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Bio 280 Normal Flora
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
Bio 280 Normal Flora
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.
Bio 280 Normal Flora
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
Normal flora of the skin (cont.)
The dermis and subcutaneous tissue are normally ____________.
Bio 280 Normal Flora
Microorganisms primarily associated with glands:
1) Eccrine glands l Main glands for ________________ l Widely distributed l Relatively ________________ of microorganisms, probably due to extensive _____________
Apocrine glands l Restricted to underarms, genitals, etc. l Don’t develop before ________________ l Population numbers can be high
Sebacious glands -- associated with __________
Normal flora of the skin (cont.)
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.
Bio 280 Normal Flora
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.
Bio 280 Normal Flora
Plaque accumulates calcium salts to form tartar
http://www.buckman.com/eng/biofilm3.htm
Ca 3 (PO 4 ) 2 scale (tartar) from human tooth
Scale magnified 7,000x to show imbedded
bacterial __________
http://www.buckman.com/eng/biofilm3.htm
Bio 280 Normal Flora
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
Bio 280 Normal Flora
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.)
Bio 280 Normal Flora
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/
Normal flora of other places
Urogenital tract -- bladder usually
_______________ but ________________
epithelium colonized by facultative Gram-
neg. rods like E. coli. These can become
opportunistic pathogens.
Bio 280 Normal Flora
Upper respiratory tract -- Staphylococcus, Streptococcus, diphtheroid bacilli, Gram-neg. cocci. Also some pathogens
Lower respiratory tract -- essentially
