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Step 1 > SketchyMicro: Bacteria > Flashcards

SketchyMicro: Bacteria Flashcards

Bacteria -G+ Cocci (strep, staph, enterococcus) -G+ bacilli (bacillus, clostridium, listeria) -G+ filamentous rods (actinomyces, nocardia) -G- Diplococci (Neisseria

1
Q

Which gram positive bacteria weakly stains acid fast

(a) Name another organism that stains acid fast that is not Tb

A

Nocardia species weakly stain acid fast
-b/c some mycolic acid in the cell wall

(pulmonary and brain abscesses, cutaneous lesions)

(a) Another acid fast positive = mycobacterium leprae (aka causes leprosy)

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2
Q

Main virulence factor of

(a) Staph aureus
(b) GAS responsible for rheumatic fever

A

(a) Staph aureus: protein A is the main virulence factor, binds Fc to prevent complement from binding (prevents opsonization)
(b) M-protein: prevents opsonization and molecular mimcry to cause mitral valve damage seen in rheumatic fever

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3
Q

2 features of clostridum species

A
  1. obligate anaerobes
    - only flourish in environmnets w/o oxygen
  2. spore forming
    - often found in soil (C. tetani, C. perfingens)
    - improper canning of food (C. Botulinum)
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4
Q

Tb virulence factors

(a) Cord factor
(b) Sulfatides

A

Tb virulence factors

(a) Cord factor (shows serpentine growth in vitro) causes granuloma formation to wall off infection
(b) Sulfatides inhibit phagolysosome formation
- prevents phagosomes and lysosomes from fusing = how Tb survives in macrophages

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5
Q

What type of hypersensitivity is seen in a positive PPD skin test?

A

Type IV hypersensitivity: delayed cellular response

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6
Q

Bacteria responsible for

(a) Scarlet fever
(b) MC cause septic arthritis in adults
(c) Impetigo
(d) MC cause osteo in adults
(e) TSS

A

(a) Scarlet fever (strawberry tongue, pharyngitis, face-sparing rash) = strep pyogenes = group A strep
- encapsulated w/ hyaluronic acid, beta-hemolytic

(b,d) MC cause of both septic arthritis and osteomyelitis in adults = staph aureus
-beta-hemolytic, protein A virulence factor, coagulase positive

(c) Impetigo = from group A strep
(e) TSSS = toxic shock syndrome from staph aureus

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7
Q

What are the two virulence factors of Neisseria species

A

Neisseria species (neisseria meningites and neisseria gonorrhea) virulence factors

  • pili that demonstrates antigenic variation (why we can’t form super long lasting immunity to it)
  • IgA protease: cleaves IgA and its hinge region
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8
Q

Abx of choice for

(a) MSSA
(b) MRSA
(c) Staph epidermidis
(d) VRE

A

Abx of choice for

(a) MSSA = Nafcillin “naf for staph”
(b) MRSA = Vanc
(c) Staph epidermidis (endocarditis) = Vanc
- or replace infected implanted joint
(d) VRE = Vanc-resistant enterococci- need to tx w/ Linezolid or Tigecycline

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9
Q

Tuberculoid vs. lepromatous leprosy

(a) T cell reaction
(b) Skin manifestation

A

Tuberculoid leprosy: bacteria very well contained inside marcophages

(a) Th1 reaction
(b) well demarcated hairless skin lesion: biopsy of this lesion shows small amount of bacteria

Lepromatous reaction

(a) Th2 reaction (if Th1 not strong enough so bacteria are not contained in macrophages)
(b) Poorly demarcated skin lesions on extensor surfaces

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10
Q

MC infections caused by

(a) Staph epidermidis
(b) Staph saprophyticus

A

Both gram positive cocci: catalase positive and coagulase negative

(a) Staph epidermidis infects artificial heart valves and artificial joints, also indwelling catheters
(b) Staph saprophyticus = UTIs in sexually active females

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11
Q

Which organism uniquely causes a double zone of hemolysis on agar

A

Clostridium perfinges (gas gangrene and food poisoning) causes a double zone of hemolysis

-differentiate it from other hemolytic strains (GAS/GBS) b/c it’s an obligate anerobe

