Microbial Diseases of the Digestive and Urinary Tracts

Fungal Diseases

Histoplasmosis

• Caused by Histoplasma capsulatum. This is a dimorphic fungus.

• Yeast-form grows intracellularly in macrophages.

• Forms lung lesions; in 0.1% of cases it becomes a severe, generalized disease.

• Symptoms: fever, cough, and fatigue.

• Acquired from airborne conidia in areas with bird or bat droppings.

Aspergillus

• Aspergillus fumigatus is commonly inhaled every day.

• Individuals with weakened immune systems, asthma, and lung disease are at higher risk of infection.

• Causes aspergillosis.

• Airborne conidia are found in soil, compost, rotting plant debris, dust, damp buildings, and air-conditioning systems.

Mold Intoxication

• Mold poisoning is caused by exposure to toxic fungal spores (mycotoxins).

• Immune reaction results in allergy-like symptoms such as runny nose, itchy eyes, and shortness of breath.

• Chemical and inflammatory reactions are caused by the immune response to mycotoxins.

• Symptoms include cognitive difficulties, unexplained weight gain or loss, metallic taste in mouth, vertigo, ringing ears, digestive issues, chronic fatigue, and dehydration.

• Treatment involves removing the source of mold and using binders to remove toxins.

Finding the Source of Mold Toxicity

• Caused by many different fungi species; most often caused by Stachybotrys chartarum (black mold), Aspergillus, Penicillium, and Fusarium.

• Mold fungi like to grow in dark, moist, cool environments.

Structures of the Digestive System

• Gastrointestinal (GI) tract or alimentary canal includes:

  • Mouth

  • Pharynx (throat)

  • Esophagus

  • Stomach

  • Small and large intestine

• Accessory structures include:

  • Teeth and tongue

  • Salivary glands

  • Liver

  • Gallbladder

  • Pancreas

• Infections of any of the above structures represent digestive system disorders.

Microbiota of the Digestive System

• Millions of bacteria per milliliter of saliva.

• Few microorganisms in the stomach due to HCl (acid) production.

• Small intestine contains Paneth cells, which are granule-filled phagocytic cells that produce defensins.

• Large numbers of bacteria are found in the large intestine, including anaerobes and facultative anaerobes.

• 100 billion bacteria per gram of feces.

Microbes and Dental Caries (Tooth Decay)

• Dental plaque is a biofilm involved in the formation of dental caries.

• 700 species of bacteria in the oral cavity.

• Streptococcus mutans is the most important cariogenic organism; it is a Gram-positive coccus that converts sucrose to lactic acid and produces dextran, a polysaccharide that forms plaque.

• Plaques attract other cariogenic bacteria such as streptococci and filamentous Actinomyces.

Periodontal Disease (Gum Disease)

• Gingivitis is inflammation and infection of the gums caused by streptococci, actinomycetes, and anaerobic Gram-negative bacteria.

• Periodontitis involves the destruction of bone and tissue supporting the teeth and is caused by Porphyromonas.

Staphylococcal Food Poisoning

• Caused by enterotoxins produced by Staphylococcus aureus.

• Enterotoxins are toxins that act on intestines in digestive diseases.

• The toxin is not killed by boiling.

• Toxins are produced when the organism is allowed to incubate in food (temperature abuse).

• S. aureus outgrows most bacteria in high osmotic pressure and high temperature.

• Food is usually contaminated by a worker with poor hand hygiene and left at room temperature, where S. aureus incubates and releases toxins.

Salmonellosis (Salmonella Gastroenteritis)

• Caused by Salmonella enterica, a Gram-negative, facultative anaerobe, nonendospore-forming rod.

• It is a normal inhabitant of the human intestinal tract.

• Contaminated food and water due to fecal matter residue causes salmonellosis.

• Invades intestinal mucosa and multiplies.

• Incubation of 12 to 36 hours; symptoms include fever, nausea, pain and cramps, and diarrhea.

• 1 million cases; 380 deaths annually.

• Associated with commercial chicken and egg production, unpasteurized milk, and unclean food products.

Typhoid Fever

• Caused by Salmonella serotype Typhi, which is spread only by human feces.

