Unit 5 Study Guide: Chapter 19
Describe the disease caused by Clostridium difficile and explain why it's an increasing concern in healthcare settings.
C. diff causes -in mild cases: diarrhea and moderate abdominal pain -in serious cases: severe abdominal pain, fever, nausea, and abundant water diarrhea; may progress to dysentery; pseudomembranous colitis; toxic megacolon -considered most common healthcare-acquired infection Why it is increasing concern -most pathogenic strains release two toxins, A and B toxins; an emerging strain makes BINARY toxin -forms dormant endospores -resists antibiotics -normal microbiota are removed via a course of antibiotics, giving C. diff the opportunity to thrive
Describe the major tapeworm and roundworm infections of the human GI tract.
ALL SPECIES NEED TO BE ITALICIZED WHEN NAMED, THIS QUIZLET DOES NOT REFLECT THAT All helminthic infections: -eosinophilia is a hallmark for diagnosis -diagnosis also include the discovery of eggs, larvae, or adult worms in stool and tissues -cause a large burden of disease in the poorest countries in the word -pathogenesis and virulence factors generally include specialized mouthparts for attachment and feeding, enzymes to liquify and penetrate tissues, cuticle for protection from host defenses -no vaccines; treatment includes antihelminthic drugs -prevention includes proper sewage disposal, avoiding using human feces as a fertilizer, disinfection of the water supply, thoroughly washing and cooking vegetables and meats, freezing food TAPEWORMS -flattened, segmented bodies with scolex (head) at one end (possesses hook and/or sucker structures for attachment) -mature and release eggs and proglottids in the definitive host; eggs and proglottids released in feces -most tapeworm infections are caused by: Hymenolepis nana, Taenia species, Diphyllobothrium latum Hymenolepis nana: -transmitted by fecal-oral route or accidental ingestion of infected arthropods -light worm loads are asymptomatic but can last for years; heavy worm loads may lead to diarrhea, nausea, and loss of appetite -eggs can hatch inside the same host leading to heavy worm loads Taenia species: -T. saginata, T. solium, T. asiatica all have definitive host as human -animal eats contaminated feces; eggs hatch inside an ANIMAL'S intestines; hatched larvae migrate to the animal's muscle and become cysticerci; can survive for years -followed by HUMAN ingestion of cysticerci in raw or undercooked meat -most infections are asymptomatic but tapeworms can become very long, causing intestinal irritation and bowel obstruction -when humans ingest the eggs instead of the cysticerci, it causes cysticercosis where larvae burrow through the intestines and migrate to tissues (e.g., brain, muscle, eyes) to form cysticerci, impairing tissue function; major cause of adult onset seizures in most low-income countries; potentially deadly symptoms -treatment involves antihelminthic drugs (e.g., praziquantel), anti-inflammatory agents, and surgery to remove cysticerci Diphyllobothrium latum (fish tapeworm): -requires three hosts: crustaceans, fish, mammals -mammal defecates eggs into freshwater, eggs become ciliated embryos then eaten by crustaceans where they mature into the first larval stage; fish eat the infected crustation, migrate to the flesh and form larval cysts; humans consume infected fish and larva become an immature worm, attach to intestinal wall, mature into adult worm, and release eggs after 6 weeks and growing 1-15 meters in length ROUNDWORMS -pinworms, hookworms, Ascariasis, Trichinellosis/trichinosis Pinworms (Enterobius vermicularis) -white roundworms, 4-12 mm long, reside in colon -while the infected person is sleeping, the female worm migrates to anus to lay eggs; eggs cause intense anal itching; person scratches and eggs stick to fingers (children more likely to scratch); pinworm eggs are ingested from contaminated surfaces or fingers; surfaces (e.g., toys, clothing) can harbor eggs for up to 3 weeks -signs and symptoms: disturbed sleep, teeth grinding, anus itching Hookworm (Necator americanus) -roundworms -soil is contaminated with human feces harboring eggs; eggs hatch and mature into adult worms then burrow into bare feet and legs; larvae enter the bloodstream, migrate to lungs where they are coughed up and then swallowed; attach to intestinal wall, mature, mate, and release fertilized eggs -heavy worm load leads to symptoms like iron and nutrient deficiencies and impaired growth of children Ascariasis (Acsaris lumbrioides) -contaminated soil contains eggs, unwashed fruit and vegetables are consumed, introducing eggs to GI tract where they hatch; larvae enter bloodstream, migrate