Old Micro Written Exams 2 Flashcards
- Hematologic findings in blood smear with the following conditions:
a. Babesiosis
b. Diphyllobothrium
c. Ehrlichia
d. EBV
a. Babesiosis – Intracellular and extracellular small ring forms, maltese cross conformation
b. Diphyllobothrium – Megaloblastic anemia (Vitamin B12 deficiency)
c. Ehrlichia – detection of morulae in the cytoplasm of infected monocytes
d. EBV – Reactive (atypical) lymphocytosis
- Name 2 quality indicators each in the pre-analytic, analytic, and post-analytic phases.
Pre-Analytical: Blood culture volumes, Specimen mislabelling , Blood culture contamination rates, Sample delivery times
Analytical: Time to reporting of stat Gram Stains, QC performed accurately and on schedule, Sample contamination
Post-Analytical: Correct antibiotics given based on susceptibility report, Report delivery turn around times, Critical result reporting, proportion of corrected reports
- Your lab wants to replace GC culture with urinary PCR for women. Name 3 disadvantages or limitations.
- Unable to perform susceptibility
- High costs
- Carryover contamination risk
- High QC requirements
- Assays are susceptible to inhibition from substances found in the urine
- Cross reaction with Neisseria lactamica (QMPLS document)
- Name 2 disadvantages for Chlamydia PCR.
- Can not use for medico-legical purposes
2. Nongenital specimens have not been FDA approved
- Safety for PGFE: what precaution should personnel take in handling the gel? What document should always accompany this product? What safety procedure must be done while taking the UV picture?
Always wear gloves when handling the gel due to the Ethidium Bromide.
An MSDS should always be with this product
When taking the UV picture make sure to wear protective eye wear
UV source should be contained
Kidney transplant with increasing creatinine. There are decoy cells in urine. What infection do you suspect? What are 2 test specimens to submit?
BK Virus
- Urine and serum for PCR for BK Virus
- Renal Biopsy to detect cytopathic effect and positive immunohistochemistry staining for SV40 large T antigen
- You suspect coccidiomycosis. Name two method to confirm.
Culture
Histopatholgy of biopsy
Serology
Antigen Testing
EIA for IgM and IgG are the most sensitive screening tests. The immunodiffusion tests are less sensitive but more specific.
Note: Gram stain does not stain the spherules. They can be seen with a saline or KOH wet mount, Calcoflour staining, or PAP stain. For tissue can use H&E, PAS or Silver Staining.
GenProbe has an antigen detection kit that can be used from cultures and detects C. immitans specific DNA.
- Coxiella serology: phase I antibodies 1/1600; phase II 1/50. Interpret.
Chronic Q fever Infection
- Name 3 yeast that are urease +.
- Cryptococcus
- Rhodotorula
- Trichosporon
- Malessezia
- Candida krusei
- Candidia lipolytica
- Women with parvovirus B19 IgM +. 3 interpretations. What should you do next?
1) Acute infection (IgM present in 7-10 days)
2) Infection in the past 3 months (IgM lasts 2-3 months, but can last up to 6 months)
3) False positive IgM (due to Rheumatoid Factor)
Determine if pregnant
Check IgG Ab, if acute may have negative IgG, if 3 months ago IgG should be present. Can test IgG avidity to help distinguish between recent and past infections. (High avidity = past infection, low avidity = recent). Not commercially available.
Can test blood for Parvovirus DNA to determine possible infection via NAT (PCR).
Order CBC to assess for aplastic anemia.
Can also repeat serology to determine if there was
- Fusiform GNB in blood in splenectomised patient. What is the likely organism? Name another organism with similar gram stain morphology.
Capnocytophaga
Fusobacterium nucleatum
Leptotricia buccalis
- Contact lens wearer went swimming w/ his contacts on and develops keratitis.
a. What is the likely diagnosis?
b. What two stains should be done on the corneal
c. What is the best culture medium?
Acanthaomeba keratitis
b. What two stains should be done on the corneal scraping? Trichrome Modified Fields Stain Hemacolor Stain Fluorescent Dye Calcoflour Geimsa
c. What is the best culture medium?
Create a lawn of E.Coli or Enterobacter aerogenes on a petri dish with 1.5% Difco agar made with Page’s amoeba saline. This is a non nutrient media. Then inoculate the specimen
Because of several years of high-level West Nile circulation, your lab wants to institute an IgM test. What are 2 disadvantages? What test do you use for detecting WNV in organs?
Disadvantages: 1) Cross reaction with other Flaviviridae viruses – need to follow a positive IgM with a neutralization test to determine which virus is causing the positive IgM
2) West Nile Virus IgM can remain positive for up to 2 years
after infection
3) IgM may be negative very early on in infection
Advantages: Short period of viremia, so hard to detect early. IgM is present within 3-5 days of the illness and appears early in the CSF (2-3 days).
Diagnosis in Organs = PCR
- Patient on ganciclovir for CMV has persistant positive antigenemia. Name 2 resistance mechanisms for gancyclovir to CMV. Name 2 tests for susceptibility testing of CMV against ganciclovir. What 2 antivirals can you use if ganciclovir is resistant?
