In Vitro Efficacy and Pharmacodynamic Indices for Antibiotics against Coagulase-Negative Staphylococcus Endophthalmitis Isolates

Coagulase-negative staphylococcal endophthalmitis: clinical severity and outcomes based on speciation

OBJECTIVE

To identify characteristics and visual outcomes of coagulase-negative staphylococcal (CoNS) endophthalmitis in the era after the Endophthalmitis Vitrectomy Study.

DESIGN

Single-centre retrospective analysis.

PARTICIPANTS

Forty-two samples from 40 patients with documented CoNS endophthalmitis.

METHODS

Visual acuity outcomes of CoNS endophthalmitis were assessed in relation to species and type of treatment instituted (i.e., pars plana vitrectomy [PPV] versus vitreous tap and injection of intravitreal antibiotics [T&I]) on 42 samples from 40 patients.

RESULTS

Staphylococcus epidermidis was the most prevalent CoNS in our study. Cataract surgery and intravitreal injections were the most common sources for acute CoNS endophthalmitis. Eyes presenting with hand motion or better vision had similar mean final vision after either intravitreal antibiotics or PPV, whereas those with light perception or worse vision at onset had better outcomes after PPV only. Subanalysis showed that patients with S. epidermidis endophthalmitis (n = 39 eyes) had similar visual outcomes with either intravitreal injections or PPV regardless of visual acuity. Hypopyon and vitritis are not always present.

CONCLUSIONS

Patients with S. epidermidis endophthalmitis may benefit similarly from either early vitrectomy or intravitreal antibiotic injections regardless of visual acuity. This finding may be a supplement to the complements the management standards set forth by the Endophthalmitis Vitrectomy Study.

Acute postoperative endophthalmitis: Microbiology from the laboratory to the bedside

Postoperative endophthalmitis is a dreaded complication of intraocular surgery. Acute presentations need prompt management and good knowledge of differential diagnoses. In the last 10 years, progress in direct microbial detection and identification from intraocular samples included the use of blood culture systems and, more recently, matrix-assisted laser desorption ionization time-of-flight mass spectrometry, improving the rate of bacterial identification. Whatever the method used, diagnostic sensitivity is better for vitreous samples than for aqueous humor samples. Besides, molecular biology techniques have further improved the identification rate of infectious agents in intraocular samples. They also provide faster results compared to culture-based techniques. Quantitative real-time PCR (qPCR) can also determine the bacterial load in intraocular samples. Several studies have shown that intraocular bacterial loads in endophthalmitis patients are usually high, which helps differentiating infection from contamination. The prognostic value of qPCR remains to be validated. Whole genome DNA sequencing technologies facilitate direct and sequencing of single DNA molecules. They have the potential to increase the rate of microbiological identification. Some antibiotic resistance markers (e.g., methicillin resistance in staphylococci and vancomycin resistance in enterococci) may be detected earlier using molecular techniques (usually real-time PCR tests). Early determination of the involved microorganism and their antibiotic resistances can help establishing an earlier therapeutic strategy.

Ten-Year Analysis of Pathogenic Factors and Etiological Characteristics of Endophthalmitis from a Tertiary Eye Center in North China

Purpose

To describe the etiology and spectrum of isolated pathogens in endophthalmitis over 10 years from an ophthalmic hospital in North China and report their antimicrobial susceptibilities.

Patients and Methods

The data covered the patients with endophthalmitis treated at Qingdao Eye Hospital from January 2011 to December 2020. Patients’ medical history, pathogenic factors, bacterial and fungal culture results of intraocular specimens, and in vitro drug sensitivity test results were assessed.

Results

A total of 524 cases were counted in this study. Exogenous endophthalmitis was the main component, accounting for 94.66%, of which 49.62% of eyes had a history of ophthalmic trauma, intraocular surgery in 26.72% and suppurative keratitis in 17.37%. By comparison, endogenous endophthalmitis was found in only 5.34% of eyes. Among the 292 strains of pathogenic organisms obtained by co-culture, gram-positive bacteria accounted for 64.04%, with Staphylococcus epidermidis as the predominant pathogen (29.45%). Gram-positive cocci were identified in 76.77% of eyes with traumatic endophthalmitis, while 53.70% of keratitis-associated endophthalmitis was caused by fungi. The high susceptibility of bacteria to vancomycin (77.78%~98.33%) supported its continued use as empirical treatment. Among the fluoroquinolones, gram-positive cocci showed a higher susceptibility to gatifloxacin (94.83%), while there was a significant decrease to levofloxacin (51.67%). Gram-negative bacteria were less sensitive to cephalosporins (45.95%~66.67%) than fluoroquinolones (68.42%~78.05%) and aminoglycosides (75.00%~78.05%). Fungal susceptibilities to voriconazole and amphotericin B were 90.16% and 70.31% respectively. More than half of the 11 antibiotics were observed to exhibit a trend of reduced susceptibility.

