Trends in Fluoroquinolone Nonsusceptibility Among Coagulase-Negative Staphylococcus Isolates Causing Endophthalmitis, 1995-2016

Comparison of iodine compounds and levofloxacin as postoperative instillation; conjunctival bacterial flora and antimicrobial susceptibility following cataract surgery

PURPOSE

To compare the cleanliness of the conjunctival sac following the use of iodine compounds (PAI) and levofloxacin as postoperative eye drops.

STUDY DESIGN

A prospective open-label study.

PATIENTS AND METHODS

Either topical levofloxacin or fourfold-diluted PAI was administered for 1 week postoperatively in 128 eyes of 128 patients who underwent routine cataract surgery. Conjunctival samples were obtained at three time points: pre-surgery, 1 week postoperatively, and 1 month postoperatively.

RESULTS

The respective positive bacterial culture rates for postoperative iodine and levofloxacin were 88.1% and 85.2% pre-surgery, 71.6% and 50.8% 1 week postoperatively, and 92.5% and 86.5% 1 month postoperatively. Positive bacterial culture rates in both groups significantly declined at 1 week, and the rates returned to the baseline level 1 month postoperatively. The magnitude of reduction of DNA copy number detected by polymerase chain reaction at 1 week was larger in the levofloxacin group, although no significant differences were seen at pre-surgery or 1 month postoperatively. In the levofloxacin group, only one strain was culture positive at 1 week, however, its minimum inhibitory concentration (MIC) against S. epidermidis was high (128 µg/ml). The MIC value increased from 2.31 ± 2.19 µg/ml pre-surgery to 57.14 ± 22.34 µg/ml 1 month postoperatively, while no significant change was found in the iodine group.

CONCLUSION

Postoperative iodine and levofloxacin eye drops both reduced bacterial contamination in the conjunctival sac, with a superior level of disinfection in the levofloxacin group. However, postoperative levofloxacin eye drops enhanced the emergence of highly resistant bacteria, whereas no such development was seen in the iodine group.

Microbiological Profile of Post-cataract Surgery Endophthalmitis with Usage of Prophylactic Intracameral Moxifloxacin

PURPOSE

To study the effect of prophylactic intracameral moxifloxacin (ICM) on microbiological profile and antimicrobial sensitivity of culture-proven postoperative endophthalmitis (POE).

METHODS

This study evaluated culture-proven POE diagnosed within 6 weeks of cataract surgery over two periods, period-1 (January 2010-March 2015) and period-2 (April 2015-December 2019), before and after introduction of prophylactic ICM, respectively.

RESULTS

In period-1, 100 cases of culture-positive POE were reported (1 in 4879, 0.02%), while 20 cases (1 in 24635, 0.004%) were reported in period-2 (5-fold reduction, p < .001). The cumulative culture positivity rate decreased from 27.6% to 17.1% (1.6-fold) . Coagulase-negative Staphylococci (CoNS) were significantly reduced (p = .005).

CONCLUSIONS

ICM reduced the incidence of culture-proven POE, CoNS in particular. In future, POE caused by rarer pathogens may become more prevalent due to reduction in the rate of commoner and more virulent pathogens with use of intracameral antibiotics. The moxifloxacin sensitivity of CONS did not show change with the use of ICM. Studies with larger population of POE will be more helpful to understand the trend better.

Endophthalmitis in children with open eye injury: epidemiology, risk factors, treatment

The article provides an overview of endophthalmitis cases in children with open eye injury — prevalence, causes and treatment results in Great Britain, USA, China, India, Vietnam, Saudi Arabia, and other countries with different healthcare facilities, lifestyle and traditions.

