chapter 20 (module 7) Flashcards
20.1 The Gastrointestinal Tract and Its Defenses
long tube extending from mouth to anus, composed of eight main sections and augmented by four accessory organs
eight sections of gastro tract + other accessory components
mouth, pharynx, esophagus, stomach, small intestine, large intestine, rectum, anus
salivary glands, liver, gallbladder, and pancreas add digestive fluids
intestinal surfaces and their antimicrobial components
lots of microorganisms, and new ones every day
- all intestinal surfaces are coated with a layer of mucus, which confers mechanical protection
- Secretory IgA can be found on MOST intestinal surfaces
peristalsis keeps things moving through intestinal tract (inc. microbes)
various fluids in the GI tract have antimicrobe properties
saliva contains lysozyme and lactoferrin
stomach fluid is antimicrobial by virtue and is extremely highly acidic
bile is also antimicrobial
GALT (gut associated lymphoid tissue)
-tonsils and adenoids in the oral cavity and pharynx, small areas of lymphoid tissue in the esophagus, Peyer’s patches in small intestine, and the appendix are all packets of lymphoid tissue consisting of T and B cells and cells of innate immunity
some normal biota cloak themselves with host sugars to avoid destruction
20.2 Normal Biota of the Gastrointestinal Tract
- large variety of normal biota
- oral cavity alone has more than 600 species including Actinomyces, Lactobacillus, Neisseria, Prevotella, Streptococcus, Treponema, Veillonella
- –> and fungi such as Candida albicans
- –> protozoa such as Trichomonas tenax, Entamoeba gingivalis
what are the biofilms on the teeth
dental plaque
what are generally the first colonizers of the tooth surface after they have been cleaned?
Alpha-hemolytic streptococci, they attach to the pellicle (a membranous cover that has proteins on it)
the large intestines has _________ if microbes, even some archaea species have been found
billions
the gut microbiome influences the _________ system
nervous
In the gut, E. coli synthesizes ___________
vitamin K
Oral defenses and biota
saliva, sIgA, lysozyme, tonsils, adenoids
Biota: hundreds of gram positive and gram negative bacteria, protozoa, and fungi
other GI tract defenses and biota
GALT, lymphoid tissue, Peyer’s patches, appendix, sIgA, normal biota
biota: thousands of microbes of all kinds, aerobic and anaerobic
stomach was previously thought to be sterile due to low pH, but has lots of biota
Accessory organs of GI tract biota
salivary glands, liver, gallbladder, pancreas
–>free of natural microbiome but can be exposed to microbes when normal barriers in the gut are disrupted by a condition broadly called dysbiosis
Dysbiosis: refers to an unhealthy mix of gut microbes in the intestinal tract
–> can result in leakage of bacteria or their metabolic products into internal organs
20.3 GI Tract Diseases Caused by Microorganisms (Nonhelminthic)
Highlight Disease: Acute Diarrhea
diarrhea is usually defined as:
three or more loose stools in a 24 hour period
more than ____________ infants die a year from diarrhea
700,000
diarrheal illnesses are often accompanied by:
fever, abdominal pain and/or cramping, nausea, vomiting, and dehydration
most common culprits of foodborne illness in US
Salmonella, norovirus, Campylobacter, E. coli, Staphylococcus aureus, and Clostridium perfringens
what are the three types of data used to link illnesses to contaminated foods and solve outbreaks?
Epidemiological data:
- patterns in where and when people got sick, and past outbreaks caused by the same microbe
- interviews with sick people to look for foods or other exposures occurring more often than expected
- discovery of clusters or unrelated sick people who ate at the same restaurant, shopped at the same grocery store, or attended same event
Traceback data
- common point of contamination in distribution chain from farm to fork, found by looking into records collected
- inspections in food production facilities, or farms, and in restaurants that identify food safety risks
Food and Environment Testing Data
- the microbe that caused illness is found in a food item collected from a sick person’s home, from a retail location, or in the food production environment
- the same DNA fingerprint linking microbes found in foods or production environment to microbes is found in sick people
antimicrobials are contraindicated in most diarrheal illnesses, but in some, such as in ____________, it is a quick call for antibiotics
shigellosis
Salmonella species characteristics
motile, ferment glucose with acid and sometimes gas
- most produce hydrogen sulfide but not urease
- grow readily on most lab media and can survive outside the host in inhospitable environments such as freshwater and freezing temperatures
- resistant to bile and dyes (which are basis for isolation on selective media)
outbreaks linked to:
small pet turtles, cut fruit, ground beef, ear dog treats, frozen raw tuna, pre-cut melon, pet hedgehogs, papayas, etc.
