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75 Cards in this Set
- Front
- Back
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Does enteritis due to E. Coli O157:H7 present with fever?
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No, because it is not invasive
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Common bacterial causes of enteritis/desentery with fever?
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SSYC
Other nonbacterial conditions to consider are protozoal infections, Crohn disease, and Ulcerative Colitis |
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20 y/o old white male present with severe abd cramping and bloody diarrhea for 3 days. During Hx. pt revealed that he had a bbq chicken dinner at a local restaurant 30 hrs before the symptoms, and that he roommates also complained of the same symptoms, although milder. Exam shows a fever of 38.1 C. What organisms must you suspect?
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SSYC
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What infectious organism is almost always associated with antibiotic use
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C. Difficile
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Campylobacter coli and fetus cause systemic infection in what groups?
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Neonates and young children
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Major virulence factor of C. jejuni
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Flagella
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What conditions must labs use to grow C. jejuni?
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Selective media, microaerophilic conditions, and incubation at 42C
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What type of organism is C. jejuni? What is the antigen?
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Gram negative curved rod
LPS |
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Most common cause of bacterial diarrhea illness in the United States and the world. What is the cause of most cases?
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C. jejuni
Improper food handling and preparation of poultry. Person-person spread is uncommon. |
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Pt. reports to the hosptal complaining of flaccid ascending paralysis. Pt. reports having had diarrheal infection recently in the past. What must you suspect?
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Guillain-Barre syndrome that is associated with C. jejuni infection
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What pattern of tissue damage is seen in C. jejuni? What is this similiar to?
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an acute, nonspecific neutrophilic and monocytic inflammatory reaction causing tissue damage in the lamina propria and jejunal epithelium.
Similar to Crohns and ulcerative colitis |
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Primary choice of management for C. jejuni
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Rehydration. possibly Erythromycin
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C. jejuni infection in the elderly and immunocompromised may lead to?
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bacteremia
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Undercooked or improperly prepared poultry is most likely to cause infection with what organisms?
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C. jejuni and Salmonella
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What infectious organisms are extremely likely to cause bloody diarrhea?
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E Coli and Shigella
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Six individuals of a single family present with 2 days of fever, abdominal cramps, vomiting, and diarrhea. This occurs after having eaten a Thanksgiving turkey dinner 24 hours before symptoms began. What organisms are most likely? What is txmt?
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Salmonella and C. jejuni. These organisms are very common with poultry. E. Coli and Shigella would most likely also show bloody diarrhea, although it is common in C. jejuni infections also. E. Coli also does not produce fever.
There is no txmt in an otherwise healthy person. |
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What type of bacteria are Salmonella?
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Gram- non-spore forming, Faculative anaerobic enteric rod
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What undergoes phase variation in Salmonella to create variant strains?
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H antigens
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What Salmonella serotype is encapsulated?
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S. typhi, the rest are unencapsulated
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What is the main reservoir of salmonella
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Animals:
Poultry, eggs, dairy products |
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Do Salmonella ferment lactose
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NO
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In Salmonella induced complicated enteritis, what causes bacteremia?
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Phagocytosis of the organism into macrophages results in dissemination throughout the reticuloendothelial system and invasion into the blood stream.
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How does Salmonella adhere to the small intestine? Explain the pathogenesis
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Fimbrial adhesions
Once adhered, Salmonella alters the structure of the brush border. Invasion of the intestinal epithelial cells, mediated by invasins then occurs. Overwhelming neutrophil response causes inflammation and damage to the mucosa, that results in bloody diarrhea. |
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41 y/o man is brought to the ER with a 3-day Hx of shaking, chills, high fever, abd pn, and weakness. He had diarrhea for 2 days, which improved when the fever began. He recently has returned from india. Exam showed tender abd, w/ enlarged liver and spleen. He also has a maculopapular rash. What is a possible cause? Txmt?
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Typhoid fever presents with these symptoms including the rash, however, there are several other possible causes
Txmt: Cipro(flouroquinolones) |
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How is S typhi transmitted? What population is high risk?
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Fecal-Oral route
International travelers |
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What type of bacteria are S. typhi?
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Gram- enteric rods that are faculative anerobes. They contain a capsule containing the Vi antigen
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Where does S. typhi bind? Explain its pathogenesis
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Binds to and invades M cells, causing their death. The bacteria then spreads to the Peyer patches of the lamina propria and migrate though the mucosa of the terminal ileum into submucosal lymph nodes. They are then picked up by monocytes, but inhibit the respiratory burst (Vi antigen). Once through the mucosal barrier, the bacteria cause primary bacteremia (prodromic fever). They are carried to the liver and spleen causing enlargement of the organs. When bacteremia occurs, fever and abd pn result, caused by secretion of cytokines and pyrogens by macrophages. The LPS elicits a systemic inflammatory response, leading to sepsis.
