Whole Genome Sequencing of Escherichia coli From Store-Bought Produce
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The role of agriculture in the transfer of drug resistant pathogens to humans is widely debated and poorly understood. Escherichia coli is a valuable indicator organism for contamination and carriage of antimicrobial resistance in foods. Whilst whole genome sequences for E. coli from animals and associated meats are common, sequences from produce are scarce. Produce may acquire drug resistant E. coli from animal manure fertilizers, contaminated irrigation water and wildlife, particularly birds. Whole genome sequencing was used to characterize 120 tetracycline (TET) resistant E. coli from store-bought, ready-to-eat cilantro, arugula and mixed salad from two German cities. E. coli were recovered on the day of purchase and after 7 days of refrigeration. Cilantro was far more frequently contaminated with TET resistant E. coli providing 102 (85%) sequenced strains. Phylogroup B1 dominated the collection (n=84, 70%) with multi-locus sequence types B1-ST6186 (n=37, 31%), C-ST165 (n=17, 14%), B1-ST58 (n=14, 12%), B1-ST641 (n=8, 7%) and C-ST88 (n=5, 4%) frequently identified. Notably, seven strains of diverse ST carried genetic indicators of ColV virulence plasmid carriage. A number of previously identified and novel integrons associated with insertion elements including IS26 were also identified. Storage may affect the lineages of E. coli isolated however further studies are needed. Our study indicates produce predominantly carry E. coli with a commensal phylogroup and a variety of antimicrobial resistance and virulence-associated traits. Genomic surveillance of bacteria that contaminate produce should be a matter of public health importance in order to develop a holistic understanding of the environmental dimensions of antimicrobial resistance.<p>The conventional biological treatment process can provide a favorable environment for the maintenance and dissemination of antibiotic- resistant bacteria and the antibiotic resistance genes (ARG) they carry. This study investigated the occurrence of antibiotic resistance in three wastewater treatment plants (WWTP) to determine the role they play in the dissemination of ARGs. Bacterial isolates resistant to tetracycline were collected, and tested against eight antibiotics to determine their resistance profiles and the prevalence of multiple antibiotic resistance. It was found that bacteria resistant to tetracycline were more likely to display resistance to multiple antibiotics compared to those isolates that were not tetracycline resistant. Polymerase chain reaction (PCR) was used to identify the tetracycline resistance determinants present within the bacterial communities of the WWTPs and receiving waters, and it was found that ARGs may not be released from the treatment process. Identification of isolates showed that there was a large diversity of species in both the tetracycline- resistant and tetracycline- sensitive populations and that the two groups were significantly different in composition. Antibiotic resistance profiles of each population showed that a large diversity of resistance patterns existed within genera suggesting that transmission of ARG may progress by both horizontal gene and vertical proliferation.</p> <p><br></p>
Tetracycline antibiotics
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A comparative study of virulence of P. aeruginosa strains PAO containing and not containing plasmids has been made. A number of plasmids which are present in strains PAO decrease their virulence for mice 3-7 times. The virulence-affecting plasmids considerably differ in their biological properties. Bacterial mutations rpm, selected as mutations stabilizing RP4 plasmid in PAO cells, have also been found to affect virulence of bacteria, decreasing its level several times. The introduction of plasmids into PAO cells carrying mutations rpm is not accompanied by decrease of virulence.
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Abstract The conventional biological treatment process can provide a favorable environment for the maintenance and dissemination of antibiotic‐resistant bacteria and the antibiotic resistance genes (ARG) they carry. This study investigated the occurrence of antibiotic resistance in three wastewater treatment plants (WWTP) to determine the role they play in the dissemination of ARGs. Bacterial isolates resistant to tetracycline were collected, and tested against eight antibiotics to determine their resistance profiles and the prevalence of multiple antibiotic resistance. It was found that bacteria resistant to tetracycline were more likely to display resistance to multiple antibiotics compared to those isolates that were not tetracycline resistant. Polymerase chain reaction (PCR) was used to identify the tetracycline resistance determinants present within the bacterial communities of the WWTPs and receiving waters, and it was found that ARGs may not be released from the treatment process. Identification of isolates showed that there was a large diversity of species in both the tetracycline‐resistant and tetracycline‐sensitive populations and that the two groups were significantly different in composition. Antibiotic resistance profiles of each population showed that a large diversity of resistance patterns existed within genera suggesting that transmission of ARG may progress by both horizontal gene and vertical proliferation.
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The uptakes of 3 H-tetracycline by 12 tetracycline-sensitive and 24 tetracycline-resistant Escherichia coli hospital cultures were found to be 270 and 75 nmoles of tetracycline per milliliter of cell water per 20 min, respectively. This confirms reports by other investigators who, by using only one or two cultures, suggested a relationship between tetracycline uptake and tetracycline resistance. However, minimum inhibitory concentrations of tetracycline for the cultures bore no relation to the tetracycline uptake values, suggesting that loss of tetracycline uptake may not be the primary cause of resistance. In addition there were three resistant cultures with uptake values greater than 140 and two sensitive cultures with uptakes lower than 180, raising the question of how these tetracycline-resistant cultures could grow with tetracycline at concentrations nearly as high as those found to inhibit growth of sensitive organisms. Of the tetracycline-resistant cultures, 15 were able to transfer tetracycline resistance to a recipient organism and 9 were not. Two of the cultures transferred TC-resistance to a recipient with no modification-restriction system ( E. coli C) but did not transfer resistance to a recipient with a known modification-restriction system ( E. coli K-12).
