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Diseases The world of microbes Bacteria www.youtube.com/watch?v=EIqwggzbBo A&t=14s Understanding Bacteria Bacteria are prokaryotes (single cells that do not contain a nucleus). Bacteria lack the membrane-bound nuclei of eukaryotes; their DNA forms a tangle known as a nucleoid, but there is no membrane around the nucleoid, and the DNA is not bound to proteins as it is in eukaryotes. Prokaryotes Bacteria are living things that are neither plants nor animals, but belong to a group all by themselves. They are very small--individually not more than one single cell--however there are normally millions of them together, for they can multiply really fast. Bacteria Morphology Most bacteria are very small, a few micrometers in length. Come in a variety of shapes and sizes. Shape is used for classification. Size and Shape Sphere (coccus) May exist as a single Most often exits as a multi-cell form. Multi-celled arrangements Two cocci joined together (diplococcus) Chains of cocci (streptococcus) Clusters (staphylococcus) Packets of eight (Sarcina) Rod-like (bacillus) Short to very long filaments Multi-celled arrangements Two bacilli joined together (diplobacillus) Chains of bacilli (streptobacillus) Clusters (staphylobacillus) Packets of eight (Sarcina) Spirals Corkscrew appearance The cell membrane is surrounded by a cell wall in all bacteria except one group, the Mollicutes, which includes pathogens such as the mycoplasmas. The composition of the cell wall varies among species and is an important character for identifying and classifying bacteria. Cell Wall There are broadly speaking two different types of cell wall in bacteria, called Grampositive and Gram-negative. ◦ The names originate from the reaction of cells to the Gram stain, a test long-employed for the classification of bacterial species. Cell Wall In this diagram, the bacterium has a fairly thick cell wall made of peptidoglycan (carbohydrate polymers crosslinked by proteins); such bacteria retain a purple color when stained with a dye known as crystal violet, and are known as GramGram positive. Positive Gram Positive Other bacteria have double cell walls, with a thin inner wall of peptidoglycan and an outer wall of carbohydrates, proteins, and lipids. Such bacteria do not stain purple with crystal violet and are known as Gram-negative. Gram Negative Gram Negative Many but not all bacteria exhibit motility, i.e. self-propelled motion Motion can be achieved by one of three mechanisms: Flagella (singular, flagellum) Axial filament (a specialized internal structure which is responsible for rotation of the cell in a spiral fashion and consequent locomotion of the Spirochaetes a helical bacteria.) Slime (as seen with gliding bacteria) Bacterial Motility In some bacteria, there is only a single flagellum such cells are called monotrichous. the flagellum is usually located at one end of the cell (polar). Some bacteria have a single flagellum at both ends - amphitrichous. Many bacteria have numerous flagella; if these are located as a tuft at one end of the cell, this is described as lophotrichous (e.g. Chromatium), if they are distributed all over the cell, as peritrichous. Flagellum http://www.sheppardsoftware.com/health /anatomy/cell/bacteria_cell_game.htm Bacteria anatomy Structures Flagella consist of a hollow, rigid cylinder composed of a protein called flagellin, 20 nm in diameter and 1520 µm long which protrude from the cell surface. A-Monotrichous B-Lophotrichous C-Amphitrichous D-Peritrichous Flagella Flagellae are, in effect, rotary motors comprising a number of proteinaceous rings embedded in the cell wall. In action, the filament rotates at speeds from 200 to more than 1,000 revolutions per second, driving the rotation of the flagellum. The direction of rotation determines the movement of the cell. Rotation Fimbriae and pili are interchangeable terms used to designate short, hair-like structures on the surfaces of procaryotic cells. They are composed of protein. Generally, fimbriae have nothing to do with bacterial movement. They are most often involved in adherence of bacteria to surfaces, substrates and other cells or tissues in nature. Fimbriae are very common in Gramnegative bacteria, but occur in some archaea and Gram-positive bacteria as well. Pilli Bacteria species differ greatly in the conditions they need for growth. Some grow best in cool places such as soil or bodies of water, but others are able to grow in hot springs, hot water heaters, or undersea volcanoes. Temperatures The bacteria which cause disease in mammals and birds, usually grow best at body temperatures. Many bacteria which cause diseases in hydra, snakes, turtles, and other cold-blooded animals, are not able to cause disease in birds or mammals because the high body temperatures kill these bacteria or limit their growth. Competition for food Predation Antibiotics produced by others Reproduction control Another method used for classification is to determine the biochemical pathway it uses. Bacteria are single-cell organisms and most of them must find foods to live. Many bacteria use carbohydrates(carbon compounds) as energy sources, digesting complex carbohydrates such as starches and table sugar down to simple sugars Find food by responding to chemical signals - CO Energy Source Other bacteria can digest proteins down to amino acids. Bacteria can be cultured to determine whether they can ferment various carbohydrates or hydrolyze starches, lipids and proteins. Energy Microstatic antibiotics prevent growth and reproduction. Microcidal antibiotics actually destroy the organism. Antibiotics Antibiotics and similar drugs, together called antimicrobial agents, have been used for the last 70 years to treat patients who have infectious diseases. Since the 1940s, these drugs have greatly reduced illness and death from infectious diseases. Antibiotic use has been beneficial and, when prescribed and taken correctly, their value in patient care is enormous. Antibiotic use Antibiotics are effective in small concentrations. Four modes of action: ◦ Inhibition of cell wall formation (penicillin) ◦ Damage to the cell membrane (novobiocin) ◦ Interference with protein synthesis (tetracycline) ◦ Inhibition of nucleic acid activities (actinomycin) Various combinations of antibiotics are sometimes used against a pathogen that is not affected by a single antibiotic. Antibiotics are classified according to three criteria and although that category contains several drugs each one of them is unique in some features and effects. Classification of antibiotics Classification Criteria the number of the organisms affected by the same drug. There are narrow and wide spectrum antibiotics. The wide spectrum antibiotics affect several types of bacteria and it is usually used where the specific type of the microorganism is unknown. 