Transcript Antibiotic Resistance in Microbes

Antibiotic Resistance in
Microbes
A few microbes to be concerned about
How some antibiotics and Antimicrobials
work
Resistance mechanisms
Some factors involved in resistance
Reversing resistance
Conclusions
References
A Few Microbes to Be
Concerned About
Mycobacterium tuberculosis: tuberculosis
Resistant to: streptomycin, Pyrazinamide,
Ethambutol, isoniazid, and rifampin
Staphylococcus aureus: Staph infections
Resistant to: penicillin, erythromycin, Gentomycin
MRSA and VRSA
Salmonella typhimurium:: typhoid fever
Resistant to: Ampicillin, Chloramphenicol,
streptomycin, Sulfanamides, tetracycline
A Few More Microbes...
Yersinia pestis : plague - multi resistant
Treponema palladium : syphilis - multi resistant
Neisseria gonorrhoeae: Gonorrhoeae - multi
resistant
A Few More Microbes...
Campylobacter jejuni : Campylobacter - Multi Resistant
Shigella dysenteriae : Dysentery - Multi Resistant
Eschericia Coli (including E. coli 0157 : H7) : Hemorrhagic
Diarrhea, Kidney failure - Multi Resistant
How Some Antibiotics Work
Penicillin G (Gram + Bacteria) :
B lactam ring binds to transpeptidase inhibiting
cross-linking of cell wall resulting in cell lysis
Aminoglycosides : Streptomycin, Gentomycin
Inhibits protein synthesis on 30s ribosomal subunit
Tetracyclines ( Broad Spectrum - Gram - and Gram + ) :
Inhibits protein synthesis on 30s ribosomal subunit
Macrolide Antibiotics : Erythromycin, Spiramycin
Inhibits protein synthesis on 50s ribosomal subunit
How Some Antimicrobials Work
Sulfa Drugs : Sulfanilamide
Blocks synthesis of folic acid
Quinolones : Norflaxin, Ciproflaxin (Broad Spectrum)
Prevents bacterial DNA gyrase from supercoiling
bacterial DNA
Resistance Mechanisms
B-lactamases :
B-lactamases cleave B-lactam rings from
penicillin
Modification of Drugs :
Some enzymes have the ability to
phosphorylate, adenylate, or acetylate
antibiotics-chloramphenicols and
aminoglycosides
Resistance Mechanisms
Efflux Pumps and Prevention of Uptake :
• Enzymes actively pump out drugs or the drug
is not taken into the cell at all-tetracycline
Enzymes with Altered Shapes :
• Enzyme proteins with altered shapes are
produced so that the drug no longer fits to
inhibit-Rifampin and Quinolones
Some Factors Involved in
Resistance
Chromosomal Resistance :
Tends to involve modification of the target
drug
R-Plasmids (R-Factors) :
Tend to involve inactivation of drugs
Can be shared with many different strains and
species
Multi-resistant R-plasmids have several genes
which encode for different enzymes
Some Factors Involved in
Resistance
Antibiotic Treatment :
• Taking antibiotics can clear out naturally
occurring gut flora
Multiple Resistance From One Antibiotic :
• Some studies have shown that after exposure
to only one antibiotic, resistance to multiple
antibiotics can be produced
Reversing Resistance
Natural Selection :
Many resistant strains do not compete as well
as non-resistant strains
When not artificially selected for, resistant
microbes tend to return to naturally low levels
in populations
Conclusion
Multi-Resistant microbes are a major concern
Come from many places in the environment
Microbes have many ingenious ways of
dealing with antibiotics
Resistance is generally a reversible process
References
Ackerman, Jennifer. Food: How Safe? National Geographic Magazine, National
Geographic Society, May 2002, p.2-p.31.
Bryan, L.E., Bacterial resistance and susceptibility to chemotheraputic agents.
Cambridge University Press, Cambridge, 1982.
Harrison, Polly F., Lederberg, Joshua, et.al. ANTIMICROBIAL RESISTANCE: Issues
and Options-Workshop report. Forum on Emerging Infections, Institute of
Medicine. National Academy Press, Washington, D.C. 1998
Moore, Pete, BSc, PhD. Killer Germs: Rogue Diseases of the Twenty First Century.
Carlton Books Limited, London, 2001.
Reichman, Lee B., M.D., M.P.H., Tanne, Janice Hopkins. Timebomb: The Global
Epidemic of Multi-Resistant Tuberculosis. McGraw-Hill, New York, 2002.
Weiss, Rick. War on Disease: Deadly New Threats. National Geographic Magazine,
National Geographic Society, February 2002. P.4-p.31.