Antibiotic resistance lasts up to a year

Antibiotic resistance is greatest in the month after treatment but may last for up to a year, possibly driving high levels of resistance in the community, a meta-analysis concluded. Longer treatment courses and multiple treatment courses were associated with higher rates of resistance.

British researchers analyzed 24 published studies of antibiotic resistance in primary care patients, who were mainly treated for respiratory or urinary infections. The paper appeared online May 18 in BMJ.

Of the studies, 22 involved patients with symptomatic infection and two involved healthy volunteers. Nineteen were observational studies (two prospective) and five were randomized.

Five studies of urinary tract bacteria (14,348 participants) found the pooled odds ratio (OR) for resistance was 2.5 (95% CI, 2.1 to 2.9) within two months of antibiotic treatment and 1.33 (95% CI, 1.2 to 1.5) within 12 months. Seven studies of respiratory tract bacteria (2,605 participants) found pooled ORs of 2.4 (95% CI, 1.4 to 3.9) within two months and 2.4 (95% CI, 1.3 to 4.5) within 12 months.

Researchers found a dose-response relationship for amoxicillin and trimethoprim. Also, longer duration and multiple courses of antibiotics were associated with higher resistance rates. The authors concluded that the only way to avoid the resistance is to avoid using antibiotics whenever possible.

An accompanying economic analysis said that although new antibiotics are needed, the research pipeline is nearly devoid of promising new alternatives. Financial incentives and medical-legal changes could persuade drug companies to develop new lines. But until new drugs are developed, said an editorial, steps must be taken to conserve existing medications.