EXAM UNIT TWO “Survey of Microbes”

1. EXAM UNIT TWO“Survey of Microbes” ACELLULAR INFECTIOUS AGENTS PROKARYOTIC MICROBES EUKARYOTIC MICROBES

2. Introduction • Infectious agents can be classified as cellular or acellular. • Cellular microbes include bacteria, archaea, algae, protozoa, and fungi. • Acellular microbes include viruses, viroids, and prions.

3. ACELLULAR INFECTIOUS AGENTS • Also known as infectious particles. • Includes viruses, viroids, and Prions. • All of these particles are non-living.

4. VIRUSES • Also known as viroids. • First virus was discovered in 1892 by DimitriIvanowski, viruses were not observed until the 1930s. • Most range in size from 10 to 300 nm. • Infect all major groups of organisms: animals, plants, fungi, protists, and bacteria. • Consist of a protein capsule surrounding a nucleic acid core (RNA or DNA).

5. VIRUSES The Five Specific Properties of a virus are: • Have either RNA or DNA, not both. • Cannot replicate (copy) themselves, they must be replicated by a host cell. • Do not divide by mitosis, meiosis, or binary fission. • They cannot harvest energy or produce their own proteins. • Depend on the host cell for protein production, energy harvest, and other metabolic processes.

6. VIRUSES • Some are oncogenic (cancer causing) and cause various forms of carcinomas, lymphomas, and leukemias. • Rabies, Polio, Influenza, Measels, Mumps, Small Pox, Chicken Pox, Herpes, and Hepatitis are all examples of viral infections. • Bacteriophages only infect bacteria, animal virionsinfect animal tissue, and plant virionsinfect plant tissue. • Some viruses lyse the host and are released, and some pass through the cell membrane in a process called budding.

7. BACTERIOPHAGES • Viruses that infect bacteria. (“bacteria eaters”). • Occur in various forms containing DNA or RNA. • Virulent bacteriophages cause the direct death of the host through lysis of the host. • Temperate (lysogenic) bacteriophages incorporate their nucleic acid into the host where it sits dormant, in some cases for generations. It may then be expressed at a later time.

8. LATENT VIRAL INFECTIONS • Viral infections that sit dormant for periods of time and are periodically expressed. • Herpes infections are an example (cold sores, shingles, genital herpes). • Outbreaks are often triggered by stress (fever, U.V. radiation, emotional stress).

9. ONCOGENIC VIRUSES • Cancer-causing viruses. • Examples include the following: Epstein-Barr (type of herpes virus) causes infectious mononucleosis as well as various cancers. Human Herpes Virus 8 common in AIDS patients causes Kaposi sarcoma. Human papillomaviruses (HPV) cause genital warts and cancers of the reproductive tract.

10. Antiviral Agents and Antibiotics • Antiviral agents interfere with viral production or disrupt virus specific enzymes. • Antibiotics do not work against virions, they are designed to target structures that bacterial cells have.

11. HIV and AIDS • HIV (Human Immunodeficiency Virus) is an RNA containing virus. • It infects cells of the immune system such as Helper T lymphocytes and Macrophages. • It compromises the host’s immune response and makes them vulnerable to opportunistic infections. • When the immune system is compromised the individual develops AIDS (Acquired Immunity Deficiency Syndrome).

12. The Impact of HIV / AIDS • Worldwide, over 33 million people are infected with HIV. Roughly 2.5 million are children. • There are over 2.5 million new cases very year. • There are close to 2 million AIDs deaths per year. • In the U.S., over 1 million people are infected with HIV, over 18,000 die of AIDS annually. • In the U.S., over 45% of new cases are in the southern states, especially large urban areas. • There are over 50,000 new cases of HIV infection in the U.S. annually.

13. Mimivirions • Mimiviruses are very large viruses that “mimic” bacteria. • They can be seen with a compound microscope and are 750 nm in diameter. • They are larger than some bacteria and may cause some forms of pneumonia.

14. VIROIDS • Short naked strands of RNA. • They are known to cause at least 12 different plant diseases. • They have not been found to cause any diseases in animals.

15. PRIONS • Proteinaceous Infectious Particles that cause disease. • Disease causing proteins in nervous tissue that corrupt healthy proteins and ultimately cause cellular death. This causes “pockets” to form in the tissue. • Protein Only Hypothesis was first proposed by Stanley Prusiner in the 1980s. This theory states that abnormal proteins corrupt healthy proteins and cause disease. There is no nucleic acid involved.

16. PRIONS • Various prions cause a range of TSEs (Transmissible Spongiform Encephalopathies) • For example: Scrapie in sheep; Chronic Wasting Disease in deer and elk; Bovine Spongiform Encephalopathy (mad cow disease); Kuru, CJD & vCJD (Creutzfeldt-Jakob disease) in humans.