to lungs, reside for 10-14 days before being coughed up and swallowed; in small intestine, they mature, mate, and feed on intestinal contents WITHOUT attaching to intestinal wall; can grow 30 cm in length and adult females can produce ~200,000 fertilized eggs per day for roughly a year -infections are usually asymptomatic -can cause coughing and wheezing while residing in lungs; high worm load can lead to severe abdominal pain, malnutrition, and intestinal blockage Trichinellosis/Trichinosis (Trichinella species, most notably T. spiralis) -transmitted by eating pork and sometimes other wildlife containing Trichinella cysts -larvae embedded in undercooked meat is consumed; larvae mature into worms in the intestine, migrate to blood, and embed in muscles -symptoms range from unnoticeable to life threatening; severity depends on how many cysts were ingested; eventually disappears within a few months -first phase: diarrhea, nausea, abdominal pains, fever, sweating -second phase: puffiness around the eyes, intense muscle and joint pain, shortness of breath, eosinophilia; rash may occur -high load of worms may lead to cardiovascular and nervous system effects; death is also possible, but rare
Identify where normal microbiota exist in the digestive system and describe the factors that limit microbial growth in certain parts of the GI tract.
Microbes reside on mucous membranes throughout the digestive tract. Different locations along the GI tract harbor different microbial genera. Accessory organs (salivary glands, liver, gallbladder, and pancreas) are free of resident microorganisms. Factors that limit microbial growth in certain parts of the GI tract -lysozyme and lactoferrin (AMPs) in saliva -acidic environment of stomach limits microbial growth -salts in bile inhibit the growth of many bacteria, especially Gram-positive bacteria -mucus lining acts as a physical barrier preventing many microbes from attaching -specific immune cells and lymphatic tissue (mucosa-associated lymphoid tissue; MALT; specially gut-associated GALT) filters lymph -peristalsis; waste is expelled at the end of the GI tract -secretory IgA -microbiome limits available surfaces for colonization; competes for nutrients; excretes antimicrobial products; provides nutrients for the body
Describe the symptoms and related clinical terms associated with GI tract infections.
Milder signs and symptoms of GI tract infections may include: -Abdominal pain -Diarrhea: loose or watery stools (may contain blood or mucus) -Fever and/or vomiting More severe signs and symptoms of GI tract infections may include: -Enteritis: intestinal inflammation -Gastritis: stomach inflammation -Gastroenteritis: inflammation of both the stomach and intestines -Dysentery: severe gastroenteritis with painful diarrhea containing blood and mucus -Dehydration: excess water loss -Hypovolemic shock: organ failure Other associated information: -Most intestinal pathogens that cause diarrhea or dysentery transmit via the fecal-oral route -Most common means of fecal-oral transmission is contaminated food or water -All of us are exposed to some degree of fecal contamination in our daily lives; The CDC estimates 1 in 6 Americans will suffer from a foodborne illness each year -Hand washing, sewer management, water sanitation practices, and food processing regulations all help limit fecal-oral transmission -In developing nations, poor water sanitation and limited food-handling regulations make these illnesses even more prevalent -World-wide, diarrhea and dysentery kill about 2.2 million people each year; Majority of deaths occur in children under five years old who live in developing nations
Explain differences between protozoan and helminthic parasites and state how they are mainly transmitted.
Protozoans: single-celled eukaryotes -protected cysts are ingested -transmitted by fecal-oral route -microscopic Helminths: multicellular eukaryotes -usually transmitted as microscopic eggs or larvae in either soil or water; -either round worms or flat worms
Describe the features of infections caused by Campylobacter species, Shigella species, Escherichia coli, Salmonella species, and Listeria monocytogenes.
THESE ARE ALL COMMON ETIOLOGICAL AGENTS FOR FOODBORNE INFECTIONS. As foodborne infections, after ingestion, pathogen establishes infection in host. The result from ingesting food that harbors live bacterial pathogens that infect the GI tract, NOT INTOXICATION. Symptom onset: 1-5 days (or longer) after exposure Signs and symptoms: may include fever, headache, muscle aches, nausea, diarrhea, abdominal pain Recovery: days to weeks
Explain some of the basic tools used to diagnose GI tract infections.
