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Aim: The objective of this study was to investigate the antimicrobial resistance genes (ARGs) in plasmids of Enterobacteriaceae from soil, sewage, and feces of food-producing animals and humans., Methods and Results: The plasmid sequences were obtained from the NCBI database. For the identification of ARG, comprehensive antibiotic resistance database (CARD), and ResFinder were used. Gene conservation and evolution were investigated using DnaSP v.6. The transfer potential of the plasmids was evaluated using oriTfinder and a MOB-based phylogenetic tree was reconstructed using Fastree. We identified a total of 1064 ARGs in all plasmids analyzed, conferring resistance to 15 groups of antibiotics, mostly aminoglycosides, beta-lactams, and sulfonamides. The greatest number of ARGs per plasmid was found in enterobacteria from chicken feces. Plasmids from Escherichia coli carrying multiple ARGs were found in all ecosystems. Some of the most abundant genes were shared among all ecosystems, including aph(6)-Id, aph(3'')-Ib, tet(A), and sul2. A high level of sequence conservation was found among these genes, and tet(A) and sul2 are under positive selective pressure. Approximately 62% of the plasmids carrying at least one ARG were potentially transferable. Phylogenetic analysis indicated a potential co-evolution of Enterobacteriaceae plasmids in nature., Conclusion: The high abundance of Enterobacteriaceae plasmids from diverse ecosystems carrying ARGs reveals their widespread distribution and importance., (© The Author(s) 2024. Published by Oxford University Press on behalf of Applied Microbiology International.)

Antibiotic resistance in Citrobacter freundii is a public health concern. This study evaluated the closed genome of a C. freundii isolated from the stool of a hospitalized patient initially related to a Salmonella outbreak. Confirmation of the isolate was determined by whole-genome sequencing. Nanopore sequencing was performed using a MinION with a Flongle flow cell. Assembly using SPAdes and Unicycler yielded a closed genome annotated by National Center for Biotechnology Information Prokaryotic Genome Annotation Pipeline. Genomic analyses employed MLST 2.0, ResFinder4.1, PlasmidFinder2.1, and VFanalyzer. Phylogenetic comparison utilized the Center for Food Safety and Applied Nutrition (CFSAN)-single nucleotide polymorphism pipeline and Genetic Algorithm for Rapid Likelihood Inference. Antimicrobial susceptibility was tested by broth microdilution following Clinical and Laboratory Standards Institute criteria. Multi-locus sequence type in silico analysis assigned the C. freundii as sequence type 64 and the blaCMY-41 gene was detected in resistome investigation. The susceptibility to antibiotics, determined using Sensititre® plates, revealed resistance to aztreonam, colistin, cefoxitin, amoxicillin/clavulanic acid, sulfisoxazole, ampicillin, and streptomycin. The genetic relatedness of the C. freundii CFSAN077772 with publicly available C. freundii genomes revealed a close relationship to a C. freundii SRR1186659, isolated in 2009 from human stool in Tanzania. In addition, C. freundii CFSAN077772 is nested in the same cluster with C. freundii clinical strains isolated in Denmark, Mexico, Myanmar, and Canada, suggesting a successful intercontinental spread., (© The Author(s) 2024. Published by Oxford University Press on behalf of Applied Microbiology International.)

Aims: To evaluate the composition and functions of the gut microbiota in patients with decompensated alcohol-associated cirrhosis, with and without hepatic encephalopathy (HE)., Methods and Results: Faecal samples from 31 inpatients (20 with HE, 11 without HE), and from 18 age-balanced healthy controls (HC), were included. Microbial composition was determined by 16S rRNA amplicon sequencing and analysed using QIIME2. Metabolic pathways were inferred by PICRUSt2, and short-chain fatty acids (SCFAs) quantification was performed by gas chromatography. The gut microbiota of patients with HE was characterized by a diminished α-diversity, compared to no-HE (P < 0.01) and HC (P < 0.001) groups; β-diversity also differed between HE vs no-HE patients (P < 0.05), and between HE vs HC (P < 0.001). In patients with HE, Escherichia/Shigella, Burkholderiales and Lactobacillales taxa predominated. In contrast, patients without HE were characterized by Veillonella and Bacteroides. Reduced levels of faecal SCFAs in both groups correlated with a depletion of beneficial taxa, such as Ruminococcus or Faecalibacterium. PICRUSt2 analysis showed both an enhanced catabolism of arginine through ammonia-producing pathways and chorismate biosynthesis in HE patients, a key precursor of aromatic amino acids., Conclusions: The gut microbiota of HE patients exhibits a proinflammatory dysbiotic profile, plus metabolic pathways that produce potentially neurotoxic byproducts., (© The Author(s) 2023. Published by Oxford University Press on behalf of Applied Microbiology International.)

