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Antibiotic Resistance
Immune deficiency (physiologically or due to chemotherapy) in cancer patients, allows for serious exposure to opportunistic micro organisms that may cause death (2). Often transmission of these organisms may occur due to (a) direct contact (b) a non- existent carrier or by an (c) existent carrier. Transmission of these opportunistic organisms may occur when cancer patients are in contact with items that are not thoroughly sterilized such as personal clothing, towels, or tooth brushes. Transmission through non- existent carriers may occur, for example, when patients drink tap water at home or from water fountains in public places. Transmission through existent carriers occur when a patient is directly in contact with, either physically or inadvertently, a healthy individual who is a natural carrier of a bacterium (e.g. Staphylococcus aureus). In contemporary use of a wide spectrum of antibiotics has proven very successful in preventing opportunistic bacterial infections. However, it should be noted that the use of antibiotics has both positive and negative consequences. Positive impacts include the prevention of rapid opportunistic bacteria invasions in patients who otherwise would be seriously threatened. The negative effect involves the resistance of the bacteria to the antibiotic. Antibiotic resistance may seriously jeopardize the life of the patient. Medical research has found that unnecessary and incorrectly used antibiotic therapy can produce resistant strains of bacteria. Indeed, evidence indicates that antibiotic resistant strains are rapidly increasing. Physicians and medical researchers have recognized this phenomenon and they are concerned. Who should we blame for the negative consequences associated with the improper use of antibiotics? Unfortunately, we are all to blame. The overuse of antibiotics is motivated by fear, ignorance and greed (1). Patients who demand antibiotics from their Doctors (fear), health care professionals who prescribe them inappropriately (ignorance), and pharmaceutical companies who manufacture them (greed)(1) are all to blame as the root of the problem(l). What should we do? I believe that public education and awareness is the first crucial step in correcting the problem. In order to understand the facts related to antibiotic resistance and its implications, a brief overview of the micro organisms, biology and the genetics of bacteria, including definitions, are required. Division of Micro-organisms Micro-organisms are divided into four categories. These are viruses, parasites, fungi and bacteria. Viruses lack a cell wall and are therefore not affected or destroyed by antibiotics. Parasites are unicellular micro organisms that are antigenically and biochemically complex. Fungi, unlike bacteria and viruses, are eukaryotic micro organisms that posses a plasma membrane. Bacteria, however, have a cell wall but lack membrane bound cytoplasmic organelles. The mechanism in which antibiotics act affect the cell wall of the organism and will therefore inhibit or prevent bacterial growth.
Bacterial Genome Bacterial genome consists of replicon, plasmids and transposons. A replicon is a circular molecule of DNA that functions as a self replicating genetic element. Plasmids are extra chromosomal genetic elements in bacteria which control medically important properties of pathogenic bacteria that include resistance to one or several antibiotics. Plasmids that determine resistance to antibiotics are referred to as R plasmids. Transposons are segments of DNA that can move from one site in a DNA to other. Transposons are important genetic elements because they may cause mutations in younger generations of bacteria. They could carry R plasmids with them. Mutations are heritable changes in bacterial genome. Mutation has a great medical importance (6).
Definition of Antibiotic Antibiotic is defined as chemical substance, either produced by micro organisms or by synthetic means, that is capable of killing or suppressing growth of micro organisms such as bacteria. Their mechanism of actions involved: 1) Inhibition or destruction of bacterial cell wall synthesis 2) Blocking of DNA synthesis 3) Blocking of RNA synthesis by binding to DNA- directed RNA polymerase (6). Therefore, unnecessary consumption or improper usage of antibiotic therapies (e.g= viral infection) may subsequently cause enhanced drug resistance due to the presence of R plasmids (mentioned earlier) that play a significant role in this process.
Facts Recent findings (predominately in United States) indicate that some of the death reported among cancer patients was caused by antibiotic resistant agents (2) and not the therapeutic drugs used for treatment of cancer. R plasmids were responsible of this tragic phenomenon. Some examples are shown below (3) (4) (5) (7):
Organisms 1)Strep. pneumonia 2)Entercocci 3)Pseudomonas aeroginosa 4)Nocardia farcinica
Causes(From organisms above accordingly) 1)Meningitis, sepsis 2)Septicemia 3)Septicemia 4)Pulmonary or systemic disease
Drug Resistant(Accordingly from Causes and Organisms Above) 1)Beta lactam penicillin 2)Vancomycin(Van.a, Van.b) 3)Chloromphenicol, ampicillin 4)Ciprofloxacin, tobramycin Statistics also indicate that the increase in the cancer mortality rate is due to the cause of antibiotic resistant agents. It seems that the "golden years" of antibiotic therapies are coming to the end and substitutes must be found.
Suggestions For now, researchers are suggesting the following: 1) Cancer patients should closely monitor their personal hygiene to decrease the chance of multi microbial infections. 2) Decrease the length of stay at the hospital to prevent potential infection agents through contact with personnel and visitors. 3) Have a microbiology laboratory perform antibiotics susceptibility testing prior to all physician prescribed antibiotics. 4) Have a microbiology laboratory perform routine checks on pH and ion concentration that have a direct effect on susceptibility profiles of antibiotic disks. 5) Make physicians aware of the tables of known antibiotic resistant strains of bacteria prior the preparation of prescriptions. Alireza H.
Reference (1)- Revenge of the Microbes, ASM Press, 2005, ISBN# 1-55581-298-8 (2)- Journal of Clinical Microbiology (JCM), First report of a case of meningitis caused by micro organism in a patient with AML. January 2004. (3)- Cancer Control Journal: Vancomycin- Resistant Enterococci, Dept. of Pharmacy, H. Lee Moffitt Cancer Center and Research Institute. (4)- WHC, Broad Spectrum Against Antibiotic- Super bug, Nov. 2002. (5)- American Journal of Respiratory and Clinical Medicine (ARC), Nov. 2000, Emerging Issues in Antibiotic Resistance in b100d- born infections. (6)- Medical Microbiology Text, Samuel Brown, 3rd edition, 1991. (7)- Topics and Issues, Journal of Continuing Education, Official publication of the American Medical Technologists, Article 305, Vol. 8 NO.2, April 2006
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