1-29 Enteric Bacteria

Question 1

What are some examples of Enterobacteriaceae?

Answer 1

• Salmonella
• Yersinia
• E. coli
• Shigella
• Campylobacter
• Helicobacter
• Klebsiella
• Enterobacter
• Serratia
• Proteus
• Providencia
• Morganella

Question 2

What traits define Enterobacteriaceae?

Answer 2

• Gram(-)
• Non-sporulating
• Straight rods
• Facultative aerobes
• Catalase (+), Oxidase (-)
• Glucose fermenters

Question 3

How promiscuous are Enterobacteriaceae?

Answer 3

Very.

They often incorporate foreign DNA, which can lead to antibiotic resistance.

Question 4

What is antimicrobial sensitivity testing?

Answer 4

• Antibiotic resistance testing must be performed for any Enterobacteriaceae infection that requires treatment
• Solid-state method: Spread liquid culture of the patient isolate on large agar plates (NOT streaked for pure colonies); soak disks of filter paper in various antibiotics and place them on the plate prior to overnight incubation. Successful plating produces a solid lawn of bacteria interrupted by zones of clearing around the effective antibiotics; measurements of the clear zones can be compared to a table to determine the most effective antibiotic.

Question 5

What are the gut virulence factors for foodborne Enterobacteriaceae?

Answer 5

• Pili: adhesion
• Type 3 secretion system: adhesion, subversion of gut macrophage

These virulence factors are acquired.

Question 6

What do foodborne Enterobacteriaceae cause, and how do they do it?

Answer 6

Foodborne Enterobacteriaceae cause gastroenteritis.

• Enterobacteriaceae in the gut often allow/encourage themselves to be sampled by M cells in the Peyer’s patches, then alter the local macrophages for bacterial survival and spread to the exterior surface of the gut (T3SS).
• Some can further use macrophages as Trojan Horses for passage into the lymph nodes locally (Y. enterocolicita, false appendicitis) or system-wide (S. typhi, typhoid fever).

Question 7

What is hemolytic-uremic syndrome?

Answer 7

HUS is a complication caused by release of shiga toxin into the bloodstream.

• Infection by Shigella OR infection when enterohemorrhagic strain of E. coli breaches gut
• Hemolysis, thrombocytopenia, uremia, 5-10% mortality
• Sphistocytes visible in blood smear
• Predominantly pediatric

Question 8

What is reactive arthritis?

Answer 8

A complication that may develop in patients positive for Human Leukocyte Antigen (HLA)-B27.

• Following infection by Shigella, Salmonella, Yersinia, Campylobacter, or Chlamydia
• Conjunctivitis, urethritis, arthritis
• Can also involve mouth, fingers, soles of feet
• Can be treated with non-steroidal anti-inflammatories (usu. resolves in 2-5mos)

Question 9

What are some non-foodborne opportunistic Enterobacteriaceae pathogens, and why are they so difficult to treat?

Answer 9

• Klebsiella, Enterobacter, Serratia, Proteus, Providencia, and Morganella (aka “ICU Bugs”)
• Major opportunistic nosocomial pathogens; seldom cause symptoms in previously-healthy people
• Very difficult to treat once they have been introduced by catheter infection, wound infection, or general debilitation due to the combination of debilitated patient and antibiotic resistance

Question 10

What are the best ways to prevent infection by foodborne Enterobacteriaceae?

Answer 10

Hygiene!

• Wash food fully
• Cook food fully
• Wash hands
• Treat water

Question 11

What are the best ways to prevent infection by opportunistic Enterobacteriaceae?

Answer 11

• Switch IV lines and catheters
• ICU and patient scrubdowns
• Minimization of hospital stays