A case report of Mycobacterium chelonae keratitis and a review of mycobacterial infections of the eye and orbit

Paradox of complex diversity: Challenges in the diagnosis and management of bacterial keratitis

Bacterial keratitis continues to be one of the leading causes of corneal blindness in the developed as well as the developing world, despite swift progress since the dawn of the "anti-biotic era". Although, we are expeditiously developing our understanding about the different causative organisms and associated pathology leading to keratitis, extensive gaps in knowledge continue to dampen the efforts for early and accurate diagnosis, and management in these patients, resulting in poor clinical outcomes. The ability of the causative bacteria to subdue the therapeutic challenge stems from their large genome encoding complex regulatory networks, variety of unique virulence factors, and rapid secretion of tissue damaging proteases and toxins. In this review article, we have provided an overview of the established classical diagnostic techniques and therapeutics for keratitis caused by various bacteria. We have extensively reported our recent in-roads through novel tools for accurate diagnosis of mono- and poly-bacterial corneal infections. Furthermore, we outlined the recent progress by our group and others in understanding the sub-cellular genomic changes that lead to antibiotic resistance in these organisms. Finally, we discussed in detail, the novel therapies and drug delivery systems in development for the efficacious management of bacterial keratitis.

Mycobacterium Chelonae Keratitis in a Patient with SjöGren's Syndrome

Purpose

In this report a case of Mycobacterium chelonae keratitis in a patient without any previously described risk factors is described. The only risk factor found was a rheumatoid arthritis related Sjögren's syndrome.

Methods

Case report.

Results

A 60-year-old woman was referred to the hospital with an infectious keratitis of the left eye of 3 months duration, unresponsive to empirical therapy with ofloxacin and tobramycin drops. Her medical history included a longstanding rheumatoid arthritis and a secondary ocular surface syndrome. Upon arrival the left eye showed diffuse corneal edema and centrally several large infiltrates with fluffy edges, surrounded by several smaller satellite infiltrates. The cornea was scraped for culture and grew M chelonae and sensitivity testing showed sensitivity to ciprofloxacin, clofazimine, and clarithromycin. Systemically ciprofloxacin 750 mg and clarithromycin 500 mg twice daily were prescribed orally. Topical therapy consisted of topical erythromycin 10 mg/mL and ofloxacin 3 mg/mL every 2 hours. Treatment was continued for a total of 10 months during which the infiltrates cleared completely, but the central cornea remained scarred.

Conclusions

M chelonae can be a cause of infectious keratitis in patients without known risk factors for rapidly growing mycobacterium keratitis. Especially in the case of ocular infections that show no response to regular antibacterial treatment, mycobacterial infection should be considered. Good communication between the ophthalmologist and the microbiologist is crucial for a rapid diagnosis.

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.

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.

Spectrum of CNS disease caused by rapidly growing mycobacteria

We present a case of a patient with chronic meningoencephalitis caused by Mycobacterium abscessus. We also summarise the clinical features and outcomes of cases of CNS infection caused by rapidly growing mycobacteria that have been described in the literature. Rapidly growing mycobacteria are notorious for causing skin and soft-tissue infections after trauma or surgery, pulmonary disease in patients with cystic fibrosis, and disseminated disease in immunocompromised patients. CNS infection with this organism is extremely rare. Patients usually present with subacute to chronic meningitis, neutrophilic pleocytosis, and have a history of trauma or neurosurgery. The smears are often negative for acid-fast organisms, but may show Gram-positive rods. Treatment requires a long course of two or more antibiotics that have the ability to penetrate the blood-brain barrier, and possibly of steroids as immunomodulatory agents, such as those used in tuberculous meningitis.

Nontuberculous (atypical) mycobacterial keratitis after LASIK: current status and clinical implications

PURPOSE

Corneal infection with unfamiliar organisms such as nontuberculous (atypical) mycobacteria after laser in situ keratomileusis (LASIK) can be a significant clinical problem, and mismanagement of such corneal infection in an otherwise healthy, young individual can lead to significant medicolegal issues for the refractive surgeon. Because nontuberculous (atypical) mycobacterial keratitis is the most common infection after LASIK, the refractive surgeon should be aware of all aspects of this dreaded infection to be better prepared to manage such cases.

