Ocular TRUST: nationwide antimicrobial susceptibility patterns in ocular isolates

Antimicrobial resistance in ocular infection: A review

Antimicrobial resistance (AMR) is a global public health threat with significant impact on treatment outcomes. The World Health Organization's Global Action Plan on AMR recommended strengthening the evidence base through surveillance programs and research. Comprehensive, timely data on AMR for organisms isolated from ocular infections are needed to guide treatment decisions and inform researchers and microbiologists of emerging trends. This article aims to provide an update on the development of AMR in ocular organisms, AMR in bacterial ocular infections and on AMR stewardship programs globally. The most common ocular pathogens are Pseudomonas aeruginosa, Staphylococcus spp., Streptococcus pneumoniae, and Haemophilus influenzae in ocular infections. A variety of studies and a few surveillance programs worldwide have reported on AMR in these infections over time. Fluoroquinolone resistance has increased particularly in Asia and North America. For conjunctivitis, the ARMOR cumulative study in the USA reported a slight decrease in resistance to ciprofloxacin. For keratitis, resistance to methicillin has remained stable for S. aureus and CoNS, while resistance to ciprofloxacin has decreased for MRSA globally. Methicillin-resistance and multidrug resistance are also emerging, requiring ongoing monitoring. Antimicrobial stewardship (AMS) programmes have a critical role in reducing the threat of AMR and improving treatment outcomes. To be successful AMS must be informed by up-to-date AMR surveillance data. As a profession it is timely for ophthalmology to act to prevent AMR leading to greater visual loss through supporting surveillance programmes and establishing AMS.

New Approaches to Overcoming Antimicrobial Resistance in Endophthalmitis

Endophthalmitis is a rare but vision-threatening infection characterized by marked inflammation of intraocular fluids and tissues, uncommonly seen following surgery and intravitreal injection. Antimicrobials are used worldwide in the prophylaxis and treatment of bacterial and fungal infections of the eye and are standard treatment in the preoperative and postoperative care of surgical patients. However, antimicrobials are reported to be overprescribed in many parts of the world, which contributes to antimicrobial resistance (AMR). AMR complicates the prophylaxis and treatment of endophthalmitis. This article examines the prevalence and mechanisms of AMR in ocular microorganisms, emphasizing the importance of understanding AMR patterns for tailored treatments. It also explores prophylaxis and management strategies for endophthalmitis, with a discussion on the use of intracameral antibiotic administration. The use of prophylactic intracameral antibiotics during cataract surgery is common in many parts of the world but is still controversial in some locations, especially in the US. Finally, it highlights the role of stewardship in ophthalmology and its benefits in the treatment of endophthalmitis.

[Bacterial Conjunctivitis: Current Aspects of Diagnosis and Therapy]

Bacterial conjunctivitis is a leading cause of infectious conjunctivitis in children and second most common cause in adults. Although often self-limiting, it can lead to complications like corneal scarring and systemic infections in high-risk groups including newborns and immunocompromised patients. Thus, prompt diagnosis and treatment are essential for these vulnerable populations. Common bacterial causes are Staphylococcus aureus and Streptococcus pneumoniae in adults and Haemophilus influenzae and Moraxella catarrhalis in children. Clinical features alone do not reliably identify the causative pathogen. Microbiological testing is necessary for persistent or severe cases. Topical antibiotics like azithromycin or fluorochinolones are usually prescribed. However, gonococcal and chlamydial conjunctivitis warrant systemic antibiotics due to their potential for severe complications. Increasing antibiotic resistance might even necessitate tailored therapy based on antibiotic susceptibility profiles. Screening and treating pregnant women is an effective prevention strategy by reducing perinatal transmission (especially of gonococcal and chlamydial infections). In summary, while often self-limiting, potential complications and rising antibiotic resistance underscore the importance of timely diagnosis and treatment of bacterial conjunctivitis. Preventive measures including maternal screening are crucial public health initiatives to curb the risks associated with this common eye infection.

Antibiotic resistance of bacterial pathogens isolated from the conjunctiva in the Antibiotic Resistance Monitoring in Ocular micRoorganisms (ARMOR) surveillance study (2009-2021)

Antibiotic resistance in bacterial ocular infections is of significant clinical concern and may affect treatment outcomes. We report on in vitro antibiotic susceptibility rates and trends among conjunctival-sourced isolates collected in the Antibiotic Resistance Monitoring in Ocular micRoorganisms (ARMOR) surveillance study. A total of 2214 conjunctival isolates (918 Staphylococcus aureus, 589 coagulase-negative staphylococci [CoNS], 194 Streptococcus pneumoniae, 171 Pseudomonas aeruginosa, and 342 Haemophilus influenzae) obtained between 2009-2021 were analyzed. Staphylococci were commonly resistant to azithromycin (≥54.8%) and oxacillin (≥29.3%). Resistance among S. pneumoniae isolates was notable for azithromycin (34.0%) and penicillin (28.9%), while P. aeruginosa and H. influenzae isolates were highly susceptible to most tested antibiotics. Methicillin-resistant staphylococci demonstrated greater concurrent resistance to other antibiotics than methicillin-susceptible isolates and exhibited high rates of multidrug resistance (≥74.0%). Among staphylococci, antibiotic resistance increased with patient age, and there were small decreases in resistance to several drugs over the 13-year period. These findings indicate that resistance to antibiotics routinely used in ophthalmic practice remains high among conjunctival isolates.

Bovine pericardium membrane (TutoPatch) for emergency repair of total corneal melting over an infected corneal graft

Purpose

Corneal perforation due to severe melting is a very dangerous, sight-threatening condition requiring immediate management due to the high risk of endophthalmitis and critical hypotony. In the case of perforated corneal grafts, retransplantation is usually postponed to avoid the detrimental effects of inflammation on the new graft. We describe the first case of the use of a TutoPatch graft for emergency replacement of a lamellar graft perforation over acute infectious total melting.

Observations

A 42-year-old male patient presented to the Emergency Department with pain in the left eye, which was red photophobic. He had been treated with bilateral deep anterior lamellar keratoplasty (DALK) for advanced keratoconus 5 years previously and had been experiencing recurrent corneal ulcers in the left eye within the last 8 months. Clinical examination documented corneal perforation over acute infectious melting involving the total graft surface in the left eye. The infected graft was removed along with the perforated infected residual Descemet membrane, and a double-layer TutoPatch covering was sutured to the host's margin with 10.0 nylon. The covering was left in place for three weeks, allowing the patient to undergo retransplant three weeks later without complications.

Conclusions and importance

TutoPatch covering can be safely used as an easy-to-preserve emergency material for a temporary bridge to retransplantation in large acute infectious corneal melting.

Reducing Ophthalmic Antibiotic Use for Non-severe Conjunctivitis in Children

BACKGROUND

Antibiotics are often overprescribed for pediatric conjunctivitis. We implemented a system-level quality improvement (QI) intervention to reduce unnecessary ophthalmic antibiotic use.

METHODS

The multi-faceted intervention in Denver, CO comprised a clinical care pathway, nurse protocol modifications, electronic health record (EHR) changes, parent education materials, and clinician education. We evaluated children aged 6 months-17 years with conjunctivitis seen between November 2018 and December 2022. A multi-interrupted time series model evaluated the effectiveness of the intervention over three time periods: Pre-COVID, Pre-Intervention (November 2018-February 2020), COVID, Pre-Intervention (March 2020-March 2021), and Post-Intervention (April 2021-December 2022). Fisher's exact tests compared treatment failure and healthcare utilization rates between time periods and among children receiving or not receiving ophthalmic antibiotics.

RESULTS

Among 6960 eligible encounters, ophthalmic antibiotic use was reduced by 18.8% (95% CI: 16.3, 21.3) from Pre-COVID, Pre-Intervention to Post-Intervention. During the Pre-Intervention period following the onset of COVID, a reduction of 16.1% (95% CI: 12.9, 19.3) was observed. Implementation of the intervention resulted in an additional 2.7% (95% CI: -0.4, 5.7) reduction in antibiotic prescribing, primarily in younger children (ages 6 months-5 years). The greatest reduction in prescribing occurred for nurse triage encounters with an 82.1% (95% CI: 76.8, 87.5) reduction in prescribing rates (92.6%-10.5%). Treatment failure occurred in 1301 (18.7%) children and was more common among children that received an ophthalmic antibiotic than those that did not (20.0 vs 17.9%; P = .03).

CONCLUSION

The QI intervention significantly reduced ophthalmic antibiotic prescribing for pediatric conjunctivitis without increasing treatment failure rates or health care utilization.

ALTERNATIVE INTRAVITREAL ANTIBIOTICS: A Systematic Review for Consideration in Recalcitrant or Resistant Endophthalmitis

PURPOSE

To organize, categorize, and create a quick reference guide for the use of intravitreal antibiotic alternatives to the standard combination of vancomycin and ceftazidime for the treatment of endophthalmitis.

METHODS

A systematic review was conducted in accordance with the Preferred Reporting Items for Systematic Review and Meta-Analyses guidelines. The authors searched for all available information regarding intravitreal antibiotics in the last 21 years. Manuscripts were selected according to relevance, level of information, and the available data regarding intravitreal dose, potential adverse effects, bacterial coverage, and relevant pharmacokinetic information.

