intro to microbio Flashcards
what is the most common helminth infection in the USA and what is unique about it
nematodes (roundworms) [pinworm]
have a complete digestive system unlike the others
worm is an example of what
helminths
3 types of helminths
nematodes (roundworms)
cestodes (tapeworms)
trematodes (flukes)
virus particle is called what
viron
all prokaryotic organisms are classified as what
bacteria
what is the human microbiome
the total # and diversity of microbes in and on the human body
what are the most common sites of the body inhabited by normal microbiota
those in contact or in communication w the outside world
important place w microbiota in body
INTESTINAL TRACT
skin
eye
mouth and nose
urogenital tract
what can colonize plastic catheters
staphylococcus epidermidis (90% of skin aeroboes)
what causes skin infections
staphlococcus aureus
what is associated w acne
propionibacterium acnes (anaerobic)
resides in deeper layers of skin, hair follicles, sweat glands and sebaceous glands
what microbe is associated w mouth and nose
streptococcus mutans
where does streptococcus mutans colonize
teeth and gingival tissue
what does streptococcus mutan damage
colonize damaged or prosethetic heart valves
streptococcus mutans leads to what fatal infective thing
leads to fatal infective endocarditis
does density of microbes increase or decrease along the alimentary canal
density increases
what species constitutes a significant % in the large in
Bacteroides species
where is the greatest number of bacteria and greatest number of species
gut microbiota
most of fecal bacteria is anaerobes or aerobes
anaerobes
what bacteria species maintains the low pH of vagina
lactobacillus species
some bacteria of the bowel produce what substances
antimicrobial substances
opportunistic microbes
some microbes that cause disease only under certain conditions
subclinical infection
infection w no detectable symptoms
latent infection
infection w the potential to become active at some time
primary infection
infection by an organism that may become latent and later cause other disease manifestations
secondary infection
reactivation of latent infection or second stage of an infection
mixed infection
2 or more bacteria infecting the same tissue
pyrogenic infection
pus forming
fulminant infection
infections that occur suddenly and intensely
stages of pathogenesis
-entry
-adhesion
-invasion
-propagation
-damage
-progression/resolution
what are virulence factors
those characteristics of a bacterium that enhance its pathogenicity
what is infections dose ID 50
how any organisms are required to cause disease in 50% of those exposed
lethal dose LD 50
how many organisms kill 50% of test animals
virulence factors (5 of them)
-capsule
-surface adhesion molecule
-bacterial enzymes such as collagenase and hyaluronidase
-iron-binding proteins to obtain iron for growth
-bacterial toxins
exotoxins are proteins secreted by gram positive or gram negative
both
is exotoxins more toxic or endotoxins
exotoxic
how are endotoxins released
by bacterial lysis and are not secreted
endotoxins are components of outer membrane in what gram bacteria
gram negative
lipopolysaccharide (LPS) is endotoxin or exotoxins
endotoxin
tissue damage in bacterial infections is caused by what and released from what
various cytokines released from the lymphocytes, macrophages, and polymorphonuclear leukocytes at the site of infection or in the bloodstream
tissue damage in bacterial infections is caused by what and released from what
various cytokines released from the lymphocytes, macrophages, and polymorphonuclear leukocytes at the site of infection or in the bloodstream
(inflammatory cytokines)
viral infections can lead to (4 things)
-cell death
-transformation (normal cels into malignant cells)
-cell fusion
-cytopathic effect (any visible change in appearance)
indication of this symptom - erythema migrans (large skin lesion with bright red outer border and partially clear central area)
early localized lyme disease
indication of these symptoms - chills, fever, cardiovascular instability
bacteremia
indication of these symptoms - pulmonary consolidation (fluid in lung)
pneumonia
indication of these symptoms - stupor (near unconsciousness) and stiff neck
infection may have spread to the meninges therefore cerebrospinal fluid (CSF) needs to be evaluated
Gram Stain what color is gram positive and what color is gram negative
gram positive - purple
gram negative - pink /red
when can microorganisms not be identified in gram staining
if they lack cell walls
what are the colors for the acid fast bacteria and non acid fast bacteria in acid fast stating
acid fast organisms will be pink/red after staining
non acid fast staining will be blue
acid fast organisms contain large amounts of what
acid fast organisms contain large amounts of mycolic acids (fatty acids)
when is india ink useful
useful in detecting crytococcus neoformans in CSF
how are crytococcus identified in india ink
by their large, transparent capsules that displace India ink particles
how does potassium hydroxide preparation work
treatment w KOH dissolves host cells and bacteria, sparing fungi
how are fungi recognized in potassium hydroxide prep
recognized by their filamentous (hyphae) or round (oval) structures
all clinically important bacteria require what element and what does that make them
heterotrophs (requires organic carbon for growth)
what does a fastidious organism mean
requires either a large number of growth factors or very specific ones
facultative anaerobes
have the ability to grow anaerobically, but grows better w O2
aerotolerant anaerobes
does not use oxygen for growth but can tolerate it
microaerophilies
requires oxygen [ ] lower than O2 found in the air
when is solid medium (nutrient agar used)
isolation of bacterium
when is liquid medium (nutrient broth used)
to grow larger quantities of a culture of bacteria that have already been isolated as a pure culture
defined media
contains known quantities of all ingredients
undefined (complex)
contains some complex ingredients such as yeast extract w has unknown proportions
enriched
contains the nutrients required to support the growth of a wide variety of organisms, including some of the more fastidious ones
ex of enriched media
blood agar (sheep/horse)
chocolate agar
differential media
used to differentiate one microorganism from another
reducing media
used for growth of obligate anaerobes
selecive media
used for growth of only selected microorganisms
catalase test how does it work
catalyzes the degradation of h2o2 to water and oxygen
catalse test results
catalse + will produce bubbles when exposed to a solution of h2o2
staphylococci catalase + or -
catalase +
streptococci and enterococci catalase + or -
catalase -
oxidase test results
cytochrome c can accept e- from artificial substances, producing a dark, oxidized product
how does coagulase test work
coagulase causes a clot to form when bacteria are incubated w plasma
staphyloccocus aureus coagulase + or -
coagulase +
staphylococci coagulase + or -
coagulase -
how does urease test work
urease hydrolzyses urea to NH3 and CO2
ammonia produced and detected w pH indicates (phenol red) that change color in response to increased alkalinity
metabolic pathway test what does color change indicate
color change indicates the presence or absence of the bacteria’s ability to metabolize a particular substrate
quelling reaction result
makes bacteria w CAPSULE more visible (appears SWOLLEN [+]) when organisms are treated w serum w specific antibodies
latex agglutination test result
latex and other particles can be readily coated w either antibody (for antigen detection) or antigen (for antibody detection)
addition of antigen to antibody-coated latex beads causes AGGLUTINATION +
complement fixation test result
solution turns PINK
detects ability of the antibody to bind complement
ELISA result
enzyme converts substrate into a colored product (antigen/antibody mechanism)
Western blotting results
protein detection SDS PAGE w weight
disk diffusion method (kirby-bauer disk-diffusion method) result
disks w exact amounts of different antimicrobial agents are placed on culture dishes inoculated w the microbe to be tested
SIZE OF ZONE GROWTH inhibition is influenced
minimal inhibitory [ ] results
dilution technique to see sensitivity to antibiotic
bactericidal vs bacteriostatic
bacteriostatic - drug arrest the growth and replication and limits spread while body’s immune system handles the pathogen
bactericidal - kills bacteria