Resistance Mechanisms:
- Alternation in phosphorylation of gancyclovir, therefore the drug is not rendered active (UL97 - phosophotransferase gene mutation)
- Alteration in the viral DNA polymerase gene (UL54) : Also R to foscarnet
Susceptibility Testing:
- Phenotypic Assay – measures the ability of CMV to grow in cell culture in the prescence of various concentrations of antiviral drugs
- Genotypic Assay – to detect the known resistance genes via PCR and sequencing, or probes
Antivirals:
- Cidofovir
- Foscarnet
- For rapid-growing mycobacteria, list 4 antibiotics found in the antibiogram.
- Clarithromycin
- Doxycycline
- Amikacin
- Cefoxitin
- Linezolid
- TMP-SMX
- Imipenem
- Moxifloxacin
- Tobramycin
- Ciprofloxacin
- African with general deterioration. Negative HIV serology 6 months ago. Returns from trip to Africa. Rapid test HIV negative, but ELISA pos, WB indeterminate at reference lab.
a. What are two possible explanations?
1) HIV2 infection (will be negative on rapid test)
2) Early HIV1 infection with false negative rapid HIV result
3) Group O HIV1 infection
4) Group M, non B infection
5) False positive ELISA due to immune complexes (this is a problem with the p24 antigen ELISAs, not the 3rd generation tests but maybe the 4th generation tests. That’s why the positives have to be confirmed with NAAT or Western blot)
- African with general deterioration. Negative HIV serology 6 months ago. Returns from trip to Africa. Rapid test HIV negative, but ELISA pos, WB indeterminate at reference lab.
b. What 2 tests should you do to supplement?
1) HIV1 NAT
2) HIV2 NAT
3) HIV2 specific Western Blot
4) Repeat the ELISA
5) Use an IFA to resolve the discrepant Western Blot result
- Man with chronic cough. Dog was diagnosed with canine pertussis. A throat culture is growing on Bordet Gengou, coryneform that is oxidase positive.
a. What is the most likely etiologic agent?
b. Name 3 phenotypic tests for this bacterium.
c. What biosafety containment level is needed?
Bordetella bronchoseptica
b. Name 3 phenotypic tests for this bacterium.
1) Catalase positive
2) Motility positive
3) Reduction of Nitrate positive
4) Urea Reduction Positive
c. What biosafety containment level is needed?
Biosafety Containment Level 2
- Differentiate between B anthracis & cereus.
hemolysis
colonial morphology
motility
β-lactamase
Hunter gets sick. Blood cultures show small GNCB that is oxidase -, catalase weak +, urea -, only growing on chocolate.
a. What is the diagnosis?
b. What special nutrient does this bacterium need?
c. What 4 antibiotics does a reference lab need to test for?
Tuleremia (Fransicella tularensis) b. What special nutrient does this bacterium need? Cysteine c. What 4 antibiotics does a reference lab need to test for? 1) Gentamicin 2) Doxycycline 3) Ciprofloxacin 4) Chloramphenicol
- What are 4 CLSI criteria for cumulative antibiotic susceptibility reports?
1) Data verification – only report final, verified results
2) Only report one isolate of the same species per patient during the time frame of the report
3) Data should be analysed at least annually
4) Include only species with testing data for >=30 isolates
5) Include only diagnostic isolates (not surveillance)
6) Include only routinely tested antimicrobial agents
- POW from world war II in Japan complains of itchy skin, description of larva currens on the trunk. What is the diagnosis? Name 2 methods for finding this parasite in the stool?
Strongyloides stercoralis
To find the parasite in the stool:
1) Agar plate culture – look for the larvae to drag bacteria around the plate, then flood with saline and centrifuge to look for the rhabdiform larvae
2) Harada-Mori technique – feces on a filter paper dipped in water, the parasites migrate to the water and can then be detected via microscopy
3) Microscopy of feces (low sensitivity) after concentration
- Your technician drops a blood culture bottle growing M. tuberculosis. What are the 5 steps to take in chronological order?
- Hold your breath (if you are not already wearing PPE)
- Put on appropriate PPE
- Turn off centrifuges?
- Turn on BSC?
- Contain the spill so it doesn’t continue to spread
- Exit the area safely and wait 30 minutes until returning
- How do you confirm the presence of an ESBL by broth dilution w/MIC? Name 4 bacteria that should be screened for ESBL if found in blood culture.
Using CAMHB agar do MIC testing of Ceftazidime and Cefotaxime both with and without Clavulanate. A ≥3 twofold dilution concentration decrease in MIC in either agent in combination with clavulanate compared to either agent alone is positive for ESBL.
Example: CAZ MIC =8, CAZ/CV MIC = 1 would be an ESBL
4 bacteria to screen for ESBL
i. Klebsiella pneumonia
ii. Klebsiella oxytoca
iii. Proteus mirabilis
iv. E. coli
- A woman is 12 wks pregnant. Toxo serology done at 0 & 12 wks show IgM & IgG positive
a. Give 2 possible explanations.
b. What are 2 other serologic tests that would aid the
c. If a PCR will be needed, what specimen should be sent?
a. Give 2 possible explanations.
1) Infection with toxoplasmosis during the past year
2) Acute infection during pregnancy
3) False positive IgM
b. What are 2 other serologic tests that would aid the diagnosis?
1) IgG avidity test – High avidity = 3-5 months, most helpful in the first 16 weeks. Low avidity can persist for many weeks.
2) Toxoplasma specific IgA antibody (usually falls faster than the IgM)
3) Toxoplasma specific IgE antibody serology (falls faster than IgA and IgM, more acute)
c. If a PCR will be needed, what specimen should be sent?
