Exam 1 Flashcards
List the two Gram+ aerobic cocci:
Staphylococcus
Micrococcus
What differentiates S. aureus from S. epi/sap?
*S. aureus is Coagulase+ and beta hemolytic
+S.epi/sap are Coagulase- and gamma hemolytic
This media is selective for S. aureus due to what:
Mannitol Salt
Due to increased NaCl and lactose fermentation (yellow halo)
T/F Staphylococci spp. are Bacitracin resistant:
True
Staphylococci is lysostaphin ______:
susceptible
Are Staphylococci spp. microdase + or -?
negative (will stay original color)
Describe the Gram stain morphology of Staphylococci spp.:
Gram+ grape like clusters (some tetrads and pairs)
T/F Staphylococci are facultative anaerobes:
True
What media will Staphylococci spp. grow on:
SBAP
Chocolate
Mannitol Salt (selective)
What type of growth will S. epi and S. sap show on Mannitol Salt agar:
- S. epi: growth but no ferment
* S. sap: growth but varied ferment
Which bacteria can cause Ritter disease aka Scalded Skin Syndrome:
Staph aureus
Is Staph aureus coagulase+ for bound factor, free factor, or both:
Both
Confirmed via tube test
(slide test only shows bound factor)
Gram+, catalase+, coagulase+, medium to large creamy yellow colonies w/ beta hemolysis:
Staph aureus
Which bacteria causes tampon related TSS:
Staph aureus
What pathologies can Staph aureus cause:
Ritter disease TSS Folliculitis, stye, furuncles Food poisoning Impetigo Bacteremia (catheters) Endocartitis (can be nosocomial)
T/F Endocarditis caused by S. aureus can be nosocomial and mortality rate can reach ~50%:
True
Extracellular enzymes and toxins are associated with what bacteria:
Staph aureus
This enzyme breaks down fibrinogen into fibrin, and helps protect bacteria from phagocytosis:
Coagulase
This enzyme dissolves fibrin/clot, enabling infection to spread:
Staphylokinase
These cause lysis of neutrophils and macrophages, inhibiting phagocytosis:
Leukocidins
These lyse RBC’s:
Hemolysins
(alpha, beta, gamma, delta all lyse RBC’s)
(all but beta may lyse WBC’s)
Which hemolysin does not also lyse WBC’s:
Beta
This enzyme hydrolyzes hyaluronic acid in connective tissues, spreading infection:
hyaluronidase
Lipase enzymes hydrolyze plasma and skin lipids, enabling organism to colonize this part of the body:
Skin (boils, etc)
This enzyme hydrolyzes tissue and are prevalent in Ritter’s Disease:
Exfoliatins
These enzymes consist of 7 heat stable proteins:
Enterotoxins
A, B, C, C2, D, E, F
Which two enterotoxins are responsible for most food poisoning:
A and B
Which enterotoxin is also known as TSST-1 (toxic shock):
F
Enterotoxin F is associated with this pathology:
TSS
Enterotoxins A and B are associated with this pathology:
Food poisoning
This cell wall protein is capable of binding IgG molecules at the Fc/Fab region of B cell receptors, impairing opsonization and phagocytosis:
Protein A
What do beta-lactamases do:
They are bacterial enzymes that bind to the beta-lactam ring in antibiotics, making them ineffective
Bullous impetigo is associated with this bacteria and will culture ___:
S. aureus
positive
What differentiates Staph epi from Staph sap:
S. epi: Sensitive to novobiocin
S. sap: Resistant to novobiocin
Which Staph sp is resistant to novobiocin:
Staph saprophyticus
Which Staph sp is NOT nosocomial:
Staph saprophyticus
