Microbiology 241



BIO241 – MICROBIOLOGY

Bacterial & Fungal Infections – Chapters 21-26

Infectious Diseases Affecting the Skin and Eyes

• Acne

o epidemiology: Propionibacterium acnes; normal bacterial microbiota; up to 85% of adolescents suffer from acne at some time

o pathogenesis: hair follicle infection that spreads into surrounding tissue, generating an abscess; complications - skin disfigurement (scars)

o treatment: tetracycline, blue light therapy, oral contraceptives, vitamin A derivatives (Retin A cream ... can cause dry skin; Accutane, an oral medication which is unfortunately also a teratogen (it causes birth defects, so it should not be used by pregnant women) ... Accutane may be linked to psychiatric problems, including a potential risk for suicide; Americans spend ~$1 billion/year on prescription drugs to treat acne

o prevention: decrease sebum accumulation by thorough personal hygiene and depress bacterial growth with topical peroxide-containing medications

• Impetigo

o epidemiology: Staphylococcus aureus and/or Streptococcus pyogenes; this bacterial disease is highly contagious in children

o pathogenesis: superficial infection leads to formation of thin-walled abscesses that look like blisters or "weeping" lesions with scabs; complications - "blood poisoning" (toxemia or septicemia)

o treatment: bacitracin salve or other antimicrobial agents resistant to bacterial enzymes that destroy penicillins

o prevention: personal hygiene; avoid contact with lesions on other people

• Furuncle (boil)

o epidemiology: Staphylococcus aureus; normal bacterial microbiota in up to 30% of normal humans

o pathogenesis: infected skin follicle leads to formation of an abscess; complications - multiple abscesses (carbuncles); "blood poisoning" (toxemia) due to systemic distribution of toxin or bacteria; osteomyelitis

o treatment: "lance" abscess; treat with bacitracin, vancomycin or other antimicrobial agents that are resistant to bacterial enzymes that destroy penicillins

o prevention: personal hygiene; avoid contact with boils on other people; newly-developed vaccine StaphVAX

• Necrotizing Fasciitis

o epidemiology: Streptococcus pyogenes (bacterium); according to CDC, there were 500-1500 cases in the US in 1996 and 20% were fatal

o pathogenesis: rapidly-spreading infection leads to destruction of tissues at sites of infection ... aka Flesh-Eating Disease; complications - formation of abscesses throughout the body and "blood poisoning" (toxemia or septicemia)

o treatment: penicillin, erythromycin, or tetracycline; surgery, when necessary

o prevention: personal hygiene

• Candidiasis

o epidemiology: Candida albicans, this dimorphic fungus is a member of the normal microbiota; likelihood of developing disease is enhanced by chronic skin moisture, especially in immunosuppressed individuals (AIDS, diabetes, etc.)

o pathogenesis: as Candida grows on the skin, it induces a bright red inflammation, blister-like superficial lesions or more severe lesions all of which are perhaps related to hypersensitivity; it sometimes occurs around the mouth (angular chelitis); complications include systemic infection, which can lead to fulminating disease and death

o treatment: clotrimazole, miconazole or nystatin for skin infections; oral ketoconazole for systemic infections

o prevention: avoid excessive skin moisture, immunosuppression

• Tineas (Ringworm)

o epidemiology: dermatophytic fungi such as Epidermophyton, Microsporium, or Trichophyton; prevalent in athletes

o pathogenesis: superficial skin infection causes granulomas on head/scalp (tinea capitis), groin (tinea curis), body (tinea corporus), foot (tinea pedis)

o treatment: lamisil (terbinafine-HCl cream ... topical); shampoo containing selenium; ketoconazole or itraconazole for initial antimicrobial agent therapy; griseofulvin (oral) for chronic infections

o prevention: avoid contact with lesions on other people's skin

o prevention: Varicella vaccine (more vaccine info); avoid contact with respiratory secretions of infected persons; varicella-zoster immune globulin (VZIG)

