incidence - About 76 million people are sickened
annually by food-borne bacteria, with 325,000 hospitalized and
500 deaths
Gastrointestinal
Diseases
Dental Caries
epidemiology:
Streptococcus mutans - other acidogenic normal
microbiota, including S. sanguis, S. mitis and
S. salivarius (bacteria)
pathogenesis: Streptococci adhere to tooth surface
via glucans and levans produced from carbohydrates such as
sucrose (develops into plaque as salts are incorporated);
caries (cavities) generated as lactic acid (produced during
sugar catabolism) dissolves tooth enamel
treatment: physical removal of brownish-black
"rotted" material, then "filling" with dental amalgam (problem:
amalgam contains mercury)
prevention: tooth brushing and flossing; fluoride
treatment (toothpaste, drinking
water, dentist's office); reduction of simple sugar content
of diet
pathogenesis:
dental plaque accumulation leads to punched-out ulcers in
gingival (gum) tissue (spreads to soft palate, tonsilar areas)
which leads to decay of gingiva (foul odor, vile taste) which
causes loosening and loss of teeth as a result of bone
resorption
treatment: surgery, antimicrobial agent
treatment
prevention:
reduce plaque accumulation by brushing and flossing teeth as
well as by reducing dietary sugar content
Oral Herpes and Herpes
Labialis
epidemiology: Herpes Simplex Virus 1
(HSV-1)
is transmitted by direct oral contact and most people are infected as children;
as many as 90% of US adults have anti-HSV1 antibodies
pathogenesis:
recurrent chronic lesions ("cold" sores or fever blisters) near junction
between lip and facial tissue (herpes labialis) or inside the mouth (oral herpes)
treatment:
acyclovir, famvir,
or valtrex shorten disease episodes,
slow recurrence, but don't cure
prevention: avoid contact with cold sores on other
people
Thrush
epidemiology: Candida
albicans, a fungal member of normal microbiota, is an opportunistic
fungus that frequently infects immunocompromised patients
pathogenesis: throat inflammation with superficial damage ... unless
the patient is immunocompromised, then infection is chronic and damaging
treatment: nystatin or clotrimazole for routine infections; fluconazole or itraconazole
for systemic therapy, particularly in immunocompromised people
prevention: avoid broad spectrum antibiotics and immunocompromise
Peptic Ulcers
epidemiology:
Helicobacter pylori
(bacterium)
is transmitted, probably by oral or fecal/oral contact, early
in life; 80% of people in developing countries (40% in
developed countries) are infected; relationship
between H. pylori and ulcers first discovered in 1982 by Marshall
and Warren;
ulcers affect ~25 million people in the US during their
lifetime; each year:
~4 million people in the US develop ulcers
~40,000 of them are hospitalized due to this
condition
~6,000 people die of complications of ulcers, which
include bleeding, perforation of the organ walls, and
narrowing and obstruction of digestive tract passages
pathogenesis:
bacterium lives in gastric mucus, moves toward gastric
epithelial cells using its flagella, adheres to these
cells by binding proteins or glycoproteins (especially
Lewisb antigens on type O cells), produces
urease (neutralizes stomach acid; induces inflammation)
and vacuolating cytotoxin (damages gastric cells);
infiltrating phagocytes secrete cytokines that augment and
prolong inflammation, leading to formation of ulcers,
which generate a gnawing or burning pain in the abdomen ...
from the navel upwards to the breastbone; less common signs
and symptoms include: belching, nausea, vomiting, poor
appetite, weight loss, feeling tired and weak;
complications include perforated
ulcers and an up to 12-fold increased rate of gastric
adenocarcinoma (a form of cancer); possible link with sudden infant death syndrome
(SIDS)
treatment:
two combination drug therapy approaches are:
Two-week, triple therapy - 90% effective
in curing ulcers, but hard for patients to accomplish
and causes a number of unpleasant side-effects (yeast
infection in women, stomach upset, nausea, vomiting, bad
taste, loose or dark bowel movements, and dizziness):
Metronidazole (or clarithromycin) 4 times/day
Tetracycline (or amoxicillin) 4 times/day
Bismuth subsalicylate (active ingredient in
PeptoBismol) 4 times/day
Rantidine (Zantac)
may also be used to block acid production (optional)
Two-week, dual therapy - 80% effective in
curing ulcers, and is simpler for patients with fewer
side-effects:
Omeprazole (Prilosec) 2 times/day to block acid
production
prevention: avoidance of contact with feces or
vomitus (which may contain H. pylori); decreasing
smoking, decreasing caffeine intake, decreasing use of nonsteroidal anti-inflammatory
drugs (NSAIDs) and stress reduction may also help, because these all seem
to be cofactors in prolonging or worsening ulcers
Staphylococcal
Intoxication
epidemiology: ingestion of enterotoxin produced by
Staphylococcus aureus (bacterium)
in foods contaminated with it by food handlers with lesions, then "incubated" before
serving; millions of cases each year in the US (Did ya know . . . food
poisoning costs more than $22 billion per year in treatment and
lost productivity in the US?)
