Microbiology Lect1 Flashcards
who discovered penicillin
alexander helming in 1929
ruminants
bacteria in rumen; breakdown cellulose
most diverse of all living microorganisms
parasites
exist as yeast or molds. most are free living
fungi
smallest independently living cells with no organelles
bacteria
how do bacteria replicate
binary fission
viruses
obligate intracellular parasite. protein coat surrounding nucleic acid (DNA or RNA)
tissue tropism
viruses only infect certain cells in the body
symbiotic
benefit host (gut bacteria)
commensals
neutral relationship to the host (oral streptococci). important in the mouth and teeth
parasitic relationship
harm to host (tape worm)
residents
established niche at a particular body site. important in the mouth and teeth
transients
acquired from the environment and establish themselves briefly (inhabited by resident bacteria or immune system)
carrier state
potentially pathogenic organisms becomes a resident (streptococcus mutans)
how do we acquire our immune system
as babies we are sterile. first microbes are from mothers vagina. bacteria colonize at the locations they are best suited for physiologically
what factors do bacteria consider when determining location to colonize
available nutrients, PH, oxidation-reduction potential, resistance to local antibacterial substances, adhesion mediated affinity to receptor on host cells, microbial interactions (what is already there, competition and inhibition)
most common potential pathogen on skin
staphylococcus aureus
most common potential pathogens on mouth
candida albicans
bacteria flora is highest on ___ skin areas
moist (armpits, perineum, between toes)
bacteria type in mouth and pharynx
many bacteria types. differ at different sites. Lots of streptococci. also neisseria and morazella
bacteria type in oropharynx
neisseria and streptococci
bacteria type stomach and small bowel
few organisms due to low ph. helicobacter pylori
bacteria type in colon
most abundant and diverse. 90% bacteria are anaerobes. bacteroids, fusobacterium, eubacterium, and clostridium. remainder are facultative organisms like e coli , yeast etc
the larynx and lower respirator tract protect health via
epithelial cilia and movement of mucocilary blanket
which parts of the body are normally sterile
accessory sinuses and urinary tract
what affects the vaginal tract flora
hormonal fluctuations and different ages. pre-puberty and menopause are similar. they are scant and non specific mostly from skin flora and colon.
vaginal tract flora during childbearing years
mostly lactobacillus and some anaerobic gran negative rods and gram positive yeast. slightly lower ph
what hormone affects the vaginal epithelium and what does it cause?
estrogen; causes glycogen to be deposited which the lactobacilli feed on
opportunistic infections
occur when microbes invade normally sterile locations (urinary tract, abdominal cavity). or reduce immunological response result in invasion by flora
exclusionary effect
competition between normal flora and potential invaders; like when antibiotics wipe out normal flora and give pathogens an advantage
priming the immune system
presence of microbiota is important for the development of our immune system (hygiene hypothesis)
what separates a pathogen from a commensal?
organism must cause damage to host
diphtheria makes a toxin that inhibits what?
protein synthesis
ways pathogens can damage the host
the host immune reponspe to the organic can cause damage, bacteria can produce toxins that act on host cells, bacteria can secrete enzymes that degrade host tissue and facilitate spread
ways that pathogens can evade the immune response
- attack immune effector cells
- secrete enzymes that degrade host effector molecules(antibodies)
- change surface structure to evade the immune response, so antibodies don’t work
- hide inside host cells (macrophage)
three ways to collect a specimen
- direct specimen (highest quality)
- indirect specimen
- sample from site with normal flora
direct specimen
localized in an otherwise sterile location (deep abscess or cerebrospinal fluid)
indirect sample
must pass through a site containing normal flora do be collected (expectorated sputum and voided urine)
sample from site with normal flora`
pathogen and nonpathogenic flora are mixed (throat and sty-ool)
issues with sample collection
- time- time between sample collection and isolation is critical (3-4 hours)
- viability- some organisms don’t survive long outside body
- bacteria growth - particularly problematic if pathogen if pathogens found in low numbers
- transporting media- must prevent sample from drying out and minimal nutrients
direct examination
light microscopy, detects bacteria fungi and parasites
two types of bacterial stains
1.primary (crystal violet, carbon-fuchsin red)
2. counter stains (safranin(gram stain), methyelene blue)
(methylene blue stains everything)
gram staining colors
positive= purple
negative=pink
acid fast stain colors
acid-fast bacteria= red
non acid fast bacteria/cell=blue
immunofluorescence
stain used for viral infections; will make the antibody fluorescent
selective media
used to select and isolate a specific group of bacteria.
- can contain chemical substances that inhibit growth of one type of bacteria and permit growth of another. example: potassium tellurite inhibits growth of gram-negative bacteria
differential media
distinguishes between closely related species of bacteria based on characteristics on media (color change or colony morphology; like blood agar)
temperature for atmospheric conditions for culturing
35-37 degrees c
do microaerophilic require more oxygen or co2
co2
ways to identify cultures of isolated colonies
- culture characteristics
- biochemical tests
- toxin production and pathogenicity
- antigenic structure
- genomic structure
culture chacateristics
nutritional requirements, pigment production etc
biochemical tests
ability to attack various substrates or produce metabolic by products
antigenic structure (serology)
ability to interact with antibodies
genomic structure
dna sequence relatedness as determined by holy or direct sequence comparison
how do you diagnose viral infections
Evidence of cytopathic effects (CPE).
- look for morphological changes to cells
- immunological tests- antibodies against the virus can be detected in blood
precipitation reactions
type of immunological test when antibody and antigen interact they form a precipitate
hemagglutination
type of immunological tests some viruses bind to red blood cells causing cross linking
mononucleosis test
uses horse or sheep red blood cells, which cross react to antibodies against EBV (virus that causes mono) resulting in agglutination of red blood cells (Cross linking)
DNA hybridization
target DNA is bound to a membrane and complementary DNA probe attached to a color producing enzyme is reacted with membrane. signal produced only if DNA finds its target (positive test)
polymerase chain reaction (PCR)
DNA specific “primers” are used to amplify a target DNA molecule. a product signified target is present in sample (positive result)
