WORLD OF MICROBIOLOGY AND IMMUNOLOGY Typhoid fever559•
S. typhibacteria are passed into the stool and urine of
infected patients, and may continue to be present in the stool
of asymptomatic carriers (individuals who have recovered
from the symptoms of the disease, but continue to carry the
bacteria). This carrier state occurs in about 3% of all individ-
uals recovered from typhoid fever.
The disease is passed between humans, then, through
poor hygiene, such as deficient hand washing after toileting.
Individuals who are carriers of the disease and who handle
food can be the source of epidemic spread of typhoid. One
such individual was the inspiration for the expression
“Typhoid Mary,” a name given to someone with whom others
wish to avoid all contact. The real “Typhoid Mary” was a cook
named Mary Mallon (1855–1938) who lived in New York City
around 1900. She was a carrier of typhoid and was the cause
of at least 53 outbreaks of typhoid fever.
Typhoid fever is a particularly difficult problem in parts
of the world with less-than-adequate sanitation practices. In
the United States, many patients who become afflicted with
typhoid fever have recently returned from travel to another
country, where typhoid is much more prevalent, such as
Mexico, Peru, Chile, India, and Pakistan.
To cause disease, the S. typhibacteria must be ingested.
This often occurs when a carrier does not wash hands suffi-
ciently well after defecation, and then serves food to others. In
countries where open sewage is accessible to flies, the insects
land on the sewage, pick up the bacteria, and then land on food
to be eaten by humans.
Ingested bacteria travel down the gastrointestinal tract,
where they are taken in by cells called mononuclear phago-
cytes. These phagocytes usually serve to engulf and kill invad-
ing bacteria and viruses. However, in the case of S. typhi, the
bacteria survive ingestion by the phagocytes, and multiply
within these cells. This period of time, during which the bac-
teria are multiplying within the phagocytes, is the 10–14 dayincubation period. When huge numbers of bacteria fill an
individual phagocyte, the bacteria are discharged out of the
cell and into the bloodstream, where their presence begins to
cause symptoms.
The presence of increasingly large numbers of bacteria
in the bloodstream (called bacteremia) is responsible for an
increasingly high fever, which lasts throughout the four to
eight weeks of the disease, in untreated individuals. Other
symptoms include constipation (initially), extreme fatigue,
headache, a rash across the abdomen known as “rose spots,”
and joint pain.
The bacteria move from the bloodstream into certain tis-
sues of the body, including the gallbladder and lymph tissue of
the intestine (called Peyer’s patches). The tissue’s inflamma-
tory response to this invasion causes symptoms ranging from
inflammationof the gallbladder (cholecystitis) to intestinal
bleeding and actual perforation of the intestine. Perforation of
the intestine refers to an actual hole occurring in the wall of
the intestine, with leakage of intestinal contents into the
abdominal cavity. This causes severe irritation and inflamma-
tion of the lining of the abdominal cavity, called peritonitis,
which is frequently a fatal outcome of typhoid fever.
Other complications of typhoid fever include liver and
spleen enlargement (sometimes so extreme that the spleen rup-
tures), anemia (low red blood cell count due to blood loss from
the intestinal bleeding), joint infections (especially frequent in
patients with sickle cell anemia and immune systemdisorders),
pneumonia(due to a superimposed infection, usually by Strep-
tococcus pneumoniae), heart infections, meningitis, and infec-
tions of the brain (causing confusion and even coma). Untreated
typhoid fever may take several months to resolve fully.
Samples of a patient’s stool, urine, blood, and bone mar-
row can all be used to culture(grow) the S. typhibacteria in a
laboratory for identification under a microscope. These types
of cultures are the most accurate methods of diagnosis.Mary Mallon (“Typhoid Mary”) spread the typhoid bacterium before she was quarantined.womi_T 5/7/03 11:03 AM Page 559