RESULTS

The authors included 164 of 1810 manuscripts. The antibiotics were classified according to their class into fluoroquinolones, cephalosporins, glycopeptide and lipopeptide, penicillins and beta-lactams, tetracyclines, and miscellaneous. The authors also included information regarding intravitreal adjuvants for the treatment of endophthalmitis and one ocular antiseptic.

CONCLUSION

The treatment of infectious endophthalmitis is a therapeutic challenge. The current review summarizes the properties of possible intravitreal antibiotic alternatives that should be considered in cases of suboptimal response to initial treatment.

Bacterial keratitis in a tertiary hospital in São Paulo: a 21-year review of the epidemiological, laboratory, and clinical data

Infectious keratitis is a sight-threatening condition that is usually an ocular emergency. The visual outcome depends on prompt and accurate clinical management as well as geographic and epidemiological awareness. We conducted a retrospective observational study to define the epidemiological and laboratory profile, as well as the clinical course of bacterial keratitis in a tertiary hospital in São Paulo over 21 years. Information about age, sex, predisposing factors, topical and surgical treatment, visual acuity, ulcers' classification, bacterioscopy, culture, and antibiotic sensitivity tests were collected. This study included 160 patients. The mean age was 65.1 ± 18.4 years and risk factors were identified in 83.1 % of the patients. Empirical topical fortified cephalosporin with an aminoglycoside or fourth-generation fluoroquinolone was curative for 66.2 % of the cases. The mean treatment duration was 22.5 ± 9 days. The mean variation of visual acuity was -0.25 logMAR, p < 0.001. Culture revealed 64 % of Gram-positive bacteria. All Gram-positive bacteria were sensitive to cephalothin, vancomycin, and quinolones. All Gram-negative bacteria were sensitive to gentamicin, tobramycin, amikacin, and ciprofloxacin. These findings reinforce the importance of prompt empirical treatment of severe corneal ulcers with a fortified cephalosporin and aminoglycoside or a fourth-generation fluoroquinolone as there are equally effective. Collected data was insufficient to evaluate resistance of ocular infections over time in this population.

Pediatric Conjunctivitis: A Review of Clinical Manifestations, Diagnosis, and Management

Conjunctivitis is a common pediatric problem and is broadly divided into infectious and non-infectious etiologies. Bacterial conjunctivitis makes up the majority of cases in children and often presents with purulent discharge and mattering of the eyelids. Treatment is supportive with an individual approach to antibiotic use in uncomplicated cases since it may shorten symptom duration, but is not without risks. Viral conjunctivitis is the other infectious cause and is primarily caused by adenovirus, with a burning, gritty feeling and watery discharge. Treatment is supportive. Allergic conjunctivitis is largely seasonal and presents with bilateral itching and watery discharge. Treatment can include topical lubricants, topical antihistamine agents, or systemic antihistamines. Other causes of conjunctivitis include foreign bodies and non-allergic environmental causes. Contact lens wearers should always be treated for bacterial conjunctivitis and referred to evaluate for corneal ulcers. Neonatal conjunctivitis requires special care with unique pathogens and considerations. This review covers essential information for the primary care pediatric provider as they assess cases of conjunctivitis.

Urgent unmet needs in the care of bacterial keratitis: An evidence-based synthesis

Bacterial corneal infections, or bacterial keratitis (BK), are ophthalmic emergencies that frequently lead to irreversible visual impairment. Though increasingly recognized as a major cause of global blindness, modern paradigms of evidence-based care in BK have remained at a diagnostic and therapeutic impasse for over half a century. Current standards of management - based on the collection of corneal cultures and the application of broad-spectrum topical antibiotics - are beset by important yet widely underrecognized limitations, including approximately 30% of all patients who will develop moderate to severe vision loss in the affected eye. Though recent advances have involved a more clearly defined role for adjunctive topical corticosteroids, and novel therapies such as corneal crosslinking, overall progress to improve patient and population-based outcomes remains incommensurate to the chronic morbidity caused by this disease. Recognizing that the care of BK is guided by the clinical axiom, "time equals vision", this chapter offers an evidence-based synthesis for the clinical management of these infections, underscoring critical unmet needs in disease prevention, diagnosis, and treatment.

Practice patterns in the management of bacterial keratitis: a five-continent survey

PURPOSE

To assess the current diagnostic and therapeutic practice patterns in early management of bacterial keratitis over five continents.

METHODS

Between March and August 2019, we distributed an online survey including two clinical scenarios of bacterial keratitis, namely, a mild case and severe case, to 2936 ophthalmologists from 144 countries around the world. The survey consisted of 29 questions. We performed descriptive statistics and a comparative analysis of the answers according to the participants' continent of practice, practice setting, seniority, and subspecialty.

RESULTS

We received 237 surveys from 54 countries (8% response rate). The proportion of respondents performing microbiological investigations was higher in North America, Asia, Europe, and Oceania than Africa and South America (p < 0.05). This ratio was also higher among ocular surface specialists than for other ophthalmologists (p < 0.001). For mild cases, fluoroquinolone monotherapy and a combination of two or more antibiotics were prescribed by 46% and 41% respondents, respectively. For severe cases, fluoroquinolone monotherapy and a combination of antibiotics were prescribed by 20% and 78% respondents, respectively. Fluoroquinolone monotherapy was the most commonly prescribed treatment in South America, Africa, and Oceania. A combination of two antibiotics was preferentially prescribed in the rest of the world. Topical steroids were prescribed in both circumstances, respectively, in 72% and 75% of cases.

CONCLUSION

Our results highlight essential geographical disparities in the current management of bacterial keratitis over five continents.

A Literature-Based Review and Analysis of the Pharmacodynamics of the Dose Frequency of Topical 0.3% Ciprofloxacin and 0.3% Ofloxacin in the Day-1 Treatment of Bacterial Keratitis

Purpose: To determine the appropriate dose frequency for the second-generation fluoroquinolones (2FQs), ciprofloxacin 0.3% and ofloxacin 0.3%, in the day-1 treatment of bacterial keratitis (BK) based on the corneal concentrations achievable and required Minimum Inhibitory Concentration₉₀ (MIC₉₀) of common BK isolates. Methods: Literature-based ocular MIC₉₀ required to treat bacterial isolates of BK patients were determined for each fluoroquinolone. Published corneal concentrations for each 2FQ, and the drop regimens used to reach these concentrations, were then analyzed to determine the relationship between the corneal 2FQ concentration and the amount of drug applied per hour and the total amount applied. Results: Significant relationships were found to exist for corneal concentrations of both ciprofloxacin and ofloxacin and the amount of drug applied per hour (both P = 0.005), and the total amount of drug applied (P = 0.003 and P = 0.0004, respectively). Derived ciprofloxacin drops/hour corneal concentrations agreed well with both a literature-based regimen and the manufacturers' day-1 drop regimen for various MIC₉₀. Derived ofloxacin drops per hour indicated a higher rate than that suggested by the manufacturer. Conclusions: Both a literature-based and the manufacturers' drop regimens for the day-1 treatment of BK using 0.3% ciprofloxacin have a pharmacodynamic basis, which is related to the required MIC₉₀ of commonly encountered isolates in BK. Dose frequency for 0.3% ofloxacin should be in line with the manufacturers' maximum suggested drop regimen. Commonly suggested drop regimens below these recommendations for either FQ may need to be revised in view of these findings.

Bacterial isolates and antimicrobial susceptibility pattern of ocular infection at a tertiary referral hospital in the South of Italy

PURPOSE

The present study aimed to determine the prevalence of bacterial and fungal infections of the eye and also to assess the antibiotic susceptibility pattern of bacterial isolates at a tertiary referral eye care hospital in Bari, Italy.

METHODS

Two hundred seventy three samples collected during a 2-year observation period. Culture, Gram's stain, potassium hydroxide mount and occasionally Giemsa staining was done for the clinical specimens. Antibiotic susceptibility testing was performed for bacterial growth.

RESULTS

Out of 273 samples processed, 236 (86.4%) yielded growth: of them, 183 (77,5%) were bacterial, 26 (11%) fungal, and 23 (9,7%) specimens showed the presence of Acanthamoeba. Among bacterial infections, 99 (54.5%) bacterial isolates were Gram-positives, and 82 (44.8%) were Gram-negatives. Among Gram positives, Tigecycline showed the greatest susceptibility (93.8%), followed by Linezolid (97%) and Daptomycin (95.18%). Gram negative bacteria strains were susceptible to Imipenem (95%), Meropenem (98,5%) and Amikacin (91%) Multidrug in vitro resistance (resistance >3 classes of antibiotics) was found in 45 Gram positive (63%). and 33 Gram negative (44%).

CONCLUSION

Conjunctival specimens yielded mainly bacterial growth with Staphylococcus species being the predominant isolate followed by Pseudomonas species. Findings from the current analysis evidence a substantial level of in vitro resistance to ≥3 antibiotics.

