Resistance of ocular flora to gatifloxacin in patients undergoing intravitreal injections

Ocular Bacterial Infections: A Ten-Year Survey and Review of Causative Organisms Based on the Oklahoma Experience

Ocular infections can be medical emergencies that result in permanent visual impairment or blindness and loss of quality of life. Bacteria are a major cause of ocular infections. Effective treatment of ocular infections requires knowledge of which bacteria are the likely cause of the infection. This survey of ocular bacterial isolates and review of ocular pathogens is based on a survey of a collection of isolates banked over a ten-year span at the Dean McGee Eye Institute in Oklahoma. These findings illustrate the diversity of bacteria isolated from the eye, ranging from common species to rare and unique species. At all sampled sites, staphylococci were the predominant bacteria isolated. Pseudomonads were the most common Gram-negative bacterial isolate, except in vitreous, where Serratia was the most common Gram-negative bacterial isolate. Here, we discuss the range of ocular infections that these species have been documented to cause and treatment options for these infections. Although a highly diverse spectrum of species has been isolated from the eye, the majority of infections are caused by Gram-positive species, and in most infections, empiric treatments are effective.

Temporal impacts of topical ceftazidime and tobramycin-vancomycin mixtures on the ocular surface microbiota in rabbits

Antibiotics are one of the important factors that can alter the diversity and composition of ocular surface microbiota. At present, there are a few studies about the antibiotic effect on ocular surface microbiota, including its time-dependent changes. However, these limited studies have revealed various results, and more experiments are required. In this study, we used 16 S rRNA sequencing method to investigate the effects of topical ceftazidime and tobramycin-vancomycin mixtures on the ocular surface microbiota and the temporal changes of the microbiota after discontinuing antibiotic treatment in rabbits. Seventeen healthy rabbits were treated with 5% ceftazidime and a mixture of 0.3% tobramycin-5% vancomycin (CTV) eye drops on one eye four times a day for 7 days. Swab samples of conjunctiva sacs were collected before antibiotic treatment (D0), 12 h after the last antibiotic treatment (D8) and two further time points on Day 15 (D15) and Day 30 (D30). We found that the species diversity of the ocular surface microbiota increased significantly at D8 and was restored at D15, namely, one week after antibiotic cessation. The community structure of the ocular surface microbiota changed after treatment with CTV but recovered at D30. At D8, the relative abundances of 13 bacterial phyla of the initial top 20 phyla and 11 bacterial genera of the initial top 20 genera were significantly different from the relative abundances of the phyla and genera at D0. Furthermore, the relative abundance of the dominant phylum Epsilonbacteraeota obviously decreased, while Proteobacteria and Bacteroidetes markedly increased. For dominant genera, the relative abundance of Helicobacter notably decreased, while Acinetobacter and Pasteurella greatly increased. Thirteen altered bacterial phyla and 7 of 11 altered bacterial genera recovered to preantibiotic levels at D30. In addition, there was a group of nondominant and rare bacteria enriched at D8, and most of them were restored at D30. In conclusion, the species diversity, community structure and composition of the ocular surface microbiota changed greatly after exposure to CTV, but they tended to be restored within weeks after discontinuing antibiotic treatment.

Ocular flora in patients undergoing intravitreal injections: antibiotic resistance patterns and susceptibility to antiseptic picloxydine

AIM

To study antibiotic resistance patterns and susceptibility to eye antiseptic picloxydine of conjunctival flora in patients undergoing intravitreal injections (IVIs).

METHODS

Conjunctival swabs were taken in 4 groups of patients, 20 patients in each group (n=80): without IVIs and ophthalmic operations in history (group N1; control group); with the first IVI and antibiotic eye drops Tobrex applied 3d before IVI and 5d after it (group N2); with 20 or more IVIs and repeated courses of antibiotic eye drops (group N3); with the first IVI and antiseptic eye drops Vitabact (picloxydine) applied 3d before IVI and 5d after it (group N4). In groups N2 and N4 swabs were taken at baseline and after the treatment. Efficacy of picloxydine in inhibition of growth of conjunctival isolates susceptible and resistant to antibiotic was studied in vitro. Minimal inhibition concentrations (MIC) were determined with microdilution test.

