Transcript Infection and Disease I

Infection and Disease I
The Normal Microflora of the
Human Body
Humans as Habitats
Bodies are great places to be!
Warm, stable, lots of __________ available, constant pH and osmotic
pressure, etc.
Our bodies are not _____________ __________________, though
Each region or organ differs: skin, GI tract, respiratory tract, etc. provide
different conditions
Animals possess great ________________ mechanisms
The successful colonizers (and the successful pathogens -- more on this next
lecture) are those that can get around these defenses
“Normal” doesn’t mean non-pathogenic; we sometimes have
___________________________ (S. pyogenes, S. aureus, etc.)
in low numbers in and on us
Humans as Habitats (cont.)
Colonization (and infection) frequently begin at
mucous membranes
These are found throughout the body. Consist of single or multiple
layers of epithelial cells, tightly packed cells in direct contact with the
external _____________________________.
Bacteria may
associate loosely
or firmly
Breaches in the
_______________
barrier can result
in infection
(pathogenesis)by
opportunistic
pathogens
How we get our indigenous microflora?
•
Normally, a human fetus has no ______________
microorganisms
•
Initial colonization comes during breaking of fetal
_______________ and, especially, birth itself.
•
__________________ in general is colonization source:
mother, father, doctor, etc. Can vary by wards.
•
Initial microflora depends on whether infant is
________________ or not. Bifidobacterium vs. others.
Effects of breastfeeding vs. bottle-feeding on
indigenous microflora
•
Large effect seen -- breastfed infants develop primarily
Bifidobacterium populations, bottle-fed get a mixture of various
species of coliforms, Clostridium, Staphylococcus,
Streptococcus, Lactobacillus, etc.
•
Breastfed infants have ________________ and less
__________________________ capacity in large intestine. This
disfavors enterobacteria and favors Bifidobacteria.
•
Bifidobacterium seem to ___________________ with potential
pathogens like Clostridium difficile and some enterobacteria.
One study demonstrated that bottle-fed infants were ______X as likely as
breastfed ones to harbor C. difficile.
Normal flora of specific regions
(outline)
•
•
•
•
Skin
Oral cavity
Gastrointestinal tract
Other areas
 Upper
respiratory tract
 Lower respiratory tract
 Urogenital tract
Microorganisms are normally not found in the
organs, ______________, or lymph. (if they are,
you’re in trouble!)
Normal flora of the skin
Skin surface is unfavorable habitat.

Usually only populated by transient microbes

Exceptions are ___________________ areas: scalp,
face, ears, underarms, genitourinary, palms, toes.
Most resident skin microorganisms inhabit
_______________ layers of the epidermis, sweat
glands, and follicles.
Most of the residents are Gram-________________,
especially Staphylococcus and Propionibacterium
Normal flora of the skin (cont.)
The dermis and subcutaneous tissue are normally ____________.
Normal flora of the skin (cont.)
Microorganisms are primarily associated with glands:
1) Eccrine glands



Widely distributed
Main glands for ________________; secrete a hypotonic _____________
solution with a variety of organic and inorganic substances
Relatively devoid of microorganisms, probably due to salinity and ________
2) Apocrine glands




Restricted to underarms, genitals, etc.
Don’t develop before ___________
Apocrine sweat has __________________ than eccrine sweat
Population numbers can be high
3) Sebacious glands -- associated with ______________

