Gastroenteritis Flashcards
Where does colonization and normal flora occur in the human body?
Eyes (tears, lysozymes) Skin (structural barrier, sweat, sebum, lactic acid, propionic acid) Urinary tract (acidic urine, vaginal lactic acid, lysozyme) GI tract (stomach acidity, peristalsis, normal flora) Respiratory tract (cough and sneezing, mucus, ciliary action, phagocytes and lysozymes)
What are the micro-organisms present in oral cavity?
Viridans streptococcus
Candida
anaerobic gram positive
anaerobic gram negative
What are the micro-organisms present in the large bowel?
Enterobacteriaceae - E.coli, klebsiella spp. , enterobacter spp., proteus spp.,
Milleri grp. streptococcus
anaerobic gram positives - clostridium, candida
anaerobic gram negative - bacterioidess
Define virulence
The likelihood of causing a disease
Steps of pathogenic infection
- Exposure
- Adhesion
- Invasioin
- Colonisation
- Toxicity
- Tissue and organ damage
What is the common complication of E.coli 0157 infection?
HUS - Haemolytic Uraemic syndrome
What is the incubation period?
It is the colonization phase during which the pathogens replicate in their hosts
What is the prodromal period?
It is the phase during which the early symptoms and signs of the disease are presented
What immune system component get activated in response to the following bugs? Bacteria Virus Fungi Protozoans Worms
Bacteria - phagocytes, antibodies and B-lymphocytes, compliment
Virus - T - lymphocytes and B- lymphocytes
Fungi - phagocytes, T-lymphocytes and eosinophils
Protozoans - T-lymphocytes and eosinophils
Worms - Mast cells, eosinophils
What are the special features of gram negative bacteria?
Thin peptigoglycan layer outer LPS layer (lipopolysachharide) Produces endotoxins More resistant to antibiotics Purple on gram stain
What are the features of gram positive bacteria?
Thick peptidoglycan layer No outer LPS layer Produces exotoxins More susceptible to antibiotics Violet on gram stain
What is an enterobacteriaceae?
It is a gram negative rod bacteria
Examples of lactose fermenting enterobacteriaceae
E.coli, Klebsiella spp., Enterobacter spp.
Examples of non-lactose fermenting enterobacteriaceae
Shigella spp., salmonella spp., Yersinia spp.
What are the features of Enterobacteriaceae?
Gram negative straight rods non-spore producing mobile or non-mobile facultative anaerobes increasing resistance ferment sugars oxidase negative
What is pseudomonas?
It is a gram negative, glucose non-fermenting, non-lactose fermenting, oxidase positive bacilli
Which bugs in enterobacteriaceae are non-motile?
Shigella and klebsiella
What are the microbiological tests for enterobacteriaceae?
1.Gram stain
2. Culture/ primary isolation media -
Blood agar 18-24 hrs
McConkey agar 18-24 hrs - lactose fermentors
turn it pink
3. Cystine-lactose-electrolyte deficient (CLED)
4. Chromogenic agar
5. biochemical tests - Oxidase, Indole, Lactose
Molecular methods to detect enterobacteriaceae
MALDI-TOF (Mass SpectrometryMatrix-Assisted Laser Desorption/Ionisation - Time of Flight)
very quick
not that expensive
can discriminate btw highly genetically similar organisms
difficult to differentiate btw salmonella, species of ecoli and shigella
What are the various serotyping methods used to identify enterobacteriaceae?
Based on the immuno-reactivity of various antigens.
i.e., cell wall (O) polysaccharides, flagella (H) proteins and other cell wall carbohydrates
How does enterobacteriaceae cause infections?
- Motility - flagella allows movement( except in shigella and klebsiella)
- Adherence - fimbriae (shorter than flagella and helps to adhere to the tissues)
- endotoxins - from the LPS layer which cause fever
- enterotoxins - eg. shiga toxin
What happen to the environmental growth characteristics as you go further down the GI tract?
It goes from an aerobic(upper GIT) to an anaerobic environment (lower GIT)
pH increases from 2 to 7
What is the normal flora in the jejunum?
coliforms and anaerobes
what is the normal flora in the colon(faecal flora)?
