Chapter 20
The Gram-Negative Bacilli of Medical Importance
I.
Introduction
After the major tsunami in Southeast Asia in December 2004, a number of unusual cases
developed that were called “tsunami lung.” In the case described here, a young woman
with a severe headache and nausea developed muscle weakness and difficulty
swallowing. X-rays showed cavities in her lungs. Subsequent samples from both the
lungs and central nervous system (CNS) were negative for any microorganisms.
Preventive measures included appropriate antibiotic and supportive therapy, yet the
patient continued to present with neurological symptoms, including paralysis.
Examination showed an abscess of the left cerebral cortex of the brain. Potential
diagnoses included TB, tetanus, and meningitis, but since no microorganisms had been
isolated, all possible treatments were included. Eventually, the patient recovered and it
was believed that she was suffering from infection with Burkholderia pseudomallei, an
opportunistic pathogen, endemic to Southeast Asia.
II.
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Facts of the Case
A young woman with a severe headache and nausea developed muscle weakness
and difficulty swallowing.
Her lung showed cavities and she had abnormal breathing sounds.
No organisms were isolated from CNS or lung samples.
Preliminary broad-spectrum antibiotic therapy appeared to have no effect and the
patient continued to develop more neurological symptoms including loss of
speech and paralysis.
An abscess on the brain was found.
More treatment was provided including vaccination and different antibiotics.
Student questions:
1. Systemic disease can be brought about by a number of things. Distinguish
between bacteremia, septicemia, and toxemia.
2. There were several possible microorganisms that may have been responsible
for the patient’s symptoms, many of which were systemic. Discuss the
possible virulence factors that may have contributed to these symptoms.
3. What is special about the antibiotic metronidazole? Why was this a good
choice for this patient?
4. Compare and contrast exotoxins and endotoxins.
5. How was it determined that the patient’s infection was caused by
Burkholderia pseudomallei?
6. If the final diagnosis was correct, which treatment probably had the most
effect on the patient’s disease? Which was least effective?
7. One problem associated with some gram-negative infections is sepsis. What is
septic shock and how does it happen?
8. Tsunamis are, thankfully, rare. Do you believe the difficulty in the correct
diagnosis of this disease was due to the rarity of the disease or the rarity of
the situation? In other words, was the endemic nature of this opportunistic
pathogen overlooked?