Infectious crystalline keratopathy caused by Mycobacterium fortuitum and Pseudomonas aeruginosa

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.

Infectious crystalline keratopathy

Infectious crystalline keratopathy was first reported by Gorovoy and colleagues in 1983 when they identified bacteria colonizing a cornea after a penetrating keratoplasty. Subsequent cases have elaborated on the organisms responsible and the management outcomes. Patients present with a white or gray branching opacity originating from an epithelial defect, commonly after a penetrating keratoplasty. Local immunosuppression contributes to the quiescent nature and the limited inflammatory response associated with infectious crystalline keratopathy. Diagnosis of the infective pathogens may be difficult, with a corneal scraping often being too superficial to obtain an adequate specimen. A biofilm is present that advantages microorganism survival, reduces antibiotic bioavailability, and inhibits diagnostic microbial detection. Treatment begins with topical antimicrobials, initially broad spectrum and then targeted to microorganism sensitivity. Adjunctive therapies to enhance the efficacy of treatment include disruption of the microorganism biofilm by laser, intrastromal antibiotics, and keratectomy. In recalcitrant cases, or where corneal scarring ensues, corneal transplantation is required.

Infectious crystalline keratopathy caused by Pseudomonas fluorescens

OBJECTIVE

To demonstrate a case of infectious crystalline keratopathy (ICK) caused by Pseudomonas fluoresecens (PF).

METHODS

Case report description.

RESULTS

A 15-year-old female contact lens wearer presented complaining of eye pain and redness in the left eye. The patient reported that she had suffered a corneal scratch a few months earlier, which was treated by her family physician, and that she had felt some discomfort since then. The biomicroscopy showed a central corneal abscess with a crystalline appearance, stromal edema, the Tyndall effect, and abundant fibrin in the anterior chamber. A diagnosis of ICK was made. The culture was positive for gram-negative PF. Pseudomonas fluoresecens was sensitive to cephalosporins, quinolones, and tobramycin.

CONCLUSIONS

No cases of ICK caused by PF have been reported previously. Two previous studies reported that the gram-negative Pseudomonas aeruginosa caused ICK. Unlike other ICK cases in which there is minimal stromal inflammation, the patient presented with an intense inflammatory reaction in the anterior chamber.

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.

Non-tuberculous mycobacterial keratitis

Non-tuberculous mycobacteria are environmental, opportunistic pathogens that are increasingly being recognized as important causes of many human diseases. Among them, rapidly growing mycobacteria are the most notorious organisms causing infectious keratitis. Non-tuberculous mycobacterial (NTM) keratitis commonly occurs after trauma or refractive surgery, and can masquerade as fungal, herpetic or amoebic keratitis. Therefore, the diagnosis is often delayed. Prolonged medical treatment and judicious surgical debridement are required in order to eradicate the pathogens. Combination therapy with aminoglycosides, macrolides and fluoroquinolones improves the prognosis and decreases the occurrence of drug resistance. However, regardless of the development of new diagnostic techniques and antimicrobials, NTM keratitis remains a clinical challenge for most ophthalmologists. In this article, we provide a concise introduction to the epidemiological features and clinical characteristics of NTM keratitis, and the modern diagnostic tools used for it. We also summarize the current concepts of prevention and treatment for this potentially devastating condition.

Brilliant crystallisation in the anterior chamber and subretinal space following adjunctive intravitreal ranibizumab for diabetic vitrectomy

To report a unique case of crystallisation in the anterior chamber and subretinal space in a Malay lady following inadvertent subretinal injection of ranibizumab prior to vitrectomy for proliferative diabetic retinopathy.

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.

Infectious crystalline keratopathy associated with Klebsiella oxytoca

Purpose

The purpose of this study is to report a novel case of a Klebsiella oxytoca-associated infectious crystalline keratopathy

Methods

This is a case report study.

Results

An 80-year-old woman presented with complaint of noticing a white spot in the left eye for 2 to 3 days, as well as mild soreness and discharge. Past ocular history was notable for a failed left corneal transplant for which she was taking prednisolone acetate 1 % twice per day. On slit-lamp examination, there was an extensive stromal ulcer and infiltrate in the inferior half of the transplant. Extending superiorly in the graft were branching, needle-like deep stromal opacities, characteristic of infectious crystalline keratopathy. Diagnostic scrapings revealed Gram-negative bacilli, subsequently identified on culture as K. oxytoca. There was also light growth of Staphylococcus species. The patient was placed on double topical antibiotic therapy with moxifloxacin and fortified tobramycin. After 2 months of treatment there was gradual resolution of the infection.