Large numbers of coliforms
Anaerobes
Enterococcus faecalis
what are the common anaerobes present in the colon?
Clostridium spp. and bacteriodes spp.(gram negative)
What do bacteria need to multiply?
Time
Temperature
Food source
Moisture
What does having an antibiotic dose increase your risk to?
Infection to C.difficile
What do the following factors increase your risk to? Foreign Travel Day care exposure Recent Antibiotics Raw seafood Cruise ships
1.Foreign travel: diarrhea - Enterotoxigenic E.coli
South-east asia - Vibrio
S. America, Asia, Africa - Rotavirus
2. Day care exposure - Rotavirus
3. Recent antibiotics - C. difficile
4. Raw seafood - Non- cholera vibrio
5. Cruise ships - norovirus
Features of bacillus cereus
sources
disease caused
management
Gram positive, rod shaped, aerobic/ facultative anaerobic beta haemolytic bacterium.
Source:- 1) FRIED RICE syndrome - Improperly refrigerated cooked rice or meat
incubation time - 1-6 hrs
Disease:- Upper GIT severe nausea and vomiting, diarrhea and
2) Meat, stew, gravy, vanilla sauce
incubation time - 10-16 hrs
Disease:- abdominal cramps, watery diarrhea and nause
Treatment:- supportive care, oral re-hydration and rest
Features of E.coli 0157 and complications of E.coli 0157?
E.coli 0157 is a gram negative stain.
Produces Shiga-like toxin (STEC) - toxigenic
Complications - HUS ( Haemolytic Uraemic Syndrome)
Renal Failure
What are the Sources and mode of transmission of E.coli 0157?
Sources and transmission - Faceal-oral route
Raw and unpasteurised milk
Under-cooked beef/ meat
Raw leafy vegetables, unpasteurized juices
touching infected animals
Drinking contaminated water
Touching infected people and not washing
hands properly
What is the incubation period, presentations and its duration in E.coli 0157 infections?
Presentations - diarrhoea
blood in poo
vomiting
stomach cramps
fever
Incubation - 3-5 days
Duration - 5-10 days
What is the management for E.coli 0157?
Management:- NO ANTIBIOTICS
NO NSAIDS
NO ANTI-MOTILITY DRUGS
Supportive treatment, Oral re-hydration
Hygiene
Diagnosis investigations for E.coli .
McConkey agar Sorbitol McConkey agar Antisera for serotypes ELISA identifies toxins DNA of toxin genes can be identified
Bloody stool but culture negative? Sent for more specialist tests Low numbers Detection of verotxoin gene Typing to trace source
Selective culture
Sorbitol non fermenter (SNF)
E coli isolated
Check for O157 antigen
what are the features sources and mode of transmission disease and presentation + duration incubation period complications treatment management (next)
Gram positive anaerobe, spore- producing, spores which are acid resistant, produces toxin A and B
Risk + Mode of transmission - Indv. with a previous antibiotic therapy in the past 3-6 months
Risk - Old patients, PPI’s, any Ab course esp 4c’s
4 C’s - Co-amoxiclav, Cephalosporin, Ciprofloxacillin and Clindamycin
MoT- Faecal-oral route (unwashed hands of healthcare workers and others)
Presentation - Watery diarrhoea with streaks of blood
Fever
Abdominal pain and tenderness
Severe dehydration - dry mouth and tongue
High Resp rate
Low BP
High pulse rate
Complications - Toxic megacolon
Pseudomembranous colon
Perforation of the colon
Sepsis
Treatment :- Metronidazole ( PO 10 days tds)
severe- Vancomycin - (po 10 days)
+ IV metronizaol
Management of those with C.diff infection
Hygiene and infection control
Keep patient in isolated, side rooms and use PPE
Wash hands and blood tray with SOAP AND WATER , NOT GEL
As spores can only be killed by soap and water
Wash contaminated clothes, sheets and towels daily
Wash hands frequently
Clean contaminated surfaces