• Rare in the United States today due to sanitation.

• Bacteria spread throughout the body in phagocytes and releases organism into the bloodstream.

• Symptoms include high fever, headache, intestinal wall ulceration.

• 1-3% of patients become chronic carriers and harbor the organism in the gallbladder.

Cholera

• Caused by Vibrio cholerae, a slightly curved, Gram-negative rod with a single polar flagellum.

• Associated with salty waters.

• Produces the cholera toxin, which causes the host cells to secrete electrolytes and water, leading to “rice water stools”.

• Can lose 12 to 20 liters of fluid per day, causing shock, collapse, organ failure, and death.

• Individuals can be asymptomatic carriers and infect others via fecal matter.

• Causes 95,000 deaths a year, predominantly in Africa and Asia.

• Treatment includes IV fluid replacement.

Cholera and Natural Disasters

• Cholera increases when sanitation and sewage disposal systems are compromised.

• Outbreak in Haiti after earthquake due to deficient septic systems and water sanitation.

• Increased incidence when public forced to live in overcrowded unsanitary conditions.

Escherichia coli Gastroenteritis

• Gastroenteritis is characterized by inflammation of the stomach and intestines, resulting in vomiting and diarrhea.

• Enteropathogenic E. coli (EPEC) causes diarrhea in developing countries by causing the host cells to form pedestals where the bacteria attach.

• Enteroinvasive E. coli (EIEC) causes Shigella-like dysentery.

• Enteroaggregative E. coli (EAEC) is only in humans and produces an enterotoxin causing watery diarrhea.

Traveler’s Diarrhea

• The most common cause of traveler’s diarrhea is enterotoxigenic Escherichia coli (ETEC), which is prominent in lower-income countries and transmitted by fecal contamination of food or water.

• Can also be caused by Salmonella, Shigella, and Campylobacter.

• Treatment includes oral rehydration therapy and bismuth-containing preparations/over-the-counter antidiarrheal medications like Pepto-Bismol.

Campylobacteriosis (Campylobacter Gastroenteritis)

• Caused by Campylobacter jejuni, a Gram-negative, microaerophilic, spirally curved bacterium.

• Most common cause of foodborne illness in the United States.

• Common in the intestines of poultry; 60% of cattle excrete the organism in feces and milk.

• Eating raw or undercooked poultry (or foods contaminated by them) results in fever, cramping, abdominal pain, diarrhea, dysentery.

• One in 1000 cases leads to Guillain-Barré syndrome.

Helicobacter Peptic Ulcer Disease

• Caused by Helicobacter pylori, which infects 30-50% of the population in the developed world.

• Grows in the stomach acid by producing urease, which converts urea to alkaline ammonia.

• Disrupts stomach mucosa, causing inflammation and weakened stomach tissue, resulting in painful ulcers.

• Treated with aggressive antimicrobial drugs and bismuth subsalicylate.

• Diagnostic test requires a biopsy, culture, and urea breath test.

Helicobacter pylori and its benefits

• Helicobacter pylori is commonly found in many individuals and is often harmless.

• History of fear around H. pylori has eliminated this microbe from natural microbiome over the past few generations.

• Studies now show a benefit to having H. pylori.

• Believed to assist in immune response to certain vaccines.

• Known to regulate ghrelin (hunger hormone).

Yersinia Gastroenteritis

• Yersinia gastroenteritis is caused by Yersinia enterocolitica and Yersinia pseudotuberculosis, which are Gram-negative and inhabit animals; transmitted most often by undercooked meat and pork.

• Symptoms include diarrhea, fever, headache, abdominal pain and is often misdiagnosed as appendicitis.

• Treatment with antibiotics and oral rehydration.

Clostridium and the Digestive System

Clostridium perfringens Gastroenteritis

• Associated with foods containing animal intestinal contents.

• Creates low oxygen level, causes gas gangrene by exotoxin.

• Some infections very mild while other may cause death.

• Symptoms from 6 to 24 hours after ingesting contaminated foods.

• Occur predominantly in foods made in large batches and kept out for extended periods.

Clostridium difficile Associated Diarrhea

• Causes more deaths than all other intestinal infections combined and is mostly in health care settings.

