LECOM Microbiology Lectures 9 and 10 GI Infections

Owl's Eye Inclusions

adenovirus, CMV

Cowdry type A

HSV, measles virus

Guarneri Bodies

smallpox

Negri Bodies

rabies

what are the characteristics of Staphylococcus aureus

§ Gram positive grape-like clusters

§ Catalase-positive

§ Salt tolerant

· Mannitol Salt Agar- differential and selective

o S. aureus uses mannitol to produce acid

§ Changing the pH of plate, becoming yellow

o S. epidermidis

§ More basic, turns pinkish color

§ Normally found in the nose

what are the diseases associated with S. aureus

· Food poisoning

o Virulence factors: Enterotoxins A-E

§ Toxins are heat stable, organism is killed by heat

o Store food properly to avoid staph from growing and making toxin

o Symptoms:

§ 3-6 hours after ingestion

§ Severe vomiting, cramps, with or without diarrhea

§ Recovery: 24-48 hours

what are the characteristics of Bacillus cereus

§ Gram positive rod

§ Produces endospores.

§ Gastroenteritis (food poisoning also)- Ingestion

what are the two forms of enterotoxins caused by Bacillus cereus

emetic and diarrhea

emetic enterotoxin

§ Incubation: less than 6 hours

§ Duration: 8-10 hours

§ Rice

§ Rapid onset vomiting and cramps

§ Heat stable enterotoxin

diarrhea enterotoxin

§ Incubation: greater than 6 hours

§ Duration: 20-36 hours

§ Meat and vegetables

§ Heat labile enterotoxin

· Increase cAMP, profuse watery diarrhea

Enterobacteriaceae characterisitcs

E. coli

§ Found anywhere: mainly GI and Urinary tract

§ Gram neg. rod

§ Facultative anaerobes

§ Ferments glucose

§ MacConkey agar positive

· Light pink color

· Detects lactose fermenters

§ EMB agar

· Lactose fermenter: dark colonies

· E. coli: metallic green sheen

§ Catalase positive

§ Oxidase negative

§ Gastroenteritis

· ETEC, EIEC, EHEC

what is enterotoxigenic (ETEC) and what are the virulence factors, transmission, onset, duration, and symptoms

§ Traveler's diarrhea

· Mexico, Central America, Caribbean

§ Virulence factors

· LT1: heat labile, increases cAMP

· STa: heat stable, increase cGMP

§ Transmission

· Fecal-contaminated food and water

§ Onset: 24-72 hours

§ Symptoms: watery diarrhea, abdominal cramps, fever, nausea/vomiting (possible but not always)

§ Duration: 3-5 days

what is enteroinvasive (EIEC) and what are the virulence factors, transmission, onset, duration, and symptoms

§ Rare in U.S.

§ Virulence factor

· No enterotoxin is produced

· Invades GI epithelium to cause illness

§ Onset: 10-18 hours

§ Duration: 3-5 days

§ Symptoms

· Watery diarrhea, bloody diarrhea with leukocytes, fever, abdominal cramps

what are the characteristics of enterohemorrhagic (EHEC)

§ E. coli serotype O157:H7

· O is O antigen of LPS

· H is flagella antigen

§ Found in GI tract of cattle, goats, sheep

what is the transmission and susceptible population of EHEC

§ Transmission: fecal-oral spread

§ Small infective dose

§ Susceptible population: children

what is the virulence factor for EHEC

· Produces shiga-like toxin

o Stx1 and Stx2 (verotoxin)

o Encoded by phage

§ Binds to 28SrRNA, disrupting protein synthesis

§ Receptors found in intestinal and kidney cells

· Eat organism, needs energy/nutrients, produces toxin form ingesting receptor, kidney failure

what is the incubation, duration, and symptoms of EHEC

§ Incubation: 3-4 days

§ Duration: 3-7 days

§ Symptoms

· Start with watery diarrhea, progress to gross bloody diarrhea

· Severe stomach cramps

· Low grade/no fever

what are the syndromes that can result due to EHEC

· Hemorrhagic Colitis- bloody diarrhea

· Hemolytic uremic syndrome (HUS)

o Decreased platelets: thrombocytopenia

o Hemolytic anemia

o Renal failure: put on dialysis until kidney transplant

o Supportive care

§ NO antibiotics- can exacerbate the disease

o Lab diagnostics

§ Sorbitol-MacConkey (EHEC)

· Sorbitol negative, lactose positive

§ Direct detection of shiga-like toxin

§ Direct PCR to detect presence of SLT genes

What are the characteristics of the main cause of UTIs

E. coli

· Endogenous infection- from our own fecal material

· Colon- urethra- ascends to bladder

· Virulence factor: pili for adherence

salmonella is caused by

Salmonella enterica (S. bongeri in cold-blooded animals)

