MRSA is the “super-bug” that unfortunately kills many people due to infections they receive in hospitals, so that what was previously a haven for sick people has become the dreaded source of deadly infections. This is what happened to my mother, who was weakened by several illnesses while in hospital for some time, but eventually died of MRSA infection. What is MRSA? It is methicillin resistant staphylococcus aureus, a form of staphylococcus bacteria that has become multiply resistant, i.e resistant to most drugs.
How does ordinary staphylococcus make people ill and even kill them, for example when they get a throat infection? By producing toxins that cannot be handled effectively by the immune system, and that prevent the process of respiration from occuring at the molecular level in our cells, thus killing the cells. To prevent this happening we have developed various drugs that can kill the ordinary staphylococcus, drugs such as methicillin. But, even if the drug kills say 99% or even 99.9% of the SA, a minute remainder may survive the effect of the drug, because of genetic selection. Namely a minute proportion of the bacteria may have a genetic mutation that allows it to survive the toxic effect of the drug, and this drug resistant SA clone can then reproduce even in the presence of the drug and can go on to colonize the tissues and produce its toxins.
Well, what about using a different drug against the staphylococcal infection, such as oxacillin? But, what is often found is that once a clone of SA is resistant to one drug it becomes resistant to other drugs, presumably by the same mechanism, and is in fact multiply drug resistant. Therefore, none of the usual drugs can be used to fight it, and the infection cannot be stopped. This is similar to the process whereby a drug resistant cancer can develop from a clone of cancer cells that have become multiply drug resistant and these cells then go on to form a tumor and kill the patient.
What is the mechanism whereby the cells or bacteria become multiply resistant? One such mechanism is by efficiently exporting or excreting the drug, which must enter the cell or bacteria in order to have its pharmacological effect. If the cells/bacteria develop a mechanism that exports the drug faster than it can enter the cells and get to the bacteria and kill them, then they will survive and reproduce, thus eventually killing the cells. It is this fine balance between bacterial kill and survival that can be be tipped towards the negative side by a process of efficient drug exclusion.
These drugs may be quite different and work by different molecular mechanisms, but they may be sufficiently alike in their method of entering the cell or bacteria that they respond similarly to the process of drug exclusion. Of course, the aim of the pharmacologist is to find a drug that overcomes this resistance, but so far this search has been unsuccessful. Levofloxacin is a drug that has been used in these cases, but its effectiveness is limited, and there are other claims for various natural products that are completely unproven. Hence the best defense is to avoid infections by making sure that all operations are completely sterile and that all hospital interiors are cleaned with caustic materials that destroy bacteria. This is the ideal, although as we know it is unfortunately rarely achieved. For the foreseeable future MRSA will remain a scourge of patients everywhere.
(Note: the writer is neither a clincial pharmacologist nor a medical doctor and cannot answer medical queries).


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