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A given strain of Bact. aertrycke Mutton has been tested repeatedly for its virulence to mice, and on some of these occasions the virulence of 10 single colony cultures taken from this strain has likewise been tested. Between these single colony cultures such marked differences in virulence have been found as to constitute definite discontinuous variations. Side by side in the same culture there have been found virulent and avirulent organisms. Daily subculture in broth under certain atmospheric conditions resulted in the fall in virulence of the whole culture; this was accompanied by a replacement of the virulent organisms by organisms that were either completely avirulent or were only weakly virulent. The evidence suggests that the fall in virulence of the whole culture is not due to a simultaneous fall in the virulence of each of its constituent organisms, but to a replacement of the highly virulent organisms by organisms of a lower degree of virulence. During the process of replacement two or three different variants, showing discontinuous variations in virulence, may be demonstrated together in the same culture. The conclusions to be drawn from these findings, and their bearing on the interpretation of the results of experimental epidemiology, are discussed.
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ABSTRACT Strains of Vibrio vulnificus , a marine bacterial species pathogenic for humans and eels, are divided into three biotypes, and those virulent for eels are classified as biotype 2. All biotype 2 strains possess one or more plasmids, which have been shown to harbor the biotype 2-specific DNA sequences. In this study we determined the DNA sequences of three biotype 2 plasmids: pR99 (68.4 kbp) in strain CECT4999 and pC4602-1 (56.6 kb) and pC4602-2 (66.9 kb) in strain CECT4602. Plasmid pC4602-2 showed 92% sequence identity with pR99. Curing of pR99 from strain CECT4999 resulted in loss of resistance to eel serum and virulence for eels but had no effect on the virulence for mice, an animal model, and resistance to human serum. Plasmids pC4602-2 and pR99 could be transferred to the plasmid-cured strain by conjugation in the presence of pC4602-1, which was self-transmissible, and acquisition of pC4602-2 restored the virulence of the cured strain for eels. Therefore, both pR99 and pC4602-2 were virulence plasmids for eels but not mice. A gene in pR99, which encoded a novel protein and had an equivalent in pC4602-2, was further shown to be essential, but not sufficient, for the resistance to eel serum and virulence for eels. There was evidence showing that pC4602-2 may form a cointegrate with pC4602-1. An investigation of six other biotype 2 strains for the presence of various plasmid markers revealed that they all harbored the virulence plasmid and four of them possessed the conjugal plasmid in addition.
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Minocycline (7-dimethylamino-6-demethyl-6-deoxytetracycline) is a new semisynthetic tetracycline with potent activity against tetracycline-susceptible bacterial pathogens and unique activity against tetracycline-resistant staphylococci. Studies to determine the basis for this unique activity showed that, whereas tetracycline-resistant staphylococci took up less 3 H-tetracycline than the susceptible cells, both the tetracycline-resistant and -susceptible cells accumulated equivalent amounts of 14 C-minocycline. In contrast, tetracycline-resistant Escherichia coli cells were relatively resistant to minocycline and accumulated less of both drugs than did the susceptible organisms. It is proposed that minocycline is effective against tetracycline-resistant staphylococci because of its ability to penetrate the cells sufficiently to reach inhibiting concentrations at sensitive reaction sites.
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<p>The conventional biological treatment process can provide a favorable environment for the maintenance and dissemination of antibiotic- resistant bacteria and the antibiotic resistance genes (ARG) they carry. This study investigated the occurrence of antibiotic resistance in three wastewater treatment plants (WWTP) to determine the role they play in the dissemination of ARGs. Bacterial isolates resistant to tetracycline were collected, and tested against eight antibiotics to determine their resistance profiles and the prevalence of multiple antibiotic resistance. It was found that bacteria resistant to tetracycline were more likely to display resistance to multiple antibiotics compared to those isolates that were not tetracycline resistant. Polymerase chain reaction (PCR) was used to identify the tetracycline resistance determinants present within the bacterial communities of the WWTPs and receiving waters, and it was found that ARGs may not be released from the treatment process. Identification of isolates showed that there was a large diversity of species in both the tetracycline- resistant and tetracycline- sensitive populations and that the two groups were significantly different in composition. Antibiotic resistance profiles of each population showed that a large diversity of resistance patterns existed within genera suggesting that transmission of ARG may progress by both horizontal gene and vertical proliferation.</p> <p><br></p>
Tetracycline antibiotics
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The uptakes of 3H-tetracycline by 12 tetracycline-sensitive and 24 tetracycline-resistant Escherichia coli hospital cultures were found to be 270 and 75 nmoles of tetracycline per milliliter of cell water per 20 min, respectively. This confirms reports by other investigators who, by using only one or two cultures, suggested a relationship between tetracycline uptake and tetracycline resistance. However, minimum inhibitory concentrations of tetracycline for the cultures bore no relation to the tetracycline uptake values, suggesting that loss of tetracycline uptake may not be the primary cause of resistance. In addition there were three resistant cultures with uptake values greater than 140 and two sensitive cultures with uptakes lower than 180, raising the question of how these tetracycline-resistant cultures could grow with tetracycline at concentrations nearly as high as those found to inhibit growth of sensitive organisms. Of the tetracycline-resistant cultures, 15 were able to transfer tetracycline resistance to a recipient organism and 9 were not. Two of the cultures transferred TC-resistance to a recipient with no modification-restriction system (E. coli C) but did not transfer resistance to a recipient with a known modification-restriction system (E. coli K-12).
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