Fourth-generation fluoroquinolone-resistant mycobacterial keratitis after laser in situ keratomileusis

Atypical microbial keratitis

Atypical microbial keratitis refers to corneal infections caused by micro-organisms not commonly encountered in clinical practice. Unlike infections caused by common bacteria, cases of atypical microbial keratitis are often associated with worse clinical outcomes and visual prognosis. This is due to the challenges in the identification of causative organisms with standard diagnostic techniques, resulting in delays in the initiation of appropriate therapies. Furthermore, due to the comparatively lower incidence of atypical microbial keratitis, there is limited literature on effective management strategies for some of these difficult to manage corneal infections. This review highlights the current management and available evidence of atypical microbial keratitis, focusing on atypical mycobacteria keratitis, nocardia keratitis, achromobacter keratitis, and pythium keratitis. It will also describe the management of two uncommonly encountered conditions, infectious crystalline keratopathy and post-refractive infectious keratitis. This review can be used as a guide for clinicians managing patients with such challenging corneal infections.

Bilateral Non-tuberculous Mycobacterial Keratitis After Small Incision Lenticule Extraction

PURPOSE

To report a case of bilateral non-tuberculous mycobacterial keratitis after small incision lenticule extraction (SMILE) that was successfully treated with oral and topical fortified antibiotics.

METHODS

Case report and literature review.

RESULTS

An otherwise healthy 21-year-old woman presented with culture-proven bilateral Mycobacterium abscessus keratitis 8 days after undergoing SMILE, showing multiple white stromal infiltrates in the interface in both eyes. Progressive, diffuse flap edema followed by pocket abscess, exudation in the anterior chamber, granulation tissue formation in the pocket, intrastromal neovascularization, and eventually partial resolution of corneal opacity were noted after topical and oral antibiotic treatment for 6 months. Her corrected distance visual acuity was 20/32 and 20/50 in the right and left eyes, respectively, 12 months after initial presentation.

CONCLUSIONS

This is the first report of successful medical management of bilateral non-tuberculous mycobacterial keratitis after SMILE. The manifestations are different from and even more difficult to treat than those of keratitis after LASIK. [J Refract Surg. 2018;34(9):633-636.].

Identification of the Infection Source of an Outbreak of Mycobacterium Chelonae Keratitis After Laser in Situ Keratomileusis

PURPOSE

Nontuberculous mycobacteria keratitis is a rare but challenging complication of laser in situ keratomileusis (LASIK). This study was conducted to determine the source(s) of infection in a cluster of cases of keratitis after LASIK and to describe this outbreak and patients' outcomes.

METHODS

In this retrospective, case series, single-center study, 86 patients were included who underwent LASIK or photorefractive keratectomy between December 2011 and February 2012. Corneal scrapes from the affected eyes, samples of tap and distilled water, water from the reservoir of the distilling equipment, steamer, and autoclave cassette; antiseptic and anesthetic solutions and surgical instrument imprints were cultivated in liquid and on solid media. Gram-negative bacteria and yeasts were identified using automated systems and mycobacteria by polymerase chain reaction-restriction enzyme analysis of the hsp65 gene (PRA-hsp65) and DNA sequencing. Mycobacterial isolates were typed by pulsed-field gel electrophoresis. The cases and outcomes are described. The main outcome measure was identification of the source(s) of the mycobacterial infections.

RESULTS

Eight (15 eyes) of 86 patients (172 eyes) who underwent LASIK developed infections postoperatively; no patients who underwent photorefractive keratectomy developed infections. Mycobacterium chelonae was isolated from 4 eyes. The distilled water collected in the surgical facility contained the same M. chelonae strain isolated from the patients' eyes. Different gram-negative bacteria and yeasts were isolated from samples collected at the clinic but not from the patients' eyes.

CONCLUSIONS

Tap water distilled locally in surgical facilities may be a source of infection after ocular surgery and its use should be avoided.

