Intra-abdominal Infections I (Dr. Neely)

• Virulence factors
• Motility - Single flagella, "vibrating" or "fast-moving"
• Adherence - Pili
• Mucinase
• Toxin - Cholera toxin, AB type, stimulates AC
• Etiology/Pathogenesis
• Rapid onset, 2-3 days after inoculation
• Vomiting and massive watery diarrhea 
• Dehydration and electrolyte loss
• Transmission
• Fecal-route
• Carriers
• Avoid eating raw oysters
• Clinical ID
• Stool 
• TCBS medium
• Oxidase + Test
• O Antigen Markers

• Virulence factors
• Adhesion - "colonizing factors"
• Pili
• Exotoxins - Heat labile toxin (LT) is an AB toxin, Heat stable toxin (ST)
• Etiology/Pathogenesis
• Contaminated food and drinks
• Highest incidence in tropics and young children
• Incubation period = 1-2 days
• Vomiting, weakness, dizziness, nausea, abdominal pain, watery diarrhea
• Transmission
• Fecal-Oral route
• Clinical ID
• ELISA
• Agglutination tests for presence of toxins
• DNA probes for LT or ST genes

• Virulence factors 
• "Bundle-forming pilus"
• "Effacement"
• Type III secretion
• Etiology/Pathogenesis
• Dehydration and electrolyte imbalance
• Fatal
• Malabsorptive diarrhea
• Transmission
• Fecal-oral route
• Daycare centers
• Always remember to wash hands!
• Clinical ID
• ELISA
• Multiplex PCR

• Virulence factors
• Botulinal toxin, AB type
• Etiology/Pathogenesis
• Highly heat resistant
• Food, infant, wound botulism
• No diarrhea
• Prolonged recovery period 
• Blocks presynaptic release of ACh
• Transmission
• Fecal-Oral
• Clinical ID
• Anaerobic Gram+, spore-forming bacillus
• Grow in oxygen-free lab environment
• Immuno assay for toxin in food, gastric substances or blood

• Virulence factors
• Enterotoxin
• Heat stable toxins 
• Etiology/Pathogenesis?
• Projectile vomiting, Nausea
• Stimulates neural receptors
• Diarrhea less common, no fever or chills
• Transmission
• Fecal-oral 
• Clinical ID
• Coagulase test, Catalase test, Beta-hemolytic test, Susceptibility test

• Emetic (vomiting) form
• Virulence factors
• Heat stable enterotoxin
• Etiology/Pathogenesis
• Rapid onset
• Short incubation period, 1-6 hours
• N/V, abdominal cramps 
• Transmission
• Ingestion of fried rice that has been cooked and left at warm temperatures for several hours
• Diarrheal form
• Virulence factors
• Heat-labile enterotoxin
• Etiology/Pathogenesis
• Slow onset
• Severe abdominal cramps and diarrhea
• Activates inetstinal AC and causes intestinal fluid secretion
• Transmission
• Ingestion of meat or vegetable-containing foods that has been cooked and left above room temperature for several hours

• Virulence factors
• Enterotoxin Type A
• Etiology/Pathogenesis
• Abdominal cramps and watery diarrhea without fever, nausea, or vomiting
• Transmission
• Ingestion of temperature abuse of prepared food

• Virulence factors
• Flagellated enteric protozoan - motility and attachment
• Adhesion to upper small intestine
• Etiology/Pathogenesis
• Incubation period of 7-10 days
• Watery diarrhea, abdominal cramps, bloating, flatulence, weight loss
• Chronic diarrhea with weight loss is less common
• Transmission
• Ingestion of food or water contaminated with cysts
• Clinical ID
• Microscopic exam of stool, duodenal aspiration, or duodenal biopsy
• Antigen test for G. lamblia in stool
• String test

• Etiology/Pathogenesis
• Severe, watery, prolonged diarrhea in immunocompromised patients
• Mild diarrhea in immunocompetent patients
• Transmission
• Fecal-oral route
• Ingestion of oocysts in contaminated water
• Clinical ID
• Small coccidian protozoan parasites

Obligate intracellular, spore forming protists

Prolonged diarrhea (up to 7 weeks) and is more severe in AIDS patients

• Giardiasis, cryptosporidiosis and microsporidiosis
• Diarrhea without blood or leukocytes
• Infects entire intestines
• More severe in AIDS patients

• Virulence factors
• Enterotoxin - Toxin A, accumulation of viscous, bloody fluid
• Cytotoxin - Toxin B, disrupts actin polymerization and cytoskeletal architecture, decreases cellular protein synthesis
• Etiology/Pathogenesis
• "Antibiotic associated colitis"
• Asymptomatic, mild diarrhea or pseudomembranous colitis
• Transmission
• Endogenous or nosocomial
• Clinical ID?
• Spore-forming, anaerobic, Gram+ rod
• CCFA selective medium
• EIA test on stool

