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150 Cards in this Set

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T/F the "miscellaneous gram negative bacteria" (Pseudomonas, Acinetobacter, Stenotrophomonas, Burkholderia, Bordetella, and Pasteurella) are normal flora of the human body
False. They are not normal flora of humans but they can trasiently infect people without symptoms
What types of infections develop from Pseudomonas aeruginosa
noscomial pneumonia, UTI, bacterima, and localized infections following surgey or burns
Descrbie the prognosis following Pseudomonas aeruginosa infection
prognosis is poor. The organism is resistant to most antimicrobials and mortalitly rates are high.
T/F P. aeruginosa can replicate in hospital environments such as sink drains, respirators, plants and even weak antiseptics and standing water
True
You have a gram negative bacilli that produces pigment on BAP. It is most likley (2)
P. aeruginosa or Stenotrophomonas maltophilia
Where can P. aeruginosa be found naturally?
widely dispersed in the environment
Where can Acinetobacter species be found in the environment
widely dispersed in soil or water
Where does Acinetobacter colonize humans when it transiently infects them?
moist areas (mucosal surfaces)
Describe the cellular morphology of Acinetobacter
coccobacillary, can be diplococci
Which o the mis. gram negative bacilli grow on MacConkey's plates
all except Pasteurella
Which of the mis. gram negtaive bacilli are oxidase negative?
positive?
negative- Stenotrophomonas, Acinetobacter baumannii
positive- P. aeruginosa, Burkholderia cepacia, Pasteurella, Bordatella
How is Acinetobacter differentiate from Neisseria
Acinetobacter is resistant to penicillin, Neisseria is susceptible. Acinetobacter is resistant to many antimicrobials
What diseases are caused by Acinetobacter
pneumonia, genitourinary infections
Burkholderia is a major cause of nosocomial infections associated with
contaminated equipment, disinfectants, and medications
What is the cellular morphology of Bordetella
coccobacillary
What is the causitive agent of whooping caugh
Bordetella pertussis
Which two mis. gram negative bacilli cause infections in people who work closley with animals (zoonotic)
Bordetella bronchiseptica and Pasteurella
T/F Bordetella species are resistant to many antibiotics
False most strains are sensitive to many antibiotics
Infections with Pasteurella multocida are usually associated with
cat or dog bites
Which mis. gram negative bacteria smells like grapes on BAP and has a pearlescent colony
P. aeruginosa
What does a positive glucose O/F tube look like? negative?
positive- yellow at the top indicates oxidative glucose utilization
negative- green throughout
why do some of the mis. gram negative bacteria show a "sick" TSI
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
What test might sugesst that a gram negative bacilli is not an enterobacteriaceae
1. all entero's ferment glucose
2. all entero's are oxidase negative
3. All entero's grow on MacConkey's
Where must there be a low concentration of peptones in glucose O/F media
you don't want the alkaline products from peptone utilization to neutralize the weak acids from oxidative glucose utilization
what is the most common non-enterobacteriacea gram negative m.o. islated in clinical lab
Pseudomonas aeruginosa
In addition to pigments and a grape odor what else is produced by Pseudomonas aeruginosa that can be detected on a BAP plate
slime (alginate), exopolysaccharide of biofilm
Which mo is responsible for wounds with blue pus
P. aeruginosa
In addition to penicillian resistance, how can acinetobacter be distinguished from nessiera and morxella
Acinetobacter is oxidase negative, nessieria/ morxella are oxidase positive
T/F Bordetella pertussis is a zoonotic diseas
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
What is the causitive agent of kennel cough
Bordetella bronchiseptica
What are the three main tests used to characterize the mis. gram negative bacilli
growth on MacConkey's, oxidase activity, OF dextrose
define saprobic
free living in soil
Which two groups of Mycobacterium are primarily responsible for causing disease
M. tuberculosis Complex and M. avium Complex (MAC)
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
What is unique about the mycobacterial cell wall and how does this aid in their detection
the cell wall is composed of mycolic acids (unique lipids). These bind teh dye carbolfuchsin which is used in the acid fast stain
T/F a gram stain can be used on mybobacteria
false, it is not generally used
Describe the growth rate and nutritional requirements of mycobacteria
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
What two media are used to isolate mycobacteria
Lowenstein-Jensen and Middlebrook
what four categories is the identification of mycobacteria based on
1. rate of growth
2. temperature at which growth occurs
3. chromogenicity (effect of light on pigment production)
4. biochemical properties
When is tuberculosis suspected
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
what populations most commonly present with TB
urban areas of poverty and overcrowding, racial factors may predisose nonwhites to the disease
What 3 tests can be used to screen for TB infection and how do they work
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
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
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.
