Term
True or False:
The late-phase features of an exogenous infection often reflect its transmission. |
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Definition
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Term
| Which important pathogens are transmitted via inhalation? |
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Definition
| M. tuberculosis and Influenza |
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Term
| How does food-borne botulism differ from other ingestion-acquired intoxications? |
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Definition
| It occurs slowly and involves in vivo toxin synthesis |
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Term
| What are the defining features of an Ingestion-acquired Intoxication? |
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Definition
1) Heat- and pH- stable toxins (Except botulism)
2) Symptoms develop quickly (Except botulism)
3) vomiting, diarrhea and cramps
** Botulism develops slowly and makes toxins in vivo** |
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Term
| What are the defining features of an Ingestion-acquired Infection with Invasive Pathogens? |
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Definition
1) Inflammation with fecal leucocytes
2) Cramps, diarrhea and fever (sometimes) develop rather slowly (several days)
3) Local (Shigella or nontyphoid Salmonella) vs. Disseminated (S. typhi and Hep A) |
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Term
| What are the defining features of an Ingestion-acquired Infection with "in vivo" enterotoxin productions? |
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Definition
Virbrio cholerae (cholera toxin), ETEC (ST and LT), C. perfringens (alpha toxin)
1) Noninvasive (except Shigella dysenteriae)
2) Cause GI only (cramps and diarrhea), except EHEC (shiga toxin goes to kidney as well as colon) |
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Term
| What are the 6 most common food poisoning bacteria in the USA? |
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Definition
1) non-typhoid Salmonella (invasive and inflammatory)
2) Campylobacter jejuni (invasive)
3) C. perfringens (in vivo enterotoxin)
4) E. coli
5) Staph aureus (stable enterotoxin causing intoxication)
6) Shigella spp. |
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Term
| Where are Cryptosporidiosis infections most prevalent (environmental acquisition) |
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Definition
| Water-borne and can be fatal in immunocompromised states. |
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Term
| What are the most common waterborne microbial pathogens (Bacterial, Parasitic, Viral)? |
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Definition
BACTERIAL
1) Vibrio cholerae
2) Other gram negatives (E. coli and Shigella)
PARASITIC (longer than bacteria)
1) Giardia spp.
2) Cryptosporidious
3) Entameoba histolytica
VIRUSES
1) Hep A
2) Norovirus
3) Rotovirus
4) Enterovirus |
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Term
| What are the normal physical and chemical defenses of the GI tract? |
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Definition
1) Mucosa
2) Proteases
3) Bile (O antigen)
4) Gastric acid
5) Intestinal motility |
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Term
| What is the role of Urease in bacterial avoidance of enteric defenses? |
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Definition
| Urease raises the pH of the gastric environment, preventing their own destruction. |
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Term
| How do GI pathogens avoid normal microbial protection from flora? |
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Definition
| Sprout new pili for adherence to alternate spots. |
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Term
A patient presents with curved, gram (-) rods that grow at 42 degrees. He is experiencing bloody loose stools (which contain leucocytes), cramping and fever.
What is going on and how do you treat? |
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Definition
Campylobacter jejuni infection
- Fastidious gram-negative that requires microaerophillic environment and grow at 42 degrees.
- Ingested by fecally-contaminated food or handling sick pet
- If mild, fluid replacement
- If severe, try antimicrobials |
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Term
| Explain the pathogenesis of Campylobacter jejuni infection. |
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Definition
Starts 1 day after exposure and resolves 5 days later.
Uses Adhesins, LPS (inflammation), Enterotoxin (sometimes)
1) Ingested by contaminated food (water also possible) and attaches to lower small intestine/upper large intestine
2) Invasion with LPS leads to inflammation (cramps, diarrhea and fever) and resolves 1-5 days later.
3) Sequele can include Arthritis and Guillain-Barre syndrome (autoimmune). |
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Term
| Explain the pathogenesis of Giardia spp. infection. |
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Definition
Often passed by water or food (less common)- Zoonotic reservoir
1) Ingested cysts (infectious and Cl-resistant) go to small intestine and convert into Trophozoites, which multiple in duodenum (mostly asymptomatic carriers)
2) Infectious Cysts form in colon, from which they are excreted (persistent in enviornment and resistance to chlorination) |
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Term
A patient presents with explosive, (no blood or mucous) sudden onset diarrhea. They are also IgA deficient.
What pathogen are you concerned about and how would you take care of the patient? |
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Definition
Sounds like Giardia (explosive diarrhea without blood)- Zoonotic reservoir
1) Usually occur from malabsorption of fats and carbs in small intestine because of replicating trophozoites.
2) Treat with Metranidazole. |
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Term
Your patient has recently been swimming in a contaminated lake and is now suffering from prolonged diarrheal episodes.
You discover oocysts in the stool by acid-fast stain.
What is going on and what is the pathogenesis of the condition? |
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Definition
Sounds like Cryptosporidium parvum (protozoan)
1) Ingested oocysts develop into sporozoites in the intestines
2) Sporozoites attach to and then invade Enterocytes, developing into Trophozoites in the intestinal epithelial cells under the brush border.
