MICROBIOLOGY Flashcards
Capsule can be used for
Serotype by swelling
To demonstrate capsule, grow the culture on media containing
- milk
* serum
The Quellung test depends on the antigenic specificity of the
capsule
Dark staining granules
Metachromatic
Organisms that vary in size and shape
Pleomorphic
In the bacterial growth cycle, growth ceases because nutrients are exhausted or toxic metabolic products have accumulated in the
Stationary/Plateau Phase
Bacteria form spores
- Clostridium
* Bacillus
Bacteria that grow in the absence of athmospheric (free) oxygen and obtain oxygen from oxygen containing compounds
Anaerobes
The temperature at which bacteria grow best
Optimum
A slimy colony on blood agar medium indicates which of the following characteristics may be present?
Organism has a capsule
On blood agar plates a small zone of alpha-hemolysis surrounded by zone beta hemolysis after refrigeration
Alpha-prime
When using fractional sterilization the sequence
Heating (kill vegetative bacteria)
Incubation (spores germinate)
Heating (kills remaining vegetative bacteria)
Most effective method of sterilization
Autoclave
Used for quality control for the dry heat oven
Bacillus subtilis
Filters can give 100% sterility
Millipore (0.22um)
Media that cannot be heated can be sterilized by
Filtration
Which of the following is not a disinfectant?
70% alcohol
Iodophors are composed of
Iodine and Detergent
Quarternary ammonium disinfectants are easily inactivated by
Organic Material
Term that describes a process or treatment that renders a medical device, instrument or environment surface to handle
Decontamination
Gram positive bacteria stain
Purple
The mordant used in the Ziehl-Neelsen acid fast stain
Heat
Smear for an acid fast stain fixed
Slide warmer at 65C for 2 hours
Acid fast bacteria appear what color microscopically
Red
Acid fast organism in tissue are best stained by
Kinyoun
In the Ziehl-Neelsen staining mtd, the decolorizer
Alcohol + HCl
An exmaple of negative stain
India Ink stain
NOT gram negative
Peptococcus
NOT an anaerobe
Campylobacter
If a patient is taking antimicrobials, which can neutralize the antimicrobials
Thiol broth
From a bronchial washing, organisms are seen on a Gram stain, but no growth occurs aerobically and anaerobically. This most likely due to
Inhibition by antibiotic therapy
Use to remove antimicrobials before culturing
Antimicrobial Removal Device
Sodium Polyanethol sulfonate may be used as an anticoagulant in blood cultures because it
- Prevents phagocytosis
* Neutralizes the bactericidal effect of human serum
Most abundant normal flora in throat culture
Alpha hemolytic Streptococcus
Most common pathogen in throat culture
Group A Streptococcus
Why must blood agar plates for throat cultures can be incubated aerobically and anaerobically when beta hemolytic streptococci are suspected
Some may produce beta hemolysis under aerobic conditions
Nasopharyngeal swabs are recommended for the detection of carriers such as
Haemophilus influenzae
Neisseria
Bordetella pertussis
Todd- Hewitt broth is recommended for
Culture of beta-hemolytic streptococci for fluorescence microscopy
Phenylethyl alcohol is used in media to
Inhibit gram negative bacteria
Why is a first morning urine specimen preferred for urine cultures
Specimen is more concentrated
what indicates vaginal or urethral contamination of urine
Many squamous epithelial cells
In the pour-plate mtd for colony counts, how does the amount of agar added affect the dilution
Dilution is not affected
Smears of CSF are usually stained with
Gram stain
India ink stain
Smears of CSF are prepared from
CSF sediment
Test for bacterial antigen on cultures isolated from CSF is more sensitive and faster
Latex agglutination tests
Staphylococcal protein A coated with antiserum is used in which of the serological test on CSF
Coagglutination test
NOT cause of venereal disease
Staphylococcus aureus
Using sheep blood agar plates eliminates beta hemolytic
Hemophilus
A positive tube coagulase test is observed for
clotting of plasma
Type of plasma is used for the tube coagulase test
Rabbit
Some citrate positive organism cause a false positive tube coagulase test because the organism uses the citrate
and releases Calcium
A nonhemolytic, catalase positive, coagulase negative, gram possitive coccus
Staphylococcus epidermidis
Preferred mtd of differentiating S.aureus from S. epidermidis
Coagulase test
Staphylococci that cause of UTI in young females
S. saphrophyticus
S. aureus can be isolated from stool cultures by the use of
Medium with 7.5% salt concentration
Most common cause of bacterial food poisoning in the US
Staphylococcus aureus
Gram positive cocci that ferment glucose
Staphylococci
Produced by beta hemolytic streptococci, is oxygen stable and non antigenic
Streptolysin S
Cultures for beta hemolytic streptococci must include
Anaerobic incubation to detect hemolysis in all strains
Destroyed by oxygen
Streptolysin O
Group A beta hemolytic streptococci
Bacitracin Susceptible
Streptococcus pneumoniae
Optochin susceptible
Alpha hemolytic streptococci
Optochin resistant
Group B, beta hemolytic streptococci
Hippurate hydrolysis positive
CAMP test positive
Enterococcus
Bile esculin positive
Whenever a biochemical test is substituted for a serological test is reported
As “presumptive” with the name of the biochemical test
CAMP is a factor produced by group B beta-hemolytic streptococci that
Enlarges the zone of lysis formed by staphylococcal beta-hemolysin
A positive Quellung test is
From capsular swelling due to an antigen-antibody reaction
Serological test used for a confirmatory test for streptococci
Phadebac test
Fluorescent antibody test
Lancefield precipitin test
When performing a bacitracin differentiation test for group A beta hemolytic streptococci, use disks that have how many units?
