This study aims to evaluate the interspecific variation in polyphenolic profiles and biological activities of acorn flours from three native Tunisian Quercus L. species (Q. ilex L., Q. suber L., and Q. canariensis Willd.). Q. canariensis extracts are the richest in total phenolic, flavonoid and hydrolysable tannin contents. Six phenolic compounds were identified by HPLC-DAD analysis. Chlorogenic acid was the dominant compound in Q. canariensis and Q. ilex acorns. Whereas in Q. suber, caffeic acid was the main component and, along with trans-ferulic acid, was exclusive to this species. Hyperoside was notably identified in Q. canariensis. The UHPLC-DAD-MS analysis of hydrolysable tannins revealed twelve compounds. Acorns of Q. canariensis and Q. suber were dominated by ellagitannins, whereas Q. ilex contained mainly gallotannins. To our knowledge, these compounds are identified for the first time in Tunisian acorns. Q. canariensis exhibited the strongest antioxidant potential with DPPH, ABTS and FRAP assays, as well as the highest antibiofilm and anti-α-amylase activities. All extracts inhibited ATCC pathogenic bacterial strains while largely sparing the beneficial probiotic Limosilactobacillus fermentum. This result indicates a selective antibacterial effect not previously reported for Quercus acorns. Q. canariensis may represent a potential source of functional food ingredient, nutraceuticals, and pharmaceuticals, which remains to be confirmed through in vivo investigations.

Klebsiella pneumoniae is a leading cause of hospital‐acquired infections, particularly in intensive care units (ICUs), where multidrug‐resistant (MDR) and hypervirulent strains represent major therapeutic challenges. This study investigated the phenotypic and molecular features of isolates recovered from ICU patients and the hospital environment in Benghazi, Libya. Antimicrobial susceptibility was determined using disk diffusion and the colistin broth disk elution method. Extended‐spectrum‐ β ‐lactamase (ESBL) and carbapenemase production were assessed phenotypically and confirmed by PCR and sequencing, whereas clonal relatedness was analyzed through OmpK36 typing. Hypervirulence was evaluated using the string test, PCR detection of virulence genes, and biofilm formation assays. A total of 56 isolates (46 clinical and 10 environmental) were included. All isolates were resistant to ceftriaxone, with high resistance rates to ceftazidime, cefotaxime, carbapenems, ciprofloxacin, and gentamicin. ESBL production was observed in 76% of clinical and 80% of environmental isolates, and 95% of all isolates were classified as MDR. A significant proportion of K. pneumoniae isolates ( n = 15) exhibited resistance to colistin in the absence of detectable mcr genes. Strong and moderate biofilm production was detected in 30.4% and 17.9% of isolates, respectively. The bla _NDM-5 was prevalent among clinical (45/46; 97.8%) and environmental (9/10; 90%) isolates. Similarly, bla _CTX-M-15 was detected in 35/46 (76%) clinical isolates and 8/10 (80%) environmental isolates, whereas bla _OXA-48 was detected in 26/46 (56.5%) clinical and 10/10 (100%) environmental isolates. A potentially hypervirulent phenotype was observed in 17.8% of the isolates, associated with the virulence genes iuc A, iut A, and peg ‐344. OmpK36 Groups C and D predominated. These results highlight the alarming spread of MDR and hypervirulent strains in ICUs and underscore the need for reinforced infection control strategies.