Susceptibility of methicillin-resistant Staphylococci clinical isolates to netilmicin and other antibiotics commonly used in ophthalmic therapy

Occurrence of Methicillin-Resistant Staphylococcus aureus (MRSA) in Bovine Bulk Milk and Farm Workers in Smallholder Dairy Farming Systems in Northwestern Ethiopia

Background and Purpose

Staphylococcus aureus is a common pathogen responsible for causing various human and animal infections and is well known for its ability to develop resistance to multiple antibiotics. This study aimed to evaluate the occurrence of methicillin-resistant Staphylococcus aureus (MRSA) in bulk milk and dairy farms in northwestern Ethiopia and to determine their phenotypic and genotypic antimicrobial susceptibility patterns.

Methods

We collected 50 bulk milk samples from 50 dairy farms and 50 hand swabs from dairy milkers. The cefoxitin disk diffusion test and PCR-based assays were used to identify MRSA isolates. In addition, cefoxitin-resistant isolates were tested for susceptibility to other antibiotics using the Kirby-Bauer disk diffusion method.

Results

The results showed that MRSA was detected in 8 samples: 6 from bulk milk samples (12%) and 2 from hand swabs (4%). All MRSA isolates exhibited a high resistance rate to penicillin (100%), followed by tetracycline (75%), ciprofloxacin (25%), chloramphenicol (25%), erythromycin (25%), gentamycin (12.5%), and trimethoprim-sulfamethoxazole (12.5%). Moreover, 72% of the isolates showed resistance to three or more antibiotic classes and were classified as multidrug-resistant.

Conclusion

This study identified methicillin-resistant Staphylococcus aureus and multidrug-resistant MRSA in bulk milk and dairy farms in northwestern Ethiopia. These findings highlight the potential risk of transmission of these antibiotic-resistant bacteria to humans and the need for improved antibiotic stewardship in the dairy sector using the One Health approach.

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

INTRODUCTION

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Reduced Posology of an Ophthalmic Hydrogel Containing Dexamethasone/Netilmicin to Prevent and Treat Ocular Inflammation After Cataract Surgery: Efficacy and Tolerability

INTRODUCTION

To demonstrate efficacy and safety of an ophthalmic hydrogel formulation of netilmicin/dexamethasone, containing xanthan gum twice a day (b.i.d.) versus netilmicin/dexamethasone eye drops four times a day (q.i.d) to treat inflammation and prevention of infection after cataract surgery.

METHODS

Patients undergoing phacoemulsification with intraocular lens implantation (IOL) were randomised in two groups: group 1, twice daily (b.i.d.) dexamethasone 0.1%/netilmicin 0.3% (Netildex) ophthalmic gel; group 2, four times daily (q.i.d.) dexamethasone 0.1%/netilmicin 0.3% (Netildex) eye drops. Both treatments were administered for 14 days after surgery. Patients were evaluated before surgery, on the day of surgery and at 1, 7, 15 and 60 postoperative days. The primary efficacy endpoint was evaluation of cellularity and flare in the anterior chamber through slit-lamp biomicroscopy 7 days after surgery. Secondary endpoints included: presence of signs/symptoms of postoperative ocular inflammation and incidence of infection.

RESULTS

One hundred seventy-three patients were randomised and 168 were evaluable. Flare and cellularity were resolved at day 7 in 92.5% of patients and almost completely by day 15. In both intent to treat (ITT) and per-protocol (PP) populations, the efficacy analysis demonstrated that the gel formulation administered twice a day was non-inferior to the eye drops administered four times a day. For ITT analysis, the lower limit of the 97.5% confidence interval (- 0.0535) was greater than the non-inferiority limit of -0.10. For the PP analysis, the lower limit of the 97.5% confidence interval (- 0.0526) was greater than the non-inferiority limit of - 0.10. The patient's global tolerability and reported symptoms were similar between treatment groups. No microbial load and no safety events were observed.

CONCLUSIONS

Efficacy of the gel reduced posology (twice a day) is not inferior to four times a day eye drops. Both treatments were well tolerated and efficacious. The new reduced posology hydrogel formulation may improve patient compliance and quality of life.

TRIAL REGISTRATION

Eudract: 2016-0021138-63; ClinicalTrial.gov: NCT029738880.

Short-Term Use of Dexamethasone/Netilmicin Fixed Combination in Controlling Ocular Inflammation After Uncomplicated Cataract Surgery

Purpose

To evaluate the short-term anti-inflammatory effect of dexamethasone/netilmicin fixed combination in the management of ocular inflammation after cataract surgery.

