Our aim was to determine the reasons for appropriate Piperacillin-tazobactam (Pip-Taz) prescriptions.

This was a prospective multicentre study of two-month Pip-Taz prescription in France. Reading of patient charts allowed for classification of diagnoses as definitive, suspected or unknown. Appropriateness of Pip-Taz was defined according to eight indications: post-operative infection in digestive surgery or urology, fever in onco-hematological patients, healthcare-associated infections (HCAI) in intensive care units, polymicrobial HCAI, infection due to multidrug-resistant bacteria, avoidance of carbapenem use, pulmonary infection in patients with chronic pulmonary disease, and following an internal guideline. Antibiotic reassessment was defined by any modification of Pip-Taz. Risk factors for erroneous Pip-Taz prescription were identified through a multivariate analysis, and participating physicians were interrogated on the subject.

From April to July 2024, 259 prescriptions from 14 institutions were included. The diagnosis of infection was definitive in 127 cases (49 %), suspected in 97 (37 %), and unknown in 37 (14 %). Prescriptions were deemed appropriate in 204 cases (79 %). In logistic regression, appropriate Pip-Taz prescription was associated with definitive diagnoses, HCAI, microbiological investigations, advice by infectious disease specialists, and antibiotic reassessment (all adjusted OR ≥ 2.19). All in all, 37/55 prescriptions outside the scope of guidelines were elucidated by the prescribers, the main reason for them being “out of habit” (13/37), and we found a relationship between “unknown diagnosis” and no explanation for Pip-Taz prescription (p < 0.001).

Pip-Taz appropriateness was associated with correct management, i.e. written diagnosis, microbiological investigation, and reassessment, while prescriptions outside guidelines were related to physician habits, including no written diagnosis.