Conclusions

K. oxytoca is a microorganism which can be associated with clinical infectious crystalline keratopathy, presenting as a mixed infection along with Staphylococcus species.

Post-LASIK Infectious Crystalline Keratopathy Caused by Alternaria

PURPOSE

To describe a case of infectious crystalline keratopathy (ICK) after laser in situ keratomileusis (LASIK) caused by Alternaria species.

METHODS

A case report of a 29-year-old woman who presented with clinical features of ICK 3 weeks after LASIK surgery.

RESULTS

Medical therapy failed to control and resolve the corneal infection. Penetrating keratoplasty was performed, which controlled the infection and aided in visual recovery of 20/30. The culture of the corneal button revealed the presence of Alternaria species fungus.

CONCLUSIONS

Alternaria species fungus may cause ICK after LASIK.

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.

An outbreak of Mycobacterium chelonae infection after LASIK

OBJECTIVE

To describe an outbreak of mycobacterial keratitis after laser in situ keratomileusis (LASIK), including the microbiologic investigation, clinical findings, treatment response, and outcome.

DESIGN

Retrospective, noncomparative, interventional case series.

PARTICIPANTS

Patients (n = 10) who underwent LASIK surgery between August 22 and September 4, 2000, and developed mycobacterial infection.

METHODS

Patients were prospectively followed in relation to microbiologic investigation, clinical findings, treatment response, and outcome.

MAIN OUTCOME MEASURES

Most patients underwent bilateral simultaneous LASIK. Postoperative infection was signaled by the appearance of corneal infiltrates in the third postoperative week. The microbiologic workup was performed on cultures obtained either by direct scraping of the cornea or by lifting the flap. Medical therapy was instituted based on drug susceptibility testing. Surgical interventions such as corneal debridement and flap removal were performed during recurrences or when there was no satisfactory clinical response.

RESULTS

Cultures revealed Mycobacterium subspecies chelonae. Patients were treated with topical clarithromycin (1%), tobramycin (1.4%), and ofloxacin (0.3%). Oral clarithromycin (500 mg twice a day) was prescribed for those patients who did not respond clinically to topical treatment. Four eyes healed on this regimen. Flap removal was necessary in seven eyes.

CONCLUSIONS

This report highlights mycobacteria as an etiologic infectious agent after LASIK. Diagnosis can be difficult and is often delayed. The treatment mainstay is prolonged antibiotic therapy. Surgical debridement and flap removal may shorten the disease course.

Infectious post-LASIK crystalline keratopathy caused by nontuberculous mycobacteria

PURPOSE

To report three cases of infectious crystalline keratopathy caused by non-tuberculous mycobacteria after LASIK surgery.

METHODS

Interventional case reports and literature review.

RESULTS

Infectious keratitis with clinical features of crystalline keratopathy after LASIK is described. Culture revealed Mycobacterium chelonae from the corneal scrapings of the three patients, all of whom underwent medical and surgical (debridement) treatment.

CONCLUSIONS

Mycobacteria may cause infectious crystalline keratopathy after LASIK. The presence of crystalline keratopathy in patients that underwent LASIK must be considered an indicator of nontuberculous mycobacteria infection. Microbiologic work-up of a corneal specimen is required for the institution of appropriate therapy.

Non-tuberculous Mycobacterial Keratitis at the Interface After Laser in situ Keratomileusis

PURPOSE

To describe two cases of bacterial keratitis with atypical mycobacteria after laser in situ keratomileusis (LASIK).

METHODS

Two cases of non-tuberculous mycobacterial keratitis occurred in the interface between the stromal bed and flap, 20 days and 14 days after LASIK. The keratitis progressed slowly and worsened after attempts were made to remove the colonies. Mycobacterium fortuitum was confirmed 2 months after initial presentation following culture of the excised flap tissue in one case, and Mycobacterium chelonae was identified by culture of removed material and by RT-PCR with primers in the other case. The patients were treated medically and by surgical flap removal.

RESULTS

In the first case, the keratitis was controlled only after removal of the partially melted flap and intensive medical treatment. In the second case, the lesion cleared after 2 months of antibiotics, but after tapering of antibiotics, the infiltrate progressed. Eventually, the keratitis was controlled after removal of the flap.

CONCLUSIONS

Non-tuberculous Mycobacterium should be considered as one of the causes of keratitis when presenting as white colonies in the lamellar bed after LASIK. Treatment for 2 months may not be enough to eradicate the infection and excision of the flap may be necessary.

Cluster of Mycobacterium chelonae keratitis cases following laser in-situ keratomileusis

PURPOSE

To describe a cluster of Mycobacterium chelonae keratitis cases involving patients who underwent laser in-situ keratomileusis (LASIK) at a single refractive surgery center.

