Lactic acid bacteria (LAB) and bifidobacteria deliberately introduced into the food chain may act as a reservoir of antimicrobial resistance (AR), which is considered a safety concern. In the present study, resistance to antimicrobials of own and commercial probiotic and starter culture lactobacilli and bifidobacteria (n=20) was characterized based on integration of phenotypic and in silico data. Minimum inhibitory concentrations (MICs) were determined using broth microdilution and/or E-test. Antimicrobial resistance genes (ARG), mutations, genomic islands (GIs), and mobile genetic elements (MGE) were predicted in whole genome sequences (WGS) using different databases and tools (CARD, Resfams, ResFinder, ARG-ANNOT, FARME DB, IslandViewer4, PlasmidFinder, PointFinder, BLAST, HMMER3). In addition, a comprehensive in silico analysis of the prevalence of the tetW gene and its flanking sequences (FStetWs) across lactobacilli and bifidobacteria (n =1423) was conducted. Several strains exhibited phenotypic resistance to kanamycin, tetracycline, chloramphenicol, quinupristin-dalfopristin, ciprofloxacin, and neomycin. These resistances, however, did not always correspond to the presence of ARG and vice versa. We detected an acquired tetW gene in four probiotic strains of Bifidobacterium animalis subsp. lactis, whereas no acquired ARG were identified in genomes of lactobacilli. Nevertheless, homologs of AR proteins were predicted in all 20 proteomes. The prevalence of tetW, which is often flanked by MGE, was higher in analysed bifidobacteria (31.9 %) than lactobacilli (6.3 %). Results suggest that FStetWs may be associated with GIs and were conserved in several strains, including potential pathogens. Our findings provide an insight into AR of probiotic and starter cultures with an emphasis on tetracycline and into the safety of these strains in context of AR.
COBISS.SI-ID: 4320904
This paper describes the examination of human milk microbiota and is in close linkage to the topic of project “J4-1769 Resistomes of probiotic and starter cultures as potential risk factors for the spread of antibiotic resistance” since the isolates from human milk present an important group studied in the project, and since the methods introduced in the presented study, i.e. 16S rRNA gene next-generation sequencing (NGS) and cultivation/MALDI-TOF mass spectrometry, are important also in the project J4-1769. Moreover, all authors of this paper are members of the J4-1769 project team. The paper presented the factors that might influence human milk microbiota (HMM). Beside known factors that shape HMM, the association between infant’s consumption of probiotics and HMM was analysed. Staphylococcus and Streptococcus were found predominant genera in HMM. Administration of probiotics to infants was correlated with changes in HMM by increased OTU’s assigned to Firmicutes or Actinobacteria, specifically genus Lactobacillus. The study suggested that administration of probiotics to the suckling infant can influence HMM by increased abundance of lactobacilli and presence of viable probiotic bacteria in human milk. The observed association is most probably due to the possible transfer of bacteria from the infant’s mouth into the mammary gland via retrograde flow during suckling.
COBISS.SI-ID: 4326792