Lecture 3 Gram Negative Flashcards
ToD: Gram negative bacteria make up the largest group of human bacterial pathogens
True
What do gram negative bacteria tend to look like?
Cocci, bacilli and coccobacilli
What is an important identifying factor for gram negative bacteria?
Lipid A
Where can Lipid A be found?
Cell wall
What symptoms can Lipid A cause?
Fever, vasodilation, inflammation, shock and DIC (disseminated intravascular coagulation which is the formation of blood clots within the blood vessels in the body)
Where can enterobacteriaceae be found?
The flora of the intestines in both humans and animals
Water
Soil
Decaying vegetation
ToD: Enterobacteriaceae are opportunistic
False. It’s a mix of pathogenic and opportunistic
What kind of infections are enterobacteriaceae mostly responsible for?
Nosocomial infections
What do enterobacteriaceae look like? (think shape & structures)
Coccobacilli
Bacilli
Some have flagella or are covered in them
Capsulated/Slime/Biofilm
ToD: Enterobacteriaceae are all oxidase negative
True
ToD: All enterobacteriaceae reduce nitrite to nitrate
False.
Nitrate -> Nitrite
Not the other way around
What kind of respiration does Enterobacteriaceae do?
Prefers aerobic but can able to ferment glucose anaerobic
What 3 major components are found in the cell wall of Gram-ve?
Strain-specific O-polysaccharide
Core Polysaccharide
Lipid A
What do flagellar proteins contain?
H antigens
What is found in the protein and polysaccharide capsular? (antigen)
K antigens
How are Gram-ve bacteria able to evade the immune system?
Can control the genetic expression of antigens (K or H antigens)
What are the 7 virulence factors for Gram-ve?
Lipid A
Capsules
Fimbriae
Exotoxins
Iron binding compounds
Haemolysins
Type III secretion system
What antigens can be used to identify E.coli?
O, H and K antigens
What is the term for the transfer of genetic material between unicellular or multicellular organisms?
Horizontal gene transfer or lateral gene transfer
What diseases can the virulent strains of E.coli produce?
UTIs
Neonatal meningitis
Gastroenteritis
Severe to fatal haemorrhagic colitis
What is the name of the toxin produced by enterohemorrhagic E.coli?
Shiga toxin or Vero toxin
What treatment and prevention methods are there for E.coli?
Good personal hygiene
Various antimicrobials
Don’t ingest infected substances
Why is bactericide not recommended for E.coli?
Lysing the cell can distribute more toxins into the blood as Lipid A is stored in the cell wall
Name the 3 pathogenic enterobacteriaceae
Salmonella, Shigella and Yesinia
What do all 3 pathogenic enterobacteriaceae have in common?
All synthesise type III
Has secretion systems
What are the characteristics of Salmonella?
Gram negative
Facultatively anaerobic
Most motile due to peritrichous flagella
Pathogenic to both humans and animals
How is Salmonella distributed in the environment?
Intestinal tract of birds (magpie) /animals
Sewage
Fertilisers
Slurry
Animal feeds
Human carriers
Name some foods that may contain salmonella
Meat
Milk
Fish
Egg
Confectioner
Dried Yeast
Frogs legs
Marijuana
Peanut butter
What are the symptoms that you might have salmonella?
Enteritis
Diarrhoea
Abdominal pain
Mild fever
Chills
Nausea
Vomiting
What two strains of Salmonella can cause enteric fevers?
S.typhi
S. paratyphi
Where does salmonella like to reside in the body when its invaded?
Sticks to the epithelial lining of the ileum using their fimbriae, where they invade cells and multiply
What is produced by salmonella that endangers the body?
On the third day of Xmas…
3 enterotoxins, some cytotoxin and the Lipid A in the cell wall
What are some methods to prevent salmonella infection?
Basic food hygiene
Control starts at the farm and continues through the chain until it reaches the consumer
Don’t be stupid
Agriculture + Food sectors are held responsible
Where can you find S.typhi?
Contaminated food/water
How does S.typhi infect the body?
Bacteria pass through the intestinal wall to the bloodstream.
WBCs phagocytose S.typhi however it’s not killed, allowing it to travel across the body to prime locations such as the liver, spleen, bone marrow and gall bladder
What are the symptoms of S.typhi infection?
Fever
Headache
Malaise
Muscle pain
Loss of appetite
All last about a week
Can you explain why S.typhi causes the symptoms seen in the infected? (Two points)
Bacteria is released from the gallbladder which reinfects the intestines = Gastroenteritis abdominal pain and recurring bacteremia
Some bacteria can ulcerate and perforate intestinal wall causing peritonitis in the abdominal cavity
What are the characteristics of Shigella?
Gram negative
Non-spore forming
Rod-shaped bacteria
Causes disease in primates but not other mammals
What disease does Shigella cause?
Shigellosis.
What symptoms does Shigella cause?
Dysentery
Why does dysentery occur during a Shigella infection?
The epithelial cells of the intestinal mucosa are destroyed in the cecum and rectum.
Using the Type III secretion system, it invades the epithelial cells of the large intestine.
What three toxins are created by the various strains of Shigella?
Shiga toxin
Verotoxin
Enterotoxin
How does a Shigella infection usually occur?
Ingestion (fecal-oral contamination)
What does each Shigella genome include?
The virulence plasmid. This encodes the conserved primary virulence determinants
What disease does Shigella chromosomes have in common?
Shigella chromosomes share most of their genes with E.coli K12 strain MG1655
What is the treatment for someone that is infected by Shigella?
Replacing fluids/electrolytes
Oral antibiotics (e.g Ciprofloxacina & Cephalosprins) to reduce the spread in close contacts
ToD: There is a vaccine against Shigella
False. The vaccine is still being developed.
It’s seen some success against S.flexneri
What are the 3 notable species of Yersina?
Y.enterocolitica
Y.pseudotuberculosis
Y.pestis
In Yersina how many virulence plasmids are there?
3
What do the virulence plasmids in Yersina encode for?
Adhesions and Type III systems
Who does Yersina like to infect?
Typically animals
What is the infection pathway of Y.enterocolitica and Y.pseudotuberculosis?
Contaminated food/water by animal faeces
What are the symptoms of Y.enterocolitica in children?
Fever
Abdominal pain
Diarrhea (often bloody)
What are the symptoms of Y.enterocolitica in older children and adults?
Right-sided abdominal pain
Fever
Inflammation of mesenteric lymph nodes
Can be confused for appendicitis
What is Yersinia pestis also known as?
The Black Death
How was Yersinia pestis spread?
Rodent fleas
What can treat Yersina pestis?
Modern antibiotics
What are the symptoms of the bubonic plague?
Swollen lymph nodes
Bacteremia which results in disseminated intravascular coagulation
Subcutaneous haemorrhaging
Tissue death
What are the symptoms of the Pneumonic plague?
Pulmonary distress within a day
How is the Pneumonic plague spread?
Spreads via person to person via aerosols and sputum
