BMD 330 Chapter 23 - Infectious Diseases Manifesting in the Gastrointestinal Tract Flashcards

Mouth, Pharynx, Esophagus, Stomach, Small Intestine, Large Intestine, Rectum, and Anus

Salivary Glands, Liver, Gallbladder, and Pancreas

• Layer of mucus coating intestinal surfaces
• Secretory IgA
• Peristalsis keeps microbes moving
• Saliva (includes lysozyme, lactoferrin)
• Stomach (has extremely low pH)
• Bile is antimicrobial
• GALT (gut-associated lymphoid tissue) - Includes Peyer's patches and isolated lymphoid follicles

• Dominated by bacterial species
• Methane-producing archaea
• Fungi (Candida albicans is the most common)
• Few protozoa species
• Virome is still being studied

• Consists of 200 different species
• Most common types belong to Firmicutes (Streptococcus, Staphylococcus, Clostridium, and Bacillus species)

• The large intestine is known to have billions of microorganisms (10^11)
• Includes bacteria, fungi, and several protozoa

Accessory organs (salivary glands, pancreas, liver, gallbladder) are free of normal biota

• Protective function
• Teach immune system to react properly to microbial antigens
• Aid digestion and provide nutrients that we cannot produce ourselves

True; When the gut microbiome loses its diversity, deviations from gastrointestinal -- and systemic -- health can occur. Disruptions may come from antibody treatment, illness, pregnancy, or dietary changes.

Oral Cavity

rest of the GI tract

• Most common infectious disease of human beings
• Dissolution of the tooth surface due to the metabolic action of bacteria (results in minor to complete disruption of enamel; destruction of deeper layers can result in infection of the pulp)

Streptococcus mutans and S. sobrinus

Blood vessels and nerves

Lactic Acid

• Incidence of dental carries varies according to carbohydrate consumption, oral hygiene, and genetic factors
• Streptococci produce sticky polymers of glucose, called fructans and glucan, aiding in the formation of plaque biofilm

The bacteria forms a biofilm (can be made of multiple bacteria and some fungi) called plaque which is usually fuzzy.

Gingivitis

• Swelling
• Loss of normal contour
• Patches of redness
• Increased bleeding

• Development of spaces or pockets between tooth and gingiva
• Disease extends into the periodontal membrane and cementum
• Deeper involvement increases the size of pockets, causes bone resorption, and tooth loss

• Presence of Methanobrevibacter oralis
• Behavior (lack of flossing will put you at risk)
• Genetic influences
• Tooth position
• Presence of mineralized plaque called calculus

Necrotizing Ulcerative Gingivitis; Necrotizing Ulcerative Periodonitis

NUP is associated with advanced bone destruction

Necrotizing Ulcerative Gingivitis and Periodontitis

• Severe pain, bleeding, pseudomembrane formation, and necrosis
• NUP is associated with advanced bone destruction

Mumps

Paramyxovirus (A single-stranded RNA virus)

• Fever, nasal discharge, muscle pain, malaise
• Followed by inflammation of the salivary glands, producing swelling of cheeks

At the angle of the jaw

2-3 weeks

True

• Can invade other organs: testes, ovaries, thyroid glands, pancreas, meninges, heart, and kidney
• Occurs in 20%-30% of young adult males where infection localizes in the epididymis and testes; does not cause sterility.

• It causes cell to cell fusion, causing giant cells that are multi-nucleated.
• A virus-infected cell is modified by the insertion of proteins called HN spikes into its cell membrane. The HN spikes immediately bind an uninfected neighboring cell, and in the presence of another type of spike called F spikes, two cells permanently fuse.
• A chain reaction of multiple cell fusion then produces a syncytium with cytoplasmic inclusion bodies, which is useful for diagnostic.

Gastritis

Gastric or Peptide Ulcers

Bloody stools, vomiting, or both

Worse at night, after eating, or under conditions of psychological stress

Helicobacter pylori

Gram-Negative; Rod

Clarithromycin

Oral-Oral; Fecal-Oral

H. pylori

• This test is a noninvasive method in which patients ingest urea that has radioactive tag on the carbon molecule. If Helicobacter is present, the bacterium's urease breaks down the urea and the patient exhales the radioactively labeled carbon.

False; Acute diarrhea can occur with or without vomiting.