What are the characteristics of Salmonella enterica

· Humans and warm-blooded animals

· Lactose non-fermenter

· H2S positive

· S. enterica typhi causes typhoid fever, humans only

· S. enterica enteritidis causes enteric infections with diarrhea

typhoid fever is caused by what bacteria

Salmonella enterica typhi

what is the transmission of typhoid fever

o Fecal-oral

§ Bacteria spread from small intestine to macrophages, lymphoid tissue, liver, and gallbladder

how can someone be a carrier for typhoid fever

Ex: Typhoid Mary

o Ex: typhoid Mary

o Bacteria grow in gallbladder and reach intestine through bile duct

§ Shedding salmonella in feces/urine one year later

what are the symptoms of typhoid fever

o Constipation, anorexia (loss of appetite), malaise, fever, headache, abdominal pain

o Characteristic rose spots (rash) on abdomen

o Sickle cell anemia predisposed to Salmonella infections (osteomyelitis)

Salmonellosis is caused by what bacteria

Salmonella enterica enteritidis

what is the transmission for Salmonellosis

Contaminated food/water ingestion

what are the symptoms and duration of Salmonellosis

o Duration: 2-7 days

o Bacteria multiply and invade intestinal mucose

o Symptoms

§ Diarrhea with mucus or blood, fever, abdominal cramping

what is the treatment for Salmonellosis

Prevent dehydration with fluids and electrolytes

Salmonella virulence mechanisms

· Relies on ability to attach, ability to enter M cells, and divide in the phagocytic vesicles

· 1. Taken up by M cell or epithelial cell

· 2. Destroys M cell

· 3. Replicates in phagocytic cells

What are the 4 species of shigella

§ S. sonnei (most common in U.S.), S. flexneri, S. boydii, S. dysenteriae (most severe disease)

What is the reservoir and vector of shigella

no animal reservoir, only humans

how is shigella transmitted

fecal-oral

what are the characteristics of shigella

§ Lactose non-fermenter

§ H2S negative

what is the transmission and at risk population of Shigellosis (Bacillary Dysentery)

· Transmission: fecal-oral

· Very small infective dose (10 cells)

· Population: children, daycare centers, schools

what is the incubation, duration, and symptoms of Shigellosis

· Incubation: 1-4 days

· Duration: 2-3 days

· Symptoms

o Watery diarrhea, bloody diarrhea with mucus

what is the treatment for shigellosis

supportive care, prevent dehydration

what is the pathogenesis of shigellosis

o Translocation through M cell

§ Apoptosis in macrophage, releasing bacteria, enters epithelial cells, multiply and spread

what is the virulence factor of Shigellosis

o Shiga toxin

§ 1A, 5B subunit toxin

· Cleaves 28s rRNA, inhibiting protein synthesis (leads to bloody diarrhea)

§ Damages intestinal epithelial cells and kidney cells

· Hemolytic uremic syndrome

what is the virulence factor for Vibrio cholerae

o Phage-mediated, ctxA and ctxB

o ADP ribsylates a protein that regulates adenylate cyclase

§ Activates G protein, activating adenylate cyclase, cAMP increase, water is pumped from bloodstream into intestinal tract

· Causing diarrhea

· Presence of toxin results in massive loss of water and electrolytes

what is the transmission of Vibrio cholerae

· Ingestion of contaminated food/water

· Marine organisms

o Associated with sea (salt) water (Halophiles- salt loving)

what are the lab diagnostics for Vibrio cholerae

· Gram negative, curved rod (boomerang, coma-shape)

· Facultative anaerobes

· Oxidase positive

· Selective agar- Thiosulfate-citrate bile salt agar

o Thiosulfate citrate bile salts sucrose agar

§ Green agar turns orange for vibrio species

what is the incubation and symptoms of Vibrio cholerae infections

· Incubation: 2-3 days

· Symptoms

o diarrhea

o Rice-water stools (mucus being release)

what is the virulence factor for Vibrio parahaemolyticus

· Thermostable direct hemolysin (Kanagawa hemolysin, enterotoxin)

what is the transmission of Vibrio parahaemolyticus

· Marine organisms- shellfish are natural reservoirs

o Associated with sea (salt) water (Halophiles- salt loving)

what are the lab diagnostics and characteristics for Vibrio parahaemolyticus

· Gram negative, curved rod (boomerang, coma-shape)

· Facultative anaerobes

· Oxidase positive

· Selective agar- Thiosulfate-citrate bile salt agar

o Thiosulfate citrate bile salts sucrose agar

§ Green agar turns orange for vibrio species

what are the symptoms of a Vibrio parahaemolyticus infection

explosive, watery diarrhea

what is the virulence factor of Campylobacter jejuni

· Flagella

o Invades epithelium of small intestine, causing inflammation

what is the transmission of Campylobacter jejuni

· Ingestions of contaminated food, poultry, milk, water

o Requires large dose

what are the lab diagnostics and characteristics of Campylobacter jejuni

· Gram negative spiral (corkscrew)

· Microaerophilic

o Capnophilic- likes CO2

· Prefers 42 degrees

· Agar containing antibiotics

what are the infections and symptoms that can occur due to Campylobacter jejuni

· Gastroenteritis (in U.S.)

