Gram (-) Rods

Question 1

Inflammatory diarrhea (blood and pus), oxidase +, gull’s wings, low infectious dose, grows at 42C, transmitted from poultry

Answer 1

Campylobacter jejuni

Question 2

Most common cause of bacterial gastroenteritis (direct infection of GI) in U.S.

Answer 2

Campylobacter jejuni (more frequent than salmonella and shigella combined)

Question 3

Potential complications of C. jejuni infection?

Answer 3

• most often self-limiting (tx is supportive)
• Guillain Barre syndrome - accounts for 1/3 of GBS in U.S., cross reactivity with neural tissues
• Reactive arthritis

Question 4

Oxidase +, UREASE +, microaerophilic, grows at 37C, causes chronic gastritis and duodenal ulcers

Answer 4

Helicobacter pylori

Question 5

Type I carcinogen, causes gastric adenocarcinoma, MALT-oma, or B cell lymphoma

Answer 5

Helicobacter pylori

Question 6

Associated with consumption of undercooked or raw seafood

Answer 6

Vibrio parahaemolyticus or vulnificus

• V. vulnificus also associated with a rapidly spreading cellulitis

Question 7

Noninflammatory diarrhea, oxidase +, shooting star motility, growth on alkaline TCBS, high infectious dose, human reservoir with fecal oral spread, associated with natural disasters and standing water

Answer 7

Vibrio cholerae

Question 8

Describe how cholera toxin works

Answer 8

• activates adenylate cyclase (Gs)
• increases cAMP
• efflux of Cl and H20

Question 9

Ricewater stool with tremendous fluid loss, must replace fluids and treatment with doxycycline or ciprofloxacin shortens disease course

Answer 9

Vibrio cholerae

Question 10

Gastroenteritis, non-lactose fermenter, motile H2S producer

Answer 10

Salmonella (think salmon swim upstream/are motile)

• compare with Shigella, which is a non lactose fermenter but nonmotile, non H2S producer!

Question 11

What are common features of all members of Enterobacteriaceae?

Answer 11

• facultative anaerobes
• ferment glucose
• Oxidase (-)
• catalase +
• reduce nitrates to nitrites

Question 12

You grow a MacConkey agar plate and see pink colonies. What does this mean and what could these be?

Answer 12

• MacConkey agar differentiates lactose fermentation
• pink = fermenters, colorless = nonfermenters
• Lactose fermenters are Escherichia, Klebsiella, Enterobacter, and Citrobacter

Question 13

Oxidase (-), lactose fermenter, virulence associated with P pili, most common cause of UTI

Answer 13

Escherichia coli

Question 14

Oxidase (-), lactose fermenter, K1 serotype (aka capsule), contamination during birth, second most common cause of neonatal meningitis

Answer 14

Escherichia coli

Question 15

Mechanism that E. coli can cause septicemia

Answer 15

LPS lipid A endotoxin

Question 16

Mechanism that ETEC causes diarrhea

Answer 16

• LT toxin stimulates adenylate cyclase, increases cAMP, and causes efflux of Cl and H20 (like cholera)
• attachment is also an important factor, because otherwise the massive amounts of diarrhea would just flush the bacteria out

Question 17

Second most common cause of infantile diarrhea

Answer 17

EPEC (p = pathogenic or pediatric)

- important adherence to M cells to cause effacement of brush border

Question 18

Only cause of inflammatory diarrhea in the Escherichia genus

Answer 18

EIEC - invades large bowel similar to shigella

Question 19

Diarrhea that is bloody but non-inflammatory, toxin works by interfering with 60S ribosomal subunit and decreasing protein synthesis, does not ferment sorbitol (differs from others in genus this way), can progress to HUS

Answer 19

EHEC O157:H7

Question 20

Enterobacteriaceae, lactose fermenter, oxidase (-), non foul smelling sputum in an alcoholic with pneumonia

Answer 20

Klebsiella pneumoniae

• non foul smelling differentiates from anaerobic aspiration pneumonia, which also occurs in alcoholics and will smell
• Extras: sputum is described as currant jelly and Klebsiella has a capsule

Question 21

Enterobacteriaceae (facultative anaerobe), non lactose fermenter, nonmotile, non H2S producer, extremely low infectious dose (1-10), diarrhea that starts watery and progresses to bloody

Answer 21

Shigella

S. sonnei is most common in U.S.
S. dysenteriae is most common in developing countries and produces the most severe disease

Question 22

Describe the different mechanisms of pathogenesis seen with Shigella

Answer 22

1) Endotoxin - inflammation
2) Invasion of M cells - actin jet trails to move laterally, avoid immune system and produce shallow ulcers
3) Shiga toxin - inhibits protein synthesis by clipping 60S ribosomal subunit (similar to EHEC)

Question 23

Enterobacteriaceae (facultative anaerobe), non lactose fermenter, non H2S producer, associated with drinking unpasteurized milk in cold climates, causes different presentations based on age

Answer 23

Yersinia enterocolitica

• exhibits cold growth, motile at 25C
• very young: febrile diarrhea
• older kids/young adults: pseudoappendicitis
• adults: enterocolitis with reactive arthritis

Question 24

Enterobacteriaceae (facultative anaerobe), non lactose fermenter, non H2S producer, coagulase positive, U.S. Southwest

Answer 24

Yersinia pestis

Question 25

What are the two disease presentations caused by Yersinia pestis?