Staphylococcus aureus Keratitis in Taiwan: Genotyping, Antibiotic Susceptibility, and Clinical Features

Staphylococcus aureus is an important pathogen for keratitis, a vision-threatening disease. We aimed to investigate the genotyping, antibiotic susceptibility, and clinical features of S. aureus keratitis, and to explore the possible role of Panton–Valentine leucocidin (PVL), a major virulence factor of S. aureus. We recruited 49 patients with culture-proven S. aureus keratitis between 2013 and 2017 at Chang Gung Memorial Hospital, Taiwan. PVL gene, multilocus sequence type (MLST), staphylococcal cassette chromosome mec (SCCmec), and pulsed-field gel electrophoresis (PFGE) were performed. Antibiotic susceptibility was verified using disk diffusion/E test. There were 49 patients with S. aureus keratitis; 17 (34.7%) were caused by methicillin-resistant S. aureus (MRSA) and 9 (18.4%) isolates had PVL genes. The predominant genotyping of MRSA isolates was CC59/PFGE type D/SCCmec VT/PVL (+). All methicillin-sensitive S. aureus (MSSA) and approximately 60% MRSA were susceptible to fluoroquinolones. No significant differences in clinical features, treatments, and visual outcomes were observed between MRSA/MSSA or PVL(+)/PVL(−) groups. In Taiwan, approximately one third of S. aureus keratitis was caused by MRSA, mainly community-associated MRSA. Although MRSA isolates were more resistant than MSSA, clinical characteristics were similar between two groups. Fluoroquinolones could be good empiric antibiotics for S. aureus keratitis.

Infectious Keratitis Isolates and Susceptibility in Southern California

PURPOSE

The purpose of this study was to determine longitudinal trends in prevalence and resistance profiles for infectious keratitis at referral centers in Southern California.

METHODS

Cultured infectious keratitis cases from January 1, 2006, through December 31, 2009, and January 1, 2016, through December 31, 2019, at the University of California, Los Angeles, were evaluated. Outcome measures included microbial isolate prevalence and antibiotic/antifungal susceptibility and resistance patterns.

RESULTS

One hundred thirty-nine and 315 culture-positive isolates were obtained between 2006-2009 and 2016-2019, respectively. Gram-positive organisms accounted for 65% (2006-2009) and 74% (2016-2019) of bacterial isolates ( P = 0.076). Staphylococcus infections, the most common gram-positive and bacterial isolate in both study epochs, demonstrated increased prevalence from 2006-2009 to 2016-2019 (41% vs. 53%, P = 0.019). Although coagulase-negative Staphylococcus (CoNS) increased from 40% to 58% ( P = 0.0012), the prevalence of methicillin-resistant Staphylococcus aureus was unchanged (28% vs. 28%, P = 0.99). Pseudomonas aeruginosa , the most common gram-negative organism, demonstrated decreased prevalence from 18% to 10% ( P = 0.027). Candida species comprised 3.5% of culture-positive isolates in both epochs. All gram-positive isolates were susceptible to vancomycin, and all Staphylococcus isolates were susceptible to linezolid. Pseudomonas aeruginosa remained susceptible to tested fluoroquinolones (>93%) and aminoglycosides (100%) over time.

CONCLUSIONS

In southern California between 2006 and 2019, there was a shift toward Staphylococcus species, with increased CoNS, decreased methicillin-sensitive Staphylococcus aureus , and decreased prevalence of P. aeruginosa . Empiric therapy of vancomycin and a fluoroquinolone or aminoglycoside provides effective antibacterial coverage for predominant bacterial species when culture sensitivities are pending.

Trends in Infectious Keratitis in Taiwan: An Update on Predisposing Factors, Microbiological and Antibiotic Susceptibility Patterns

Infectious keratitis (IK) represents a major cause of corneal blindness. This study aims to investigate the demographics, risk factors, microbiological characteristics and antibiotic susceptibility patterns of IK in Taiwan over the past 15 years. A retrospective population-based study was conducted using the Chang Gung Research Database. Patients with IK were identified by diagnostic codes for corneal ulcer from 2004 to 2019. Of 7807 included subjects, 45.2% of patients had positive corneal cultures. The proportion of contact lens-related IK declined, while that of IK related to systemic diseases grew. The percentage of isolated gram-positive bacteria surpassed that of gram-negative bacteria in the 15-year period. The prevalence of Pseudomonas aeruginosa showed a decreasing trend (p = 0.004), whereas coagulase-negative Staphylococcus (CNS) and Propionibacterium species were increasingly detected (p < 0.001). Overall, the trend of antibiotic susceptibility of both gram-positive and gram-negative bacteria did not change throughout the study period. The susceptibility to the test antibiotics maintained over 90% in gram-negative isolates over 15 years. Vancomycin preserved 100% susceptibility to all gram-positive isolates. Since most tested antibiotics exhibited stable susceptibility over decades, this study reinforced that fluoroquinolones and fortified vancomycin continue to be good empiric therapies for treating bacterial keratitis in Taiwan.

Clinical characteristics of external bacterial ocular and periocular infections and their antimicrobial treatment patterns among a Ghanaian ophthalmic population

Empirical antimicrobial therapy is linked to a surge in antimicrobial resistant infections. However, an insight on the bacteria etiology of ocular infections is essential in the appropriation of choice of antimicrobial among clinicians, yet there remains a dearth of data from Ghana. We investigated the bacteria etiology of external ocular and periocular infections and antimicrobial treatment patterns among a Ghanaian ophthalmic population. A multicenter study design with purposive sampling approach was employed. Patients demographics and clinical data were collated using a pretested structure questionnaire. Cornea specimens and conjunctival swabs were obtained for bacterial isolation following standard protocols. About 95% (98/103) of ocular samples were positive for bacteria culture. The proportion of Gram-negative bacteria was 58.2%, and the predominant bacteria species were Pseudomonas aeruginosa 38.8% and Staphylococcus aureus 27.6%. Conjunctivitis 40.0% and keratitis 75.0% were mostly caused by Pseudomonas aeruginosa. The routinely administered antimicrobial therapy were polymyxin B 41.2%, neomycin 35.1% and ciprofloxacin 31.6%. Participants demographic and clinical characteristics were unrelated with positive bacteria culture (p > 0.05). Our results showed a markedly high burden of ocular bacterial infections and variations in etiology. Bacterial infection-control and antimicrobial agent management programs should be urgently institutionalized to prevent the emergence of resistant infections.

Microbiological profile of canaliculitis and their antibiotic susceptibility patterns: A 11-year review at a referral eye care centre

PURPOSE

To analyze the microbiological profile and in vitro antibiotic susceptibility patterns of bacterial isolates in canaliculitis, an infection of the lacrimal drainage system of the eye.

METHODS

The laboratory records of patients presenting with canaliculitis from whom specimens were obtained for microbiological investigations at our tertiary eye care centre in South India from January 2010 to December 2020, were reviewed.

RESULTS

A total of 130 canalicular pus samples were collected from 112 patients and submitted for microbiological studies during the study period. A total of 183 micro-organisms were isolated from 115 culture-positive specimens. The micro-organisms isolated were predominantly aerobic Gram-positive bacteria (83.44%), with Coagulase-negative Staphylococci (CoNS/Other Staphylococcus spp) (31.69%), Corynebacterium spp (15.3%), Staphylococcus aureus (9.84%) and Viridans Streptococci (9.84%) accounting for a majority of the isolates. Actinomycesspp (6.56%) was the most common anaerobic bacterium isolated. Our study revealed several bacteria not previously associated with canaliculitis namely Ottowia spp, Elizabethkingiameningoseptica, Aeromonassalmonicida, Capnocytophagaochracea and Campylobacter gracilis. Polymicrobial aetiology was observed in 39.13% of culture-positive samples. Analysis of antibiotic susceptibility patterns of the isolates revealed a high proportion of Gram-positive bacteria susceptible to chloramphenicol (90.16%) compared to fluoroquinolones including ciprofloxacin (74.42%), norfloxacin (64.15%) and gatifloxacin (60.49%).

CONCLUSION

This study represents the largest series of canaliculitis reporting the microbiological profile and antibiotic susceptibilities of the isolated micro-organisms, till date. Gram-positive bacteria accounted for a majority of isolates, predominated by Staphylococcus spp. The increasing resistance of Gram-positive bacteria to fluoroquinolones warrants antibiotic treatment in canaliculitis is based on in vitro antimicrobial susceptibility patterns.

In vitro antimicrobial activity of ozonated oil in liposome eyedrop against multidrug-resistant bacteria

Bacteria are the most common causative agents of ocular infections. Treatment with topical broad-spectrum antibiotics is recommended in severe cases. However, antibiotic resistance has become a major concern in recent years, although antibiotics are generally effective in treating ocular infections. Antibacterial compound screening is performed to identify alternative therapeutic options to antibiotics. The aim of this study was to assess the in vitro antimicrobial activity of an ophthalmic solution containing ozonated oil. Strains of bacterial species with a multidrug resistance profile, which are responsible for a large proportion of ocular infections, were isolated and selected from different biological samples. The bacterial isolates were cultured, and ozonated oil was used to evaluate the inhibition zones at different time points. The treatment exhibited antibacterial activity against all the tested species. The effect was lower against the strains of Pseudomonas aeruginosa and more evident against Staphylococcus and Streptococcus spp. Our results suggest that the administration of ozonated oil may be a candidate agent to treat some infections of the ocular surface with a potential role in antimicrobial prophylaxis.

