Aspergillus fumigatus keratitis with wreath pattern infiltrates

Corneal ring infiltrate- far more than Acanthamoeba keratitis: review of pathophysiology, morphology, differential diagnosis and management

OBJECTIVE

Ring infiltrates usually accompany numerous infectious and sterile ocular disorders. Nevertheless, systemic conditions, drugs toxicity and contact lens wear may present with corneal ring infiltrate in substantial part. Considering its detrimental effect on vision, detailed knowledge on etiology, pathophysiology, differential diagnosis, and management should be considered essential for every ophthalmologist.

METHODS

The PUBMED database was searched for "corneal ring infiltrate" and "ring infiltrate" phrases, "sterile corneal infiltrate" and "corneal infiltrate". We analyzed articles written in English on risk factors, pathophysiology, clinical manifestation, morphological features, ancillary tests (anterior-segment optical coherence tomography, corneal scraping, in vivo confocal microscopy), differential diagnosis and management of corneal ring infiltrate.

RESULTS

Available literature depicts multifactorial origin of corneal ring infiltrate. Dual immunological pathophysiology, involving both antibodies-dependent and -independent complement activation, is underlined. Furthermore, we found that the worldwide most prevalent among non-infectious and infectious ring infiltrates are ring infiltrates related to contact-lens wear and bacterial keratitis respectively. Despite low incidence of Acanthamoeba keratitis, it manifests with corneal ring infiltrate with the highest proportion of the affected patients (one third). However, similar ring infiltrate might appear as a first sign of general diseases manifestation and require targeted treatment. Every corneal ring infiltrate with compromised epithelium should be scraped and treat as an infectious infiltrate until not proven otherwise. Of note, microbiological ulcer might also lead to immunological ring and therefore require anti-inflammatory treatment.

CONCLUSION

Corneal ring infiltrate might be triggered not only by ocular infectious and non-infectious factors, but also by systemic conditions. Clinical assessment is crucial for empirical diagnosis. Furthermore, treatment is targeted towards the underlying condition but should begin with anti-infectious regimen until not proven otherwise.

Exploratory Use of Fluorescent SmartProbes for the Rapid Detection of Microbial Isolates Causing Corneal Ulcer

PURPOSE

To explore the use of optical SmartProbes for the rapid evaluation of corneal scrapes from patients with suspected microbial keratitis, as a clinical alternative to Gram stain.

DESIGN

Experimental study with evaluation of a diagnostic technology.

METHODS

Corneal scrapes were collected from 267 patients presenting with microbial keratitis at a referral cornea clinic in South India. Corneal scrapes were flooded with SmartProbes (BAC One or BAC Two) and evaluated by fluorescence microscopy (without the need for sample washing or further processing). The SmartProbe-labeled samples were scored as bacteria/fungi/none (BAC One) or gram-negative bacteria/none (BAC Two) and compared to Gram stain results.

RESULTS

Compared to Gram stain, BAC One demonstrated sensitivity and specificity of 80.0% and 87.5%, respectively, positive and negative predictive values (PPV, NPV) of 93.8% and 65.1%, and an accuracy of 82.2. BAC Two demonstrated sensitivity and specificity of 93.3% and 84.8%, respectively, an NPV of 99.2%, and an accuracy of 85.6%. When the corresponding culture results were compared to the Gram stain result, the sensitivity and specificity were 73.4% and 70.7%, the PPV and NPVs were 86.5% and 51.0%, and overall accuracy was 72.6.

CONCLUSIONS

Fluorescent SmartProbes offer a comparative method to Gram stain for delineating gram-positive or gram-negative bacteria or fungi within corneal scrapes. We demonstrate equivalent or higher sensitivity, specificity, PPV and NPVs, and accuracy than culture to Gram stain. Our approach has scope for point-of-care clinical application to aid in the diagnosis of microbial keratitis.

Epidemiological, clinical and laboratory findings of infectious keratitis at Mansoura Ophthalmic Center, Egypt

AIM

To analyze the epidemiological, clinical and laboratory findings of infectious keratitis.