• Virulence factors
• Adhesins - binds to mucosal cells
• Toxins - Shiga toxin, AB type toxin
• Type III secretion
• O, H, and K antigens
• Etiology/Pathogenesis
• Colonize the intestinal tracts of cattle (other farm animals)
• Small number of organisms can cause infection
• Incubation period: 3-4 days
• Severe abdominal pain, copious watery, bloody diarrhea with little or no fever
• Transmission
• Ingestion of contaminated meat, milk, or apple cider
• Avoid eating rare or "bloody" hamburger meat
• Clinical ID
• Serotype O157:H7 does not ferment sorbitol
• Serogroup with specific anti-O157:H7 serum
• Cytoxic activity with Vero Cells
• DNA probe for detection of Shiga-toxin genes

• Virulence factors
• Invasion - Attach to M cells on apical surface
• Type III secretion
• "Actin-based" motility
• Bacillary dysentery, invasion of intestinal mucosa
• Etiology/Pathogenesis
• Cause inflammatory response - loosening of tight junctions, follow PMNs between cells and make their way to basolateral surface
• Spread from cell-to-cell
• Remains at mucosal layer
• Bacillary dysentery (blood and mucus in stool)
• Highly infectious
• Serogroups - Group A (S. dysenteriae) is largest producer of toxin, Group B (S. flexneri), Group C (S. Boydii), Group D (S. sonnei) is most common
• Multiply in small intestine
• 0-12 hrs: abdominal pain, cramping, and fever
• 12-72 hrs: No longer detectable in upper intestine, fever decreases, but pain becomes more severe and localizes to lower quadrants
• Transmission
• Person-to-person
• Clinical ID
• Non-motile Gram- bacilli
• Lactose negative colonies on MacConkey or Hektoen selective media
• Oxidase negative
• Serotyping of groups

Similar to Shigella, but does not produce any Shiga toxin; spreads cell-to-cell

• Virulence factors
• Adherence and Invasion - invades M cells and epithelial cells 
• Type III secretion - actin rearrangement, "ruffling" of mucosal membrane, engulfed and multiply inside vesicle
• Endotoxin - Lipid A of LPS, invades and causes systemic infection
• O and H antigens
• Etiology/Pathogenesis
• Large inoculum needed
• Replictates inside vacuole of mucosal cells
• Gastroenteritis, bacteremia, enteric fever (typhoid fever)
• Exits cells via basolateral side and is picked up by macrophages (and dendritic cells), entering the blood stream
• Systemic/Septic
• Transmission
• Ingestion of food (poultry meat or eggs) that is contaminated with eggs, eating "raw" cookie dough
• Clinical ID
• Motile, facultative anaerobic, non-spore forming, Gram- bacilli
• Gastroenteritis - stool cultures
• Bacteremia - blood and stool cultures
• Typhoid fever - blood culture (early stage), Stool culture (late stage)

• Virulence factors
• Flagella
• Enterotoxins, endotoxins (LPS) and cytotoxins
• Protein S - capsid
• Autoimmune-mediated attack against nerve tissue
• Etiology/Pathogenesis
• ID of 500-1,000,000
• Fever, malaise, abdominal pain and cramps
• Profuse watery and/or bloody diarrhea, mucosal inflammation
• Incubation period: 1-7 days
• Variety of syndromes
• Transmission
• Ingestion of contaminated chicken, milk or water
• Clinical ID
• Small motile, non-spore forming, comma-shaped, Gram- bacilli
• Oxidase positive
• Gastroenteritis - stool smear
• Selective medium culture 
• Microaerophilic and capnophilic

• Transmission - Ingestion of contaminated food
• Virulence - Invades intestinal cells, produces heat stable cytotoxin, halophilic ("salt loving")
• Location prevalence - Japan

• Enterocolitis is most common Yersinia enterocolitica infection
• Etiology/Pathogenesis
• Bloody diarrhea, fever, abdominal pain
• Duration: 1-2 weeks
• Mesenteric lymphadenitis, most common in children
• Transfusion-related septicemia, grows at lower temperatures and can multiply to toxic levels in refrigerated blood stored for sevral weeks
• Transmission
• Ingestion of contaminated food, water or blood products from livestock, rabbits, and rodents

• Virulence factors
• Cyst stage
• Trophozoite stage
• Adherence to luminal surface of bowel
• Proteolytic (Cytolytic) enzymes
• Etiology/Pathogenesis
• Found worldwide
• Life cycle: ingestion of cyst and breakdown of cyst wall in small intestine > trophozoites colonise colon > erosion of colonic mucosa beginning at base of crypts > trophozoites may enter venules of colon wall and be carried to liver and lead to amebic liver abscess
• Transmission
• Ingestion of cysts
• Clinical ID
• Microscopic exam of stool
• Irregular shedding of organisms in stool
• Cyst and/or trophozoite ultra-structure

