Shifting trends in in vitro antibiotic susceptibilities for common ocular isolates during a period of 15 years

Levofloxacin susceptibility of Staphylococci from conjunctiva in patients with atopic dermatitis

PURPOSE

The ocular surface in patients with atopic dermatitis (AD) is known to harbor an abundance of gram-positive cocci, particularly Staphylococcus aureus (S. aureus). This study reviewed the results of microbial cultures from the conjunctiva in AD patients, with special attention to the levofloxacin susceptibility of Staphylococci.

STUDY DESIGN

Retrospective, single-center study.

METHODS

This study involved 131 eyes of 112 Japanese patients with AD (87 men and 25 women, mean age: 40.4 ± 12.2 years) who underwent ocular surgery at Kyorin University Hospital. Bacterial isolates were collected from the conjunctival sacs in the preoperative period. Drug resistance to methicillin and levofloxacin was judged using the minimal inhibitory concentrations of oxacillin and levofloxacin determined by the broth dilution method.

RESULTS

One hundred and fifty-seven strains were identified in 103 of the 131 eyes examined. S. aureus was isolated from 74 eyes (56.5%), followed by Staphylococcus epidermidis (S. epidermidis). In S. aureus, 11 strains (14.9%) were methicillin-resistant, and 18 (24.3%) were levofloxacin-resistant. In S. epidermidis, 15 strains (26.8%) were methicillin-resistant, and 17 (30.4%) were levofloxacin-resistant. No significant differences were observed in levofloxacin susceptibility with age, sex, previous ocular surgery, or duration of previous surgery. However, logistic multivariate analysis revealed that levofloxacin-resistant Staphylococci were concurrently resistant to methicillin, suggesting multidrug resistance.

CONCLUSION

Distinctive bacterial distribution and drug resistance need consideration in the managing of ocular disorders among patients with AD.

Trends in antibiotic resistance in ocular samples in a tertiary eye centre in Saudi Arabia in 2003-2019

OBJECTIVE

The aim of this study was to analyze the antibiotic resistance in ocular samples over a 16-year period.

METHODS

This was a retrospective cohort study conducted at King Khaled Eye Specialist Hospital, Riyadh, Saudi Arabia (2003-2019). The study included corneal and conjunctival swabs and aqueous and vitreous samples.

RESULTS

Coagulase-negative staphylococci exhibited a significant trend of increasing resistance over time to erythromycin (p < 0.001), oxacillin (p < 0.001), fusidic acid (p < 0.001), and moxifloxacin (p = 0.003). Staphylococcus aureus also showed a significant increase in oxacillin (p = 0.001), ofloxacin (p = 0.003), and moxifloxacin (p = 0.001) resistance patterns. Streptococcus pneumoniae demonstrated a significant increase in resistance to erythromycin (p = 0.01) and ofloxacin, which jumped from 0.80% in 2003 to 80% in 2019 (p = 0.015). No statistically significant increase in antibiotic resistance trend was observed for Pseudomonas.

CONCLUSIONS

An increasing antibiotic resistance pattern was demonstrated, particularly among gram-positive organisms. Such findings warrant revision of the common ocular antibiotic prescribing strategy and consideration of alternative antibiotics.

Managing Corneal Infections: Out with the old, in with the new?

There have been multiple reports of eye infections caused by antibiotic-resistant bacteria, with increasing evidence of ineffective treatment outcomes from existing therapies. With respect to corneal infections, the most commonly used antibiotics (fluoroquinolones, aminoglycosides, and cephalosporines) are demonstrating reduced efficacy against bacterial keratitis isolates. While traditional methods are losing efficacy, several novel technologies are under investigation, including light-based anti-infective technology with or without chemical substrates, phage therapy, and probiotics. Many of these methods show non-selective antimicrobial activity with potential development as broad-spectrum antimicrobial agents. Multiple preclinical studies and a limited number of clinical case studies have confirmed the efficacy of some of these novel methods. However, given the rapid evolution of corneal infections, their treatment requires rapid institution to limit the impact on vision and prevent complications such as scarring and corneal perforation. Given their rapid effects on microbial viability, light-based technologies seem particularly promising in this regard.

Antibiotic resistance in ocular bacterial infections: an integrative review of ophthalmic chloramphenicol

INTRODUCTION

Chloramphenicol is a broad-spectrum antibiotic widely used for treating ophthalmic infections, but concerns about rising bacterial resistance to chloramphenicol have been observed due to its frequent use as an over-the-counter medication. This review assessed the common ophthalmic bacterial pathogens, their chloramphenicol resistance mechanisms, and rates of drug resistance.

METHODS

PubMed and Google Scholar databases were searched for relevant publications from the years 2000 to 2022, bordering on ophthalmic bacterial infections, chloramphenicol susceptibility profiles, and drug resistance mechanisms against chloramphenicol. A total of 53 journal publications met the inclusion criteria, with data on the antibiotic susceptibility profiles available in 44 of the reviewed studies, which were extracted and analyzed.

RESULTS

The mean resistance rates to chloramphenicol from antibiotic susceptibility profiles varied between 0% and 74.1%, with the majority of the studies (86.4%) showing chloramphenicol resistance rates below 50%, and more than half (23 out of 44) of the studies showed resistance rates lower than 20%. The majority of the publications (n = 27; 61.4%) were from developed nations, compared to developing nations (n = 14; 31.8%), while a fraction (n = 3; 6.8%) of the studies were regional cohort studies in Europe, with no country-specific drug resistance rates. No pattern of cumulative increase or decrease in ophthalmic bacterial resistance to chloramphenicol was observed.

CONCLUSIONS

Chloramphenicol is still active against ophthalmic bacterial infections and is suitable as a topical antibiotic for ophthalmic infections. However, concerns remain about the drug becoming unsuitable in the long run due to some proof of high drug resistance rates.

The landscape of bacterial antibiotic susceptibility in a multi-tier ophthalmology network in India: an electronic medical record driven analytics report

Introduction. Injudicious use of antibiotics often leads to antibiotic resistance which contributes to significant morbidity and mortality. Knowledge of local antibiogram is important in informing appropriate empiric antimicrobial therapy.

Hypothesis / Gap. It is the first and largest study that examines bacterial isolates from multiple ocular infections across South India and provides a overview of susceptibility patterns for each individual bacteria in the detailed interactive dashboard.

Aim. To study the landscape of bacterial antibiotic susceptibility patterns of ocular infections in patients undergoing microbiological investigations across a multi-tier ophthalmology network in India.

Methodology. This cross-sectional hospital-based study included 15 822 patients in whom microbiology samples were analysed between September 2013 and December 2021. Ocular tissue of patients in whom a microbiology sample was processed in at least one eye were included as cases. The data were collected using an indigenously developed electronic medical record (EMR) system.

Results. Among the 15 822 patients, bacteria (51.06 %) was the most common aetiology, followed by fungus (38.27 %). The majority of the patients were male (68.10 %) and the majority were adults (90.01 %). The most common age group was during the sixth decade with 2914 (18.42 %) patients. The patients were more commonly from the lower socio-economic status (51.61 %) and rural geography (46.82 %). The majority of the specimens sent for microbiological analysis were corneal scraping (68.61 %). Gram-positive cocci and Gram-positive bacilli were most sensitive towards vancomycin (86.83 and 92.89% respectively) followed by cefazolin (80.88 %) and amikacin, while Gram-negative bacilli were most sensitive towards ofloxacin (65.24%).

Conclusion. The most common aetiology of infection in ocular disease is bacterial and the majority of the patients presented from the rural geography and from lower socio-economic status. While vancomycin continues to be the drug of choice for Gram-positive organisms, increasing resistance to fluoroquinolones and ceftazidime was observed. Adoption of this model will enable access to antimicrobial susceptibility data, leading to reliable decisions and better clinical outcomes.

