Uw- Micro 1St Assessment

Front 1

5 yo boy came to your office with facial edema adn smokey urine. his med hx is significant for a mild skin infection on his face 3 weeks ago. ua is + for protein. the bacteria responsible for this pts presentation have with of ff cx?
A. catalase positive
B. bacitracin sensitive
C. coagulase positive
D. non-hemolytic
E. quellung

Back 1

Bacitracin sensitive

Most likely dx is acute post strep glomerulonephritis by GAS (group A strep). know the GAS cx: cataalse (-), gram (+), cocci, sensitive to bacitracin

Front 2

53 yo, m, emigrated from russia is being evaluated for persistent cough with occasional hemoptysis. his past med hx is significnt for TB adn chronic bronchitis. he has smoked cigarettes for the psast 20 years. ppd testing yields 15mm indurated erythema. suputum microscopy stained wiht methemaine silver is shown bellow: (histology pic of broom stick fungus)..which of the following is most liekly cause of his current sx?
A. mycobacterium
B. candida
C. aspergillus fumigatus
D. pneumoycsits jirovce
E. actinomyces israelii

Back 2

Aspergillus fumigatus.

-know cx "broomstick appearance"
Methemanime silver stain- used for fungus
-pts with hx of TB may develop aspergillus w/n the caviites to look like fungus balls causing hemoptysis
-tx is surigcal removal of mass

Front 3

A colonly of bacteria resistant to gentamicin and colonly of bacteria resitant to ampicillin are mixed on a plate containg both antibiotics. bacterial growth is noted. same experiment is repeated but DNAse is added to the plate and no growth is seen. what is the most likely mechanism of bacteiral survival in the 1st experiment?
A. new mutation
B. transformation
C. conjugation
D. transduction
E. transposons

Back 3

TRANSFORMATION

Process of bacteria taking up another DNA and making it into their own.
Remember: 3 main mechanisms for genetic transfer bw bacteria.
1. transformation
2. conjugation- direct cell to cell interaction using sex pilus. but here the genetic material will not be degraded by DNAse.
3. transduction- bacteriophage mediated transfer of genetic information. DNase will also NOT inhibit this process
Transposons- mediate transfer of info within a bacteriium from one location to another, ex. from plasmid to chromosomal DNA. this will not be subject to DNAse inhibition

Front 4

An intestinal aspirate from a young male who recently returned from a trip to Russia has the following microscopic findings: Giardia lamblia...the patient is most likely to experience which of the following?
A. bloody diarrhea
B. malabsorption
C. liver abscess
D. ascites
E. symmetric arthritis

Back 4

MALABSORPTION

Giardia lambila is a protozoan that causes malabsorption diarrhea follwoing consumption of contaminated water. it does NOTcause invasive disease
-the sx og giardiasis are the result of malabsorption, secondary to dysfunction of the brush border enzymes.
Exist in both cyst and trophozoite form. cyst is the infecttious form.

Front 5

The pt is dx with hematological malginancy and started on chemo. four weeks later, he complain of cough, fever and chest discompfort. cxr demo a patchy infiltrate in r upper lung lobe wiht small area of cavitation. bronchoalveolar fluid obtained uring bonrhcoscopy shows hte ff: histology of aspergillus fumigatus (gram stain).
Which of the ff is the virulence factor for the organism resp. for this pts ccurent condition?
A. large polysaccharid capusuel
B. lipid rich cell wall
. intracytoplasmic location
Productionof alveolar exuate
E. vascular invasion

Back 5

Vascular invasion

-aspergillosis is opportunistic seen in immunocompromosided pts due to acute leukemia.
-exhibits septate hyphae in 45 degree branching and tendsto form fungus balls in the uppper lobes at sites of prior TB activity.
-vascular invasion is a prominent feature

Front 6

A new test is designed for diagnosing parvovirus B19 infection. the test uses parvovires B18 antigen attached to wells aloing with a chromogen for a peroxidase enzyme. what else should be added to make the test kit complete?
A. antibodies agains parvovirs b19
B. antibodies againts peroxidase
C. anti-human immunoglobulin
D. latex particles
E. complement components

Back 6

Indirect ELISA- serologic test the identifies presence of antibody directed againts a known target antigetn in pts serum. steps are as follows:

1. known antigen (ex. parv. b19) fixed to bottom of well
2. pt serum added. if present, antigetn specific ab bind and remain fixed to the well. the plate is then washed to rmove unbound pt ab.
3. anti human ig--coupled to substrate is added-->binds to antigent bound ab in the wells. the plate is then washed.
4. a substrate or chromogen is added, which is modified by enzyme to eliecit a detectable signal such as color change.