RESULTS

Two of the three patients who had to undergo the IVI procedure showed conjunctiva bacterial contamination. Along with few Staphylococcus aureus and Gram-negative isolates susceptible to most antibiotics, the majority (71%-77%) of causative agents were coagulase-negative Staphylococci (CoNS), 40%-50% of which were multidrug resistant (MDR). Eye disinfection in the operating room and peri-injection courses of Tobrex or Vitabact resulted in total elimination of isolates found at baseline. However, in 10% and 20% of patients, respectively, recolonization of the conjunctiva with differing strains occurred. In patients with repeated IVI and Tobrex/Maxitrol treatment, the conjunctival flora showed high resistance rates: 90% of CoNS were MDR. In the in vitro study, picloxydine showed bactericidal effect against Staphylococci isolates both antibiotic resistant and susceptible with MIC≥13.56 µg/mL. Incubation of bacteria for 15min in Vitabact eye drops, commercially available form of picloxydine, 434 µg/mL, showed total loss of colony forming units of all tested isolates including Pseudomonas aeruginosa.

CONCLUSION

The confirmed efficacy of eye antiseptic picloxydine against conjunctival bacterial isolates and the presence of its commercial form, 0.05% eye drops, convenient for use by patients before and after injection, make this eye antiseptic promising for prophylaxis of IVI-associated infectious complications.

[Antibiotic resistance in patients after serial intravitreal injections]

Despite the lack of convincing data on the effectiveness of antibiotic therapy in the prevention of Post-Injection Endophthalmitis (PIE), the use of topical antibiotics for intravitreal injections is still a common practice. Frequent, monthly use of antibiotics results in changes of the composition of conjunctival flora and spontaneous mutations of bacteria, and leads to selective survival of resistant and virulent strains that can cause serious damage inside the eye.

[Conjunctival microflora and its antibiotic sensitivity after serial intravitreal injections]

INTRODUCTION

The approach to post-procedure management of patients undergoing intravitreal injections should be unified and consistent. Frequent use of antibiotic drugs leads to generation of resistant conjunctival strains.

PURPOSE

To study the composition of conjunctival microflora and its antibiotic susceptibility in patients who received 20 or more intravitreal injections and concomitant antibiotic therapy, and in a group of patients of the same age without history of intravitreal injections or ophthalmological operations.

MATERIAL AND METHODS

A total of 40 inoculations were performed (20 patients in each group, 40 eyes). In case of culture growth, species identification and antibiotic sensitivity of the microorganisms were investigated using automated identification and susceptibility testing system BD Phoenix 100.

RESULTS

Culture growth was observed in 70% of the control group patients. All isolated microorganisms were different types of staphylococci - Staphylococcus epidermidis (78.57%), S. caprae (7.14%), S. hominis (7.14%), and S. aureus (7.14%). In the second group, we observed culture growth in 55% of cases. Eleven cultures were Gram-positive bacteria: S. epidermidis (72.73%), S. haemolyticus (18.18%), S. aureus (9.09%). Gram-negative Pseudomonas aeruginosa was detected in 1 patient. In the control group, multi-resistant cultures accounted for 42.86%. In the group of patients with multiple intravitreal injections, 75% of cases showed multiresistance (9 out of 12 isolates). In the group of patients who have undergone 20 or more injections, greatest resistance was observed to penicillin G, doxycycline, gentamicin, erythromycin, clindamycin, moxifloxacin, fusidic acid, chloramphenicol, and trimethoprim/sulfamethoxazole compared to the control group.

CONCLUSION

Overuse of antibiotics in the management of patients receiving intravitreal injections leads to selection of resistant strains.

Genetic diversity and persistent colonization of Enterococcus faecalis on ocular surfaces

PURPOSE

Enterococcus faecalis causes severe acute endophthalmitis and often leads to poor visual outcomes. Conjunctival bacterial cultures occasionally grow atypical bacteria including E. faecalis, which can potentially contribute to the development of postoperative endophthalmitis. However, the characteristics of these ocular E. faecalis strains are unknown. This study is the first attempt to determine the population characteristics of E. faecalis clinical isolates from eye infections and ocular commensals.