Salmonella S/S
typhoid fever until recently was most severe manifestation
more recently a milder disease called salmonellosis has been more common, sometimes it is called enteric fever or gastroenteritis
-typhoid fever is caused by the Typhi serotype, gastroenteritises are generally caused by the serotypes known as Typhimurium, Enteritidis, Heidelberg, Newport, and Javiana
–> salmonella bacteria are normal intestinal biota in cattle, poultry, rodents, and reptiles, AND each has been a documented source of infection an disease in humans
can be relatively severe with an elevated body temperature and septicemia as more PROMINENT features than GI tract disturbance
-can also be mild with gastroenteritis, with vomiting, diarrhea, mucosal irritation as its major feature (blood can appear in the stool)
salmonella V Factors
ability to adhere to gut mucosa, evade the immune system
ENDOTOXIN LPS in gram neg bacteria
ID: 50 cells
prevention and tx
avoid contact with bacterium
uncomplicated cases treated with fluid and electrolyte replacement
if patient has underlying immunocompromise or if disease is severe, CIPROFLAXACIN is recommended
Shigella
do not produce urease or hydrogen sulfide
nonmotile, non endospore forming
resemble some types of pathogenic E. coli very closely
Shigella S/S
frequent watery stools, fever, intense abdominal pain
-nausea/vomiting
-blood in stool, and occult blood
diarrhea containing blood is called dysentery
-mucus from GI tract
shigella differs from other GI tract infections in that it invades the villus cells of the______ intestine rather than _______ intestine. and it is not as invasive as salmonella
large
small
Shiga toxin
produced by Shigella dysentery (and some other species); heat labile exotoxin
-seems to be responsible for the more serious damage to the intestine as well as any systemic effects, including injury to nerve cells
trans and epi of Shigella
oral route, direct person-to-person contact, largely b/c of small ID (10-200 bacteria)
mostly associated with lax sanitation, malnutrition, and overcrowding
-spreads epidemically in day cares, nursing homes, military camps, mental institutions
Shiga-Toxin-Producing E. coli (STEC)
S/S
agent of a spectrum of conditions, ranging from mild gastroenteritis with fever to bloody diarrhea
–> minority of patients will develop hemolytic uremic syndrome (HUS), a severe hemolytic anemia that can cause kidney damage and failure
-neurologic sx such as blindness, seizure, stroke, and long-term debilitation are possible
STEC V Factors
Shiga toxins,, are present on prophage genes donated by bacteriophage in E. coli but are on the chromosome of Shigella dysentery, suggesting that E. coli acquired the virulence factor through phage mediated transfer (transduction)
shiga toxin disrupts protein synthesis in target cells
- another V factor: the ability of STEC to efface (rub out or destroy) enterocytes (creates lesion in the gut, usually in large intestine)
- microvilli are lost from the gut epithelium and the lesions produce blood diarrhea
STEC trans and epi
ingestion of contaminated foodstuffs
STEC culture and dx
stool culture
test for shiga toxin
STEC px and tx
good food hygiene
shiga toxin is heat labile and E.coli is killed by heat aa well
antibiotics may be contraindicated due to that they may release more toxin
supportive therapy, plasma transfusion to dilute toxin in blood
other types of E. coli that can cause diarrheal diseases
Enterotoxigenic E. coli (ETEC) Enteroinvasive E. coli (EIEC) Enteropathogenic E. coli (EPEC) (pathogenic to the alimentary canal) Diffusely Adherent E. coli (DAEC) Enteroaggregate E. coli (EAEC)
Campylobacter
one of most common bacterial causes of diarrhea in US, especially Campylobacter jejuni
S/S: frequent watery stools, fever, vomiting, headaches, and abdominal pain
propelled by polar flagella at one or both poles
tend to be microaerophilic
Trans: ingestion of contaminated food or beverage, especially water, milk, chicken, and meat
V Factors: heatlabile enterotoxin, adherence and multiplication in mucus
Infection can lead to Guillain Barre syndrome, (most common precipitating event for onset of GBS)
C. difficile
G+, endospore forming rod
causes condition called pseudomembranous colitis (antibiotic-associated colitis) –> precipitated by therapy with broadspectrum antibiotics (ampicillin, clindamycin, etc.)
