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154 Cards in this Set

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What genera are included in the Micrococcaceae family
1. Staphhylococcus
2. Micrococcus
Describe the cellular morphology of members of the Micrococcacae family (Staphylococcus, micrococcus)
gram positive cocci that commonly occur in clusters
Where do Stahylococci species colonize the normal human
-skin
-mucous membranes
What is the coagulase reaction of Staphylococcus aureus
S. aureus is coagulase positive
What is the coagulase reaction of Staphylococcus epidermidis and S. saprophyticus
S. epidermidis and S. saprophyticus are coagulase negative
What is coagulase? What does it do? What is its function in vivo
-A bacteria made protein that has a prothrombin like activity
-It converts fibrinogen to fibrin resulting in the formation of a visible clot
-In vivo, it is thought to form a fibrin barrier at the site of staphylococcal infection, localizing the organism into abscesses
What differentiation is the coagulase test used for?
Coagulase differentiates Staphylococcus aureus (positive) from other staphylococci and micrococci
List some Staphylococcus aureus associated human diseases
-cutaneous infections (boils, furuncles, carbuncles, impetigo, folliculitis, surgical and stich wounds
-toxin mediated diseases (food intox, toxic shock, scalded skin syndrome)
-bacteremia, bone, organ infection
T/F Staphylococcus aureus is part of the normal flora of a healthy human
True. S. aureus may apper chronically or intermittently in the nares of on the hands of healthy people (carriers)
T/F coagulase negative staphylococci (S. epidermidis, S. saprophyticus) are pathogenic
Sort of true. They are opportunistic pathogens. S. epidermidis can infect catheters, grafts, prostethis, and implants leading to endocarditis. S. saprophyticus can lead to acute UTI in young females
Where do Micrococcus species colonize the normal human
transient flora of the skin
What is the catalase result of micrococcaceae (Staphylococcus and Micrococcus)
catalase positive
How can Micrococcus species be differentiated from Staphylococcus species (3 ways)
-cellular morphology (Staph is bigger, Micrococcus usually appears in tetrads)
-Oxidase (Micrococcus is positive, Staph is negative)
-bacitracin (Micrococcus is suceptible, Staph is resistant
Describe the pigments produced by Staphylococci
the pigments are lipochromes (insoluble in water but soluble in organic solvents) S. epidermidis and S. saprophyticus each produce a white to gray pigmented colony. Many S. aureus strains produce a golden yellow pigment but some are white
T/F most coagulase negative streptococci produce strong zones of beta hemolysis
false, most coag negative streptococci do not show a strong zone of beta hemolysis
What does the novobiocin test differentiate
it is used to identify coagulase negative streptococci, S. saprohyticus is resistant, S. epidermidis is sensitive
Describe mannitol salt agar. How is it selective? How is it differential?
Mannitol salt agar is used to select and differentiate staphylococci species.
Selectivity- 7.5% salt concentration supresses growth of most bacteria except Staphylococci and Enterococci.
Differerntial-manitol fermenting bacteria such as S. aureus and S. saprophyticus produce a yellow halo, indicating the productiong of acid from mannitol fermentation. Phenol red is the pH indicator
What is the principle test used for the identification of S. aureus?
coagulase. S. aureus is coagulase positive
What are the two forms of coagulase produced by S. aureus
1. cell bound aka clumping factor
2. free
Describe the steps of the coagulase test
1.A drop of water and a drop of plasma are placed on a slide
2. A colony is removed with a wooden stick and mixed into the water, another is placed in the plasma
3. Look for clumping to indicate a positive reaction
What is the negative control in the coagulase test
the colony is transfered into water
Describe what is occuring biochemically during a positive coagulase test
the cell bound clumping factor acts on fibrinogen binds it so that it aggregates
free coagulase causes the conversion of fibrinogen to fibrin and leads to the formation of a fibrin clot
T/F a slide coagulase detects free coagulase
False. The slide test detects only bound coagulase, a tube test must be used to detect both free and bound coagulase
What is the purpose of doing a tube coagulase test
The tube coagulase test detects both free and bound coagulase. It is more sensitive than the slide test btu requires more time.