The bactericidal effect of two photoactivated chromophore for keratitis-corneal crosslinking protocols (standard vs. accelerated) on bacterial isolates associated with infectious keratitis in companion animals

Background

Bacterial corneal infections are common and potentially blinding diseases in all species. As antibiotic resistance is a growing concern, alternative treatment methods are an important focus of research. Photoactivated chromophore for keratitis-corneal crosslinking (PACK-CXL) is a promising oxygen radical-mediated alternative to antibiotic treatment. The main goal of this study was to assess the anti-bactericidal efficacy on clinical bacterial isolates of the current standard and an accelerated PACK-CXL treatment protocol delivering the same energy dose (5.4 J/cm²).

Methods

Clinical bacterial isolates from 11 dogs, five horses, one cat and one guinea pig were cultured, brought into suspension with 0.1% riboflavin and subsequently irradiated. Irradiation was performed with a 365 nm UVA light source for 30 min at 3mW/cm² (standard protocol) or for 5 min at 18mW/cm² (accelerated protocol), respectively. After treatment, the samples were cultured and colony forming units (CFU’s) were counted and the weighted average mean of CFU’s per μl was calculated. Results were statistically compared between treated and control samples using a linear mixed effects model.

Results

Both PACK-CXL protocols demonstrated a significant bactericidal effect on all tested isolates when compared to untreated controls. No efficacy difference between the two PACK-CXL protocols was observed.

Conclusion

The accelerated PACK-CXL protocol can be recommended for empirical use in the treatment of bacterial corneal infections in veterinary patients while awaiting culture results. This will facilitate immediate treatment, the delivery of higher fluence PACK-CXL treatment within a reasonable time, and minimize the required anesthetic time or even obviate the need for general anesthesia.

Susceptibility of Ocular Staphylococcus aureus to Antibiotics and Multipurpose Disinfecting Solutions

Staphylococcus aureus is a frequent cause of ocular surface infections worldwide. Of these surface infections, those involving the cornea (microbial keratitis) are most sight-threatening. S. aureus can also cause conjunctivitis and contact lens-related non-infectious corneal infiltrative events (niCIE). The aim of this study was to determine the rates of resistance of S. aureus isolates to antibiotics and disinfecting solutions from these different ocular surface conditions. In total, 63 S. aureus strains from the USA and Australia were evaluated; 14 were from niCIE, 26 from conjunctivitis, and 23 from microbial keratitis (MK). The minimum inhibitory (MIC) and minimum bactericidal concentrations (MBC) of all the strains to ciprofloxacin, ceftazidime, oxacillin, gentamicin, vancomycin, chloramphenicol, azithromycin, and polymyxin B were determined. The MIC and MBC of the niCIE strains to contact lens multipurpose disinfectant solutions (MPDSs) was determined. All isolates were susceptible to vancomycin (100%). The susceptibility to other antibiotics decreased in the following order: gentamicin (98%), chloramphenicol (76%), oxacillin (74%), ciprofloxacin (46%), ceftazidime (11%), azithromycin (8%), and polymyxin B (8%). In total, 87% of all the isolates were multidrug resistant and 17% of the isolates from microbial keratitis were extensively drug resistant. The microbial keratitis strains from Australia were usually susceptible to ciprofloxacin (57% vs. 11%; p = 0.04) and oxacillin (93% vs. 11%; p = 0.02) compared to microbial keratitis isolates from the USA. Microbial keratitis isolates from the USA were less susceptible (55%) to chloramphenicol compared to conjunctivitis strains (95%; p = 0.01). Similarly, 75% of conjunctivitis strains from Australia were susceptible to chloramphenicol compared to 14% of microbial keratitis strains (p = 0.04). Most (93%) strains isolated from contact lens wearers were killed in 100% MPDS, except S. aureus 27. OPTI-FREE PureMoist was the most active MPDS against all strains with 35% of strains having an MIC ≤ 11.36%. There was a significant difference in susceptibility between OPTI-FREE PureMoist and Biotrue (p = 0.02). S. aureus non-infectious CIE strains were more susceptible to antibiotics than conjunctivitis strains and conjunctivitis strains were more susceptible than microbial keratitis strains. Microbial keratitis strains from Australia (isolated between 2006 and 2018) were more susceptible to antibiotics in comparison with microbial keratitis strains from the USA (isolated in 2004). Most of the strains were multidrug-resistant. There was variability in the susceptibility of contact lens isolates to MPDSs with one S. aureus strain, S. aureus 27, isolated from niCIE, in Australia in 1997 being highly resistant to all four MPDSs and three different types of antibiotics. Knowledge of the rates of resistance to antibiotics in different conditions and regions could help guide treatment of these diseases.

Study of Conjunctival Microbial Flora in Patients of Intensive Care Unit

Purpose

The objective of the study was to evaluate the type of conjunctival microbial flora in intensive care unit patients and their antimicrobial sensitivity pattern.

Methods

A total of 272 samples (conjunctival swabs) were taken from patients in various intensive care units and sent for culture and sensitivity. An ocular examination was done to look for lagophthalmos, conjunctival discharge, exposure keratitis, and corneal perforation.

Results

Majority (82.1%) of the samples showed at least one microbial isolate while 29 (10.7%) samples showed multiple microbial growth. The most common microbes were coagulase negative Staphylococcus spp. (41.5% of isolates), diphtheroids (11.0% of isolates), and Staphylococcus aureus (9.6% of isolates) which are the usual commensals of the ocular surface. Of the other microbes isolated, Pseudomonas aeruginosa (4.0%) was the most common. Eighty-four percent isolates of coagulase negative Staphylococcus sp., 81.8% isolates of diphtheroids and 100% isolates of Staphylococcus aureus were penicillin resistant. All isolates of Enterococcus fecalis were sensitive only to vancomycin. Two hundred and twenty eyes (80.9%) had varying degrees of lagophthalmos. Nineteen (7.0%) had severe corneal exposure changes leading to infectious corneal ulcer and perforation in all of them.

Conclusions

The isolates in patients of intensive care units were no different from the normal conjunctival flora though few pathogenic organisms such as Pseudomonas aeruginosa and Acinetobacter sp. were also isolated. Most of the isolates were penicillin resistant. This knowledge will help take appropriate prophylactic measures to contain ocular infections in the intensive care units.

Marine Actinomycetes, New Sources of Biotechnological Products

The Actinomycetales order is one of great genetic and functional diversity, including diversity in the production of secondary metabolites which have uses in medical, environmental rehabilitation, and industrial applications. Secondary metabolites produced by actinomycete species are an abundant source of antibiotics, antitumor agents, anthelmintics, and antifungals. These actinomycete-derived medicines are in circulation as current treatments, but actinomycetes are also being explored as potential sources of new compounds to combat multidrug resistance in pathogenic bacteria. Actinomycetes as a potential to solve environmental concerns is another area of recent investigation, particularly their utility in the bioremediation of pesticides, toxic metals, radioactive wastes, and biofouling. Other applications include biofuels, detergents, and food preservatives/additives. Exploring other unique properties of actinomycetes will allow for a deeper understanding of this interesting taxonomic group. Combined with genetic engineering, microbial experimental evolution, and other enhancement techniques, it is reasonable to assume that the use of marine actinomycetes will continue to increase. Novel products will begin to be developed for diverse applied research purposes, including zymology and enology. This paper outlines the current knowledge of actinomycete usage in applied research, focusing on marine isolates and providing direction for future research.

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.

