Bacteria & Viruses

QUIZ TIME (30 MIN)

Staphylococcus aureus commonly causes boils and soft-tissue infections as well as more serious conditions such as pneumonia or bloodstream infections. According to the Centers for Disease Control and Prevention (CDC), 20-35% of adults and children in the United States are positive for the bacteria but do not cause illness. Staphylococcus aureus colonization usually occurs in the armpit, groin, genital area, and, most frequently, the inside of the nose. Most infections occur through direct physical contact of the staph bacteria with a break in the skin (cut or scrape) or during contact with inanimate objects (such as clothing, bed linens, or furniture) soiled with wound drainage. The most common transmission location are in schools and hospitals. Warm Up

Analyze the graph: 1. Which location has the highest occurrence of resistance? 2. Based on the graph, make an inference about why penicillin resistant S. aureus is greater in one location compared to another. 3. Why did methicillin resistance lag behind penicillin resistance? Based on the trend seen with penicillin, what would you expect to see happen with methicillin?

What do you already know? What are the differences between viruses and bacteria? Are all bacteria harmful? When you get a cold, should you take an antibiotic to help you get better? What’s the best and easiest thing to do to avoid getting sick?

Bacteria Bacteriology is the study of bacteria Bacteria are prokaryotic, unicellular organisms containing DNA and ribosomes. Bacteria have ALL the characteristics of living things. Bacteria have the greatest percentage of the biomass on Earth!

Basic structure of bacteria: Bacterial Structure Basic structure of bacteria: Cell wall Cell membrane Ribosome Peptidoglycan* Flagellum DNA Pili

VIDEO CLIP: Understanding Bacteria A rather vocal minority (less than 1%) of bacteria cause disease in humans, animals, and plants. Bacteria can cause a variety of diseases: Food Poisoning – Scarlet Fever Tuberculosis – Whooping Cough Cholera – Bacterial Meningitis Syphilis – Pneumonia Ulcers – Leprosy Strep Throat – Tetanus VIDEO CLIP: Understanding Bacteria

*So are viruses living or non-living?* Virology is the study of viruses Viruses are “biological entities” containing either DNA or RNA that require another cell to survive. Viruses have some, but not all, of the characteristics of life. *So are viruses living or non-living?* Viruses seem to exist only to make more viruses!

Nucleic acid core (DNA or RNA) Viral Structure All viruses have the same basic structure: Nucleic acid core (DNA or RNA) Capsid (Protein coat) Surface Markers

Without a host cell, viruses cannot function (i.e.-are harmless!) How Do Viruses Work? In order to replicate and make copies of itself, viruses need a host cell. Any living cell can become a host cell (human, animal, plant, and even bacterial cells!) Without a host cell, viruses cannot function (i.e.-are harmless!) Although any cell can theoretically become a host cell, specific viruses will only infect specific cells (EX: HIV will only infect human T cells, a part of your immune system)

Transmission of Viruses Respiratory transmission Influenza A virus Fecal-oral transmission Enterovirus Blood-borne transmission Hepatitis B virus Sexual Transmission HIV Animal or insect vectors Rabies virus ·         As with many infections viruses can be transmitted between susceptible individuals by a variety of means. The details provided related mainly to viruses infecting humans. ·         Many animal viruses do not remain infectious for very long outside the host. Ø     Respiratory: Influenza A virus (and rhinovirus). Transmission in the form of aerosols during coughing and sneezing. The viruses are fairly sensitive to drying and their transmission is highest when individuals are in close contact. Ø     Faecal-oral: Enteroviruses (e.g. poliovirus) A lot of viruses are excreted in faeces following high levels of replication in the gut. Ø     Blood borne: Hepatitis B (and HIV). Transferred through contaminated blood products or via shared needles with drug abuse. Ø     Sexual transmission: (HIV) Animal/insect vector: Rabies. In many instances the virus infection is a specific pathogen of the animal and is not normally transmitted to humans by any other means.

How Do Viruses Work? Attach: The capsid of the virus binds to receptor proteins on the surface of a host cell, tricking the host cell into thinking it’s not a foreign invader. Inject: The virus then injects its genetic material (DNA or RNA) into the host cell. Assemble: The viral genes are expressed, turning the host cell into a virus-making factory. Repeat: The host cell eventually bursts, releasing the hundreds of newly formed viruses to infect surrounding cells! VIDEO CLIP: How Viruses Work

Viruses Viruses can cause disease in humans, animals, plants, and even bacteria! Viruses can cause a variety of diseases: Common cold – Polio Hepatitis A, B & C – Influenza Herpes – Mumps Mononucleosis – Measles Warts – Viral Meningitis Chickenpox – AIDS VIDEO CLIP: Viral Disease

Bacteria

Acute Virus Infection Symptoms Amount of virus Time Virus ·         The graph illustrates the typical pattern of virus replication during an acute virus infection: Ä            Following a short incubation period of a few days there a maximal virus production Ä            Visible symptoms generally appear just after this peak of virus replication. Depending on the virus the symptoms may last just a few days. Ä            The patient recovers and an immune response is generated and the virus is eliminated within 1 or 2 weeks. ·        

Poliovirus ·         A human virus infection that is largely controlled by vaccination and is likely to be fully eradicated in the next few years. The infection here is associated with infantile paralysis affecting the lower limbs but in severe cases there can be paralysis of the muscles controlling respiration.

Poliovirus Properties of the virus Enterovirus. Possesses a RNA genome. Transmitted by the faecal oral route. Cause of gastrointestinal illness and poliomyelitis. Enterovirus. Possesses a RNA genome. Transmitted by the faecal oral route. Cause of gastrointestinal illness and poliomyelitis.

Protection There are a few big ways to protect yourself against pathogens (disease causing agents) Antibiotics (drugs to kill bacteria) Antivirals (drugs to treat viruses) Vaccination (using your body’s own immune system to preemptively guard against attack)

Antibiotics Antibiotics can only be used to treat bacterial infections! Target specific structures on bacteria to kill them. First made from a fungus (penicillin), now most are made artificially. Unfortunately, antibiotic resistance (where the antibiotic doesn’t kill the target bacteria anymore) is becoming a major problem.

Antivirals Antivirals can only be used to treat certain viral infections! Does not “kill” or disarm the virus permanently; only shortens symptoms by 1-2 days. Usually only prescribed to patients with life threatening symptoms or those that have a greater chance of developing complications (because of their age or they have a high-risk medical condition). Just like antibiotics, there is evidence of antiviral resistance too!

Vaccination Vaccines can only be used to prevent infections (both viral and bacterial) from leading to disease. “Trick” your immune system to make antibodies that destroy foreign “bodies” or particles (such as bacteria and viruses). Your body remembers how to make these antibodies when the real thing invades. Made from a weakened virus, inactivated virus, or by using only part of the virus/bacteria itself. VIDEO CLIP: Vaccination

To Review.... What are the differences between viruses and bacteria? Are all bacteria harmful? Explain. When you get a cold, should you take an antibiotic to help you get better? Why? What’s the best and easiest thing to do to avoid getting sick?

http://www.youtube.com/watch?v=3xRttWuf3wQ

Bacteria Virus Both