Answer 25

A) Bubonic plague - flea bite, rapidly increasing fever, regional buboes, conjunctivitis, DIC B) Pneumonic plague - inhalation of organisms, septic pulmonary emboli, highly contagious and has potential as biowarfare agent

Question 26

Pathogenesis includes coagulase, endotoxin, exotoxin, F-1 envelope antigen, and Type III secretion system. Appears as a bipolar rod or safety pin on staining. Vaccine available to high risk populations.

Answer 26

Yersinia pestis

Question 27

Enterobacteriaceae (facultative anaerobe), non lactose fermenter, highly motile with swarming motility, UREASE +, causes UTIs and kidney stones (staghorn calculi)

Answer 27

Proteus mirabilis/vulgaris

Question 28

Enterobacteriaceae, non lactose fermenter, motile, more than 2400 serotypes based on O antigen

Answer 28

Salmonella - high infectious doses needed, as organism is acid sensitive - Typhi species only in humans; non typhi species transmitted in chicken products and reptiles

Question 29

Patient presents with fever, abdominal pain, rose spots, fluctuating diarrhea and constipation, and positive Widal test. What bug is this, what disease does it cause, and where does it hide chronically?

Answer 29

Salmonella enterica subsp. typhi - Causes typhoid fever - Lies in gall bladder of carriers - Widal test: agglutination of Abs to O, Vi, H antigens in patient's serum

Question 30

How does Salmonella typhi resist being killed by macrophages?

Answer 30

- decreases the fusion of lysosomes with phagosomes - defensins provide protection - Vi capsular antigen survives complement-mediated killing

Question 31

How does Salmonella enteritidis/typhimurium cause diarrhea?

Answer 31

- NO TOXIN! | - invades mucosa, causing inflammation and increase of cAMP

Question 32

Osteomyelitis in a patient with sickle cell disease

Answer 32

- Salmonella, more specifically choleraesuis, paratyphi, dublin, or typhi

Question 33

Aerobic, facultative intracellular zoonosis, Dermacentor tick vector, reservoir in rabbits, ulceroglandular or pneumonic disease treated with streptomycin

Answer 33

Francisella tularensis

Question 34

Aerobic, facultative intracellular zoonosis, no vector, usually due to ingesting unpasteurized dairy products or direct contact with animal. Disease is characterized by undulating fevers and profuse sweating. Name the potential pathogens and associated livestock.

Answer 34

Brucella B. abortus - cattle B. melitensis - goats B. suis - pigs

Question 35

Facultative anaerobe with capsule, resides in human nasopharynx and is common cause of meningitis, epiglottitis, or otitis media in unvaccinated children

Answer 35

Haemophilus influenzae vaccine is against type b capsule and induces a T-cell dependent response - will need boosters

Question 36

What are the main virulence factors of Haemophilus influenzae? What are the requirements to grow?

Answer 36

VFs: A) polysaccharide capsule (use latex particle agglutination to detect) B) IgA protease Growth Reqs: chocolate agar, because missing X and V factors to lyse blood (can satellite grow around S. aureus)

Question 37

Facultative anaerobe, transmitted via sexual contact, presents with soft, painful chancre

Answer 37

Haemophilis ducreyi (chancroid)

Question 38

Female presents with thin gray vaginal discharge. She recently was on a course of antibiotics. Vaginal pH is 5 and the whiff test is positive.

Answer 38

Bacterial vaginosis, due to overgrowth of Gardnerella vaginalis (facultative anaerobe) - reduction of lactobacillus allows vaginal pH to increase >4.5 and normal flora of G. vaginalis flourishes

Question 39

Facultative anaerobe, causes vaginal discharge, positive whiff test, not sexually transmitted, clue cells present on smear

Answer 39

Gardnerella vaginalis

Question 40

Facultative anaerobe, associated with rapidly spreading cellulitis and lymphadenitis following a cat bite, prophylaxis and treatment with amoxicillin/clavulanate

Answer 40

Pasturella multocida

Question 41

Associated with cat scratch fever in immunocompetant and bacillary angiomatosis in immunosuppressed

Answer 41

Bartonella henselae

Question 42

Guy on the street takes bath salts, then takes a bite out of innocent bystander. Innocent bystander comes to see you after developing a cellulitis. You culture the wound and the next morning the agar is corroded and smells like bleach.