-produces Enterotoxins A and B and they cause areas of necrosis in the intestinal walls
more severe cases show: abdominal cramping, fever, leukocytosis
-colon is inflamed and gradually sloughs off loose, membranelike patches called pseudo membranes consisting of fibrin and cells
- in MILD cases of C. diff: metronidazole should be administered
- if more SEVERE vancomycin is choice
–> fecal implants or stool transplantation from healthy donors has been a success
Vibrio cholerae
single polar flagellum
- slightly resemble a comma
- fermentative and grow on ordinary or selective media containing bile at 37 C
- possess unique O and H antigens and membrane receptor antigens
- two major types: classic and El Tor
Vibrio cholerae S/S
inc period of few hours to a few days
-abrupt symptoms of vomiting, copious amounts of watery feces called secretory diarrhea
-intestinal contents are lost very quickly leaving only secreted fluids
so voided fluid contains flecks of mucus hence “rice-water stool”
causes loss of blood volume, acidosis from bicarbonate loss, potassium depletion which manifests as muscle cramps, severe thirst, flaccid skin, sunken eyes, and in young children coma and convulsions
secondary circulatory consequences include hypotension, tachycardia, cyanosis, collapse from shock within 18-24 hours
**if left untreated death can occur in less than 48 hours, and mortality rate is between 55% and 70%
V. cholerae V factor and trans and epi
enterotoxin : cholera toxin (CT)
cold, acidic, dry environments inhibit the migration and survival of Vibrio,
–>whereas warm, monsoon, alkaline, and saline conditions favor them
in nonendemic areas it is spread by water and food contaminated by asymptomatic carriers, but is relatively uncommon
V. cholerae tx and px
proper sewage tx and water purification
-vaccines are available for travelers and people living in endemic regions
prompt replacement of water and lytes rehydration techniques (ie. ORT is very effective
WHO solution consists of a solution of sodium chloride, sodium bicarbonate, potassium chloride, glucose or sucrose dissolved in water and can bring people back from brink of death (GREAT b/c does not require clean needles)
doxycycline in developed countries
Non Cholera Vibrio Species
vibrioses, and two most prominent species are:
- V. vulnificus
- V. parahaemolyticus
infection can be from exposure to sea water but more often is associated with eating contaminated shellfish
scientists suspect the increase in cases is due to:
- increased demand for raw oysters
- increased awareness, meaning more people are diagnoses
- climate change causing a wider habitat for bacteria in bodies of water
in people who are immunocompromised, the infections can be fatal, especially with V. vulnificus
Cryptosporidium
intestinal protozoan of the apicomplexan type
zoonosis
- humans accidentally ingest oocytes with water or food that has been contaminated by feces from infected animals
- oocytes are highly infectious and extremely resistant to disinfectants
cryptosporidium S/S + culture/dx
headache, sweating, vomiting, severe abdominal cramps, and diarrhea
-AIDS patients may experience chronic persistent cryptosporidal diarrhea which can be a criterion to help dx aids
agent can be detected in fecal samples or in biopsies using ELISA or acid-fast staining
—>stool cultures should be performed to rule our bacterial causes on infection
*many diarrheal outbreaks are assoicated with
Rotavirus
consists of an unusual double-stranded RNA genome with both an inner and outer capsid; resembles a spoked wheel
-globally rotavirus the is the primary viral cause of morbidity and mortality resulting from diarrhea, accounting for nearly 50% of all cases
- ->rotavirus vaccine
- ->transmitted by fecal-oral route, including through contaminated water, food, and fomites (for this reason the disease is most common in areas of world with poor sanitation)
- ->babies from 6-24 months old are at greatest risk
S/S: watery diarrhea vomiting dehydration shock intestinal mucosa can be chronically compromised
Norovirus
second most common cause of hospitalizations from foodborne disease in the US, cruise ships are a common place for norovirus outbreak
noroviruses can cause about five times as much foodborne illness as Salmonella
Trans: fecal-oral route via contamination of food and water
-viruses generally cause a profuse, watery diarrhea lasting 3-5 days, mild fever is often seen
Tx: focuses on rehydration
Food Poisoning
refers to symptoms in the gut caused by a preformed toxin of some sort
- -> in many cases the toxin comes from S. aureus, but can also be from Bacillus cereus and Clostridium perfringens
- -> toxin occasionally comes from nonmicrobial sources such as fish, shellfish, or mushrooms
*In any case, if the sx are violent and inc. period is very short, this condition, which is called intoxication, rather an infection, should be considered
Food Poisoning: S. aureus Exotoxin
illness associated with eating foods such as custards, sauces, cream pastries, processed meats, chicken salad, or ham that have been contaminated by handling and then left in unrefrigerated for a few hours (most often the S. aureus comes from food handler’s skin or nose)
because of high salt tolerance: even foods containing salt as a preservative can still be affected
Exotoxin (Enterotoxin): heat-stable, inactivation requires 100 C for at least 30 minutes, for this reason, heating the food after toxin production (which can usually not be seen or smelled) may not prevent disease
–>ingested toxin acts about gastro epithelium and stimulates nerves
S/S: acute, cramping, vomiting, diarrhea
-recovery is usually rapid, within 24 hours
NO ANTIBIOTICS WARRANTED
Food Poisoning: Bacillus cereus Exotoxin
sporulating G+ bacterium that is naturally present in soil
–> produces two endotoxins
1. Produces a diarrheal-type disease
2. Produces an emetic or vomiting disease
(depends on the type of food that is contaminated) - emetic form is mostly linked to rice and pasta, diarrheal is usually cooked meats or veg that have been held at warm temps for long periods of time)
Food Poisoning: Clostridium perfringens Exotoxin (HEATLABILE)
sporulating G+ bacterium causing intestinal sx
-endospores can contaminate many kind of foods, most frequently are animal flesh (meat, fish) and vegetables such as beans that have not been cooked thoroughly enough)
-acute abdominal pain, diarrhea, nausea in 8 to 16 hours, recovery is rapid and deaths are extremely rare
also causes enterocolitis, which is acquired from contaminated foods or inanimate objects (this condition is similar to the condition caused by C. diff)
Dx: detection of toxin in stool
Chronic Diarrhea
diarrhea lasting longer than 14 days
- can be result of infectious or non-infectious causes ie. IBS, ulcerative colitis
- people suffering from AIDS frequently suffer from chronic diarrhea which may be caused by opportunistic orgs like Cryptosporidium, Mycobacterium avium, etc.
