Leys Flashcards
A biofilm is a mixture of _____ and a matrix made up of ________
microbes
extracellular polymers.
Bacteria form _____ within a biofilm.
complex structures
Most biofilms are mixtures of ___
different species of bacteria.
T o F: Biofilms can include microorganisms other than bacteria
True
Biofilms have complex structures that give accessibility to _____ and removal of _____
nutrients
waste products.
Bacteria in a biofilm are more or less resistant to antibiotics and host attacks?
More
Where do most bacteria form biofilms?
in an environment where there is liquid flowing.
Wild bacteria have extracellular______ that allow them to bind to surfaces or other bacteria.
polymers attached to their surface
Wild bacteria have extracellular polymers attached to their surface that allow them to ____
bind to surfaces or other bacteria.
Biofilms are associated with many diseases including ___
periodontal disease and caries.
Many bacterial diseases (including oral infections) are ___
polymicrobial where several species are involved.
_________ is the communication between bacteria.
Quorum sensing
What are the two general mechanisms for quorum sensing?
One that recognizes similar bacteria (same species) and one that recognizes all bacteria.
Do most bacteria have mechanisms for quorum sensing?
Essentially all bacteria have mechanisms for quorum sensing.
When do the quorum sensing mechanisms produce a response?
when a certain threshold concentration of secreted molecules in reached.
Quorum sensing is an essential process ____
in biofilm formation.
Strict vs obligate vs facultative anaerobes
Strict aerobes must have oxygen to grow. Obligate anaerobes cannot tolerate oxygen and facultative anaerobes can grow with or without oxygen.
DNA that enters a bacterial cell can be treated three ways:
1) degraded
2) integrated into the host chromosome
3) integrated into a plasmid (extrachromosomal element).
How do bacteria degrade foreign DNA?
Restriction endonucleases or restriction enzymes
What is transformation?
uptake of naked DNA by “competent cells.”
What is transduction?
the transfer of DNA between bacteria through a virus.
What is conjugation?
transfer of DNA through cell to cell contact using a sex pilus.
Mutations in DNA can cause _____
antibiotic resistance
Mutations can be the result of _____. Which are the least likely to cause antibiotic resistance?
base changes, deletions, insertions, duplications or rearrangements.
Deletions are the least likely to cause resistance
Bacteria remove oxygen radicals from the cell by converting them to ______ with _______.
Hydrogen peroxide with superoxide dismutase.
Catalase converts ______ to ______
hydrogen peroxide
water and oxygen
Bacteria that do not have ________ will not tolerate oxygen; they are anaerobic.
superoxide dismutase and catalase
Bacteroides are the most numerous members of
the normal flora of the human colon.
Spillage of intestinal material into the ____ typically results in a biphasic disease: _______
peritoneal cavity
acute inflammation followed by localized abcesses.
There are a _____ number of bacterial species present during the acute phase and a ____ number of species that predominate in abcesses.
large
small
______ is the most common isolate from intra-abdominal abscesses.
Bacteriodes fragilis
Bacteriodes fragilis is the most common isolate from ______
intra-abdominal abscesses.
What is unique about the LPS on the surface of B. fragilis?
It is not toxic. This is unlike other gram neg bacteria
Of the hundreds of species that are introduced into the peritoneal cavity by spillage from the colon, those (including B. fragilis) that have a _____ survive phagocytosis by the host.
polysaccharide capsule
Intra-abdonimal abcesses cause by B. fragilis or other bacteria can lead to
bacteremia and septic shock.
What is bacteremia?
the presence of bacteria in the blood, with or without the presence of an illness.
What is sepsis?
a severe systemic illness marked by hemodynamic derangement and organ malfunction.
Why is treatment of sepsis with antibiotics difficult?
because the dead bacteria can release toxins that initially cause more damage.
Spirochetes are widespread in nature, many or few cause disease?
Few
The corkscrew-like movement of spirochetes is facilitated by _____
periplasmic flagella.
What is the causative agent of syphilis?
Treponema pallidum
Why is treponema pallidum difficult to study?
Cannot be grown in lab
When T. pallidum enters the body it becomes systemic almost immediately by
traveling through the lymphatic channels to the systemic circulation.
How does the primary chancre formed by T. pallidum differ from the entire infection?
primary chancre heals spontaneously
Entire infection is systemic
What happens to 50% of patients that do not receive treatment for syphilis?
They enter the secondary stage of the disease
______ produced by secondary syphilis is often mistaken for other problems.
The rash
Tertiary syphilis, if left untreated, can progress to the CNS, causing _____
ataxic gait, paresis, blindness, dementia and death.
____ is one of the easiest STDs to control. There are good diagnostic tests and treatment is available and inexpensive.
Syphilis
Borrelia burgdorferi is the causative agent of
Lyme’s disease.
What causes Lyme’s disease?
Borrelia burgdorferi
Like syphilis, Lyme’s disease progresses in stages from an _____ to a ______
acute and local skin infection
chronic disease of the CNS and joints.
B. burgdorferi is transmitted by
ticks.
Which microbe is transmitted by ticks?
B. burgdorferi
There are _______ bacterial species found in the oral cavity, from a wide variety of phyla.
500 – 1000
Different bacteria occupy different environmental niches. Subgingival bacteria are generally ______. Supragingival bacteria are generally________.
proteolytic
sacchrolytic
Factors that promote colonization in the oral cavity include _______
adherence properties synergistic bacteria nutritional substrates temperature moisture content.
Factors that inhibit colonization in the oral cavity include
antimicrobial properties of saliva
mechanical shearing
antagonistic bacteria.
There are many bacterial species that are associated with periodontitis, while fewer species are associated with
periodontal health.
Shifts in microbial composition occur in _____, however no bacterium is found in all patients with periodontitis and never found in healthy subjects.
periodontitis
The tissue destruction that occurs during periodontitis is mainly the result of
a host response.
There is a small shift from ____ to ______ during periodontitis.
gram positive
gram negative
The complexity of the ______ increases during periodontal disease.
microbial community
There is a slight shift to ______ in periodontitis.
more uncultivated bacteria
Microbial diversity ____ in caries.
declines
There is a progression of ____ as caries progresses.
dominant species
Each location in the ____ has its own associated microbial composition. However there is overlap of species.
oral cavity