A qualitative evaluation of pediatric conjunctivitis medical decision making and opportunities to improve care

BACKGROUND

Acute infectious conjunctivitis is a common childhood illness, and the role of antibiotic treatment remains unclear. The purpose of this study was to describe the decision-making process providers use when managing infectious conjunctivitis, to identify factors that reduce unnecessary antibiotic prescribing, and to evaluate how the COVID-19 pandemic influenced prescribing behavior.

METHODS

We conducted semi-structured interviews with 20 providers caring for children in primary care, urgent cares, and emergency departments in Denver, Colorado. Interviews were evaluated for major themes using deductive and inductive content analysis methods.

RESULTS

Significant drivers for deciding to treat infectious conjunctivitis with antibiotics included patient's clinical presentation, family expectations, antibiotic stewardship concerns, etiological diagnostic uncertainty, and school/daycare policies. High variability existed in approaches used to distinguish viral from bacterial conjunctivitis. No providers were aware of pediatric treatment guidelines or standardized recommendations for return to school or daycare. Providers reported higher antibiotic prescribing during the COVID-19 pandemic. Factors identified that could reduce unnecessary antibiotic prescribing included family education, a reliable diagnostic test to decrease diagnostic uncertainty, pediatric clinical guidelines, and standardizing exclusion policies for school/daycare.

CONCLUSIONS

Management of pediatric infectious conjunctivitis is inconsistent. Creation of guidelines for the evaluation and management of infectious conjunctivitis in children could help reduce unnecessary prescribing and the burden for families and the health care system. In addition, updated guidelines for school/daycare exclusion may be important to establish streamlined and evidence-based exclusion practices.

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.

Ophthalmic antibiotic use for acute infectious conjunctivitis in children

BACKGROUND

Infectious conjunctivitis is among the most common pediatric infections worldwide; antibiotics are often not indicated. We aimed to determine factors associated with ophthalmic antibiotic prescribing and changes in prescribing prior to and during the COVID-19 pandemic at a single center.

METHODS

Encounters for children with infectious conjunctivitis from 2017 to 2020 at Denver Health and Hospital Authority clinics were analyzed retrospectively. Factors associated with prescribing were evaluated using multivariable logistic regression modeling. Encounter numbers and prescribing patterns for telephone versus in-person visits before and during the pandemic were compared and stratified.

RESULTS

Of 5,283 patients encounters for conjunctivitis, 3,841 (72.7%) resulted in an ophthalmic antibiotic prescription. Concurrent diagnosis with acute otitis media (adjusted odds ratio [aOR] 0.20 (95% CI, 0.16-0.25) and later study year (2018-aOR = 0.76 [95% CI, 0.65-0.89]; 2019- aOR = 0.57 [95% CI, 0.48-0.67]) were associated with reduced odds of prescribing. Compared with those evaluated in pediatric clinics, patients evaluated in family medicine (aOR = 0.69 [95% CI, 0.58-0.83]) or optometry/ophthalmology clinics (aOR = 0.06 [95% CI, 0.02-0.14]) were less likely to have antibiotics prescribed, whereas, patients evaluated via telephone had a 5.43 (95% CI, 3.97-7.42) greater odds of being prescribed ophthalmic antibiotics. Antibiotic prescribing increased from 67.8% prior to the COVID-19 pandemic to 81.9% during the pandemic (P < 0.0001).

CONCLUSIONS

Discordant with national guideline recommendations, ophthalmic antibiotic use for conjunctivitis was high. Telephone visits were associated with higher rates of prescribing. Rates of prescribing increased significantly during the COVID-19 pandemic.

Clinical Features and Molecular Characteristics of Methicillin-Susceptible Staphylococcus aureus Ocular Infection in Taiwan

This study analyzed the clinical features and molecular characteristics of methicillin-susceptible Staphylococcus aureus (MSSA) ocular infections in Taiwan and compared them between community-associated (CA) and health-care-associated (HA) infections. We collected S. aureus ocular isolates from patients at Chang Gung Memorial Hospital between 2010 and 2017. The infections were classified as CA or HA using epidemiological criteria, and the isolates were molecularly characterized using pulsed-field gel electrophoresis, multilocus sequence typing, and Panton-Valentine leukocidin (PVL) gene detection. Antibiotic susceptibility was evaluated using disk diffusion and an E test. A total of 104 MSSA ocular isolates were identified; 46 (44.2%) were CA-MSSA and 58 (55.8%) were HA-MSSA. Compared with HA-MSSA strains, CA-MSSA strains caused a significantly higher rate of keratitis, but a lower rate of conjunctivitis. We identified 14 pulsotypes. ST 7/pulsotype BA was frequently identified in both CA-MSSA (28.3%) and HA-MSSA (37.9%) cases. PVL genes were identified in seven isolates (6.7%). Both CA-MSSA and HA-MSSA isolates were highly susceptible to vancomycin, teicoplanin, tigecycline, sulfamethoxazole–trimethoprim, and fluoroquinolones. The most common ocular manifestations were keratitis and conjunctivitis for CA-MSSA and HA-MSSA, respectively. The MSSA ocular isolates had diverse molecular characteristics; no specific genotype differentiated CA-MSSA from HA-MSSA. Both strains exhibited similar antibiotic susceptibility.

Characterization of antibiotic resistance and virulence genes of ocular methicillin-resistant Staphylococcus aureus strains through complete genome analysis

Virulence-factor encoding genes (VFGs) and antimicrobial resistance genes (ARGs) of ocular Methicillin-Resistant Staphylococcus aureus (MRSA), are the reason behind the common cause of severe and untreatable ocular infection and are largely unknown. The unavailability of the complete genome sequence of ocular MRSA strains hinders the unambiguous determination of ARGs and VRGs role in disease pathogenesis and their genomic location. To fulfill this critical need, we achieved the high-quality complete genome of four ocular MRSA strains (AMRF3 - AMRF6) by combining MinION nanopore sequencing technology, followed by polishing with Illumina sequence reads. We obtained a single chromosome and a plasmid in each strain. Sequence typing revealed that AMRF3 and AMRF5 strains harbored ST772, whereas AMRF4 and AMRF6 harbored ST 2066. All plasmids carried heavy metal cadmium resistance genes cadC and cadD, while cadA was detected only in the plasmid pSaa6159 of AMRF4 and AMRF6 strains. Further, pSaa6159 contains a complete Tn552 transposon with beta-lactamase genes, blaI, blaR1, and blaZ. Interestingly, pSaa6159 in AMRF6 carried five copies of Tn552 transposon. Several exotoxins and enterotoxins were identified across ocular MRSA strains and ST2066 strains found to be not carried any enterotoxins; this finding suggests that these two strains are exotoxigenic. Besides, ST2066 strains carried serine proteases (splA, splB, splD, splE and spIF) and exotoxin (seb and set 21) for their virulence, while ST772 carried antimicrobial resistance genes (blaZ, dfrG, msrA, mphC and fosB) and enterotoxin sec for virulence, suggesting sequence type-specific resistance and virulence. Also, we identified many VFGs and ARGs, that provided multi-drug resistance, enterotoxigenic, exotoxigenic, biofilm-forming, host tissue adhesion and immune response evasion in ocular MRSA strains. Thus, our study provides a better insight into the genomes of ocular MRSA strains that would provide more effective treatment strategies for ocular MRSA infection.

In Vitro Antibiotic Resistance among Bacteria from the Cornea in the Antibiotic Resistance Monitoring in Ocular MicRoorganisms Surveillance Study

PURPOSE

This study aimed to report on in vitro susceptibility patterns among corneal isolates collected in the Antibiotic Resistance Monitoring in Ocular micRoorganisms (ARMOR) study.

METHODS

Each year, from 2009 to 2019, Staphylococcus aureus, coagulase-negative staphylococci (CoNS), Streptococcus pneumoniae, Pseudomonas aeruginosa, and Haemophilus influenzae isolates cultured from patients with ocular infections at participating ARMOR sites were submitted to a central laboratory for species confirmation and antibiotic susceptibility testing. In this analysis of corneal isolates, odds ratios for concurrent resistance were based on sample proportions, one-way ANOVA was used to evaluate resistance by patient age, and Cochran-Armitage tests were used to examine changes in antibiotic resistance over time.

RESULTS

A total of 1499 corneal isolates were collected from 61 sites over the 11-year period. Overall, 34.5% (148 of 429) of S. aureus and 41.9% (220 of 525) of CoNS isolates were methicillin resistant and had higher odds ratios for concurrent resistance to azithromycin (17.44 and 5.67), ciprofloxacin (39.63 and 12.81), and tobramycin (19.56 and 19.95), respectively, relative to methicillin-susceptible isolates (P < .001, all); also, a high proportion of methicillin-resistant S. aureus (85.1%) and methicillin-resistant CoNS (81.8%) were multidrug resistant (at least three classes of antibiotics). Resistance among S. pneumoniae isolates was highest for azithromycin (33.1%), whereas P. aeruginosa and H. influenzae isolates demonstrated low resistance overall. Among staphylococci, antibiotic resistance differed by patient age (S. aureus: F = 6.46, P < .001; CoNS: F = 4.82, P < .001), and few small changes in resistance (≤3.60% per year), mostly decreases, were observed over time.

CONCLUSIONS

Although rates of in vitro antibiotic resistance among presumed keratitis isolates obtained in ARMOR seemed stable between 2009 and 2019, resistance among staphylococci and pneumococci remains high (and should be considered when treating keratitis).

