Sample collection
A total of 460 samples were randomly been recovered from pneumonic
(n =210) and apparently healthy (n =250) lungs of imported
one humped camels during February to April 2018. The animals were
submitted for routine slaughter. For the purpose of this study‘
pneumonic lungs’ was referred to those lungs that had gross lesions such
as consolidation, fibrin deposition on the pleura, pleurisy, and/or
adhesion; while ‘apparently healthy lungs’ was used to describe those
without any gross lesions. Specimens were obtained aseptically while
taking precautions to prevent surface contamination. Following
collection, the samples were transported to the microbiology laboratory
in special ice-filled containers within 2 h of sampling. Primary
isolation of mycoplasmas from lung samples was performed in liquid
medium using pleuropneumonia-like organism broth and agar media (PPLO;
Difco, Fisher Scientific, Waltham, MA, USA). Purified isolates were
maintained on PPLO agar media. Preliminary identification of the
isolates was performed based on colony morphology as examined under
stereo-microscope (Leitz, Germany), to scan the surface of the medium to
visualize the colonies. Digitonin sensitivity test was carried out to
differentiate between Mycoplasma and Acholeplasma genera
using filter paper discs impregnated with 0.2 mL of 1.5% (W/V) ethanol
solution of digitonin and dried overnight. Mycoplasma spp. show
digitonin sensitivity while Acholeplasma spp. are resistant
(Freundt et al., 1973). Biochemical identification was used for further
testing of Mycoplasma spp. Glucose fermentation, arginine
deamination and urea hydrolysis tests were performed as described
previously (Erno and Stipkovits, 1973; Howard et al., 1994). Serological
confirmation of Mycoplasma spp. was additionally conducted as
described by Clyde (1964), while the species-specific identification was
performed with anti-M. bovis hyperimmune serum
(Lauerman
et al., 1994) by the growth inhibition test utilizing dried antiserum
impregnated paper discs. Standard antisera were used as control,M. bovis PG45, M. bovirhinis PG43 and M. argininiG230. Final identification of the isolates was achieved by PCR.