Complete genome sequence of a tetracycline-resistant Streptococcus mutans strain carrying the tet(M) gene. - Related Documents




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599801.0000Complete genome sequence of a tetracycline-resistant Streptococcus mutans strain carrying the tet(M) gene. INTRODUCTION: Tetracyclines are widely used in dental treatment. Here, we report the genomic information of the tetracycline-resistant Streptococcus mutans strain, HSM45, for the first time. METHODS: Susceptibility to tetracycline was determined using the microdilution method. The complete genome sequence of HSM45 was determined and compared with public genome data. RESULTS: HSM45 was resistant to tetracycline. The tetracycline resistance gene tet(M) was carried by Tn916, a conjugative transposon that is widely found in Gram-positive bacteria. CONCLUSION: This study showed that S. mutans can acquire tetracycline resistance and it can also be a source of horizontal transfer of resistance genes.202540545135
600010.9998Incidence and behaviour of Tn916-like elements within tetracycline-resistant bacteria isolated from root canals. INTRODUCTION: Tetracycline resistance is commonly found in endodontic bacteria. One of the most common tetracycline-resistance genes is tet(M), which is often encoded on the broad-host-range conjugative transposon Tn916. This study aimed to determine whether tet(M) was present in bacteria isolated from endodontic patients at the Eastman Dental Institute and whether this gene was carried on the transferable conjugative transposon Tn916. METHODS: The cultivable microflora isolated from 15 endodontic patients was screened for resistance to tetracycline. Polymerase chain reactions for tet(M) and for unique regions of Tn916 were carried out on the DNA of all tetracycline-resistant bacteria. Filter-mating experiments were used to see if transfer of any Tn916-like elements could occur. RESULTS: Eight out of 15 tetracycline-resistant bacteria isolated were shown to possess tet(M). Furthermore, four of these eight were shown to possess the Tn916-unique regions linked to the tet(M) gene. Transfer experiments demonstrated that a Neisseria sp. donor could transfer an extremely unstable Tn916-like element to Enterococcus faecalis. CONCLUSIONS: The tet(M) gene is present in the majority of tetracycline-resistant bacteria isolated in this study and the conjugative transposon Tn916 has been shown to be responsible for the support and transfer of this gene in some of the bacteria isolated.200616842505
599320.9998Genetic basis of erythromycin resistance in oral bacteria. We determined the prevalence of erythromycin-resistant bacteria in the oral cavity and identified mef and erm(B) as the most common resistance determinants. In addition, we demonstrate the genetic linkage, on various Tn1545-like conjugative transposons, between erythromycin and tetracycline resistance in a number of isolates.200415155239
599630.9997Molecular characterization of intrinsic and acquired antibiotic resistance in lactic acid bacteria and bifidobacteria. The minimum inhibitory concentrations (MICs) of 6 different antibiotics (chloramphenicol, clindamycin, erythromycin, streptomycin, tetracycline and vancomycin) were determined for 143 strains of lactic acid bacteria and bifidobacteria using the Etest. Different MICs were found for different species and strains. Based on the distribution of these MIC values, most of the strains were either susceptible or intrinsically resistant to these antibiotics. However, the MIC range of some of these antibiotics showed a bimodal distribution, which suggested that some of the tested strains possess acquired antibiotic resistance. Screening for resistance genes was performed by PCR using specific primers, or using a DNA microarray with around 300 nucleotide probes representing 7 classes of antibiotic resistance genes. The genes identified encoded resistance to tetracycline [tet(M), tet(W), tet(O) and tet(O/W)], erythromycin and clindamycin [erm(B)] and streptomycin [aph(E) and sat(3)]. Internal portions of some of these determinants were sequenced and found to be identical to genes described in other bacteria. All resistance determinants were located on the bacterial chromosome, except for tet(M), which was identified on plasmids in Lactococcus lactis. The contribution of intrinsic multidrug transporters to the antibiotic resistance was investigated by cloning and measuring the expression of Bifidobacterium breve genes in L. lactis.200817957105
585340.9997Identification of the tet(B) resistance gene in Streptococcus suis. The tetracycline resistance gene, tet(B), has been described previously in gram negative bacteria. In this study tet(B) was detected in plasmid extracts from 17/111 (15%) Streptococcus suis isolates from diseased pigs, representing the first report of this resistance gene in gram positive bacteria.201120696603
599550.9997In 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