Conclusion

Ophthalmic trauma was the primary pathogenic factor of endophthalmitis. Gram-positive cocci were the most common pathogens of traumatic and postoperative endophthalmitis, while suppurative keratitis-associated endophthalmitis often resulted from fungal pathogens. Levofloxacin as the preferred antibiotic in the perioperative period and cephalosporin as the first-line drug for the treatment of empiric endophthalmitis need to be vigilant.

A Systematic Review of Multi-decade Antibiotic Resistance Data for Ocular Bacterial Pathogens in the United States

INTRODUCTION

Since 2009, the Antibiotic Resistance Monitoring in Ocular Microorganisms (ARMOR) surveillance study has been assessing in vitro antibiotic resistance for bacterial isolates sourced from ocular infections in the US. The main goal of this systematic review was to compare in vitro resistance data for ocular pathogens from published US studies with the most recently published data from the ARMOR study (2009-2018) and, where possible, to evaluate trends in bacterial resistance over time over all studies.

METHODS

A literature search was conducted using MEDLINE®, BIOSIS Previews®, and EMBASE^® databases (1/1/1995-6/30/2021). Data were extracted from relevant studies and antibiotic susceptibility rates for common ocular pathogens (Staphylococcus aureus, coagulase-negative staphylococci [CoNS], Streptococcus pneumoniae, Pseudomonas aeruginosa, and Haemophilus influenzae), longitudinal changes in susceptibility, and multidrug resistance (MDR) were compared descriptively.

RESULTS

Thirty-two relevant studies were identified. High in vitro resistance was found among S. aureus and CoNS to fluoroquinolones, macrolides, and methicillin/oxacillin across studies, with high rates of MDR noted, specifically among methicillin-resistant staphylococci. Data from studies pre-dating or overlapping the early years of ARMOR reflected increasing rates of S. aureus resistance to fluoroquinolones, macrolides, methicillin/oxacillin, and aminoglycosides, while the ARMOR data suggested slight decreases in resistance to these classes between 2009 and 2018. Overall, methicillin-resistant S. aureus (MRSA) prevalence peaked from 2005 to 2015 with a possible decreasing trend in more recent years.

DISCUSSION AND CONCLUSIONS

Data from local and regional US datasets were generally consistent with data from the national ARMOR surveillance study. Continued surveillance of ocular bacterial pathogens is needed to track trends such as methicillin resistance and MDR prevalence and any new emerging antibiotic resistance phenotypes. Susceptibility data from ARMOR can inform initial choice of therapy, especially in practice areas where local antibiograms are unavailable.

Microbes of the human eye: Microbiome, antimicrobial resistance and biofilm formation

BACKGROUND

The review focuses on the bacteria associated with the human eye using the dual approach of detecting cultivable bacteria and the total microbiome using next generation sequencing. The purpose of this review was to highlight the connection between antimicrobial resistance and biofilm formation in ocular bacteria.

METHODS

Pubmed was used as the source to catalogue culturable bacteria and ocular microbiomes associated with the normal eyes and those with ocular diseases, to ascertain the emergence of anti-microbial resistance with special reference to biofilm formation.

RESULTS

This review highlights the genetic strategies used by microorganisms to evade the lethal effects of anti-microbial agents by tracing the connections between candidate genes and biofilm formation.

CONCLUSION

The eye has its own microbiome which needs to be extensively studied under different physiological conditions; data on eye microbiomes of people from different ethnicities, geographical regions etc. are also needed to understand how these microbiomes affect ocular health.

Antibiotics and antifungals in silicone oil

Background

Antimicrobials may be injected into silicone oil-filled eyes with endophthalmitis, but the interaction with oil is unclear. The purpose of the experiment is to determine whether vancomycin, amikacin, and amphotericin B mix with silicone oil.

Methods

Using the relative proportions of the human eye, 4 ml of 1000 centistokes silicone oil was centrifuged with 0.1 ml of vancomycin 1 mg/0.1 ml, amikacin 0.4 mg/0.1 ml, or amphotericin B 5 µg/0.1 ml in vitro and eluted. The aqueous was immediately analyzed with a liquid chromatographer/mass spectrometer and after 24 h.

Results

Within 24 h, a mean of 26.9 μmol/L of vancomycin, 0 nmol/L of amikacin, and 0 nmol/L of amphotericin B were recovered. When the concentrations of amikacin and amphotericin B were increased 100-fold, 0 nmol/L of amikacin and 75.7 µmol/L of amphotericin B were recovered.