Chronic Diarrhea: Enteroaggregate E. coli (EAEC)
- especially in children
- distinguished by ability to adhere to human cells in aggregates rather than as single cells
- its presence stimulates secretion of large amounts of mucus in the gut
Chronic Diarrhea: Cyclospora (P)
- first case in 1979, but since 1990 has become very common
- fecal-oral route (most cases associated with consumption of fresh produce and water, presumably contaminated with feces
- primarily of human origin but is not spread from person to person (when shed from a person it is in noninfective oocyst stage (takes days or weeks for oocysts to become active and infective)
- outbreaks have been traced to imported raspberries, salad made with fresh greens, and drinking water (outbreak in 2019 traced to fresh basil)
Chronic Diarrhea: Giardia (P)
- Giardia duodenalis (also known as Giardia lamblia or Giardia intestinalis)
- pathogenic flagellated protozoan (first observed by Antonie van Leeuwenhook in his own feces)
- most common flagellate isolated in clinical specimens
- trophozoite (stage in P life cycle where they are absorbing nutrients from host)
- Giardia cysts contain four nuclei (resemble face)
- four pairs of flagella emerge from ventral surface
S/S: diarrhea for long period of time, abdominal pain, flatulence, stools have greasy, foul-smelling quality to them, FEVER USUALLY NOT PRESENT
Chronic Diarrhea: Giardiasis Trans and Epi
cysts play a greater role in transmission than trophozoites
- cysts can survive two months in environment
- usually ingested with water and food or swallowed after close contact with infected person or contaminated objects
- ID: 10-100 cysts
-avoid drinking from freshwater sources to prevent infection
TX: tinidazole or nitazoxanide
Chronic Diarrhea: Entamoeba
- one of most significant pathogenic amoebas is Entamoeba histolytica
- pseudopods
- trophozoite version lacks most organelles and has single large nucleus that contains prominent nucleolus called a KARYOSOME
- mature cyst contains four nuclei and distinctive cigar-shaped bodies called CHROMATOIDAL BODIES (dense clusters of ribosomes)
V Factors: lytic enzymes, induction of apoptosis, invasiveness
DX: PCR, stool examination, ELISA, serology
Trans: ingesting food or drink contaminated with cysts released by asymptomatic carrier
Px: purification of water, no vaccine, boiling and iodine methods required to kill cysts
Tx: metronidazole (Flagyl) or paromomycin, drugs to relieve diarrhea and cramps, fluid+lyte loss treated with oral or IV therapy
- permanent immunity is unlikely and reinfection may occur
S/S:
- dysentery (bloody, mucus-filled stools)
- abdominal pain
- fever
- diarrhea
- weight loss
Life Threat S/S: hemorrhage, perforation, appendicitis, tumorlike growths called amoebomas, lesions in mucosa of colon have FLASKLIKE shape
can cause amoebic hepatitis after invasion of liver, pulmonary amoebiasis, other infrequent targets of infection are spleen, adrenals, kidney, skin and brain
Tooth and Gum Infections
if left undisturbed, biofilm structure eventually contains anerobic bacteria that can damage soft tissues and bones (referred to as periodontium) surrounding the teeth
Tooth and Gum Infections: Dental Carries (Tooth Decay)
- dental carries is the most common infectious disease of human beings
- process involves the dissolution of solid tooth surface due to the metabolic action of bacteria
Symptoms often not noticeable but range from minor disruption of enamel (outer) surface of tooth, to complete destruction of the enamel and then destruction of deeper layers
–> deeper lesions can result in infection to the soft tissue inside the tooth, called the PULP, which contains blood vessels and nerves; deeper infections lead to pain referred to as a “toothache”
Tooth and Gum Infections: Dental Carries (Tooth Decay)
Causative Org: a polymicrobial mixture of acid-producing bacteria
*in the absence of carbohydrates bacteria do not cause decay
Trans: direct contact
V Factors: adhesion (sticky polymers created and cause adhesion), acid production (causes carious lesions)
Culture/Dx: — based on tooth condition —
