Gram-Negative Rods Related to the Enteric Tract

Question 1

TALK ABOUT THE E COLI

Answer 1

E. coli is a Gram-negative, facultative anaerobe, rod-shaped, coliform
bacterium of the genus Escherichia that is commonly found in
the lower intestine of warm-blooded organisms

• Strains with flagella are motile
It also attaches To the microvilli of the intestines via intimin

E. coli is a chemoheterotroph and uses a source of carbon and energy

Question 2

what are the diseases that are caused by E.coli

Answer 2

• Escherichia coli is the most common cause of urinary tract infection and gram-negative rod sepsis.

It is one of the two important causes of neonatal meningitis and is the bacterium most frequently associated with “traveler’s diarrhea,” a
watery diarrhea.

Question 3

how can we distinguish E coli from the two major intestinal pathogens, Shigella and Salmonella

Answer 3

Escherichia coli ferments lactose

Question 4

Cultural characteristics of Escherichia coli - grows on many commonly used cultivation media. name them ?

Answer 4

MacConkey agar (MCA), 
Trypticase soy agar 
Brain heart infusion agar  
Endo agar 

E. coli strains are typically lactose positive

Question 5

how does E coli transmit ( the one that cause disease )

Answer 5

The types of E. coli that can cause diarrhea can be transmitted through contaminated water or food, or through contact with animals or persons.

Question 6

THERE ARE • Six pathotypes are associated with diarrhea and collectively are referred to as
diarrhoeagenic E. coli mention them

Answer 6

1. Shiga toxin-producing E. coli (STEC)—STEC may also be referred to as
   Verocytotoxin-producing E. coli (VTEC) or enterohemorrhagic E. coli (EHEC). (associated with foodborne outbreaks).
2. Enterotoxigenic E. coli (ETEC)
3. Enteropathogenic E. coli (EPEC)
4. Enteroaggregative E. coli (EAEC)
5. Enteroinvasive E. coli (EIEC)
6. Diffusely adherent E. coli (DAEC

Question 7

what are the diseases by each toxin of ecoli

Shiga - Uropathogenic - • Enterotoxigenic

Answer 7

Bloody diarrhea that is a symptom of a Shiga toxin

Uropathogenic E. coli (UPEC) is one of the main causes of urinary tract
infections.

Enterotoxigenic E. coli (ETEC) is the most common cause of traveler’s
diarrhea,

Question 8

what are the virulence factors of E coli

Answer 8

Escherichia coli has several virulence factors that contribute to its ability to
cause disease: pili, a capsule, endotoxin, and three exotoxins
(enterotoxins), two that causes watery diarrhea and one that causes bloody
diarrhea and hemolytic-uremic syndrome

Question 9

how there is infection by the E coli to the intestinal tract

Answer 9

The first step is the adherence of the organism to the cells of the jejunum and
ileum by pili. THEN the bacteria synthesize enterotoxins CAUSING diarrhea

Question 10

Enterotoxigenic strains of E. coli (ETEC) can produce either or both of two
enterotoxins mention them

Answer 10

1 - ) The heat-labile toxin (LT) acts by stimulating adenylate cyclase

2- ) The other enterotoxin is a low-molecular-weight, heat-stable toxin (ST), which
stimulates guanylate cyclase

Question 11

what are The Enterohemorrhagic strains of E. coli ( cause bloody diarrhea )

Answer 11

O157:H7 serotype - Shiga toxin-producing E Coli that produce Shiga toxin

• Shiga toxin acts by removing an adenine from the large (28S) ribosomal
  RNA, and stopping protein synthesis

Question 12

what are The Enterohemorrhagic strains of E. coli ( cause bloody diarrhea )

Answer 12

O157:H7 serotype - Shiga toxin-producing E Coli that produces Shiga toxin

• Shiga toxin acts by removing an adenine from the large (28S) ribosomal
  RNA, and stopping protein synthesis

Question 13

talk about Hemolytic-Uremic Syndrome

Answer 13

(HUS), which occurs when Shiga toxin enters the bloodstream

consists of hemolytic anemia, thrombocytopenia, and acute
renal failure.

