Impact of pH on the activity of novel cephalosporin cefiderocol in human urine.

BACKGROUND: Antimicrobial activity of antibiotics can be impacted by pH, enhancing or reducing their bactericidal properties. Cefiderocol, a novel cephalosporin antibiotic that is among others indicated for the treatment of complicated urinary tract infections (cUTIs), lacks data on activity in urine. METHODS: Pooled human urine (iron levels ∼0.05 mg/L/24 h), CAMHB and iron-depleted CAMHB (ID-CAMHB) at pH 5, 7 and 8 served as media. MIC testing was done according to EUCAST with the broth microdilution method for 17 clinical isolates of Escherichia coli and ATCC 25922 (including isolates with ESBL activity), 17 clinical isolates of Klebsiella pneumoniae and ATCC 700603 (also with ESBL), and 6 clinical isolates of Pseudomonas aeruginosa and ATCC 27853. Time-kill curves (TKCs) were performed for selected strains at pH 5, 7 and 8 in urine. RESULTS: MIC values in urine, CAMHB and ID-CAMHB exhibited isolate-specific variations when assessed under identical pH conditions, ranging from a 1-fold dilution to changes of up to 4-fold dilutions in either direction. Median MICs of cefiderocol were up to 50-fold higher in pH 5 than in pH 7 for P. aeruginosa isolates and 32-fold higher in E. coli and K. pneumoniae isolates. TKCs with 650 and 1300 mg/L cefiderocol in urine showed that ATCC strains were efficiently eradicated despite the pH set. CONCLUSIONS: Acidic pH had a significant negative impact on cefiderocol activity. Yet, after a recommended IV administration of 2 g cefiderocol every 8 h, a concentration of approximately 1300 mg/L can be achieved in urine, suggesting that efficient killing of all tested pathogens could have been possible even under acidic conditions in vivo.

Frequent and possibly inappropriate use of combination therapy with an oral anticoagulant and antiplatelet agents in patients with atrial fibrillation in Europe.

PURPOSE: Combined oral anticoagulant (OAC) and antiplatelet (AP) therapy is generally discouraged in atrial fibrillation (AF) outside of acute coronary syndromes or stenting because of increased bleeding. We evaluated its frequency and possible reasons in a contemporary European AF population. METHODS: The PREvention oF thromboembolic events-European Registry in Atrial Fibrillation (PREFER in AF) prospectively enrolled AF patients in France, Germany, Austria, Switzerland, Italy, Spain and the UK from January 2012 to January 2013. We evaluated patterns of combined VKA-AP therapy in this population. RESULTS: Out of 7243 patients enrolled, 5170 (71.4%) were treated with OAC alone, 808 (11.2%) with AP alone and 791 (10.9%) with a combination of OAC and one (dual) or two AP (triple combination therapy). Compared with patients only prescribed OAC, patients on combination treatment had similar Body Mass Index, but more frequently diabetes (p<0.05), dyslipidaemia (p<0.01), coronary heart disease (54.2 vs 18.6%; p<0.01) or peripheral arterial disease (10.2 vs 3.7%; p<0.01). Accordingly, they had a higher mean CHA2DS2VASc (3.7 vs 3.4), and HAS-BLED (2.7 vs 1.9) scores (for both, p<0.01). Of the 660 patients on dual AP+OAC combination therapy, 629 (95.3%) did not have an accepted indication. Out of the 105 patients receiving triple combination therapy, 67 (63.8%) did not have an accepted indication. CONCLUSIONS: The combined use of OAC and AP therapy is not uncommon in AF, largely inappropriate, explained by the coexistence of coronary or peripheral arterial disease, and not influenced by considerations on the risk of bleeding.