Transfer of Antibiotic Resistance Plasmid from Commensal E. coli Towards Human Intestinal Microbiota in the M-SHIME: Effect of E. coli dosis, Human Individual and Antibiotic Use. - Related Documents




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353201.0000Transfer of Antibiotic Resistance Plasmid from Commensal E. coli Towards Human Intestinal Microbiota in the M-SHIME: Effect of E. coli dosis, Human Individual and Antibiotic Use. Along with (in) direct contact with animals and a contaminated environment, humans are exposed to antibiotic-resistant bacteria by consumption of food. The implications of ingesting antibiotic-resistant commensal bacteria are unknown, as dose-response data on resistance transfer and spreading in our gut is lacking. In this study, transfer of a resistance plasmid (IncF), harbouring several antibiotic resistance genes, from a commensal E. coli strain towards human intestinal microbiota was assessed using a Mucosal Simulator of the Human Intestinal Ecosystem (M-SHIME). More specifically, the effect of the initial E. coli plasmid donor concentration (10(5) and 10(7) CFU/meal), antibiotic treatment (cefotaxime) and human individual (n = 6) on plasmid transfer towards lumen coliforms and anaerobes was determined. Transfer of the resistance plasmid to luminal coliforms and anaerobes was observed shortly after the donor strain arrived in the colon and was independent of the ingested dose. Transfer occurred in all six simulated colons and despite their unique microbial community composition, no differences could be detected in antibiotic resistance transfer rates between the simulated human colons. After 72 h, resistant coliform transconjugants levels ranged from 7.6 × 10(4) to 7.9 × 10(6) CFU(cefotaxime resistant)/Ml colon lumen. Presence of the resistance plasmid was confirmed and quantified by PCR and qPCR. Cefotaxime treatment led to a significant reduction (85%) in resistant coliforms, however no significant effect on the total number of cultivable coliforms and anaerobes was observed.202133670965
353110.9999Commensal 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
528920.9999Examination 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
314330.9998Impact of colistin sulfate treatment of broilers on the presence of resistant bacteria and resistance genes in stored or composted manure. The application of manure may result in contamination of the environment with antimicrobials, antimicrobial-resistant bacteria, resistance genes and plasmids. The aim of this study was to investigate the impact of the administration of colistin and of manure management on (i) the presence of colistin-resistant Escherichia coli, Klebsiella pneumoniae and Pseudomonas aeruginosa and (ii) the prevalence of various antimicrobial resistance genes in feces and in composted or stored manure. One flock of chickens was treated with colistin at the recommended dosage and a second flock was kept as an untreated control. Samples of feces, litter and stored or composted manure from both flocks were collected for isolation and determination of the colistin-susceptibility of E. coli, K. pneumoniae and P. aeruginosa and quantification of genes coding for resistance to different antimicrobials. The persistence of plasmids in stored or composted manure from colistin-treated broilers was also evaluated by plasmid capturing experiments. Results revealed that colistin administration to chickens had no apparent impact on the antimicrobial resistance of the dominant Enterobacteriaceae and P. aeruginosa populations in the chicken gut. Composting stimulated an apparently limited decrease in genes coding for resistance to different antimicrobial families. Importantly, it was shown that even after six weeks of composting or storage, plasmids carrying antimicrobial resistance genes could still be transferred to a recipient E. coli. In conclusion, composting is insufficient to completely eliminate the risk of spreading antimicrobial resistance through chicken manure.201626616601
339640.9998Extended antibiotic treatment in salmon farms select multiresistant gut bacteria with a high prevalence of antibiotic resistance genes. The high use of antibiotics for the treatment of bacterial diseases is one of the main problems in the mass production of animal protein. Salmon farming in Chile is a clear example of the above statement, where more than 5,500 tonnes of antibiotics have been used over the last 10 years. This has caused a great impact both at the production level and on the environment; however, there are still few works in relation to it. In order to demonstrate the impact of the high use of antibiotics on fish gut microbiota, we have selected four salmon farms presenting a similar amount of fish of the Atlantic salmon species (Salmo salar), ranging from 4,500 to 6,000 tonnes. All of these farms used treatments with high doses of antibiotics. Thus, 15 healthy fish were selected and euthanised in order to isolate the bacteria resistant to the antibiotics oxytetracycline and florfenicol from the gut microbiota. In total, 47 bacterial isolates resistant to florfenicol and 44 resistant to oxytetracycline were isolated, among which isolates with Minimum Inhibitory Concentrations (MIC) exceeding 2048 μg/mL for florfenicol and 1024 μg/mL for oxytetracycline were found. In addition, another six different antibiotics were tested