how is a tube coagulase test carried out
Colonies are emulsified in a tube containing 0.5 ml rabbit plasma. The tube is incuabted for 4 hours, checked and then incuabted overnight if negative (just in case fibrinolysin is present) A positive test is the formation of a clot
What does the oxidase test detect? How is the test preformed
It detects the presence of cytochrome oxidase
A colony is swabed and if it contains oxidase, the substrate 1% tetramethyl-p-phenylenediamine dihydrochloride is oxidized to a purple color
What two situations could give a false positive oxidase test result
1. Using a colony that was growing on selective media
2. Using a colony that was growing on glucose containing media
how can a strain of S. aureus be slide coagulase negative but tube coagullase positive
If the slide coag test is negative the strain does not have bound clumping factor. If the tube test is positive the strain has free coagulase
What test would differentiate S. aureus from S. epidermidis
coagulase
S. aureus is positive
S. epidermidis is negative
What test would differentiat S. epidermidis from S. saprophyticus
novobiocin
S. epidermidis is susceptible
S. saporphyticus is resistant
What test differentiates Staphylococcus species from streptococcus species
catalase
Staphylococcus are positive
Streptococcus are negative
describe the SCV (small colony variant) of S. aureus
It is a slower growing strain that causes persistant infections. It is resistant to antibiotics due to its slow metabolism
Define opportunistic pathogen
causes an infection in a compromised host. Can also occur if a huge number infect a healthy person
Define noscomial infection
hospital aquired
define bactermia
bacteria in the blood
define Iatrogenic
infection due to procedure or treatment (IV, cathetar, etc)
Define Endocarditis
inflamation/ infection of heart valve/heart lining, usually occurs with artificial valave
define tropism
affinity for
What are the 3 mucous membranes that are most important when considering infection
1. respiratory tract
2. gastrointestinal tract
3. genitourinary tract
What is they oxygen relationship of Staphyloccus species
falcultative
describe staphylococcus gram stain and morphology
gram positive clusters, division on more than one plain leads to clustering (contrast to planer divison that gives tetrads and strepping)
Define fomite
inaniment surface where bacteria (esp. staph) colonize eg. bedding, clothing, keyboard, etc
Where are Staphylococcus species normally found
nasal (nares), skin, mucous membranes
Describe the steps of biofilm formation
How do they affect antibiotic efficacy
1. plantonic (free floating cells)
2. attachment
3. cell-cell adhesion and proliferation
4. maturation
5. detachment
Need 1000x higher antimicrobial dose, usual the device has to be removed
What is quarum sensing
the ability of bacteria to communicate and coordiante behavior via chemical signaling molecules
When the molecule binds to the receptor, it activates transcription of various genes including signal molecule synthesis, when the bacterial reach a threshold density a positive feedback loop is engage for signaling molecule and the receptor becomes fully activated. This can up regulate other genes like virulence or biofilm formation
What disease is associated with S. Saprophyticus (where does it have a tropism)
urinary tract infection usually in young, sexually active women
what disease is associated with S. epidermidis
Infections of surgical implants, catheters, prosthetic heart valves, can lead to endocarditis
What does Staphylococcus epidermidis secrete that helps it adhere to implants
EPS (extracellular polymeric substance)
What are some virulence factors produced by S. aureus
cytolytic toxins, enzymes, coagulase, cell wall protein A
What diseases are caused by S. aureus
Skin wound infections which can progress to osteomyelitis, lesions (furuncles, carbuncles, stich wounds, impetigo)
Pneumonia, UTI
Describe the food INOTOXICATION (not infection) caused by S. aureus
