Bugs Flashcards
S. aureus
shape & stain, toxins, symptoms, contraction
Gram + cocci in clusters preformed enterotoxins N/V, watery diarrhea rapid onset within 6 hours; rapid resolution 24-48 hours Contracted from ham, poultry, dairy, EGGS, CREAM PASTRIES, POTATO SALAD, MAYONNAISE
Bacillus cereus
shape & stain, toxins, symptoms, contraction
Gram + rods Preformed enterotoxins Vomiting (mainly), watery diarrhea Rapid onset within 6 hours; rapid resolution 24-48 hours Contracted from FRIED RICE, meats, veggies, dried beans, cereals
Clostridium perfringens
Gram + spore-forming rods
Preformed enterotoxins
Watery diarrhea (no fever or vomiting), crampy abd pain
Rapid onset within 8-16 hours;
Rapid resolution within 24-48 hours
Contracted from beef, ham, poultry, legumes, gravy (inadequately cooked)
Shigella spp
shape & stain, toxin, Symptoms, Contraction,
Dx, Tx, Complications
Gram - Rods, nonmotile
Shiga toxin
dystentery: bloody diarrhea (begins watery -> bloody with fever), abd cramps
Lasts 1-2 weeks
Tests: fecal leukocytes +, lactose - on stool culture
Tx: bismuth, ampicillin, fluoroquinolone, or trimethoprim/sulfamethoxazole
Complications: respiratory complaints and seizures (children), reactive arthritis, HUS
Reactive arthritis
Can’t see, can’t pee, can’t climb a tree
- conjunctivitis - discharge, erythema, burning, photophobia
- urethritis - dysuria, urgency, frequency, discharge
- arthritis - knees/ankles/feet
Salmonella typhimurium
shape & stain, symptoms, contraction, Dx, Tx, complications
gram -, non-lactose fermenting, motile, rod-shaped
watery -> bloody diarrhea, fever, abd cramping, N/V
Lasts 5-10 days, self-limited
Fecal leukocytes +
Contraction by food, esp EGGS, POULTRY, milk/dairy products, beef, shellfish or from animals - TURTLES, ducks, birds
Increased risk with immunocompromised (esp sickle cell)
Labs: stool culture
Do NOT give antibiotics
Complications: reactive arthritis, endocarditis, septic arthritis, osteomyelitis
Salmonella typhi
shape & stain, transmission, symptoms, Dx, Tx
gram - rod
International travel (humans are the only carrier), poor sanitation, fecal-oral
Sx: typhoid fever: systemic sustained febrile, high ever, weakness, headache, anorexia, RLQ pain, rash of flat rose-colored spots, diarrhea
Dx: samples of stool or blood; fecal leukocyte +
Tx: fluoroquinolones, ceftriaxone, azithromycin
Campylobacter jejuni
shape & stain, transmission, Sx, Dx, Tx, complications
gram - curved/spiral shaped rod
ingestion of raw/undercooked meat (POULTRY), diary (raw milk), birds and ducks are hosts, cross-contamination during food prep, contaminated water
Self-limited watery -> bloody diarrhea, fever, cramps abd pain
Dx: stool culture with campy blood agar, oxidase +, motile
Tx: supportive
Complications: 1-8 weeks post diarrhea: reactive arthritis, Guillian-Barre Syndrome
Vibrio cholerae
shape & stain, Sx, transmission, Dx, Tx
gram - bacilli, anaerobic, curve/comma shaped with flagellum
N/V, abd cramping, profuse watery (rice water) diarrhea, dehydration
12-48 hour incubation
waterborne illness (saltwater); eat raw oysters, sewage)
Duration: 1 week
Dx: stool microscopy
Tx: rehydration, antibiotics
Vibrio Parahemolyticus
shape & stain, toxin, transmission, Dx, Sx
gram - bacilli
