Microbiology: Parisitology Flashcards
What are the key aspects of treating Trichomonas vaginalis infections?
Metronidazole should be given to both the patient and the sexual partner for prophylaxis; screen for STIs as well
What pathological findings are seen in schistosomiasis?
Hepatosplenomegaly, liver and spleen fibrosis, portal hypertension
Which nematodes are transmitted through bites?
Loa loa, Onchocerca volvulus, Wuchereria bancrofti (Lay LOW to avoid getting bitten)
What are the characteristics of a heavy infection with Trichuris trichiura?
Loose stools, rectal prolapse (usually in children), and anemia
What are the 4 tissue nematodes?
Toxocara, Onchocerca, Loa loa, Wuchereria
Why should pregnant women avoid cat litter boxes?
Cat feces may contain Toxoplasma oocysts, which can cross the placenta and cause birth defects
How is visceral larva migrans treated?
Bendazoles (diagnosis: Toxocara canis infection)
What are 2 different presentations of leishmaniasis?
Cutaneous: skin ulcers; visceral (kala-azar): spiking fevers, hepatosplenomegaly, pancytopenia
How is Chagas disease transmitted?
Triatomine insect (“kissing”), with a painless bite, much like a kiss; the insect defecates around the mouth or eyes; there is fecal transmission into the bite or mucosa
What is the treatment of choice for Wuchereria bancrofti infection?
Diethylcarbamazine
What complications of chronic Trypanosoma cruzi infections characterize Chagas disease?
Dilated cardiomyopathy with apical atrophy; megaesophagus; megacolon
Elephantiasis is a feature of which helminthic infection?
Wuchereria bancrofti infection
What infections can the blood-sucking insects known as lice transmit to humans?
Rickettsia prowazekii (typhus), Borrelia recurrentis (relapsing fever), and Bartonella quintana (trench fever)
Name the helminth that causes portal hypertension.
Schistosoma mansoni or Schistosoma japonicum
In a patient with river blindness caused by Onchocerca volvulus, anaphylaxis may develop as a result of exposure to what?
Microfilaria
How do you treat hookworm infections?
Bendazoles or pyrantel pamoate
What is the common name for Ancylostoma duodenale and Necator americanus?
Hookworms
A woman from a rural area has new-onset skin swelling and conjunctival worms. You suspect a nematode infection. How is the organism responsible acquired?
By way of deer, horse, and mango flies (diagnosis: Loa loa infection)
What lab finding might be expected with a hookworm infection?
Microcytic anemia
A patient had cercariae penetrate his skin while swimming in a freshwater lake. Years later, he has painless hematuria. Why is this concerning?
He could have squamous cell carcinoma of the bladder from a chronic Schistosoma haematobium infection
How does a patient acquire an infection with Trypanosoma cruzi?
From the painless bite by a triatomine insect (“kissing” bug), which deposits feces containing the protozoa
What treatment is used in life-threatening forms of malaria?
IV quinidine or artesunate
What is the treatment of choice for African sleeping sickness with CNS involvement?
Melarsoprol (versus suramin for blood-borne disease); “I sure am mellow when I’m sleeping”; remember melatonin helps with sleep
What test is used to diagnose malaria, and what findings are expected?
Blood smear, look for trophozoite ring forms and RBC schizonts with merozoites
How do you treat an infection with Strongyloides stercoralis?
Ivermectin or bendazoles
Name the helminth that causes biliary tract disease and is associated with cholangiocarcinoma.
Clonorchis sinensis
A woman bitten by a deerfly exhibits skin swelling and worms in the conjunctiva. What is the treatment for this condition?
Diethylcarbamazine; (diagnosis: Loa loa infection)
How are infections with Clonorchis sinensis treated?
Praziquantel
What is the mechanism that causes the itching that occurs in scabies?
Mites burrow into the stratum corneum, which causes pruritus
What is the mode of transmission of Diphyllobothrium latum?
Ingestion of larvae in uncooked freshwater fish
How is Cryptosporidium diarrhea treated in immunocompetent patients?