What are the two types of acid fast stainds that can be used for direct detection of TB
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)
what disease are caused by non tuberculosis mycobacteria (NTM)? How are these mo's classified
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
Describe the disease caused by Mycobacterium leprae
Hansen's disease (leprosy), capable of causing disease in nin banded armadillos, and humans
How is TB spread
human to human by aerosols
How does the progression of TB compare to NTM
TB progresses slowly, NTM progresses quickly
Describe the cellular morpholog of TB
beaded rods, roping
Describe the sample needed to determine if a Pt has TB
-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)
What are teh two types of carbolfuchsin stain (acid fast stain) that are used to stain TB? How are they preformed
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
T/F the flurochrome stain (Auramine O) used to stain TB uses an antibody
false, it chemically binds the lipids of the cell wall
Describe how TB stains are evaluated
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)
Descirbe the conditions used to culture TB
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
Which detection tests for TB will the BCG vaccination effect
PPD and Mantoux but not Interferon gamma release assays
define obligate aerobe
bacteria that grow in the prescence of atmospheric oxygen and will not grow in the abscence of O2
define obligate anaerobe
bacteria that only grow in the absence of oxygen
define a facultative bacteria
organism is ableto grow in either the presence or the absence of oxygen
define microaerophilic
bacteria that grow optimally when the oxygen content is reduced
define EOS and compare to aerotolerant anaerobe
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
Where can most anaerobes be found as normal flora
mucosal sites (oral, intestinal, genitourinary, skin)
T/F most anaerobes are primary pathogens
false, most anaerobes are opportunistic endogenous infections that cause infections when the indigenous flora breacehs the barrier of the mucous membrane
T/F infections with anaerobes usually consist of one species of bacteria
false, anaerobic infections are usually polymicrobial containing multiple species of anaerobic and/or facultative aerobic bacteria
Since anaerobic infections are frequently polymicrobial, all clinical specimens from appropriate sites are cultured
for aerobic and anaerobic organisms
list serveral ways anaerobic culture can be acheived
anaerobic jars, gas impermeable bags with anaerobic generating envelops, anaerobic chamber
How are anaerobic bacteria presumptivly identified
morphology, suceptibility to antibiotic disks (GNB only), fementation of carbs, other phsiologic characterisitcs
How are anaerobes definitivly identified
gas liquid chromatographic analysis of volatile fatty acids and nonvolatile organic acids produced during glucose fermentation
What genera do all pathogenic gram postive spore forming bacilli belong to?
Clostridium
describe the infections caused by Clostridium perfringes
most common species isolated from anaerobic infections, produce variuos exotoxins and proteolytic enzymes causing gas gangreen (myonecrosis) and food poisoning
describe the infections cause by Clostridium diffcile
toxin mediated pseudomembranous colitis, linked to use of antibiotics
List 4 anaerobic gram negative bacilli of medical importance
Bacteroides, Prevotella, Porphyromonas, Fusobacterium
The bacteroides group is bile tolerant, idigenous flora of the intestinal tract (colon). How do infections arise?
Infections with Bacteroides arise from endogenous spread from the colon to normally sterile sites.
