Micro Lab Final
Terms in this set (212)
morphology (cocci, bacilli, spirilla); arrangement (single, diplo, strepto, staphylo, tetrad, sarcina); gram reaction (Gram (-) organism, Gram (+) organism)
individual cells not touching
two cells or pair of cells touching end to end
chain of cells touching end to end
grape like cluster of circular/round cells
circular/round cells arranged in a square
circular/round cells arranged in a 3-D cube
red or pink cells
Gram (-) organism
Gram (+) organism
utilization of a sugar in the absence of O2 (a type of anaerobic respiration)
what is the purpose of a Durham tube?
traps/collects any gas that's produced during fermentation
purpose of fermentation tests (glucose, lactose, sucrose, xylose, trehalose, mannitol)
test the ability of the organism to ferment the specified carbohydrate
organism uses the _____ instead of the sugar resulting in _____
peptone, NH3 (ammonia)
true fermentation =
acid AND gas produced
only acid is produced
_____ coloration indicates acid production; pH indicator is ______
yellow; phenol red
catabolism is _____ _____ proteins; anabolism is _____ _____ proteins
breaking down, building up
purpose of MIO test (motility, indole, ornithine)
determines if an organism is 1) motile, 2) can produce indole, 3) can decarboxylate ornithine
ornithine is an _____ _____; pH indicator is _____
amino acid; bromcresol purple
love a SMALL amt of O2 and increased CO2 gas
to grow bacteria
purpose of dilution techniques:
reduce/dilute the original concentration of bacteria so that isolated colonies can form
what is a colony?
a visible population of cells that arose from one single bacteria cell
dilution techniques help us ascertain the:
types of bacterial cultures [pure (one type), mixed (more than one), contaminated (unwanted - aseptic techniques not followed)]
Bacteria in our lab are ALWAYS _____ charged.
simple stains are:
direct (methylene blue) and negative (nigrosin); used to determine morphology, size and arrangement
differential stain is:
gram stain (uses crystal violet - primary stain; Gram's iodine - mordant; decolorizing agent - ethyl alcohol; secondary stain - safranin); used to confirm morphology, arrangement, and Gram reaction
direct stain uses a(n) _____ stain (basic or acidic?)
negative stain uses a(n) _____ stain (basic or acidic)
Gram _____ bacteria have a _____ cell wall composed of _____
positive; thick; peptidoglycan ("Positive Peptidonly")
Gram _____ bacteria have a thin layer of _____ and an additional layer called _____ layer
negative; peptidoglycan; lippopolysaccharide (LPS) ("Negative two")
The Gram stain is a _______ stain that allows you to ____________________.
differential; classify bacteria as either gram-positive or gram-negative
The mordant, Gram's iodine, combines with the crystal violet in the cell to form a _______ compex
crystal violet-iodine (CV-I)
Gram ____ decolorize easy because the decolorizing agent dissolves the outer LPS layer and the CV-I complex washes out through the thin layer of peptidoglycan. CV-I cannot be washed out of _____ _____ cells.
The Gram stain is most consistent when done on young cultures of bacteria (less than ___ hours old) because when bacteria die, their _____ _____ degrade and may not retain the primary stain, giving inaccurate results.
24, cell walls
If you performed a Gram stain on human cells, what would happen?
Human cells do not have a cell wall, so they would not be affected by the Gram stain. The crystal violet would wash out.
three ways to identify an unknown microorganism:
stain organism (gram rxn, arrangement, morphology), culture bacteria (PURE culture required - one organism all by itself), perform biochemical testing (tells us about METABOLISM...what FOOD they can eat)
biochemical tests are:
selective, enrichment, differential
culture medium that ONLY allows your desired org to grow WELL (contain chemicals that prevent the growth of unwanted bacteria)
culture medium that contains special ingredients that ENHANCE growth of DESIRED microbe (usually liquid media, contain chemicals that enhance the growth of desired bacteria)
allows us to differentiate between organisms based on physical changes in medium (contain various nutrients that allow the investigator to distinguish one bacterium from another by how they metabolize or change the media with a waste product)
Substrate, water, exoenzymes --> outside cell; endoenzymes, energy, cellular material --> inside cell = waste products
simple sugars (glucose/fructose) - _____enzyme - create what waste byproduct?
