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Microbiology of The Gut - Coggle Diagram
Microbiology of The Gut
Normal Intestinal Microbiota
Characteristics
More bacteria further into the digestive tract you go
Role of Normal Flora
Nutrient Metabolism
Carbohydrate metabolism: SCFA, Protein metabolism, Lipid metabolism, Synthesis of vitamin K, Conversion of bile acids, Conversion of polyphenols
Antimicrobial protection
Antimicrobial protein synthesis, Induction of local immunoglobulins
Immunomodulation
Role in innate and adaptive immune system, maturation of dendritic cells, normal GALT development, Development of Th1, Th17 and colonic Treg cells
Integrity of gut barrier and structure of GI tract
Maintenance of desmosomes in villi, Intestinal microvasculature
Stability of Bowel Microbiota Maintained by
Gastric Acid, Intestinal motility, Anatomical integrity, Intestinal mucosal immunity, pancreatic and biliary secretions
Gastroenteritis
Mechanisms
Acquisition may be, food borne, water borne, person to person
Non-Inflammatroy Causes
Enterotoxins, Viruses: Disrupt absorptive/secretory process without mucosal destruction or inflammation
Inflammatory Causes
Cytotoxin: EAEC, EHEC, C Diff, adher to mucosa, activate cytokines, stimulate mucosa to release inflammatory mediators
Invasive Organisms: Salmonella, shigella, campylobacter, produce cytokines, and invade intestinal mucosa to induce inflammatory response
Pathophysiology
Inflammation of gut related to an infection
Pathogens
Viruses
Organisms
Norovirus
Affects all people, common in winter months, fecal/oral transmission, highly contagious, acute onset and acute offset
Rotavirus
Common cause of severe gastroenteritis, incidence has decreased since introduction of vaccine, fecal/oral transmission, highly, incubation 1-3 days
Astrovirus,
More common in winter, fecal to oral transmission
Adenovirus,
Usually in young children, fecal oral transmission, may have fever/respiratory symptoms
CMV, Enterovirus
Mechanism
Infect enterocytes in villous epithelium of small bowel, transudation of fluid and electrolytes into intestinal lumen
Bacteria
Enterotoxins
Made by certain species that adhere to mucosa without invading, impair absorption without causing inflammation, and cause secretion of electroltyes and water (stimulation of adenyl cyclase)
Examples: Vibrio Cholerae, Enterotoxin of E.Coli
Cholera Characteristics
Inhibits GTP to GDP -> Increase Adenyl Cyclase -> cAMP -> decrease Na+ absorption and increase Cl- secretion -> Watery diarrhea
Exotoxins
Produced by bacteria and ingested in contaminated food
Causes acute nausea, vomiting, diarrhea
Examples: S. Aureus, Bacillus Cereus, Clostridium perfinges
Cytotoxins
Bacteria adhere to mucosa -> Activate cytokines (inflammatory) -> Inflammatory diarrhea
Examples: E. Coli, C Diff
Mucosal Invasion
Bacteria invade mucosa in small and large intestine, disrupt structure, cause ulcerations, bleeding, exudation of protein rich fluid, secretes electrolytes and water
Impairs absorption and secretion
Diarrhea is inflammatory (WBCs, RBCs, Gross Blood)
E. Coli
Mechanism
Plasmid Adhesins, invasins, and microvillus disrupting proteins
Shigella
Agent for dysentery, disease where there is poor sanitation
Affects secretory proteins, and leads to apoptosis of macrophage, survial of bacteria, and inflammation
Salmonella Typhi
Entrance, macrophage uptake, mesenteric lymph node, spleen/liver -> Gall bladder -> Peyers patch ulcer
Risk Factors
Consumption of Contaminated food/water
Alteration in host flora
Antibiotics, decrease in gastric activity, diet, hospitalization, age
Alteration in host defense
Loss of gastric acidity, IgA, Malnutrition
Symptoms
Nausea, Vomiting, abdominal pain/discomfort, decreased appetite, diarrhea, fevers, malaise, myalgias, Dehydrations
Investigation
Stool virology, Culture, ova/parasites, C diff,
Treatment
Supportive care (rehydration), Treatment for certain infections
C.Diff
Characteristics
Gram +ve, anaerobic, spore former, enterotoxin, cytotoxin, binary toxin
Types
Healthcare onset, community onset, hospital associated, community onset
Risk Factors
Age, Hospitalization, antibiotic exposure, chronic condition, immunocompromised status, feeding devices, PPI exposure
Transmission
Person - Person, Exposure to contaminated surface
Pathogenesis
Alteration of microbial environemnt, cytotoxin and enterotoxin
Presentation
Watery diarrhea, bloody diarrhea, symtpomatically unwell, asymptomatic
Diagnosis
Test if >3 unformed stools, Toxin B detection by nucleic acid or by enzyme immunoassays
Treatment
Vancomycin (125 mg QID) or flagyl (200 mg BID)
Vanco + Taper if recurrent
Prevention
Limit antibiotics, limit spread (infection control), Wash hands with soap + water