• Life-threatening colitis, ulceration and perforation of the intestinal wall.

• Precipitated by the extended use of antibiotics, which eliminates competing intestinal bacteria.

Common Digestive Tract Issues

• Choking: food entered the trachea instead of the esophagus.

• Belching: ingested air while speaking or eating.

• Gas: microbiome metabolism produced sulfur.

• Heartburn: interruption of peristalsis because of large unchewed lumps or meal.

• Vomiting: body’s adaptive mechanism to get rid of irritating substances.

• Diarrhea: frequent, loose, watery stools; food passed through the intestinal tract too quickly.

• Constipation: strained and infrequent bowel movements and hard stool caused by lifestyle or lack of fiber.

• Many of these caused by a rushed lifestyle, always best to eat slowly and relax after a meal.

Irritable Bowel Syndrome

• Irritable Bowel Syndrome is characterized by reoccurring abdominal pain related to defecation.

• Gastrointestinal tract contractions are faster or slower than normal, which leads to discomfort, bloating, gas, and diarrhea.

• Cause not known but linked to stress.

• Eating smaller meals, tracking your food, and using probiotics are recommended to help.

Maintaining a Healthy Gut

• Diversity in microbe species indicates a healthy microbiome; includes bacteria, fungi, protozoa, and other microorganisms, primarily located in the small and large intestines.

• Acidity of stomach not suitable for bacteria.

• Similarities of microbiota found in people with similar health issues.

• Diet influences abundance of good or bad microbes.

• Prebiotics are often fibers or indigestible materials serving as food for microbes.

• Probiotics are stabilized colonies of beneficial microbes.

Recovery for Disturbed Microbiomes

• Chronic gut conditions can require intensive microbiome care.

• Conditions linked to disbalance in microbiome include: Diarrhea, Irritable bowel syndrome, Declining health at a young age.

• Could be a candidate for fecal transplant surgery.

• Supplementing the microbiome with probiotics and fermented foods alleviates symptoms but does not always lead to long term solutions.

Viral Diseases of Digestive Systems: Mumps

• Mumps affects the parotid glands 16-18 days after exposure, causing swelling of the salivary glands.

• Symptoms include fever, headache, aches, tiredness, loss of appetite.

• May cause orchitis (swelling of testes), meningitis, ovary inflammation, and pancreatitis.

• Prevented with MMR vaccine.

Hepatitis

• Hepatitis is inflammation of the liver that may result from drug or chemical toxicity, Epstein-Barr virus (EBV), cytomegalovirus (CMV), or the hepatitis viruses (Hepatitis A, Hepatitis B, Hepatitis C).

Hepatitis A

• Highly contagious, multiplies on the epithelial lining of the intestinal tract, spreads to kidneys, liver, and spleen.

• Symptoms include anorexia, nausea, diarrhea, fever, and chills.

• Severe cases lead to jaundice and dark urine.

• Lasts 2-21 days.

• Treated with immune globulin and there is an inactivated vaccine for prevention.

Hepatitis B

• Caused by the Hepatitis B virus (HBV) and is transmitted via the blood and bodily fluids; up to 1 billion viruses per ml of blood

• Acute hepatitis B has similar symptoms to hepatitis A; gradual recovery.

• Fulminant hepatitis in 1% of cases leads to sudden massive liver damage and is fatal.

• Chronic HBV occurs for 10% of patients and may lead to liver cancer.

• Prevented by a vaccine, with no specific treatment; may ultimately require liver transplantation

Hepatitis C

• Caused by the Hepatitis C virus (HCV).

• Destroys the liver by using genetic variation to evade the immune response.

• Kills more in the United States than AIDS.

• 85% of cases become chronic, and 25% develop liver cirrhosis or cancer.

• Treated with HCV protease and polymerase inhibitors, interferon, and ribavirin.

• No vaccine available.

Fungal Diseases of the Digestive System

• Primarily driven by mycotoxins:

  • Ergot poisoning: Mycotoxins produced by Claviceps purpurea, which occurs in grains and restricts blood flow (gangrene) and causes hallucinations.