Chloramphenicol Resurrected: A Journey from Antibiotic Resistance in Eye Infections to Biofilm and Ocular Microbiota

The advent of multidrug resistance among pathogenic bacteria is devastating the worth of antibiotics and changing the way of their administration, as well as the approach to use new or old drugs. The crisis of antimicrobial resistance is also due to the unavailability of newer drugs, attributable to exigent regulatory requirements and reduced financial inducements. The emerging resistance to antibiotics worldwide has led to renewed interest in old drugs that have fallen into disuse because of toxic side effects. Thus, comprehensive efforts are needed to minimize the pace of resistance by studying emergent microorganisms and optimize the use of old antimicrobial agents able to maintain their profile of susceptibility. Chloramphenicol is experiencing its renaissance because it is widely used in the treatment and prevention of superficial eye infections due to its broad spectrum of activity and other useful antimicrobial peculiarities, such as the antibiofilm properties. Concerns have been raised in the past for the risk of aplastic anemia when chloramphenicol is given intravenously. Chloramphenicol seems suitable to be used as topical eye formulation for the limited rate of resistance compared to fluoroquinolones, for its scarce induction of bacterial resistance and antibiofilm activity, and for the hypothetical low impact on ocular microbiota disturbance. Further in-vitro and in vivo studies on pharmacodynamics properties of ocular formulation of chloramphenicol, as well as its real impact against biofilm and the ocular microbiota, need to be better addressed in the near future.

Bacterial Keratitis in Toronto: A 16-Year Review of the Microorganisms Isolated and the Resistance Patterns Observed

PURPOSE

To review the incidence, distribution, current trends, and resistance patterns of bacterial keratitis isolates in Toronto over the past 16 years.

METHODS

Microbiology records of suspected bacterial keratitis that underwent a diagnostic corneal scraping and cultures from January 1, 2000, through December 31, 2015, were retrospectively reviewed. The distribution of the main isolated pathogens and in vitro laboratory minimum inhibitory concentration testing results were used to identify resistance patterns.

RESULTS

A total of 2330 corneal scrapings were taken over 16 years. A pathogen was recovered in 1335 samples (57.3%), with bacterial keratitis accounting for 1189 of the positive cultures (86.0% of all isolates). The total number of gram-positive and gram-negative isolates was 963 and 324, respectively. Coagulase-negative Staphylococcus and Pseudomonas aeruginosa were the most common gram-positive and gram-negative bacteria isolates, respectively. A decreasing trend in the number of isolates in gram-positive bacteria (P = 0.01), specifically among Staphylococcus aureus (P < 0.0001) and Streptococcus species (P = 0.005), was identified. When analyzing the susceptibilities of gram-positive and gram-negative isolates, an increasing trend in antibiotic resistance was observed in erythromycin (P = 0.018), ceftazidime (P = 0.046), and piperacillin/tazobactam (P = 0.005). The susceptibility of tested gram-positive microorganisms to vancomycin was 99.6%.

CONCLUSIONS

There has been a decreasing trend in the number of isolates in gram-positive microorganisms over the past 16 years. An increasing trend in resistance for various antibiotics against gram-negative and gram-positive isolates was identified. High susceptibility to vancomycin reinforced the empirical use of fortified tobramycin and vancomycin in the initial management of severe bacterial keratitis.

Twelve-year analysis of microbial keratitis trends at a UK tertiary hospital

PurposeTo investigate the frequencies, trends, and in vitro drug susceptibilities of the causative pathogens in microbial keratitis in Manchester Royal Eye Hospital.Patients and methodsCorneal scrape results recorded by the microbiology service between 2004 and 2015 were extracted from an established database. A total of 4229 corneal scrape specimens were identified from an established database. First-line antibiotic treatment in our centre during the study period was ofloxacin and second line was cefuroxime and gentamicin.ResultsMean age was 45.9±21.0. A total of 1379 samples (32.6%) were culture positive. One hundred forty-eight (10.7%) specimens cultured multiple organisms. Of the 1539 organisms identified, 63.3% were Gram-positive bacteria, 27.3% Gram-negative bacteria, 7.1% fungi, and 2.3% Acanthamoebae. A decreasing trend in Gram-positive isolates was found together with a stable trend in Gram negatives and an increasing trend in Acanthamoeba and fungi. There appeared to be a significant increasing trend of Moraxella infection (P=0.001). In all, 83.1 and 90.8% of Gram-positive and -negative isolates tested were susceptible to ofloxacin, respectively. Cefuroxime covered 86.6% of Gram-positive and 61.4% of Gram-negative isolates, whereas gentamicin covered 88.8 and 96.5% of Gram-positive and -negative isolates, respectively.ConclusionWe found a change in the type of Gram-negative organisms isolated over time, with the Moraxella species on the rise. Reassuringly, no significant increase in resistance was observed in vitro for any of the commonly used antibiotics. Ofloxacin remains a good first-line antibiotic treatment but duo-therapy does have broader coverage and should be considered in non-responsive cases.

The comparison of antimicrobial effectiveness of contact lens solutions

PURPOSE

The aim of this study was to compare the effects of widely used multipurpose contact lens solutions against Staphylococcus aureus and Pseudomonas aeruginosa, in addition to cystic and trophozoite forms of Acanthamoeba castellanii and A. polyphaga, that cause microbial keratitis.

METHODS

Three multipurpose solutions were tested: SOLO-care, ReNu, and Opti-Free Express. The test solutions were challenged with P. aeruginosa (ATCC 27853) and S. aureus (ATCC 2913) based on the ISO stand-alone and regiment test procedure for disinfecting products, A. polyphaga (ATCC 30871) and A. castellanii (1501/1A) cystic and trophozoite forms. Multipurpose solutions were sampled for surviving microorganisms at manufacturer's minimum recommended disinfection time. The number of viable organisms was determined, and log reductions were calculated.

RESULTS

ReNu and SOLO-care resulted in a reduction greater than the required mean 3.0 logarithmic reduction against S. aureus, and SOLO-care and Opti-Free Express resulted in a reduction more than the required mean 3.0 logarithmic reduction against P. aeruginosa. Against the cystic and trophozoite forms of A. castellanii, the log reduction provided by SOLO-care was 1.01 and 1.31 log, respectively. ReNu provided a 0.83 log reduction of the cystic form and a 1.21 log reduction of the trophozoite form. Using Opti-Free Express, the log reduction for both forms was 1.31. SOLO-care led to a 0.61 log reduction of the cystic form of A. polyphaga and a 1.01 log reduction of the trophozoite form. ReNu provided a 0.41 log reduction of the cystic form and a 4.99 log reduction of the trophozoite form. Opti-free Express resulted in a 0.89 log reduction of the cystic form and a 3.11 log reduction of the trophozoite form.

CONCLUSIONS

Multipurpose contact lens solutions using similar regimens can show different disinfection abilities.

Shifting Trends in Bacterial Keratitis in Taiwan: A 10-Year Review in a Tertiary-Care Hospital

PURPOSE

To investigate the distribution, current trends, and antibiotic susceptibility profiles of bacterial keratitis isolates over 10 years.

METHODS

We retrospectively reviewed the microbiology records of all corneal scrapings undertaken for cultures at Chang Gung Memorial Hospital from 2003 through 2012. We identified bacterial isolates and verified antibiotic susceptibilities by using the disk diffusion method. The Mantel-Haenszel linear-by-linear association χ test was used to detect the trends.

RESULTS

We collected 2012 corneal scrapings, and the culture was positive in 992 samples (49.3%), yielding 1282 isolates. Bacterial isolates were identified for 1039 isolates (81.1%), including 533 gram-positive and 506 gram-negative isolates. An increase in the percentage of gram-positive isolates was significant (P = 0.008), as was a decrease in that of gram-negative isolates (P = 0.002). The most common bacterial isolates were Pseudomonas aeruginosa (24.4%) and coagulase-negative Staphylococcus (16.6%). For gram-positive organisms, the susceptibilities were as follows: vancomycin 100%, ciprofloxacin 88.9%, sulfamethoxazole-trimethoprim 86.8%, clindamycin 73.2%, and oxacillin 56.5%. The susceptibility of gram-positive bacteria to clindamycin and oxacillin increased significantly (P = 0.009 and P = 0.001). For gram-negative organisms, the susceptibilities were as follows: ciprofloxacin 93.7%, piperacillin 91.9%, ceftazidime 90.9%, amikacin 88.3%, and gentamicin 84.7%. No change in trend occurred.

