Bugs Week 4 Flashcards
3 MC intestinal protozoans in U.S?
- Giardia
- ) Cryptosporidium
- ) Entamoeba
Giardia lamblia (intestinalis)
Sketchy: Giardia Jungle Ride
MC intestinal parasite in US
AKA beaver fever
Symptoms for 1-2 weeks or more. May seem to resolve and come back.
FOUL SMELLING diarrhea, flatulence, stools are greasy (float), malabsorbtion of fats, lipids, vitmains
Mechanism: Presence of parasite causes loss of surface area.
Trophozoite form - attachment, but not penetration
Cysts
Fecal matter = trophozoites and cysts = positive dx
Prevent w/ water filter
Rx: Metronidazole
MSM have increased risk
Cryptosporidium parvum
Sketchy: Tales from Crypts
Water parks = Crypto country. Often seen when sanitation system fails. Chlorination/UV treatment. Storms w/ drinking water (Milwaukee outbreak –> killed AIDS patients)
Sx: Diarrhea sx for 1-2 weeks to 1 month. May seem to resolve and then come back.
Mechanism: Absorption impaired and secretion enhanced
Opportunistic infection –> HIV –> chronic diarrhea/fluid loss –> can be fatal.
Ddx: WATERY, frequent non-bloody stools. Fever and nausea sometimes.
Small acid fast oocysts in feces.
Sporozoites in the gut.
Not immediately infectious. No direct fecal to oral.
Immunocomprimed Rx: Nitazoxanide (+metronidazole?) + HAART + Loperamide + Hydration
Cyclospora cayetanensis
Coccidia sublcass organism that can cause outbreaks of GI infections.
Entomoeba histolytica
Sketchy: Enter the Historical Dig
Causes amebiasis (amebic dysentery) and amebic liver abscesses.
More prevalent in tropical/subtropical climates
Only 10-20% of infected people become ill.
Male homosexuals are most at risk.
DDx: bloody mucus-ey loose stool. Relatively mild sx, but can invade the liver and form an abcess (single abscess in right lobe; RUQ pain, fever, and weigh loss)
Lab dx: Cysts in stool.
Histolytica = tissue lysis
Rx: Tissue antiparasitic (metronidazole) and luminal antiparasitic (i.e. iodoquine/paromomycin)
Amebic vs Bacillary Dysentery
Amebic: Onset - gradual Fever - no Chills - no PUS- no Prostration - less Course - chronic
Bacillary Onset - sudden Fever - yes Chills - yes PUS - Yes Prostration - More Course - acute
Enterobius vermicularis
Sketchy: Super Worms (Vermin lady)
Nematodes (Roundworms) Pinworm
Causes: Enterobiasis (AKA pinworm infectoion)
Staple sized worms
MC helminth infection in the US
Symptom: Perianal pruritis (may also present w/ insomnia, abdominal pain, anorexia, irritability. Rarely peritoneal granulomas and vulvovaginalis.
Acquired by ingestion of pinworm eggs (viable on surfaces for 2-3 weeks.
Retroinfection!
Dx: anal itching, confirm w/ appearance of worms 2-3hrs. after asleep. AM scotch tape test. Sample from under fingernails. No eggs in stool
Rx: Albendazole, Ivermectin, pyrantel pamoate, or levamisole
Nemacantor americanus
Sketchy: Super worms (America Dude)
Nematodes/Roundworms: AKA hookworm
Eggs in stool sample for dx
Life cycle: larvae in soil –> skin penetration –> circulatory –> lungs –> cough/swallow –> GI.
Can cause pruritic papular erythemetous rash at site of infection.
Major sx is IDA (1/4ml/day/worm)
Rx: Albendazole, Ivermectin, pyrantel pamoate, levamisole
Anclyostoma duodenale
Sketchy: Super worms (American Dude)
Nematodes/Roundworms: AKA hookworm
Life cycle: larvae in soil –> skin penetration –> circulatory –> lungs –> cough/swallow –> GI.
Can cause pruritic papular erythemetous rash at site of infection.
