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MICROBIOLOGY. OBJECTIVES. Define the key terms related to microbiology List the conditions required by microorganisms in order to grow Explain how microorganisms grow and replicate Identify the significant characteristics of viruses Describe the importance of normal flora

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  2. OBJECTIVES • Define the key terms related to microbiology • List the conditions required by microorganisms in order to grow • Explain how microorganisms grow and replicate • Identify the significant characteristics of viruses • Describe the importance of normal flora • Explain the different groups of microorganisms capable of causing diseases in humans • Learn the “Chain of Infection” and the role of MA in breaking it

  3. OVERVIEW • Microbiology is the study of microorganisms. • A microbiologist is a specialist in microbiology • Microbiology is a broad term which includes Virology – the study of virus Bacteriology – the study of bacteria Mycology – the study of fungi Parasitology – the study of parasites • A microorganism also spelt micro-organism, or microbe is a microscopic organism that is either a single cell (unicellular), cell clusters, or no cell at all (acellular).

  4. HISTORY • Anton van Leeuwenhoek was one of the first people to observe microorganisms, using a microscope of his own design, and made one of the most important contributions to biology • Louis Pasteur, ended the long-held belief that life spontaneously appeared from non-living substances during the process of spoilage. • Robert Koch in 1876 established that microbes can cause disease.

  5. CLASSIFICATION • NON PATHOGENIC – unable to cause disease • PATHOGENIC – capable of causing disease


  7. BACTERIA • Bacteria, (bacterium) are a large group of prokaryotic microorganisms. • Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals. • The vast majority of the bacteria in the body are rendered non pathogenic and a few are beneficial. • However, a few species of bacteria are pathogenic and cause infectious diseases

  8. PATHOGENIC BACTERIA 1. Coccus(plural cocci) can be used to describe any bacterium that has a spherical shape.

  9. CLASSIFICATION OF COCCI • Diplococciare arranged in two-cell pairs • Streptococciare arranged in chains • Staphylococci are type of bacteria characterized by cells arranged in tetrad clusters (four cells in a square formation) or large, often irregular, clusters • Sarcinatypically form a cuboidal arrangement of eight cells.





  14. PATHOGENIC BACTERIA 2. Bacillus / Bacilli - the word bacillus may be used to describe any rod-shaped bacterium • There is no connection between the shape of a bacterium and its colors in the Gram staining. • Under unfavorable conditions majority of bacilli can form spores • Many Bacillus species are able to secrete large quantities of toxic enzymes.

  15. DISEASES CAUSED BY BACILLI • Tuberculosis- two organisms cause tuberculosis -- Mycobacterium tuberculosis and Mycobacterium bovis. • M. tuberculosis is a rod-shaped, slow-growing bacterium. • TB cases have increased since 1985, most likely due to the increase in HIV infection. • Symptoms - common cough with a progressive increase in production of mucus and coughing blood, fever, loss of appetite, weight loss, night sweats • Only about 10% of people infected with M. tuberculosis ever develop tuberculosis disease.


  17. DISEASES CAUSED BY BACILLI • Botulism also known as botulinus intoxication is a serious illness that causes paralysis, caused by the botulinumtoxin. • Foodborne botulism - as a result of eating foodstuffs with the toxin. • Wound botulism - when botulinum toxin contaminates a wound. • All types of botulism eventually lead to paralysis, which generally starts with the face muscles and then spreads to the limbs. In severe cases there is respiratory failure when the breathing muscles become paralyzed.


  19. DISEASES CAUSED BY BACILLI • Tetanus • Clostridium tetani is a gram-positive rod-shaped bacterium that is found worldwide in soil; it is usually in its dormant form, spores, and becomes the rod-shaped bacterium when it multiplies. • Tetanus may develop in people who are not immunized against it or in people who have failed to maintain adequate immunity with active booster doses of vaccine. • Irritability, muscle cramps, sore muscles, weakness, or difficulty swallowing are commonly seen.


  21. 3. Spirillum / Spirilla- in microbiology refers to a bacterium with a cell body that twists like a spiral. It is a genus comprising elongated forms having tufts of flagellae at both poles and usually living in stagnant water rich in organic matter. Spirals come in one of three forms: • a vibrio • a spirillum • a spirochete

  22. DISEASES CAUSED BY SPIRILLA • Cholera is an infection of the small intestine that is caused by the bacterium Vibrio cholerae. • The main symptoms are profuse watery diarrhea and vomiting. • Transmission occurs primarily by drinking or eating water or food that has been contaminated

  23. Syphilis is a sexually transmitted infection caused by the spirochete bacterium Treponemapallidum • The primary route of transmission is through sexual contact • It may also be transmitted from mother to fetus during pregnancy or at birth, resulting in congenital syphilis.

  24. FUNGUS / FUNGI • The fungi are more evolutionarily advanced forms of microorganisms, • They are classified as eukaryotes • In general, humans have a high level of innate immunity to fungi and most of the infections they cause are mild and self-limiting.

  25. DISEASES CAUSED BY FINGI • Superficial mycoses- infections limited to the outermost layers of the skin and hair. • Cutaneous mycoses - infections that extend deeper into the epidermis, as well as invasive hair and nail diseases- ring worm, athlete’s foot • Systemic mycoses - infections that originate primarily in the lung and may spread to many organ systems.