Prophylactic antibiotics for postcataract surgery endophthalmitis: a systematic review and network meta-analysis of 6.8 million eyes

To reveal optimal antibiotic prophylactic regimen for postoperative endophthalmitis (POE), we conducted systematic review and network meta-analysis. A total of 51 eligible original articles, including two randomized controlled trials, were identified. In total, 4502 POE cases occurred in 6,809,732 eyes (0.066%). Intracameral injection of vancomycin had the best preventive effect (odds ratio [OR] 0.03, 99.6% confidence interval [CI] 0.00-0.53, corrected P-value = 0.006, P-score = 0.945) followed by intracameral injection of cefazoline (OR 0.09, 99.6% CI 0.02-0.42, corrected P-value < 0.001, P-score = 0.821), cefuroxime (OR 0.18, 99.6% CI 0.09-0.35, corrected P-value < 0.001, P-score = 0.660), and moxifloxacin (OR 0.36, 99.6% CI 0.16-0.79, corrected P-value = 0.003, P-score = 0.455). While one randomized controlled trial supported each of intracameral cefuroxime and moxifloxacin, no randomized controlled trial evaluated vancomycin and cefazoline. Sensitivity analysis focusing on the administration route revealed that only intracameral injection (OR 0.19, 99.4% CI 0.12-0.30, corrected P-value < 0.001, P-score = 0.726) significantly decreased the risk of postoperative endophthalmitis. In conclusion, intracameral injection of either vancomycin, cefazoline, cefuroxime, or moxifloxacin prevented POE.

Acute postoperative endophthalmitis: Microbiology from the laboratory to the bedside

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

Emerging Antibiotic Resistance Patterns Affect Visual Outcome Treating Acute Endophthalmitis

Background: Examining the effect of antibiotic resistance, use of intravitreal antibiotics and systemic corticosteroids on visual outcome of eyes with acute endophthalmitis. Methods: We included 226 eyes with acute endophthalmitis, treated using a standardized protocol. Visual outcome up to 12 months was assessed related to biopsy results, antibiotics resistance and treatment regimens. Results: Vitreous biopsies were more likely to be culture-positive (41.1%) than anterior chamber biopsies (21.6%, p < 0.0001). Antibiotic resistance for amikacin was found in 19 eyes (24.7%), vancomycin in 29 eyes (31.5%) and moxiflocacin in 14 eyes (16.1%). At presentation 91.53% of eyes had BCVA < 20/40, reducing by 1 month to 69.94% (p < 0.0001) and remaining stable at 12 months. There was no difference in visual outcome for those receiving early systemic corticosteroids. Endophthalmitis following cataract surgery (OR 1.66, 1.04−2.66 95% CI, p = 0.03) and receiving intravitreal vancomycin (OR 3.15, 1.18−8.42 95% CI, p = 0.02) were associated with a greater chance of final BCVA ≥ 20/40. Conclusion: Using vitreous taps with intravitreal antibiotics, despite an increase in resistance to both vancomycin and moxifloxacin, results in a final BCVA > 20/200 in half of eyes and ≥20/40 in a third. Early treatment with intravitreal antibiotics should not be delayed.

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.

Genotypic and Phenotypic Antibiotic Resistance in Staphylococcus Epidermidis Endophthalmitis

BACKGROUND AND OBJECTIVE

To evaluate antibiotic resistance patterns in Staphylococcus epidermis endophthalmitis isolates, identify antibiotic resistance genes, and compare this to their phenotypic resistance.

MATERIALS AND METHODS

Retrospective case series of S. epidermidis isolates from January 2012 to December 2017. Phenotypic resistance was determined from minimum inhibitory concentration values. Genotypic resistance was determined from DNA microarray. The relationship between these was analyzed using Cohen's kappa and predictive value.

RESULTS

Seventy-five isolates were included. More than 60% were resistant to methicillin and erythromycin. Approximately 60% possessed the resistance genes for methicillin and erythromycin, and 25% for clindamycin. There was near perfect agreement between genotype and phenotype for erythromycin and methicillin (kappa = 0.88 and 0.89, respectively). Approximately 98% (P < 0.0001) of isolates with erythromycin and methicillin resistance genes and 90% (P = 0.0006) with clindamycin resistance genes were phenotypically resistant to those antibiotics. None were resistant to vancomycin.