Amniotic fluid
- Name 2 GNB anaerobes that are resistant to kanamycin & do not grow on BBE.
1) Prevotella species (RRV) KVC
2) Porphyromonas species (KR, VS, CR, Will not grow on bile)
- Child with VP shunt presents with his fifth episode of meningitis. GPC, cat -, PYR -, LAP -, vanco R.
a. What is the species?
b. Name 3 other catalase-negative GPC with intrinsic vanco resistance.
a. What is the species? Leuconostoc species (Also could be Weisiella)??
b. Name 3 other catalase-negative GPC with intrinsic vanco resistance.
Pediococcus
Weisiella
Enterococcus gallinarum
- Explain 2 methods of sequencing.
- Dideoxynucleotide Chain Termination –
Decreased quality after 700-900 bases
First 50 bases are not reliable
Sanger method - Pyrosequencing – luminometric detection of pyrophosphate generated during DNA synthesis. (New Generation Sequencing)
a. Name 2 staphylococci that are PYR +.
Staphylococcus lugdunensis Stapylococcus schleferi Staphylococcus hemolyticus Staphylococcus intermedius/pseudointermedius Staphylococcus carnosus
b. Which staphylococcus is PYR + and ODC +? What oxacillin breakpoint is used? This particular bacterium is sensitive to cefoxitin - what is the treatment?
Staphylococcus lugdunensis
Use the break point for Staphylococcus aureus (MIC <=2) but if using disk testing oxacillin disk testing is not reliable and cefoxitin should be used as a surrogate.
If sensitive to cefoxitin can use Cloxacilin to treat.
- Name one dermatophyte that does not affect the hair?
1) Microsporum cookie
2) Epdiermophyton floccosum
- Name 2 methods for finding cryptosporidium in the stool.
1) Modified Acid Fast Staining
2) Wet mount
3) DFA
4) Stool EIA Antigen Test
- Name two tests to distinguish Gram + from Gram - anaerobes, other than the KOH/string test.
1) GramSure? May fail to give expected results
2) Vancomycin susceptibility
- Gastroenteritis outbreak in geriatric ward, on EM, you see a particle that is 32 nm in diameter. What is the most likely agent? What is the most sensitive test to diagnose it?
Small Round Virus
Norovirus
PCR is the most sensitive test
- Name 2 phenotypic tests to differentiate Nocardia from Mycobacteria.
1) Kinyoun Stain (Nocardia NEG, Mycobacteria POS)
2) Aerial Hyphae (Nocardia POS, Mycobacteria NEG) ?? Variable for Mycobacteria….
3) ? Branching on gram stain
- Name 2 methods to screen for high level gentamicin resistance in Enterococcus, and include media, antibiotic concentrations, incubation conditions, and interpretation.
1) Disk Diffusion – Muiller Hinton Agar, Gentamicin 120 ug disk, Incubate in Ambient Air, 35 +/- 2 degrees Celsius for 16-18 hours. 6 mm = Resistant, ≥10 mm = Susceptible, 7-9mm = Indeterminate. If Resistant it is not synergistic with a cell wall agent, if Susceptible there is synergy with a cell wall active agent. If inconclusive do Broth Microdilution or Agar Dilution.
2) Broth Microdilution – BHI broth, Gentamicin Concentration 500 ug/mL, Incubate in Ambient Air, 35 +/-2 degrees for 24 hours. 0.5 MacFarland Any growth is Resistant.
3) Agar Dilution – BHI agar, Gentamicin concentration 500 ug/mL, Spot 10ul of a 0.5 MacFarland onto agar surface. Incubate in Ambient Air, 35 +/-2 degrees x 24 hours. >1 colony = Resistant.
- Name 4 indications for measles vaccination.
- Children aged 12 months – 17 years (Routine childhood immunization)
- Adults born after 1970 without documented vaccine receipt immunity to measles virus
- Health care workers without 2 doses of measles vaccine, or no evidence of immunity, or no evidence of previous measles virus infection
- Military personnel who do not have documentation of 2 doses of measles vaccine, no immunity to measles, or do not have documentation of laboratory confirmed measles infection
- Travellers to destinations outside of North America
Contraindications for Measles Vaccine:
- Persons with previous anaphylaxis to any component of the vaccine
- Persons with impaired immune function, including primary and secondary immune disorders
- Pregnancy
- Individuals with active, untreated tuberculosis (Only in PHAC CIG)
- Name 3 indications for IGRA.
- Persons previously vaccinated with BCG vaccine
- Persons unlikely to return for reading of a TST
- In place of TST when testing indicated
- In combination with TST if risk of infection progression to disease and poor likelihood of poor outcome do both
- Children and suspect active TB can use TST and IGRA to support diagnosis
- Skin conditions prohibiting TST testing
- Teen with headache, fever and nuchal rigidity. LP shows gram negative diplococci.
a. 3 actions to be undertaken immediately?
- Start empiric antibiotics to cover Neisseria meningitits (Ceftriaxone 2 g IV q12h)
- Place the patient on Droplet precautions until 24 hours after antimicrobial therapy
- Notify public health of a presumptive case of N. meningitidis
b. Meningococcus is confirmed; 2 subsequent actions or modifications?