DESIGN

Descriptive case series of four patients and cohort study to identify disease associations.

METHODS

Examination schedules, diagnostic tests, and therapy were based on best medical judgment. Isolates from three patients were compared by pulsed-field gel electrophoresis. Epidemiologic studies were performed to identify the source of infection.

RESULTS

Seven of eight eyes developed M. chelonae keratitis following bilateral simultaneous LASIK. Each patient was thought to have diffuse lamellar keratitis initially, but all seven eyes were noted to have opacities suggestive of infectious keratitis by 13 to 21 days after surgery. All eyes had undergone hyperopic LASIK over four days in April 2001 by one surgeon in a community-based refractive surgery center. A cohort study of all patients undergoing LASIK at the same center in April 2001 revealed that M. chelonae keratitis occurred only in persons undergoing correction of hyperopia (seven of 14 eyes vs. none of 217 eyes undergoing myopic LASIK, P <.001). The only difference identified between procedures was use of masks created from a soft contact lens in hyperopic LASIK. Three isolates (three patients) were indistinguishable by pulsed-field gel electrophoresis. Eyes were treated with a combination of antimicrobial agents, including topical azithromycin in three patients, with resolution of infection in all eyes over 6 to 14 weeks. The source of infection was not identified on environmental cultures.

CONCLUSION

Postoperative nontuberculous mycobacterial keratitis can occur in an epidemic fashion following LASIK. Topical amikacin, azithromycin, clarithromycin, ciprofloxacin, or a combination of these agents, appears to be effective treatment for these infections.

Demonstration of biofilm in infectious crystalline keratopathy using ruthenium red and electron microscopy

OBJECTIVE

Bacterial biofilm formation has been implicated in the pathogenesis of infectious crystalline keratopathy. Biofilm cannot be visualized by electron microscopy without the addition of a fixative that stabilizes the polysaccharide-rich bacterial extracellular matrix that surrounds the bacterial colonies in a biofilm. We used ruthenium red as a fixative to evaluate corneal biopsy specimens for the presence of bacterial biofilm in three cases of infectious crystalline keratopathy (ICK) and five cases of chronic microbial keratitis without crystalline changes.

DESIGN

Case series with clinicopathologic correlation.

PARTICIPANTS

Eight patients underwent corneal biopsy or therapeutic keratoplasty as part of their management for chronic unresponsive microbial keratitis.

METHODS

The corneal specimens removed were trisected for microbiology, pathology, and transmission electron microscopy (TEM). The TEM specimens were fixed in 2.5% glutaraldehyde in 0.1 M sodium cacodylate buffer with 0.05% ruthenium red.

MAIN OUTCOME MEASURES

Demonstration of bacterial biofilm with TEM.

RESULTS

TEM demonstrated organisms with a surrounding extracellular matrix consistent with a bacterial biofilm in the three cases of ICK but not in the five other cases of chronic microbial keratitis.

CONCLUSIONS

The presence of biofilm in ICK can be demonstrated with TEM with appropriate fixation techniques that stabilize the bacterial extracellular matrix. Biofilm stains intensely with periodic acid-Schiff because of the polysaccharide-rich extracellular matrix and weakly with Gram stain because of the high proportion of nonviable organisms. Biofilm formation occurs in ICK but probably not in chronic bacterial keratitis without crystalline changes. Secretion of an extracellular matrix by bacteria to form a biofilm is a response to a nutrient-deprived environment in which growth and replication is depressed. The extracellular matrix of the biofilm may mask bacterial antigens, explaining the relative lack of inflammatory response in these infections. It may also be one of the mechanisms explaining the resistance to in vivo antimicrobial therapy when in vitro sensitivities have been proven.

Periocular atypical mycobacterial infections

OBJECTIVE

To examine the clinical characteristics and management of periocular infections caused by atypical mycobacteria.

DESIGN

Retrospective, noncomparative case series.

PARTICIPANTS

Six patients were identified with periocular atypical mycobacterial infections: four with Mycobacterium chelonae and two with Mycobacterium fortuitum.

INTERVENTION

The treatment of these infections included removal of the foreign bodies with debridement of the lesions. Specimens were sent for histopathologic examination, routine cultures, and fresh tissue for culture after homogenization.

MAIN OUTCOME MEASURES

A retrospective review of culture-proven atypical mycobacterial infections involving the periocular tissues was performed. Charts were reviewed for age, gender, infectious organism, medical history, surgical history, presenting symptoms, clinical features, and treatment.

