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| Year : 2021 | Volume
: 64
| Issue : 1 | Page : 210-211 |
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| Nocardia puris: A rare cause of keratitis |
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S Meera, B Aishwarya, S Sreelatha, K Prithi Nair
Department of Microbiology, GMC, Thrissur, Kerala, India
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| Date of Submission | 02-Oct-2019 |
| Date of Decision | 12-Jan-2020 |
| Date of Acceptance | 02-Feb-2020 |
| Date of Web Publication | 8-Jan-2021 |
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How to cite this article:
Meera S, Aishwarya B, Sreelatha S, Nair K P. Nocardia puris: A rare cause of keratitis. Indian J Pathol Microbiol 2021;64:210-1 |
Dear Editor,
Nocardia species are filamentous, Gram-positive, partially acid–fast bacteria, commonly found as soil saprophytes. They are frequently associated with pulmonary infections, mycetoma, and disseminated nocardiosis.
While ocular nocardiosis is less common, it has mostly been associated with infectious keratitis, with the reported incidence varying from 0.3% to 4.2%.[1],[2],[3] The most common species causing Nocardia keratitis has been found to be N. asteroides followed by Nippostrongylus brasiliensis and Nocardia otitidiscaviarum.[4] Predisposing factors are trauma to the eye, ocular surgery like cataract surgery, long-term corticosteroid use, and use of contact lens.[5] As Nocardia infections do not respond to the commonly used medications for bacterial keratitis like fluroquinolones, timely identification of the organism is essential.
We present a case of a 70-year-old man presented to the ophthalmology OPD with complaints of pain, redness, and watering from the left eye of 4 days duration [Figure 1]a. He was on topical medication for glaucoma of the same eye for the past 5 years and was on antihypertensives for systemic hypertension over the past one year. He had no history of surgery to the eye, wearing of contact lens but mentioned about trauma to the eye with fingers of grandchild one month back. He had no history of any other chronic illnesses or long-term corticosteroid therapy. The patient was started on oral Ciprofloxacin, topical Amikacin, Vancomycin, and Natamycin along with oral Fluconazole. Corneal scraping was sent for microscopy and culture before initiating the treatment. Gram stain showed 2-3 pus cells/OIF; KOH mount did not contain any fungal filament. Bacterial culture on blood agar after 48 h grew dry, chalky white colonies [Figure 1]c. Similar colonies grew on Lowenstein–Jensen medium and Sabouraud's Dextrose agar (without antibiotics) [Figure 1]b and [Figure 2]. No growth was obtained on MacConkey agar and Sabouraud's Dextrose agar (with antibiotics). Gram stain from the growth on blood agar showed beaded Gram-positive, thin, branching, filamentous organisms. 1% Kinyon's stain showed partially acid-fast organisms [Figure 1]d. The organism was catalase positive, oxidase negative, urease positive, and reduced nitrate. It was phenotypically identified as Nocardia species. Antibiotic susceptibility testing was done by Kirby Baeur's disc diffusion method as per CLSI guidelines.[6] It was sensitive to Ciprofloxacin, Cotrimoxazole, Amikacin, Amoxicillin-clavulanic acid, and Imipenem [Figure 1]e. After the report was informed the ophthalmology department, the antifungals were stopped and Cotrimoxazole was started. The isolate was sent for further identification to PGI, Chandigarh. It was identified as Nocardia puris by 16s ribosomal RNA gene sequencing. Patient showed improvement in symptoms but was discharged against medical advice in 3 days and was lost for follow-up. | Figure 1: (a) Left eye with corneal ulcer, (b) Culture of Nocardia on blood agar, (c) Culture of Nocardia on Lowenstein–Jensen media, (d) Nocardia on 1% Ziehl–Neelsen staining (Resolution 400×), (e) Antibiotic susceptibility testing of Nocardia on blood agar
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The genus Nocardia and the genus Actinomyces are members of the family Actinomycetaceae. Both genera grow as fragile branching filaments which easily fragments into bacillary rod and twig-like elements. While Nocardiae are aerobic and weakly acid-fast, actinomyces are anaerobic and non-acid-fast. Nocardia is also often confused with rapidly growing Mycobacteria. The genus Mycobacterium and the genus Nocardia have been found to be similar with respect to their antigenic structure, cell-wall composition, and bacteriophage susceptibility. But Nocardia is weakly acid-fast, forms fragmenting mycelia, and has true branching.[7],[8],[9]
Nocardia infections are less frequently seen affecting the eye although they are present all over the world.[7],[8],[9] Ocular pathology of nocardiosis includes uveitis, exudative choroiditis, retinal abscess, retinal detachment, keratitis, and iritis.[4],[10] Corneal infections are the most common.
Accurate identification of Nocardia to the species level has become very important because differences among species have been observed in terms of epidemiology, virulence, and antibiotic susceptibility.[6] Molecular methods such as polymerase chain reaction, restriction fragment length polymorphism, and 16S ribosomal RNA sequencing can speciate all medically relevant Nocardia isolates, but, not all laboratories in our country have the capability to performing these tests on a routine basis. Biochemical identification as described by Kiska et al. can be used to identify medically important Nocardia species in routine laboratories.[11]
Amikacin is emerging as the best drug for the treatment of Nocardia keratitis with the lowest MIC for Nocardia isolates from corneal ulcers. Traditionally used sulfa group drugs are now being replaced with aminoglycosides and biguanides.[12],[13] Alternatives include imipenem, meropenem, and third-generation cephalosporins. Combination therapy is recommended for serious infections. Minocycline, amoxicillin/clavulanate, and linezolid are oral alternatives. Three to 10 days are required to observe clinical response.[14]
Acknowledgements
We are thankful to the staff in the Department of Ophthalmology and Department of Microbiology for their valuable inputs.
Financial support and sponsorship
Nil.
Conflicts of interest
There are no conflicts of interest.
 References | |  |
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| 6. | Clinical Laboratory Standards Institute. M-24A:23. Susceptibility testing of Mycobacteria, Nocardiae and other aerobic Actiniomycetes. Approved standards. Second edition, 2011. |
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| 10. | King LP, Furlong WB, Gilbert WS, Levy C. Nocardia asteroides infection following scleral buckling. Ophthalmic Surg 1991;22:150-2. |
| 11. | Brown-Elliott BA, Brown JM, Conville PS, Wallace RJ Jr. Clinical and laboratory features of Nocardia spp. based on current molecular taxonomy. Clin Microbiol Rev 2006;19:259-82. |
| 12. | Kiska DL, Hicks K, Pettit DJ. Identification of medically relevant Nocardia species with an abbreviated battery of tests. J Clin Microbiol 2002;40:1346-51. |
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| 14. | Karumanchi D, Oommen S, Sivan Pillai PM, Angel J. Nocardiosis in central Kerala: A case series. Int J Med Public Health 2015;5:384-6. [Full text] |
Correspondence Address:
B Aishwarya
Chinmaya, NH By Pass Road, Nadathara P.O, Thrissur, Kerala - 680 751
India
 Source of Support: None, Conflict of Interest: None  | Check |
DOI: 10.4103/IJPM.IJPM_760_19
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