Watery Diarrhea

Intestinal Infections

-caused by E.coli begin with mild watery diarrhea - duration of diarrhea is limited to a few days - with EIEC and EHEC, a dysenteric illness follows - EHEC disease often also includes vomiting, this is followed in 1 to 2 days by intense abdominal pain and bloody diarrhea. - resolution usually takes place over a 2-10 day period. - HUS about 10% of cases of EHEC hemorrhagic colitis, primarily in children - disease begins with oliguria, edema, pallor, progressing to the triad of microangiopathic hemolytic anemia, thrombocytopenia, and renal failure - often life -threatening, requiring transfusion and hemodialysis for survival

Cholera Epidemiology

-cholera is endemic in Indian subcontinent and Africa - Virulent V. cholerae now lurks in coastal waters throughout this hemisphere and in the drinking water of locales with poor sanitation

Campylobacter pathogenesis

-colonization of the intestinal mucosa - enter cells in endocytotic vacuoles - association between C jejuni infection and Guillain-Barre syndrome, an acute demyelinating neuropathy - mechanism is believed to involve antibody elicited by C. jejuni the cross-react.

Enterobacter diagnosis

-culture -MacConkey agar is commonly used -E.Coli and Klebsiella typically ferment lactose --> producing pink colonies; - salmonella and shigella -> do not

Vibrio, Campylobacter, helicobacter

-curved gram negative rods includes vibrio cholerae, helicobacter, and campylobacter -PUD caused by H pylori -Campylobacter jejuni is one of the most common causes of diarrhea

C. diff manifestations

-diarrhea is common side effect of antimicrobic treatment - may be mild or watery or bloody and accompanied by abdominal cramping, leukocytosis, and fever - PMC progresses to severe, occasionally lethal, inflammation of colon seen by colonoscopy

Campylobacter enteritis

-diarrhea may be watery or dysenteric, with blood and pus in the stool -most patients are febrile -illness resolves spontaneously after a few days to 1 week

C. diff treatment

-discontinuing implicated antimicrobic usually results in resolution of clinical symptoms - patients are severely ill or fail to respond to drug withdrawal, they should receive metronidazole or vancomycin administered orally

E.coli clinical capsule

-enterotoxigenic (travelers diarrhea) and enteropathogenic E.coli strains produce a watery diarrhea ***** enterohemorrhagic strains produce a bloody diarrhea -> most dangerous - enteroinvasive strains may cause dysentery with blood and pus in the stool -diarrhea is usually self-limiting after only 1 to 3 days - enterohemorrhagic E.coli are an exception, with life-threatening manifestations outside GI tract

Cholera Prevention

-epidemic cholera, a disease of poor sanitation, does not persist where treatment and disposal of human waste are adequate - good sanitary conditions do not exist in much of the world, secondary local measures such as boiling and chlorination of water during epidemics are required

Gastroenteritis

-episode begins 1 to 2 days after ingestion, with nausea and vomiting followed by abdominal cramps and diarrhea - diarrhea usually resolves spontaneously within 7 days - fever is present in about 50% of patients

EnteroINVASIVE E.coli (EIEC)

-essentially mild version of shigellosis - infections are primarily seen in children younger than 5 years living in developing nations

Norovirus epidemiology

-family and community outbreaks - particularly a major issue in closed settings -common in older children and adults - fecal-oral transmission - consumption of contaminated water, uncooked shellfish, and other foods

Salmonella treatment

-fluid and electrolyte replacement and the control of nausea and vomiting -antibiotic therapy is usually not appropriate -use of antimicrobial agents in S enterica gastroeneteritis is restricted to those with severe infections or underlying risk factors (especially children)

Clostridium difficile bacteriology

-gram positive rod readily forms spores - ability to produce toxins - two distinct large polypeptide toxin, A and B, are released during late growth - A toxin causes cell rounding and disruption of intercellular tight junctions followed by altered membrane permeability and fluid secretion - B toxin has cytotoxic potency

Salmonella clinical capsule

- "food poisoning" from picnics, prepare poultry, salads - one to two days after, develop abdominal pain, nausea, vomiting and diarrhea lasting for 3 or 4 days - bloody diarrhea