• Keratitis

o epidemiology: Staphylococcus aureus (bacterium), Aspergilus (fungus), Herpes simplex virus, Acanthamoeba (protozoan) transmitted by contact with contaminated water or objects; ~30,000 cases per year in the US, especially in contact lens wearers

o pathogenesis: infection results in inflammation and eventual formation of corneal ulcers, which can result in scar tissue formation (and may lead to blindness) if left untreated

o treatment: antibiotic, antiviral or antifungal ointments (plus cortocosteroids in some cases)

▪ bacterial keratitis - fluoroquinolones

▪ herpetic keratitis - acyclovir ointment

▪ Acanthamoeba keratitis - chlorhexidine or polyhexamethylene biguanide (PHMB) in combination with propamidine isethionate and neomycin

o prevention: avoid contact with infected people or objects contaminated with any or these infectious agents

Infectious Diseases Affecting the Nervous System

• Meningitis

o epidemiology: Streptococcus pneumoniae (affects children most); Haemophilus influenzae (this bacterium mostly affects children 6 months to 2 years old); Neisseria meningitidis (~2500 cases per year ... affects young adults most); Listeria monocytogenes (actually infects via the gastrointestinal tract, but ends up causing the same syndrome as the others) - all these microbes are bacteria, but viruses and fungi can also cause meningitis; ~8000 cases of aseptic (viral) meningitis per year in the US

o pathogenesis: damage to meninges (headache, coma) - complications include disseminated intravascular coagulopathy (DIC), kidney and skin damage (purperal lesions), death (~250 per year in the US)

o treatment: ampicillin (Haemophilus); penicillin (Listeria, Neisseria, and Streptococcus); amphotericin B (fungi); TLC, symptomatic relief (viruses)

o prevention:

▪ vaccines

▪ Hib vaccine induces immunity against meningitis caused by Haemophilus influenza b

▪ Menomune induces immunity against major strains of Neisserial meningitis

▪ Prevnar protects against Streptococcal meningitis

▪ avoid contact with respiratory secretions of others

• Encephalitis

o epidemiology: Encephalitis viruses are transmitted by mosquitoes (Culex tarsalis; others); reservoirs are other animals, including birds, reptiles and horses; infection is most prevalent in Summer and Fall; ~600 primary cases of encephalitis (not including West Nile) per year in the US (~100 post-infection cases); West Nile Fever is a recently emerging encephalitic disease in the US, with 9862 cases reported to CDC in 2003; we spend ~$150 million per year trying to minimize encephalitis virus transmission

o pathogenesis: mosquito "injects" virus into bloodstream; virus replicates in the CNS, causing fever and headache, vomitting,stiff back and neck, drowsiness, tremors, loss of coordination, convulsions, seizures; complications - may lead to coma as a result of CNS damage (can lead to retardation, paralysis) and death occurs in 1-60%, depending upon the virus responsible

o treatment: TLC ... management of symptoms and complications; FDA has recently approved alpha-interferon as a possible treatment for West Nile Fever

o prevention: vaccines (none for West Nile Fever); mosquito repellent use; mosquito control

• Tetanus

o epidemiology: Clostridium tetani; endospores of this bacterium enter body via animal bites, scratches, puncture wounds; fewer than 10 cases per year in US

o pathogenesis: toxin (tetanospasmin) causes CNS damage (4-21 days); complications - respiratory failure causes death (70% of patients die)

o treatment: antitoxin; penicillin; valium, barbituates (minimize damage)

o prevention: antitoxin, vaccine (DPT vaccine @ 2, 4, 6, 18 months and Td vaccine boosters at 7-10 year intervals)

• Botulism

o epidemiology: Clostridium botulinum - foods contaminated with spores (from soil) and improperly canned; ~20 cases per year in US

o 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 nonpasteurized honey, which contains Clostridium botulinum spores?)

o treatment: antitoxin (available from CDC)

o prevention: avoid ingestion of contaminated foods via better food washing and canning techniques (sanitation)