Front 7

A 24 year old male, accidentally nicks his chin while shaving. over the next 2 days, his cut growns increasingly inflamed and develops a yellowsh crust. which of the following is most likely responsible for this change?
A. pseudomonas aeruginosa
B. staphyloccoucs aureus
C. staphyloccoucs epidermidis
D. group b streptoccocus
E. bacteroides fragilis

Back 7

Staph Aureus

-Impetigo- superficial infxn of skin assoc. with erythema and yellow "honey" crust. it most commonly caused by STAPH AUREUS and GROUP A STREPTOCCOCUS. in cases caued by s. aureus, bullae may form due to toxin production (bullous impetigo)

Pseudomonas aeruginosa- does not cause impetigo; found in skin disease like ecthyma gangrenosusm, hot tub follicultis, pyoderma, green nail syndrome adn botryomycosis
S. epidermidis- normal skin flora not common. assoc. with skin disease. it should be regarded as a contaminat if found in would culture
B. fragilis- intrabod. abscesses following abd. trauma or surgery. it is also a cause of endometritis and abscesses ff gynecologic procedures.

Front 8

A scientist is studying acquired antibiotic resistance in particular bacteria strain. resistant bacteria are noted to have decreased intracellular conc. of the antibiotic. when the scientist adds protons tto the growth media, intrabacterial conc. of the drug sharply increased. the most likely mechanism of acquired antibiotic resistance in these bacteria is:
A. poor drug penetrance into the cell
B. enzymatic drug destruction
C. drug pumped out of the cell
D. impaired drug target binding
E. alternative route of metab. bypassing drug effect

Back 8

DRUG PUMPED OUT OF THE CELL

Bacterial antib. efflux pumps rquire energy to move antibiotic agains teh conc. grdient out of the cell. this energy is most commonly derived from protons (hydrogen ions), though sodium gradient or direct ATp expenditure may also be used.
This question describes teh bacteria that develop resistance by dec. their intracellular accumulation of the drug. potentially, this could occur by bacteria decreasing their permeability to teh drug or acquiring an ability to pump the drug out. most antibiotics freely cross the membranes making efflux pumping the likely mechanist of resistance here. After she saturates teh medium with proton in inhibited the efflux pumps.

Front 9

An investigator isolates an organismis that has a haploid genome. it has inner and outer cell membrane but no nuclear membrane. it is sensitive to some but not all penicillin antibiotics. which of the ff organisms was isolated?
A. virus
B. chlamydia
C. mycoplasma
D. yeast
E. gram negative rod

Back 9

GRAM NEGATIVE ROD

Prokaryotes are microorg. with haploid genomes (single chromosome or DNA strand; no cell nuclei present) a prokryotic cell that has cell wall sandwich etween outer and inner plasma membranes is most likely a gram negative bacterium, further confirmed by sensitivity to penicillins (which inhbit peptidoglycan cross linking in the bacterial cell wall).

Chlamydia- obligate intracellular bacteria, have mult. copies of circular plasmid like genomes. LACK peptidoglycan thereofre insensitive to penicillin.
DNA virus- lack inner membranes and do NOT have peptidoglycan, so also insensitive to pcn.
Mycoplasma- no cell wall, same as above
Yeast- eukaryotes have diploid genome and chitinous cell wall impervious to pcn.

Front 10

A eukaryotic cell contains equimolar amouts of 18S and 28S rRNA molecules. which of the ff best explains this finding?

Back 10

Both rRNA molecules are transcribed from a single chromosome as a single transcript that subsequently udnergoes cleavage.

IN eukaryotes the 28S, 18S and 5.8S rRNA are formed together when a signle 45S pre-rRNA is cleaved, hence they occur in equimolar amouts. the 45S pre rRNA itself is transcribed by RNA polymerase I. the 5s rRNA is formed separtely by RNA pol III.

-remember: 4 main rRNA in eurkaryotes: 28S, 18S, 5.8S and 5S forms based on their unique surface are adn molecular weight. the "S" units are not additive (do not expect 28s + 18S+ 5.8 S to equal 45S), but are instead based on molecule size and how they move durign centrifugation.

