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Microbiology unit 3 Cheat Sheet (DRAFT) by

This is a draft cheat sheet. It is a work in progress and is not finished yet.


Hypers­ens­itivity is an antigenic response that isn't normal; allergies are an example
There are four types of hypers­ens­itivity reactions: type 1 (anaph­yla­ctic), type 2 (cytot­oxic), type 3 (immune complex), and type 4 (delayed cell-m­edi­ated, or delayed hypers­ens­iti­vity)

Type 1 reactions - anaphy­lactic reacti­ons

Anaphy­lactic reactions occur within 2 to 30 minutes of coming into contact with an antigen
IgE antibodies bind to mast cells or basophils; causes degran­ulation of mast cells or basophils, and causes the release of reactive substances like histamine
There are two types of anaphy­lactic reactions: systemic anaphy­laxis and localized anaphy­laxis
Systemic anaphy­laxis is the result of an indivi­dual, who is sensitized to a particular antigen, is exposed to the particular antigen again. An example is an allergic reaction to penicillin
Localized anaphy­laxis is the result of someone ingesting (eating a food) inhaling (things like pollen) an antigen, and the symptoms depend on the way the antigen entered the body
Sensit­ivity to an antigen is shown by a rapid inflam­mation reaction that causes swelling, redness, and itching at the inocul­ation site. The inocul­ation site is called a wheal
Desens­iti­zation is one way to prevent anaphy­lactic reactions, and avoiding the antigens known to cause reactions is another way to prevent an anaphy­lactic reaction
Desens­iti­zation involves increasing the dosages of the antigen, and carefully injecting the dosages beneath the skin

Micr­obial diseases of the skin

Caused by bacteria, viruses, and fungi/­par­asites

Bact­erial diseases of the skin

The bacteria that cause well known diseases are Staphy­lococci, Strept­ococci, Micrococci, Propio­nib­act­erium acnes, and Pseudo­monas aeruginosa

Viral diseases of the skin

The viruses that cause well known skin diseases are Morbil­livirus, the mumps virus, Togavi­ruses, Papillomas coxsac­kie­vir­us/­ent­ovirus, Smallpox, and Haemop­hilus influenzae

Fungal and parasitic diseases of the skin

The fungi and parasites that cause well known diseases of the skin are ringworm, Candida albicans, and Sarcoptes scabiei mites*


Most parasitic animals belong to one of two phyla: Platyh­elm­inthes (flatw­orms) and Nematoda (round­worms)

The Nematodes, aka the roundworms

The roundworms have cylind­rical bodies and have a complete digestive system
The roundworms are dioecious
The males have spicules, which are used to take the sperm to the female's genital pore
There are free-l­iving and parasitic nematodes
Some nematodes have eggs that are infective for humans
The nematodes that have infective eggs are Ascaris lumbri­coides (infects human intest­ines), Trichuris trichiura (whipworm transm­itted by fecal-oral transm­ission or feces-­con­tam­inated food), and Enterobius vermic­ularis (pinworm that spends its life in a human host; adult pinworms are found in the host's large intestine)
Some nematodes have larvae that infect humans
The nematode larvae that infect humans are Strong­yloides (there is a reemer­gence of Strong­yloides infect­ions; the larvae can travel to the intestine or the lungs), the hookworms (enter the skin and are carried to the intest­ines), and Dirofi­laria immitis (causes heartworm and is spread by mosqui­toes)

The Protozoa

The protozoa are unicel­lular eukaryotes that inhabit water and soil
The protozoans have complex life cycles and animal­-like nutrition
They require a large supply of water
Some protozoa have a pellicle, which is an outer protective covering. The protozoa that have pellicles require specia­lized structures to take in food
Protozoa's food is digested in vacuoles and wastes are eliminated through an anal pore
There are some medically important protozoa: the Excavata, Amebae, Apicom­plexa, and the Ciliates
Amebae move by extending pseudopods*
The amebae Entamoeba histol­ytica causes amebic dysentery
The amebae Acanth­amoeba infects the corneas and causes blindness
The amebae Balamuthia causes granul­omatous amebic enceph­alitis
Apicom­plexa are nonmotile, obligate intrac­ellular parasites that have complex life cycles
The apicom­plexan parasite Plasmodium causes malaria, and it's transm­itted by insect bites
The apicom­plexan paraside Babesia affects the red blood cells of its host. It causes fever and anemia of immuno­com­pro­mised people. It's transm­itted by an insect bite
The apicom­plexan parasite Toxoplasma gondii is transm­itted by cats and causes fetal infections
The apicom­plexan parasite Crypto­spo­ridium is transm­itted by feces and causes waterbone illness

Platyh­elm­inths, aka the flatworms

There are two types of flatworms: tremat­odes, or flukes and the cestodes, or tapeworms
The trematodes usually have flat, leaf-s­haped bodies with a ventral sucker and an oral sucker
The lung fluke (lung trematode) is a member of the Parago­nimus species
The Asian liver fluke (Asian liver trematode) is known as Clonorchis sinensis
The blood flukes (blood trematode) are members of the Schist­osoma species
The trematodes are given common names according to the tissue of the definitive host that the adult trematodes live in
The trematodes absorb food through their nonliving outer covering, which is called the cuticle
Cestodes are intestinal parasites
The head of cestodes is known as the scolex, and the body is made up of segments called proglo­ttids
Cestodes don't have a digestive system, so to obtain nutrients from the host's small intestine, they absorb food through their cuticle

Phylum Platyh­elm­inthes (flatw­orms)

The trematodes are also known as the flukes
The trematodes have a flat, leaf-s­haped body. They also have an oral and ventral sucker
The Parago­nimus species is known as the lung fluke
The Schist­osoma species is known as the blood fluke
The cestodes are known as the tapeworms
The head is known as the scolex, and it has suckers for attachment
The body segments of the cestodes are called proglo­ttids; the proglo­ttids have male and female reprod­uctive organs
The cestode Taenia solium uses humans as a definitive host
The cestodes that use humans as a definitive host produce eggs in the human, the eggs hatch in to larvae, and the larvae bore into the intestinal wall
The cestodes produce cysticerci in pigs
When humans are the interm­ediate hosts for cestodes, humans ingest the eggs, and the eggs hatch in the intestine. The larvae migrate to the liver or the lungs of the host and form a hydatid cyst
The cestode species Echino­coccus granulosus uses humans as an interm­ediate host

Charac­ter­istics of helminths

They might lack a digestive system
They have a reduced nervous system
Their means of moving (locom­otion) are occasi­onally reduced or are completely lacking
The reprod­uctive system is usually complex
Adult helminths life cycle can be dioecious or monoec­ious, or hermap­hro­ditic
Dioecious adult helminths have male reprod­uctive organs in one indivi­dual, and female reprod­uctive organs in another individual
Monoecious adult helminths have male and female reprod­uctive structures in the same individual