1) Switch antimicrobial therapy to Penicillin G 4 MU IV q4 h for 7 days if susceptible
2) Initiate antimicrobial prophylaxsis and vaccination for close contacts of the patient
i. Prophylaxis (adults) =
Ceftriaxone 250 mg IM x 1 OR
Ciprfloxacin 500 mg PO x 1 OR
Rifampin 600 mg po q12h x 2 days
3) Give vaccine to contacts
c. List 4 indications of vaccination against meningococcus.
1) All children and young adults <=24 years old
2) Laboratory workers potentially exposed to N. meningitidis
3) Travellers to areas where vaccine is recommended
4) Persons with functional or anatomical asplenia
5) Military personnel during training
6) Persons with complement deficiencies
- Name 6 treatment options for MRSA
Vancomyin Linezolid Daptomycin Tigecycline Septra Clindamycin Telavancin
Ceftaroline has been approved for what indication?
SSTI
CAP
- Fever, pancytopenia, and hypergammaglobulinemia from Northern India. Weight loss, HSM, adenopathy & thrombocytopenia. What is the diagnosis, what tests should you do, and what is the treatment?
Viseral leishmaniasis Bone marrow biopsy Splenic aspirate (gold standard) Pathology Culture and PCR for species Antigen test K39 (Mayo) Treatment = Amphotericin B miltefosone, antimony, paromomycin
- Chronic meningitis in HIV. Two specific tests to be requested?
Crytococcal Ag test from CSF, India ink, silver stain, culture Culture CSF for mycobacteria (TB) Syphilis (CSF VDRL) HSV Nocardia
- Name 4 indications for endocarditis prophylaxis, and list 2 oral medications that can be used. What if patient has a non-anaphylactic allergy to penicillin? Include dosage.
- Patients with prior IE, prosthetic valves, or prosthetic material used to repair a valve undergoing a dental procedure that involves manipulation of gingival tissue, periapical tooth region, or perforation of oral mucous (not for routine cleanings)
- Patients with prior IE, prosthetic valves, or prosthetic material used to repair a valve undergoing respiratory tract mucosa incision or biopsy.
- GU or GI procedure if there is active infection
2 oral medications = Amoxicillin or Cephalexin
Non Anaphylaxis Penicillin Allergy = Cephalexin 2 g in one single dose 30-60 min prior to procedure
Anaphylaxis to Penicillin = Clindamycin or Azithromycin or Clarithromycin
- Enterococcus faecalis endocarditis. Penicillin MIC of 2, gentamicin MIC>500. Name treatment and duration.
Treatment =
Ampicillin 2 g IV q4h x 6 weeks PLUS
Streptomycin 15 mg/kg IV divided in 2 doses x 6 weeks
CLSI Penicillin breakpoints for Enterococcus = ≤8, -, ≥16. Therefore it’s Susceptible to penicillin.
CLSI screening for HLAR uses an MIC of 500 as the breakpoint, >500 is Resistant, ≤500 is susceptible.
Therefore this isolate is Susceptible to Penicillin and resistant to Gentamycin.
- Treatment for HSV encephalitis in newborn. Dosage and duration.
Acyclovir 60 mg/kg per day IV divided q8h x 21 days. Some do repeat LP then and if positive continue treatment and weekly LPs until HSV DNA is not detected.
- Case of gout crisis in a patient recently started on TB meds including PZA. What 2 things would you do?
1) Discontinue PZA
2) Treat gout with NSAID therapy
3) Start a fluoroquinolone (moxifloxacin)?
- 65M w/ previous history of VZV wants Zostivax.
a. What is the efficacy?
b. This patient is on Valtrex. Do you give the vaccine? Justify.
c. Patient now wants pneumococcal vaccine. Can you give it at the same time?
a. What is the efficacy?
51% for incidence of herpes zoster, and 66% for post herpatic neuralgia
b. This patient is on Valtrex. Do you give the vaccine? Justify.
No. It is a live vaccine and Valtrex will decrease the efficacy of the vaccine. Should not take Valtrex for 24 hours before vaccine and 14 days after.
c. Patient now wants pneumococcal vaccine. Can you give it at the same time?
Yes
- Woman exposed to VZV during 1st trimester.
a. What is her risk for transmission to fetus?
0.4% for first trimester
2% for second trimester
Congenital varicella syndrome
b. What is the post-exposure treatment for VZV exposure in pregnancy?
VZIG (or VariZIG): Varicella specific immunoglobulin as soon as possible after the exposure and up to 10 days post exposure
- Name 4 clinical features of congenital VZV.
Congenital Varicella Syndrome:
Cutaneous scars in dermatomal pattern
Neurological abnormalities (MR, microcephaly, hydrocephalus, Sz, Horner’s syndrome)
Ocular abnormalities (optic nerve atrophy, cataracts, chorioretinitis, microophthalmus, nystagmus)
Limb abnormalities (hypoplasia, atrophy, paresis)
GI abnormalities (GERD, stenotic bowel)
Low birth weight
- Name numerator and denominator for surveillance of VAP.
Numerator = Number of patients undergoing mechanical ventilation who have VAP (NHSN definition) Denominator = Number of ventilator days
- Woman from Niger with chronic pruritus, dermatitis, and skin nodule on iliac crest. What is the diagnosis, method to confirm diagnosis, and treatment?
Onchocerciasis
Skin snip then incubate in saline for 24 hours and look for motile microfilaria
Treatment = Ivermectin
First have to rule out Loa Loa because if they have a high burden of LoaLoa microfilarie can precipitate an encephalopathy. If they were to have high levels of Loa Loa may have to do plasmaphoresis first. The treatment for Loa Loa is DEC but you can’t use that if they have oncocerciasis because they can go blind (kills the adult worm).
