Pathology of bacterial infections in the GI system

Question 1

Cell type in intestine responsible for Absorption

Answer 1

Enterocyte

Question 2

Cell type in intestine responsible for Antimicrobial proteins

Answer 2

Paneth cell

Question 3

Cell type in intestine responsible for Mucus production

Answer 3

Goblet cell

Question 4

Cell type in intestine responsible for microorganisms, particles and macromolecules uptake and transfer

Answer 4

M cell

Question 5

Cell type in intestine responsible for regulation of
intestinal motility, secretion, appetite etc

Answer 5

Neuroendocrine cell

Question 6

3 Mechanisms of Diarrhoea

Answer 6

1. Secretory
2. Osmotic
3. Inflammatory

Question 7

Mechanisms of secretory diarrhoea induced by bacterial toxins

Answer 7

Secretory diarrhea from bacterial toxins involves adenylate cyclase activation, raising cAMP levels, stimulating ion secretion, and inhibiting absorption, resulting in watery diarrhea and electrolyte imbalance.

Question 8

Mechanisms of malabsorption diarrhoea due to bacterial overgrowth

Answer 8

Excessive growth of bacteria in the small intestine, disrupting normal nutrient absorption. Mechanisms include bacterial fermentation of carbohydrates, bile acid deconjugation, mucosal damage, and competition for nutrients, leading to impaired absorption of nutrients and water, resulting in diarrhea with characteristic features such as steatorrhea (excess fat in stool) and nutrient deficiencies.

Question 9

3 Consequences of diarrhoea

Answer 9

Dehydration
Electrolyte depletion and imbalance
Metabolic acidosis

Question 10

What do endotoxins do

Answer 10

Stimulate macrophages and endothelial cells to secrete proinflammatory cytokines and nitric oxide.
Cause cell dysfunction and lysis.

Question 11

What do exotoxins do

Answer 11

Inhibit biochemical pathways within a cell.

Question 12

E.coli mechanism of action

Answer 12

Adhere to microvilli on intestinal epithelium
Cl- secretion from enterocytes causing Secretory diarrhoea

Question 13

Salmonella mechanism of action

Answer 13

bacteria survive within macrophage phagolysosomes
Toxins interfere with closure of Chloride channels  secretory diarrhoea

Question 14

Salmonellosis – pathogenesis of infection

Answer 14

M cells in intestinal epithelium> macrophages in lamina propria
and Peyer’s patches >transferred to mesenteric lymph nodes >via portal circulation to liver

Question 15

Peracute Septicemic Salmonellosis

Answer 15

Multisystemic vascular lesions with fibrinoid change, thrombosis and necrosis
Disease of calves, foals and pigs – younger animals most sensitive
Usually fatal in animals 1-6 months of age

Question 16

Signs of Peracute Septicemic Salmonellosis

Answer 16

petechiation and blue discolouration (cyanosis)
of ventral abdomen, extremities (ears commonly affected)

Question 17

Peracute Septicemic Salmonellosis cause of death

Answer 17

Disseminated intravascular coagulation (DIC)

Question 18

Acute Enteric Salmonellosis mostly affects….

Answer 18

Horses

Question 19

Pathogenic effects of Acute Enteric Salmonellosis

Answer 19

Interference with Chloride channels = Secretory diarrhoea
induction of enterocyte apoptosis + recruitment of neutrophils
endotoxins = vascular thrombosis

Question 20

Button ulcers are commonly caused by

Answer 20

Chronic Enteric Salmonellosis

Question 21

Lawsonia intracellularis mostly infects

Answer 21

Swine

Question 22

Swine clinicopathological presentations

Answer 22

Porcine Proliferative Enteropathy (PPE)
- Porcine Intestinal Adenomatosis (PIA)
- Necrotic enteritis
- Proliferative Haemorrhagic Enteropathy (PHE)

Question 23

Diagnosis of Lawsonia intracellularis

Answer 23

ELISA (serum) L. intracellularis specific IgG
(indicating exposure to infection rather than active disease)

PCR on faeces L. intracellularis DNA
(indicating active infection with faecal shedding)

Distinctive gross PM findings

Immunohistochemistry

Question 24

Bacteria that causes suppurative bronchopneumonia in foals and ulcerative colitis

Answer 24

Rhodococcus equi

Question 25

Mechanisms of Clostridial disease

Answer 25

1. Local effects of toxins on the mucosa- haemorrhagic, fibrinous or necrotic enteritis
2. Secretory effects of locally acting enterotoxin- diarrhoea and minor mucosal lesions
3. Systemic absorption of (entero)toxins- affects sites distant from the gut

Question 26

Causes of massive expansion of enteric populations of clostridia

Answer 26

Changes in the enteric microenvironment
- change in feed, abnormally nutrient-rich digesta – CHO dumping
- antibiotic therapy
- altered pancreatic exocrine function or trypsin inhibitors
- reduced intestinal motility
- primary infections (CPV-2 in dogs or Coccidiosis in piglets & chickens)

Question 27

Focal symmetrical encephalomalacia (FSE) Pulpy kidney disease is caused by…?

Answer 27

Cl. perfringens type D enterotoxaemia

Question 28

Haemorrhagic canine gastroenteritis is caused by….?

Answer 28

Clostridium perfringens type A

Question 29

Necrotising-haemorrhagic enteritis in foals / enterocolitis in adult horses is caused by…?

Answer 29

Clostridium perfringens type A

Question 30

Potomac Horse Fever (Equine Monocytic Ehrlichiosis) is caused by ..?

Answer 30

Neorickettsia risticii

Question 31

Idiopathic Inflammatory Bowel Disease (IBD) pathophysiology

Answer 31

Villus blunting (and possible alteration of superficial epithelium)
Variable crypt dilation (filled with mucus and cellular debris)
Possible crypt epithelial hyperplasia
Inflammatory cell infiltration in lamina propria (and variably intraepithelial)

Question 32

Breeds predisposed to IBD

Answer 32

Basenji
German Shepherds
Boxer (see GCB)
Irish Setter- enteritis associated with familial hypersensitivity to wheat protein

Question 33

Diagnosis of Inflammatory Bowel Disease (IBD)

Answer 33

Endoscopic biopsies
Diagnostic pathology approach & work up
Histological assessment (revised WSAVA standards / other algorithms)
Differential diagnosis with intestinal lymphoma small cell (EATCL-2)
Immunohistochemistry