97 terms

Microbiology Quiz 3

single largest reservoir of microbes in body
large intestine
how microbes shed from body to environment; 20% by volume; 10^11 per gram
most of microbes in feces are this
obligate anaerobes
about 1-5% of feces microbes
facultative anaerobes
facultatively anaerobic, G- rods found in intestines of humans and animals, simple growth requirements
sub-classifications of enteric bacteria
intestinal pathogens, harmless commensals, and opportunistic pathogens
Salmonella and Shigella species, many Yersinia, and some E. coli; cause diarrheal disease worldwide
intestinal pathogens
cause of typhoid
Salmonella typhi
cause of severe dysentry
Shigella and E. coli O157:H7
do not cause disease in normal habitat of intestines but can cause UTIs, septicemia, pneumonia, and other infections in compromised hosts
opportunistic enteric bacteria
genera of opportunistic enteric bacteria
Escherichia, Enterobacter, Klebsiella, Proteus, Serratia, Citrobacter
#1 cause of UTI and nosocomial infections in USA
opportunistic enteric bacteria
used to detect and isolate enteric bacteria from urine, blood and food samples
MacConkey's agar
inhibit growth of non-enteric bacteria on MacConkey's
bile salts
inhibit G+ bacteria on MacConkey's
neutral red and crystal violet dyes
enteric lactose fermenters on MacConkey's
form red or pink colonies
enteric non-lactose fermenters
form transparent, colorless colonies on MacConkey's
used to detect and isolate enteric bacteria from water samples
Levine's Eosin-Methylene Blue agar
inhibit growth of G+ bacteria on EMB
eosin and methylene blue dyes
enteric lactose fermenters on EMB
blue back with green metallic sheen (Escherichia) or dark brown colonies (Enterobacter/Klebsiella)
enteric non-lactose fermenters on EMB
transparent, amber colonies
lactose fermenting enteric bacteria
Escherichia, Enterobacter, Klebsiella
used to detect and isolate Salmonella and Shigella from fecal, food and water samples
Hektoen agar
inhibit growth of non-enteric bacteria on hektoen
bile salts
inhibit growth of G+ bacteria on Hektoen
acid fuchsin and bromthymol blue dyes
inhibits the growth of most enteric bacteria on Hektoen
differential ingredients in Hektoen agar
Ferric ammonium sulfate, lactose, sucrose, salicin
microbes that can ferment at least one of lactose, sucrose, and salicin on Hektoen
orange or yellow colonies
microbes that can't ferment lactose, sucrose, and salicin on Hektoen
greenish-blue (Shigella), black if they produce H2S (most Salmonella)
Why do Salmonella and Shigella grow well on Hektoen agar when most other enterics do not?
They can survive in the Na2S2O3
long test tube with twelve separate compartments of varying media to test for enteric bacteria; gives a series of 5 numbers
Enterotube Multitest System
single tube medium that has phenol red dye, ferrous sulfate, sodium thiosulfate, and three sugars
Triple Sugar Iron agar
test using indole, methyl red, Vokes-Proskauer, and citrate used to differentiate between Escherichia, Enterobacter, and Klebsiella
IMViC test
rapidly ferment lactose to acids and gas; most of facultative flora in large intestine & feces; help indicate fecal contamination; facultatively anaerobic, G- rods; Escherichia, Klebsiella, Enterobacteria
Why is presence of e. coli in water a better indication of fecal contamination than if Klebsiella and Enterobacter were found in water?
E. coli is not a free-living microbe
measures ability of a microbe to produce tryptophanase which breaks tryptophan into indole, pyruvic acid, and ammonia
indole test
detects indole in IMViC test, combines with indole to make a cherry red reaction product
Kovac's reagent
Indole reactions of coliforms
positive: E. coli, negative: Klebsiella and Enterobacter
measures ability of microbe to ferment glucose to stable acidic end products; red at pH 4-5 and yellow at pH 6+
methyl red test
Methyl red reactions of coliforms
Acidic: e. coli, Basic: enterobacter and most klebsiella
measures ability of a microbe to produce acetoin, an intermediate in fermenting glucose to 2,3 butylene glycol
Voges-Proskauer test
detects acetoin in VP test by oxidizing acetoin to diacetyl which reacts with argine to form a pink complex
Barritt's reagent
VP reactions
positive: enterobacter and most klebsiella, negative: E. coli
measures the ability of a microbe to use citrate as its sole carbon source
Simmons citrate test
How is citrate utilization detected?
growth on agar surface, intense blue color of agar
why does the agar turn blue in citrate positive IMViC results?