• Virulence factors
• Urease, converts urea to ammonia and carbon dioxide
• Flagella
• Cytotoxin and mucinase
• Etiology/Pathogenesis 
• Stomach colonization
• Duodenal and gastric ulcers
• Chronic Type B Gastritis, may progress to gastric adenocarcinoma
• Transmission?
• Fecal-oral route
• Clinical ID
• Small Gram-, microaerophilic, curved bacilli
• Enriched medium in 6-8% oxygen at 37 degrees Celsius
• Incubation period: 3-7 days
• Gastric biospy for culture
• Urease test (CLOtest)

• Virulence factors?
• Bacterial surface protein (internalin)
• Listeriolysin O (LLO)
• Actin-mediated motility
• Lipoteichoic acid (LTA)
• Etiology/Pathogenesis?
• Decreased motility at room temperature and non-motile at 37 degrees Celsius
• Ubiquitous in nature
• Highest infection rate in infants, or in patients with lypmhomas, AIDS, organ transplantations, or those receiving corticosteroid therapy
• Pregnant women account for about 30% of all cases
• Incubation period: 11-70 days
• Crosses mucosal barrier and enters bloodstream through M cells
• Transmission?
• Ingestion of contaminated soil, decaying vegetation and fecal flora of animals, raw foods
• Clinical ID?
• Small, facultatively anaerobic, non-spore forming
• Catalase positive, oxidase negative, beta-hemolytic, Gram+ bacillus

• C. botulinum
• B. cereus
• S. aureus

C.B.S.!

• V. cholerae
• B. cereus
• E. coli (ETEC, EHEC)
• C. perfringens

V.B.E.C.!

• Etiology/Pathogenesis
• Larval stages passes through lungs, adults inhabit lumen of small intestine
• Asypmtomatic in low infestation, or may experience GI upset, colic or loss of appetitie
• Heavy infection the adults ball up in small intestine and cause  obstruction
• Very common, found worldwide
• Transmission
• Ingestion of viable eggs from contaminated soil or food

• Etiology/Pathogenesis
• Worldwide distribution
• Most commone helminth
• Lives in cecum
• Female deposits eggs at night in the perineal area
• Severe itching of the perianal area
• Transmission
• Fecal-oral route

• Etiology/Pathogenesis
• Infects 24% of world's population
• Larvae pass through lungs, adults live in small intestines
• Withdraws up to 0.2 ml of blood/day
• Necator is found in worldwide tropics and N. America
• Ancylostoma is found in temperate zones
• Transmission
• Through skin from infected soil or from drinking contaminated water

• Etiology/Pathogenesis
• Adult is 3-10 meters in length
• Inhabits small intestine
• Worldwide distribution 
• Transmission
• Ingestion of uncooked beef

• Etiology/Pathogenesis? 
• Inhabits small intestine
• Invade gut wall and migrate to various tissues
• Can cause cysticerocosis
• Transmission?
• Ingestion of uncooked pork

• 1) Stomach acid
• 2) Bile salts
• 3) Rapid flow through the small intestine
• 4) Secretion of sIgA
• 5) CD4+ T cells
• 6) Macrophages
• 7) Dendritic cells
• 8) Production of mucus

Enterobacteriaceae

Campylobacteriaceae

Vibronaceae

Pseudomonadaceae

Water gets reduced; cytochrome C gets oxidized

Pinkish-red

Clear

• Oxidative
• Use oxygen as terminal electron acceptor
• Fermentative
• Use an element other than oxygen as a terminal electron acceptor
• Inert
• Do not produc acid from carbohydrates

A) E. coli B) Shigella C) V. cholera

H) C. botulinum E) B. cereus F) S. aureus

E) G. lamblia H) C. parvum

Ingestion of cysts (ID <10) > trophozoites released in duodenum > attachment via sucker disk > reproduction via binary fission > may revert to cyst and shed in stool

• Gastroenteritis
• Most common form
• Mild diarrhea to fulminate, low grade fever, N/V/D
• Incubation period: 8-48 hrs
• Abrupt onset
• Duration: 2-5 days
• Blood cultures (-)
• Stool cultures (+)
• Bacteremia
• RARE, develops after gastroenteritis, high spiking fever, maybe GI symptoms (not common), 2nd infection can occur anywhere
• Incubation period: variable
• Onset and duration are variable
• Blood cultures (+)
• Stool cultures (-)/(+)
• Enteric fever (Typhoid fever)
• Most severe Salmonella infection
• Infection cycle: invade macrophages in lamina propria > replicate in membrane-bound vacuoles > reticuloendothelial system, blood stream > other organs > re-enter intestinal tract > sepsis develops after 10-14 days > intetstinal symptoms develop after re-entry into intestinal tract
• Incubation period: 7-20 days
• Insidious onset
• Gradual increase in fever then hits a plateau
• Duration: weeks
• Early sonstipation; late diarrhea
• Blood cultures (+) at weeks 1 and 2
• Stool cultures (-) early stage, (+) late stage