UWorld-Microbiology Flashcards
what stage of the malaria life cycle does primaquine attack
what part of the life cycle does chloroquine attack
primaquine attacks the intrahepatic stage (this is why it’s useful against latent ovale and vivax infections)
chloroquine attacks the erythrocytic stage
the tetanus vaccine is specific to what aspect of the pathogenesis of tetanus
vaccine to tetanus toxoid (leading to development of antibodies against the toxin)
what aspect/ characteristic of H. flu contributes most to its virulence
capsule (type b is particularly virulent because its capsule contains ribose instead of hexose, which prevents phagocytosis and intracellular killing)
what does coccidioides immitis look like on histology
sphrules containing endospores
what does histoplasma capsulatum look like on histology
small oval yeast forms within macrophages
what’s the difference between transformation and transduction in bacteria
bacterial transformation involves direct uptake of naked DNA from environment while bacterial transduction involves phage-mediated transfer of DNA
which bacteria are known for having the capability for transformation
S. pneumo, H. flu, Neisseria gonorrhoeae and meningitidis
which catalase negative gram positive coccus is pyrrolidonyl arylamidase (PYR) positive
S. pyogenes
fever, vesiculoulcerative gingivostomatitis and cervical LAD should make you think of what infection
HSV-1
what do you call a smear of an oral ulcer scraping and what stain is most commonly used
Tzanck preparation;
Wright-Giemsa stain
what is P-glycoprotein
multidrug resistance protein 1 (MDR1);
it is expressed by some cancers to pump out toxins, including chemotherapeutic agents
list the relative amounts of pathogen needed to innoculate a host for the following:
Salmonella, Vibrio cholera, ETEC, Shigella, C. perfringens
Salmonella= 10^7; V. cholera=10^6; ETEC=10^8-10^10; Shigella= 10-200; C. perfringens= 500
which gram positive, catalase negative organism grows in 6.5% NaCl
Enterococcus (grows in bile also, as does S. bovis, but S. bovis doesn’t grow in 6.5% NaCl)
antibodies against polyribitol ribose phosphate indicate infection with what pathogen
Haemophilus influenzae (PRP is part of the capsule)
the main bacterial cause of epiglottitis is
Haemophilus influenzae
ether and organic solvents inactivate what kind of viruses
enveloped
S. epidermidis is a common cause of foreign body infections (e.g. prosthetic devices) due to what particular survival advantage/ trait
ability to produce extracellular polysaccharide matrix known as biofilm
which bacteria produces lecinthinase
lecithinase (aka C. perfringens alpha toxin aka phospholipase C) is produced by C. perfringens
what is the mechanism of action of C. diphtheriae AB exotoxin;
which other toxin acts via this mechanism
AB exotoxin from C. diphtheriae ribosylates and thereby inactivates elongation factor 2 (EF-2);
Protein A from P. aeruginosa has the same MOA
what is the primary site of complement production
the liver
complement C3 deficiency vs. C5-9 predisposes to what particular infections
C3 deficiency leads to recurrent infections of encapsulated bacteria
C5-9 predisposes to N. gonorrheae and meningitidis infections
list the top 3 causes of osteomyelitis in sickle cell patients from most common to least common
- Salmonella (most common)
- E. coli
- Staph aureus
a woman with rubella will most likely experience what sequelae of the disease
polyarthralgia and polyarthritis
a maculopapular rash beginning at the head and neck and spreading downward is characteristic of what two viral infections
Measles (rubeola) and German measles (rubella)
first trimester infection with rubella can lead to what neonatal medical issues
sensorineural deafness, cardiac abnormalities (e.g. patent ductus arteriosus), and cataracts
when in the course of Hepatitis B infection does anti-HBsAg IgG appear in the patient’s serum
after successful vaccination or successful clearance of the virus
what kinds of viruses tend to reproduce polycistronic gene via host production of a polypeptide that is subsequently cleaved
+ sense, ssRNA, linear, non-segmented viruses (e.g. echovirus)
50% of all UTI’s in sexually active women is caused by what gram positive organism
S. saprophyticus
what are the symptoms of mononucleosis
fever, hepatosplenomegaly, pharyngitis and LAD (especially post-cervical nodes)
Waterhouse-Friedrichson syndrome is associated with what pathogen and involves what symptoms
caused by N. meningitidis;
involves hemorrhagic destruction of the adrenal glands, DIC and shock
describe the route of N. meningitidis from primary entry site to the meninges (4 steps)
pharynx –> blood –> choroid plexus –> meninges
in order for naked RNA to be infectious on its own what qualities must it have
positive sense ssRNA (not negative sense or double stranded RNA)
what is the quelling reaction
swelling of the capsule seen on microscopy after addition of anti-capsular antibodies
gram positive rods with tumbling motility are likely to be contracted how?
what illnesses do they commonly cause?