Cholera Toxin

- A and B subunits - B unit binds to a receptor found on the cell surface - target of toxic A1 subunit is a guanine nucleotide (G) protein, Gs - Cholera toxin catalyzes the ADP ribosylation of the G protein - causes hypersecretion of chloride, potassium, bicarb, and associated water molecules out of the cell

Clostridial food poisoning

- C. perfingens can cause food poisoning if the spores of an enterotoxin-producing strain contaminate food - common in developed countries and is third among food-borne illnesses in the US

Enterobacteriaceae bacteriology

- O antigen: lipopolysaccharide (LPS) - K antigen: well defined capsule - H antigen: motile strains with flagella - many have surface pili (fimbriae) *O,K, and H have many serotypes - E.coli O157:H7, cause of numerous food-borne outbreaks -genera containing the species most virulent for humans are Escherichia, Shigella, Salmonella, Klebsiella, Yersinia - salmonella and shigella species are not considered normal flora

Salmonella epidemiology

- S. enterica gastroenteritis is predominantly a disease of industrialized societies and improper food handling -food preparation practices that allow growth of the bacteria -40,000 to 50,000 cases per year - peak in summer and fall - children less than 5 years old, persons aged 20 to 30 and those older than 70 - nursing homes, hospitals, mental health facilities, and other institutions - chronic carriers who are food handlers

treatment of E.coli

- acute uncomplicated UTIs are often treated empirically - trimethoprim/sulfamethoxazole (TMP-SMX) of fluoroquinolones are used for this purpose - most E.coli diarrheas are self-limiting, rehydrating, and supportive measures - EHEC with hemorrhagic colitis and HUS, hemodialysis or hemapheresis - treatment with TMP-SMX or fluoroquinolones reduces the duration of diarrhea in ETEC, EIEC, and EPEC infection -use of antimicrobial agents is contraindicated when EHEC is suspected -antimotility agents are not helpful

enteroaggregative E.coli (EAEC)

- associated with protracted (more than 14 days) watery diarrhea occasionally with blood and mucus - seen in infants and children in developing countries

e.coli pili

- bind to D-mannose residues commonly present on epithelial cell surfaces and thus mediate binding to a wife variety of cell types

Bacteremia and Metastatic infection

- can be associated with bacteremia - Salmonella infection in patients with AIDS is common and often severe. -Bacteremia can cause septic shock and death -Salmonella infection of the bone typically involves the long bones; in particular, sites of trauma, sickle cell injury, and skeletal prosthesis are at risk

Camylobacter treatment

- cases of campylobacter infection are usually not treated unless the disease is severe or prolonged (lasting longer than 1 week) - C. jejuni is typically susceptible to macrolides and fluoroquinolones but resistant to beta-lactams

Causes of Staphylococcal food poisoning

- characteristically, the food is moist and rich (red meat, poultry, creamy dishes)

Clostridium perfringens bacteriology

- clostridia are large, spore-forming, gram-positive bacilli - clostridia have spores that are resistant to heat, desiccation, and disinfectants - they are able to survive for years in the environment and return to the vegetative form when placed in a favorable milieu - it grows overnight under anaerobic conditions, producing hemolytic colonies on blood agar - growth C perfringens is accompanied by the production of large amounts of gas, which can also be produced in necrotic tissues; hence the term gas gangrene (cultures vary considerable, small to medium, grey-yellow and translucent)

C. perfringens diagnosis

-based ultimately on clinical observations -bacteriologic studies are adjunctive

Cholera pathogenesis

- colonization of the intestinal tract from jejunum to the colon by V cholerae - outstanding feature of V cholerae pathogenicity is the ability of virulent strains to secrete cholera toxin

Vibrio

- curved, gram-negative rods found in saltwater - V. cholerae is prototype cause of a water-loss diarrhea -> Cholera

diagnosis rotavirus

- detection of virus particles or antigen in the stools

C. diff diagnosis

- direct detection of toxins in the stool has largely replaced culture for diagnostic purposes - C. diff is only pathogen for which detection of its toxin has become routine

enteroPATHogenic E.coli Epidemiology

- disease seems to have disappeared in industrialized nations - in developing countries throughout the world, EPEC account for up to 20% of diarrhea in bottle-fed infants younger than 1 years old