This bacteria is known to produce biofilm, causing nosocomial infections w/ prosthetics, etc:
Staph epidermidis
This bacteria is the 2nd most common cause of UTI’s in females:
Staph saprophyticus
Gram+, Catalase +, Coagulase-, opaque small gray-white colonies, gamma hemolytic, shows growth but NO fermentation of Mannitol salt agar:
Staph epidermidis
Gram+, catalase+, coagulase-, bright white creamy colonies, gamma hemolytic, shows growth and varied degrees of fermentation on Mannitol salt agar:
Staph saprophyticus
T/F Most coagulase- Staph spp are normal flora; thus are common contaminants in clinical specimens:
True
Most frequently encountered coagulase- Staph spp:
Staph epidermidis
What imparts wide range of antibiotic resistance to MRSA:
mecA gene
What are the two forms of MRSA:
- community acquired
* hospital acquired (nosocomial)
What is the treatment for MRSA:
Macrolide antibiotics
clindamyciin or vancomycin
What is used for susceptibility testing of MRSA and why:
Oxacillin or Cefotoxin
*because Methicillin is no longer available in US
What media is selective and differential for MRSA:
BBL CHROMagar MRSA II
What makes BBL CHROMagar MRSA II selective and differential for MRSA:
- Selective: Cefotoxin (inhibits Gram- and yeasts)
* Differential: Chromagen additives (MRSA hydrolyzes chromagen, producing mauve colonies)
Micrococcus is strictly ______:
aerobic
Describe the Gram stain morphology of Micrococcus:
Gram+ tetrads
T/F Micrococcus is normal flora of skin, mucosa, oral pharynx, and is common contaminant of clinical specimens:
True
T/F Micrococcus is highly pathogenic:
False
Is normal flora and common contaminant of clinical specimens
Describe presumptive vs definitive ID of MRSA on BBL CHROMagar:
- Presumptive: mauve colony growth w/in 48
* Definitive: mauve colony growth w/in 24 hours
Micrococcus spp. is bacitracin ____ and lysostaphin _____:
- Bacitracin susceptible
* Lysostaphin resistant
Colonies of this bacteria on SBAP can be white, tan, yellow, golden yellow, orange, pink:
Micrococcus spp.
This bacteria is strictly aerobic, appears as Gram+ tetrads, microdase+, is bacitracin susceptible, lysostaphin resistant, and colony color is varied:
Micrococcus spp.
List the bacteria included in the group Gram+, Catalase-, Oxidase-:
Streptococcus spp. Enterococcus spp. Viridans Strep Leuconostoc Aerococcus Abiotrophia
Gram+ cocci are commonly normal flora of upper respiratory tract, but can be pathogenic in _____:
throat
Staph is catalse ___ and Strep is catalase___:
Staph: catalase+
Strep: catalase-
T/F Strep pyogenes can be normal flora:
False.
All Strep spp EXCEPT S. pyogenes can be normal flora
What is the drug of choice for S. pyogenes, S. agalactieae, and groups C, F, G:
Penicillin
if allergy, use erythromycin
Susceptibility testing is indicated for which species of Strep due to resistance:
S. pneumoniae
Viridans Strep
The serologrouping based on surface carbohydrate antigens of various Strep species:
Lancefield group
A, B, C, D, F, G
Which Lancefield groups are clinically significant:
A, B, C, D
What antibiotics are used for susceptibility testing in Strep spp.:
Bacitracin
Optochin
Bile solubility test is positive (turns brown) in this Strep sp?
S. pneumoniae
Which Gram+, catalase- cocci are PYR positive (turns pink) :
Strep pyogenes
Enterococcus sp.