17. PRION INFECTED TISSUE (BSE)

18. SCRAPIE • TSE First encountered in the 18th century (1732). • Fatal generative disease that infects the nervous tissue of goats and sheep. • Infected animals typically scrap off their skin due to the irritation. • Also display lip-smacking, altered gait, and convulsive collapse. • It is infectious and transmissible. The biology is poorly understood

19. SCRAPPIE

20. Bovine Spongiform Encephalopathy • Also known as mad cow disease. • Linked to vCJD (a prion infection in humans). • Degenerative neurologic disease caused by prions. • Results in loss of coordination, aggression, and eventual death.

21. USDA recalls 143 million pounds of beef • Mon., Feb. 18, 2008 • LOS ANGELES - An undercover video showing crippled and sick animals being shoved with forklifts has led to the largest beef recall in the United States and a scramble to find out if any of the meat is still destined for school children’s lunches. • Officials estimate that about 37 million pounds of the recalled beef went to school programs, but they believe most of the meat probably has already been eaten. • Authorities said the video showed workers kicking, shocking and otherwise abusing “downer” animals that were apparently too sick or injured to walk into the slaughterhouse. Some animals had water forced down their throats, San Bernardino County prosecutor Michael Ramos said. • Federal regulations call for keeping downed cattle out of the food supply because they may pose a higher risk of contamination from E. coli, salmonella or mad cow disease since they typically wallow in feces and their immune systems are often weak.

23. KURU • A rare and fatal nervous disorder (TSE) that occurs in the Fore (pronounced “foray”) people of New Guinea. The word kuru means to tremble. • It reached epidemic proportions in the 1950s and 1960s. • Transmitted through ritualistic cannibalism, they would eat their dead to honor them. • Typically infected the woman and young because they would feed on the brain and organs of the dead. The men would eat the muscle tissue. • The government has since discouraged this practice and few cases occur today.

25. CJD & vCJD • CJD (Creutzfeldt-Jakob disease) and its variants such as vCJD are rare and fatal TSEs that affect humans. • CJD typically affects 1 person in 1 million. It has late onset, typically showing up at age 60. Infected individuals typically die within a year of the first symptoms. • vCJD affects younger individuals and may be linked with BSE. It has a slower progression but is ultimately fatal. • Both of these are rare and poorly understood.

26. PROKARYOTIC MICROBES • There are two Domains that represent prokaryotic microbes: Domain Archaea Domain Bacteria Domain Archaea contains primitive, prokaryotic organisms that are adapted to extreme environments. Many scientists do not consider them to be bacteria. Domain Bacteria contains the “modern” bacteria.

27. Domain Archaea • Archaea means “ancient”. These organisms were once called archaeobacteria, but many scientists believe they are not true bacteria. • This Domain represents primitive prokaryotic cells, but genetically they are more closely related to eukaryotic cells than bacteria. Do not have peptidoglycan in their cell walls. • Archaea vary in shape from round, to rod-shaped, to filamentous. Many are adapted to environments with extreme pH, temperature, pressure, etc. • They are not a concern medically.

28. Domain Bacteria • All bacteria are prokaryotic cells. • Most range in size from 0.2 to 10.0 um. • They are divided into three basic groups based on their physical (phenotypic) properties: Gram-Negative Bacteria Gram-Positive Bacteria Cell Wall Deficient (CWD) Bacteria

29. Domain Bacteria • Gram Negative and Gram Positive bacteria have cell walls made of peptidoglycan and display variations of three basic forms: bacilli, cocci, and spiral. • These cells may be arranged individually, in pairs (diplo), chains (strep), or in grape-like clusters (staphyl). Examples: diplococci, streptobacilli, staphylococci. • Cell Wall Deficient bacteria do not have a cell wall and can change their shape. A special staining technique called acid-fast staining is used to stain them. Mycobacteria are in this Domain.

30. Unique Bacteria • Also known as Rudimentary bacteria. • They are very small (0.5 to 0.10 um) and were once thought to be viruses. • Includes Rickettsias, Chlamydias, Mycoplasmas, and their close relatives. • Many are medically significant.

31. Rickettsias • All are gram negative, obligate intracellular pathogens. They must live within a host cell to survive. • All are transmitted by arthropod vectors such as lice, fleas, and ticks. • Typhus and Rocky Mountain Spotted Fever are both examples of Rickettsial diseases.

32. Rocky Mountain Spotted Fever • Transmitted by ticks. • Characterized by fever, exhaustion, severe headache and muscle pain, chills, a rash that spread throughout most of the body (day 3), and small purple areas under the skin (petechial hemorrhaging – day 4). • Death can occur but is rare.