• Toxoplasmosis

o epidemiology: Toxoplasma gondii (protozoan) infection occurs via oocysts transmitted via cat feces or tissue cysts transmitted by eating undercooked meat, especially pork, lamb or venison; >20% of adults in US and >30% of world population have been infected

o pathogenesis: cysts develop into tachyzoites in intestines, invade the intestinal lining and multiply in the intestinal cells, then spread throughout the body to multiply in other cells, causing disseminated infection that leads to chronic fatigue, fever, malaise, sore throat, headache, muscle pain, swelling of spleen, liver, and lymph nodes; these signs and symptoms last several weeks, then subside as the immune system controls (but does not eliminate) the infection; some people are asymptomatic; complications include chronic latent infection often with neurologic or retinal disease (retinochoroiditis); birth defects if infected during third trimester of pregnancy; this disease is a big problem in AIDS and other immunocompromised patients

o treatment: pyrimethamine and sulfadiazine, plus folinic acid.

o prevention: cook meat to safe temperatures; avoid cat feces (pregnant women should not clean cat litter boxes)

Infectious Diseases Affecting the Cardiovascular and Lymphoid Systems

• Septicemia and Septic Shock

o epidemiology: numerous bacteria, including: Gram-negative bacteria such as Escherichia coli, Salmonella typhi, Neisseria meningiditis, Yersinia pestis and many others; several Gram-positive bacteria, such as Staphylococcus aureus, Streptococcus pyogenes, and Bacillus anthracis; these bacteria enter and grow in the bloodstream as a result of food borne infections as well as iatrogenic infections contracted in hospitals (nosocomial infections) and other health care facilities where indwelling catheters and/or intravenous feeding tubes are often used; death rate for septicemia has been increasing recently; as many as 500,000 cases each year in the US, causing 31,224 deaths in 2000, making it the number 10 killer in the country

o pathogenesis: bacteria enter the bloodstream from sites of infection and multiply there (septicemia ... aka "blood poisoning"), releasing toxic substances (endotoxin, cell wall breakdown products) that trigger neutrophils (PMNs) to release cytokines that cause fever and inflammation; this leads to skin lesions (due to hemorrhage, disseminated intravascular coagulopathy (DIC), and lymphangitis (localized red streaks representing inflammed lymph vessels)) and systemic vascular permeability which causes leakage of fluid into the tissues that leads to decreased blood pressure (hypotension) and brings on hypovascular shock (septic shock) as a result of lack of blood flow to vital organs (signs and symptoms include chills and fever (and acute respiratory disease if the lungs are involved); this leads to shutdown of one vital organ after another, which can cause death; complications include meningitis, encephalitis, limb loss; death ... untreated septic shock is 40-60% fatal

o treatment: early diagnosis and effective treatment with antibiotics can intervene in the development of this disease; if diagnosed too late, antibiotic therapy can actually enhance development of septic shock because it can cause release of bacterial toxins into the bloodstream

o prevention: avoidance of contamination of indwelling catheters and intravenous feeding tubes; early diagnosis and effective treatment with antibiotics (this is a problem these days because many hospitals have been decreasing their clinical microbiology laboratory services in an effort to save money)

• Anthrax

o epidemiology: Bacillus anthracis, an endospore-forming soil bacterium; this zoonotic disease primarily affects grazing animals such as cattle, sheep and goats, but can be transmitted to humans by contact with the endospores, either via skin wounds or by inhalation; this disease is considered to be a good candidate for biological warfare, and has been used in terrorist activities ... view a set of online CDC videos on bioterrorism

o pathogenesis: as endospores germinate, the vegetative bacterial cells begin to produce a necrotizing toxin that causes development of pustular lesions called eschars characterized by necrotic centers that will eventually be filled with black fluid; complications include fulminating septicemia that frequently leads to death, especially from the pulmonary form of the disease characterized by necrotic centers that will eventually be filled with black fluid; complications include fulminating septicemia that frequently leads to death, especially from the pulmonary form of the disease

o treatment: penicillin ... cipro (ciprofloxacin) was approved in 2000

o prevention: vaccine; avoid contact with endospore-contaminated articles such as unwashed or unsterilized wool, goat hair, cattle hides, etc.