complex sugar (lactose/sucrose) - ____enzyme - simple sugar - ____enzyme - create what waste byproduct?
exo; endo; acid
[building blocks of protein] amino acids (ornithine/tryptophan) - ____enzyme - create what waste byproduct?
endo; ammonia (NH3)
protein (peptone/gelatin) - ___enzyme - amino acid - ___enzyme - create what waste byproduct?
exo; endo; ammonia (NH3)
decarboxylation is the:
removal of CO from amino acid (removal of carboxyl group)
deamination is the:
removal of the amino group from an AMINO ACID
whenever substrates are catabolized, _____ are released. electron acceptors combine with the released _____, resulting in _____. Aerobic respiration - the final or terminal electron acceptor is _____.
electrons; electrons; reduction; molecular O2
anaerobic respiration =
the final or terminal electron acceptor is a molecule other than molecular oxygen
what is the purpose of a buffer?
keeps us from misinterpreting which substrate is utilized
If a bacterium cannot ferment glucose, why not test its ability to ferment other carbohydrates?
glucose is a simple sugar. if bacterium cannot ferment a simple sugar, then it will not be able to ferment a complex sugar.
the subunits that make up a protein are called ...
amino acids bond together by _____ bonds forming a small chain (_____) or a larger molecule (_______)
peptide, peptide, polypeptide
why is agar used as solidifying agent in culture media instead of gelatin?
bacteria can digest gelatin more readily than agar; also, gelatin melts at a lower temperature than agar (would not hold out as well under incubation temperature)
for breakdown, amino acids need a(n) ______; for breakdown, proteins need a(n) ______
motility, indole production, ornithine decarboxylation
glucose, ornithine (amino acid), tryptophan (amino acid), peptone, agar, pH indicator (bromcresol purple)
bromcresol purple - yellow=_____; dark purple=_____
acidic pH, basic/alkaline pH
In an MIO test, what do you add to detect indole production?
endoenzyme used in ornithine decarboxylation:
endoenzyme used in tryptophan deamination
Why look for black precipitate (FeS) in the butt instead of on the surface of an H2S test?
A precipitate will usually sink to the bottom of the container the reaction took place in
Catalase test - with sterile toothpick, touch center of colony & transfer to slide. drop hydrogen peroxide on the organisms & observe for bubbles (catalase-positive). What gas is in the bubbles?
O2 - oxygen [2H2O2 (hydrogen peroxide) --> 2H2O + O2
the microorganisms that establish more or less permanent residence without producing diseases
microorganisms that may be present for a few days or months
the relationship between normal microbiota and a healthy person may be classified as one of two types of _____
one type of symbiosis where one organism is benefited and the other is unharmed is a _____ relationship
another type of symbiosis where both organisms are benefited is a _____ relationship
the type of symbiosis where one organism gains while the other is harmed is called _____
in a disease state, the microorganism is a parasite and is harming its human host; this is called a _____
some members of the normal microbiota become parasites under certain conditions (normally good, but become bad). these are called _____
in order for a pathogen to cause a disease it must gain access to human body through the _____ _____ _____
portal of entry
Characteristics of skin
keratin, salty, acidic, oily
the dry layers of _____-containing cells that make up the _____ (outermost layer of skin) are not easily colonized by most microbes
skin is salty because of _____
skin has an acidic pH because of:
propionic acid produced by microbes
skin is oily because of:
sebaceous glands / oil glands produce sebum
_____, secreted by oil glands, inhibits bacterial growth, and _____ in perspiration create a _____ environment
Sebum, salts, hypertonic
perspiration and sebum are nutritive for certain microorganisms, however, which establishes them as part of the _____ _____ of the skin
the most predominant genus of bacteria on the skin is:
staphylococcus (cocci, Gram (+), staphylo arrangement)
normal microbiota of the skin tend to be resistant to drying and to relatively high salt concentrations. more bacteria are found in _____ areas, such as the _____ and the sides of the _____.
