The Bacillus subtilis Rescue¶
In 1835, the German naturalist Christian Gottfried Ehrenberg first described a slender, agile filamentous bacterium he named Vibrio subtilis. Decades later, in 1872, the botanist and microbiologist Ferdinand Julius Cohn reclassified it as Bacillus subtilis — the “subtle rod” — the name it still bears today. No one could have imagined that seventy years later, this humble soil microorganism would become the unlikely protagonist of one of the most curious episodes in wartime medicine.
The setting was Libya, 1941. General Erwin Rommel’s Afrika Korps was advancing with tactical precision across North Africa, but inside the camps a far deadlier enemy carried no weapons: Shigella, the bacterium responsible for bacillary dysentery. Hundreds of soldiers were falling ill each week, weakened by severe diarrhea, fever, and dehydration. Antibiotics were not yet widely available — penicillin was only beginning to be produced experimentally — and the sulfonamides on hand were used primarily for topical applications. The German army’s medical corps found itself, as contemporary accounts put it, “without pharmaceutical ammunition.”
According to the most widely cited version of the story — reconstructed from an article by Dr. Jörg Bernhardt of the Ernst Moritz Arndt University of Greifswald — physicians in the Afrika Korps noticed something puzzling: local Bedouins also contracted dysentery, yet they recovered with a consistency the German troops could not match.
Closer observation revealed the reason. At the first sign of symptoms, the Bedouins would closely follow a camel or horse until it defecated — and then ingest the dung while it was still warm. The only empirical rule passed down through generations was simple: the remedy did not work once the dung had cooled.
Medical officers and bacteriologists dispatched to investigate analyzed fresh animal feces and found it rich in Bacillus subtilis — a spore-forming bacterium resistant to heat and known for its ability to inhibit pathogenic microorganisms, including species of Shigella. Based on this finding, the German army began producing concentrated cultures of B. subtilis for its troops. Dysentery ceased to be the silent threat it once was.
But the story does not end there — it carries an uncomfortable scientific epilogue.
In 2022, a team of researchers published a rigorous analysis in PLOS ONE examining the historical account. After an extensive literature review, they found that every reference to the camel dung episode ultimately traced back to a single source — Bernhardt’s article — with no independent corroborating evidence.
More strikingly, when researchers analyzed fecal samples from Egyptian dromedaries using 16S sequencing and ethanol-resistant culture techniques, they detected B. subtilis spores in quantities comparable to those found in human feces and soil — several orders of magnitude below the documented minimum therapeutic dose (10⁹ spores per day). The conclusion was direct: the amount of B. subtilis present in camel dung is, in all likelihood, insufficient to explain a clinical improvement through that route.
What is historically well established is that, beginning in 1946, B. subtilis cultures were commercialized in Europe and the Americas under brand names such as Bacti-Subtil. They were used as immunostimulants in the treatment of gastrointestinal and urinary tract infections. Today, their mechanism of action is linked, among other effects, to the production of subtilosin — a broad-spectrum antibiotic — and to stimulation of humoral immunity through the secretion of IgM, IgG, and IgA.
The rise of synthetic antibiotics in the 1950s pushed these preparations to the margins of pharmacology. Yet interest in B. subtilis as a probiotic has never disappeared. In 2023, the German Association for General and Applied Microbiology named it “Microbe of the Year.”
Whether the camel dung story is true or apocryphal, it illustrates something microbiologists understand well: traditional empirical knowledge can point in the right direction long before formal science finds the language to explain it. That the explanation later proves more complex than expected is not a failure — it is simply how science works.