Prevention: oral hygiene, Fluoride supplementation, dietary restriction of sucrose and other refined carbos), regular brushing and flossing, fluoride added to drinking water to reduce decay (hardens tooth and encourage remineralization of decaying teeth)
Tx: removal of diseased tooth material
Epi Feats: globally, 60-90% prevalence in school aged children
Tooth and Gum Infections: Periodontitis
initial stage of periodontal disease is GINGIVITIS (inflamm. of gum tissue in contact with roots of teeth)
- signs of Gingivitis: swelling, loss of normal contour, patches of redness, and increased bleeding of gums (gingiva), spaces or pockets of varying depth also develop between the tooth and gingiva
- -> if disease develops it turns into periodontitis (the deeper involvement increases the size of the pockets and can cause bone resorption severe enough to loosen the tooth in its socket, can lead to TOOTH LOSS
Cause Org: biofilm community
predisposing condition: calculus (hard porous substance) occurs above and below the gingival margin and can induce degrees of periodontal damage
–> some of these microbes can escape into the bloodstream and increase risk of coronary diseases, autoimmune diseases, and even meningitis
V Factors: induction of inflammation (calculus), enzymatic destruction of tissues
Tx: removal of plaque and calculus, gum reconstruction, possibly anti-inflammatory treatments
A client has been diagnosed with Guillain-Barre Syndrome, which observation found in the client’s past medical hx is relevant?
a. CHF
b. Campylobacter infection
c. Dehydration
d. DM
b
Mumps (Mumps virus - genus Paramyxovirus)
Old English for lump or bump
characterized in the fifth century by Hippocrates as a self-limited, mildly epidemic illness associated with painful swelling of the angle of the jaw
Mumps: S/S
inc. period of 2-3 weeks
- symptoms of fever, nasal discharge, muscle pain, and malaise develop
- may be followed by inflammation of the salivary glands, especially the parotids (causing classic gopher like look, called parotitis)
-viral multiplication in salivary glands is followed by invasion of other organs like ovaries, testes, meninges, heart, kidney, thyroid gland, pancreas
most often ends with complete, uncomplicated recovery
–> in 20%-30% of young adult males, mumps infection localizes in the epididymis and testis, usually on one side only. The resultant syndrome of orchitis and epididymitis may be rather painful but usually does not cause long-term damage
Mumps trans and epi
humans are exclusive natural hosts of mumps virus
- communicated primarily through salivary and respiratory secretions
- lasting immunity follows infection
Mumps px and tx
general pathology of mumps is mild enough that symptomatic tx to relieve fever, dehydration, and pain is usually adequate
-vaccine recommendations call for a dose of MMR at 12-15 months and a second dose at 4-6 years
Mumps V Factors and dx
spike-induced syncytium formation
clinical, fluorescent Ag tests, ELISA for Ab
Gastritis and Gastric Ulcers
S/S and cause agent
sharp or burning pain emanating from the abdomen
- gastric or peptic ulcers are actual lesions in the mucosa of the stomach (gastric ulcers) or in the uppermost portion of the small intestine (duodenal ulcers)
- severe ulcers can be accompanied by bloody stools, vomiting, or both
*symptoms often worse at night and after eating or under psychological stress
long-term infection with helicobacter pylori is a major contributing factor to stomach cancer
Causative Org: Helicobacter pylori, closely related to Campylobacter
H. pylori transmission
probably by oral-oral route or fecal-oral route
- may also be a zoonosis
- also been found in water sources
Gastric ulcers px and tx
avoid aggravating factors ie. spicy foods, caffeine, etc.
- OTC remedies offer symptom relief; most often to neutralize stomach acid
- best tx is antibiotics augmented by acid suppressors (Helicobacter is becoming resistant to number of drugs)
Virulence Factors of Helicobacter pylori (G-) and Culture/dx
adhesins
urease (enzyme)
endoscopy
urea breath test, stool antigen test
what is jaundice caused by?
elevated levels of bilirubin in the blood
-progresses gradually from face to trunk to extremities
why are the effects of jaundice so widespread?