METHODS

A retrospective study on cases of infective keratitis, attended our institution from Mar. 2013 to Feb. 2015, was done at Mansoura Ophthalmic Center, Egypt. Corneal scrapings were performed and processed for direct microscopy and culture in appropriate media using standard laboratory protocols.

RESULTS

Out of 245 patients enrolled for study, 247 corneal scrapings were obtained. Ocular trauma was the most common predisposing factor (51.4%), followed by diabetes mellitus (15.1%). Cultures were positive in 110 scraping samples (44.5%): 45.5% samples had pure fungal infection, 40% had pure bacterial infections and 10% had mixed fungal and bacterial growths. Acanthamoeba was detected in 5 (4.5%) samples. The most common fungal pathogen was Aspergillus spp. (41%). The most common bacterial isolates were Staphylococcus aureus (38.2%) and Pseudomonas aeruginosa (21.8%).

CONCLUSION

Incidence of fungal keratitis is high in our region. Therapeutic approach can initially be based on clinical features and sensitivity/resistance patterns. Microbiological research should direct the antimicrobial treatment. Antibiotic resistance to fluoroquinolones and aminoglycosides is an important consideration.

Nocardia Keratitis

PURPOSE

To correlate the clinical presentation and treatment outcome of Nocardia keratitis with the time to diagnosis, different species and with the drug sensitivity pattern.

METHOD

Patients with Nocardia corneal ulcers were studied at a tertiary eye care center. Speciation of Nocardia isolates was done by sequencing the 16s rRNA gene. Clinical response to treatment was assessed by chart review.

RESULTS

Twenty one (65.3%) patients presented within 15 days of the onset of symptoms with typical clinical features of Nocardia keratitis, ie, a ring-like distribution of superficial infiltrates in a wreath pattern. Eight patients (25%) who presented after 15 days and within 30 days had an ulcer resembling fungal keratitis. N. Cyriacigeorgica (n = 11; 34.37%), N. asteroides (n = 9; 28%), N. farcinica (n = 7; 22%,) and N. Otitidiscaviarum (n = 5; 16%). All the species had 100% sensitivity to amikacin, sulphamethoxazole, imipenem and co-trimoxazole. Time to diagnosis of the infection was significantly associated with the different types of clinical presentation; those presenting early having the typical clinical picture (P = 0.004). Patients (73%) presenting within 15 days showed a highest recovery rate. (P = 0.045). The recovery time of the patients when compared with species showed those who were infected with N. cyriageorgica had a healing time of less than 15 days. Clinically, healing was faster when treated with 2% amikacin. Visual outcome improved in fourteen patients (44%) and sixteen (50%) patients remained the same (P = 0.0001).

CONCLUSION

Characteristic clinical picture of Nocardia is dependant on early presentation. It could be mistaken for fungal keratitis. Microbiological confirmation is important. Drug of choice for Nocardia keratitis is amikacin.

Microbiological diagnosis of infective keratitis: comparative evaluation of direct microscopy and culture results

AIMS

To determine the sensitivity, specificity and predictive values of potassium hydroxide (KOH) wet mount, Gram stain, Giemsa stain and Kinyoun's acid-fast stain in the diagnosis of infective keratitis.

METHODS

A retrospective analysis of all patients with clinically diagnosed infective keratitis presenting between September 1999 and September 2002 was carried out. Corneal scrapes were taken and subjected to direct microscopy and culture.

RESULTS

3298 eyes of 3295 consecutive patients with infective keratitis were evaluated, of which 1138 (34.51%) eyes had fungal growth alone, 1069 (32.41%) had bacterial growth alone, 33 (1%) had Acanthamoeba growth alone, 83 (2.5%) had mixed microbial growth and the remaining 975 (29.56%) had no growth. The sensitivity of KOH wet mount was higher (99.3%; 95% confidence interval (CI) 98.6 to 99.6) in the detection of fungi, 100% (95% CI 90.4 to 100) in the detection of Nocardia and 91.4% (95% CI 75.8 to 97) in the detection of Acanthamoeba) than that of Gram-stained smears (89.2% (95% CI 87.3 to 90.8) in fungi, 87% (95% CI 73.0 to 94.6) in Nocardia and 60% (95% CI 42.2 to 75.6) in the detection of Acanthamoeba) in the detection of fungi, Nocardia and Acanthamoeba. 1764 of 3295 (53.54%) patients presented more than 7 days after onset of illness and 84.69% of the eyes had corneal ulcers with size >2 mm in diameter. Positivities of KOH (44.46%; p<0.001) and Gram-stained smears (77.37%; p<0.001) were found to be higher among eyes with larger ulcers (>2 mm) than among eyes with smaller ulcers (<2 mm).

