Lower GI Micro Flashcards
1
Q
Food poisoning vs. Food-associated infection
A
Poison - food contains pre-formed toxins. sxs begin w/ 30 min to 6 hrs
Food-associated - organisms produce toxin in GI tract or invade mucosal epithelium
2
Q
staph aureus characteristics
A
bacteria gram + cocci catalase + coagulase + s. aureus
3
Q
bacillus cereus characteristics
A
bacteria gram + large bacilli endospore-forming facultative anaerobe mostly motile B-hemolytic b. cereus
4
Q
clostridium botulinum
A
bacteria gram + bacilli spore-forming obligate anaerobe motile c. botulinum
5
Q
s. aureus sxs
A
N/V, stomach cramps, diarrhea 1-3 days
appears 1-7 hours after ingestion of food
6
Q
S. aureus food reservoirs
A
Reservoirs are food that sits around a long time, allowing bacteria to start producing toxin. High salt concentrations are not enough to keep S. aureus from growing.
potato salad, ham, eclairs
7
Q
which bug is frequently found on skin and is a threat in hospitals because it produces biofilms
A
bacillus cereus
8
Q
box-car shaped gram + rods
A
bacillus cereus
9
Q
where are bacillus cereus spores commonly found
A
in the soil and sometimes in plant foods that are grown close to the ground – such legumes, cereals, spices etc..
reservoir = rice
10
Q
two forms of bacillus cereus food poisoning
A
emetic: 1-6 hrs, N/V, looks like s. aureus illness
diarrheal: 6-15 hrs, watery diarrhea and cramping, looks like c. perfringens infection
lasts 24 hours
11
Q
mechanism of emetic b. cereus illness
A
Caused by preformed enterotoxin that forms holes in membranes:
cereulide, an ionophoric low molecular-weight peptide that is pH-stable and heat- and protease- resistant
Self limiting
12
Q
mechanism of diarrheal b. cereus illness
A
Caused by large molecular weight enterotoxin that causes intestinal fluid secretion, probably by several mechanisms
This toxin is not likely pre-formed!
Ingestion of large amounts of bacteria cause it to generate the toxin in the small intestine
13
Q
types of botulism
A
Foodborne botulism - ingest toxin in food
Wound botulism - generating toxin in wound
Infant botulism - ingest spores
14
Q
botulinum toxin
A
a neurotoxin
irreversibly blocks the release of acetylcholine from the motoric end plate which results in muscle weakness and paralysis
15
Q
sxs botulism
A
botulism
double vision, blurred vision, drooping eyelids, slurred speech, difficulty swallowing, dry mouth, and muscle weakness
16
Q
sxs infant botulism
A
Incubation period, spores have to produce toxin-forming bacteria
lethargic, feed poorly, are constipated, and have a weak cry and poor muscle tone
Can lead to paralysis of respiratory system and other muscles
17
Q
bacteria generating pre-formed toxins in food
A
s. aureus
b. cereus
c. botulinum
18
Q
bacteria that are primarily transmitted through food
A
c. perfringens* salmonella enterica ssp.* campylobacter jejuni* listeria monocytogenes vibrio parahaemolyticus
19
Q
characteristics c. perfringens
A
bacteria gram + bacilli spore-forming obligate anaerobe non-motile c. perfringens
20
Q
salmonella enterica characteristics
A
bacteria gram - bacillii non-spore forming H2S positive and Lactose negative motile, flagellated salmonella enterica
21
Q
campylobacter jejuni characteristics
A
bacteria gram - bacilli (spirilli) motile cold sensitive c. jejuni
22
Q
listeria monocytogenes characteristics
A
bacteria gram + bacillus non-fastidious flagellated, motile non-spore forming oxidase (-) listeria monocytogenes
23
Q
vibrio spp. characteristics
A
bacteria gram - vibrio (curved rod) facultative anaerobes flagellated, motile oxidase + vibrio spp.
24
Q
c. perfringens also responsible for
A
gas gangrene
25
special thing about c. perfringens
non-motile
26
sxs c. perfringens food-assoicated illness
Diarrhea and abdominal cramps
Incubation 6 to 24 hours (typically 8-12)
Symptoms last for less than 24 hours
Usually NO fever or vomiting
The illness is not passed from one person to another
27
reservoir c. perfringens
“C. perfringens infection often occurs when foods are prepared in large quantities and kept warm for a long time before serving”
Gives spores in food a chance to start bacterial growth
28
campylobacter jejuni reservoir
Campylobacteriosis is a zoonosis, a disease transmitted to humans from animals or animal products. Harbored often in poultry
29
what agar for c. jejuni
Karmali agar is a selective medium:
Charcoal-based.
