Zimmer: Lower GI Microbiology Flashcards
1
Q
What are the GI system defenses in the intestine?
A
Peyers patches Normal flora (microbiome)
2
Q
What is the normal flora of the large intestine?
A
Microbe rich, “microbiome” studied here
Anaerobes
Gram-negative rods
Enterococcus – can survive wide range of stressors and environmental conditions
Spirochetes
3
Q
What is the GI tract like at birth and what happens to it over time?
A
Sterile> becomes rapidly colonized> composition changes over time
4
Q
What are some of the first colonizers in breast fed infants?
A
bifidobacteria
5
Q
Why does the GI tract vary in individuals?
A
Antibiotic use
age, diet, genetics, culture
6
Q
What happens to bacterial loads as you move down the GI tract?
A
increase in concentation
7
Q
What are the benefits of the bacteria in the GI tract?
A
prevent establishment and infection by alien microbes
8
Q
What sxs hit you more suddenly–GI parasite infections or lower GI bacterial infection?
A
Lower GI bacterial infection
9
Q
What percent of food borne out breaks are caused by bacteria and parasites?
A
Norovirus- 49%
Bacteria- 40%
Parasites 1%
10
Q
What causes food poisoning?
A
Eat food containing toxins (preformed)>
30 min- 6 hr incubation>
symptoms
11
Q
How do food assocaited infections differ from food poisoning?
A
Symptoms begin after a LONGER incubation period>
organism produces toxin in the GI tract or invades the mucosal epithelium
12
Q
What bacteria cause EITHER food poisoning or food-associated infections?
A
Bacilus cereus
Clostridium botulinum
13
Q
The bacteria responsible for food poisoning cause disease by…
A
toxin production–specifically an ENTEROtoxin that targets the INTESTINE
14
Q
What bacteria generate pre-formed toxins in food?
A
S. aureus
Bacillus cereus
Clostridium botulinum
15
Q
S. Aureus
A
bacteria
gram + cocci, bunch like grapes
Catalase +
Coagulase +
16
Q
Bacillus cereus
A
Bacteria Gram + rod (box car shape) Large bacilli endospore forming Facultative anaerobe Mostly motile B hemolytic
17
Q
Clostridium botulinum
A
Bacteria Gram + bacilli spore-forming obligate anaerobe motile
18
Q
What is a common infectious agent of surgical wounds and a cause of scalded skin syndrome?
A
s. aureus
19
Q
A pt presents w:
Nausea, vomiting, stomach cramps and diarrhea for 1-3 days. Symptoms appeared 1-7 hrs following ingestion of food.
Dx?
A
S. Aureus food poisoning
Similar to Norovirus
20
Q
How long does s. aureus food poisoning last?
A
self limiting–> toxin gone> illness gone
21
Q
How do you dx s. aureus food poisoning?
A
S. aureus can be identified in the stool or vomit
Conclusive test: link illness w/ specific food, or detect pre-formed enterotoxin in food samples *way to track outbreaks
22
Q
How many different toxins can s. aureus produce?
A
7
Found on skin and in noses of healthy people
23
Q
What causes s. aureus food poisoning?
A
Ingestion of TOXIN not the bacterium
*toxin can survive at high temps and is one of the most resistant non-spore forming human pathogens that survives in dry state for extended period of time
24
Q
What is the temp range for S. aureus?
A
15-45 C but they can also survive high NaCl
25
What are typical s. aureus food reservoirs?
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
pmeats
custard filled bake goods...like eclairs
26
Is antibiotic treatment a good option for S. aureus food poisoning?
NO
The toxin not the bug itself is in your system
27
Where is bacillus cereus frequently found?
On skin and is a threat in hospitals as it produces BIOFILMS that adhere easily to invasive devices. This produces chronic persistent infection, as the biofilm can periodically release B. cereus into the bloodstream
28
Where are bacillus cereus spores commonly found?
soil
| plant foods grown close to the ground (rice)
29
What is the reservoir for bacillus cereus?
spores can survive rice cooking process
30
What are the two forms that bacillus cereus food poisoning can take?
1. Emetic (vomiting)
| 2. Diarrheal
31
A person eats rice that has been sitting out, then 1-6 hrs later begins to vomit and feels naseous. Dx?
Emetic Bacillus Food poisoning
*resembles vomiting illness caused by s. aureus enterotoxins
32
A person eats rice that has been sitting out, than 6-15 hrs latter begins to experience abdominal cramps and have watery diarrhea. Dx?
Diarrheal Bacillus cereus Food poisoning
* similar to sxs of clostridium perfringens
33
How long does bacillus cereus food poisoning last?
24 hrs-- self limiting
34
What is the mechanism for the emetic type of bacillus cereus FP?
