October 2024 Comprehensive Review Program Tier 1 Handout PDF

OCTOBER 2024 COMPREHENSIVE REVIEW PROGRAM | TIER I HANDOUT | MICROBIOLOGY AND PARASITOLOGY III. MEDICAL PARASITOLOGY ▪ Cutaneous/mucocutaneus Definition of Terms Skin...

OCTOBER 2024 COMPREHENSIVE REVIEW PROGRAM | TIER I HANDOUT | MICROBIOLOGY AND PARASITOLOGY III. MEDICAL PARASITOLOGY ▪ Cutaneous/mucocutaneus Definition of Terms Skin ulcers Parasitism- an organism (parasite) gains food and shelter ▪ visceral leishmaniasis from another (host) which suffers from the relationship spiking fevers Endoparasite- inside the body, connotes infection hepatosplenomegaly Ectoparasite- outside the body, connotes infestation pancytopenia Obligate parasite- Type of parasite that requires host o Key Terms: Facultative parasite- may exist as free living or parasitic ▪ Oriental sore within host ▪ Espundia Vector- living invertebrate carrier that transmits pathogen ▪ Kala-azar ▪ Tx: Amphotericin B, sodium stibogluconate Babesia microtti o Transmission: ▪ Bite of Ixodes tick o Disease: ▪ Babesiosis fever and hemolytic anemia; predominantly in northeastern and north central United States asplenia inc. risk of severe disease due to inability to clear infected RBCs o Key Terms: ▪ Maltese Cross ▪ Treatment: Atovaquone + Azithromycin Plasmodium spp. o Transmission: Protozoa ▪ Bite of Anopheles mosquito One-celled eukaryotes o Disease: Terms ▪ Malaria o Trophozoites – motile, reproducing form, flexible cyclic fevers, headache, anemia, membrane splenomegaly; hypoglycemia in severe o Cyst – nonmotile, nonreproducing, thick walled disease o Flagellated – pro/trypomastigotes P. falciparum o Nonflagellated – amastigotes o Severe, irregular fever pattern; parasitized RBCs may occlude capillaries in brain (cerebral malaria), kidneys, lungs P. vivax/ovale o 48-hr fever cycle (tertian); o dormant form (hypnozoite) in liver P. malariae o 72-hr fever cycle (quartan) o Key Terms: ▪ RBC with dots or rings – P. falciparum ▪ RBC with band – P. malariae Blood and Tissue Protozoa ▪ Trophozoites and Schüffner stippling (small red Toxoplasma gondii granules) within RBC – P. ovale/Vivax o Transmission: o Treatment: ▪ Ingestion ▪ If sensitive, chloroquine ▪ Transplacental ▪ if resistant, mefloquine, doxycycline or o Disease: atovaquone/proguanil ▪ Congenital toxoplasmosis ▪ If life threatening, use intravenous quinine or o Key Terms: artesunate (test for G6PD deficiency) ▪ Heterophil-negative mononucleosis ▪ Add primaquine to target hypnozoites Naegleria fowleri Trypanosoma cruzi o Transmission: o Transmission: ▪ Swimming in warm freshwaters ▪ Feces of reduviid bug/triatomine insect on bite ▪ Enters CNS through olfactory nerve via o Disease: cribriform plate ▪ Chagas disease/American Trypanosomiasis o Disease: Dilated cardiomyopathy with apical ▪ Rapidly fatal meningoencephalitis atrophy, megacolon, megaesophagus. Leishmania spp. o (T cruzi causes big problems); o Transmission: predominantly in South America ▪ Bite of sandfly Unilateral periorbital swelling (Romaña o Disease: sign) characteristic of acute stage FOCUS REVIEW CENTER | Focus Review Center | [email protected] Page 18 of 40 OCTOBER 2024 COMPREHENSIVE REVIEW PROGRAM | TIER I HANDOUT | MICROBIOLOGY AND PARASITOLOGY o Treatment o Transmission: ▪ Benznidazole ▪ Fecal-oral ▪ nifurtimox o Key Terms: Trypanosoma brucei ▪ Largest and only ciliated protozoan that causes o Transmission: disease ▪ Bite of tsetse fly o Disease: Urogenital