Chapter 4
An Introduction to the Prokaryotic Cell, Its Organization, and
Members
I.
Introduction
An outbreak of pneumonia amongst elderly patients occurs at a long-term care facility in
New Jersey. Epidemiological studies of the outbreak indicate that the organism
responsible, Streptococcus pneumoniae, caused disease only in those patients who had
not been vaccinated with the pneumococcal polysaccharide vaccine (PPV). Vaccination
was offered to all patients who had not yet been vaccinated in order to decrease the
likelihood of such an outbreak occurring again at the facility.
II.
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Facts of the Case
Nine patients developed pneumonia from infection with S. pneumoniae.
Because all isolates were serotype 14, the source of the infection must have been
the same.
The patients who developed pneumonia had never been vaccinated with the PPV.
About 50% of those patients who did not develop pneumonia had received the
PPV.
PPV was offered to the 55 residents who had never been vaccinated; the facility
also refused admission to new patients who had not been vaccinated.
Student questions:
1. What is the purpose of vaccination? What vaccines are commonly used to protect
the elderly from dangerous diseases often deadly to this population?
2. How are respiratory pathogens such as Streptococcus pneumoniae transmitted?
What is the significance of seven of the nine patients living in the same wing of the
nursing home?
3. Epidemiologists are highly trained individuals who analyze outbreaks of
infectious disease. What are some of the clues found by those who studied this
outbreak?
4. How do epidemiologists work to obtain clues about an outbreak of infectious
disease?
5. What is a capsule? What purpose does it serve in bacteria? What special
advantage does the capsule confer on the pathogen S. pneumoniae?
6. Define the term virulence.
7. Why are those who have been vaccinated against S. pneumoniae more resistant to
infection by this agent?
8. The PPV is made up of what components from S. pneumoniae? The vaccine
protects against how many different serotypes of this organism? How many
serotypes does the vaccine not protect against?
9. Is it significant that the serotype of S. pneumoniae found in all patients was the
same (serotype 14)? How might a S. pneumoniae carrier have played a role in
this outbreak?
10. What are phagocytes and what is their function in the body?
11. What other bacterial species produce a capsule for protection against
phagocytes? Do these capsules vary in their composition? Are capsules unique to
bacteria, or can they be found in other types of microorganisms?
12. Not all of the patients had S. pneumoniae present in their blood cultures. Two of
the nine were culture negative in their blood but had gram-positive diplococci
present in their sputum. In the seven patients who were positive in their blood
cultures, how did the organism cross from the lungs into the bloodstream?