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12
Q

How to diagnose CDif

(a) MC abx culprit

A

Detect toxin (not the organism) in stool

(a) Clindamycin

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13
Q

Name 2 gram positive filamentous rods

A

Gram positive filamentous rods = actinomyces israelii and nocardia

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14
Q

2 gram + bacilli that cause formation of pseudomembranes

A
  • clostridium difficile: yellow pseudomembranes in colon

- corynebacterium diphtheriae: gray pseudomembranes in oropharynx

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15
Q

How to differentiate the 2 gram positive filamentous rods

(a) O2 use
(b) Clinically
(c) Tx

A

Actinomyces israelii vs. nocardia

Actinomyces israelii

(a) Obligate anerobe
(b) Gradual skin infection after jaw trauma
(c) PenG

Nocardia

(a) Obligate aerobe (like bacillus anthracis too)
(b) Pulmonary cavitations/abcesses, brain abscesses, cutaneous lesions
(c) Tx = sulfonamides

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16
Q

Differentiating neisseria meningities vs. neisseria gonorrhea

(a) Capsule
(b) Clinically
(c) Tx

A

Neisseria meningitides

(a) Has polysaccharide capsule (this is what the vaccine is made of)
(b) Clinically: meningitis w/ petechia, associated w/ Waterson-Freidhouse syndrome 2/2 shock
(c) Ceftriaxone- 3rd gen ceph w/ good CNS penetration

Neisseria gonorrhea

(a) No capsule!!!!
(b) White purulent discharge, PID, association w/ FItz-Hugh-Curtis syndrome
(c) Ceftriaxone AND azithromycin (for assumed chlamydial co-infection)

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17
Q

Gram positive cocci: beta-hemolytic vs. alpha hemolytic

A

Both staph aureus and strep A/B are beta-hemolytic (glow in red background)
While strep pneumo and strep viridans are alpha hemolytic (green color on agar plate)

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18
Q

Neisseria species

(a) 2 key organisms
(b) 2 agars on whcih they grow
(c) Which immunodeficiency increases risk specifically for neisseria infections?

A

Neisseria species

(a) Neisseria meningitis (encapsulated) and neisseria gonorrhea (non-encapsulated)
(b) Both grow on chocolate agar and VPN agar
- don’t grow on blood agar => need to heat up the blood agar which makes chocolate agar
(c) C5-C9 deficiency b/c pts can’t form MAC complex

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19
Q

Clinical features of lepromatous leprosy

A
  • symmetric distal neuropathy (stocking glove distribution): mycobacterium leprosae prefers cold environments => extremities
  • poorly demarcated skin lesion: biopsy shows tons and tons of bacteria
  • profound facial deformity: “Leonine facies”
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20
Q

3 stages of Lyme’s disease (think the targets)

A
  1. Erythema migrans (‘bull’s eye rash’) w/ flu-like symptoms (fevers and chills)
  2. Heart block and b/l facial palsy (b/l Bell’s)
  3. Migrating polyarthritis of large joints (knees) and encephalopathy
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21
Q

Tx of Lyme’s disease

A

Doxyclcyine

If really severe infection = Ceftriaxone

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22
Q

Mechanism of Tb reactivation

(a) Clinical correlate

A

Immunosuppression (HIV etc) decreases release of TNF-alpha that was containing the infection in the granulomas in macrophages

=> reduced TNF-alpha increases risk of reactivation

(a) Clinical correlate: need to check PPD test before starting pt on TNF-alpha inhibitor

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23
Q

Treponema pallidum

(a) Direct visualization
(b) Treponemal vs. non-treponemal diagnostic tests

A

Treponema pallidum => syphilis

(a) Direct visualization under dark microscopy
(b) Non-treponemal tests = screening tests (VDRL and RPR): but these aren’t testing directly for the treponema
- can have false positives from cross-reactivitiy: seen in +RF, SLE, mono, leprosy

If one of those is positive, then do FTA-Abs test (direct treponemal test) to confirm dx

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24
Q

Differentiate CDif endotoxin A and B

A

Endotoxin A works at the intestinal brush border to cause watery diarrhea

Endotoxin B polymerizes actin filaments causing formation of yellow pseudomembranes in the colon (seen on colonoscopy)