moist, axilla (armpit), nose
_____ _____ are present on hands and arms in contact with the environment.
Propionibacterium live in hair follicles on sebum from oil glands. The _____ _____ they produce maintains the pH of the skin between ____ and ____, which suppresses the growth of other bacteria.
propionic acid, 3, 5
most bacteria on the skin are ____-____ and ____-____; salt inhibits most ____-____ organisms
gram-positive; salt-tolerant; gram-negative
Staph aureus is part of normal microbiota of skin and considered a pathogen. S. aureus, which produces _____ (exoenzyme), is pathogenic because the enzyme _____ the fibrin in blood.
coagulase, coagulates (clots)
Coagulase test is used to distinguish _____ _____ from other species of _____.
staph aureus, staphylococcus
What is an mannitol salt agar (MSA) test used for?
to determine if staphylococcus ferments mannitol (pathogenic staph) or does not ferment mannitol (non-pathogenic staph)
ingredients of MSA test:
mannitol (sugar), salt, agar, peptone, pH indicator
MSA is what sort of test?
differential for mannitol fermentation and selective for salt tolerant organisms
MSA has growth=_____; no growth=_____; plate has yellow color change=_____; plate has fuchsia pink, red OR no color change=_____
salt tolerant; not salt tolerant; (+) mannitol fermentation (acid produced); (-) mannitol fermentation (ammonia produced)
what is the coagulase test (a.k.a. staph latex test) for?
if produces coagulase = pathogenic staph; doesn't produce coagulase = non-pathogenic staph
blue clumps - _____; no blue clumps - _____
(+) coagulase; (-) coagulase
characteristics of the throat
moist, warm, streptococcus - most predominant bacteria, microaerophilic environment
the moist throat is made of _____ _____ cells
the warmth and moisture allow what to occur in the throat?
more microbes to inhabit
the most predominant genus of bacteria found in the throat is:
Streptococcus - strepto arrangement, cocci, gram (+)
upper respiratory tract consists of:
nose and throat
lower respiratory tract consists of:
larynx, trachea, bronchial tubes, and alveoli
lower resp tract normally sterile bc of:
efficient functioning of the ciliary escalator
why is upper respiratory tract more susceptible to contamination with microorganisms?
because it is in contact with the air we breathe
examples of species of many different genera that are normal microbiota of the throat
Staphylococcus, Streptococcus, Neisseria, and Haemophilus
despite the presence of potentially pathogenic bacteria in the upper respiratory tract, the rate of infection is minimized by _____ _____
certain microorganisms of the normal microbiota _____ the growth of other microorganisms through competition for _____ and production of _____ substances
suppress, nutrients, inhibitory
_____ species are predominant organisms in throat cultures, and some species are the major cause of bacterial sore throats (acute pharyngitis).
streptococci are identified by biochemical characteristics, including hemolytic reactions, and antigenic characteristics (hemolysins are produced by strep while growing on blood-enriched agar). three patterns of hemolysis can occur on blood agar:
beta-hemolysis, alpha-hemolysis, gamma-hemolysis
complete hemolysis, giving a clear zone with a clean edge around the colony (complete lysis, or destruction, of RBCs)
beta-hemolysis (results=clearing of medium)
green, cloudy zone around the colony. partial destruction of red blood cells due to bacteria-produced hydrogen peroxide (partial lysis of RBCs - non-pathogenic)
alpha-hemolysis (results=greenish coloration/darkening of medium)
no hemolysis, and no change in the blood agar around the colony (no lysis of RBCs - nonpathogenic strep)
gamma-hemolysis (results=no change in medium)
which streptococci are frequently pathogens?