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What causes the distinct maculopapular rash seen in typhoid fever?
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Thrombocytopenia (due to enlarged spleen and liver) and vascular capillary leakage, that are characteristic of enteric fever.
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What is a chracteristic finding of enteric fever?
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Infiltration of monocytes into the colonic mucosa, in which the organism survives and replicates, by inhibiting the oxidative burst
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How does S. typhi spread systemically?
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They are faculative intracellular organisms that travel within monocytes.
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Primary bacteremia in S. typhi? Secondary?
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Prodromal fever:
Occurs once the organism has left the intestinal mucosal barrier Enteric fever, abd pn, and sepsis: Occurs once the organism has reached the blood stream and the reticuloendothelial system |
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How does S. typhi affect the gallbladder?
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It is infected either from the blood or from the liver via the biliary tract. The organism can survive in bile and spreads back to the intestines to cause diarrhea after days of febrile illness.
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What must you consider in presumed food-borne illness?
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The time to onset of symptoms after eating the suspected food items. Organisms that cause an actual infection, generally take 24-72 hrs to cause symtpoms. Those that produce pre-formed toxins lead to symptoms within hours
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Characteristics of S. Aureus enterotoxin
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Heat-Stable
Found in meats, mayo, and custard N/V (acute upper GI symptoms) |
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Characteristics of Bacillus Cereus enterotoxin
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Heat stable:
Emetic Found in fried rice N/V (acute upper GI symptoms) Heat Labile: Diarrheogenic Found in Cream Sauce Watery diarrhea (Lower GI symptoms) |
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Characteristics of C. Perfringens enterotoxins
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Heat Labile
Reheated meats, gravy Watery diarrhea |
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What type of bacteria are S Aureus. What are they resistant to?
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Gram + cocci that are NON-MOTILE and nonspore forming. High salt concentrations.
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From where does S. Aureus entertoxin come from in cases of food poisoning?
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Human origin:
Purulent discharges of an infected finger, eye, abscess... |
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Heat stable enterotoxins are stable at?
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Boiling temps, thus tolerating cooking conditions that kill the organisms that produced them.
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a 71 y/o male returned home from a trip to mexico. A day after his return he developed acute fever, abd pn, and watery diarrhea. The next day, the stools became mucousy with blood and he experienced tenesmus. The stools then became grossly bloody and increased in number. During his stay in Mexico, he had stayed in rural areas and drank the water. Physical exam shows fever, tachycardia, and a normal WBC. Rectal exam was painful and bloody. Diagnosis? Txmt?
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Shigella flexneri:
A rapid, descending course of infection, with fever and abd pn progressing to mucoid diarrhea with bloody stools. Sulfa w/trimethoprim, unless the pt was recently in Asia, South America, or Africa. If this is the case, the txmt would be a flouroquinolone |
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What type of bacteria are Shigella?
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Gram - Nonmotile, noncapsulate, faculative anaerobes.
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In the U.S., what species of Shigella is most prominent? worldwide? Which is most virulent?
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Shigella Sonnei
Shigella flexneri Shigella dysenteri |
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How is Shigella transmitted?
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Via direct or indirect fecal-oral transmission. Outbreaks occur among the elderly and young children, especially daycare centers
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Pathogenesis of Shiga Toxin
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Inhibitor of protein synthesis, targeting the 23s ribosomal RNA. Thus, it kills intestinal epithelial cells and endothelial cells resulting in blood loss. Hemolytic-uremic syndrome, TTP are systemic complications.
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What happens once a significant number of invaded cells die owing to intracellular multiplication of Shigella?
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The colonic mucosa sloughs off causing an ulcer
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Neutrophils can be found in the stools of those infected with?
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Shigella
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How are Shigella unique among enteric pathogens
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Requires a very low infective dose
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Explain the pathogenesis of Shigella
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The bacteria enters the M cells of colonic mucosa and are taken up by macrophages in the lamina propria. The macrophages secrete cytokines and infected intestinal epithelial cells attrct neutrophils which migrate between the epi cells and breakdown the tight junctions and enhancing the spread of the bacteria from one cell to another via LCAM
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What host protein is essential for the cell to cell spread of the infection
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LCAM:
Target of Shigella. Helps with the breakdown of tight junctions due to cytokine attraction of macrophages and neutrophils which bind to LCAM between epithelial cells. |
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A young man returned from a long trip to india. Once back he developed profuse watery diarrhea with a rice-water appearance. He vomited several times and complained of wkns and cramps. Exam showed no fever, dehydration, and hypochloronemia/kalemia/natremia. He was on an H2 blocker. What bacteria? What txmt? What is the significanceof H2 blocker?
