Bacteriology of the Colon Flashcards

Question

Gastroenteritis due to Salmonella

Answer 1

- Infection and replication induces an inflammatory response - Disruption of the enterocytes and malabsorption - Release of prostoglandins, stimulation of CAMP and fluid secretion

Answer 2

- Bacteria invade cells and replicate as in gastroenteritis - Typhi also replicates in macrophages and spreads through the reticuloendotheilal system to liver, spleen, blood and bone marrow - Bacteremia causes the fever and may lead to localized suppurative infections or in rare cases perforation of the intestine

Answer 3

1. Ingestion 2. Incidence is greatest in children (under 5) and adults (older than 60) 3. Occurs most frequently during the summer months 4. Common food sources include poultry, eggs, dairy products, ground beef 5. Nontyphoidal US infections > 1.4 million with 600 deaths/year 6. Infectious dose is high (10^6 - 10^8 bacteria)

Answer 4

- Relative to strains causing gastroenteritis, the inoculum for Typhi is low - Transmission person to person and through fecal contamination - Enteric fever is endemic to India, South/Central America, Africa - Travelers should be vaccinated when going to endemic areas

Answer 5

PET TURTLES!

Answer 6

- S. Gastroenteritis: Symptoms - 6 - 48 hours after consumption of contaminated food (fever, cramps, headache, nausea, vomiting) - persists for 7 days but self limiting - S. Septicemia: ALL SALMONELLA SPECIES CAN CAUSE A BACTEREMIA - Immunocompromised patients at risk for septicemia - Enteric Fever: 10-14 days after ingestion - gradual fever, headache, myalgias, anorexia, rose spots - After bacteremic phase gastrointestinal symptoms occur: colonization of gall bladder and reinfection of the intestines

Answer 7

- First person identified in US as asymptomatic carrier of S. Typhi - She was a cook - infected 51 people, three of whom died - Typhoid fever was traced to the places where she worked - Arrested and quarantined She died of pneumonia and complications of a stroke

Answer 8

- Stool culture - must use selective medium to recover salmonella versus normal flora - Lactose negative, motile, makes H2S, other differential biochemical tests - Epidemiological investigations use pulsed-field electrophoresis

Answer 9

- Symptomatic relief but no antibiotics for Salmonella gastritis - Careful food preparation and storage, hand washing - Ampicillin, trimethoprim-sulfamethoxazole for systemic infections

Answer 10

Live attenuated vaccine Ty21a: good for 5yrs, 6 capsules every other day, booster at 4 yrs, not recommended for children Typhim - Vi polysaccharide capsular vaccine, not recommended for children under 2 years of age

Answer 11

- Family member of the Enterobacteriaceae (Gram negative) - Non motile (no flagella), does not ferment lactose, no capsule - Infectious dose is low, easily spread person to person by the fecal oral route - 4 recognized biogroups - dysenteriae, flexneri, boydii, sonei

Answer 12

dysenteriae, flexneri, boydii, sonei

Answer 13

1. Shigella replicate intracellularly in the colon 2. They invade M cells in Peyer patches and initially colonize the small intestine 3. Bacteria inject type III "effectors" into cells to instruct the cytoskeleton to engulf them 4. The effectors are called Invasion Protein Antigens or IpaA, IpaB, IpaC and IpaD 5. Once inside of host cells the bacterium lyses the vacuole and replicates free in the cytoplasm 6. Similar to Listeria, Shigella polymerize host actin to move to the membrane to penetrate uninfected cells 7. Shigella induce apoptosis in phagocytic cells which leads to a release of IL-1β resulting in intense inflammatory response

Answer 14

Ipa proteins - induce bacterial uptake - injected by the type III secretory system Shigella secrete Shiga toxin - Exported by a type II secretory pathway - Shiga toxin is a typical A:5B toxin *B = recognizes the host glycolipid GB3 *A = enzymatic activity of the toxin; cleaves 28S ribosomal RNA disrupts protein synthesis and colonic epithelium dies and cells and mucous are lost from the large intestine

Answer 15

Humans | Shigellosis

Answer 16

Infectious dose is low (100-200 bacteria) so person to person transmission is easy through fecal-oral route