CONCLUSION

The relationship between genotypic and phenotypic antibiotic resistance highlights that resistance may be polygenic, and genes may be silent. [Ophthalmic Surg Lasers Imaging Retina. 2020;51:S13-S16.].

Surveillance of post-cataract endophthalmitis at a tertiary referral center: a 10-year critical evaluation

BACKGROUND

Acute post-cataract endophthalmitis (APE) is a rare complication potentially causing irreversible visual loss. A 10-year study of APE was conducted to determine its incidence, microbiological spectra and antibiotic resistance profile of APE-related pathogens at a major tertiary referral center in Brazil.

METHODS

APE cases reported between January 2010 and December 2019 were included. Phacoemulsification and extracapsular cataract techniques were eligible; combined procedures, traumatic and congenital cataract were excluded. Vitreous samples were cultured and antimicrobial resistance was compared for the periods of 2010-2014 and 2015-2019. The results were analyzed with Fisher's exact test.

RESULTS

Our sample consisted of 40,491 cataract surgeries and 51 (0.126%) APE cases. Culture was positive in 35 cases (71.4%), of which 31 (88.6%) Gram-positive, 3 (8.6%) Gram-negative, and 1 (2.9%) fungal. The most frequently isolated organism was Staphylococcus epidermidis (n = 17/35, 48.6%), followed by Staphylococcus aureus (n = 4/35, 11.4%). From 2010-2014 to 2015-2019, antimicrobial resistance increased against moxifloxacin (11.1-54.5%, p = 0.07), ciprofloxacin (54.5-72.7%, p = 0.659) and oxacillin (66.7-93.3%, p = 0.13).

CONCLUSIONS

The observed incidence and microbial spectra were compatible with previous studies. A trend towards growing moxifloxacin and ciprofloxacin resistance was observed. Surveillance remains crucial to prevent treatment failure from antimicrobial resistance.

The Role of Systemic Antimicrobials in the Treatment of Endophthalmitis: A Review and an International Perspective

Background

The optimal management of patients with endophthalmitis is challenging and includes both intravitreal and, in some cases, systemic antimicrobials. Systemic antimicrobials may be administered either intravenously or orally. In this article we review systemic antimicrobial options currently available for the treatment of types of endophthalmitis and the role of systemic antimicrobials (antibiotics and antifungals) in these treatments.

Review

While systemic antimicrobials are not universally utilized in the management of endophthalmitis, they may be helpful in some circumstances. The blood–retinal barrier affects the penetration of systemic medications into the posterior segment of the eye differently; for example, moxifloxacin and imipenem cross the blood–retinal barrier relatively easily while vancomycin and amikacin do not. However, inflammation, including endophthalmitis, may disrupt the blood–retinal barrier, enhancing the penetration of systemic agents into the eye.

Conclusion

Systemic antimicrobials may be particularly beneficial in patients with certain types of endophthalmitis; as such, they are standard treatment in the management of endogenous endophthalmitis (fungal and bacterial) and also widely used for prophylaxis and treatment of open-globe injuries. Although systemic antimicrobials are used in some patients with acute-onset postoperative endophthalmitis following cataract surgery, the literature generally does not support this practice. It is noted that there are currently no randomized clinical trials demonstrating a benefit of systemic antibiotics for any category of endophthalmitis.

Conjunctival bacterial flora and antimicrobial susceptibility in bacterial pathogens isolated prior to cataract surgery

PURPOSE

To optimize prophylactic antibiotic administration, antibiotic susceptibility before cataract surgery was investigated using ocular bacteria isolated preoperatively.

DESIGN

Retrospective cross-sectional study.