Some toxins produce a preformed enterotoxin that can cause sickness within 1-12 hours. Foods invovled include processed meat, salted ham, creme filled pastries, custards, mayonaise. An outbreak can be ID if >10^5 CFU/ml are detected in unheated food, the heat stable toxin can be detected
What diseases are associated with the exotoxins produces by S. aureus
Toxic shock syndrome, scalded skin syndrome
Which two strains of Staphylococcus are resistnat to mehicillin
S. aureus and S. epidermidis
define pyrogenic
fever producing (cytokines lead to fever)
define pyogenic aka. suppurative
pus producing
What type of hemolysis do Staphylococcus species produce
beta hemolysis due to cytolytic toxin or hemolysin
What tests differentiates Micrococcaceae from Streptococcus and Enterococcus
The micrococcaceae (staphylocuccus and micrococcus) are all catalase positive. Staphylococcus and enterococcus are catalase negative
What is detected in the tube coagulase test? Slide
tube= free coagulase
slide= bound coagulase
Which Staphylococcus species is suceptible to novobiocin
S. epidermidis is suceptible, S. saprophyticus is resistant
What is being detected when using the latex agglutination test to identify S. aureus
bound clumping factor and protein A, The Fc of Ig molecues (which are boudn to the latex) binds protein A and pulls the latex together giving a visible matrix. IF bound coagulase is also present, the will be strands of fibrin
Describe the morphology of Streptococcus and Enterococcus species
non-motile gram positive cocci
they can have spherical, oval, or elongated shapes
Why do Streptococcus and Enterococcus species usually form pairs or chains
the cocci divide in one plane
What is the colony morphology of streptococus and enterococcus species
very small, various colors
What are the catalase and oxiase results for streptococcus and enterococcus species
catalase negative (differentiate from staphylococcus)
oxidase negative (differentiate from Neisseria)
Describe alpha hemolysis
production of a greenish discoloration on BAP due to incomplete lysis of RBCs
describe beta hemolysis
colonies are surounded by a clear zone due to complete lysis of RBC and breakdown of hemoglobin
What are the two hemolysins that can be produced by group A streptococci?
Streptolysin O- antigenic, oxygen labile
Strepolysin S- non anitgenic, oxygen stable
Why is it necessary to stab the agar of a BAP if trying to test for Beta hemolytic streptococci
streptolysin O is oxygen labile and will only produce hemolysis if it is in the low oxygen environment beneth the agar
What are lancefield groups
a classification system for human infection streptococci and enterococci based on group specific cell wall antigens. Some species do not react (viridans strep and S. pnuemoniae)
S. pnuemoniae does not react with lancefield group antisera, how can it be identified antigenically?
capsular polysaccharide antigens
Considering Streptococcus pyogenes...
Lancefield group?
Normal Flora location?
Disease?
Streptococcus pyogenes is in Lancefield group A.
Normal flora-low numbers by carriers 2-20% on skin and URT
Disease-pharyngitis, skin infections, scarlet fever
What are two types of sequelae that can follow an infection with Streptococcus pyogenes
1.rheumatic fever
2. acute glomerularnephritis
If a patient presents with rheumatic fever or acute glomerularnephritis, what test should be done to identify the cause?
an ASO antibody titer to detect antibodies to streptolysin O. A positive test would confirm a previous infection with S. pyogenes or another member of streptococcal group A
In terms of Streptococcus agalactiae
Lacefield group
normal flora location

Disease
Streptococcus agalactiae is in lancefield group B
It normally colonizes in low numbers the female genital tract or URT
disease- neonatal infections (sepsis and meningitis) aquired in utero/delivery (early onset) or post delivery (late onset), can infect compromised adults and causes mastitis in cows
Streptococcus bovis
lancefield group
normal flora?