beta-hemolytic streptococci (pathogenic, so you might want to take a "beta" path)
using a blood agar plate for throat culture is testing for _____
blood agar distinguishes _____ _____ from _____ _____ based upon hemolysis
pathogenic streptococci, nonpathogenic streptococci
blood agar test ingredients
sheep's blood, agar, peptone
blood agar is what kind of test?
enrichment medium (due to sheep's blood which enhances growth of selected microbe) and differential for types of hemolysis (color change)
When staining an unknown microbe, you should use _____ _____ to help confirm you performed the Gram stain correctly 100%.
normal flora of the mouth
Streptococcus mutans and S. sanguis - live on teeth; S. salivarius - lives on the tongue
sucrose-->exoenzyme-->glucose--> endoenzyme-->acid - indicates:
S. mutans and S. sanguis
sucrose-->exoenzyme-->fructose--> endoenzyme-->levan - FRUCTOSE / LEVAN indicates:
sucrose-->exo-->glucose-->endo--> dextran. the dextran capsule enables the bacteria to adhere to surfaces in the mouth.
S. salivarius to the tongue and S. sanguis/S. mutans to the teeth
_____ forms a sticky capsule (glycocalyx) around S. sanguis and S. mutans
sucrose-->exo-->fructose-->endo-->lactic acid - erodes tooth enamel - indicates:
_____ production increases the extent of dental caries.
# of S. mutans present in stimulated saliva correlational to formation of _____ _____
The media used contains sucrose to promote capsule formation and _____ inhibits the growth of most oral bacteria, except S. mutans
mitis-salivarius-bacitracin (MSB) [called a contact plate or Rodac plate]
The _____ _____ creates an artificial anaerobic environment (devoid of oxygen) which permits the growth of anaerobic bacteria.
Anaerobic jar (Brewer's Gas Pak) - without oxygen: the anaerobic jar employs a chemical reaction to generate _____ gas. In the presence of a palladium catalyst, they hydrogen gas will react with free _____ in the air to form water. This reaction removes the _____ from the sealed atmosphere. The jar is then incubated at the desired temperature.
hydrogen, oxygen, oxygen
ALL OF OUR TESTS ARE DIFFERENTIAL EXCEPT FOR:
sabouraud agar (SAB), tomato juice agar (TJA) and mitis-salivarius-bacitracin (MSB)
MSA, MSB, MAC, SF broth, SAB
blood agar (BA), sucrose blood agar (SBA or sSBA), tomato juice agar (TJA)
sucrose blood agar ingredients:
sucrose, blood, agar, peptone (backup)
substrates of sucrose blood agar, which are used to grow S. mutans, S. salivarius, S. sanguis:
sucrose, blood, peptone
mitis salivarius bacitracin (MSB) ingredients:
bacitracin (antibiotic), typan blue, agar, sucrose, tellurite solution
purpose of MSB:
to grow only S. mutans
which 3 ingredients make MSB selective?
bacitracin, typan blue, tellurite solution
Why is it not recommended to perform catalase test directly on blood agar?
because the red blood cells themselves may produce a weekly positive catalase reaction
Sucrose Blood Agar Procedure - the 1st saliva sample must be diluted using _____ dilution. This dilutes the saliva enough so that colonies can form when the plate is inoculated.
formula for calculating dilution factors: DF#1
DF#1 = amt transferred to #1 / total volume of #1 AFTER transfer (example: 1 ml / 99ml+1ml = 1/100 or 1:100)
formula for calculating dilution factors: DF#2
DF#2 = amt transferred to #1 / total volume of #1 AFTER transfer X amt transferred to #2 / total volume #2 AFTER transfer (example: 1/100 X 1/100 = 1/10,000)
why do the stomach and small intestine have relatively few microorganisms?
a result of the hydrochloric acid produced by stomach and the rapid movement of food through the small intestine
microbial populations in the _____ _____ are enormous. There are more microbes present in our _____ than in other areas of GI tract.
large intestine; colon (*
most diseases of the gastrointestinal system result from the ingestion of _____ or _____ that contains _____ microorganisms
food, water, pathogenic
Gram-_____, _____ anaerobic _____ are a large and diverse group of bacteria that includes the enteric family.
negative, facultatively, rods
Most organisms don't cause us harm as long as they:
stay exactly where they belong.
