Background Extended spectrum beta-lactamases (ESBL) are enzymes produced by gram negative bacilli pathogens (mainly Escherichia coli and Klebsiella pneumoniae) than confer resistance against penicillins, cephalosporins and aztreonam. Persistent exposure to a multitude of beta-lactams has induced dynamic and continuous production and mutation of beta-lactamases. The proper use of antibiotics can help minimise this problem and pharmacists are a key component for the appropriate use of drugs.

Purpose To analyse the relationship between the consumption of carbapenems over time and the incidence of ESBL producing pathogens among the total microbiological samples in a tertiary hospital.

Material and methods We calculated defined daily doses per 1000 patient days (DDD/1000 PD) for carbapenems (including meropenem, imipenem/cilastatin and ertapenem) for every year between 2009 and 2015, according to ATC/DDD-WHO Nordic Council methodology. We recorded the number of isolates of ESBL producing both E coli and K pneumoniae, according to data from the microbiology laboratory. These data were correlated with DDD/1000e of carbapenems through the correlation coefficient r of Pearson. Consistent with the analysis carried out, the level of bilateral statistical significance was 0.01. Analysis of the results was performed using SPSS Statistics IBP-19 version.

Results DDD/1000 PD for carbapenems were 53.4, 58.6, 69.5, 70.9, 59.9, 54.1 and 54.3 in 2009, 2010, 2011, 2012, 2013, 2014 and 2015, respectively. The number of isolates per year of ESBL producing E coli were 173/215/420/383/110/123/99 and the number of isolates per year of ESBL producing K pneumoniae were 23/43/92/140/82/61/47 between 2009 and 2015. The correlation coefficients of the analysis performed between use of carbapenems and the incidence of ESBL producing pathogens were: r=−0.906 for ESBL producing E coli (p=0.005), r=0.880 for ESBL producing K pneumoniae (p=0.009) and r=0.959 for the overall of ESBL producing microorganisms (p=0.001).

Conclusion These results demonstrated a strong positive correlation between antibiotic pressure due to carbapenems and the emergence of ESBL microorganisms. Therefore, it is essential to optimise the use of such broad spectrum antibiotics due to the clinical relevance associated with this type of resistance. An antibiotic prescription programme based on a multidisciplinary approach could improve antibiotic use, and clinical pharmacists have a determining role in this team.

References and/or acknowledgements WHO Collaborating Centre for Drug Statistics Methodology. ATC-Index with DDDs.

No conflict of interest