by Luningning Sugbu

Created on: February 01, 2010

     Multi-drug resistance is basically the ability of an organism such as bacteria, parasite or virus to survive in the presence of antibiotic drugs by evolving cellular mechanisms that neutralize the individual drug's destructive activities. This ability is conferred by the presence of a plasmid, a circular DNA material that exists inside a bacterial cell. The plasmid confers an edge for survival by determining the production of proteins that can kill other bacteria (col factors) or determining the ability to resist antimicrobial drugs made by man (R factors). Since the plasmid is independent of the bacterial chromosome, it can transfer itself from one bacterial cell to another.

    In 1945, the famous English scientist, Alexander Fleming who discovered penicillin cautioned that too much reliance and overuse of this drug would eventually erode its efficacy which held true as well with other antibiotics that were later discovered. Attempts to heed his warning came in the form of a requirement for a prescription in order to purchase penicillin which was implemented a decade later in the mid-1950's. Even then, the evolution of these multi-drug resistant organisms wasn't halted due to excessive reliance on antibiotics, leading to its random and improper use. Using antibiotics as prophylaxis also contributed to this frightening resistance. Another contributing factor is the emergence of patients whose immune systems are compromised such as those with HIV or AIDS and elderly patients who are undergoing invasive procedures with the  use of a greater diversity of medical devices and instruments which become vehicles of infection.

    Staphylococcus aureus is the best studied multi-drug resitant organism, having acquired resistance to beta lactam antibiotics such as penicillin and methicillin, thus the name "MRSA" which is the acronym for methicillin resistant Staphyloccus aureus. It was dubbed as the "super bug" by the media when it killed 18,000 of the 94,000 Americans it infected in 2005. Mycobacterium tuberculosis, the causative agent for TB has become resistant to isoniazid and rifampin which are the commonly used drugs to treat patients. Those patients with AIDS or HIV and are stricken with TB at the same time are the hardest to treat. TB is dormant in a person's body when the immune system is functioning properly, rendering it harmless. Becoming opportunistic, they emerge and cause debilitating illness when the AIDS virus destroys the immune system, the natural defense mechanism of the body. Since there is still no definite cure for AIDS or HIV,  TB caused by a multi-drug resistant mycobacteria certainly spells disaster.

   Other organisms that were previously susceptible to antibiotics and acquired resistance include Yersinia pestis, the causative agent of the plague, Vibrio cholerae, the causative agent for cholera and Plasmodium falciparum, the causative agent of malaria. Hospital acquired infections involve a significant number of these multi-drug resistant organisms. Acinetobater baumanni, a normal inhabitant of the skin, mucous membrane and soil is an indiscriminate organism that utilizes a number of organic material for food and it is able to grow at various temperatures in both wet and dry environments. Its acquisition of multi-drug resistance catapulted its prominence in the healthcare environment. If a formerly ubiquitous and harmless organism becomes a deadly killer after becoming resistant to antibiotic drugs, we have certainly come to the end of the antibiotic age.

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