Worksheets610 Exam 3
Total questions: 52
Worksheet time: 30mins
What is the reason that Gram positive organisms are purple in a Gram stain?
The thicker peptidoglycan is too saturated with purple dye to be displaced
The peptidoglycan prevents penetration of purple dye
Diluting the purple dye with alcohol reacts with the outer membrane
The bacterial biofilm promotes metabolism of pink dye
(Multiple answers) Which of the following are characteristics of Gram positive organisms?
Large peptidoglycan stains purple
Teichoic acid
Outer membrane with porins
Periplasmic space
(Multiple answers) Gram negatives have which of the following attributes?
Large peptidoglycan stains purple
Teichoic acid
Outer membrane with porins
Periplasmic space
You're an ID lab supervisor and your tech just informed you they think Legionella, a fastidious pathogen, just grew in a standard agar plate. What do you think?
No, fastidious organisms won't grow under standard conditions
Get out of my lab
I appreciate and agree with your judgement
Legionella is an acid fast organism and therefore can't grow on agar plates
Which of the following is not a typical investigative method for a micro lab who just received blood cultures x2 for a standard bacteremia?
Pulse field gel electrophoresis
PCR singleplex/multiplex
MALDI-TOF MS
MacConkey and Chocolate agar
(Multiple answers) Which of the following are structures involved in bacterial walls?
NAM-NAM crosslinked by pentapeptides
NAM-NAG links
Transpeptidase/Penicillin Binding Protein
D-Ala-D-Ala linking pentapeptides
Which of the following is an incorrect characteristic of real-time polymerase chain reaction (RT-PCR) for microbial identification?
Can test for one or more targets
Generally cheaper than culturing pathogens
Greatly decreases the time to narrow antimicrobial therapy
Confirmative but not quantifying
What correctly describes a selective culture?
Inhibits some groups of microbes
An all-in-one answer to fastidious organisms being hard to grow
Creates a visible difference between colonies, typically based on metabolic differences changing color
Easily distinguishes similar species from the same family or group
What correctly describes a differential culture?
Inhibits some groups of microbes
Used to determine susceptibilities
Creates a visible difference between colonies, typically based on metabolic differences changing color
Prevents microbial growth
(Multiple answers) MacConkey agar could be defined as which of the following?
Selective in favor of gram-negative bacteria
Turns lactose fermenting colonies pink-red
Both selective and differential culture
Determines microbial hemolysis and catalase efficacy
Your tech asks you if you're able to use EMB agar, a differential-selective agar, to tell the difference between KPC and non-KPC producing Klebsiella. What should you tell them?
It would be a better idea to use RT PCR for that
Yes, cultures can quickly and easily distinguish antibiotic resistance mechanisms
No, cultures are much too complicated to use on Klebsiella
No, get out of my lab
Which of the following is applicable to RT PCR use for microbe identification?
Relatively quick but could report dead organisms or pathogens that aren't causative for the disease
Generally cheaper than culturing
Can distinguish closely related species but not their resistance mechanisms
Only targets RNA and therefore can't find herpesviruses
An NP sends your a sample with suspected polymicrobial infection. What is your best tool for identifying the pathogens?
MALDI-TOF MS
RT PCR
Kirby-Bauer Disk Diffusion
Series of selective-differential cultures for likely pathogens
Which of the following could determine MICs
Epsilometer tests
MALDI-TOF MS
MacConkey agar
Anaerobic bottle culture
Which of the following has both the highest throughput and widest variety of organisms for microbe identification?
Broth dilution tests
RT PCR Multiplex
RT PCR singleplex
MALDI-TOF MS
Which of the following attributes are incorrectly matched?
MALDI-TOF MS - high initial cost but cheap reagents
RT PCR - unsuitable for polymicrobial samples
MALDI-TOF MS - requires a pure colony
RT PCR - requires a fully developed culture
A nurse sends you a blood sample that you decide to put in the MALDI-TOF MS. What must you do first?
Just put the blood sample straight in
Use PCR to determine likely species first
Throw some lactose at it to see if it ferments
Grow a pure colony
Which of the following could be an MIC?
The first clear vial in a broth dilution using escalating antimicrobial doses
Categorized as ~4x the minimal bactericidal concentration
Only determinable by RT PCR
The only way to determine definitive therapy
Your tech reports an MIC of 4 for a broth dilution. You know the S breakpoint is <2, the I breakpoint is 6, and the R breakpoint is 32. What do you put in the final report?
Pathogen is likely Klebsiella pneumoniae
MIC 4, Intermediate
MIC <2, Susceptible
MIC <32, resistant
Which of the following are determinable from broth dilution tests?
MIC
Pathogen species
Mechanism of resistance
MBC
Your technician reports a blood culture has shown alpha hemolysis. What does this mean?
Pathogen ID Staph auricularis
The pathogen has no hemolytic ability
The pathogen has shown incomplete hemolytic ability
The pathogen has shown strong hemolytic ability
Your technician reports a blood culture has shown beta hemolysis. What does this mean?
Pathogen ID Staph auricularis
Pathogen ID Burkholderia pseudomallei
The pathogen has shown strong hemolytic ability
The pathogen has shown no hemolytic ability
When are biochemical tests for identification best indicated?
Pathogen is most likely to be a species with an enzyme other species in the group don't have
Your technician have too little time to clean the PCR
You left all your cultures at home
Your hospital has frequently catalase + microbes
Your tech reports a positive Catalase test on a Gram positive coccus sample. What is your next step?
