Infections based on predominant disease location (tropism)
Healthy Head Chest Abdomen Extremities Skin Systemic/Sepsis Abdomen/Ascites Echinococcal cysts, Entamoeba histolytica (liver abscess), visceral leishmaniasis, Schistosoma portal hypertension with ascites, without cirrhosis. Lymphatics Microfilaria (e.g., Wuchereria), Trypanosoma. Muscle Trichinosis, Cysticercosis, Onchocerciasis. Skin Cutaneous larva migrans, cutaneous leishmaniasis, Onchocerciasis, myiasis, scabies, lice (and other ectoparasites). Image credits Unless otherwise noted, images are from Adobe Stock.
Outline of parasitic diseases and organisms according to site/specimen
Blood Plasmodium, Babesia, Trypanosoma, Microfilaria (Leishmania and Toxoplasma can be blood-bourne, but are not usually seen on the peripheral blood smear.). CSF Trypanosoma brucei, Naegleria, Angiostrongylus (eosinophilic meningitis). Brain Neurocysticercosis (Tinea solium), Toxoplasma. Eye Acanthamoeba, Toxoplasmosis, Onchocerciasis, Loa loa, visceral larva migrans (Toxocariasis). Mouth/Throat Ascaris. Sputum/Lung Ascaris, Strongyloides, Pneumocystis, Paragonimus. Abdomen/Ascites Echinococcal cysts, Entamoeba histolytica […]
Pharmacology: Introduction to antimicrobial therapy
Learning goals Describe the five basic mechanisms of action of antimicrobials against bacterial cells (inhibition of cell wall synthesis, inhibition of protein synthesis, alteration of cell membranes, inhibition of nucleic acid synthesis, and antimetabolite activity) Define empiric versus directed antimicrobial therapy and describe the basic principles behind selecting an empiric antimicrobial regimen Discuss the pharmacokinetic […]
Principles of laboratory diagnosis
Learning goals Describe considerations used to select microbiologic diagnostic tests Compare and contrast direct examination, culture, serologic, and molecular laboratory methods for identifying microorganisms in terms of the benefits and limitations of each Compare and contrast laboratory methods used to identify and characterize bacteria versus viruses Study materials These materials are not required; they are […]
Microbiome, normal flora, and antimicrobial stewardship
Learning goals Explain virulence and how it relates to benign versus pathogenic microorganisms Name common bacterial species that are considered normal human flora for each of the following locations: skin, mouth, colon, and vagina, and describe how these organisms enhance host immunity Explain the impact of a distorted microbiome, related to antibiotic exposure or hospitalization, […]
Ectoparasites
Scabies/Sarcoptes Human-to-human spread. Clinical: intensely itchy papular rash (hands, wrists, elbows, webbing between fingers, penis, scrotum), or occasionally diffuse non-pruritic rash in immune suppressed patients (crusted scabies). Secondary bacterial infection is common. Dx: Skin scraping or adhesive tape (look for mites, eggs or feces). Rx: Lindane, etc. Lice/Pediculosis Three types: Head louse Body louse Pubic […]
Trematodes
check yourself Fill in these summary tables to check your learning. Flukes Non-segmented flat worms. Schistosomiasis (Blood fluke) A very common parasitic disease with significant morbidity and mortality. Human reservoir (or animal reservoir for some species) with snails in life cycle. Infection occurs when humans are in water and schistosomal cercariae (from snails) penetrate human […]
Cestodes
check yourself Fill in these summary tables to check your learning. Tapeworms Segmented flat worms. Taenia sagniata (Beef tapeworm) Humans ingest undercooked beef containing cysticerci, larvae attach to bowel wall and mature to adult worms that eventually shed proglottids into feces that are eaten by cattle. Humans are the definitive host, and cows the intermediate […]
Nematodes
check yourself Fill in these summary tables to check your learning. Round worms GI Enterobius (Pin worm) Transmitted by ingestion of eggs, which develop into adults within the gut. Females migrate to rectum/anus to lay eggs on skin. Symptoms are associated with this migration and lead to intense anal pruritis (itchy butt). Re-infection is common […]
Protozoa
check yourself Fill in these summary tables to check your learning. Amoeba About the size of WBCs, but move by pseudopodia. Entamoeba histolytica (amebiasis) Obligate human parasite that are transmitted to humans by ingestion of the cysts shed in asymptomatic carriers’ stool. Cysts form trophozoites in intestine where they can eat RBCs and invade the […]