· Symptoms

o Bloody diarrhea, fever, abdominal pain

· Guillain-Barre syndrome (complication)

o Autoimmune disorder of PNS

§ Lower Extremity issues

· Dragging foot, foot drop, difficulty walking

o Antigenic cross reactivity of LPS and gangliosides of PNS

§ Cross reactivity example- rheumatic fever due to M cells- strep. pyogenes

· Reactive arthritis (complication)

what is the virulence factor of Helicobacter pylori

· Urease

o Converts urea to ammonia, making stomach pH more neutral, allowing bacteria to survive.

· 4-6 flagella

o Can burrow into stomach tissue

what is the transmission of Helicobacter pylori

endogenous

what are the lab diagnostics and characteristics for Helicobacter pylori

· Spiral shape (as culture ages, shape changes)

· Gram negative

· Can live in stomach- acidophile

o Microaerophile- likes low Oxygen

· Fastidious- difficult to grow in lab

what are the infections and symptoms' that can arise from Helicobacter pylori

· Symptoms

o Fullness, vomiting, nausea

o Can progress to ulcer in stomach

o Chronic gastritis -> peptic ulcers -> gastric cancer

· Higher risk: hypochlorhydria and people who consume a lot of antacids

o People born with this have low HCl (low stomach acid)

· Peptic Ulcer/chronic gastritis

o Block acid production

o Neutralize acid with ammonia (urease)

o Burrow into mucus (flagella)

o Attach to epithelial cells

what are the characteristics of Clostridia species

· Gram positive

· Rod shaped

· Spore former- anaerobic (bacillus is aerobic)

· Ubiquitous

· Produces exotoxins

· Opportunistic pathogens

what are the characteristics of Clostridioides difficile

o Antibiotic-resistant diarrhea

§ All antibiotics cause C. difficile

§ Broad spectrum agents are highest-risk (kills any bacteria, may kill too many good bacteria, bad bacteria outweigh good)

§ Cephalosporins and Clindamycin

what are the symptoms and signs for Clostridioides difficile

o Diarrhea (most common hospital acquired diarrhea)

o Antibiotic disrupts normal flora

§ 4-9 days of antibiotic course

§ All within 3 months of antibiotics

o Symptoms

§ Low grade fever and frequenct diarrhea that's very malodorous (anaerobe= bad smell)

§ Mucus and blood present- over time due to destruction of cells in GI

what are the complications that can occur due to Clostridioides difficile

§ Recurrent infections

§ Colitis (inflammation of large intestine)

· Leading to necrosis and removing part of intestine, maybe lead to ostomy bag

§ Pseudomembranous colitis

· Severe colitis involving formation of pseudomembranes (like diphtheria)

· Can be fatal

what is the transmission of Clostridioides difficile

o Spores

§ Ingest spores, get more bacteria, offsets balance of good and bad bacteria

what are the virulence factors for Clostridioides difficile

spores and toxins

what is the treatment and prevention of Clostridioides difficile infections

o Prevention

§ Avoid broad-spectrum antibiotic use

§ Increase probiotic ingestion

§ Prevent spore spread

o Treatment

§ Metronidazole

· Against protozoa and anaerobe infection.

· Drug of choice

§ Vancomycin

· Second line to metronidazole

· Risk of resistance

§ Fecal transplant

what is the pathogenesis of Clostridioides difficile

o Pathogenicity islands encode two toxins

§ Toxin A: enterotoxin

§ Toxin B: cytotoxin (kills cells)

· These toxins disrupt tight junctions in intestinal epithelial cells leading to increased permeability

o Leads to diarrhea, mucosal injury, and inflammation

o 24 hours in body

§ Cells of colon lining are normal

o 30 hours

§ C. difficile toxin starts to damage cells, triggering inflammation and fluid build up

o 36 hours

§ Inflamed cells burst and die

§ Spores leave colon via diarrhea and await next host

what are the characteristics of Clostridium botulinum

o Human botulism refers to Foodborne botulism and infant botulism

§ Canned-food products

o Botulinum toxins (multiple strains) are one of the most lethal substances known

how do botulinum toxins work

o Botulinum toxin binds to presynaptic nerve terminal

§ Binding is irreversible

· Prevents presynaptic acetylcholine release

· Results in flaccid paralysis and skeletal muscle weakness

o Paralysis goes from head-down

what are the signs and symptoms of Clostridium botulinum infections

o Incubation: 12-36 hours

o Fatigue, vertigo, blurred vision, diarrhea or constipation, abdominal pain

o Descending flaccid paralysis, causing respiratory failure

infant botulism

C. botulinum

§ Under 6 months

§ Ingest spores (like in honey)