Question 14

what cause urinary tract infection ?

Answer 14

O serotypes of E. coli (strains with O antigen) preferentially cause urinary tract
infections. These uropathic strains are characterized by pili with adhesin proteins
that bind to specific receptors on the urinary tract epithelium

Question 15

state the clinical findings for e coli within the intestinal tract and outside of the intestinal tract

Answer 15

Diarrhea caused by enterotoxigenic E. coli (ETEC) is usually watery,
Infection with enterohemorrhagic E. coli (EHEC) characterized by bloody diarrhea
———————————————————————————–
(outside of the intestinal tract )
Escherichia coli is the leading cause of community-acquired urinary tract
infections
Escherichia coli is also a major cause, of meningitis and sepsis in neonates
Escherichia coli causes hospital-acquired sepsis

Question 16

laboratory diagnosis of Ecoli

Answer 16

Some of the important features that help distinguish E. coli from other
lactose-fermenting gram-negative rods are as follows:
• (1) it produces indole from tryptophan,
• (2) it decarboxylates lysine,
• (3) it uses acetate as its only source of carbon,
• (4) it is motile

Question 17

what are the treatment and preventions of E coli

Answer 17

urinary tract infection (cystitis) can be treated using oral trimethoprim-sulfamethoxazole or nitrofurantoin.

sepsis requires treatment with parenteral antibiotics

For the treatment of neonatal meningitis, a combination of
ampicillin and cefotaxime are usually given.
—————————————————————
There is no specific prevention for E. coli infections, such as active or
passive immunization
Ingestion of uncooked foods and contaminated water should be avoided
while traveling in certain countries.

Question 18

TALK ABOUT SALMONELLA

Answer 18

IT is a genus of rod-shaped Gram-negative bacteria

The two species of Salmonella are Salmonella enterica and Salmonella
bongori.

Salmonella species are non-spore-forming, motile enterobacteria

They are chemotrophs, They are also facultative
anaerobes,

Question 19

Important Properties for Salmonellae

Answer 19

Salmonellae are gram-negative rods that do not ferment lactose but produce hydrogen sulfide (H2S)—main features that are used in their laboratory identification

Salmonella antigens are—cell wall O, flagellar H, and capsular Vi (virulence)—are
important for taxonomic and epidemiologic purposes.

Question 20

Detection, culture of salmonella

Answer 20

Salmonella produce hydrogen sulfide which can readily be detected
by growing them on media containing ferrous sulfate, such as is used in the triple sugar iron test

To
protect against Salmonella infection, heating food to 75 °C (167 °F) is recommended.

Question 21

where can Salmonella species be found

Answer 21

Salmonella species can be found in the digestive tracts of humans and animals, especially reptiles. Salmonella on the skin of reptiles or amphibians can be passed to people who
handle the animals. Food and water can also be contaminated with the bacteria if they come in contact with the feces of infected people or animals.

Question 22

Clinically, the Salmonella species are divided into two main serotypes: mention them

Answer 22

• 1. Typhoidal species (invasive - those that cause typhoid fever)

• 2. Nontyphoidal species (noninvasive - those that cause diarrhea [enterocolitis] and metastatic
infections, such as osteomyelitis).

Question 23

compare between the. Typhoidal species and The nontyphoidal (noninvasive) of salmonella

Answer 23

The typhoidal (invasive) species are S. typhi and S. paratyphi.
salmonellae pass through the
lymphatic system of the intestine into the blood of the patients (typhoid form) and are carried to various organs (liver, spleen, kidneys) to form
secondary foci (septic form).
————————————————————————
Nontyphoidal serotypes of Salmonella cause food poisoning(GI infection) the species are diff. stereotypes of S enterica but Most cases of invasive nontyphoidal Salmonella infection (iNTS) are caused
by Salmonella enterica Typhimurium or Salmonella enterica Enteritidis

Question 24

Molecular mechanisms of infection for typhoidal and non typhoidal

Answer 24

Nontyphoidal serotypes enter M cells on the intestinal wall by bacterial-mediated endocytosis, a process associated with intestinal inflammation and diarrhea.

for typhoidal
Salmonellae are also able to pass the intestinal barrier via phagocytosis and trafficking by CD18-positive immune cells, which may be a mechanism key to
typhoidal Salmonella infection also Salmonella cells are able to enter macrophages via macropinocytosis.

also, typhoidal Salmonella use two type III secretion systems (T3SS) to invade
the host cell. T3SS is the mechanism of delivery of bacteria inside the host
cell.
• The T3SS-1 enables the injection of bacterial effector proteins within
the host cytosol.