cytotoxin production
Sx: N/V, abd cramps, watery -> bloody diarrhea
Dx: fecal leukocyte +, stool culture
Lasts 2-5 days
Sea-food associated: shellfish, oysters, shrimp
Vibrio Vulnificus
shape & stain, transmission, Sx
gram - bacillus
transmitted in coastal salt water through open wounds, and eating raw shellfish (oysters)
Sx: vomiting, diarrhea, abd within 16 hours of ingestion, bullies skin lesions
*life-threatening in immunocompromised (esp cirrhosis and hemochromatosis)
Aeromonas hydrophila
shape & stain, transmission, Sx, Tx
gram -, non-spore forming, rod-shaped, motile
fresh water environment, eating fish or shellfish, foot and ankle wounds in water
Sx: necrotizing fasciitis, cholera-like (watery rice water stools) OR bloody mucoid stools
Tx: ampicillin
Causes of Travelers diarrhea
most common = ETEC
Others: campylobacter (Asia), salmonella, shigella, aeromonas, EAEC, coronavirus, Giardia (Russia, campers, backpackers, swimmers in wilderness), Cyclospora (Nepal), Norovirus (cruise ships)
ETEC
shape & stain, transmission, Sx, Dx, Tx
gram - rod
ingestion of contaminated food or water
Sx: N, occasional fever & vomiting, watery diarrhea
Sudden onset, 3-6 day duration
Dx: fecal leukocyte -
Tx: Antibiotics (trimethoprim/sulfamethoxazole, doxycycline, ciprofloxacin), bismuth
EHEC
shape & strain, toxin, transmission, Sx, Tx, complications
(O157:H7) gram - rod, shiga-toxin
food-borne: undercooked meat, raw veggies, raw milk, unpasteurized apple cider
animal contact
Sx: watery -> bloody diarrhea -> ischemic colitis, no fever, peripheral leukocytes +, fecal leukocytes +
Tx: supportive, rehydration
Complications: HUS 5-10 days into course; more likely in kids and if treated with antibiotics
Other E. coli
EAEC - persistent diarrhea in kids
EPEC - infantile watery or bloody diarrhea
EIEC - fever, abd pain, watery -> bloody diarrhea with leukocytes (dysentery)
Yersinia enterocolitica
shape & strain, transmission, Sx, Dx, Tx, complications
gram - coccobacilli
transmission by contaminated food/water or dairy, contaminated domestic animal feces
Sx: bloody diarrhea, fecal leukocytes +, fever, cramps, N/V, Abd pain & pharyngitis
Duration 10-20 days
Dx: stool/blood cultures
Tx: supportive care
Complications: rash, reactive arthritis
Note** - higher risk in those with derangements of iron metabolism, diabetes, and preexisting GI disorders
Note** - can mimic appendicitis
Listeria monocytogenes
shape & strain, transmission, Sx, Dx, Tx, Complications
gram + rod
get from contaminated food (raw milk, unpasteurized diary, and deli meats)
Sx: fever, non-bloody diarrhea, headache, N/V 2-3 days duration
Dx: blood culture or CSF, stool cultures
Tx: ampicillin and trimethoprim/sulfamethoxazole
Complications: causes meningoencephalitis and listeria placentis
- Note it has a predilection for pregnant women, extremes of age, immunosuppressed, and those with hemochromatosis
- Note that this can grow at cold temps
Clostridium difficile
shape & strain, toxin, transmission, Sx, Dx, Tx, complications
anaerobic, gram +, spore-forming bacillus
Cytotoxin production (exotoxin mediated)
Transmission: within last 2 months - hospital stay or ill contact? antibiotic use? Especially clindamycin, cephalosporins, and fluoroquinolones? PPI?
