Infections of the Alimentary System

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Infections of the Alimentary System
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The digestive tract
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Normal flora upper

• Many bacteria are found in the mouth.
• Many are species of streptococci

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Normal flora lower

• Bacteria (some Gram negative bacilli,
  streptococci, lactobacilli) and yeasts (Candida
  albicans) are relatively sparse in the small
  intestine.
• The large intestine however, contains many
  bacteria from _at_ 300 species (making up about 1/3
  of the weight of feces).
• The primary species are Bacteroides, and the
  coliforms (e.g., Esherichia coli, Enterobactor,
  Klebsiella, Proteus).
• These bacteria are beneficial in that they
  outcompete potential pathogens and play a role in
  vitamin metabolism.
• Yeasts (e.g., Candida albicans) and other
  bacteria that can cause disease (e.g.,
  Clostridium difficile antibiotic associated
  colitis or pseudomembranus colitis which can be
  life-threatening) are also present.

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Dental caries

• The most common infectious disease and the main
  reason for tooth decay.
• Cause- primarily S. mutans and closely related
  species.
• Dx- symptoms, clinical manifestations
• Tx fillings tooth extraction etc.
• Prevention - dental hygiene (home and twice
  yearly professional cleanings), diets low in
  sugar, use of fluoride

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Periodontal disease

• a chronic inflammatory process of the gums.
• develops over years and is one of the primary
  causes of tooth loss
• mostly asympomatic but bleeding gums,
  sensitivity, bad breath, and loose teeth occur in
  the later stages
• Brushing, flossing, professional cleanings help
  treat and prevent this so that the teeth can be
  saved for as long as possible.
• Trench mouth is a severe acute infection of the
  gums. Symptoms include fever, bleeding gums,
  pain, odor

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Herpes simplex

• Herpes simplex virus (usually type 1)
• Often begins in childhood and produces fever and
  vesicles that ulcerate. The infection then
  becomes latent with sporadic recurrences (e.g.,
  cold sores, fever blisters, herpes simplex
  labialis). It is widespread infecting up to 90
  of people and causing recurrent infections in
  20-40 of the people in the US. Symptoms
  include tingling, itching, burning or painful
  sensations. The blisters usually heal within
  7-10 days. Occasionally leads to encephalitis.
  Herpetic whitlow (a skin infection) occurs due to
  contact of open skin with saliva. Also
  infections of the eye can occur resulting in
  corneal blindness. It is transmitted by close
  direct contact or by indirect contact with
  contaminated inanimate objects (the virus can
  live for up to several hrs.)
• Dx - symptoms, tissue culture
• Tx - Acyclovir for active infections
• Prevention- sun screens help stop UV light and
  reduce relapses of herpes simplex I

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Mumps

• a paramyxovirus
• Begins with fever, loss of appetite, and a
  headache. Followed by swelling of one or both
  parotid glands with difficulty in talking and
  swallowing. Symptoms last about a week.
  Involvement of the testis (orchitis) and ovaries
  can occur in males and females past puberty.
  Spread by saliva or droplet nuclei that are
  breathed in. Humans are the only natural host.
  Serious consequences are rare sterility,
  deafness, meningitis, and encephalitis. It
  often causes miscarriage if the infected person
  is pregnant.
• DX tissue cultures and serology
• Tx- symptoms, it usually is resolved in a week
• Prevention - vaccination

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Helicobacter pylori Gastritis

• Helicobacter pylori
• This bacterium attaches to mucus-producing cells
  of the stomach resulting in a decrease in mucus
  production. This can lead to the formation of
  ulcers (65-80 of gastric ulcers and 95 of
  duodenal ulcers). Often asymtomatic. Localized
  abdominal pain, tenderness, and bleeding are
  symptoms of the complications. It produces
  urease that converts urea to ammonia resulting in
  a decrease in pH
• Dx - urease in stomach tissue, culture and
  isolation, and microscopy
• Tx - bismuth compounds and antibiotics (two kinds)

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Cholera

• Vibrio cholerae
• Symptoms include vomiting and the production of a
  secretory diarrhea (copious amounts of watery
  feces that are odorless and contain mucus AKA
  rice-water stools). World-wide morbidity is
  100,000 cases/year. The severe diarrhea (fluid
  loss can be up to 20 liters/day) can easily
  result in dehydration and then death (untreated
  mortality 55) however, with prompt fluid and
  electrolyte replacement, mortality is decreased
  to 1. The symptoms are the result of cholera
  toxin. Fecally contaminated water is the most
  common source of infection.
• Dx - symptoms, dark-field microscopy, culture and
  isolation
• Tx - fluid and electrolyte replacement and
  antibiotics
• Prevention - handwashing, proper sewage disposal,
  water purification, adequate washing or cooking
  of foods, vaccination (only 50 effective).

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Shigellosis

• Shigella species (e.g., S. dysenteriae)
• This dysentery is characterized by crippling
  abdominal cramps and diarrhea (watery stools with
  mucus and blood). There are about reported
  21,500 cases in the US/year (but probably much
  higher due to unreported cases) and about 150
  million/yr world-wide). Toxins are involved
  which produce a fever, and inflammation and
  erosion of the large intestine epithelium. One
  toxin may cause neurological symptoms and coma.
  Hemolytic uremic syndrome may also occur (when
  the strain produces shiga toxin). The ID is low
  and it is highly communicable
• Dx - culture and isolation
• Tx antibiotics
• Prevention - No vaccine, but handwashing and
  increased sanitation.