Conclusions

Vancomycin and amphotericin B partially mixed with the silicone oil. Amikacin was not recovered from the antibiotic–silicone oil mixture.

Genetic and Phenotypic Traits of Staphylococcus Epidermidis Strains Causing Postcataract Endophthalmitis Compared to Commensal Conjunctival Flora

PURPOSE

The aim of this study was to compare the virulence and antibiotic resistance traits of Staphylococcus epidermidis strains causing acute postcataract endophthalmitis to those isolated from the conjunctiva of uninfected control patients.

DESIGN

Case-control study.

METHODS

We isolated an S epidermidis strain from each of the 22 endophthalmitis patients, and from 43 of the 72 controls. Species identification was confirmed using both Matrix-assisted laser desorption ionization-time of flight (MALDI-TOF) mass spectrometry and tuf gene amplification and sequencing. Antibiotic susceptibilities were evaluated using the AST-P631 card and the Vitek II automated system. The S epidermidis strains were tested for the presence of 7 virulence genes (icaA, icaB, icaC, icaD, atlE, aap, and capA), the insertion sequence IS256, and the mecA gene.

RESULTS

The S epidermidis strains from the endophthalmitis patients displayed higher prevalence rates for aap, atlE, and mecA gene carriage compared to those of the control group (77% vs 42%, P = .007; 100% vs 79%, P = .02; and 54% vs 11%, P < .001, respectively). They also harbored the combination of the mecA and icaA genes more frequently compared to the control group (13% vs 2%, P = .01). They were significantly more resistant than control strains to methicillin, fluoroquinolones, and the aminoglycosides.

CONCLUSIONS

A higher capacity of adhesion to the intraocular lens and formation of biofilms as well as greater resistance to antibiotics were found in S epidermidis strains causing postcataract endophthalmitis. The usefulness of such virulence and antibiotic resistance markers warrants further evaluation for prevention, treatment, and prognostic evaluation of S epidermidis endophthalmitis.

Comparative activity of antimicrobials against Pseudomonas aeruginosa, Achromobacter xylosoxidans and Stenotrophomonas maltophilia keratitis isolates

BACKGROUND/AIMS

Achromobacter xylosoxidans and Stenotrophomonas maltophilia are emerging corneal pathogens, which are closely related to Pseudomonas aeruginosa, and have intrinsic resistance to many commonly available antimicrobials. The purpose of this study is to compare the in vitro efficacy of 12 antimicrobial agents against A. xylosoxidans, S. maltophilia and P. aeruginosa isolates recovered from clinical cases of keratitis.

METHODS

Recovered corneal isolates (n=58) were identified and extracted from the Microbiology Data Bank of the Bascom Palmer Eye Institute. Comparative in vitro minimum inhibitory concentration (MIC) susceptibility profiles for fluoroquinolones, aminoglycosides, beta-lactams and miscellaneous antibiotics were recorded using the E-test methodology. Pharmacodynamic indices (Cmax/MIC) were calculated.

RESULTS

A. xylosoxidans and S. maltophilia isolates were resistant to fluoroquinolones, aminoglycosides and ceftazidime (susceptibility rate ranging from 0% to 30%) while P. aeruginosa isolates showed a susceptibility rate of 95%-100% to these antimicrobials (P<0.00001 for the various antimicrobials). Exception was moxifloxacin with 80% of susceptibility rate to S. maltophilia isolates and Cmax/MIC=10.19. Ninety to 100% susceptibility rates were found for minocycline and trimethoprim/sulfamethoxazole for both A. xylosoxidans and S. maltophilia. One hundred per cent of the A. xylosoxidans isolates were susceptible to piperacillin/tazobactam and ticarcillin/clavulanic acid.

CONCLUSIONS

There is a significant difference in susceptibility patterns between A. xylosoxidans, S. maltophilia and P. aeruginosa. Fluoroquinolones and aminoglycosides may not be effective against A. xylosoxidans and S. maltophilia. Antibiotics that are not commercially available as eye drops, such as beta-lactams for A. xylosoxidans, and trimethoprim/sulfamethoxazole and minocycline for both A. xylosoxidans and S. maltophilia should be considered.

Clinical Features, Antibiotic Susceptibilities, and Treatment Outcomes of Endophthalmitis Caused by Staphylococcus epidermidis

PURPOSE

To report the clinical features, antibiotic susceptibilities, and visual acuity outcomes with endophthalmitis caused by methicillin-sensitive Staphylococcus epidermidis and methicillin-resistant S. epidermidis.

DESIGN

Retrospective case series.

