MCB2000 - Lecture final 19-21

Upper GI tract

Mouth, pharynx, esophagus, stomach

Lower GI tract

Small and large intestines, rectum, anus

Accessory organs of the digestive system

Salivary glands, liver, gallbladder, pancreas

Lymphatic tissues associated with the GI tract

Tonsils, appendix, and Peyer's patches

Importance of lymphatic tissues in the GI tract

Major entry portal for pathogens

Organic macromolecules that begin digestion in the mouth

Lipid and carbohydrate digestion starts in the mouth (salivary glands secrete enzymes)

Chemical barriers in the digestive system

Lysozyme in saliva, acid of gastric juices, bile salts kill bacteria, mucus is a physical barrier of attachment, specific immune cells and lymph tissue, mucosa-associated lymphoid tissue (MALT)

Strategies of normal gut microbiota against pathogens

Limit open surfaces for colonization, nutrient competition, excrete antimicrobial products, digestion assistance and nutrient production, E. Coli produces vitamin K

Diarrhea

Frequent passing of loose or watery stool

Enteritis

Inflammation of the intestines

Gastritis

Inflammation of the stomach

Gastroenteritis

Inflammation of the stomach and intestines

Dysentery

Diarrhea accompanied by pain, blood, and/or mucus

Dehydration

Excessive loss of body fluid ← usually diarrhea and vomiting

Hypovolemic shock

Low blood volume from loss of blood or severe dehydration → organ failure

EMB agar

Selects for Gram-negative bacteria (inhibits positive) and differentiates lactose fermenters (dark purple/metallic green)

MAC agar

Selects for Gram-negative using bile salts and crystal violet (inhibits positive) and differentiates lactose (pink color change) from non-fermenters

Endoscopy

Can determine the presence of tissue damage and inflammation in the GI tract but cannot identify specific pathogens

Mumps

Caused by a virus that mainly infects the parotid salivary gland

Paramyxovirus

Infects parotid salivary glands → swollen cheeks

Rotavirus

Leading cause of enteritis in children under 5; transmitted via fecal-oral route.

Norovirus

Leading cause of gastroenteritis in the U.S.; transmitted via fecal-oral route.

Hepatitis

Inflammation of the liver

Jaundice

Yellowing of skin and sclera

Viremia

When virions enter the bloodstream

Hepatitis B (HBV) Transmission

Contact with bodily fluids or open sores from an infected individual (sex, contaminated needles, razors, toothbrushes); accidental percutaneous exposures; vertical transmission during childbirth.

HBV Prophylaxes

HBV vaccine and HBIG (hepatitis B immune globulin) administered to a newly delivered baby if the mother is infected with HBV.

Cirrhosis

Chronic, irreversible scarring of the liver

Hepatitis C

Referred to as the silent killer because early infection is asymptomatic.

Dental Caries

Bacterial breakdown of enamel → tooth cavities

Gingivitis

Plaque buildup → inflammation of gums

Periodontitis

Severe gum infection; inflammation spreads to ligaments and bones supporting teeth.

Dental Plaque

Sticky, biofilm layer of bacteria built up on teeth

Streptococcus mutans

Main bacterial species that causes dental caries.

Helicobacter pylori

Main bacterial species that causes gastritis and stomach ulcers; microaerophilic, gram-negative, curved rod-shaped bacteria.

Foodborne Infection

Pathogen establishes infection in host.

Food Poisoning

No infection; toxin causes symptoms.

H. pylori

Infection with this bacteria has been linked to gastric cancer.

Enterotoxin

Exotoxin targeting intestines → diarrhea, cramps.

Emetic

A substance that triggers vomiting.

Botulism

Paralyzing illness caused by neurotoxins from Clostridium botulinum; enters through the blood, targets nerves.

Aflatoxin

Toxin produced by Aspergillus flavus that can cause food poisoning.

Campylobacter jejuni

Found in the intestinal tract of healthy birds

Campylobacteriosis

Consuming undercooked poultry/foods with raw poultry juices

GBS (Guillain-Barre syndrome)

Autoimmune neuro disease

Septic shock

Dangerously advanced sepsis → organs shut down, 20-30% mortality

Bacteremia

Bacteria in the blood

Sepsis

Body-wide immune response to persistent/large numbers of microbes in the blood...can lead to septic shock

Shiga toxin

What toxin is made by no other Shigella sp. except Shigella dysenteriae, and can cause hemolytic uremic syndrome?