0.02-0.04 units
Group A streptococci
“strep throat”
Scarlet fever
Group B streptococci
Major pathogen of the newborn
Alpha hemolytic streptococci
Subacute bacteria Endocarditis
What do optochin and bacitracin tests have in common
Growth inhibition is a positive result
Bile esculin test is used to differentiate
Group D streptococci from other strep
Hippurate hydrolysis is used to differentiate
Group A from Group B streptococci
A bacitracin resistant, hippurate hydrolysis positive, bile esculin positive, beta hemolytic Streptococcus that grows in 6.5% NaCl
Enterococcus
Pneumococci that are resistant to penicillin should be tested for
Production of beta lactamase
Gram negative, coffee bean shaped diplococci with adjacent sides flattened
Neisseria
Diagnosis of gonorrhea in males can be made from
Positive urethral smear
Symptoms
History
Specimens may be appropriate for culturing Neisseria gonorrhea
Eyes
Rectum
Oral cavity
Medium choice for culturing gonococci and meningococci
Modified Thayer Martin
Differentiates Thayer Martin medium from Modified Thayer Martin medium
Trimethoprim lactate
Thayer Martin medium is basically an
Enriched chocolate agar
Color of a positive oxidase test
Dark Purple
Genera that are oxidase positive
Moraxella
Aeromonas
Neisseria
Techniques that can be used when performing the oxidase test
Put a drop of reagent on the colony
Rub colony on a filter paper strip and add a drop of reagent
Rub the colony on a piece of filter paper containing the reagent
What do “PPNG” gonococci produce
Penicillinase-producing gonococci
Methods for testing for the production of beta lactamase
Chromogenic cephalosphorin mtd
Acidometric mtd
Iodometric mtd
Positive reaction for the beta lactamase chromogenic cephalosphorin mtd
Color change
An oxidase positive, gram neg coccus from a throat culture
Neissseria
A fastidious, oxidase positive, gram negative coccus from rectal swab
Neisseria gonorrhea
Neisseria meningitidis degrades what sugars
Glucose
Maltose
Which of the following test can give a presumptive identification of Branhamella catarrhalis if the isolate is a gram neg diplococcus that is oxidase positive and isolated from middle ear fluid
Beta lactamase test
Why should beta lactamase tests be performed with growth from primary isolation media
Plasmid coding for the enzyme may be lost in subculturing
Purpose of potassium tellurite in tellurite medium
Inhibits the normal flora
Potassium tellurite medium produces what color colonies of Corynebacterium diphtheriae
Gray-black
When culturing Corynebacterium diphtheriae, which of the following media will enhance pleomorphism and granule production
Leoffler serum agar
Pai coagulated egg medium
Morphology of Corynebacterium diphtheriae
Gram positive, nonmotile rods
The term “pallisading” “picket fence” and “chinese letter” describe the common arrangement of cells of
Corynebacterium
Babes Ernst granules are characteristics of
Corynebacterium diphtheriae
Considered diphtheroids
Corynebacterium xeroxis
Corynebacterium JK
Diphtheroids found in the normal throat
Corynebacterium pseudodiphtheriticum
Elek test is for the detection of
Corynebacterium diphtheriae toxin, in vitro
The morphological cycle of Rhodococcus equi from coccoid to rod form tales
24 hours
Gram positive to gram variable coccobacillus
Listeria monocytogenes
Listeria monocytogenes produces a positive of what biochemical test
Catalase
Virulence test for Listeria monocytogenes
Anton test
Refrigeration of the specimen for several months may enhance isolation of
Listeria monocytogenes
Differentiate Listeria monocytogenes from the corynebacteria
Non motile and salicin negative
Spore forming cells in bamboo pole arrangement of bacillus anthracis can be found in
Cultures
Aerobic, gram positive, sporulating rods can cause food poisoning
Bacillus cereus
Very large gram negative rods with spores are seen in a non turbid thioglycollatebroth culture of spinal fluid, but there is no growth anaerobically or aerobically. This most likely due to:
