MICROBES Biomedical Technology I MICROBES THAT CAUSE INFECTIOUS

MICROBES Biomedical Technology I

MICROBES THAT CAUSE INFECTIOUS DISEASE Bacteria: *Unicellular Prokaryotic organisms *Reproduce by growing and dividing into tow cells in a process known as “binary fission” *Three common shapes: Bacillus (rodshaped), Coccus (spherical) and Spirillum (helical rods)

BACTERIA Frequently divided into two broad classes based on cell wall structures that influence their Gram stain reaction: Gram negative bacteria appear pink after staining process. Familiar pathogenic gram-negative organisms: 1. Salmonella typhi: causes typhoid fever 2. Yersinia pestis: causes plaque

BACTERIA Examples of gram positive bacteria: Gram positive bacteria appear purple after staining. 1. Staphylococcus aureus: Causes skin, respiratory, and wound infections 2. Clostridium tetani: Produces a toxin that can be lethal for humans, and causes tetanus

VIRUSES Viruses are classified using a variety of criteria, including shape, size and type of genome Apart from a host cell, they have no metabolism and cannot reproduce Examples of DNA viruses: 1. Herpes viruses that cause chicken pox, cold sores and genital lesions 2. Poxvirus that causes smallpox.

VIRUSES Examples of RNA viruses: 1. Rhinoviruses: Causes most common colds 2. Myxoviruses and Paramyxoviruses: Causes influenza, measles, and mumps 3. Rotaviruses: Causes gastroenteritis 4. Retroviruses: Causes AIDS and several types of cancer.

FUNGI Eukaryotic, heterotrophic organisms Reproduce primarily by forming spores Decomposers in the environment Many fungi also infect plants and animals Examples of diseases caused by fungi: 1. Ringworm (highly contagious, fungal infection of the skin or scalp) 2. Histoplasmosis ( a mild to severe lung infection transmitted by bat or bird droppings)

FUNGI 3. Yeast infections (Candida genus are opportunistic pathogens that may cause diseases such as vaginal yeast infections and thrush (a throat infection). Happens among people who are immunocompromised or undergoing antiobiotic therapy. *Antibiotics reduce the bacterial population normally present in the throat and vagina, allowing the yeast to grow out of control

PROTOZOA Unicellular, heterotrophic eukaryotes Capable of a variety of rapid and flexible movements because they do not have cell walls Can be acquired through contaminated food or water Also acquired by the bite of an infected mosquito Two common protozoan parasites: Giardia lamblia and Cryptosporidium parvum Plasmodium causes Malaria, a tropical illness that causes 300 -500 million cases worldwide

HELMINTHS Simple invertebrate animals, some of which are infectious parasites Multicellular Because they are animals, their physiology is similar in some ways to ours, This makes parasitic helminth infections difficult to treat because drugs that kill helminths are frequently toxic to human cells Helminths have complex reproductive cycles that include multiple stages that require a host

HELMINTHS Schistosoma, a flatworm, causes the mild disease swimmer’s itch in the U. S. Another speicies of Schistosoma causes the much more serious disease Schistosomiasis: an endemic in Africa and Latin America Schistosome eggs hatch in freshwater and the larvae infect snails The snails shed the larvae and the larvae attach to and penetrate human skin They then feed, grow, and mate in the human bloodstream

HELMINTH Disease symptoms of Schistosome is diarrhea and abdominal pain. Liver and spleen involvement are common Trichinosis is another disease caused by the roundworm, Trichinella spiralis This agent is typically ingested in improperly cooked pork from infected pigs Disease symptoms include vomiting, diarrhea, and fever, intense muscle pain Fatal cases often show congestive heart failure and respiratory paralysis

HELMINTHS: INFECTIOUS PARASITES

PRIONS Infectious particles that consist only of protein Creutzfeldt-Jakob disease ( in humans) Scrapie (in sheep) Bovine spongiform encephalopathy (mad cow disease in cattle) All known prion diseases frequently result in brain tissue that is riddled with holes. Some prion diseases are inherited, while others are due to infection by eating infected tissue or through medical procedures such as tissue transplants

PRIONS