed consent.

Data Availability

The datasets generated during and/or analyzed during the current study are available from the corresponding author on reasonable request.

Open Access

This article is distributed under the terms of the Creative Commons Attribution-NonCommercial 4.0 International License (http://creativecommons.org/licenses/by-nc/4.0/), which permits any noncommercial use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made.

References

  1. 1.
    O’Callaghan RJ. The pathogenesis of Staphylococcus aureus eye Infections. Pathogens. 2018;7(1):E9.PubMedCrossRefPubMedCentralGoogle Scholar
  2. 2.
    Jevons MP. “Celbenin”-resistant Staphylococci. Br Med J. 1961;1(5219):124–5.PubMedCentralCrossRefGoogle Scholar
  3. 3.
    Chambers HF. The changing epidemiology of staphylococcus aureus? Emerg Infect Dis. 2001;7(2):178–82.PubMedPubMedCentralCrossRefGoogle Scholar
  4. 4.
    Harada D, Nakaminami H, Miyajima E, et al. Change in genotype of methicillin-resistant Staphylococcus aureus (MRSA) affects the antibiogram of hospital-acquired MRSA. J Infect Chemother. 2018;24(7):563–9.PubMedCrossRefPubMedCentralGoogle Scholar
  5. 5.
    Chen SY, Liao CH, Wang JL, et al. Methicillin-resistant Staphylococcus aureus (MRSA) staphylococcal cassette chromosome mec genotype effects outcomes of patients with healthcare-associated MRSA bacteremia independently of vancomycin minimum inhibitory concentration. Clin Infect Dis. 2012;55(10):1329–37.PubMedCrossRefPubMedCentralGoogle Scholar
  6. 6.
    Kempker RR, Farley MM, Ladson JL, Satola S, Ray SM. Association of methicillin-resistant Staphylococcus aureus (MRSA) USA300 genotype with mortality in MRSA bacteremia. J Infect. 2010;61(5):372–81.PubMedPubMedCentralCrossRefGoogle Scholar
  7. 7.
    Goudarzi M, Seyedjavadi SS, Nasiri MJ, et al. Molecular characteristics of methicillin-resistant Staphylococcus aureus (MRSA) strains isolated from patients with bacteremia based on MLST, SCCmec, spa, and agr locus types analysis. Microb Pathog. 2017;104:328–35.PubMedCrossRefPubMedCentralGoogle Scholar
  8. 8.
    Hesari MR, Salehzadeh A, Darsanaki RK. Prevalence and molecular typing of methicillin-resistant Staphylococcus aureus carrying Panton-Valentine leukocidin gene. Acta Microbiol Immunol Hung. 2018;65(1):93–106.PubMedCrossRefPubMedCentralGoogle Scholar
  9. 9.
    Petinaki E, Arvaniti A, Dimitracopoulos G, Spiliopoulou I. Detection of mecA, mecR1 and mecI genes among clinical isolates of methicillin-resistant staphylococci by combined polymerase chain reactions. J Antimicrob Chemother. 2001;47(3):297–304.PubMedCrossRefPubMedCentralGoogle Scholar
  10. 10.
    Wielders CL, Fluit AC, Brisse S, Verhoef J, Schmitz FJ. mecA gene is widely disseminated in Staphylococcus aureus population. J Clin Microbiol. 2002;40(11):3970–5.PubMedPubMedCentralCrossRefGoogle Scholar
  11. 11.
    Hanssen AM, Kjeldsen G, Sollid JU. Local variants of Staphylococcal cassette chromosome mec in sporadic methicillin-resistant Staphylococcus aureus and methicillin-resistant coagulase-negative Staphylococci: evidence of horizontal gene transfer? Antimicrob Agents Chemother. 2004;48(1):285–96.PubMedPubMedCentralCrossRefGoogle Scholar
  12. 12.
    Naimi TS, LeDell KH, Como-Sabetti K, et al. Comparison of community- and health care-associated methicillin-resistant Staphylococcus aureus infection. JAMA. 2003;290(22):2976–84.PubMedCrossRefPubMedCentralGoogle Scholar