Nitazoxanide; otherwise, prevent by water filtration
Taenia solium, Diphyllobothrium latum, and Echinococcus granulosus are examples of what type of organism?
Cestodes (tapeworms)
How is Strongyloides stercoralis transmitted?
Larvae from soil penetrate the skin.
How is Toxocara canis transmitted?
Via the fecal-oral route
What are the characteristics of a Clonorchis sinensis infection?
Biliary tract inflammation and pigmented gallstones
Name 4 other nematodes that can be acquired via the same route as Ascaris.
Enterobius, Toxocara, Trichinella, and Trichuris are acquired by ingestion, similar to Ascaris
How can you distinguish Schistosoma mansoni from Schistosoma hematobium?
Schistosoma mansoni has an egg with a lateral spine; Schistosoma haematobium has an egg with a terminal spine
What is the classic triad of congenital toxoplasmosis?
Chorioretinitis, hydrocephalus, and intracranial calcifications
Which 2 species of Plasmodium form dormant hypnozoites in the liver, leading to relapsing malaria?
P vivax and P ovale
What is the mode of transmission of intestinal Taenia solium?
Consumption of undercooked pork containing encysted larvae
What is the treatment for the tapeworm infection associated with vitamin B12 deficiency and anemia?
Praziquantel; (diagnosis: Diphyllobothrium latum infection)
How are acute infections of Trypanosoma cruzi treated?
Benznidazole or nifurtimox (cruzing in my Benz, with a fur coat on) to treat T cruzi
What is the mode of transmission of Ancylostomaspp and Necator americanus infestations?
Larvae penetrate the skin
For school-aged children who are diagnosed with head lice, how is their school attendance generally affected?
Minimally, if at all; most children with head lice can continue to attend school while receiving treatment at home
How can scabies be treated?
Permethrin cream, laundering of all bedding and clothing, and treating close contacts
What are the possible intestinal complications associated with Ascaris lumbricoides infections?
Ileocecal valve obstruction, intestinal perforation, biliary obstruction
Name the helminth(s) that classically cause(s) microcytic anemia.
Ancylostoma and Necator
A boy contracted a rapidly fatal meningoencephalitis after swimming in a freshwater lake. What is the most appropriate diagnostic test for his condition?
Test for amoebas in the cerebrospinal fluid (diagnosis: Naegleria fowleri)
How does Trichinella spiralis cause muscle inflammation?
Larvae enter the bloodstream and are encysted in striated muscle cells, leading to inflammation of the muscle
How are diarrhea-causing protozoans transmitted?
Via oocysts/cysts in contaminated water
How does an infection with Diphyllobothrium latum cause megaloblastic anemia?
The tapeworm competes for vitamin B12 in the intestines
Name 2 other nematodes that can be acquired via the same route as Strongyloides.
Ancylostoma and Necator are acquired through the skin similar to Strongyloides
What is the mode of transmission of a Strongyloides stercoralis infestation?
Larvae found in the soil penetrate the skin and infect the intestines
What group of people are at risk for severe infections of babesiosis?
Patients with asplenia
What are the presenting signs and symptoms of Pediculus humanus/Phthirus pubis infections?
Severe pruritus with excoriations; may arise on the scalp and neck (head lice), axillae and waistband (body lice), or perianal and pubic regions (pubic lice)
With which anti-malarials is it important to screen for G6PD deficiency prior to use?
Quinidine, artesunate, primaquine
How is transmission of Taenia solium different in terms of its presentation as a tapeworm versus cysticercosis/neurocysticercosis?
Tapeworms are acquired through ingestion of larvae; cysticercosis/neurocysticercosis develop through ingestion of eggs
How is African sleeping sickness transmitted?
Trypomastigotes are transmitted through the bite of a tsetse fly
How does scabies present?
Pruritis and serpiginous burrows between fingers and toes
Where might Plasmodium vivax and P ovale remain dormant in the body, and in what form do they remain dormant?
The liver as hypnozoites
How is Naegleria fowleri transmitted?
