Gram-Negative Rods Related to the Enteric Tract Flashcards
TALK ABOUT THE E COLI
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
what are the diseases that are caused by E.coli
• 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.
how can we distinguish E coli from the two major intestinal pathogens, Shigella and Salmonella
Escherichia coli ferments lactose
Cultural characteristics of Escherichia coli - grows on many commonly used cultivation media. name them ?
MacConkey agar (MCA), Trypticase soy agar Brain heart infusion agar Endo agar
E. coli strains are typically lactose positive
how does E coli transmit ( the one that cause disease )
The types of E. coli that can cause diarrhea can be transmitted through contaminated water or food, or through contact with animals or persons.
THERE ARE • Six pathotypes are associated with diarrhea and collectively are referred to as
diarrhoeagenic E. coli mention them
- 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). - Enterotoxigenic E. coli (ETEC)
- Enteropathogenic E. coli (EPEC)
- Enteroaggregative E. coli (EAEC)
- Enteroinvasive E. coli (EIEC)
- Diffusely adherent E. coli (DAEC
what are the diseases by each toxin of ecoli
Shiga - Uropathogenic - • Enterotoxigenic
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,
what are the virulence factors of E coli
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
how there is infection by the E coli to the intestinal tract
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
Enterotoxigenic strains of E. coli (ETEC) can produce either or both of two
enterotoxins mention them
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
what are The Enterohemorrhagic strains of E. coli ( cause bloody diarrhea )
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
what are The Enterohemorrhagic strains of E. coli ( cause bloody diarrhea )
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
talk about Hemolytic-Uremic Syndrome
(HUS), which occurs when Shiga toxin enters the bloodstream
consists of hemolytic anemia, thrombocytopenia, and acute
renal failure.
what cause urinary tract infection ?
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
state the clinical findings for e coli within the intestinal tract and outside of the intestinal tract
Diarrhea caused by enterotoxigenic E. coli (ETEC) is usually watery,
Infection with enterohemorrhagic E. coli (EHEC) characterized by bloody diarrhea
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(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
laboratory diagnosis of Ecoli
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
what are the treatment and preventions of E coli
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.
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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.
TALK ABOUT SALMONELLA
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,
Important Properties for Salmonellae
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.
Detection, culture of salmonella
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.
where can Salmonella species be found
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.
Clinically, the Salmonella species are divided into two main serotypes: mention them
• 1. Typhoidal species (invasive - those that cause typhoid fever)
• 2. Nontyphoidal species (noninvasive - those that cause diarrhea [enterocolitis] and metastatic
infections, such as osteomyelitis).
compare between the. Typhoidal species and The nontyphoidal (noninvasive) of salmonella
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).
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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
Molecular mechanisms of infection for typhoidal and non typhoidal
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.