because jaundice is the visible effect of elevated bilirubin levels in the bloodstream, and blood infiltrates every organ
Hepatitis
when certain viruses infect the liver, they cause hepatitis, an inflammatory response that swells and disrupts the liver architecture
–> interferes with the liver’s excretion of bile pigments such as bilirubin into the intestine
when bilirubin, a greenish-yellow pigment, accumulates in the blood and tissues it causes jaundice, a yellow tinge to the skin and eyes
NOTE: noninfectious conditions can also cause inflammation and disease in the liver ie. drugs, alcohol overuse, some autoimmune conditions
Hepatitis A and E viruses
HAV and HEV are both single-stranded noneveloped RNA viruses
- considered together because both transmitted through fecal-oral route, and both cause relatively minor, self-limited hepatitis
- -> exception is infection in pregnant women, with fatality rate of 10-30%; can also be dangerous to people who have received an organ transplant and are on immunosuppressive therapy
Hepatitis A and E viruses S/S
most infections are either subclinical (asymptomatic) or accompanied by vague, flu-like symptoms
-in more overt cases, the presenting symptoms may include jaundice, swollen liver
*viruses are not oncogenic, and mostly uncomplicated (except in pregnant women and transplant patients)
Hep A and E
Trans and epi
diseases is associated with deficient personal hygiene and lack of public health measures
- in countries with inadequate sewage control, most outbreaks are associated with fecally contaminated water and food
- most infections result from close institutional contact, unhygienic food handling, eating infected shellfish, sexual transmission, or travel to other countries
*Hep A can be spread by blood or blood products, but this is the exception rather than rule
in developing countries children are the most common victims
*virus not carried chronically, so PRINCIPAL RESERVOIRS are asymptomatic, short-term carriers, or people with clinical disease
Hep A and E
px and tx
vaccine/immunization: inactivated viral vaccine (Havrix)
-short term protection can be conferred by passive immune globulin
Vaccine Twinrix can be given for people who are at risk for both hep A and B
-Hep E has NO VACCINE
drinking lots of fluids and avoiding liver irritants such as aspirin will speed recovery
Hep B and D
HBV: enveloped DNA virus in the family Hepadnaviridae; genome is partly doubles-stranded and partly single-stranded
HDV: enveloped RNA virus, and is actually a SUBVIRUS SATELLITE of HBV
—> can only propagate in the presence of HBV
intact viruses are often called _________ particles
Dane
A pt with hepatitis is admitted to an inpatient medical unit, the nurse educates her about the clinical manifestations that accompany the disease. All of the following findings may be associated with jaundice except:
a. Yellow sclerae
b. pruritus
c. clay-colored stools
d. decreased bilirubin levels
e. dark colored urine
d.
they would be high
Hep B and D S/S
in addition to direct damage to the liver cells
- may include fever, chills, malaise, anorexia, abdominal discomfort, diarrhea, and nausea
- rashes and arthritis may occur
Hep B infection may be serious and life threatening
- -> small number of patients develop glomerulonephritis and arterial inflammation
- -> in some cases chronic HBV infection can lead to liver cancer
when B and D are together it can be more severe and progress to permanent liver damage
HBV transmission
breaks in the skin or mucous membranes, or by injection into the blood stream
- multiplies exclusively in the kidneys, so continuously seeds the blood with viruses
- -> abundance of circulating virions is so high and the ID is so low that even just sharing a toothbrush or razor can spread the virus
can be spread through semen and vaginal secretions
- -> can remain active in dried blood for days, for months when stored in serum at room temp, and for decades when frozen
- boiling for 4 hours can destroy it
- disinfectants containing chlorine, iodine, and glutaraldehyde show potent anti-hepatitis B activity
Kidney fx
filter the blood (exits through urine)
HEP B culture/dx
serological tests detect either virus antigen or antibodies
Radioimmunoassay and ELISA testing are used to detect the important surface antigen of HBV very early in infection
antibody tests are most valuable in patients who are negative for the antigen
Hep B px and tx
vaccination
-recombinant, containing the pure surface antigen cloned in yeast cells
–> vaccine is a must for patients receiving multiple transfusions, immunodeficient persons, and cancer patients (and HC workers, dentists, students)
strongly recommended for newborns
Pediarix contains protection against Hep B, diphtheria, tetanus, pertussis, and polio
passive immunization with Hep B immune globulin (HBIG) gives significant immediate protection to people who have been exposed to the virus through needle puncture, broken blood containers, or skin and mucosal contact with blood
–> recommended for newborns born to an infected mother
Hep C
“silent epidemic”
RNA virus in the Flaviviridae family
many are infected and asymptomatic for decades
shares many sx with Hep B but is more likely to become chronic
possible to have severe sx without permanent liver damage
-cancer may result
Trans: blood contact more common than bodily fluid contact, vertical transmission is possible
Hep C tx and px
no vaccine
two-drug regimen: known as Direct Acting Agents (DAA)
-produces excellent results, including complete cure
Hep B px and tx
px: HBC recombinant vaccine
tx: interferon, tenofovir, or entecavir
20.4 GI Tract Diseases caused by helminths
helminths that parasitize humans are amazingly diverse, ranging from barely visible roundworms (0.3mm) to huge tapeworms (25m)
3 categories:
- Nematodes (roundworms)
- Trematodes (flukes)
- Cestodes (tapeworms)
helminthic infections usually provoke an increase in leukocytes called ____, which have specialized capacity to destroy multicellular parasites
eosinophils
“eosinophilia”; is a mark of helminthic infections and is detectable in blood counts
Helminthic infections: transmission
may be acquired through fecal-oral route or through penetration of the skin, but most of these organisms spend part of their life in the intestinal tract
Helminthic infections: Pathogenesis and V Factors in general
- have numerous adaptations that allow them to survive in their hosts
- specialized mouthparts for attaching to tissues and for feeding
- enzymes with which they liquefy and penetrate tissues
- cuticle or other covering to protect them from host defenses
- organ systems are reduced to the essentials: getting food and processing it, moving, and reproducing (reproduction system is most developed)
–> damage they cause is very often the result of the host’s response to the presence of the invader
- many helminths have more than one host during their lifetimes
- > if this is the case, the host in which the ADULT worm is found is called the DEFINITIVE HOST (usually a verebrate)
- > larval stages of helminths are found in intermediate hosts
Blood in the stool may occur in which of the following?