The aim of this work was to evaluate the anti-Escherichia coli effect of cell-free supernatant (CFS) of Lactobacillus spp. against planktonic and biofilm forms of foodborne isolates. Escherichiacoli strains (P12, P25, P35 and P36), previously isolated from fresh filets of fish, were subjected to antimicrobial susceptibility determination by the disc-diffusion agar method. Subsequently, the antagonistic effect between probiotic and pathogenic strains was determined by spot overlay assay. Finally, the CFS activity against pre-established (12 h) biofilms was demonstrated through biomass quantification by crystal violet staining and scanning electron microscopy (SEM). All isolates presented some pattern of resistance, primarily to ampicillin and tetracycline. Probiotic strains presented high antagonistic effects against all E. coli strains, presenting inhibition zones (R) ranging from 15.60 to 20.67 mm. Additionally, the residual biomass of pre-established (12 h) biofilm was drastically reduced about 50% after CFS treatment (P < 0.01). What can be noted by SEM images, which show less surface-attached cells of CFS-treated biofilms of E. coli (P12). Thus, cell-free preparations produced from Lactobacillus spp. may represent a tool in the battle against planktonic cells and biofilm forms of antibiotic-resistant E. coli., (© The Author(s) 2022. Published by Oxford University Press on behalf of Applied Microbiology International.)

Aim: To characterize a novel bacteriophage, En5822, isolated from the environment against Enterobacter cloacae and exploring its application as an alternate antimicrobial., Methods and Results: Bacteriophage was isolated from sewage sample by membrane-filtration immobilization technique. It was purified and studied for its various physical properties like microscopic structure, thermal and pH stability, latent period and burst time, antimicrobial and anti-biofilm activity as well as molecular aspects by genome sequencing and analysis. En5822 is a myovirus with relative pH and thermal stability. En5822 shows a notable reduction of host bacterial biofilm as well as planktonic cultures. Whole genome sequence analysis revealed that the En5822 genome does not contain undesirable temperate lifestyle genes, antibiotic resistance genes and toxin-encoding genes., Conclusions: En5822 displays high lytic activity, specificity and biofilm reduction capability. It has a short latent period and high burst size that aid faster activity. Its genomic and physical attributes offer possibilities for its as an alternative antimicrobial for the treatment of drug-resistant E. cloacae infections., Significance and Impact of Study: The study describes a novel, naturally virulent bacteriophage from environment capable of lysing multi-drug resistant E. cloacae effectively. The phage could potentially serve as an alternative strategy for treating antibiotic-resistant infections., (© 2021 The Society for Applied Microbiology.)

Legume root nodules harbor rhizobia and other non-nodulating endophytes known as nodule-associated bacteria (NAB) whose role in the legume symbiosis is still unknown. We analysed the genetic diversity of 34 NAB isolates obtained from the root nodules of faba bean grown under various soil conditions in Egypt using 16S rRNA and concatenated sequences of three housekeeping genes. All isolates were identified as members of the family Enterobacteriaceae belonging to the genera Klebsiella, Enterobacter and Raoultella. We identified nine enterobacterial genospecies, most of which have not been previously reported as NAB. All isolated strains harbored nifH gene sequences and most of them possessed plant growth-promoting (PGP) traits. Upon co-inoculation with an N2 fixing rhizobium (Rlv NGB-FR128), two strains (Enterobacter sichanensis NGB-FR97 and Klebsiella variicola NGB-FR116) significantly increased nodulation, growth and N-uptake of faba bean plants over the single treatments or the uninoculated control. The presence of these enterobacteria in nodules was significantly affected by the host plant genotype, symbiotic rhizobium genotype and endophyte genotype, indicating that the nodule colonization process is regulated by plant-microbe-microbe interactions. This study emphasizes the importance of nodule-associated enterobacteria and suggests their potential role in improving the effectiveness of rhizobial inoculants., (© The Author(s) 2021. Published by Oxford University Press on behalf of FEMS. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

