Page 146 - Review of Medical Microbiology and Immunology ( PDFDrive )

mebooksfree.com
mebooksfree.com

mebooksfree.com
mebooksfree.com
mebooksfree.com
mebooksfree.com
mebooksfree.com
mebooksfree.com mebooksfree.com mebooksfree.com mebooksfree.com C H A P T E R mebooksfree.com
17

Gram-Positive Rods

mebooksfree.com
mebooksfree.com mebooksfree.com mebooksfree.com Listeria monocytogenes mebooksfree.com mebooksfree.com

CHAPTER C ONTENT S

Introduction
Gardnerella vaginalis
SPORE-FORMING GRAM-POSITIVE RODS
Bacillus
Self-Assessment Questions
Clostridium
Summaries of Organisms
NON–SPORE-FORMING GRAM-POSITIVE RODS
Practice Questions: USMLE & Course Examinations
Corynebacterium diphtheriae

mebooksfree.com
mebooksfree.com
mebooksfree.com mebooksfree.com mebooksfree.com Clostridium species are longer and more deeply staining than mebooksfree.com
INTRODUCTION
Corynebacterium and Listeria species. Corynebacterium
There are five medically important genera of gram-positive
species are club-shaped (i.e., they are thinner on one end
rods: Bacillus, Clostridium, Corynebacterium, Listeria, and
than the other). Corynebacterium and Listeria species char-
Gardnerella. Bacillus and Clostridium form spores, whereas
acteristically appear as V- or L-shaped rods. Gardnerella
Corynebacterium, Listeria, and Gardnerella do not. Members
vaginalis is a short gram-variable rod.
of the genus Bacillus are aerobic, whereas those of the genus
Additional information regarding the clinical aspects of
Clostridium are anaerobic (Table 17–1).
infections caused by the organisms in this chapter is provided
These gram-positive rods can also be distinguished
in Part IX entitled Infectious Diseases beginning on page 593.
based on their appearance on Gram stain. Bacillus and
mebooksfree.com mebooksfree.com mebooksfree.com 1. Bacillus anthracis mebooksfree.com mebooksfree.com
mebooksfree.com
SPORE-FORMING GRAM-POSITIVE RODS

BACILLUS
Disease
There are two medically important Bacillus species: Bacillus
anthracis and Bacillus cereus. Important features of pathogen-
Bacillus anthracis causes anthrax (Figure 17–1), which is
esis by these two Bacillus species are described in Table 17–2.
common in animals but rare in humans. Human disease
occurs in three main forms: cutaneous, pulmonary (inhala-
TABLE 17–1 Gram-Positive Rods of Medical
Importance
inhalation and cutaneous anthrax occurred in the United
States. The outbreak was caused by sending spores of the
Important in
Anaerobic Spore Exotoxins tion), and gastrointestinal. In 2001, an outbreak of both
organism through the mail. There were 18 cases, causing 5
Growth
Pathogenesis
Formation
Growth
mebooksfree.com mebooksfree.com – – – mebooksfree.com Important Properties mebooksfree.com mebooksfree.com
mebooksfree.com
deaths in this outbreak.
+
–
+
Bacillus
Clostridium
+
+
+
–
Corynebacterium
+
Bacillus anthracis is a large gram-positive rod with
–
Listeria
–
square ends, frequently found in chains (Figure 17–2).
–
–
Gardnerella
Its antiphagocytic capsule is composed of D-glutamate.
135
mebooksfree.com mebooksfree.com mebooksfree.com mebooksfree.com mebooksfree.com mebooksfree.com