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STEP1 > Micro > Flashcards

Micro Flashcards

1
Q

Classic signs of leprosy

A

Loss of sensation on the cool parts of the body associated with granuloma formation from acid fast bacilli

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2
Q

To what would a patient be susceptible if they wre deficient in the C5 complement protein?

A

Gram-negative bacteria, especially Neisseria species

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3
Q

gram-positive, catalase-negative, alpha-hemolytic diplococcus

A

streptococcus pneumoniae

viridans streptococci

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4
Q

atypical fungus

A

pneumocystis jiroveci

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5
Q

gram-negative, catalase-positive bacillus

A

pseudomonas aeruginosa

gram negative
rod (bacillus)
lactose nonfermenter
oxidase positive

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6
Q

gram-positive, catalase-positive, beta-hemolytic coccus in clusters

A

staphylococcus aureus

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7
Q

What is a common cause of pneumonia in patients with cystic fibrosis?

A

pseudomonas

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8
Q

gram + cocci
catalase +
coagulase +

A

s. aureus

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9
Q

gram+ cocci
catalase +
coagulase -

A

s. epidermidis (novobiocin sensitive)

s. saprophyticus (novobiocin resistant)

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10
Q

gram + cocci
catalase -
alpha-hemolytic

A 
s. pneumoniae (capsule, optochin sensitive, bile soluble)
viridans streptococci (no capsule, optochin resistant, bile insoluble)
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11
Q

gram + cocci
catalase -
beta-hemolytic

A

s. pyogenes (bacitracin sensitive) (group A)

s. agalactiae (bacitracin resistant) (group B)

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12
Q

gram + cocci
catalase -
gamma-hemolytic

A

group D (enterococcus, e.g., E. faecalis) - growth in bile and 6.5% NaCl

Nonenterococcus (S. bovis) - growth in bile, not in 6.5% NaCl

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13
Q

gram + bacilli

A 
clostridium (anaerobic)
bacillus (aerobic)
corynebacterium
mycobacterium tuberculosis (acid fast)
listeria monocytogenes (beta-hemolytic)
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14
Q

gram + branching filaments

A

nocardia - aerobic, acid fast

actinomyces - anaerobic, not acid fast

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15
Q

gram - diplococci

A 
Neisseria meningitidis (maltose fermenter)
Neisseria gonorrhoeae (maltose nonfermenter)

Both produce IgA protease and ferment glucose

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16
Q

gram - “coccoid” rods

A

Haemophilus influenza

Bordatella pertussis

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17
Q

gram - rods

lactose fermenters

A

Fast:
Klebsiella
E. Coli
enterobacter

Slow:
citrobacter
serratia

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18
Q

gram - rods

lactose nonfermenters

A 
oxidase (-):
shigella
salmonella
proteus
yersinia

oxidase (+)
pseudomonas

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19
Q

gram (-) comma-shaped

oxidase +

A 
campylobacter jejuni (grows in 42 degrees)
helicobacter pylori (produces urease)
vibrio cholerae (grows in alkaline media)
20
Q

Characteristics of Salmonella

A
  • has flagella
  • hematogenous spread
  • produces hydrogen sulfide
  • intestinal epithelial invasion –> monocytic response
  • may cause bloody diarrhea
  • has many animal reserviors
  • antibiotics may prolong duration fecal excretion of organism
  • does not ferment lactose
21
Q

Characteristics of shigella

A
  • no flagella
  • cell-to-cell transmission (no hematogenous spread)
  • does not produce hydgrogen sulfide
  • intestinal epithelial invasion –> neutrophilic response
  • often causes bloody diarrhea
  • only found in humans and primates
  • antibiotics shorten duration of fecal excretion of organism
  • does not ferment lactose
22
Q

Characteristics of N. gonorrhoeae

A

(1) no pollysaccharide capsule
(2) does not ferment maltose
(3) sexually transmitted
(4) no vaccine (due to rapid antigenic variation in pilus protein
(5) leads to: gonorrhea, septic arthritis, pelvic inflammatory disease, neonatal conjunctivitis, Fitz-Hugh_Curtis Syndrome
(6) condoms prevent sexual transmission; erythromycin ointment prevent neonatal transmission
(7) treatment: ceftriaxone (+ doxycycline or azithromycin for possible chlamydia infection)
(8) often intracellular (in neutrophils)

23
Q

Characteristics of N. meningitidis

A

(1) polysaccharide capsule
(2) ferments maltose
(3) respiratory and oral secretions
(4) vaccine available (except for type B)
(5) leads to: meningococcemia, meningitis, Waterhouse-Friderichsen syndrome
(6) rifampin, ciprofloxacin, or ceftriaxone prophylaxis for close contacts
(7) treatment: ceftriaxone or penicillin G

24
Q

Common characteristics of Neisseria

A
  • -gram negative
  • -diplococci
  • -ferment glucose
  • -produce IgA proteases
25
Q

Klebsiella characteristics

A

Four As:

(1) Aspiration pneumonia (lobar)
(2) Abscess formation in lungs and liver
(3) Alcoholics
(4) diAbetics

Patients often produce “red currant jelly” sputum due to abundant polysaccharide capsules

26
Q

Whats the relationship between penicillin and gram-negative bugs?