Patients and Methods

Open-label, randomized, active-controlled, clinical study conducted in 6 sites in Italy; 238 patients were randomized 2:1 to dexamethasone/netilmicin (dexa/net, n=158) or betamethasone/chloramphenicol (beta/chl, n=80). Treatment started the day of surgery and continued 4 times daily for 7 days. The primary efficacy parameter was the anterior chamber (AC) flare. The percentage of patients displaying none or mild (ie, only barely detectable) AC flare was defined as “efficacy rate”, whereas the percentage of patients showing a decrease of AC flare score from baseline was defined as “percentage of responders”. Additional parameters evaluated were AC cells, conjunctival hyperaemia, corneal and lid oedema, symptoms of ocular discomfort, visual acuity, and intraocular pressure. Dexa/net was considered effective if the efficacy rate was not inferior (by means of 97.5% confidence interval) to that of beta/chl.

Results

After 7 days of treatment, no AC flare was observed in 92.8% (dexa/net) and 92.3% (beta/chl) of patients, whereas no AC cells were observed in 91.5% (dexa/net) and 93.6% (beta/chl) of patients, respectively. The “efficacy rate” was 100% in both groups, whereas the “percentage of responders” was 94.1% in the dexa/net and 93.6% in the beta/chl group. The p-value to reject the null hypothesis of inferiority was <0.001. Other efficacy parameters confirmed both treatments as highly effective, despite their difference in steroid content (2 mg/mL for beta/chl vs 1 mg/mL for dexa/net). IOP and visual acuity at the end of the study were comparable. Two cases of allergic conjunctivitis were considered adverse events and were both related to dexa/net.

Conclusion

Short-term use of dexa/net fixed combination is safe and effective in the control of post-operative inflammation following uncomplicated cataract surgery.

Dexamethasone/Netilmicin Eye Drops and Eye Gel for the Treatment of Ocular Inflammation After Micro-Incisional Vitreoretinal Surgery

PURPOSE

To evaluate the effect of dexamethasone/netilmicin (dexa/net) fixed combination in the treatment of ocular inflammation after sutureless micro-incisional vitreoretinal surgery (MIVS).

PATIENTS AND METHODS

This multicenter, open, randomized, active-controlled, parallel-group, clinical trial was run in 6 sites in Italy. Treatment started the day of surgery and continued 4 times daily for 14 days. Patients were 1:1 randomized to dexa/net (eyedrops solution and eye gel) or dexamethasone/tobramycin (dexa/tobra) eyedrops suspension and ointment. Viscous formulations (gel or ointment) were used alone during the early post-operative phase; afterwards, a combination of eye drops during daytime and viscous formulations at bedtime was adopted. The primary efficacy parameter evaluated was bulbar conjunctival hyperemia. Additional efficacy and safety parameters (palpebral conjunctival hyperemia, anterior chamber flare and cells, symptoms of ocular discomfort and ocular tolerance, adverse events and intraocular pressure) were also evaluated. Control visits were performed at day 1, day 4 and day 14 after surgery; the endpoint of the study was set at 14±2 days after surgery.

RESULTS

A complete resolution of bulbar conjunctiva hyperaemia at the study end point was reached in 92.9% of patients treated with dexa/net and 75.0% of those treated with dexa/tobra (p=0.02, Fisher's exact test). No differences were observed between treatments for other efficacy parameters. Statistically significant differences in favour of dexa/net (p< 0.0001, ANOVA) were observed for most of subjective tolerance variables examined (blurred vision, foreign body sensation, stickiness, burning) starting day 1 after surgery when only the viscous formulations were used. No increase in intraocular pressure or adverse events was observed during the study.

CONCLUSION

The combination dexa/net is safe and effective in the treatment of post-operative inflammation following sutureless MIVS. In particular, the use of eye gel formulation is characterized by a great tolerability.

Microorganism detection and contamination rate of donor eyes in Japan

PURPOSE

To evaluate the microorganism detection and contamination rate of donor eyes.

STUDY DESIGN

Retrospective study.

METHODS

In this retrospective study, we reviewed all donor cornea data collected from Kyoto Prefectural University of Medicine (KPUM) Eye Bank, Kyoto, Japan from April 2015 to June 2018, including microbiologic data obtained from conjunctival swabs and preservation medium and findings of postoperative infection from the medical records.

