Detection of natural infection with Mycobacterium intracellulare in healthy wild-caught Chacma baboons (Papio ursinus) by ESAT-6 and CFP-10 IFN-gamma ELISPOT tests following a tuberculosis outbreak.
BACKGROUND
Both tuberculous and non-tuberculous mycobacteria can cause infection in nonhuman primates (NHP), indicating the existence of potential zoonotic transmission between these animals and visitors to zoos or animal handlers in primate facilities. Screening of mycobacterial infections in NHP is traditionally done by tuberculin skin test (TST), which is unable to distinguish between pathogenic and non-pathogenic mycobacterial infections. In this study, we investigated the use of ESAT-6 and CFP-10 for detection of mycobacterial infections in a wild-caught baboon colony after one baboon died of tuberculosis (TB).


METHODS
Peripheral blood lymphocytes for interferon-gamma enzyme-linked immunospot assay (IFN-gamma ELISPOT) assay were obtained from TST positive baboons and those in contact with tuberculous baboons before being euthanased, autopsied and lung tissues taken for histology and mycobacterial culture.


RESULTS
Both ESAT-6 and CFP-10 IFN-gamma ELISPOT assays were able to detect early M. tuberculosis but also M. intracellulare infection. Although this indicates potential cross-reactivity with M. intracellulare antigens, the method was able to distinguish M. bovis BCG vaccination from M. tuberculosis infection. This assay performed better than the TST, which failed to detect one M. tuberculosis and two early M. intracellulare infections.


CONCLUSIONS
These results suggest that the IFN-gamma ELISPOT assay could improve the detection of M tuberculosis infections when screening NHP. There is some doubt, however, concerning specificity, as the assay scored positive three animals infected with M. intracellulare.
Chege
Gerald K
GK
Department of Clinical Laboratory Sciences, Faculty of Health Sciences, University of Cape Town, Anzio Road, Observatory 7925, Cape Town, South Africa. Gerald.Chege@uct.ac.za
Warren
Robin M
RM
Gey van Pittius
Nico C
NC
Burgers
Wendy A
WA
Wilkinson
Robert J
RJ
Shephard
Enid G
EG
Williamson
Anna-Lise
AL
D000818:Animals; D000942:Antigens, Bacterial; D001426:Bacterial Proteins; D002353:Carrier State / Q000175:diagnosis; D003429:Cross Reactions; D003937:Diagnosis, Differential; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods*; D007371:Interferon-gamma; D007963:Leukocytes, Mononuclear; D015269:Mycobacterium avium Complex; D015270:Mycobacterium avium-intracellulare Infection / Q000175:diagnosis* / Q000453:epidemiology; D009169:Mycobacterium tuberculosis; D048549:Papio ursinus; D013019:South Africa / Q000453:epidemiology; D014376:Tuberculosis / Q000175:diagnosis / Q000453:epidemiology
D000942:Antigens, Bacterial; D001426:Bacterial Proteins; C117940:CFP-10 protein, Mycobacterium tuberculosis; C093276:ESAT-6 protein, Mycobacterium tuberculosis; D007371:Interferon-gamma