Chapter 25Digestive system infections

Medgar Evers College, CUNY

Bio 261

Prof. Santos

Basic anatomy of the human digestive system

IIeumof small intestine Duodenum of

small intestine

Appendix

Cecum

Ascendingportion of large intestine

Anus

Small intestine

Large intestine

Rectum

Liver

Gall-bladder

Tongue

Oral cavity

Pharynx

Esophagus

Stomach

Pyloricsphincter

Cardiacorifice

Mouth

Esophagus

Salivaryglands

Stomach

Liver

Pancreas

Gall-bladder

Large intestines

Small intestines

RectumAnus

Parotid glandSublingual gland

Submandibular gland

Salivaryglands

A schematic diagram of the human digestive system

Pancreas

• Food is pushed along the digestive tract by peristalsis– Rhythmic waves of contraction of smooth

muscles in the wall of the canal

• In the oral cavity, food is lubricated and digestion begins– And teeth chew food into smaller particles that

are exposed to salivary amylase, initiating the breakdown of glucose polymers

• The region we call our throat is the pharynx– A junction that opens to both the esophagus

and the windpipe (trachea)

• The esophagus– Conducts food from the pharynx down to the

stomach by peristalsis

• The stomach stores food– And secretes gastric juice, which converts a

meal to acid chyme

• Gastric juice– Is made up of hydrochloric acid and the

enzyme pepsin

• The lining of the stomach– Is coated with mucus, which prevents the

gastric juice from destroying the cells

• The small intestine– Is the longest section of the alimentary canal– Is the major organ of digestion and absorption

• The first portion of the small intestine is the duodenum– Where acid chyme from the stomach mixes

with digestive juices from the pancreas, liver, gallbladder, and intestine itself

• The pancreas produces proteases, protein-digesting enzymes– That are activated once they enter the

duodenum

PancreasMembrane-boundenteropeptidase

Trypsin

Active proteases

Lumen of duodenum

Inactivetrypsinogen

Other inactiveproteases

• The small intestine has a huge surface area– Due to the presence of villi and microvilli that

are exposed to the intestinal lumen

• The enormous microvillar surface– Is an adaptation that greatly increases the

rate of nutrient absorption

• The large intestine, or colon– Is connected to the small intestine

• A major function of the colon– Is to recover water that has entered the

alimentary canal

• The wastes of the digestive tract, the feces– Become more solid as they move through the

colon– Pass through the rectum and exit via the anus

Normal microbiota of the digestive system

• Different species colonize the mouth depending on their ability to attach to specific receptors.

• Dental plaque consists of many bacteria of different species attached to the teeth or each other.

• Anaerobic bacteria are also present.

Bacterial infections of upper digestive system

Disease Cause symptoms pathogenesis

treatment

Dental caries or tooth decay*incubation period is 1 to 24 months

Streptococcus mutans

Severe pain, discoloration of tooth or breakage

Glucan is produced from sucrose. This is needed for dental caries production

Restrict sugar, fluoride in toothpastesee dentist regularly

Bacterial infections of upper digestive system

Disease Cause symptoms pathogenesis

treatment

Periodontal disease

Dental plaque Bleeding, sensitive gums, bad breath, loosening of the tooth,

Bacteria produces inflammatory response, plaque forms, widens and anaerobic bacteria grow, toxins and enzymes degrade tissue

Avoid buildup of plaque and surgery if needed

Bacterial infections of upper digestive system

Disease Cause symptoms pathogenesis

treatment

Trench mouth

(acute necrotizing ulcerative gingervitis)

A spirochete of genus Treponema

Fever, painful bleeding gums, foul mouth odor

Tissue destruction, ulceration and tissue invasion by spirochete.

Antibiotic treatment

Bacterial infections of upper digestive system

Disease Cause symptoms pathogenesis

treatment

Helicobacter pylori

gastritis

H. pylori Vomiting, belching, abdominal pain and tenderness and bleeding if ulcer or cancer associated

Pathogen survives acidity of stomach, penetrates mucus, inflammatory response, thinning of mucus can occur if ulcer forms

Antibiotics and medication to suppress acid formation

H. pylori

• Gram –

• Microaerophile

• Multiple polar flagella for motility

• Produces urease to neutralize acidity of stomach

• Buries itself on the mucus layer to survive

Viral infections of upper digestive system

Disease Cause symptoms pathogenesis

treatment

Herpes HSV Type 1

Fever, sore throat, pain in lip followed by blisters

Virus replicates in the epithelium, an immune response follows, but virus hides in sensory nerves

Anti viral medication such as acyclovir, penciclovir

Viral infections of upper digestive system

Disease Cause symptoms pathogenesis

treatment

Mumps

*incubation period is 15 to 21 days

Mump virus Fever, headache, loss of appetite, painful swollen parotid glands, painful enlarged testicles, pelvic pain in women

Virus replicates in the upper respiratory tract and then travels to parotid glands, inflammatory response occurs

An effective attenuated vaccine since 1967 has been in place since then.

