[BIO 120.3] Q2: Gram Negative Rods - Enterics: Introduction and E. coli

Part of normal gut microflora or may cause GI infections

The enterics are very common in the sense that ____

FALSE

T/F: Since Enterics are normal gut microflora, they cannot cause GI infections

TRUE

T/F: Enterics are both part of the normal gut microflora but may also cause GI infections

TRUE

T/F: In the case of Enterics, sometimes there are no systemic infections (fever, headaches, lethargy, malaise)

FALSE

T/F: In the case of Enterics, systemic infections (fever, headaches, lethargy, malaise) are always involved.

Enterobacteriaceae, Vibrionaceae, Bacteroidaceae, Pseudomonadaceae

What are the 4 bacterial groups discussed under Enterics?

They are part of normal flora and affect immunocompromised

Why are enterics very hard to eradicate and are problematic at hospitals?

Gram - rods

Morphology: The Enterics

Some motile with peritrichous flagella, some nonmotile

What are the 2 possible morphologies (motilities) of the Enterics?

Fecal-Oral

Transmission of the Enterics is usually via what mode?

Fecal-Oral, Migration up the urethra, Colonization of catheters in hospitalized patients

What are the 3 modes of transmission for Enterics?

Salmonella, Shigella, Pseudomonas

What are the only 3 groups of Enterics that are negative for lactose fermentation?

E. coli and others

What are the groups of Enterics that are positive for lactose fermentation

Gas and Acid

What is produced in lactose fermentation?

Black color change

What is an indication of hydrogen sulfide production?

Indole, Methyl Red, Voges-Proskauer, Citrate

What does IMViC stand for?

Triple Sugar Iron Agar

What does TSIA stand for?

glucose, lactose, sucrose

Three Sugars of TSI?

Coliforms

The MPN test is usually used for the detection of?

K = alkaline = red; A = acid = yellow

What are two interpretations for TSIA? Formula [K/A] = [pH] = [color change]

Break in media

In TSIA, what is used as an indicator of gas production

Slant/Butt

How is the TSI slant read?

O antigen, K antigen, H antigen

What are the three antigens that are used as basis for antigenic classification of the Enterics?

Outer membrane, 160+ subtypes

Where is the O antigen found and how many subtypes are present?

Capsule, 100 subtypes

Where is the K antigen found and how many subtypes are present?

Flagella, 50 subtypes

Where is the H antigen found and how many subtypes are present?

E. coli O157:H7

What is an example of an E. coli strain that has an outer membrane and a flagella?

No cell invasion, Invasion of intestinal epithelial cells, Invasion of lymph nodes and blood stream

What are the 3 degrees of intestinal invasion by the Enterics?

No cell invasion

Degree of intestinal invasion: Bacteria binds only to the cell

No cell invasion

Degree of intestinal invasion: Exotoxins (enterotoxins) cause diarrhea

No cell invasion

Degree of intestinal invasion: Causes watery diarrhea

ETEC, V. cholerae

What are 2 examples of bacteria that cause no cell invasion type of intestinal invasion?

Invasion of intestinal epithelial cells

Degree of intestinal invasion: Bacteria binds and invades the mucosa

Invasion of intestinal epithelial cells

Degree of intestinal invasion: Cell death occurs

Invasion of intestinal epithelial cells

Degree of intestinal invasion: Systemic immune response occurs

EIEC, Shigella, Salmonella enteritidis

What are 3 examples of bacteria that causes an invasion of intestinal epithelial cells type of degree of intestinal invasion?

Invasion of intestinal epithelial cells

Degree of intestinal invasion: Blood and pus in stool, WBCs may be present as well

Invasion of lymph nodes and bloodstream

Degree of intestinal invasion: Fever and headache are present

Invasion of lymph nodes and bloodstream

Degree of intestinal invasion: WBC count is elevated

Bacteremia, Sepsis

In the invasion of lymph nodes and bloodstream type of intestinal invasion, what are 2 conditions that we might likely see?

Salmonella typhi, Yersinia enterocolitica, Campylobacter jejuni

What are 3 examples of bacteria that may cause invasion of lymph nodes and bloodstream as a type of degree of intestinal invasion?

63 genera

How many genera are there under Family Enterobacterioceae?

20-25 species

How many species under Family Enterobacterioceae are clinically significant?

Pilus, Exotoxin: LT and ST + Shiga-Like, Endotoxin (Lipid A), Iron binding siderophores

What are the 4 virulence factors of E. coli?

Epithelial cell invasion (colonization)

What is the function of the pilus?

TRUE

T/F: The pilus of the E. coli is meant only for invasion or colonization

FALSE

T/F: The pilus of the E. coli is meant for both colonization and host penetration

Heat labile (LT), Heat stable (ST), Shiga-like toxin

What are the exotoxins produced by E. coli?