RESULTS

Four associations with infection were identified in these patients: immunosuppression, nasolacrimal duct obstruction, the presence of a foreign body, and a history of recent surgery. All six of the patients had at least one of these associations and five of the patients had at least two. Clinical characteristics that may distinguish atypical mycobacterial infections from acute bacterial infections include subacute presentation, firm nodular lesions, mild erythema, mild tenderness, and minimal purulent discharge. All patients had resolution of their infections after debridement and several weeks of systemic antibiotic therapy guided by susceptibility testing.

CONCLUSIONS

Periocular atypical mycobacterial infections are uncommon. The clinical history and examination can raise the suspicion of this infection by revealing the clinical characteristics of these infections. Treatment includes removal of foreign bodies, debridement, and long-term systemic antibiotic therapy.

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.

Infectious crystalline keratopathy caused by gram-negative bacteria

PURPOSE

To identify the characteristics and outcomes of infectious crystalline keratopathy caused by gram-negative bacteria.

METHODS

We reviewed all patients treated at a university eye center for infectious crystalline keratopathy from 1978 through 1995 and performed a nested case-comparison study by comparing patients with keratitis caused by gram-negative rods and those with keratitis caused by gram-positive cocci.

RESULTS

Eighteen patients (mean age +/- SD, 59 +/- 17 years) displayed unilateral culture-positive infectious crystalline keratopathy. Among 18 eyes with crystalline keratopathy, five occurrences (28%) were caused by gram-negative rods (Acinetobacter lwoffi, Citrobacter koseri, Enterobacter aerogenes, Pseudomonas aeruginosa, and Stenotrophomonas maltophilia), 10 (55%) were caused primarily by gram-positive cocci, and three (17%) were caused primarily by yeasts. Four cases grew two different isolates. No significant difference in predisposing factors, clinical appearance, or visual outcome was found between infections caused by gram-negative bacteria and those caused by gram-positive bacteria.

CONCLUSIONS

Gram-negative bacteria can cause infectious crystalline keratopathy but have no distinguishing features from infectious crystalline keratopathy caused by streptococci and other gram-positive bacteria. Appropriate laboratory evaluation is therefore necessary to guide specific antimicrobial therapy.

Non-tuberculous mycobacterial keratitis: a study of 22 cases

AIM

To investigate causes and clinical findings of non-tuberculous mycobacterial keratitis, and to study its response to topical antibiotic therapy and surgical extirpative keratectomy.

METHOD

A single centre, retrospective review of 22 patients with non-tuberculous mycobacterial keratitis seen in a 3 year period. Laboratory diagnoses were established with Ziehl-Nielsen acid fast staining and Löwenstein-Jensen cultures.

RESULTS

In 20 patients (91%), there was an antecedent history of foreign body eye trauma (18 patients) or elective surgery (two patients). There were 19 cases of Mycobacterium chelonei, and three of M fortuitum. Clinical signs included epithelial defects, satellite or ring stromal infiltrates, crystalline keratopathy, and hypopyon. For topical antibiotic therapy, 20 patients received amikacin, while one patient received rifampin and another received ciprofloxacin, each in accordance with the results of the in vitro drug sensitivities. An extirpative keratectomy was performed in 15 cases; four of these cases additionally required a temporary conjunctival flap in order to finally eradicate the infection. At the end of the follow up period (median 18 months; range 3 months to 3 years) all eyes were stable and free of infection, with 19 (86%) having final visual acuities of 20/200 or better.

CONCLUSION

Early clinical recognition and prompt laboratory diagnosis, together with aggressive topical antibiotic therapy and early keratectomy, may shorten morbidity and improve the clinical outcome of non-tuberculous mycobacterial keratitis.

Extensive lamellar keratectomy for treatment of nontuberculous mycobacterial keratitis

PURPOSE

To determine the efficacy of using extensive lamellar keratectomy for treating patients who have nontuberculous mycobacterial keratitis that is unresponsive to medical treatment.

METHODS

Nine patients with bacteriologically proven nontuberculous keratitis, who had poor response to medical treatment and whose corneal infiltrate was not deeper than 80% of corneal thickness, were selected for extensive lamellar keratectomy. This procedure was performed freehand to remove all the corneal infiltration visible by operation-microscopic examination, to have a clean stromal bed.

RESULTS

Corneal infection was eradicated in seven patients by a single procedure. In the other two patients, the condition was controlled by a second operation. Epithelialization was rapid and complete in all cases within ten days (mean, 4.8 days). Pain relief was dramatic after surgery. Visual acuity after surgery was improved in seven patients, but remained the same in two. There were no complications as a result of the lamellar keratectomy.

CONCLUSIONS

Lamellar keratectomy should be considered as a treatment option for patients with nontuberculous mycobacterial keratitis who are unresponsive to medical therapy.