Bacterial infections of lower digestive system

Disease Cause symptoms pathogenesis

treatment

Cholera Vibrio cholerea

Massive diarrhea, vomiting, muscle cramps

Exotoxins that cause excessive excretion of electrolytes by the intestinal epithelium; leads to dehydration and shock

Purification of water supply, rehydration with electrolyte and glucose

mumps

• Only one antigenic type of the mumps is known.

Bacterial infections of lower digestive system

Disease Cause symptoms pathogenesis

treatment

Shigellosis Species of shigella

Fever, dysentery, vomiting headache, stiff neck, painful joints

Pathogen invades and multiplies within the intestinal epithelium

Antibiotics such as ampicillin, sanitary measures,

Bacterial infections of upper digestive system

Disease Cause symptoms pathogenesis

treatment

Gastroenteritis caused by E.coli

E. coli Vomiting and diarrhea, sometimes dysentery (crampy abdominal pain and bloody diarrhea)

Attachment, toxins, invasion of intestinal epithelium, loss of microvilli

Bismuth compound treatment, sanitary conditions, replacement of fluids loss

Bacterial infections of lower digestive system

Disease Cause symptoms pathogenesis

treatment

Salmonellosis Salmonella enterica

Diarrhea, vomiting,

Invasion and penetration of tissue, inflammatory response

No treatment unless tissue invasion then antimicrobial agent

Bacterial infections of lower digestive system

Disease Cause symptoms pathogenesis

treatment

Campylobacteriosis

Campylobacter jejuni

Diarrhea, fever, abdominal cramps, nausea, vomiting, bloody stool

Low infecting dose, pathogen multiplies within and beneath the epithelial cells, inflammatory response

Sanitary measures, and no antimicrobial treatment

Viral infections of lower digestive system

Disease Cause symptoms pathogenesis

treatment

Hepatitis A

(acute and rarely leads to long term liver or permanent damage)

Nonenveloped ss RNA picorna virus

Fatigue, fever, loss of appetite, nausea, right sided abdominal pain, dark colored urine

Viral replication and damage restricted to liver. How it gets there is still being investigated

Inactivated vaccine

Viral infections of lower digestive system

Disease Cause symptoms pathogenesis

treatment

Hepatitis B

(infected blood or body fliud/oral)

Enveloped ds DNA hepadnavirus

More severe than A, progressive liver damage, can lead to cirrhosis and cancer

HBV is carried to liver by bloodstream, attaches and invades liver cells

Combined Hepatitis A and B vaccine

Viral infections of lower digestive system

Disease Cause symptoms pathogenesis

treatment

Hepatitis C

(most commonly transmitted by sharing needles)

Enveloped ss RNA flavivirus

Few or no symptoms, progressive liver damage or cancer in 10 to 20% of cases

Liver cells are infected and replication occurs, inflammatory response occurs

No vaccine but one should avoid alcohol use and anti viral medication if needed

2 other viral infections of the lower

• 1- rotaviral gastroenteritis, most common cause of viral gastroenteritis in children and infants

• 2- noroviral gastroenteritis, most common cause of viral gastroenteritis in the USA

Protozoan infections of lower digestive system

Disease Cause symptoms pathogenesis

treatment

Giardiasis Giardia lamblia, a pear shaped protozoan

Flatulence, nausea, vomiting, diarrhea, abdominal cramps, weight loss

Host immune response to attachment of pathogen to epithelial lining

Antimicrobial medications such as atabrine or flagyl

Protozoan infections of lower digestive system

Disease Cause symptoms pathogenesis

treatment

Cryptosporidiosis Cryptosporidium parvum

Fever, loss of appetite, nausea, crampy abdominal pain, watery diarrhea lasting 10 to 14 days

Invasion of epithelial cells, inflammatory response

No effective treatment exists but sanitary conditions should be kept, pasteurization of beverages

Protozoan infections of lower digestive system

Disease Cause symptoms pathogenesis

treatment

Cyclosporiasis Cyclospora cayetanensis

Fatigue, loss of appetite, vomiting, watery diarrhea, weight loss

Very little is known

Bactrim, Septra antimicrobial agents, boil water before drinking

Protozoan infections of lower digestive system

Disease Cause symptoms pathogenesis

treatment

Amebiasis Entamoeba histolytica

Diarrhea, abdominal pain, blood in feces

Ingested cysts liberate the pathogen, reach large intestine, feed on mucus and cells lining the intestine, and sometimes they penetrate the lining by using enzymes

Metronidazole or paromomycin