pathogenesis: 2-6 hours after ingestion, enterotoxin
causes emesis (vomiting) and accumulation of water in small
intestine, which causes abdominal cramps and hypermotility,
that results in diarrhea
treatment: TLC; self-limiting disease (antimicrobial
agents generally not necessary . . . nor recommended)
prevention: avoid ingestion of contaminated foods
(sanitation, hygiene)
Botulism
epidemiology: Clostridium botulinum (bacterium)
- foods contaminated with spores (from soil) and improperly canned; 20-40
cases of adult foodborne botulism per year
pathogenesis: after 12-36 hour incubation period,
exotoxin (botulin) causes flaccid paralysis of neck and chest,
which can cause death (up to 70% of untreated cases; ~5% of
treated cases) due to cardiac and/or respiratory failure (Did
ya know ... infant
botulism is an infectious disease transmitted by infants
eating honey,
which may contain Clostridium botulinum spores?; 80-90
cases per year)
treatment: antitoxin (available from CDC)
prevention: avoid ingestion of contaminated foods
via better food washing and canning techniques
(sanitation)
Enteritis
epidemiology:
Bacteria - Salmonella
enteritidis (ingested with milk, poultry, eggs; ~50,000
cases per year), Enterotoxic Escherichia
coli (ETEC;
food, water; millions of cases per year);
Bacillus cereus (rice, potatoes; hundreds of cases per
year); Clostridium perfringens (meat; hundreds of cases
per year); Campylobacter
jejuni (food and water; 5-11% of diarrheal disease
Viruses - Rotavirus (~870,000
cases per year ... ~50,000 hospitalized), Coxsackie virus and
Echovirus (water; millions of cases per year)
Cryptosporidium parvum (fecally contaminated water; ~11,000 cases/year); grows in GI tract of calves, pigs, chickens and other poultry;
transmitted to humans via improperly treated drinking water;
disease first recognized in US in 1976;
~one-third of all surface waters contain Cryptosporidium cysts
Giardia
lamblia (fecally contaminated water; ~20,000 cases/year... most commonly detected protozoan disease in US)
pathogenesis:
bacterial - damage via enterotoxins or LPS triggers accumulation of water in small intestine,
causing abdominal cramps and hypermotility, resulting in
diarrhea (~accompanied by fever, nausea and vomiting); complications - dehydration, electrolyte loss; death (rare)... E.