· Germinate into bacteria that colonize gut and release toxins

§ Incubation: 3-30 days (takes longer to produce spores)

§ Symptoms:

· Constipation, loss of appetite, weakness, an altered cry and a striking loss of head control

· Flaccid paralysis from head-down

what is the transmission of Clostridium botulinum

ingest spores and neurotoxin

foodborne illnesses are due to what

o Ingestion of spores or toxin

§ Toxins A and B in the U.S.

§ Infant botulism- spores

§ Intoxication- ingestion of preformed toxin

what is the virulence factor for Clostridium botulinum

spores

what is the treatment for Clostridium botulinum

o Antitoxin

o May shorten disease course if used early

o Trivalent equine antitoxin

§ Effective if given early

Botox

o Medical use of botulinum toxin

o Purified and heavily diluted neurotoxin type A

§ Used to selectively paralyze muscles to temporarily relieve muscle contraction

viral gastroenteritis is caused by what virus

rotavirus

what are the characteristics of rotavirus

o Reoviridae, Naked, dsRNA virus

o Most common cause of diarrhea in infants and young children (less than 2)

§ Infants can die from dehydration

o Seasonal: cooler months

o Low infectious dose

what is the transmission of rotavirus

fecal-oral

what is the incubation, duration, and signs/symptoms of rotavirus

· Incubation: 1-2 days

· Signs and symptoms

o Acute onset vomiting and diarrhea

o Cough and coryza (cold-like symptoms)

o Duration: 4-7 days

o Dehydration, treat with fluid and electrolytes

what is the prevention of rotavirus

oral vaccine available

pathogenesis of rotavirus

o Ingested virus infects cell, spreads to infect large number of small intestine cells

§ Releases virus particles causing reduced absorptive capacity (causes diarrhea)

Characteristics of Norovirus

§ Caliciviridae

· Naked, (+) ssRNA virus

§ "Winter vomiting disease"

§ Older children and adults

§ Highly infectious

what is the transmission, incubation, and signs/symptoms of Norovirus

§ Transmission

· Fecal-oral

§ Incubation: 12-72 hours

§ Signs/symptoms

· Chills, headache, myalgia, nausea, vomiting, diarrhea, abdominal pain

· Self-limiting: 1-3 days

what is the treatment for Norovirus

Treat with fluid and electrolytes to prevent dehydration

what are the characteristics of Giardia lambia

o (aka G. intestinalis, G. duodenalis)

§ Protozoa (eukaryote)

§ 2 stages

what are the two stages of Giardia lambia infections

resistant stage and active stage

resistant stage of Giardia lambia

· Cysts (what is ingested)

o Shed in stools

o Infective stage

o Spread fecal-oral

active stage of Giardia lambia

· trophozoites

o Cyst changes into trophozoite

§ Trophozoite is surrounded with adhesive disk, surrounds the lecturenucleus, allows attachment to intestine

§ Live in intestines

what is the geographic location and transmission of Giardia lambia

§ Geographic location

· Streams, lakes, wild and domestic animals

· Contaminated water, fruits, and vegetables

§ Transmission

· Ingestion of cysts

what is the pathogenesis of Giardia lambia

· Gastric acid causes change from cyst to trophozoite

o Trophozoite attaches to intestinal villi

o Causes localized tissue damage

· Can re-infect person

what is the incubation, duration, and signs/symptoms of Giardia lambia infections

§ Incubation: 1-4 weeks, average 10 days

§ Symptoms

· Acute, onset of foul smelling, watery diarrhea, cramps, flatulence, and steatorrhea

· 10-14 days

what is the lab diagnosis for Giardia lambia

· Microscopy of stool sample, 1 per day for 3 days

· Also based on signs and symptoms

what is the treatment for Giardia lambia

Metronidazole

what causes pinworm

Enterobius vermicularis

who is at risk for pinworm (Enterobius vermicularis)

· Effects children

· Found in daycares, schools

what is the transmission of Enterobius vermicularis

§ Transmission

· Ingestion of eggs

§ Migration to large intestine, mature into adults (2-6 weeks)

· Females lay eggs in perianal folds.

· Eggs have chemical surrounding them, makes them itchy

o Causes the infected person to itch their bottom

o Worms on hand, reinfection can occur.

what are the symptoms of Enterobius vermicularis

pruritus, loss of sleep, fatigue

check "Scotch tape test"

what is the treatment of Enterobius vermicularis

· Treat once with medication, then 2-3 weeks later

· Treat entire family