METHODS

In 204 eyes of 102 patients who underwent routine bilateral cataract surgery, conjunctival sac scrapings were collected 1-2 weeks before surgery. A total of 192 major pathogens among the 470 isolated bacteria were subjected to susceptibility testing. The major pathogens included Staphylococcus aureus, Staphylococcus epidermidis, coagulase-negative staphylococci (CNS) other than S. epidermidis, Enterococcus faecalis, and Streptococcus spp. The following antibiotics were tested: cefmenoxime (CMX), ceftazidime (CAZ), tobramycin (TOB), vancomycin (VAN), erythromycin (EM), moxifloxacin (MFLX), gatifloxacin (GFLX), levofloxacin (LVFX), chloramphenicol (CP), and imipenem (IP).

RESULTS

The proportions of isolates with minimum inhibitory concentration (MIC) of S. epidermidis (N = 82), exceeding 4 μg/ml were high for CAZ (95.1%), EM (32.9%), LVFX (39.0%), and CP (82.9%). Susceptible (S) proportion was high for CMX (98.8%), VAN (100%), CP (93.9%), and IP (97.6%) but relatively low for MFLX (59.8%), GFLX (54.9%), and LVFX (54.9%). The MIC₉₀ values were high for CMX (16 μg/ml), CAZ (64 μg/ml), TOB (32 μg/ml), EM (128 μg/ml), LVFX (16 μg/ml), and CP (8 μg/ml). The MIC of quinolonesof pathogenic bacteria other than S.epidermidis (N = 108), exceeded 4 μg/ml for 11 isolates, including two Methicillin-resistant Staphylococcus aureus.

CONCLUSIONS

The increase in resistance of resident bacteria present in the conjunctival sac to antibiotics indicates that systemic and topical antibiotics are no longer effective, especially against external organisms affecting the eye.

In vitro Susceptibilities of Methicillin-Susceptible and Resistant Staphylococci to Traditional Antibiotics Compared to a Novel Fluoroquinolone

Background

To assess the in-vitro efficacy of delafloxacin, a new fourth generation fluoroquinolone, against Staphylococcus vitreous isolates from patients with clinically diagnosed endophthalmitis. This is the first investigation of delafloxacin in ocular tissues.

Methods

Intravitreal isolates of culture-proven S. aureus and S. epidermidis were identified between 2014 and 2018. Minimum inhibitor concentrations (MIC) were determined using ETEST strips. The antibiotic susceptibilities were tested against a panel of drugs including glycopeptides such as vancomycin, as well as traditional and newer fluoroquinolones (levofloxacin, moxifloxacin, and delafloxacin).

Results

Of 45 total isolates identified between 2014 and 2018, 13% (6) were methicillin-resistant S. aureus (MRSA), 9% (4) were methicillin-sensitive S. aureus (MSSA), 53% (24) were methicillin-resistant S. epidermidis (MRSE), and 24% (11) were methicillin-sensitive S. epidermidis (MSSE). Among the fluoroquinolones, resistance rates were 61% for levofloxacin, 50% for moxifloxacin, and 12% for delafloxacin. Inter-class comparisons between delafloxacin and the two other fluoroquinolones demonstrated higher Gram-positive susceptibility to delafloxacin (p < 0.01). MIC90 values were lowest for delafloxacin (1.0 μg/mL) compared to levofloxacin (8.0 μg/mL) and moxifloxacin (8.0 μg/mL). Vancomycin was 100% effective against all isolates with MIC90 value of 0.75 μg/mL.

Conclusion

Compared to levofloxacin and moxifloxacin, the newer fluoroquinolone delafloxacin demonstrated the lowest MICs values and lowest rates of resistance for Gram-positive in-vitro S. epidermidis and S. aureus vitreous isolates.

Effectiveness of intraoperative iodine in cataract surgery: cleanliness of the surgical field without preoperative topical antibiotics

PURPOSE

To verify the possibility that preoperative topical antibiotics are not essential as long as iodine disinfection is performed during surgery.

STUDY DESIGN

Crossover equivalence trial.