STUDY DESIGN

Retrospective METHODS: Twenty-eight E. faecalis ocular isolates were collected from 23 patients at 3 referring hospitals. The multilocus sequence typing (MLST) data were analyzed using the eBURST program. Phenotypes of cytolysin and gelatinase, antibiotic susceptibility, and mutations of the quinolone resistance-determining regions (QRDRs) of gyrA and parC were also examined. Pulsed-field gel electrophoresis (PFGE) was performed for strains from the same patients.

RESULTS

PFGE revealed that 3 patients retained identical strains for 10 months to 2 and a half years. MLST identified 12 sequence types (STs), which were clustered into 3 clonal complexes (CCs) and 8 singletons, with ST179 the largest. Thirteen of the 23 isolates (56.5%) belonged to CC58, CC8, or CC2, which have previously been reported to be major CCs. Six of the 23 strains (26.0%) exhibited high-level quinolone resistance derived from mutations of the QRDRs in both gyrA and parC.

CONCLUSIONS

The sequence types of E. faecalis ocular isolates were divergent, with no eye-specific lineages observed. Persistent colonization of E. faecalis on the ocular surface was demonstrated in patients with chronic ocular surface diseases.

Topical antibiotics and intravitreal injections

There is increasing evidence that topical antibiotics, given before and/or after intravitreal injections, are ineffective in preventing endophthalmitis and are possibly harmful. In addition to the lack of efficacy and increased development of resistant organisms, the use of topical antibiotics adds significantly to the cost of delivering intravitreal therapy. Despite this, in many countries, it is still common practice to use pre- and/or postinjection topical antibiotics. This review outlines the general principles of effective antibiotic prophylaxis, and the evidence regarding topical antibiotic use as a prophylactic measure for endophthalmitis following intravitreal injections. A key distinguishing feature of intravitreal injections from most other invasive procedures is the fact that they are often repeated on multiple occasions to the same eye. Given the lack of evidence to support topical antibiotics as an effective method of prophylaxis for postinjection endophthalmitis, it appears that more widespread education of ophthalmologists is required to avoid continued inappropriate use. Revision of drug labels in some jurisdictions, and amendment of local/professional society guidelines, may be required to assist in achieving this goal. Emphasis should be placed on antisepsis and aseptic technique, which are the major proven methods of endophthalmitis prevention, rather than antibiotics.

Alterations in conjunctival bacteria and antimicrobial susceptibility during topical administration of ofloxacin after cataract surgery in dogs

OBJECTIVE To evaluate changes in conjunctival bacteria and antimicrobial susceptibility of bacteria after cataract surgery in dogs. ANIMALS 16 client-owned dogs. PROCEDURES Samples for aerobic and anaerobic culture were obtained from the conjunctival fornices of both eyes of dogs 24 hours before (week 0) and 1, 3, and 6 weeks after cataract surgery. Topical administration of ofloxacin (every 6 hours) was initiated 12 hours before surgery and continued for 3 weeks. In vitro antimicrobial susceptibility was determined by Kirby-Bauer disk diffusion and a commercially available test for ofloxacin. RESULTS Frequency of positive culture results was significantly higher at week 6 than at weeks 0 and 1. Bacterial load was more likely to be moderate or high at weeks 3 and 6 than at weeks 0 and 1. The most frequently cultured organism was Staphylococcus pseudintermedius (21/78 [26.9%]), followed by coagulase-negative Staphylococcus spp (19/78 [24.4%]). Staphylococcus pseudintermedius was the organism most frequently cultured at weeks 0 (5/12), 1 (4/12), and 6 (8/19), whereas frequency of this organism was lowest at week 3 (1/20). In contrast, coagulase-negative Staphylococcus spp were the most frequently cultured organisms at week 3 (10/20). There was a significant increase in the proportion of organisms resistant to ofloxacin at week 3, compared with the proportion at week 0. CONCLUSIONS AND CLINICAL RELEVANCE The number of bacterial organisms increased and the population of conjunctival bacteria was altered and had a higher proportion resistant to ofloxacin during the 6 weeks after cataract surgery for dogs treated by use of this protocol.