Gram (-) Bacteria Flashcards
Stephanie moved into her dorm and soon after came down with meningitis. What bacterium infected her?
Neisseria meningitidis
If you see a gram (-) diplococci that looks like “kissing kidney beans” under a microscope, what genus does it belong to?
Neisseria
The outer membrane of Neisseria sp. contains what lipid?
LPS - lipopolysaccharide
LPS contains what toxins? What do the toxins cause?
Lipid A- endotoxin - causes sepsis
O antigen - used for serotyping
Describe the main virulence factors of N. meningitidis.
Lipid A (endotoxin) and Polysaccharide capsule (13 serotypes)
What is meningococcemia?
Meningitis and sepsis occurring simultaneously, due to infection with N. meningitidis.
By what route is N. meningitidis spread?
Respiratory route. Breathe it. (That’s why people in close quarters…dorms, bunkers…. get it so easily)
Why is the N. meningitidis vaccine not always helpful?
There are 13 serotypes of the polysaccharide capsule. The vaccine doesn’t cover them all.
If your patient walks in and has “purulent urethritis or cervicitis,” what does she have and why did she get it?
Gonorrhea. STD.
Gonorrhea is second only to ___________ for reported bacterial infections, and the two often occur simultaneously.
Chlamydia
Leading cause of Pelvic Inflammatory Disease?
Gonorrhea
Key virulence factors for N. gonorrheae?
PILI
Attachment, antiphagocytic
ANTIGENIC VARIATION OF THE PILI - more than 100 serotypes!
IgA protease as well.
What member of the normal throat flora (also considered part of the Neisseria family) can cause sinusitis, otitis media, bronchitis, and pneumonia?
Moraxella catarrhalis
What is the morphology of gram (-) glucose fermenters?
RODS!
What is the most famous Gram (-) rod? (Also the top cause of of UTIs)
Escherichia coli
What virulence factor does E. coli possess that makes it the top cause of UTI’s?
P-type pills lets it adhere to upper urinary tract epithelium.
What disease can babies get from mom’s normal flora gone wild? (E.coli) What virulence factor contributes to this disease?
Neonatal meningitis…. K1 capsule.
Remember: all bacteria that cause meningitis are encapsulated
T/F: Normal flora E.coli can cause enteric (diarrheal) diseases.
FALSE: can only get enteric diseases from external sources of E. coli.
Bloody diarrhea is characteristic of which toxin produced by what species of bacteria?
Shiga toxin, produced by E. coli.
What type of toxin is Shiga Toxin and how does it work?
A exotoxin that inhibits protein synthesis.
What type of secretion system does E.coli predominately use?
Type 3: pilus!!
Enterohemmorragic diarrhea is characterized by what symptom, and it caused by what specific species of E. coli?
Bloody diarrhea: from shiga toxin.
EHEC - enterohemorrhagic E. coli.
Bacterial infection of the blood is called_____________. What virulence factors of E. coli contribute to this infection?
Bacteremia: caused by capsule and LPS
The award for top cause of food poisoning goes to………? (name the bacterial species)
Salmonella
You go camping and break your water bottle. You are forced to drink from a river. Later, it feels like the river is coming out your butt. You have traveler’s diarrhea. What bacteria caused it? What toxins contributed?
ETEC (enterotoxigenic E.coli) - 2 exotoxins, one of which is similar to cholera toxin.
Not endogenous to the gut!
Remember: watery diarrhea = cholera toxin, or cholera- like toxin.
What is Hemolytic Uremic Syndrome, and what toxin causes it?
Siga toxin disseminates through the blood to cause anemia and renal failure. Result of E.coli infection of the very young.
What category of pathogens do Salmonella sp. fall under? (Frank, Opportunistic)
Frank.
What are the 2 species of Salmonella that cause Entercolitis (Salmonellosis)? …. AKA food poisoning.
What virulence factor is used?
S. Typhimurium and S. Enteriditis.
Have type 3 secretion systems and the ability to kill macrophages
What bacteria begins in the GI tract, then insidiously disseminates to reside within macrophages and kill you?
Salmonella Typhi. Typoid fever.
How does death by S. Typhi occur?
hemorrhage at ruptured Peyer’s patches.
What are the main virulence factors of S. Typhi?
Ability to reside within macrophages, and
Vi antigen that inhibits neutrophil phagocytosis.
How is S. Typhi able to reside in macrophages?
Prevents phagolysosome fusion.
You’re on the Oregon Trail, but you don’t make it. Not because your conestoga wagon got stuck in the river, but because you died of Dysentery. What is dysentery and what bacteria causes it?
Dysentery is bloody diarrhea caused by Shigella sp.
Since the Oregon trail is in America, the specific shigella species is S. sonnei.
If you got dysentery in another country, what species of bacterium would cause it?
Shigella dysenteriae. More severe symptoms than dysentery caused by S. sonnei, which id more common in the US.
What is the virulence factor associated with Shigella?
Shiga Toxins
What is the most common bacterial GI infection in developed countries? what do you eat to get it?
Camphylobacter jejuni
Low dose needed.
Undercooked meat, unpasteurized milk.
What is the O2 requirement of Camphylobacter jejuni?
microaerophillic
What kind of GI disturbance does Camphylobacter Jejuni cause?
Watery diarrhea that progresses to inflammatory (bloody) diarrhea. No shiga toxin though.
Curved, gram negative rods are more commonly referred to as what morphology?
Vibrio
The “rice water stool” associated with __________(disease) is caused by ____________(virulence factor).
Cholera - Cholera toxin.
Cholera toxin works by what mechanism?
