Jul 12, 2007

Romans, dried figs and Streptomyces

In the year 79 AD, the Roman towns of Herculaneum and Pompeii were devastated by a terrible eruption of Mount Vesuvius. As a result, the towns were buried under many meters of volcanic ash, which left buildings, food remains and human bodies in a remarkable state of preservation. This allows to study the state of health of ancient Romans and its relationship to nutrition and other environmental conditions. For instance, analysis of human remains from Herculaneum showed lesions typically produced by tuberculosis and, especially, brucellosis. The high frequency of brucellosis has been related to the eating of contaminated cheese: Herculaneum had an important production of goat's milk and cheese. Remarkably, the study of carbonized cheese showed particles of the right size and shape, suggesting that they were bacteria of the Brucella group.

However, the Herculaneum inhabitants appeared to suffer few non-specific infections, which were common in antiquity due to poor sanitary conditions. A recent study suggests that people were protected against these infections due to consumption of dried fruits contaminated by antibiotic-producing Streptomyces!

The author of the work arrived to this conclusion through two kinds of experimental evidences:

First, examination of food remains under the microscope (both light and scanning electron) revealed the presence of virus and possible Salmonella on eggshells, and Saccharomyces in wine and bread. More important for us was the observation, under the skin of pomegranate seeds and figs, of a dense net of branching filaments resembling those of Streptomyces. These fruits were originally dried as a mode of preservation: Romans buried them in straw under a weight to achieve dehydration. This technique may explain the proliferation of Streptomyces. And we all know that Streptomycetes are prolific producers of antibiotics, right?

Second, histological study of bone samples from human remains (using a confocal microscope) showed presence of auto-fluorescence with characteristics typical of tetracycline-labeled bone occurring during life. Tetracycline antibiotics mark human bone, as it has been established for both modern and ancient humans. An example of tetracycline-labeled human bones was previously described from a cemetery in Sudanese Nubia dated 350-550 AD; in this case, a possible source of tetracycline was the grain stored in mud containers, which provided a proper environment for proliferation of Streptomyces.

I found that the paper and the whole story (mixing archeology and microbiology together) are fascinating. Of course, I'd certainly appreciate more experimental evidence concerning unequivocal identification of tetracycline in bones (could the fluorescence be due to any other molecule with similar properties but different to tetracycline?). And I wonder how common is tetracycline production among Streptomycetes. It would be very nice if the hypothesized conditions could be replicated, i.e. grow some figs and pomegranates (Roman style = "organically" produced?), and dry them using the Roman technique (ideally in the Herculaneum region). Then, try to detect tetracycline in the fruits. You can even isolate some Streptomycetes from the dried fruits, and screen the isolates for tetracycline production...

Capasso, L. (2007). Infectious diseases and eating habits at Herculaneum (1st century AD, southern Italy). International Journal of Osteoarchaeology, 17(4), 350-357. DOI: 10.1002/oa.906

[Sadly, the author uses the word "mould" for Streptomyces, which is a bacterium, not a fungus. This mistake can still be found in medical and other technical literature]

(Image: Mosaic on a wall in the House of Neptune and Amphitrite, in Herculaneum, Italy. Source: Wikipedia)

UPDATE (September 3, 2010):
A scientific article has been published confirming the presence of tetracycline in the Nubian bones! The reference is:
Mass spectroscopic characterization of tetracycline in the skeletal remains of an ancient population from Sudanese Nubia 350–550 CE
Am. J. Phys. Anthropol. (2010) 143, 151-154.
DOI: 10.1002/ajpa.21340
(Found via Biounalm: Los antibióticos se usaban desde hace 2000 años?)

UPDATE (September 10, 2010):
See other blogs (in Spanish): Los nubios ya usaban antibióticos hace 2.000 años (Amazings.es), Una pinta de tetraciclina (Curiosidades de la Microbiología).

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