A positive result with this test gives a presumptive ID for Group B strep (agalactieae):
Hippurate hydrolysis (positive= purple)
The CAMP test is positive in this Gram+, catalase-, aerobic cocci:
Strep agalactieae
What can interfere with the CAMP test:
CO2 (don’t use a candle jar)
Is Enterococci pos or neg for Salt Tolerance Test:
positive
turns yellow or turbid
Is Group D Strep pos or neg for Salt Tolerance Test:
negative
stays purple
Describe Gram stain morphology of Strep pyogenes:
Gram+ cocci in chains
What would you do to SBAP when culturing a throat swab:
inoculate plate with SXT antibiotic to inhibit growth of normal flora
Describe colony morphology of Strep pyogenes on SBAP:
gray-white colonies w/ beta hemolysis
What can be a complication of Strep throat in children due to M protein:
Glomerulonephritis)
95% recover w/ treatment
Necrotizing fasciitis is associated with this bacteria:
Strep pyogenes
TSS with bacteremia and necrotizing fasciitis is associated with this bacteria:
Strep pyogenes
List the 4 virulence factors associated with Strep pyogenes:
Streptolysin O
Streptolysin S
M protein
SPE’s
Streptolysin O is oxygen_____, Streptolysin S is oxygen_____:
O: oxygen LABILE (inactived by O2)
S: oxygen STABLE
Which Streptolysin is antigenic:
Streptolysin O is antigenic
induces host immune response w/ antibody production
These virulence factors induce lysis of RBC’s, WBC’s, and platelets:
Streptolysins O and S
Which virulence factor of Strep induces antibody formation and may cause disease post-infection:
M protein
Which diseases can M protein virulence factor cause post-infection with Strep pyogenes:
- Rheumatic fever (fever, endocarditis)
* Glomerulonephritis
This virulence factor associated with S. pyogenes can induce fevers, inflammation, shock, Scarlet fever:
Streptococcal Pyrogenic Exotoxins (SPE’s)
What virulence factors cause Rheumatic Fever and Scarlet Fever:
- Rheumatic: M Protein
* Scarlet: SPE’s
This can occur from S. pyogenes related SPE’s and involves red rash, skin peeling, sore throat, fever:
Scarlet Fever
treat w/ 10 day course antibiotics
Which test would be ordered if recent strep infection suspected and experiencing other disease symptoms such as glomerulonephritis:
ASO
(anti- streptolysin O)
***will only show if pt had recent strep infection
Lancefield grouping is done via this test:
latex agglutination
Group B strep:
Strep agalactieae
Which bacteria is associated with respiratory distress, sepsis, pneumonia, meningitis, and death in neonates if mother is not treated:
Strep agalactieae
Group B
T/F Strep agalactieae is beta hemolytic
True
Which Strep species are alpha hemolytic:
S. pneumoniae Strep Viridans (occasionally gamma)
This bacteria has small gray colonies resembling donuts:
Strep pneumoniae
This bacteria is the leading cause of bacterial pneumonia and meningitis:
Strep pneumoniae
at risk under 2, over 65
PCV13 and PPSV23 are vaccines for what bacteria:
Strep pneumoniae
Does Strep pneumoniae contain any virulence factors:
Yes. C Polysaccharide
impedes phagocytosis
S. sanguis, S. mitis, S. gordonii, S. anginosus, and S. mutans belong to this group:
Strep Viridans
Which species within Strep Viridans is linked to dental caries:
Strep mutans
Do species within Strep Viridans possess group antigens?
No.
Are species within Strep Viridans highly pathogenic?
No. Low virulence, but maybe cause endocarditis and meningitis.
What test differentiates Viridans Strep from Enterococcus and Group D Strep:
Bile Esculin
*is negative in Viridans Strep
This Gram+, catalase- cocci may display alpha, beta, or gamma hemolysis:
Enterococcus spp.
Treatment for Enterococcus spp:
Vancomycin + aminoglycoside
Enterococcus spp is resistant to ____ and ___, and is becoming increasingly resistant to ______:
Cephalosporins and Aminoglycosides
Vancomycin (VRE)
VRE:
Vancomycin Resistant Enterococcus
This bacteria used to be named Streptococcus faecalis (Group D Strep), but is now:
Enterococcus faecalis
T/F Enterococcus spp mostly causes nosocomial UTI’s, but is also a significant cause of endocarditis:
True
This bacteria is becoming increasingly resistant to Vancomycin:
Enterococcus spp.
Enterococcus spp is ______ for Salt Tolerance test, PYR test, and Pyruvate broth:
Positive
What test differentiates E. faecalis (positive) from E. faecium (negative):
Pyruvate broth
Natural habitat is plants, veggies, dairy:
Leuconostoc spp.
This bacteria is rarely pathogenic, but can cause meningitis, bacteremia in immunocompromised, also linked to nosocomial outbreak in Spain:
Leuconostoc spp.
