Extensive lamellar keratectomy for treatment of nontuberculous mycobacterial keratitis

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.

Nontuberculous mycobacterial lung disease epidemiology in Taiwan: A systematic review

Nontuberculous mycobacteria (NTM) are critical emerging global infectious pathogens. Though NTM can be mere colonizers when isolated from human specimens, NTM are also responsible for diverse human infections. NTM-lung disease (NTM-LD) is the most common human disease entity. The present review aims to provide general insight into NTM-LD epidemiology in Taiwan. In reviewing NTM epidemiology in Taiwan, we discovered three distinguishing features. First, NTM disease incidence has increased in Taiwan over the past decade. Second, the distribution of NTM varies geographically in Taiwan. Mycobacterium avium-intracellulare complex (MAC) is the dominant species in northern Taiwan, whereas Mycobacterium abscessus complex and MAC may be equally dominant in southern Taiwan. Third, researchers in Taiwan have published valuable research investigating NTM among special patient populations, including patients in intensive care units, with ventilator dependency, with pulmonary tuberculosis, and who are infected with specific NTM species. The largest obstacle to clarifying NTM epidemiology in Taiwan may be the lack of routine NTM species identification in laboratories. Increased awareness of NTM diseases and acknowledgment that NTM species identification is crucial and guides clinical management are essential steps for facilitating the identification of NTM species in laboratories.

Modified ulcer debridement in the treatment of the superficial fungal infection of the cornea

AIM

To evaluate the efficacy of modified corneal ulcer debridement in superficial fungal keratitis unresponsive to medications.

METHODS

A total of 209 patients (209 eyes) with fungal keratitis, involving no more than 50% of the stromal depth and not responding to antifungal agents for 2wk, were recruited in this retrospective, noncomparative study. The patients were treated with modified corneal ulcer debridement. All visible corneal infiltrates were removed under an operating microscope to obtain a clean stromal bed and smooth incised edges. Antifungal drugs were used immediately after surgery. Healing time of the ulcers was recorded. Fungal recurrence, visual acuity, corneal thickness and risk factors for treatment failure were monitored.

RESULTS

The follow-up was 13.6±5.8mo. The corneal ulcers healed in 195 of 209 eyes (93.3%), with a mean healing time of 8.4±6.8d. The other 14 eyes were further treated by penetrating keratoplasty (PK) (1 eye), anterior lamellar keratoplasty (LK) (7 eyes), conjunctival flap covering (4 eyes) or amniotic membrane transplantation (2 eyes). The best corrected visual acuity (BCVA) was ≥20/70 in 80.3% of the eyes, ≥20/40 in 56.9% of the eyes, and ≥20/25 in 27.3% of the eyes. The corneas at the lesions became thinner, but all in the safe range. No fungal recurrence or corneal ectasis developed during the follow-up. The risk of treatment failure was higher in patients with preoperative hypopyon (P=0.036) and ever using steroid (P=0.025).

CONCLUSION

Modified surgical debridement is a simple and effective method for the treatment of superficial fungal infection of the cornea, with improved visual acuity and no recurrence. Such an intervention in time can rapidly control fungal infection and largely shorten corneal ulcer healing time.

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.

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.

Effectiveness of fluoroquinolones against Mycobacterium abscessus in vivo

PURPOSE

To determine the effectiveness of fluoroquinolones against Mycobacterium abscessus in vivo.

METHODS

M. abscessus growth was determined quantitatively in rabbit corneas after intrastromal bacterial injection (10(4) CFU/cornea; n >or= 4 corneas per group). Eyes were treated topically with 0.3% ciprofloxacin, 0.5% levofloxacin, or 0.5% moxifloxacin by three protocols: (1) 1 drop of antibiotic applied hourly for 10 hr on day 3 postinfection (PI); (2) 1 drop applied every 2 hr for 10 hr on days 2 and 3 PI; or (3) 1 drop applied every 2 hr for 10 hr on days 1, 2, and 3 PI. Corneas were cultured 1 hr after the last topical drop. Results are expressed as the log CFU.