PARTICIPANTS

All patients seeking treatment at a tertiary referral center between 2006 and 2016 with endophthalmitis caused by S. epidermidis.

METHODS

All records were reviewed for patients with a clinical diagnosis of endophthalmitis and positive vitreous culture results for S. epidermidis. Data were compared with the prior series at the same institution.

MAIN OUTCOME MEASURES

Clinical settings, antibiotic susceptibilities, and visual acuity.

RESULTS

Among 96 eyes of 96 patients, the most common postprocedural clinical settings were cataract surgery (47/96 [49%]), intravitreal injection (21/96 [22%]), trauma (8/96 [8%]), glaucoma surgery (7/96 [7%]), and penetrating keratoplasty (5/96 [5%]). The initial treatment included intravitreal vancomycin and ceftazidime in 89 of 96 eyes (93%) and intravitreal vancomycin and amikacin in 7 of 96 eyes (7%). A vitreous tap and injection with antibiotics was performed as the initial treatment in 83 of 96 eyes (86%) and pars plana vitrectomy was performed in 13 of 96 eyes (14%). All isolates were sensitive to vancomycin in both decades. In the most recent series, visual acuity at last follow-up was 5/200 or better in 68 of 96 eyes (71%) compared with 71 of 86 eyes (83%) in the prior study. In the current study, susceptibility to methicillin and moxifloxacin was present in 45 of 96 eyes (47%) and 29 of 85 eyes (34%), respectively, compared with 34 of 86 eyes (40%) and 27 of 39 eyes (69%) in the prior study. Final visual acuity was not significantly different between those eyes that were methicillin or fluoroquinolone sensitive and those that were resistant.

CONCLUSIONS

In the current and prior series, all S. epidermidis isolates were sensitive to vancomycin. Visual acuity outcomes were not dependent on methicillin or fluoroquinolone sensitivity.

Antibiotic prophylaxis in cataract surgery in the setting of penicillin allergy: A decision-making algorithm

Cataract surgery is the most commonly performed surgical procedure in many developed countries. Postoperative endophthalmitis is a rare complication with potentially devastating visual outcomes. Currently, there is no global consensus regarding antibiotic prophylaxis in cataract surgery despite growing evidence of the benefits of prophylactic intracameral cefuroxime at the conclusion of surgery. The decision about which antibiotic regimen to use is further complicated in patients reporting penicillin allergy. Historic statistics suggesting crossreactivity of penicillins and cephalosporins have persisted into modern surgery. It is important for ophthalmologists to consider all available antibiotic options and have an up-to-date knowledge of antibiotic crossreactivity when faced with the dilemma of choosing appropriate antibiotic prophylaxis for patients undergoing cataract surgery with a history of penicillin allergy. Each option carries risks, and the choice may have medicolegal implications in the event of an adverse outcome. We assess the options for antibiotic prophylaxis in cataract surgery in the setting of penicillin allergy and provide an algorithm to assist decision-making for individual patients.

Aqueous Humor Antimicrobial Activity: In Vitro Analysis after Topical 0.5% Chloramphenicol Application

PURPOSE

To assess aqueous humor antimicrobial activity in vitro after topical 0.5% chloramphenicol application.

MATERIALS AND METHODS

This investigation included 63 eyes from 65 cataract surgery patients. The study group of 48 eyes received preoperatively four topical applications of 0.5% chloramphenicol. The control group of 15 eyes was given no topical applications. Aqueous humor samples were collected for in vitro antimicrobial analysis using Streptococcus pneumoniae, Haemophilus influenzae, Moraxella catarrhalis, and Pasteurella multocida organisms by means of disk diffusion test.

RESULTS

No inhibition halo was observed around all aqueous humor samples from all chloramphenicol-treated patients, irrespective of the sample quantity added to the paper disks, with no significant difference from aqueous humor from untreated control patients.

CONCLUSIONS

Aqueous humor displayed no bactericidal effect against any of the microorganisms evaluated after topical 0.5% chloramphenicol application.

Postcataract endophthalmitis prophylaxis using irrigation, incision hydration, and eye pressurization with vancomycin

PURPOSE

This study aimed to determine whether switching from balanced salt solution (BSS) to vancomycin 20 g/mL BSS for incision hydration and eye pressurization reduces the rate of postcataract endophthalmitis.

METHODS

This was a patient safety/quality improvement project, including all patients undergoing cataract surgery at the Kaiser Permanente Colorado Ophthalmology Department from January 2002 to December 2014. Throughout the study, patients received vancomycin 20 μg/mL in the irrigating solution. During the baseline period from 2002 to 2005, surgeons pressurized eyes and hydrated incisions with plain BSS. During the intervention period from 2006 through 2014, surgeons switched from BSS to the vancomycin/BSS irrigating solution for eye pressurization and incision hydration.

