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150 Cards in this Set
- Front
- Back
T/F the "miscellaneous gram negative bacteria" (Pseudomonas, Acinetobacter, Stenotrophomonas, Burkholderia, Bordetella, and Pasteurella) are normal flora of the human body
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False. They are not normal flora of humans but they can trasiently infect people without symptoms
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What types of infections develop from Pseudomonas aeruginosa
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noscomial pneumonia, UTI, bacterima, and localized infections following surgey or burns
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Descrbie the prognosis following Pseudomonas aeruginosa infection
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prognosis is poor. The organism is resistant to most antimicrobials and mortalitly rates are high.
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T/F P. aeruginosa can replicate in hospital environments such as sink drains, respirators, plants and even weak antiseptics and standing water
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True
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You have a gram negative bacilli that produces pigment on BAP. It is most likley (2)
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P. aeruginosa or Stenotrophomonas maltophilia
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Where can P. aeruginosa be found naturally?
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widely dispersed in the environment
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Where can Acinetobacter species be found in the environment
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widely dispersed in soil or water
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Where does Acinetobacter colonize humans when it transiently infects them?
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moist areas (mucosal surfaces)
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Describe the cellular morphology of Acinetobacter
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coccobacillary, can be diplococci
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Which o the mis. gram negative bacilli grow on MacConkey's plates
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all except Pasteurella
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Which of the mis. gram negtaive bacilli are oxidase negative?
positive? |
negative- Stenotrophomonas, Acinetobacter baumannii
positive- P. aeruginosa, Burkholderia cepacia, Pasteurella, Bordatella |
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How is Acinetobacter differentiate from Neisseria
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Acinetobacter is resistant to penicillin, Neisseria is susceptible. Acinetobacter is resistant to many antimicrobials
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What diseases are caused by Acinetobacter
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pneumonia, genitourinary infections
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Burkholderia is a major cause of nosocomial infections associated with
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contaminated equipment, disinfectants, and medications
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What is the cellular morphology of Bordetella
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coccobacillary
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What is the causitive agent of whooping caugh
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Bordetella pertussis
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Which two mis. gram negative bacilli cause infections in people who work closley with animals (zoonotic)
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Bordetella bronchiseptica and Pasteurella
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T/F Bordetella species are resistant to many antibiotics
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False most strains are sensitive to many antibiotics
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Infections with Pasteurella multocida are usually associated with
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cat or dog bites
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Which mis. gram negative bacteria smells like grapes on BAP and has a pearlescent colony
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P. aeruginosa
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What does a positive glucose O/F tube look like? negative?
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positive- yellow at the top indicates oxidative glucose utilization
negative- green throughout |
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why do some of the mis. gram negative bacteria show a "sick" TSI
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glucose is only used oxidativley at the top of the slab producing only weak acids. Some species will ferment sucrose which contributes to the orange but not yellow TSI
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What test might sugesst that a gram negative bacilli is not an enterobacteriaceae
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1. all entero's ferment glucose
2. all entero's are oxidase negative 3. All entero's grow on MacConkey's |
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Where must there be a low concentration of peptones in glucose O/F media
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you don't want the alkaline products from peptone utilization to neutralize the weak acids from oxidative glucose utilization
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what is the most common non-enterobacteriacea gram negative m.o. islated in clinical lab
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Pseudomonas aeruginosa
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In addition to pigments and a grape odor what else is produced by Pseudomonas aeruginosa that can be detected on a BAP plate
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slime (alginate), exopolysaccharide of biofilm
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Which mo is responsible for wounds with blue pus
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P. aeruginosa
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In addition to penicillian resistance, how can acinetobacter be distinguished from nessiera and morxella
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Acinetobacter is oxidase negative, nessieria/ morxella are oxidase positive
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T/F Bordetella pertussis is a zoonotic diseas
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False. B. pertussis has no animal or soil resevoirs, it is human to human only. B. bronchiseptica however is zoonotic and can be spread from animals to humans
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What is the causitive agent of kennel cough
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Bordetella bronchiseptica
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What are the three main tests used to characterize the mis. gram negative bacilli
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growth on MacConkey's, oxidase activity, OF dextrose
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define saprobic
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free living in soil
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Which two groups of Mycobacterium are primarily responsible for causing disease
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M. tuberculosis Complex and M. avium Complex (MAC)
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What allows for the chronicity of mycobacterial infections?
