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Microbiology First Aid USMLE Step 1 > Gram Negative Bugs > Flashcards

Gram Negative Bugs Flashcards

1
Q

HaEMOPhilus Causes

A

Epiglottitis (cherry red in children), Meningitis, Otitis Media (Nontypeable strains), and Pneumonia

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2
Q

Most invasive disease caused by capsular type B, it is a small gram-neg (coccobacillary) rod that produces IgA protease and is transmitted by aerosols.

A

Haemophilus Influenza

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3
Q

What type of agar do you culture H. Flu on?

A
  • Chocolate agar with factors V(NAD+) and X (hematin).

- Can also be grown with Staph Aureus which will lyse the cells giving H. flu access to V and X.

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4
Q

H. Flu vaccine contains what?

A

Type B capsular polysaccharide (polyribosylribitol phosphate) conjugated to dphtheria toxoid or other protein.

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5
Q

Treat meningitis with? Give what as prophylaxis to close contacts?

A

Treat with ceftriaxone and give Rifampin to close contacts.

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6
Q

Pt presents as a child that has to hunch over in order to breathe and drools like a zombie, what do they have and what is the cause?

A

Epiglottitis and most often Strep Pneumo but if the kid is not vaccinated then it would be H. Flu.

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7
Q

Gram neg diplococci that ferments glucose, produces IgA proteases and is Oxidase Positive.

A

Neisseria (Gonococci and Meningococci)

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8
Q

What does N. Meningococci Ferment?

A

Maltose and Glucose

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9
Q

What does N. Gonococci Ferment?

A

Glucose

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10
Q

What’s so special about N. Meningococci?

A
  • Polysaccharide capsule
  • Maltose fermentation
  • Vaccine (none for type B)
  • Respiratory and Oral Secretions.
  • Causes meningococcemia, meningitis, and Waterhouse-Friderichsen syndrome.
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11
Q

What’s so special about N. Gonococci?

A
  • No capsule, no maltose fermentation, No vaccine (due to antigenic variation)
  • Sexually Transmitted
  • Causes gonorrhea, septic arthritis, neonatal conjuntivitis, PID, and Fitz-Hugh-Curtis Syndrome.
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12
Q
  • Presents with Severe Pneumonia, Fever, GI issues (diarrhea), and CNS symptoms (Mental Confusion)
  • Typically in smokers >55 yrs with high alcohol intake or in immunosuppressed.
A
  • Legionnaires’ Disease (Legionella Pneumophila)
  • Think of a French Legionnaire with his silver helmet, sitting around a campfire (charcoal) with his iron dagger - he is no sissy (cysteine).
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13
Q

Mild flu-like syndrome with no fatalities. Related to Legionnaires’.

A

Pontiac Fever

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14
Q
  • Gram neg rod that stains poorly, use a silver stain.
  • Transmitted by Aerosol WATER DROPLETS FROM ENVIRONMENTAL WATER SOURCE HABITAT. (Could come from a lake, river, shower, drinking fountain, misters at the store, etc).
  • NO PERSON TO PERSON SPREAD.
A

Legionella Pneumophila (Legionnaires’ Disease)

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15
Q
  • Grows on charcoal yeast extract with iron and cysteine.
  • Diagnosed by presence of antigen in urine.
  • Facultative Intracellular = Granulomas.
  • Treat with macrolide or quinolone.
A

Legionnaires’ Disease

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16
Q
  • Associated with wound/burn infections, Pneumonia (especially in cystic fibrosis), sepsis (black lesions on skin), External Otitis (swimmer’s ear), UTI, Drug use, Diabetic Osteomyelitis, and hot tub folliculitis (healthy pts)
  • Also Malignant otitis externa in diabetics, eye ulcers from prolonged contact lens wear, and erythema gangrenosum.
A

Pseudomonas Aeruginosa

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17
Q

Aerobic, encapsulated gram-neg rod, non-lactose fermenting, oxidase positive (granulomas), and produces pyocyanin (blue-green) pigment that has a grape-like odor.

A

Pseudomonas Aeruginosa

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18
Q
  • Produces endotoxin (fever, shock) and exotoxin A (ribosylates EF-2 to inactivate it)
A

Pseudomonas Aeruginosa

19
Q

Treat Pseudomonas Aeruginosa with….

