CASESTUDY
Foodborne Illness from Home-Prepared Fermented Tofu
In early November, LeNa, a 67-year-old Asian-American woman, made a fermented tofu at home using a traditional recipe she learned in Taiwan. She started with commercially packaged tofu purchased at a retail market. She boiled the tofu, which kills bacterial cells quickly but not endospores. The tofu was towel dried and cut it into cubes. The cubes were placed in a bowl, covered with plastic wrap, and stored at room temperature for about 2 weeks. The tofu was then transferred to glass jars with chili powder, salt, white cooking wine, vegetable oil, and chicken bouillon to marinate at room temperature for several more days. The fermented tofu was stored at room temperature before being eaten. LeNa and her 75-year-old husband ate the fermented tofu for several days; however, LeNa ate more than her husband.
After several days, LeNa began to suffer from double vision. Six days later, when she visited her doctor, he noticed additional facial paralysis (Figure a). LeNa also complained of dizziness, drooling, and difficulty swallowing. Further examination indicated sluggish tongue movement, slurred speech, and weakness in her right arm. LeNa’s husband reported 3 days of worsening double vision, dizziness, and difficulty swallowing. On physical examination, he also had sluggish tongue movement.
a.
1.
Describe the paralysis seen in the photos.
Cultures of stool specimens revealed Clostridium botulinum (Figure b). The same pathogen was found in the fermented tofu samples, which had a pH of 6.8. Environmental conditions that facilitate endospore germination and growth of C. botulinum include a pH greater than 4.6, anaerobic conditions, low salt or sugar content, and temperatures above 4C (39.2F).
b.
2.
Which cells would have survived in the tofu after boiling?
INVESTIGATE:
3.
Name the disease that is affecting this couple.
4.
What are the early signs and symptoms of the disease?
5.
In general, how is this disease normally prevented?
Both patients were admitted to an intensive care unit, administered botulinum antitoxin, and recovered after hospitalization for more than 1 week.
Think critically and try the interactive case study related to pathogens discussed in this chapter.
Copyright 2017 John Wiley & Sons, Inc. All rights reserved.
CASESTUDY
The Spread of a Drug-resistance Gene
A Rhode Island resident (patient 1) travelled to Cambodia, where she was diagnosed with spinal cord compression and was hospitalized from December 20 to 30. She had an indwelling catheter placed during her medical care and was given multiple antibiotics. On January 6, she returned to Rhode Island and was hospitalized for lymphoma. She underwent chemotherapy and required prolonged bladder catheterization and was given more than 20 different antibiotics during her treatment. On March 4, a urine culture grew carbapenemase-producing Klebsiella pneumoniae containing the New Delhi metallo-beta-lactamase (NDM) gene.
1.
How does antibiotic therapy reveal the presence of drug-resistant bacteria?
The drug-resistance gene NDM was first reported in a patient who had been hospitalized in New Delhi, India, in 2007. Resistant bacteria carrying NDM are of particular concern because NDM resistance genes are usually encoded on plasmids that harbor multiple resistance gene clusters and are transmitted easily to other genera of bacteria (Figure a).
a. A plasmid showing the NDM gene and clusters of drugresistance genes
2.
REVIEW: How did some Klebsiella bacteria probably acquire the NDM gene and the multidrug resistance characteristic shown in the diagram?
3.
What does the abundant amount of insertion sequences imply about the how the plasmid acquired the many other drug-resistance genes?
K. pneumoniae is a gram-negative, bacillus-shaped pathogen that is often resistant to antibiotics. Although found in the normal flora of the mouth, skin, and intestines, it can cause destructive infections in people with a weakened immune system including persons with diabetes, alcoholism, malignancy, and chronic obstructive pulmonary disease. The pathogen is normally transmitted to other patients by hands or material contaminated with feces.
Patient 2, one of seven patients on the same unit at the time of this patient’s stay, also grew multidrug-resistant K. pneumoniae from a rectal swab specimen collected March 30. It was genetically identical to the first isolate and contained the NDM gene. A study of contacts between hospital personnel was completed to determine possible sources for spread of the pathogen. Those who potentially had direct contact with patient 1 were screened to determine who also had contact with patient 2 (Figure b).
b.
Position
Contact with
patient 1
Contact with
patient 2
Physicians
+
Nurse practitioners
+
Nursing staff
+
+
Janitorial staff
+
Food service staff
+
Family/visitors
+
(Data from Hardy EJ et al. (2012) Carbapenem-Resistant Enterobacteriacea
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