Practical Guidance for Clinical Microbiology Laboratories: Diagnosis of Ocular Infections

The variety and complexity of ocular infections have increased significantly in the last decade since the publication of Cumitech 13B, Laboratory Diagnosis of Ocular Infections (L. D. Gray, P. H. Gilligan, and W. C. Fowler, Cumitech 13B, Laboratory Diagnosis of Ocular Infections, 2010). The purpose of this practical guidance document is to review, for individuals working in clinical microbiology laboratories, current tools used in the laboratory diagnosis of ocular infections. This document begins by describing the complex, delicate anatomy of the eye, which often leads to limitations in specimen quantity, requiring a close working bond between laboratorians and ophthalmologists to ensure high-quality diagnostic care. Descriptions are provided of common ocular infections in developed nations and neglected ocular infections seen in developing nations. Subsequently, preanalytic, analytic, and postanalytic aspects of laboratory diagnosis and antimicrobial susceptibility testing are explored in depth.

In Vitro Time-Kill of Common Ocular Pathogens with Besifloxacin Alone and in Combination with Benzalkonium Chloride

BACKGROUND

Besifloxacin ophthalmic suspension 0.6% (w/v%) contains benzalkonium chloride (BAK) as a preservative. We evaluated the in vitro time-kill activity of besifloxacin, alone and in combination with BAK, against common bacteria implicated in ophthalmic infections.

METHODS

The activity of besifloxacin (100 µg/mL), BAK (10, 15, 20, and 100 µg/mL), and combinations of besifloxacin and BAK were evaluated against isolates of Staphylococcus epidermidis (n = 4), Staphylococcus aureus (n = 3), Haemophilus influenzae (n = 2), and Pseudomonas aeruginosa (n = 2) in time-kill experiments of 180 min duration. With the exception of one S. aureus isolate, all of the staphylococcal isolates were methicillin- and/or ciprofloxacin-resistant; one P. aeruginosa isolate was ciprofloxacin-resistant. The reductions in the viable colony counts (log₁₀ CFU/mL) were plotted against time, and the differences among the time-kill curves were evaluated using an analysis of variance. Areas-under-the-killing-curve (AUKCs) were also computed.

RESULTS

Besifloxacin alone demonstrated ≥3-log killing of P. aeruginosa (<5 min) and H. influenzae (<120 min), and approached 3-log kills of S. aureus. BAK alone demonstrated concentration-dependent killing of S. epidermidis, S. aureus and H. influenzae, and at 100 µg/mL produced ≥3-log kills in <5 min against these species. The addition of BAK (10, 15, and 20 µg/mL) to besifloxacin increased the rate of killing compared to besifloxacin alone, with earlier 3-log kills of all species except P. aeruginosa and a variable impact on S. aureus. The greatest reductions in AUKC were observed among H. influenzae (8-fold) and S. epidermidis (≥5-fold). Similar results were found when the isolates were evaluated individually by their resistance phenotype.

CONCLUSIONS

In addition to confirming the activity of 100 µg/mL BAK as a preservative in the bottle, these data suggest that BAK may help besifloxacin to achieve faster time-kills on-eye in the immediate timeframe post-instillation before extensive dilution against bacterial species implicated in ophthalmic infections, including drug-resistant S. epidermidis. Greater killing activity may help prevent resistance development and/or help treat resistant organisms.

Stability Evaluation of Extemporaneously Compounded Vancomycin Ophthalmic Drops: Effect of Solvents and Storage Conditions

Vancomycin is the drug of choice for methicillin-resistant Staphylococcus aureus keratitis and other ocular infections. Vancomycin ophthalmic drops are not commercially available and require compounding. The present study was designed to investigate the stability of vancomycin ophthalmic drops in normal saline, phosphate-buffered saline (PBS), and balanced salt solution (BSS) while stored at room temperature or under refrigeration. Vancomycin ophthalmic drops (50 mg/mL) were aseptically prepared from commercially available intravenous powder using PBS, BSS, and saline. Solutions were stored at room temperature and in a refrigerator for 28 days. The vancomycin stability was tested by a microbiology assay and high-performance liquid chromatography HPLC analysis immediately after formulation and at days 7, 14, and 28 after storage at room temperature or under refrigeration. The pH, turbidity was also tested. Vancomycin formulations in PBS, BSS and normal saline had initial pH of 5; 5.5; 3 respectively. The formulation in PBS developed turbidity and a slight decrease in pH upon storage. Microbiological assay did not show any change in zone of inhibition with any of the formulation upon storage either at room temperature or under refrigeration. HPLC analysis did not detect any decrease in vancomycin concentration or the accumulation of degraded products in any of the formulations upon storage either at room temperature or under refrigeration. Vancomycin ophthalmic drops prepared using PBS, BSS, and normal saline were stable up to the tested time point of 28 days, irrespective of their storage temperature.

Trends in Antibiotic Resistance Among Ocular Microorganisms in the United States From 2009 to 2018

Question

What are the antibiotic resistance profiles and trends among common ocular pathogens across the United States?

Findings

In this cross-sectional study of more than 6000 ocular isolates of Staphylococcus aureus, coagulase-negative staphylococci, Streptococcus pneumoniae, Pseudomonas aeruginosa, and Haemophilus influenzae collected between 2009 and 2018, methicillin resistance and multidrug resistance were prevalent among staphylococci. Antibiotic resistance profiles were mostly unchanged during 10 years.

Meaning

These in vitro antibiotic resistance data may assist clinicians in selecting appropriate antibiotics for treatment of ocular infections.

Importance

Antibiotic resistance in ocular infections can affect treatment outcomes. Surveillance data on evolving antibacterial susceptibility patterns inform the treatment of such infections.

Objective

To assess overall antibiotic resistance profiles and trends among bacterial isolates from ocular sources collected during 10 years.

Design, Setting, and Participants

This cross-sectional study of longitudinal data from the ongoing, nationwide, prospective, laboratory-based surveillance study, the Antibiotic Resistance Monitoring in Ocular Microorganisms (ARMOR) study, included clinically relevant isolates of Staphylococcus aureus, coagulase-negative staphylococci (CoNS), Streptococcus pneumoniae, Pseudomonas aeruginosa, and Haemophilus influenzae cultured from patients with ocular infections at US centers from January 1, 2009, to December 31, 2018.

Main Outcomes and Measures

Minimum inhibitory concentrations were determined for various combinations of antibiotics and species. Odds ratios (ORs) were determined for concurrent antibiotic resistance; analysis of variance and χ² tests were used to evaluate resistance rates by patient age and geographic region; Cochran-Armitage tests identified changing antibiotic susceptibility trends over time.

Results

A total of 6091 isolates (2189 S aureus, 1765 CoNS, 590 S pneumoniae, 767 P aeruginosa, and 780 H influenzae) from 6091 patients were submitted by 88 sites. Overall, 765 S aureus (34.9%) and 871 CoNS (49.3%) isolates were methicillin resistant and more likely to be concurrently resistant to macrolides (azithromycin: S aureus: OR, 18.34 [95% CI, 13.64-24.67]; CoNS: OR, 4.59 [95% CI, 3.72-5.66]), fluoroquinolones (ciprofloxacin: S aureus: OR, 22.61 [95% CI, 17.96-28.47]; CoNS: OR, 9.73 [95% CI, 7.63-12.40]), and aminoglycosides (tobramycin: S aureus: OR, 18.29 [95% CI, 13.21-25.32]; CoNS: OR, 6.28 [95% CI, 4.61-8.56]) compared with methicillin-susceptible isolates (P < .001 for all). Multidrug resistance was observed among methicillin-resistant S aureus (577 [75.4%]) and CoNS (642 [73.7%]) isolates. Antibiotic resistance among S pneumoniae isolates was highest for azithromycin (214 [36.3%]), whereas P aeruginosa and H influenzae isolates showed low resistance overall. Differences in antibiotic resistance were found among isolates by patient age (S aureus: F = 28.07, P < .001; CoNS: F = 11.46, P < .001) and geographic region (S aureus: F = 8.03, P < .001; CoNS: F = 4.79, P = .003; S pneumoniae: F = 8.14, P < .001; P aeruginosa: F = 4.32, P = .005). Small changes in antibiotic resistance were noted over time (≤2.5% per year), with decreases in resistance to oxacillin/methicillin (oxacillin: −2.16%; 95% CI, −3.91% to −0.41%; P < .001) and other antibiotics among S aureus isolates, a decrease in ciprofloxacin resistance among CoNS (−1.38%; 95% CI, −2.24% to −0.52%; P < .001), and an increase in tobramycin resistance among CoNS (0.71%; 95% CI, –0.29% to 1.71%; P = .03). Besifloxacin retained consistently low minimum inhibitory concentrations.

Conclusions and Relevance

Antibiotic resistance may be prevalent among staphylococcal isolates, particularly among older patients. In this study, a few small differences in antibiotic resistance were observed by geographic region or longitudinally.