Diarrhea is defined as 3 or more loose stools in a 24 hour period.

• In the United States: average of 1.2 to 1.9 cases per person per year
• A third of cases are transmitted by contaminated food
• In tropical countries, children experience more than 10 episodes per year
• More than 700,000 children die from diarrhea per year, mostly in developing countries

Salmonella

Gram-Negative

• H - flagellar antigen
• K - Capsular antigen
• O - Cell wall antigen, the polysaccharide portion of LPS

• They ferment glucose with acid and sometimes gas; and most of them produce hydrogen sulfide (H2S) but not urease.
• Grow readily on most laboratory media and can survive outside the host in inhospitable environments, such as freshwater and freezing temperatures.
• Resistant to chemicals such as bile and dyes, which are the bases for isolation on selective media.

They are acid producers

• Causes a variety of diseases resulting in 1 million cases and 400 deaths a year
• Salmonellosis - Enteric fever or gastroenteritis (can range from mild gastroenteritis such as vomitting, diarrhea, and mucosal irritation to fever and septicemia)
• Typhoid fever - Produced by a specific Salmonella; Salmonella enterica serotype Typhi
• Ability to cause disease is dependent on its ability to adhere to the gut mucosa (has a high ID50; many organisms have to be ingested for disease to result)

The only prevention for salmonellosis is avoiding contact with the bacterium.

Endotoxin

Gram-Negative; Straight Rod

Motile; Nonmotile

Unable to form endospores and produce unrease or H2S

Shigella dysenteriae

Diarrhea containing blood

• Frequent, watery stools, fever, and intense abdominal pain
• Nausea and vomiting are common
• Dysentery
• Mucus from GI tract will also be present in stools

Shigella dysenteriae

Parasite; Bloody Diarrhea

This most severe form is primarily common in the Eastern Hemisphere. It is uncommon in the United States.

• Shigella invades the villus cells of the large intestine rather than small intestine.
• Not as invasive as Salmonella and does not perforate the intestine or invade the blood

It enters the intestinal mucosa by means of lymphoid cells in Peyer's patches. Once in the mucosa, Shigella instigates an inflammatory response that causes the extensive tissue destruction.

Fever

Affects the entire GI tract, damages the mucosa and villi, and gives rise to bleeding and secretion of mucus

is responsible for more serious damage to the intestine as well as systemic effects; it interrupts protein synthesis in its target cells

Localized to the intestines

• Another shiga toxin producer
• Some common signs and symptoms are those GI problems, and very rarely, sometimes you can see hemolytic uremic syndrome
• Toxins are identical to shiga toxins produced by Shigella

Ingestion of undercooked beef and other contaminated foods and beverages

Severe hemolytic anemia that can cause kidney damage and failure

Campylobacter

• Frequent watery stools, fever, vomiting, headaches, and severe abdominal pain
• Symptoms may last longer than 2 weeks and recur

Curved or Spiral Gram-Negative with polar flagella

These tend to be microaerophilic inhabitants of the intestinal tract, genitourinary tract, and oral cavity of humans and animals

Ingestion of contaminated beverages, food, water, milk, meat, and chicken

Guillain-Barre syndrome

• Leading cause of acute paralysis in the US (good news is that many patients recover completely)

• Rehydration and electrolyte-balance therapy
• Azithromycin in severely affected patients
• Prevention depends on rigid sanitary control of water and milk supplies and care in food preparation

Clostridioides difficile is a gram-positive, endospore-forming rod

True; It was once considered relatively harmless but now is known to cause a condition called pseudomembranous colitis, also known as antibiotic-associated colitis.

Pseudomembranous colitis is known as a antibiotic-associated colitis because in many cases, this infection is precipitated by therapy with broad-spectrum antibiotics. --> Major cause of diarrhea

necrosis in the wall of the intestine --> in more severe cases the colon is inflamed and gradually sloughs off loose, membranelike patches called pseudomembranes consisting of fibrin and cells --> if not stopped, perforation of the cecum and death can result

Diarrhea (in some severe cases, it can cause abdominal cramps, fever, and leukocytosis)

• Withdrawal of antibiotics, replacement of fluids
• Fidaxomicin or vancomycin
• Fecal transplant

Curved rod with a single polar flagellum

• Fermentative
• Grow on ordinary or selective media containing bile at 37 degrees Celsius
• Possess unique O and H antigens and other membrane receptor antigens