RESULTS

Bacteria in control group reached maximal numbers in vivo by day 3 PI (approximately 6 logs CFU/cornea). Treatment of infected eyes on day 3 with moxifloxacin or levofloxacin resulted in approximately 2.0 log decrease in CFU/cornea relative to the untreated control. Treatment on days 2 and 3 with moxifloxacin or levofloxacin resulted in approximately 3.0 and 2.5 log CFU/cornea decrease, respectively. Ciprofloxacin had no effect on bacterial load. Treatment on days 1, 2, and 3 with moxifloxacin resulted in a 5.5 log CFU decrease, whereas treatment with levofloxacin or ciprofloxacin resulted in a approximately 4.0 log CFU decrease.

CONCLUSIONS

Moxifloxacin, and to a lesser extent levofloxacin and ciprofloxacin, demonstrated significant effectiveness for reducing the number of M. abscessus in vivo, suggesting the potential usage of these agents in prevention of M. abscessus keratitis.

In Vitro Activity of Fluoroquinolones Against Mycobacterium abscessus and Mycobacterium chelonae Causing Infectious Keratitis After LASIK in Brazil

PURPOSE

To evaluate the in vitro activity of fluoroquinolones against Mycobacterium abscessus and Mycobacterium chelonae isolated from outbreaks of infectious keratitis in Brazil.

MATERIAL AND METHODS

Micobacterial isolates were recovered from infectious keratitis cases related outbreaks that occurred in Brazil after LASIK for myopia. Two outbreaks occurred in Rio de Janeiro in 1998 and 1999, and 3 in São Paulo between 2000 and 2003. All laboratorial analysis, including molecular identification and antibiotic susceptibility testing with determination of the minimum inhibitory concentration (MIC) levels for ciprofloxacin, ofloxacin, gatifloxacin, and moxifloxacin, were performed at Universidade Federal de São Paulo in Brazil.

RESULTS

Fifteen samples were identified as M. chelonae, and 3 were identified as M. abscessus. The outbreaks studied were designated SP-1 in 2000; SP-2 in 2000-2001; and SP-3 in 2003, R1 in 1988 and R2 in 1999. All but 1 of the M. chelonae were resistant to all fluoroquinolones with an MIC90 greater than 32 microg/mL. The only susceptible isolate had MIC levels for ciprofloxacin, ofloxacin, gatifloxacin, and moxifloxacin of 0.38 microg/mL, 0.032 microg/mL, 0.047 microg/mL, and 0.19 microg/mL, respectively. MIC levels for all 3 M. abscessus isolates tested were greater then 32 microg/mL for all fluoroquinolones tested.

CONCLUSIONS

Fluoroquinolone MICs for 17 M. abscessus and M. chelonae isolates recovered from infectious keratitis cases in Brazil indicate that they are not susceptible to these drugs in vitro. Further studies to investigate the in vivo effectiveness of fluoroquinolones against mycobacteria are required because in vitro tests do not support their use in the treatment of micobacterial keratitis in this particular geographic area.

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.

Lamellar Keratectomy Using an Automated Microkeratome

PURPOSE

To evaluate the effectiveness of treating anterior corneal pathology by performing a superficial lamellar keratectomy with an automated microkeratome.

METHODS

Retrospective chart review of 10 eyes (8 patients) seen in a subspecialty referral practice for anterior segment disease. With the use of an automated microkeratome, a lamellar flap was created, which was then surgically excised.

RESULTS

Ten eyes of eight patients were followed for a mean of 5.4 months (range, 4 to 10 months). Subjective visual acuity and/or sensation of ocular irritation improved in 10 of 10 eyes. Mean improvement in Snellen best-corrected visual acuity was 1.8 lines (range, -1 to +3 lines). One patient lost 1 line of Snellen acuity due to progression of a posterior subcapsular cataract. Mean change in spherical equivalent was +0.5 diopters (range, -1.60 to +4.25 diopters), and mean improvement in corneal clarity (1 to 4 scale) was 1.8. Mean preoperative pachymetry was 589.0 microm (range, 507 to 741 microm). Mean postoperative pachymetry was 461.3 microm (range, 370 to 564 microm). Recurrence of pathology (band keratopathy and Salzmann's nodular degeneration) occurred in two patients. In one patient, immunohistochemical staining of corneal tissue from the lamellar dissection confirmed the diagnosis of herpes simplex virus type 1 stromal keratitis, improving the course of postoperative care.