Acquired from warm freshwater lakes; enters the CNS through the cribriform plate
Name the parasite that is associated with the development of hematuria and squamous cell bladder cancer.
Schistosoma haematobium
What form of the nematode is excreted in the stool of an individual infected with Strongyloides stercoralis?
Rhabditiform larvae
How is giardiasis treated?
Metronidazole
How is Schistosoma transmitted to humans?
Through penetration of the skin by cercariae (eg, while swimming or bathing)
In patients with Plasmodium falciparum infections, RBCs tend to occlude capillaries in which 3 organs?
Kidneys, lungs, and brain (cerebral malaria)
How does Cryptosporidium present in immunocompetent hosts?
Mild, watery diarrhea
A man bitten by a female black fly experiences skin hyperpigmentation and blindness. What is the diagnosis?
Onchocerca volvulus infection (black flies, black skin nodules, “black sight”)
Before using chloroquine to treat malaria, what should be verified about the patient’s particular strain of malaria?
That the strain is sensitive to chloroquine; some have developed resistance to this drug, and other agents should be used instead
Name 2 nematodes that can be acquired via a similar route as Loa loa.
Onchocerca volvulus and Wuchereria bancrofti (acquired via insect bites)
What is a possible fatal complication of Onchocerca infections?
Allergic reaction to the microfilaria
What is the mode of transmission of an Ascaris lumbricoides infestation?
Fecal-oral route (“knobby-coated” eggs are visible in feces under a microscope)
What are the 6 intestinal nematodes?
Enterobius, Ascaris, Strongyloides, Ancylostoma/Necator, Trichinella, Trichuris
In what populations is scabies common?
Children, prison inmates, and nursing home residents (crowded conditions)
What methods are used to diagnose an Entamoeba histolytica infection in a blood sample?
Serology and serum antigen testing
What disease is associated with a Clonorchis sinensis infection?
Cholangiocarcinoma
How is an Enterobius infection diagnosed?
Tape test to look for the presence of eggs stuck to the tape
How is Entamoeba histolytica transmitted?
Via cysts in the water
How does treatment of amebiasis differ between symptomatic and asymptomatic patients?
Symptomatic: use metronidazole; asymptomatic: use paromomycin or iodoquinol
What is the treatment of choice of congenital toxoplasmosis?
Sulfadiazine + pyrimethamine
What protozoan infection is characterized by bloody diarrhea, RUQ abdominal pain, and liver abscesses?
Entamoeba histolytica infection
How is cysticercosis transmitted?
By ingestion of food contaminated with human feces containing Taenia solium eggs
Name the parasite that forms hydatid liver cysts
Echinococcus granulosus
What is the most common clinical presentation of Trichuris trichiura infection?
Asymptomatic
How does toxoplasmosis present in immunocompetent adults?
As a mononucleosis-like syndrome but without heterophile antibodies
Toxoplasma causes severe disease in what 2 patient populations?
Patients with AIDS (reactivation) and neonates (congenital toxoplasmosis)
A man is bitten by a sandfly and develops spiking fevers, hepatosplenomegaly, and pancytopenia. What is the most appropriate treatment for this condition?
Amphotericin B with sodium stibogluconate (diagnosis: visceral leishmaniasis, or kala-azar)
How does African sleeping sickness present?
Recurrent fevers, somnolence, coma, lymphadenopathy
What acid-fast organism causes watery diarrhea in healthy patients?
Cryptosporidium
What is the intermediate host of Schistosoma flukes?
Snails
Enterobius vermicularis causes infection of what organ?
The intestines (although it typically manifests as anal pruritus)
How do you treat Onchocerca volvulus infections?
Ivermectin (for river blindness)
What is the treatment for Trichinella spiralis infection?
Bendazoles
Name the parasite that causes brain cysts and seizures.
Taenia solium (neurocysticercosis)
What are 2 other classic findings associated with the infection causing river blindness?
Skin changes and loss of elastic fibers; (diagnosis: Onchocerca volvulus infection)
What is the common name for Enterobius vermicularis?