Because it is difficult to grow, must eliminate competing microorganisms
Contains vancomycin active against the gram-positive organisms, cefoperazone active against many normal flora, cycloheximide active against yeasts
30
sxs campylobacteriosis
diarrhea, cramping, abdominal pain, and fever
2-5 day incubation
Symptoms can last a week
Can have vomiting, diarrhea can be bloody
31
mechanism c. jejuni illness
Symptoms are an inflammatory response to cell invasion
32
important complication of c. jejuni
Guillain-Barré syndrome (also reactive arthritis)
33
guillain-barre presentation
Initial symptoms: weakness or tingling sensations in the legs.
Symmetrical weakness and abnormal sensations spread to the arms and upper body.
Possible increase in intensity until certain muscles cannot be used at all and, when severe, the person is almost totally paralyzed.
34
guillain-barre risk factors
Infection with Campylobacter jejuni or having the flu or other infections (such as cytomegalovirus and Epstein Barr virus, respiratory infection)
vaccination.
35
salmonella serotypes for typhoid fever (not food-related)
s. paratyphi A
| s. typhi
36
salmonella serotypes for gastroenteritis (salmonellosis)
s. enteritidis
s. typhimurium
others
37
agar for salmonella
Salmonella Shigella (SS) agar has bile salts that inhibit gram-positive and coliform organisms. Contains indicator, lactose fermenting organisms would appear red from the acid produced (not present here), Ferric citrate added for indication of H2S production (black color is the produced iron sulfide precipitate)
38
sxs salmonellosis
diarrhea, fever, and abdominal cramps
12 hr to 3 day incubation
Symptoms typically last 4 to 7 days
Most persons recover without treatment
39
possible complication of salmonellosis
reactive arthritis
40
tx salmonellosis
Hydration. Antibiotics only necessary if infection spreads beyond gut.
41
mechanism salmonellosis
Salmonella replicates in host cells as well as invades
Some genes expressed by Salmonella mediate closure of ion channels to that water and electrolytes are secreted to the lumen
42
reservoir salmonella
eggs, raw milk, veggies
| turtles/reptiles
43
vibrio spp. causes
V. cholerae causes cholera, other species cause diarrhea and other GI distress
44
how to identify vibrio in culture
Mixed culture of oxidase-negative Escherichia coli (colorless) and oxidase-positive Vibrio cholerae (purple) showing how the direct oxidase test differentiates between the two organisms.
Kovács oxidase reagent was added directly to the plate.
45
what distinguishes vibrio from enterics
flagellated, motile
| oxidase +
46
sxs vibrio parahaemolyticus
Fairly mild bloody diarrhea, stomach cramps, fever, nausea, and/or vomiting,
Symptoms last less than a week.
In the immunocompromised, it can spread to the blood and cause serious or deadly infections in other parts of the body
47
mechanism of disease v. parahaemolyticus
Likely through enterotoxins: hemolysins TDH (thermostable direct hemolysin) and/or TRH
V. parahaemolyticus lacking these toxins is not pathogenic
Form pores in red blood cells but also in epithelial cells, disrupting gut homeostasis
48
vibrio parahaemolyticus reservoirs
shellfish
49
listeria monocytogenes hemolysis
β-hemolytic but zone of discoloration is really only directly under the colonies
50
Listeriosis presentation
Mild GI infection for most
More vulnerable are older adults, pregnant women, newborns, and adults with weakened immune systems OPPORTUNISTIC
Fever and muscle aches or stiff neck, or if you develop while pregnant: fever and chills
Meningitis and sepsis in vulnerable populations
51
mechanism listeria monocytogenes
Invasive mechanism
If you have the classic clinical symptoms, the disease has already reached the invasive stage
Immune cells spread Listeria to other organs = Trojan horse
Once escaped from the vacuole, cells in cytosol utilize actin polymerization to move and spread to new cell
Liver is a major target
52
listeria monocytogenes
Foods you don’t cook
Hardy bacterium can hang a long time at food processing facilities
sprouts, deli meats/hot dogs, smoked seafood, soft cheese, raw milk
53
shigella subtypes
Shigella sonnei: most Shigella-caused GI illnesses
Shigella flexnori: causes bacillary dysentery
Shigella dysenteriae: rarest but most severe dysentery
Invasive and produces a toxin
54
shigella transmission
Mostly bacterium passing from stools or soiled fingers of one person to the mouth of another person.
