Prevalence and diversity of tetracycline resistant lactic acid bacteria and their tet genes along the process line of fermented dry sausages. - Related Documents




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358901.0000Prevalence and diversity of tetracycline resistant lactic acid bacteria and their tet genes along the process line of fermented dry sausages. In order to study the prevalence and diversity of tetracycline resistant lactic acid bacteria (Tc(r) LAB) along the process line of two different fermented dry sausage (FDS) types, samples from the raw meat, the meat batter and the fermented end product were analysed quantitatively and qualitatively by using a culture-dependent approach. Both the diversity of the tet genes and their bacterial hosts in the different stages of FDS production were determined. Quantitative analysis showed that all raw meat components of both FDS types (FDS-01 and FDS-08) contained a subpopulation of Tc(r) LAB, and that for FDS-01 no Tc(r) LAB could be recovered from the samples after fermentation. Qualitative analysis of the Tc(r) LAB subpopulation in FDS-08 included identification and typing of Tc(r) LAB isolates by (GTG)5-PCR fingerprinting, plasmid profiling, protein profiling and a characterization of the resistance by PCR detection of tet genes. Two remarks can be made when the results of this analysis for the different samples are compared. (i) The taxonomic diversity of Tc(r) LAB varies along the process line, with a higher diversity in the raw meat (lactococci, lactobacilli, streptococci, and enterococci), and a decrease after fermentation (only lactobacilli). (ii) Also the genetic diversity of the tet genes varies along the process line. Both tet(M) and tet(S) were found in the raw meat, whereas only tet(M) was found after fermentation. A possible relationship was found between the disappearing of species other than lactobacilli and tet(S), because tet(S) was only found in lacotocci, enterococci, and streptococci. These data suggest that fermented dry sausages are among those food products that can serve as vehicles for Tc(r) LAB and that the raw meat already contains a subpopulation of these bacteria. Whether these results reflect the transfer of resistant bacteria or of bacterial resistance genes from animals to man via the food chain is difficult to ascertain and may require a combination of cultivation-dependent and cultivation-independent approaches.200312866855
279510.9998Molecular identification and quantification of tetracycline and erythromycin resistance genes in Spanish and Italian retail cheeses. Large antibiotic resistance gene pools in the microbiota of foods may ultimately pose a risk for human health. This study reports the identification and quantification of tetracycline- and erythromycin-resistant populations, resistance genes, and gene diversity in traditional Spanish and Italian cheeses, via culturing, conventional PCR, real-time quantitative PCR (qPCR), and denaturing gradient gel electrophoresis (DGGE). The numbers of resistant bacteria varied widely among the antibiotics and the different cheese varieties; in some cheeses, all the bacterial populations seemed to be resistant. Up to eight antibiotic resistance genes were sought by gene-specific PCR, six with respect to tetracycline, that is, tet(K), tet(L), tet(M), tet(O), tet(S), and tet(W), and two with respect to erythromycin, that is, erm(B) and erm(F). The most common resistance genes in the analysed cheeses were tet(S), tet(W), tet(M), and erm(B). The copy numbers of these genes, as quantified by qPCR, ranged widely between cheeses (from 4.94 to 10.18log10/g). DGGE analysis revealed distinct banding profiles and two polymorphic nucleotide positions for tet(W)-carrying cheeses, though the similarity of the sequences suggests this tet(W) to have a monophyletic origin. Traditional cheeses would therefore appear to act as reservoirs for large numbers of many types of antibiotic resistance determinants.201425302306
279620.9997Distribution of specific tetracycline and erythromycin resistance genes in environmental samples assessed by macroarray detection. A macroarray system was developed to screen environmental samples for the presence of specific tetracycline (Tc(R)) and erythromycin (erm(R)) resistance genes. The macroarray was loaded with polymerase chain reaction (PCR) amplicons of 23 Tc(R) genes and 10 erm(R) genes. Total bacterial genomic DNA was extracted from soil and animal faecal samples collected from different European countries. Macroarray hybridization was performed under stringent conditions and the results were analysed by fluorescence scanning. Pig herds in Norway, reared without antibiotic use, had a significantly lower incidence of antibiotic resistant bacteria than those reared in other European