Infectious DiseasesBIOMEDICAL TECHNOLOGY

Part One

OVERVIEW

* An Infectious Disease is a disease that is caused by the invasion of a host by agents whose activities harm the host’s tissues.

* They cause disease (by impairing normal tissue function) and can be transmitted to other individuals (they are infectious)

Vocabulary

• Pathogens – Microorganisms that are capable of causing disease.

• Infection – Results when a pathogen invades and begin growing within a host.

• Disease – results only if and when tissue function is impaired (i.e. burns, skin lesions)

Infectious Process

• The body has defense mechanisms to prevent infection and to prevent disease after infection occurs.

• In order to cause disease, pathogens must be able to enter the host body, adhere to specific host cells, invade and colonize host tissues, and inflict damage on those tissues.

Infectious Process Cont.

• Entrances to the host: mouth, eyes, genital openings, or wounds.

• Growth of pathogens or the production of toxins/enzymes cause disease.

• Some normal flora prevent disease.

Latent Period

• A "latent period" is the lag time between exposure to a disease-causing agent and the onset of the disease the agent causes.

• For instance, the latent period between exposure to HIV infection and the onset of AIDS may be many years.

• Example: Magic Johnson

MICROBES THAT CAUSE INFECTIOUS DISEASES

BACTERIA

• Small unicellular microorganism that multiplies by cell division.

• Found as bacillus (rod shaped), coccus (spherical), or spirillum (spiral)

• Anthrax, Cholera, Legionellosis, Lyme Disease, Salmonellas, Strep, TB, Typhoid, Yersinia pestis (plague)

• Treatable with antibiotics

Bacteria Cont.

• Staphylococcus aureus (Staph)– Favorite hangout: skin and nose– Likes: getting inside the body where it can cause a minor

infection like a boil, or serious, sometimes fatal infections such as blood infections or pneumonia.

– Dislikes: many antibiotics

Bacteria Cont.

• AEROBES• Reproduces only in the

presence of oxygen

• ANAEROBES• Reproduce only in the

absence of oxygen

Facultative anaerobic bacteria:can produce in either environment

BACTERIA EXAMPLES:

Gram positive– STAPHYLOCOCCUS

Gram negative– SALMONELLA

Staph infections

• Flesh eating early • Impetigo

• Flesh Eating bacteria ADVANCED

Yersinia Pestis (looks like Pests)

• Bacterium that causes Plague

• Transmitted via rodents typically

VIRUSES

Viruses

• Apart from the host cell, have no metabolism and cannot reproduce or survive unless they take over a living cell

Retroviruses – a classification of viruses

• HIV• Certain types of

CA• Retroviruses are

viruses whose genome consists of RNA not DNA.

Think about IT• In February 1997 it wasreported that pig cellscontain a retroviruscapable of infectinghuman cells. This istroublesome because ofthe efforts that are beingmade to transplant pigtissue into humans (e.g.,fetal pig cells into thebrains of patients withParkinson's disease/hearts etc).

Virus Examples• Chicken pox• Cold sores• Genital herpes• Shingles• Small pox• AIDS• Influenza• Rabies-direct contact• West Nile Virus• Ebola →• Hantavirus

• Many viruses are preventable via vaccinations• Can be treated with Antiviral drugs• ANTIBIOTICS do not work

Smallpox virus

More virus examples:

• Rhinovirus– The common cold

• Influenza• Measles• Mumps↓

Rotaviruses

• Gastroenteritis• Wheel shaped virus

causing diarrhea

• Every year it kills approximately 1 Million children world wide

FUNGI

Fungi

• Have a cell wall and a cell membrane

• Includes molds and yeast

• Treat with antifungal medication, sometimes with antibiotics.

Fungi examples

• Ringworm• Histoplasmosis• Athletes foot• Thrush

• Yeast or candida are opportunists

• Yeast infections are the most common opportunistic infection

• Antibiotics reduce normal flora and allow yeast to grow making the pt susceptible to an opportunistic infection

PROTOZOA

• Acquired through contaminated food or water, or bite of an arthropod (mosquito)

• More common in wet climates like the tropics• Amoebic dysentery• Malaria- re-emerging d/t drug resistance and

fear of vaccination• Treatable with antibiotics

HELMINTHS (WORMS) ewwww!

• Simple, invertibrate animals, some infectious parasites

• In intestine, blood, body tissue• Medications to force evacuation or death of

worms

• Swimmer’s itch in US– Schistosoma (flatworm)– Symptoms include

abdominal pain and diarrhea

• Trichinella spiralis (roundworm)– Ingested in undercooked

pork from infected pigs.– Symptoms include

vomiting, diarrhea, and abdominal pain

SEE NEXT SLIDE FOR PICTURE!!!

FilariasisFilariasis- worm infestation in lymphatic system that prevents normal draining of lymphatic fluids. Causes SEVERE swelling.

PRIONS (pree-ons)

• Extremely smallparticles that consistonly of protein.• Resistant to heat andDisinfectants• No known treatments– Creutzfeldt-Jakob disease– “mad cow disease” in cattle