Biofilms of Pathogenic Nontuberculous Mycobacteria Targeted by New Therapeutic Approaches

Microbial infections of the cornea are potentially devastating and can result in permanent visual loss or require vision-rescuing surgery. In recent years, there has been an increasing number of reports on nontuberculous mycobacterial infections of the cornea. Challenges to the management of nontuberculous mycobacterial keratitis include delayed laboratory detection, low index of clinical suspicion, poor drug penetration, slow response to therapy, and prolonged use of antibiotic combinations. The ability of nontuberculous mycobacteria to evade the host immune response and the ability to adhere and to form biofilms on biological and synthetic substrates contribute to the issue. Therefore, there is an urgent need for new antimicrobial compounds that can overcome these problems. In this study, we evaluated the biofilm architectures for Mycobacterium chelonae and Mycobacterium fortuitum in dynamic flow cell chamber and 8-well chamber slide models. Our results showed that mycobacterial biofilms were quite resistant to conventional antibiotics. However, DNase treatment could be used to overcome biofilm resistance. Moreover, we successfully evaluated a new antimicrobial compound (AM-228) that was effective not only for planktonic mycobacterial cells but also for biofilm treatment and was compared favorably with the most successful “fourth-generation” fluoroquinolone, gatifloxacin. Finally, a new treatment strategy emerged: a combination of DNase with an antibiotic was more effective than an antibiotic alone.

Comparison of the Anti-angiogenic and Anti-inflammatory Effects of Two Antibiotics: Clarithromycin Versus Moxifloxacin

PURPOSE

Clarithromycin is a 14-membered ring macrolide antibiotic with anti-inflammatory as well as antibacterial activity, and has been used worldwide. Moxifloxacin is a leading fourth generation quinolone antibiotic that has been used worldwide perioperatively. We intended to evaluate whether clarithromycin can suppress angiogenesis and inflammation in the cornea, and to compare the anti-inflammatory and anti-angiogenic effects of the two antibiotics, clarithromycin and moxifloxacin.

METHODS

We made a murine corneal suture model and tested the anti-inflammatory and anti-angiogenic effects of clarithromycin (5 mg/ml) and moxifloxacin (5 mg/ml) in two randomly divided groups. Dexamethasone (5 mg/ml) was used as a positive control. After making two sutures on the cornea, we performed subconjunctival injections (10 μl) on each group on the day of suture, and every day thereafter until the 8th day post-suture. After harvesting corneas on the 8th post-suture day for immunohistochemical staining, we compared neovascularization (NV), lymphangiogenesis (LY) and inflammatory cell infiltration among the groups.

RESULTS

Clarithromycin suppressed NV, LY and inflammatory infiltration, compared with phosphate-buffered saline (PBS). However, moxifloxacin did not suppress NV, LY, or inflammatory infiltration, compared with PBS. Comparison between clarithromycin and moxifloxacin, clarithromycin showed a tendency of decreasing LY (p = 0.063) and had less inflammatory cell infiltration (p < 0.05) than did the moxifloxacin group. The anti-(lymph)angiogenic and anti-inflammatory effects of clarithromycin were as high as those of dexamethasone.

CONCLUSION

Clarithromycin suppressed LY and inflammation in the cornea, and its anti-inflammatory effect was significantly superior to that of moxifloxacin.

Use of Topical Besifloxacin in the Treatment of Mycobacterium chelonae Ocular Surface Infections

PURPOSE

To present the clinical outcome of 3 cases of ocular surface infections by Mycobacterium chelonae treated with besifloxacin (0.6%, Besivance; Bausch & Lomb, Tampa, FL).

METHODS

In this retrospective review of a small case series, we reviewed the medical records of 3 clinical patients with M. chelonae infection involving the ocular surface. Besifloxacin was used as an adjunct in 2 cases of keratitis and as the principal therapeutic agent in a case of nodular conjunctivitis.

RESULTS

Two patients who presented with culture-proven M. chelonae keratitis initially had been treated with topical amikacin and oral clarithromycin for 6 months in the first case and for 2 months in the second without complete resolution. Topical besifloxacin was added as an adjunct therapy to amikacin with progressive weaning of clarithromycin. Both cases of keratitis eventually resolved without recurrence after discontinuation of topical amikacin and besifloxacin. A third patient presented with nodular conjunctival inflammation, which initially had been treated with topical ciprofloxacin and corticosteroids without improvement. One nodular lesion was excised and submitted for microbial culture, which revealed the growth of M. chelonae. Marked improvement of the conjunctivitis was noted after 3 weeks of treatment with topical besifloxacin. Complete resolution of the conjunctival nodules was achieved after 10 weeks of treatment with besifloxacin.