Protozoa ▪ African sleeping sickness/ African Trichomonas vaginalis trypanosomiasis o Transmission: enlarged lymph nodes, recurring fever ▪ sexual (due to antigenic variation), o Disease: somnolence, coma ▪ Trichomoniasis o Key Terms: foul-smelling, ▪ Trypanosomal chancre greenish discharge; ▪ Dx: Trypamastigote in blood smear itching and burning; ▪ Tx: Suramin for bloodborne disease or do not confuse with Gardnerella melarsoprol for CNS penetration vaginalis, a gram-variable bacterium M: (“I sure am mellow when I’m associated with bacterial vaginosis sleeping”) o Key Terms: ▪ Trophozoites (motile) on wet mount. Intestinal Protozoa ▪ Strawberry cervix Entamoeba histolytica punctate cervical hemorrhages o Transmission: ▪ Tx: Metronidazole for both patient and partner ▪ Fecal-oral, cysts in water o Disease: Trematodes ▪ Amebiasis Flat, unsegmented, leaf shaped Bloody diarrhea Hermaphroditic (EXCEPT Schistosoma) ▪ Amebic colitis Transmitted by ingestion of metacercariae (EXCEPT Histology: flask-shaped ulcers Schistosoma – skin penetration by forked-tail cercariae) ▪ Amebic liver abscess All eggs are operculated (EXCEPT Schistosoma) Anchovy paste exudate ALL FIRST Intermediate Host are SNAILS o Key Terms: ALL have a SECONDARY Intermediate Host (EXCEPT ▪ Trophozoites with engulfed RBCs (Entamoeba Schistosoma) Eats RBCs) ▪ Treatment: Paragonimus westermani Metronidazole Adult flukes in Lungs Paromomycin for asymptomatic cyst Resembles tuberculosis – chronic cough with bloody sputum passers Provokes granulamotous reaction Giardia lamblia Ingestion of crab meat o Transmission: ▪ Fecal-oral, cyst in water o Disease: ▪ Giardiasis Giardiasis—bloating, flatulence, foul- smelling, nonbloody, fatty diarrhea (steatorrhea) (often seen in campers/hikers) o Key Terms: ▪ Falling leaf motility ▪ Old man’s face ▪ Treatment: Tinidazole, nitazoxanide or metronidazole Cryptosporidium parvum o Transmission: ▪ Fecal-oral, oocysts in water Clonorchis sinensis o Disease: ▪ Opportunistic infection with AIDS (severe Adult flukes in the liver esp. in the Common Bile Duct diarrhea) Hyperplasia and fibrosis of the biliary tract ▪ Mild watery diarrhea in immunocompetent Chronic disease causes cholangiocarcinoma hosts Ingestion of undercooked fish o Key Terms: ▪ Acid fast oocysts ▪ Prevention (eg, filtering) ▪ nitazoxanide (severe disease and/or immunocompromised Balantidium coli FOCUS REVIEW CENTER | Focus Review Center | [email protected] Page 19 of 40 OCTOBER 2024 COMPREHENSIVE REVIEW PROGRAM | TIER I HANDOUT | MICROBIOLOGY AND PARASITOLOGY Nematode routes of infection Ingested: Enterobius, Ascaris, Toxocara, Trichinella, Trichuris Mnemonic: You’ll get sick if you EAT These Things! Cutaneous penetration: Strongyloides, Ancylostoma, Necator Mnemonic: These will get into your feet from the SANd Schistosoma spp Bites: Loa loa, Onchocerca volvulus, Wuchereria bancrofti Mnemonic: Lay LOW to avoid getting bitten Cylindrical not leaf shaped Skin penetration by cercaria not ingestion of metacercaria Eggs are not operculated Ascaris lumbricoides Kato-katz technique to detect Giant intestinal roundworm Disease: Acute Schistosomiasis/Swimmer’s itch/Katayama most common and largest fever Principal site of tissue reaction: Lungs o Intestinal Schistosomiasis – veins of small intestines, o Migration of larvae to alveoli → Löeffler syndrome liver, colon (pulmonary eosinophilia). ▪ Caused by – Heavy worm burden in small intestine →malnutrition