Drug resistant bacteria, killer at large

When first discovered, antibiotics were touted as a miracle cure and they literally were. Infections that were fatal were tamed to mere inconveniences. The misuse, overprescription and abuse of antibiotics has allowed resistant strains of bacteria to develop and once again threaten health and life. HORROR MOVIES graphically reveal the ravages of killer plagues and flesh eating bacteria but behind this filmi-hype is a story of real and imminent danger. Recently the deadly bacterium Staphylococcus aureus, a major cause of hospital acquired infections, was found to respond poorly to a once reliable antidote {frac12}the antibiotic vancomycin. This emergence of forms of the bacteria, lacking sensitivity to vancomycin signifies that variants untreatable by every known antibiotic are on their way and this bacterium has thus moved one step closer to becoming an unstoppable killer. In addition, strains of at least three bacteria capable of causing life-threatening illness, Enterococcus faecalis, Mycobacterium tuberculosis and Pseudomonas aeruginosa already evade every antibiotic in the clinicians armamentarium, a stockpile of more than 100 drugs. The looming threat of such incurable bacterial species is just the latest twist in an international public health nightmare increased bacterial resistance to many antibiotics that once cured bacterial diseases readily.

The World Health Organization(WHO) in fact in a very recently released report on " Overcoming Antimicrobial Resistance " has issued an urgent call for action on the fight against increasing microbial resistance to therapeutic drugs.

"If nothing is done in this decade to tackle the problem, the window of opportunity may be closed forever," says WHO in its report. The effect of antimicrobial resistance , the report emphasizes, "is that it can reduce the curative power of once life-saving medicines to that of a sugar pill".

When first discovered, antibiotics were touted as a miracle cure and they literally were. Infections that were fatal were tamed to mere inconveniences. The misuse, over prescription and abuse of antibiotics has allowed resistant strains of bacteria to develop and once again threaten health and life. With each passing decade, bacteria that defy not only single but multiple antibiotics and therefore are extremely difficult to control have become increasingly common.

The WHO report points out that there are two reasons for the increasing resistance to antimicrobial therapies: in the developed world it is overuse of drugs and in the developing world it is their underuse. As a result, diseases that were virtually eliminated with the introduction of antibiotics are mutating, gaining strength and resisting treatment. About 10% of TB patients have strains resistant to the two most powerful TB medicines. A small but growing number of HIV patients is becoming resistant to AZT treatment. Penicillin has become virtually useless for treating gonnorrhoea and even in industrialized countries, up to 60% of hospital-acquired infections are caused by drug-resistant microbes. The economic impact of drug resistance is enormous. It costs 100 times more to treat a patient with drug resistant TB than one with normal TB.

In an effort to combat the menace of drug resistant bacteria, it is important to realize that although antibiotics are needed to control bacterial infections, they can have broad, undesirable effects on microbial ecology.

That is, they can produce long - lasting change in the kinds and proportions of bacteria - and the mix of antibiotic-resistant and antibiotic-susceptible types- not only in the treated individual but also in the environment and society at large. Antibiotics should thus be used only when they are truly needed and we can all help in reversing the growth of resistant bacteria by doing the following:

Complete the full course of antibiotic therapy to ensure that all the pathogen bacteria are killed. Also do not skip doses since this causes the level of antibiotic in the blood to drop providing bacteria with a `breather'. As a result, some may survive.

Refrain from taking antibiotics for colds and other viral infections because antibiotics DO NOT harm viruses. One should also consider seeking non-antibiotic therapies for minor ailments.

It is believed that approximately one third to one half of all antibiotic prescriptions are not needed.

Wash raw fruits and vegetables to thoroughly clear off any resistant bacteria. The amount of resistant bacteria people acquire from food is not trivial. It has been shown in a study conducted by the National Institute for Agricultural Research in Toulouse, France that when human volunteers went on a diet consisting only of bacteria free foods, the number of resistant bacteria in their feces decreased 1000 fold.

The ultimate weapon for outwitting the resistant bacteria would of course be to develop altogether new types of antibiotics. And there is very definite hope in this direction. Only in April 1999 the United States Food and Drug Administration (USFDA) approved the drug `Zyvox' for use by adults with pneumonia and other infections caused by the deadly supergerm enterococcus faecium which is resistant to all antibiotics including vancomycin. More importantly, Zyvox is a synthetic chemical designed from scratch to fight germs at an entirely different point in their life cycle than any other antibiotic.

In contrast to present day antibiotics, Zyvox stops bacteria from multiplying by halting production of proteins vital to their growth early in their life cycle.

It is believed that because Zyvox works differently than traditional antibiotics, it would probably be harder for bacteria to evolve resistance to it. There is also new hope from the findings of the Human Genome Project. Analysis of bacterial genomic sequences has shown that there could be 20-200 novel targets on the bacteria for attack by antibiotics.

The existing seven classes of antibiotics are known to attack only a handful of these bacterial sites. There is scope therefore for the development of newer class of antibiotics that will kill bacteria by binding to these newly discovered bacterial targets.

Scientists are also working on strategies that will give new life to existing antibiotics. Many bacteria for instance evade penicillin and its relatives by switching on an enzyme, penicillinase that degrades those compounds. An antidote already on pharmacy shelves contains an inhibitor of penicillinase.

It prevents the breakdown of penicillin by the bacteria and so frees the antibiotic to work normally. Similarly scientists are working towards developing a compound to jam a microbial pump that ejects the drug tetracycline from bacteria. With the pump inactivated tetracycline can penetrate bacterial cells effectively.

Anirudha Datta

Indian Institute Of Petroleum

Dehradun

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