Diagnosis of GI tract infections may occur by: a) Collecting fecal samples for... -Culturing on selective and differential media (e.g., MacConkey agar) -Molecular diagnostic analysis -Microscopic examination to identify parasites or their eggs b) Observing tissue damage (e.g., ulcers or inflammation) using... -Upper GI endoscopy: insertion of a fiber-optic camera through the mouth to view the esophagus, stomach, and small intestine -Lower endoscopy (colonoscopy): an endoscope is inserted via the anus to view the large intestine (colon) *Note: these techniques can't confirm the specific pathogen
Compare and contrast foodborne infection to food poisoning (intoxication).
FOODBORNE INFECTION Description: after ingestion, pathogen establishes infection in host; result from ingesting food that harbors live bacterial pathogens that infect the GI tract Common bacterial agents [needs to be italicized]: Campylobacter jejuni, Shigella species, E. coli, Salmonella species, and Listeria monocytogenes Symptom onset: 1-5 days (or longer) after exposure Signs and symptoms: May include fever, headache, muscle aches, nausea, diarrhea, abdominal pain Recovery: days to weeks FOOD POISONING (INTOXICATION) Description: No infection; an ingested toxin causes the illness symptoms; bacteria don't actively grow n the host, intoxication rather than infection Common bacterial agents [needs to be italicized]: Toxins from Staphylococcus aureus, Bacillus cereus, and Clostridium perfringens; symptoms triggered by ingested enterotoxins (a type of exotoxin) and they may be emetic (trigger vomiting) Symptom onset: 30 minutes to 6 hours after exposure Signs and symptoms: Most commonly nausea and vomiting and occasionally diarrhea and abdominal pain; causes inflammation of intestinal cells, prevents water absorption Recovery: usually within 24 hours; up to several days in severe cases
Explain how Helicobacter pylori causes stomach ulcers.
Helicobacter pylori—microaerophilic, Gram-negative, curved rod-shaped bacteria Progression and stomach ulcers: -inflammatory response causes ulcers to form where the stomach lining is damaged by the bacterium. 1) [After entering into the GI tract via the fecal-oral route] Helicobacter pylori infects the mucosal linings of the stomach to colonize; polar flagella help bacteria to burrow into mucosal lining to escape stomach acid; enzymes decrease the acidity around them 2) Inflammation causes tissue damage and stomach lining erosion; they release toxin VacA, which triggers host cell death 3) The epithelial layer of the stomach becomes exposed to stomach acid, and is further damage 4) an ulcer develops
State the features of Vibrio cholerae and discuss the disease it causes.
Features; -comma-shaped ("vibrio") -Gram-negative -single flagellum (monotrichous arrangement) Disease it causes: cholera Cholera -poor sanitation contributes to outbreaks; endemic in areas lacking water sanitation -can be caused by consuming raw shellfish -warm, monsoon, alkaline, and saline conditions favor growth of Vibrio -4.3 million cases with 142,000 deaths per year worldwide -large infectious dose required (~1,000,000 bacteria) -bacteria that pass the stomach burrow past the mucous layer of the small intestines; adhere to surface of intestinal epithelial cells and release cholera toxin -cholera toxin triggers intestinal epithelial cells to release electrolytes and water into the intestine Signs and symptoms: -begin within hours to a few days after ingestion of contaminated food or water -vomiting, copious watery feces, "rice-water stool" -Fluid losses of 1 liter per hour in severe cases -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 -in severe cases, up to 20 liters of fluid can be excreted in a day -sever dehydration without prompt fluid replacement; can lead to decreased blood volume, hypovolemic shock, organ failure, and death Treatment includes oral rehydration and antibiotics; IV fluids and antibiotics for severe cases
Describe the causative agents and features of giardiasis, amoebiasis, and cryptosporidiosis.