METHODS

Literature search.

RESULTS/CONCLUSIONS

This article provides a comprehensive compilation of all reported cases of nontuberculous (atypical) mycobacterial keratitis in the English literature and provides some useful recommendations for the clinical management of such corneal infection after LASIK.

Mycobacterium chelonae Keratitis

PURPOSE

To describe the microbiologic diagnosis of putative Mycobacterium chelonae keratitis in a soft contact lens wearer by initial evaluation of Gram- and Kinyoun (acid fast)-stained smears of fluid from patient's contact lens care system.

METHODS

Corneal ulcer of suspected Acanthamoeba etiology developed in a 28-year-old soft contact lens wearer. After corneal scrapings were negative, microbiologic consultation led to evaluation of stained smears and culture of fluid from patient's contact lens care system.

RESULTS

Gram stain of smears showed a polymicrobic flora distinguished by numerous gram-positive, beaded, tightly banded, "diphtheroid-like" bacilli strongly suggestive of a rapidly growing mycobacterial species. Kinyoun-stained smears revealed innumerable acid-fast bacilli singly and in tightly woven bundles (cords), which culturally proved to be M. chelonae. Treatment with ciprofloxacin and amikacin resolved the ulcer.

CONCLUSION

Diagnosis of M. chelonae keratitis in contact lens wearers is often delayed or even overlooked. Additionally, in the absence of overt corneal injury, eg, trauma or surgery, a source for the infecting mycobacterial species in the setting of contact lens wear has not been identified. If searched for, however, as in the present case, the patient's contact lens care system may serve as the reservoir for the microorganism. Staining for acid-fast bacilli is further recommended when smears of contact lens care solution of a patient with a corneal ulcer shows the presence of gram-positive "diphtheroid-like" organisms.

Topical antibacterial therapy for mycobacterial keratitis: potential for surgical prophylaxis and treatment

BACKGROUND

Mycobacterium chelonae and Mycobacterium fortuitum are the 2 most commonly implicated species of nontuberculous mycobacteria in cases of bacterial keratitis.

OBJECTIVES

This article summarizes available data on the in vitro antibacterial activity against M chelonae or M fortuitum of 2 agents-amikacin and clarithromycin-that have been used in the treatment of bacterial keratitis. In addition, the article reviews the in vitro activity of 5 commercially available topical ocular fluoro-quinolones (in order of availability, ciprofloxacin, ofloxacin, levofloxacin, gatifloxacin, and moxifloxacin) that may have potential in the surgical prophylaxis and treatment of keratitis caused by M chelonae or M fortuitum.

METHODS

A search of the English-language literature indexed on the MEDLINE, Life Sciences, EMBASE, BIOSIS, and Pharmaprojects databases from 1966 to October 7, 2003, was conducted using the terms Mycobacterium chelonae, Mycobacterium fortuitum, bacterial keratitis, topical antibiotic therapy, ocular infection-mycobacteria, and LASIK infections. Data on the minimum concentrations at which 90% of isolates were inhibited (MIC(90)s) were reviewed and compared.

RESULTS

In the literature reviewed, the MIC(90) against M fortuitum was from 1 to 16 microg/mL for amikacin, from </=2 to >/=8 microg/mL for clarithromycin, from 0.1 to 1 microg/mL for ciprofloxacin, from 0.5 to 3.13 microg/mL for ofloxacin, and </=2 microg/mL for levofloxacin. The results were similar against M chelonae. The fourth-generation fluoroquinolones-gatifloxacin and moxifloxacin-had similar MIC(90)s against M fortuitum (both, 0.2 to 1 microg/mL); however, moxifloxacin had greater activity than gatifloxacin against M chelonae (minimum inhibitory concentration range: moxifloxacin, </=1 to 1.6 microg/mL; gatifloxacin, 3.2 to 6.25 microg/mL).