Campylobacter manifestations and diagnosis

- illness typically begins 1 to 7 days after ingestion, with fever and lower abdominal pain that may be severe - these are followed within hours by dysenteric stools - illness is typically self-limiting after 3 to 5 days but may last 1 to 2 weeks - diagnosis is confirmed by isolation of the organism from the stool - required a special medium made selective for campylobacter -plates must be incubated in a microaerophilic atmosphere

Salmonella pathogenesis

- invasion of enterocytes accounts for the diarrhea - process usually remains localized - some invade more deeply, reaching bloodstream and distant organs -some serotypes (choleraesuis) invade rapidly, isolated from the blood

Staphylococcal food poisoning

- is one of the most common food-borne illnesses in the world - if food isnt refrigerated for hours between preparation and serving, the staphylococci are able to multiply and produce enterotoxin in the food - because of the heat resistance of the toxin, toxicity persists even if the food is subsequently cooked before eating - ingestion of staphylococcal enterotoxin - contaminated food results in acute vomiting and diarrhea within 1 to 5 hours - there is prostration, but usually no fever - recovery is rapid, except sometimes in the elderly and in those with another disease

epidemiology of rotavirus

- outbreaks are common, cooler months, 1 to 24 months old - older children and adults can be affected too - outbreaks among elderly, institutionalized patients

Causes clostridial food poisoning

- outbreaks usually involve rich meat dishes such as stews, soups, or gravies, that have been kept warm

Cholera Fluid Loss

- outpouring of fluid and electrolytes is greatest in the small intestine - diarrheal fluid can amount to many liters per day with high potassium and bicarb concentrations -result is dehydration (isotonic fluid loss), hypokalemia (potassium loss), and metabolic acidosis (bicarb loss)

Campylobacter epidemiology

- over 2 million cases occur each year in the US - low infecting dose of C. jejuni - only a few hundred cells - bacteria are transmitted to humans by ingestion of contaminated food or by direct contact with pets

Alpha-hemolysin

- pore-forming cytotoxin, -causes leakage of cytoplasmic contents and eventually cell deat

C. perfringens prevention

- prevention of gas gangrene is surgical debridement of traumatic injuries as soon as possible - prevention of food poisoning involved good cooking hygienes and adequate refrigeration

Diagnosis of E.coli

- readily isolated in culture - in UTI's readily detectable by Gram stain - EHEC, O157:H7 serotype typically fails to ferment sorbitol

GI Viruses: general features

- rotaviruses, caliciviruses, astroviruses, and some adenovirus serotypes ("enteric" adenoviruses) - brief incubation periods - fecal-oral spread - and production of vomiting and diarrhea

rotaviruses

-40-60% of acute gastroeneteritis occurring during the cooler months in less than 2 years of age - deaths in the US are rare

Labile toxin (LT)

-AB toxin - A subunit catalyzes the ASP-ribosylation of a regulatory G protein - result is secretion of water and electrolytes into bowel lumen

EnteroTOXIgenic E.Coli Epidemiology (ETEC)

-ETEC cause traveler's diarrhea in visitors to developing countries -transmission is by consumption of food and water contaminated

Enterobacter manifestations

-UTIs are manifested by dysuria and urinary frequency, bladder -fever and flank pain, kidney -most common is E.Coli

C. difficile pathogenesis

-altercation of colonic flora with antimicrobics (particularly ampicillin, cephalosporins, and clindamycin) - most strains produce both toxins, enterotoxic properties of A toxin seems to dominate watery diarrhea cases - PMC, colonic mucosa is studded w inflammatory plaques, which may coalesce into a overlying "pseudomembrane" composed of fibrin, leukocytes, and necrotic colonic cells. (looks yellow and gross and lots of growths and stuff)

Prevention of E.coli

-avoiding uncertain water, ice, salads, and raw vegetables is a wise precaution when traveling in developing countries -chemoprophylaxis against traveler's diarrhea is not routinely recommended -cooking meat all the way through is sensible

Cholera Diagnosis

-bacteriologic diagnosis is accomplished by isolation of V vholerae from the stool - its isolation is enhanced by a selective medium (thiosulfate-citrate-bile salt-sucrose agar) -once isolated, the organism is readily identified by biochemical reactions

Enterobacteriaceae

-gram-negative rods -most common cause of urinary tract infections and diarrhea - spread to the bloodstream causes gram-negative endotoxic shock - most are lower in the GI tract of humans and animals

Campylobacter Jejuni

-grows well only on enriched media under microaerophilic conditions. - requires oxygen at reduced tension (5-10%)