A

Gram (-) bacilli are resistant to penicillin G but may be susceptible to penicillin derivatives such as ampicillin and amoxicillin.

The gram negative outer membrane layer inhibits entry of penicillin G and vancomycin

27
Q

Beta-hemolytic bacteria

A

Form a clear area of hemolysis on blood agar

streptococcus pyogenes
streptococcus agalactiae
staphylococcus aureus
listeria monocytogenes

28
Q

What microorganism causes syphilis?

A

Treponema pallidum

29
Q

Describe primary syphilis.

presentation, serology/diagnosis

A
  • -localized disease
  • -presents with painless, non-itchy, nodule (chancre)
  • -screen with: VDRL, RPR
  • -confirm diagnosis with FTA-ABS
  • -can use dark-field microscopy to visualize treponemes in fluid from chancre
30
Q

What do VDRL, RPR and FTA-ABS stand for?

A

VDRL - venereal disease research laboratory
RPR - rapid plasma reagin
FTA-ABS - fluorescent treponemal antibody absorption

31
Q

Describe secondary syphilis.

presentation, screening/diagnosis

A

–disseminated disease that presents with:

  • fever
  • lymphadenopathy
  • maculopapullar rash, often including palms and soles
  • condylomata lata - whitish, wart-like lesion on genitals

VDRL/RPR for screening, FTA-ABS for confirmation
Dark field microscopy to visualize treponemes

*Followed by latent syphilis - (+) serology, asymptomatic

32
Q

Describe tertiary syphilis

presentation, screening/diagnosis

A

(1) gummatous syphilis (chronic granulomas)
(2) cardiovascular syphilis (aortitis, vaso vasorum destruction –> increased risk of aortic aneurysm)
(3) late neurosyphilis (tabes dorsalis, Argyll-Robertson pupil)
- ->presents with broad-based ataxia, (+) Romberg sign, stroke without hypertension, Charcot joint

For neurosyphilis: test CSF with VDRL or RPR

33
Q

What is VDRL?

A

venereal disease research laboratory

  • -detects nonspecific antibody that reacts with beef cardiolipin
  • -screening test for syphilis, sensitive, nonspecific, many false positives
34
Q

Causes of false positives in VDRL test

A

VDRL:

Viruses (hepatitis, mononucleosis [EBV])
Drugs
Rheumatic fever
Lupus and leprosy

35
Q

What is congenital syphilis?

A

syphilis present in utero and at birth

occurs when a child is born to a mother with syphilis

36
Q

What are the clinical manifestations of neonatal syphilis?

A 
Saber shins
Hutchinson teetch (notched incisors)
Mulberry molars
Saddle nose
CNVIII deafness
Often results in stillbirth, hydrops fetalis
37
Q

How should you treat neonatal syphilis?

A

Treat the mother early in pregnancy, as placental transmission typically occurs after the first trimester.

38
Q

What are the serological tests for HIV diagnosis?

A

–ELISA - highly sensitive test used for screening; has a high false positive rate; a positive must be confirmed with: –Western Blot - specific test; high false negative rate, used to “rule in”

39
Q

What test is used to monitor HIV prognosis and effect of therapy

A
  • -HIV PCR/viral load - used to determine the amount of viral RNA in plasma.
  • -High viral load is associated with a poor prognosis
  • -Used to also monitor effect of drug therapy
40
Q

What defines an AIDS diagnosis?

A

<14% of all lymphocytes

41
Q

What do the ELISA and Western Blot tests look for?

A

antibodies produced to viral proteins

42
Q

Why should ELISA and Western Blot tests be interpreted with caution?

A

These tests can be falsely negative in the first 1-2 months after HIV infection.

These tests can also be falsely positive initially in babies born to HIV positive mothers because the anti-gp120 antibody (IgG) crosses the placenta

43
Q

Where does HIV replicate during the latent phase of the infection?

A

In the lymph nodes (where the CD4+ cells would normally be found)

44
Q

What are the four general stages of untreated HIV infection?

A

(1) Flu-like symptoms
(2) Feeling fine (latent)
(3) Falling count (CD4+)
(4) Final crisis

45
Q

How would you diagnose diphyllobothrium latum?

A

diagnost by finding operculated eggs or proglottids in feces

STEP1 (53 decks)

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