Question 24

Molecular mechanisms of infection for typhoidal and non typhoidal

Answer 24

Nontyphoidal serotypes enter M cells on the intestinal wall by bacterial- mediated endocytosis, a process associated with intestinal inflammation and diarrhea. Salmonellae are also able to pass the intestinal barrier via phagocytosis and trafficking by CD18-positive immune cells, which may be a mechanism key to typhoidal Salmonella infection

Question 25

what are the four mechanisms of infection for salmonella

Answer 25

``` mechanisms of infection • enters M cells • enters via phagocytosis • enters via macropinocytosis • type III secretion systems (T3SS) ```

Question 26

Laboratory Diagnosis for salmonella

Answer 26

Culturing is a gold standard for identification/isolation of salmonella species • Salmonella forms black colonies on SS agar due to H2S production • Salmonellae form non–lactose-fermenting (colorless) colonies on MacConkey’s or EMB agar. • On TSI agar, an alkaline slant and an acid butt, frequently are produced both gas and H2S (black color in the butt),

Question 27

treatment and prevention for salmonella

Answer 27

• Plasmid-mediated antibiotic resistance is common, and antibiotic sensitivity tests should be done Salmonella infections are prevented mainly by public health and personal hygiene measures. Proper sewage treatment, a chlorinated water supply that is monitored for contamination by coliform bacteria, cultures of stool samples from food handlers to detect carriers, hand washing prior to food handling, pasteurization of milk, and proper cooking of poultry, eggs, and meat are all important.

Question 28

vaccines for salmonella

Answer 28

Two vaccines are available, but their protection limited is 50–80% against S. typhi. One contains the Vi capsular polysaccharide of S. typhi (given intramuscularly), and second is a live, attenuated strain (Ty21a) of S. typhi (given orally).

Question 29

PATHOGENS BOTH WITHIN & OUTSIDE THE ENTERIC TRACT MENTION

Answer 29

* Genus - Escherichia | * Genus - Salmonella

Question 30

PATHOGENS PRIMARILY WITHIN THE ENTERIC TRACT MENTION

Answer 30

* Genus - Shigella * Genus - Vibrio * Genus - Campylobacter * Genus - Helicobacter

Question 31

TALK ABOUT SHIGELLA

Answer 31

Shigellae are non–lactose-fermenting, gram-negative rods that can be distinguished from salmonellae by three criteria: they produce no gas from the fermentation of glucose, they do not produce H2S, and they are nonmotile

Question 32

All shigellae have O antigens (polysaccharide) in their cell walls, and these antigens are used to DIVIDE TO ?

Answer 32

these antigens are used to divide the genus into four groups: A, B, C, and D. • Shigella species are classified by three serogroups and one serotype: • Serogroup A: S. dysenteriae (15 serotypes) • Serogroup B: S. flexneri (9 serotypes) • Serogroup C: S. boydii (19 serotypes) • Serogroup D: S. sonnei (one serotype

Question 33

what are the Three Shigella groups that are the major disease-causing species:

Answer 33

S. dysenteriae is usually the cause of epidemics of dysentery, particularly in confined populations such as refugee camps cause bloody diahrea S. flexneri is the most frequently isolated species worldwide, and accounts for 60% of cases in the developing world; • S. sonnei causes 77% of cases in the developed world.

Question 34

what is the mechanisms of infection for Shigella

Answer 34

• Shigella cause disease by invading and replicating in cells lining the colon. • Structural gene proteins mediate the adherence of the organisms to the cells, as well as their invasion, intracellular replication, and cell-to-cell spread They don't attach to mucosal cells; they first attach to and invade the M cells located in Peyer patches.

Question 35

Pathogenesis of shigella

Answer 35