33. Typhus Fever (Rickettsial) • Transmitted by body lice: human > louse > human. • Infected lice defecate while feeding and the bacteria are rubbed into the bite or other abrasion. • Symptoms include a sudden headache, chills, prostration, fever, and general pain. A rash appears by the 5th day and spreads across most of the body (not the face).

34. Chlamydias • All are gram negative, obligate intracellular pathogens. They must live within a host cell to survive. • Different serotypes of the same species can cause different diseases. Serotypes have different surface antigens, but are the same species. • Transmitted by direct contact with an infected host or the inhalation of infected aerosols. Not transmitted by arthropod vectors. • Trachoma, nongonococcal urethritis, and psittacosis are examples chlamydial diseases.

35. Trachoma (Chlamydial) • Leading cause of blindness worldwide. • Transmitted by contact with infectious ocular or nasal secretions, contaminated articles, or flies. • Highly contagious. Causes scarring of conjunctiva and cornea leading to blindness. Common in impoverished areas of the Far East.

36. Nongonococcal Urethritis (Chlamydial) • Genital chlamydial infections are the most common STDs in the U.S. with approx. a million new cases per yr. • Transmitted by direct sexual contact or mother to neonate at birth. • Symptoms include urethral discharge, burning urination, and itching. Can lead to infertility and neonate pneumonia and conjunctivitis.

37. Psittacosis (Chlamydial) • Also known as parrot fever. • Acquired by inhalation of respiratory secretions and desiccated droppings of infected birds (parrots and parakeets). • Causes pneumonia with fever, a productive cough with sputum, acute chest pain, chills, and shortness of breath.

38. Mycoplasmas • Smallest cellular microbes (0.1 um). • Do not have a cell wall and assume various shapes. • Resistant to antibiotics that target the cell wall (e.g. penicillin). • Free-living or parasitic. Pathogenic in animals and plants. • Cause atypical pneumonia and genitourinary infections in humans.

39. Photosynthetic Bacteria • These are also known as blue-green algae, even though they are not true algae. This includes the purple, green, and cyanobacteria. • These bacteria contain photosynthetic pigments within their cytoplasm. However, not all produce oxygen as a waste product. • Some produce neurotoxins, hepatotoxins, or cytotoxins and can cause microbial intoxications when consumed in contaminated water.

40. EUKARYOTIC MICROBES • Eukaryotic microbes include algae, protozoans, and fungi. • Eukaryotic microbes are composed of single or colonial eukaryotic cells. These are large, advanced cells containing a nucleus and membrane-bound organelles. • Some eukaryotic microbes are medically significant.

41. Algae • Photosynthetic eukaryotic cells with a cell wall composed of cellulose. • Range in size from single-celled organisms to large seaweeds. • Photosynthetic algae are classified as green, golden, brown, or red. • Diatoms are single-celled algae that have shells made of silicon dioxide (glass). • Dinoflagellates are flagellated, single-celled algae that cause red tides. • Diatoms and dinoflagellates are important phytoplankton that produce oxygen and provide food in aquatic systems.

42. Algal Intoxications • Algae rarely cause infectious diseases in humans, but many secrete phycotoxins that are poisonous to humans, fish, and other animals. • Some examples are Amnesic shellfish poisoning, Ciguatera fish poisoning, and Paralytic shellfish poisoning.

43. Amnesic shellfish poisoning • Caused by ingestion of shellfish (mussels) containing toxins of the diatom, Nitzchia pungens. • Associated with red tides. • Causes gastrointestinal and neurologic symptoms. • Can be fatal.

44. Fish Kill in Corpus Christi, TX

45. Ciguatera Fish Poisoning • Most commonly reported cause of nonbacterial illness associated with eating fish in the U.S. and its territories. • Caused by eating fish containing dinoflagellate toxins. • Gastrointestinal, neurologic, and cardiovascular symptoms. Can be fatal.

46. Paralytic Shellfish Poisoning • Result of ingesting shellfish (mussels, clams, scallops, and oysters) containing dinoflagellate toxins. • Causes neurologic symptoms and can be fatal.

49. Protozoans • Protozoans are animal-like microbes that are composed of single-celled or colonial eukaryotic cells. • Classified based on their mode of locomotion: • Ciliates use cilia, example is Paramecium. • Amebae use pseudopodia, example is Amoeba. • Flagellates use flagella, example is Giardia. • Sporozoa are nonmotile, example is Plasmodium.

50. Protozoans • Most are free-living, but some are parasitic. • They typically have two basic stages in their life cycle; the adult trophozoite stage and the dormant cyst stage. • Some parasitic protozoans are significant human pathogens. Examples include Plasmodium spp., Trypanosomes, Trichomonasvaginalis, Giardia lamblia, Cryptosporidium parvum, and Toxoplasma gondii.