Front 11

A virus isolated from huhman epithelia cells replicates in the nucleus using host enzymes. the organism most likely belong to which of hte ff virus families? A. togavirus B. parmyxovirus C. poxvirus d. papovavirus e. picornavirus

Back 11

Papovaviridae family!
Also includes papillomavirues and polyomaviruses. these viruses replicate wn the host cell DNA and RNa polymerase.

Poxviruses on the other hand are unique among DNA viruses in that they DO NOT replicate in the host cell nucleus.

Front 12

A 43 yo male complains of low grade fever, chest pain and cough productive of blood streaked sputum. he also notes recent dvmpt of a skin rash on his arms. he has a history of recent business travel to mexico and south america. he smokes one pack of cigarettes per day and consumes alcohol occasionaly. chest x-ray show a thin walled cavitary
Lesion in the right middle lobe. which of the following organsims is most likely responsible?
A. legionella penumophila
B. klebsiella pneumonia
C. pneumocystis jiroveci
D. mycoplasma pneum.
E. coccidiodies immitis

Back 12

Coccidioides immitis

-dimorphic fungus that grows as mold but converts to spherule withihost organisms
-*classically contracted by people in san joaquin valley in california ("valley fever") though it is also endemic in southern arizona, new mexico, texas, mexico and south america.
-MC causes asymptomatic infection or mild pneumonia with pleural effusion. rarely, it can cause formation of thin walled cavities in the lung; in these cases, pts may have hemoptysis in addition to fever and cough.
________
Legionella pneum: gram (-) bacillus, cause disease when aerosolized organisms are inhaled from contaminated water sources. it can cause self limited flu like illness known as pontiac fever or legionnaires disease.
Klebsiella- gram (-), rod, classically causes lobar pneumonia with "currant jelly" hemoptysis is alcoholics
Pneumocystis jiroveci- atypical fungal causing pneumo in HIV infected pts with cd4 cell count <200/ml3. pneumonitiswith weakness and dyspnea and a "ground glass" appearance on cxr ar etypical manifestations of infxn.
Mycoplasma pneum: atypical bacterium (no cell wall), casuisng walking pneumonia. affected individuals develop fever, malaise, non-productive cough that resolves slowly over the course of weeks.

Front 13

An 8 yo, m, brough to ER, with 2 days hx of ha, vomiting and fever. he starts to cry when you turn on the examination lights. lumbar puncture is peforme dand postive sense ssRNA is isolated. This virus is most likely belongs to which of the ff families?
A. picornavirus
B. reovirus
C. corona virus
D. arenavirus
E. paramyxovirus

Back 13

PicoRNA virus - small RNA virus

Pt has aseptic meningitis: acute fever, ha, photophobia, n/v, nuchal rigidity on PE.
CSF analysis will reveal lymphocytic pleocytosis with normal glucose and normal or slightly elevated protein levels. enteroviruses are most commonly the culprit, accounting for 90% of cases.
Enterovirus the most common cause of aseptic meningitis.

Front 14

A 34 yo, f, complains of lower abd pain for 2 days after giving birth to her 2nd child via spontaneous vaginal delivery. her temp is 37.8, bp is 110/70. pulse is 110 and resp are 18/min. bimanual examination reveals a tender uterus adn fould smelling vaginal dc. which of the ff organisms is most likely responsible for her symptoms?
A. cytomegalovirus
B. chlamydia
C. pseudomonals aeruginonsa
D. gardeneralla vaginalis
E. bacteroides species

Back 14

Bacteroides species
Endometritis is an infection of the uterus. most cases follow delivery. signs and symptoms inlcude fever, leukocytosis, uterine tenderness, fould smelling dc. most commonly caused by mixed flora with bacteroides mc isolated organisms.

Cmv- not known cause of endometritis but MC acquired by fetuses in utero
Chlamydia- may cause it but bacteroides is more common.
Pseudomonas- not a common cause; diabetics and burn pts are predispose to this
HSV- not common either. Mc occur in mouth or genitials.
Gardnerella vaginalis- bacterial vaginosis, not endometritis. BV causes clear to gray dc that has a fish odor when potassium hydroxide is added.

Front 15

32 yo, HIV, male, office with confusion and innapropriate behavior for one week. today be assaulted his coworkers because he felt like he was staring at him. he appears agitated but reports that he feels fine. MRI shows increased signal in right temporal lobe. which of hte ff organisims most likely isolated from affected area?

Back 15

Herpes Simplex Encephalitis