55
shigella sxs
```
diarrhea (often bloody)
fever
stomach cramps
Symptoms start 1-2 days following exposure
Usually resolves in 5 to 7 days.
```
56
What is dysentery?
Frequent, small bowel movements with blood and mucus, accompanied by rectal pain and spasms (tenesmus)
57
shigella characteristics
```
bacteria
gram (-)
Bacillus
facultative anaerobe
nonmotile
non spore-forming
mainly lactose negative, H2S (-)
Shigella ssp.
```
58
Shigella spp. mechanism of diesease
gain access through M cells - mediated by type III secretory system and other effector proteins and cytoskeletal rearrangements --> apoptosis of macrophage, survival of bacteria --> inflammation
59
shigella use _____ to move around
actin rockets
60
Do you treat shigella?
Since Shigella is invasive, if not treated it can spread beyond the GI tract and cause complications
Antibiotics for more severe cases, most usually resolve without antibiotics
61
possible complcation of shigella
hemolytic uremic syndrome
| s. flexnori can also cause reactive arthritis
62
why is shigella systenteriae so bad?
Invasive, plus has a phage-borne toxin
Shiga toxin, also called the verotoxin (act on Gb3 receptor on epithelial cells)
Toxin acts on vascular endothelial cells
--> most severe dysentery
63
Diseases caused by E. coli
Diarrhea
Urinary tract infection
Neonatal sepsis
Gram-negative sepsis
64
e. coli characteristics
```
bacteria
gram (-)
bacillus
facultative anaerobe
motile
non spore forming
mainly lactose positive
e. coli
```
65
STEC
Shiga toxin-producing E. coli (STEC)—Also known as VTEC or enterohemorrhagic E. coli (EHEC)
Outbreaks in U.S. O157:H7
66
ETEC
Enterotoxigenic E. coli (ETEC)
| Traveler’s Diarrhea, diarrhea in children
67
how does ETEC deliver toxin
on top of microvilli - deliver of LT or ST enterotoxins
68
mechanism of ETEC toxin
activates adenylate cyclase, end result water into lumen, NO bacterial penetration.
69
How does STEC deliver toxin
intimate attachment of bacteria --> actin condensation and microvillus effacement --> delivery (much more, closer)
70
sxs ETEC/STEC
profuse watery diarrhea and abdominal cramping
Can progress to bloody diarrhea for STEC
Fever, chills
Nausea with or without vomiting, loss of appetite
Less common: headache, muscle aches and bloating
Incubation:1-3 days ETEC, 3-8 for STEC
Illness typically lasts 3-4 days, less than 10.
71
possible complications STEC
hemorrhagic colitis (HC) and/or HUS can result as a complication; children more vulnerable
72
do you treat e. coli
abx NOT recommended (HUS)
73
typical E. coli food reservoirs
fecal-oral
| ground beef, leafy vegetables
74
primary reservoir for V. cholerae
water
75
vibrio cholerae: only ____ produce ____ and cause ____
Typically only serogroups O1 and O139 produce cholera toxin and thus cause cholera
76
mechanism cholera toxin
Activates adenylate cyclase
inc. cAMP → dec. Na+ absorption, inc. Cl- excretion
Water moves into lumen
77
cholera presentation
```
profuse watery diarrhea, sometimes described as “rice-water stools,”
vomiting
rapid heart rate
loss of skin elasticity
dry mucous membranes
low blood pressure
thirst
muscle cramps
restlessness or irritability
```
78
tx cholera
antibiotic therapy may help for severe cases, rehydration therapy is really the biggest factor in treatment.
79
S. Typhi reservoir
Untreated water is the source, humans are the only carriers
80
Typhoid fever
Life-threatening illness
In GI tract and then to bloodstream
High fevers (103-104 °F)
Weakness and headache
Stomach pains, loss of appetite, diarrhea or constipation
Sometimes, a rash of flat, rose-colored spots
After symptoms clear, person could become a carrier
81
abx for typhoid fever?
YES. because of the danger of having a S. Typhi symptomless carrier…feces still contain the bacteria, and illness could reoccur.
82
Low inoculum organisms
Tens to hundreds of virions/cysts/bacteria will cause disease
Shigella, Giardia, Entamoeba, Norovirus
STEC E. coli, only 100 organisms
83
High inoculum organisms
Tens of thousands or more needed
| Vibrio cholerae, C. perfringens
84
clostridium difficile characteristics
```
bacteria
gram + (variable?)
bacilli
spore-forming
obligate anaerobe
motile
clostridium
```