What else demonstrates their hardyness |
ability to survive and thrivie within the phagocyte,
resistant to disinfectants, alcohols, acids, alkaline, and dry conditions |
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What is unique about the mycobacterial cell wall and how does this aid in their detection
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the cell wall is composed of mycolic acids (unique lipids). These bind teh dye carbolfuchsin which is used in the acid fast stain
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T/F a gram stain can be used on mybobacteria
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false, it is not generally used
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Describe the growth rate and nutritional requirements of mycobacteria
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slow, simple nutritional requriments, grow on synthetic media, preference for media supplemented with egg, potato flour, and glycerol, most medias also contian malachite green and antimicrobials to inhibit growth of contaminating bacteria
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What two media are used to isolate mycobacteria
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Lowenstein-Jensen and Middlebrook
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what four categories is the identification of mycobacteria based on
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1. rate of growth
2. temperature at which growth occurs 3. chromogenicity (effect of light on pigment production) 4. biochemical properties |
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When is tuberculosis suspected
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Pt presents with chronic cough, weight loss or other evidence of chronic granulomatous process along with consisten radiographic evidence, there may be infection at extrapumonary sites
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what populations most commonly present with TB
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urban areas of poverty and overcrowding, racial factors may predisose nonwhites to the disease
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What 3 tests can be used to screen for TB infection and how do they work
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1. delayed type hypersensitivity to PPD- inject purified protein derivative tuberculoprotein antigens subcutaneously and look for raised bump and redness
2.Mantoux- detects reactors or converters reveals a pervious or current infection with TB 2. QuantiFERON-TB- detects gamma interferon using lymphocytes form whole blood, expensive and not in general use |
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TB can be isolated from sterile sites of sites with normal flora. How must samples from normal flora sites be processed before TB can be isolated
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Digest to liquigy mucus then decontaminate by killing the contaminating bacteria using a controlled treatment with strong alkaline and acids solutions. THen concentrate the TB by centrifugation.
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What are the two types of acid fast stainds that can be used for direct detection of TB
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1.carbolfuchsin (kinyoun cold stain)
non 2. non immunogenic floorochrome stain (Auramine 0). The acid fast smears are examined for characteristic cellular morphology (coccobacillary/ pleomorphic rods that may be baeded or banded) (Kinyoun stain) or using florescent microscopy to detect bright yellow bacteria agianst a dark background (Auramine fluorochrome stain) |
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what disease are caused by non tuberculosis mycobacteria (NTM)? How are these mo's classified
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pumonary infections not not characterize by plmonary infiltrates
characterized by ability to produce pigments scotochromongens- produce pigments with no light photochromogens- produce pigments with light nonphotochromogens- no pigments in light or dark |
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Describe the disease caused by Mycobacterium leprae
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Hansen's disease (leprosy), capable of causing disease in nin banded armadillos, and humans
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How is TB spread
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human to human by aerosols
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How does the progression of TB compare to NTM
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TB progresses slowly, NTM progresses quickly
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Describe the cellular morpholog of TB
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beaded rods, roping
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Describe the sample needed to determine if a Pt has TB
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-minimum of 3-5 collections due to intermittent shedding of mo's
-sterile sites fluids (CSF, joint), blood, uring, biopsies, -process mixed flora site (sputum, bronchial wash, BAL, feces) |
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What are teh two types of carbolfuchsin stain (acid fast stain) that are used to stain TB? How are they preformed
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1. ziehl-neelsen = hot
2. kinyoun= cold primary stain is fuchsin + phenol (carbolic acid), decolorize with acid-aocohol, but mycolic acids retain stain counterstain with methylene blue |
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T/F the flurochrome stain (Auramine O) used to stain TB uses an antibody
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false, it chemically binds the lipids of the cell wall
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Describe how TB stains are evaluated
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flurochrome- 400x fluorescent scope, use for screening smear but be carful for false + with debris
carbolfuchsin- scan with 1000x oil w/ bright field scope to confirm flurosecent findings, need to examine ~ 300 fields, look for bright red beaded rods against blue background, confirm cellular morphology Quantify smear with 1+ (1-9 per 100 fields) to 4+( > 9 mo per field) |
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Descirbe the conditions used to culture TB
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5-10% CO2, humidity, 37 C, hold for 8 weeks, colonies take 2-7 days for rapid growers and 2-8 weeks for slow growers
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Which detection tests for TB will the BCG vaccination effect
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PPD and Mantoux but not Interferon gamma release assays
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define obligate aerobe
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bacteria that grow in the prescence of atmospheric oxygen and will not grow in the abscence of O2
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define obligate anaerobe
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bacteria that only grow in the absence of oxygen
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define a facultative bacteria
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organism is ableto grow in either the presence or the absence of oxygen