in order to demonstrate the multiresistance phenomenon. In this regard, six isolates of 91 showed elevated resistance values for the eight tested antibiotics, including florfenicol and oxytetracycline, were found. These bacteria were called "super-resistant" bacteria. This phenotypic resistance was verified at a genotypic level since most isolates showed antibiotic resistance genes (ARGs) to florfenicol and oxytetracycline. Specifically, 77% of antibiotic resistant bacteria showed at least one gene resistant to florfenicol and 89% showed at least one gene resistant to oxytetracycline. In the present study, it was demonstrated that the high use of the antibiotics florfenicol and oxytetracycline has, as a consequence, the selection of multiresistant bacteria in the gut microbiota of farmed fish of the Salmo salar species at the seawater stage. Also, the phenotypic resistance of these bacteria can be correlated with the presence of antibiotic resistance genes.201830204782
339150.9998Phenotypic and genotypic analysis of bacteria isolated from three municipal wastewater treatment plants on tetracycline-amended and ciprofloxacin-amended growth media. AIMS: The goal of this study was to determine the antimicrobial susceptibility of bacteria isolated from three municipal wastewater treatment plants. METHODS AND RESULTS: Numerous bacterial strains were isolated from three municipal wastewater treatment facilities on tetracycline- (n=164) and ciprofloxacin-amended (n=65) growth media. These bacteria were then characterized with respect to their resistance to as many as 10 different antimicrobials, the presence of 14 common genes that encode resistance to tetracycline, the presence of integrons and/or the ability to transfer resistance via conjugation. All of the characterized strains exhibited some degree of multiple antimicrobial resistance, with nearly 50% demonstrating resistance to every antimicrobial that was tested. Genes encoding resistance to tetracycline were commonly detected among these strains, although intriguingly the frequency of detection was slightly higher for the bacteria isolated on ciprofloxacin-amended growth media (62%) compared to the bacteria isolated on tetracycline-amended growth media (53%). Class 1 integrons were also detected in 100% of the queried tetracycline-resistant bacteria and almost half of the ciprofloxacin-resistant strains. Conjugation experiments demonstrated that at least one of the tetracycline-resistant bacteria was capable of lateral gene transfer. CONCLUSIONS: Our results demonstrate that multiple antimicrobial resistance is a common trait among tetracycline-resistant and ciprofloxacin-resistant bacteria in municipal wastewater. SIGNIFICANCE AND IMPACT OF THE STUDY: These organisms are potentially important in the proliferation of antimicrobial resistance because they appear to have acquired multiple genetic determinants that confer resistance and because they have the potential to laterally transfer these genetic determinants to strains of clinical importance.201020629799
337060.9998Microbiological contamination and resistance genes in biofilms occurring during the drinking water treatment process. Biofilms are the predominant mode of microbial growth in drinking water systems. A dynamic exchange of individuals occurs between the attached and planktonic populations, while lateral gene transfer mediates genetic exchange in these bacterial communities. Integrons are important vectors for the spread of antimicrobial resistance. The presence of class 1 integrons (intI1, qac and sul genes) was assessed in biofilms occurring throughout the drinking water treatment process. Isolates from general and specific culture media, covering a wide range of environmental bacteria, fecal indicators and opportunistic pathogens were tested. From 96 isolates tested, 9.37% were found to possess genetic determinants of putative antimicrobial resistance, and these occurred in both Gram-positive and Gram-negative bacteria. Class 1 integron integrase gene was present in 8.33% of bacteria, all positive for the qacEΔ1 gene. The sul1 gene was present in 3.12% of total isolates, representing 37.5% of the class 1 integron positive cells. The present study shows that biofilm communities in a drinking water treatment plant are a reservoir of class 1 integrons, mainly in bacteria that may be associated with microbiological contamination. Eight out of nine integron bearing strains (88.8%) were identified based on 16S rRNA gene sequencing as either enteric bacteria or species that may be connected to animal and anthropogenic disturbance.201323247295
353070.9998Occurrence 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