Outbreaks of cholera are expected to happen after natural disasters, war, or large refugee movements

Class and El Tor

• Vomiting
• Copious watery feces, "rice-water stool"
• Profuse water loss (so you get really dehydrated and that gives you hypotension --> get tachycardia --> go into shock)
• Loss of blood volume, acidosis, potassium depletion, muscle cramps, severe thirst, flaccid skin, and sunken eyes; convulsions and coma in young children
• Hypotension, tachycardia, cyanosis, shock
• 55% to 70% mortality rate

Produces cholera toxin which disrupts the normal physiology of intestinal cells, causing them to shed large amounts of electrolytes into the intestine

• Cholera toxin
• Uses quorum sensing to regulate the expression of virulence factors

Warm, monsoon, alkaline, and saline conditions

Oral Rehydration Therapy

Rita Cowell helped reduce the amount of cholera in endemic areas, where she helped understand cholera could be found in dormant water and the water can be filtered using sari's.

Cholera toxin

True; These infections are called vibrioses.

V. vulnificus and V. parahaemolyticus

• Increased consumption of raw oysters
• Increased awareness; more people are diagnosed
• A warming climate increases the microbe's habitats

Protozoa

• The oocyst form is resilient and can immediately infect
• Once inside the intestines, the oocytes releases sporozytes that attach to the epithelium of small intestines where it will live inside. It will eventually make more of these protozoa that are released into the gut and release through the stool to infect others
• The symptoms are similar to other gastroenteritis, and these are very resistant to chlorine and other disinfectants
• Symptoms include headache, sweating, vomiting, severe abdominal cramps, and diarrhea

Swimming pools

• Double-stranded RNA with an inner and outer capsid
• Primary cause of morbidity and mortality resulting from diarrhea

Fecal-Oral Route, including contaminated food, water, and fomites

• Via oral replacement therapy
• RotaTeq and Rotarix are live attenuated vaccines

Norovirus; It has a low infectious dose (1 to 20 viruses)

Profuse, watery diarrhea for 3 to 5 days, vomiting in the early stages, mild fever

• Fecal-Oral transmission or via contamination of food and water
• Many outbreaks associated with cruise ships

• Food poisoning is nausea and vomiting accompanied by diarrhea, often companions that shared a meal suffer the same fate
• Symptoms are caused by exotoxin (therefore, sometimes thought of as an intoxication rather than infection)
• Occasionally comes from nonmicrobial sources such as fish, shellfish, or mushrooms
• This is acute diarrhea with vomiting caused by exotoxins

• Staphylococcus aeureus exotoxin
• Bacillus cereus exotoxin
• Clostridium perfringens exotoxin

Staphylococcus aureus

• Thrives due to high salt tolerance
• Enterotoxin is heat stable and induces symptoms of cramping, nausea, vomiting, and diarrhea
• Onset within 1-6 hr, recovery within 24 hours
• Self-limiting, antibiotics are warranted

Bacillus cereus exotoxin is gram-positive bacterium that lives in the soil.

• Emetic (vomiting) from frequently tied to fried rice that has been cooked and kept warm for long periods of time
• Diarrheal form associated with cooked meats or vegetables held at a warm temperature for long periods of time (profuse, watery diarrhea that lasts about 24 hours)

Clostridium perfringens exotoxin is also the causative agent of gas gangrene.

• Contaminates meat, fish, and beans that have not been cooked thoroughly enough to destroy endospores
• Endospores germinate in foods, C. perfringens cells enter the small intestine and release exotoxin
• Abdominal pain, diarrhea, and nausea in 8 to 16 hr
• Also causes enterocolitis similar to that caused by C. difficile

• Diarrhea that lasts longer than 14 days
• Can have an infectious or noninfectious cause; Irritable bowel syndrome (can be caused by microbiota or genetic), ulcerative colitis
• Microbes in this section cause chronic diarrhea in otherwise healthy people

• Associated with chronic disease, particularly in children
• Adheres to human cells in aggregates rather than single cells
• Stimulates large amounts of mucus in the gut
• Transmission through food and water

• Emerging protozoan pathogen; numerous outbreaks in United States and Canada
• Fecal-oral transmission from fresh produce and water
• Oocytes can be visualized when feces is exposed to UV light
• Only infectious when sporulated oocyst are ingested
• Symptoms: watery diarrhea, stomach cramps, bloating, fever, and muscle aches