  26. VIRUSES • A virus is a small infectious agent that can replicate only inside the living cells of organisms. • Most viruses are too small to be seen directly with a light microscope. • Viruses depend on the host cells that they infect to reproduce. • Some viruses may remain dormant inside host cells for long periods, causing no obvious change in their host cells

  27. Flu virus • Swine flu • Herpes virus • HBV

  28. DISEASSES CAUSED BY VIRUSES • Acquired immune deficiency syndrome or acquired immunodeficiency syndrome (AIDS) is a disease of the human immune system caused by the human immunodeficiency virus (HIV). • HIV is transmitted in many ways, such as • anal, vaginal or oral sex • blood transfusion • contaminated hypodermic needles • exchange between mother and baby during pregnancy, childbirth, and breastfeeding

  29. DISEASES CAUSED BY VIRUSES • Rubella, also known as the German measles, is an infection in which there is a rash on the skin. Symptoms: Children generally have few symptoms. Adults may experience a fever, headache, general discomfort (malaise), and a runny nose.

  30. DISEASES CAUSED BY VIRUSES • Herpes simplex, is a viral disease caused by both Herpes simplex virus type 1 (HSV-1) and type 2 (HSV-2) • Herpes zoster(or simply zoster), commonly known as shinglesis a viral disease characterized by a painful skin rash with blisters in a limited area on one side of the body.

  31. DISEASES CAUSED BY VIRUSES • Hepatitis B is an infectious illness caused by hepatitis. • The acute illness causes liver inflammation, vomiting, jaundice, and (rarely) death. • Chronic hepatitis B may eventually cause cirrhosis and liver cancer—a fatal disease with very poor response to current chemotherapy. • The infection is preventable by vaccination.

  32. PRIONS • Prion: A disease-causing agent that is neither bacterial nor fungal nor viral and contains no genetic material. A prion is a protein that occurs normally in a harmless form. By folding into an aberrant shape, the normal prion turns into a rogue agent • When a prion enters a healthy organism, it induces existing, properly folded proteins to convert into the disease-associated, prion form

  33. PRIONS • All known prion diseases, collectively called Transmissible spongiform encephalopathies (TSEs), are untreatable and fatal • The human prion disease variant Creutzfeldt-Jakob disease, however, is believed to be caused by a prion which typically infects cattle, causing Bovine spongiform encephalopathy and is transmitted through infected meat.

  34. CHAIN OF INFECTION • Epidemiology is the study of the determinants, occurrence, and distribution of health and disease in a defined population • Infection is the replication of organisms in host tissue, which may cause disease. • A carrier is an individual with no overt disease who harbors infectious organisms. • Dissemination is the spread of the organism in the environment.

  35. CHAIN OF INFECTION • A model used to understand the infection process is the chain of infection- a circle of links each representing a component of the cycle • Each link must be present in the correct order for an infection to occur • The links are: Infectious agent Mode of transmission Reservoir host Portal of entry Portal of exit New host



  38. DIRECT TRANSMISSION • Direct contact transmission occurs when there is physical contact between an infected person and a susceptible person. • Direct contact infections spread when disease-causing microorganisms pass from the infected person to the healthy person via direct physical contact with blood or body fluids. Examples of direct contact are touching, kissing, sexual contact, contact with oral secretions, or contact with body lesions.

  39. INDIRECT TRANSMISSION • Indirect contact transmission occurs when there is no direct human-to-human contact. Contact occurs from a reservoir to contaminated surfaces or objects, or to vectors such as mosquitoes, flies, mites, fleas, ticks, rodents or dogs. • Indirect contact infections spread when an infected person sneezes or coughs, sending infectious droplets into the air • Droplets generally travel between three and six feet and land on surfaces or objects including tables, doorknobs and telephones. Healthy people touch the contaminated objects with their hands, and then touch their eyes, nose or mouth.

  40. OTHER CONSIDERATIONS • A vector is an organism that does not cause disease itself but that transmits infection by conveying pathogens from one host to another. • The spread of infectious agents through a common reservoir such as food or water supply is referred to as vehicle or common supply transmission. Food products may become contaminated after being handled by unwashed hands or processed by unclean equipment.

  41. FACTORS AFFECTING MICROBIAL GROWTH • Water -- Bacteria need water to dissolve the food they use for energy and growth. • Food/Nutrients -- All bacteria require energy to live and grow. Energy sources such as sugars, starch, protein, fats and other compounds provide the nutrients. • Oxygen -- Some bacteria require oxygen to grow (aerobes) while others can grow only in the absence of oxygen (anaerobes). However, many bacteria grow under either condition and they are facultative anaerobes. • Temperature -- Bacteria in general are capable of growing over a wide range of temperatures and are usually classified according to the temperature at which they grow. Most bacteria thrive at temperatures at or around that of the human body 98.6°F • pH -- pH is a measure of acid or alkali in a product. It is indicated on a scale from 0 to 14, with seven being neutral. If the pH value is below 7, the food is classified as acid; if it is above 7, the food is classified as alkaline. Most bacteria grow well at neutral pH, but many can reproduce in a pH range from 4.5 - 10.0. • Light – most microorganisms grow well in dark

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