countries, and organic herds contained lower numbers of resistant bacteria than intensively farmed animals. The relative proportions of the different genes were constant across the different countries. Ribosome protection type Tc(R) genes were the most common resistance genes in animal faecal samples, with the tet(W) gene the most abundant, followed by tet(O) and tet(Q). Different resistance genes were present in soil samples, where erm(V) and erm(E) were the most prevalent followed by the efflux type Tc(R) genes. The macroarray proved a powerful tool to screen DNA extracted from environmental samples to identify the most abundant Tc(R) and erm(R) genes within those tested, avoiding the need for culturing and biased PCR amplification steps.200717298370
360330.9997Diversity of tet resistance genes in tetracycline-resistant bacteria isolated from a swine lagoon with low antibiotic impact. Tetracycline resistance has been extensively studied and shown to be widespread. A number of previous studies have clearly demonstrated that a variety of tetracycline resistance genes are present in swine fecal material, treatment lagoons, and the environments surrounding concentrated animal feeding operations (CAFOs). The diversity of tetracycline resistance within a swine lagoon located at a CAFO that used only bacitricin methylene disalicylate as an antibiotic was evaluated by screening 85 tetracycline-resistant isolates for the presence of 18 different genes by performing PCR with primers that target tetracycline efflux genes of Gram-negative bacteria and ribosomal protection proteins. In addition, partial 16S rRNA sequences from each of these isolates were sequenced to determine the identity of these isolates. Of the 85 isolates examined, 17 may represent potential novel species based on BLAST results. Greater than 50% of the isolates (48 out of 85) were found to not contain targeted tet efflux genes. Though minimum inhibitory concentrations ranged widely (16 - >256 mg/L), these values did not give an indication of the tet genes present. Ten new genera were identified that contain at least one tet efflux gene. Five other genera possessed tet efflux genes that were not found in these organisms previously. Interestingly, none of the isolates possessed any of the selected ribosomal protection protein genes. Though tetracycline resistance was found in bacteria isolated from a swine CAFO lagoon, it appears that the limited antibiotic use at this CAFO might have impacted the presence and diversity of tetracycline resistance genes.200718059563
590840.9997Evaluation of Tetracycline Resistance and Determination of the Tentative Microbiological Cutoff Values in Lactic Acid Bacterial Species. Lactic acid bacteria (LAB) are widely used as probiotics in the food industry owing to their beneficial effects on human health. However, numerous antibiotic resistance genes have been found in LAB strains, especially tetracycline resistance genes. Notably, the potential transferability of these genes poses safety risks. To comprehensively evaluate tetracycline resistance in LAB, we determined the tetracycline susceptibility patterns of 478 LAB strains belonging to four genera and eight species. By comparing phenotypes with genotypes based on genome-wide annotations, five tetracycline resistance genes, tet(M), tet(W/N/W), tet(L), tet(S), and tet(45), were detected in LAB. Multiple LAB strains without tetracycline resistance genes were found to be resistant to tetracycline at the currently recommended cutoff values. Thus, based on the minimum inhibitory concentrations of tetracycline for these LAB strains, the species-specific microbiological cutoff values for Lactobacillus (para)gasseri, Lactobacillus johnsonii, and Lactobacillus crispatus to tetracycline were first developed using the Turnidge, Kronvall, and eyeball methods. The cutoff values for Lactiplantibacillus plantarum were re-established and could be used to better distinguish susceptible strains from strains with acquired resistance. Finally, we verified that these five genes play a role in tetracycline resistance and found that tet(M) and tet(W/N/W) are the most widely distributed tetracycline resistance genes in LAB.202134683449