Produce sebum, chief component of _________________

These lipids have antibacterial activity, esp. against Gram-positive cocci.
Common Skin Bacterium May Be New Opportunistic
Pathogen
(A.H. Chagla, A.A. Borczyk, R.R. Facklam, and M. Lovgren. 1998. Breast abscess
associated with Helocococcus kunzii. Journal of Clinical Microbiology. 36:2377-2379.)
A usually harmless bacterium, commonly found on human skin, may be
an emerging opportunistic pathogen, say researchers from the London Public
Health Laboratory; the Central Public Health Laboratory of Toronto; the National
Center for Streptococcus in Edmonton, Alberta, Canada; and the U.S. Centers for
Disease Control and Prevention. They report a case of infection by this organism
the August 1998 issue of the Journal of Clinical Microbiology.
Helococcus kunzii is a recently identified bacterium that is thought to be
a nonpathogenic member of normal human skin flora and is rarely associated with
skin infections. In the study though, the researchers report the isolation of the
organism from an infected cyst on the breast of a 57-year-old
immunocompromised woman.
"Our finding provides further support for the opportunistic role of H.
kunzii in causing infection in both immunosuppressed and immunocompetent
patients," say the researchers.
Aromabacter malodorens is the bacterium that colonizes healthy human skin. This
organism grows on sweat and produces butyrate and other organic acids which
smell bad in high concentrations.
This past year, scientists affiliated with the International Society for Microbial
Ecology created a genetically engineered strain of this microorganism that can
help banish unpleasant underarm odor.
Scientists removed the butyrate synthase gene that causes one of the unpleasant
odors. Scientists then inserted the DNA from an Asian Musk Deer that encodes
muskolic acid. Muskolic acid is the compound that gives musk oil its
characteristic smell.
In preliminary studies, this new strain of Aromabacter malodorens survives well on
the human skin. Scientists are now working on ways for the genetically
engineered bacteria to out compete native populations of foul-smelling bacteria.
The ISME plans to market an underarm deodorant containing these new bacteria
and license this technology to other deodorant manufacturers. Because the
deodorant is self-replicating, it requires only monthly application.
If this microorganism sells well, the ISME plans to genetically engineer a mintflavored bacterium for the mouth.
If you would like more information or would like to participate in a deodorant trial,
please email Dr. Gutensmell. Enjoy April Foolery.
Normal flora of the mouth
A great place to live! (in contrast to the skin)
The only negatives: salivary ______________ (lysozyme and
lactoperoxidase), and constant need to _______________.
Initially (i.e. at birth), there are only a limited number of
bacterial types (aerotolerant anaerobes like
Lactobacillus and Streptococcus), then as ___________
erupt there are more anaerobes and bacteria adapted to
living in _____________ and on smooth surfaces.
Biofilm (plaque) formation
Begins as thin film of glycoproteins in
______________
This is colonized (quickly) by individual
__________________ (S. mutans, etc.)
cells, which grow to microcolonies
Extensive growth of these results in
formation of a thick ______________.
Further colonization can include
filamentous forms, spirochetes, and
various _________________.
Scanning electron micrograph of dental plaque. The many
different kinds of bacteria composing the plaque exhibit
specific _______________ to the tooth and to each other.
Plaque accumulates calcium salts to form tartar
Ca3(PO4) 2 scale (tartar) from human
tooth
http://www.buckman.com/eng/biofilm3.htm
Scale magnified 7,000x to show imbedded
bacterial __________
http://www.buckman.com/eng/biofilm3.htm
Normal flora of the GI tract
The body is like a
__________, with
the alimentary
canal the ‘inside’
of the donut.
Things inside the
alimentary canal
are not truly
‘inside’ the body
Normal flora of the GI tract (cont.)
Stomach
•
pH of stomach is low, around ____
•
Acts as a microbiological _________
•
Bacterial __________ of stomach contents
is low, but walls can be heavily
________________.
Primarily Lactobacillus and Streptococcus
Gram-stained preparation of the stomach wall of a 14-day old
mouse, showing extensive development of lactic acid
bacteria in association with the epithelial layer
Helicobacter pylori,
cause of stomach ___________
Infection with Helicobacter pylori, the bacteria
responsible for peptic ulcers, may be transmitted via
the hands
In the study, researchers analyzed H. pylori infections in a small,
rural population in Guatemala, testing blood samples, oral
samples and samples from underneath the fingernails. They
found that over half of the subjects tested positive via blood test,
nearly 90 percent tested positive for oral carriage of the
infection and over half tested positive for fingernail carriage.
"Helicobacter pylori infection remains one of the most common in
humans, but the route of transmission of the bacterium is still
uncertain," say the researchers. "The results of this study suggest
that oral carriage of H. pylori may play a role in the
transmission of infection and that the hand may be instrumental
in transmission.”
(S.A. Dowsett, L. Archila, V.A. Segreto, C.R. Gonzalez, A. Silva, K.A. Vastola, R.D. Bartizek and M.J. Kowolik. 1999.
Journal of Clinical Microbiology. 37: 2456-2460.)
Normal flora of the GI tract (cont.)
The upper portions of the small intestine are
_____________ and resemble the
______________. The lower portions have
increasing numbers of bacteria, from 105 to
107 per gram.
The large intestine has enormous numbers of
bacteria, 1010 to 1011 cells/gram! Is
essentially a fermentation vessel.
Why don’t all these commensal bacteria
produce a constant and massive inflammation
of the GI tract epithelial cells?
A recent study published in the journal
Science indicates that the normal flora
apparently shuts off the inflammation
response in host epithelial cells
See http://www.sciencemag.org/cgi/content/full/289/5484/1483
Normal flora of other places
Urogenital tract -- bladder usually
_______________ but ________________
epithelium colonized by facultative Gramneg. rods like E. coli. These can become
opportunistic pathogens.
Upper respiratory tract -Staphylococcus, Streptococcus,
diphtheroid bacilli, Gram-neg.
cocci. Also some pathogens
Lower respiratory
tract -- essentially
_____________