Answer 17

``` Incubation period after ingestion 1-3 days Symptoms - Abdominal cramps - Tenesmus or straining to defecate - Diarrhea - Pus and blood in stools - Neutrophils and mucous in stool ```

Answer 18

Term coined by Hippocrates to describe the frequent passage of stool containing blood and mucous

Answer 19

- Lactose negative colonies on selective medium (colorless as opposed to pink colonies on MacConkey agar) - Shigella is NOT motile while salmonella is flagellated and motile and Shigella does not produce H2S

Answer 20

- Mild infections are usually self limiting - Antibiotic treatment may shorten illness but are only used for severe illness - Antidiarrheal agents such as loperamide or diphenoxylate with atropine can make illness worse - In presence of antidiarrheal agents, Shiga toxin is not flushed from the system, leading to more extensive cell death and inflammation

Answer 21

Family member of the Enterobacteriaceae (Gram Negative) Infectious dose is low (100-200 bacteria) - spread person to person by fecal oral route Member of the family of pathogenic E. coli

Answer 22

Culture filtrates from these bacteria were cytotoxic to Vero cells Toxic activity could be neutralized with antibodies to Shiga toxin Produce a distinct histopathology called attaching and effacing lesions EPEC = EHEC that do not synthesize Shiga toxins Alterations in the cellular cytoskeleton due to bacterial type III secretion EHEC also injects a protein called Tir Bacteria grow in place and release shiga toxin

Answer 23

EHEC protein that integrates into the mammalian cellular membrane and binds tightly to a bacterial outer membrane protein called intimin

Answer 24

``` Stx-1 = Shiga toxin Stx-2 = 60% homology to Shiga toxin (A:5B) ```

Answer 25

Stops host protein synthesis by cleaving host ribosomal RNA Binds to cell with GB3 receptor Strains expressing both toxins are more virulent Stimulate the expression of inflammatory cytokines

Answer 26

EHEC associated with certain H and C serotypes Certain serotypes may be selected for in the intestinal tract of cattle Undercooked beef, meat, cattle feces

Answer 27

Hemorrhagic colitis: Characterized by severe abdominal pain and bloody diarrhea that occurs 3-4 days after ingestion of contaminated food Hemolytic uremic syndrome (HUS): Occurs in children under 10 years of age - acute renal failure; thrombocytopenia; microangiopathic hemolytic anemia *vomiting in about 50% of patients

Answer 28

Culture - differential identification based on the inability to ferment sorbitol EHEC is colorless and normal Look for certain serotypes associated with HC or HUS Immunoassays to detect the presence of Stx-1 or Stx-2

Answer 29

Treatment consists of supportive care Monitoring of the development of microangiopathic complications (HUS) Antiperistaltic agents increase the risk of systemic complications Antibiotic therapy is generally not beneficial - may increase shiga toxin production and release Careful cooking of food

Answer 30

Gram negative curved rod Microaerophilic, can grow at 42° Non-fermentative Motile with single flagellum at one or both poles

Answer 31

C. jejuni C. upsalensis C. coli C. fetus

Answer 32

1. Inflammation - gastrointestinal infections produce histologic damage to the mucosal surfaces of the jejunum, ileum and colon 2. Infection is associated with the development of autoimmune disorders (Guillan-Barre syndrome; reactive arthritis) 3. Other than LPS and antigenic cross-reactivity, one toxin has been discovered that stops cell division - cytolethal distending toxin (cdt)

Answer 33

Infections are associated with the consumption of contaminated food, particularly chicken Not a reportable disease - difficult to grow and identify bacteria

Answer 34

Summer and early fall

Answer 35

Acute enteritis: Gastrointestinal infection characterized by bloody stools, inflammation, ulcerated mucosa, diarrhea Extraintestinal infections: C. fetus in compromised patients - resistant to serum antibody and complement killing

Answer 36

Microscopy - darting motility in fresh fecal samples - S shaped organism in stool - Presence of RBCs and WBCs in stool Antigenic detection Culture - difficult - slow growth; microaerophilic

Answer 37

Treatment recommendations - Fluid replacement as long as diarrhea lasts Severe cases are treated with azithromycin or erythromycin Severe infections include: high fever; bloody stool; symptoms lasting over 1 week