Although different feeding habits have been reported for Sarcophaginae (Diptera, Sarcophagidae), most species are associated with decomposing organic matter such as feces and decaying corpses. This study provides the synanthropy index for males of species of Sarcophaginae collected during a 12-mo period in three different environments (urban, rural, and wild) of the state of Rio Grande do Sul, in Southern Brazil, linking this parameter with the sanitary issue. This article also investigated the presence of pathogenic bacteria on the external surface of Oxysarcodexia paulistanensis (Mattos), the most abundant species collected using a sanitized entomological net. Almost all the species collected most abundantly, including O. paulistanensis (n = 241), Ravinia advena (Walker) (n = 87), and O. thornax (Walker) (n = 58), were classified as synanthropic; O. thornax was the species with the highest synanthropy index (+80.3). Escherichia coli (Escherich), Shigella spp. (Enterobacteriaceae), and Staphylococcus aureus (Rosenbach) (Staphylococcaceae) were isolated and identified from the external surface of O. paulistanensis. The isolation and identification of pathogenic bacteria, and their synanthropic behavior, adds weight to potential role of some flesh flies, as O. paulistanensis, in a sanitary context., (© The Author(s) 2020. Published by Oxford University Press on behalf of Entomological Society of America. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

Aims: To investigate the microbiological and nutritional quality of liquid finisher pig feed on commercial production units and the factors influencing this., Methods and Results: Microbiological and physio-chemical analyses were performed on liquid feed sampled from the mixing tank and troughs of the finisher section of eight commercial pig units. Lactic acid bacteria, yeast and Escherichia coli counts, as well as lactic acid, ethanol and acetate concentrations were higher in residual feed sampled from the troughs compared with mixing tank samples (P < 0·001). Feed pH, as well as lysine, methionine and threonine concentrations and gross energy were all lower in the residual trough samples (P < 0·001). Liquid co-products reduced E. coli counts in the residual trough samples (P < 0·05), pH in the mixing tank (P < 0·01) and fresh trough samples (P < 0·05) and mould counts at all three sampling locations (P < 0·01) but sanitation practices had no impact., Conclusions: Even when considered unfermented, a considerable degree of spontaneous fermentation occurs in liquid feed, with resultant negative effects on nutritional quality., Significance and Impact of the Study: This is one of the first studies showing that uncontrolled fermentation of fresh liquid pig feed is commonplace on commercial units, highlighting the need for implementation of suitable control strategies., (© 2020 Society for Applied Microbiology.)

Escherichia coli O157:H7 is an important pathogenic Bacterium that threatens human health. A convenient, sensitive and specific method for the E. coli O157:H7 detection is necessary. We developed two pairs of monoclonal antibodies through traditional hybridoma technology, one specifically against E. coli O157 antigen and the other specifically against E. coli H7 antigen. Using these two pairs of antibodies, we developed two rapid test kits to specifically detect E. coli O157 antigen and E. coli H7 antigen, respectively. The detection sensitivity for O157 positive E. coli is 1 × 10 3 CFU per ml and for H7 positive E. coli is 1 × 10 4 CFU per ml. Combining these two pairs of antibodies together, we developed a combo test strip that can specifically detect O157: H7, with a detection sensitivity of 1 × 10 4 CFU per ml, when two detection lines are visible to the naked eye. This is currently the only rapid detection reagent that specifically detects O157: H7 by simultaneously detecting O157 antigen and H7 antigens of E. coli. Our product has advantages of simplicity and precision, and can be a very useful on-site inspection tool for accurate and rapid detection of E. coli O157:H7 infection., (© 2020 The Society for Applied Microbiology.)

Aim: Following previous research on improving the cleaning of crates used to transport broiler chickens from the farm to the abattoir, a demonstration project was undertaken to investigate improvements in crate washing on a commercial scale., Methods and Results: The soak tank of a conventional crate washing system was replaced with a high-performance washer fitted with high-volume, high-pressure nozzles. The wash water could be heated, and a greatly improved filtration system ensured that the nozzles did not lose performance or become blocked. Visual cleanliness scores and microbial counts were determined for naturally contaminated crates which had been randomly assigned to different cleaning protocols., Conclusions: When a combination of mechanical energy, heat and chemicals (i.e. detergent and disinfectant) was used, the results showed significant improvements to crate cleaning. Reductions of up to 3·6 and 3·8 log 10 CFU per crate base were achieved for Campylobacter and Enterobacteriaceae, respectively, along with a marked improvement in visual cleanliness., Significance and Impact of the Study: Broiler transport crates may become heavily contaminated with faeces and this may contribute to the spread of disease between farms. The results of this trial may be of use in reducing the spread of zoonotic pathogens in the poultry meat supply chain., (© 2020 The Society for Applied Microbiology.)