RESULTS

A total of 57,263 cataract operations were performed by 24 surgeons at seven surgical centers: 12,400 in the baseline period and 44,863 in the intervention period. The rate of post-cataract endophthalmitis declined significantly from 5/12,400 (rate: 0.4/1,000) in the baseline period to 1/44,863 (rate: 0.022/1,000) during the intervention period (odds ratio [OR]: 18.1, 95% confidence interval [CI]: 2.11-154.9; χ (2)=13.5, P=0.00024). Accounting for an estimated 2.05-fold risk reduction due to confounding variables, the risk reduction attributed to the intervention remained significant: (adjusted OR: 8.78, 95% CI: 1.73-44.5; χ (2)=10.06, P=0.0015). Since 2009, we have not experienced any cases of postcataract endophthalmitis after 32,753 operations.

CONCLUSION

We experienced a significant reduction in postcataract endophthalmitis when we switched from BSS to the vancomycin/BSS irrigating solution for incision hydration and eye pressurization. The pharmacokinetics profile indicates that this switch was important for effective prophylaxis.

In vitro antimicrobial analysis of aqueous humor after topical application of moxifloxacin hydrochloride 0.5%

PURPOSE

To evaluate the in vitro antimicrobial activity of aqueous humor in patients who had preoperative topical application of moxifloxacin hydrochloride 0.5%.

SETTING

Department of Ophthalmology, Santa Casa de Misericórdia de São Paulo, Brazil.

DESIGN

Comparative case series.

METHODS

Twenty-nine eyes from 29 cataract surgery patients were included in this study. In the study group (n = 15 eyes), 3 topical applications of moxifloxacin hydrochloride 0.5% were administered preoperatively; in the control group (n = 14 eyes), no topical applications were administered. Aqueous humor samples were collected and stored in sterile microtubes at -80°C until analysis. Antimicrobial analysis was performed using standard strains with standard sterile filter paper disks. Inhibition halos were measured in millimeters, and both bactericidal and bacteriostatic effects were analyzed.

RESULTS

Inhibition halos were observed on most of the study group plates except those with Streptococcus pneumoniae: Escherichia coli (13.93 mm ± 0.64 [SD]), Klebsiella pneumoniae (10.63 ± 0.61 mm), Staphylococcus aureus (7.47 ± 0.68 mm), and S epidermidis (4.20 ± 3.33 mm) The differences between the mean inhibition halo diameters were statistically significant (P < .0001) in all samples. No bactericidal effect was observed against any of the microorganisms studied.

CONCLUSIONS

After topical application of moxifloxacin 0.5%, aqueous humor showed bacteriostatic effect against E coli, K pneumoniae, S aureus, and S epidermidis. No bactericidal effect was observed against any of the microorganisms evaluated. No antimicrobial effect against S pneumoniae was observed.

FINANCIAL DISCLOSURE

No author has a financial or proprietary interest in any material or method mentioned.

Microbiological spectrum and antibiotic sensitivity in endophthalmitis: a 25-year review

PURPOSE

To identify the spectrum and susceptibility pattern of pathogens responsible for culture-positive endophthalmitis referred to a single institution and investigate possible trends in both pathogens and antibiotic sensitivities over the past 25 years.

DESIGN

A retrospective, laboratory-based study of consecutive microbiological isolates.

PARTICIPANTS

A total of 988 consecutive culture-positive endophthalmitis isolates from 911 eyes.

METHODS

All culture-positive endophthalmitis isolates collected from 1987 to 2011 were identified. Susceptibility rates to a variety of antibiotics were calculated. Chi-square test for trend was used to detect changes in spectrum or susceptibility over time.

MAIN OUTCOME MEASURES

Microbial spectrum and susceptibility pattern over time.

RESULTS

A total of 988 isolates were identified from 911 eyes. The average patient age was 67 ± 18 years, and 55% of the patients were female. The most prevalent pathogens were coagulase-negative staphylococcus (39.4%), followed by Streptococcus viridans species (12.1%) and Staphylococcus aureus (11.1%). Gram-negative organisms and fungi accounted for 10.3% and 4.6% of all isolates, respectively. With the exception of 2 isolates, Enterococcus faecium and Nocardia exalbida, all the other 725 (99.7%) gram-positive bacteria tested were susceptible to vancomycin. Of the 94 gram-negative organisms tested against ceftazidime, 2 were of intermediate sensitivity and 6 were resistant. For 8 antibiotics, increasing microbial resistance over time was observed: cefazolin (P = 0.02), cefotetan (P = 0.006), cephalothin (P<0.0001), clindamycin (P = 0.04), erythromycin (P<0.0001), methicillin/oxacillin (P<0.0001), ampicillin (P = 0.01), and ceftriaxone (P = 0.006). For 3 antibiotics, increasing microbial susceptibility was observed: gentamicin (P<0.0001), tobramycin (P = 0.005), and imipenem (P<0.0001).