360650.9997Presence of specific antibiotic (tet) resistance genes in infant faecal microbiota. The widespread use of antibiotics for medical and veterinary purposes has led to an increase of microbial resistance. The antibiotic resistance of pathogenic bacteria has been studied extensively. However, antibiotics are not only selective for pathogens: they also affect all members of the gut microbiota. These microorganisms may constitute a reservoir of genes carrying resistance to specific antibiotics. This study was designed to characterize the gut microbiota with regard to the presence of genes encoding tetracycline resistance proteins (tet) in the gut of healthy exclusively breast-fed infants and their mothers. For this purpose we determined the prevalence of genes encoding ribosomal protection proteins (tet M, tet W, tet O, tet S, tet T and tet B) by PCR and characterized the gut microbiota by FISH in stools of infants and their mothers. The gene tet M was found in all the breast-fed infants and their mothers. tet O was found in all of the mothers' samples, whilst only 35% of the infants harboured this gene. tet W was less frequently found (85% of the mothers and 13% of the infants). None of the other genes analysed was found in any sample. Our results suggest that genes carrying antibiotic resistance are common in the environment, as even healthy breast-fed infants with no direct or indirect previous exposure to antibiotics harbour these genes.200616965348
281460.9997Fate of antimicrobial-resistant enterococci and staphylococci and resistance determinants in stored poultry litter. The use of antimicrobials in commercial broiler poultry production results in the presence of drug-resistant bacteria shed in the excreta of these birds. Because these wastes are largely land-disposed these pathogens can affect the surrounding environment and population. In this analysis, we characterized the survival of antimicrobial-resistant enterococci and staphylococci and resistance genes in poultry litter. Temperature, moisture, and pH were measured in the litter over a 120-day period from storage sheds at three conventional US broiler chicken farms, as well as colony-forming units of Enterococcus spp. and Staphylococcus spp. Selected isolates from each sampling event were tested for resistance to eight antimicrobials used in poultry feeds as well as the presence of resistance genes and mobile genetic elements. Temperatures greater than 60 degrees C were only intermittently observed in the core of the litter piles. Both antimicrobial-resistant enterococci and staphylococci, as well as resistance genes persisted throughout the 120-day study period. Resistance genes identified in the study include: erm(A), erm(B), erm (C), msr(A/B), msr(C), and vat(E). This study indicates that typical storage practices of poultry litter are insufficient for eliminating drug-resistant enterococci and staphylococci, which may then be released into the environment through land disposal.200919541298
528970.9997Examination of the Aerobic Microflora of Swine Feces and Stored Swine Manure. Understanding antibiotic resistance in agricultural ecosystems is critical for determining the effects of subtherapeutic and therapeutic uses of antibiotics for domestic animals. This study was conducted to ascertain the relative levels of antibiotic resistance in the aerobic bacterial population to tetracycline, tylosin, and erythromycin. Swine feces and manure samples were plated onto various agar media with and without antibiotics and incubated at 37°C. Colonies were counted daily. Randomly selected colonies were isolated and characterized by 16S rRNA sequence analyses and additional antibiotic resistance and biochemical analyses. Colonies were recovered at levels of 10 to 10 CFU mL for swine slurry and 10 to 10 CFU g swine feces, approximately 100-fold lower than numbers obtained under anaerobic conditions. Addition of antibiotics to the media resulted in counts that were 60 to 80% of those in control media without added antibiotics. Polymerase chain reaction analyses for antibiotic resistance genes demonstrated the presence of a number of different resistance genes from the isolates. The recoverable aerobic microflora of swine feces and manure contain high percentages of antibiotic-resistant bacteria, which include both known and novel genera and species, and a variety of antibiotic resistance genes. Further analyses of these and additional isolates should provide additional information on these organisms as potential reservoirs of antibiotic resistance genes in these ecosystems.201627065407
600180.9997Assessment of horizontal gene transfer in Lactic acid bacteria--a comparison of mating techniques with a view to optimising conjugation conditions. Plate, filter and broth mating techniques were assessed over a range of pHs using three Lactococcus lactis donor strains (one with an erythromycin resistance marker and two with tetracycline resistance markers, all located on transferable genetic elements) and one L. lactis recipient strain. Transconjugants were confirmed using antibiotic selection, E-tests to determine MICs, PCR assays to detect the corresponding marker genes, DNA fingerprinting by pulsed-field gel electrophoresis (PFGE), and Southern blotting. Horizontal gene transfer (HGT) rates varied (ranging from 1.6 x 10(-1) to 2.3 x 10(-8)). The general trend observed was plate > filter > broth, independent of pH. Our data suggests that standardisation of methodologies to be used to assess HGT, is warranted and would provide a meaningful assessment of the ability of commensal and other bacteria in different environments to transfer relevant markers.200919135099