Bacillus sp. in the dehydrated medium are killed and made gram negative by autoclaving the medium
Ziehl-Neelsen acid fast staining:
- Primary dye
- Mordant
- Decolorizer
- Counterstain
- Carbol fuchsin
- Heat to speed staining
- Acid (3% HCl) alcohol
- dilute methylene blue
Color of non acid fast bacilli stain
blue
Acid fast bacilli retain the dye
Carbol fuchsin
An acid fast stain that does not use heat as a mordant
Kinyoun stain
Media is clear so that the colonies of mycobacteria can be examined microscopically
Middlebrook 7H11
Color of negative enzymatic hydrolysis of Tween 80 test
Amber
Mycobacterial cultures should be incubated
in 5% Carbon Dioxide
A slow growing, unbranched, acid fast rod that is nitrate reduction negative and niacin negative
Mycobacterium bovis
Mycobacterium tuberculosis is best differentiated form M. bovis by
Niacin and nitrate reduction test
Slow growers
M. kasasii
MAI
M. tb
Differential test for identifying the species of Mycobacterium splits phenolphthalein form tripotassium phenolphthalein sulfate within 2-3 days
Arylsulfatase test
Used for identification of mycobacteria
Growth rate
Pigment production
Biochemical reactions
One tube of Lowenstein-Jensen medium is incubated covered with foil and one tube is incubated uncovered. When is the covered tube observed
When growth appears on the uncovered tube
Group IV (rapid growers)
M. fortuitum
M.chelonae
M. phlei
M. smegmatis
Macrophages containing acid fast bacilli
Lepra cells
Acid fast rods in a specimen from nasal mucosa
Are not a diagnostic point
The Fite-Faracco acid fast stain is different from other acid fast stains because it uses
Hematoxylin rather than methylene blue as a counterstain
Specimen usually used for the diagnosis of Hansen’s disease
Tissue juice
Lumpy jaw is caused by
Actinomyces israelli
NOT anaerobic
Actinomyces
Urease Positive
Nocardia
Nocardia will grow on any media that does not contain
Antibiotics
Haemophilus influenzae (dis)
Meningitis
H. ducreyi (dis)
Ulcerative chancroid
H. aegypticus (dis)
Pink eye
H. haemolyticus (dis)
Normal flora in respiratory tract
Medium preferred for the culture of most Haemophilus
enriched chocolate agar
A fastidious, small to filamentous, gram neg rod from nasopharyngeal swab
H. influenzae
Cultures of Staphylococcus supplies what for cultures of Haemophilus
V factor
Type of blood used in blood agar plates for better production of beta hemolysis of Haemophilus
Horse
Organism cause whooping cough
Bordetella pertussis
Specie of Bordetella that is urease and oxidase positive
B. parapertussis
Preferred medium for the isolation of Bordetella pertussis
Charcoal-cephalexin agar
A Brucella isolate that does not produce H2S, does not require CO2 and is not inhibited by thionin or basic fuchsin
Brucella melitensis, biotype 1
Gram negative, fastidious bacillus that has been isolated from air conditioning towers
Legionella pneumophila
Gram negative, fastidious bacillus that is difficult to stain by Gram stain
Legionella pneumophila
A relatively slow growing and fastidious, gram negative rod that produces a characteristic brown pigment on Feeley-Gorman agar
Legionella pneumophila
Most sensitive for the diagnosis of infections with Legionella pneumophila
Detection of soluble microbial products in body fluids
Best medium for the isolation of Legionella
Buffered charcoal yeast extract agar
Composition of Campy gas mixture
10% CO2
5% O2
85% Nitrogen
“Rice water” stools often contain
A pure culture of Vibrio cholorae
A curved, gram negative rod that is non fermentive, nitrate positive and microaerophilic
Campylobacter jejuni
Campylobacter is an
Obligate microaerophile
A gram negative, slender, curved rod with a single polar flagellum is the cause of gastroenteritis and best isolated on
Campy blood agar
Clue cells may be found in infections with
Gardnerella vaginalis
Mycoplasma are not true bacteria because they
Have no cell wall
