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Year : 2013  |  Volume : 56  |  Issue : 4  |  Page : 485-486
Utility of Cysteine lactose electrolyte-deficient agar for rapid isolation of Nocardia species

Department of Microbiology, BLK Superspeciality Hospital, Pusa Road, New Delhi, India

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Date of Web Publication18-Jan-2014

How to cite this article:
Jain S, Sharma N, Chugh TD. Utility of Cysteine lactose electrolyte-deficient agar for rapid isolation of Nocardia species. Indian J Pathol Microbiol 2013;56:485-6

How to cite this URL:
Jain S, Sharma N, Chugh TD. Utility of Cysteine lactose electrolyte-deficient agar for rapid isolation of Nocardia species. Indian J Pathol Microbiol [serial online] 2013 [cited 2022 Jun 28];56:485-6. Available from: https://www.ijpmonline.org/text.asp?2013/56/4/485/125420


Nocardial infections, earlier considered uncommon, are now being increasingly observed, especially with a rise in the immunocompromised population over the past few decades. The incidence of nocardiosis was reported to be eight cases per year in a 15-year study from Pakistan [1] and 12 cases over 26 months in a report from North India. [2] A much higher annual incidence of 150-200 cases is described in France. [3] Nevertheless, the diagnosis of nocardiosis is challenging as clinical presentation and radiological findings are non-specific owing to its close resemblance with chronic suppurative bacterial or fungal infections, tuberculosis or malignancies. These infections are therefore often misdiagnosed and the true incidence is unknown. The treatment duration is prolonged, with a high recurrence rate if inadequately treated. [4] Extrapulmonary dissemination often culminates in a fatal course, with a mortality rate of >85%. [4] Timely diagnosis and specific treatment of nocardial infections is of paramount importance in reducing morbidity and mortality.

Direct smear examination and culture of appropriate specimens remains the primary method of diagnosis. Nocardia spp. are non-fastidious but slow-growing organisms, requiring prolonged incubation of inoculated culture media beyond 48 h. [5] The growth normally appears within 3-7 days, but may take up to 1 month. Unfortunately, routine bacterial cultures are discarded in the microbiology laboratory after 24-48 h of incubation unless alerted by the clinician of a possibility of nocardiosis. In pulmonary or purulent samples, the situation is further complicated by the heavily contaminated culture, wherein overgrowing gram negative or other organisms may obscure the tiny and scanty Nocardia colonies if present. It is difficult to isolate Nocardia from such heavily contaminated specimens showing polymicrobial growth, and addition of selective media such as colistin-nalidixic acid agar, modified Thayer-Martin agar and buffered charcoal-yeast extract agars may be required for optimal recovery of Nocardia. [4] Moreover, a direct gram-stained smear of a clinical specimen is not routinely examined in many laboratories, which, if performed, can provide an early clue to the diagnosis. Microscopic visualization of typical beaded gram-positive, thin, lateral branching, filamentous bacilli surrounded by many polymorphonuclear leukocytes on a direct gram-stained smear of clinical specimens provides the initial and one of the most important indications of nocardiosis.

We have earlier isolated five Nocardia species from seven hospitalized patients over a period of 1 year from various clinical samples, mostly respiratory specimens (under review). The isolates included N. otitidiscavarium (2), N. farcinica (2) and N. brasiliensis (1). The first suspicion of nocardiosis in all the cases emerged on the primary gram-stained smear findings, which were consistent with Nocardia. Based on these findings, cultures were subjected to incubation beyond a conventional protocol of 48 h. Growth in all culture media was obtained between 3 and 8 days.

Recently, we observed pure and moderate growth of chalky white, dry, 0.5-1.0-mm-sized colonies on cysteine lactose electrolyte-deficient (CLED) agar after overnight incubation from the urine culture of a diabetic patient [Figure 1]a . The growth was confirmed as Nocardia spp. by the characteristic morphology on Grams and modified acid fast staining of the colonies, and further by standard biochemical reactions. [4] Based on this observation of rapid isolation of nocardia on CLED agar, we then subcultured one of our previous nocardial isolates, N. otitidiscavarium, on CLED agar, which grew with well-sized colonies after an overnight incubation [Figure 1]b. Further, to check for the recovery of Nocardia from a mixed culture, we experimentally introduced a loopful of non-lactose fermenting (NLF) growth in the urine sample of the above patient and re-inoculated it on a CLED agar plate. Typical growth of Nocardia could be easily discerned from that of the NLF organism after overnight incubation [Figure 1]c.
Figure 1: Cysteine lactose electrolyte-defi cient Agar showing the growth of Nocardia species. (a) Nocardia isolate from the urine of a patient. (b) Subculture of a previous clinical isolate, N. oti ti discavarium. (c) Mixed growth of Nocardia spp. isolated from urine and non-lactosefermenting colonies

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CLED agar appears to be an optimum media allowing rapid and luxuriant growth of Nocardia spp. Its chalky-white and dry growth is easily distinguishable from that of gram-positive cocci and yeasts on CLED agar. It can therefore be used for isolating Nocardia from mixed cultures obtained on primary plating if direct gram stain findings are suggestive of the presence of Nocardia in a specimen. It may also be included in the primary inoculation of clinical samples for which a high clinical index of suspicion for nocardiosis is indicated by the clinician. Further studies appraising this media for nocardial isolation from different clinical specimens, particularly those with polymicrobial growth, are necessitated.

   References Top

1.Bibi S, Irfan S, Zafar A, Khan E. Isolation frequency and susceptibility patterns of Nocardia species at a tertiary hospital laboratory in Karachi, Pakistan. J Infect Dev Ctries 2011;5:499-501.  Back to cited text no. 1
2.Shivaprakash MR, Rao P, Mandal J, Biswal M, Gupta S, Ray P, et al. Nocardiosis in a tertiary care hospital in North India and review of patients reported from India. Mycopathologia 2007;163:267-74.  Back to cited text no. 2
3.Boiron P, Provost F, Chevrier G, Dupont B. Review of nocardial infections in France 1987 to 1990. Eur J Clin Microbiol Infect Dis 1992;11:709-14.  Back to cited text no. 3
4.Brown JM, McNeil MM. Nocardia, Rhodococcus, Gordonia, Actinomadura, Streptomyces and other aerobic actinomycetes. In: Manual of Clinical Microbiology. 8 th ed. In: Murray PR, Baron EJ, Pfaller MA, Tenover FC, Yolken RH, editors. Washington DC: American Society for Microbiology; 2003. p. 502-31.  Back to cited text no. 4
5.Ambriosini J, Lew D, Garbino J. Nocardiosis: Updated clinical review and experience at a tertiary center. Infection 2010;38:89-97.  Back to cited text no. 5

Correspondence Address:
Sarika Jain
Department of Microbiology, BLK Superspeciality Hospital, Pusa Road, New Delhi - 110 005
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/0377-4929.125420

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