Antibiotic prescribing patterns of general practice registrars for infective conjunctivitis: a cross-sectional analysis

INTRODUCTION Over-prescription of antibiotics for common infective conditions is an important health issue. Infective conjunctivitis represents one of the most common eye-related complaints in general practice. Despite its self-limiting nature, there is evidence of frequent general practitioner (GP) antibiotic prescribing for this condition, which is inconsistent with evidence-based guidelines. AIM To investigate the prevalence and associations of GP registrars' (trainees') prescription of antibiotics for infective conjunctivitis. METHODS We performed a cross-sectional analysis of the Registrar Encounters in Clinical Training (ReCEnT) ongoing prospective cohort study, which documents GP registrars' clinical consultations (involving collection of information from 60 consecutive consultations, at three points during registrar training). The outcome of the analyses was antibiotic prescription for a new diagnosis of conjunctivitis. Patient, registrar, practice and consultation variables were included in uni- and multivariable logistic regression analyses to test associations of these prescriptions. RESULTS In total, 2333 registrars participated in 18 data collection rounds from 2010 to 2018. There were 1580 new cases of infective conjunctivitis (0.31% of all problems). Antibiotics (mainly topical) were prescribed in 1170 (74%) of these cases. Variables associated with antibiotic prescription included patients' Aboriginal or Torres Strait Islander status, registrar organisation of a follow up (both registrar and other GP follow up), and earlier registrar training term (more junior status). DISCUSSION GP registrars, like established GPs, prescribe antibiotics for conjunctivitis in excess of guideline recommendations, but prescribing rates are lower in later training. These prescribing patterns have educational, social and economic consequences. Further educational strategies may enhance attenuation of registrars' prescribing during training.

Bacterial Ocular Surveillance System (BOSS) Sydney, Australia 2017-2018

Abstract

This study investigated antimicrobial resistance (AMR) profiles from a cohort of patients with bacterial keratitis treated at Sydney Eye Hospital, 1 January 2017 - 31 December 2018. These AMR profiles were analysed in the context of the current Australian empiric regimens for topical therapy: ciprofloxacin/ofloxacin monotherapy versus combination therapy of cefalotin/cephazolin plus gentamicin. At our Centre, combinations of (i) chloramphenicol plus gentamicin and (ii) chloramphenicol plus ciprofloxacin are alternatively used, so were also analysed. Three hundred and seventy-four isolates were cultured prospectively: 280/374 (75%) were gram positive, and 94/374 (25%) were gram negative. Coagulase-negative staphylococci comprised 173/374 (46%). Isolates included Staphylococcus aureus (n = 43/374) 11%; Streptococcus pneumoniae (n = 14/374) 3.7%; and Pseudomonas aeruginosa (n = 50/374) 13%. Statistical comparison was performed. There was no significant difference between cover provided either of the current Australian recommendations: ciprofloxacin/ofloxacin vs cefalotin/cephazolin plus gentamicin (5.3% vs 4.8%, respectively; p = 0.655). However, the combination of chloramphenicol plus an anti-pseudomonal agent (ciprofloxacin/ofloxacin or gentamicin) had significantly improved cover. Chloramphenicol plus gentamicin was superior to ciprofloxacin/ofloxacin (1.9% vs 5.3% resistance respectively; p = 0.007), and cefalotin/cephazolin plus gentamicin (1.9% vs 4.8%; p = 0.005). Chloramphenicol plus ciprofloxacin was superior to ciprofloxacin/ofloxacin monotherapy (1.3% vs 5.3%; p ≤ 0.001), and to cefalotin/cephazolin plus gentamicin (1.3% vs 4.8%; p = 0.003). Chloramphenicol plus gentamicin versus chloramphenicol plus ciprofloxacin/ofloxacin were equivalent (p = 0.48). There was no demonstrated in vitro superiority of either the current empiric antibiotic regimens. For our setting, for bacterial keratitis, chloramphenicol in combination offered superior in vitro cover. Broadened surveillance for ocular AMR is urgently needed across jurisdictions.

Antibacterial effects of antibiotics and cell-free preparations of probiotics against Staphylococcus aureus and Staphylococcus epidermidis associated with conjunctivitis

Conjunctivitis, caused by bacterial infections, represents health concern and diagnosis of the disease is pivotal for the proper selection of the treatment. The main causes of bacterial conjunctivitis vary in different countries. The current study investigated the common bacterial causes of bacterial conjunctivitis from eye clinics' attendants and evaluated the effectiveness of different therapeutic approaches. Eye swabs from patients, diagnosed with conjunctivitis, were assessed microbiologically and the isolated bacteria were identified using the standard biochemical identification and sequencing of the 16S rRNA gene. Antibiotics' susceptibility of the conjunctivitis-associated bacterial pathogens was evaluated against nineteen broad-spectrum antibiotics. In the meanwhile, cell-free preparations from probiotic Lactobacillus and Bifidobacterium strains were used to evaluate their antagonistic activities. Findings from this study showed that out of 52 specimen, 17 eye swabs from patients with conjunctivitis were bacterial culture-positive. The identity of the bacterial species, using the biochemical identification system, was Staphylococcus aureus (4 isolates) and S. epidermidis (13 isolates). Staphylococcus spp. showed susceptibility to linezolid, vancomycin, novobiocin, and fluoroquinolones (norfloxacin, ofloxacin, ciprofloxacin and levofloxacin). However, isolates from the two Staphylococcus spp. expressed resistance to penicillin G, oxacillin, and cephalexin. As alternatives to antibiotics, the growth of Staphylococcus spp., including isolates with antibiotic resistance, was inhibited by cell-free preparations of the 4 probiotic Lactobacillus and the 2 Bifidobacterium strains. These findings provide evidence that topical antibiotics such as fluoroquinolones are still effective antimicrobial agents against staphylococci associated with conjunctivitis whereas probiotic preparations could be promising for further research to pave the way for their therapeutic applications against ophthalmic diseases.

Multidrug-Resistant Organisms from Ophthalmic Cultures: Antibiotic Resistance and Visual Acuity

INTRODUCTION

There is a growing trend of multidrug-resistant organisms (MDRO). The goal of this study was to characterize MDRO at a single center from ophthalmic cultures to better understand how treatments were tailored and to assess effect on visual acuity.

MATERIALS AND METHODS

The MDRO data were collected by the Multidrug-Resistant Organism Repository and Surveillance Network from the Brooke Army Medical Center clinical laboratory. Both patient- and isolate-specific data were collected and qualitatively analyzed. Primary outcome measures were organism and type of resistance, anatomic location of isolate, initial and final antibiotic choice, and visual acuity.

RESULTS

Thirty-one bacterial culture samples were analyzed from 29 patients. Twenty-two (72%) were Gram-positive and all were methicillin-resistant Staphylococcus aureus (MRSA). Nine (29%) were Gram-negative and of these five were Pseudomonas spp. Fourteen (45%) isolates were cultured from the cornea, nine (29%) from the lid, four (13%) from the conjunctiva, and four (13%) from other locations. The majority (66.6%) required adjustment of initial antibiotics following ocular culture results. Sixteen adult patients had recorded initial and final visual acuities. Fifteen of those 16 patients had stable or improved visual acuities following treatment of the infection, but five patients had a final visual acuity less than 20/200.

CONCLUSION

This study demonstrated a high frequency of corneal MDRO infections and specifically MRSA and Pseudomonas spp. isolates. Antibiotic treatments frequently required adjustment. Further prospective study of visual outcomes from ophthalmic MDRO cultures is needed.

Hospital-Associated Multidrug-Resistant MRSA Lineages Are Trophic to the Ocular Surface and Cause Severe Microbial Keratitis

Methicillin-resistant Staphylococcus aureus (MRSA) is a common cause of severe and difficult to treat ocular infection. In this study, the population structure of 68 ocular MRSA isolates collected at Massachusetts Eye and Ear between January 2014 and June 2016 was assessed. By using a combination of multilocus sequence typing (MLST) analysis, SCCmec typing and detection of the panton-valentine leukocidin (PVL) gene, we found that the population structure of ocular MRSA is composed of lineages with community and hospital origins. As determined by eBURST analysis of MLST data, the ocular MRSA population consisted of 14 different sequence types (STs) that grouped within two predominant clonal complexes: CC8 (47.0%) and CC5 (41.2%). Most CC8 strains were ST8, harbored type IV SCCmec and were positive for the PVL-toxin (93.7%). The CC5 group was divided between strains carrying SCCmec type II (71.4%) and SCCmec type IV (28.6%). Remaining isolates grouped in 6 different clonal complexes with 3 isolates in CC6 and the other clonal complexes being represented by a single isolate. Interestingly, major MRSA CC5 and CC8 lineages were isolated from discrete ocular niches. Orbital and preseptal abscess/cellulitis were predominantly caused by CC8-SCCmec IV PVL-positive strains. In contrast, infections of the cornea, conjunctiva and lacrimal system were associated with the MDR CC5 lineage, particularly as causes of severe infectious keratitis. This niche specialization of MRSA is consistent with a model where CC8-SCCmec IV PVL-positive strains are better adapted to cause infections of the keratinized and soft adnexal eye tissues, whereas MDR CC5 appear to have greater ability in overcoming innate defense mechanisms of the wet epithelium of the ocular surface.

Cost comparison of commonly used postoperative topical ophthalmic antibiotics

PURPOSE

To provide information on the actual fill level and cost of currently available antibiotic drops used perioperatively.

DESIGN

Prospective laboratory investigation.

SETTING

Robert Cizik Eye Clinic, Houston, Texas USA.

