Antibiotics and Resistance Prepared by Stephanie Aldret Cell Physiology Fall 2002

What is an Antibiotic ?  An Antibiotic is a chemical substance that inhibits bacterial growth or kills bacteria; it is produced naturally by bacteria and fungi.

How does an Antibiotic Work?  An Antibiotic …  Prevents the cell wall from forming  Prevents protein synthesis  Interferes with nucleic acid synthesis  Disrupts plasma and/or outer membranes  Serves as an antimetabolite

Types of Antibiotics : Beta-lactam antibiotics keep the cell wall from forming. Tetracyclines, Aminoglycosides, and Macrolides interfere with translation or inhibit polypeptide growth. Quinolones bind to bacterial RNA polymerase and inhibit RNA synthesis. Polymixins act as detergents and bind to phospholipids in the plasma membrane; Polyenes bind to sterols in fungi. Sulfa drugs interfere with bacterial metabolism.

What is Antibiotic Resistance ?  Antibiotic Resistance is the ability to resist the harmful effects of antibiotics by…  Alteration of target receptor proteins  Prevention of entry into the cell  Destruction of antibiotic upon entry  Association with antibiotic which blocks entry  Pump antibiotic out of cell before activation  Bypass affected step in the metabolic pathway It is rare for a bacterium to possess more than 1, but it is known that the Mycobacterium tuberculosis is resistant to all present antibiotics.

How does a bacterium become Antibiotic Resistant ?  Genetic Mutation  Genetic material taken in by a cell and incorporated into chromosomal DNA or a plasmid.  Plasmid resistant bacterium are referred to as strains and only progeny of the resistant cells will remain resistant. Antibiotic Resistance is most easily acquired within a limited environment with routine, consistent antibiotic exposure (ie. Hospitals, individuals on long-term antibiotic therapy, farm animals treated with low, non-therapeutic doses of antibiotics for weight gain).

Side Effects of Antibiotics  Toxicity  Allergy  Disruption of Normal Microflora

Limiting Antibiotic Resistance  Use high doses of antibiotics long enough to kill or weaken bacteria enough for natural defenses to kill them  Synergism/Potentiating drug interactions  Restrict to essential use only

Summary  Antibiotics are chemical substances produced by bacteria and fungi that are used to kill bacteria by interfering with cellular processes.  Antibiotic Resistance is the ability to resist the harmful effects of antibiotics.  Resistance is acquired through genetic mutation, the ingestion of genetic material for resistance, or continuous exposure to low doses of antibiotics.  Resistance can be prevented by taking all of your prescribed antibiotics, taking multiple antibiotics at one time, and restricting antibiotic use to individuals with weakened immune systems.

Questions ????