E. coli and Salmonella

Digestive System Purpose

Release food nutrients for absorption and use

GI Tract/Organs

Entry/exit portal for pathogens

GI-related Lymphoid Tissue

MALT/GALT/Peyer’s Patches/M-cells in small intestine

Gastritis

Stomach Inflammation

Enteritis

Intestinal Inflammation

Gastroenteritis

Stomach and intestinal inflammation

GI Barriers Limiting Pathogens

1. Protective mucus

2. Microbial Death/Inactivation by enzymes, acid, bile salt

3. MALT immune cells initiate inflammation and adaptive immune response

4. Microbiota

Roles of GI Microbiome

1. Protect against pathogens (take space, nutrients, excrete antimicrobial)

2. Structure and function

3. Vitamin Synthesis

Which group causes many GI Infections?

Enterobacteriacae

Fecal contamination of food or water

Environmental cause of GI Infections, availability of bacteria

General Symptoms of GI Food-borne Infections

1. Diarrhea

2. Dehydration

3. Dysentery

4. Hypovolemic Shock

Dysentery

Severe gastroenteritis; prolonged diarrhea with blood/mucus often leading to hypovolemic shock

Hypovolemic Shock

Life-threatening low blood volume leading to multi-organ failure and death

Transmission of Intestinal Pathogens

Fecal-oral route (usually ingestion)

8 F’s of Fecal-Oral Tranmission

Feces →

Fluids, Fields, Flies, Fingers, Fomites, Food →

Folks (new hosts)

Enterobacteriaceae

• Short, straight Gram-negative bacilli

• Grow on MacConkey

• Motile

Oxygen Requirements of Enterobacteriaceae

Facultative anaerobes

3 Surface Antigens of Enterobacteriaceae

O, K, H

Reservoir for Enterobacteriaceae

Human or animal intestinal tract (Enteric)

Which bacteria is opportunistic?

E. coli

Which bacteria is always pathogenic?

Salmonella enterica

E. coli Characteristics

• Motile

• Gram-negative bacilli

• Produce exotoxins if virulent

Is E. coli part of the normal microbiota?

Yes, E. coli is commonly found in our microbiota

Are E. coli usually pathogenic or non?

Most E. coli is nonpathogenic, instead being mutualistic (produces Vitamin K for us)

Which bacteria is the most important coliform?

E. coli; fecal contamination of water

Primary disease of E. coli

Gastroenteritis

Opportunistic disease of E. coli

UTIs, septicemia, pneumonia

E. Coli Pathotypes

• Intestinal Pathogenic (IPEC)

• Extraintestinal Pathogenic (ExPEC)

• Shiga-toxin Producing (STEC)

• Uropathogenic (UPEC)

Uropathogenic E. Coli

Most common cause of UTIs (more common in women)

What is the most common IPEC Disease?

Gastroenteritis is most common by E. coli

How is gastroenteritis transmitted?

Fecal-oral transmission to gastroenteritis

Mediator of E. coli Gastroenteritis

Enterotoxins that target intestines

Symptoms of E. coli gastroenteritis

Diarrhea, cramps, N/V, pediatric diarrhea

STEC/EHEC

Produces Shiga toxin, leads to cell death (enterohemorrhagic E. coli)

Diseases associated with STEC

Dysentery, kidney damage from severe diarrhea

What is STEC resistant to?

Stomach acids (not deactivated by low pH)

Risk factors for STEC

Contamination of meat, unpasteurized milk/juice/produce, petting zoos

Prototype Strain of STEC

O157:H7

Transmission of O157:H7

• Gut microbiota of healthy cattle

• Consuming contaminated food/beverage

• Person-person or animal-to-person

O Antigen

Lipopolysaccharide antigen

K Antigen

Capsular-forming antigen

H Antigen

Flagellar antigen

Symptoms of O157:H7

Pain, diarrhea, fever, bloody stool, cramping

Severe Cases of O157:H7

UTI, sepsis, hemorrhagic colitis, Hemolytic Uremic Syndrome

Treatment of O157:H7

Fluid replacement to avoid dehydration

Which treatments should NOT be used for O157:H7

• Antibiotics - increase Shiga Toxin Production → HUS

• Antidiarrheal - prolongs illness

Prevention of O157:H7

• Washing hands

• Avoiding raw beef, unpasteurized products

Salmonella enterica Characteristics

• Gram-negative Flagellated

• Acid-sensitive

• Facultative intracellular

How is salmonella mainly acquired?

Salmonella is from fecal-contaminated food or water

Two subspecies of Salmonella

1. Typhi causes Typhoid Fever

2. Enteritidis causes Gastroenteritis

S. Typhi Oxygen Requirement

Facultative anaerobe

Which organism does S. typhi infect?

Humans ONLY

Typhoid Fever

Invasive, life-threatening, systemic disease

S. typhi Virulence Factors

Adhesion, colonization, evasion, invasion, replication inside and outside cells

Is a high or low dose of S. typhi required for infection?

High dose, because it has a low acid tolerance

Colonization of S. typhi

Begins at small intestine mucosa → Breach epithelium to spread systemically

Does breach of epithelium by S. typhi cause inflammation?

No, S. typhi doesn’t cause inflammation after breach

S. typhi Host Organs

Spleen, liver, gallbladder (as biofilms)

S. typhi Symptoms

High fever from toxin, diarrhea, rash, fatigue, delirium

Sever S. typhi Symptoms

Hypovolemic shock, perforations, endotoxic shock, myocarditis, meningitis

S. typhi Chronic Carriers

Gallbladder biofilms shed bacteria causing chronic infection

Which organ is the reservoir for S. typhi biofilms?

Gallbladder

Diagnosis of S. typhi

NAATs for H, K, O antigens

Treatment of S. typhi

Antibiotics in early stages, but leads to resistance

Prevention of S. typhi

1. Healthy gut microbiota

2. Treated water

3. Vaccination

Salmonellosis

Disease of the intestines, usually from food poisoining

Which subspecies of Salmonella causes food poisoning?

Enteriditis

What is salmonella food poisoning spread from?

Birds and reptiles (zoonotic)

Is Salmonella enteriditis invasive?

No, it is not invasive and is self-limiting

Common source of salmonella food poisoning

Poultry, fecal contamination of produce, eggs, meat, seafood

Symptoms of S. Enteritidis

Fever, cramping, nausea, diarrhea, dysentery is progressed

Treatment of S. Enteritidis

Fluids/electrolytes, diet, antibiotics, Immodium (only is O157:H7 is ruled out)

Preventing S. Enteritidis

• Washing hands/surface in contact with raw meat

• Treated water

• Pasteurization

• Refrigeration