By Alisdair Stirling
Ampicillin, amoxicillin and macrolides may not be as effective against pneumonia and lower respiratory tract infections associated with influenza-like illness as tetracyclines and co-amoxiclav, suggests a major new HPA study.
The findings appear to call into question the agency’s own guidelines suggesting GPs should use these antibiotics for treating the respiratory complications of flu and flu-like illness.
Guidelines for the clinical management of patients with influenza-like illness during an influenza pandemic – jointly published in 2007 by the British Infection Society, British Thoracic Society and the HPA in collaboration with the Department of Health – recommend GPs use ampicillin and amoxicillin for treating pneumonia as a complication of flu when S.pneumoniae or H.influenzae ‘is the most likely cause’, and recommended macrolides as an alternative to tetracyclines or co-amoxiclav.
The research team from the HPA’s centre for infections analysed 86,845 lower respiratory tract specimens – two-thirds of them from GP surgeries and the remainder from outpatients – collected by sentinel laboratories in England, Wales and Northern Ireland between January 2007 and March 2010.
Their analysis showed microbial susceptibility to tetracyclines or co-amoxiclav was high. Of the 70,288 and 45,288 isolates where susceptibility results for tetracyclines or co-amoxiclav were available, 96% and 92% were susceptible, respectively.
However, susceptibility to ampicillin and amoxicillin or macrolides was lower at 77% and 49% respectively and varied markedly with organism, the researchers said.
There were few ‘clinically relevant’ variations in susceptibility to tetracyclines such as doxycycline or co-amoxiclav over time, geographically or between age groups.
Lead author Dr Ruth Blackburn, an information analyst in the HPA’s department of healthcare-associated infection and antimicrobial resistance concluded: ‘These data clearly indicate that lower respiratory tract isolates of the pathogens studied retain high levels of susceptibility to the antibiotics recommended in the UK guidelines.
‘Susceptibility to ampicillin/amoxicillin and macrolides was well below that recorded for tetracyclines or co-amoxiclav, suggesting that the former drugs are less appropriate for empirical treatment.
‘However, susceptibility to ciprofloxacin for H. influenzae or ampicillin/amoxicillin for S. pneumoniae was high and these antibiotics may be preferable to tetracyclines or co-amoxiclav where the organism is known’, she added.
Dr George Kassianos, a GP in Bracknell, Berkshire and RCGP spokesperson for flu and immunisation, said: ‘These studies are very important. This one backs up what I would do, which is to favour co-amoxiclav as first-line treatment and if the infection doesn’t clear, to give tetracycline rather than macrolides.’
Co-amoxiclav backed in flu complications