Listeria monocytogenes is an opportunistic pathogen usually contracted in contaminated food (unpasteurized milk, undercooked meat);
cause sepsis, meningitis and neonatal meningitis
unilateral vesicular rash in an older patient is most likely what condition?
what sequelae usually arises afterwards?
herpes zoster due to reactivation of VZV in a dorsal root ganglion;
post-herpetic neuralgia is the most common neurologic complication of VZV and is more common as age increases
list the live attenuated vaccines
MMR (measles, mumps, rubella), Sabin polio, intranasal influenza, varicella and yellow fever
list the killed or inactivated vaccines
cholera, hepatitis A, Salk polio, influenza infection, rabies
what acts as endotoxin in N. meningitidis infection
lipooligosaccharide (LOS)
where does Candida tend to be found
skin and mucus membranes (mouth, vagina, intestines)
why can’t the body mount a sufficient response against hepatitis C envelope antigen
hepatitis C envelope is constantly changing its antigenic structure via mutation because it has a hypervariable region and there is no 3’ to 5’ exonuclease activity in the virally encoded RNA polymerase
what does cryptococcus neoformans look like under the microscope
yeast only; round or oval encapsulated cells with narrow-based budding
what is the most common cause of hematogenous osteomyelitis
S. aureus (then S. epidermitis)
what are two major symptoms associated with acute-streptococcal glomerulonephritis
facial edema and dark urine
what is the most common site of colonization for MRSA and MSSA?
the nares
LPS in E.coli causes what two diseases and what is the mechanism of action
causes pneumonia and neonatal meningitis;
LPS activates macrophages which leads to widespread release of IL-1, IL-6 and TNF-alpha
95% of cases of gas gangrene are due to what organism?
how is it contracted and what else does it cause?
Clostridium perfringens;
found in soil;
also causes transient watery diarrhea
what are the two main components of the H. flu type b vaccine
PRP (polyribose-ribitol-phosphate) from Hib capsule conjugated to either diptheria or tetanus toxin
what is cold agglutinins and what conditions can it indicate
cold agglutinins are antibodies that cause RBC agglutination at cold temperatures;
they can be seen in infection with Mycoplasma pneumoniae and EBV or in cases of hematologic malignancy
mucicarmine stain is used to detect which pathogen
the mucicarmine-rich polysaccharide capsule of cryptococcus neoformans appears red on mucicarmine stain
how can recurrence of genital herpes (HSV-2) be prevented
daily valacyclovir, acyclovir or famciclovir
in the U.S. how is Hep A virus commonly contracted
contaminated shellfish
facial pain and headache in a patient with DKA is suggestive of….?
how is it diagnosed?
mucormycosis (Mucor, Rhizopus or Absidia);
diagnosed by mucosal biopsy
where is the primary focus of cryptococcal infection usually located
in the lungs
what virus-related malignancy are HIV patients at increased risk for
EBV-associated diffuse B-cell non-Hodgkin’s lymphoma (note: 90% of people have latent EBV)
what are Koplik spots and what disease do they suggest?
what symptom usually follows 1-2 days later?