Ivermectin only kills the microfilaria
Wolbachia treated at the same time or prior with Doxycycline. Effective at reducing microfilarial production by adult worms.
Have to retreat until the adults eventually die off (10-14 years)
Onchocerciasis can cause blindness.
- List 6 manifestations of chronic Lyme disease. What is the treatment of CNS Lyme?
1) Fatigue
2) Headache
3) Arthralgias
4) Myalgias
5) Cognitive difficulties
6) Acrodermatitis chronica trophicans
7) Radiculopathy
8) Keratitis
Treatment for CNS Lyme = Ceftriaxone 2 g IV daily 2-4 weeks
- List 2 treatment options for an HIV patient with PCP, but with allergy to Septra. What are 3 options for prophylaxis? What is an indication to add steroids?
Treatment:
1) Pentamidine
2) Clindamycin + Primaquine
3) Dapsone + Trimethoprim
4) Atovaquone
Prophylaxis:
1) Pentamidine 300 mg monthly aerosolized via nebulizer
2) Atovaquone 750 mg po bid
3) Dapsone 100 mg po daily (monitor closely for possible hypersensitivity)
Steroids if moderate to severe disease (Pa)O2 35 mmHg
- List 6 organisms that can cause culture-negative endocarditis.
1) Coxiella burnetii
2) Bartonella species
3) Trpheryma whippelii
4) Chlamydia species
5) Legionella species
6) Brucella species
7) Non-Candida fungus
8) Rickettsia
- 53F w/ fever & pulmonary infiltrate. Sputum ZN - but culture grows MAC. Do you treat?
- 53F w/ fever & pulmonary infiltrate. Sputum ZN - but culture grows MAC. Do you treat?
Treatment for MAC?
Macrolide (Clarithro 500 BID, or Azithro 250 Daily)
+ Ethambutol 15 mg/kg
+ Rifampin 600 mg daily or Rifabutin 300 mg daily
+/- Aminogylcoside (Streptomycin or Amikacin intermittently)
Duration = 12 months after cultures are negative
- 32 y.o. Nigerian male with spastic paraparesis, but normal bladder & anal function. Name 1 parasitic cause, 2 bacterial causes, and 3 viral causes.
Parasites: Toxocara canis, Diphylobothrium latum (Vit B12 deficiency)
Bacterial: Mycoplasma, Borrellia burgdorferi, Treponema pallidum
Viral: HTLV1, HIV, CMV, HSV, EBV
- 42 M w/ dementia for last 6 months. LP shows slightly elevated protein, MRI shows elevated signal on T2 in the thalamus. What is the most likely diagnosis? List 2 tests that can be done antemortem. Name 2 clinical forms of this disease.
Pulvnar sign
CJD (Creutzfeldt-Jakob Disease)
Tests:
1) Demonstatration of abnormal prion protein forms on brain tissue via immunohisotchemistury
2) Western immunoblot to analyze protease resistant form of prion protein
Clinical forms:
1) Sporadic CJD – older, rapid progression
2) Variant CJD – younger, slower progression (6-12 months), more psychiatric manifestations
Biopsy shows vaculation of neutrophils, reactive gliosis, neuronal loss = Spongioform change
2 known familial forms: FFI, GSG
Kuru infection from canabolism
- 22M presents w/history of multiple sexual partners & chancre on black base. Diagnosed as primary syphilis. What is the treatment & duration?
a. The patient calls you with a fever, myalgias, and chills the next day. Why?
b. What contact tracing needs to be done for him, and how far back must it go?
Benzathine Penicillin G 2.4 Millon Units IM X 1
a. The patient calls you with a fever, myalgias, and chills the next day. Why?
Jarisch-Herxheimer reaction
b. What contact tracing needs to be done for him, and how far back must it go?
All sexual partners in the past 90 days (Mandells)
- Name the pathogen that causes:
a. donovanosis/granuloma inguinale
b. chancroid
c. LGV
d. condyloma acuminate
e. condyloma lata
f. molluscum contagiosum
- Name the pathogen that causes:
a. donovanosis/granuloma inguinale – Klebsiella granulomatis
b. chancroid – Haemophilus ducreyi
c. LGV – Chlamydia tracomatis (serovars L1-L3)
d. condyloma acuminate – Human papilloma virus
e. condyloma lata – Treponema pallidum
f. molluscum contagiosum – Poxvirus
- 20F w/otitis treated w/clavulin develops a fever, decreased mental status & CT head shows jugular thrombosis. No intracerebral mass, but there is meningeal enhancement. Blood cultures are+ for polymorphic anaerobic GNB. CSF culture is negative. What is the organism? What other test must be done? What is your treatment?
Organism = Fusobacterium necrophorum
Other Tests = Chest Xray to look for pulmonary emboli? (Not sure…)
Treatment = PipTazo
- Name 2 infectious causes of congenital cataracts.
1) CMV
2) Rubella
3) Toxoplasmosis
4) HSV
5) Syphilis
6) Varicella
- For Parvovirus B19, list 4 clinical syndromes.
