Previous Article | Next Article ![]()
Journal of Clinical Microbiology, December 2002, p. 4738-4740, Vol. 40, No. 12
0095-1137/02/$04.00+0 DOI: 10.1128/JCM.40.12.4738-4740.2002
Copyright © 2002, American Society for Microbiology. All Rights Reserved.
Department of Pathology, Mount Sinai School of Medicine, New York University,1 American Museum of Natural History, New York, New York2
Received 20 June 2002/ Returned for modification 18 July 2002/ Accepted 3 September 2002
|
|
|---|
|
|
|---|
Molecular studies performed to date on bacteria and other microorganisms in ancient human remains have mainly addressed typing and characterization of pathogen DNA. Several recent reports describe the isolation of Mycobacterium tuberculosis in ancient human skeletal remains and soft tissue remains (1, 2, 6, 8, 10-12). We used PCR analysis of genital tissue samples from 12 ancient mummies from South America in order to detect the presence of mycobacteria in this population.
Twelve dried tissue samples were obtained from mummies in the collection of the American Museum of Natural History in New York, N.Y. Archaeological findings and radiocarbon dating estimate that the mummies date to before A.D. 1220. The tissue samples, taken from histologically confirmed skin samples in the pelvic region, were in dried form. Specifically, skin samples were taken from preserved genitalia when identifiable or from adjacent skin. Positive controls of M. tuberculosis specimens were obtained from a clinical laboratory.
Mummy tissue samples were cut into small fragments (5 mm3), placed in 1.5-ml microcentrifuge tubes, homogenized in 50 to 100 µl of phosphate-buffered saline (PBS) (Sigma, St. Louis, Mo.) with a homogenizer, and further diluted with 1,000 µl of PBS. After centrifugation, the supernatants were aspirated and the pellets were washed with PBS three times. The pellets were lysed in a 5 M guanidinium thiocyanate (GTC) buffer containing 5 M GTC (Sigma), 0.5% bovine serum albumin (Sigma), 80 mM EDTA, 400 mM Tris HCl (pH 7.5), and 0.5% sodium-N-lauroylsarcosine (Sigma) at 60°C for 1 h and then at 37°C overnight (7). DNA was extracted twice with phenol-chloroform (Sigma) at a 1:1 ratio, followed by chloroform once, and then precipitated by the addition of a 1/10 volume of 3 M sodium acetate (pH 5.2) and 2.5 volumes of absolute ethanol. The pellets were washed with 70% ethanol and air dried. They were dissolved in Tris-EDTA (10 mM Tris-HCl [pH 8.0], 1 mM EDTA) buffer (Sigma) and stored at -20°C for later use.
PCR was carried out in 50 µl of a reaction mixture composed of 1.5 mM MgCl2, 200 µM (each) deoxynucleoside triphosphate, various concentrations of each primer, 2 U of AmpliTaq Gold DNA polymerase (Roche, Indianapolis, Ind.), 50 mM KCl, and 10 mM Tris-HCl (pH 8.3). The PCR was initiated by preheating the mixture at 95°C for 10 min, followed by temperature cycles (for GAPDH [glyceraldehyde-3-phosphate dehydrogenase], 94°C for 1 min, 55°C for 30 s, and 72°C for 1 min for 40 cycles; for M. tuberculosis, 94°C for 1 min, 64°C for 30 s, and 72°C for 1 min for 40 cycles; for MOTB, 94°C for 1 min, 60°C for 30 s, and 72°C for 1 min for 45 cycles), in a thermal cycler (Perkin-Elmer model 9600). These temperature cycles were followed by a final extension step at 72°C for 5 min. PCR primers were used to detect the GAPDH gene (TCACTGCCACCCAGAAGACT and TTCTAGACGGCAGGTCAGGT) (15), M. tuberculosis (Tb-A, CTCGTCCAGCGCCGCTTCGG; Tb-B, CCTGCGAGCGTAGGCGTCGG) (4, 10), and MOTB (Tb11, ACCAACGATGGTGTGTCCAT; Tb12, CTTGTCGAACCGCATACCCT) (9, 13). To increase the detection sensitivity, a second PCR was carried out for M. tuberculosis. Two microliters of the first PCR product was transferred to a tube containing the second set of PCR primers (Tb-C, GCTTCGGACCACCAGCACCT; Tb-D, GCGTCGGTGACAAAGGCCAC) and amplified with the appropriate temperature cycles (94°C for 1 min, 50°C for 30 s, and 72°C for 1 min for 40 cycles). The PCR products were examined by electrophoresis and visualized under UV light after being stained with ethidium bromide.
Restriction fragment length polymorphism analyses were used to ensure that the PCR products were specific for the M. tuberculosis complex (4, 10) and to specify MOTB. For M. tuberculosis, the second group of PCR products was digested with 10 U of SalI (GIBCO BRL, Grand Island, N.Y.) in a 20-µl reaction mixture in the presence of the appropriate buffer at 37°C for 3 h. For MOTB (9, 13), the PCR products were analyzed by digestion with 7 U of BstEII (GIBCO BRL) for 1 h at 60°C or with 10 U of HaeIII (GIBCO BRL) for 1 h at 37°C in a 20-µl reaction mixture with the appropriate buffer.
To confirm that the DNA in mummy tissues was still intact after hundreds of years and that the DNA could be detected in and extracted from the dried samples, the GAPDH gene was used as a marker DNA for PCR. Our results showed that DNAs were efficiently isolated from mummy tissues by the 5 M GTC method and that they were adequate for PCR amplification. Human genomic DNA was detected in all samples by PCR with the GAPDH gene (Fig. 1).
![]() View larger version (30K): [in a new window] |
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.
|
![]() View larger version (97K): [in a new window] |
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).
|
![]() View larger version (30K): [in a new window] |
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.
|
|
|
|---|
This article has been cited by other articles:
| |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Copyright © 2009 by the American Society for Microbiology. For an alternate route to Journals.ASM.org, visit: http://intl-journals.asm.org | More Info»