  13. 13.
    Deurenberg RH, Stobberingh EE. The molecular evolution of hospital- and community-associated methicillin-resistant Staphylococcus aureus. Curr Mol Med. 2009;9(2):100–15.PubMedCrossRefPubMedCentralGoogle Scholar
  14. 14.
    Tsuji BT, Rybak MJ, Cheung CM, Amjad M, Kaatz GW. Community- and health care-associated methicillin-resistant Staphylococcus aureus: a comparison of molecular epidemiology and antimicrobial activities of various agents. Diagn Microbiol Infect Dis. 2007;58(1):41–7.PubMedCrossRefGoogle Scholar
  15. 15.
    Vandenesch F, Naimi T, Enright MC, et al. Community-acquired methicillin-resistant Staphylococcus aureus carrying Panton-Valentine leukocidin genes: worldwide emergence. Emerg Infect Dis. 2003;9(8):978–84.PubMedPubMedCentralCrossRefGoogle Scholar
  16. 16.
    Hesje CK, Sanfilippo CM, Haas W, Morris TW. Molecular epidemiology of methicillin-resistant and methicillin-susceptible Staphylococcus aureus isolated from the eye. Curr Eye Res. 2011;36(2):94–102.PubMedCrossRefPubMedCentralGoogle Scholar
  17. 17.
    Lo WT, Wang CC. Panton-Valentine leukocidin in the pathogenesis of community-associated methicillin-resistant Staphylococcus aureus infection. Pediatr Neonatol. 2011;52(2):59–65.PubMedCrossRefPubMedCentralGoogle Scholar
  18. 18.
    Kilic A, Li H, Stratton CW, Tang YW. Antimicrobial susceptibility patterns and staphylococcal cassette chromosome mec types of, as well as Panton-Valentine leukocidin occurrence among, methicillin-resistant Staphylococcus aureus isolates from children and adults in middle Tennessee. J Clin Microbiol. 2006;44(12):4436–40.PubMedPubMedCentralCrossRefGoogle Scholar
  19. 19.
    Bispo PJ, Hofling-Lima AL, Pignatari AC. Characterization of ocular methicillin-resistant Staphylococcus epidermidis isolates belonging predominantly to clonal complex 2 subcluster II. J Clin Microbiol. 2014;52(5):1412–7.PubMedPubMedCentralCrossRefGoogle Scholar
  20. 20.
    Jena S, Panda S, Nayak KC, Singh DV. Identification of major sequence types among multidrug-resistant Staphylococcus epidermidis strains isolated from infected eyes and healthy conjunctiva. Front Microbiol. 2017;8:1430.PubMedPubMedCentralCrossRefGoogle Scholar
  21. 21.
    Garcia LS. Clinical microbiology procedures handbook. 3rd ed. Washington, DC: ASM Press; American Society for Microbiology; 2014.Google Scholar
  22. 22.
    CLSI. Methods for dilution antimicrobial susceptibility tests for bacteria that grow aerobically: approved standard. 10th ed. CLSI document M7-A10. Wayne: Clinical and Laboratory Standards Institute; 2015.Google Scholar
  23. 23.
    CLSI. Performance standards for antimicrobial susceptibility testing. 27th ed. CLSI supplement M100. Wayne: Clinical and Laboratory Standards Institute; 2017.Google Scholar
  24. 24.
    Zhang K, McClure JA, Conly JM. Enhanced multiplex PCR assay for typing of staphylococcal cassette chromosome mec types I to V in methicillin-resistant Staphylococcus aureus. Mol Cell Probes. 2012;26(5):218–21.PubMedCrossRefPubMedCentralGoogle Scholar
  25. 25.
    Lina G, Piémont Y, Godail-Gamot F, et al. Involvement of panton-valentine leukocidin-producing Staphylococcus aureus in primary skin infections and pneumonia. Clin Infect Dis. 1999;29(5):1128–32.PubMedCrossRefPubMedCentralGoogle Scholar