  • Aflatoxin poisoning: Mycotoxins produced by Aspergillus flavus, likely to be found on peanuts, causes liver cirrhosis and liver cancer.

Protozoal Infections of the Digestive Tract

• Giardiasis: Prolonged diarrhea, malaise, weight loss, flatulence, cramps; hydrogen sulfide detected in the breath or stools.

• Cryptosporidiosis: Cholera-like diarrhea for 10 to 14 days; transmitted through drinking water and is resistant to chlorination.

• Cyclospora: Days or weeks of watery diarrhea; oocysts are ingested from drinking water contaminated with feces.

Protozoan Highlight: Entamoeba histolytica

• Amebic Dysentery (Amebiasis):

  • Microbe produces cysts that survive stomach acid and is contracted by contaminated food and water.

  • Trophozoites are produced from cysts in the intestines, multiply in the wall of the large intestine.

  • Feces contain blood and mucus.

  • Can perforate the intestinal wall, causing abscesses; organisms invade the liver.

Animals of the Gut: Tapeworms

• Tapeworms have a three-stage life cycle:

  • Eggs are excreted in the feces and ingested by animals.

  • Eggs hatch into a larval cysticercus that lodges in the muscle.

  • Human ingests undercooked meat containing cysticerci, which develop into adult tapeworms in the intestine.

• Diagnosis with eggs or segments in the feces.

• Treatment with praziquantel and niclosamide.

Hydatid Disease

• Hydatid disease is caused by the tapeworm Echinococcus granulosus.

• Eggs are ingested and migrate to the liver, lungs, or brain, developing a hydatid cyst.

• Can grow and hold up to 15 liters of fluid and may rupture, causing anaphylactic shock.

• Treatment with surgical removal or albendazole.

• Must ingest parasite to get disease through soil contaminated foods, where canine are carriers.

Hookworms

• Caused by the nematodes Necator americanus and Ancylostoma duodenale.

• Hookworms attach to the intestinal wall and feed on blood and tissue.

• Causes anemia, lethargic behavior, and craving for peculiar foods (pica).

• Carried from human feces in soil that contacts bare skin.

• Treatment with mebendazole.

Structure & Function of the Urinary System

• Urinary system includes two kidneys, two ureters, one urinary bladder, one urethra.

• Infection prevented by:

  • Valves that prevent backflow to the kidneys.

  • Acidity of urine.

  • Mechanical flushing.

Normal Microbiota

• Normal urine is not sterile.

• Predominant microbes of the vagina:

  • Lactobacilli (growth promoted by estrogen).

  • Streptococci, anaerobes, some Gram-negatives.

  • Candida albicans yeast.

• Male urethra introduces bacteria into semen.

• Microbes of the seminal vesicles: Proprionibacterium, Corynebacterium, Pseudomonas.

Bacterial Diseases of the Urinary System

• Urethritis: An inflammation of the urethra.

• Cystitis: An inflammation of the urinary bladder.

• Ureteritis: Infection of the ureters.

• Pyelonephritis: An inflammation of one or both kidneys.

• 8 million urinary tract infections annually and most due to Escherichia coli.

Cystitis

• Cystitis is commonly caused by E. coli; also caused by Staphylococcus saprophyticus.

• Symptoms include dysuria (difficult or painful urination) and pyuria

• Urge to urinate more often.

• Eight times more common in women than men due to the short length of the urethra and its proximity to the anal opening.

Diseases of the Reproductive Systems

• Sexually transmitted diseases (STDs), now referred to as sexually transmitted infections (STIs) generally have no signs or symptoms.

• Over 30 types of infections; 20 million new cases in the United States annually, half of which occur in 15- to 24-year-olds.

• Most prevented with condoms.

• STI Home test kits are available for chlamydia, gonorrhea, trichomoniasis and HIV.

Gonorrhea

• Gonorrhea is caused by Neisseria gonorrhoeae, a Gram-negative diplococcus.

• In the United States the incidence increased in 2016 to 130 cases per 100,000 people.

• Attaches to the epithelial mucosa by the fimbriae and invades the spaces between the columnar epithelial cells, causing inflammation and forming pus.

• Pharyngeal gonorrhea (infection of pharynx) and anal gonorrhea

• No adaptive immunity due to antigenic variability.