Major sx is IDA (1/4ml/day/worm)
Rx: Albendazole, Ivermectin, pyrantel pamoate, levamisole
Strongyloides stearcolis
Sketchy: Super worms (Strong guy)
Nematodes/Roundworms: AKA hookworm
Larva in stool sample for dx.
Life cycle: larvae in soil –> skin penetration –> circulatory –> lungs –> cough/swallow –> GI.
Sx: Stomach and GI complaints. Respiratory dry cough/throat irritation. Can cause pruritic papular erythemetous rash at site of infection. Recurrent raised red rash typically along thighs/buttocks.
Autoinfection, especially w/ immunosuppressed!
Rx: Ivermectin
Trichuris trichiura
Nematodes/Roundworms:whipworm
Trichuriasis
2.2 million cases/year in the US
Dx: eggs in feces = barrel shaped appearance
Finger clubbing is best indicator of infestation
Bloody diarrhea –> IDA
Heavy cases: frequent, painful stools w/ mucus, water and blood, tenesmus. Rectal prolapse.
Rx: Albendazole, Ivermectin, pyrantel pamoate, levamisole
Ascaris lumbricoides
Sketchy: Super Worms (Lumbering tree man)
Nematodes/Roundworms: Giant roundworm
Causes ascariasis
About half the population in tropical and subtropical areas are infected (about 1 billion affected per year)
If sx are experienced = abdominal discomfort. Severe = intestinal blockages –> dx w/ ultrasonography and radiology
Can cause cough (lung life cycle) –> Charcot Leyden crystals.
Dx: eggs w/ thick shells
Rx: Albendazole, Ivermectin, pyrantel pamoate, levamisole
Taenia
Sketchy: Cestode County Carnival (Tents)
Cestode/Tapeworm
Beef or pork tapeworm - obtained through improperly cooked meat.
Rare in US (livestock)
Dx: standard intestinal problems. Stool contains eggs and/or proglottids.
Cyticercosis possible if cysticeri migrate to muscle, brain, or other tissue.
Rx: Praziquantel or Albendazole
Diphyllobothrium
Sketchy: Cestode County Carnival (guy running to bathroom)
Cestode/Tapeworm
Fish tapeworm (huge!!!)
Life cycle: uncooked fish.
Sx: standard intestinal problems. Anemia due to B12 loss*.
Dx: Stool contains eggs and/or proglottids
Rx: Praziquantel or Albendazole
Echinococcus
Sketchy: Cestode County Carnival (Cocker spaniel)
Cestode/Tapeworm
Causes ecchinococcosis
Eggs in feces of dog –> oncosphere hatches –> slow growing cysts in organs (mainly liver).
Dx: Not GI illness, pain or discomfort in UQs or chest.
Risk: sheep farming + uncontrolled living w/ canines; trappers.
Rx: Praziquantel or Albendazole
Schistoma mansoni
Sketchy: San Franschisto Ocean Park (Man and his son)
Trematodes/Flukes
Schistosomiasis -2nd only to malaria for impact of parasitic disease
Two major forms: intestinal and urogenital (haematobium)
Definitive host = humans; intermediate = snail
Sx are caused by immune response to egg stage of schistoma.
Eggs are shed by adult worms causing inflammation in scarring. Years of damage–> liver, intestine, spleen, lungs, and bladder damage.
Repeatedly infected children can develop anemia, malnutrition, and learning difficulties.
Sx: within days = rash or itchy skin. 1-2 months = fever, chills, cough, and muscle aches; chronic = abdominal pain, enlarged liver, blood in urine/stool, and dysuria (risk of bladder cancer)
Rx: Praziquantel
Shistoma japonicum
Sketchy: San Franschisto Ocean Park (Japanese tourist)
Trematodes/Fluke
Schistosomiasis -2nd only to malaria for impact of parasitic disease
Two major forms: intestinal and urogenital (haematobium)
Definitive host = humans; intermediate = snail
Sx are caused by immune response to egg stage of schistoma.
Eggs are shed by adult worms causing inflammation in scarring. Years of damage–> liver, intestine, spleen, lungs, and bladder damage.
Repeatedly infected children can develop anemia, malnutrition, and learning difficulties.