CONCLUSIONS

In Taiwan, we documented an increasing trend in the percentage of gram-positive bacteria. Methicillin-resistant microorganisms accounted for 43.5% of all gram-positive bacteria, but the trend of resistance to oxacillin and clindamycin significantly decreased. Ciprofloxacin continued to be a good empiric antibiotic for treating bacterial keratitis.

Bacterial spectrum and resistance patterns in corneal infections at a Tertiary Eye Care Center in South China

AIM

To investigate the spectrum and antibiotic susceptibility of bacteria isolated from patients with suspected corneal infections in Zhongshan Ophthalmic Center in South China over the past four years retrospectively.

METHODS

Totally 1943 corneal scrapes from patients with corneal infections from 2010 to 2013 were cultured and processed using standard microbiological procedures to identify bacterial isolates. Simultaneously, the bacterial isolates were tested for antibiotic susceptibility to 8 antibiotics (ceftazidime, cefuroxim, cefazolin, levofloxacin, ofloxacin, neomycin, tobramycin, chloramphenicol) using the Kirby-Bauer disc diffusion technique.

RESULTS

Of the total 1943 scrapes, 397 (20.43%) were culture-positive, of which 294 (74.06%) were gram-positive (GP) and 103 (25.94%) were gram-negative (GN) bacteria. Of the GP organisms, the most prevalent genera were Staphylococcus spp. (56.17%, n=223), Kocuria spp. (5.29%, n=21) and Micrococcus spp. (1.26%, n=5). On the other hand, the most prevalent genera were Pseudomonas spp. (12.85%, n=51), Burkholderia spp. (2.02%, n=8) and Acinetobacter spp. (1.51%, n=6) for the GN organisms. Among five antibiotics that have eye drop products, the resistant to neomycin of GP (7.82%, 95% CI: 4.72%-10.92%) and GN isolates (9.71%, 95% CI: 4.01%-15.41%) was lowest, while the resistant to chloramphenicol was highest (GP: 34.35%, 95% CI: 28.92%-39.78%; GN: 60.19%, 95% CI: 50.74%-69.64%).

CONCLUSION

Staphylococcus spp. was the most common bacterial pathogens isolated from patients with corneal infections in this setting. High percentages of GP and GN bacteria were mostly susceptible to neomycin and highly resistant to chloramphenicol.

Spectrum and Sensitivity of Bacterial Keratitis Isolates in Auckland

Background. The bacteria isolated from severe cases of keratitis and their antibiotic sensitivity are recognised to vary geographically and over time. Objectives. To identify the most commonly isolated bacteria in keratitis cases admitted over a 24-month period to a public hospital in Auckland, New Zealand, and to investigate in vitro sensitivity to antibiotics. Methods. Hospital admissions for culture-proven bacterial keratitis between January 2013 and December 2014 were identified. Laboratory records of 89 culture positive cases were retrospectively reviewed and antibiotic sensitivity patterns compared with previous studies from other NZ centres. Results. From 126 positive cultures, 35 species were identified. Staphylococcus was identified to be the most common isolate (38.2%), followed by Pseudomonas (21.3%). Over the last decade, infection due to Pseudomonas species, in the same setting, has increased (p ≤ 0.05). Aminoglycosides, cefazolin, ceftazidime, erythromycin, tetracycline, and doxycycline were 100% effective against tested isolates in vitro. Amoxicillin (41.6%), cefuroxime (33.3%), and chloramphenicol (94.7%) showed reduced efficacy against Gram-negative bacteria, whereas penicillin (51%) and ciprofloxacin (98.8%) showed reduced efficacy against Gram-positive bacteria. Conclusions. Despite a shift in the spectrum of bacterial keratitis isolates, antibiotic sensitivity patterns have generally remained stable and show comparability to results within the last decade from NZ centres.

Study on Prevalence, Antibiotic Susceptibility, and tuf Gene Sequence-Based Genotyping of Species-Level of Coagulase-Negative Staphylococcus Isolated From Keratitis Caused by Using Soft Contact Lenses

OBJECTIVE

To study on antibiotic susceptibility and identify coagulase-negative Staphylococcus (CoNS) species based on tuf gene sequencing from keratitis followed by using soft contact lenses in Isfahan, Iran, 2013.

METHODS

This study examined 77 keratitis cases. The samples were cultured and the isolation of CoNS was done by phenotypic tests, and in vitro sensitivity testing was done by Kirby-Bauer disk diffusion susceptibility method.

RESULTS

Thirty-eight of isolates were conveniently identified as CoNS. In this study, 27 (71.1%), 21 (55.3%), and 16 (42.1%) were resistant to penicillin, erythromycin, and tetracycline, respectively. One hundred percent of isolates were sensitive to gentamicin, and 36 (94.7%) and 33 (86.8%) of isolates were sensitive to chloramphenicol and ciprofloxacin, respectively. Also, resistances to cefoxitin were 7 (18.4%). Analysis of tuf gene proved to be discriminative and sensitive in which all the isolates were identified with 99.0% similarity to reference strains, and Staphylococcus epidermidis had the highest prevalence among other species.

CONCLUSIONS

Results of this study showed that CoNS are the most common agents causing contact lens-associated microbial keratitis, and the tuf gene sequencing analysis is a reliable method for distinguishing CoNS species. Also gentamycin, chloramphenicol, and ciprofloxacin are more effective than the other antibacterial agents against these types of bacteria.

Bacterial Spectrum and Antibiotic Resistance Patterns of Ocular Infection: Differences between External and Intraocular Diseases

This study aimed to compare the differences of microbial spectrum and antibiotic resistance patterns between external and intraocular bacterial infections in an eye hospital in South China. A total of 737 bacteria isolates from suspected ocular infections were included in this retrospective study covering the period 2010–2013. The organisms cultured from the ocular surface (cornea, conjunctiva) accounted for the majority of the isolates (82.77%, n = 610), followed by the intraocular (aqueous humor, vitreous fluid), which accounted for 17.23% (n = 127). The top three species accounting for the external ocular infections were S. epidermidis (35.25%), P. aeruginosa (8.03%), and S. simulans (4.43%). The top three species for the intraocular infections were S. epidermidis (14.96%), S. hominis (8.66%), and B. subtilis (7.87%). The bacteria from the external ocular surface were more sensitive to neomycin, while those from the intraocular specimens were more sensitive to levofloxacin (P < 0.01). Multidrug resistance was found in 89 bacteria (12.08%), including isolates from both external (13.28%) and intraocular samples (6.30%). The results of this study indicate that the bacteria spectrum of external and intraocular infections is variable in the setting. A high percentage of bacterial organisms were found to be primarily susceptible to neomycin for external infection and levofloxacin for intraocular infection.

Surveillance of the Activity of Aminoglycosides and Fluoroquinolones Against Ophthalmic Pathogens from Europe in 2010-2011

PURPOSE/AIM

Bacterial infections of the ocular surface are commonly treated empirically with broad spectrum antibiotics. Due to concerns over increasing antibiotic resistance, we evaluated current susceptibility patterns of the ocular bacterial pathogens in Europe.

