Atypical mycobacteria keratitis after laser in situ keratomileusis unresponsive to fourth-generation fluoroquinolone therapy

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.

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.

Infectious endophthalmitis in Boston keratoprosthesis: incidence and prevention

PURPOSE

To determine the cumulative worldwide incidence of infectious endophthalmitis and associated vision loss after Boston keratoprosthesis (B-KPro) Type I/II implantation and to propose both safe and inexpensive prophylactic antibiotic regimens.

METHODS

Two retrospective methods were used to determine the incidence, visual outcomes and aetiologies of infectious endophthalmitis associated with the B-KPro divided per decade: (i) systematic review of the literature from 1990 through January 2013 and (ii) a surveillance survey sent to all surgeons who implanted B-KPros through 2010 with 1-year minimum follow-up. In addition, a single-Boston surgeon 20-year experience was examined.

RESULTS

From 1990 through 2010, there were 4729 B-KPros implanted worldwide by 209 U.S. surgeons and 159 international surgeons. The endophthalmitis cumulative mean incidence declined from 12% during its first decade of use to about 3% during its second decade in the Unites States and about 5% internationally during the second decade. There remains a large incidence range both in the United States (1-12.5%) and internationally (up to 17%). Poor compliance with daily topical antibiotics is an important risk factor. While Gram-positive organisms remained dominant, fungal infections emerged during the second decade.

CONCLUSIONS

Daily prophylactic topical antibiotics have dramatically reduced the endophthalmitis incidence. Although Gram-positive organisms are the most common aetiology, antimicrobials must be inclusive of Gram-negative organisms. Selection of prophylactic regimens should be tailored to local antibiotic susceptibility patterns, be cost-effective, and should not promote the emergence of antimicrobial resistance. An example of a broad-spectrum, low-cost prophylactic option for non-autoimmune patients includes trimethoprim/polymyxinB once daily.

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.

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.

Micobactérias não tuberculosas em cirurgias: desafio passível de enfrentamento no Brasil?

Infecções por micobactéria não tuberculosa (MNT) representam uma emergência epidemiológica e sanitária, especialmente, em pacientes submetidos a procedimentos invasivos. Frente ao exposto, objetivou-se analisar as evidências científicas, na literatura científica, sobre a ocorrência no Brasil de infecções por MNT em pacientes cirúrgicos. Utilizou-se como método de pesquisa a revisão integrativa da literatura nas bases de dados Lilacs, Medline/Pubmed, ISI Web of Science e Biblioteca Cochrane. Foram selecionadas 15 publicações sobre a temática nos últimos 30 anos que estavam direcionadas às medidas de prevenção e controle com foco na vigilância pós-alta, no uso de antibioticoterapia e glutaraldeído. Cirurgias oftalmológicas, estéticas, cardíacas e procedimentos laparoscópicos e artroscópicos foram as mais investigadas. A situação nacional das MNTs é preocupante, ainda mais quando se reconhece a possibilidade de subnotificação.

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.