wildlife and zoo assay data sheet

Mycobacterium xenopi in amphibians

Test code: B0070 - Ultrasensitive detection of Mycobacterium xenopi by real time PCR.

B0070 is included in P0030 - PCR panel for mycobacteriosis in amphibians

Mycobacteriosis in amphibians, especially frogs, is caused by acid-fast bacilli of the genus Mycobacterium. Many mycobacterial species found in the environment can cause infection in amphibians, including M. marinum, M. chelonae, M. ulcerans, M. liflandii and M. xenopi (Mve-Obiang et al., 2005, Trott et al., 2004). All these mycobacerial species are ubiquitous in nature and can be found in water. They are resistant to normal water treatment.

Mycobacteriosis is a serious threat to the health of a frog colony, although tuberculosis usually only results in frogs which are already ill, are stressed or have weakened immune systems. Infected frogs will usually develop cutaneous and visceral milliary granulomas (white millet-like bumps) and ulcerative lesions on the skin. Any of these mycobacteria can also gain entry to a frog’s body through the skin wounds and lesions. Once through the skin, these mycobacteria can also affect internal organs.

Mycobacterium xenopi is a slow-growing, waterborne, scotochromogenic species of Mycobacterium. It was first isolated from skin lesions of the frog, Xenopus laevis (Schwabacher, et al., 1959). The organism is very resistant to most disinfectants used to clean water systems and has been isolated in samples collected from water systems in homes and hospitals.

Diagnosis of infections caused by mycobacteria, especially nontuberculous mycobacteria, remains a difficult task both in microbiology and pathology. Culture identification followed by biochemical analysis is often slow and may not differentiate pathogenic from nonpathogenic mycobacteria species due to their close similarity. False positives occur in this way in both staining and culture, particularly in environmental specimens.  Molecular detection by PCR, on the other hand, is a rapid, sensitive and specific technique for sensitive mycobacterial detection and differentiation.

Utilities:

• Confirm the disease causing agent
• Shorten the time required to confirm a clinical diagnosis
• Ensure that animal facilities or amphibian populations are free of this mycobacterium
• Early prevention of spread of this mycobacterium in a facility or geographic area
• Minimize human exposure to this mycobacterium
• Safety monitoring of biological products that derive from susceptible animals

References:
Schwabacher H. (1959) A strain of Mycobacterium isolated from skin lesions of a cold blooded animal, Xenopus laevus, and its relation to atypical acid-fast bacilli occurring in man. J. Hygiene, 57:57-67
Mve-Obiang, A., Lee, R.E., Umstot, E.S., Trott, K.A., Grammer, T.C.,  Parker, J.M.,  Ranger, B., Grainger, R., Mahrous, E.A. and Small, P.L.C. (2005) A newly discovered mycobacterial pathogen isolated from lethal infections in laboratory colonies of Xenopus species produces a novel form of the M. ulcerans macrolide toxin, mycolactone. Infect. and Immun. 73: 3307-3312.
Trott, K.A., Stacy, B.A., Lifland, B.D., Diggs, H.E., Harland, R.M., Khokha, M.K., Grammer, T.C. and Parker, J.M. (2004) Characterization of a Mycobacterium ulcerans-like infection in a colony of African Tropical Clawed Frogs (Xenopus tropicalis) Comp. Med. 54: 309-317.
Green, S. L., Lifland, B. D., Bouley, D. M., Brown, B. A., Wallace, R. J., Jr. and Ferrell, J. E., Jr. (2000) Disease attributed to Mycobacterium chelonae in South African clawed frogs (Xenopus laevis). Comp. Med. 50: 675-679.
Wünschmann, A., Armien, A., Beth Harris, N., Brown-Elliott, B.A., Wallace R.J., Jr., Rasmussen, J., Willette, M. and Wolf, T. (2008) Disseminated Panniculitis in a Bottlenose Dolphin (Tursiops truncatus) due to Mycobacterium chelonae Infection. J. Zoo Wildlife Med. 39: 412-420.

Specimen requirements: Cloacal and skin swab, or lesion swab, or skin scraping.

For specimen types other than those listed here, please call to confirm specimen acceptability and shipping instructions.

For all specimen types, if there will be a delay in shipping, or during very warm weather, refrigerate specimens until shipped and ship with a cold pack unless more stringent shipping requirements are specified. Frozen specimens should be shipped so as to remain frozen in transit. See shipping instructions for more information.

Turnaround time: 2 business days

Methodology: Qualitative real time PCR panel

Normal range: Nondetected