Antibiotic Resistant Bacteria: a lesson in evolution

Antibiotic Resistant Bacteria:Natural Selection at Work

Bacteria are everywhere

•Bacteria are single-celled organisms thatgrow in populations called colonies.

•Many different kinds of bacteria can growtogether in similar environments.

•Demo showing growth of bacteria fromvarious sources

Pictures taken with an electron microscope

Serratia marcescens

•Rod shaped motile bacterium

•Naturally grow a red color byproduction of a reddish-orange pigment calledprodigiosin

•Grow in damp places such asbathrooms, soil, biofilms ofteeth, digestive tract

•As a human pathogen, canbe associated with urinarytract and wound infections

•Powerful medicines that treat

bacterial infections

•They work by either killing bacteria orpreventing growth and reproduction ofbacteria

What are antibiotics?

Antibiotic Resistance Lab

•You will be investigating the presence ofantibiotic resistance within a population ofSerratia bacteria.

How do bacteria become resistant?

•A gene encodes a protein thatallows them to avoid the harmfuleffects of the antibiotic

•Genes for resistance can emerge ina bacterial population spontaneously(genetic mutation), they can obtainthem from other bacteria (sharingDNA), or scientists can put genesinto bacteria.

Natural Antibiotic Resistance

•Mutations allowing for bacteria to grow in thepresence of antibiotics already exists in thebacterial population.

•Not all bacterial cells within a population areidentical

•Like a population of humans, they

all contain slight differences in their

DNA

Why do you think this may be a good

idea for the bacteria?

-survival of the fittest

Can the misuse of antibiotics resultin resistant bacteria?

•Antibiotics are prescribed by doctorsto fight bacterial infections.

•Antibiotics do not treat viral infections!

•How do doctors know what toprescribe?

–throat, urine cultures

•Why is it important to finish yourprescription?

•Why shouldn’t you use unfinishedprescriptions from other people?

Tuberculosis

•TB mainly affects your lungs(pulmonary tuberculosis), andcoughing is often the onlyindication of infection initially.

•In the United States, cases oftuberculosis began decliningsteadily in the 1940s and 1950smainly because of antibiotictherapy and improved public healthprograms.

•TB is a re-emerging bacterial lunginfection

•World Health Organizationindicates that rates of tuberculosisresistant to multiple drugs (MDR-TB) are now at their highest levelever. (Reuters Health. Feb 28,2008. “Drug resistant tuberculosisreaches new high”)

Mycobacterium tuberculosis

TB lung infection