RESULTS

During the study period, 77 eyes from 44 deceased individuals (mean age at time of death: 75 ± 17.3 years [range, 30-102 years]) were donated to the KPUM Eye Bank after being harvested using standard safety precautions and disinfection procedures. In 49 of the 77 eyes (63.6%), the conjunctival-swab culture revealed microorganisms, with the 3 most commonly detected being methicillin-resistant Staphylococcus epidermidis (MRSE), methicillin-sensitive S aureus (MSSA), and methicillin-resistant S aureus (MRSA). The data revealed positive microorganism detection in only 4 (5.2%) of the 77 donor-cornea storage-medium cultures. Positive microorganism detection was found in all the age groups, with no statistical difference between the groups (P > .05). In the eyes enucleated ≥ 2.5 h postmortem, a higher positive microorganism detection occurred (P = .03). During the postoperative follow-up period, there was no record of corneal infection.

CONCLUSIONS

The preenucleation conjunctival-swab-culture findings revealed that the rate of positive microorganism detection was similar for advanced-age and younger-age donors and that a shorter elapsed time from donor death to postmortem enucleation resulted in less donor-microorganism contamination.

Epidemiology, Drug Resistance, and Virulence of Staphylococcus aureus Isolated from Ocular Infections in Polish Patients

Analysis of the epidemiology of Staphylococcus aureus (SA) ocular infections and virulence factors of the isolates with a special emphasis on their drug resistance, and the ability of biofilm formation. In a period from 2009 to 2013, 83 isolates of SA were prospectively collected and preserved in a multicenter laboratory-based study carried out in southern Poland. Epidemiological, phenotypic, and genotypic analyses were performed. The resistance and virulence genes were analyzed. Screening for the biofilm formation was provided. Among the materials derived from ocular infections from 456 patients, SA was found in 18.2% (n = 83) of cases (one SA isolate per one patient). Most infections were identified in the age group of over 65 years (OR 8.4 95%CI; 1.03-68.49). The majority of patients (73.4%) were hospitalized. Among the virulence and resistance genes, the most frequently detected were the lukE (72.2%, n = 60) and ermA (15.6%, n = 13) genes. A positive result of the CRA test (the ability of biofilm formation) was found in 66.2% (n = 55) of isolates. Among the strains under study, 6.0% (n = 5) had the methicillin-resistant Staphylococcus aureus phenotype, and 26.5% (n = 22) had the macrolide-lincosamide-streptogramin B phenotype. In 48 (57.8%) isolates the neomycin resistance was revealed. All isolates under study were sensitive to vancomycin. The population most susceptible to ocular SA infections consists of hospitalized patients aged 65 and more. The SA strains under study showed the increased ability to biofilm formation. In the strains tested, high susceptibility to chloramphenicol and fluoroquinolones was demonstrated. However, the high level of drug resistance to neomycin detected in this study among SA isolates and the blood-ocular barrier makes it difficult to treat ocular infections.

Ocular flora and their antibiotic susceptibility in patients having cataract surgery in Italy

PURPOSE

To characterize the ocular flora in a consecutive group of patients having cataract surgery and to determine the antibiotic susceptibility profile of isolates to several ophthalmic antibiotics.

SETTING

Hospital Di Stefano, Catania, Italy.

DESIGN

Observational case series.

METHODS

Conjunctival and eyelid cultures from patients were obtained 14 days before surgery and, if positive, repeated the day of the surgery. Antimicrobial susceptibility for aminoglycosides (netilmicin and tobramycin), fluoroquinolones (ofloxacin, levofloxacin, and moxifloxacin), chloramphenicol, and azithromycin was tested using the Kirby-Bauer disk diffusion method. Susceptibility was also tested for oxacillin, cefuroxime, and vancomycin. All positive patients received a 2-day preoperative course of 3 mg/mL netilmicin ophthalmic solution 4 times a day. The recovery rate of microorganisms after antibiotic treatment compared with baseline was calculated.

RESULTS

One hundred twenty consecutive patients were included in the study. Cultures were positive in 72.5% of patients; 131 isolates, mainly gram-positive, were identified. Staphylococcus epidermidis (58.0%) and Staphylococcus aureus (15.3%) were the most frequently isolated microorganisms. Methicillin-resistant staphylococci accounted for 3.8% of S epidermidis and 20.0% of S aureus. A high in vitro susceptibility (>90%) for all isolates, including multiresistant coagulase-negative Staphylococcus, was obtained for netilmicin, vancomycin, and cefuroxime. The recovery rate of isolates before surgery was reduced by 93.9% (P < .001).