What is the most common of all anaerobic organissm isolated from clinical infections, often from sites where an abscess has formed
Bacteroides fragilis
List 3 anaerobic gram negative bacteria that are normal flora of the oral cavity/ upper respiratory tract
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.
Which gram negative anaerobic bacteria produces a brown/ black pigment on blood agar?
Prevotella melaninoenica
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
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)
Veillonella
A double zone of beta hemolysis is characteristic of which anaerobic pathogen?
Clostridium perfringens
Which gram negative pathogen has lecithinase? What does this enzyme do and how is it detected
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.
Which gram negative pathogen has lipase? What does this enzyme do and how is it detected?
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
IS EYA selective or differential?
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
List two notable characteristics of Clostridium difficile that can be detected on BAP
chartreuse pigment in UV light and odor
Which two anaerobic bacteria produce pigments under anaerobic light? What color?
Clostridium difficile- chartreuse
Prevotella melaninogenica- brick redi from young colonies, black from older
How is PEA useful for culturing gram negative anaerobes?
It inhibits facultative anaerobes like the enteric bacteria
What clues suggesting an infection with an anaerobe can be obtained from a direct exam?
foul odor, purulent, necrotic, gram stain morphology (fusiform shape or spores)
What does PRAS stand for
Pre Reduced Anaerobically Sterilized media
What type of media is Bacteroides Bile Esculin Agar (BBE)
selecive and differential for Bacteroides fragilis, the most common clinically relevant AnO2
Describe thioglycollate broth
nutrient rich (not selective)
Does not allow O2 to diffuse so can determine O2 relationship based on position of growth (differential)
will an EOS organism grow in a AnO2 jar with a gas pack
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
List 3 ways to create an anaerobic environment
1. Anaerobic packet + jar
2. Bio Bag with generator packet and gas impermeable bag
3. AnO2 chamber and a transfer chamber
what is the habitat of clostridium species
soil, GI (not predominate), sewaqge, contaminated H2O
Why won't you see PMN's from a gram stain of C.perfringes?
they have been lysed by lecithinase
Describe the hemolysis produced by C. perfringens
double zone
outer- alpha toxin (weak)
inner- theta toxin (strong)
Describe the motility of spirochetes
actively motile by rotation or undulation
What are the three genera of spirochetes associated with human disease? What is their gram stain (although they stain poorly)
Treponema, Borrelia, Leptospira
How can spirochetes be detected directly
special staining techniques (silver impregnation to increase width) or darkfield microscopy, use serological techniques to detect presence of infection
T/F some Treponema species are normal flora
true, some Treponema species are indigenous flora of the mouth of humans
What is the causitive agent of syphilis
Treponema pallidum
What are the two approaches used to detect syphilis
1. Direct microscopic demonstration of T. pallium in exudate of chancres or secondary lesions
2. Serological tests
Describe the nonspecific nontreponemal antibody tests used as screenings for syphilis
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
Describe the 2 specific antitreponemal antibody tests used for confirmatory Dx of syphilis
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)
what two diseases are causted by Borrelia spp. and are transmited by insect vectors?
relapsing fever (B. recurrentis) and Lyme disease (B. burgdorferi)
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
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
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?
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
The VDRL, RPR and FTA-ABS, and TPI tests are all used to test for syphilis. What do the stand for? Which are specific?
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
what two sites can Leptospira interrogans gain access to humans when they come in contact with urine contaminated water
mucous membrane or open skin
T/F gram stains are routinely done on spirochetes
false, they are to thin to stain well
What disease is caused by Leptospira interrogans
Weil's disease
how do males and females differ in presentation of syphilis infection
males-symptomatic
females- asymtomatic
Breifly describe how dark field micro works
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
How can syphilis be transmitted
sexual contact (even unprotected oral sex), congenital via the placenta
human disease only
What is the RPR test for syphilis detecting? What is the antigen? What are the antibodies
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
What is the VDRL test for syphilis detecting?