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define microaerophilic
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bacteria that grow optimally when the oxygen content is reduced
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define EOS and compare to aerotolerant anaerobe
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extremely oxygen sensitve anaerobe, killed with exposure to even small amounts of O2
aerotolerant-surive exposure to oxygen and are able to grow when reintroduced to anaerobic conditions |
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Where can most anaerobes be found as normal flora
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mucosal sites (oral, intestinal, genitourinary, skin)
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T/F most anaerobes are primary pathogens
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false, most anaerobes are opportunistic endogenous infections that cause infections when the indigenous flora breacehs the barrier of the mucous membrane
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T/F infections with anaerobes usually consist of one species of bacteria
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false, anaerobic infections are usually polymicrobial containing multiple species of anaerobic and/or facultative aerobic bacteria
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Since anaerobic infections are frequently polymicrobial, all clinical specimens from appropriate sites are cultured
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for aerobic and anaerobic organisms
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list serveral ways anaerobic culture can be acheived
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anaerobic jars, gas impermeable bags with anaerobic generating envelops, anaerobic chamber
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How are anaerobic bacteria presumptivly identified
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morphology, suceptibility to antibiotic disks (GNB only), fementation of carbs, other phsiologic characterisitcs
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How are anaerobes definitivly identified
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gas liquid chromatographic analysis of volatile fatty acids and nonvolatile organic acids produced during glucose fermentation
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What genera do all pathogenic gram postive spore forming bacilli belong to?
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Clostridium
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describe the infections caused by Clostridium perfringes
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most common species isolated from anaerobic infections, produce variuos exotoxins and proteolytic enzymes causing gas gangreen (myonecrosis) and food poisoning
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describe the infections cause by Clostridium diffcile
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toxin mediated pseudomembranous colitis, linked to use of antibiotics
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List 4 anaerobic gram negative bacilli of medical importance
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Bacteroides, Prevotella, Porphyromonas, Fusobacterium
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The bacteroides group is bile tolerant, idigenous flora of the intestinal tract (colon). How do infections arise?
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Infections with Bacteroides arise from endogenous spread from the colon to normally sterile sites.
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What is the most common of all anaerobic organissm isolated from clinical infections, often from sites where an abscess has formed
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Bacteroides fragilis
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List 3 anaerobic gram negative bacteria that are normal flora of the oral cavity/ upper respiratory tract
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Prevotella spp, Porphyromonas spp, Fusarium spp
These are possible agents in oral, dental, and human bite infections. They cause infections of the head/ neck and respiratory tract. |
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Which gram negative anaerobic bacteria produces a brown/ black pigment on blood agar?
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Prevotella melaninoenica
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What genus do the patogenic gram positive cocci belong to?
Where are they found? What types of infections do they cause? |
Peptostreptococcus
They are indigenous flora of the mouth, URT, vagina, and large intestine all types of infections- abscesses, surgical wounds, septic arthritis etc |
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What genus of gram negative cocci is found with some frequency in clinical specimens (the gram negative anaerobic cocci are less significant pathogens than their gram positive counterparts)
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Veillonella
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A double zone of beta hemolysis is characteristic of which anaerobic pathogen?
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Clostridium perfringens
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Which gram negative pathogen has lecithinase? What does this enzyme do and how is it detected
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Clostridium perfringens
Lecithinase alpha toxin disrupts the lecithin in RBCs, muscle and PMN cells. The colonies on the plate are surrouned by a halo of white precipitate. |
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Which gram negative pathogen has lipase? What does this enzyme do and how is it detected?
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Clostridium sporogenes
Lipase degrades the lipids detected by an iridescent sheen or "oil on water" appearnace on the surface of the colony growth and surrounding media |
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IS EYA selective or differential?
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Differential media used for isolation and presumpitve identification of Clostridium species and other anaerobic bacteria.
Lipase activity is detected by an irridescent sheen, Lecithinase activity is detected by a white, opaque precipitate |
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List two notable characteristics of Clostridium difficile that can be detected on BAP
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chartreuse pigment in UV light and odor
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Which two anaerobic bacteria produce pigments under anaerobic light? What color?
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Clostridium difficile- chartreuse
Prevotella melaninogenica- brick redi from young colonies, black from older |
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How is PEA useful for culturing gram negative anaerobes?
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It inhibits facultative anaerobes like the enteric bacteria
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What clues suggesting an infection with an anaerobe can be obtained from a direct exam?