313190.9997Integron-containing bacteria in faeces of cattle from different production systems at slaughter. AIMS: To determine the prevalence and characteristics of integron-containing bacteria in faeces of cattle from grass-fed, lot-fed, or organically produced cattle. METHODS AND RESULTS: Faecal samples from grass-fed (n = 125), lot-fed (n = 125) and organic (n = 135) cattle were tested for the presence of class 1 and class 2 integrons by using PCR and colony hybridisation. The prevalence of class 1 and class 2 integrase were higher in lot-fed cattle (71% and 62%) than grass-fed cattle (52% and 30%) which in turn were higher than organic cattle (25% and 11%). Isolation rates of integron-containing bacteria were reflective of PCR prevalence results. CONCLUSIONS: The antimicrobial resistance genes harboured by the integrons differed little across the three systems and were typically to antimicrobials that would rarely be used therapeutically or for growth promotion purposes. The differences in prevalence observed between the systems may be a function of the intensiveness of each system. SIGNIFICANCE AND IMPACT OF THE STUDY: Integron-containing bacteria may be present in all cattle production systems regardless of the amount of antimicrobial use and confirms that the prudent use of antimicrobials is required so that the development of integrons harbouring genes significant to human medicine is avoided.200919302491
2813100.9997Quantity of the tetracycline resistance gene tet(M) differs substantially between meat at slaughterhouses and at retail. Concentrations of the tetracycline resistance gene tet(M) per square centimeter were assessed in meat from the slaughterhouse (n = 100) and from retail (n = 100) by real-time quantitative PCR. The study revealed a substantial contamination of retail meat with the tetracycline resistance gene tet(M), with a mean of 4.34 log copies per cm² fasces in chicken and 5.58 log copies per cm² fasces in pork. Quantitative resistance gene analysis provides an interesting tool for risk assessment and is becoming increasingly important. For both chicken and pork, tet(M) concentrations were significantly higher in meat at retail, compared to meat at slaughter. Cultural investigations revealed substantial differences in the prevalence of listeria and enterococci, and of E. coli and coliforms, between meat at slaughter (n = 500) and at retail (n = 500). However, the differences in the prevalence of 2 investigated groups of potential tet(M)-carriers (enterococci, listeria) could not sufficiently explain the differences in tet(M) concentrations, since increasing concentrations of tet(M) were accompanied by decreasing prevalences of these potential tet(M)-carriers. The percentage of tetracycline susceptible indicator bacteria (E. faecalis, E. coli) did not differ between meat at slaughter and meat at retail. Higher concentrations of tet(M) at retail might correlate with the proliferation of other genera than enterococci and listeria, but there is also a reason to discuss whether secondary contaminants might carry tet(M) more often than the primary flora of meat. PRACTICAL APPLICATION: We successfully applied the direct quantitative monitoring of resistance genes in meat, which generally might aid as a useful and rapid additional tool for risk assessment. We know that bacteria provide a large pool of resistance genes, which are widely shared between each other-the larger the pool is, the more genes might be exchanged. Thus, in terms of resistance gene monitoring, we should sometimes overcome the restricted view on single bacteria and look at the gene pool, instead.201121729069
5995110.9997In vitro conjugal transfer of tetracycline resistance from Lactobacillus isolates to other Gram-positive bacteria. The ability of 14 Lactobacillus strains, isolated from fermented dry sausages, to transfer tetracycline resistance encoded by tet(M) through conjugation was examined using filter mating experiments. Seven out of 14 tetracycline-resistant Lactobacillus isolates were able to transfer in vitro this resistance to Enterococcus faecalis at frequencies ranging from 10(-4) to 10(-6) transconjugants per recipient. Two of these strains could also transfer their resistance to Lactococcus lactis subsp. lactis, whereas no conjugal transfer to a Staphylococcus aureus recipient was found. These data suggest that meat lactobacilli might be reservoir organisms for acquired resistance genes that can be spread to other lactic acid bacteria. In order to assess the risk of this potential hazard, the magnitude of transfer along the food chain merits further research.200312900030