S. japonicum (ova: small lateral spine) Transmission: ingestion of embryonated eggs S. mansoni (ova: large lateral spine) Diagnostic: Ova in feces o Urinary schistosomiasis – veins of urinary bladder Treatment of choice: Albendazole ▪ Caused by: S. haematobium (ova: Large Terminal spine) ▪ Chronic infection → squamous cell CA of bladder Necator americanus/ Ancylostoma duodenale Hookworms Blood-sucking worms – which may cause Anemia (IDA) Soil-transmitted helminth Transmitted by skin penetration by L3 (filariform) Diagnostic: Ova in feces Cutaneous larva migrans Nematodes/Roundworms Main habitat is small and large intestines Largest and most visible Generally, soil-transmitted helminths FOCUS REVIEW CENTER | Focus Review Center | [email protected] Page 20 of 40 OCTOBER 2024 COMPREHENSIVE REVIEW PROGRAM | TIER I HANDOUT | MICROBIOLOGY AND PARASITOLOGY Trichuris trichiura Whipworm Soil-transmitted helminth Transmitted via ingestion of embryonated eggs Diagnostic: Ova in feces (bipolar plugs) Causes diarrhea and rectal prolapse Wuchereria bancrofti/Brugia malayi Most debilitating nematode infection Adult worms in the LN causes inflammation → obstruction → lymphedema Transmitted via mosquito bite Enterobius vermicularis Pinworm/seatworm Soil-transmitted helminth Transmitted via ingestion of embryonated eggs Most common in children ages 5-10 Disease: Pruritus ani, worse at night Dx: Scotch tape method Trichinella spiralis Causes myalgia, periorbital edema, myocarditis, respiratory myositis Muscle biopsy is the most definitive test: nurse cell Transmitted via ingestion of encysted larvae in undercooked pork Strongyloides stercoralis Threadworm Soil Transmitted Helminth, facultative parasite The only helminth that causes great disease in AIDS patients Causes stongyloidiasis Transmitted via skin penetration by L3 (filariform larvae) Diagnostic stage: rhabditiform larvae Treatment: Ivermectin FOCUS REVIEW CENTER | Focus Review Center | [email protected] Page 21 of 40 OCTOBER 2024 COMPREHENSIVE REVIEW PROGRAM | TIER I HANDOUT | MICROBIOLOGY AND PARASITOLOGY Longest of the tapeworms Vitamin B12 deficiency – uptake of the worm then causes megaloblastic anemia Transmitted via ingestion of larvae in fish Treatment of choice: Praziquantel Cestodes/Flatworms Ribbon like worms Longest and flat; can grow over 20m Segmented body – tapeworm Echinococcus granulosus Smallest of the tapeworms Taenia solium Causes unilocular hydatid cests esp. in the liver Intermediate host: Pig Rupture of cyst causes anaphylactic shock Has 4 suckers, circle of hooks around rostellum Transmitted via ingestion of eggs in dog feces Causes taeniasis and cysticercosis Tx: Albendazole Gravid proglottids in the stool Transmitted via ingestion of larvae in pork Taenia saginata Intermediate host: cow Has 4 suckers no hooks an no rostellum (compare with T. solium) Causes taeniasis but not cysticercosis Gravid proglottids in stool Transmitted via ingestion of larvae in beef Parasite Hints Left, T. solium scolex; Right, T. saginata scolex Diphyllobothrium latum FOCUS REVIEW CENTER | Focus Review Center | [email protected] Page 22 of 40 OCTOBER 2024 COMPREHENSIVE REVIEW PROGRAM | TIER I HANDOUT | MICROBIOLOGY AND PARASITOLOGY How to remember drug options for nematodes, cestodes, and trematodes? Arthropods of Medical Significance END OF MICROBIOLOGY AND PARASITOLOGY TIER I PART I HANDOUT FOCUS REVIEW CENTER | Focus Review Center | [email protected] Page 23 of 40