clinical microbiology pt 2

what are protozoa?

single celled organisms that have nuclei and more complex cellular machinery than bacteria

what does entamoeba histolytica cause?

amebic liver disease, liver abscesses (anchovy paste)

what are diagnostic studies for entamoeba histolytica?

mucosal biopsy - flask shaped ulcers

stool - cysts, trophozoites

what does giardia lamblia cause?

giardiasis

what is the mechanism of giardia lamblia?

invades enterocytes and prevents absorption

what does giardiasis result in?

steatorrhea (fatty diarrhea)

what are diagnostic tests for giardia lamblia?

stool - double nucleated flagellated organisms

what is the typical context of getting giardia lamblia?

drinking untreated water (hiking/camping)

what does toxoplasma gondii cause?

toxoplasmosis

what are diagnostic tests for toxoplasma gondii?

serology via ELISA - antitoxoplasma IgM and IgG antibodies

where is toxoplasma gondii most commonly found?

litter boxes

who needs extra caution with toxoplasma gondii?

high risk patients and pregnant women

what does trichomonas vaginalis cause?

trichomoniasis

what are the diagnostic tests for trichomonas vaginalis?

microscopy wet mount of genital discharge - motile flagella

what does cryptosporidiosis cause?

diarrheal disease

what is the course of diarrheal disease?

self limited in immunocompetent host

severe in AIDS or immunodeficiency

how is cryptosporidiosis transmitted?

waterborne

person to person (daycare centers)

what are diagnostic tests for cryptosporidiosis?

specialized O&P stool - acid fast or immunofluorescent

PCR

what does naegleria fowleri cause?

primary meningoencephalitis

what are the symptoms of primary meningoencephalitis?

abrupt HA, fever, nausea, vomiting, pharyngitis

what are common contexts of naegleria fowleri transmission?

neti pots w/tap water

warm lakes

what is a diagnostic test for naegleria fowleri?

CSF will be purulent w/trophozoites but no bacteria

what does acanthomoeba cause?

keratitis

ocular pain/corneal ulceration

granulomatous amebic encephalitis

what tests should you do for acanthomoeba?

corneal scraping

brain biopsy

Giemsa, gram, or calcofluorostained smear

what is malaria?

mosquito borne cyclical flu like illness that ranges from mild to fatal

what are plasmodium?

parasitic protozoan

what 4 species of plasmodium cause malaria?

p. falciparum

p. malariae

p. ovale

p. vivax

which species of malaria plasmodium is most fatal?

p. falciparum

which species of malaria plasmodium is least virulent but has chronic symptoms?

p. malariae

which species of malaria plasmodium can form hypnozoites that lay dormant and cause relapse?

p. ovale

p. vivax

how is malaria transmitted?

from anopheles mosquito's saliva into blood

what is the first stage of malaria transmission?

sporozoite infects the liver and replicates until hepatocyte bursts, releasing merozoites

what is the second stage of malaria transmission?

merozoites infect RBCs

lysis occurs which infects more RBCs

what is the third stage of malaria transmission?

gametocytes are produced and drawn up by mosquito vector

what are 3 tests you can do for malaria?

blood smear

rapid test

PCR test

which test is the best for diagnosing malaria?

blood smear - thick and thin direct examination

what does a thick/thin blood smear test tell us about malaria?

confirms infection

identifies species

quantifies parasitemia

(labor intensive)

what does a rapid test tell us about malaria?

detects parasite antigens

(useful when microscopy is limited)

what does a PCR test tell us about malaria?

amplifies parasite DNA for species differentiation

what is the best test for monitoring treatment of malaria?

PCR test

what are 4 characteristics of mycoses?

nuclei

mitochondria

plasma membrane (ergosterol)

cell walls (chitin + beta glycan, NO peptidogylcan)

what are 4 microscopy tests for mycoses?

saline wet mounts

KOH

calcofluor white stain

india ink

what are 3 serologic tests for mycoses?

immunodiffusion

complement fixation

enzyme immunoessay (EIA)

what molecular test can you do for mycoses?