  26. 26.
    Salgado-Pabón W, Case-Cook LC, Schlievert PM. Molecular analysis of staphylococcal superantigens. In: Ji Y, editor. Methicillin-resistant Staphylococcus aureus (MRSA) protocols. Methods in molecular biology (methods and protocols), vol. 1085. Totowa: Humana Press; 2014.Google Scholar
  27. 27.
    Sueke H, Shankar J, Neal T, et al. lukSF-PV in Staphylococcus aureus keratitis isolates and association with clinical outcome. Invest Ophthalmol Vis Sci. 2013;54(5):3410–6.PubMedCrossRefPubMedCentralGoogle Scholar
  28. 28.
    Kang YC, Hsiao CH, Yeh LK, et al. Methicillin-resistant staphylococcus aureus ocular infection in Taiwan: clinical features, genotying, and antibiotic susceptibility. Medicine (Baltimore). 2015;94(42):e1620.PubMedPubMedCentralCrossRefGoogle Scholar
  29. 29.
    Hsiao CH, Ong SJ, Chuang CC, Ma DH, Huang YC. A comparison of clinical features between community-associated and healthcare-associated methicillin-resistant Staphylococcus aureus keratitis. J Ophthalmol. 2015;2015:923941.PubMedPubMedCentralGoogle Scholar
  30. 30.
    Thomas RK, Melton R, Asbell PA. Antibiotic resistance among ocular pathogens: current trends from the ARMOR surveillance study (2009–2016). Clin Optom (Auckl). 2019;11:12–26.Google Scholar
  31. 31.
    Asbell PA, DeCory HH. Antibiotic resistance among bacterial conjunctival pathogens collected in the Antibiotic Resistance Monitoring in Ocular Microorganisms (ARMOR) surveillance study. PLoS One. 2018;13(10):e0205814.PubMedPubMedCentralCrossRefGoogle Scholar
  32. 32.
    Cambau E, Matrat S, Pan XS, et al. Target specificity of the new fluoroquinolone besifloxacin in Streptococcus pneumoniae, Staphylococcus aureus and Escherichia coli. J Antimicrob Chemother. 2009;63(3):443–50.PubMedCrossRefPubMedCentralGoogle Scholar
  33. 33.
    Haas W, Pillar CM, Zurenko GE, et al. Besifloxacin, a novel fluoroquinolone, has broad-spectrum in vitro activity against aerobic and anaerobic bacteria. Antimicrob Agents Chemother. 2009;53(8):3552–60.PubMedPubMedCentralCrossRefGoogle Scholar
  34. 34.
    Haas W, Pillar CM, Hesje CK, Sanfilippo CM, Morris TW. Bactericidal activity of besifloxacin against staphylococci, Streptococcus pneumoniae and Haemophilus influenzae. J Antimicrob Chemother. 2010;65(7):1441–7.PubMedPubMedCentralCrossRefGoogle Scholar
  35. 35.
    Haas W, Gearinger LS, Usner DW, Decory HH, Morris TW. Integrated analysis of three bacterial conjunctivitis trials of besifloxacin ophthalmic suspension, 0.6%: etiology of bacterial conjunctivitis and antibacterial susceptibility profile. Clin Ophthalmol. 2011;5:1369–79.PubMedPubMedCentralGoogle Scholar
  36. 36.
    Miller D, Chang JS, Flynn HW, Alfonso EC. Comparative in vitro susceptibility of besifloxacin and seven comparators against ciprofloxacin- and methicillin-susceptible/nonsusceptible staphylococci. J Ocul Pharmacol Ther. 2013;29(3):339–44.PubMedCrossRefPubMedCentralGoogle Scholar
  37. 37.
    Karpecki P, Depaolis M, Hunter JA, et al. Besifloxacin ophthalmic suspension 0.6% in patients with bacterial conjunctivitis: a multicenter, prospective, randomized, double-masked, vehicle-controlled, 5-day efficacy and safety study. Clin Ther. 2009;31(3):514–26.PubMedCrossRefPubMedCentralGoogle Scholar
  38. 38.
