Detection of mycobacterial DNA in Andean mummies

Abstract

The identification of genetic material from pathogenic organisms in ancient tissues provides a powerful tool for the study of certain infectious diseases in historic populations. We have obtained tissue samples from the genital areas of 12 mummies in the American Museum of Natural History collection in New York, N.Y. The mummies were excavated in the Andes Mountain region of South America, and radiocarbon dating estimates that the mummies date from A.D. 140 to 1200. DNAs were successfully extracted from all tissues and were suitable for PCR analysis. PCRs were carried out to detect Mycobacterium tuberculosis complex and mycobacteria other than M. tuberculosis (MOTB). M. tuberculosis complex was detected in 2 out of 12 samples, and MOTB were detected in 7 samples. This study confirmed the adequate preservation of genetic material in mummified tissues and the existence of mycobacteria, including M. tuberculosis, in historic populations in South America.

FIG. 1.

Detection of GAPDH and mycobacterial DNA in mummified tissues. DNAs were extracted from the genital tissues of 12 mummies. The PCR products were examined on a 10% polyacrylamide gel. GAPDH DNA was detected in all mummified tissues, indicating that the DNA was adequate for PCR analysis. DNAs of M. tuberculosis complex were detected in 2 of the 12 samples, and MOTB DNAs were detected in 7 of the 12 samples. Lane M, DNA size markers (PBR322 DNA digested with MspI); lanes 1 to 12, mummy samples; lane P, positive control; lane N, negative control.

FIG. 2.

Confirmation of M. tuberculosis complex by SalI digestion. PCR products from two positive samples and one positive control were further digested with SalI and separated on a 10% polyacrylamide gel. We observed two bands (55 and 42 bp), which are identical to those of the positive control (M. tuberculosis). These results confirmed the presence of M. tuberculosis complex in these two samples. Lane M, DNA size markers (PBR322 DNA digested with MspI); lanes 9 and 11, mummy samples 9 and 11, respectively; lane P, positive control (M. tuberculosis).

FIG. 3.

Identification of MOTB by BstEII and HaeIII. PCR products from seven positive samples were further digested with BstEII and HaeIII and separated on a 2.5% agarose gel. A 441-bp band was seen in all seven samples after digestion with BstEII. However, sample 1 gave rise to two bands of 245 and 220 bp. After digestion with HaeIII, a 140-bp band was seen in all samples; however, two bands of 175 and l15 bp were observed in sample 1. The results suggest that M. flavescens I was present in all samples and that there was an additional species present in sample 1. Lane P, positive control (M. leprae); lanes M, DNA size markers; lanes 1, 2, 3, 5, 6, 9, and 11, mummy samples 1, 2, 3, 5, 6, 9, and 11, respectively.