Bugs causing diarrhea and food poisoning (Medbullets) Flashcards
Which organisms are transmitted via fecal oral? (10 total - CC GRREEANS)
E. coli (EHEC, EIEC, ETEC); Shigella dysenteriae, Campylobacter jejuni; Adenovirus; Norwalk virus; Reovirus; Rotavirus; Giardia lamblia; Entamoeba histolytica; Cryptosporidium
Which organisms cause watery diarrhea? (9 total)
Clostriudm perfringens; E. coli (ETEC); Vibrio cholerae; Adenovirus; Norwalk virus; Rotavirus; Giardia lamblia: Entamoeba histolytica (can cause bloody diarrhea as well); Cryptosporidium
Which organisms cause bloody diarrhea? (7 total - SEECCY)
Clostridium difficile; E. coli (EHEC, and EIEC); Salmonella enteridis; Campylobacter jejuni (Bloody and PUS); Yersinia enterocolitica; Entamoeba histolytic (can cause watery diarrhea as well)
Transmission: Custards, mayonnaise/potato salad, canned meats, foods not kept refrigerated
- Usually food handler
- Gm (+) cocci, catalase and coagulase (+)
- Growth at 7.5% NaCl, mannitol fermentation
- Reservoir: HUMAN NOSE, skin, low levels in colon and vaginal tract
- Heat stable - 100°C for 30 min
- Symptoms start and end early - (
Staphylococcus aureus
Transmission Reheated rice/pasta, food kept warm but not hot, consumption of contaminated food with soil, cooked and kept warm
- Gm (+) spore forming rod, aerobic
- Patients typically present with emetic syndrome (vomiting and nausea) about 1-5 hours after ingestion or diarrheal syndrome 15-20 hours after ingestion.
- Symptoms start and end quickly
- Emetic: Profuse vomiting, nausea, and abdominal cramps but FEVER and DIARRHEA ABSENT
- Diarrheal: heat labile toxin - 5 min 56°C or 30 min at 45°C - WATERY DIARRHEA, nausea, abdominal cramps, vomiting, fever absent (Assoc. with protein rich foods, such as meats, stews, gravies, vegetable dishes, puddings, vanilla sauce, milk)
- Can cause keratitis (inflammation of cornea); endophthalmitis (inflammatory condition of intraocular cavities); or panopthalmitis (inflammation of entire eye)
Bacillus cereus
Transmission: Canned food, home-canned alkaline vegetables (green beans, peppers, mushrooms, smoked fish) - ingestion of preformed toxin; trauma and wound infection, ingestion of spore by infants, inhalation
- Infants - gm (+) spore forming rods, strict ANAEROBE
- Incubation time: 18-72 hrs after ingesting toxin
- Causes flaccid paralysis - bilateral descending; may include abdominal pain, either diarrhea or constipation
- Neurotoxin (8 different types): Toxin A and B assoc. with canned food variety; type E assoc. with FISH PRODUCTS
- Neurotoxin absorbed from gut through blood stream, binds to presynaptic neuron and cleaves a protein involved in release of ACh at synapse (SNARE proteins - synaptobrevin and syntaxin) - leads to bilateral flaccid paralysis
Clostridium botulinum
Transmission: Reheated meat
- Gm (+) spore forming rod, anaerobic
- Ingestion of large number of bacteria grown on precooked and not refrigerated meat dishes
- Meat products, poultry, gravy
- Incubation: 8-16 hrs
- Duration: 24 hrs or less
- High infective dose - toxin acts on SMALL INTESTINE
- Enterotoxin: heat labile (like B. cereus diarrhea toxin) - INC cAMP - Watery diarrhea
- Type A strain is most infectious in humans
- Abdominal cramps, watery diarrhea, nausea, NO FEVER OR VOMITING
- Pig-Bel: DIARRHEA AND NECROTIZING ENTERITIS due to undercooked pig meat/sweet potatoes/malnutrition; assoc. with Type C that produce ß-toxin (cause necrotic lesions to progress to necrotizing enteritis)
- Assoc. with eating pork with sweet potatoes which contain heat resistant trypsin inhibitor. This protects toxin from inactivation by trypsin. Common in Papua New Guinea
- Acute abdominal pain, bloody diarrhea, vomiting, ulceration of small intestine, perforation of intestinal wall
Clostridium perfringens
Transmission: Endogenous/nosocomial (NOT food poisoning) - think hospital setting
- Bloody diarrhea
- Antibiotic associated diarrhea (AAD)
- Gm (+) rod, SPORE FORMER