• Gangrene (myonecrosis)

o epidemiology: Clostridium perfringens; wound is infected with endospores of this bacterium from soil, clothing, etc.

o pathogenesis: superficial infection leads to cellulitis, then to myonecrosis due to toxins; complications - death due to CNS damage caused by toxins (sometimes complicated by gas formation, hence the name "gas" gangrene)

o treatment: debridement, penicillin; hyperbaric chamber (exposure to very high concentrations of oxygen kills this anaerobe)

o prevention: early treatment may prevent full-blown disease

• Plague

o epidemiology: Yersinia pestis; this bacterium is transmitted by rat fleas; endemic in many places throughout the world, including Southwestern US (in prairie dogs, especially in the southern regions of the west); 10-20 human cases per year in the US; 1994 epidemic in India led to ~700 cases and ~60 deaths

o pathogenesis: infects and kills macrophages; whole body (liver, spleen, lymph nodes (buboes), lungs, meninges, skin) damaged, causing fever and massive blood clotting, which leads to shock, which may cause death (major complication)

o treatment: streptomycin or tetracycline

o prevention: vaccine; control rats and fleas; avoid contact

• Lyme Disease

o epidemiology:

▪ Borrelia burgdorferi (bacterium) is spread by the nymph stage (poppy-seed sized) of deer (black-legged) ticks ... it takes ~36 hours for the tick to infect you with enough bacteria to cause disease

▪ reservoirs are white-tailed deer and white-footed mice

▪ 15,000 cases reported in the US each year, mostly in children 2-15 and adults 30-55 years old who live in the Northeast and upper Midwest (more epidemiology)

▪ Lyme disease was first discovered near Lyme, CT

▪ most frequently diagnosed tick-borne disease in the US

o pathogenesis: - 60-85% of patients develop an expanding, ring-shaped ("Bull's-eye") red rash (erythema chronicum migrans or ECM) at the site of a tick-bite ... after 3 days to one month; accompanied by flu-like symptoms (malaise and fatigue, headache, fever and chills, nausea, muscle and joint pain, neck stiffness) and patients may develop secondary skin lesions, facial paralysis, forgetfulness; chronic, untreated systemic infection leads to arthritis, heart inflammation, neurological abnormalities (weeks to months); nerve demyelination may lead to multiple sclerosis-like symptoms (years after infection)

o treatment: ceftin (cefuroxime axetil), penicillin or tetracycline (after diagnosis with a newly-approved test kit, "PreVue B"); although there is controversy, it appears that long-term intravenous antimicrobial agent therapy may be required in chronic cases

o prevention: vaccine ("LYMErix") has been approved for people from age 15 to 70, but not for those under 15 ... not 100% effective, so it is still important to avoid tick-bite (wear protective clothing, use tick repellent, remove attached ticks)

• Malaria

o epidemiology: Plasmodium (falciparum, malariae, ovale, vivax) this protozoan is "injected" into the bloodstream by female Anopheles mosquitoes

▪ 41% of the world's people live in regions where malaria is transmitted

▪ with ~500,000 new cases each year, there are now 350-500 million people infected with malaria in the world, and ~1,200 cases are imported into the US each year

▪ more than 1 million people die of malaria each year (especially children under 5)

▪ malaria had even more impact prior to the mosquito eradication programs of the past 50 years, and was a major problem during World War II on the Pacific islands and Sicily

o pathogenesis: infection of liver and erythrocytes causes damage leading to chronic recurrent chills followed by high fever (104 F causes delirium, convulsions), sweating, headache, nausea, splenomegaly; complications - red blood cell loss causes anemia, "black" urine (hence "blackwater fever"); accumulation of cell fragments in small blood vessels causes cerebral hemorrhage, kidney failure, heart attack, liver damage (jaundice) and death

o treatment: quinine derivatives (chloroquine, primaquine)

o prevention: vaccine; avoid contact with female Anopheles mosquitoes (mosquito control, insect repellents, bed nets).