PREFORMED enterotoxin> 1-6 hrs>
forms holes in membranes
Enterotoxin= cereulide, an ionophoric low molecular-weight peptide that is pH-stable and heat- and protease- resistant
35
What is the mechanism for the diarrheal type of bacillus cereus FBI?
Ingestion of LARGE amts of bacteria>
generation of toxin in SMALL INTESTINE>
large molecular wght enterotoxin causes intestinal fluid secretion
*Toxin is NOT preformed
36
What is generally the drug of choice for baciilus cereus FBI?
vancomycin
*vulnerable pops may be more affected and require antibiotics
37
How do you dx bacillus cereus?
Fairly ubiquitous
Found in food, vomitus or feces of the same serotype
large number of serotypes are known to produce toxins
*only necessary when tracking outbreaks
38
How does clostridium botulinum appear?
gram +, spore forming rod
39
How is botulism transmitted?
spores or toxin
40
What are the three types of botulinism?
1. Food borne- ingesting toxin in food
2. wound- generating toxin in wound
3. infant- ingesting spores> toxin produced
41
Is c. botulinum a GI illness?
not really b/c diarrhea isn't prominent
42
How do you tx foodborne botulism?
Ventilator if respiratory failure and paralysis
Antitoxin if paralysis is not yet complete
Remove contaminated food if still likely in gut
43
What type of toxin is c. botulinum? What is the mechanism of the neurotoxin?
Neuotoxin that irreversibly blocks the release of acetylcholine from the motoric end plate which results in muscle weakness and paralysis
44
How is c. botulinum absorbed?
Absorbed form GI tract to bloodstream
45
What are the sxs of botulinism?
Toxin already produced>
symptoms can begin when toxin hits GI tract>
double vision, blurred vision, drooping eyelids, slurred speech, difficulty swallowing, dry mouth, and muscle weakness
46
What are sxs of infant botulism?
Incubation period>
spores have to produce toxin-forming bacteria>
```
Sxs:
lethargy
poor feeding
constipation
weak cry
poor muscle tone
```
Can lead to paralysis of respiratory system and other muscles
47
What is botox?
c. botulinum
48
What are food reservoirs for c. botulinum?
canned food improperly processed
honey
49
What bacteria are primarily transmitted through food?
```
Clostridium perfringens
Salmonella enterica ssp.
Campylobacter jejuni
Listeria monocytogenes
Vibrio parahaemolyticus
```
50
Clostridium perfringens
```
Bacteria
Gram +
Bacilli
Spore-forming
Obligate anaerobe
Non-motile
C. perfringens
```
51
Salmonella enterica ssp
```
Bacteria
Gram -
Bacilli
Non spore forming
H2S positive & lactose negative
Motile, flagellated
Salmonella enterica
```
52
camylobacter jejuni
```
Bacteria
Gram -
Bacilli (Spirilli)
microaerophilic
Motile
Cold sensitive
Campylobacter jejuni
```
53
listeria monocytogenes
```
Bacteria
Gram (+)
Bacillus
Non-fastidious!!!
Flagellated, motile
Non spore forming
Oxidase -
Listeria monocytogenes
```
54
vibrio parahaemolyticus
```
Bacteria
Gram (-)
Vibrio (curved rod)
facultative anaerobes
Flagellated, motile
Oxidase +
Vibrio spp.
```
55
Bacteria that are transmited through food use what mechanisms?
* secretion of exotoxin
| * direct cellular invasion
56
What are the 3 BIG sources of food borne illness in the US?
Campylobacter jejuni
Intestinal cell invasion
Salmonella enterica
Intestinal cell invasion
Clostridium perfringens
Enterotoxin
57
How does the c. perfringens enterotoxin affect host mucosa cells?
binds to receptors in endothelial cell junctions, then generates pores in host mucosa cells.
58
What bacteria is also responsible for gas gangrene and can cause a systemic infection?
c. perfringens
59
A pt presents w/ diarrhea and abdominal cramps (no fever or vomiting) after eating bad food 6-24 hrs earlier. The symptoms last less than 24 hrs.
C. perfringens
| NOT passed from one person to another
60
How do you dx c. perfringens?
Detection of toxin or high amounts of bacteria in FECES
C. perfringens normally present in the GI tract, the problem is when you ingest a C. perfringens load high enough to produce enough toxin to overwhelm natural biome and generate symptoms
61
How do you tx c. perfringens FAI?
Usually self-limiting, but more serious, longer-lasting cases in immunocompromised individuals should be treated to avoid complications
62
What foods are most likely to contain c. perfringens?