Sx: within days = rash or itchy skin. 1-2 months = fever, chills, cough, and muscle aches; chronic = abdominal pain, enlarged liver, blood in urine/stool, and dysuria (risk of bladder cancer)
Dx: stool or urine sample for eggs. Serologic test.
Rx: praziquantel (second dose often necessary. Delay if acutely dx’d)
Steroids help in acute phase.
Prevent w/ sanitation and MDA.
Rx: Praziquantel
Cercarial dermatitis
AKA swimmer’s itch
Birds pass eggs in feces –> molluscum –> humans exposed in swimming.
Bifidobacteria
First colonizers of breast-fed infants
Staph Aureus
Sketchy - Moses’s golden staff
Gram + Cocci
Catalase +
Coagulase +
Sx of food poisoning: N/V, stomach cramps, and diarrhea for 1-3 days.
Incubation = 1-7 hrs.
Rx: Self limiting (once toxin clears = no illness)
Toxin producing S. Aureus can be identified in stool/vomit.
Most conclusive test is linking of illness w/ a specific food containing preformed enterotoxin (only necessary in outbreaks)
Toxin can survive high temperatures (cooking doesn’t help).
S. Aureus can survive salt up to 15% and temps 15-45 degrees c. –> common foods = mayo/ham/custard
Bacillus cereus
Sketchy - King Anthra’s Axe
Gram + Large (box-car shaped) Bacilli Endospore forming Facultative anaerobe Mostly motile B-hemolytic
Spores are commonly found in the soil and sometimes in plant foods grown close to ground.
REHEATED RICE (spores can survive rice cooking process!)
Two forms:
1.) Emetic - 1-6 hrs incubation. N/V. (Similar to SA food poisoning.) Mechanism = preformed enterotoxin that forms holes in membranes - cerulide.
2.)Diarrheal - 6-15 years incubation. Watery diarrhea and abdominal cramps (similar to C. perf infection). Mechanism = caused by large enterotoxin that cuases intestinal fluid secretion. Not preformed –> ingest large amounts of bacteria –> toxin produced in gut. Vulnerables may require abx.
Duration for both is only 24 hrs.
Dx: Often ignored/dismissed. B. cereus in food and vomitus or feces of same serotype. Only for outbreaks.
Some produce endotoxin!
Clostridium botulinum
Sketchy - Robotulism
Gram + Bacilli
Spore forming
Obligate anaerobe
Motile
Botulism - ingesting toxin in food (home canned)
Wound botulism - generating toxin in wound (penetrating injury)
Infant botulism - ingesting spores (honey)
Rx: ventilator for respiratory failure. Antitoxin. Remove good if still in gut.
Toxin = neurotoxin that blocks SNARE proteins –> no release of Ach from motoric end plate –> descending muscle weakness and paralysis (diploplia, drooping eyelids, dry mouth, etc.)
Infants = lethargic, feed poorly, are constipated, weak cry.
Clostridium perfringens
Sketchy - Private Ringen’s motorcyle accident
Gram + Bacilli
Spore Forming
Obligate anaerobe
Non-motile
3rd MCC of bacterial food borne illness.
Sx: Diarrhea and abdominal cramps. Last less than 24 hours. Usually no fever or vomiting. Illness not passed from person to person.
Incubation = 6-24 (8-12 is MC)
Positive dx = detection of toxin or high amounts of bacteria in feces.
Mechanism = toxin widens epithelial junctions in gut.
Occurs when foods are prepared in large quantities and kept warm for a long time. Gives spore in food a chance to start bacterial growth.
Salmonella enterica
Sketchy - Salmon dinner
Gram - Bacillus
NON spore forming
H2S positive and lactose negative
Motile, flagellated
2nd MCC of bacterial food born illness
Salmonella Shigella (SS) agar (contains bile salts; indicator (lactose frementors = red) and ferric citrate (indication of H2S production –> black color)
Salmonellosis:
Sx: diarrhea (can be bloody), fever, and abdominal cramps. Usually last 4-7 days.
Reactive arthritis.
Incubation period: 12hr. to 3 day.