CONCLUSIONS

Coagulase-negative staphylococcus remains the most frequently identified cause of endophthalmitis. Vancomycin and ceftazidime seem to be excellent empiric antibiotics for treating endophthalmitis. Although a statistically significant trend toward increasing microbial resistance against a variety of antibiotics, including cephalosporins and methicillin, was observed, a significant trend toward decreasing microbial resistance against aminoglycosides and imipenem also was detected.

Antibiotic susceptibility of staphylococci isolates from patients with chronic conjunctivitis: including associated factors and clinical evaluation

PURPOSE

To determine species of staphylococci in chronic conjunctivitis, their antibiotic susceptibility pattern, patient treatments, clinical course, and clinical conditions.

METHODS

In this prospective study, 243 conjunctival cultures were taken from 191 patients with chronic conjunctivitis, we obtained staphylococci susceptibility patterns with E-test, and they were analyzed in coagulase-positive and negative. The minimum inhibitory concentration for 90% of isolates (MIC90) was determined for Staphylococcus aureus and Staphylococcus epidermidis. Additionally, clinical follow-up and associated factors of all patients were analyzed depending on methicillin resistance (MR) or susceptibility (MS) bacterial state.

RESULTS

One hundred and eight (44%) cultures were positive; 81 positive cultures were Gram-positive of which, 77 were staphylococci, 29 coagulase-positive with S. aureus as the most prevalent, 89% MS, and 11% MR. And 48 were coagulase-negative with S. epidermidis as the most isolated with 36% of MS and 64% of MR. Poor susceptibility was found in the staphylococcus coagulase-negative/MR group. Moxifloxacin and vancomycin show the best in vitro activity for all isolates. The MIC90 of moxifloxacin and vancomycin were 0.064/1.5, 0.64/3.0, and 1/3.0 for S. aureus-MS, S. epidermidis-MS, and S. epidermidis-MR, respectively. The most frequently associated factors found in patients with positive culture for staphylococcus were exposure to the health care system 23 (29.87%) of 77 patients and dry eye 23 (29.87%) of 77 patients. Both with a proportion of 3 in 10.

CONCLUSION

Coagulase-negative staphylococci were the most frequently isolated from the conjunctiva with 58.33% of MR; even though multiresistance was detected, their susceptibility to a fourth-generation fluoroquinolone, commonly used, such as moxifloxacin, was preserved.

Role of topical, subconjunctival, intracameral, and irrigative antibiotics in cataract surgery

PURPOSE OF REVIEW

To summarize current understanding of antibiotic prophylaxis in cataract surgery, with particular emphasis on available evidence and change in practice patterns over the past decade.

RECENT FINDINGS

Povidone-iodine application prior to cataract surgery remains a universal practice, and is backed by good quality evidence. Subsequent to the results of the European multicenter trial documenting decreased risk of endophthalmitis with intracameral cefuroxime injection at the end of surgery, similar benefit with intracameral antibiotic use has been reported in studies with large sample sizes from multiple centers around the world. There has been a distinct change in practice patterns in many countries, with intracameral antibiotic use becoming part of routine protocol. In the USA, topical fluoroquinolone application remains the most popular mode of antibiotic prophylaxis. A promising approach is the development of novel drug delivery methods like polymeric devices designed for sustained antibiotic release.

SUMMARY

Based on current evidence, the recommended measures for endophthalmitis prophylaxis are preoperative topical instillation of povidone-iodine and intracameral antibiotic injection at the end of cataract surgery.

Antibiotic resistance in ocular bacterial pathogens

Bacterial infections of the eye are common and ophthalmologists are spoilt for choice with a variety of antibiotics available in the market. Antibiotics can be administered in the eye by a number of routes; topical, subconjunctival, subtenon and intraocular. Apart from a gamut of eye drops available, ophthalmologists also have the option of preparing fortified eye drops from parenteral formulations, thereby, achieving high concentrations; often much above the minimum inhibitory concentration (MIC), of antibiotics in ocular tissues during therapy. Antibiotic resistance among ocular pathogens is increasing in parallel with the increase seen over the years in bacteria associated with systemic infections. Although it is believed that the rise in resistant ocular bacterial isolates is linked to the rise in resistant systemic pathogens, recent evidence has correlated the emergence of resistant bacteria in the eye to prior topical antibiotic therapy. One would like to believe that either of these contributes to the emergence of resistance to antibiotics among ocular pathogens. Until recently, ocular pathogens resistant to fluoroquinolones have been minimal but the pattern is currently alarming. The new 8-fluoroquinolone on the scene-besifloxacin, is developed exclusively for ophthalmic use and it is hoped that it will escape the selective pressure for resistance because of lack of systemic use. In addition to development of new antibacterial agents, the strategies to halt or control further development of resistant ocular pathogens should always include judicious use of antibiotics in the treatment of human, animal or plant diseases.