3530120.9997Occurrence of the transferable copper resistance gene tcrB among fecal enterococci of U.S. feedlot cattle fed copper-supplemented diets. Copper, an essential micronutrient, is supplemented in the diet at elevated levels to reduce morbidity and mortality and to promote growth in feedlot cattle. Gut bacteria exposed to copper can acquire resistance, which among enterococci is conferred by a transferable copper resistance gene (tcrB) borne on a plasmid. The present study was undertaken to investigate whether the feeding of copper at levels sufficient to promote growth increases the prevalence of the tcrB gene among the fecal enterococci of feedlot cattle. The study was performed with 261 crossbred yearling heifers housed in 24 pens, with pens assigned randomly to a 2×2 factorial arrangement of treatments consisting of dietary copper and a commercial linseed meal-based energy protein supplement. A total of 22 isolates, each identified as Enterococcus faecium, were positive for tcrB with an overall prevalence of 3.8% (22/576). The prevalence was higher among the cattle fed diets supplemented with copper (6.9%) compared to normal copper levels (0.7%). The tcrB-positive isolates always contained both erm(B) and tet(M) genes. Median copper MICs for tcrB-positive and tcrB-negative enterococci were 22 and 4 mM, respectively. The transferability of the tcrB gene was demonstrated via a filter-mating assay. Multilocus variable number tandem repeat analysis revealed a genetically diverse population of enterococci. The finding of a strong association between the copper resistance gene and other antibiotic (tetracycline and tylosin) resistance determinants is significant because enterococci remain potential pathogens and have the propensity to transfer resistance genes to other bacteria in the gut.201323666328
4612130.9997Assessment of tetracycline and erythromycin resistance transfer during sausage fermentation by culture-dependent and -independent methods. The food chain is considered one of the main routes of antibiotic resistance diffusion between animal and human population. The resistance to antimicrobial agents among enterococci could be related to the efficient exchange of transferable genetic elements. In this study a sausage model was used to evaluate the persistence of antibiotic resistant enterococci during meat fermentation and to assess horizontal gene transfer among bacteria involved in meat fermentation. Enterococcus faecalis OG1rf harbouring either pCF10 or pAMβ1 plasmid was used as donor strain. The analysis of population dynamics during fermentation confirmed that the human isolate E. faecalis OG1rf was able to colonize the meat ecosystem with similar growth kinetics to that of food origin enterococci and to transfer the mobile genetic elements coding for tetracycline and erythromycin resistances. Transconjugant strains were detected after only two days of fermentation and increased their numbers during ripening even in the absence of selective antibiotic pressure. By means of culture-dependent and -independent molecular techniques, transconjugant strains carrying both tetracycline and erythromycin resistance genes were identified in enterococci, pediococci, lactobacilli and staphylococci groups. Our results suggest that the sausage model provides a suitable environment for horizontal transfer of conjugative plasmids and antibiotic resistance genes among food microbiota.201222365347
2818140.9997Tetracycline resistance associated with commensal bacteria from representative ready-to-consume deli and restaurant foods. Proper knowledge of antibiotic resistance (AR) dissemination is essential for effective mitigation. This study examined the profiles of tetracycline-resistant (Tetr) commensal bacteria from representative ready-to-consume food samples from salad bars at local grocery stores and restaurants. Out of 900 Tetr isolates examined, 158 (17.6%) carried one or more of tetM, tetL, tetS, and tetK genes by conventional PCR, 28 harbored more than one Tetr determinants. The most prevalent genotype was tetM, which was detected in 70.9% of the AR gene carriers, followed by tetL (31.6%), tetS (13.9%), and tetK (2.5%). Identified AR gene carriers included Enterococcus, Lactococcus, Staphylococcus, Brochothrix, Carnobacterium, Stenotrophomonas, Pseudomonas, and Sphingobacterium, by 16S rRNA gene sequence analysis. AR determinants were successfully transmitted, and led to resistance in Streptococcus mutans via natural gene transformation and Enterococcus faecalis via electroporation, suggesting the functionality and mobility of the AR genes from the food commensal bacteria. In addition, the AR traits in many isolates are quite stable, even in the absence of the selective pressure. The identification of new commensal carriers for representative AR genes revealed the involvement of a broad spectrum of bacteria in the horizontal transmission of AR genes. Meanwhile, the spectrum of the antibiotic-resistant bacteria differed from the spectrum of the total bacteria (by denaturing gradient gel electrophoresis) associated with the food items. Our data revealed a common avenue in AR exposure and will assist in proper risk assessment and the development of comprehensive mitigation strategies to effectively combat AR.201021067672