C. perfingens manifestations

-incubation period of 8 to 24 hours followed by nausea, abdominal pain, and diarrhea -no fever -rare vomiting - spontaneous recovery usually within 24 hours

intestinal infections

-inflammatory diarrhea called dysentery with white blood cells (WBCs) and/or blood in the stool - watery diarrhea in which fluid loss is the primary feature - systemic - enteric (typhoid) fever caused by salmonella ser typhi

Cause of campylobacter

-most common source -> undercooked poultry

E.coli manifestations

-most common symptoms are UTIs are dysuria and urinary frequency - if infection ascends the ureters to produce pyelonephritis, fever, and flank pain are common and bacteremia may develop.

Campylobacter

-motile, curved, oxidase-positive, gram-negative rods - polar flagella - often attached at their ends giving pairs "S" shapes or a "seagull" appearance - C. Jejuni is most common

rotavirus treatment and prevention

-no specific treatment -replacement of fluids and electrolytes -rotaviruses HIGHLY infectious - 2006 -> vaccine, its efficacy has been excellent, no safety concerns have arisen

Cholera Treatment

-oral and/or intravenous administration of solutions of glucose with near physiologic concentrations of sodium and chloride and higher than physiologic concentrations of potassium and bicarb -doxycycline shortens the duration of diarrhea and magnitude of fluid loss

C. difficile epidemology

-presents in stool 2-5% of general population -recognized through associated with antibiotic associated diarrhea (AAD) - in US alone, over 300,000 cases are reported each year - in simple diarrhea following antimicrobial administration, this organism is responsible for app 30% of cases - as the disease progresses to colitis, association is stronger rising to 90% if the pseudomembranous colitis (PMC) is present

V. vulnificus

-produce cellultitis in wounds sustained in seawater -produces a bacteremic infection after ingestion of raw seafood, common in Florida - also a scavenger of host iron stores and produces disease in persons with iron-overload states (thalassemia, hemochromatosis)

Cholera clinical capsule

-produces the most dramatic watery diarrhea known - intestinal fluid pour out in voluminous bowel movements; this eventually leads to dehydration and electrolyte imbalance

Causes of Salmonella

-raw milk -chicken/eggs -turtles

Salmonella bacteriology

-single species, Salmonella enterica, with serotypes - S. enterica serovar tymphimurium -> causes gastorenteritis - S. enterica serovar Typhi -> typhoid fever - salmonellae possess multiple types of pili - most strains are motile, flagella

Clostridial food poisoning pathogenesis

-spores of some C. perfringens strains are often particularly heat-resistant and can withstand temperatures of 100 degrees for an hour or more - spores that survive initial cooking can convert to vegetative form and multiple when food is not refrigerated or rewarmed - after ingestion, enterotoxin is released into upper GI tract, causing fluid outpouring in which the ileum is most severely involved.

Cholera manifestations

-stools quickly become watery, voluminous, almost odorless, and contain mucus flecks, giving it an appearance called rice-water stools -can lead to extreme dehydration, hypotension, and death within hours if untreated

Causes of E.coli

-uncooked foods such as salads or marinated meats (beef) and vegetables

Norovirus (calcivirus)

-vomiting and diarrhea -usually 1 to 2 days - electron microscopy in stools - EIA and PCR methods - no specific treatment - fluid and electrolyte replacement

rotavirus manifestations

-vomiting, followed by frequent, copious, watery, brown stools - in severe cases, stools may become clear - fever, usually low grade - severe dehydration

Meningitis

E.coli is one of the common causes of neonatal meningitis; many features of which are similar to group B streptococcal disease

6 bacterial infections causing blood diarrhea

EHEC EIEC Campylobacter Salmonella Shigella Yersinia

E.coli

ferment lactose rapidly and produce indole (pink)

Squirts

alot of pus and not much volume (shigellosis)

Shiga toxin (Stx)

is an AB toxin, released by multiple E.coli and Shigella strains - A subunit blocks protein synthesis, leading to cell death - causes the most intense abdominal pain

Opportunistic Infections

may follow ruptured intestinal diverticulum, trauma, or involve a generalized impairment of immune function

Runs

more water and salts

Immunity of E.coli

travelers from industrialized nations have much higher attack rate than adults living in the endemic area