PATIENTS AND METHODS

In 204 eyes of 102 patients who underwent routine bilateral cataract surgery, 1 eye was treated with intraoperative iodine, and the other, with preoperative topical antibiotics. For the intraoperative iodine eyes, 5 mL of 0.25% povidone-iodine was applied at 2 stages: (1) just after the placement of the speculum and (2) before intraocular lens (IOL) insertion. For the contralateral eyes, preoperative topical antibiotics were administered 3 days before surgery without intraoperative iodine. Conjunctival samples for culture were obtained at 3 time points: (a) presurgery, (b) beginning of surgery, and (c) postsurgery. Real-time polymerase chain reaction (PCR) samples were obtained at the beginning of surgery and before IOL insertion. Intracameral moxifloxacin was applied in all the cases.

RESULTS

The respective positive bacterial culture rates for intraoperative iodine eyes and preoperative topical antibiotics eyes were 95.1% and 98.0% at (a), 7.8% and 5.9% at (b), and 60.8% and 62.7% at (c). A significant difference in the positive bacterial culture rate was not found at any time point. For the intraoperative iodine eyes, the bacterial DNA copy number at (b) was significantly lower than that for the preoperative topical antibiotics eyes.

CONCLUSIONS

The cleanliness of the operative field without using topical antibiotics was revealed to be equivalent to that of the conventional method (using preoperative antibiotics without intraoperative iodine) as long as intraoperative iodine was used.

Endophthalmitis following cataract surgery and intracameral antibiotic: Moxifloxacin resistant Staphylococcus epidermidis

Purpose

To describe an immunosuppressed patient who developed acute-onset postoperative endophthalmitis caused by a moxifloxacin-resistant strain of Staphylococcus epidermidis after cataract surgery despite the use of intracameral moxifloxacin.

Observations

A 76-year old woman with a history of birdshot chorioretinopathy controlled on systemic immunosuppression underwent uneventful cataract surgery in her right eye. Compounded intracameral moxifloxacin 0.2 cc of 1mg/0.1mL (Edge Pharmacy, Syracuse, NY) was injected intraoperatively as prophylaxis, and the patient was placed on a standard regimen of trimethoprim-polymyxin b (10000-0.1unit/mL) and prednisolone acetate 1% postoperatively. Four days later, the patient experienced a sudden decrease in vision in the right eye. Anterior chamber inflammation, vitritis, and vasculitis were seen in the operated eye. The patient underwent a vitreous tap and intravitreal injections of vancomycin (1mg/0.1mL), ceftazidime (2.25mg/0.1mL), and dexamethasone (0.4mg/0.1mL). Cultures grew Staphylococcus epidermidis, resistant to moxifloxacin (MIC ≥8mg/L). The inflammation resolved over two months. Eight months later, the patient underwent uncomplicated cataract surgery in the left eye. Intracameral antibiotics were not used, however her systemic immunosuppressive therapy was held for several weeks perioperatively. One year after the initial surgeries, the patient had an uncorrected visual acuity of 20/20 in each eye.

Conclusions and Importance

S. epidermidis, the most common cause of postoperative endophthalmitis, is increasingly resistant to fluoroquinolones. Adequate concentrations of intracameral antibiotics need to be achieved in order to exceed minimal inhibitory concentration values of the targeted pathogen. Although intracameral moxifloxacin has been reported to decrease the rate of endophthalmitis after cataract surgery, it does not eliminate the risk.

The Routine Use of Intracameral Antibiotics to Prevent Endophthalmitis After Cataract Surgery: How Good is the Evidence?

Post-operative endophthalmitis (POE) following cataract surgery is an uncommon, vision-threatening complication that has been reported to occur at rates of between approximately 0.03% and 0.2%. Prompt diagnosis and treatment of endophthalmitis is critical for minimizing vision loss, but most recent efforts have focused on the prophylactic administration of antibiotics to prevent the development of endophthalmitis. Surgeons from around the world have different topical and intracameral antibiotic usage patterns to prevent endophthalmitis, and to date no general consensus regarding best practice has emerged. Several studies have reported on the routine use of intracameral cefuroxime, moxifloxacin, and vancomycin, including a single randomized clinical trial by the European Society of Cataract and Refractive Surgery (ESCRS) in 2007. These studies have notable shortcomings, but many authors suggest that intracameral cefuroxime together with topical antibiotics probably decreases the risk of endophthalmitis. However, the deleterious effects of routine prophylactic antibiotics, which include toxicity, cost, and increasing antimicrobial resistance, among others, are noteworthy. In contrast, aseptic technique with pre-operative instillation of povidone-iodine remains the only technique supported by level I evidence to reduce the incidence of endophthalmitis. Although the routine use of intracameral antibiotics continues to increase throughout the world, data from multicenter, randomized, prospective trials is needed to provide better guidance regarding the prophylactic use of antibiotics.