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foul odor, purulent, necrotic, gram stain morphology (fusiform shape or spores)
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What does PRAS stand for
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Pre Reduced Anaerobically Sterilized media
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What type of media is Bacteroides Bile Esculin Agar (BBE)
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selecive and differential for Bacteroides fragilis, the most common clinically relevant AnO2
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Describe thioglycollate broth
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nutrient rich (not selective)
Does not allow O2 to diffuse so can determine O2 relationship based on position of growth (differential) |
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will an EOS organism grow in a AnO2 jar with a gas pack
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No. the gas back generates CO2 and H2 and used a catalyst to turn oxygen gas into water. This gives >1% oxygen within minutes but this is still too much for an EOS
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List 3 ways to create an anaerobic environment
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1. Anaerobic packet + jar
2. Bio Bag with generator packet and gas impermeable bag 3. AnO2 chamber and a transfer chamber |
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what is the habitat of clostridium species
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soil, GI (not predominate), sewaqge, contaminated H2O
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Why won't you see PMN's from a gram stain of C.perfringes?
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they have been lysed by lecithinase
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Describe the hemolysis produced by C. perfringens
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double zone
outer- alpha toxin (weak) inner- theta toxin (strong) |
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Describe the motility of spirochetes
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actively motile by rotation or undulation
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What are the three genera of spirochetes associated with human disease? What is their gram stain (although they stain poorly)
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Treponema, Borrelia, Leptospira
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How can spirochetes be detected directly
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special staining techniques (silver impregnation to increase width) or darkfield microscopy, use serological techniques to detect presence of infection
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T/F some Treponema species are normal flora
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true, some Treponema species are indigenous flora of the mouth of humans
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What is the causitive agent of syphilis
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Treponema pallidum
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What are the two approaches used to detect syphilis
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1. Direct microscopic demonstration of T. pallium in exudate of chancres or secondary lesions
2. Serological tests |
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Describe the nonspecific nontreponemal antibody tests used as screenings for syphilis
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T. pallidum infection results in the development of distinct antibodies to cardiolipin, a tissue lipid. The presence of this antibody can be demonstrated with flocculation tests using a suspension of lipids from normal mammalian tissues. These tests are non immunologically specific for syphilis can can result in false positives for people with a variety of conditions
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Describe the 2 specific antitreponemal antibody tests used for confirmatory Dx of syphilis
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These tests detect antibody specific to T. pallidum antigens. 1.The fluorescent treponemal antibody absorption (FTA-ABS) is an indirect immunofluorescent antibody test using T. pallidum harvested from rabbits as the antigen and the patients serum. A fluorescent conjugated antibody binds to the patients antibodies which are bound to the syphilis.
2. T. pallidum immobilization (TPI) test determines the ability of the patient's serum to block or interfere with the motility of T. pallidum (b/c of antibodies) |
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what two diseases are causted by Borrelia spp. and are transmited by insect vectors?
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relapsing fever (B. recurrentis) and Lyme disease (B. burgdorferi)
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Kelly's medium can be used to isolate Borrelia species but this is not nomrally used for lab Dx. How is Dx made for the two clinically relevant species
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1. relapsing fever caused by B. recurrentis is Dx by microscopic examination of the BLOOD
2. lyme disease caused by B. burgdorferi is made by clinical Hx and serological tests |
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Although Leptospira interrogans is primarily an animal pathogen, it can infect humans. How are humans infected? What samples can be examined and how are they examined?
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Humans are infected via direct contact with water contaminated with urine from infected domestic or wild animals. Darkfield microscopic examination can be used to observe the tighly coiled hook ended spirochetes characteristic of Leptospira
samples can be blood, urine, or spinal fluid |
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The VDRL, RPR and FTA-ABS, and TPI tests are all used to test for syphilis. What do the stand for? Which are specific?
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VDRL- venereal disease research laboratory, non specific
RPR- rapid plasma reagin- non specific TPI- treponemal pallidum immobilization- specific FTA-ABS- fluorescent treponemal antibody absoprtion- specific |
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what two sites can Leptospira interrogans gain access to humans when they come in contact with urine contaminated water
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mucous membrane or open skin
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T/F gram stains are routinely done on spirochetes
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false, they are to thin to stain well
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What disease is caused by Leptospira interrogans
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Weil's disease
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how do males and females differ in presentation of syphilis infection
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males-symptomatic
females- asymtomatic |
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Breifly describe how dark field micro works
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specific condenser blocks central light, the light hits the MO from the side and is deflected, the MO is seen as bright white against a dark background, stain is not used
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How can syphilis be transmitted
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sexual contact (even unprotected oral sex), congenital via the placenta
human disease only |
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What is the RPR test for syphilis detecting? What is the antigen? What are the antibodies
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NON SPECIFIC
detect antibodies to syphilitic tissue Reaginic antibody antigen- cardiolipin lecithin particle The antibody is to the lesion in the tissue not T. pallidum |
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What is the VDRL test for syphilis detecting?