Sx: watery diarrhea, abd pain, fever, peripheral leukocyte +, pseudomembranes on colonic mucosa
Dx: stool - PCR for toxin
Tx: PO or IV metronidazole, PO vancomycin
Complication: toxic megacolon
Rotavirus
type, age, transmission, Sx, Dx, Tx
double stranded RNA virus
infants (children < 2), can occur in adults
spread via fecal-oral
Sx: vomiting and watery diarrhea, severe dehydration, fecal leukocytes -
symptoms begin within 72 hours and last 2-3 days, up to 5
Dx: viral culture or PCR, “wagon wheel” appearance on electron microscopy
Tx: supportive care
- Note: death can occur by dehydration
- Note: most common cause of acute diarrhea in infants
Adenovirus
type, age, Sx, Dx, Tx
double stranded DNA virus children Sx: fever, chills, myalgias, sore throat, watery diarrhea, vomiting, conjunctivitis, pharyngitis prolonged course (10 days) Dx: viral culture Tx: supportive
*Note: most common cause of viral conjunctivitis in children
Norwalk/Norovirus
type, age, transmission, Sx, Tx
small non-enveloped RNA virus
older children and adults
fecal-oral transmission; outbreaks via contaminated food, water, person-person
Sx: vomiting, watery diarrhea (4-8 stools/day)
symptoms within 24-48 hours, lasts 3 days
Tx: supportive care
*Note: strong association with nursing homes, child care centers, schools, and CRUISE SHIPS
Cytomegalovirus
type, population, Sx, Dx
herpes virus family - double-stranded linear DNA
primarily immunosuppressed/AIDS patients, CD4 < 200
Sx: fever, abd pain, bloody diarrhea
persists for several weeks
Dx: endoscopy with biopsy of ulcerated lesions using CMV stains
Entamoeba histolytica
characteristic, transmission, Sx, Dx, Tx, complications
“flask-shaped ulcer”
Transmitted fecal-oral in crowded living conditions
Endemic in Asia, Africa, Central and South America
Sx: fever, tenesmus, bloody diarrhea, abd pain, fecal leukocyte +
Persists for days-weeks
Dx: stool for ova and parasite, stool Ag (PCR for DNA)
Tx: metronidazole and paromomycin
Complications: can penetrate bowel -> portal circulation -> liver abscesses, toxic megacolon or pneumatosis coli
*Note: most common cause of dysentery in the world
Giardia lamblia
characteristic, transmission, Sx, Dx, Tx
pear-shaped, 4 flagella, 2 nuclei protozoan
fecal-oral transmission, acquired through water (lakes and streams), hiking/camping, beavers, Russia, daycares
Sx: watery (malodorous) diarrhea, steatorrhea, flatulence, abd pain, belching, weight loss, nausea, malaise, cramps, anorexia, bloating, fecal leukocyte -
lasts 14-28 days
Dx: check stool for ova parasites, stool Ag detection
Tx: metronidazole
Cryptosporidium (self-limited and life-threatening)
population, transmission, Sx, Dx, Tx
life-threatening in immunosuppressed patients (AIDS CD4 < 200)
transmission: water borne organisms, contaminated food/water, outbreaks with swimming pools, unsanitary milk production, municipal water supplies, person-person
Sx: nausea, malaise, abd cramping, large volume of watery diarrhea, fecal leukocyte -
(in AIDS patients -> biliary Dz also)
Dx: stool Ag detection or direct microscopy
modified acid-fast staining, direct fluorescent Ab
Tx: supportive care, AIDS = antivirals to increase CD4
Strongyloides stercoralis
type, transmission, Sx, Dx, Tx
nematode: roundworm
enter body through exposed skin from contaminated soil
Risk factors: poor, rural, institutionalized, immunocompromised
Sx: Abd pain, bloating, diarrhea, cough, SOB, perianal urticaria, migratory rash
Dx: rhabditiform larvae in stool, eosinophils in stool
Tx: anti-helminthic
Cyclospora cayetanensis
transmission, Sx, Dx, Tx
transmitted via produce imported from endemic areas: lettuce, basil, raspberries, travel to endemic areas: tropical and subtropical regions
Sx: malaise, anorexia, nausea, low fever, watery diarrhea, fecal leukocytes -
can last 21 days in immunocompetent, indefinitely in immunosuppressed