• Giardia intestinalis
• Giardia lamblia

Protozoa

• Symmetrical heart shape with organelles positioned in such a way that it resembles a face with four pairs of flagella emerging from the ventral surface

• Diarrhea of long duration
• Abdominal pain
• Flatulence
• Greasy and malodorous stools

In Giardia duodenalis, the presence of this protozoa leads to malabsorption of fat in the digestive tract. Usually results in significant weight loss

True

• Beavres
• Cattles
• Coyotes
• Cats
• Human Carriers

Although trophozoites and cysts escape in the stool, cysts play a greater role in transmission. Giardia cysts can survive for 2 months in environment and are usually ingested with water and food or swallowed after close contact with infected people or contaminated objects.

False; Giardiasis can be difficult to diagnose because the organism is shed in feces only intermittently.

Epidemics can be traced to water from mountain streams as well as chlorinated municipal water.

False; No human vaccine is available. Avoiding drinking from freshwater sources is the major preventive measure. The agent is killed by boiling, ozone, and iodine; however, the amount of chlorine used in municipal water supplies does not destroy the cysts.

Entamoeba is an amoeba that are widely distributed in aqueous habitats.

The Entamoeba histolytica has a relatively simple life cycle that alternates between trophozoite that is motile by means of pseudopods and a smaller, compact, nonmotile cyst.

• Trophozoite lacks most of organelles and has a single nucleolus called karyosome.
• The mature cyst is encased in a thin yet tough wall and contains four nuclei as well as chromatoidal bodies, which are actually dense clusters of ribosomes.

• Secrete enzymes that dissolve tissues
• Exist in intestinal and extraintestinal forms
• Humans are primary hosts; infection through food and water contaminated with cysts

• Initial targets are cecum, appendix, colon, and rectum
• Actively penetrates deeper layers of mucosa leaving ulcers
• Dysentery along with abdominal pain, diarrhea, fever, and weight loss
• Can lead to hemorrhage, perforation, appendicitis, and amoebomas
• Goes to intestine

• Amoeba invade the viscera of the peritoneal cavity invading the liver
• Goes to the liver

Hepatitis is the inflammatory disease of the liver:

• Necrosis of hepatocytes
• Response by mononuclear white blood cells that swells and disrupts the liver architecture
• Interferes with excretion of bile pigments and causes bilirubin to accumulate in blood and tissues, causing jaundice (yellowing of the skin and eyes)

• Non-enveloped, single-stranded RNA enterovirus
• Signs and symptoms include subclinical or vague flu-like symptoms, fever, nausea, abdominal pain, dark urine -- may have jaundice (in only about 10% of the cases)
• Transmitted via fecal-oral, associated with deficient personal hygiene and lack of public health measures
• Vaccine is available, but if contracted, bed rest and plenty of fluid are key for management
• There is no cure

• Enveloped DNA virus (able to integrate)
• Signs and Symptoms: Fever, chills, malaise (usually asymptomatic), abdominal discomfort, diarrhea, and nausea; rashes and arthritis may occur; cause of hepatocellular carcinoma
• Transmitted by minute amounts of blood (sexual, parental, and vertical)
• Vaccine is available, but there is no cure
• Vaccine is important for health care workers and students, patients receiving multiple transfusions, immunodeficient persons, and cancer patients
• No cure
• 4-6 weeks to see positive test

• Enveloped RNA virus
• Silent epidemic: 3.5 million Americans infected
• Transmission via blood transfusions and needle sharing
• Signs and symptoms include fever, fatigue, loss of appetite, nausea, vomiting, abdominal pain, dark urine, and juandice
• About 2 weeks for a positive test and symptoms
• No Vaccine
• Two drug regimen: Sofosbuvir (a nucleotide analog that “fools” the RNA polymerase of the virus) and simeprevir (a protease inhibitor)

Eosinophilia is a hallmark of helminthic infection

• Specialized mouthparts for attachment and feeding, enzymes to liquefy and penetrate tissues, and cuticle for protection from host defenses
• Definitive host: Host in which the adult worm reproduces sexually

• Eosinophilia
• Discovery of eggs, larvae, or adult worms in stool or tissues

• No vaccines available
• Regular treatment with antihelminthic drugs
• Proper sewage disposal
• Avoiding using human feces as fertilizer
• Disinfection of water supply
• Thoroughly washing and cooking vegetables and meats
• Freezing foods

Enterobius vermicularis

Pinworm

Enterobius vermicularis is a life cycle A type.