CONCLUSIONS

Topical besifloxacin seems to be a useful adjunct agent in the treatment of nontuberculous mycobacterial keratitis by M. chelonae and may be viable for use as a first-line agent in cases of nodular conjunctivitis by M. chelonae.

Nontuberculous Mycobacterial Ocular Infections: A Systematic Review of the Literature

Nontuberculous or atypical mycobacterial ocular infections have been increasing in prevalence over the past few decades. They are known to cause periocular, adnexal, ocular surface and intraocular infections and are often recalcitrant to medical therapy. These infections can potentially cause detrimental outcomes, in part due to a delay in diagnosis. We review 174 case reports and series on nontuberculous mycobacterial (NTM) ocular infections and discuss etiology, microbiology, risk factors, diagnosis, clinical presentation, and treatment of these infections. History of interventions, trauma, foreign bodies, implants, contact lenses, and steroids are linked to NTM ocular infections. Steroid use may prolong the duration of the infection and cause poorer visual outcomes. Early diagnosis and initiation of treatment with multiple antibiotics are necessary to achieve the best visual outcome.

Effect of antibiotic drops on adverse events during extended lens wear

PURPOSE

Overnight lens wear is associated with increased lens contamination and risk of developing a corneal infiltrate or infectious event. Antibacterial lenses have been proposed as a potential strategy for reducing lens contamination. A proof-of-principle study was conducted to investigate what effect control of potential pathogens, through the use of antibiotic eye drops, would have on the incidence of corneal infiltrative events (CIEs) and on the ocular microbiota and lens contamination.

METHODS

This is a prospective, open-label, controlled, parallel-group, 1-month clinical study in which 241 subjects were dispensed with lotrafilcon A silicone hydrogel lenses for 30 days of continuous wear. Subjects were randomized into either test (moxifloxacin 0.5%) or control (rewetting solution) group. One drop was instilled into each eye on waking and before sleeping, while lenses were on-eye. Follow-ups were conducted after one night and 1 month. Lid margin swabs were taken at baseline and at 1 month and worn lenses were aseptically collected at 1 month.

RESULTS

The incidence of CIEs was not significantly different between the test (2.6%) and control (3.9%) groups (p = 0.72). Microorganism levels from the test group swabs were significantly lower than those from the control group (p = 0.001). Gram-positive bacteria were less frequently recovered from lower lid swabs from the test group (39.6% vs. 66.0% [p < 0.001], test vs. control, respectively) or from contact lens samples (1.9% vs. 10.5% [p = 0.015], test vs. control, respectively), but there was no difference in gram-negative bacteria (GNB). Corneal infiltrative events were associated with higher levels of lens contamination (p = 0.014) and contamination of lenses with GNB (CIE: 7.3% vs. 0.6% [p = 0.029], GNB contamination vs. no GNB contamination, respectively).

DISCUSSION

Twice-daily antibiotic instillation during continuous wear of lenses did not significantly influence the rate of inflammatory events. Corneal infiltrative events were associated with higher levels of lens contamination in general and with contamination by GNB specifically.

Nontuberculous mycobacterial ocular and adnexal infections

The nontuberculous (also called "atypical") mycobacteria have become increasingly important causes of systemic as well as ocular morbidity in recent decades. All ocular tissues can become infected with these organisms, particularly in patients who are predisposed following ocular trauma, surgery, use of corticosteroids, or are immunocompromised. Because of their relative resistance to available antibiotics, multidrug parenteral therapy continues to be the mainstay of treatment of more serious ocular and adnexal infections caused by nontuberculous mycobacteria (NTM). Periocular cutaneous, adnexal, and orbital NTM infections remain rare and require surgical debridement and long-term parenteral antibiotic therapy. NTM scleritis may occur after trauma or scleral buckling and can cause chronic disease that responds only to appropriate antibiotic therapy and, in some cases, surgical debridement and explant removal. NTM infectious keratitis following trauma or refractive surgical procedures is commonly confused with other infections such as Herpes simplex keratitis and requires aggressive topical therapy and possible surgical debridement, particularly in those cases occuring after laser in situ keratomileusis. Only 18 cases of endophthalmitis due to NTM have been reported. Systemic and intraocular antibiotic therapy and multiple vitrectomies may be needed in NTM endophthalmitis; the prognosis remains poor, however. Disseminated NTM choroiditis in acquired immune deficiency syndrome patients with immune reconstitution during highly active anti-retroviral therapy is a rare infection that can present as a necrotizing chorioretinitis with dense vitritis, mimicking many other entities and needs to be recognized so that timely, life-saving treatment can be administered. Regardless of which ocular tissue is infected, all NTM ocular infections present similar challenges of recognition and of therapeutic intervention. We clarify diagnosis and delineate modern, effective therapy for these conditions.