5634150.9997Effects of antibiotic use in sows on resistance of E. coli and Salmonella enterica Typhimurium in their offspring. To determine effects of exposure of parental animals to antibiotics on antibiotic resistance in bacteria of offspring, sows were either treated or not treated with oxytetracycline prior to farrowing and their pigs were challenged with Salmonella enterica Typhimurium and treated or not treated with oxytetracycline and apramycin. Fecal Escherichia coli were obtained from sows, and E. coli and salmonella were recovered from pigs. Antibiotic resistance patterns of isolates were determined using a minimum inhibitory concentration (MIC) analysis. Polymerase chain reaction (PCR) and electroporation were used to characterize the genetic basis for the resistance and to determine the location of resistance genes. Treatments had little effect on resistance of the salmonella challenge organism. The greatest resistance to apramycin occurred in E. coli from pigs treated with apramycin and whose sows had earlier exposure to oxytetracycline. Resistance to oxytetracycline was consistently high throughout the study in isolates from all pigs and sows; however, greater resistance was noted in pigs nursing sows that had previous exposure to that drug. The aac(3)-IV gene, responsible for apramycin resistance, was found in approximately 90% of apramycin-resistant isolates and its location was determined to be on plasmids. Several resistant E. coli bio-types were found to contain the resistance gene. These results indicate that resistance to apramycin and oxytetracycline in E. coli of pigs is affected by previous use of oxytetracycline in sows.200516156702
2797160.9996Widespread distribution of tetracycline resistance genes in a confined animal feeding facility. We sought to determine the distribution of resistance and the tetracycline resistance genes among bacteria isolated from a swine confined animal feeding facility where tetracycline-containing feed had been in use for over 20 years. Samples collected from feed, hogs, hog houses, waste lagoon, soil, surface water and well water were screened for the presence of (a) resistant Escherichia coli and enterococci and (b) tetracycline-resistant strains of all species. Genomic DNA was extracted from the latter strain collection and fragments from 16S rDNA and ten tetracycline resistance genes (tetA, tetB, tetC, tetE, tetH, tetL, tetM, tetS, tetT and rumB) were polymerase chain reaction-amplified and a partial nucleotide sequence was obtained. In this environment, 77% of E. coli and 68% of enterococci isolated were tetracycline resistant. Tetracycline resistance was found in 26 different bacterial genera and in 60 species. Single resistance gene alleles (as defined by nucleotide sequence) were present in multiple species. There was evidence of gene recombination and multiple different tetracycline resistance genes were present in single bacterial isolates. These data provide further evidence for the widespread distribution of resistance genes in microbial populations in settings in which there is ongoing subtherapeutic antimicrobial use.200717287111
5647170.9996Resistance of bacterial isolates from poultry products to therapeutic veterinary antibiotics. Bacterial isolates from poultry products were tested for their susceptibility to 10 antibiotics commonly used in the therapeutic treatment of poultry. Bacteria were isolated from fresh whole broiler carcasses or from cut-up meat samples (breast with or without skin, wings, and thighs) that were either fresh or stored at 4 or 13 degrees C (temperatures relevant to poultry-processing facilities). The Biolog system was used to identify isolates, and a broth dilution method was used to determine the antibiotic resistance properties of both these isolates and complementary cultures from the American Type Culture Collection. The antibiotics to which the most resistance was noted were penicillin G, sulfadimethoxine, and erythromycin; the antibiotic to which the least resistance was noted was enrofloxacin. Individual isolates exhibited resistances to as many as six antibiotics, with the most common resistance pattern involving the resistance of gram-negative bacteria to penicillin G, sulfadimethoxine, and erythromycin. Differences in resistance patterns were noted among 18 gram-positive and 7 gram-negative bacteria, and comparisons were made between species within the same genus. The data obtained in this study provide a useful reference for the species and resistance properties of bacteria found on various raw poultry products, either fresh or stored at temperatures and for times relevant to commercial processing, storage, and distribution. The results of this study show that resistance to antibiotics used for the therapeutic treatment of poultry occurs in bacteria in the processing environment.200312540187