disease
lancefield group B
can be normal flora in some humans
disease-carcinoma of the colon and endocarditis
Enterococcus faecalis, E. faecium
normal flora
disease
normal flora of GI tract can be found up to 10^8 CFU/ gram feces
Disease- nosocomial infections, UTI, bacterimia, endocarditis, wounds
Streptococcus pnemoniae
normal flora
disease
normal-URT of carriers, nasopharynx in low numbers, several serological types
disease- bacterial pneumonia, menigitis, otitis media, sinusitis, pathogenicity is dependent on antiphagocytic properties of capsule, capular antigens provide the basis for serological differentiation (over 80 serotypes)
What are viridans strep
alpha hemolytic strep
Viridans (alpha hemolytic) strep
normal flora
disease
normal flora- universally present on surfaces of teeth, tounge, cheeks, saliva.
disease- subacute bacterial endocarditis, S. mutans causes tooth decay
Bacitracin sensitivity can be used to make a presumptive differentiation between the beta hemolytics group A and groups B and C strep. Which is suceptible and which is resistant?
Group A strep are suceptible to bacitracin, Groups B and C are resistant
Describe the CAMP test
Group B streptococci produce CAMP factor which enhances staphylococcal Beta lysin activity. When the two are overlayed on a BAP, enhanced hemolysis is observed. S. aureus is streaked down the middle of the plate as a source of a weak B lysin, a streak of the test strain is palced near it (do not overlap!) Incubate overnight at 37 w/o CO2 and look for enhanced hemolysis
What species could serve as a positive control for a CAMP test?
Any group B streptococcus such as S. agalactiae
Why can't a CAMP plate be incubated with CO2
CO2 incubation can result in a false positive reaction with other beta hemolytic species
What is the CAMP test used for?
To distinguish group B streptococci (like S. agalactiae) from other beta hemolytic streptococci
What is the optochin test used for
to differentiate S. pneumoniae (suceptible) from other alpha hemolytic Streptococci (resistant)
What is optochin
it's a detergent like compound that messes up the cell membrane
What does a positive bile esculin test look like?
growth, the media turns to form a dark brown or black complex
What is the Bile esculin test used for
for alpha hemolytic gram positive cocci, it differentiates enterococcus and group D (+) from the viridans strep and nonhemolytic strep (-)


note that some group D and enterococcus are alpha hemolytic and some are non hemolytic so the bile esculein test is used in both places. For alpha hemolytic, the optochin test is done first to separate out S. pneumonaie
What is the salt broth test used for
to differentiate enterococcus from group D strep (S. bovis)
What is the purpose of using a 2 swap method for identification of throat infections
The first swab can be used to do a rapid latex agglutination test for group A strep. If the test is negative, the 2nd swab is used for culture on BAP and identification by traditional methods
What type of identification is lancefield grouping
definitive
How is the RADT (rapid antigen identification test) preformed?
1. extraction procedure to expose the cell wall antigen
2. Antigen is detected with group specific antibodies using latex agglutination or coagglutination
What is the gram stain mophology of S. pneumoniae
gram + lancet shapped diplococci
How do you differentiate the alpha hemolytic Enterococcus faecalis from strep pneumoniae
optochin disk test
Enterococcus is resistant, strep pneumo is suceptible
How do you differentiate enterococcus species from streotococcus bovis (group D)
PYR or salt broth test
enterococcus is positive
group D is negative
describe the PYR disk test
what groups can it identify?
How does it work?
rapid and presumptive test for identifying group A strep (s. pyogenes) and enterococci. Both have an enzyme that can hydrolyse PYR and form a product that makes a red complex, requres culture in log phase growth 18-24 hr
define pyoderma
strep infection of the skin leading to pus production
What is the oxidase test result for
Neisseria
Micrococcus
Streptococcus
Staphylococcus
Nessieria and micrococcus are positive
Streptococcus and Staphylococcus are negative
What type of antigens are used for lancefield grouping of beta hemolytic strep? group D strep?
