Transcript Foundations in Microbiology

Lecture PowerPoint to accompany
Foundations in
Microbiology
Seventh Edition
Talaro
Chapter 19
The Gram-Positive
Bacilli of Medical
Importance
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
19.1 Medically Important GramPositive Bacilli
Can be subdivided into three general groups,
based on presence or absence of endospores
and acid-fastness
Three general groups:
1. Endospore-formers
2. Non-endospore-formers
3. Irregular shaped and staining properties
2
3
19.2 Spore-Forming Bacilli
Genus Bacillus
Genus Clostridium
Genus Sporolactobacillus
4
General Characteristics of the Genus
Bacillus
•
•
•
•
•
•
•
Gram-positive, endospore-forming, motile rods
Mostly saprobic
Aerobic and catalase positive
Versatile in degrading complex macromolecules
Source of antibiotics
Primary habitat is soil
2 species of medical importance:
– Bacillus anthracis
– Bacillus cereus
5
Bacillus Anthracis
• Large, block-shaped rods
• Central spores that develop under all conditions
except in the living body
• Virulence factors – polypeptide capsule and
exotoxins
• 3 types of anthrax:
– Cutaneous – spores enter through skin, black soreeschar; least dangerous
– Pulmonary –inhalation of spores
– Gastrointestinal – ingested spores
6
Figure 19.2 Cutaneous anthrax
7
Control and Treatment
• Treated with penicillin, tetracycline, or
ciprofloxacin
• Vaccines
– Live spores and toxoid to protect livestock
– Purified toxoid; for high risk occupations and
military personnel; toxoid 6 inoculations over
1.5 years; annual boosters
8
Figure 19.1 (a) Bacillus anthracis
9
Lecture PowerPoint to accompany
Foundations in
Microbiology
Seventh Edition
Talaro
Chapter 20
The Gram-Negative
Bacilli of Medical
Importance
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
20.1 Aerobic Gram-Negative
Nonenteric Bacilli
• Large, diverse group of non-spore-forming
bacteria
• Wide range of habitats – large intestines
(enteric), zoonotic, respiratory, soil, water
• Most are not medically important; some are
true pathogens, some are opportunists
• All have a lipopolysaccharide outer
membrane of cell wall – endotoxin
11
12
20.4 Coliform Organisms and
Diseases
13
Escherichia Coli: The Most
Prevalent Enteric Bacillus
• Most common aerobic and non-fastidious
bacterium in gut
• 150 strains
• Some have developed virulence through
plasmid transfer, others are opportunists
14
Pathogenic Strains of E. Coli
• Enterotoxigenic E. coli causes severe diarrhea due to
heat-labile toxin and heat-stable toxin – stimulate
secretion and fluid loss; also has fimbriae
• Enteroinvasive E. coli causes inflammatory disease of
the large intestine
• Enteropathogenic E. coli linked to wasting form
infantile diarrhea
• Enterohemorrhagic E. coli, O157:H7 strain, causes
hemorrhagic syndrome and kidney damage
15
Escherichia coli
• Pathogenic strains frequent agents of infantile
diarrhea – greatest cause of mortality among
babies
• Causes ~70% of traveler’s diarrhea
• Causes 50-80% UTI
• Coliform count – indicator of fecal
contamination in water
16
Figure 20.14 Rapid identification of
E. coli O157:H7
17
Other Coliforms
Clinically important mainly as opportunists
• Klebsiella pneumoniae – normal inhabitant of
respiratory tract, has large capsule, cause of
nosocomial pneumonia, meningitis, bacteremia,
wound infections, and UTIs
• Enterobacter sp. – UTIs, surgical wounds
• Citrobacter sp. – opportunistic UTIs and
bacteremia
• Serratia marcescens – produces a red pigment;
causes pneumonia, burn and wound infections,
septicemia and meningitis
18
Lecture PowerPoint to accompany
Foundations in
Microbiology
Seventh Edition
Talaro
Chapter 21
Miscellaneous Bacterial
Agents of Disease
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
21.2 Curviform Gram-Negative
Bacteria and Enteric Diseases
Three genera:
1. Vibrio – comma-shaped rods, single polar
flagellum
2. Campylobacter – short spirals or curved
rods; one flagellum
3. Helicobacter – spirochete with tight
spirals and several polar flagella
20
Vibrio Cholera
•
•
•
•
•
Comma-shaped, possess unique O and H Ags
El Tor biotype: survives longer, more infectious
Infectious dose 108
Infects mucous barrier of small intestine, noninvasive
Cholera toxin causes electrolyte and water loss
through secretory diarrhea, “rice water stool”;
resulting dehydration leads to muscle, circulatory,
and neurological symptoms
• Treatment: oral rehydration, tetracycline
• Vaccine available
21
Figure 21.14 (a-b) Alterations in intestinal
function caused by cholera toxin
22
Figure 21.14 (c)
Alterations in
intestinal
function caused
by cholera toxin
23