Comparative meta-analysis of prevalence and molecular features of high-priority <i>Enterococcus faecium</i> and <i>E. faecalis</i> from the guts of food-producing and wild birds

Birds harbour <i>Enterococcus faecium</i> and <i>Enterococcus faecalis</i> as gut commensals but could acquire and transmit high-priority strains. Following the PRISMA guidelines, eligible studies that reported the antimicrobial resistance (AMR) profiles of <i>E. faecium</i> and <i>E. faecalis</i> from gut samples of food-producing (FPBs) and wild birds (WBs) published from 2005–2024 were screened from major bibliographic databases. Random-effect models were used to determine the pooled prevalences (PPs) of vancomycin (VAN^R), ampicillin (AMP^R), and linezolid (LZD^R) resistant <i>E. faecium</i> and <i>E. faecalis</i> from non-duplicated gut samples of FPBs and WBs. Of the 36 eligible studies, the overall PP of VAN^R-<i>E. faecium</i> and VAN^R-<i>E. faecalis</i> were 1.8% and 0.7%, respectively. AMP^R-<i>E. faecium</i> and AMP^R-<i>E. faecalis</i> were 1.6% and 0.6%, respectively. LZD^R-<i>E. faecium</i> and LZD^R-<i>E. faecalis</i> were 1% and 0.8%, respectively. Subgroup analyses revealed significant temporal variations in the PPs of VAN^R-<i>E. faecium</i> (<i>P</i> &lt; 0.05). FPBs had significantly higher PPs of VAN^R, AMP^R and LZD^R <i>E. faecium</i> and <i>E. faecalis</i> than WBs (<i>P</i> &lt; 0.05). Healthcare-associated <i>vanA</i>-carrying <i>E. faecium</i> lineages from WBs (ST16, ST17, ST18, and ST412) and <i>optrA</i>-carrying <i>E. faecalis</i> lineages (ST32, ST59, ST330) from FPBs were identified. In FPBs, Egypt had the highest PP of VAN^R-<i>E. faecium</i> (11.9%) and LZD^R-<i>E. faecalis</i> (2.8%). Conversely, the USA had the highest PP of VAN^R-<i>E. faecium</i> in WBs (2.4%). A higher frequency of vancomycin- than linezolid-resistant strains exists, and VAN^R-<i>E. faecium</i> are disproportionately distributed based on bird species, year of study, and country, indicating varied selection pressure. Significantly higher prevalence of VAN^R-<i>E. faecium</i> than VAN^R-<i>E. faecalis</i> was found, highlighting the higher capacity of <i>E. faecium</i> to acquire ampicillin and vancomycin resistance in birds. <b>RESEARCH HIGHLIGHTS</b>Vancomycin, ampicillin, and linezolid resistance in <i>E. faecium</i> and <i>E. faecalis</i> are considered high-priority public health concerns.This is a meta-analysis of high-priority <i>E. faecium</i> and <i>E. faecalis</i> from gut samples of birds.Food-producing birds had significantly higher frequency of priority <i>E. faecium</i> and <i>E. faecalis</i> than wild birds.Vancomycin resistance in <i>E. faecium</i> and <i>E. faecalis</i> exists more frequently than linezolid resistance.<i>E. faecium</i> has a higher capacity to acquire ampicillin and vancomycin resistance than <i>E. faecalis</i>.Genetically related human-adapted vancomycin- and linezolid-resistant strains were identified in food-producing and wild birds. Vancomycin, ampicillin, and linezolid resistance in <i>E. faecium</i> and <i>E. faecalis</i> are considered high-priority public health concerns. This is a meta-analysis of high-priority <i>E. faecium</i> and <i>E. faecalis</i> from gut samples of birds. Food-producing birds had significantly higher frequency of priority <i>E. faecium</i> and <i>E. faecalis</i> than wild birds. Vancomycin resistance in <i>E. faecium</i> and <i>E. faecalis</i> exists more frequently than linezolid resistance. <i>E. faecium</i> has a higher capacity to acquire ampicillin and vancomycin resistance than <i>E. faecalis</i>. Genetically related human-adapted vancomycin- and linezolid-resistant strains were identified in food-producing and wild birds.