They have a very low ID50 - Ingestion of as few as 100 organisms causes disease it's a human-only disease the organism is transmitted by the fecal-oral route. The four — fingers, flies, food, and feces—are the principal factors in transmission. Shigellae cause disease in the gastrointestinal tract. They produce bloody diarrhea (dysentery) by invading the cells of the mucosa of the distal ileum and colon.

Question 36

Laboratory Diagnosis of Shigellae

Answer 36

• Shigellae form non–lactose-fermenting (colorless) colonies on MacConkey’s or EMB agar. • On TSI agar, they cause an alkaline slant (red) and an acid butt (yellow), with no gas and no H2S (black color).

Question 37

treatment and prevention of shigella

Answer 37

Treatment • The main treatment for shigellosis is fluid and electrolyte replacement. • In severe cases, a fluoroquinolone, Trimethoprim-sulfamethoxazole is an alternative choice. • Antiperistaltic drugs are contraindicated in shigellosis, because they prolong the fever, diarrhea, and excretion of the organism. Prevention by proper sewage disposal, chlorination of water, and personal hygiene (handwashing by food handlers). • There is no vaccine, and prophylactic antibiotics are not recommended.

Question 38

TALK ABOUT Genus VIBRIO

Answer 38

Vibrio is a genus of Gram-negative, curved, comma-shaped rods. • Typically found in salt water; Vibrio species are facultative anaerobes, oxidase-positive and do not form spores. • Several species of vibrio can cause foodborne infection, usually associated by eating undercooked seafood. • Main pathogenic species are - Vibrio cholerae, Vibrio parahaemolyticus, Vibrio vulnificus

Question 38

TALK ABOUT Genus VIBRIO

Answer 38

Vibrio is a genus of Gram-negative, curved, comma-shaped rods. • Typically found in salt water; Vibrio species are facultative anaerobes, oxidase-positive and do not form spores. • Several species of vibrio can cause foodborne infection, usually associated by eating undercooked seafood. • Main pathogenic species are - Vibrio cholerae, Vibrio parahaemolyticus, Vibrio vulnificus V. cholerae bacterium has a flagellum at one pole and several pili throughout its cell surface

Question 39

what are the diseases OF VIBRO

Answer 39

• Vibrio cholera, is the cause of cholera • Vibrio parahaemolyticus causes diarrhea associated with eating raw or improperly cooked seafood. • Vibrio vulnificus causes cellulitis and sepsis.

Question 40

Important Properties of V. cholerae

Answer 40

is divided into serogroups based on the nature of its O cell wall antigen The O1 organisms have two biotypes, called classic and ElTor, and three serotypes, called Ogawa, Inaba, and Hikojima • Only the O1 and O139 organisms cause cholera because only they produce cholera toxin.

Question 41

what are the Vibrio cholera - Pathogenesis & Epidemiology

Answer 41

Vibrio cholerae is transmitted by fecal contamination of water and food, primarily from human sources • The pathogenesis of cholera is dependent on colonization of the small intestine by the organism and secretion of enterotoxin After adhering, the organism multiplies and secretes an enterotoxin called choleragen (cholera toxin). This exotoxin can reproduce the symptoms of cholera

Question 42

what are the Vibrio cholera clinical findings

Answer 42

Watery diarrhea in large volumes Rice-water stool The loss of fluid and electrolytes leads to cardiac and renal failure. There are no red blood cells or white blood cells in the stool

Question 43

what are the Laboratory diagnoses for vibrio cholera

Answer 43

V. cholera will show colorless colonies on MacConkey’s agar because lactose is fermented slowly. Thiosulfate-Citrate-Bile Salts-Sucrose (TCBS) Agar • TCBS Agar is Selective and differentiate culture media used for the selective isolation of cholera vibrios and Vibrio parahaemolyticus from a variety of clinical and nonclinical specimens. • V.cholera forms yellow colonies; V. parahaemolyticus forms green colonies

Question 44

treatment and prevention of vibrio cholera

Answer 44