T/F Only some Leuconostoc spp are resistant to Vancomycin:
False.
ALL Leuconostoc spp. are Vancomycin resistant.
Gram+, Catalase-, PYR-, cocci in chains and pairs, alpha hemolysis, produces CO2 from glucose:
Leuconostoc spp.
Should Leuconostoc spp. first be considered a contaminant in a clinical specimen?
Yes. It is rarely pathogenic.
What is the natural habitat of Leuconostoc spp?
Plants, veggies, dairy
List the 3 organisms for Gram- diplococci, oxidase+:
Neisseria meningitidis
Neisseria gonorrhoeae
Moraxella catarrhalis
Are there non-pathogenic Neisseria spp that can be normal flora of upper respiratory tract:
yes
The Gram- diplococci grow best under what conditions:
Increased CO2 and humid conditions
Is Neisseria meningitidis normal flora?
Yes, of oropharyngeal/nasopharyngeal mucous membranes.
Presumptive ID of what organism: Gram- diplocci, oxidase+, Strong positive w/ 30% H202:
N. meningitidis
What is required to make a definitive ID of N. meningitidis:
GGAP- and BG-
Must grow on selective agar
What is the treatment for Neisseria meningitidis:
Broad spectrum antibiotic + corticosteroids
IV penicillin still a possibility, but resistance developing
What is the prophylactic treatment for N. meningitidis:
Rifampin
MCV4 and MPSV4 are vaccines against what organism:
N. meningitidis
Diptheria protein can be added to a vaccine to do this:
Large size will elicit stronger immune response (used for healthy young adults)
What media will grow Neisseria meningitidis:
SBAP
Chocolate
Modified Thayer-Martin (selective)
Martin Lewis (selective)
What should be done with specimens of suspected N. meningitidis:
Should be plated immediately to appropriate culture media and transported in CO2 environment
Why do you not want to use cotton swabs for gathering bacterial specimen:
toxic fatty acids present in cotton– use Dacron swabs instead
JEMBEC, Bio-Bag, and Gono-Pack System are all types of what:
CO2 transport systems
JEMBEC CO2 transport system comes as transport swabs with Amie’s Media w/ charcoal. What is the purpose of the charcoal?
Charcoal inhibits toxic fatty acids present in cotton fibers
What are the 1st and 2nd causes of bacterial meningitis in the US:
1) Strep pneumoniae (pneumococcus)
2) N. meningitidis (meningococcus)
What are the mortality rates for N. meningitidis meningitis, treated vs untreated:
Mortality rate:
Treated 10%
Untreated 100%
What is the syndrome associated with overwhelming bacteremia caused by Neisseria meningitidis:
Waterhouse-Friderichsen Syndrome
Describe the symptoms of Waterhouse-Friderichsen Syndrome:
Bacteremia w/ N. meningitidis
Sudden onset fever, cyanosis, petechiae
Bilateral adrenal hemorrhage, shock
20% mortality rate
Bacteria responsible for most cases of newborn meningitis:
Strep agalactieae (Group B)
Bacteria responsible for most cases of meningitis in infants/children:
Strep pneumoniae (pneumococcal)
Bacteria responsible for most cases of meningitis in adolescents/young adults:
Neisseria meningitidis (meningococcal)
Bacteria responsible for most cases of meningitis in older adults:
Strep pneumoniae (pneumococcal)
Strep pneumoniae is the primary bacteria responsible for causing meningitis in these age groups:
Children
Older adults
Can people be asymptomatic carriers of Neisseria gonorrhoeae:
Yes, but it is NEVER normal flora.
Presumptive ID of what bacteria is derived from Gram-, oxidase+ diplococci, glistening non-hemolytic on BAP:
Neisseria gonorrhoeae
What is required for a definitive ID of N. gonorrhoeae:
GGAP+
remember N. meningitidis is GGAP-
What are the 1st and 2nd most common STD’s in the US:
1) chlamydia
2) gonorrhoeae
Where does N. gonorrhoeae infect in males vs females:
Males: urethra
Females: cervix
Gonococcal opthalmia neonatorum:
Occurs in neonates delivered vaginally by N. gonorrhoeae infected mothers; causes blindness
Which 3 agar medias are selective for N. gonorrhoeae?
