Micro images

Question 1

What would you expect to see on gram stain of the organism cultured from the finding here?

Answer 1

Gram - coccobacilli

(Intra-abdominal abscess = bacteroides fragilis)

Question 2

List 4 virulence factors of this organism.

Answer 2

1. VacA
2. CagA
3. Urease
4. PAI-assc. Type III secretion system

Question 3

Organism in 2nd and 3rd tube?

Answer 3

2nd = Salmonella (produces H2S = black butt)

3rd = Shigella (ferments glucose only = yellow butt + red slant)

Question 4

What two species could be represented on this MacConkey agar?

Answer 4

Shigella or Salmonella (lac -)

Question 5

How do you get this infection?

Answer 5

Prior antibiotic use

(Note the pseudomembrane over the colonic mucosa)

Question 6

In which patients would this complication occur?

Answer 6

Immunocompromised and chronic liver disease patients

(Bullae = V. vulnificus)

Question 7

Histology of tissue infected with this microbe would reveal ____. What symptoms would the patient exhibit?

Answer 7

Cytoplasmic inclusion bodies (viroplasms where assembly occurs)

Young child/infant with diarrhea

(Two outer shells + double-stranded RNA = rotavirus)

Question 8

How would the infection represented below present?

Answer 8

Persistent diarrhea in a young kid with no inflammation or fever

(Aggregation of bacteria = EAEC)

Question 9

How would the patient from whom this sample was collected present?

Answer 9

Fever, appendicitis-like abdominal pain, watery diarrhea followed by dysentery

(Gull-winged appearance = C. jejuni)

Question 10

This finding on a fecal smear is indicative of:

Answer 10

Shigella

(Lots of leukocytes due to propulsion from M cells into epithelial cells = shallow ulcers)

Question 11

This schematic represents which infection?

Answer 11

Typhoid fever

Question 12

Who is most likely to become ill due to this organism?

Answer 12

Immunocompromised patients

(Currant jelly = Klebsiella; opportunistic pathogen)

Question 13

What virulence factor causes this finding?

Answer 13

Shiga-like toxin (Stx) of EHEC

(Causes inhibition of protein synthesis, thus cell death, of enterocytes)

Question 14

The pathogenesis of which microbe is shown below?

Answer 14

ETEC

(LT - activates AC; ST - activates CFTR)

Question 15

A patient presents with high fever and confusion. His vitals are 102, 100/60, 50, 22. You notice the below finding on physical exam as well as splenomegaly. CBC reveals WBC 2.0 with PMNs 20%. Dx?

Answer 15

Typhoid fever

(Rose spots; neutropenia + splenomegaly + bradycardia = S. typhi)

Question 16

Which enteric organisms can cause the findings below?

Answer 16

Shigella, Salmonella, Yersinia, Campylobacter

(Reiter’s syndrome = polyarthritis in large joints, urethritis, conjunctivitis))

Question 17

This type of infection is particularly common in which susceptible group?

Answer 17

Sickle cell anemia kids

(Salmonella osteomyelitis)

Question 18

Which results are consistent with inflammatory diarrhea?

Answer 18

Lactoferrin and calprotectin + samples

(Both indicators of WBCs in stool)

Question 19

What other manifestation common to the causative agent of this finding may be present?

Answer 19

Conjunctivits

(Enanthema = vesicles on oral mucosa = coxsackie A; coxsackie and echoviruses can cause conjunctivitis)

Question 20

This is the most common cause of:

Answer 20

Hemorrhagic colitis

(Stx = shiga-like toxin = EHEC)

Question 21

Ddx?

Answer 21

Bacteroides fragilis (intra-abd abscess, PID, or pulmonary infection)

Prevotella melaninogencia (pulmonary or periodontal abscess)

Question 22

A patient presents with sudden onset of joint pain in both knees. His eyes are red and swollen, about which he says he must have picked up “pink eye” from his son. He also admits a couple week history of watery diarrhea, fever, and abdominal pain radiating to the back. CT reveals the below finding, indicated by the arrow. Diagnosis?