CONCLUSIONS

Topical fluoroquinolones may be beneficial for ocular surgical prophylaxis and for the treatment of keratitis caused by M chelonae or M fortuitum. Based on their reported MIC(90)s, none of the antibacterials reviewed had greater in vitro activity than moxifloxacin. In addition, moxifloxacin had greater in vitro activity than gatifloxacin against M chelonae, one of the predominant nontuberculous mycobacterial species involved in bacterial keratitis. Pending the conduct of controlled clinical studies, these findings suggest that moxifloxacin may have utility in the prevention and treatment of atypical mycobacterial keratitis.

Clinical and taxonomic status of pathogenic nonpigmented or late-pigmenting rapidly growing mycobacteria

The history, taxonomy, geographic distribution, clinical disease, and therapy of the pathogenic nonpigmented or late-pigmenting rapidly growing mycobacteria (RGM) are reviewed. Community-acquired disease and health care-associated disease are highlighted for each species. The latter grouping includes health care-associated outbreaks and pseudo-outbreaks as well as sporadic disease cases. Treatment recommendations for each species and type of disease are also described. Special emphasis is on the Mycobacterium fortuitum group, including M. fortuitum, M. peregrinum, and the unnamed third biovariant complex with its recent taxonomic changes and newly recognized species (including M. septicum, M. mageritense, and proposed species M. houstonense and M. bonickei). The clinical and taxonomic status of M. chelonae, M. abscessus, and M. mucogenicum is also detailed, along with that of the closely related new species, M. immunogenum. Additionally, newly recognized species, M. wolinskyi and M. goodii, as well as M. smegmatis sensu stricto, are included in a discussion of the M. smegmatis group. Laboratory diagnosis of RGM using phenotypic methods such as biochemical testing and high-performance liquid chromatography and molecular methods of diagnosis are also discussed. The latter includes PCR-restriction fragment length polymorphism analysis, hybridization, ribotyping, and sequence analysis. Susceptibility testing and antibiotic susceptibility patterns of the RGM are also annotated, along with the current recommendations from the National Committee for Clinical Laboratory Standards (NCCLS) for mycobacterial susceptibility testing.

Delayed-onset mycobacterial keratitis after LASIK

PURPOSE

To describe the time course, diagnosis, clinical features, and treatment of seven patients with Mycobacterium szulgai keratitis that developed from 7 to 24 weeks after laser in situ keratomileusis (LASIK).

METHODS

Seven of 30 eyes of 18 patients were identified with keratitis after LASIK. The first two patients presented 12 to 14 weeks after LASIK; nontuberculous mycobacteria were identified 1 month after the flaps were cultured. Patient recall identified three additional cases by culture and two cases by clinical features alone. Pulsed-field gel electrophoresis (PFGE) was used to type the isolates, and treatment was modified based on susceptibilities.

RESULTS

M. szulgai was identified in five patients for whom cultures were performed, but response to empiric therapy based on cultures proved unsatisfactory. The keratitis resolved in all patients with treatment including clarithromycin based on susceptibilities. Medical therapy was sufficient, although one patient required flap amputation. Six of seven patients recovered best-corrected visual acuity (BCVA), while one patient lost one line of BCVA. Two patients lost one line of postoperative uncorrected visual acuity (UCVA), two patients gained one line of UCVA, and three patients recovered postoperative UCVA. PFGE analysis revealed that the M. szulgai strains were identical, and the infection source was contaminated ice used to chill syringes for saline lavage.

CONCLUSIONS

Nontuberculous mycobacterial keratitis after LASIK is a diagnostic and management challenge, but outcomes can be preserved with treatment based on susceptibilities. This cluster underscores the importance of adherence to sterile protocol during LASIK.