Symptoms of Gonorrhea

• Men: painful urination and discharge of pus; epididymitis.

• Women: fewer symptoms; pelvic inflammatory disease.

• If left untreated, may disseminate and become systemic, leading to endocarditis, meningitis, or arthritis.

• Ophthalmia neonatorum: infant blindness due to a gonorrheal infection of the eyes

Nongonococcal Urethritis (NGU)

• Also known as nonspecific urethritis (NSU).

• Any inflammation of the urethra not caused by N. gonorrhoeae.

• Caused by: Chlamydia trachomatis (Chlamydia), Mycoplasma genitalium, Ureaplasma urealyticum.

• Symptoms include painful urination and watery discharge; often asymptomatic; pelvic inflammatory disease (PID) in women.

  • Clarification you cannot get Chlamydia infection of the reproductive tract from swimming pools, you can get conjunctivitis of the eyes

Syphilis

• Syphilis is caused by Treponema pallidum, an STI that invades the mucosa or through skin breaks and enters the bloodstream and induces an inflammatory response.

  1. Primary stage highly infectious (most infectious)

  2. Secondary stage leads to skin rashes (still infectious).

  3. Third stage appears after years of latency and affects the heart and CNS, causing dementia (early third stage infectious).

• Congenital: neurological damage to the fetus (due to latent or active infection).

Bacterial Vaginosis

• Bacterial vaginosis is caused by Gardnerella vaginalis, a pleomorphic Gram-negative rod.

• Vaginitis: inflammation of the vagina due to infection.

• Vaginosis: no sign of inflammation; pH above 4.5, with fishy odor and copious frothy discharge.

• Clue cells: sloughed-off vaginal epithelial cells covered with a biofilm of G. vaginalis.

Genital Herpes

• Caused by genital herpes simplex virus type 2 (HSV - 2).

• In the United States, one in four over age 30 are infected.

• Painful vesicles on the genitals; painful urination that heals within 2 weeks.

• Recurrences from viruses latent in nerve cells due to menstruation, emotional stress, or illness.

• Asymptomatic individuals can still spread herpes.

• No cure; suppression and management; use condoms

Neonatal Herpes

• Herpesvirus crosses the placental barrier and infects the fetus and cause neonatal herpes causing damage to the CNS, developmental delays, blindness, and hearing loss and a survival rate of 40%.

• Newborns infected from HSV exposure during delivery.

• Rare that it gets passed on if herpes infection occurred at start of pregnancy.
  Highest risk is if herpes infection occurred in third trimester.

Genital Warts

• Genital warts are also known as condyloma acuminata and are caused by human papillomaviruses.

• About 5 million new cases in the US each year.

• Visible warts caused by serotypes 6 and 11, while serotypes 16 and 18 cause cervical cancer (kills 4000 women in the United States annually).

• Treatment via removal of warts; podofilox and imiquimod.

• Prevention with the quadrivalent or nine-valent HPV vaccines.

Candidiasis (Yeast Infection)

• Candidiasis is caused by C. albicans and grows on the mucosa of the mouth, the intestinal tract, and the genitourinary tract due to opportunistic overgrowth from antibiotic use, diabetes, or hormones.

• Oral candidiasis: thrush

• Vulvovaginal candidiasis: vaginitis, causing a yeasty, thick, yellow discharge.

• Treatment with clotrimazole or fluconazole.

End of Lectures

• All lectures for the semester are complete!

• Final exam will be Monday May 19th in the same room from 8:30-10:30am, and will follow a similar format to previous exams, worth 25% of the grade.

• Extra credit is due Friday 16th at 11:59pm.

Exam Review Questions

• Poultry products are a likely source of infection by:

  • B) Salmonella enterica.

• Furuncles, toxic shock syndrome, and scalded skin syndrome all are caused by:

  • B) Staphylococcus aureus.

• A patient has been complaining of loose stools but otherwise feels no discomfort. Upon examination tests show Helicobacter pylori in the stomach. What do you do?

  • C) Monitor the patient further to identify cause of illness.

• Which of the following is categorized by a distinctive bulls-eye rash?

  • C) Lyme disease.