3) Trophozoites under brush border can cause malabsorption and inflammation (most severe in immunocompromised individuals) |
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Term
| How can you treat Cryptosporidium parvum infections? |
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Definition
| In immunocompromised individuals, try Paromomycin, but rely on SUPPORTIVE THERAPY. |
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Term
Which viral infections produce NSP4 (enterotoxin-like) and are most common in the winter time?
What is their pathogenesis? |
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Definition
Rotavirus (acid-resistant, non-enveloped dsRNA virus with icosahedral symmetry)- Most common cause of diarrhea in kids <2
1) Oral fecal transmission leading to multiplication in the intestinal mucosa
2) Intense, infectious diarrhea, fever and vomiting arise within 48 hours in children |
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Term
| How is prevention of Rotavirus infection achieved? How is it diagnosed/treated? |
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Definition
1) Live-attenuated vaccine (not for infant for immunodeficient)
2) EM and Serology/ Restore fluid-electrolyte balance. |
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Term
| Explain how Hep A is transmitted and how it progresses? |
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Definition
Picorna virus- unenveloped, ssRNA+
1) Human reservoir transmitted via fecal-orgal route (common worldwide- mostly in western, southwestern US)
2) Ingestion..replication in gut...flu-like illness in 50%
- If insufficient neutralizing Ab, can invade blood and spread to liver, presenting with acute inflammatory disease and Juandice (1% aexperience fulminant hepatitis which can be fatal)
- Complete recovery is common within 2 months (NOT CHRONIC), usually with life-long immunity |
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Term
| Why would you be especially concerned about Jaundice in a patient with pre-existing liver disease? |
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Definition
| Hep A causes fulminant hepatitis in 1% of individuals, which can be fatal |
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Term
| How can you definitely diagnose Hep A infection? |
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Definition
1) anti-HAV IgM antibodies (disappear 6 months after disease)
- Can't be distinguished from other hepatidis based on clinical symptoms.
-Cannot rely on IgG for active disease, since they can be left over forever. |
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Term
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Definition
1) if recently exposed, try HAV-IG for passive coverage
2) HAV killed virus vaccine in infants at 12 months or for travelers at high risk can be preventative (BETTER OPTION) |
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Term
| Which Ingestion-Acquired pathogens have strictly human reservoirs? |
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Definition
1) Hepatitis A (unenveloped, ssRNA +)
2) Rotavirus (unenveloped dsRNA) |
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Term
Most in vivo enterotoxin production by ingestion-acquired pathogens occurs strictly in the GI tract.
What is an exception to this? |
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Definition
| EHEC produces Shiga-like toxin which can be absorbed into circulation and damage kidneys (HUS) |
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Term
| How does the ingestion-acquired EPEC elicit pathogenesis? |
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Definition
Attaching/effacing lesions cause Infant diarrhea in developing countries
1) EPEC adheres to enterocytes with plasmid-encoded bfp
2) TIR is delivered (Type III) to enterocytes and Intimin on EPEC binds TIRs that are now on host cell, leading to pedestal-formation.
3) EPEC sitting on pedestal is such a close association that diarrhea ensures. |
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Term
| What intoxicating pathogen is most commonly found in Ill-prepared Fried Rice? |
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Definition
Bacillus cerius, which uses ST to cause vomiting with 1-6 hours
Remember, intoxication is fast! |
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Term
| What are the 3 important intoxicating pathogens? |
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Definition
Remember, shorter time to symptoms!
1) S. aureus (ST with vomiting)
2) B. cereus (ST with vomiting)
3) C. botulinum (LT with flaccid paralysis) |
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Term
| What are 4 important intestine-invading bacterial pathogens? |
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Definition
Remember, Invasion= fever and inflammation
1) Nontyphoid Salmonella
2) Shigella spp.
3) Campylobacter spp.
4) Listeria monocytogenes (flu-like) |
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Term
| What is the most common cause of diarrhea? |
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Definition
Norovirus (Calicivirus- ssRNA (+), un-enveloped virus)
1-2 day incubation followed by 1-2 days of sickness
C. dif is also common in hospitals |
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Term
True or False:
Giardia is very infectious |
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Definition
| True, it only requires 10 cysts!!!!!!! |
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Term
| How do you diagnose a case of Giardia infection? |
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Definition
Find trophozoites or cysts in stool.
No vaccine for Giardia or Campylobacter |
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Term
Name the reservoir of each of the following ingestion-acquired pathogens
1) Campylobacter
2) Giardia lambdia
3) Crytosporidium
4) Rotavirus
5) HAV |
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Definition
1) Zoonotic
2) Zoonotic
3) Zoonotic
4) Human
5) Human |
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Term
| Which bacterial intoxication has a particularly short incubation time (generally in 6 hours or less)? |
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Definition
S. aureus
C. perfringens is a little longer at 12h and others are much slower (like Campylobacter) |
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