Sketchy Micro: Parasites and Fungi Flashcards
Foul smelling dio after drinking fresh water on a camping trip
Giardia
- travelers or campers, found in river/fresh/poorly purified drinking water
- foul smelling diarrhea 2/2 steatorrhea, no bloddy dio b/c giardia doesn’t invade the enterocytes
Giardia
(a) How to dx
(b) Tx
Giardia = parasite of the intestinal tract => foul smelling dio from fresh water
(a) Dx from Stool O&P showing trophozoites, or ELISA stool antigen
(b) Tx w/ metronidazole
Buzzword
(a) Anchovy paste
(b) Diarrhea in HIV pt
(a) Anchovy paste = buzzword for the consistently of material inside liver abscess of entamoeba histolytica
(b) Diarrhea in an HIV pt, esp if partially acid fast = cryptosporidium (parasite)
MC site of amoebic abscess
(a) Clinical presentation of intestinal amebiasis
(b) Endoscopic finding of intestinal amebiasis
Amoebic abscess from Entamoeba histolytica MC location = R lobe of liver (‘anchovy paste’ pus, nasty)
(a) R. lobe abscess => RUQ pain, intestinal amebiasis is invasive => bloody dio
(b) Causes ulcerations in colon and characteristic ‘flask shaped’ ulcers on endoscopy
Entamoeba Histolytica
(a) Dx
(b) Tx
Entamoeba histolytica
(a) Make dx by O&P showing RBC w/ endocytosed trophozoites
-or ELISA antigen
(b) Tx w/ Metronidazole and a luminal agent to elimiate cysts in the intestinal lumen
Luminal agents = paramycin and Iodoquinol
Name a liver abscess that you would treat medically instead of draining
Entamoeba Histolytica abscess (usually R liver lobe): tx medically w/ metronidazole and a luminal agent (paromomycin or iodoquinol) instead of draining
Parasite
(a) Stains partially acid fast
(b) Stool O&P shows trophozoites w/ endocytosed RBCs
Parasite
(a) Partially acid fast staining = cryptosporidium (causes dio in immunocompromised)
(b) RBCs inside trophozoites = Entamoeba Histolytica
Parasite transmitted by
(a) Cat feces
(b) Water sports, contact solution
(c) Kissing bug
(a) Cat feces = toxoplasmosis gondii
(b) Water sports or infected contact solution = Naegleria fowleri (rapidly fatal meningoencephalitis)
(c) Kissing bug = Trypanosoma Cruzi (Chagas)
Why should pregger ladies not scoop kitty litter
Risk of toxoplasmosis that congenitally causes: intracranial calcifications, hydrocephalus (seizures), chorioretinitis
How to differentiate toxoplasmosis from CNS lymphoma?
Toxo: multiple ring enhancing lesions
vs.
CNS lymphoma: singular lesion, associated w/ EBV
But need biopsy to truly differentiate
Tx for toxo
Sulfadiazine and Pyrimethamine (both of which inhibit folate synthesis)
Who gets ppx for toxo?
HIV pts w/ CD4 under 100 who test positive for IgG positive for toxo!