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The test looks for aggultination of lipids (wooly appearane), caused by non specific antibodies that result from syphilis infeciton. This test can be used to determine that antibody titer but it is NONSPECIFIC
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What might cause a false positive nontreponemal test
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non-pathogenic treponemas as normal flora, pregnancy, hepatitis, autoimmune diseases, other spirochetes
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which syphilis test is used to follow the success of therapy
which test will continue to show a high titier? |
RPR can be used to follow therapy
FTA-ABS will remain high |
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What are the two states of Weil's disease and what are the associated sxs?
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asymptomatic carrier
disease state-rash or signs of renal involvement |
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What are the sources and vector of lyme disease caused by B. burgdorferi
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sources- white footed mouse and white tail deer
vector- deer tick (Ixodes) |
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What are the two steps used to Dx lyme disease
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1. Indirect immunoassay (ELISA)
2. Western blot |
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what are the three stages of Lyme disease and the associated sxs
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1. early infection- FLS, EM, joint pain
2. Dissemination- neuro and cardio abnormalities, arthrities, 3. Persistence- progression of sxs |
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define test sensitivity
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Does the test detect the disease in people who have it?
True positive |
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define test specificity
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Does the test show negative results for people who are negative?
True negative |
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What constitunes a positive wetern blot for lyme disease
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bands at 5 of 10 kDa locations, most have band at 41 kDa, spirochete flagellar antigen
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where is Legionella found
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ubiquitous in man made water systems (not killed by chlorine)
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gram stain of Legionella
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gram negative rods
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What two special nutrients does Legionella require for growth
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L-cysteine and iron salts
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what media is used to culture Legionella pneumophila
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BCYE (buffered charcoal yeast extract agar)
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What is the presumptive clue for Legionella Dx
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growth on BCYE and no growth on BAP
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List 4 ways to Dx Legionellla
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1. culture
2. urine antigen 3. paired serology (before and after) 4. direct fluorescent antibody stain |
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What is unique about Legionella colonies on BCYE
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crystalline/ broken glass like internal structures visible with dissecting scope
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What type of media is BCYE
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selective and enriched, not differential
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T/F Legionella can be transmitted person to person
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false
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What two diseased are caused by Legionella
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1.Legionnaires disease (pneumonia, cough, fever, chest pain
2. Pontiac fever (mild flu like) |
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List some predisposing factors to Legionella infection and disease
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low immune status, smoking, inoculum size
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list four ways Legionella can be directly detected
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1. immunofluorescent antibody stain
2. urinary antigen detection 3. serological tests 4. molecular techniques |
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what contributes to the pleomorphicity or mycoplasma
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no cell wall
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why don't mycoplasma gram stain
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no cell wall
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What human infections arise from mycoplasma
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respiratory tract and genitourinary tract
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what is the causative agent of primary atypical pneumonia
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Mycoplasma pneumoniae
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describe the media needed to culture mycoplasma species
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enriched with serum protein, lipids (sterols), nucleic acid precursors, antimicrobials
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which bacteria has the "fried egg" colony morpholgy
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Mycoplasma hominis
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Since culture is seldom done to isolate Mycoplasma pneumoniae, how is it Dx'ed
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clinical presentation- dry unproductive cough, radiograph
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Which Mycoplasma species cause cervicitis, PID, endometriitis, and complications for the neonate
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M. hominis, M. genitalium
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Which Mycoplasmataceae species cause nongonococcal urethritis
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U. urealyticum and M. genitalium
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How can M. hominis and M. genitalium be transmitted sexually
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the can travel with the spermatozoa and lead to ascending infections
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which organism is responsible for "walking" or atypical pneumoniae
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Mycoplasma pneumoniae
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What would you see in the gram stain of a urethral exudate from a male with NSU/ NGU
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no bacteria but lots of PMNs because the Mycoplasma ore Ureplasma are too small to see
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List some sites that are unsuitable for AnO2 culture. Why?
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sputum, feces, swabs,
loaded with normal flora and exposed to oxygen |
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List some sites that are suitable for AnO2 culture. Why?
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bile, biospy of tissue, blood, bronchial wash, CSF, base of ulcer
normally sterile fluids |
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what are 3 ways to get 'reduced' media
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1. 4-16 hrs in AnO2 conditions
2. PRAS 3. boil broth to drive off O2 |
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what type of media is thioglycollate?
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enriched and differential, not selective
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