- Pseudomembranous colitis
- Onset: 4-10 days after start of antibiotic, up to 2 weeks after termination
Clostridium difficile
Transmission: Undercooked meat, contaminated food, fecal-oral
- Gm (-), lactose fermenter, indole (+)
- Watery diarrhea followed by Bloody diarrhea
E. coli (EHEC - no invasion, no WBCs; EIEC - invasion + WBCs)
What is the different types of E. coli and what are their distinguishing factors? (I.e. invasive or not, etc)
EHEC (enterohemorrhagic)- no invasion, no WBCs
-EIEC (enteroinvasive) - invasion, and WBCs present
What is the different types of E. coli and what are their distinguishing factors? (I.e. invasive or not, etc)
EHEC (enterohemorrhagic)- no invasion, no WBCs, no fever
-EIEC (enteroinvasive) - invasion, and WBCs present
Transmission: Chicken products (eggs, raw chicken)
- Bloody diarrhea
- Incubation time: 6-48 hrs after consumption
- Lasts 2-7 days, spontaneously resolve
- Dx: Hektoen enteric agar - blue green colonies (non-lactose fermenter); black deposits in center of colonies (Hydrogen sulfide H2S producer)
- H2S (+)
- May enter blood stream and cause septicemia, invade brain, bone, lungs, causing meningitis, pneumonia, osteomyelitis (especially in sickle cell patients since their monocyte/macrophage are overextended in cleaning up red cell debris from the sickle disease and can’t fight the infection and contain it to the GI tract).
Salmonella enteridis
Transmission: Poultry, unpasteurized milk, fecal-oral
- Bloody diarrhea WITH PUS
- Gm (-), curved rod, motile, microaerophilic
- Grows best at 42°C
Campylobacter jejuni
Transmission: Fecal-oral
- Profuse watery diarrhea after 48 hrs followed by Bloody diarrhea
- Incubation period: 36-72 hrs
- Lasts 2-7 days, spontaneously resolves
- Gm (-) rod, non-lactose fermenter, non-motile, H2S negative
- 4 F’s: Fingers, Food, Flies, Feces
- Primarily pediatric disease (
Shigella dysenteriae
Transmission: Poultry, unpasteurized milk, fecal-oral
- Bloody diarrhea WITH PUS
- Watery diarrhea followed by FOUL SMELLING BLOODY DIARRHEA
- Intense abdominal pain, FEVER, vomiting, mimic acute appendicitis
- Gm (-), curved rod, motile, microaerophilic
- Grows best at 42°C and microaerophilic
- Toxin production, invasion of epithelial cells, survival in monocytes like salmonella
- Enterotoxin: electrolyte movement - watery diarrhea followed by inflammatory diarrhea due to invasion of epithelial cells - leads to ulcers in bowel mucosa and induces acute inflammatory response
- Self-limiting
- Guillain-barre syndrome and Reactive arthritis
- Campy-BAP or Skirrow media contain antibiotics, vancomycin, polymyxin B and trimethoprim that reduce growth of other enteric microorganisms
Campylobacter jejuni
Transmission: Seafood, sushi (leading cause of diarrhea in Japan)
Vibrio parahaemolyticus/vulnificus
Transmission: contaminated milk, pork, pet feces
- Bloody diarrhea
- Grows best at 25/22°C
- Gm (-) rod, non-lactose fermenter
Yersinia enterocolitica
Transmission: contaminated milk, pork, pet feces
- Bloody diarrhea - may last 1-2 weeks
- Grows best at 25/22°C - motile at these temps
- Gm (-) rod, non-lactose fermenter
- Enterotoxin and invasion of mucosa. Inflammation and ulceration, may extend to MESENTERIC LYMPH NODES
- Complications: Reiter’s syndrome (reactive arthritis) or peripheral joints/HLA-B27
Yersinia enterocolitica
Transmission: Fecal-oral
- Watery diarrhea
- Pediatric
Adenovirus and Norwalk virus
Transmission: Fecal-oral
- Watery diarrhea
- Infant mortalit
Rotavirus
Transmission: Fecal-oral
- Watery diarrhea
- Associated with campers/hikers
Giardia lamblia
Transmission: Fecal-oral
-Watery OR Bloody diarrhea
Entamoeba histolytica
Transmission: Fecal-oral
-Diarrhea in AIDs
Cryptosporidium
What patients are at risk of developing systemic infections from salmonella spp.? (5)
- Neonates,
- persons over 50 yrs
- immunocompromised patients
- patients with sickle cell
- patients with prosthetic valves or vascular grafts.