CONCLUSION

KOH smear is of greater diagnostic value in the management of infective keratitis, and it is recommended in all clinics without exception for establishing timely treatment.

Characteristic clinical features as an aid to the diagnosis of suppurative keratitis caused by filamentous fungi

AIM

To assess whether the presence of characteristic clinical features can be used as a diagnostic aid for suppurative keratitis caused by filamentous fungi.

METHODS

Patients presenting with suppurative keratitis in India underwent detailed clinical examination followed by microbiological investigation of corneal scrapes. A partial diagnostic score based upon the strength of the association, as estimated by the odds ratio, between reported clinical features and laboratory confirmed diagnoses was devised and subsequently tested using a case series from Ghana.

RESULTS

Serrated margins, raised slough, dry texture, satellite lesions and coloration other than yellow occurred more frequently in cases of filamentous fungal keratitis than bacterial keratitis (p<0.05). Hypopyon and fibrinous exudate were observed more frequently in bacterial keratitis (p<0.05). When incorporated into a backwards stepwise logisitic regression model only serrated margins, raised slough, and colour were independently associated with fungal keratitis; these features were used in the scoring system. The probability of fungal infection if one clinical feature was present was 63%, increasing to 83% if all three features were present.

CONCLUSIONS

Microbiological investigations should be performed whenever possible; however, where facilities are not available, a rapid presumptive diagnosis of suppurative keratitis may be possible by scoring clinical features.

Nocardia keratitis after laser in situ keratomileusis: Clinicopathologic correlation

A case of Nocardia asteroides keratitis occurring 3 weeks after laser in situ keratomileusis (LASIK) in a nontraumatized eye is reported. The patient presented with decreased vision, inflammation, and stromal melting of the LASIK flap, discrete infiltrates, and an anterior chamber cellular reaction. Cultures for acid-fast bacteria grew Nocardia asteroides after 5 days. Infection progressed despite treatment with topical antibiotics and eventually required penetrating keratoplasty (PKP). Postoperatively, the patient was placed on moxifloxacin, a fourth-generation flouroquinolone. The patient experienced a recurrence of Nocardia keratitis at the graft-host interface 2 months after the PKP. This eventually resolved with a combination of topical moxifloxacin and imipenem therapy.

Efficiency of blood culture bottles for the fungal sterility testing of corneal organ culture media

BACKGROUND/AIM

The consequences of fungal contamination of an organ cultured cornea, though exceptional, are often disastrous for the recipient. Consequently, eye banks often quarantine corneas for 10 days or more before passing them for grafting. This period, though detrimental to the endothelial cell density of the delivered cornea, is necessary to detect contamination using conventional microbiological methods. The authors previously validated the use of a pair of aerobic and anaerobic blood bottles for sensitive and rapid detection of bacteria. To allow a short quarantine period, it remained only to optimise detection of fungi. The authors aimed to compare sensitivity and rapidity of fungal contamination detection by three methods: blood bottles, Sabouraud, and daily visual inspection of the organ culture medium.