GIARDIASIS Causative agent: protozoan Giardia lambia Transmission: fecal-oral route; ingestion of cyst form when consuming feces-contaminated food or water; animals to people Signs and symptoms: diarrhea, abdominal cramps, nausea, excessive flatulence, vomiting; chronic infections can cause nutrient malabsorption Mechanism: cyst passes through stomach into small intestines, hatches, and releases two trophozoites; trophozoites attach and leech off host, reproduce asexually, progress toward the colon, and cysts and trophozoites are expelled in feces Treatment: symptoms usually subside without treatment in 2-6 weeks; drug treatment like metronidazole is available AMOEBIASIS Causative agent: protozoan Entamoeba histolytica Transmission: fecal-oral route; direct contact; feces-contaminated fomites Signs and symptoms: 90% of infections are asymptomatic; symptomatic infections range from mild diarrhea to severe dysentery; in the invasive form, trophozoites may enter the bloodstream and can cause abscesses in the liver, lungs, and brain Mechanism: Ingested cysts become trophozoites in the intestine and feed on bacteria; invasive disease may develop as trophozoites release enzymes that kill epithelial cells and cause ulcers Treatment: all infections should be treated; metronidazole is prescribed first, followed by paromomycin CRYPTOSPORIDIOSIS Causative agent: protozoan Cryptosporidium species (C. parvum and C. hominis) Transmission: fecal-oral route; infectious dose as few as 10 oocysts Signs and symptoms: most show diarrheal symptoms for 1 to 2 weeks; infections of immunocompromised can lead to more serious diarrhea and death Mechanism: oocysts enter the intestines and release sporozoites; sporozoites attach to the epithelial cells and multiply, eliciting an inflammatory response; parasites undergo asexual reproduction and later sexual reproduction, producing macrogametes (female) and microgametes (male); fertilization produces oocysts that are excreted in feces Treatment: cases usually self-resolve, as long as the patient keeps hydrated. Nitazoxanide is prescribed for more severe infections or for immune-compromised patients.
Describe the role of mucosa-associated lymphoid tissues in relation to the digestive system.
Mucosa-associated lymphoid tissues (MALT) include tonsils, Peyer's patches, and the appendix. Role in relation to digestive system: limit digestive system infections From Chapter 11: Mucosa-associated lymphoid tissue (MALT) -secondary lymphoid tissue (filters lymph) -Diffuse system of lymphoid tissue -Found in all mucosal linings -Examples: Tonsils, appendix, and Peyer's patches -MALT is often more specifically named based on its location in the body, i.e., GALT—gut-associated lymphoid tissue. Peyer's patches are small masses of lymphatic tissue found throughout the ileum region of the small intestine; they form an important part of the immune system by monitoring intestinal bacteria populations and preventing the growth of pathogenic bacteria in the intestines.
Describe the features of mumps virus infections.
Mumps: caused by RNA Mumps virus, spreads through infected saliva/droplet contact -2-3 week incubation period -released in saliva almost a week before symptoms develop Signs and symptoms: -SWELLING UNDER THE CHIN AND AROUND THE JAW is typical of a mumps infection; Inflammation of the salivary glands producing gopher-like swelling of cheeks -Dry mouth, headache -Fever, nasal discharge, muscle pain, malaise -Can invade other organs: testes, ovaries, thyroid gland, pancreas, meninges, heart, and kidney -20 to 30% of young adult males, the virus localizes in the epididymis and testes, but does not cause sterility Progression -Mumps virus enters the nose or mouth -Spike-induced syncytium formation -Replicates in the upper respiratory tract -Enters the bloodstream to infect salivary glands Prevented by MMR vaccine
State some of the roles of our normal gut microbiota in health and disease.
Normal gut microbiota have essential roles in both our health and in disease -Limit available surfaces for colonization -Compete for nutrients -Excrete antimicrobial products -Assist in digestion -Provide nutrients for the body (i.e., Escherichia coli produces vitamin K) -Impacts metabolism and obesity -Affects the development of depression and diseases (e.g., diabetes) -Trains and modulates immune responses
Compare and contrast rotavirus and norovirus.