351980.9998Fate of chlortetracycline- and tylosin-resistant bacteria in an aerobic thermophilic sequencing batch reactor treating swine waste. Antibiotics have been added to animal feed for decades. Consequently, food animals and their wastes constitute a reservoir of antibiotic-resistant bacteria. The objective of this work was to characterize the impact of an aerobic thermophilic biotreatment on aerobic, antibiotic-resistant bacteria in swine waste. The proportion of tylosin- and chlortetracycline-resistant bacteria grown at 25 degrees C, 37 degrees C, and 60 degrees C decreased after treatment, but they were still abundant (10(2) to 10(8) most probable number ml(-1)) in the treated swine waste. The presence of 14 genes conferring resistance to tylosin and chlortetracycline was assessed by polymerase chain reaction in bacterial populations grown at 25 degrees C, 37 degrees C, and 60 degrees C, with or without antibiotics. In 22 cases, genes were detected before but not after treatment. The overall gene diversity was wider before [tet(BLMOSY), erm(AB)] than after [tet(LMOS), erm(B)] treatment. Analysis by denaturing gradient gel electrophoresis of amplified 16S ribosomal DNA (rDNA) fragments generally showed a reduction of the bacterial diversity, except for total populations grown at 60 degrees C and for tylosin-resistant populations grown at 37 degrees C. The latter were further investigated by cloning and sequencing their 16S rDNA. Phylotypes found before treatment were all closely related to Enterococcus hirae, whereas six different phylotypes, related to Pseudomonas, Alcaligenes, and Pusillimonas, were found after treatment. This work demonstrated that the aerobic thermophilic biotreatment cannot be considered as a means for preventing the dissemination of aerobic antibiotic-resistant bacteria and their resistance genes to the environment. However, since pathogens do not survive the biotreatment, the effluent does not represent an immediate threat to animal or human health.200919125305
313190.9998Integron-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
3428100.9998Effect of oxytetracycline-medicated feed on antibiotic resistance of gram-negative bacteria in catfish ponds. The effect of oxytetracycline-medicated feeds on antibiotic resistance in gram-negative bacteria from fish intestines and water in catfish ponds was investigated. In experiments in the fall and spring, using ponds with no previous history of antibiotic usage, percentages of tetracycline-resistant bacteria in catfish intestines obtained from medicated ponds increased significantly after 10 days of treatment. In the fall, resistance of the intestinal and aquatic bacteria returned to pretreatment levels within 21 days after treatment. In the spring, resistance declined after treatment but remained higher than pretreatment levels for at least 21 days in intestinal bacteria and for 5 months in aquatic bacteria. Plesiomonas shigelloides, Aeromonas hydrophila, and Citrobacter freundii were isolated frequently in both spring and fall; Escherichia coli, Klebsiella pneumoniae, Edwardsiella tarda, and Enterobacter spp. were isolated primarily in the spring. Oxytetracycline treatment did not affect the distribution of bacterial species in the fall but may have accelerated a shift toward greater prevalence of members of the family Enterobacteriaceae in the spring. Multiple antibiotic resistance did not appear to be elicited by oxytetracycline treatment.19957793953
5634110.9998Effects 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
5292120.9998Antibiotic-Resistant Bacteria in Hydroponic Lettuce in Retail: A Comparative Survey. Hydroponic produce is gaining popularity due to its suitability for urban agriculture. The general public also considers that hydroponic produce is free from microbiological contamination. In this study, we compared the frequency and abundance of tetracycline-resistant and sulphadiazine-resistant bacteria and the minimal inhibitory concentration (MIC) of these isolates in conventional, organic, and hydroponic lettuce sold in retail. We also determined the frequency of samples carrying tetB, tetX, sul1, sul2, and int1 genes by PCR and further quantified the copy number of tetX, sul1, and int1 genes in samples positive for these genes using qPCR. As expected, the number of resistant bacteria and the MICs of these isolates were lowest in hydroponic lettuce and highest in organic lettuce. All tested resistant genes, except int1, were detected in samples of all three production methods, but no significant difference was observed between the three groups in the frequency of samples carrying the resistance genes examined or in their copy number. To the best of our knowledge, it is the first study directly reporting the existence of antibiotic-resistant bacteria and resistance genes in hydroponic vegetables sold in retail. The result highlights that the risk of antibiotic-resistant bacteria contamination in hydroponic produce should be further investigated.202032967196
3397130.9998Characterization of antibiotic resistance in commensal bacteria from an aquaculture ecosystem. The objective of the study was to improve the understanding of antibiotic resistance (AR) ecology through characterization of antibiotic-resistant commensal isolates associated with an aquaculture production system. A total of 4767 isolates non-susceptible to sulfamethoxazole/trimethoprim (Sul/Tri), tetracycline (Tet), erythromycin (Erm), or cefotaxime (Ctx), originated from fish, feed, and environmental samples of an aquaculture farm with no known history of antibiotic applications were examined. Close to 80% of the isolates exhibited multi-drug resistance in media containing the corresponding antibiotics, and representative AR genes were detected in various isolates by PCR, with feed isolates had the highest positive rate detected. Identified AR gene carriers involved 18 bacterial genera. Selected AR genes led to acquired resistance in other bacteria by transformation. The AR traits in many isolates were stable in the absence of selective pressure. AR-rich feed and possibly environmental factors may contribute to AR in the aquaculture ecosystem. For minimum inhibitory concentration test, brain heart infusion medium was found more suitable for majority of the bacteria examined than cation-adjusted Mueller Hinton broth, with latter being the recommended medium for clinical isolates by standard protocol. The data indicated a need to update the methodology due to genetic diversity of microbiota for better understanding of the AR ecology.201526441859
