Antibiotic Resistance: How it happens and why all the fuss? (in your packet)

Bacteria are Everywhere! 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? Bacterial chromosome (DNA) Cell membrane Cell wall or envelope 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 Haemophilus influenzae - meningitis Streptococcus pyogenes - strep throat Staphylococcus aureus - wound infections Helicobacter pylori - Stomach ulcers

How antibiotics work Antibiotics are chemicals that disrupt bacterial processes Stop protein building: cell dies Stop cell wall 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 All killed Antibiotic X 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: Modify or destroy the antibiotic. Force out antibiotic. Alter the target. Essential Bacterial Protein Essential Bacterial Protein

“Superbugs” Bacteria that are resistant to many antibiotics 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 Doctors Take for prescribed period of time. Don’t go to doctor with expectation of receiving prescription. Only prescribe when necessary. Narrow spectrum drugs.

Subtherapeutic Dosage Problem 1/2 Dose Full Dose Stop Taking Antibiotic Resistant bacteria Highly susceptible bacteria Less susceptible bacteria

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

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.