The hallmark of Enterobius vermicularis is anal itching

The infection is not fatal and most cases are asymptomatic. When one member of the family is diagnosed, the entire family should be tested and/or treated because it is likely that multiple members are infected.

Trichuris trichuria is whipworm and is life cycle A.

In the Trichuris trichuria, humans are the sole host.

In the tropics and subtropics that have poor sanitation

3,000 to 5,000

• Localized hemorrhage of the bowel
• Dysentery
• Loss of muscle tone
• Rectal prolapse (can be fatal in children)

Diphyllobothrium latum is a tapeworm disease in which humans are definitive host and fish are intermediate host.

• Can be transmitted via sushi and sashimi
• Also transmitted in the Great Lakes, Alaska, and Canada
• Symptoms include abdominal discomfort or nausea, anemia

Hymenolepsis species includes small tapeworms and its life cycle is C. There are two species Hymenolepis nana and Hymenolepsis diminuta.

• Hymenolepsis nana - Dwarf tapeworm
• Hymenolepsis diminuta - Rat tapeworm

Cysticerosis

Tapeworm

Cysticercosis occurs when humans ingest tapeworm eggs rather than infected meat

Life Cycle C

Distributed worldwide, but concentrated in areas where humans live in close proximity with pigs or eat undercooked pork

Liver fluke

vomiting, diarrhea, hepatomegaly, and bile obstruction if infected with a large number of flukes

Mammals

Fasciola hepatica

Liver

Schistosoma masoni and S. japonicum

• Morphologically and geographically distinct
• Similar life cycles, transmission methods, and disease manifestations
• Can invade intact skin

• Itchiness in the area where the worm enters the body, fever, chills, diarrhea, and cough
• Chronic infection: hepatomegaly, liver disease, splenomegaly
• Bladder obstruction, and blood in the urine
• Can cause a granulomatous response in the nervous system and heart

• Pathogenesis and virulence factors:
• Parasite coats its outer surface with proteins from the bloodstream, cloaking itself from the host defense system
• Diagnosed through identifying eggs in urine or feces
• Cycle of infection cannot be broken as long as people are exposed to untreated sewage
• Praziquantel is the drug of choice

D

• Gram-Positive
• Causes Dental Caries

• Gram-Negative
• Causes Gastritis/Gastric Ulcers

• Gram-Positive, Endospore-Forming Bacteria
• Causes antibiotic-associated diarrhea

• RNA Virus
• Causes "Infectious" Hepatitis

• DNA Virus
• Causes "Serum" Hepatitis

• RNA Virus
• Causes "Serum" Hepatitis

• Helminths - Trematodes
• Causes Schistosomiasis

• RNA Virus
• Causes Acute Diarrhea

• RNA Virus
• Causes Mumps

• Protozoa
• Causes Chronic Diarrhea

• Helminths - Nematodes
• Causes intestinal distress

• Helminths - Cestodes
• Causes Cysticerosis ( Formation of sacs of fluid (cysts) to form in your body)
• Pork tapeworm

• Helminths - Trematodes
• Causes liver and intestinal disease

• Gram-Negative
• Causes Acute Diarrhea

• Gram-Negative
• Causes Acute Diarrhea and Dysentery

• Gram-Negative
• Causes Acute Diarrhea plus Hemolytic Syndrome

• Gram-Negative
• Causes Acute or Chronic Diarrhea

• Gram-Negative
• Causes Acute Diarrhea

• Gram-Positive, Endospore-Forming Bacteria
• Causes antibiotic-associated diarrhea

• Gram-Negative
• Causes cholera

• Gram-Negative
• Causes Vibrioses

• Protozoa
• Causes Acute Diarrhea

• RNA Virus
• Causes Acute Diarrhea

• RNA Virus
• Causes Acute Diarrhea

• Gram-Positive
• Causes Food Poisoning

• Gram-Positive, Endospore-Forming Bacteria
• Causes Food Poisoning

• Gram-Positive, Endospore-Forming Bacteria
• Causes Food Poisoning