MATERIALS AND METHODS

Non-consecutive ocular isolates of Staphylococcus aureus, coagulase-negative staphylococci (CoNS), Streptococcus pneumoniae, Haemophilus influenzae, and Pseudomonas aeruginosa were collected in 2011 from centers in France, Germany, Italy, Poland, Slovak Republic, Spain, and the United Kingdom. Centers were asked to provide similar numbers of methicillin-susceptible and -resistant staphylococcal isolates. Minimum inhibitory concentrations were determined for fluoroquinolones (besifloxacin, ciprofloxacin, moxifloxacin), aminoglycosides (tobramycin, gentamicin, netilmicin), oxacillin, chloramphenicol and erythromycin. Isolates were categorized as susceptible, intermediate, or resistant according to European Committee on Antimicrobial Susceptibility Testing (EUCAST) criteria.

RESULTS

A total of 741 ocular isolates were obtained. Antibiotic resistance rates depended not only on the antibiotic and species, but also varied greatly by the country of origin. Resistance to ciprofloxacin, tobramycin, erythromycin, and to a lesser extent, chloramphenicol, was a concern for all staphylococci. Multidrug resistance was common among methicillin-resistant S. aureus (MRSA) and MRCoNS and isolates of S. pneumoniae, H. influenzae, and P. aeruginosa were frequently non-susceptible to erythromycin, beta-lactams, and ciprofloxacin/tobramycin, respectively. Resistance rates showed substantial differences among the seven countries tested. Fluoroquinolones and aminoglycosides showed differences in antibacterial potency and resilience toward the antibiotic resistance mechanisms.

CONCLUSIONS

Methicillin-resistant staphylococcal isolates were frequently non-susceptible to a multitude of other antibiotics, making MRSA and MRCoNS a potentially significant concern. The broad range of resistance rates observed across Europe in this study confirms the importance of considering current local resistance patterns when antibacterial agents are chosen for empiric management of ocular infections.

Current knowledge about and recommendations for ocular methicillin-resistant Staphylococcus aureus

Staphylococcus aureus is the most important and common pathogen that infects patients following cataract surgery, laser in situ keratomileusis, and photorefractive keratectomy. It is reported to be the second most common pathogen causing bacterial keratitis around the world. Of special concern are increasing reports of postoperative methicillin-resistant S aureus (MRSA) infection. For example, MRSA wound infections have been reported with clear corneal phacoemulsification wounds, penetrating keratoplasty, lamellar keratoplasty, and following ex vivo epithelial transplantation associated with amniotic membrane grafts. These and other data suggest that MRSA has become increasingly prevalent worldwide. In this article, we review the current medical literature and describe the current challenge of ocular MRSA infections. Recommendations are made based on an evidence-based review to identify, treat, and possibly reduce the overall problem of this organism.

FINANCIAL DISCLOSURE

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

Pediatric microbial keratitis in Taiwan: clinical and microbiological profiles, 1998-2002 versus 2008-2012

PURPOSE

To identify the change in clinical and microbiological profiles of pediatric microbial keratitis in Taiwan between 1998-2002 and 2008-2012.

DESIGN

Retrospective, observational study.

METHOD

setting: Chang Gung Memorial Hospital, a referral center in Taiwan. patient population: We retrospectively reviewed the medical records of 68 eyes of 67 children aged 16 years or younger who were diagnosed with microbial keratitis and treated at our hospital between July 2008 and December 2012. main outcomes and measures: Predisposing factors, isolated organisms, antibiotic susceptibility, and clinical outcomes. The findings were compared with the results of our previous study conducted between July 1998 and December 2002.

RESULTS

As in 1998-2002, the leading risk factor for microbial keratitis during 2008-2012 was contact lens use, and the infection rate significantly increased from 40.7% to 52.9% (P = .024), which was mainly attributable to the recent increase in the rate of orthokeratology-related keratitis from 9.9% to 19.1% (P = .011). Pseudomonas aeruginosa remained the most commonly isolated organism (30.6%), but the number of isolated coagulase-negative Staphylococcus cases increased significantly in the 2008-2012 cases (P = .04). Antibiotic susceptibility of organisms did not change significantly between the 2 study periods. By using multiple linear stepwise regression analysis, we found that gram-negative bacterial infection played a crucial role in poor visual outcome.

CONCLUSIONS

Contact lens-related microbial keratitis increased in Taiwanese children over time, especially because of the use of overnight orthokeratology. Clinicians must understand the infection background and pay further attention to contact lens use in pediatric patients.

Ocular surface infections in northeastern state of malaysia: a 10-year review of bacterial isolates and antimicrobial susceptibility

OBJECTIVE

Ocular surface infections that include infections of conjunctiva, adnexa, and cornea have the potential risk of causing blindness within a given population. Empirical antibiotic therapy is usually initiated based on epidemiological data of common causative agents. Thus, the aims of this study were to determine the bacterial agents and their susceptibility patterns of isolates from ocular surface specimens in our hospital.

METHODS

This is a retrospective analysis and records of bacterial isolates from ocular surface specimens in Hospital Universiti Sains Malaysia from January 2001 to December 2010 were examined. Specimens were processed according to standard laboratory procedures. Antimicrobial susceptibility testing was conducted based on Clinical and Laboratory Standards Institute recommendations. Only single, nonrepetitive isolates were included in the analysis.

RESULTS

A total of 1,267 isolates were obtained during the study period, which comprised Staphylococcus aureus (n = 299, 23.6%), Pseudomonas aeruginosa (n = 194, 15.3%), Streptococcus pneumoniae (n = 108, 8.5%), Haemophilus influenzae (n = 100, 7.9%), Haemophilus parainfluenzae (n = 84, 6.6%), and Enterobacter spp. (n = 81, 6.4%). Fungi contributed to 4.4% of the total isolates. The antimicrobial susceptibility testing demonstrated that gram-positive bacteria were generally resistant to gentamicin (19%-57%), whereas gram-negative bacteria were resistant to chloramphenicol (27%-58%).

CONCLUSIONS

Based on the above results, knowledge of the initial Gram stain findings is imperative before the commencement of empirical antibiotic therapy. Therefore, a simple Gram staining for all eye specimens is highly recommended.

Could chloramphenicol be used against ESKAPE pathogens? A review of in vitro data in the literature from the 21st century

The widespread use of antibiotics has been associated with the emergence of antimicrobial resistance among bacteria. 'ESKAPE' (Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acintobacter baumannii, Pseudomonas aeruginosa and Enterobacter spp.) pathogens play a major role in the rapidly changing scenario of antimicrobial resistance in the 21st century. Chloramphenicol is a broad spectrum antibiotic that was abandoned in developed countries due to its association with fatal aplastic anemia. However, it is still widely used in the developing world. In light of the emerging problem of multi-drug resistant pathogens, its role should be reassessed. Our paper reviews in vitro data on the activity of chloramphenicol against ESKAPE pathogens. Susceptibility patterns for Gram-positives were good, although less favorable for Gram-negatives. However, in combination with colistin, chloramphenicol was found to have synergistic activity. The risk-benefit related to chloramphenicol toxicity has not been analyzed. Therefore, extra precautions should be taken when prescribing this agent.

External ocular surface bacterial isolates and their antimicrobial susceptibility patterns among pre-operative cataract patients at Mulago National Hospital in Kampala, Uganda

BACKGROUND

Endophthalmitis is a severe complication of cataract surgery which leads to high ocular morbidity and visual loss even with antibiotic treatment. Bacterial ocular floras are the implicated causative agents. This study was undertaken to evaluate the external ocular surface bacterial isolates and their antimicrobial susceptibility patterns among pre-operative cataract patients at Mulago National Hospital.

METHODS

This cross sectional study enrolled consecutively 131 patients scheduled for routine cataract surgery in the Department of Ophthalmology at Mulago National Hospital in Kampala, Uganda. Eyelid margin and conjunctival swabs were collected and processed using standard microbiological procedures to identify bacterial isolates and their respective antimicrobial susceptibility patterns.