1) Erythema infectiousum (EI)
2) Transient Aplastic Crisis (TAC)
3) Pure Red Cell Aplasia (PRCA)
4) Fetal Hydrops
5) Glove and Stocking Papular Purpuric Syndrome
6) Polyarthropathy
- Patient post-allogeneic HSCT, on treatment for GVHD & taking voriconazole for aspergillosis prevention. Develops temperature, purpura on legs, & new lung infiltrates.
a. What are the 2 most likely diagnostic hypotheses?
b. List 4 tests to do.
c. What antimicrobials should you give?
a. What are the 2 most likely diagnostic hypotheses?
1) Infection with a fungus resistant to Voriconazole (Zygomyces)
2) Bacteremia with sepsis
b. List 4 tests to do. Blood cultures x 2 sets Bronchoscopy for bacteriology, fungal, viral, and mycobacterial culture Tissue biopsy of skin lesions CT Scan
c. What antimicrobials should you give?
Amphotericin B +/- posaconazole
Broad spectrum antibiotics
- Giardia treated with Flagyl for 10d has recurrence. Symptoms & stool + 2 wks later.
a. What are 2 possible explanations?
b. What are 2 other possible treatments?
a. What are 2 possible explanations? Reinfection Failed treatment with Flagyl Post infectious irritable bowel Immunodeficiency leads to chronicity (IBD)
b. What are 2 other possible treatments?
Albendazole 400 mg po daily x 5 days
Paromomycin 500 mg po TID x 5-10 days
Tinidazole
- What is the treatment for Dientamoeba fragilis? Name 2 other parasitic infections commonly found in daycare instititutions.
Treatment = Metronidazole 500-750 mg po TID x 10 days
OR Paromomycin 25-35 mg/kg divided in 3 doses PO x 7 days
Iodoquinol
Treat when Dientamoeba fragilis is the only pathogen in the stool with diarrhea or abdominal pain for 1 week.
Only see the trophozoite form. No flagella, 1 or 2 nuclei.
Can have peripheral eosinophilia with D. fragilis.
2 other parasites in daycares:
1) Giardia lamblia
2) Cryptosporidium
- Macaque bite from monkey just delivered from Morocco. Name 4 infections that are preventable by prophylaxis.
1) Rabies
2) Herpes B (Acyclovir/Valacyclovir)
3) Bacterial infection
4) Clostridium tetanus
a. Name 2 ways to measure response to treatment for HCV.
Viral DNA
Liver function tests?
b. The patient has genotype 1A. What is the treatment & duration? This patient is HIV/HCV co-infected
Ledipasvir + Sofosbuvir x 12 weeks OR (8 weeks if no cirrhosis)
Simepravir + Sofosbuvir x 24 weeks (12 weeks if no cirrhosis)
Don’t use Sofosbuvir + Ribavirin: It did worse in the coinfected patients
c. What is the test done at the start of HCV treatment that predicts good outcome?
IL28 polymorphism
d. What 2 ARV are contraindicated during HCV treatment & why?
1) Ritonavir boosted Tipanivir – Decreases Sofosbuvir levels
2) Tenofovir – Uncertain safety of increased tenofovir levels
3) Didanosine with ribavirin
4) Atazanvir with ritonavir (jaundice)
- Name 4 indications for 2nd dose of MMR to prevent mumps.
1) Routine immunization of all children
2) Health care workers born after 1970
3) Military personnel born after 1970
4) Students in Secondary or Post Secondary Institutions
5) Outbreak control
6) Travel outside of North America
- 22M with clinical picture of mumps.
a. Name 3 tests to confirm the diagnosis.
b. What are 4 possible complications?
c. How long can it be isolated for?
a. Name 3 tests to confirm the diagnosis.
Positive IgM serology with an epidemiological link
4 fold rise in IgG between acute and convalescent serology
Virus isolation from culture or PCR from buccal swab
b. What are 4 possible complications?
1) Orchitis
2) Oophritis
3) Aseptic meningitis
4) Deafness
5) Encephalitis
6) Pancreatitis
7) Sailatasia
8) Epididymitis
c. How long can it be isolated for?
14 days after onset of symptoms
- Inuit child in respiratory distress, fever, throat culture pos suspicious for C. diphtheriae
a. What agar to use?
b. What 3 actions to take immediately, in addition to antibiotic treatment?
c. Once ID is confirmed, what other 2 actions to take?
d. What is the best treatment?
Tinsdale Agar
b. What 3 actions to take immediately, in addition to antibiotic treatment?
1) Diptheria antitoxin administration
2) Place patient on respiratory droplet precautions until 2 cultures 24 hours apart are negative
3) Intubate if airway concerns exist or may arise
c. Once ID is confirmed, what other 2 actions to take?
1) Notify public health (now or earlier?)
2) Treat close contacts with penicillin or erythromycin and offer unvaccinatinated patients vaccine
d. What is the best treatment?
Erythromycin 500 mg po QID x 14 days
(Penicillin is also good)
- List 6 genera of fungi that are resistant to caspofungin.
1) Cryptococcus
2) Histoplasma
3) Blastomyces
4) Coccidioides
5) Sporothrix
6) Scedosporium
7) Trichosporon
8) Mucor
9) Fusarium
10) Paracoccidioides
- Name 4 mechanisms of colonization of central catheters.
1) Hematogenous spread
2) Skin organisms
3) Instillation of infected material
4) Colonized hub
- In an HIV treatment naïve patient, name 2 preferred treatments (one with PI & one without) that are dosed once daily.