Dx: stool culture
Rx: supportive unless spreads beyond gut.
Resevoirs: eggs, raw milk, veggies
Campylobacter jejuni
Sketchy - Camping Guy and Bears
Gram - Bacilli
Microaerophilic
Motile
Cold sensitive
MCC of bacterial food borne illness
Zoonosis from animals/animal products (chicken).
Karmali agar is selective medium (charcoal-based w/ vanco, cefoperzone, and cyclohexamide). Sensitive organism.
Sx:Diarrhea and cramping, abdominal pain, and fever. Can last a week. Can be bloody diarrhea. Can have vomiting.
Mechanism = inflammatory response to cell invasion.
Incubation period: 2-5 days.
Positive dx: stool culture
Possible complication = Guillain-Barre; Reactive arthritis
Listeria monocytogenes
Sketchy - Santa’s list
Gram + Bacilli Non-fastidious* Flagellated, motile Non spore forming Oxidase -
B-hemolytic (under colonies)
Rare illness, a leading cause of death by food born illness.
Listeriosis = mild GI infection for most. Most vulnerable are older adults, pregnant women, newborns, and opportunistic.
Meningitis and sepsis in vulnerable populations.
Dx: Bacterium in normally sterile site (not stool!)
Mechanism for invasion: immune cells spread listeria to other organs; trojan horse; liver is a major target.
Common sources: Sprouts, deli meats and hot dogs, smoked seafood, soft cheeses, raw milk
Vibrio parahemolytica
Sketchy - Colonel Cholera sets up Base cAMP
Gram negative Vibrio (curved rod) Facultative anaerobes Flagellated, motile Oxidase +
Water loving
Kovacs oxidase reagent turns purple.
Sx: Fairly mild bloody diarrhea, stomach cramps, fever, nausea and/or vomiting. Sx last less than a week.
Immunocompromised it can spread to the blood –> deadly infections.
Mechanism = enterotoxins: hemolysins TDH and or TRH. Form pores in RBCs but also in epithelial cells
Dx: vibrio isolated
Resevoirs = shell fish.
Shigella spp.
Sketchy: She Gorilla’s Circus
Gram negative bacillus Facultative anaerobe Nonmotile Non spore forming Mainly lactose negative H2S negative
Very closel related E. coli.
Invasive
Shigella sonnei: most shigella caused GI illness
Shigella flexnori: causes bacillary dysentery (and reactive arthritis)
Shigella dysenteriae: Rarest but most severe dysentery.
Transmission: fecal-oral
Many access through M cells thorugh type III secretion system.
Actin rockets to move around
Antibiotics in severe cases.
Can cause HUS.
Shigella sonnei
Most shigella caused GI illness
Sx: Diarrhea (often bloody), fever, stomach cramps, sx start 1-2 days following exposure. Usually resolve in 5-7 days.
Shigella Dysentery
Frequent, small bowel movements w/ blood and mucus. Accompanied by rectal pain and spasms (tenesmus)
MC bacillary form is Shigella flexnori
Most severe bacillary dysentery = Shigella dysenteriae
Amebic dysentery = Entomoeba histolytica
Invasive plus has a phage-born toxin
Shiga toxin, also casued verotoxin (A-B) toxin that acts on vascular endothelial cells.
Ecoli ETEC
Sketchy - E cola’s fountain soda (traveling water truck)
Gram negative bacillus Facultative anaerobe Motile Non spore forming Mainly lactose positive
Traveler’s diarrhea, diarrhea in children
SX: profuse watery diarrhea and abdominal cramping. Fever, chills. N/V, anorexia. Typically lasts 3-4 days, less than 10
Incubation period: 1-3 days
Rx: not abx
Track outbreaks w/ commercial PCR and antibody based kits.
Typical reservoir = under-cooked beef or unclean veggies
E coli STEC (EHEC)
Sketchy - E cola’s fountain soda (kid on red stool)
Gram negative bacillus Facultative anaerobe Motile Non spore forming Mainly lactose positive
Shiga toxin w/ outbreaks in US O157:H7. Toxin is an AB5 toxin.