RESULTS

Of 131 patients involved (mean age 63.3 ± 14.5 years), 54.2% (71/131) were females. The eyelid margin and conjunctival samples were culture positive in 59.5% (78/138) and 45.8% (60/138) respectively. The most common organisms identified were Coagulase-negative Staphylococci (CoNS) [65.9% (91/138)] and Staphylococcus aureus [21.0% (29/138)]. CoNS showed the highest resistance to tetracycline (58.2%, 53/91) and erythromycin (38.5%, 35/91), whereas in S. aureus the resistance to tetracycline and erythromycin were 55.2% (16/29) and 31.0% (9/29) respectively. Methicillin resistant CoNS (MRS) and Methicillin resistance S. aureus (MRSA) were 31.9% (29/91) and 27.6% (8/29) respectively. There were low resistance rates for CoNS, S. aureus and other bacterial isolates to ciprofloxacin (11.1%-24.2%), gentamicin (5.6-31.0%), tobramycin (17.2% -25.3%) and vancomycin (0.0%).

CONCLUSION

CoNS and S. aureus are the most common bacterial isolates found on the external ocular surface of the pre-operative cataract patients. Ciprofloxacin, gentamicin, tobramycin and vancomycin showed the lowest resistance rates to all bacterial isolates, therefore may be used to reduce bacteria load in the conjunctiva sac among cataract patients prior to surgery.

Clinical and microbiological profile of infectious keratitis in children

Background

Infectious keratitis is a sight-threatening condition for children. The purpose of this study was to describe the clinical profile, risk factors and microbiological profile of infectious keratitis in children.

Methods

Retrospective review of clinical records of patients under 16 years of age with history of microbial keratitis seen at a tertiary referral center. Clinical characteristics, risk factors, visual and surgical outcomes as well as the microbiological profile are analyzed.

Results

Forty-one eyes of 41 patients. Mean age was 8.7 years. Time between the onset of symptoms and ophthalmological examination was 12.7 days. Predisposing factors were found in 78%; ocular trauma was the most common (25%). Visual acuity equal or worse than 20/200 at admission correlated positively with a poorer visual outcome, p=0.002. Positivity of cultures was 34%. Gram-positive bacteria were isolated in 78.5%; Staphylococcus epidermidis (28.6%) was the most common microorganism.

Conclusions

Our study emphasizes the importance of a prompt diagnosis and treatment of infectious corneal ulcers in children. Trauma and contact lenses were the main predisposing factors. Gram-positive organisms were isolated in the vast majority of cases and visual outcomes are usually poor.

Paediatric bacterial keratitis cases in Shanghai: microbiological profile, antibiotic susceptibility and visual outcomes

PURPOSE

The purpose of this study was to review the microbiological profile, in vitro antibiotic susceptibility and visual outcomes of paediatric microbial keratitis in Shanghai, China over the past 6 years.

METHODS

Medical records of patients aged ≤16 years were reviewed, who were diagnosed as having bacterial keratitis between 1 January 2005 and 31 December 2010. Bacterial culture results and in vitro antibiotic susceptibility were analysed. A logistic regression analysis was conducted to evaluate the relationship between visual impairment and possible risk factors.

RESULTS

Eighty consecutive cases of paediatric bacterial keratitis cases were included, among which 59 were identified as having positive culture. Staphylococcus epidermidis was the most commonly isolated organism (n=23; 39.0%), followed by Streptococcus pneumoniae (n=11; 18.6%) and Pseudomonas aeruginosa (n=6; 10.2%). Antibiotic sensitivities revealed that tested bacteria had low resistance rates to fluoroquinolones and aminoglycosides (8.3-18.4% and 12.5-24.4%, respectively). Multivariate logistic regression analysis proved that visual impairment was significantly associated with Gram-negative bacterial infection (odds ratio (OR)=7.626; P=0.043) and an increasing number of resistant antibiotics (OR=0.385; P=0.040).

CONCLUSIONS

S. epidermidis was the most common isolated organism in Shanghai paediatric keratitis. The fluoroquinolones and aminoglycosides remained good choices for treating these patients. Gram-negative bacterial infection and an increasing number of resistant antibiotics were associated with worse visual prognoses in paediatric keratitis.

Besifloxacin ophthalmic suspension, 0.6%: a novel topical fluoroquinolone for bacterial conjunctivitis

Acute bacterial conjunctivitis, the most common cause of conjunctivitis, is responsible for approximately 1% of all primary-care consultations. Of the topical ophthalmic antibiotics used to treat acute bacterial conjunctivitis, fluoroquinolones are especially useful because they possess a broad antibacterial spectrum, are bactericidal in action, are generally well tolerated, and have been less prone to development of bacterial resistance. Besifloxacin, the latest advanced fluoroquinolone approved for treating bacterial conjunctivitis, is the first fluoroquinolone developed specifically for topical ophthalmic use. It has a C-8 chlorine substituent and is known as a chloro-fluoroquinolone. Besifloxacin possesses relatively balanced dual-targeting activity against bacterial topoisomerase IV and DNA gyrase (topoisomerse II), two essential enzymes involved in bacterial DNA replication, leading to increased potency and decreased likelihood of bacterial resistance developing to besifloxacin. Microbiological data suggest a relatively high potency and rapid bactericidal activity for besifloxacin against common ocular pathogens, including bacteria resistant to other fluoroquinolones, especially resistant staphylococcal species. Randomized, double-masked, controlled clinical studies demonstrated the clinical efficacy of besifloxacin ophthalmic suspension 0.6% administered three-times daily for 5 days to be superior to the vehicle alone and similar to moxifloxacin ophthalmic solution 0.5% for bacterial conjunctivitis. In addition, besifloxacin ophthalmic suspension 0.6% administered two-times daily for 3 days was clinically more effective than the vehicle alone for bacterial conjunctivitis. Besifloxacin has also been shown in preclinical animal studies to be potentially effective for the "off-label" treatment of infections following ocular surgery, prophylaxis of endophthalmitis, and the treatment of bacterial keratitis. Taken together, clinical and preclinical animal studies indicate that besifloxacin is an important new option for the treatment of ocular infections.

In vitro susceptibility to different topical ophthalmic antibiotics of bacterial isolates from patients with conjunctivitis

PURPOSE

To test in vitro the susceptibility to different commercially-available topical antibiotics of isolates from patients with conjunctivitis, evaluated at the Microbiology Service of Turin Ophthalmic Hospital between January 2005-February 2007.

METHODS

Bacterial isolates were cultured using both liquid and solid media. The four most frequent isolates were analyzed and their in vitro susceptibility to levofloxacin, ofloxacin, norfloxacin, lomefloxacin, tobramycin, netilmycin, ampicillin, and chloramphenicol was tested, using the Kirby-Bauer diffusion method and National Committee for Clinical Laboratory Standards (NCCLS) serum standards.

RESULTS

The four most common bacteria isolates were: Staphylococcus aureus (27%), viridians Streptococci (22%), Staphylococcus epidermidis (16%) and Streptococcus pneumoniae (13%). The in vitro susceptibility to levofloxacin was highest (p<0.01) for all bacterial isolates.

CONCLUSIONS

In vitro susceptibility tests showed that levofloxacin had the highest cumulative efficacy against bacterial isolates. Netilmycin showed the highest efficacy against staphylococcus aureus, the most common bacterial isolate in this study.

[Bacteriological analysis in the management of conjunctivitis. Comparison of antibiotic resistance between 1982 and 2008]

OBJECTIVE

To demonstrate the need for bacteriological analysis for the rational treatment of infections of the corneal surface, including conjunctivitis.

