(A–C) Genetic analysis of β-lactamase and PBP genes of AMA16 (A), AB0057 (B), and AB5075 (C) A. baumannii strains and qRT-PCR of genes associated with β-lactams resistance expressed in LB, LB supplemented with HPF, or in HS. Fold changes were calculated using double ΔCt analysis. At least three independent samples were used. LB was used as the reference condition. Statistical significance (p < 0.05) was determined by ANOVA followed by Tukey’s multiple comparison test: one asterisk: p < 0.05; two asterisks: p < 0.01; and three asterisks: p < 0.001. (D) Effect of HSA and HPF on the antimicrobial susceptibility of A. baumannii representative strains AMA40 and AMA113 grown in LB broth, LB broth plus 3.5% HSA, or HPF, that were used to perform cefiderocol (CFDC) susceptibility. Minimum inhibitory concentration (MIC) on cation-adjusted Mueller–Hinton agar was performed by MTS (Liofilchem S.r.l., 64026 Roseto degli Abruzzi TE, Italy), following the manufacturer’s recommendations.