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Trimethoprim 'close to obsolete' as antibiotic resistance soars

By Lilian Anekwe

Trimethoprim resistance is rising so fast it is in danger of becoming obsolete as a treatment for urinary tracy infections – a general practice study has shown - prompting microbiologists to describe plans to make it available OTC as ‘scary'.

Researchers found resistance to trimethoprim has risen by 6% in just four years with 13% of all samples now resistant, raising the threat that resistance may reach a point beyond which it will be effectively useless.

Trimethoprim is currently under consideration by the MHRA for reclassification as an OTC treatment for cystitis.

Researchers at a hospital laboratory in Manchester analysed more than 38,000 urine samples taken from patients in general practices in the city between 2004 and 2008.

The study found trimethoprim sensitivity significantly declined, with 6% more UTI-causing bacterial samples having developed resistant to the antibiotic in 2008 compared to 2004. Overall 13% of all samples resistant to the drug.

The sensitivity of bacterial organisms other drugs used against UTIs also fell, with sensitivity to ciproflaxin down by 5% over the period and sensitivity to amoxicillin also decreased by 3%.

But sensitivity to nitrofurantoin - also earmarked by the MHRA for reclassification - remained largely unchanged at around 90% over the four years, prompting the researchers to urge GPs to switch from trimethoprim to nitrofurantoin for UTI treatment.

The research is presented at the European Congress of Clinical Microbiology and Infectious Diseases in Helsinki, Finland this week.

It concluded: ‘There has been an increase in antibiotic resistance to the first line antibiotics used by GPs to treat UTIs. The increased use of nitrofurantoin as an empiric agent for community UTI may be considered.'

Dr Neelam Doshi, consultant microbiologist at the University Hospital South Manchester and one of the study authors, warned GPs a threshold of resistance to trimethoprim may be looming.

‘The precise threshold will vary depending on a GP's locality. The OTC trimethoprim proposal is a scary one. I'm sure that if trimethoprim is made available over the counter the sensitivity will continue to drop.

‘It's time to sit back, tighten our seat belts and think long and hard about trimethoprim use. In general practice people still have faith in trimethoprim but I think nitrofurantoin might be a better option because for the moment at least sensitivity remains high.'

Dr Michael Moore, a GP in Southampton who worked on a recent health technology assessment of delayed antibiotics for UTIs, said: ‘GPs often only send samples for analysis if they suspect they are resistant infections, so hospital studies can sometimes overestimate resistance.

‘But these kinds of findings are always a concern. Antibiotic resistance figures have been creeping up for some time, and it suggests it might be time for GPs to consider alternative methods of managing UTIs. Once we reach a point where more than half of bacteria are resistant to trimethoprim we probably won't be able to use it anymore.'

Professor Jonathan Cooke, chief pharmacist at the university hospital of south Manchester and member of the DH's advisory committee on antimicrobial resistance, said: ‘These kinds of studies echo the point that rather than make more antibiotics available OTC we need to monitor their resistance to make sure we preserve them.'

Hospital labs are finding trimethoprim resistance rising fast Hospital labs are finding trimethoprim resistance rising fast

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