METHODS

Four inocula (10(6), 10(4), 10(2), 10 colony forming unit (CFU) per ml) of 11 fungi (Candida albicans, C tropicalis, C glabrata, Saccharomyces cerevisiae, Rhodotorula rubra, Cryptococcus neoformans, Fusarium oxysporum, Aspergillus niger, A fumigatus, A flavus, Acremonium falciforme) were inoculated in a commercial organ culture medium containing a coloured pH indicator (CorneaMax, Eurobio, Les Ulis, France). The real live fungal inoculum was verified immediately after inoculation. After 48 hours at 31 degrees C, samples of the contaminated media were inoculated in three blood bottles: Bactec Aerobic/F, Bactec Mycosis IC/F, and Bactec Myco/F Lytic (Becton Dickinson, Le Pont de Claix, France), then placed in a Bactec 9240 rocking automat, and in four Sabouraud media (solid and liquid, 28 degrees C and 37 degrees C) with daily observation. Contaminated organ culture media were also checked daily for any change in turbidity and/or colour. Experiments were performed in triplicate.

RESULTS

Mycosis IC/F and Myco/F Lytic bottles were neither faster nor more sensitive than the aerobic bottle. The three methods were positive for all inocula, even the lowest (viable inoculum below 10 CFU/ml for each fungus). Contamination was detected within 24 hours by the aerobic bottles in 91% (40/44), by Sabouraud in 98% (43/44) (no significant difference) and by visual inspection in 66% of cases (29/44) (p<0.001 with the two others). Maximum times to detection were 46, 48 and 72 hours respectively.

CONCLUSION

This study further counters the preconception that fungal contamination is hard to detect in corneal organ culture media. This study is the last step in validating the use of a pair of blood bottles for the sterility testing of organ culture media, this time for fungi. Their use should make it possible to shorten microbiological quarantine and thus deliver corneas with higher endothelial cell density, without increasing the risk of recipient contamination.

Trimethoprim-sulphamethoxazole therapy in Nocardia keratitis

PURPOSE

To describe the clinical features, microbiological features and treatment outcome of nine patients with Nocardia keratitis treated with topical trimethoprim- sulphamethoxazole drops.

METHODS

Retrospective review of nine patients with culture-proven Nocardia keratitis.

RESULTS

Nine patients with Nocardia keratitis were treated with topical trimethoprim-sulphamethoxazole drops. The average duration of treatment was 25 +/- 9 days. Five of the nine patients presented with superficial ulcers with margins studded with yellowish white discrete pinhead sized infiltration; the other four patients had deep stromal infiltration. Complete healing of the ulcer was achieved in six out of the nine patients with topical trimethoprim- sulphamethoxazole alone or in combination with ciprofloxacin 0.3% eye drops.

CONCLUSION

Topical application of trimethoprim-sulphamethoxazole appears to be effective therapy for superficial keratitis due to Nocardia.

Current perspectives on ophthalmic mycoses

Fungi may infect the cornea, orbit and other ocular structures. Species of Fusarium, Aspergillus, Candida, dematiaceous fungi, and Scedosporium predominate. Diagnosis is aided by recognition of typical clinical features and by direct microscopic detection of fungi in scrapes, biopsy specimens, and other samples. Culture confirms the diagnosis. Histopathological, immunohistochemical, or DNA-based tests may also be needed. Pathogenesis involves agent (invasiveness, toxigenicity) and host factors. Specific antifungal therapy is instituted as soon as the diagnosis is made. Amphotericin B by various routes is the mainstay of treatment for life-threatening and severe ophthalmic mycoses. Topical natamycin is usually the first choice for filamentous fungal keratitis, and topical amphotericin B is the first choice for yeast keratitis. Increasingly, the triazoles itraconazole and fluconazole are being evaluated as therapeutic options in ophthalmic mycoses. Medical therapy alone does not usually suffice for invasive fungal orbital infections, scleritis, and keratitis due to Fusarium spp., Lasiodiplodia theobromae, and Pythium insidiosum. Surgical debridement is essential in orbital infections, while various surgical procedures may be required for other infections not responding to medical therapy. Corticosteroids are contraindicated in most ophthalmic mycoses; therefore, other methods are being sought to control inflammatory tissue damage. Fungal infections following ophthalmic surgical procedures, in patients with AIDS, and due to use of various ocular biomaterials are unique subsets of ophthalmic mycoses. Future research needs to focus on the development of rapid, species-specific diagnostic aids, broad-spectrum fungicidal compounds that are active by various routes, and therapeutic modalities which curtail the harmful effects of fungus- and host tissue-derived factors.