Answer 38

``` Gram negative curved rods Multiple polar flagella, highly motile Microaerophilic Produce a powerful urease enzyme that converts urea to NH3 and CO2 Difficult to culture and isolate ```

Answer 39

Gastric colonization can be lifelong so part of the pathogenesis involves survival in this extreme environment 1. Urease expression allows the bacterium to survive in acidic gastric juice 2. They swim through the mucus using flagella 3. They adhere to the gastric epithelium via specific receptors that include the Lewis blood-group Ags and laminin 4. pH at the epithelial surface is 7.0

Answer 40

Peptic ulcers; two

Answer 41

A multifunctional toxin - Forms anion specific channels - forms large vacuoles in cultured cells - alters tight junctions - induces gastric epithelial erosion in animal models

Answer 42

Second locus encodes many genes including: Specialized secretion system called a type IV secretory system This secretion system injects CagA which induces IL-8 release - also induces pedestal formation Other products also enhance IL-8 transcription in epithelial cells

Answer 43

Urease: secretion to survive in gastric juice Flagella: allows them to propel into mucus layer and to reach the gastric epithelial cells Adhesins: allow bacterium to stick to the apical region of epithelial cell

Answer 44

Reservoir: Humans only Transmission: fecal-oral route Highest Incidence: Developing countries Asymptomatic: 70-80% of infected individuals Increased risk: Persons with gastritis, gastric ulcer or duodenal ulcers Associated diseases: infection is also associated with gastric adenocarcinoma and gastric B-cell lymphomas

Answer 45

Clinical outcome depends on site of colonization Gastric Helicobacters: H. pylori; gastritis, peptic ulcer, gastric adenocarcinoma, gastric mucosa-associated lymphoid tissue (MALT) B-cell lymphomas Enterohepatic Helicobacters: Isolates from homosexual men with procititis, proctocolitis, or enteritis

Answer 46

1. Urea breathing test 2. Histologic examination of gastric biopsy 3. Biochemical detection of urease activity from gastric biopsy 4. Detection of H. pylori antigens from stool samples

Answer 47

Recommended treatment: Proton pump inhibitor + macrolide + β-lactam NO vaccine - not sure whether eradication is good

Answer 48

Structure: Gram negative curved rods Important human pathogens: - Vibrio cholerae serogroups 01 and 0139 - produce cholera toxin - Vibrio vilnificus - associated with wound infections and septicemia - Vibrio parahaemolyticus - gastroenteritis, wound infection, septicemia

Answer 49

``` Curved rods with single polar flagella Require NaCl for growth Oxidase positive Toxin co-regulated pili Serogroups are based on LPS ```

Answer 50

Serotypes O1 and O139 produce cholera toxin and are associated with epidemic disease Serotype O1 is subdivided into Classical and El Tor biotypes - Current pandemic is due to El Tor

Answer 51

Cholera Toxin is an A:5B protein Cholera toxin and Labile toxin (ETEC) are structurally and functionally similar Toxins bind ganglioside receptors on intestinal epithelial cells = GM1 The A subunit ADP-ribosylates the G protein and induces cAMP production Camp stimulates the CFTR inducing Cl- secretion, inhibiting NaCl absorption and causing water efflux - tremendous loss of water

Answer 52

TCP = Toxin coregulated pilus; used by bactera to adhere to the mucosal epithelium and used by the phage to infect the bacteria Chemotaxis proteins - also used for adherence to host epithelial cells Zona Occludens toxin (ZOT) - disrupts tight junctions Accessory cholera enterotoxin (Ace) - increases fluid secretion

Answer 53

The expression of toxins prevents the development of live attenuated vaccines

Answer 54

Vibrio grows in nature in estuarine and marine environments Pathogenic vibrios infect shellfish Asymptomatic individuals can shed the organism Cholera is transmitted by contaminated water and food Infectious dose = approximately 10^8 with normal stomach acid levels

Answer 55

2-3 days after ingestion, abrupt onset of watery diarrhea and vomiting DIarrhea becomes colorless and odorless and contains small specks of mucous = rice water stool Dehydration, cramps, metabolic acidosis Mortality rate can be 60% if untreated V. Parahaemolyticus: gastritis ranging from mild to severe V. Vulnificus: wound infection/septicemia

Answer 56

Microscopy - curved gram-negative rods in large numbers in stool material from wound infections Culture - Relatively easy to isolate in the laboratory; confirmation by a relatively small number of biochemical tests

Answer 57

1. Fluid electrolyte replacement 2. Antibiotics can reduce toxin production and decrease transmission 3. Improvements in sanitation 4. Vaccines - Formalin inactivated whole cell vaccine (IM) - Dukoral given PO - also given for travelers diarrhea due to ETEC

Answer 58

Heat and formalin killed O1 classical and El Tor strains - IgA response prevents colonization Non-toxic B subunits - IgA response prevents toxin binding

Answer 59

Cephalosporins and Carbapenems are antibiotics usually reserved to treat the sickest patients Difficult to control, can be fatal in up to 40% of cases

Answer 60

1. Enterotoxigenic E. coli (ETEC) - Labile toxin (LT‐1) and stable toxin (STa) 2. Enteropathogenic E. coli (EPEC) - attaching and effacing lesion 3. Enteroinvasive E. coli (EIEC) - like Shigella, invasive, inflammatory 4. Enteroaggregative E. coli (EAEC) - adherence, colonization 5. Uropathogenic E. coli (UPEC) - fimbrial adherence, UTI

Bacteriology of the Colon Flashcards

(85 cards)