2 BROAD categories of GI microbes:
enterics and non-enterics
_____ make up less than 10% of population, they are facultative anaerobes, bacilli (rod-shaped result), nonendospore formers, and all are gram-negative
_____ make up greater than 90% of the population, they are strict anaerobes (can't break down hydrogen peroxide), cocci and bacilli, a few that do form spores (clostridium), some are gram (-), some are gram (+)
subcategory for enterics:
coliform and non-coliform
Media have been developed to differentiate bt lactose-fermenting enterics and nonlactose fermenting enterics. Lactose fermenters are called _____ and are generally _____ _____.
coliforms, not pathogenic
Non-coliforms do not ____ ____ and are frequently _____.
ferment lactose, pathogenic
The nonlactose-fermenting group includes such pathogens as _____ and _____.
MacConkey agar (MAC) is used to grow _____
MAC is _____ in that bile salts are inhibitory to gram-_____ organisms; thus they allow the medium to selectively culture gram-_____ organisms.
selective, positive, negative
MAC is differential in that lactose-fermenting organisms (coliforms) give ____, ____ colonies and nonlactose fermenters produce _____, _____ colonies
red, opaque ("color"forms); colorless, translucent ("noncolor"forms)
MAC growth = _____; no growth = ______
gram (-) organism; not gram (-)
lactose, peptone, agar, neutral red (pH indicator)
If the growth on MAC plate turns red, hot pink, or magenta:
it eats lactose (+ lactose fermentation) and has low pH (non-coliform)
If the growth on MAC plate turns tan/beige or is colorless:
it eats peptone (- lactose fermentation) and has a high pH (coliform)
Triple Sugar Iron (TSI) slant used to further categorize _____ after they are grown on MAC plate. If ferments only glucose, phenol red indicator will turn _____;
if organism in TSI slant ferments _____, _____ and/or _____, the butt and slant will turn yellow and remain yellow for days due to increased level of ____ production
glucose, lactose, sucrose, acid
If black precipitate is produced in TSI slant, this indicates ____ ____ has been produced due to desulfurization of sulfur-containing amino acids
hydrogen sulfide (H2S)
TSI slant - will turn darker shade of red if aerobic - red slant and red butt =
(-) for sugar fermentation
sucrose 1%, lactose 1%, glucose 0.1%, agar, peptone, phenol red (pH indicator), ferrous sulfate (helps detect H2S (hydrogen sulfide production)
SF broth is used to detect the presence of _____
enterococci (Enterococcus faecalis a.k.a. Streptococcus faecalis)
presence of enterococci can be used to indicate _____ contamination
Enterococci are ____-_____ cocci, non-enteric, _____ anaerobe
SF broth ingredients:
1) sodium azide (inhibits growth of gram-negative bacteria, 2) glucose (substrate), 3) bromcresol purple (pH indicator)
SF broth is _____ for enterococci; _____ for glucose fermentation
tomato juice agar (TJA) is used to grow _______, which is gram-_____ bacilli
Lactobacillus is ___-_____, _____ anaerobe because it is gram (+)
tomato juice, agar, peptonized milk, peptone
MAC and TSI used to grow _____; TJA used to grow _____; SF broth used to grow _____.