A Cluster of cases of Mycobacterium szulgai keratitis that occurred after laser-assisted in situ keratomileusis

Laser-assisted in situ keratomileusis (LASIK) is a recently developed ophthalmic procedure. When 2 patients developed keratitis caused by Mycobacterium szulgai after they underwent LASIK surgery, we conducted a retrospective cohort study of all LASIK procedures performed at Scott & White Clinic (Temple, Texas) during a 4.5-month period. Seven patients had compatible symptoms and signs, 5 of whom had confirmed M. szulgai keratitis. Five cases occurred among 30 procedures performed by doctor A, and there were no cases among 62 procedures performed by doctor B (approximate relative risk, 12.0; 95% confidence interval, 1.6-679.0; P=.0029). Doctor A had chilled syringes of saline solution in ice for intraoperative lavage-the only factor that differentiated the procedures of the 2 surgeons. Cultures of samples from the source ice machine's drain identified M. szulgai; the strain was identical to isolates recovered from all confirmed cases and differed from 4 standard M. szulgai strains, as determined by pulsed-field gel electrophoresis. Intraoperative contamination from ice water apparently led to M. szulgai keratitis in these patients.

Cutaneous Mycobacterium chelonae in a liver transplant patient

A 51-year-old woman with an orthotopic liver transplant on tacrolimus (SKF 506) and prednisone presented with an erythematous ulcerated nodule on the knee. No preceding trauma was noted. A skin biopsy specimen demonstrated beaded gram-positive, acid-fast rods and the skin culture grew Mycobacterium chelonae (formerly M chelonae subsp chelonae ). This report describes the first case in a liver transplant patient of cutaneous Mycobacterium chelonae under the current method of designating atypical Mycobacterium species.

Nontuberculous mycobacterial keratitis in south Florida

OBJECTIVE

This study aimed to review the clinical features, therapeutic response, and histopathology of cases of nontuberculous mycobacterial keratitis at the Bascom Palmer Eye Institute.

DESIGN AND PARTICIPANTS

Retrospective review of medical records, clinical photographs, histopathology, and microbiology of 24 cases of nontuberculous acid-fast keratitis over the past 15 years.

RESULTS

Causal organisms included Mycobacterium chelonae (16), M. fortuitum (3), M. avium-intracellulare (2), M. nonchromogenicum (1), M. triviale (1), and M. asiaticum (1). Clinically, the keratitis had a superficial location except in those patients with a history of surgery. Amikacin was the most commonly used antibiotic (63%). Three patients were treated with Clarithromycin. In one patient, it was stopped because of toxicity; the other two had resolution of their infiltrates. Fifty-five percent did not respond to topical antimicrobial therapy. The organisms as a group were sensitive to amikacin and Clarithromycin and resistant to the fluoroquinolones. Sixty-four percent of the group that failed to respond to medical treatment were treated with steroids after the diagnosis was known, in comparison to 44% of the group treated successfully with medications. The histopathology of the patients treated with steroids showed minimal inflammation despite a large number of organisms, in contrast to the dense infiltrates seen in the specimens from patients not treated with topical steroids.

CONCLUSION

Nontuberculous mycobacterial keratitis is a chronic insidious infection that is often unresponsive to medical therapy. The authors recommend that steroids be withheld. Based on the authors' experience of three patients, topical Clarithromycin may hold promise as a therapeutic agent. Lamellar keratectomy or penetrating keratoplasty should be considered in those patients who do not respond to medical therapy or those who have recurrent exacerbations on attempted weaning of topical antibiotic therapy.

Iatrogenic outbreak of M. chelonae skin abscesses

We describe an outbreak of skin lesions due to Mycobacterium chelonae subsp. abscessus associated with injections of lidocaine (lignocaine) given by a 'bioenergetic' (a practitioner of alternative medicine) in Colombia. The lidocaine carpules and the lesions of the patients yielded mycobacteria with identical biochemical characteristics. Using the methodology of Sartwell and a case control design we examined the incubation period and assessed risk factors. Of 667 potentially exposed individuals, a total of 298 patients were interviewed, of whom 232 had skin lesions. The median incubation period was 30.5 days (range 15-59 days). Male sex (OR 2.85, 95% CI 1.26-6.51), increasing age (OR 1.25, 95% CI 1.03-1.53), subcutaneous injection route (OR 3.72, 95% CI 1.09-12.7) and number of injections (OR 1.01, 95% CI 1.00-1.03) were risk factors for disease. To our knowledge, this is the largest reported outbreak of M. chelonae infection, the first in which the organism has been isolated from the putative vehicle of infection, and the first in which the incubation period could be determined.