a. salmonella infection
b. rotavirus
c. C. diff infection
d. Shigella infection
e. b, c, and d
f. a, c, and d
f
Helminthic infection DX
O&P Test
-microscopic examination of a stool sample to look for ova or parasites
differential blood count showing increased eosinophils
serological tests indicating sensitivity to helminthic antigens
hx of travel to tropics or immigration from these regions
–> even if it was a while ago: some flukes and nematodes persist for decades
Helminthic Infections: Px and Tx in general
no vaccines
in populations in which the infections are common, prophylactic tx twice a year with anthelminthic drugs has been shown to keep people healthy
- antihelminthic drugs exist, but can be harmful to humans due to resemblance between helminthic and human cellular physiology
- -> some suppress a metabolic process that is more important to the worm than to the human
- -> others inhibit worm movement and prevent it from maintaining its position in a certain organ
*some drug resistance so surgery to remove worms or larvae may be necessary
Highlight Disease (helminthic infections with intestinal distress as primary sx)
both tapeworms and roundworms can infect the intestinal tract in such a way to cause primary symptoms there
Helminthic Infections: Enterobius vermicularis
Transmission and S/S and Dx
nematode often called the pinworm or seatworm
- transmission is cycle A type (eggs stick under fingernails and then to fomites, and upon drying become airborne and settle in house dust — eggs are then ingested from food and drink and self-inoculation from one’s own fingers)
- -> eggs hatch in small intestine and release larvae that migrate into large intestine to mature into adult worms and mate
S/S: intense anal itching
most infections are asymptomatic, but child infected can suffer from disrupted sleep, diarrhea, abdominal cramping, nausea
Dx: simple rapid test of pressing a piece of transparent adhesive tape to anal skin and then applying it to a slide for microscopic examination
- -> when one family member is diagnosed the entire family should be tested
- Eggs not present in stool so standard O&P testing is not useful in this case
Other Helminthic Infections Responsible for Intestinal Distress:
Trichuris trichiura
Trichuris trichiura, the whipworm, follows the cycle A lifestyle
(like Enterobius vermicularis (seatworm/pinworm))
-highest incidence in areas of tropics and subtropics that have poor sanitation
S/S: localized hemorrhagic of bowel caused by worms burrowing and piercing intestinal mucosa (which also provides portal of entry for secondary bacterial infection)
-heavier infections can cause dysentery, loss of muscle tone, and rectal prolapse (which may be fatal in children)
Other Helminthic Infections Responsible for Intestinal Distress: Diphyllobothrium latum (tapeworm)
has an intermediate host in fish
follows cycle C lifestyle (humans eating infected animal flesh)
-most common in Great Lakes, Alaska, and Canada
-mammals, including humans, act as definitive hosts
-can cause long-term symptoms
-can be transmitted in raw food such as sushi and sashimi made from salmon
-largest known human tapeworm, growing up to 30ft
-Tx: Praziquantel
Other Helminthic Infections Responsible for Intestinal Distress:
Hymenolepis species
small tapeworms
-MOST COMMON human tapeworm infections in the world
-follow C cycle lifestyle
Two Species:
1. Hymenolepis nana – known as dwarf tapeworm because it is only 15-40mm in length
2. Hymenolepis diminuta – the rat tapeworm which is usually 20-60 cm in length as an adult
-vehicle (ingesting insects), fecal-oral route
blood count, serology, egg or worm detection
Treatment: praziquantel
Helminthic Infections: Intestinal Distress Accompanied by Migratory Symptoms
a diverse group of helminths enter the body as larvae or eggs, mature to worm stage in the intestine and then MIGRATE into the circulatory and lymphatic systems, after which they travel to the heart and lungs, migrate up the resp tree to the throat and are swallowed –> puts mature worms in the intestinal tract where they take up residence
Helminthic Infections: Intestinal Distress Accompanied by Migratory Symptoms: Toxocara Species
Cause Org: Toxocara species
Trans: Cycle A: dog or cat feces
V Factors: –
Culture/dx: blood count, serology, egg or worm detection
Prevention: hygiene
Tx: Albendazole
