The Case of the Dubious Dye

Most of the patients already had difficult-to-diagnose intestinal trouble, which was one reason why they were in Boston's famed Massachusetts General Hospital in the first place. Many of them were children. But unaccountably, when doctors gave them tests, some of the patients developed worse diarrhea.

Not until Mass General Bacteriologist Lawrence J. Kunz examined some of the children's stool specimens did he discover the alarming and unexpected reason: the relatively uncommon bacterium Salmonella cubana.

Detection of any kind of highly infectious Salmonella* anywhere in the U.S.--particularly in a hospital--is enough to set disease detectives working overtime. Salmonellosis is a particularly severe diarrhea, often accompanied by vomiting, acute cramps and fever; and it can be fatal to feeble youngsters and oldsters. In the Boston case, it fell to Pediatrician David J. Lang to find out whatdunit. From case records, Dr. Lang concluded that while some of the children had been infected with S. cubana when they entered the hospital, others had picked up the infection there. That made the job tougher. Dr. Lang found that the hospital-acquired cases had been bedded in four different buildings. No help there. He cross-examined the doctors and nurses of 20 of the children, checked out what they had eaten. Still no clues.

Proof in a Capsule. But the 21st case was an infant, "so young," as Dr. Lang puts it, "that we could look at practically everything that had gone into that baby." One of the things, it turned out, was a capsule of carmine red. A substance that goes through the intestines at the same speed as food, the brilliant red dye can tell a physician how long nourishment is staying in a disturbed digestive tract. Where had the dye come from? A small New York City manufacturer. What was in it? Boiled and ground masses of female cochineal bugs, Dactylopius coccus, whose fat contains the dye. And where had they come from? The Canary Islands and Peru. In both places the insects appeared to be infected with cubana.

Sure enough, Dr. Kunz was able to grow S. cubana from the dye capsules. Mass General notified state and federal health authorities and substituted a black carbon marker for carmine red as an intestinal tracer. Cases of cubana salmonellosis in three other states were traced to carmine red, and supplies were called in. So far, so good. But authorities have been checking other places for carmine red, knowing that it is a favorite coloring in candy, chewing gum, ice cream, cough syrups and drugs. Manufacturers like to use it because of a legal quirk: being a natural rather than a synthetic product, it does not have to be mentioned on labels.

* Named for Bacteriologist Daniel Salmon (1850-1914).

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