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
What might cause a false positive nontreponemal test
non-pathogenic treponemas as normal flora, pregnancy, hepatitis, autoimmune diseases, other spirochetes
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
What are the two states of Weil's disease and what are the associated sxs?
asymptomatic carrier
disease state-rash or signs of renal involvement
What are the sources and vector of lyme disease caused by B. burgdorferi
sources- white footed mouse and white tail deer
vector- deer tick (Ixodes)
What are the two steps used to Dx lyme disease
1. Indirect immunoassay (ELISA)
2. Western blot
what are the three stages of Lyme disease and the associated sxs
1. early infection- FLS, EM, joint pain
2. Dissemination- neuro and cardio abnormalities, arthrities,
3. Persistence- progression of sxs
define test sensitivity
Does the test detect the disease in people who have it?
True positive
define test specificity
Does the test show negative results for people who are negative?
True negative
What constitunes a positive wetern blot for lyme disease
bands at 5 of 10 kDa locations, most have band at 41 kDa, spirochete flagellar antigen
where is Legionella found
ubiquitous in man made water systems (not killed by chlorine)
gram stain of Legionella
gram negative rods
What two special nutrients does Legionella require for growth
L-cysteine and iron salts
what media is used to culture Legionella pneumophila
BCYE (buffered charcoal yeast extract agar)
What is the presumptive clue for Legionella Dx
growth on BCYE and no growth on BAP
List 4 ways to Dx Legionellla
1. culture
2. urine antigen
3. paired serology (before and after)
4. direct fluorescent antibody stain
What is unique about Legionella colonies on BCYE
crystalline/ broken glass like internal structures visible with dissecting scope
What type of media is BCYE
selective and enriched, not differential
T/F Legionella can be transmitted person to person
false
What two diseased are caused by Legionella
1.Legionnaires disease (pneumonia, cough, fever, chest pain
2. Pontiac fever (mild flu like)
List some predisposing factors to Legionella infection and disease
low immune status, smoking, inoculum size
list four ways Legionella can be directly detected
1. immunofluorescent antibody stain
2. urinary antigen detection
3. serological tests
4. molecular techniques
what contributes to the pleomorphicity or mycoplasma
no cell wall
why don't mycoplasma gram stain
no cell wall
What human infections arise from mycoplasma
respiratory tract and genitourinary tract
what is the causative agent of primary atypical pneumonia
Mycoplasma pneumoniae
describe the media needed to culture mycoplasma species
enriched with serum protein, lipids (sterols), nucleic acid precursors, antimicrobials
which bacteria has the "fried egg" colony morpholgy
Mycoplasma hominis
Since culture is seldom done to isolate Mycoplasma pneumoniae, how is it Dx'ed
clinical presentation- dry unproductive cough, radiograph
Which Mycoplasma species cause cervicitis, PID, endometriitis, and complications for the neonate
M. hominis, M. genitalium
Which Mycoplasmataceae species cause nongonococcal urethritis
U. urealyticum and M. genitalium
How can M. hominis and M. genitalium be transmitted sexually
the can travel with the spermatozoa and lead to ascending infections
which organism is responsible for "walking" or atypical pneumoniae
Mycoplasma pneumoniae
What would you see in the gram stain of a urethral exudate from a male with NSU/ NGU
no bacteria but lots of PMNs because the Mycoplasma ore Ureplasma are too small to see
List some sites that are unsuitable for AnO2 culture. Why?
sputum, feces, swabs,
loaded with normal flora and exposed to oxygen
List some sites that are suitable for AnO2 culture. Why?
bile, biospy of tissue, blood, bronchial wash, CSF, base of ulcer
normally sterile fluids
what are 3 ways to get 'reduced' media
1. 4-16 hrs in AnO2 conditions
2. PRAS
3. boil broth to drive off O2
what type of media is thioglycollate?
enriched and differential, not selective