Phenotypic and Molecular Typing of Tuberculous and Nontuberculous Mycobacterium Species from Slaughtered Pigs in Egypt

Abstract

A total of 745 slaughtered pigs were examined during routine meat inspection for suspected tuberculous lesions. Specimens from suspected lesions were collected for conventional mycobacteriologic examinations. Suspected mycobacterial colonies were subjected to molecular typing based on the Mycobacterium species-specific intergenic spacer (IGS) target. The study resulted in detection of suspected lesions in 110 (14.8%) carcasses, from which only 67 specimens produced suspected mycobacterial colonies. Conventional examination was only able to identify 56 isolates as Mycobacterium species, which was confirmed by polymerase chain reaction amplification of the IGS target. Interestingly, out of these, 18 and 12 isolates were Mycobacterium tuberculosis and Mycobacterium bovis, respectively. Sequence analysis of IGS resolved the identities of 10 of the 11 conventionally unidentified isolates as being 4 different nontuberculous Mycobacterium species. The last isolate was proposed as a non -Mycobacterium species and was confirmed by its identification as Rhodococcus equi based on the 16S ribosomal DNA sequence analysis. The study described the isolation of Mycobacterium tuberculosis from pigs and revealed high burden of infection with both tuberculous and nontuberculous mycobacterial species among pigs in Egypt. In addition, the study showed the usefulness of IGS sequence analysis as a reliable molecular tool that would be useful for further epidemiologic and public health studies.