CONCLUSION

Lamellar keratectomy with the use of an automated microkeratome is a safe and effective method for removing superficial anterior corneal opacities. For selected cases, it offers specific advantages over other surgical modalities. In particular, this procedure may induce far less hyperopic shift than would the equivalent amount of tissue removal by performing excimer laser phototherapeutic keratectomy.

Clinical characteristics of microbial keratitis in a university hospital in Taiwan

PURPOSE

To analyze the clinical and microbiological characteristics of microbial keratitis at the National Taiwan University Hospital in the preceding 10 years.

DESIGN

Retrospective cross-sectional study.

METHODS

Medical records were reviewed for all patients with clinically diagnosed microbial keratitis presenting at the National Taiwan University Hospital from January 1992 to December 2001. Risk factors, microbial isolations, clinical patterns, treatment, and outcomes were analyzed.

RESULTS

Microbial keratitis was diagnosed for 476 eyes in 453 patients (220 female and 233 male; mean age, 40.7 years). Pseudomonas species were the most commonly isolated organisms (37.7%), followed by fungi (13.5%), staphylococci (8.4%), nontuberculous mycobacteria (7.9%), streptococci (7.6%), and Acanthamoeba (4.4%). Contact-lens wear was the most common predisposing factor (44.3%). Medical treatment was successful for a total of 344 eyes (72.3%), with 132 eyes (27.7%) requiring surgery. The duration from symptom onset to diagnosis of microbial keratitis was statistically significantly shorter for the cases treated medically than the cases treated surgically (7.70 +/- 14.37 and 20.53 +/- 28.85 days, respectively, p =.000000332). Response to medical treatment was more favorable for bacterial infection (except nontuberculous mycobacterial infection) as compared with fungal or Acanthamoeba infection. A total of 84.4% of pseudomonal keratitis cases were cured by medical treatment, while 85% of nontuberculous mycobacterial keratitis cases eventually required surgical treatment to control the infection.

CONCLUSION

Contact-lens related pseudomonal keratitis was the most common form of microbial keratitis in Taiwan. Early diagnosis and prompt treatment are important for successful management of microbial keratitis.

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.

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.

Mycobacterium Chelonae Keratitis Following Laser in situ Keratomileusis

Corneal infection after laser in situ keratomileusis (LASIK) is rare. However, surgical trauma or breakdown of epithelium increases the risk of surface infection. We present the case of a 45 year old woman who developed keratitis due to Mycobacterium chelonae 1 month after LASIK with the Mini-Laser Sight 2000 excimer laser. After an initial improvement following antibiotic therapy the infection progressed until it was necessary to perform penetrating keratoplasty, with a successful result.

Topical ciprofloxacin for treating nontuberculous mycobacterial keratitis

OBJECTIVE

This study aimed to evaluate the clinical efficacy of topical ciprofloxacin for treating Mycobacterium fortuitum and Mycobacterium chelonae keratitis refractory to amikacin therapy.

DESIGN

A prospective clinical trial of topical ciprofloxacin treatment for nontuberculous mycobacterial keratitis was conducted.

PARTICIPANTS

Eleven patients with nontuberculous mycobacterial keratitis diagnosed from 1992 to 1996 were enrolled.

INTERVENTION

All 11 patients were treated initially with topical fortified amikacin, but only 2 patients responded. The other nine patients, four with M. fortuitum and five with M. chelonae keratitis, were refractory to amikacin therapy and received topical ciprofloxacin treatment. Bacterial culture and drug susceptibility tests using the broth microdilution method were performed on all 11 patients.

MAIN OUTCOME MEASURES

The clinical response to amikacin or ciprofloxacin treatment was judged by corneal re-epithelialization and density and/or size of corneal infiltrates.

RESULTS

M. chelonae isolates were more resistant to amikacin and ciprofloxacin than M. fortuitum isolates based on the in vitro susceptibility test. Clinically, three patients with M. fortuitum keratitis were responsive to ciprofloxacin therapy; however, only one patient with M. chelonae keratitis responded to the same therapy.

CONCLUSIONS

Topical ciprofloxacin offers a therapeutic alternative for nontuberculous mycobacterial keratitis, which was refractory to amikacin treatment. However, topical ciprofloxacin was more effective for treating M. fortuitum keratitis than for M. chelonae keratitis.

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.