Rotavirus (acute viral gastroenteritis): -caused by RNA rotavirus with a three-layer capsule -leading cause of enteritis in children under five -fecal-oral transmission; contaminated fomite transmission -can cause dehydration; children tend to experience fever and vomiting followed by watery diarrhea that lasts 3-8 days; adults tend to have less obvious signs and symptoms -rapid identification of rotavirus antigens in stool samples for diagnosis -preventable by vaccines, good hygiene practices, and access to sanitized water Norovirus (acute viral gastroenteritis) -caused by RNA norovirus -leading cause of acute viral gastroenteritis in the U.S.; >50% of all outbreaks occur in long-term-care facilities; many outbreaks associated with cruise ships -fecal-oral transmission; contagious up to three days post recovery -requires bleach concentrations at 5-8% to destroy the virus; hand sanitizers NOT as effective as washing with soap and water -can cause dehydration; signs and symptoms develop within 12-48 hours; acute, profuse, watery diarrhea for 3 to 5 days, projectile vomiting in the early stages, mild fever -stool sample for reverse transcriptase PCR and diagnosis -no vaccine currently available, prevention involves decontamination of surfaces with chlorine bleach solution and hand washing
Distinguish the features of hepatitis A, B, and C. Compare and contrast acute and chronic hepatitis infections.
SIGNS AND SYMPTOMS OF ALL HEPATITIS *MAY* INCLUDE: -fever -loss of appetite -joint pain -fatigue -abdominal pain -nausea -clay-colored bowel movements -jaundice HEPATITIS A Cause: enveloped, single-stranded RNA virus of Picornaviridae family Transmission: mainly fecal-oral; rare contact transmission Prevention: vaccine; proper hygiene/hand washing Complications: infection in those with preexisting liver condition can be severe and even life threatening Chronic Infections: none Diagnosis: Blood tests detect HAV antibodies. Treatment: Rest, proper nutrition, and fluids; antibodies given within 2 weeks of primary exposure can sometimes limit infection HEPATITIS B Cause: enveloped, double-stranded DNA virus of Hepadnaviridae family Transmission: bloodborne, sexual, and vertical transmission Prevention: vaccine; condom usage; not sharing needles; if pregnant woman is infected, administer vaccine to baby within 12 hours of bird Complications: chronic infection with intermittent inflammation; cirrhosis; eventual liver failure; hepatocellular carcinoma Chronic infections: 90% of those under age 1; up to 50% in ages 1-5; up to 10% in ages 6 and older Diagnosis: Blood tests detect HBV viral DNA, surface antigens, or antibodies. Treatment: Rest, proper nutrition, and fluids; for chronic cases, antivirals can reduce viral load and help to clear infections HEPATITIS C Cause: enveloped, single-stranded RNA virus of Flaviviridae family Transmission: bloodborne, sexual, and vertical transmission Prevention: NO VACCINE; condom usage and not sharing needles Complications: Liver cancer and cirrhosis Chronic infections: 75-85% of patients Diagnosis: Blood tests detect HCV antibodies and surface antigens. Treatment: Most cases now curable with antivirals such as Havoni, Dalinza, and Eplcusa [all extremely expensive]
Discuss the virulence factors of Shigella and E. coli O157:H7.
Shigella virulence factors -release of endotoxin cause fever -enterotoxin: affects the entire GI tract damages the mucosa and villi, and gives rise to bleeding and secretion of mucus -Shiga toxin: only made by S. dysenteriae; responsible for more serious damage to the intestines as well as systemic effects -actin propulsion system allow it to pass between infected cells -induces endocytosis -can escape phagocytosis by causing apoptosis of macrophages -Gram-negative: endotoxic lipopolysaccharides in outer membrane E. coli O157:H7 virulence factors: -identical shiga toxin: kills host cells by inhibiting protein synthesis -resists stomach/gastric acids -low infectious dose -Gram-negative: endotoxic lipopolysaccharides in outer membrane
State the signs and symptoms of dental caries and periodontal disease and explain the role of biofilms in these conditions.
Signs and symptoms: -plaque -eroded enamel, exposing dentin -holes/cavities in teeth May result in: -pulp infection and subsequent abscess -swollen gums that pull away from the tooth (recessed gums) -tartar buildup Bioflims: Dental plaque is a biofilm -Streptococcus and Actinomyces species first attach to the tooth enamel -Viellonella and Haemophilus attach next, forming dental plaque -plaque promotes tooth decay, holding bacteria close to the tooth enamel -bacteria metabolize sugars, creating acids that erode enamel -as a biofilm, the dense, mat-like structure prevents salivary enzymes from penetrating -may calcify into tartar