1) Atripla – Efavrinez/Emtricitabine/Tenofovir (no PI)
2) Stribild – Elvitegravir/Cobistat/Emtricitabine/Tenofovir (No PI)
3) Complera – Rilpilverine/Emtricibaine/Tenofovir (No PI)
4) Triumeq – Dolutegravir/Abacavir/Lamivudine
5) Dolutegravir + Truvada (Emtricitabine/Tenofovir)
6) Darunavir/Ritonavir/Emtricitabine/Tenofovir (Has a PI)
7) Atazanavir/Ritonavir/Emtricitabine/Tenofovir (Has a PI)
- EBV: list 4 related cancers.
1) Burkitt’s Lymphoma
2) Nasopharyngeal Carcinoma
3) T Cell Lymphoma
4) Hodkin’s Lymphoma
5) PTLD – post transplant lymphoproliferative disease
6) Primary CNS Lymphoma
7) Primary Effusion Lymphoma
- 50 y.o. diabetic with sinusitis progressing to proptosis, dark nasal discharge & with a black spot on his palate. What is the etiology, and what are 3 interventions to take?
Zygomyces
3 interventions:
1) Start Amphotericin B (5-10 mg/kg IV daily)
2) Consult surgery re: Surgical debridement
3) Correct hyperglycemia
- Pneumonia secondary to nosocomial Legionella in 2 patients.
a. What are 2 treatment options?
b. What are 2 interventions to stop transmission?
a. What are 2 treatment options?
Azithromycin
Levofloxacin
b. What are 2 interventions to stop transmission?
Heat water to 70 degrees celcius and flush water system for 30 minutes
Copper-Silver ionization units
Hyperchlorination
- Name 2 contra-indications for flu vaccine.
1) Severe allergy to any components of the vaccine
2) Previous Guillain-Barre Syndrome within 6 weeks of influenza vaccine
3) Less than 6 months of age
- Name 2 indications to look for & treat an asymptomatic bacteruria.
1) Pregnancy
2) Prior to Transurethral Resection of the Prostate (TURP)
3) Prior to undergoing an urological procedure with anticipated mucosal bleeding
- S. aureus grows on oxacillin screen, and R to cefoxitin. Testing shows that it is mecA -.
a. What is the resistance mechanism?
b. What else should be tested?
1) Resistance mechanism is hyperproduction of Beta lactamase (BORSA)
2) mecC in Europe, not yet in Canada, not detected by mecA PBP or mecA PCR. mecC is an altered PBP but is different from the one caused by mecA
b. What else should be tested?
1) B – lactamase – would show that it has a beta lactamase. Could do an oxacillin MIC
Other things we came up with….
2) Test for PBP2a with latex agglutination and an anti-PBP2a monoclonal antibody – Baldwin said no for this because if it’s mecA negative then the PBP2a would not be helpful. But it could be helpful if the mecA PCR was false negative to see if it’s an MRSA. The PBP2a test will also be negative for mecC as it produces a different PBP2a(mecC).
3) Inhibitor test with Oxicillin and a B-lactamase inhibitor – Baldwin thought this was reasonable but didn’t know if the test exists
4) Look for mecC – specific mecC primers for PCR
- Cervical swab received, with a request for anaerobes. What 2 things you should do?
1) Inform the physician that the specimen type is inappropriate for anaerobic culture due to the large number of anaerobes present as normal vaginal flora
2) If an IUD was present can look for actinomyces on a gram stain
- Table: 3 distinguishing characteristics of endotoxins vs. exotoxins.
Exotoxin: Released from cell Protein Produced by gram Pos and Neg High antigenicity
Endotoxins: Integral part of cell wall Lipid A of the LPS Only on gram Neg Low antigenicity
- For each organism & drug combination, list one susceptibility testing method with the media and the incubation conditions:
a. N. gonorrhoeae and ciprofloxacin
b. Aeromonas in blood
c. H. influenzae in CSF
d. Enterococcus screening
a. N. gonorrhoeae and ciprofloxacin – Agar dilution or Disk Diffusion – GC agar base and 1% defined growth supplement, 36 +/-1 degree, CO2, 20-24 hours
b. Aeromonas in blood – Disk Diffusion – Muiller Hinton Agar – 35 degrees, ambient air, 16-18 hours
c. H. influenzae in CSF – Disk Diffusion with Haemophilus Test Media, 35 degrees CO2, 16-18 hours
d. Enterococcus screening – Agar Dilution BHI agar with 6 ug/mL of Vancomycin, 35 +/-2 degrees, ambient air, 24 hours
- List 3 yeast that are urease +, other than Cryptococcus. Name a colour indicator for urease.
1) Trichosporon
2) Rhoduroturula
3) Sporobolomyces
4) Candida krusei
Color indicator for urease = Phenol red
List 3 causes of a false + cryptococcal antigen.
1) Rheumatoid factor
2) Tricosporon
3) Aspergillus
4) Capnocytophaga canimorsus septicemia
5) Malignancy
6) Sinuresis fluid
7) Rothia bacteremia
8) Soaps and disinfectants
- List 6 causes as to why an ordinary light microscope would produce a blurry image.
1) Not in focus
2) Oil on the lens
3) Dust or dirt on the eyepiece
4) Improper kolher
5) Using an oil lens without oil on the slide
6) Vibration
7) Air bubbles in the oil
- S. aureus tests with vancomycin MIC of 8 mg/L. What is your interpretation ?