small whitish, bluish or grayish spots on the buccal mucosa near the molars;
Koplik spots are pathognemonic of rubeola (measles);
a maculopapular rash will develop in 1-2 days
what is the classic triad of congenital toxoplasmosis
hydrocephalus, intracranial calcifications and chorioretinitis
what is the main toxin of C. perfringens and what does it do
lecithinase, also known as phospholipase C or alpha toxin;
it breaks down phospholipids
what is the most common cause of Candida vaginitis
antibiotic use
name a non-infective envelope glycoprotein of a hepatitis-causing virus that forms spheres and tubules 22nm in diameter
HBsAg
how does M. pneumoniae cause anemia
cold agglutinins are antibodies that cross-react between the bacteria and RBCs;
they bind RBCs and can cause hemolysis
what is ecthyma gangrenosum; its associated pathogen; and the virulence factors that mediate this presentation
a cutaneous necrotic disease presenting with dots of purpuric/necrotic lesions on the skin; P. aeruginosa; exotoxin A (inhibits protein synthesis), phospholipase C (destroys membranes), elastase, pyocyanin (generates ROS)
is HAV infection in children more commonly icteric or anicteric
anicteric; in children HAV is commonly subclinical or asymptomatic
which HIV structural gene is glycosylated and then cleaved to produce gp120 and gp41
env
what is cord factor and what does it correlate with
cord factor is a mycoside (composed of mycolic acids) found in virulent strains of Mycobacterium;
correlates with virulence because it inhibits neutrophils, destroys mitochondria and induces release of TNF
which virus(es) obtain(s) its envelope from the host nuclear membrane instead of the host plasma membrane
herpesviruses (1-8)
most common cause of viral meningitis in children
enteroviruses (poliovirus, echovirus, coxsakievirus, enterovirus)
explain the acid fast stain
carbolfuschin (an aniline dye) is used to stain mycolic acid red; then hydrochloric acid and alcohol is added to decolorize (dissolve outer cell membranes); mycolic acids prevents decolorization; methylene blue is added after as a counterstain; red= acid fast (has mycolic acid), blue= not acid fast
which bacteria are acid-fast
mycobacterium and nocardia
what is the causative bacterium and characteristics of chancroid
caused by haemophilus ducreyi;
deep, painful ulcers with gray/yellow base
Donovan bodies (deeply staining gram-negative intracytoplasmic cysts) are seen in what disease and with what pathogen?
donovanosis aka granuloma inguinale;
Klebsiella inguinale
list 3 unique facts about L. monocytogenes with respect to culture
can be cultured at 4 degrees Celcius
shows tumbling motility at 22 degrees Celcius
has a narrow zone of beta-hemolysis on blood agar
how is M. leprae transmitted and what are the symptoms of the two forms
transmitted via respiratory droplets; armadillo reservoir
lepromatous form= more severe, lion facies, hypopigmented plaques, focal sensory paresis and loss of sensation, testicular destruction, blindness
tuberculoid form=self-limited due to cell-mediated response; hypopigmented plaque with diminished sensation
why must HDV coinfect with HBV
HDV needs the viral coat of HBV (HBsAg) in order to infect hepatocytes
which bacterial toxins increase intracellular cAMP
ETEC heat labile toxin, B. cereus heat labile enterotoxin, B. anthracis edema factor, cholera toxin, C. jejuni enterotoxin, pertussis toxin
list the three things needed to treat diptheria (in order of most important to least)
- antitoxin (provides passive immunity, but doesn’t affect toxins that have already reached cardiac and CNS)
- erythromycin or azithromycin
- DPT vaccine
a patient with defective NADPH oxidase has what disease?
what pathogens is the patient easily infected with?
chronic granulomatous disease;
infected by catalse positive organisms: pseudomonas cepacia, staph aureus, serratia marcecens, nocardia, aspergillus
what two viruses causes maculopapular rashes that start at the head and spread downward;
which is more often associated with postauricular LAD
rubeola (measles) and rubella (German measles);
rubella is more associated with postauricular LAD
which toxin acts via the same mechanism of action as edema factor
adenylate cyclase toxin of Bordatella pertusis also acts as a calmodulin-dependent adenylate cyclase
(other toxins that increase cAMP: cholera toxin and labile toxin of ETEC permanently activate Gs; pertussis toxin inactivates Gi)
this virus causes self-limited hepatitis, but has a high rate of mortality in pregnant women
hepatitis E virus; a hepevirus
pharyngitis with pharyngeal exudates, cervical lymphadenopathy and myocarditis suggests what pathogen
Corynebacterium diptheriae
what does the HIV protein gag encode
nucleocapsid proteins p24 and p7
list the most common causes of post-viral bacterial PNA in order
most common: S. pneumo
then S. aureus
then H. flu