Diarrhea, UTI, Neonatal meningitis, Sepsis

What are the 4 clinical findings for E. coli? DUNS

A. E. coli

Family Enterobacteriaceae: Circular, convex, and smooth colonies, some may be hemolytic

A. E. coli
B. Enterobacter
C. Klebsiella
D. Salmonella and Shigella

B. Enterobacter

Family Enterobacteriaceae: Mucoid colonies

A. E. coli
B. Enterobacter
C. Klebsiella
D. Salmonella and Shigella

C. Klebsiella

Family Enterobacteriaceae: Large and mucoid colonies

A. E. coli
B. Enterobacter
C. Klebsiella
D. Salmonella and Shigella

D. Salmonella and Shigella

Family Enterobacteriaceae: Colonies like E. coli but do not ferment lactose

A. E. coli
B. Enterobacter
C. Klebsiella
D. Salmonella and Shigella

Women, Patients hooked in catheters

UTI caused by E. coli is mostly common in what groups of people?

Pilus, Fimbriae (travels up to urethra), Hemolysin

What are the virulence factors involved in E. coli UTI?

Urethral lining -> Bladder (Cystitis) -> Kidneys (Pyelonephritis)

Describe the journey of E. coli as it causes UTI

Cystitis, Pyelonephritis

What are the clinical findings for UTI caused by E. coli?

Cystitis

Inflammation of the bladder

Pyelonephritis

Inflammation of the kidney

Dysuria

Symptom wherein a patient feels a burning sensation whenever they pee

Dysuria, Hematuria, Pyuria, Frequent urination

What are the 4 symptoms of UTI caused by E. coli?

Hematuria

Clinical sign wherein RBCs are present in the urine

Pyuria

Clinical sign wherein WBCs are present in the urine

TRUE

T/F: E. coli is the most common cause of UTI

FALSE

T/F: Proteus mirabilis is the most common cause of UTI

>10^6 cells (more than 100,000 cells or high threshold)

How many cells are required to diagnose UTI caused by E. coli?

Sepsis

What is a disease that is usually secondary to UTI caused by E. coli?

Endotoxins of Lipid A

What is the virulence factor for sepsis caused by E. coli?

TRUE

T/F: In addition to UTI, E. coli is also the most common cause of gram (-) sepsis

Immunocompromised, neonates

What are 2 groups of people that are susceptible to sepsis caused by E. coli?

Capsule

What is the virulence factor associated with neonatal meningitis caused by E. coli?

Irritability, Lethargy, Vomiting, Seizures, Lack of appetite

What are 5 symptoms of neonatal meningitis caused by E. coli?

E. coli K1

What strain of E. coli is the cause of majority of neonatal meningitis?

Enterpathogenic E. coli

What does EPEC mean?

Enterotoxigenic E. coli

What does ETEC mean?

Enterhemorrhagic E. coli

What does EHEC mean?

Enteroinvasive E. coli

What does EIEC mean?

Enteroaggregative E. coli

What does EAEC mean?

EPEC, ETEC, EHEC, EIEC, EAEC

What are the 5 strains of E. coli that can cause diarrhea?

EPEC, ETEC

What are 2 strains of E. coli that produce watery diarrhea (rice water stool)

Pilus - EPEC Adherence Factor (EAF)

What is the virulence factor of EPEC-caused diarrhea?

Watery Diarrhea, Vomiting, Fever (in infants)

What are 3 clinical findings for EPEC-caused diarrhea?

Pilus of EPEC attaches to intestinal epithelial cells, microvilli of intestines gets effaced

What is the mechanism for EPEC-caused diarrhea?

EPEC

EPEC or ETEC: Diarrhea in infants

ETEC

EPEC or ETEC: Diarrhea in children < 5 years

ETEC

EPEC or ETEC: Traveler's Diarrhea

Pilus (CFA), LT and/or ST

What are the two virulence factors for ETEC-caused diarrhea?

ETEC

EPEC or ETEC: Diarrhea lasts for several days

Antibiotics

Treatment for EPEC

Shorten duration of disease

What is the function of antibiotics in treating ETEC-caused diarrhea?

AB toxin

The LT (heat labile) virulence factor in ETEC is what kind of exotoxin?

B subunit binds to intestine -> A subunit enters -> continuous secretion of cAMP -> overproduction of fluids -> fluids cannot be reabsorbed by intestinal lumen hence a buildup -> watery diarrhea

Explain the mechanism of the LT exotoxin (AB toxin) of the ETEC: from B subunit to watery diarrhea production

Montezuma's revenge

Alternative name for Traveler's Diarrhea

20 L/day

How many fluids are lost due to ETEC diarrhea per day?

Pilus (like ETEC), Capsule, Shiga-like toxins (verotoxins)

What are 3 virulence factors of EHEC?

FALSE

T/F: ETEC is distinct in that it does not cause any fever when infecting a host.

TRUE

T/F: EHEC is distinct in that it does not cause any fever when infecting a host.

No fever, Hemorrhagic colitis, Hemolytic uremic syndrome (HUS)

What are 3 clinical manifestations of EHEC infection?

Kidneys

What organ does Hemolytic Uremic Syndrome by EHEC affect?

Anemia, Thrombocytopenia (reduction in platelet count)

Hemolytic Uremic Syndrome is associated with these 2 conditions