Dx: oocysts in stool sample
Tx: TMP/SMX
Cystoisospora belli
endemic, transmission, Sx, Dx, Tx
Most common in tropical and subtropical areas
Spread by contaminated food or water
Sx: acute, non-bloody, watery diarrhea with abd cramping
can last for weeks -> malabsorption & weightless, eosinophilia
Dx: repeat stool examinations for oocysts
Tx: TMP/SMX
Ascaris lumbricoides
type, transmission, Sx
hookworm, fecal oral transmission, can cause bowel obstruction
Diphyllobothrium latum
type, transmission, Sx
fish tapeworm, transmission with raw/undercooked fish, can cause B12 def -> pernicious anemia
Schistosoma mansoni
endemic, transmission, Sx
Africa, transmitted by freshwater snails through skin, causes bloody stools, bladder cancer, liver cysts
*Note: 2nd most common cause of esophageal varies in Africa
Taenia solium
type, Sx
pork tapeworm, mostly asymptomatic -> rare, serious cases of seizures and muscle or eye disease
Echinococcus granulosus
type, transmission, Dx
tapeworm
transmitted by unsanitary livestock, especially sheep and dogs, humans are infected fecal-oral, poor sanitation through infected dogs
form cysts in liver or lungs
looks like free-flowing “hydatid sand” on CT
Name the symptoms of a pathogen that commonly affects the small bowel
Presents with: large volume, watery stools, abdominal cramps, weight loss, fecal leukocytes -, mid abdomen or diffuse pain, dehydration/malabsoprtion
Name examples of pathogens that commonly affect the small bowel (15)
Salmonella, Vibrio cholerae, ETEC, EPEC, Yersinia, Rotavirus, Norovirus, CMV, Adenovirus, Giardia, Cryptosporidium, Cyclospora, Clostridium perfringens, Staph aureus, Bacillis cereus
Name the symptoms of a pathogen that commonly affects the large bowel
Presents with: frequent, small volume stools
May be associated with fever, blood in stool, fecal leukocyte +, lower abd or rectum pain
Name examples of pathogens that commonly affect the large bowel (12)
Campylobacter, Salmonella, Shigella, Yersinia, EIEC, EHEC, C. diff, Vibrio parahaemolyticus, E. histolytic, CMV, Adenovirus, Herpes simplex
What infections are AIDS patients more likely to acquire? (10)
Cryptosporidium, Cystoisospora belli, Cyclospora, Salmonella, Campylobacter, Shigella, Mycobacterium avium complex, CMV, Herpes, Adenovirus
What infections are patients with hemochromatosis more likely to acquire? (3)
Vibrio species, Listeria, Yersinia infections
HAV
family, prodrome, duration, risk factors, Sx, Labs, vaccine, acute/chronic, mortality
family: hepatovirus/picornavirus family, single stranded RNA genome
prodrome: anorexia, N/V, malaise, aversion to smoking
Duration: 2-3 weeks
Risk factors: international travel, contaminated water or food, shellfish
Sx: fever, malaise, myalgia, arthralgia, UR, anorexia, enlarged and tender liver, jaundice, N/V, diarrhea/constipation
Labs: markedly elevated AST/ALT, mild proteinuria, bilirubinuria, anti-HAV Ab, IgG anti-HAV (in the absence of IgM) indicates previous exposure
Vaccine: HAV vaccine in US
Acute only
Low mortality
HBV
family, prodrome, duration, risk factor, Sx, Transmission, Labs, Vaccine, acute/chronic, complications
Family: hepadnavirus, partially double-stranded DNA genome
Prodrome: anorexia, N/V, malaise, aversion to smoking
Duration: 2-3 weeks
Risk factors: men who have sex with men, those at hemodialysis centers, previously incarcerated, previously treated for STI, drug abusers
Sx: low grade fever, enlarged and tender liver, jaundice; may also be associated with glomerulonephritis, serum sickness, and polyarteritis nodosa
Transmission: endemic in Africa and Southeast Asia
Labs: markedly elevated aminotransferases early in course
Vaccine: yes
90% acute & recover
Complications: cirrhosis, HDV superinfection, hepatocellular carcinoma (men > women)
What does the HBV serology look like during the window period?