595360.9997CAT III chloramphenicol resistance in Pasteurella haemolytica and Pasteurella multocida isolated from calves. Chloramphenicol, which had been used extensively for antimicrobial veterinary therapy, was prohibited in Europe in 1994. Soon after it became available, resistance to this drug was detected, generally conferred by plasmids encoding inactivating enzymes, the chloramphenicol acetyltransferases (CAT), in Gram-negative as well as in Gram-positive bacteria. In the last few years, resistance to antibiotics emerged in Pasteurella strains from breeding herds and this evolution was followed by a national surveillance network. Chloramphenicol-resistance was more recently detected in multiresistant strains. We studied 25 strains of Pasteurella, selected for their resistance to chloramphenicol. Production of a CAT was demonstrated in all these strains. PCR amplification indicated that the CAT produced was of type III for 23 of them. In these strains, chloramphenicol-resistance was mediated by plasmids of about 5.1 kb. Southern blots on restriction fragments suggested a high degree of homology between these 5.1 kb plasmids. In the two other strains, production of a CAT type I was demonstrated, and the corresponding genes were either shown on a plasmid of 17 or 5.5 kb.19968877534
598570.9997Alternative quinolone-resistance pathway caused by simultaneous horizontal gene transfer in Haemophilus influenzae. BACKGROUND: Quinolone-resistant bacteria are known to emerge via the accumulation of mutations in a stepwise manner. Recent studies reported the emergence of quinolone low-susceptible Haemophilus influenzae ST422 isolates harbouring two relevant mutations, although ST422 isolates harbouring one mutation were never identified. OBJECTIVES: To investigate if GyrA and ParC from quinolone low-susceptible isolates can be transferred horizontally and simultaneously to susceptible isolates. METHODS: Genomic DNA was extracted from an H. influenzae isolate harbouring amino acid substitutions in both gyrA and parC and mixed with clinical isolates. The emergence of resistant isolates was compared, and WGS analysis was performed. RESULTS: By adding the genomic DNA harbouring both mutated gyrA and parC, resistant bacteria exhibiting recombination at gyrA only or both gyrA and parC loci were obtained on nalidixic acid and pipemidic acid plates, and the frequency was found to increase with the amount of DNA. Recombination events in gyrA only and in both gyrA and parC occurred with at least 1 and 1-100 ng of DNA, respectively. The genome sequence of a representative strain showed recombination events throughout the genome. The MIC of quinolone for the resulting strains was found to be similar to that of the donor. Although the recombination efficacy was different among the various strains, all strains used in this study obtained multiple genes simultaneously. CONCLUSIONS: These findings indicate that H. influenzae can simultaneously obtain more than two mutated genes. This mechanism of horizontal transfer could be an alternative pathway for attaining quinolone resistance.202236124853
547980.9997Novel linezolid resistance plasmids in Enterococcus from food animals in the USA. OBJECTIVES: To sequence the genomes and determine the genetic mechanisms for linezolid resistance identified in three strains of Enterococcus isolated from cattle and swine caecal contents as part of the US National Antimicrobial Resistance Monitoring System (NARMS) surveillance programme. METHODS: Broth microdilution was used for in vitro antimicrobial susceptibility testing to assess linezolid resistance. Resistance mechanisms and plasmid types were identified from data generated by WGS on Illumina® and PacBio® platforms. Conjugation experiments were performed to determine whether identified mechanisms were transmissible. RESULTS: Linezolid resistance plasmids containing optrA were identified in two Enterococcus faecalis isolates and one Enterococcus faecium. The E. faecium isolate also carried the linezolid resistance gene cfr on the same plasmid as optrA. The linezolid resistance plasmids had various combinations of additional resistance genes conferring resistance to phenicols (fexA), aminoglycosides [spc and aph(3')-III] and macrolides [erm(A) and erm(B)]. One of the plasmids was confirmed to be transmissible by conjugation, resulting in linezolid resistance in the transconjugant. CONCLUSIONS: To the best of our knowledge, this is the first identification of linezolid resistance in the USA in bacteria isolated from food animals. The oxazolidinone class of antibiotics is not used in food animals in the USA, but the genes responsible for resistance were identified on plasmids with other resistance markers, indicating that there may be co-selection for these plasmids due to the use of different antimicrobials. The transmissibility of one of the plasmids demonstrated the potential for linezolid resistance to spread horizontally. Additional surveillance is necessary to determine whether similar plasmids are present in human strains of Enterococcus.201830272180
452790.9997Study on the excision and integration mediated by class 1 integron in Enterococcus faecalis. Recognized as a mobile genetic element, integron is correlated to the excision and integration of exogenous genes, especially bacterial resistance genes. However, most of the investigations focused on Gram-positive bacteria with few exceptions. In this study, Enterococcus faecalis was selected to investigate the excision and integration of class 1 integron. A total of eight plasmids were subjected to establish the transformants for excision and integration test. As results showed, positive excision assay was observed, which had been confirmed by the further integration assays and PCR amplification. The observation of class 1 integron mediated excision and integration of various exogenous antibiotics resistance genes should raise the attention of integrons as novel antibiotic resistance determinant in Gram-positive bacteria, especially in Enterococcus.201728390978