SX: profuse watery diarrhea and abdominal cramping. Can progress to bloody diarrhea. Fever, chills. N/V, anorexia. Typically lasts 3-4 days, less than 10
Hemorrhagic colitis and/or HUS. Children more vulnerable.
Incubation period: 1-3 days
Rx: not abx
Track outbreaks w/ commercial PCR and antibody based kits.
Typical reservoir = under cooked beef or unclean veggies
Vibrio cholerae
Sketchy - Colonel Cholera’s Base cAMP.
Gram negative Vibrio (curved rod) Facultative anaerobes Flagellated, motile Oxidase +
Kovacs oxidase reagent turns purple.
Water is primary resevoir. Fecal oral transmission.
Typically only serogroups O1 and O139 produce cholera toxin –> acitvates AC –> increase cAMP –> chloride in lumen –> water follows.
Acute illness: Rice water stools w/ severe dehydration.
Dx: by isolating causative organism from stools.
Rx: ORS/IV fluids.
Salmonella Typhi
Sketchy - Salmon dinner
Gram - Bacillus
NON spore forming
H2S positive and lactose negative
Motile, flagellated
Infections are 50x less common than nontyphoidable salmonellosis in US
Typhoid fever not typhus (rickettsial infection)
Fecal oral transmission
Vaccine available.
Life threatening illness in GI tract –> bloodstream.
Sx: high fevers (103-104), weakness and headache. Stomach pains, anorexia, diarrhea OR constipation. Sometimes a rash of flat, rose colored spots
Antibiotic treatment is recommended!
Low inoculum organisms
Shigella, Giardia, Entamoeba, Norovirus, cryptosporidosis and STEC (EHEC) E coli.
Medium is not grossly infected
Secondary cases common. Can be spread in day-care centers, families.
Example: toddler contacts cryptosporidosis in wading poool
High inoculum organisms
Vibrio cholera, C. perfingens.
Medium is highly contaminated
Secondary cases are rare
I.e. traveler gets cholera from seafood carried to US from Ecuador on luggage
Clostridium difficile
Sketchy - Field trip to the Chocolate Factory
Gram + (variable) bacilli
Spore forming
Obligate anaerobe
Motile
Exotoxins cause cell death, shallow ulcers, pseudomembranes. Early lesions are superficial. May enventually invade. Pseudomembranous colitis.
Can cause diarrhea (MC), pseudomembranous colitis, fulminant colitis (danger for perforation).
Infection induces enterocyte apoptosis.
Dx: w/ toxin detection
Rx: Metronidazole, oral vancomycin (and fidaxamicin); bowel resection or fecal transplant.
Severe disease
Rotavirus
RNA virus Icosahedral nucleocapsid Nonenveloped DS segmented Genome (III) Reovirdae (Repetovirus)
Spread fecal-oral
Cytolytic and toxin-like action on intestinal epithelium causes loss of electrolytes
Most serious in individuals under 2 (not before 6 months –> IgA in breast milk). Asymptomatic over 5 years old.
Large amounts of virus are released during diarrheal phase. Maximal at 2-5 days after the beginning of diarrhea.
Outbreaks MC at day care centers, preschools, and among hospitalized infants. –> higher cases in winter.
ELISA, RTPCR, or electron microscopy
Double capsid structure (removed by stomach –> ISVP is infectious
Group A most common (determined by VP6)
NSP4 stimulates release and cell lysis
2 vaccines: Rotarix (single strain) and Rotateq (5 strains)
Norwalk Virus
MCC of foodborne disease outbreaks in the US.
SS + RNA virus (Class IV)
Icosahedral Nucleocapsid
Nonenveloped
Calcivirae
Fecal-oral transmission
Outbreaks of gastroenteritis.
Disease resolves after 48 hrs. w/o serious consequences
Can mutate quickly (drift)
Adenovirus (serotypes 40-42)
DS DNA Virus Linear (class I)
Icosahedral nucleocapsid
Nonenveloped
Adenoviridae
ELISA or PCR
Careful handwashing, chlorination of swimming pools, supportive care.
Live oral vaccine for types 4 and 7 given to Military