CONCLUSIONS

Conjunctival and lid margin isolates were sensitive to netilmicin, vancomycin, and cefuroxime. Microorganisms were less susceptible to other ophthalmic antibiotics, with the exception of moxifloxacin. A 2-day preoperative course with topical netilmicin reduced most bacteria identified on the conjunctiva and eyelids.

FINANCIAL DISCLOSURE

Dr. Papa and Ms. Blanco are employees of Società Industria Farmaceutica Italiana SpA. Dr. Santocono has no financial or proprietary interest in any material or method mentioned.

Retrospective report of antimicrobial susceptibility observed in bacterial pathogens isolated from ocular samples at Mount Sinai Hospital, 2010 to 2015

BACKGROUND

Antimicrobial resistance has emerged as a major threat to global public health. Thus, the surveillance of changes in antimicrobial resistance in local and global settings is a paramount necessity. While many studies have tracked antimicrobial resistance, only a small percentage surveyed ocular isolates. The purpose of this study was to report the in vitro susceptibility of bacterial pathogens isolated from ocular samples in New York, NY from 2010 to 2015.

METHODS

A retrospective review of ocular isolates was conducted. All organisms were collected by 25 separate inpatient wards and outpatient clinics, and were analyzed by the clinical microbiology laboratory at Mount Sinai Hospital. Clinical Laboratory and Standards Institute (CLSI) guidelines were followed for susceptibility testing and breakpoint interpretations.

RESULTS

A total of 549 bacterial organisms were isolated from 1664 cultures (33%) during the 6-year study period. Of these, 358 isolates (65.2%) underwent susceptibility testing. 182 (50.8%) isolates were Gram-positive. The most common Gram-positive bacterium was Staphylococcus aureus (62.1%). Methicillin-resistance decreased in S. aureus isolates (31.3% in 2010, 14.1% in 2015) but was without significant change (p = 0.25). When analyzing all S. aureus isolates recovered during the study period, there were significantly more methicillin-resistant S. aureus (MRSA) isolates resistant to fluoroquinolones (p <0.0001), erythromycin (p <0.0001), and trimethoprim/sulfamethoxazole (TMP/SMZ; p <0.05). Overall, Streptococcus pneumoniae isolates showed reduced susceptibility to erythromycin, but were otherwise susceptible to the other antimicrobials tested. Haemophilus influenzae (26.1%) and Pseudomonas aeruginosa (23.9%) were the most common Gram-negative bacteria isolated. Resistance to ampicillin and TMP/SMZ was observed in several of the H. influenzae isolates. P. aeruginosa isolates did not show high resistance overall, however, it was noted that isolates resistant to meropenem were also resistant to other antimicrobials (p < 0.01).

CONCLUSION

Overall, antimicrobial resistance was infrequent for the Gram-negative and Gram-positive bacteria analyzed. While the MRSA isolates demonstrated increased resistance to multiple antimicrobial classes, this is expected for this pathogen. Due to the continued use of broad-spectrum oral and systemic antimicrobials to treat ocular infections, findings of this study and other surveillance studies specific to ocular isolates should be used as resources in effective decision making in the treatment of ocular disease.

Synthesis and antibacterial activity of novel 11-[3-[(arylcarbamoyl)oxy]propylamino]-11-deoxy-6-O-methyl-3-oxoerythromycin A 11-N,12-O-cyclic carbamate derivatives

A series of novel 11-[3-[(arylcarbamoyl)oxy]propylamino]-11-deoxy-6-O-methyl-3-oxoerythromycin A 11-N,12-O-cyclic carbamate derivatives (6a-h) were designed, synthesized and evaluated for their antibacterial activities in vitro. Most of these compounds had significant antibacterial activity against two groups of pathogens of Methicillin-sensitive Staphylococcus aureus (MIC₅₀=0.031-2 μg ml^-1) except 6g and Methicillin-sensitive S. epidermidis (MIC₅₀=0.031-0.5 μg ml^-1). MIC₉₀ of 6d against Methicillin-resistant S. epidermidis was at least 16-fold better than that of erythromycin (EMA), azithromycin (AZM) and ABT-773. 6d and 6e had more potent antibacterial activity against S. pneumoniae than EMA, AZM and ABT-773. In particular, compounds 6d and 6e also showed relatively potent activity against Haemophilus influenzae and Streptococcus hemolyticus.