Ppx w/ TMP-SMX
Cause of African sleeping sickness
(a) Vector
African sleeping sickness (comw, lymphadnopathy, recurrent fevers) = Trypanosoma Brucei (parasite)
(a) Vector = tsetse fly
Clinical features of trypanoseoma brucei
Trypanosoma brucei (parasite) => African sleeping sickness
-coma, lymphadnopathy (infects LN), recurrent fever
Tx of trypanosoma brucei w/
Melarsoprol vs. Suramin
Trypanosoma brucei = parasite causing African sleeping sickness
Melarsoprol for CNS infection (how it causes coma)
Suramin for the peripheral blood infection)
How to Naegleria fowleri enter the CNS
(a) Clinical presentation
Naegleria fowleri = parasite from freshwater lakes that enters the CNS thru the cribiform plate
(a) Presents w/ rapidly fatal meningoencephalitis
Meningitis => nuchal rigidity and fever
Encephalitis => altered mental status
Primary ameobic encephalitis
(a) Bug
(b) How to dx
(c) Tx
Primary ameobic encephalitis
(a) Naegleria fowleri
(b) Dx by visualization of ameoba in CSF
- pt will present w/ meningoencephalitis so you’ll do spinal tap
(c) Tx = amphotericin
What causes Chagas disease
(a) Endemic area
(b) Transmission
Chagas disease 2/2 Trypanosoma cruzi
(a) Endemic to S. America
(b) Transmitted by kissing bug (Reduviid bug) that deposits its feces on skin, then pt itches it and introduces feces under skin
Clinical features of T. Cruzi disease
T. Cruzi (Chagas) think everything dilated
- Megacolon- constipation, risk of intestinal perf
- Dilated cardiomyopathy- often what they die from
- Mega-esophagus
Clinical features of Babesiosis
Babesiosis = parasitic infection by babesia
Mostly blood related: hemolytic anemia => jaundice, also irregularly cycling fever
Dx Maltese cross of peripheral thick blood smear
Tx for babesiosis
Babesiosis (hemolytic anemia, irregular fever) tx = atorvaquone and macrolide (specifically azithromycin)
Endemic area for
(a) T. cruzi
(b) Babesia
Endemic area for
(a) T. cruzi (chagasd siease) = S. America
(b) Babesia = NE US
How to clinically distinguish the species of plasmodium
Plasmodium species present w/ different fever cycles
P. malariae: q72 hrs (day 1, day 4)
P. vivax and ovale: tertian fever cycle day 1 and 3 (q48h)
P. falciparum: irregular fever pattern
Malaria species w/ the most severe clinical course
(a) Fever pattern
(b) How does it cause cerebral/renal/pulm issues?
P. falciparum has most severe clinical course
(a) Irregular fever pattern
(b) Can present w/ CNS features/pulm/kidney as parasitized RBCs occlude vessels leading to vital organs
2 indications for atovaquone
- Tx of babesiosis (in combo w/ Azithromycin)
2. Used in combo w/ Proquanil for malaria ppx in travelers
First line tx for malaria
a) Change in tx for resistant (most African species
Malaria tx = chloroqine (blacks plasmodium heme polymerase) and primaquine (destroy hypnozoites in liver)
(a) But lots of African species are resistant to chloroquine => use mefloquine
Sickle cell risk for
(a) Babesia
(b) Plasmodium falciparum
SCD
(a) Increase risk of severe disease 2/2 babesia => severe anemia
(b) Protective against malaria
Differentiate Leishmaniasis Donovi and Baziliensis
Leishmaniasis donovi => visceral leishmaniasis = black fever
vs. cutaneous Leishmaniasis from Baziliensis
Tx for
(a) Cutaneous (Baziliensis) Leishmaniasis
(b) Visceral Leishmaniasis
Tx for
(a) Cutaneous leishmaniasis = stibugluconate
(b) Visceral leishmaniasis needs amphotericin
Cause of strawberry cervix
Strawberry cervix = trichomoniasis vaginalis (parasite)
Clinical features of trichomoniasis vaginalis
Trich => vaginitis w/ green/yellow malodorous discharge
- vaginal burning/itching (vaginitis)
- strawberry cervicitis
Differentiate the wet mount findings of
(a) Trichomoniasis
(b) Gardnerella
(c) Candida
Wet mount
(a) Trichomonas (parasite) = motile trophozoites
(b) Gardnerella (gram variable bacteria) = clue cells
(c) Candida (fungi) = pseudohyphae w/ budding yeast
Vaginitis at
(a) pH over 4.5
(b) pH under 4.5
Vaginitis
(a) pH above 4.5: vaginitis by trich and Gardnerella
(b) While only candida vaginitis seen at pH under 4.5
Tx for trichomoniasis vaginalis
Metronidazole for both partners!
Males will be asymptomatic but just will pass it back to their female partner…
Main drug for tx w/ helminths
Helminths generall tx w/ Albendazole
What is the scotch tape test used to diagnose?
Scotch tape test used to diagnose pinworm (intestinal nematode)- Enterobius Vermicularis
Scotch tape over anus in the morning, then visualize eggs under the microscope
Helmnith dx by larvae (not eggs) in stool
Strongyloides stercoralis
Eggs laid in the intestines, only larvae found in stool
Buzzword for parasites
(a) Swiss cheese appearance on MRI
(b) Hydatid cysts w/ egg-shell calcifications
Parasites
(a) Swiss cheese appearance on MRI = neurocysticercosis from infection of Taenia eggs (not cysts or larvae, just eggs)
(b) Cestode: Echinococcus granulosus causes hydatid liver cysts w/ egg shell caclifications
Drug of choice for all trematodes
Treat all tresmatodes (schisto) w/ Praziquantel
37 yo from E. Europe p/w ride-sided abdominal discomfort and large liver mass w/ cystic lesions, precaution while undergoing surgery
MC cause of hydatid cyst = Echinococcus granulosus
-associated w/ eggshell calcifications histologically
Manipulation of cyst can release contents causing anphylactic shock
What does it mean to be dimorphic?