2866140.9998Characterization of tetracycline-resistant bacteria in an urbanizing subtropical watershed. AIMS: The objective of this study was to determine whether varying levels of urbanization influence the dominant bacterial species of mildly resistant (0·03 mmol l(-1) tetracycline) and highly resistant (0·06 mmol l(-1) tetracycline) bacteria in sediment and water. Also, the level of urbanization was further evaluated to determine whether the diversity of tetracycline resistance genes present in the isolates and the capability of transferring their resistance were influenced. METHODS AND RESULTS: Sediment and water samples collected from five sampling sites were plated in triplicate on nutrient agar plates with a mild dose (0·03 mmol l(-1) ) and a high dose (0·06 mmol l(-1) ) of tetracycline. Five colonies from each plate plus an additional five from each triplicate group were randomly selected and isolated on nutrient agar containing 0·03 mmol l(-1) tetracycline (400 isolates). The isolates were identified by 16S rRNA gene sequencing and comparison to GenBank using blast. The isolates were also screened for 15 tetracycline resistance genes using a multiplex PCR assay and their ability to transfer resistance through conjugation experiments using a kanamycin-resistant Escherichia. coli K-12 strain labelled with a green fluorescent protein gene. Results from this study indicate that the dominant resistant organisms in this watershed are Acinetobacter spp., Chryseobacterium spp., Serratia spp., Pseudomonas spp., Aeromonas spp. and E. coli. All of these organisms are Gram negative and are closely related to pathogenic species. A majority of the isolates (66%) were capable of transferring their resistance, and there was a greater incidence of tet resistance transfer with increasing urbanization. Also, it was determined that the dominant resistance genes in the watershed are tet(W) and tet(A). CONCLUSION: Urbanization significantly affected dominant tetracycline-resistant bacteria species, but did not affect dominant resistance genes. There was correlation between increased urbanization with an increase in the ability to transfer tetracycline resistance. This indicates that urban areas may select for bacterial species that are capable of transferring resistance. SIGNIFICANCE AND IMPACT OF STUDY: These results indicate that urbanization influences the occurrence of tetracycline-resistant bacteria and the potential for transfer of resistance genes.201323773226
3129150.9998Effect of therapeutic administration of β-lactam antibiotics on the bacterial community and antibiotic resistance patterns in milk. Dairy cows with mastitis are frequently treated with antibiotics. The potential effect of antibiotics on the milk microbiome is still not clear. Therefore, the objective of this research was to investigate the effect of 2 commonly used cephalosporins on the milk microbiota of dairy cows and the antibiotic resistance genes in the milk. The milk samples were collected from 7 dairy cows at the period before medication (d 0), medication (d 1, 2, 3), withdrawal period (d 4, 6, 8), and the period after withdrawal (d 9, 11, 13, 15). We applied 16S rRNA sequencing to explore the microbiota changes, and antibiotic resistance patterns were investigated by quantitative PCR. The microbiota richness and diversity in each sample were calculated using the Chao 1 (richness), Shannon (diversity), and Simpson (diversity) indices. The cephalosporins treatment lowered the Simpson diversity value at the period of withdrawal. Members of the Enterobacter genera were the most affected bacteria associated with mastitis. Meanwhile, antibiotic resistance genes in the milk were also influenced by antibiotic treatment. The cephalosporins treatment raised the proportion of bla(TEM) in milk samples at the period of withdrawal. Therefore, the treatment of cephalosporins led to change in the milk microbiota and increase of β-lactam resistance gene in the milk at the time of withdrawal period.202133741154
3425160.9998Horizontal transfer of antibiotic resistance genes among gram negative bacteria in sewage and lake water and influence of some physico-chemical parameters of water on conjugation process. Transfer of antibiotic resistance genes among gram negative bacteria in sewage and lake water and easy access of these bacteria to the community are major environmental and public health concern. The aim of this study was to determine transfer of the antimicrobial resistance genes from resistant to susceptible gram negative bacteria in the sewage and lake water by conjugation process and to determine the influence of some physico-chemical parameters of sewage and lake water on the transfer of these resistance genes. For this reason, we isolated 20 liter of each sewage and lake water from coconut area within university campus and Lingambudi lake