METHODS

The following 9 medications were tested: moxifloxacin, gatifloxacin (branded and generic), besifloxacin, levofloxacin, ciprofloxacin, ofloxacin, trimethoprim/polymyxin B, tobramycin, and gentamicin. Actual bottle-fill volume and number of drops per bottle were measured using 10 bottles of each formulation. The percentage of the bottle used and the perioperative cost (using average wholesale price) were calculated for 3 times a day and 4 times a day dosing for 7-day, 10-day, and 14-day courses. Formulations were compared using 1-way analysis of variance with Tukey multiple comparisons.

RESULTS

For medications with sticker volumes of at least 5 mL, all but 2 medications (ofloxacin, 4 times a day for 14 days; gentamicin, 4 times a day for 14 days) covered 2 perioperative courses. Besifloxacin had a fill volume less than the sticker volume. The most cost-effective perioperative antibiotic prophylaxis was trimethoprim-polymyxin B (4 times a day: $12.87 for 7-day, 10-day, and 14-day courses, and $46.88 for 4-day course; 3 times a day: $12.87 for 7-day, 10-day, and 14-day courses).

CONCLUSIONS

Most antibiotics had an actual fill volume greater than sticker volume, which is a sufficient drug regimen for 2 perioperative courses. The costs of common postoperative topical antibiotic regimens vary widely depending on the drug and dosing regimen. Cost considerations for perioperative antibiotics will be increasingly important because the number of cataract surgeries is expected to increase with the growing and aging population.

Orbital abscess treated by ultrasound-guided fine needle aspiration and catheter drainage: A case report

RATIONALE

Periorbital cellulitis or an orbital abscess caused by acute sinusitis is a serious acute infectious disease. If not treated in time, serious complications may occur.

PATIENT CONCERNS

A 16-year-old girl with a history of right-sided proptosis, periorbital swelling, chemosis, hypophasis, restricted ocular movement in the upward direction, and diminution of vision was referred to our institution. The clinic, computed tomography (CT) and magnetic resonance imaging (MRI) examination indicate right orbital abscess in the upper quadrant and sinusitis.

DIAGNOSES

She was diagnosed with orbital abscess, acute sinusitis.

INTERVENTIONS

She underwent medical management, transnasal endoscopic surgery and then ultrasound-guided fine needle aspiration (FNA) and catheter drainage.

OUTCOMES

She was completely cured without any complications or sequelae.

LESSONS

Performance of surgical drainage in a timely manner and administration of effective antibiotic treatment according to bacterial culture can reduce the complications of orbital abscesses. Ultrasound-guided FNA and catheter drainage is a safe, simple, and effective method for the treatment of orbital abscess.

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.

In Vitro Effect of Toluidine Blue Antimicrobial Photodynamic Chemotherapy on Staphylococcus epidermidis and Staphylococcus aureus Isolated from Ocular Surface Infection

Purpose

We evaluate the antimicrobial effect of toluidine blue O (TBO)-mediated photodynamic antimicrobial chemotherapy (PACT) on Staphylococcus epidermidis and Staphylococcus aureus isolated from ocular surface infection.

Methods

We selected 24 strains of bacteria for this study. The antimicrobial effect of different TBO concentrations, light irradiation, and duration were evaluated. After determining the optimal PACT parameters, four experimental groups were included: Group 1, TBO alone (T+L−); Group 2, light-emitting diode (LED) irradiation alone (T−L+); Group 3, TBO–LED irradiation combination (T+L+); and Group 4, no treatment group (T−L−). The antibacterial effect of PACT was evaluated with the colony survival fraction (SF) methods.

Results

The antibacterial effect of PACT on S. epidermidis and S. aureus was dose-dependent to light irradiation and TBO concentration. The optimal PACT parameters were a TBO concentration of 60 μM, light irradiation of 5.27 mW/cm²_, and an irradiation duration of 30 minutes. In group 1, 60 μM TBO without irradiation did not show any antibacterial effect on S. epidermidis (1.48E7 ± 1.5E6 colony-forming units [CFU]/mL) or S. aureus (1.45E7 ± 9E5 CFU/mL). In group 2, irradiation alone with 5.27 mW/cm² did not modify bacterial growth (S. epidermidis, 1.49E7 ± 1.43E6; S. aureus, 1.5E7 ± 1.2E6). In group 3, after treatment, bacteria density dropped to 4000 ± 1000 and 3E5 ± 1E5 CFU/mL in S. epidermidis and S. aureus groups, respectively (P < 0.001, P = 0.030). In group 4, there was uniform bacterial growth (S. epidermidis, 1.51E7 ± 1.5E6; S. aureus, 1.48E7 ± 1.5E6) before and after treatment.

Conclusions

TBO-mediated PACT had an antibacterial efficacy in vitro on S. epidermidis and S. aureus isolated from ocular surface infection.

Translational Relevance

As TBO-mediated PACT has a strong antibacterial effect to S. epidermidis and S. aureus in vitro, this approach may assist in the treatment of ocular surface infectious diseases.

Types of organisms and in-vitro susceptibility of bacterial isolates from patients with microbial keratitis: A trend analysis of 8 years

Purpose

To report the distribution and trends of types of organisms and antibiotic susceptibility of the bacterial isolates obtained from patients with microbial keratitis.

Methods

Microbiology records of culture-positive microbial keratitis that underwent a diagnostic corneal scraping and cultures were reviewed. Fungal, bacterial, and parasitic culture results and antibiotic susceptibility profile of bacteria were analyzed and comparisons were made between two halves of the study period (2007-2010 vs. 2011-2014).

Results

A total of 3981 corneal scrapings were processed during the 8-year study period. Pathogen was recovered in culture in 1914 (48.1%) samples. Fungi, bacteria, and parasites constituted 38.7%, 60%, and 1.3% of the total isolates, respectively. The common fungal isolates were Aspergillus spp. (224/868, 25.8%) and Fusarium spp. (200/868, 23.0%), while common Gram-positive bacteria were Streptococcus pneumoniae (217/1125, 19.3%) and Staphylococcus aureus (185/1125, 16.4%), and common Gram-negative bacteria was Pseudomonas spp. (99/219, 45.2%). There was no significant difference in proportion of bacterial (P = 0.225) and fungal (P = 0.421) keratitis between the first half and second half of the study period. There was a significant increase in proportion of Gram-positive isolates (P = 0.015) [353/758 (46.6%) vs. 772/1482 (52.1%)] and decrease in proportion of Gram-negative organisms (P = 0.044) [88/758 (11.6%) vs. 131/1482 (8.8%)] in the recent years. In-vitro antibiotic susceptibility testing showed decrease in susceptibility to moxifloxacin for Pseudomonas spp. (P = 0.016) in recent years.

Conclusion

Prevalence of fungal and bacterial keratitis has remained unchanged over the years. This study shows a significant increase in Gram-positive bacterial infection and decrease in Gram-negative bacterial infection of the cornea in the recent years.

Laboratory Results, Epidemiologic Features, and Outcome Analyses of Microbial Keratitis: A 15-Year Review From St. Louis

PURPOSE

To evaluate the laboratory results and prognostic factors of poor clinical outcomes in microbial keratitis cases over 15 years at Saint Louis University.

DESIGN

Retrospective cohort and trend study.

METHODS

Microbiological and clinical information from culture-positive cases seen at Saint Louis University from 1999 to 2013 were reviewed retrospectively. Statistical analyses were used to determine microbiological and antibiotic susceptibility trends. Prognostic factors of poor clinical outcome from the literature were used to create multivariate regression models to describe our cohort.

RESULTS

Gram-positive organisms predominated (48%), followed by gram-negative organisms (34%) and fungi (16%). The most commonly isolated organism was Pseudomonas aeruginosa (21%). Oxacillin-resistant rates of Staphylococcus aureus and coagulase-negative staphylococci were 45% and 43%, respectively. Only the proportion of Pseudomonas changed significantly over time (P = .02). The only antibiotic found to lose efficacy over time was gentamicin for gram-positive organisms (P = .005). Multivariate logistic regression analyses revealed that major complications were associated with large ulcers (P < .006), fungal cases (P < .001), and comorbid ophthalmic conditions (P < .001). Poor healing was associated with large ulcers (P < .001) and fungal cases (P < .001). Lastly, poor visual outcome was associated with large ulcers (P < .01) and age ≥ 60 years (P < .02).

CONCLUSIONS

In the St Louis area, oxacillin-resistant organisms, Pseudomonas aeruginosa, and fungi are commonly recovered from microbial keratitis cases with a disproportionally high incidence. Hence, empiric antibiotic choice should reflect these trends. Special care needs to be taken for patients with large ulcers and fungal infections, as well as elderly patients with comorbid ophthalmic conditions, as these patients have worse clinical outcomes.

Antibiotic Resistance Among Pediatric-Sourced Ocular Pathogens: 8-Year Findings From the Antibiotic Resistance Monitoring in Ocular Microorganisms (ARMOR) Surveillance Study

BACKGROUND

The Antibiotic Resistance Monitoring in Ocular Microorganisms (ARMOR) study is a nationwide longitudinal antibiotic resistance surveillance program specific to bacterial pathogens commonly encountered in ocular infections. We evaluated in vitro resistance rates and trends among isolates obtained from pediatric patients (≤17 years of age).