Dimorphic = form of fungi depends on the temp
-all systemic fungi are dimorphic, most are “yeast in the heat, mold in the cold” but exceptions
Exception:
- candida is yeast in cold while mold in heat
- coccidioidomycosis is mold in cold but spherule containing endospores in heat
Which disseminated fungal infxn can mimic Tb in chronic form?
In chronic form histoplasma can cause calcified nodules and granulomas which mimic Tb
If not clinically silent, describe presentation of Histoplasma capsulatum infxn in immunocompetent individual
Histo in immunocompetent = usually subclinical, can cause pneumonia and erythema nodosum
Erythema nodosum = painful red nodules on shins
Tx of histo vs blasto
Both histo, blasto, and while were at it coccidio (3 systemic fungal infxns) tx:
- azoles for local/mild disease
- amphotericin B for disseminated/serious/systemic disease
Differentiate clinically systemic infxn in immuncompromised pt infected w/ Histo vs. Blasto
Clinical presentation: both have lung involvement, then more when disseminates
Histo: hepatosplenomegaly (b/c histo infects macrophages and there’s a shitton of macrophages in the liver and spleen): get calcifications of liver and spleen
Blasto: skin and bones, can even be osteomyelitis
2 fungi associated w/ erythema nodosum
Erythema nodosum = red painful nodules on shins, only seen in immuncompetent b/c indicates very robust immune response
Associated w/ both
- histoplasmosis
- coccidiodomycosis (even more so than histo!)
Differentiate infxn of blastomycosis in immunocompetent vs. immunocompromised
Blasto (S and E US, Great Lakes and Ohio River Valley)
Immunocompetent: patchy alveolar infiltrate, ‘hazziness’ w/ possibly cavitary lesions on CXR, stays in lungs
Immunocompromised: spreads to skin and bone
-osteomyelitis
Differentiate the systemic mycoses by size
Smallest (hundreds fit in one macrophage that’s just slightly bigger than an RBC) = Histoplasma
Then blasto is about the size of an RBC
Then coccidio is just about the same or a bit bigger than blasto
Then paracoccidioidomycosis is the largest! huge!
Mycosis buzzwords
(a) Dust storm/earth quake
(b) Captain’s wheel
(a) Dust storm/earth quake in California or SW US = coccidioidomycosis from inhaled dust spores
(b) Captain’s wheel = yeast form of paracoccidioidomycosis = multiple buds radiating out from a central capsule (S. America => mucocutaneous lesions w/ lymphadenopathy)
2 fungi that go against “yeast in the heat, mold in the cold”
Coccidioidomycosis: mold in the cold, thick-walled spherule containing endospores in heat (in the body)
Candida: mold in heat, yeast in cold
Differentiate coccidiodomycosis in immunocompetent vs. immunocompromised
Coccidioidomycosis
Immunocompetent: subclinical or fever cough arthralgia, erythema nodosum
Immunocompromised: disseminate to bone and meninges => meningitis
Location of coccidio vs. paracoccidioidomycosis
Coccidio in SW US and California
Paracoccidio in S. America
MC mode of transmission of systemic mycosis
Air/respiratory droplets = mode of transmission for histo/blasto/coccidio/paracoccidio
Coccidio also by dust spores
Clinical presentation of paracoccidiodomycosis
Mucocutaneous lesions (mucosal ulcers, esp in oral cavity) and lymphadenopathy
Tx for malassezia furfur
Malassezia furfur = cutaneous mycosis (fungi) that causes pityriasis versicolor = hypo and hyperpigmented skin lesions by production of melanocyte-damaging acids
Confined to the stratum corneum => treat w/ Selsun blue (selenium sulfide) that promotes shedding of stratum corneum)
What are dermatophytes?
(a) Tx
Dermatophytes = cutaneous fungi that cause tinea infection named by location = ringworm
tinea capitus
tinea corpus
tinea cruris (jock itch)
tinea pedis (athlete’s foot)
(a) Tx = topical azole
How to diagnose tinea infection?