METHODS

The results of 1,970 consecutive bacteriological analysis obtained from 2001 to 2008 in patients with ocular hyperemia and discharge were analysed and compared with a similar study done in 1982 in the same geographical area.

RESULTS

Bacterial growth was obtained in 1,044 cases (53%). The most frequent bacteria were Staphylococci spp. (56.6%), followed by Streptococci spp. (21.4%), Haemophili spp. (12.1%), and other gram-negative bacteria (9.9%). No antibiotic was effective against all the bacteria isolated. The frequency of resistant bacteria against neomycin, tobramycin, erythromycin and gentamicin was significantly increased with respect to the study of 1982.

CONCLUSIONS

Bacteriological analysis of conjunctival specimens are necessary to ensure the choice of an effective antibiotic against bacteria of the ocular surface when the initial treatment fails.

[In vitro antibiotic susceptibility to fluoroquinolones]

OBJECTIVE

To determine the antibiotic susceptibility of bacteria recovered from cultures of ocular infections in the Fundación Oftalmológica de Santander - Clínica Carlos Ardila Lulle (FOSCAL).

MATERIALS AND METHODS

Retrospective descriptive study of a series of registries of cultures of samples from ocular surfaces and intraocular fluids from the OCULAB-FOSCAL laboratory in Floridablanca (Colombia) made between January and December of 2007. Antibiotic sensitivity screening by the method of Kirby-Bauer with impregnated Sensi-Discs™ of determined antibiotic concentrations was performed.

RESULTS

A total of 352 samples were studied: 160 from conjunctiva, 150 from cornea and 42 from intraocular fluids. Of the total of the samples more than one microorganism was recovered 45.65% of the samples. Gram positive and Gram negative bacteria were identified in 78.7 and 18.4%, respectively. Resistance to gatifloxacin, moxifloxacin, ciprofloxacin and levofloxacin was observed in 6.3, 8.9, 33.2 and 35.6%, respectively, of Gram positive bacteria. Resistance to gatifloxacin, moxifloxacin, ciprofloxacin and levofloxacin was also observed in 7.4, 16.7, 16.7%and 25.9%, respectively, of Gram negative bacteria. The overall bacterial resistance (Gram positive and Gram negative) to moxifloxacin was 10.15%, and to gatifloxacin it was 6.46%, being which showed a statistically significant difference (P<.05).

CONCLUSIONS

In our study the development of bacterial resistance to fourth generation fluoroquinolones was demonstrated in ocular samples. However, lower levels of resistance to fourth generation fluoroquinolones compared with that of third and second generation were found, particularly to Gram positive. Gatifloxacin showed lower resistance levels than moxifloxacin. Nevertheless, interpretation of this superiority must be made with caution in the clinical field, since other factors, like tissue penetration and in vivo activity, must be taken into account.

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.

Contact lens disinfecting solutions antibacterial efficacy: comparison between clinical isolates and the standard ISO ATCC strains of Pseudomonas aeruginosa and Staphylococcus aureus

PURPOSE

To evaluate the disinfectant properties of the three multipurpose contact lens disinfecting solutions available in Iran, against clinical isolates and the standard ISO ATCC strains of Pseudomonas aeruginosa and Staphylococcus aureus, based on the international organization for standardization (ISO) 14729 guidelines.

METHODS

Three multipurpose solutions that were tested were ReNu Multiplus, Solo Care Aqua and All-Clean Soft. The test solutions were challenged with clinical isolates and the standard strains of P. aeruginosa(ATCC 9027) and S. aureus(ATCC 6538), based on the ISO Stand-alone procedure for disinfecting products. Solutions were sampled for surviving microorganisms at manufacturer's minimum recommended disinfection time. The number of viable organisms was determined and log reductions calculated.

RESULTS

All of the three test solutions in this study provided a reduction greater than the required mean 3.0 logarithmic reduction against the recommended standard ATCC strains of P. aeruginosa and S. aureus. Antibacterial effectiveness of Solo Care Aqua and All-Clean Soft against clinical isolates of P. aeruginosa and S. aureus were acceptable based on ISO 14729 Stand-alone test. ReNu MultiPlus showed a minimum acceptable efficacy against the clinical isolate of S. aureus, but did not reduce the clinical isolate by the same amount.

CONCLUSIONS

Although the contact lens disinfecting solutions meet/exceed the ISO 14729 Stand-alone primary acceptance criteria for standard strains of P. aeruginosa and S. aureus, their efficacy may be insufficient against clinical isolates of these organisms.

Antibiotic resistance in microbial keratitis: ten-year experience of corneal scrapes in the United Kingdom

PURPOSE

To determine the scale of antibiotic resistance in microbial keratitis in East Kent, United Kingdom.

DESIGN

Retrospective, observational case series.

PARTICIPANTS

Corneal scrapes over a 10-year period to December 2008 were identified using the local microbiology database, which provided culture results and antibiotic sensitivity-resistance profiles.

TESTING

Isolate sensitivity to chloramphenicol, cefuroxime, gentamicin, and ciprofloxacin was determined by microdilution using the Microscan System (Siemens Diagnostics, Dearfield, IL).

MAIN OUTCOME MEASURES

Isolates were graded as sensitive, intermediate, or resistant to the tested antibiotics, with minimal inhibitory concentrations interpreted against breakpoints from the Clinical and Laboratory Standards Institute.

RESULTS

There were 476 scrapes from 440 patients (female, 57.6%; mean age, 53.5 years). All samples were cultured. Culture was positive in 163 samples (34.2%), growing 172 organisms. Bacterial keratitis accounted for 162 isolates (94.2%), of which 99 (61.1%) were gram-negative. There was a general increase in the number of gram-negative isolates with time (P=0.003). In vitro testing showed widespread gram-negative resistance to chloramphenicol (74.1%), with reducing sensitivity over the study period (P=0.004). There was 97.3% sensitivity to combination gentamicin and cefuroxime, and 94.4% sensitivity to ciprofloxacin. Ciprofloxacin resistance was found in 8 (17.0%) of 47 gram-positive isolates tested, with no trend toward increasing resistance.

CONCLUSIONS

This study has documented the highest levels of gram-negative keratitis in any open retrospective survey to date and highlights a trend of increasing gram-negative infection. We have demonstrated reducing chloramphenicol sensitivity, with high sensitivity to combination gentamicin and cefuroxime, as well as ciprofloxacin. Gram-positive fluoroquinolone resistance was higher than previously reported in the United Kingdom, but showed no evidence of increasing resistance. Second-generation fluoroquinolone monotherapy remains the recommended empirical treatment in microbial keratitis in the United Kingdom, and a change to fourth-generation compounds is not advised. Continued testing is essential to monitor for increasing resistance.

FINANCIAL DISCLOSURE(S)

The author(s) have no proprietary or commercial interest in any materials discussed in this article.

Limitations of current antibiotics for the treatment of bacterial conjunctivitis

Bacterial conjunctivitis is a common ocular infection that is generally treated empirically with a broad-spectrum antibiotic. The more common pathogens causing bacterial conjunctivitis include Staphylococcus aureus, Haemophilus influenzae, Streptococcus pneumoniae, Staphylococcus epidermidis, and Moraxella species. Several antibiotics traditionally used to treat bacterial conjunctivitis are no longer widely prescribed because of increased bacterial resistance and/or safety concerns. The introduction of the fluoroquinolone class of anti-infectives offered effective and better tolerated treatment options. Nonetheless, successful therapy for bacterial conjunctivitis continues to be limited by several factors. A primary concern is the development of bacterial resistance that may be impacted not only by widespread antibiotic use but also by antibacterial pharmacokinetics, such as maintenance of insufficient bactericidal concentrations at the site of infection. In addition, poor adherence to prescribed regimens that require frequent administration, along with undesirable adverse events, affects the development of bacterial resistance and the success of treatment regimens. This article reviews current antibacterial agents used to treat bacterial conjunctivitis, factors that limit their successful use in treatment, and options for future development of more effective topical ophthalmic anti-infective agents.