Microorganisms form colonies that are embedded in the agar giving a fried egg appearance
Mycoplasma pneumoniae
Best method for the identification of Mycoplasma species
Inhibition of growth by specific antisera
Purpose of enrichment fluid media when culturing Enterobacteriaceae
Decreases lag phase of pathogens
Extends lag phase of normal flora
Crystal violet Bile salts Neutral red Lactose Brick red colonies Colorless colonies
MacConkey medium
Eosin Y and Methylene bllue
lactose and sucrose
black or purple colonies
colorless colonies
Holt harris EMB medium
Eosin Y and Methylene bllue
Lactose only
black or purple colonies
colorless colonies
Levine’s EMB agar
Non fermenters produce what reaction in triple sugar iron (TSI)
Alkaline slant, alkaline or neutral butt
Hydrogen sulfide indicator in Triple Sugar Iron (TSI)
Sodium thiosulfate
IMViC is a series of which of the following tests
Indole
Methyl Red
Vogues-Proskauer
Citrate
Indicator of methyl red test
Methyl Red
Most Enterobacteriaceae give what type of Methyl Red and Voges-Proskauer reactions
Opposite
Indicators of Simmons citrate agar
Bromthymol blue
Lactose only Bile salts and brilliant green Neutral red Citrate to inhibit coliforms and Proteus Red colonies Colorless colonies
Salmonella- Shigella (SSA)
Glucose (dextrose)
Ferrous sulfate
Brilliant Green only; inhibitor for gram positive organisms and coliforms
Black colonies surrounded by black zone with metallic sheen
Green colonies
Bismuth-sulfite (BSA)
Phenol Red
Ferric (ammonium) citrate + sodium thiosulfate
xylose, lactose, sucrose
Red colonies with black center
Xylose-Lysine deoxycholate (XLD)
Lactose, Sucrose, Salicin
Bromthymol blue
Blue-green colonies with black center
orange salmon pink colonies
Hektoen Enteric Agar (HEA)
Whitish snowflake colony surrounded by brilliant red agar
Brillian Green Agar
Amino acids that are used in the test for decarboxylase
Lysine
Ornithine
Arginine
Why the testing 3 amino acids would require 4 tubes
1 tube is needed for control
Enzyme that removes the amino group (NH2) from an amino acid
Deaminase
Organisms that produce urease do what to medium
Hydrolyze urea to NH4OH
Hydrogen sulfide production, other than in TSI agars requires
An organic source of sulfur
A source of metal
Negative result in the malonate utilization test
Green
Yellow
Gelatinase breaks down gelatin to
Amino acids
What indicates a positive DNAse result after 0.1 N HCl is added to plate
Agar clears around the colony
The DNAse test is based on
Destruction of sugars in the culture medium
If the negative nitrate reduction test does not change color after the powdered zinc is added, how it is reported?
Positive
Salmonella, Shigella, E.coli and Serratia are all
Members of Enterobacteriaceae
Purpose of the ONPG test
Detects slows lactose fermenters
From urine culture: Gram negative rod TSI= A/A +G IMViC= ++-- Urease= negative
Escherichia coli
From Blood Culture: Gram Neg Rod TSI= A/A +G IMViC= --++ motile Lysine decarboxylase= negative No Capsule
Enterobacter cloacae
From Blood Culture: Gram Neg Rod Urease and Phenylalanine deaminase = positive TSI= K/A +G -H2S Lysine Decarboxylase= negative Ornithine Decarboxylase= positive Motility= positive or negative
Morganella morganii
From Stool Culture: Gram Neg Rod Urease and Phenylalanine Deaminase = negative TSI K/A -G -H2s Lysine decarboxylase= negative Non motile
Shigella spp.
Allows viability of acid production by oxidizers in oxidation-fermentation (OF) medium
Peptone content is low
From stool culture: Gram Neg Rod Urease and Phenylalanine deaminase= negative TSI= K/A +G +H2S Motile Lysine Decarboxylase= positive Indole= positive
Aeromonas hydrophila
Oxidase positive
Aeromonas hydrophila
Moraxella osloensis
Reagent used for string test
0.5% sodium desoxycholate
Any organism that is indole positive and nitrate reduction positive is also
Cholera red- positive
How many tubes of oxidation-fermentation media is/are inoculated and what precautions should be taken?
