Micro-ID topics
Key zoonoses
Naturally transmitted from animals to humans. Arthropod-borne bacteria and parasites Fleas Endemic typhus/murine typhus/Rickettsia typhi, epidemic typhus/Rickettsia prowazekii, Tunga penetrans Flies Sand Fly/Phlebotomus-cutaneous and visceral leishmaniasis, Tsetse Fly-African Sleeping Sickness/ T. brucei), Black Fly/Simulium-Onchocerciasis, Mango Fly/Chrysops-Loa Loa, Bot flies-Myiasis Mites/Chiggers Scrub typhus/Orientia tsutsugamushi, Scabies, Hair follicle mite/Demodex Mosquitos Malaria/Plasmodium, lymphatic filariasis/e.g. Wuchereria (many ARBO viruses […]
Notable bacterial toxins and mechanisms
These are exemplars of the most notable toxins and their mechanisms. Organisms such as Clostridia perfringens, Staphyloccoccus aureus, and Pseudomonas have a variety of toxins, some of which use similar mechanisms. Anthrax A/B toxin with three-protein components. Cell binding component is called protective antigen. There are two enzyme components: Edema factor Acts as adenylate cyclase […]
Infections based on predominant disease location (tropism)
Healthy Organisms associated with a healthy microbiome Bacteroides (GI tract) Lactobacillus (Vagina) Staphylococcus epidermidis (Skin) Head Central Nervous System (CNS) Meningitis: Differentiate by age (newborn, adult, elderly) and by “septic” (culture +) vs “aseptic” (culture negative – usually virus, prior antibiotics, or drug-induced). Bacteria: Neonate: E. coli, Group B Strep, Listeria Infant: Neisseria meningitidis, Strep […]
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 […]
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 […]