Antibiotics and Resistant Bacteria

Penicillium Fungus
Penicillium fungus, a source of the antibiotic penicillin. Credit: J. L. Carson/Custom Medical Stock Photo/Getty Images


Antibiotics and antimicrobial agents are drugs or chemicals that are used to kill or hinder the growth of bacteria. Antibiotics specifically target bacteria for destruction while leaving other cells of the body unharmed. Under normal conditions, our immune system is capable of handling the germs that invade the body. Certain white blood cells known as lymphocytes protect the body against cancerous cells, pathogens (bacteria, viruses, parasites), and foreign matter.

They produce antibodies which bind to a specific antigen (disease causing agent) and label the antigen for destruction by other white blood cells. When our immune system gets overwhelmed, antibiotics can be useful in assisting the body's natural defenses in controlling bacterial infections. While antibiotics have proven to be powerful antibacterial agents, they are not effective against viruses. Viruses are not independent living organisms. They infect cells and rely on the host's cellular machinery for viral replication.

Antibiotics Discovery

Penicillin was the first antibiotic to be discovered. Penicillin is derived from a substance produced from molds of the Penicillium fungi. Penicillin works by disrupting bacterial cell wall assembly processes and interfering with bacterial reproduction. Alexander Fleming discovered penicillin in 1928, but it wasn't until the 1940s that antibiotic use revolutionized medical care and substantially reduced death rates and illnesses from bacterial infections.

Today, other penicillin-related antibiotics including ampicillin, amoxicillin, methicillin, and flucloxacillin are used to treat a variety of infections.

Antibiotic Resistance

Antibiotic resistance is becoming more and more common. Due to the prevalent use of antibiotics, resistant strains of bacteria are becoming much more difficult to treat.

Antibiotic resistance has been observed in bacteria such as E.coli and MRSA. These "super bugs" represent a threat to public health since they are resistant to most commonly used antibiotics. Health officials warn that antibiotics should not be used to treat common colds, most sore throats, or the flu because these infections are caused by viruses. When used unnecessarily, antibiotics can lead to the spread of resistant bacteria.

Some strains of Staphylococcus aureus bacteria have become resistant to antibiotics. These common bacteria infect about 30 percent of all people. In some people, S. aureus is a part of the normal group of bacteria that inhabit the body and may be found in areas such as the skin and the nasal cavities. While some staph strains are harmless, others pose serious health problems including foodborne illness, skin infections, heart disease, and meningitis. S. aureus bacteria favor the iron which is contained within the oxygen-carrying protein hemoglobin found within red blood cells. S. aureus bacteria break open blood cells to obtain the iron within the cells. Changes within some strains of S. aureus have helped them to survive antibiotic treatments. Current antibiotics work by disrupting so-called cell viability processes.

Disruption of cell membrane assembly processes or DNA translation are common modes of operation for current generation antibiotics. To combat this, S. aureus have developed a single gene mutation that alters the organism's cell wall. This enables them to prevent breaches of the cell wall by antibiotic substances. Other antibiotic resistant bacteria, such as Streptococcus pneumoniae, produce a protein called MurM. This protein counteracts the effects of antibiotics by helping to rebuild the bacterial cell wall.

Fighting Antibiotic Resistance

Scientists are taking various approaches to dealing with the issue of antibiotic resistance. One method focuses on interrupting the cellular processes involved in the sharing of genes among bacteria such as Streptococcus pneumoniae. These bacteria share resistant genes among themselves and can even bind to DNA in their environment and transport the DNA across the bacterial cell membrane.

The new DNA containing the resistant genes is then incorporated into the bacterial cell's DNA. Using antibiotics to treat this type of infection can actually induce this transfer of genes. Researchers are focusing on ways to block certain bacterial proteins to prevent the transfer of genes between bacteria. Another approach to fighting antibiotic resistance actually focuses on keeping the bacteria alive. Instead of trying to kill the resistant bacteria, scientists are looking to disarm them and make them incapable of causing infection. The intent of this approach is to keep the bacteria alive, but harmless. It is thought that this will help prevent the development and spread of antibiotic resistant bacteria. As scientists better understand how bacteria gain resistance to antibiotics, improved methods for treating antibiotic resistance can be developed.

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