At four on a still-black Monday morning, 76-year-old Robert
Kilgalen came to the emergency room gripping his stomach.

His wife said
he’d been alternating between explosive diarrhea and vomiting for two
hours. He was so dizzy from loss of fluid that he could hardly stand,
and his temperature was 101.5 degrees.

The staff started him on fluids intravenously, then began to
examine him for clues. Toxic chemicals, viruses, and pathogenic
bacteria such as shigella, E. coli, and salmonella can cause
debilitating diarrhea. But sometimes chronic intestinal inflammation
can provoke it too.

The first step was to examine blood and stool cultures for
infection. The following day, Ellie, the lab technician, came up from
the microbiology lab. She held a small glass vial of stool culture up
to the light. "Look. There’s nothing, not even normal flora." The
antibiotics the patient had taken on the way to the hospital had wiped
out any telltale signs. The other lab results indicated only
dehydration and a slightly elevated white blood cell count. We hadn’t a
clue what was wrong.

But before long, a feverish 8-year-old girl arrived, sick from
vomiting and diarrhea. Then an 81-year-old woman and a 3-month-old boy
came in with the same symptoms. Was this the start of an epidemic? None
of the new patients had taken antibiotics, so I hoped one of the
cultures would be positive.

The following morning Ellie showed me the tubes. I could see that
the samples teemed with bacterial colonies. She took small samples of
the fluid and spread it out on agar plates specially prepared to
promote the growth of pathogenic bacteria and suppress normal gut flora.

The next morning I went into the lab and Ellie opened the incubator
containing the cultures. She held the agar plate under the light. There
were hundreds of shiny black colonies–salmonella. All three cultures,
she said, were positive.

AS MANY AS 4 MILLION SALMONELLA cases break out in the United
States each year, making it the country’s most common food poisoning.
More than 2,000 varieties of the bacterium live in the guts of such
animals as pigs, cows, and chickens, without causing them harm. (The
infection can also pass from a hen to her eggs.) One type–Salmonella
typhi–lives only in humans. It causes typhoid fever, which can be
deadly. While typhoid fever is not uncommon in countries with poor
sewage treatment, it is rare in the United States.

To thrive in a human, salmonellae must survive the acidic
conditions in the stomach, reach the small intestine, and attach to its
lining. If enough live salmonellae get to the intestine, diarrhea and
vomiting–the host’s effort to expel the pathogen–will follow within
six to 48 hours. In severe cases, the bacteria can slip into the
bloodstream and cause systemic infections. And in rare instances,
mostly occurring in the very young, weak, or old, salmonella infection
can lead to death from dehydration or septic shock.

Given the timing of their illnesses, I guessed that all four
patients must have had a common source of infection. I talked with each
patient’s doctor and learned that all but the 3-month-old had recently
eaten tapioca at a local restaurant. The 3-month-old, whose parents
were turkey farmers, proved to be infected with a different type of
salmonella.

Next I notified the state board of health. An inspector found the
problem: The restaurant’s tapioca cooker wasn’t heating the pudding
enough to kill bacteria. Instead it was warming the pudding just enough
to help bacteria grow. In the end, 13 diners at the restaurant were
diagnosed with salmonella food poisoning.

The key to controlling salmonella is understanding its rapid
growth. Bacterial colonies can double every 20 minutes, a rate of
growth so exponential that a single colony bred under perfect
conditions could reach the size of Earth in less than 48 hours.
Salmonellae grow best at about 100 degrees, making the human body a
great host. Keeping food colder than 40 degrees or hotter than 140
degrees reins in bacterial growth remarkably.

Although restaurant outbreaks make the news, most food poisonings
probably occur at home. I know just how this can happen. Some 20 years
ago, to save money during my residency, I dialed my refrigerator
thermostat up to 45 degrees (my first mistake). Then I made meat loaf
with eggs, failing to cook it long enough (second mistake), left it
overnight on the counter (third mistake), put it back in the
refrigerator (fourth mistake), reheated it in a microwave oven (fifth
mistake), and ate it. Six hours later I discovered first-hand
salmonella’s incubation period.

This week I went back to the restaurant for a fine traditional
meal: mashed potatoes, fresh bread, and fried chicken. Tapioca pudding
wasn’t on the menu.

By Daniel C. Weaver
findarticles.com