Modified Thayer Martin
Martin Lewis
New York City Media
Which two medias are selective for both N. gonorrhoeae and N. meningitidis?
Modified Thayer Martin
Martin Lewis
Does N. gonorrheae require special transport?
Yes. It requires a CO2 environment.
JEMBEC, Bio-Bag, Gono-Pack
What has to be done to N. gonorrhoeae before Gram staining?
Fluids must be centrifuged to concentrate organisms.
Why is presence of Gram- diplococci in vaginal secretions NOT dx for N. gonorrhoeae in females?
Normal flora of female GI/GU tract can resemble Neisseria spp.
What is a definitive ID of N. gonorrhoeae in males?
Gram- diplococci inside PMN’s from urethral discharge
Why is it important to do an oxidase test on N. gonorrhoeae even though all three Gram- diplococci are oxidase+?
Can exclude Neisseria spp. and other oxidase- coccobacilli
Medicolegal require this for definitive dx:
two forms of ID via combination of tests
What is required for presumptive ID of N. gonorrhoeae in sexually active adults:
Sample from genital sites
Gram-, oxidase+ diplococci grown on selective media
This process differentiates strains of N. gonorrhoeae based on growth with media with different nutrient sources that allow for subtyping (L-proline, etc):
Auxotyping
Why is auxotyping valuable in N. gonorrhoeae:
valuable epidemiological tool, distinguishes between treatment failure vs reinfection
How would you distinguish between treatment failure vs reinfection of N. gonorrhoeae of a patient:
Auxotyping
13 serotypes exist for N. gonorrhoeae, which are the 5 most encountered in the US?
A, B, C, Y, W135
Which serotypes of N. gonorrhoeae are the most frequent cause of epidemics:
Group A and C
Serogrouping is achieved via this method:
agglutination tests
This is a significant pathogen in sputum, can cause otitis media, sinusitis, and pneumonia:
M. catarrhalis
Gram-, oxidase+, tributyrin hydrolysis+ diplococci:
M. catarrhalis
Neisseria spp are tributyrin hydrolysis-
This colony can be slide across an SBAP culture plate like a hockey puck:
M. catarrhalis
T/F Moraxella catarrhalis is normal flora of upper respiratory tract, possibly female genital tract:
True
Does M. catarrhalis produce beta-lactamase?L
Yes, though beta-lactams remain effective.
What is used to differentiate M. catarrhalis from Neisseria spp. for a definitive dx:
DNase Test Agar
M. catarrhalis is positive = turns green media colorless
What phase does exponential bacterial growth occur:
Log phase
What do prokaryotes have instead of a nucleus?
- Nucleoid containing DNA
* Plasmids containing extrachromosomal DNA
What does the cell envelope consist of in Gram positive bacteria:
- Cell wall (pg, teichoic acids)
* cell membrane (encloses cytoplasm)
What does the cell envelope consist of in Gram negative bacteria:
- Outer membrane
- Periplasmic space (pg)
- cell membrane (encloses cytoplasm)
List the 3 cellular appendages:
1) capsule
2) fimbriae/pili
3) flagella
This is the outermost layer of both Gram+/-, made of polysaccharides, helps bacteria evade immune system and aids in formation of biofilms:
Capsule
A hardy state that allows bacteria to survive harsh conditions and escape common treatments:
endospores
List the 4 outcomes of bacterial infection:
- Resolution (return to normal)
- Restoration of health (w/ lasting effects)
- Survival (severely compromised)
- Death
What is the goal of the microbiology lab?
To tailor treatment via correct microbial identification.