Infectious Diseases Affecting the Respiratory System

• Streptococcal Pharyngitis (strep throat)

o epidemiology: Streptococcus pyogenes (bacterium); occurs mostly in children and young adults; frequently related to tonsillitis and its complications

o pathogenesis: bacteria produce pyrogenic toxin which causes pharyngitis (cell damage, inflammation leads to sore throat, coughing); complications include scarlet fever ( more info), rheumatic fever and toxic shock syndrome ... check out the online diagnostic form for strep throat!

o treatment: penicillin (erythromycin if patient is allergic to penicillin); symptomatic relief

o prevention: avoid contact with respiratory secretions of infected persons

• Otitis Media

o epidemiology: Streptococcus pneumoniae, Haemophilus influenzae (bacteria) or various viruses; most often affects children aged 3 months to 3 years old, but may occur at any age

o pathogenesis: microbes invade the middle ear via the eustacean tube, causing inflammation that results in swelling and fluid accumulation which can result in pain, fever, discharge and damage to the eardrum, causing impaired hearing (and sometimes affecting balance); complications include perforation of the eardrum or necrosis of the middle ear, leading to conductive hearing loss

o treatment: antibiotics in conjunction with corticosteroids

o prevention: avoid contact with respiratory secretions of infected persons

• Diphtheria

o epidemiology: Corynebacterium diphtheriae (bacterium) - few cases in US due to vaccine-induced "herd" immunity (fewer than 10 cases per year in the US); Elisha Otis, the inventor of the elevator, died of diphtheria; countries of the former Soviet Union have reported >150,000 cases in an epidemic the began in 1990

o pathogenesis: pharyngitis (cell damage, inflammation leads to sore throat, coughing); diphtheria toxin causes pseudomembrane formation in the throat, then toxin goes systemic to cause heart, kidney and CNS damage (inhibits cellular protein synthesis); complications include paralysis, death

o treatment: antitoxin, then penicillin

o prevention: vaccine (DPT vaccine @ 2, 4, 6, 18 months and Td vaccine boosters at 7-10 year intervals); avoid contact with respiratory secretions

• Pertussis (whooping cough)

o epidemiology: Bordetella pertussis (bacterium) - human reservoir; 25,616 cases in US during 2005 (~250,000 cases in 1950; lower now because of vaccine use)

o pathogenesis: 2-5 day incubation period leads to pharyngitis (cell damage, inflammation due to pertussis toxin causes sore throat, coughing), then progresses to bronchitis (loss of ciliated epithelial cells) causing bronchial accumulation of mucus and repetitive coughing; complications - 0.5-10% die

o treatment: erythromycin

o prevention: vaccine (DPT vaccine @ 2, 4, 6, 18 months); avoid contact with respiratory secretions

• Pneumonia

o epidemiology:

▪ ~5 million cases reported each year in the US; 61,472 people died of pneumonia (together with influenza) in 2004 ... making this combination the number 8 killer in the US

▪ Streptococcus pneumonia (this bacterium generally causes secondary infections); other bacteria, including Legionalla pneumophila, which causes Legionaires' Disease, and Mycoplasma pneumoniae or Chlamydia pneumoniae which both cause primary atypical or "walking" pneumonia; Pneumocystis carinii (opportunistic fungus that infects mostly immunocompromised individuals); Respiratory Syncytial Virus (causes disease mostly in children under the age of two)

o pathogenesis: infection of alveoli leads to accumulation of fluid in lungs, which causes congestion (difficulty breathing, loss of energy, fever); complications include congestive heart failure, meningitis, death

o treatment:

▪ CTAs for bacteria ... penicillin for S. pneumoniae; tetracycline or erythromycin for M. pneumoniae, C. pneumoniae, or L. pneumophila

▪ CTAs for P. carinii ... pentamidine, sulfa drugs (SxT)

▪ TLC, including symptomatic relief, for viruses such as RSV

o prevention: vaccine (S. pneumoniae); avoid contact with respiratory secretions of infected persons ... especially those with influenza; disinfection of water-based evaporative air conditioning systems (L. pneumophila)

• Tuberculosis

o epidemiology: Mycobacterium tuberculosis (bacterium) - 14,097 cases (and ~1500 deaths) in 2005 in the US; during the 1940s, ~100,000 cases each year (and ~40,000 deaths); there are now ~2 billion infected people worldwide, with ~8 million new cases and ~3 million deaths each year in the world ... TB is the leading cause of death from a single identifiable infectious disease in the world as a whole, and the main cause of preventable death people ages 15-40

o pathogenesis: survives inside macrophages; chronic lung infection leads to granuloma formation, causes poor lung function (cough, bloody sputum, pain, lack of energy, weight loss, night sweats); complications include chronic progressive lung disease, death (50% mortality without treatment)

o treatment:

▪ 6-24 months combination CTA therapy (often including rifampin and isoniazid)

▪ Directly Observed Therapy Short-course (DOTS) strategy using daily combination therapy (up to four CTAs) for 6-8 months is used frequently

▪ DOTS-Plus is a new approach in which patients take up to seven CTAs daily for 18-24 months (better cure rate)

▪ there is much concern about drug resistant TB ... see where it is most problematic

▪ with the currently recommended treatment, 249 million additional cases and 90 million deaths are predicted during the next 30 years

o prevention: avoid contact with respiratory secretions of infected persons; early detection, treatment prevents spread; BCG vaccine, Europe and Asia

• Histoplasmosis

o epidemiology: Histoplasma capsulatum (fungus) - inhalation of spores present in bird droppings transmits; ~500,000 new cases per year in US; highest incidence in people between 15-34 years old; H. capsulatum infections clustered geographically (primarily SE US)

o pathogenesis: lung infection (5-18 days) leads to granuloma formation and causes loss of lung function (lack of energy) together with fever, chills, cough that brings up mucus or pus, and possible joint stiffness; very similar to TB, but less serious; complications - chronic, progressive lung disease, spread via blood to other organs (more likely in immunosuppressed people or in very young children); death ... mortality rate of 0.05 per 100,000 (138 deaths per year)

o treatment: amphotericin B, ketoconazole or itraconazole

o prevention: avoid contact with bird droppings (which contain spores)

Infectious Diseases Affecting the Gastrointestinal Tract

Dental Caries

• epidemiology: Streptococcus mutans - other acidogenic normal microbiota, including S. sanguis, S. mitis and S. salivarius

• 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

Periodontal Disease - Acute Necrotizing Ulcerative Gingivitis (ANUG)

• epidemiology: Bacteriodes forsythus, Leptotrichia buccalis, Pophyromonas gingivalis, Treponema vincentii and Eikenella spp. (normal bacterial microbiota)gingival (gum) tissue (spreads to soft palate, tonsilar areas) leads to decay of gingiva (foul odor, vile taste), which causes loosening and loss of teeth

• pathogenesis: dental plaque accumulation leads to punched-out ulcers in gingival (gum) tissue (spreads to soft palate, tonsilar areas) leads to decay of gingiva (foul odor, vile taste), which causes loosening and loss of teeth

• treatment: surgery, antibiotic treatment

• prevention: reduce plaque accumulation by brushing and flossing teeth as well as by reducing dietary sugar content

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

• prevention: avoid broad spectrum antibiotics, immunocompromise

Helicobacter Peptic Disease Syndrome (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:

o ~4 million people in the US develop ulcers

o ~40,000 of them are hospitalized due to this condition

o ~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 cancer; possible link with sudden infant death syndrome (SIDS)