coli O157:H7 (4847
cases in US during 2007) causes more severe disease, often
complicated by hemolytic-uremic syndrome that leads to kidney
damage
viruses - damage intestinal epithelial cells directly via replication within them
protozoa:
Cryptosporidium - protozoal damage causes headache, low-grade fever, sweating,
nausea, anorexia, vomiting, severe abdominal cramping and
diarrhea of short duration in normal, healthy humans; but
causes chronic severe (sometimes uncontrollable) diarrhea in
immunosuppressed people and may cause death in addition to
wasting syndrome
Giardia - cyst survives stomach, develops into
trophozoite in the intestines where it adheres and proliferates
rapidly, causing maladsorption and tissue damage leading to
nausea, abdominal cramps, flatulence, foul-smelling watery
diarrhea; complications - chronic disease; carrier state
treatment:
replace water and salts as needed for all enteritis cases
antimicrobial agent therapy (sulfa drugs, ampicillin for bacteria... used
in life-threatening cases only; nitazoxanide for Cryptosporidium; furazolidone or metronidazole for Giardia... but due to side-effects of these drugs, physicians sometimes
prefer to let disease run its course without treatment)
epidemiology: Clostridium difficile – normal microbiota in the lower intestinal tract; 10-15 thousand cases per year in the US; Follows broad spectrum antibiotic therapy in the elderly – 80% of cases; Community-acquired infection is now on the rise – 20% of cases; Clostridium difficile NAP1/B1/027 is resistant to clindamycin, cephalosporins and fluoroquinolones
pathogenesis: Clostridium difficile NAP1/B1/027 produces three toxins: TcdA – enterotoxin (16x higher production than in previous C. diff); TcdB – cytotoxin (23x higher production than in previous C. diff); Binary toxin – uncertain how this toxin is involved in disease induction; Toxin-mediated damage causes pseudomembranous enterocolitis; Signs and symptoms include: watery diarrhea – at least 3 bowel movements per day for 2 or more days, fever, loss of appetite, nausea, abdominal pain/tenderness; Complications: pseudomembranous colitis (PMC), toxic megacolon, perforations of the colon, sepsis, death (rare)
treatment: ~25% of CDI patients recover on their own within 2-3 days of discontinuing broad spectrum antibiotic therapy; ~75% of CDI patients require ~10 days of therapy with oral metronidazole or vancomycin (or nitazoxanide a recently-approved synthetic nitrothiazolyl-salicylamide); ~20% of metronidazole- or vancomycin-treated CDI patients experience recurrence of disease and require additional antibiotic therapy
prevention: Avoid broad spectrum antibiotic therapy; Sanitation - Wash hands with soap and water, especially after using toilet and before eating; Clean surfaces in bathrooms, kitchens and other areas on a regular basis with household detergent/disinfectants
Cholera
epidemiology: Vibrio
cholerae (bacterium)
- present in water throughout world; ~10 cases per year in US; an epidemic that began in 1991
in South America resulted in more than a million cases and several thousand deaths; there
were ~223,000 cases of cholera worldwide in 1999, leading to ~8,500 deaths
pathogenesis:
after 2-3 days' intestinal colonization, these bacteria produce enough cholera toxin to cause
massive accumulation of water in small intestine leading to "explosive" diarrhea (rice-water
stools) and vomiting, which leads to dehydration and electrolyte loss; complications - coma
(poor blood flow to brain) and death due to shock (mortality rate is 60% in untreated cases,
~1% in treated cases)
treatment:
replace water and salts (i.v. and/or oral); tetracycline
epidemiology: Polio
Virus (virus) is transmitted via water
(summer); fewer than 10 cases per year in the US; ~270,000 cases (~25,000 deaths) per
year, worldwide;
polio costs ~$1.5 billion per year ($230 million in the
US)
pathogenesis: intestinal infection leads to
infection of motor neurons, damage causes paralysis;
complications include muscle
atrophy, paralysis, death (postpolio
syndrome, which only affects
those who had polio earlier in their lives, and for which
there is some help)
treatment: TLC, supportive measures ... such as
braces,
wheelchairs
or iron
lungs
prevention:
sanitation ... adequate treatment of drinking
water and prevention of its contamination with sewage
vaccines
injectable polio vaccine (IPV)
inactivated viruses - doesn't cause disease, but
induces production of neutralizing antibodies
(only)
Jonas
Salk developed this vaccine
oral polio vaccine (OPV)
attenuated, infectious viruses - can cause disease
in immunocompromised children, but induces CTLs as
well as neutralizing antibodies
Albert
Sabin developed this vaccine
CDC recently decreed that only IPV should
be used for vaccinating infants in the US
World
Health Organization (WHO) is spearheading a move
to eradicate
polio, and good progress
is being made in this effort
Hepatitis
A and E
epidemiology:
Hepatitis A or Hepatitis
E virus; ~3500 cases
per year in US; transmitted via raw shellfish, produce, other fecally-contaminated foods, especially
in institutions
pathogenesis: intestinal infection with Hepatitis A or E virus leads to anorexia, nausea,
vomiting, low-grade fever; systemic distribution leads to liver damage, which causes jaundice;
some people are asymptomatic, however; complications - chronic disease, relapses
are common; ~100 deaths per year in US