Ideally, (but maybe not realistic) all specimens should be transported to the lab within ____ hours of collection:
2 hours
What is a holding media:
Amie’s and Stuart’s
*maintains viability but does not support growth
List the special preservatives for each specimen-
Urine:
Stool:
Blood:
urine–> Boric acid
stool–> PVA
blood–> anticoagulants (SPS most common)
What specimens have priority in the microbiology lab:
CSF and blood
What stain is used for bacteria that won’t stain well with Gram:
Acid Fast
Primary stain is carbolfuchsin
What kind of dilution is a 4 phase plate streak:
semi-quantitative
grade 1+ to 4+
How do you streak for urines:
Streak down the middle and then side to side from initial streak. (quantitative method as loops are calibrated)
Most bacteria are incubated at this tempL
35-37 degrees C
These bacteria can grow under aerobic OR anaerobic conditions:
facultative anaerobes
Chocolate agar-
- enriched with:
- heat releases:
- supports growth of:
- incubate with:
- can only detect ___ hemolysis:
- BAP hemolyzed red cells by heat
- X factor and V factor
- N. gonorrhoeae
- CO2
- alpha
PEA agar
- selective for Gram__ __:
- inhibits ___ and ___:
- can be enriched with __ for staph and strep:
- selective for Gram+ cocci
- inhibits Gram- bacilli and swarming Proteus
- enriched with sheep blood
Modified Thayer-Martin Media is highly selective for ____:
N. gonorrhoeae
These can be added to Modified Thayer Martin Media for selectivity-
- Colistin, inhibits____:
- Vancomycin, inhibits ____:
- Nystatin, inhibits ____:
- Trimethoprin, inhibits ___:
- Colistin inhibits gram-
- Vancomycin inhibits Gram+
- Nystatin inhibits yeasts
- Trimethoprim inhibits spreading of Proteus
Modified Thayer-Martin Media is enriched with _____ and _____:
Chocolate agar + hemoglobin
This agar is selective for N. gonorrhoeae, Ureaplasma urealyticum, and Mycoplasma spp.:
New York City agar
XLD agar is selective and differential for _____ and ____:
Salmonella spp. and Shigella spp.
XLD agar contains 3 sugars for fermentation differentiation, acid production turns red media this color:
yellow
How can you tell Salmonella and Shigella apart on XLD agar, since they are both non-fermenters:
Salmonella produces hydrogen sulfide, creating black centers of colonies
LIM broth is prepared from ___ and ___:
Todd Hewitt broth + added antibiotics
LIM is a selective enrichment broth to promote growth of this bacteria:
Strep agalactiae
What is the most widely used enrichment broth in bacteriology:
Thioglycollate broth
This media contains casein, yeast, beef extracts, vitamins, and an agar supplement to make it semi-solid:
Thioglycollate broth
What is the purpose of thioglycollate broth being semi-solid:
to support growth of anaerobes deep in tube
What are the 3 enzyme tests used for Gram+ bacteria:
PYR test
Catalase
Coagulase
A positive PYR is:
disk turns red 5 minutes after addition of PYR reagent
A positive catalase test is:
bubbling
A positive coagulase test is:
agglutination
A positive PYR test is presumptive ID for ___ and ____:
S. pyogenes and Enterococci
Catalase test is used to differentiate ___ from ____:
Micrococcus (catalase+)
Staphylococci (catalase-)
Coagulase test is used to differentiate ____ from ____:
Staph aureus (coagulase+) other Staph spp. (coagulase-)
What 3 enzyme tests are used for Gram- bacteria:
Indole
Oxidase
Urease
Indole test is used for presumptive ID of ____:
E. coli
A positive indole test:
blue color development
This test is used to differentiate among Gram- bacteria:
Oxidase
Microdase test is a modified oxidase test used to differentiate ____ from _____:
Micrococcus (+)
Staphylococcus (-)
A positive oxidase test:
dark purple
Urease test is used to presumptively ID _____:
Proteus spp (positive)
A positive urea test:
slant turns red
The % of people in whom the organism is present actually test positive:
Sensitivity
The % of people without the disease that test negative for the organism:
Specificity
This media is selective for Staph aureus, differential for S. epi and S. sap:
Mannitol Salt Agar
What would the test results be for Enterococcus with-
PYR:
Salt Tolerance:
Pyruvate Broth:
+
+
+