Advances in micro-organism identification techniques have resulted in increased knowledge of the diversity of prokaryotes and eukaryotes in silage. Such knowledge has enhanced the understanding of how fermentation occurs in forage crops with different characteristics and how the process can be improved to enhance silage quality. Undesirable micro-organisms can grow in silage when fermentation does not occur properly. Such micro-organisms may be pathogenic and/or produce toxic metabolic compounds; however, information on the consequences of these metabolites on the health of animals that consume silage is still lacking. The major challenge of ensilage is to produce high-quality feed that is nutritional, sanitary and stable, with a high dry matter recovery rate, in a process involving no interventions during fermentation and considerable variation in the characteristics of the substrates. It is important to note that each substrate has particularities and that we can only improve fermentation if we fully understand microbial diversity. This review is intended to update information related to the fermentation profile of silage, focusing on microbial diversity., (© 2019 The Society for Applied Microbiology.)

The increasing frequency of class A KPC enzymes, class B metallo-β-lactamases (MBLs) and class D OXA-48 enzymes in Enterobacteriaceae makes their early identification urgent. A simple commercial MASTDISCS combi Carba plus disc system (MAST-Carba plus) was designed for the identification of MBLs, KPC and OXA-48 carbapenemase genes in Enterobacteriaceae. To validate the MAST-Carba plus, a total of 77 isolates of carbapenemase-producing Enterobacteriaceae (CPE) and 84 isolates of noncarbapenemase-producing Enterobacteriaceae (non-CPE) were selected for differentiation of the genes of Enterobacteriaceae by MAST-Carba plus. Meanwhile, the carbapenemase genes such as bla KPC , bla IMP , bla VIM , bla NDM-1 and bla OXA-48 were detected by PCR (polymerase chain reaction). Thus, when considered on the basis of PCR results, the sensitivity of MAST-Carba plus detection of KPC strains is 82·3%, the specificity is 100·0%, the positive predictive value is 100·0% and the negative predictive value is 92·4%. For MBLs strains, the sensitivity is 100·0%, the specificity is 97·1%, the positive predictive value is 84·6% and the negative predictive value is 100·0%. For OXA-48 strains, the sensitivity is 100·0%, the specificity is 99·4%, the positive predictive value is 80·0% and the negative predictive value is 100·0%. Our findings suggest that MAST-Carba plus is a rapid and promising method for identifying the MBLs, KPC and OXA-48 carbapenemase genes in Enterobacteriaceae, which could be exploited in basic microbiology laboratory to prevent the transmission of CPE. SIGNIFICANCE AND IMPACT OF THE STUDY: Not only detection of carbapenemases but also identification of their genes accurately and rapidly in Enterobacteriaceae is still a major challenge for clinical laboratories in order to prevent the transmission of carbapenemase-producing Enterobacteriaceae (CPE). Therefore, this study aimed to evaluate the performance of a new rapid method (MASTDISCS combi Carba plus) for the identification of metallo-β-lactamases (MBLs), KPC and OXA-48 carbapenemase genes in Enterobacteriaceae clinical isolates., (© 2019 The Society for Applied Microbiology.)

Salmonella enterica is one of the most common pathogens associated with produce outbreaks worldwide; nonetheless, the mechanisms uncovering their interaction with plants are elusive. Previous reports demonstrate that S. enterica ser. Typhimurium (STm), similar to the phytopathogen Pseudomonas syringae pv. tomato (Pst) DC3000, triggers a transient stomatal closure suggesting its ability to overcome this plant defense and colonize the leaf apoplast. In order to discover new molecular players that function in the stomatal reopening by STm and Pst DC3000, we performed an Arabidopsis mutant screening using thermal imaging. Further stomatal bioassay confirmed that the mutant plants exo70h4-3, sce1-3, bbe8, stp1, and lsu2 have smaller stomatal aperture widths than the wild type Col-0 in response to STm 14028s. The mutants bbe8, stp1 and lsu2 have impaired stomatal movement in response to Pst DC3000. These findings indicate that EXO70H4 and SCE1 are involved in bacterial-specific responses, while BBE8, STP1, and LSU2 may be required for stomatal response to a broad range of bacteria. The identification of new molecular components of the guard cell movement induced by bacteria will enable a better understanding of the initial stages of plant colonization and facilitate targeted prevention of leaf contamination with harmful pathogens., (© FEMS 2019.)