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Vibrio Cholerae
Intravenous and oral rehydration Hypochlorydia is a significant risk factor for cholera. Antacids reduce gastric acidity are ar risk for cholera. THey are able to reach the small int in sufficient numbers and multiply and colonize the small intestine via long filament pili. |
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How does cholerae colonize the small int?
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Via Pili
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What is the domain organization of cholera
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A-B type ADP ribosylating enterotoxin.
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How does the A subunit of cholera toxin cause toxicity?
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Activates the adenyl cyclase cascade system by irreversable action on the Gs subunit, thereby raising cAMP levels and activating the CFTR gene to cause Cl- excretion. This leads to passive diffusion of Na and water into the lumen, and massive amounts of watery diarrhea.
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What type of bacteria is V. Cholera
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Curved, gram- rods. They are highly mobile, and faculative anaerobes
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Transmission of V. parahemolyticus?
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contaminated seafood
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How is V. Cholerae transmitted?
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Ingestion of contaminated water and food is the major mode of transmission.
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What txmt is used for E. Coli
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None, just fluids
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Major vehicles of infection of E Coli
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Ground beef and unpasteurized milk
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Txmt for CDAD
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Metronidazole
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How do primary cases of CDAD occur? Secondary?
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Via endogenous growth in precolonized patients exposed to antibiotics
Exogenous transmission of spores in the hospital environment. |
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Antimicrobial agents associated with CDAD
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Clindamycin
Cephalosporins Ampicillin |
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Serious sequelae of CDAD
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Pseudomembraneous colitis:
Untreated Cases Multiple, elevated yellowish white plaques within the colon. May lead to Toxic Megacolon, with sepsis due to bowel perforation and and polymicrobial infection of colonic flora |
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What type of bacteria is C. difficile
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Anaerobic, gram+ spore forming rods. They also produce a toxin.
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How does use of antimicrobials lead to CDAD? Explain the pathogenesis.
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C. difficile is normally suppressed by the normal colonic flora, however, broad-spectrum antibiotics suppress normal flora. The overgrowth of C. difficile produces an AB toxin that binds to GTP and inactivates it by glycosylation. THis disrupts the cytoskeleton of the epithelial cells of the colonic mucosa and causes depolymerization of actin. The break-up of actin leads to damage of the bowel wall and causes ERYTHRMATOUS and FRIABLE COLONIC MUCOSA, ulceration, and hemhorragic necrosis.
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A 9-month old baby was brought the ER during the winter with a 2 day Hx of vomiting, watery diarrhea, and fever. Her parents admitted that the child has been going to a day care center often. Exam showed fever, with supple neck, nontender abd, and normal bowel sounds. WBC was normal. Possible pathogen?
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Virus:
Rotavirus Enteric adenovirus Noravirus |
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Txmt for Rotavirus
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None
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Most widely used methods for diagnosis of rotavirus
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ELISA
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Responsible for the majority of gastroenteritis worldwide
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Enteric viruses:
Rota and Nora |
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Structure of Rotavirus
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Nonenveloped RNA virus
Icosohedral shapes capsid |
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Single most important cause of severe dehydrating diarrhea in infants and younger children worldwide. How is it transmitted?
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Rotavirus
Fecal-oral route |
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Pathogenesis of Rotavirus
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After ingestion, the virus infects mature villi of the small intestine that results in their destruction. These cells are replaced by immature crypt cells that cannot absorb nutrients, resulting in osmotic diarrhea.
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150 college students staying within the same dorm present with complains of N/V, and diarrhea. Several hundred others were also infected. Exam showed no fevers, mild distress, but otherwise normal. Most likely cause? Txmt?
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Most likely viral gastroenteritis, given the fact that there were no fevers.
No txmt |
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Explain the structure of norovirus
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Single stranded +sense RNA virus. Nonenveloped.
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Differentiate Norovirus from other enteric viruses
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1. Incubation is long: 24-48 hrs
2. Vomiting is very common 3. Duration of illness is 12-60 hrs 4. Rapid spread |
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Morphology of Norovirus
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Atrophy of intestinal villi, crypt hyperplasia, and infiltration of the lamina propria by PMN's and monocytes. These changes cause nutrient malabsorption and osmotic diarrhea.
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