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Antibiotic resistance lasts up to 12 months

A person's antibiotic resistance can last up to a year after taking it

OnMedica staff

Wednesday, 19 May 2010

In a person prescribed an antimicrobial in primary care, for a urinary or respiratory infection, resistance to that drug might develop and last for up to 12 months, shows research published on bmj.com.

Researchers from Bristol and Oxford conducted a systematic review and meta-analysis of 24 previous studies that had investigated the development of antimicrobial resistance in individual patients in primary care. The patients had, in the main, been prescribed the drugs for respiratory or urinary infections, although two of the studies were of healthy volunteers.

The authors say that although most doctors and patients do not regard the problem of widespread resistance as a reason not to prescribe antibiotics, their study produced strong evidence that individual patients prescribed an antibiotic in primary care for a respiratory or urinary infection develop a resistance.

Resistance was particularly marked in the first month after antibiotic treatment, but was still notable at 6 months and could be present up to a year after treatment. The authors say that this might be an important factor in the development of drug resistance in the community.

The studies that assessed the effect of antibiotic quantity, reported an association of longer or multiple courses with higher rates of resistance. No consistent association was found across the studies between different antibiotics and the potential for inducing resistance.

The authors conclude: “Individuals prescribed an antibiotic in primary care for a respiratory or urinary infection develop bacterial resistance to that antibiotic. The effect is greatest in the month immediately after treatment but may persist for up to 12 months.

“This effect not only increases the population carriage of organisms resistant to first line antibiotics, but also creates the conditions for increased use of second line antibiotics in the community.”

They say that their review gives enough evidence to quantify the link between individual prescribing decisions and the problem of resistance, and they claim it shows that the only way to avoid the “vicious cycle of resistance” is to avoid the initial use of antibiotics wherever possible. However, they also call for more clinical trials to strengthen the evidence base.

In an accompanying editorial, three international experts argue: “Proof that antibiotic prescribing contributes to resistance in the individual patient and not just at the societal level is the kind of evidence that needs to be communicated to clinicians.”

They call for economic strategies to bring new drugs to market, and to conserve existing antibacterials. “Nothing less than the future of medicine, from organ transplants to chemotherapy, is at stake, and there will be no second chances,” they conclude.

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