1. Spectrum The prevalent route of administration is the oral route but, there are other routes of administration that are more effective in certain cases like injection or topical applications. 2. Route of administration of the drug It could be bactericidal or bacteriostatic 3. Type of action The bactericidal antibiotics kill the harmful microorganism The bacteriostatic ones tend to slow down their growth and give the body the chance to use its immune system against the microorganisms Over the past decade, antimicrobial resistance has emerged in all kinds of microorganisms worldwide. This is primarily due to the increase in antibiotic abuse. Early detection of emerging trends in antimicrobial resistance may facilitate implementation of effective control measures. People/animals infected with antimicrobialresistant organisms are more likely to have longer, more expensive hospital stays, and may be more likely to die as a result of the infection. Antibiotic Sensitivity Identify infecting organism Evaluate drug sensitivity Target site of infection Drug safety/side effect profile Patient factors Cost Antibiotic Therapy Bacteria and other microorganisms that cause infections are remarkably resilient and can develop ways to survive drugs meant to kill or weaken them. ◦ This antibiotic resistance, also known as antimicrobial resistance or drug resistance, is due largely to the increasing use of antibiotics. Antimicrobial Resistance Repeated use of the same antibiotics increases the resistance of the Bacteria to that antibiotic Resistance A growing number of disease-causing organisms, (pathogens), are resistant to one or more antimicrobial drugs. A wide range of pathogens—including the bacteria that cause tuberculosis, the viruses that causes influenza, the parasites that cause malaria, and the fungi that cause yeast infections—are becoming resistant to the antimicrobial agents used for treatment. Antibiotic resistance evolves naturally via natural selection through random mutation, but it could also be engineered by applying an evolutionary stress on a population. Once such a gene is generated, bacteria can then transfer the genetic information in a horizontal fashion (between individuals) by plasmid exchange. Resistant pathogen Staphylococcus aureus ( "Staph aureus" or a Staph infection) is one of the major resistant pathogens. Found on the mucous membranes and the skin of around a third of the population, it is extremely adaptable to antibiotic pressure. It was the first bacterium in which penicillin resistance was found—in 1947, just four years after the drug started being mass-produced. Methicillin was then the antibiotic of choice, but has since been replaced by oxacillin due to significant kidney toxicity. MRSA (methicillin-resistant Staphylococcus aureus) was first detected in Britain in 1961 and is now "quite common" in hospitals. The addition of antibiotics to the feeds of animals to increase the growth rate by 10-50%. Over prescribing of antibiotics to patients with virus caused infections. Prescribing antibiotics as preventions. Not completing the full course of the prescription of antibiotic. Antibiotic Abuse The Kirby-Bauer test for antibiotic susceptibility, called the disc diffusion test, is a standard that has been used for years. It has been superceded in clinical labs by automated tests. But the K-B is still used in some labs, or used with certain bacteria that automation does not work well with. Kirby-Bauer test The basics are easy: ◦ The bacterium is swabbed on the agar and the antibiotic discs are placed on top. ◦ The antibiotic diffuses from the disc into the agar in decreasing amounts the further it is away from the disc. Procedure If the organism is killed or inhibited by the concentration of the antibiotic, there will be NO growth in the immediate area around the disc: This is called the zone of inhibition . The zone sizes are looked up on a standardized chart to give a result of sensititive, resistant, or intermediate. Many charts have a corresponding column that also gives the MIC (minimal inhibitory concentration) for that drug. ZONE OF INHIBITION Agar Plates Results from the plates will help determine what antibiotics could be used. This is needed when dealing with bacteria that have developed resistance to many of the commonly prescribed antibiotics. What’s in a name? Shape plus configuration =name Bacilli = rod shaped Coccus – globular – sphere Spirillium = helix shape Strepto = chains Diplocci = pairs of spheres Tetrads = four cells arranges as squares Shapes & Configuration Gram positive Ferment lactid acid contained in milk = Bleu cheese Streptocarpus lactid lactococci Gram positive, non motile Non spore forming Chains or pairs May present as: ◦ Strep throat ◦ Scarlet fever (rash) ◦ Impetigo (infection of the superficial layers of skin ◦ Cellulitis (infection of the deep layers of skin Streptocarpus pyogenes Large gram positive anaerobic bacillus Motile with flagella Spore forming Botulism Bacillus botulinum botulinum clostridium Gram positive Aerobic bacillus Non motile Spore forming Anthrax Bacillus anthracis Obligate Gram positive Spore-forming Rod shaped Exotoxin Bacillus tetani Clostridium tetani Gram positive Non-Sporing rod Non-motile Create lactic acid from carbohydrates consumed Lactic acid causes destruction Tooth decay Used in food science Bread, milk and cheese Bacillus lactis Lactobacillus Rod shape with flagella Motile Transmitted in fluids Gram negative Can be carriers Typhoid fever Bacillus typhoid salmonella typhi Gram negative spheres Encapsulated Menigitis Septicaemia Diplococcus meningitidis (Neisseria) Gram positive Unencapsulated Diplococuus pneumonia Streptoccocus Gram positive Spheres Clusters like grapes Non motile Non spore Staph infection ◦ Boils, impetigo, toxic shock syndrome, folliculitis Staphlococcus aureus Spirochete with flagella Syphilis H. pilori, ulcers Treponema pallidum http://www.hhmi.org/biointeractive/vlabs/ bacterial_id/index.html Do first sample completely, identify bacteria Complete 2 additional samples of your choice 30 extra credit points Extra Credit