beta hemolytic- carbohydrate antigens
group D- lipoteichoic acid
what organism causes mastitis in cows
S. agalactiae
T/F group C strep are usually vetrinary pathogens
True but they can infect humans also
What are the presumptive tests for identifying group A strep? Definitive
presumptive= bacitracin, PYR
definitive= Lancefield grouping
What are the presumptive tests for identifying S. pyogenes (group A) vs. S. agalatiae (group B)
bacitracin -S. pyogenes (group A) is suceptible, S. agalactiae is suceptible (group B)
CAMP- S. agalactiae is positive
Which organism has the unique concave or "doughnut" shaped colony
S. pneumoniae
What it the seletive component of the bile esculin test? differential
selective- bile
differential- esculin (hydrolysed to form dark brown/ black complex)
What are 3 ways to do antigen detection tests
1. latex agglutination
2. coagglutination
3. ELISA
What genera make up the gram positive non spore forming bacilli
Corynebacterium, Listeria, Lactobacillus
Describe the gram stain morphology of corynebacterium
gram positive
diptheroid/club shaped bacillus exhibiting palisade (acute angle chinese character) arrangemetns due to the snapping of dividng cells
Describe L monocytogens
-intreacelluar parasite
-widely distributed in the environment
-found in imporpery handeld dairy, meat products
Which human populations are most suceptible to Listeria monocytogenes infection
pregnant women, newborns, immunocompromised host
What are some manifestations of listeriosis
septicemia, gastroenteritis
Describe the two forms of fetal infection with L. monocytogenes
1. early onset- aquire infection in utero resulting in still birth or early onset of disease
2. Late onset-exposure at/ after birth resulting in septicemia and/or menigitis
Both Listeria monocytogenes and group B strep (S. agalactiae) produce weak beta hemolysis on BAP. How can these groups be differentiated?
1. catalase- listeria is positive, group B strep negative
2. umbrella motility
3. cold enrichment
4. gram stain- Listeria is a rod, group B strep is a cocci
What are the normal flora sites of Lactobacillus
low numbers in oral cavity, large numbers in GI and female genital tract
Describe the genus bacillus
gram positive spore forming rods, that form endospores and grow aerobically. Found in nature
How do humans become infected with B. anthracis
handling infected food. animals, or animal products (usually causes anthrax in sheep, cattle, and horses)
What two toxins does B. cereus make and how to they differ
1. emetic, preformed, heat stable toxin, causes intoxcation in 1-6 hrs, common in rice dishes
2. diarrheal, heat labile toxin, 10-12 hrs until sxs, contaminates, meat, veggies
We studied two organisms that produce toxins in food. What were they?
B. cereus- emetic and diarreal toxin,
S. aureus preforemd enterotoxin and exotoxin
What two organisms that we studied are particularly dangeous to newborns
listeria monocytogenes and group B strep
What rapid test will distinguish L. monocytogenes from S. agalactiae
catalase, Listeria is positive, Strep agalactiae is negative
How can you differentiate lactobacillus and streptococcus
gram stain cell morphology
In addition to food poisoning, B. cereus can cause opportunistic infections. Where/how?
trauma, implantation, IV drug use, catheter, ocular
What types of infections can result from B. anthracis
pulmonary, cutaneous (eschar lesion), gastrointestinal
Describe the unique colony and gram stain morphology of B. anthracis
granular, dry, nonhemolytic (hard to pick)
gram stain- long chains of gram positive bacilli, non motile
Describe Neisseria gram stain
small gram negative cocci that grow in pairs with adjacent sides flattened
Which two rapid tests are positive for all Neisseria spp.
oxidase and catalase
Neisseria subflava, N. lactamica, and N. sicca are nonpathogenic Neisseria species. Where do they inhabit
URT, genital tract
The only known rerservoir for meningococcus (N. meningitidis) is the nasopharynx of carrier adults. What diseases are cased when someone is infected?