AB toxin. ADP-ribosylates G proteins, leading to release of electrolytes and water from enterocytes.
How do you treat cholera?
Oral rehydration and antibiotics.
Most common form of transmission of Cholera?
Fecal/oral transmission.
What bacterial species causes cholera?
Vibrio cholera
You ate fecal-contaminated shellfish while visiting Japan. What bacteria did you get?
Vibrio parahemolyticus
Which bacteria has UREASE enzymes? what does Urease do?
Helicobacter pylori - Urease cleaves urea to ammonia and CO2 –> decreases the pH of the stomach so it can live.
What does infection with Helicobacter pylori cause, and what is the toxin?
GI ulcers caused by Urease
FACT: H pylori infection (if untreated) can lead to chronic GI ulcers, which ca lead to MALT B-cell tumors.
Mucosal associated lymphoid tissue B-cells tumors.
After GI surgery, you develop an intraabdominal cyst, but tests show bacteria of your normal flora in the cyst. Name the most likely bacterium.
Bacteriodes - Predominant species of the colon.
O2 requirements of bacteriodes.
Obligate anaerobes
Blue/Green colonies are…. What makes them blue?
Pseudomonas aeruginosa - have Pyocyanin: a blue enzyme that damages lung cilia.
Prominent diseases caused by Pseudomonas aeruginosa.
1- Skin of burn patients (infection)
2- Cystic Fibrosis (pyocyanin…lung cilia)
3- Nosocomial pneumonia
4- Sepsis
If you get asked a nosocomial infection question that deals with pneumonia caused by ventilators, what bacteria will it be?
Pseudomonas aeruginosa
What is the O2 requirement of Pseudomonas aeruginosa?
Obligate Aerobe
What type of bacteria is Pseudomonas aeruginosa? (Primary/Opportunistic)
Opportunistic. MULTI-DRUG RESISTANT
Key virulence factors of Pseudomonas aeruginosa
LPS endotoxin
Degradative enzymes - elastase and protease
Exotoxin A: AB exotoxin
Type III secretion system
PYOCYANIN
Who does the AB Exotoxin of Pseudomonas aeruginosa work?
Similar to diphtheria toxin - tissue necrosis
Currant jelly sputum and goopy colonies. What bacteria is it? What’s the most common disease it causes?
Klebsiella pneumoniae - nosocomial pneumonia
There is a resistant strain of Klebsiella pneumoniae. What is it resistant to, and what is its abbreviation?
KPC (Carbapenem resistant K pneumoniae)
90% of acute diarrheas are caused by _______.
Viruses.
Name the 3 gram (-) rods associated with the respiratory tract.
Haemophilus influenzae
Bordetella pertussis
Legionella pneumophila
Under the microscope, you see a gram (-) coccobacillus. The 3-year old patient it was taken from has epiglottitis, and otitis media. What is the most likely cause of infection?
Haemophilus influenzae
Haemophilus influenza is the 2nd most common cause of sinusitis and otitis media. Second to what?
Strep pneumoniae
Meningitis caused by Haemophilus influenzae is less common now due to a vaccine that targets what virulence factor?
The Type B capsule.
Bordella pertusis causes what?
Whooping cough
What 2 toxins does Bordella pertusis utilize?
Pertussis toxin - AB toxin that acts like cholera toxin
Cytotoxin - fragments cell walls of host. Kills lung cilia.
The Bordella Pertussis vaccine is composed of what?
REMEMBER: bordella pertussis is included in the DTaP and TdaP vaccine.
Acellular vaccine that contains altered pertussis toxin.
Legionella pneumophila is usually found where? What does it cause?
Water. Atypical pneumonia.
Generally hospital/community acquired
You got infected 4 hours ago and just started showing symptoms. Is this an infection or an intoxication?
Within 4 hours = TOXIN
8+hours = infection
Neisseria can only be grown on what specific media?
Thayer Martin
Gram (-) rods of the GI/UG tract have what oxygen requirements?
They are facultative anaerobes.
Name some Gram (-) rods of the GI/UG tract.
E.coli, Salmonella, Shigella, Vibrio, etc… 2 1/2 pages of em.
What is the serotype of EHEC?
O157:H7
How do E/coli strains cause diarrheal disease if they are part of the normal flora of the colon?
External strains pickup PAI’s from other strains via Pili (conjugation) and this increases their virulence.
SHiga toxin is what type of toxin? What does it inhibit?
Shiga toxin is an AB exotoxin that inhibits protein synthesis.
What is it called when shiga toxin distributes throughout the blood to fuse anemia and renal failure.
HUS: Hemolytic Uremic Syndrome
Top cause of food poisoning?
Salmonella Typhimurium and Enteriditis.
Your Peyer’s patches rupture. What bacteria did you die of? How?
Salmonella Typhi. You died of Typhoid Fever. S. Typhi can survive in macrophages and move into the Peyer’s patches (2ndary lymph tissues) and wreak havoc.
How does cholera toxin work?
It ADP-ribosylates G-Proteins. Leads to the release of electrolytes and water from enterocytes in the gut.
Which of the Gram (-) rods are obligate aerobes? Need air, on a ventilator… these guys will infect you.
Pseudomonas aeruginosa
What specific tissue does Pyocyanin mess up?
Lung cilia.
Intra-abdominal abscesses.
Bacteriodes
Currant jelly sputum. Goopy colonies
Klebsiella Pneumoniae
Cocobacillus?
Haemophilus influenzae
The most likely cause of otitis media and sinusitis is…. Second? Third?
Strep pneumoniae, Haemophilus influenzae, Moraxella catarrhalis