Complication of an Ahmed glaucoma valve implant: tube exposure with methicillin-resistant Staphylococcus aureus infection

Neovascular glaucoma is commonly treated surgically with implantation of glaucoma drainage devices. We report the case of a 57-year-old man who underwent an uneventful Ahmed glaucoma valve (AGV) placement for radiation-induced neovascular glaucoma but later developed early postoperative infection with tube exposure. The infection was identified 3 weeks postoperatively and antibiotic treatment was immediately initiated. However, the conjunctival melt progressed, and the AGV had to be removed. Culture of the device revealed methicillin-resistant Staphylococcus aureus (MRSA). There is a potential increased risk of postoperative infection and tube exposure following glaucoma valve implantation in patients with previous radiation therapy. To our knowledge, this is the second case in the literature of MRSA causing early postoperative infection following drainage device placement that required explantation.

Novel Therapy for Primary Canaliculitis: A Pilot Study of Intracanalicular Ophthalmic Corticosteroid/Antibiotic Combination Ointment Infiltration

In patients with primary canaliculitis, conservative medical therapy is associated with a high recurrence rate. Surgical treatments carry a great resolution rate but sometimes can result in the lacrimal pump dysfunction and canalicular scarring. The aim of this study is to introduce a minimally invasive approach, intracanalicular ophthalmic corticosteroid/antibiotic combination ointment infiltration (IOI, intracanalicular ointment infiltration), and to report our preliminary results for treating primary canaliculitis. In this retrospective, interventional case series, 68 consecutive patients with newly developed primary canaliculitis at a major tertiary eye center between January 2012 and January 2015. Thirty-six patients received conservative medical treatment alone (group 1; 36 eyes). Twenty-two patients and 10 medically uncontrolled patients from group 1 underwent IOI therapy (group 2; 32 eyes). Ten patients and 26 recurrent patients from group 1 and group 2 underwent surgery (group 3; 36 eyes). Patients were followed-up for at least 8 weeks. Clinical characteristics and outcomes were analyzed and compared. In this study, patients' age, sex, onset location, and durations of disease among 3 groups showed no significant difference. The resolution rate in group 2 was 72.7% (16/22) for new patients and 68.8% (22/32) for gross patients, respectively, both of which are higher than that of group 1 (22.2%, 10/36) but lower than that of group 3 (100%, 36/36). Of group 3, 2 patients received 2 surgical interventions and resolved finally. Microbiological workup was available in 51 patients. The most common isolates were staphylococcus species (27.9%) and streptococcus species (20%). Canalicular laceration developed in 1 patient during the IOI procedure and 1 patient undergoing surgery. Only 2 had postoperative lacrimal pump dysfunction and 1 had canalicular scarring in group 3. The IOI may be an effective and minimally invasive technique for treating primary canaliculitis and obviate the need for further intensive surgery.

Netilmicin/dexamethasone fixed combination in the treatment of conjunctival inflammation

Purpose

To compare the efficacy and safety of 0.1% dexamethasone/0.3% netilmicin (Netildex), with that of 0.1% dexamethasone/0.3% tobramycin (Tobradex) in the treatment of external ocular inflammation requiring antibiotic therapy.

Methods

In this randomized, double-blind study, 139 subjects with conjunctival inflammation associated with signs of ocular infection were treated with Netildex (n = 71) or Tobradex (n = 68) four times daily for 6 days. The primary efficacy analysis was based on the percentage of patients with at least a 50% decrease in conjunctival hyperemia at the endpoint visit (Day 6 [± 1]) with respect to baseline (responder rate). An equivalence margin of 20% was set for this study. A follow-up visit was performed at Day 14 (± 1). Other efficacy parameters were: conjunctival edema, conjunctival discharge, lid hyperemia, lid edema, presence of ocular infection, and symptoms of ocular discomfort. Safety evaluations included intraocular pressure, visual acuity, and adverse events.

Results

At Day 6, a decrease of conjunctival hyperemia was observed in 87.3% and 90.9% of the patients treated with Netildex and Tobradex, respectively. The 95% confidence interval for the difference between groups (−15.3 ÷ 8.0) satisfied the equivalence hypothesis. Subjects treated with Netildex had a better control of lid hyperemia (P = 0.016), tearing (P = 0.001), burning (P = 0.007), and stinging (P = 0.004). No adverse reactions were observed during the study except one case of keratitis in the Tobradex group.

Conclusion

Netildex was as effective and safe as Tobradex in reducing signs and symptoms in patients with conjunctival inflammation when ocular infection was suspected.