Gastroenteritis

Question 1

Where does colonization and normal flora occur in the human body?

Answer 1

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)

Question 2

What are the micro-organisms present in oral cavity?

Answer 2

Viridans streptococcus
Candida
anaerobic gram positive
anaerobic gram negative

Question 3

What are the micro-organisms present in the large bowel?

Answer 3

Enterobacteriaceae - E.coli, klebsiella spp. , enterobacter spp., proteus spp.,
Milleri grp. streptococcus
anaerobic gram positives - clostridium, candida
anaerobic gram negative - bacterioidess

Question 4

Define virulence

Answer 4

The likelihood of causing a disease

Question 5

Steps of pathogenic infection

Answer 5

1. Exposure
2. Adhesion
3. Invasioin
4. Colonisation
5. Toxicity
6. Tissue and organ damage

Question 6

What is the common complication of E.coli 0157 infection?

Answer 6

HUS - Haemolytic Uraemic syndrome

Question 7

What is the incubation period?

Answer 7

It is the colonization phase during which the pathogens replicate in their hosts

Question 8

What is the prodromal period?

Answer 8

It is the phase during which the early symptoms and signs of the disease are presented

Question 9

What immune system component get activated in response to the following bugs?
Bacteria
Virus
Fungi
Protozoans
Worms

Answer 9

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

Question 10

What are the special features of gram negative bacteria?

Answer 10

Thin peptigoglycan layer
outer LPS layer (lipopolysachharide)
Produces endotoxins
More resistant to antibiotics
Purple on gram stain

Question 11

What are the features of gram positive bacteria?

Answer 11

Thick peptidoglycan layer
No outer LPS layer
Produces exotoxins
More susceptible to antibiotics
Violet on gram stain

Question 12

What is an enterobacteriaceae?

Answer 12

It is a gram negative rod bacteria

Question 13

Examples of lactose fermenting enterobacteriaceae

Answer 13

E.coli, Klebsiella spp., Enterobacter spp.

Question 14

Examples of non-lactose fermenting enterobacteriaceae

Answer 14

Shigella spp., salmonella spp., Yersinia spp.

Question 15

What are the features of Enterobacteriaceae?

Answer 15

Gram negative
straight rods
non-spore producing
mobile or non-mobile
facultative anaerobes
increasing resistance
ferment sugars 
oxidase negative

Question 16

What is pseudomonas?

Answer 16

It is a gram negative, glucose non-fermenting, non-lactose fermenting, oxidase positive bacilli

Question 17

Which bugs in enterobacteriaceae are non-motile?

Answer 17

Shigella and klebsiella

Question 18

What are the microbiological tests for enterobacteriaceae?

Answer 18

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

Question 19

Molecular methods to detect enterobacteriaceae

Answer 19

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

Question 20

What are the various serotyping methods used to identify enterobacteriaceae?

Answer 20

Based on the immuno-reactivity of various antigens.

i.e., cell wall (O) polysaccharides, flagella (H) proteins and other cell wall carbohydrates

Question 21

How does enterobacteriaceae cause infections?

Answer 21

1. Motility - flagella allows movement( except in shigella and klebsiella)
2. Adherence - fimbriae (shorter than flagella and helps to adhere to the tissues)
3. endotoxins - from the LPS layer which cause fever
4. enterotoxins - eg. shiga toxin

Question 22

What happen to the environmental growth characteristics as you go further down the GI tract?

Answer 22

It goes from an aerobic(upper GIT) to an anaerobic environment (lower GIT)
pH increases from 2 to 7

Question 23

What is the normal flora in the jejunum?

Answer 23

coliforms and anaerobes

Question 24

what is the normal flora in the colon(faecal flora)?

Answer 24

Large numbers of coliforms
Anaerobes
Enterococcus faecalis

Question 25

what are the common anaerobes present in the colon?

Answer 25

Clostridium spp. and bacteriodes spp.(gram negative)

Question 26

What do bacteria need to multiply?

Answer 26

Time Temperature Food source Moisture

Question 27

What does having an antibiotic dose increase your risk to?

Answer 27

Infection to C.difficile

Question 28

``` What do the following factors increase your risk to? Foreign Travel Day care exposure Recent Antibiotics Raw seafood Cruise ships ```

Answer 28

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

Question 29

Features of bacillus cereus sources disease caused management

Answer 29

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

Question 30

Features of E.coli 0157 and complications of E.coli 0157?

Answer 30

E.coli 0157 is a gram negative stain. Produces Shiga-like toxin (STEC) - toxigenic Complications - HUS ( Haemolytic Uraemic Syndrome) Renal Failure

Question 31

What are the Sources and mode of transmission of E.coli 0157?

Answer 31

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

Question 32

What is the incubation period, presentations and its duration in E.coli 0157 infections?

Answer 32

Presentations - diarrhoea blood in poo vomiting stomach cramps fever Incubation - 3-5 days Duration - 5-10 days

Question 33

What is the management for E.coli 0157?

Answer 33

Management:- NO ANTIBIOTICS NO NSAIDS NO ANTI-MOTILITY DRUGS Supportive treatment, Oral re-hydration Hygiene

Question 34

Diagnosis investigations for E.coli .

Answer 34

``` 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

Question 35

``` what are the features sources and mode of transmission disease and presentation + duration incubation period complications treatment management (next) ```

Answer 35

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

Question 36

Management of those with C.diff infection

Answer 36

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