Pinworm
A patient has unilateral, nontender periorbital swelling after recent travel to Bolivia. How do you confirm the diagnosis?
Observe trypomastigotes on blood smear (this patient has the Romaña sign of acute Chagas disease)
What is the mechanism of anemia in hookworm infestations?
The worms suck blood through the intestinal walls, leading to a microcytic anemia
Describe the phenomenon of autoinfection with Strongyloides stercoralis infection
Some larvae penetrate the colonic wall and enter the blood circulation without leaving the body
How is an infection with Schistosoma spp. treated?
Praziquantel
Which fluke is transmitted in undercooked fish?
Clonorchis sinensis
Name the helminth that causes vitamin B12 deficiency.
Diphyllobothrium latum
How is a diagnosis of visceral leishmaniasis made?
Blood smear showing macrophages containing amastigotes
How is a lice infection treated?
Pyrethroids, ivermectin lotion, malathion, and/or nit combing
How is an Entamoeba histolytica infection diagnosed from a stool sample?
Stool antigen testing and/or visualization of trophozoites (with engulfed RBCs in the cytoplasm) or cysts (up to 4 nuclei each)
What are the diagnostic findings of Trichomonas vaginalis infection?
Motile trophozoites on wet mount and/or “strawberry cervix” on exam
What is the common name for Ascaris lumbricoides?
Giant roundworm
Which nematodes are transmitted cutaneously?
Strongyloides, Ancylostoma, Necator (They get into your feet from the SANd)
Name the helminth that causes perianal pruritus.
Enterobius
Which nematodes are transmitted by ingestion of contaminated food?
Enterobius, Ascaris, Toxocara, Trichinella, Trichuris (you’ll get sick if you EATTT these)
Name the parasite that causes myalgias and periorbital edema.
Trichinella spiralis (trichinosis)
What is the Romaña sign?
Unilateral periorbital swelling indicative of acute Trypanosoma cruzi infections
What disease can develop secondary to chronic infection with Schistosoma?
Squamous cell bladder cancer (with Schistosoma haematobium)
What organism causes scabies?
Sarcoptes scabiei
How can you diagnose babesiosis?
With a blood smear (look for “Maltese cross” or ring forms) or polymerase chain reaction test
What is the treatment for pinworm infection?
Pyrantel pamoate or bendazoles (because worms are bendy)
How is Trichomonas vaginalis transmitted?
Sexually (T vaginalis can only exist inside the human body to be able to form cysts)
How do you treat neurocysticerosis?
Albendazole
What protozoan infection is characterized by a foul-smelling, itching, burning vaginitis with green discharge?
Trichomoniasis (Trichomonas vaginalis)
Where do the insects prefer to live in a patient with lice?
Scalp and neck (head lice); waistline and axillae (body lice)
What are the findings on colon biopsy of a patient with an Entamoeba histolytica infection?
Flask-shaped ulcers
In what region of the world is Babesia infection most common?
Northeastern United States
How do you treat the dormant form of malaria?
Primaquine
In a patient with confirmed Toxocara canis infection, which organs tend to be infected most often?
Heart (leading to myocarditis), liver, eyes (visual impairment), and CNS (leading to seizures and/or coma)
What is noted in the blood smear of patients with African sleeping sickness?
Trypomastigotes (Trypanosoma brucei)
How does the fever pattern differ in malaria caused by Plasmodium vivax, P ovale, P falciparum, and P malariae?
P malariae: every 72 hours (quartan); P vivax/P ovale: every 48 hours (tertian); P falciparum: irregular
How is cutaneous larva migrans acquired?
Penetration of exposed skin (often feet) by hookworms
What is the mode of transmission of the Plasmodium species that cause malaria?
Bite of the female Anopheles mosquitoes, which usually occurs at night
What disease is transmitted in a similar manner to babesiosis?
Lyme disease; both are transmitted by Ixodes ticks
What is the treatment of choice for a blood-borne Trypanosoma brucei infection?
Suramin (versus melarsoprol for CNS disease); “I sure am mellow when I’m sleeping”; remember melatonin helps with sleep
