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Chapter 4: Infection Ms. Harris Pathophysiology Fall 2009 • What is an infection? – Colonization of a host organism by a foreign species. – The infecting organism is called a pathogen. • Can be infected by a number of microscopic organisms including bacteria, protozoa, fungi, and viruses (although viruses are NOT considered living). Germ Theory • Provided a link between microorganisms and disease – Was not verified until Robert Koch (Koch’s Postulates) proved this by experimenting with mice and anthrax cultures in the 1880s. Types of microbes • BACTERIA – Prokaryotes- ??? • No nucleus • Unicellular – Can be good or bad • Normal flora Normal Flora Resident flora present Sterile areas Skin Blood and cerebrospinal fluid Nose, pharynx, mouth Lungs, stomach Colon, rectum, vagina, distal urethra Uterus, fallopian tubes, ovary; bladder and kidney Bacteria continued… • Classified by their shape – Cocci = round (MRSA) – Bacilli = tic-tac or rod shaped (Clostridium tetani) – Spirilla = spiral (Treponema pallidum) Bacterial Structure • Cell walls are either – Gram positive: has peptidoglycan in the cell wall stains purple – Gram negative: no peptidoglycan in the cell wall stains pinkishy red • Antibiotics work on the cell walls of bacteria, that’s why they cannot hurt our cells! • Bacteria usually cause disease by producing toxins and/or enzymes – Exotoxins- usually produced by G+. Can interfere with nerve conduction (neurotoxin), cause vomiting (enterotoxin). Stimulate antibody production – Endotoxins- usually produced by G-. Released once the bacteria dies. Causes fever, weakness, serious effects on circulatory system. – Enzymes- you already know Last bit of bacteria stuff • Bacteria can form spores – Allow bacteria to survive long periods; highly resistant (tetanus and botulism). • Bacteria repro. By binary fission VIRUSES • Non-living- do NOT listen to your book! – Requires a living host to reproduce • Capsid (protein coat) surrounding some DNA(usually) or RNA. – If RNA, its called a retrovirus…can you name a retrovirus? How viruses cause disease • Attach to host cell and injects its genetic material • Uses the host cell’s machinery to reproduce • Lyses the cell (too many virus babies makes the cell explode) • Some can enter latent phases • Viruses are famous for mutating – Flu, colds • Difficult to control • Some are capable of causing cancer because they alter the host’s DNA…think HPV and link to cervical cancer. Infection Part 2 Chapter 4 K. Harris Major Grade Poster • Create a disease awareness poster for your assigned disease • Must include: – – – – – – – Prevelance/incidence/death rate Is it epidemic or pandemic Signs and symptoms Potential complications Geographic location of disease Pictures Pathophysiology of the disease Fungal Infections • Fungi are found everywhere. – Usually on places where its warm and moist. • Fungal Infections are also called mycotic infections. • Eukaryotic – Uni or multicellular Good vs. Bad • Just like bacteria and people, some fungi are good and some fungi are bad. – Good: a source of antibiotic drugs like penicillin – Bad: the ones that cause disease. Examples of Fungal Diseases • Athletes foot • Candida species – Cause of vaginal yeast infections and thrush in infants • Histoplasmas cause lung infections Protozoan Infections • Also called protists – Eukaryotic, can be uni or multicellular • Examples include malaria, trichomonas, amebic dysentery, etc. Other parasites • Helminths (actually worms…ewww…) – Eggs and larvae are found in contaminated water and can be ingested. Transmission of infection • Direct contact • Indirect contact (contaminated food or surfaces) • Droplet transmission (oral or respiratory) • Vector borne (carried by insect or other animal) • Nosocomal infections- occurs in a healthcare facility Host Resistance • Interferons are produced by host cells in response to a virus to help nearby cells become resistant to viral attachment. • Age, genetics, immunodeficiency, malnutrition, chronic disease Other terms • Pathogenicity- capability to become disease • Virulence- degree of pathogenicity – Mutation of microbe • “Superbugs” like MRSA---huge issue, especially in hospitals. Infection Control • • • • Isolation; quarantine Universal precautions like handwashing Sterilization of materials (autoclaving) Disinfectants- chemicals to clean inanimate objects • Antiseptics- chemicals to clean animate objects Onset and Course • Incubation period, then prodromal period, then acute period, then (usually) recovery. • If not recovery: – Chronic infection – Septicemia- life threatening, systemic, infection is active in the bloodstream (BAD) Signs and symptoms • Local: inflammation- pain, swelling, redness and warmth; purulent exudate if infection is bacterial in nature; serous exudate if viral; necrosis • Systemic: fatigue, nausea, headache, pyrexia, subnormal temp., disorientation, seizures Diagnosis • Culture/staining to figure out what specifically is causing the infection Drugs • Usually, body can fight off infection on its own. Sometimes, drugs are required. • Prophylactic treatment- given as a precaution. Types of drugs • Antibiotic- derived from living organisms (usually molds like penicillin and amoxycillin) – Broad spectrum: both G+ and G– Narrow spectrum: either G+ or G-, not both • Better because it is less likely to kill normal flora • Antibacterials, antivirals, antifungals • Bactericidal- kill bacteria • Bacteriostatic- reduce reproduction rate DRUUUUUUUUUUUGS • How do they work? – Read and take notes on mode of action for infection fighting drugs on pgs 98-99. – In your notes, after your summary, answer the Think About questions on page 99. Current Event 1. Write three cause/effect statements from the article. 2. What are the potential problems of antibiotics becoming obsolete. 3. Write a letter to your senator explaining the problem and what you think should be done about it. Current event article http://www.cnn.com/2009/HEALTH/10/01/ant ibiotic.penicillin.resistance/index.html?iref= newssearch