HBsAg -, Anti-HBs -, Anti-HBc IgM +, Anti-HBc IgG -, HBeAg -, HBV DNA -
What does the HBV serology look like during the acute infection?
HBsAg +, Anti-HBs -, Anti-HBc IgM +, Anti-HBc IgG -, HBeAg +, HBV DNA +
What does the HBV serology look like with prior infection?
HBsAg-, Anti-HBs +, Anti-HBc IgM -, Anti-HBc IgG +, HBeAg -, HBV DNA -
What does the HBV serology look like with chronic infection?
HBsAg +, Anti-HBs -, Anti-HBc IgM +, Anti-HBc IgG +, HBeAg +, HBV DNA +
What does the HBV serology look like with immunization?
HBsAg -, Anti-HBs +, Anti-HBc IgG -, Anti-HBc IgG -, HBeAg -, HBV DNA -
What does HBsAg indicate?
surface Ag, first evidence of infection, positive during acute and carrier (chronic) state
What does HBsAb indicate?
surface Ab, immunity to HBV
What does HBcAg indicate? HBcAg IgM/IgG?
core Ag
IgM = appears shortly after HBsAg is detected, only thing detectable during the GAP/Window period -> considered acute HBV
IgG = appears during late in acute phase and persists indefinitely whether person gets chronic infection or immunity (prior infection)
What does HBeAg indicate?
correlates with viral proliferation and infectivity, positive during acute and active chronic, negative in the inactive chronic carrier state
What does HBV DNA indicate?
detectable during current infection, typically parallels the presence of HBeAg
HDV
family, risk factors, labs, vaccine, mortality
Family: defective virus that requires HBV for replication
Risk Factors: co-infects with HBV or supenrinfects those with HBV, endemic along Mediterranean Basin where it spreads non-percutaneously
Nonendemic areas it spreads percutaneously in HBsAg+ IV drug users or hemophiliac transfusion
Labs: Anti-HDV serum
Vaccine: vaccinate against HBV
Mortality: enhances severity of HBV
HEV
Family, Duration, Risk Factors, Transmission, Labs, Acute/Chronic, Mortality, Complications
Family: RNA hepevirus
Duration: self-limited
Risk Factors: epidemic form in Asia, Middle East, North Africa, Central America, India; having a pet in the home or consuming undercooked organ meat are risk factors
Transmission: enterically - waterborne epidemics, undercooked meat, spread by swine
Labs: IgM anti-HEV
Acute/Chronic: acute, no carrier state
Mortality: high in pregnant women
Complications: arthritis, pancreatitis, thrombocytopenia, Guillian Barre, peripheral neuropathy
HCV
Family, Duration, Risk Factors, Sx, Labs, Acute/Chronic, Complications, Tx
Family: flavin-like virus
Duration: most commonly chronic
Risk Factors: not sexual, confection with HIV-infected persons, IV drug use, body piercing, tattoos, hemodialysis
Sx: clinically mild and asymptomatic
Labs: Anti-HCV in serum; most sensitive = HCV RNA, enzyme immunoassay that detects Abs to HCV
Acute/Chronic: >50% likelihood of chronicity
Complications: cirrhosis, hepatocellular carcinoma, HIV co-infection, mixed cryoglobulinemia, chronic HCV infection is associated with a decrease in serum cholesterol
Tx: curable