respectively in Mysore city, India, during monsoon season and studied different physical parameters of the water samples like pH, temperature, conductivity turbidity and color as well as chemical parameters like BOD, COD, field DO and total chloride ion. The gram negative bacteria were isolated and identified from the above water samples using microbiological and biochemical methods and their sensitivity to different antibiotics was determined by disc diffusion break point assay. Conjugation between two multiple antibiotic resistant isolates Pseudomonas aeuginosa and E. coli as donor and E. coli Rif(r) (sensitive to antibiotics) as recipient were carried out in 5ml sterile sewage and lake water. All isolates were resistant to Am, moderately resistant to Te and E, while majority were sensitive to Cip, Gm and CAZ antibiotics. Horizontal transfer of antibiotic resistance genes by conjugation process revealed transfer of Gm, Te and E resistant genes from Ps. aeruginosa to E. coli Rif(r) recipient with mean frequency of +/- 2.3 x 10(-4) in sewage and +/- 2.6 x 10(-6) in lake water respectively Frequency of conjugation in sewage was two fold more as compared to lake water (p< or =0.05). Co- transfer study revealed simultaneous transfer of above resistant markers together to the recipient cells. As the above results indicate, due to selective pressure in sewage (presence of antibiotics), the isolates from sewage were more resistant to different antibiotics as compared to those from lake water. Furthermore, these resistance genes can transfer to sensitive bacteria by conjugation. Physico-chemical parameters of water may play role in this process.200920112862
3417170.9998tet genes as indicators of changes in the water environment: relationships between culture-dependent and culture-independent approaches. The aim of this study was to identify tetracycline resistance determinants that could be used as molecular indicators of anthropogenic changes in aquatic environments. Two parallel approaches were used to examine the prevalence of tet genes: a culture-based method involving standard PCR and a method relying on quantitative PCR. The studied site was the Łyna River in Olsztyn (Poland). The culture-dependent method revealed that the concentrations of doxycycline-resistant bacteria harboring the tet(B) gene were higher in wastewater and downstream river samples than in upstream water samples. The tet(B) gene was transferred from environmental bacteria to Escherichia coli. The results generated by the culture-independent method validated statistically significant differences in tet(B) concentrations between upstream and downstream river sections, and revealed that tet(B) levels were correlated with the presence of other tetracycline resistance genes, dissolved oxygen concentrations, temperature and doxycycline concentrations in water. Our findings indicate that doxycycline-resistant bacteria, in particular E. coli harboring tet(B) or increased concentrations of tet(B), are potentially robust indicators of changes in water environments.201525461073
3125180.9998Development of a rapid method for direct detection of tet(M) genes in soil from Danish farmland. A method for direct detection of antibiotic resistance genes in soil samples has been developed. The tetracycline resistance gene, tet(M), was used as a model. The method was validated on Danish farmland soil that had repeatedly been treated with pig manure slurry containing resistant bacteria. The tet(M) gene was directly detected in 10-80% of the samples from the various farmland soils and could be detected in all samples tested after selective enrichment. To validate the obtained results, the method was applied to garden soil samples where lower prevalence of resistance was found. RESULT: A detection limit of 10(2)-10(3) copies of the tet(M) gene per gram of soil (in a Bacillus cereus group bacterium) was achieved. tet(M) gene was detected in soil samples with the highest prevalence on farmland treated with pig manure slurry.200414664871
5544190.9998Assessing the Effect of Oxytetracycline on the Selection of Resistant Escherichia coli in Treated and Untreated Broiler Chickens. Oxytetracycline (OTC) is administered in the poultry industry for the treatment of digestive and respiratory diseases. The use of OTC may contribute to the selection of resistant bacteria in the gastrointestinal tract of birds or in the environment. To determine the effect of OTC on the selection of resistant Escherichia coli strains post-treatment, bacteria were isolated from droppings and litter sampled from untreated and treated birds. Bacterial susceptibility to tetracyclines was determined by the Kirby-Bauer test. A total of 187 resistant isolates were analyzed for the presence of tet(A), (B), (C), (D), (E), and (M) genes by PCR. Fifty-four strains were analyzed by PFGE for subtyping. The proportion of tetracycline-resistant E. coli strains isolated was 42.88%. The susceptibility of the strains was treatment-dependent. A high clonal diversity was observed, with the tet(A) gene being the most prevalent, followed by tet(C). Even at therapeutic doses, there is selection pressure on resistant E. coli strains. The most prevalent resistance genes were tet(A) and tet(C), which could suggest that one of the main mechanisms of resistance of E. coli to tetracyclines is through active efflux pumps.202338136686