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25
Q

Mycobacterium Tb

(a) Stain
(b) Primary infects what cells

A

(a) Lowenstein-Jensen stain
(b) Primarily infects macrophages
- so macrophages are the cells that are involved in reactivation (aka where Tb remains latent)

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26
Q

Differentiate the treatment for tuberculoid vs. lepromatous leprosy

A

Tuberculoid (well contained infection): Dapsone and Rifampin x6mo

Lepromatous (much more severe infection): Dapsone, Rifampin, and Clofazimine for 2-5 years

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27
Q

Name the main features of primary, secondary, and tertiary syphilis

A

Syphilis

Primary = painless chancre at site on infection
Secondary = rash involving palms of hands and soles of feet, condyloma lata

Tertiary = gummas (soft growths w/ firm necrotic center)

  • aneurysm of the ascending aorta
  • tabes dorsalis = demyelination of the posterior column
  • Argyll-Robertson’s pupils
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28
Q

Describe the make up of TDaP vaccine

A

Tetanus toxoid and corynebacterium diptheriae toxoid vaccines- meaning they have the inactivated toxin (NOT the bacteria’s antigens) bound to protein to spark immunogenic repsonse

Then have acellular pertussis

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29
Q

What feature causes positive AFB stain

A

Mycolic acid is a part of cell walls in mycobacterium (both tuberculosis and leprae)

-also partially acid fast = nocardia (gram positive branching filamentous rod)

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30
Q

Name 2 spirochetes that infect humans (and the disease they cause)

A

Spirchoetes = spiral shaped bacteria

Borrelia burgdorferi => Lyme’s disease
Treponema Pallidum => Syphilis

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31
Q

Clinical relevance of novobiocin test

A

Novobiocin test- used to differentiate coagulase negative gram positive cocci

-Staph epidermidis is novobiocin sensitive in culture while staph saprophyticus is novobiocin resistant

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32
Q

Catalase test is most helpful to differentiate which gram positive cocci

A

Catalase (enzyme that catalyzes H2O2 –> H2O) is used to differentiate staph and strep

Staph = catalase + (cocci in clusters)
Streph = catalase - (cocci in long chains/pairs)
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33
Q

2 other body systems involved in Tb reactivation (besides pulmonary)

A

Spinal- Pott’s disease- infection of vertebral bodies

CNS- tuberculoma (cavitary lesions) or meningitis

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34
Q

Which staph species are coagulase positive vs. negative

A

Coagulase + = staph aureus

Coagulase - = staph epidermidis and staph saprophyticus

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35
Q

1st,2nd,3rd MC causes of neonatal meningitis

A

Neonatal meningitis

  1. GBS (strep agalactiae) = gram + cocci
  2. E. Coli
  3. Listeria monocytonegens = gram+ bacilli
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36
Q

Gram positive cocci in clusters vs. pairs

A

G+ cocci in

(a) Staph aureus grows in clusters, while strep genus grows in long chains or pairs

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37
Q

Differentiate the toxin excreted by clostridium tetani and clostridium botulinum

A

Both form toxins that are proteases against SNARE proteins

  • tetanus toxin: cleaves SNARE protein preventing release of inhibitory nt (GABA and glycine), so no inhibitory signal => uncontrolled muscle spasms
  • botulinum toxin: cleaves SNAREs in motor neurons preventing ACh release => causes descending flaccid paralysis (muscles can’t contract)
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38
Q

Test to differentiate group B strep from all other strep

A

CAMP test- increased zone of hemolysis when plated w/ staph aureus

GBS produces a CAMP factor that enlarges the area caused by staph aureus
-used to differentiate GBS from other strep species

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39
Q

What are Argyll-Robertson’s pupils?

