Review - Reviewer's Assessment

1. Short summary / abstract
The consumption of anti-pseudomonal antibiotics and the resistance rates of P. aeruginosa were monitored over a 3-year period. Prescription of imipenem varied significantly over the study period. A high usage was followed by a reduction during a period of imipenem restriction. Prescription rates increased again when the restriction was relaxed. Rates of imipenem resistance in P. aeruginosa showed a time course similar to rate of consumption. Monthly rates of resistance to imipenem, ceftazidime and piperacillin-tazobactam were significantly associated with imipenem prescription rates in the same and preceding month. Consumption of ceftazidime and piperacillin-tazobactam had no association with resistance.

2. What question is the document addressing?
Does the resistance rate in P. aeruginosa correlate with the rate of consumption of anti-pseudomonal antibiotics?

3. Type of study
Observational cohort study.

4. Methods valid & appropriate?

The method is the best that can be achieved when considering this difficult subject. Although the events observed (resistance rates) are susceptible to many influences the fact that they mirrored the consumption of imipenem as it rose and fell during the study period helps to provide evidence for causation.

5. Results / recommendations reliable?
The results are reasonably reliable, given the reservations expressed above.

6. Any major problems and biases?
The possibility that the results are due to the spread of a resistant clone has not been fully excluded. Molecular typing of the isolates would have been useful.

7. Any other important / relevant studies which confirm or contradict?
Many studies have shown an association between antimicrobial prescribing and bacterial resistance although none have provided definitive proof of the link.

8. Keywords

Reviewer's Details:

Name:Tim Weller
Post:Consultant Microbiologist
(Society / Organisation / Advisory Committee):

*** Note: These are the views of a professional expert rather than an official statement from his or her society, organisation or advisory committee.

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