septicemia
meningitis
How can gonorrhea be diagnosted in a male
-finding gram negative, kidney bean shaped diplococci within PMNs in a purulent urethral exudate
Why is a gram stain revealing gram negative kdney bean shpaed diplococci within PMNs in an exudate from a female not a definitive diagnosis of gonorrhea for a female
Non pathogenic species of resident flora may ave similar cell morphology. To confirm Dx, N. gonorrhoeae must be isloated and identified
N. gonorrhoeae and N. meningitids are obligate parasites of man so they must be grown in very specific conditions. This usually helps distinguish them from nonpathogenic strains expect for________ which can only be distinguished by biochemical tests
Nesseria lactamica
where is Moraxella catarrhalis usually a pathogen and where is it normal flora
it is a common inhabitant of the URT but it can cause opportunistic infections such as otitis media, sinusitis, an pneumonia
What media does N. gonorrhoeae require for growth. Describe how its made
N. gonorrehhoeae requires Modified Thayer Martin (MTM) media and a 5% CO2 atmosphere, MTM is chocoalte agar made by adding partially lysed RBCs with additional antifungal and antibacterial agents. It also contains selective agents to select against normal mucosal flora Nesseria spp.
Normal flora N. lactamica grows on selective/ differential MTM media. How then can it be differentiated from N. gonorreaheae
Use CTA carbohydrate utilization tests
What is the basis of the oxidase test
Neisseria (and others) produce oxidase enzyme that in the prescence of oxygen, cytochrome C and an oxidizing reagent, oxidizes the reagent and forms a dark purple color
How must Neisseria spp. be transported after a sample is taken
need room temperautre selective GC media with CO2
define capnophilic
CO2 loving
What one rapid test will differnetiate Neissiera from Staph and Strep
Oxidase
Neisseria is positive
staph and strep are negative
Besides the common infections sites as a result of sexual transmission (oral, anal, genital) where can N. gonorrhoeae be found
-ascending infection to upper reproductive tract of women
-dissemination to joints
-ocular infections in newborsn and clinical microbiologists
Describe the special steps that must be taken to obtain a sample for isolation of GC
-specail swab, no wood or cotton
-can't tolerate temperature changes
-need ~%5 CO2
Does GC grow on BAP with CO2?
No but normal flora Neisseria species do
what is an endogenous disease
a disease caused when a normal flora bacteria gets into the wrong location
What are some benefits to normal flora
-prevent colonization by pathogenic bacteria
-help synthesize vitamin K
-immune stimulation
How should a throat culture be obtained
-patient opens mouth and says "ah"
-tounge is depressed
-glide swab over tounge into the posterior phayrnx
-the mucosa behind the uvula and between and including the tonsillar pillars is swabbed with a gentle back and forth sweeping motino
How should a nasopharyngeal sample be obtained
insert swab into nostril and press swap tip on the mucosal surface of the midinferior portion of the inferior turbinate
-rub several times across the mucosal surface
what is the most perdominate oraganism in a throat culture (healthy)
viridans strep
What organisms on a BAP plante would indiaation a URT infection
-beta hemolytic group A strep
-brops B and C strep
-S. pnuemoniae
-pure culture of any gram negative bacilli
-pure culture of Staphylococcus species
What are the sterile sites of the body
blood, CSF, urine, virius of the eye, sinovial fluid, peritoneal and pleural cavity
what are bacteriocins
secreted by MOs, toxic to others usualy of similar species
What are the innate defenses of the upper respiratory tract URT
nasal turbinates and hair, mucus and cell sloughing, reflexes, antibacterial substances, phagocytes, normal flora
Does the lower respiratory tract (trachea, bronchi, alveolar spaces) have normal flora
NO!
How can a sample be collected frm the LRT
-sputum
-brochial brush (BB)
-lung biopsy or fine needle aspirate
-brochocalverlar lavage (BAL)
-bronchial wash (BW)
What two gram positive organisms are likely to cause infections in newborns
L. monocytogenes S. agalactiae (group B strep)
What two organisms that are arranged as diplococci can cause meningitis
S. pneumonaie, N. menigititis