Intermediate
S: =16
CoNS has different Vanco breakpoints. Instead S: =32
- GPC testing slide coag +, tube coag -. What are two possibilities? What if it is PYR + and ODC +? Interpret the susceptibility of this organism if the oxacillin MIC is 1 mg/L.
2 possibilities: S. lugdenesis, S. schleiferi
If PYR+, Orn+ then S. lugdenesis
If the Oxacillin MIC = 1: Susceptible. (=4 resistant for S. aureus and S. ludg)
*Note for CoNS other than S. lugd the breakpoints are instead =0.5 for Oxacillin
- How can a beta-metallolactamase be detected? Explain the principle of this test.
Disk diffusion inhibitor testing with meropenem alone and in combination with dipicolonic acid. If there is increase in zone diameter with addition of dipicolonic acid it is an MBL as the dipicolonic acid inhibits the effect of the MBL allowing the meropenem to be functional. Can also use EDTA.
- Name and explain the mechanisms of resistance for the following combinations:
b. Pseudomonas testing R to carbapenems, ceftaz 4, piptazo 16
c. E. coli R to cefoxitin, S to carbapenems, no change with beta-lactamase inhibitors
d. Enterococcus with a vanco MIC of 32, and a teico MIC of 2
b. Pseudomonas testing R to carbapenems, ceftaz 4, piptazo 16
Pseudo: Piptazo =128
Ceftaz =32
Porin mutation
c. E. coli R to cefoxitin, S to carbapenems, no change with beta-lactamase inhibitors AmpC
d. Enterococcus with a vanco MIC of 32, and a teico MIC of 2
Van B
Or it could also be a vanC with species E. gallinarum or E. casseliflavis (MIC Vanco 8-32)
Van B – Shows in vitro resistance to Vanco and not Teico, but with use of Teico will develop resistance. (MIC Vanco 8-1000)
VanA would have tested resistance to both Vanco and Teico at the beginning
- For the interferon-gamma release assay, what are 2 antigens? What is the necessary transport time? List 2 benefits.
2 Antigens = ESAT6 and CFP10
Early Secreted Antigenic Target 6
Culture Filtrate Protein 10
Transport time – 16 hours for Quantiferon, 8 hours for TSpot
2 Benefits:
1) No false positive in patients who have received BCG vaccine
2) Only 1 appointment needed
- GNCB, testing ox +, cat +, ODC +, indole +, no growth on Mac. Identify.
Pasteurella species
- List 4 biological contaminants of cell monolayers.
1) Bacteria (especially mycoplasma)
2) Yeast
3) Virus
4) Filamentous Fungi
5) WBCs or Epithelial cells
List 3 new respiratory viruses discovered in the past 5 years.
1) MERSCoV
2) Avian Influenza H7N9
3) Enterovirus D68
- List for types of winter resp. viruses that can be grown in cell culture, and list 2 cell lines used.
1) Influenza
2) RSV
3) Parainfluenza
4) Adenovirus
- List 2 molecular assays each that correspond to signal amplification, DNA amp., and RNA amp.
Signal amplification:
1) Branched DNA Signal Amplification (bDNA)
2) Hybrid Capture
DNA Amplification:
1) Polymerase Chain Reaction (PCR)
2) Strand Displacement Assay (SDA)
RNA Amplification:
1) Transcription Mediated Amplification (TMA)
2) Nucleic Acid Sequence Based Amplificatoin (NASBA)
3) RT-PCR
- List 2 nucleic amplification tests that are isothermal.
1) LAMP (Loop Mediated Isothermal Amplification)
2) Strand Displacement Assay
3) Transcription Mediated Amplification (AMTD)
4) NASBA (Nucleic Acid Sequence Based Amplification)
- List 2 methods of diagnosis of LGV.
PCR
Cell Culture – McCoy or HeLa 229 cells
- Name 2 specimens recommended by public health for the detection of measles.
Urine
NP Swab
Throat Swab
- What are 3 modes of transmission of botulism? What are 2 diagnostic methods? What is the treatment for infant botulism?
Modes of transmission:
Ingestion (home canned foods, honey)
Cutaneous (wound botulism, Botox)
Inhalational (bioterrorism)
Diagnostic Methods:
1) Mouse neutralization test (test for the toxin from serum, gastric secretions, stool, or food)
2) Isolation of Clostridium botulinum via culture (from serum, stool or food)
Treatment for infant botulism = BabyBIG – Botulism Immunoglobulin (<1 year olds)
For adults is hBAT (hepavalent Botulism Antitoxin – A,B,C,D,E,F,G)
Botulism is a descending paralysis, involves cranial nerves, toxin mediated
If it is wound botulism add Penicillin and Metronidazole to the treatment
- Why is the cefoxitin disk test done for S. aureus? For coagulase-negative staphylococci?
It is more a surrogate for oxacillin resistance as the oxacillin disk is not reliable to detect resistance for Staph aureus. Indicated the presence of the mecA gene.
For CoNS that are non-S. epidermidis oxacillin MIC may overcall resistance (Oxacillin MIC 0.5-2 called R but may not have mecA); therefore cefoxitin disk is used.
- HIV WB with a single band (at gp41) is shown. What are 3 reasons for false negatives?
1) Acute infection (early seroconversion)
2) Infection with HIV2
3) HIV1 subtype O
4) Low viral load