Microbial keratitis after corneal laser refractive surgery

Corneal laser refractive surgery is increasingly being performed on patients with the aim of improving unaided vision. Most candidates for surgery have excellent spectacle- or contact lens-corrected vision. Although microbial keratitis following refractive surgery is a rare complication, and usually has a good visual outcome, it can be sight-threatening. The spectrum of pathogens differs to other causes of microbial keratitis, such as contact lens-associated keratitis, and a different management approach is required. Postoperatively, patients are prescribed topical steroids and broad-spectrum topical antibiotics, typically fluoroquinolones. These do not cover unusual organisms, such as fungi, Nocardia, Acanthamoeba and some atypical mycobacteria. In post-laser-assisted in situ keratomileusis microbial keratitis, the lamellar flap should be lifted to acquire samples for specific microbiological examination, including these atypical organisms. Confocal microscopy is a noninvasive test that provides morphological information, and is operator dependent, but may assist in the rapid diagnosis of fungal, Acanthamoeba or Norcardia keratitis. PCR is not in widespread use, but has high sensitivity and specificity, and may facilitate early diagnosis and specific treatment of the causative organism, which is critical in obtaining the best clinical outcome.

Ocular infections caused by non-tuberculous mycobacteria: update on epidemiology and management

BACKGROUND

  To provide an update on the frequency, distribution, risk factors and in vitro susceptibility of ocular infections caused by non-tuberculous mycobacteria.

DESIGN

  Retrospective study of university clinic patients.

PARTICIPANTS

  One hundred thirty-nine patients with culture confirmed non-tuberculous mycobacteria infections seen at Bascom Palmer Eye Institute from January 1980 to July 2007.

METHODS

  Chart review of data collected included patients' demographics, risk factors, microbiological profiles and clinical outcomes.

MAIN OUTCOME MEASURES

  Frequency, distribution, risk factors and in vitro susceptibility of ocular infections caused by non-tuberculous mycobacteria.

RESULTS

  A total of 183 non-tuberculous mycobacteria isolates from 142 eyes were identified, with a fourfold increase in the number of eyes infected with non-tuberculous mycobacteria from 1980-1989 (13.4%) to 2000-2007 (56.3%). Eighty-three percent of non-tuberculous mycobacteria isolates were identified as M. abscessus/chelonae. The majority (91%) of isolates were recovered within 10 days. Common diagnoses included keratitis (36.6%), scleral buckle infections (14.8%) and socket/implant infections (14.8%). Identifiable risk factors were presence of biomaterials (63.1%), ocular surgery (24.1%) and steroid exposure (77%). The median time from diagnosis of culture positive non-tuberculous mycobacteria infection to resolution was 13 to 24 weeks. Combination therapy was used to treat 80% of infected eyes. In vitro susceptibility of non-tuberculous mycobacteria isolates were: amikacin, 81%; clarithromycin, 93%; and moxifloxacin, 21%.

CONCLUSIONS

  The incidence of ocular infections caused by non-tuberculous mycobacteria has increased within the last 8 years, with a high number of biomaterial associated infections among this group. Clinical diagnosis and microbiological confirmation of non-tuberculous mycobacteria infections remains challenging. Patient outcomes may be improved by early diagnosis, appropriate therapy and removal of biomaterials.