    Tepedino ME, Heller WH, Usner DW, et al. Phase III efficacy and safety study of besifloxacin ophthalmic suspension 0.6% in the treatment of bacterial conjunctivitis. Curr Med Res Opin. 2009;25(5):1159–69.PubMedCrossRefPubMedCentralGoogle Scholar
  39. 39.
    McDonald MB, Protzko EE, Brunner LS, et al. Efficacy and safety of besifloxacin ophthalmic suspension 0.6% compared with moxifloxacin ophthalmic solution 0.5% for treating bacterial conjunctivitis. Ophthalmology. 2009;116(9):1615–23.PubMedCrossRefPubMedCentralGoogle Scholar
  40. 40.
    Xu Z, Shah HN, Misra R, et al. The prevalence, antibiotic resistance and mecA characterization of coagulase negative staphylococci recovered from non-healthcare settings in London, UK. Antimicrob Resist Infect Control. 2018;7:73.PubMedPubMedCentralCrossRefGoogle Scholar
  41. 41.
    Wurster JI, Bispo PJM, Van Tyne D, et al. Staphylococcus aureus from ocular and otolaryngology infections are frequently resistant to clinically important antibiotics and are associated with lineages of community and hospital origins. PLoS One. 2018;13(12):e0208518.PubMedPubMedCentralCrossRefGoogle Scholar
  42. 42.
    Saber H, Jasni AS, Jamaluddin TZMT, Ibrahim R. A review of staphylococcal cassette chromosome mec (SCCmec) types in coagulase-negative Staphylococci (CoNS) species. Malays J Med Sci. 2017;24(5):7–18.PubMedPubMedCentralGoogle Scholar
  43. 43.
    Barbier F, Ruppé E, Hernandez D, et al. Methicillin-resistant coagulase-negative staphylococci in the community: high homology of SCCmec IVa between Staphylococcus epidermidis and major clones of methicillin-resistant Staphylococcus aureus. J Infect Dis. 2010;202(2):270–81.PubMedCrossRefPubMedCentralGoogle Scholar
  44. 44.
    Hanssen AM, Ericson Sollid JU. SCCmec in staphylococci: genes on the move. FEMS Immunol Med Microbiol. 2006;46(1):8–20.PubMedCrossRefPubMedCentralGoogle Scholar
  45. 45.
    Wielders CLC, Vriens MR, Brisse S, et al. In-vivo transfer of mecA DNA to Staphylococcus aureus [corrected]. Lancet. 2001;357(9269):1674–5.PubMedCrossRefPubMedCentralGoogle Scholar
  46. 46.
    Blondeau JM, Sanfilippo CM, DeCory HH. Incidence of polybacterial infections in three bacterial conjunctivitis studies and outcomes with besifloxacin ophthalmic suspension 0.6%. In: Presented at the annual meeting of the Association for Research in Vision and Ophthalmology. Vancouver, Canada, April 28–May 3, 2019.Google Scholar
  47. 47.
    Willcox MD. Characterization of the normal microbiota of the ocular surface. Exp Eye Res. 2013;117:99–105.PubMedCrossRefPubMedCentralGoogle Scholar
  48. 48.
    Iwalokun BA, Oluwadun A, Akinsinde KA, Niemogha MT, Nwaokorie FO. Bacteriologic and plasmid analysis of etiologic agents of conjunctivitis in Lagos, Nigeria. J Ophthalmic Inflamm Infect. 2011;1(3):95–103.PubMedPubMedCentralCrossRefGoogle Scholar

Copyright information

© The Author(s) 2019

Authors and Affiliations

  • Barry A. Schechter
    • 1
  • John D. Sheppard
    • 2
  • Christine M. Sanfilippo
    • 3
    Email author
  • Heleen H. DeCory
    • 3
  • Penny A. Asbell
    • 4
  1. 1.Cornea and Cataract ServiceFlorida Eye Microsurgical InstituteBoynton BeachUSA
  2. 2.Virginia Eye ConsultantsNorfolkUSA
  3. 3.Medical Affairs, Bausch + LombRochesterUSA
  4. 4.Department of OphthalmologyHamilton Eye Institute, University Health Science CenterMemphisUSA

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