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Download Antibiotic Resistance: How and So What?
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Antibiotic Resistance: How it happens and why all the fuss? (in your packet) • Bacteria have been around for ___?___ billion years Bacteria are Everywhere! Bacteria are Everywhere! Skin: about a trillion bacteria Alimentary canal (mouth, throat, stomach, intestines): tens of trillions of bacteria! Nose, eyes, toes . . . Bacteria comprise about 1/20th of your total body weight! What is a bacterium? Cell membrane Cell wall or envelope Bacterial chromosome (DNA) Plasmid DNA - small circles of DNA that contain a few genes Human cell nucleus chromosomes E.coli bacterium Flu virus . 10 micrometers = 1/100th of a millimeter Bacterial Replication Bacteria can double in less than twenty minutes under optimal conditions! Bacteria can double in less than twenty minutes under optimal conditions! Bacteria can double in less than twenty minutes under optimal conditions! Bacteria can double in less than twenty minutes under optimal conditions! Bacteria can double in less than twenty mintues under optimal conditions! “Good” bacteria • Form defensive barrier – Skin, intestines • Aid digestion • Produce vitamin K • Clear away debris - E. Coli - Lactobacillus Pathogenic (disease-causing) bacteria Streptococcus pneumoniae pneumonia Streptococcus pyogenes strep throat Helicobacter pylori Stomach ulcers Haemophilus influenzae meningitis Staphylococcus aureus wound infections How antibiotics work • Antibiotics are chemicals that disrupt bacterial processes Stop protein Stop cell wall building: cell dies construction: cell bursts Stop copying DNA: cells can’t divide What is Antibiotic Resistance? • Resistant bacteria no longer killed in presence of specific antibiotic. Antibiotic X Antibiotic X All killed Antibiotic Y All killed How do bacteria become resistant? Spontaneous mutation of DNA • Many different random mutations are present in a population of bacteria. • Some “lucky” mutations may provide an advantage, especially if the environment changes. How Else? Acquire resistance genes from other bacteria How can the bacteria become resistant? • Spontaneous mutations • They transfer DNA in a plasmid Mechanisms of Resistance Resistant Bacteria Can: 1. Modify or destroy the antibiotic. 2. Force out antibiotic. 3. Alter the target. Essential Bacterial Protein Essential Bacterial Protein “Superbugs” Uptake of plasmid: over 12,000 in Guatemala died in 1968 of acute diarrhea Bacteria that are resistant to many antibiotics Need for stronger, newer drugs Antibiotic Resistance Not immunity!! In the absence of antibiotics, resistant bacteria are less likely to survive. Resistant strain cannot compete with all other bugs With antibiotic, resistant bacteria rapidly take over. So does this mean antibiotics are evil? Antibiotics are wonderful drugs when administered and used properly! • Penicillin on market in 1943 saved numerous lives in WWII! • Ear infections in children treatable. • Lower incidence of infection in surgical patients. But there are problems! • 4 years after introduction of penicillin, resistance began to develop. • Needless exposure to antibiotics selects for resistant strains. Who can change? • Doctors and Patients • Livestock/Poultry Industry • Antibacterial Home Products Patients and • Take for prescribed period of time. • Don’t go to doctor with expectation of receiving prescription. Doctors • Only prescribe when necessary. • Narrow spectrum drugs. Subtherapeutic Dosage Problem 1/2 Dose Highly susceptible bacteria Less susceptible bacteria Resistant bacteria Full Dose Stop Taking Antibiotic Summary • Bacteria become resistant through mutations or by getting genes from other bacteria. • We should only use antibiotics when we really need to. • Overuse in agriculture and at home encourages appearance of resistant bugs. OCVSRS • Overpopulation – lots of bacteria, not all can survive • Competition – for survival in the presence of antibiotic • Variety – Some bacteria are naturally resistant, some are not • Selection – The resistant ones are “selected for” and survive the presence of the antibiotic • Reproduction – The resistant ones are able to reproduce more and pass the resistance gene to their offspring, making it more common in the population CDC Message about antibiotic resistance QuickTime™ and a YUV420 codec decompressor are needed to see this picture. Livestock/Poultry Industry • Antibiotics given to livestock, poultry, and even to plants as a preventative measure to promote growth. • Link between this use and people infected with resistant strains. Good News • 1997 - Vancomycin banned from chicken feed in Europe. • July 2003 - McDonald’s vendors will no longer treat animals with preventative antibiotics. • In Europe, animal health maintained through improvements in living conditions. Antibacterials at Home • Triclosan resistance emerging. • Triclosan contributes to resistance of other drugs. From Dishwater to Groundwater • Triclosan very abundant in residential streams. How do bacteria become resistant? • Resistance arises from changes in the bacterial genome. – DNA -> RNA -> Protein • These changes happen randomly • These new proteins can help protect the bacteria from the antibiotic.