What is the incubation period and infective dose required for EIEC? (Enteroinvasive E. coli). What are some of the resulting symptoms (4). Where is it primarily seen?
- Incubation period: 12-72 hrs
- Infective dose: 10 organisms
- Fever, cramping, watery diarrhea may progress to dysentery
- Primarily seen in under-developed countries, rare in the US
What are the virulence factors associated with EHEC? (2)
1) Bundle forming pili (Bfp) like EPEC, attaching-effacing - wiping out of microvilli
2) Shiga-like toxin (verotoxin): inhibit protein synthesis and kills epithelial cells and endothelial cells (strain is known as STEC)
- Infective dose as small as 100 cells
What are the clinical symptoms of EHEC?
Children present with HUS following an acute diarrheal illness
- Acute onset of diarrhea, can mimic ulcerative colitis, various enteric infections or appendicitis
- Diarrhea becomes hemorrhagic (70% of cases) within 1-2 days of onset of diarrhea
- Neurologic symptoms are observed in 33% of patients and may include irritability, seizures or altered mental status
Pathogen of E. coli that cause intestinal disease: Tight adhesion and destruction of microvilli. Formation of filamentous actin pedestals or cup like structure
- Attaching and effacing - wiping out of microvilli, pedestal formation
- Bundle forming pili (Bfp); intimin
EPEC - enteropathogenic - small intestine - infant diarrhea
Pathogen of E. coli that cause intestinal disease: Involves 3 stages: (adherence (stacked bricks, ST toxin, cytolysin))
1) Adherence to mucosa
2) Enhanced mucus production that encases bacteria forming a biofilm
3) Followed by elaboration of a cytotoxin which damages the intestinal cells. Have the ability to colonize both small and large intestine.
- AAF/GVVPQ fimbriae
Enteroaggregative E. coli (EAEC) - infant diarrhea in developing countries
- Pathogen of E. coli that cause intestinal disease: Colonize the small intestine and produce a cholera-like (heat-labile, LT) toxin and a heat stable toxin (ST). Both toxins ultimately stimulate secretion of chloride by the host cells resulting in a watery diarrhea
- Type 1 pili; colonization factor antigens (CFA) and (LT)
- ST (heat stabile toxin) binds to and activates membrane guanylate cyclase receptor on epithelial cells - results in excess cGMP - blocks ion transport into cells so water moves into lumen
ETEC - enterotoxigenic - small intestine - traveler’s diarrhea
Pathogen of E. coli that cause intestinal disease: Invasive like Shigella
EIEC - enteroinvasive - large intestine - Shigellosis-like disease in developing countries
Pathogen of E. coli that cause intestinal disease: Shiga like toxin + like EPEC
-Intimin
EHEC - enterohemorrhagic - large intestine - Hemmorrhagic colitis can lead to HUS
- Gm (-) rod, non lactose fermenter, H2S producer
- Colonization of gallbladder for up to one yr of infected persons
Salmonella typhi/paratyphi
What is the clinical disease of enteric fever/typhoid fever?