2 tubes, one covered with oil so air is excluded
Normal flora of the skin
Acinetobacter calcoaceticus biotype anitratus
PRAS means
Prereduced, anaerobically sterilized
Why should thioglycollate broth be boiled for 10 minutes before being used
To drive off oxygen
Nagler agar is selective medium for
Clostridium
Peptococcus and Peptostreptococcus are both
Anaerobic, Gram Positive Cocci
Propionibacteria are
Anaerobic, Gram Positive Rods
A gram neg, anaerobic coccus that produces a red fluorescence under ultraviolet light
Veilonella
Anaerobic, gram positive rods produce terminal “lollipop” spores
Clostridium tetani
Anaerobes causes an antimicrobial associated diarrhea
Clostridium difficile
Clostridia produca a double zone of hemolysis around colonies on blood agar
Clostridium perfringens
Mycoplasmas pneumoniae is incubated
Aerobically, in a sealed container, in carbon dioxide
A positive urease test for ureaplasma is indicated by a
Brown halo surrounding the colonies
Organisms produces no haze in a broth culture
Ureaplasma urealyticum
Cause Primary Atypical Pneumoniae
Mycoplasma pneumoniae
Has both RNA and DNA
Rickettsia
Chlamydia
Rickettsia are transmitted by
Arthropod vectors
NOT caused by Rickettsia
Typhoid fever
Have a bacterial cell wall
Rickettsia
Chlamydia
Small non motile, coccobacillus that is cultured in yolk sac of a chick embryo
Rickettsia
Chlamydia are cultured in
McCoy cells
“TRIC” conjunctivitis includes
Inclusion conjuctivitis
Trachoma
Serological test done for Chlamydia trachomatis on genital smears
Direct FA using monoclonal Abs
Most common tick-borne disease in the US
Lyme disease
What is erythema chronicum migrans (ECM)
Cardinal sign of Lyme disease at site of tick bite
What are broad spectrum antibiotics
Act against gram negative bacteria
Act against gram positive bacteria
Acts against bacterial and non bacterial organisms
Substances produced by microorganisms, that in very small amounts inhibit other microorganisms are called:
Antibiotics
Inhibit the growth of the organism
Bacteriostatic agents
The time it takes half a dose of antibiotic to dissappear from the blood is called
Half- life
Resistance to an antibiotic can be transferred from a resistant to a susceptible organism
Extrachrosomal plasmid
In the Kirby Bauer susceptibility test, the 0.5 McFarland std used to
Adjust the turbidity of the inoculum
After inoculating the Mueller-Hinton plates for the Kirby Bauer susceptibility test, how long should the plates dry before adding the disks
3-5 minutes
Not more than 15 minutes
How does one measure the zone of growth inhibitor, for the Kirby-Bauer susceptibility test
On the other side of plate
With the unaided eye
Using a ruler, caliper or template
What does the size of the zone of growth inhibition correlate with if the correct procedure has been used
Minimum Inhibitory Concentration
If there is too much moisture on the surface of a Mueller-Hinton plate when performing a Kirby Bauer susceptibility test, what will happen to the growth
smaller zone
Best indicator of poor storage
Penicillin and Methicillin
In Mueller-Hinton agar, what can cause increased resistance of Pseudomonas aeruginosa to aminoglycosides
Increased Calcium and Magnesium
When doing a susceptibility test with sulfonamides there are two concentric zones around the disk. How should the zone be measured?
Measure the diameter of the outer zone
The lowest concentration of drug that will kill all but the minimum defined proportion of viable organism after incubation for a fixed time under a given set of conditions is definition of the
Minimum lethal concentration
Minimum bactericidal concentration
For quality control when monitoring reagents, how often should reagent DISKS be checked
When container is FIRST opened
Once each WEEK of use
How often should CATALASE, OXIDASE and COAGULASE reagents be tested
When vial is FIRST opened
Once each DAY of use
Record TEMPERATURES of incubators, water baths, heating blocks, refrigeration, freezers and thermometers
At each TIME of use
At the ‘beginning’ of each DAY
At the ‘end’ of each DAY
Check the face velocity of SAFETY CABINETS each
MONTH
Setting of RPMs marked on the face of the rheostat control on the CENTRIFUGE should be checked once
MONTHLY