A

“Prostitute’s pupils” highly specific for neurosyphilis

Pupils that react to accommodation, but not to light
-aka shrink when object nears, but don’t constrict to light

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40
Q

Clinical presentation of Clostridium botulinum

A

C. botulinum (G+ bacilli, obligate anaerobe, spore forming) presents w/ descending flaccid paralysis

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41
Q

Differentiate infection of C. botulinum in babies vs. adults

A

Adults do not get disease from the spores alone, instead the gut flora make a toxin (protease that cleaves SNARE in motor neurons) that cause disease

While babies don’t have this developed gut flora, so gut in an anaerobic environment in which C. botulinum can survive. So babies can get sick from the spores along (not the toxin formed by the gut)
-classically spores are found in honey

So babies get sick from the spores, while adults get sick from the preformed toxin

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42
Q

Why does the med student not get C. Dif but he/she transports it btwn pts who do get sick

A

C. Dif doesn’t compete well w/ normal gut flora, so it’s ppl who are on abx (therefore killing the normal gut flora) who are susceptible to infxn

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43
Q

Why do we test for C. Dif toxin instead of C. Dif bacteria in the stool

A

Tons fo ppl are colonized w/ C. Dif (it can be a normal part of gut flora), but most of those ppl aren’t colonized w/ toxin-producing strains

So want to test for the toxin and not the bacteria itself

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44
Q

Describe the clinical features of clostridium myonecrosis

A

Clostridium myonecrosis = gas gangrene, MC 2/2 Clostridium perfinges (G+ bacilli, obligate anaerobe, spore forming) = severe soft tissue infection

  • palpable crepitus 2/2 gas production
  • myocnecrosis due to alpha-toxin which is a lecithinase that leaves lecithin to damage the plasma membrane
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45
Q

Tx of clostridium myonecrosis

A

Tx = IV PenG

Clostridium myonecrosis = gas gangrene = soft tissue infxn MC 2/2 clostridium perfinges (G+ bacilli, obligate anaerobe, spore forming)

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46
Q

Hallmark clinical feature of Corynebacterium Diptheriae

A

C. diphtheriae classically presents w/ ‘Bull’s neck’ due to lymphadenopathy
-formation of grey pseudomembranes in the oropharynx

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47
Q

Describe the food poisoning caused by C. perfinges

A

Clostridium perfinges causes a late onset diarrhea
-slow onset watery diarrhea 2/2 spore ingestion

Late/slower onset b/c the toxin is not preformed, you consume the spores then toxin is produced

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48
Q

Name a non-strep bacteria that is beta-hemolytic

A

Listeria monocytonegenes (gram + bacilli, not cocci like strep) is beta-hemolytic

Listeria is also catalase positive (like staph species)

49
Q

What abx should be added to cover for Listeria meningitis?

A

Cover for listeria meningitis in its over 60 you w/ Ampicillin

50
Q

Clinical significance of catalase positive organisms

A

Increased risk for pts w/ CGD (chronic granulomatous disease)

51
Q

Name a non-staph species that is catalase positive

A

Nocardia species are catalase positive

52
Q

Name the prototypical oxidase positive species

A

Oxidase positive

  • pseudomonas
  • Neisseria species (both meningitis and neisseria)
  • Legionella pneumophila
53
Q

Ppx for close contact to Neisseria meningitis

(a) Define ‘close contact’ in this circumstance

A

(a) Spent at least 8+ hrs w/ a pt infected w/ Neisseria meningitis w/in the past 7 days gets you ppx tx w/ Rifampin

54
Q

In addition to capsule, name a biochemical way to differentiate the two neisseria species

A

Neisseria meningitis and gonorrhea both G- diplococci

Meningitis has polysaccharide capsule and ferments maltose and glucose

Gonorrhea does not have capsule and does not ferment maltose

55
Q

How to clinically distinguish neonatal conjunctivitis 2/2 gonorrhea vs. chlamydia

A

Timeline

Purulent neonatal conjunctivitis w/in the first 5 days is more likely gonorrhea (earlier onset)

While mucopurulent neonatal conjunctivitis after the first week of life is more likely chlamydial

56
Q

3 day old fetus p/w purulent conjunctivitis

(a) Dx
(b) Tx

A

(a) Neonatal gonorrhea- gonorrhea presents w/in first 5 days while chlamydial conjunctivitis is more likely to be mucopurulent and after the first week of life

(b) Tx for neonatal gonorrhea conjunctivitis = Ceftraixone AND Azithromycin
- tx for assumed chlamydia co-infection

57
Q

Describe the joint tap findings from a knee infected w/ disseminated gonorrhea

A

Neisseria gonorrhea (G- diploccic) can cause polyarthritis that MC presents as asymmetric arthritis of the knee