CO2 production raises pH to alkaline
Simmons citrate reactions
positive: enterobacter and klebsiella, negative: E. coli
agar used for the indole test that also determines motility and H2S production of a microbe
SIM (sulfide, indole, motility) agar
facultatively anaerobic, catalase +, G+, oxidase + cocci that grow in grapelike bunches; found on skin and mucous membranes of humans and animals (moderate in throats); opportunistic pathogens; major cause of nosocomials
most important staphylococcal pathogen that causes many skin problems, meningitis, septicemia, etc; leading cause of infection in surgery, burn, and neonatal care units; drying resistant, antibiotic resistant strain
Staph aureus
Staph that infects wounds and colonizes foreign objects, causes local infection/septicemia
S. epidermis, S. capitis, S. hominis
difference between S. aureus and other Staphylococcus species
it can produce coagulase which clots blood
virulence factors of S. aureus
produces damaging extracellular enzymes/toxins, hemolysins, and sometimes a golden pigment
selective/differential medium for staphylococci
Mannitol Salts Agar
salt in MSA
selective ingredient that selects for salt tolerant bacteria
differential ingredients in MSA
mannitol and phenol red dye
mannitol and phenyl red dye role in MSA
fermented to acids which come from growing colonies; S. aureus diffuses into agar medium surrounding the colony, lowering pH and turning agar yellow
used to ID group A strep
causes 11% of all nosocomial infections; leading cause of in-dwelling device infection/septicemia
coagulase negative staphylococci
predominant microbes in throat, catalase-, oxidase-, aerotolerant, G+ cocci; grow in pairs
a and Y-hemolytic streptococci
catalase+, oxidase-, G+ irregular rods with clubbed ends that form V shapes and are abundant in throat
catalase+, oxidase+, G- coccus that is enhanced with a 10% CO2 atmosphere; grows in pairs and is abundant in throat
Moraxella catarrhalis
B-hemolytic staph
S. aureus
moderate numbers in throat, catalase-, oxidase-, obligately anaerobic, G- rods
Bacteroides, porphyromonas, prevotella
moderate numbers in throat, fastidious catalase+, oxidase+, G- cocci that grow in pairs on chocolate agar in 10% CO2
small numbers in throat, catalase+, oxidase+, oval shaped eukaryotic cells
small numbers in throat, fastidious catalase+, oxidase-, G- rods, grown on chocolate agar in 10% CO2
small numbers in throat, fastidious small, pleomorphic bacteria w/o cell walls; grow slowly into egg shaped colonies
To what groups do most human strep pathogens belong?
B-hemolytic and Lancefield groups A and B
most important streptococcus pathogens within hemolysis groups
a: S. pneumoniae, Y: enterococcus faecalis, B-Group A strep
further testing for B-hemolytic microbes to determine Group A strep identity
gram stain, catalase test, and sensitivity to A taxo disk
G+ coccus, a hemolytic, soluble in bile, inhibited growth by detergent optochin, has quelling reaction (capsule swelling)
S. pneumoniae
key trait used to differentiate staphylococcus and Streptococcus (both G+ cocci)
catalase (staph + and strep -)
enzyme that breaks down hydrogen peroxide; produced by all obligate aerobes/facultative anaerobes (those that carry out cell respiration)
how aerotolerant bacteria and microaerophilic bacteria survive in oxygen that makes H2O2
superoxide dismutase
biochemical marker used in IDing Neiserria and distinguishing Enterobacteriaceae from pseudomonas and other aerobic G- rods found in soil/water
cytochrome oxidase
oxidase reactions
positive: neisseria, pseudomonas aeruginosa negative: enterobacteriaceae
opportunistic pathogen that is common cause of nosocomials, UTIs, wound/skin infections, etc. oxidase+, aerobic, G- in soil and water
pseudomonas aeruginosa
most common cause of diarrheal diseases
infection with enteric pathogen (e.g. typhoid, salmonellosis, cholera, E. coli, polio, etc)
fecal-oral transmission cycle
enteric pathogens shed via feces, new hosts acquire them through contaminated food/water
factors that facilitate fecal-oral transmission
enteric pathogens have simple growth requirements, many human pathogens are normal flora for animals
commonly used bacteria to determine water safety
coliform bacteria
Does Klebsiella and Enterobacter presence in water indicate fecal contamination?
Not always, but likely
examines water sample's ability to ferment lactose to acids and gas
presumptive test
presumptive test
utilizes 3 aliquots of water in triplicates utilizing 10ml lactose broth each and an inverted Durham test tube
positive presumptive test
positive for coliforms if gas bubble fills 10% or more of Durham by 48 hrs at 37C; if none positive, stop test
confirmed test
positive presumptive tubes streaked onto EMB and incubated for 24h at 37C
positive confirmed test
E.coli-blue-black with green metallic sheen; Enterobacteria and Klebsiella-dark brown, colorless after 5 days; non-coliform-transparent, amber color
completed test
positive confirmed colonies subcultured in agar slant, gram stained, and tested for lactose fermenting ability in Brilliant Green Lactose Bile Broth
Positive Brilliant Green Bile Broth
possible fecal coliform/contaminated, and tested for gram stain using agar slant subculture
Short G- rod from +BGBB test
positive-contains fecal coliforms
enzyme produced by some S. aureus penicillin resistant strains; this gene is carried on a plasmid
small circular DNA molecules that replicate independently of cell's chromosome; transfered by conjugation and transformation
transfer of DNA from one cell to another by direct contact
transfer of genes from one cell to another by naked DNA in solution
transfer of DNA from one bacterium to another via bacteriophages
plasmids that carry antibiotic resistance genes