Exam 4: gram - rods Flashcards
The bacterial group of gram negative rods are also known as ___
the enteric, because they cause digestion issues
The enterobacteriacae family contains what bacteria?
E. coli k. pneumoniae enterobacter serratia proteus salmonella shigella
What three gram negative rods are considered coliforms?
E coli
K pneumoniae
enterobacter
How are coliform bacteria defined?
- facultative anaerobes
- ferment lactose
- gram negative
- non-endospore forming
- rod shaped
What is the pathogenesis of E-coli?
septicemia, UTI, meningitis, gastroenteritis
severity is dependent on which strain of E. coli
Why is there such great serological variation in E coli?
they transfer DNA via conjugation and transposons.
lysogenic conversion allows “swapping” of virulence factors
How is E-coli diagnosed?
produces green metallic sheen on EMB agar, use IMViC to distinguish from enterobacter
There are 4 different strains of E coli that cause gastroenteritis. what are they?
- enterotoxin producing E. coli (ETEC)
- enteroinvasive E. coli (EIEC)
- enteropathogenic E. coli (EPEC)
- enterohemorrhagic E. coli (EHEC)
Which strain of E. coli causes “traveller’s diarrhea”?
enterotoxin producing E. coli
Which strain of E. coli invades the intestinal cells and has its main virulence factor encoded on plasmid that is shared by Shigella and E. coli?
enteroinvasive E. coli
Which strain of E. coli does NOT invade intestinal cells but rather adheres to them by adhesins coded on plasmid that destroy microvilli on intestinal cells where microbe attaches?
enteropathogenic E. coli
Which strain of E. coli produces verotoxin which blocks the protein that functions to prevent the cell from undergoing apoptosis which causes severe abdominal pain, bloody diarrhea and can lead to hemolytic uremic syndrome (HUS)?
enterohemorrhagic E. coli
How are strains of Klebsiella pneumoniae classified?
by their capsule proteins
Klebsiella penumoniae is the second most common cause of ____ in hospitalized patients and _____ in infants?
sepsis, septicemia
What is the most common species of enterobacter and what does it cause?
enterobacter aeruginosa causes UTI
What is unique about enterobacter aeruginosa?
it produces ornithine decarboxylase
What common opportunistic pathogen in hospitalized patients causes pneumonia, bacteremia and endocarditis and is characterized by a red pigment?
serratia
What opportunistic pathogen is characterized by a swarming behavior on agar and presence of urease enzyme that breaks urea to produce a sherry red color?
proteus
What pathogen most commonly causes typhoid (AKA enteric) fever?
salmonella typhi
After recovering from typhoid fever, humans can harbor the bacteria where?
gallbladder
How is salmonella transmitted?
oral-focal route, food/water contaminated with feces
What does it mean to say that salmonella bacteria are facultative intracellular parasites.
during invasion, the bacteria are phagocytize by monocytes but survive and divide inside the monocyte
salmonellosis starts ______ after exposure and only a low infective due is required to cause disease.
1-3 weeks
In typhoid fever, salmonella initially invades intestinal cells and then moves to _____ and other organs, especially _____.
lymph nodes, spleen
How is salmonella diagnosed?
blood, urine or feces culture and serotyping. Does not ferment lactose
What is the treatment for typhoid fever caused by salmonella?
- antibiotics: chloramphenicol, Cipro, ampicillin
- IV fluids and electrolytes
- if reservoir, remove gallbladder
- travel vaccines recommended
What are the animal reservoirs for salmonella?
chickens (eggs), reptiles, cows
What is the most common type of salmonella infection?
gastroenteritis (but typhoid fever can occur)
What is the pathogenesis of gastroenteritis from salmonella?
salmonella posses endotoxin and enterotoxin. The enterotoxin causes watery (cholera-like) diarrhea
What is the treatment for gastroenteritis caused by salmonella?
- IV fluids and electrolytes
- antibiotics do not shorten course so are typically not given
Which gram negative rods are not part of normal flora?
salmonella and shigella (all others are: E. coli, K, pneumonia, enterobacter, serrate, proteus)
There are 4 species of shigella and all are always pathogenic and do not ferment lactose. Which species is the most pathogenic?
Shigella dysenteriae
What is the only reservoir for shigella dysenteriae?
humans
How is shigella dysenteriae transmitted?
oral-fecal route
What bacteria is not easily killed by stomach acid and therefore has a low infective dose and produces a potent toxin which kills epithelial cells but rarely invades blood stream?
shigella dysenteriae
What bacteria causes a severe gastric inflammatory response that produces bloody diarrhea and can cause hemolytic uremic syndrome which is often fatal?
shigella dysenteriae
How is shigella dysenteriae diagnosed?
SS agar to distinguish from Salmonella