• treatment: two combination drug therapy approaches are:

o 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)

o Two-week, dual therapy - 80% effective in curing ulcers, and is simpler for patients with fewer side-effects:

▪ Amoxicillin 2-4 times/day (or clarithromycin 3 times/day)

▪ Omeprazole (Prilosec) 2 times/day to block acid production

• prevention: avoidance of contact with feces or vomitus (which may contain H. pylori);diminished smoking, caffeine intake, use of nonsteroidal anti-inflammatory drugs (NSAIDs) and stress 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)

Mycotoxicosis

• epidemiology:

o Aspergillus flavus (fungus) grows on food (especially peanuts) stored in moist places and produces aflatoxin

o Aminita, Clitocybe, and Psilocybes (fungi) are poisonous mushrooms due to their production of one or more of these toxins ... phalloidina, amatoxin, ibotenic acid, muscimol, muscarine, psilocybin

• pathogenesis:

o ingestion of aflatoxin along with food damages intestines and liver; complications - liver cancer

o ingestion of various toxins when one eats poisonous mushrooms can cause damage to certain portions of the body

▪ amanitin (amatoxin) causes kidney and liver toxicity followed by violent vomiting, bloody diarrhea, and severe abdominal cramps, and can cause death if the dose is high enough

▪ ibotenic acid and muscimol cause nausea and vomiting, together with CNS effects including confusion, visual distortion, a feeling of greater strength, delusions, convulsions and drowsiness (may fall asleep and cannot be roused)

▪ muscarine causes excessive salivation, sweating, tears, lactation (in pregnant women), plus severe vomiting and diarrhea

▪ psilocybin causes hallucinations

• treatment: TLC, supportive therapy aimed at eliminating toxins, possible liver transplant for amanitin poisoning

• prevention:

o avoid eating aflatoxin by preventing fungal contamination of foods that will be ingested (low-moisture storage conditions for peanuts, etc.)

o avoid eating wild (noncommercial) mushrooms

Enteritis

• epidemiology: Bacteria - Salmonella enteritidis (ingested with milk, poultry, eggs; 47,995 cases in US during 2007), 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; more about Campylobacter); Viruses - Rotavirus (~870,000 cases per year ... ~50,000 hospitalized), Coxsackie virus and Echovirus (water; millions of cases per year)

• pathogenesis: enterotoxin or LPS (bacteria) or viral cell damage lead to accumulation of water in small intestine, which causes 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

• treatment: replace water and salts as needed; antimicrobial agent therapy (sulfa drugs, ampicillin) is used in life-threatening cases only

• prevention: rotavirus vaccine; avoid contamination and ingestion of foods and water ... maintain adequate sewage treatment and drinking water purification

Bacillary Dysentery (Shigellosis)

• epidemiology: Shigella dysenteriae, Shigella boydii, Shigella flexneri, Shigella sonnei (bacteria); transmitted via fecally-contaminated drinking water or food; 19,758 cases of Shigellosis in US during 2007; ~165 million cases of severe dysentery and ~1 million deaths worldwide (mostly in developing countries) each year

• pathogenesis: Shigella damages epithelial cells of intestine, causing nausea, abdominal cramping, diarrhea (leads to dehydration and electrolyte loss), mucosal ulceration, rectal bleeding, blood and "sheets" of PMNs in stools (S. dysenteriae may produce a neurotoxin that causes vomiting and/or Shiga toxin that can lead to hemolytic uremic syndrome); may last 3-6 weeks; complications - death (10-15%) due to circulatory collapse in severe cases

• treatment: replace water and salts; trimethoprim-sulfamethoxazole, norfloxacin, ciprofloxacin, or furazolidone if patient is very young or very old and at risk of death

• prevention: avoid ingestion of contaminated water ... maintain adequate sewage treatment and drinking water purification

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

• prevention: new oral cholera vaccine; avoid ingestion of contaminated food or water ... maintain adequate sewage treatment and drinking water purification

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