replacement of water and electrolytes, either orally or intravenously. Glucose is added to the solution to enhance the uptake of water and electrolytes --------------------------------------------------------------------- An oral, live attenuated vaccine called Vaxchora is available in the United States for travelers to areas where cholera caused by serogroup O1 is endemic. Other oral vaccines containing killed organisms are available in countries where cholera epidemics occur use of tetracycline

Question 45

talk about Vibrio parahaemolyticus and V. vulnificus in general

Answer 45

they are marine organisms; they live primarily in the ocean, especially in warm salt water. They are halophilic (i.e., they require a high NaCl concentration to grow)

Question 46

transmission and prevention of Vibrio parahaemolyticus

Answer 46

Vibrio parahaemolyticus is a marine organism transmitted by ingestion of raw or undercooked seafood, especially shellfish such as oysters. it has an enterotoxin similar to cholera toxin Disease can be prevented by proper refrigeration and cooking of seafood

Question 47

how can you differentiate between Vibrio parahaemolyticus and V. cholerae

Answer 47

Vibrio parahaemolyticus is distinguished from V. cholerae mainly on the basis of growth in NaCl: V.parahaemolyticus grows in 8% NaCl solution, whereas V. cholerae does not.

Question 48

transmission and prevention of Vibrio vulnificus

Answer 48

Vibrio vulnificus is also a marine organism (i.e., it is found in warm salt waters * It causes severe skin and soft tissue infections (cellulitis) * The recommended treatment is doxycycline

Question 49

TALK ABOUT GENUS CAMPYLOBACTER

Answer 49

is a genus of Gram-negative bacteria, they are microaerophilic and motile • Some Campylobacter species can infect humans, sometimes causing campylobacteriosis, a diarrhoeal disease in humans Diseases • Campylobacter jejuni is a frequent cause of enterocolitis

Question 50

what is the Pathogenesis & Epidemiology of CAMPYLOBACTER

Answer 50

Domestic animals such as cattle, chickens, and dogs serve as a source of the organisms for humans. Transmission is usually fecal–oral. Food and water contaminated with animal feces are the major sources of human infection.

Question 51

symptoms of enterocolitis

Answer 51

Enterocolitis, caused primarily by C. jejuni, begins as watery, foul-smelling diarrhea followed by bloody stools accompanied by fever and severe abdominal pain.

Question 52

Laboratory Diagnosis for CAMPYLOBACTER

Answer 52

If the patient has diarrhea, a stool specimen is cultured on a blood agar plate containing antibiotics that inhibit most other fecal flora. Unlike Shigella and Salmonella, lactose fermentation is not used as a distinguishing feature

Question 53

treatment and prevention for CAMPYLOBACTER

Answer 53

Treatment Erythromycin Prevention • There is no vaccine or other specific preventive measure. • Proper sewage disposal and personal hygiene (handwashing) are important

Question 54

TALK ABOUT Genus - HELICOBACTER

Answer 54

it is a gram negative rode , microaerophilic and motile for the diseases it cause peptic ulcers and gastritis they are urease positive

Question 55

How can we differentiate Helicobacter and campylobacter ?

Answer 55

helicobacters are strongly urease-positive, whereas | campylobacters are urease-negative

Question 56

Pathogenesis & Epidemiology OF • Helicobacter

Answer 56

Helicobacter pylori attaches to the mucus-secreting cells of the gastric mucosa. The production of large amounts of ammonia from urea by the organism’s urease, coupled with an inflammatory response, leads to damage to the mucosa

Question 57

Clinical Findings | • Gastritis and peptic ulcer

Answer 57

are characterized by recurrent pain in the upper abdomen, frequently accompanied by bleeding into the gastrointestinal tract. No bacteremia or disseminated disease occurs

Question 58

Treatment & Prevention of helicobacter

Answer 58

amoxicillin and metronidazole Tetracycline can be used instead of amoxicillin. • There is no vaccine or other specific preventive measure