Dx tinea clinically or w/ KOH stain of stain scraping
What is onychomycosis?
(a) Tx
Onychomycosis = dermatophytosis (cutaneous fungal infection)
(a) Tx requires oral therapy (not topical): Terbinafine
Griseofulvin indications
Griseofulvin for Tx refractory or serious dermatophyte (tinea = ringworm) infections that don’t resolve w/ topical azoles
Tinea capitus, tinea corpus, tinea cruris (jock itch), tinea pedis (athlete’s foot)
Mycoses buzzword
(a) Cigar shaped yeast
(b) Diaper rash
(c) Heavily encapsulated
(a) Cigar shaped yeast = sporothrix schenckii causing ascending lymphadenitis from rose thorn prick
(b) Diaper rash = candida
(c) Heavily encapsulated = cryptococcus neoformans
Ascending lymphadenitis caused by what fungi?
Sporothrix schenckii- cutaneous fungal infection that spreads as red bumps along the lymphatics
Rose Gardener’s disease b/c get it from the thorn of a rosebush
At what CD4 count to worry about susceptibility to
(a) Candida esophagitis
(b) PCP
(a) Worry about candida w/ CD4 under 100
(b) Start bactrim ppx for PCP pneumonia at CD4 under 200
2 causes of left-sided infective endocarditis in IVDU
- S. aureus
2. Candida
Candida tx
(a) Diaper rash
(b) Candida esophagitis
(c) Oral thrush
(d) Resistant strains
Candida
(a) Topical azoles for diaper rash
(b) Amphotericin B for candida esophagitis or other disseminated infection
(c) Nystatin swish and rinse for oral thrush
(d) Resistant strains get caspofungin
CGD deficiency increases risk for what 2 fungal infections
2 fungi that are catalase positive:
- Candida
- Aspergillus
Differentiate aspergilloma and angioinvasive aspergillosis
Aspergillus fumigas can cause
Aspergillomas = fungus balls in the lungs, increased risk when cavities already present (Tb, Klebsiella)
Angioinvasive aspergillosis = invades BVs and quickly spreads through body to kidneys, heart (endocarditis), CNS => ring-enhancing lesions
Necrosis of paranasal sinuses: how to differentiate the two mycoses that can cause this
2 fungi that can cause necrosis of paranasal sinuses:
- Aspergillus fumigas that has septated hyphae w/ acute angle (under 45 degrees)
- Mucor has r. angle (90 degree) branching and is not septated
Tx for aspergilloma vs. angioinvasive aspergillosis
Asperilloma- surgical debridement w/
MC cause of fungal meningitis
MC fungal meningitis = cryptococcus neoformans
Also can cause meningitis = coccidiomycosis (Cali and SW US)
India ink
India ink stain of CSF to visualize cryptococcus neoformans (meningitis in immunocompromised)
Mycoses buzzwords
(a) Soap bubble CNS lesions
(b) Bread mold
(c) BAL sample stained w/ silver stain
(a) Soap bubble in grey matter of the brain = Cryptococcus neoformans meningitis
(b) Bread mold = rhizopus
(c) Bronchoalveolar lavage w/ silver stain- helpful for fungi, can dx PCP or crypto
3 ways to diagnose cryptococcus neoformans
(a) BAL
(b) CSF stain
(c) Detect repeating polysacc capsular antigen
Diagnose crypto w/ these bc culture takes forever
(a) BAL: stain w/ mucicarmine (red) or methanamine (silver) stain
(b) CSF stain w/ India ink
(c) Latex agglutination test causes agglutination w/ the repeating polysacc capsular antigen
Main virulence factor of cryptococcus neoformans
Cypto has capsule w/ repeating polysaccharide antigens that prevents phagocytosis
Opportunistic fungal infxn that requires certain azole
Asperigllus specifically use Voriconazole
DKA predisposes pt to what fungal infxn?
Mucormycosis b/c mucor and rhizopus (fungi that cause it) proliferate in BV walls especially if high glucose and ketones are present
Mucormycosis- clinical presentation
(a) Tx
Mucormycosis- invades BVs, then penetrates cribiform plate to enter skull => rhinocerebral mucormycosis and frontal lobe abscess
(a) Need to surgically debride necrotic tissue/drain abscess, and give amphotericin
PCP ppx in pt w/ sulfa allergy
CD4 under 200 want to protect against PCP, first line is bactrim
If pt has sulfa allergy, use pentamidine
