Considerations to the comments on the recommendations of the Spanish Antibiogram Committee (COESANT) for the preparation of Cumulative Antibiotic Sensitivity Reports

Dear Editor,

In response to the letter from Brezmes et al.,¹ which raises important points in reference to the publication by the Spanish Antibiogram Committee (COESANT)² on the preparation of cumulative antibiotic susceptibility reports, we would like to issue the following reflections.

The percentage thresholds of sensitive strains for recommending empirical use of antibiotics are disputed as they have to be adapted to the type of combination of microorganisms and antimicrobials, but also to the type of pathology, among other factors, which make it impossible to give a general recommendation. Both the publication mentioned by the authors³ and others⁴ highlight the need for different thresholds depending, above all, on the severity of the clinical signs and symptoms and on the antimicrobial. As such, thresholds of >80% may be valid, for example, for urinary tract infections and possibly >95% for severe infections such as meningitis.⁴ This is why the generic 80% proposed threshold must be considered with many nuances and should force us to be more restrictive in severe infections.

Moreover, one of the difficulties encountered by many clinical microbiology laboratories, following the new guidelines of the European Committee on Antimicrobial Susceptibility Testing (EUCAST),⁵ is to make it understood that the current "I" category indicates that the antimicrobial is susceptible with increased exposure. The fact of highlighting the percentages in colours and marking the “S + Is” in yellow when the percentage of “S” alone does not exceed 80% but 80% is exceeded when adding the “I”, and only highlighting in green those cases where the “S” alone already exceeds 80%, may lead to the interpretation that the antibiotics marked in yellow behave as resistant and not as susceptible. This is the case, for example, for Pseudomonas aeruginosa in the table presented by Brezmes et al.,¹ where only aminoglycosides and colistin are shown in green while, for example, cefepime with 87% of I strains (susceptible with increased exposure) would appear in yellow, suggesting lower activity than those in green.

Although we appreciate the authors’ attempt to improve the understanding of cumulative antibiotic susceptibility reports, we at COESANT believe that efforts should focus primarily on ensuring that these reports provide clear and quality information through homogeneous and standardised preparation in all centres, which is the intention of the recommendations published by this committee.

Funding

No specific funding has been received for the preparation of this document. COESANT activities are partially funded by the Sociedad Española de Enfermedades Infecciosas y Microbiología Clínica [Spanish Society of Infectious Diseases and Clinical Microbiology] (SEIMC) and the Agencia Española de Medicamentos y Productos Sanitarios [Spanish Agency of Medicines and Medical Devices] (AEMPS).