Joint tap shows a purulent synovial fluid that doesn’t gram stain
-big deal that this doesn’t gram stain, and it’s b/c the infection is intracellular (neisseria gonorrhea is a facultative intracellular in PMNs)

58
Q

Danger of treating treponema palladium infection

A

Tx syphillis w/ PenG (or Doxy if allergic to penicillin), but beware of Jarish-Herxheimer run = fevers, chill, headaches as spirochetes die off

Just need to support pt thru this rxn and continue to tx

59
Q

Ddx for bacteria that ferment lactose

A

Klebsiella, Enterobacter, Serratia, E. Coli (all gram negative bacilli of the enteric tract)

60
Q

How to distinguish klebsiella from enterobacter and serratia

A

All 3 (klebsiella, enterobacter, serratia) are lactose-fermenting gram negative bacilli

But Klebsiella is immotile (like shigella) while enterobacter and serratia are mobile
-also Klebsiella is catalase positive

61
Q

Bacteria fitting the buzzword

(a) Currant jelly sputum
(b) Red pigmentation
(c) Traveler’s diarrhea
(d) Comma shaped bacteria

A

Buzzword

(a) Currant jelly sputum = Klebsiella
- gram negative bacilli, nosocomial pneumonia and UTI
(b) Red pigmentation = Serratia
(c) Traveler’s dio = ETEC (enterotoxigenic E. Coli)
(d) Comma shaped bacteria = vibrio cholera

62
Q

Enteric tract infections MC from

(a) Undercooked chicken
(b) Undercooked meat
(c) Puppy feces

A

(a) Undercooked chicken => salmonella
- watery dio
(b) Undercooked meat => EHEC
- bloody dio
(c) Puppy feces => yersinia enterocolitica
- bloody dio

63
Q

Salmonella vs. Shigella

(a) Color of colonies on Hektoen agar
(b) Motility
(c) Clinical features

A

Salmonella vs. Shigella- both gram negative bacilli

Salmonella

(a) Forms black colones on Hektoen agar
(b) Motile
(c) Causes inflammatory or ‘pea-soup’ diarrhea

Shigella

(a) Green colonies on Hektoen agar
(b) Immotile
(c) Causes bloody diarrhea

64
Q

Name species that use type III secretion system

A

Gram negative bacilli of the enteric tract

  • salmonella enteritides
  • shigella
  • yersinia pestis
65
Q

Differentiate the amount of shigella and salmonella needed to cause infection

(a) Why

A

Salmonella is heat-labile, meaning it is easily destroyed by the acidity of the stomach => need a huge load of bacteria (like 10^1,000) to cause infection

While Shigella is head stable => not destroyed by gastric acidity => infection can be caused by much smaller number of organisms (like 10^100)

66
Q

Mechanism of Shiga toxin

A

Shiga (from Shigella) toxin inhibits the 60S ribosomal subunit to cause cell death

-same mechanism as ‘Shiga-like’ toxin produced by EHEC

67
Q

How to differentiate EHEC from the other E. Coli species

A

EHEC does not ferment sorbitol, while the other E. Coli species do

68
Q

Bacteria that produces Shiga-like toxin

(a) Mechanism of this toxin

A

Shiga-like toxin (aka toxin w/ same mechanism as that produced by Shigella) is produced by EHEC
-both Shigella and EHEC cause bloody diarrhea

(a) Shiga and Shiga-like toxin both inhibit ribosomal 60S subunit to inhibit translation and therefore cause cell death

69
Q

Bacteria that produces a toxin similar to cholera-toxin

(a) Mechanism of this toxin

A

ETEC (causes traveler’s diarrhea) produces two toxins, one heat labile and one heat stable

The heat-labile toxin increases cAMP production = similar to cholera toxin that increases water secretion into gut by increasing cAMP production

70
Q

Differentiate the two toxins produced by the bacteria that causes traveler’s diarrhea

A

Traveler’s diarrhea (watery dio after drinking water in Mexico) is due to ETEC (enterotoxigenic E. Coli)

Heat-labile toxin that increases cAMP, and heat-stable toxin that increases cGMP

71
Q

Name two bacteria resistant to cold temperatures

A

Both listeria (gram positive bacilli) and yersinia enterocolitica (gram negative bacilli) are resistant to cold temp => can contaminate refrigerated products such as milk

72
Q

Which bacteria can cause blood diarrhea that presents as a ‘pseudoappendicitis’?