Severe multi-systemic illness characterized by classic prolonged fever - potentially fatal if untreated
-First week: stepwise fever that becomes sustained (that is, the temperature does not return to the baseline), often with relativebradycardiaand usually with positive blood cultures.
Second week: abdominal pain, often (but < 50% of cases) with a rash consisting of faint salmon-colored macules on the trunk and abdomen (rose spots).
Third week:hepatosplenomegalywith, in severe cases, intestinal bleeding and/or perforation caused by erosions of Peyer’s patches. Complications include shock, stupor, delirium, seizures, psychosis, myelitis, and pneumonia.
What are the pathological changes in typhoid fever? (5)
1) Perforation wall of intestine
2) Fatty degernation of fat in cells resulting in enlarged spleen and liver, mesenteric glands, kidney, heart
3) Inflammation of gall bladder
4) Skin - ROSE SPOTS
5) DIC: thrombophlebitis - vein inflammation related to a blood clot
How would you diagnose typhoidal salmonella spp.? (3)
How would you treat it?
Dx:
1) Specimen: blood, bone marrow, urine, stool (chronic)
2) Culture: selective and differential media - Hektoen enteric agar
3) Serology/Widal test: test tube agglutination - detect antibody against specific O and H antigen in patient sera
tx: multi-drug resistance common: broad spectrum, fluoroquinolones, ciprofloxacin or ceftriaxone
Are there vaccines for typhoid? If so, how many and what are their characteristics?
- 2 types:
1) Capsular vaccine: Vi antigen
2) Live attenuated vaccine (Ty21a strain) - Taken orally can reduce risk of disease for travelers in endemic areas, but vaccine not 100% protective
What type of media are MacConkey and Eosin methylene blue (EMB)?
- Selective: only gram negatives grow
- Differential: differentiates lactose fermenters (colored colonies) from nonlactose fermenters (gray/white colonies)
What are general characteristics of Enterobacteriaceae? (8)
- All are gm (-) non spore forming bacilli (rods)
- Are facultative anaerobes and can ferment glucose
- Are OXIDASE NEGATIVE and REDUCE NITRATES to NITRITES
- Classification based on biochemical tests and antigenic properties of O antigen (LPS), capsular, and flagellar antigen
- Share common enterobacterial antigen - core saccharides of O antigen
- Biochemical differentiation is based on carbohydrate fermentation and activity of amino acid decarboxylases
- Culture on differential media that contain special dyes may alow rapid presumptive identification
- Ability to ferment lactose can be detected on media like MacConkey and Eosin methylene blue agar (EMB)
How do you interpret a triple sugar iron agar? (TSI)
Interpretation:
- If lactose and or sucrose is fermented, large amount of acid is produced/ both butt and slant become yellow
- If glucose is fermented, less acid produced and turns the color (yellow) only in the butt
- If none of them is fermented, no acid is produced (meaning the organism is strict aerobe)
How do you serotype enterobacteriaceae? Give an example
Three antigens are important in serotyping this group: O, K, H antigens
1) They all possess LPS as a prominent toxin - the terminal sugars of LPS, O somatic antigen is useful in id
2) Some species possess a K (CAPSULAR) or Vi (virulence) antigen
3) If motile, the flagellar or H antigens
ex: A strain of E. coli with O55:k9:H6
- somatic O55
- Capsular K9
- Flagella H6
What are some properties that differentiate E. coli from other lactose fermenters? (4)
1) Production of indole from tryptophan
2) Decarboxylates lysine
3) Use of acetate as sole carbon source
4) It is motile
What are the E. coli strains that cause noninflammatory diarrhea (in small intestines - remains lumenal) (3)
-Lactose fermenter, gm (-), most common anaerobe in GI tract
1) Enterotoxigenic E. coli (ETEC) - travelers and infant diarrhea in developing countries
2) Enteropathogenic E. coli (EPEC)
3) Enteroaggregative E. coli (EAEC)
What are the E. coli strains that cause INFLAMMATORY diarrhea? (2)
1) Enterohaemorrhagic E. coli (EHEC)
2) Enteroinvasive E. coli (EIEC)