3696180.9996Assessment of Tetracyclines Residues and Tetracycline Resistant Bacteria in Conventional and Organic Baby Foods. Children are very vulnerable to bacterial infections and they are sometimes subject to antimicrobials for healing. The presence of resistance genes may counteract effects of antimicrobials. This work has thereby compared the amount of tetracycline resistance genes, tet(A) and tet(B), between conventional and organic meat-based or vegetable-based baby foods and used the quantification of these genes to assess the presence of tetracycline residues in these samples. Counts of bacteria harboring the tet(A) gene were higher than those containing tet(B), and there was no difference between the organic and the conventional samples. Samples with detectable amounts of tetracycline residues were also positive for the presence of tet genes, and when the presence of the genes was not detected, the samples were also negative for the presence of residues. The percentages of tetracycline residues were higher in organic samples than in conventional ones. It cannot be concluded that organic formulas are safer than conventional ones for the studied parameters.201528231206
3531190.9996Commensal E. coli rapidly transfer antibiotic resistance genes to human intestinal microbiota in the Mucosal Simulator of the Human Intestinal Microbial Ecosystem (M-SHIME). Food-producing animals are indicated as a reservoir of antibiotic resistance genes and a potential vector for transmission of plasmid-encoded antibiotic resistance genes by conjugation to the human intestinal microbiota. In this study, transfer of an antibiotic resistance plasmid from a commensal E. coli originating from a broiler chicken towards the human intestinal microbiota was assessed by using a Mucosal Simulator of the Human Intestinal Microbial Ecosystem (M-SHIME). This in vitro model mimics the human intestinal ecosystem and received a single dose of 10(9)E. coli MB6212, which harbors a plasmid known to confer resistance towards several antibiotics including tetracycline, sulfamethoxazole and cefotaxime. Since the degree of stress imposed by stomach pH and bile acids vary with the consumed meal size, the effect of meal size on E. coli donor survival and on plasmid transfer towards lumen and mucosal coliforms and anaerobes was determined. The administered commensal E. coli strain survived stomach acid and bile salt stress and was able to grow in the colon environment during the timeframe of the experiment (72 h). Transfer of antibiotic resistance was observed rapidly since cultivable transconjugant coliforms and anaerobes were already detected in the lumen and mucosa after 2 h in the simulated proximal colon. The presence of the resistance plasmid in the transconjugants was confirmed by PCR. Differences in meal size and adapted digestion had neither a detectable impact on antibiotic resistance transfer, nor on the survival of the E. coli donor strain, nor on short chain fatty acid profiles. The median number of resistant indigenous coliforms in the lumen of the inoculated colon vessels was 5.00 × 10(5) cfu/ml [min - max: 3.47 × 10(4)-3.70 × 10(8) cfu/ml], and on the mucosa 1.44 × 10(7) cfu/g [min-max: 4.00 × 10(3)-4.00 × 10(8) cfu/g]. Exact quantification of the anaerobic transconjugants was difficult, as (intrinsic) resistant anaerobic background microbiota were present. QPCR data supported the observation of plasmid transfer in the simulated colon. Moreover, inoculation of E. coli MB6212 had no significant impact on the microbial diversity in the lumen as determined by 16 S ribosomal gene based next generation sequencing on lumen samples. This study demonstrates that a commensal, antibiotic resistant E. coli strain present in food can transfer its antibiotic resistance plasmid relatively quickly to intestinal microbiota in the M-SHIME. The spread and persistence of antibiotic resistance genes and resistant bacteria in our intestinal system is an alarming scenario which might present clinical challenges, since it implies a potential reservoir for dissemination to pathogenic bacteria.201931536878