Review of moxifloxacin hydrochloride ophthalmic solution in the treatment of bacterial eye infections

Moxifloxacin hydrochloride ophthalmic solution 0.5% (Vigamox((R))) is the ocular formulation/adaptation of moxifloxacin. Moxifloxacin is a broad spectrum 8-methoxyfluoroquinolone which terminates bacterial growth by binding to DNA gyrase (topoisomerase II) and topoisomerase IV, essential bacterial enzymes involved in the replication, translation, repair and recombination of deoxyribonucleic acid. Affinity for both enzymes improves potency and reduces the probability of selecting resistant bacterial subpopulations. Vigamox is a bactericidal, concentration dependent, anti-infective. It is preservative free, and well tolerated with minimal ocular side effects. It provides increased penetration into ocular tissues and fluids with improved activity against Streptococci and Staphylococci species and moderate to excellent activity against clinically relevant, gram-negative ocular pathogens.

Infectious keratitis treated with corneal crosslinking

PURPOSE

To describe 7 eyes with severe infectious keratitis treated using collagen crosslinking (CXL) with riboflavin.

MATERIALS AND METHODS

Seven eyes of 6 patients with severe infectious keratitis were treated with corneal crosslinking. Three patients were contact lens users. Symptom duration before CXL ranged between 0 and 7 days. Corneal melting was present in all cases. Photodocumentation of the keratitis was carried out and repeated at follow-up. All but 1 patient received topical antibiotic treatment in addition to the CXL treatment. CXL was conducted according to the standardized protocol for keratoconus.

RESULTS

In all but 1 eye, patients experienced improvement in symptoms within 24 hours. Two patients reported no symptoms whatsoever at this time. Corneal melting was arrested and complete epithelialization was achieved in all cases. In the 2 eyes with hypopyon, this regressed completely within 2 days after the CXL. Follow-up ranged between 1 and 6 months.

DISCUSSION

Our experience based on the above and other cases suggest that CXL could be an effective tool in battling difficult cases of infectious keratitis. This treatment could present many advantages but will need further investigation.

Oral moxifloxacin and topical amikacin for Mycobacterium abscessus keratitis after laser in situ keratomileusis

We report a case of Mycobacterium abscessus keratitis after elective laser in situ keratomileusis in a 19-year-old woman. The infection started 3 weeks after uneventful surgery, and the patient received multiple antimicrobial treatments without response. A corneal scrape isolate showed an acid-fast bacterium that was subsequently confirmed by culture to be M abscessus. Prompt treatment of oral moxifloxacin 400 mg twice daily and hourly topical amikacin 2.5% was started. Recovery occurred within the first week of treatment, with complete resolution 3 weeks after presentation. The final uncorrected distance visual acuity was 6/9. We comment on other reports of post-LASIK keratitis caused by M abscessus, the in vitro sensitivity to antibiotic agents described in the literature, and the use of oral moxifloxacin as a potential good alternative treatment based on its good ocular bioavailability, which in our case allowed resolution without the need for surgical intervention.

Evaluation of antibacterial efficacy of photo-activated riboflavin using ultraviolet light (UVA)

BACKGROUND

To evaluate the antibacterial efficacy of photo-activated riboflavin using Ultraviolet A (UVA) on three bacterial strains commonly detected in keratitis.

METHODS

Three bacterial strains (Staphylococcus epidermidis, Staphylococcus aureus and Pseudomonas aeruginosa) were cultured on blood/hematin-agar plates and dispersed in PBS. Dispersion was done of 10 microl of bacterial stock-solutions in 90 microl of RPMI, where different riboflavin molarities had been added, to achieve a bacterial concentration of 1-4 x 10 (4)/ml. Riboflavin end molarities before illumination were 0, 100, 200, 300 and 400 microM. Each solution had a negative control. The solutions were illuminated with UVA (365 nm) for 30 minutes (5.4 J/cm(2)) and then continued for a total time of 60 minutes (10.8 J/cm(2)). A count of CFU was conducted after incubation and results compared.

RESULTS

In all tested strains, a slight decrease of bacteria was seen when exposed to UV for 30 minutes. A doubling of the UV dose showed a marked decrease of bacterial count in all bacteria tested. The combination of UV and riboflavin showed a more extensive reduction of CFU, confirming an interaction effect between UV and riboflavin.

CONCLUSION

Riboflavin photo-activation using UVA (365 nm) can achieve an extensive eradication of bacteria, and the combination is more potent in reducing bacterial number than UV alone.