Record as likely Staphylococcus
Record as likely Streptococcus
Record as likely Enterococcus
Repeat the test
S. aureus is likely one of the most virulent bacteria - being the most likely pathogen in prosthetic infections, osteomyelitis, and SSTIs. What group does S. aureus belong to?
Staphylococcus
Streptococcus
Streptobacillus
Gram negative enterics
What is the function of Toxic Shock Syndrome Toxin (TSST) for Staphylococcus spp.?
Biofilm formation
Differentiating from Streptococcus spp.
Improving infection capability (virulence)
Abscess formation (purulence)
(Multiple answers) Select all of the following virulence factors for Staphylococcus aureus:
SCCmec
Coagulase
TSST
PVL
What is the purpose of penicillinase, an enzyme expressed by nearly all Staphylococcus spp.?
Virulence
Lysis of multiple penicillin drugs
Biofilm formation
Encoding PBP2a
What is the purpose of SCCmec, a gene common for Staphylococcus spp.?
Virulence
Encoding PBP2a, providing resistance to (methicillin) all beta-lactams
Encoding penicillinase, providing resistance to some beta-lactams
Providing resistance to Ceftaroline
When would you pursue further testing to determine if Coagulase Negative Staphylococcus (CoNS) is a causative pathogen?
Never, CoNS is always a contaminant
You receive a single positive culture
The patient has a prosthetic
The patient is diabetic
Select all of the most likely clinical syndromes for S. aureus:
Endocarditis
SSTIs
Osteomyelitis
Cystitis
What are the two most common clinical syndromes for CoNS?
Hospital/Ventilator-acquired pneumonia
Endocarditis
Toxic Shock Syndrome
Hardware infection
Your technician reports both a culture with gold colored cocci clusters and a positive latex agglutination test. What do you report?
Methicillin resistant Strep aureus
Actinomyces
Staph aureus
CoNS
What are the two primary results of the catalase test for Gram positive organisms?
Positive - Streptococcus
Positive - Staphylococcus
Negative - Streptococcus
Negative - Staphylococcus
Which of the following are applicable to Streptococcus spp.?
Aerobic but could be facultative anaerobes
Streptococcus viridans is the primary infective species
GBS (S. agalactiae) and GAS (S. pyogenes) are the primary beta hemolytic groups
Lancefield groups relevant to the class are A, B, and D (S. pyogenes, S. agalactiae, and S. bovis respectively)
What is the primary clinical syndrome to be expected of viridans group Strep?
Pneumonia
Community acquired meningitis
SSTIs
Endocarditis
Which of the following are common resistance factors for Streptococcus spp.?
Hyaluronidase and streptolysins
Erythrogenic toxin or pneumolysin
vanA and vanB
Mutated PBPs
What Strep species would prompt you to screen for colon/GI cancer if found in the bloodstream?
Staphylococcus aureus
S. bovis
GAS or GBS
Strep. pneumoniae
What is the most common cause of community acquired pneumonia and meningitis?
Staphylococcus aureus
Streptococcus aureus
S. pneumoniae
Enterococci spp.
The Rapid Strep test is unsensitive but very specific. What is the most likely false outcome?
False positive
False negative
Detecting Enterococci, a similar pathogen
Detecting Staphylococcus
Your panicked tech comes to you about vancomycin resistant E. faecium in a stool sample of an ocular infection patient. What is your course of action?
Vancomycin STAT
Recommend amoxicillin oral suspension
Send the final report as positive for catalase positive coagulase negative gram-positive organisms
Do nothing, it's not important
What clinical syndrome would be surprising for Enterococci?
IAI following an ill-performed colonoplasty
URTI in a 28 year old athlete
Bacteremia following advanced untreated cystitis
UTI after poor handling of a Foley catheter
What resistance mechanism is common in E. faecium and rare in E. faecalis?
vanA and vanB (altered target site)
vanA and vanB (efflux pump)
Amoxicillin efflux pumps
Amoxicillin altered binding
Which of the following are attributable to Clostridioides difficile?
Most commonly Toxin A- B+
Frequently causes pseudomembranous colitis
Infection is most commonly linked to antibiotic use (clindamycin historically)
Forms spores resistant to alcohol sanitizer
Which of the following is associated with C. diff-associated diarrhea?
Severe leukopenia
Acute and extreme leukocytosis
Food-borne illness following Dented Can Syndrome
Generalized tetanus
How is C. diff most properly diagnosed?
Testing stool samples at first sign of diarrhea
Culturing during active, serious infection
Repeating stool test after a negative 4 days ago
GDH EIA -> direct EIA for toxins
Select all of the appropriate infection control for Clostridioides difficile infection:
Alcohol foam in & out
Soap & water hand washing signs
PPE required to enter room
Terminal bleach cleaning
What are the two most common transmission pathways of Clostridium botulinum?
Fecal-oral
Aedes mosquito
Food-borne (unprocessed honey, Chipotle, dented cans)
Wound contamination
A gram stain reports racket shaped Gram positive anaerobes with heat stable spores. What pathogen do you expect?
Streptococcus aureus
Clostridioides tetani
Actinomyces
Clostridium tetani
Match the following pathogens to their correct clinical syndrome:
Staphylococcus auricularis - Impetigo
Parainfluenza - croup
Clostridium perfringens - gas gangrene
Clostridioides tetani - non-native valvular endocarditis
In which of the following circumstances would Cutibacterium be worrying?
Stool sample in a patient with impacted bowel
Expecting mother expected to deliver within a day
Prosthetic joint replacement
Nosocomial-onset meningitis
Which of the following Gram stains is incorrectly matched?
Acid fast - clear
Gram positive - pink
Gram positive - purple
Gram negative - pink