Hemolytic uremic syndrome (HUS)

A condition that can be caused by Shiga toxin

Edema

Swelling (usually in extremities); response to fluid in tissues

Purpura

Rash of purple spots/bruising caused by RBC lysis or capillary destruction

Hematuria

Blood in the urine

E. coli O157:H7

The most common dysentery-associated serovar in the United States

Shiga toxin E. coli (STEC)

Acquired toxin that makes E. coli O157:H7 cause severe symptoms

Salmonella enterica

Two serovars that cause most cases of Salmonella-associated diarrhea and dysentery are Enteritidis and Typhimurium

S. enteritidis serotype Tphi

Bacterial genus, species, and serovar that causes typhoid fever

Vibrio cholerae

Bacterial species that is the etiological agent of cholera

C. Difficile

Bacterial species on the top of the CDCs list of emerging public healthcare threats

C. diff

Bacterial species that can cause pseudomembranous colitis

Giardiasis

Most common intestinal parasite in the United States, can cause 'traveler's diarrhea'

Giardia lamblia

Protozoan that causes giardiasis

Entamoeba histolytica

Protozoan that causes amebiasis, also known as amebic dysentery

Cryptosporidium oocysts

Oocysts from which apicomplexan parasite causes cryptosporidiosis

Hymenolepis nana

Species of tapeworm known as the dwarf tapeworm and is the single most common cause of human tapeworm infection

Taenia saginata

Helminth that mainly infects cattle, commonly known as 'beef tapeworm'

Taeni solium

Helminth whose eggs cause cysticercosis

Diphyllobothrium latum

Helminth commonly known as fish tapeworm

Enterobius vermicularis

Roundworm that causes pinworm infection

Necator americanus

Roundworm that causes hookworm infection

Ascaris lumbricoides

Helminth that causes ascariasis

Trichinella

Roundworm that causes trichinellosis, mostly T. spiralis

Schistosomiasis

Illness caused by Schistosoma haematobium, S. japonicum, and S. mansoni

Urinary system organs

Two kidneys, two ureters, bladder, urethra

Benign prostatic hypertrophy

Difference from prostatitis

Noncancerous

Enlargement of prostate → constricted urethra

Prostatitis

Inflammation of the prostate gland, usually caused by bacterial infection, common in men under 50

Urinary tract infections risk in women

Urethra is shorter; urethra is closer to the anus

Diverse urinary system microbiome benefit

Prevents UTIs; promotes immune function

Pap test

Cheapest and easiest test for early cervical cancer detection

Congenital defects

Birth defects or developmental issues from birth

TORCH

Pathogens that can be vertically transmitted to a fetus

TORCH acronym

Toxoplasma gondii, Other, Rubella virus, Cytomegalovirus, Herpes simplex viruses

Pathogens in 'O' of TORCH

HIV, syphilis, parvovirus B19, listeriosis, varicella-zoster virus, coxsackievirus, enteroviruses, and Zika virus

Vaginal microbiome prevalent bacterial genus

Lactobacillus; produces lactic acid, limits microbial growth: vaginal pH lowered to 3.5-4.5

Cystitis

Inflammation of the bladder

Pyelonephritis

Inflammation of the kidneys

Uncomplicated UTIs

In otherwise healthy individuals; resolves quickly, no recurrence, first-line drugs

Complicated UTIs

In immune-compromised individuals or those with catheters or malformations

CAUTI

Catheter-associated urinary tract infections; direct pathway for microbes to enter the bladder, form biofilm on the catheter surface

Most common cause of UTIs

Enteric bacteria

Leading Gram-positive derived uncomplicated UTI

Staphylococcus saprophyticus

Leading cause of UTIs in sexually active women (16-25)

Staphylococcus saprophyticus

Etiological agent of an emerging UTI

Leptospirosis; Leptospira interrogans

Dysuria

Pain, discomfort, burning during urination

Pyuria

Pus in urine

Most common test to detect UTI

Urine dipstick test; checks WBC levels for an enzyme called leukocyte esterase

Individuals contracting viral UTIs

Immune-compromised individuals; common sign: sudden onset of hemorrhagic cystitis

Most common cause of fungal-related UTIs

Candida species (yeast in the urine)

Etiological agent of genital herpes

Herpes simplex virus 2 (HSV-2)