Gram-Negative Bacteria
• Constitute largest group of human bacterial pathogens • Due in part to lipid A (found when TRL 4 is activate) in the bacterial cell wall • Triggers fever, vasodilation, inflammation, shock
The Enterobacteriaceae: An Overview
• Intestinal microbiota of most animals and humans • Ubiquitous in water, soil, and decaying vegetation • Enteric bacteria are the most common Gramnegative pathogens of humans
The Enterobacteriaceae: An Overview
Physiology • G- Motile bacilli and coccobacilli (just cause its gram stained does not mean we know its species) • ferment glucose • Grow best in aerobic environments • Species distinguished based on: • biochemical properties • motility\ • colony characteristics
Pathogenesis Gram-Negative, Facultatively Anaerobic Bacilli
Pathogenesis • Membrane components • Protein and polysaccharide capsular antigens • Used to distinguish among strains and species • Numerous virulence factors
Pathogenic, Gram-Negative, Facultatively Anaerobic Bacilli
Uses secretion for proteins that could phagocytes it out.
The deposit type 3 toxins (exotoxins) inside the cell.
toxins are shot right into the cells to kill or live inside cells.
Pathogens use adhesion to stick to cells to transfer type 3 secretions.
Out of the human body, they don't have a capsule. within-host they use capsules as a virulence factor to infect humans.
Pathogenic, Gram-Negative, Facultatively Anaerobic Bacilli
Plasmid within bacteria contain genetic information to infect host.
• Pathogenesis Gram-Negative, Facultatively Anaerobic Bacilli
Iron-binding proteins within DNA
The Enterobacteriaceae: An Overview
MacConkey Agar are made of bio salts and are found in bile salts.
Coliform Opportunistic Enterobacteriaceae
Gram-positive dies Gram-negative salts grow in MacConkey and have a reddish-purple color.
Salt agar turns yellow.
Colonize the intestinal tracts of animals and humans
Lab test within the intestinal tracts
Turn because it ferments lactose
Positive for lactose and gas
Positive lactose and negative gas
red color are both negative neither lactose nor gas
Coliforms
Aerobic or facultatively anaerobic • Gram-negative • rod-shaped bacteria that ferment lactose to form gas in lactose broth
Yersinia and S. enteric
Both compete for nutrition in the environment (Host)
Both create a siderophore unique to it.
iron binds to the siderophore
once bonded they act as complex
Both will bind to the siderophore of one another and bind to iron.
Iron is released into cells and gets into the blood.
The two must compete for iron within the blood.
the more siderophore the more bacteria can grow within host.
Coliform Enterobacteriaceae
Escherichia coli
•Most common of the coliforms
•E. coli antigens used to identify particular strains (variation of the gene)
•Flagella (E.coli can be identified by its flagella)
•O-antigen
within the cell
different enzymes will add different carbons
Coliform Enterobacteriaceae
Virulent strains may have genes for:
•fimbriae
•adhesins
•Exotoxins
•Often dependent on TTSS
Type 3 secretion injects a toxin into the cell
(bacteria cells) secretion enter cells
How does Escherichia coli effect host?
•Pathogenic strains have virulence plasmids
•Have genes for fimbriae, adhesins, and exotoxins
What are the effects of E. coli Gastroenteritis (self-limiting) is the most common disease
•diarrhea, cramps, nausea, and vomiting
•Often mediated by enterotoxins (depending on the strain)
•Major cause of pediatric diarrhea in developing countries
Enterotoxigenic E. coli (ETEC)-
produces enterotoxins damage the microtubule forms biofilms (produces microvilli which help us absorb nutrients)
Enteroaggregative E. coli (EAEC) -
aggravate the cells
This strain of bacteria colonizes the intestinal mucosae of patients with Crohn's disease and is capable of invading with type I pili to adhere to intestinal cells.
Adherent invasive E. coli (AIEC)
yes
M cells are present in absence of microvilli.
M. cell identifies any possible infections from viruses
E.coli takes advantage of M.cells by adhering to them to get through tissue
replicating of
(EAEC)
forms biofilms
Adherent invasive E. coli (AIEC)
(take advantage of damaged microvilli and invade macrophages. the macrophages use Toll-like receptors to clear out infections. Though the process is beneficial to the body, nonetheless in this process tissues are damaged)
Enteroinvasive E. coli (EIEC)/Shigella
intracellular pathogens that penetrate the intestinal epithelium through M cells to gain access to the submucosa.