METHODS

Clinical centers across the United States were invited to submit ocular isolates of Staphylococcus aureus, coagulase-negative staphylococci (CoNS), Streptococcus pneumoniae, Haemophilus influenzae and Pseudomonas aeruginosa to a central laboratory. Minimum inhibitory concentrations for various antibiotic classes were determined by broth microdilution per Clinical and Laboratory Standards Institute guidelines and interpreted as susceptible, intermediate or resistant based on available breakpoints. Longitudinal trends were analyzed using a Cochran-Armitage test for linear trends in a proportion.

RESULTS

Of 4829 isolates collected from January 2009 to December 2016, 995 isolates, sourced primarily from hospitals and referral centers, were obtained from pediatric patients (n = 286 H. influenzae, n = 284 S. aureus, n = 213 CoNS, n = 150 S. pneumoniae and n = 62 P. aeruginosa). With few exceptions, P. aeruginosa and H. influenzae were generally susceptible to the antibiotics tested. Of S. aureus and CoNS isolates, respectively, 56% and 72% were resistant to azithromycin and 24% and 47% were methicillin-resistant (MR); concurrent resistance to other drug classes and multidrug resistance (≥3 drug classes) were prevalent among MR staphylococci. Of S. pneumoniae isolates, 38% and 35% demonstrated resistance to azithromycin and penicillin, respectively. Besifloxacin had the lowest minimum inhibitory concentration against the Gram-positive isolates.

CONCLUSIONS

These in vitro data suggest antibiotic resistance is common among staphylococcal and pneumococcal isolates collected from pediatric patients with ocular infections. Methicillin resistance was prevalent among staphylococci with many strains demonstrating multidrug resistance. These findings may not be representative of resistance trends in community-based practices.

Understanding the Role of Pro-resolving Lipid Mediators in Infectious Keratitis

Keratitis is a sight-threatening inflammatory condition of the cornea that can be caused by both infectious and non-infectious agents. Physical or chemical trauma are typically related to non-infectious keratitis, which may then become secondarily infected or remain non-infected. Etiology of infectious keratitis is most often associated with bacteria; but viruses, fungi, and parasites are common causative pathogens as well. As a global concern, common risk factors include: systemic immunosuppression (secondary to malnutrition, alcoholism, diabetes, steroid use), previous corneal surgery (refractive corneal surgery, penetrating keratoplasty), extended wear contact lens use, pre-existing ocular surface diseases (dry eye, epithelial defect) and ocular trauma (agriculture- or farm-related) [1-8]. Annual rates of incidence include nearly one million clinical visits due to keratitis in the United States, while it has been reported that roughly two million people develop corneal ulcers in India. Clinically, patients may show signs of eye pain (ranging from mild to severe), blurred vision, photophobia, chemosis and redness. Pathogenesis is generally characterized by rapid progression, focal white infiltrates with underlying stromal inflammation, corneal thinning, stromal edema, mucopurulent discharge and hypopyon, which can lead to corneal scarring, endophthalmitis, and perforation. In fact, corneal opacity is not only a complication of keratitis, but among the leading causes of legal blindness worldwide. Despite that empirical treatment effectively controls most of the pathogens implicated in infectious keratitis, improved clinical outcomes are not guaranteed. Further, if treatment is not initiated in a timely manner, good visual outcome is reduced to approximately 50% of keratitis patients [9]. Moreover, resultant structural alterations, loss of tissue and an unresolved host response remain unaddressed through current clinical management of this condition.

Antibiotic resistance among bacterial conjunctival pathogens collected in the Antibiotic Resistance Monitoring in Ocular Microorganisms (ARMOR) surveillance study

The Antibiotic Resistance Monitoring in Ocular Microorganisms (ARMOR) surveillance study evaluates in vitro antibiotic resistance among Staphylococcus aureus, coagulase-negative staphylococci (CoNS), Streptococcus pneumoniae, Pseudomonas aeruginosa, and Haemophilus influenzae isolates from ocular infections. Here we report resistance rates and trends among conjunctival-sourced ocular isolates collected across the US from 2009 through 2016. A total of 1198 conjunctival isolates (483 S. aureus, 305 CoNS, 208 H. influenzae, 118 S. pneumoniae, and 84 P. aeruginosa) were collected from patients with presumed bacterial conjunctivitis from 57 sites across 40 states. A large proportion of staphylococci demonstrated resistance to oxacillin and azithromycin, while resistance was low against the majority of antibiotics tested for S. pneumoniae, P. aeruginosa, and H. influenzae. Multidrug resistance (≥3 antibiotic classes) was found in 30.2% of S. aureus and 39.0% of CoNS isolates, and methicillin resistance more than doubled the rate of multi-drug resistance (methicillin-resistant S. aureus [MRSA], 76.5%; methicillin-resistant CoNS isolates, 72.8%). There was a pattern of increasing mean percent resistance with increasing age by decade of life among S. aureus, MRSA, and CoNS (P≤0.038). Over the eight-year study period, there were small yet significant decreases in resistance rates among S. aureus to azithromycin, ciprofloxacin, tobramycin, trimethoprim, and oxacillin (P≤0.003), and among CoNS and P. aeruginosa (both P<0.05) to ciprofloxacin. These data indicate that antibiotic resistance is high, but did not increase, among conjunctival-sourced isolates collected in the US from 2009 through 2016. For certain antibiotic/pathogen combinations, there was a trend of decreased resistance, including a decrease in oxacillin resistance among S. aureus.

Keratitis antimicrobial resistance surveillance program, Sydney, Australia: 2016 Annual Report

IMPORTANCE

Antimicrobial resistance data from bacterial keratitis in Australia are lacking.

BACKGROUND

Antimicrobial resistance is a global health threat. Bacterial keratitis is an ophthalmic emergency requiring immediate and effective treatment.

DESIGN

Retrospective cohort study of bacterial isolates and antibiotic susceptibility profiles at a quaternary hospital in Sydney, Australia.

PARTICIPANTS

Two hundred and twenty-four corneal scrapes from patients from January 1 to December 31, 2016.

METHODS

Matrix assisted laser desorption ionization-time of flight (MALDI-TOF) mass spectrometry identified bacteria. The Calibrated Dichotomous Sensitivity (CDS) method determined antibiotic susceptibilities.

MAIN OUTCOME MEASURES

Isolated organisms and antibiotic susceptibilities.

RESULTS

One hundred and sixty-eight scrapes of 224 (75%) were culture positive. One hundred and thirty-one patients had a single organism isolated and 21 had mixed bacterial growth. Of the 157 organisms isolated, 131 (83%) were Gram-positive and 27 (17%) Gram-negative. Of the Gram-positive organisms, 75 (57%) were coagulase-negative Staphylococci (CoNS), 15 (11%) Staphylococcus aureus (including one methicillin-resistant Staphylococcus aureus [MRSA]) and 8 (6%) Corynebacterium spp. Of the Gram-negative organisms, 15 (58%) were Pseudomonas aeruginosa. With methicillin-sensitive Staphylococcus aureus (MSSA) resistance to chloramphenicol was 21%, ciprofloxacin 7% and gentamicin 7%. With CoNS resistance to cefalotin was 9%, gentamicin 9% and ciprofloxacin 9%. With Corynebacterium spp. resistance was 40% to cefalotin, chloramphenicol 25% and ciprofloxacin 14%.

CONCLUSIONS AND RELEVANCE

Staphyloccocus spp. and Pseudomonas spp. were the most common microorganisms isolated. There was low resistance to cefalotin and ciprofloxacin for these isolates. More than 90% of these would be covered by current therapeutic recommendations for empiric therapy in Australia.

Occurrence and molecular composition of methicillin-resistant Staphylococcus aureus isolated from ocular surfaces of horses presented with ophthalmologic disease

Severe infections due to methicillin-resistant Staphylococcus aureus (MRSA) have been increasingly recognized in virtually all fields of veterinary medicine. Our objective was to study the occurrence, phylogenetic relationships and antimicrobial resistance properties of MRSA isolated from ocular surfaces of horses prior to invasive procedures. Within a 49-week sampling period, ocular swabs obtained from 46 eyes of 44 horses, including eyes with clinical signs of conjunctivitis/blepharitis, keratitis or uveitis were screened for the presence of S. aureus. As a result, seven samples were positive for S. aureus (15.2%), with six of them being classified as MRSA (13%). In addition, all isolates were resistant or showed reduced susceptibility to tetracyclines, the aminoglycosides gentamicin and kanamycin, fluoroquinolones, and the combination sulfamethoxazole/trimethoprim. Since a very close relationship between the MRSA isolates was assumed after pulsed-field gel electrophoresis employing the restriction endonuclease ApaI, whole genome sequencing (WGS) was used to shed more light on the phylogenetic relationships and the molecular composition of all MRSA isolates. Analysis of WGS data revealed closely related MRSA belonging to sequence type 398, spa type t011 and dru type dt10q, harboring an SCCmec IV element and the Staphylococcus aureus pathogenicity island SaPIbov5. Moreover, all MRSA were positive for a beta-hemolysin converting phage carrying genes of the immune evasion cluster (IEC). Since cases of eye infections due to MRSA were often associated with fatal outcomes, more research is needed with respect to the origin of MRSA isolated from ocular surfaces to implement sufficient barrier and infection control measures.