A

Yersinia enterocolitica (G- bacilli) can cause bloody diarrhea w/ systemic features (ex: RLQ pain, fever) that mimics appendicitis

73
Q

MC cause of gram negative sepsis

A

E. coliiiii

74
Q

Name the three curved gram negative rods

(a) What else do these all have in common?

A

3 curved gram negative rods = Campylobacter jejunin, vibrio cholerae, H. pylori (more helical)

(a) All are oxidase positive

75
Q

Name the three curved gram negative rods

(a) What else do these all have in common?

A

3 curved gram negative rods = Campylobacter jejunin, vibrio cholerae, H. pylori (more helical)

(a) All are oxidase positive

76
Q

2 complications of campylobacter jejuni infection

A

Campylobacter jejuni = gram neg bacilli that causes blood dio

Can initiate Guillain-Barre = AI condition cause demyelination => ascending paralysis

Can also initiate Reiter’s syndrome = seronegative, HLA-B27 associated reactive arthropathy

77
Q

Mechanism of cholera toxin

(a) Clinical manifestation

A

Cholera toxin: increases cAMP levels by activating Gs pathway (stimulates adenylate cyclase)

(a) Profuse watery diarrhea b/c increases fluid secretion into the intestinal lumen

78
Q

H. pylori infection increases risk of what two malignancies

A

Gastric adenocarcinoma and MALToma

79
Q

Triple therapy for H. pylori eradication

A
  1. PPI to reduce acid that is overproduced 2/2 infection
  2. Amoxicillin
  3. Clarithromycin (macrolide)
80
Q

Triple therapy for H. pylori eradication

A
  1. PPI to reduce acid that is overproduced 2/2 infection
  2. Amoxicillin
  3. Clarithromycin (macrolide)
81
Q

Buzzword

(a) Rice-water diarrhea
(b) Hot tub folliculitis
(c) Swimmer’s ear
(d) Swarming motility when plated

A

(a) Rice-water dio = vibrio cholera
(b) Pseudomonas- pruritic papular folliculitis from underchlorinated hot tub
(c) Swimmer’s ear is caused by pseudomonal infection
(d) Swarming motility = proteus mirabilis

82
Q

Feature distinguishing pseudomonas from other enterobacteraciae

A

Pseudomonas is an obligate aerobe, while the others in the class are facultative aerobes (meaning can survive w/ or w/o O2)

83
Q

Cause of osteomyelitis in IVDU and diabetics

A

Pseudomonas

84
Q

Exotoxin produced by pseuodomonas is most similar to the toxin produced by what other bacteria?

(a) Mechanism

A

Exotoxin A produced by pseudomonas ribosylates EF2 (elongation factor 2) to cause cell death

Same mechanism as Diptheria toxin

85
Q

Name the bacteria by the buzzword

(a) ‘Fishy’ odor
(b) Infection in burn pts
(c) fruity, grape-like odor
(d) 100 day cough

A

(a) Fishy odor = Proteus mirabilis
(b) Pseudomonas high yield for infection in burn pts
(c) Fruity, grape-like odor of pseudomonas
(d) 100 day cough = bordatella pertussis, b/c convalescent phase (3rd phase) can last around 3 months of lingering cough

-all of these are gram negative bacilli btwwww

86
Q

Name the bacteria by the buzzword

(a) Blue-green pigment
(b) Cherry red epiglottis in child

A

(a) Blue-green pigment seen due to pseudomonal infection 2/2 pycocyanin and pyoverdin
(b) Epiglottitis = H. influenzae B
- p/w drooling, inspiratory stridor, and erythematous (‘cherry red’) epiglottis

87
Q

Mechanism of pertussis toxin

A

Pertussis toxin increases intracellular cAMP in two ways

  1. Ribosylating Gi (therefore inhibits the inhibitor Gi protein => cAMP builds up in cell)
  2. Adenylate cyclase toxin directly increases cAMP levels
88
Q

