study shows that a prescription of antibiotics taken within
the previous two months doubles the chances of patients
carrying antibiotic resistant bacteria.
A new study has shown that a prescription of antibiotics taken
within the previous two months doubles the chances of patients
carrying antibiotic resistant bacteria. The same effect was
not seen in patients who had had antibiotics prescribed within
the previous 12 months.
While information from large data sets suggest that high
levels of antibiotic use is related to antibiotic resistance,
this is the first time that the risk to the individual has
been assessed. The study looked at whether GP prescribing
of antibiotics increases an individual's risk of developing
GPs are responsible for 80% of all antibiotics prescribed
in the United Kingdom, despite evidence of limited or marginal
effectiveness for the most common reason to prescribe, namely
respiratory tract infections such as sore throats, coughs
and earache. This could be partly due to patients' expectations
of being treated with antibiotics.
Dr Alastair Hay, from Bristol University who is also a
GP in the city said: "Although GP's are aware of the problem
in the population as a whole, when deciding whether or not
to prescribe antibiotics for an individual they may consider
the risk as being minimal."
Resistance was tested in organisms from urine samples submitted
by 3,000 adults without urinary symptoms registered with
12 GP practices in the Bristol and Gloucester areas. Hay
and colleagues from across the South West found information
on bacterial resistance and antibiotic consumption in 618
patients from their primary care medical records regarding
the number, type, strength and duration of antibiotic courses
prescribed in the 12 months prior to urine sample submission.
The urinary E. coli bacteria found in low concentrations
were defined as resistant if they demonstrated resistance
to the antibiotic amoxicillin or the antibiotic trimethoprim,
or both antibiotics.
The results showed that antibiotics prescribed in the 12
months prior to obtaining the urine sample did not influence
the resistance of organisms - presumably because the time
period in question is too long. However, the more recent
use of antibiotics - within 2 months - led to a near doubling
of the likelihood of resistance.
The team also found that over a 12 month period prior to
sampling, each additional tablet of trimethoprim (200mg)
prescribed increased the chances of developing resistance.
In addition, the degree of resistance to amoxicillin was
greater in patients prescribed any penicillin antibiotic
in the 12 months prior to urine sampling. Funded by the
British Society for Antimicrobial Chemotherapy, the results
of this work are published in the Journal of Antimicrobial
Chemotherapy this month [July 2005]
This is the first time the risk to individuals being prescribed
antibiotics by their GP has been measured. This research
should be repeated but in the meantime both patients and
GP's should take account of this information when deciding
whether to prescribe and consume antibiotics.