Lab 9: Antibiotic Resistance and The Susceptibility of Bacteria Lab

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After successfully participating in this lab, you will be able to:

• Distinguish between antiseptics, disinfectants, antibiotics, and sanitizers.

• Describe the effects of antimicrobials and antibiotics on bacteria.

• Differentiate between sterilizing and disinfecting• Differentiate between pathogenic bacteria and

probiotics.• Describe the effects of antibiotic resistance and MRSA

on humans. • Understand evolution as the underlying theme in

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• In 1928 while working with Staphylococcus bacteria, Scottish scientist Alexander Fleming noticed that a type of mold growing by accident on a laboratory plate was protected from, and even repelled, the bacteria.

• The active substance, which Fleming called penicillin, was literally an antibiotic—it killed living bacteria.

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• Thus began the age of using natural and, later, synthetic drugs to treat people with bacterial infections.

• Though not widely popular until the 1940s, antibiotics and other antimicrobials (medicines that kill or slow growth of a microbe) have saved countless lives and blunted serious complications of many feared diseases and infections.

• The success of antimicrobials against disease-causing microbes is among modern medicine's great achievements.

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Bacteria are everywhere

• There are five million, trillion, trillion bacteria on Earth – 5 with 30 zeroes after it.

• Only 1 percent of bacteria are inside living things

• Most bacteria are found in soil or in the oceans, but some have been found 40 miles up in the atmosphere.

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Are All Bacteria Bad?• No – without the bacteria in your gut, you

couldn’t survive.• Probiotics – helpful bacteria that help you digest

your foods (yogurt)• Things that kill your healthy gut bacteria – Birth

control pills, antibiotics, alcohol, smoking, stress, poor diet.

• Without these healthy bacteria, you see symptoms such as bloating, constipation, diarrhea, allergies, skin conditions.

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The Problem• After more than 70 years of widespread

use, evolution of disease-causing microbes has resulted in many antimicrobials losing their effectiveness.

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• Evolution through natural selection can

occur remarkably quickly when

selection pressures are very strong and reproductive rates

are very fast (some bacteria

generations are as short as 15-20 minutes)

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• As microbes evolve, they adapt to their environment. If something stops them from growing and spreading—such as an antimicrobial— they evolve new mechanisms to resist the antimicrobials by changing their genetic structure. Changing the genetic structure ensures that the offspring of the resistant microbes are also resistant. #NSB2014 9

• Penicillin was extensively used in Hungary in the early 1970's.

• By 1976,

more than 50% of the strains of Streptococcus pneumoniae were resistant to penicillin. #NSB2014 10

Dangers of Antibiotic Resistance

• Antibiotic resistance is one of the world's most pressing public health problems.

• This condition occurs when bacteria change in some way that reduces or eliminates the effectiveness of drugs, chemicals, or other agents designed to cure or prevent infections.

• Widespread overuse of antibiotics is fueling an increase in antibiotic-resistant bacteria.

• So the next time you really need an antibiotic for a bacterial infection, it may not work.

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If You Have a Cold or Flu, Antibiotics Won't Work for You!

• Colds and flu are caused by viruses, not bacteria. Taking antibiotics when you have a virus may do more harm than good. Get smart about when antibiotics are appropriate. Taking them for viral infections, such as a cold, cough, the flu, or acute bronchitis:

• Will not cure the infection;• Will not keep other people from

getting sick;• Will not help you feel better; and• May cause unnecessary and

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MRSA• MRSA stands for Methicillin-resistant Staphylococcus

aureus. This type of bacteria causes “staph” infections that are resistant to treatment with usual antibiotics.

• MRSA occurs most frequently among patients who undergo invasive medical procedures or who have weakened immune systems and are being treated in hospitals and healthcare facilities such as nursing homes and dialysis centers.

• MRSA in healthcare settings commonly causes serious and potentially life threatening infections, such as bloodstream infections, surgical site infections, or pneumonia.

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Coevolution• An interactive evolutionary relationship

between two or more species in which direct genetic change in one species is attributable to genetic change in the other(s).

• Antibiotics are now everywhere in the environment, and humans and bacteria are engaged in coevolution. Who is likely to win?

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Quick Facts• Many infectious diseases are

increasingly difficult to treat because of antimicrobial-resistant organisms, including staphylococcal infection, tuberculosis, gonorrhea, candida infection.

• Between 5 and 10 percent of all hospital patients develop an infection, leading to an increase of about $5 billion in annual U.S. healthcare costs.

• About 90,000 of these patients die each year as a result of their infection, up from 13,300 patient deaths in 1992.

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Why are we doing the lab today?

• Given a bacterial culture, students will demonstrate aseptic technique.

• Identify household disinfectants and antiseptics and distinguish between the two.

• Explain the consequences of antibiotic resistance.

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