D Feats: can cause migration symptoms or blindness
Epi Feats: nearly 100% of newborn puppies in US infected
Helminthic Infections: Intestinal Distress Accompanied by Migratory Symptoms:
Ascaris lumbricoides
Trans: Cycle A: vehicle (soil/fecal-oral), fomites, self-inoculation
V Factors: induction of hypersensitivity, adult worm migration, abdominal obstruction
Culture/dx: blood count, serology, egg or worm detection
Prevention: hygiene
Tx: Albendazole
D Feats: most cases mild; unnoticed
Epi Feats: internationally up to 25% prevalence (80,000-100,000 deaths per year)
Helminthic Infections: Intestinal Distress Accompanied by Migratory Symptoms:
Necator americanus and Ancylostoma duodenale (hookworms)
Trans: Cycle B: Vehicle (soil), fomite
V Factors: induction of hypersensitivity, adult worm migration, abdominal obstruction
Culture/dx: blood count, serology, egg or worm detection
Prevention: sanitation
Tx: Albendazole
D Feats: penetrates skin, serious intestinal symptoms
Epi Feats: internationally 800 million infected
Cysticercosis
Taenia solium is a tapeworm (the pig tapeworm)
- adult worms are usually around 5m long and have a scolex with hooklets and suckers to attach to the intestine
- follows C cycle, in which humans are infected by eating animal flesh that contains the worm eggs, or the worms themselves
- worldwide but mainly concentrated in areas where humans consume raw or undercooked pigs or live in close prox. to pigs
- eggs hatch in pigs intestines and the released larvae migrate throughout the organs, and encyst in pig’s muscles becoming cysticerci, young tapeworms that are the infective stage for humans
- form bladderlike sacs throughout body and can cause serious damage
- -> one of five neglected parasitic infections in US
nasty form: neurocysticercosis, in which the larvae encyst in the brain causing seizures
tx: praziquantel
Helminthic Infections: Schistosomiasis: Liver Disease
when liver swelling or malfunction is accompanied by eosinophilia
this condition should be suspected
- caused by blood flukes Schistosoma mansoni or S. japoncium
- –> species that morphologically and geographically distinct but share similar life cycles, transmission methods, and general disease manifestations
- -> **one of few infectious agents that can invade intact skin
- Another species called Schistosoma haematobium causes disease in the bladder
Helminthic Infections: Schistosomiasis: Liver Disease
S/S
most severe consequences associated with chronic infection are:
- hepatomegaly (enlarged liver)
- liver disease
- splenomegaly (enlarged spleen)
- -> occasionally, eggs from the worms are carried into the CNS and heart and create a severe granulomatous response
***Adult flukes can live for many years and elude the immune defenses, and cause chronic affliction
Helminthic Infections: Schistosomiasis: Liver Disease
Causative agent
schistosomes are TREMATODES, or FLUKES
- but are often more cylindrical than flat
- often called blood flukes
- humans are definitive hosts for the blood fluke and snails are intermediate host
Helminthic Infections: Schistosomiasis: Liver Disease
Pathogenesis and V Factors
- clever parasite
- once inside the host it coats its outer surface with proteins from host’s bloodstream, basically cloaking itself from the host defense system
- coat reduces its surface antigenicity and allows it to remain in the host indefinitely
Helminthic Infections: Schistosomiasis: Liver Disease
Trans and Epi
life cycle D, is very complex
-cycle begins when infected humans release eggs into irrigated fields or ponds either by deliberate fertilization with excreta or by defecating or urinating directly into the water
- endemic to 74 countries located in Africa, South America, and Middle East, and Far East
- –> second most prominent parasitic disease after MALARIA
Helminthic Infections: Schistosomiasis: Liver Disease
Tx
Praziquantel
endospore forming bacterium that contaminates meat and veg, and in other situations causes gas gangrene
a. Bacillus cereus
b. Clostridium perfringens
c. Shigella
d. S. aureus
B
what bacteria produces an enzyme that breaks down urea?
H. pylori
which organisms has an unusual double-stranded RNA genome?
rotavirus
the normal biota of the GI tract is most diverse in the _____ intestine
large
what organism is associated with Guillain Barre syndrome?
Campylobacter
