Infections of the gastrointestinal tract

Question 1

Homeostasis of the Gut

Answer 1

Normal microbiota confined to mouth and large intestine
Stomach pH
Small intestine immunity + speed
80% of immune system is in the gut
Transfer between areas=disease

Question 2

TYPES OF FOODBORNE DISEASES

Answer 2

Food poisoning
Disease that results from ingestion of foods containing preformed microbial toxins
The microorganisms that produced the toxins do not have to grow in the host
Food infection
Microbial infection resulting from the ingestion of pathogen-contaminated food followed by growth of pathogen in the host

Question 3

CLOSTRIDIAL FOOD POISONING

Answer 3

Clostridium perfringens and Clostridium botulinum (cause serious food poisoning
Exotoxin
Botulinum toxin
Produce tough endospores

Question 4

Clostridium difficle associated disease (CDAD)

Answer 4

C. difficile is transmitted from person to person by the fecal-oral route. The organism forms heat-resistant spores that are not killed by alcohol-based hand cleansers or routine surface cleaning. Thus, these spores survive in clinical environments for long periods. Because of this, the bacteria may be cultured from almost any surface. Once spores are ingested, their acid-resistance allows them to pass through the stomach unscathed. Upon exposure to bile acids, they germinate and multiply into vegetative cells in the colon.

Antibiotics, especially those with a broad activity spectrum (such as clindamycin) disrupt normal intestinal flora. This can lead to an overgrowth of C. difficile, which flourishes under these conditions.

The use of systemic antibiotics, including (but not limited to) any penicillin-based antibiotic such as ampicillin, cephalosporins, and clindamycin, causes the normal bacterial flora of the bowel to be altered. In particular, when the antibiotic kills off other competing bacteria in the intestine, any bacteria remaining will have less competition for space and nutrients. The net effect is to permit more extensive growth than normal of certain bacteria. Clostridium difficile is one such type of bacterium. In addition to proliferating in the bowel, C. difficile also produces toxins. Without either toxin A or toxin B, C. difficile may colonize the gut, but is unlikely to cause pseudomembranous colitis.[22] The colitis associated with severe infection is part of an inflammatory reaction, with the “pseudomembrane” formed by a viscous collection of inflammatory cells, fibrin, and necrotic cells.[4]

Question 5

Salmonellosis

Answer 5

Salmonellosis is a gastrointestinal illness caused by foodborne Salmonella infection

Caused by eating food contaminated with Salmonella or handling Salmonella-infected animals
23.4 cases per 100,000 population NZ (2011)
Onset of the disease occurs 8–48 hours after ingestion
Disease normally resolves in 2–5 days but can cause septicaemia

Question 6

Campylobacter

Answer 6

Campylobacter spp are a common cause of bacterial foodborne infections in NZ
168.7 cases per 100,000 population NZ (2011)
Transmitted to humans via contaminated food
Poultry, pork, raw shellfish, or in surface waters
Campylobacter replicates in the small intestine
Causes high fever, headache, malaise, nausea, abdominal cramps, and bloody stools

Question 7

Noroviruses

Answer 7

Noroviruses are responsible for most infections for the reasons stated in this quote from the CDC USA.
Rotavirus, hepatitis A virus and astrovirus are responsible for the rest of the viral food poisoning.
Noroviruses are perhaps the perfect human pathogen. They possess essentially all the attributes of an ideal infectious agent: highly contagious, rapidly and prolifically shed, constantly evolving, evoking limited immunity, and only moderately virulent, allowing most of those infected to full recover, thereby maintaining a large susceptible pool of hosts.

Question 8

Case study: Norovirus

Answer 8

In June 2002 the Australia Capital Territory Health Protection Service commenced investigation of an outbreak of gastroenteritis in two aged-care facilities and one hospital. A particular norovirus genotype (type II) was detected in some staff and residents/patients in each of the institutions.
The outbreak lasted just over a month, in which 291 cases were identified. The attack rate in staff in each institution ranged from 43.0 - 48.6%, and in residents from 51.3 – 66.1%.