2 species that grow on chocolate agar

(a) 2 growth factors in chocolate agar

A

Neisseria meningitis and H. influenzae grow on chocolate agar

(a) Chocolate agar contains factor V (NAD) and factor X (hematin) which are required for growth

89
Q

Tx for Haemophilus influenza meningitis

(a) PPx for close contacts

A

Only H. influenzae type B (HiB) causes meningitis, tx w/ Ceftriaxone (beta lactam)

(a) Rifampin for close contacts, just like neisseria meningitis

90
Q

What two infections use Rifampin as ppx for close contacts

A

Both Neisseria meningitis and H. influenzae B. meningitis indicate Rifampin ppx for close contacts

91
Q

2 factors on chocolate agar

A

Chocolate agar (agar used to grow H influenza B) contains both factor V (NAD) and factor X (Hematin)

Hematin is considered the ‘X-factor’ needed for neissera and H. influenzae B growth

92
Q

Legionella

(a) Visualization technique
(b) What is required for growth on agar

A

Legionella

93
Q

Features of Legionairres disease

A

Atypical pneumonia seen in smokers

Distinguishing clinical features:

  • diarrhea
  • CNS features: headache, confusion
  • hyponatremia

Very high fever

94
Q

Smoker w/ pneumonia and hyponatremia on BMP

A

Slam dunk Legionairres disease = atypical pneumonia seen in smokers that also often has diarrhea, hyponatremia, CNS effects, and high fever

95
Q

How to make diagnosis of Legionairres disease

A

Diagnose legionella (cause of legionairres disease = atypical pneumonia) w/ rapid urine antigen test

96
Q

Name the animal that transmits

(a) Bartonella Henselae
(b) Brucella
(c) Francisella tularensis
(d) Pasteurella Multocida

A

(a) Bartonella henselae (cat-scratch fever and bacillary angiomatosis) transmitted thru cats
(b) Brucella from cattle and farm animals: cows, pigs, sheep, goat
(c) Francisella tularensis from rabbits, w/ ticks as vector
(d) Pasteurella multocida from small mammals, mainly cat and dog bites

97
Q

Organism that causes bacillary angiomatosis

(a) What other clinical entity does it cause?
(b) Tx

A

Bartonella Henselae, gram negative bacilli from cat scratches that (a) also causes cat scratch fever in immunocompetent, causes bacillary angiomatosis in immuncompromised

(b) Tx for bartonella henselae infection = tetracycline (Doxycycline)

98
Q

Explain why the following are obligate intracellular
organisms

(a) Chlamydia species
(b) Rikettsia species

A

(a) Chlamydia species cannot make their own ATP => obligate intracellular organisms
(b) Rickettsia species need NAD+ and CoA from their eukaryotic hosts

99
Q

Differentiate visualization of

(a) Chlamydia
(b) Gonorrhea

A

(a) Chlamydia speices exhibit poor uptake of gram stain, instead use Giemsa stain for visualization
(b) Neisseria gonorrhea stains gram negative, visualized on gram stain

100
Q

How is chlamydia diagnosed?

A

Culture can take days to grow, so dx quickly w/ NAAT = nucleic acid amplification technique (aka PCR)

101
Q

Differentiate the clinical features of the chlamydia species

(a) Chlamydia trachomatis
(b) Chlamydia pneumoniae
(c) Chlamydia psittaci

A

(a) C. trachomatis causes blindness and STI
(b) C. pneumoniae causes walking/atypical pneumonia in adults (similar clinically to mycoplasma pneumonia)
(c) C. psittaci is transmitted by birds/parrots and causes pneumonia

102
Q

Explain why penicillin is ineffective against

(a) Chlamydia species
(b) Mycoplasma pneumoniae

A

Penicillin attacks muramic acid in bacterial cell wall

(a) Chalmydia species have no muramic acid in their cell wall
(b) Mycoplasma pneumoniae doesn’t have a cell wall at all! instead has special plasma membrane w/ cholesterol

103
Q

Tx for chlamydia infection

A

Tx chlamydia w/ macrolide (azithromycin), also single dose Ceftriaxone for presumed gonorrhea co-infection

104
Q

MC cause of blindness worldwide

A

Chlamydia trachomatis A-C

105
Q

Differentiate the clinical pictures of the subtypes of chlamydia trachomatis infection