Comparative efficacies of contact lens disinfecting solutions against Pseudomonas aeruginosa

PURPOSE

The aim of the present study was to evaluate the disinfection properties of multipurpose contact lens disinfection solutions, based on the International Organization for Standardization (ISO) 14729 guidelines.

METHODS

Three lots of each of six multi-purpose solutions were tested as follows: Renu MultiPlus, Solo Care Aqua, All-Clean Soft, Contact All-in one Advanced, Hippia, Ginza multi-purpose solution and 0.9% normal saline solution were inoculated with the standard strain of Pseudomonas aeruginosa (ATCC 9027). The surviving bacteria were quantified at specified times. An average logarithm reduction in bacterial numbers at the manufacturer's minimum recommended disinfection time was determined and compared with the criteria for stand-alone disinfection products for each multi-purpose disinfection solution against each bacterial strain.

RESULTS

Renu MultiPlus, Solo Care, All-Clean Soft and Contact All-in one Advanced were effective in achieving a four logarithmic units reduction in the bacterial count; however, Renu MultiPlus and Solo Care Aqua resulted in the greatest reduction in bacterial numbers. The other solutions were not effective against Pseudomonas aeruginosa after specified times.

CONCLUSIONS

Generally, Renu MultiPlus, Solo Care Aqua, All-Clean Soft and Contact All-in one Advanced meet the ISO 14729 guidelines for stand-alone contact lens solutions.

The patterns of in vitro antimicrobial susceptibility and resistance of bacterial keratitis isolates in Glasgow, United Kingdom

PURPOSE

Trends in antibiotic sensitivity of pathogenic bacteria change with time and the emergence of resistance to commonly used antibiotics is not uncommon. The aim of this study is to identify the antibiotic susceptibility and resistance patterns in a tertiary referral centre that commonly manages corneal infections.

METHODS

This is a retrospective review of microbiology reports of corneal scrapes in a tertiary care hospital.

RESULTS

There were 205 positive corneal scrapes (32 per cent) in 1995 to 1998 and 147 (28 per cent) in 2004 to 2007. There was increased incidence of Staphylococcus aureus (18 to 21 per cent) (p = 0.16), Moraxella catarrhalis (1.5 to 5 per cent) (p = 0.5), pseudomonas species (6 to 14.5 per cent) (p = 0.25) and non-lactose fermenting coliforms (1.5 to 7 per cent) (p = 0.5). In vitro resistance of gram-positive bacterial isolates to ciprofloxacin was increased from 5 to 7 per cent (p = 0.5). The in vitro susceptibility of gram-positive organisms to dual therapy with cefuroxime and gentamicin were 98 per cent in 1995 to 1998, and 94 per cent in 2004 to 2007 (p = 0.1). Pseudomonas species were 100 per cent susceptible to cefuroxime in the first period but developed 100 per cent resistance in the later period (p = 0.0002). However, the susceptibility of gram negative bacterial isolates to dual therapy with cefuroxime and gentamicin (p = 1) and monotherapy with ciprofloxacin (p = 1) was 100 per cent in both periods. The in vitro resistance to chloramphenicol to gram-positive organisms was reduced to 5 from 12 per cent (p = 0.19) but there was an increase in resistance of gram-negative organisms from 23 to 36 per cent (p = 0.3).

CONCLUSION

Despite limitations, this study demonstrates that the fortified antibiotics such as 5% cefuroxime 1.5% gentamicin may be the appropriate choices for most episodes of bacterial keratitis, either as an initial therapy or after identification of in vitro susceptibility of bacterial isolates.

Review of resistance of ocular isolates of Pseudomonas aeruginosa and staphylococci from keratitis to ciprofloxacin, gentamicin and cephalosporins

BACKGROUND

Microbial keratitis is a rare disease but most commonly caused by bacterial infection. Two of the most common bacteria to cause microbial keratitis are Pseudomonas aeruginosa and Staphylococcus aureus. Antibiotic therapy to treat keratitis caused by these bacteria is either monotherapy with a fluoroquinolone or combination therapy with fortified gentamicin.

METHODS

Literature searches were made in Medline and Pubmed using the search terms [Pseudomonas] or [Staphylococcus] and [fluoroquinolone] or [cephalosporin] or [gentamicin] and [keratitis] or [cornea]. Rates of resistance to ciprofloxacin, gentamicin or cephalosporins were then compared for isolates from different geographic regions.

RESULTS

There are low resistance rates of P. aeruginosa and S. aureus to ciprofloxacin in isolates from Australia. Isolates from the Indian subcontinent are more commonly resistant to ciprofloxacin, with resistance rates of greater than 20 per cent being reported. Data from USA and Europe indicate that if the S. aureus is a methicillin resistant strain, then resistance to ciprofloxacin increases, often to greater than 80 per cent of isolates. Resistance to gentamicin and cephalosporins is also generally low in isolates from Australia. Again resistance is increased in isolates from the Indian subcontinent, as well as from South America.

CONCLUSION

In Australia, the major ocular pathogens are generally sensitive to the most commonly used antibiotics to treat microbial keratitis. The prescription of fluoroquinolones, aminoglycosides and cephalosporins is generally reserved for treatment of significant or sight-threatening conditions such as microbial keratitis. This approach is not likely to contribute to an increase in resistance rates.

Etiology and antibacterial susceptibility pattern of community-acquired bacterial ocular infections in a tertiary eye care hospital in south India

AIMS

To identify the etiology, incidence and prevalence of ocular bacterial infections, and to assess the in vitro susceptibility of these ocular bacterial isolates to commonly used antibiotics.

MATERIALS AND METHODS

Retrospective analysis of consecutive samples submitted for microbiological evaluation from patients who were clinically diagnosed with ocular infections and were treated at a tertiary eye care referral center in South India between January 2002 and December 2007.

RESULTS

A total of 4417 ocular samples was submitted for microbiological evaluation, of which 2599 (58.8%) had bacterial growth, 456 (10.3%) had fungal growth, 15 (0.34%) had acanthamoebic growth, 14 (0.32%) had mixed microbial growth and the remaining 1333 (30.2%) had negative growth. The rate of culture-positivity was found to be 88% (P < 0.001) in eyelids' infection, 70% in conjunctival, 69% in lacrimal apparatus, 67.4% in corneal, 51.6% in intraocular tissues, 42.9% in orbital and 39.2% in scleral infections. The most common bacterial species isolated were Staphylococcus aureus (26.69%) followed by Streptococcus pneumoniae (22.14%). Sta. aureus was more prevalent more in eyelid infections (51.22%; P = 0.001) coagulase-negative staphylococci in endophthalmitis (53.1%; P = 0.001), Str. pneumoniae in lacrimal apparatus and corneal infections (64.19%; P = 0.001), Corynebacterium species in blepharitis and conjunctivitis (71%; P = 0.001), Pseudomonas aeruginosa in keratitis and dacryocystitis (66.5%; P = 0.001), Haemophilus species in dacryocystitis and conjunctivitis (66.7%; P = 0.001), Moraxella lacunata in blepharitis (54.17%; P = 0.001) and Moraxella catarrhalis in dacryocystitis (63.83%; P = 0.001). The largest number of gram-positive isolates was susceptible to moxifloxacin (98.7%) and vancomycin (97.9%), and gram-negative isolates to amikacin (93.5%) and gatifloxacin (92.7%).

CONCLUSIONS

Gram-positive cocci were the most frequent bacteria isolated from ocular infections and were sensitive to moxifloxacin and vancomycin, while gram-negative isolates were more sensitive to amikacin and gatifloxacin.

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.