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Salmonellosis (non typhoidal enteric fever, food
poisoning, and gastroenteritis)

• Salmonella species (e.g., S. enteritidis, and S.
  typhimurium taxonomic changes have affected
  species names).
• These zoonotic infections are acquired from
  eating foods such as undercooked meats and eggs.
  There are _at_ 47,500 reported cases each year in
  the US and the actual number may be as high as 2
  million/year. Symptoms diarrhea, abdominal pain
  and vomiting. A few strains cause a more serious
  disease (entercolitis) that can lead to death due
  to intestinal rupture.
• Dx - culture and isolation
• Tx- usually self-limited (about 1-4 days)
• Prevention - adequate food handling and cooking.

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Typhoid fever.

• Salmonella typhi
• Humans are the only reservoirs for this organism
  (under natural conditions). A severe systemic
  disease that begins in the intestine progresses
  to septicemia. Symptoms fever, diarrhea,
  abdominal pain, hemorrhage, abscess formation.
  Untreated mortality is 10-15. Transmitted by
  fecally contaminated food water. Healthy
  carriers may shed as many as 10 billion bacilli/g
  of feces.
• Dx - serology and culture and isolation
• Tx antibiotics, in carriers, removal of the
  gallbladder may be necessary (where the bacteria
  multiply)
• Prevention - handwashing, adequate cooking etc.,
  two types of vaccines give partial protection

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Escherichia coli gastroenteritis

• An enteropathogenic strain of Escherichia coli
• Symptoms vary depending on the virulence of the
  species causing the infection include vomiting
  and diarrhea (mild to severe with some producing
  shiga toxin). These strains produce toxins and
  many patients develop hemolytic-uremic syndrome
  that can be fatal in the very old and the very
  young.
• Dx - culture and isolation and serology
• Tx - fluid replacement, antibiotics and if
  necessary dialysis
• Prevention - handwashing and adequate cooking of
  food.

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Campylobactor jejuni is also one of the most
common causes of bacterial gastroenteritis
worldwide (over 2 million cases in the US each
year). The disease is usually self-limited but
fluid replacement may be necessary and can be
fatal to the elderly or immunocompromised.
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Food poisoning e.g., Staphylococcal
enterotoxicosis

• Several bacterial species primarily
  Staphylococcus aureus.
• Food poisoning results from consuming toxins
  produced by bacteria found in the food (some
  toxins are heat stabile). Thus the bacteria do
  not actually cause an infection, but the toxins
  make you sick. Symptoms include nausea,
  vomiting, and diarrhea. The disease is usually
  self-limited, but it can result in dehydration
  and thus have negative consequences for the very
  young and the very old.
• Dx- symptoms
• Tx- symptoms
• Prevention - keep foods at adequately low
  temperatures. Avoid foods that have set out at
  room temperature.

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• Food poisoning can be caused by other bacteria
  and their toxins
• Gastritis can be caused by viruses as well as
  several species of bacteria
• Diarrhea can also be caused by many species of
  bacteria as well as some viruses

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• Hepatitis A food-borne
• Hepatitis B blood and body fluids
• Hepatitis C blood and body fluids
• There are other viruses that cause hepatitis, see
  notes

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Giardiasis

• Giardia lamblia
• One of the common types of travelers diarrhea
  and is very common in economically undeveloped
  areas incidence 10 Many people are
  asymptomatic, but others develop diarrhea,
  bloated abdomens, and gas. Nutritional
  deficiencies can occur in infected children.
• Dx - direct exam of feces, serology
• Tx - antiparasitic drugs
• Prevention - boil drinking water (if not
  chlorinated or filtered).

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Amebiasis or sometimes Amebic dysentery

• Entamoeba histolytica
• Humans are the primary hosts (including chronic
  healthy carriers). Morbidity may be as great as
  400 million world-wide. Mortality about 30,000
  per year worldwide. Usually asymptomatic or mild
  but in clinical cases, the amoebas secrete
  enzymes that dissolve the tissues of the
  intestine. The symptoms are then diarrhea with
  bloody, mucus-filled stools, abdominal pain,
  fever, fatigue, and weight loss. Serious
  complication such as hemorrhage and liver abscess
  formation can occur.
• Dx- direct exam of feces
• Tx - antiparastic drugs
• Prevention - hygiene and sanitation, avoid local
  water while traveling.

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Other parasites can cause diarrheal disease.

• Cryptosporidium is an intestinal parasite causing
  cryptosporidiosis (a zoonosis). Often
  asymptomatic, or with short lived symptoms of a
  stomach flu, but in immunocompromised
  individuals it can cause a life-threatening
  diarrhea (as many as 25 stools/day with a loss of
  up to 17 liters of fluid/day) that can last for
  months. There is no cure.
• Parasitic worms cause infestations in many
  persons worldwide. Ascaris lumbricoides is
  thought to infect _at_1/4 of the worlds population
  (but a small infestation may go unnoticed).
  Enterobius vermicularis (pinworms) is the most
  common worm disease of children in the temperate
  zone. This worm causes itching and discomfort at
  night when the females come out to lay eggs.
  Trichinella spiralis is acquired from eating
  undercooked meat. The females live in the
  intestine, but the larvae encyst in muscle
  tissue. Tapeworms are acquired by eating
  contaminated undercooked beef (Taenia saginata),
  pork (T. solium) or fish (Diphyllobothrium
  latum).