Aims: This study investigated the occurrence and genetic diversity of Enterobacteriaceae with extended-spectrum β-lactamase (ESBL)-, AmpC- and carbapenemase-mediated resistance in British beef cattle, and related risk factors., Methods and Results: Faecal samples (n = 776) were obtained from farms in England and Wales (n = 20) and Scotland (n = 20) in 2015. Isolates from selective agars were identified by MALDI ToF mass spectrometry. Selected isolates were characterized by multiplex PCR (bla CTX -M, bla OXA , bla SHV and bla TEM genes), whole-genome sequencing (WGS), minimum inhibitory concentrations and pulsed-field gel electrophoresis. None of the faecal samples yielded carbapenem-resistant Escherichia coli. Ten (25%) of the farms tested positive for ESBL-producing CTX-M Enterobacteriaceae, 15 (37·5%) of the farms were positive for AmpC phenotype E. coli and none were positive for carbapenem-resistant E. coli. WGS showed a total of 30 different resistance genes associated with E. coli, Citrobacter and Serratia from ESBL agars, and colocation of resistance genes with bla CTX -M1 . Buying bulls and bringing in fattening cattle from another farm were identified as significant risk factors for positive samples harbouring CTX-M Enterobacteriaceae or AmpC phenotype E. coli respectively., Conclusions: Beef cattle on a proportion of farms in GB carry ESBL-producing Enterobacteriaceae. Factors, such as operating as a closed herd, may have an important role in reducing introduction and transmission of resistant Enterobacteriaceae. The results indicate management factors may play an important role in impacting ESBL prevalence. In particular, further study would be valuable to understand the impact of maintaining a closed herd on reducing the introduction of resistant Enterobacteriaceae., Significance and Impact of the Study: This is the first study showing the presence of ESBL-producing Enterobacteriaceae in British beef cattle., (© 2019 The Society for Applied Microbiology.)

Aim: Control of operations of catfish farmers still lacks in Nigeria due to the absence of catfish inspection programmes by relevant regulatory agencies. Thus, this study aimed at performing comprehensive surveillance of Nigerian catfish pisciculture systems so as to provide empirical evidence on the extent of contamination with multidrug-resistant bacteria due to potential abuse of standard operational procedures by catfish farmers., Methods and Results: One-way analysis of variance was performed on pond water and catfish samples which were randomized with the Wei's-Urn randomization modelling technique. Ceftriaxone-selected bacterial colonies isolated from catfish and pond water samples collected from nursery and grow-out pond systems were tested for multidrug resistance. Haemocytotoxigenic and Shiga toxigenic virulence traits in multidrug-resistant colonies, as well as detection of hyper-Ambler class C-(AmpC) beta-lactamase and carbapenemase production, were also performed using phenotypic/molecular methods. Of the 648 ceftriaxone-selected bacterial isolates examined in this study, 515 isolates were found to be multidrug-resistant bacteria, of which 366 isolates were characterized as pathogenic multidrug-resistant bacteria. Both nursery and grow-out ponds had high frequencies of bacterial resistance to ampicillin (86-93%), cotrimoxazole (47-87%) and chloramphenicol (95-100%). However, high frequencies of bacterial resistance to amoxicillin/clavulanic acid (75-83%) were only observed in the grow-out ponds. Also, hyper-AmpC beta-lactamase-producing multidrug-resistant bacteria were only seen in the grow-out ponds. Isolated multidrug-resistant bacteria were confirmed as Enterobacter cloacae, Citrobacter freundii, Bacillus cereus, Pseudomonas aeruginosa, Escherichia coli and Enterococcus faecalis., Conclusion: The findings in this study corroborate the urgent need for some form of international mediation to urge the Nigerian government and her regulatory agencies to commence monitoring of catfish pisciculture operations since multidrug-resistant bacteria could be transmitted to humans., Significance and Impact of the Study: Our study provided empirical evidence that revealed the misuse/abuse of antibiotics during pisciculture operations in Nigeria; thus, constituting these pisciculture systems into reservoirs of multidrug-resistant bacteria., (© 2018 The Society for Applied Microbiology.)

