Preliminary Molecular Characterization and Antimicrobial Activity of Enterococcus faecium Strains Isolated from...

This study characterized six Enterococcus faecium strains isolated from Algerian camel milk to assess their molecular features and antimicrobial potential as food-associated isolates. Identification was performed using phenotypic tests, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS), and 16S rRNA gene sequencing. Strain diversity was assessed by repetitive sequence-based polymerase chain reaction (rep-PCR), including (GTG)₅-PCR, BOX-PCR, and enterobacterial repetitive intergenic consensus PCR (ERIC-PCR). Polymerase chain reaction (PCR) screening for selected virulence-associated and antimicrobial resistance genes showed that the two selected isolates were negative for the targeted markers, indicating a preliminary molecular profile of interest but not allowing definitive safety conclusions without whole-genome sequencing and phenotypic antimicrobial susceptibility testing. Both strains showed antimicrobial activity against Gram-positive and Gram-negative indicators. Strain 9 showed notable inhibition against Klebsiella pneumoniae subsp. pneumoniae ATCC 13883, with an inhibition zone of 23.4 ± 2.3 mm using native supernatant, which increased after concentration. Trypsin treatment abolished activity, supporting the proteinaceous nature of the inhibitory compounds. The enterocin genes entA and entB were detected in strains 9 and 13, indicating genetic potential only. Further genomic, safety, and functional investigations are required.