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Microbes and Humans
Chapter 27
Microbes on Us
β-Hemolytic Bacteria on
Blood Agar…. streak
from throat swab.
We have many bacteria
on us: mutualistic,
commensal and
potentially pathogenic.
We are COLONIZED !!
It is all based on our
SURFACES.
Loose Association-Adhesion-Invasion
Each Surface Has Different Microbes
*
We have lots of Bacterial Symbionts
Skin
Human Skin
Where’s the Bacteria ??
After all there are 1012
on the average human:
where?.... 104 to 106
bacteria/sweat gland
Histological
Section of
Human Skin
Propionibacterium acnes
Skin Microbes
Sweat: 0.2 to 1% solutes:
minerals, lactate, urea.
Can loose 100mL to 8L/day.
Sebum: oils and waxes.
Oral and Nasal Cavities
Mouth
Dental Plaque
Dental Plaque
Dental Caries: Streptococcus mutans
*
While the teeth have plaque, the gums are
diseased
Human Gastrointestinal Tract
One of the Few in the Stomach
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SEM Mouse Columnar Epithelium: IIeum
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Normal daily gas production: 470 to 1,400 mL/day.
In 8 – 20 episodes (5 mL to 375 mL/episode)
Feces are Mainly Bacteria
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Probiotics: Adding Live Bacteria to Your
Intestine
Bifidobacterium
Lactobacillus
Probiotics: Lactic Acid Bacteria
Bifidobacterium
Lactobacillus acidophilus
Bacteroides Infection: Surgical Gas Gangrene
Result of an
unfortunate
bowel surgery.
Trachea Epithelial Surface: The Escalator Only Goes Up
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Human Urogenital Tract
Micrograph: vaginal swab, Gram stain.
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Virulence and Pathogenicity
Virulence: LD50
Attachment
Vibrio cholerae (pili)
Escherichia coli (capsule)
Bacillus anthracis
Glistening Mucoid Colonies
Fluorescent Antibody B.
anthracis capsule stain.
Streptoccus pneumoniae + E. coli
*
Do We Got
toxins !
Type of Exotoxins: Cytolytic Toxins
Clostridium perfringens
producing lecithinase on egg
yolk agar.
Streptococcus pyogenes
Lecithin = phosphotidyl choline a
membrane phosphoglycerol lipid
Type of Exotoxins: AB Toxins
What is ADP-ribosylation?
Type of Toxins: AB
Toxins
Cholera Toxin: ADP
Ribosylation of G-protein
turning on Adenylcyclase.
Types of Exotoxins: Endo-Proteases
*
Types of Exotoxins: Endoproteases
Endotoxin: LPS
Limulus amoebocytes – degranulate (and lyse) in
presence of LPS