A

Aminoglycoside with extended spectrum penicillin (piperacillin/ticarcillin)

20
Q

Virulence Factors:

  • Fibriae: cystitis and pyelonephritis
  • K capsule: pneumonia, neonatal meningitis
  • LPS endotoxin: septic shock
A

E. coli

21
Q
  • Mech: Invades intestinal mucosa and causes necrosis and inflammation (clinically like Shigella) but NO toxin produced.
  • Presents as Invasive, dysentery
A

EIEC

22
Q

Mech: Labile toxin/stable toxin. No inflammation or invasion.
- Presents as Traveler’s diarrhea (watery)

A

ETEC

23
Q

Mech: No toxin produced. Adheres to apical surface, flattens villi, prevents absorption.
- Presents as diarrhea usually in children.

A

EPEC

24
Q

Mech: Produces Shiga-like toxin and Hemolytic-uremic syndrome (triad of anemia, thrombocytopenia, and acute renal failure).
- Endothelium swells and narrows lumen, leading to mechanical hemolysis and reduced renal blood flow; damaged endothelium consumes platelets.

A

EHEC

25
Q

Most common serotype of EHEC

A

O157:H7

26
Q

Presents as Dysentery (toxin alone causes necrosis and inflammation).
- Does not ferment sorbitol (distinguishes it from other E. coli.

A

EHEC

27
Q
  • Intestinal flora that causes lobar pneumonia in alcoholics and diabetics when aspirated.
  • Very mucoid colonies caused by abundant polysaccharide capsule –> Red “currant” jelly sputum.
  • Also cause of nosocomial infections.
A

Klebsiella

28
Q

4 A’s of Klebsiella

A
  • Aspiration pneumonia
  • Abscess in lungs and liver
  • Alcoholics
  • di-A-betics
29
Q
  • No flagella, cell to cell transmission with NO heme spread.
  • Humans and primates are only reservoirs.
  • Does NOT produce hydrogen sulfide and Antibiotics prolong excretion in feces.
A

Shigella

30
Q
  • Has flagella, can disseminate hematogenously, and has many animal reservoirs.
  • Produces hydrogen sulfide and antibiotics may prolong symptoms.
A

Salmonella

31
Q
  • Invades intestinal mucosa and causes a monocytic response –> can cause bloody diarrhea.
  • No lactose fermenting.
A

Salmonella

32
Q
  • Invades intestinal mucosa and causes PMN infiltration –> OFTEN causes bloody diarrhea but does not ferment lactose.
A

Shigella

33
Q
  • Found only in humans, characterized by rose spots on abs, fever, headache, and diarrhea.
  • Can remain in gallbladder and cause a carrier state.
A

Salmonella Typhi (Typhoid Fever!)

34
Q
  • Major cause of bloody diarrhea, esp in children.

- Fecal/oral through foods like poultry, meat, unpasteurized milk.

A

Campylobacter Jejuni

35
Q

Comma or S-shaped, oxidase positive, grows at 42 degrees C and is common antecedent to Guillain-Barre syndrome and reactive arthritis.

A

Campylobacter Jejuni (Campylobacter likes the hot CAMPfire)

36
Q
  • Produces profuse rice-water diarrhea via toxin that permanently activates Gs, increases cAMP.
  • Comma shaped, oxidase pos, grows in alkaline media. Endemic to developing countries.
  • Prompt oral rehydration necessary.
A

Vibrio Cholera

37
Q
  • Usually transmitted from pet feces, contaminated milk, or pork. Causes mesenteric adenines that can mimi Crohn’s or appendicitis.
  • Gram neg w/ toxins called Yops.
A

Yersinia Enterocolitica

38
Q
  • Transmitted by rodents by aerosols or flea bites.

- Gram neg causes Buboes: massive lymph node enlargement, pneumonia and sepsis.

A

Yersinia Pestis (Black Plague)

39
Q
  • Curved, gram neg rod that causes gastritis and up to 90% of duodenal ulcers.
  • Urease positive, creates alkaline environment.
A

H. pylori

40
Q

What do you treat H. pylori with?

A

Triple Therapy: Proton Pump Inhibitor, Clarithromycin, and amoxicillin or metronidazole.

41
Q

Found in water contaminated with animal urine.

- Causes flu-like symptoms, jaundice, and photophobia with conjunctivitis. Prevalent among surfers and in tropics.

A

Leptospira Interrogans (Leptospirosis)

42
Q

Severe form of jaundice and azotemia from liver and kidney dysfunction; fever, hemorrhage, and anemia.

A

Weil’s Disease

43
Q

What is Lyme Disease caused by?

A

Borrelia Burgdorferi

Microbiology First Aid USMLE Step 1 (10 decks)

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