The results of a 20-year study published in the BMJ finds that 1 in 10 of all antibiotic prescriptions fail to treat the infection. This marks an increase in the number of antibiotic failures, which is continuing to rise.

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The results of the study show that overall antibiotic failures rose from 13.9% in 1991 to 15.4% in 2012.

Over the past 20 years, there has been such a sharp increase in strains of microbes that are resistant to antibiotics that the World Health Organization have declared the issue a global public health crisis.

Despite this, primary care clinicians rarely report problems of antibiotic resistance in their own practices.

“Both primary care clinicians and members of the public typically regard antibiotic resistance as a problem that largely affects patients in hospital,” write the researchers behind the new study, from Cardiff University in the UK.

Although many previous studies have assessed antibiotic resistance in hospitals, according to the Cardiff team, experts know “virtually nothing” about the frequency and pattern of antibiotic resistance in primary care.

The new study gathered data on antibiotic treatment failure rates in UK primary care. The researchers say that the UK is one of the few countries where it is possible to access appropriate data for assessing failure of antibiotic prescriptions, because of the way data is recorded in its National Health Service.

Data was drawn from the Clinical Practice Research Datalink, which stores the records of more than 14 million individuals, obtained from 700 primary care practices across the UK.

The Cardiff team analyzed data from 1991-2012 and focused on the four most common kinds of infection:

  • Upper respiratory tract infections
  • Lower respiratory tract infections
  • Skin and soft tissue infections
  • Acute otitis media.

The results show that overall antibiotic failures rose from 13.9% in 1991 to 15.4% in 2012. Antibiotics prescribed to treat bronchitis, pneumonia and other lower respiratory tract infections were found to be the least successful, showing an increased failure rate of 35%.

Throughout the study period, the treatment failure rates for the commonly prescribed antibiotics amoxicillin, penicillin and flucloxacillin remained below 20%.

However, the failure rate of antibiotics that are not normally prescribed as first-line treatments had risen alarmingly. One example of this rise can be observed in the failure rates of trimethoprim, normally used to treat upper respiratory tract infections, which had risen 40% across the treatment period.

Author Prof. Craig Currie says there is a strong link between the rise in antibiotic treatment failure and an increase in prescriptions. From 2002-2012, the proportion of infections being treated with antibiotics rose from 60% to 65%. This period of 2002-2012 was also when the biggest increase in antibiotic failure rates occurred.

“These episodes of failure were most striking when the antibiotic selected was not considered first choice for the condition treated,” Prof. Currie says. He adds:

Given the lack of new antibiotics being developed, the growing ineffectiveness of antibiotics delivered through primary care is very worrying indeed. There is a mistaken perception that antibiotic resistance is only a danger to hospitalized patients, but recent antibiotic use in primary care is the single most important risk factor for an infection with a resistant organism. Furthermore, what happens in primary care impacts on hospital care and vice versa.”

Recently, Medical News Today ran a spotlight feature on antibiotic resistance, where we asked experts to what extent it has become a global threat to public health.