A-C
D-K
L1-L3

A

A-C = trachoma = leading cause of blindness worldwide
-transmitted by hand to eye contact or fomites

D-K causes the prototypical STI w/ watery discharge that can progress to PID

L1-L3 is also an STI but less common, causes lymphogranuloma venereum which is a tender lymphadenopathy

106
Q

Chlamydia trachomatis D-K vs. neisseria gonorrhea

(a) Clinical presentation in adults
(b) Clinical presentation in neonates

A

(a) Adults- STI that can progress to PID => infertility :-(
Chlamydia- thin watery discharge
Gonorrhea- white mucopurulent discharge

(b) Neonates- conjunctivities and pneumonia w/ staccato cough
Chlamydia- presents after 1 week of life
Gonorrhea- presents w/in first 2-5 days of life

107
Q

2 bacteria precipitates of Reiter’s syndrome

A
  1. Campylobacter jejuni = gram negative bacilli also implicated in Guillain-Barre
  2. Chlamydia = gram indeterminant visualized by Giemsa stain
108
Q

Differentiate clinical features of coxiella burnetii and brucella infection

A

Unique b/c coxiella burnetii (gram negative, causes Q-fever) and brucella (G- bacilli zoonotic from farm animals) both cause nonspecific fever and symptoms w/ hepatitis

Unique is the hepatitis
-but brucella will have undulating fever vs. stable fever in coxiella burnetti

109
Q

How to clinically distinguish Rickettsia and Coxiella burnetii infection

A

Both Rickettsia and Coxiella burnetii (Q-fever) are obligate intracellulars that cause fever, but there is characteristically NO RASH in coxiella burnetii

-while rash is prototypical feature of Rickettsia

110
Q

Gardnerella Vaginalis

(a) Clinical features
(b) How does this change pH

A

Gardnerella vaginalis is a gram variable rod that overgrows and disrupts the balance of normal vaginal flora

(a) Thin gray-white vaginal discharge w/ ‘fishy’ odor
(b) Overgrowth disrupts the normal primarily lactobacilli vaginal flora, pH of the vaginal discharge becomes above 4.5

111
Q

Only bacteria w/ cholesterol in its plasma membrane

A

Mycoplasma pneumoniae- cause of atypical pneumonia

112
Q

Dx of mycoplasma pneumoniae

(a) Agar
(b) Alternative to Cx

A

Mycoplasma pneumoniae

(a) Eatons agar- but can take about a week for it to grow on culture, so for faster results try
(b) Dx by cold agglutinin test, mycoplasma is associated w/ IgM that clump

113
Q

Tx for mycoplasma pneumoniae

A

Mycoplasma has no cell wall => can’t use a cell wall inhibitor like penicillin

Instead use macrolide (Azithromycin)

114
Q

Rickettsia species

(a) Shape
(b) Intra or extra cellular?

A

Rickettsia

(a) Coccobacilliary- kind of between cocci and bacilli
(b) Obligate intracellular, can’t produce CoA or NAD+

115
Q

Weil-Felix test

A

Weil-Felix agglutination test is used to dx Rickettsial infections

Both rickettsia prowazekii and rickettsia rickettsii (Rocky Mtn spotted fever)

116
Q

Rickettsia species

(a) Clinical symptoms
(b) Tx

A

Ricekttsia

(a) headache, fever, myalgias, arthralgia (so nonspecific) but then vasculitis and rash
(b) Tx = tetracyclines (Doxycyclin)

117
Q

Rickettsia prowazekii vs. rickettsii

(a) Rash
(b) Transmission

A

(a) Rash
Prowazekii- starts on trunk then spreads to extremities, spares hands and feet
RIckettsii (rocky mtn spotted fever) starts on extremities then moves centrally

(b) Transmission
Prowazekii transmitted by louse (mice) poop on skin, then we scratch our skin and introduce the infection
Rickettsii (rocky mtn spotted fever) infxn directly from tick bite

118
Q

Describe the rash of Rocky Mtn Spotted Fever

A

Rocky mtn spotted fever 2/2 infection w/ Rickettsia Rickettsii: typically starts 2-14 days after infection, starts on extremities then moves centrally

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