Endophthalmitis: Then and Now

PURPOSE

To report historically evolving strategies (then and now) in prevention and management of endophthalmitis.

DESIGN

A perspective on relevant topics in the prophylaxis and management of endophthalmitis.

METHODS

This is an author-selected review of studies leading to changes in strategies for endophthalmitis management over the last 100 years.

RESULTS

The current perspective discusses the trends and strategies over the past century. Historically, 3 endophthalmitis time-periods have existed and include the pre-antimicrobial era, the predominantly systemic antimicrobial era, and the current intravitreal antimicrobial era. The management of endophthalmitis from different etiologies, including endogenous, postinjection, post-cataract surgery, and other anterior segment-related (eg, post-penetrating keratoplasty), bleb-associated, glaucoma drainage device-associated, and open globe injury-associated, are discussed. Specific etiologies may predict most common microbial causes and may guide differing management strategies. Pars plana vitrectomy offers theoretical advantages but is generally reserved for patients with more advanced disease.

CONCLUSIONS

Despite advances over the past 100 years, endophthalmitis is an important sight-threatening complication. Timely management with the appropriate use of antimicrobial agents may optimize visual outcomes.

Endophthalmitis caused by gram-positive bacteria resistant to vancomycin: Clinical settings, causative organisms, antimicrobial susceptibilities, and treatment outcomes

Purpose

To report the clinical settings, causative organisms, antimicrobial susceptibilities, and treatment outcomes of patients with endophthalmitis caused by gram-positive bacteria resistant to vancomycin.

Methods

Retrospective case series of all patients with culture-proven endophthalmitis caused by gram-positive bacteria resistant to vancomycin between January 2010 and December 2016 in LV Prasad Eye Institute, Visakhapatnam, India.

Results

The current study included 14 patients. The clinical settings were post-cataract surgery in 8/14 (57.1%) and open globe injury in 6/14 (42.8%). Primary intervention for all patients included tap and intravitreal antibiotic injection. During subsequent follow-up, pars plana vitrectomy was performed in 6 patients and one patient underwent penetrating keratoplasty. Mean number of intravitreal antibiotic injections performed were 3.4 per patient. The most common organisms isolated were coagulase-negative Staphylococci in 6/14 (42.8%), Staphylococcus aureus in 5/14 (35.7%), Streptococcus sp in 2/14 (14.2%) and Bacillus sp in 1/14 (7.14%). In addition to vancomycin, resistance to multiple drugs (three or more groups of antibiotics) was found in all 14 cases. Antimicrobial susceptibility results showed susceptibility to amikacin in 7/14 (50.0%), gatifloxacin in 6/14 (42.8%), moxifloxacin in 3/13 (23.0%), cefazoline in 5/14 (35.7%), cefuroxime in 3/14 (21.4%), ciprofloxacin in 2/14 (14.2%) and linezolid in 5/5 (100%). The mean duration of follow-up was 30.7 weeks (6 weeks–90 weeks). At last follow-up, visual acuity (VA) of 20/200 or better was recorded in 7/14 (50%) and VA < 5/200 occurred in 7/14 (50%).

Conclusion and importance

Antimicrobial susceptibility testing may help in selection of suitable antimicrobial agents for repeat intravitreal injection. Inspite of retreatment with intravitreal antibiotics, these patients generally had poor VA outcomes.