Food prepared in large quantities that are kept warm for a long time before serving (gives spores in food a chance to start bacterial growth)
*need a big load to cause symptoms
63
What is campylobacteriosis?
a zoonosis = a disease transmitted to humans from animals or animal products. Harbored often in poultry (can't usually multiply in food)
64
A gram - rod that is microaerophilic and cold sensitive (hard to culture). Grown on karmali agar.
campylobacter jejuni
65
What is Karmali agar?
a selective media: charcoal-based, contains vancomycin active only
against the gram-positive organisms cefoperazone active predominantly against the gram-negative organisms, cycloheximide active against
yeasts
(antibiotics present so all other bacteria so campylobacter will grow)
66
What are the sxs of campylobacteriosis?
bloody diarrhea, cramping, abdominal pain, and fever
2-5 day incubation
Symptoms can last a week
Can have vomiting, diarrhea can be bloody
67
What is the mechanism of campylobacteriosis?
Symptoms are an inflammatory response to cell invasion
68
How do you dx campylobacteriosis?
stool culture
69
What are possible complications of campylobacteriosis?
guillain barre syndrome
70
What is Guillain barre syndrome?
autoimmunity against peripheral nervous system>
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.
71
What are major RFs for Guillain Barre syndrome?
Infection with Campylobacter jejuni or having the flu or other infections (such as cytomegalovirus and Epstein Barr virus, respiratory infection).
On very rare occasions, one may develop GBS in the days or weeks after getting a vaccination.
72
What are the common types of salmonella in the US?
S. enteritidis
S. typhimurium
(cause salmonellosis)
73
Motile gram - bacillus, H2 S POSITIVE AND LACTOSE NEGATIVE that causes salmonellosis?
s. enteritidis
74
Why does salmonella shigella have bile salts?
BS 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)
75
What are the sxs of salmonellosis?
diarrhea, fever, and abdominal cramps
12 hr to 3 day incubation
Symptoms typically last 4 to 7 days
Most persons recover without treatment
Remember: REACTIVE ARTHRITIS as a possible complication
76
How do you dx salmonellosis?
stool culture
77
How do you treat salmonellosis?
Hydration (antibiotics only necessary if infection spreads beyond gut)
78
What is the mechanism of salmonellosis?
Replicates in host cell walls and invades
Some genes expressed by Salmonella mediate closure of ion channels to that water and electrolytes are secreted to the lumen
79
What are food reservoirs for s. enteritidis? Animal reservoir?
raw milk
eggs
vegetables
person
TURTLES!
80
What is a gram - rod w/ a single flagellum that is water loving?
Vibrio Spp
81
What distinguishes Vibrio spp. from enterics?
flagellated motile
oxidase +
Kovacs oxidase reagents makes vibrio purple
82
What sxs are associated w/ vibrio parahaemolyticus infection?
Fairly mild bloody diarrhea (lysis of the cells), 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
83
How do you dx vibrio parahaemolyticus infectin?
Vibrio may be isolated from cultures of stool, wound, or blood.
84
What is the MOA of vibrio parahaemolyticus?
enterotoxins: hemolysins TDH (thermostable direct hemolysin) and/or TRH>
Form pores in red blood cells but also in epithelial cells, disrupting gut homeostasis
V. parahaemolyticus lacking these toxins is not pathogenic
85
What are common reservoirs for vibrio parahaemolyticus?
shellfish
| uncooked fish
86
What is a gram + rod shaped, beta hemomlytic bacteria that causes a rare, but leading cause of death by foodborne illness?
Listeria monocytogenes
87
What is listeriosis?
Mild GI infection for most>
| Fever and muscle aches or stiff neck, or if you develop while pregnant: fever and chills
88
What populations are more vulnerable to listeriosis?
older adults, PREGNANT women, newborns, and adults with weakened immune systems OPPORTUNISTIC
Meningitis and sepsis in vulnerable populations
89
How do you dx listeriosis?
Positive ID is the bacterium found in a normally sterile site
90
What is the listeria monocytogenes mechanism?
INVASIVE
Immune cells act as trojan horses and spread listeria to other organs (LIVER)
91
What foods are reservoirds for listeria moncytogenes?
foods you don't cook can harbor this hardy bacterium that can stick around a long time
*why we advise pregnant women not to eat these foods
```
sprouts
deli meats/hot dogs
smoked sea food
soft cheeses
raw milk
```
92
A group of scientists on a five-day retreat in at a remote full-service resort are struck by a GI illness. Common complaints are explosive non-bloody diarrhea and frequent projectile vomiting, with some sufferers exhibiting low grade fever. The scientists talked to the food service staff and found that many had already had this illness and that it would not last longer than a day or two. If this outbreak were to be investigated, what test would be most likely to yield a positive result?
Norovirus
PCR-based assay on stool or vomitus samples
93
What is the organism responsible for a bacterial infection initiating in the GI tract but resulting in neurological symptoms including slurred speech and muscle weakness?
Clostridium (spores at ends of bacilli)