Aims: The goal of this research is to model the effects of two osmotic solutions factors on the reduction of selected microorganisms, and to assess the application in osmotic dehydration process of animal raw materials from the aspect of microbiological safety., Methods and Results: Sugar beet molasses and aquatic osmotic solution were prepared and inoculated with Escherichia coli, Listeria monocytogenes and Salmonella spp. Varied factors of osmotic solutions were: time, temperature and concentration of osmotic solutions. Samples of osmotic solutions were subjected to standard and modified microbiological ISO methods. The result showed that increase in factors had a positive effect on the reduction of microbiological load, while the time of the process was the most influential technological parameter. Number of L. monocytogenes was reduced to <10 CFU per g at the end of the process in the highest concentration of sugar beet molasses at all process temperatures., Conclusions: Developed mathematical models of reduction ratios for tested microorganisms were statistically significant, allowing good prediction of reduction ratio values based on applied factors., Significance and Impact of the Study: Obtained levels of reduction of all tested microorganisms present good base for the production of safe osmotically dehydrated products of animal origin., (© 2018 The Society for Applied Microbiology.)

Multidrug-resistant bacteria have become common all over the world, necessitating the development of new therapeutic strategies. Synergistic interactions between conventional antibiotics and natural bioactive may have therapeutic benefits in a clinical setting. There are plenty of medicinal plants that have proven efficacy against broad spectrum of micro-organisms. The aim of the work was to assess the antibacterial activity of Cladanthus arabicus, a Moroccan medicinal plant, and Bubonium imbricatum, a Moroccan endemic plant. The evaluation of the synergistic effect of extracted essential oils (EOs) together with some conventional antibiotics was also investigated. Checkerboard test was used to evaluate the interaction of EOs in combination with amoxicillin and neomycin. The results showed that EOs contain a potent activity against the tested Enterobacteriaceae isolates, with inhibition zones values in the range of 8·05 ± 0·1 and 13·1 ± 0·11 mm and MIC values between 200 μg ml -1 to 800 μg ml -1 for C. arabicus and from 400 μg ml -1 to 1600 μg ml -1 for B. imbricatum, respectively. Moreover, the current study allowed concluding that both EOs showed not only satisfactory antibacterial properties but also active effects combined with conventional antibiotics demonstrated by the Fractional Inhibitory Concentration Index (FICI). These findings are very interesting since there are no previous studies on synergistic interactions of these two plants with antibiotics., Significance and Impact of the Study: The development of antibiotic resistance is multifactorial, including the specific nature of the relationship of bacteria to antibiotics. This situation has forced scientists to search for new antimicrobial substances from various sources as novel antimicrobial chemotherapeutic agents. Recently, medicinal plants and their derivatives (essential oils, extracts) have become very important in therapeutics because they encounter minimal challenges of the emergence of resistance. In this direction, the antimicrobial activity of the endemic Bubonium imbricatum plant and medicinal Cladanthus arabicus plant essential oils against multidrug-resistant Enterobacteriaceae strains was demonstrated., (© 2018 The Society for Applied Microbiology.)

Aims: The aim of this study was to examine the antimicrobial properties of novel aqueous natural rapeseed oil/saline emulsions containing different soluble components of spruce resin., Methods and Results: The composition of aqueous resin emulsions was analysed by GC-MS and their antimicrobial properties were studied with challenge tests and with turbidometric assays. The emulsions were strongly antimicrobial against common Gram-positive and Gram-negative bacteria (including MRSA) as well as common yeasts. Furthermore, they inhibited the biofilm formation and eradicated the microbial biofilms on tested microbes. Characteristic for the emulsions was the presence of oxidized resin acids. Other main components present in emulsions, such as lignans and coumaric acids, were not antimicrobial, when tested separately., Conclusions: The results indicated that the oxidized resin acids were the antimicrobial components in the emulsions. Also, there appears to be a stoichiometric relationship between the number of resin acid molecules and the number microbe cells in the antimicrobial action., Significance and Impact of the Study: The fact that these solutions do not contain abietic acid, which is the main allergenic compound in resins, suggests that these solutions would be suitable, well-tolerated antimicrobials for various medical applications. The aqueous formulation will also allow the expansion of the use of these emulsions in from medical applications to the food preservatives and disinfectants., (© 2017 The Authors. Journal of Applied Microbiology published by John Wiley & Sons Ltd on behalf of the Society for Applied Microbiology.)