enterics, Lactobacillus, Enterococcus
In the urinary tract, normal microbiota resides in the _____ only; the bladder, kidneys and ureters are _____
when getting a urine culture, a clean catch or midstream catch sample must be obtained because:
some of the bacteria is flushed off of the skin around the urethra
traditional culture media used for urine culture:
1) MAC [used to grow enterics - greater than 90% UTI infections are caused by enterics due to fecal organisms (opportunists)]; 2) Blood Agar (BA) - enrichment medium - allows all the microbes present in urine sample to grow. allows calculation of total # of microbes that were present in original sample
allows us to perform calculations bc we know EXACT volume of sample that was used
calculation for Colony Forming Units per Milliliter of Urine
cfu/ml = # of colonies / amount plated (volume of urine in milliliters) example, 10 microliter loop is 0.01 milliliter
Criteria involved with possible UTI:
1) Blood agar ONLY - if cfu / ml calculation is greater than or equal to 10 to the fifth power. 2) MacaConkey ONLY - if cfu / ml calculation is greater than or equal to 100.
disease is ALWAYS present in population but in LOW #s:
lots of people contract the same disease within a SHORT period of time in a LOCALIZED area:
epidemic that's occurring in MULTIPLE areas of the world
the study of a) why diseases occur, b) how they occur / are spread, c) where does it occur, d) how to prevent, spread, cure and/or treat disease
can NOT be transmitted from host to host
noninfectious (noncommunicable) diseases
CAN be spread from host to host
infectious (communicable) diseases
3 methods of communicable disease transmission:
1) direct contact (sex, kissing, handshake) / droplet infection (sneezing, coughing); 2) Fomites; 3) Vectors
inanimate objects that are contaminated with microbes
insects transmit the disease from host to host
vectors (example mosquitoes)
# of NEW cases of disease in a population
the TOTAL # of cases of disease in a population
prevalence calculation formula:
# of cases of disease / Total # of people in population = 1 / 100 OR 1 out of 100 people OR 1%
All communicable diseases are caused by _____
Do all people that contact an infected person acquire the disease?
No all the people will not be infected.It depends upon the immune system and the level of infection and mainly on the type of disease. If the person who get contact with the infected person is already sensitised for that disease he may not get the disease
How can an epidemic stop without medical interventions (quarantine, chemotherapy, vaccines)?
An epidemic consists of an infection being transmitted from one individual to another. Each individual infected either dies or or overcomes the infection. In either case he is no longer a source for further infection. Some individuals in any large population will already be immune and never become a source for further infection. The epidemic stops when the people susceptible to it are too few and too scattered in the population to keep this cycle going.
a flag or marker that helps immune system distinguish bt self vs. nonself
involves testing which antigens are present on a patient's RBC
Examples of antigens:
A-antigen, B-antigen, D-antigen (a.k.a. Rh-antigen)
Blood typing ONLY involves _____.
Blood sample is mixed externally with _____ and hemagluttination reaction is noted (clumping of RBCs).
antisera (Anti-A -->A antigen, Anti-B-->B-antigen, etc.)
Agglutination reactions occur between high-molecular weight, particulate antigens and antibodies. Because many antigens are on cells, these reactions lead to the clumping, or _____, of cells. When the cells involved are ___ ___ ___, the reaction is called hemagglutination.
agglutination, red blood cells
A+ blood has ___-antigen on RBCs and Rh/D antigen
In A- blood, only the ___-antigen is present on RBCs.
Type A blood has ____ antibodies in the bloodstream; thus cannot receive RBCs that have a(n) ___-antigen on them
Type B blood has ____ antibodies in bloodstream; thus cannot receive RBCs that have a(n) ___-antigen on them
Type AB blood has ___ antibodies in bloodstream; thus, can safely receive RBCs from anyone as long as they have the same D/Rh antigen (or lack thereof)
type O blood has ____ antibodies in bloodstream; thus can NOT receive RBCs
what would you get if you received an incompatible blood type?
what is the liquid part of blood called?
If I do not have D/Rh antigen, then:
I can not receive blood that has D/Rh antigen.
what is the purpose of the DBCC?
to determine the % of WBCs present in patients blood. this can indicate health or illness