Review of moxifloxacin hydrochloride ophthalmic solution in the treatment of bacterial eye infections

Moxifloxacin hydrochloride ophthalmic solution 0.5% (Vigamox((R))) is the ocular formulation/adaptation of moxifloxacin. Moxifloxacin is a broad spectrum 8-methoxyfluoroquinolone which terminates bacterial growth by binding to DNA gyrase (topoisomerase II) and topoisomerase IV, essential bacterial enzymes involved in the replication, translation, repair and recombination of deoxyribonucleic acid. Affinity for both enzymes improves potency and reduces the probability of selecting resistant bacterial subpopulations. Vigamox is a bactericidal, concentration dependent, anti-infective. It is preservative free, and well tolerated with minimal ocular side effects. It provides increased penetration into ocular tissues and fluids with improved activity against Streptococci and Staphylococci species and moderate to excellent activity against clinically relevant, gram-negative ocular pathogens.

In vitro susceptibility patterns of methicillin-resistant Staphylococcus aureus and coagulase-negative Staphylococcus corneal isolates to antibiotics

PURPOSE

To determine the in vitro susceptibility of methicillin-resistant Staphylococcus aureus (MRSA) and methicillin-resistant coagulase-negative Staphylococcus (MRCNS) isolates to various antibiotics.

METHODS

All cases of bacterial keratitis caused by Staphylococcus species during 2006 and 2007 were identified. The isolates were divided according to species and susceptibility to methicillin into 4 groups: methicillin-susceptible S. aureus, methicillin-susceptible coagulase-negative Staphylococcus, MRSA, and MRCNS. Routine susceptibility testing for Staphylococcus species to methicillin and 19 other antibiotics was performed using the MicroScan POS Breakpoint Combo Panel Type 20.

RESULTS

One hundred fifty-seven isolates were identified. Forty isolates were S. aureus, including 21 MRSA, and 117 isolates were coagulase-negative Staphylococcus, including 29 MRCNS. All MRSA isolates were susceptible to gentamicin, linezolid, rifampin, tetracycline, and vancomycin and were resistant to penicillin, cefazolin, cefepime, azithromycin, erythromycin, and ofloxacin. Ninety percent of MRSA isolates were resistant to fourth-generation fluoroquinolones. All MRCNS isolates were susceptible to vancomycin, chloramphenicol, linezolid, and rifampin and were resistant to penicillin, cefazolin, cefepime, and azithromycin. Sixty-five percent of the MRCNS isolates were susceptible to fourth-generation fluoroquinolones and gentamicin.

CONCLUSIONS

All MRSA and MRCNS isolates were sensitive to vancomycin, linezolid, and rifampin. MRSA isolates were generally sensitive to gentamicin and tetracycline and resistant to fourth-generation fluoroquinolones. MRCNS isolates were not consistently sensitive to gentamicin, tetracycline, or fourth-generation fluoroquinolones.

Emerging antibiotic resistance in ocular infections and the role of fluoroquinolones

Resistance to antibiotic agents is becoming increasingly prevalent among ocular infections. Between 19% and 60% of Streptococcus pneumoniae and Staphylococcus aureus isolates have been shown to be resistant to macrolide antibiotic agents, penicillin, and older fluoroquinolones. Although topical fluoroquinolones are considered first-line treatment of ocular infections, as much as 85% of methicillin-resistant S aureus isolates are resistant to ophthalmic fluoroquinolones, including the newer 8-methoxy fluoroquinolones, gatifloxacin and moxifloxacin. Besifloxacin, an 8-chlorofluoroquinolone, has a lower minimum inhibitory concentration against multidrug-resistant staphylococcal strains than other fluoroquinolones and less selective pressure for resistance development because of the lack of a systemic counterpart. In addition to the development of new antibacterial agents, antibiotic resistance in ocular infections may be reduced by following the same strategies used to minimize antimicrobial resistance in systemic infections.

One-day application of topical moxifloxacin 0.5% to select for fluoroquinolone-resistant coagulase-negative Staphylococcus

PURPOSE

To compare selection for fluoroquinolone-resistant bacteria between 1-day and 3-day application of topical moxifloxacin 0.5%.