PCR

what is an opportunistic infection?

infection caused by pathogens that take advantage of an opportunity not normally available

what are 3 characteristics of an opportunistic infection?

host w/weakened immune system

altered microbiota

breached integumentary barriers

what are the 4 classifications of mycoses?

superficial

cutaneous

subcutaneous

systemic

what is candidiasis?

most common fungal infection caused by candida albicans (yeast)

what is oral thrush?

yeast infection forming white curd like patches on the oral mucocutaneous membrane

CAN be scraped off

when is vaginal candidiasis normally seen?

common after ABX tx

also seen in diabetic patients

what are 3 contexts in which candidemias are usually seen?

indwelling catheters, IVDU, immunocompromised

how do you diagnose a candida infection?

can be clinical dx

KOH prep - shows budding yeast and pseudohyphae

what is histoplasmosis?

opportunistic fungi inhaled from soil infested with bird or bat droppings

results in pneumonia

how is histoplasmosis diagnosed?

sputum culture

urine antigen assay

serum antigen assay

what is the GOLD standard of histoplasmosis dx?

sputum culture

what is cryptococcus?

bird droppings

results in pneumonia and meningitis

what 4 tests can you do for cryptococcus?

india ink

sputum culture

blood culture

CrAg detected in CSF and serum

what does pneumocystitis jirovecii (PJP) cause?

pneumonia in immune compromised patients

(AIDS defining disease)

where does PJP live?

in lungs of humans and animals

how can you detect PJP?

silver staining of sputum/bronchoalveolar lavage sample

what is aspergillus?

opportunistic fungi that we inhale all the time (mold)

how do you diagnose aspergillus infection?

sputum/BAL sample culture

galactomannan antigen assay

biopsy

what is seen of aspergillus on sputum culture stain?

filamentous fungi - hyphae with branching

what is galactomannan antigen assay?

specific for aspergillus, component of its cell walls

what is coccidiodomycosis?

valley fever; fungal disease of the lungs caused by coccidioides immitis

how is coccidiodomycosis transmitted?

inhalation from sand and dirt

when is coccidiodomycosis most common?

season association (dry periods after rain) in the SW US

what is the hallmark test for coccidiodomycosis?

isolated eosinophilia

what opportunistic infection is seen in HIV patients with CD4 levels < 250?

coccidiomycosis

what opportunistic infection is seen in HIV patients with CD4 levels < 200?

pneumocystitis

what opportunistic infection is seen in HIV patients with CD4 levels < 150?

histoplasmosis

what opportunistic infection is seen in HIV patients with CD4 levels < 100?

toxoplasmosis

what opportunistic infection is seen in HIV patients with CD4 levels < 50?

mycobacterium avium complex (MAC)

what causes tinea versicolor?

malassezia furfur

what is piedra?

infection of the hair shaft due to fungus

how is tinea versicolor diagnosed?

yellow-green scaly patches on Wood's lamp

KOH - "spaghetti and meatballs"

what causes ringworm?

candida

trichophyton

epidermophyton

microsporum

how is ringworm diagnosed?

KOH

what is ascaris?

roundworm; nematode

what is ancylostoma?

hookworm; nematode

what is enterobiasis?

pinworm; nematode

what is schistosoma?

flat worm/blood fluke; trematode

what is taenia?

tapeworm; cestode

what is the parasitic cycle of ascaris lumbricoides?

adults live in intestines and steal food

eggs are released in stool & contaminate food/water

larvae go thru mucosa to lungs

how is ascaris lumbricoides diagnosed?

O&P stool examination

respiratory secretion microscopy

clinical history

what would you see on O&P stool examination for ascaris lumbricoides?

ovoid eggs present in feces, possible worms in feces

what clinical history would be diagnostic of ascaris lumbricoides?

respiratory symptoms, eosinophilia, exposure

who is the host for ancylostoma duodenale?

humans

how is ancylostoma duodenale transmitted?

larvae penetrate skin after stepping on contaminated soil/sand/feces

travels to lungs, destroy alveoli, eggs are released in stool

how is ancylostoma duodenale diagnosed?

O&P stool examination (eggs and occult blood seen)

eosinophilia

what is the parasitic cycle for enterobius vermicularis?

adults live in the cecum

travel to lay eggs in perianal region

transferred to surfaces and food/drink

ingested and hatch in intestines

what symptoms does enterobius vermicularis cause?

pruritis

how is enterobius vermicularis diagnosed?

tape test

what is the tape test?

place clear tape over perianal region before sleep

leave on for 3 nights in a row

diagnostic for enterobius vermicularis

what is the 2nd most devastating parasitic disease worldwide?

schistosoma

how is schistosoma diagnosed?

stool examination

urine examination (for haematobium species)

what are 3 types of tapeworms?

diphyllobothrium latum

taenia solium

taenia saginata

what is diphyllobothrium latum?

fish tapeworm

associated with B12 deficiency

what is taenia solium?

pork tapeworm

what is taenia saginata?

beef tapeworm