Answer 42

Eikenella corrodens

Question 43

Cellulitis associated with dog bite wounds and an overwhelming sepsis if obtained in the absence of a spleen

Answer 43

Capnocytophaga canimorsus

Question 44

Fastidious rods that are part of normal flora and are the most common cause of G(-) endocarditis in non-IV drug users, difficult to diagnose, treat with cephalosporins or fluoroquinolones

Answer 44

``` HACEK Group Infection: Haemophilus aphrophilus Actinobacillus actinomycetemcomitans Cardiobacterium hominis Eikenella corrodens Kingella kingae ```

Question 45

Anaerobic, normal colon flora, VFs include a modified LPS with reduced activity and an antiphagocytic capsule, associated with abdominal trauma or surgery, causes septicemia, peritonitis, or abscess formation

Answer 45

Bacteroides fragilis

Question 46

Prophylactic antibiotic regimen for anyone undergoing GI surgery

Answer 46

Metronidazole, clindamycin, or cefoxitin Bacteroides fragilis has a wide range of antibiotic resistance, so prophylactic treatment is necessary

Question 47

Aerobic, oxidase positive, catalase positive, ubiquitous in water, with slime layer capsule, blue-green pyocyanin, sweet odor, non-lactose fermenting, causes GI distress in healthy people or cellulitis in burn patients

Answer 47

Pseudomonas aeruginosa

Question 48

What are the virulence factors of Pseudomonas aeruginosa?

Answer 48

Endotoxin, exotoxin for eEF-2 that inhibits protein synthesis (like diptheria toxin), capsule slime layer

Question 49

Aerobic, gram stains poorly, aerosol transmission, requires cysteine and iron to grow, facultative intracellular, associated with elderly smoker/drinker that is immunosuppressed, atypical pneumonia

Answer 49

Legionella pneumophila

Question 50

What are the two diseases Legionella pneumophila can present as?

Answer 50

1) Legionairre's - atypical pneumonia, mental confusion, diarrhea, can be severe and fatal 2) Pontiac Fever - much milder pneumonia with full recovery

Question 51

Strict aerobe, reservoir is vaccinated humans, transmitted by respiratory droplets, damages respiratory epithelium via adenylate cyclase toxin, tracheal cytotoxin, endotoxin, and its namesake toxin which also increases adenylate cyclase

Answer 51

Bordetella pertussis, the causative agent of whooping cough Pertussis toxin ribosylates Gi, which promotes lymphocytosis, induces hypoglycemia, blocks immune effector cells, and increases sensitivity to histamine

Question 52

During which stage of pertussis infection is bacterial culture most likely to grow?

Answer 52

Catarrhal Stage, when symptoms are reminiscent of the common cold and nonspecific to whooping cough Ability to culture bacteria declines as disease progresses Culture on Regan-Lowe media

Question 53

Spirochete with axial filaments, obligate pathogen (cannot culture), transmitted sexually or across the placenta, three distinct stages plus a latent period, visualized by darkfield microscopy, screen with VDRL and confirm with FTA-ABS

Answer 53

Treponema pallidum

Question 54

Baby of IV drug user - 8th nerve damage, notched (Hutchinson) teeth, tabes dorsalis, rhinitis with infectious secretions

Answer 54

Congenital syphilis

Question 55

Name the stages of syphilis and their hallmark symptoms

Answer 55

1) Primary: nontender chancre that heals spontaneously 2) Secondary: diffuse maculopapular rash that is infectious, patchy alopecia, condylomata lata 3) Latency 4) Tertiary: gummas, aortitis, CNS inflammation

Question 56

What is the treatment for syphilis and what is a potential reaction to treatment?

Answer 56

Treatment - benzathine penicillin (long acting) Reaction - Jarish-Herxheimer, may occur in successful treatment of any spirochete as bacteria is lysed and LPS released. Fever, hypotension, rigors.

Question 57

Spirochete, microaerophilic, difficult to culture, reservoir in mice or deer, vector in Ixodes tick, spreads via bloodstream to involve heart, joint, and CNS

Answer 57

Borrelia burgdorferi

Question 58

Describe the stages of lyme disease

Answer 58

Stage 1: flu-like symptoms, erythema migrans Stage 2: Worsening flu-like symptoms Stage 3: Bell palsy, arrhythmias, myocarditis, arthritis (due to immune complexes), extreme fatigue

Question 59

Spirochete, tight terminal hooks, aerobe, seen on darkfield microscopy, zoonosis, causes an influenza like disease that can rapidly progress to involve liver and kidney if not treated

Answer 59

Leptospira interrogans, causing Leptospirosis due to contact with animal urine in water

Question 60

What is Weil disease?

Answer 60

Icteric leptospirosis with renal failure and myocarditis