Answer 22

Yersinia enterocolitica with Reiter’s syndrome

(Mesenteric lymphadenitis shown in CT + appendicitis-like pain = Yersinia; arthritis + conjunctivitis + urethritis = Reiter’s syndrome, a complication of Salmonella, Shigella, Yersinia, and Campylobacter)

Question 23

This organism was cultured from a hospitalized patient with a UTI. Dx?

Answer 23

Serratia

(Brick-red colonies)

Question 24

What is denoted by the star?

Answer 24

Attachment-Effacement lesion of EHEC/EPEC

(LEE gene product causes rearrangement of actin to create pedestal that aids in EHEC/EPEC attachment)

Question 25

The results from the diagnostic method shown below would indicate treatment with:

Answer 25

Omeprazole, metronidazole, clarithromycin (Urea breath test = H. pylori)

Question 26

A person traveling to these areas may consider vaccination against:

Answer 26

Salmonella typhi

Question 27

Dx?

Answer 27

Vibrio (Gram - curved rods)

Question 28

What is unique about the bug represented below?

Answer 28

Unlike other E. coli, it's non-motile, doesn't ferment lactose, and doesn't decarboxylate lysine (Replicating in intestinal cells = EIEC)

Question 29

A patient presents with a 5 day history of diarrhea that has had some blood. She also reports LLQ cramping. You suspect a bacterial etiology and prescribe an antibiotic. She returns 10 days later with persistent diarrhea. How should you treat now?

Answer 29

Metronidazole for a parasite, like Giardia shown below (Diarrhea for \>2 weeks suggests parasite)

Question 30

The organism whose pathogenesis is depicted here produces what appearance on a KIA slant?

Answer 30

Red slant + yellow butt, no gas (**_Shigella_** = enter M cells, escapes phagocytic vesicle, extends into neighboring enterocytes)

Question 31

Which would be E. coli? What could be in tube B?

Answer 31

Tube E is E. coli (yellow butt + yellow slant b/c it's lac+) Pseudomonas (doesn't ferment carbs = red butt + red slant)

Question 32

What would you expect to see on culture of this finding?

Answer 32

Dark-colored colonies (Periodontal abscess = **_Prevotella melaninogencia_**)

Question 33

The microbe whose replication scheme is outlined below causes what kind of diarrhea?

Answer 33

Watery diarrhea (Processing in endo-lysosome --\> assembly in cytoplasmic viroplasm/inclusion body --\> release by cell lysis = **_rotavirus_**)

Question 34

Describe the pathogenesis of these lesion

Answer 34

C. diff toxin A is an enterotoxin and toxin B is cytotoxic and causes inflammation

Question 35

What this is?

Answer 35

Salmonella inside of a macrophage (Enters small intestine through M cells, then produces local infection in macrophages in lamina propria)

Question 36

What genus is represented on this MacConkey agar?

Answer 36

Enterobacteriaceae (Ferment lactose - pH indicator turns pink)

Question 37

A mother brings in her son complaining of the "rash" seen below and that he seems to be sleeping a lot more in the past few days. She mentions that he has had diarrhea for about 9 days but in the last 2 days has stopped urinating when he passes stool. She read online that diarrhea should self-resolve so has just been keeping him hydrated at home. You note that his sclera appear icteric. What labs/tests should you order?

Answer 37

Creatinine Blood smear Platelet count Sorbitol MacConkey agar (Petechia in image suggests thrombocytopenia; icterus + fatigue suggests hemolytic anemia; history of diarrhea + oliguria + other findings suggests **_HUS due to EHEC_**)

Question 38

This awesome drawing represents which pathogen?

Answer 38

S. typhi (All Salmonella have H + O antigens; S. typhi has Vi ag = capsular antigen; rest are not encapsulated)

Question 39

Which infectious disease would most likely be caused by the organism with this characteristic growth pattern?

Answer 39

UTI (**_Proteus_** = swarming)

Question 40

An otherwise healthy 7-year-old boy presents with stiff neck and fever. No bacteria are seen on gram stain of the CSF, and no capsule particles are seen on agglutination. CSF glucose is slightly low, and the white count is below 500 with mostly lymphocytes. Most likely causative agent?

Answer 40

Enterovirus (Lymphocytes + nothing on gam stain suggests viral origin; enteroviruses are the most common cause of aseptic meningitis in kids; also E coli and Citrobacter would show up as gram - rod on gram stain)