SETTING

Department of Ophthalmology, Stanford University, Stanford, California, USA.

METHODS

After investigative review board approval, patients scheduled for ocular surgery were randomized to receive topical moxifloxacin 0.5% drops 4 times a day for 1 day or 3 days preoperatively. Conjunctival cultures were obtained at baseline and after antibiotic application. Bacteria were identified and tested for resistance to a battery of antibiotic agents using the Kirby-Bauer disk-diffusion method. The differences in resistance distributions for the most commonly isolated bacteria between baseline (T0) and after antibiotic administration (T1) were compared between the 2 treatment groups.

RESULTS

Coagulase-negative Staphylococcus (CNS) were the most common bacteria isolated at T0 and T1. At T0, the proportion of CNS isolated in the 1-day group (n = 63) that was resistant to fluoroquinolones ranged from 4% to 22% depending on the antibiotic agent tested. After 1-day treatment with moxifloxacin, the percentage of resistant bacteria increased significantly (range 13% to 67%) for all fluoroquinolones except gatifloxacin (P<.05). Resistance to gentamicin and tobramycin also increased significantly. However, patients treated for 3 days (n = 57) showed no differences in bacterial resistance rates to any antibiotic agent tested.

CONCLUSION

Prophylactic topical moxifloxacin 0.5% treatment starting 1 day before ocular surgery resulted in a significant increase in fluoroquinolone-resistant bacteria, while a 3-day antibiotic regimen did not select for resistant organisms.

Intravitreal injection of therapeutic agents

BACKGROUND

Intravitreal injection (IVI) with administration of various pharmacological agents is a mainstay of treatment in ophthalmology for endopthalmitis, viral retinitis, age-related macular degeneration, cystoid macular edema, diabetic retinopathy, uveitis, vascular occlusions, and retinal detachment. The indications and therapeutic agents are reviewed in this study.

METHODS

A search of the English, German, and Spanish language MEDLINE database was conducted. A total of 654 references spanning the period through early 2008 were individually evaluated.

RESULTS

The advantage of the IVI technique is the ability to maximize intraocular levels of medications and to avoid the toxicities associated with systemic treatment. Intravitreal injection has been used to deliver several types of pharmacological agents into the vitreous cavity: antiinfective and antiinflammatory medications, immunomodulators, anticancer agents, gas, antivascular endothelial growth factor, and several others. The goal of this review is to provide a detailed description of the properties of numerous therapeutic agents that can be delivered through IVI, potential complications of the technique, and recommendations to avoid side effects.

CONCLUSION

The IVI technique is a valuable tool that can be tailored to the disease process of interest based on the pharmacological agent selected. This review provides the reader with a comprehensive summary of the IVI technique and its multitude of uses.

Visual outcome and bacterial sensitivity after methicillin-resistant Staphylococcus aureus-associated acute endophthalmitis

PURPOSE

To determine the frequency, visual outcome, and bacterial sensitivity in cases of methicillin-resistant Staphylococcus aureus (MRSA)-associated acute postoperative endophthalmitis occurring after cataract surgery.

DESIGN

Retrospective, consecutive, observational case series.

METHODS

Sixty-four cases of acute endophthalmitis occurring within six weeks after cataract surgery were identified over a three-year interval at a single vitreoretinal practice. Cases related to MRSA were studied and visual outcomes and bacterial sensitivities were recorded.

RESULTS

Thirty-three of the 64 eyes were culture positive, and six of the 33 cases (18.2%) demonstrated MRSA infection. All six eyes were started on fluoroquinolone antibiotics two or three days before surgery. Corneal abnormalities were noted in five of the six cases (83.3%), ranging from wound infection to diffuse corneal opacification. Visual acuity at last follow-up was no light perception (NLP) in two eyes, hand movements in two eyes, and 20/30 or better in two eyes. One eye with NLP vision underwent enucleation within three days of presentation because of panophthalmitis and impending sepsis. All six organisms were sensitive in vitro to both gentamicin and vancomycin. No organism was sensitive to any fluoroquinolone antibiotic, although not all organisms were tested against all fluoroquinolones.

CONCLUSIONS

MRSA infection accounts for 18% of culture-positive cases of endophthalmitis in this study and was associated with a poor visual outcome in two-thirds of our patients. MRSA organisms may be resistant in vitro to all generations of fluoroquinolone antibiotics, but do seem to be sensitive to gentamicin and vancomycin. The incidence of MRSA endophthalmitis seems to have increased significantly since the Endophthalmitis Vitrectomy Study was published in 1996.