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  Table of Contents    
Year : 2021  |  Volume : 64  |  Issue : 1  |  Page : 210-211
Nocardia puris: A rare cause of keratitis

Department of Microbiology, GMC, Thrissur, Kerala, India

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Date of Submission02-Oct-2019
Date of Decision12-Jan-2020
Date of Acceptance02-Feb-2020
Date of Web Publication8-Jan-2021

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

How to cite this URL:
Meera S, Aishwarya B, Sreelatha S, Nair K P. Nocardia puris: A rare cause of keratitis. Indian J Pathol Microbiol [serial online] 2021 [cited 2022 Jan 20];64:210-1. Available from: https://www.ijpmonline.org/text.asp?2021/64/1/210/306533

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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Figure 2: Nocardia on modified Ziehl–Neelsen staining (100× high power)

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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]


We are thankful to the staff in the Department of Ophthalmology and Department of Microbiology for their valuable inputs.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.

   References Top

Upadhyay MP, Karmacharya PC, Koirala S, Tuladhar NR, Bryan LE, Smolin G, et al. Epidemiologic characteristics, predisposing factors, and etiologic diagnosis of corneal ulceration in Nepal. Am J Ophthalmol 1991;111:92-9.  Back to cited text no. 1
Garg P, Rao GN. Corneal ulcer: Diagnosis and management. Community Eye Health 1999;12:21-3.  Back to cited text no. 2
Srinivasan M, Gonzales CA, George C, Cevallos V, Mascarenhas JM, Asokan B, et al. Epidemiology and aetiological diagnosis of corneal ulceration in Madurai, South India. Br J Ophthalmol 1997;81:965-71.  Back to cited text no. 3
Sridhar MS, Gopinathan U, Garg P, Sharma S, Rao GN. Ocular nocardia infections with special emphasis on the cornea. Surv Ophthalmol 2001;45:361-78.  Back to cited text no. 4
Sridhar MS, Sharma S, Reddy MK, Mruthyunjay P, Rao GN. Clinico microbiological review of Nocardia Keratitis. Cornea 1998;17:17-22.  Back to cited text no. 5
Clinical Laboratory Standards Institute. M-24A:23. Susceptibility testing of Mycobacteria, Nocardiae and other aerobic Actiniomycetes. Approved standards. Second edition, 2011.  Back to cited text no. 6
Bach MC. The chemotherapy of infections due to Nocardia. Int J Clin Pharmacol Biopharm 1975;11:283-5.  Back to cited text no. 7
Davis BD, Dulbecco R, Eisen HN, Ginsberg H, Wood WB. Microbiology. Vol 1. Harper and Row: New York; 1969. p. 875-7.  Back to cited text no. 8
Tsukamura M. Relationship between Mycobacterium and Nocardia. Jpn J Microbiol 1975;14:187-95.  Back to cited text no. 9
King LP, Furlong WB, Gilbert WS, Levy C. Nocardia asteroides infection following scleral buckling. Ophthalmic Surg 1991;22:150-2.  Back to cited text no. 10
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.  Back to cited text no. 11
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.  Back to cited text no. 12
Boiron P, Provost F. In-vitro susceptibility testing of Nocardia spp. and its taxonomic implication. J. Antimicrob. Chemother 1988;22:623-9.  Back to cited text no. 13
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.  Back to cited text no. 14
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Correspondence Address:
B Aishwarya
Chinmaya, NH By Pass Road, Nadathara P.O, Thrissur, Kerala - 680 751
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/IJPM.IJPM_760_19

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