Prevalence of antimicrobial resistance in bacteria intentionally added to agro-food chain

Protimikrobna zdravila so temelj moderne medicine, obenem pa njihovo učinkovitost ogroža naglo širjenje odpornosti. Tudi mlečnokislinske bakterije (MKB) in bifidobakterije so bile prepoznane kot rezervoar genov za odpornost (ARG), vendar dejansko tveganje, ki ga predstavljajo sevi, ki jih namensko dodajamo v agroživilsko verigo (SZPK), še ni raziskano. Na to vprašanje smo skušali odgovoriti v naši raziskavi. V analize smo vključili štiri skupine MKB in bifidobakterij ̶ poleg sevov iz starterskih kultur ali prehranskih dopolnil z živimi bakterijami (probiotikov) tudi izolate iz humanega mleka ali kolostruma, iz črevesne sluznice ali blata ter iz fermentiranih živil. Fenotipsko občutljivost smo ugotavljali za 474 sevov z mikrodilucijo in pokazali, da je odpornost pogostejša pri črevesnih izolatih. ARG in mobilne elemente (MGE) smo proučevali v celih genomih 1114 sevov s primerjalno genomiko. Ugotovili smo, da je 13,8 % sevov skupine SZPK vsebovalo pridobljene ARG, pri čemer so prevladovali tisti za tetraciklin, pogosto pa smo našli tudi mutacije. 75,5 % pridobljenih ARG smo povezali z MGE, katerih potencial za širjenje in vivo smo ovrednotili s pomočjo preiskovanja metagenomskih sekvenc. Ocenjujemo, da skupina sevov SZPK ne predstavlja pomembnega tveganja za širjenje odpornosti, saj so pridobljeni ARG in MGE pri teh sevih manj pogosti kot pri skupini humane črevesne sluznice/blata, vendar je pozornost potrebno nameniti predvsem posameznim probiotičnim sevom, ki vsebujejo elemente, za katere smo pokazali, da imajo potencial za širjenje med črevesno mikrobioto. Ti elementi so redkejši pri izolatih naravne mikrobiote iz fermentiranih živil in neznačilni za starterske kulture.Antimicrobials have become one of the foundations of modern medicine, yet the rapid spread of resistance threatens their effectiveness. Lactic acid bacteria (MKB) and bifidobacteria were recognised as a reservoir of resistance, but the actual risk posed by strains intentionally introduced into the agro-food chain (SZPK) has not yet been assessed. The aim of our study was to clarify whether these strains present a risk in terms of resistance. Four groups of MKB and bifidobacteria were included in the analyses ̶ in addition to strains from starter cultures or dietary supplements with live bacteria (probiotics), isolates from human milk or colostrum, intestinal mucosa or faeces, and fermented products. Phenotypic susceptibility was determined for 474 strains by microdilution and was most common in intestinal isolates. Antimicrobial resistance genes (ARG) and mobile genetic elements (MGE) were characterised in whole genomes of 1114 strains using comparative genomics. The results revealed that 13.8 % of the strains in the SZPK group contained acquired ARG, most frequently for tetracycline, however, mutations were also common. 75.5 % of acquired ARG were associated with MGE, whose potential for in vivo transmissibility was evaluated by examining metagenomic sequences. We confirmed that ARG and MGE were not as common in the SZPK group as in strains from human intestinal mucosa/faeces, suggesting that this group does not pose a significant threat. However, attention should be paid especially to individual probiotic strains that contain elements that have been shown to have high potential for transferability in the gut microbiota. These elements were uncommon in isolates of natural microbiota from fermented products and were atypical of starter cultures