5972100.9997Method of Selection of Bacteria Antibiotic Resistance Genes Based on Clustering of Similar Nucleotide Sequences. A new method for selection of bacterium antibiotic resistance genes is proposed and tested for solving the problems related to selection of primers for PCR assay. The method implies clustering of similar nucleotide sequences and selection of group primers for all genes of each cluster. Clustering of resistance genes for six groups of antibiotics (aminoglycosides, β-lactams, fluoroquinolones, glycopeptides, macrolides and lincosamides, and fusidic acid) was performed. The method was tested for 81 strains of bacteria of different genera isolated from patients (K. pneumoniae, Staphylococcus spp., S. agalactiae, E. faecalis, E. coli, and G. vaginalis). The results obtained by us are comparable to those in the selection of individual genes; this allows reducing the number of primers necessary for maximum coverage of the known antibiotic resistance genes during PCR analysis.201729063318
5931110.9997Antimicrobial resistance determinants among anaerobic bacteria isolated from footrot. Antibiotic resistance has been evaluated among 36 Gram negative and anaerobic bacilli (10 Bacteroides, 11 Prevotella, 7 Porphyromonas and 8 Fusobacterium strains) isolated from clinical cases of caprine and ovine footrot (necrotic pododermatitis). The initial analysis on this bacterial consortium evaluates the relationships existing among antimicrobial resistance determinants, phenotype expression and mobilization potential. The Bacteroides strains were generally resistant to penicillins, first-generation cephalosporins, tetracycline and erythromycin, and expressed low level of β-lactamase activity. The main determinants found among the Bacteroides strains were cepA and tetQ genes, conferring resistance to β-lactams and tetracycline, respectively. A general susceptibility to β-lactams was shown for most Prevotella, Porphyromonas and Fusobacterium strains, where none of the β-lactamase genes described in Bacteroides was detected. Resistance to tetracycline and/or erythromycin was found among the three bacterial groups. Although tetQ genes were detected for several Prevotella and Porphyromonas strains, a unique ermF positive was revealed among Prevotella strains. The expression of resistance markers was not related with the polymorphism of their coding sequences. However, the finding of sequence signatures for conjugative transposons in the vicinities of tetQ and ermF suggests a mobilization potential that might have contributed to the spread of antimicrobial resistance genes.201222177890
4613120.9997Glycopeptide-resistance transferability from vancomycin-resistant enterococci of human and animal source to Listeria spp. AIMS: The glycopeptide-resistance transferability from vancomycin-resistant enterococci (VRE) of clinical and animal origin to different species of Listeria was investigated. METHODS AND RESULTS: Of 36 matings, performed on membrane filter, the glycopeptide resistance was successfully transferred in six attempts, five with donors of animal origin and only one with donors from clinical source. The acquired glycopeptide resistance in Listeria transconjugants was confirmed by the presence of the conjugative plasmid band and by the amplification of the 732-bp fragment of vanA gene in transferred plasmids. CONCLUSIONS: Despite the lower number of bacteria used in this study, the source of enterococci influenced the outcome of mating. Moreover transferred VanA plasmid induced a different expression in Listeria transconjugants, suggesting that gene expression might be influenced by species affiliation of recipients. SIGNIFICANCE AND IMPACT OF THE STUDY: Our data strengthen the opinion that enterococci are an important source of resistance genes for Listeria via the transfer of movable genetic elements. As these strains are commonly found in the same habitats, a horizontal spread of glycopeptide resistance in Listeria spp. could be possible.200415548299
5933130.9997Novel macrolide-resistance genes, mef(C) and mph(G), carried by plasmids from Vibrio and Photobacterium isolated from sediment and seawater of a coastal aquaculture site. The aim of this study was to determine whether mef(C) and mph(G), originally found on the transferable multi-drug plasmid pAQU1 from Photobacterium damselae subsp. damselae isolated from seawater of a fish farm, are responsible for conferring macrolide resistance. Since these genes are localized head-to-tail on pAQU1 and only four nucleotides exist between them, the single- and combination-effect of these genes was examined. When mph(G) alone was introduced to Escherichia coli, the minimum inhibitory concentrations (MICs) against erythromycin, clarithromycin and azithromycin increased, whereas introduction of mef(C) alone did not influence macrolide susceptibility. Introduction of both mef(C) and mph(G) dramatically increased the MICs to the same three macrolides, i.e. >512 μg ml(-1) , >512 μg ml(-1) and 128 μg ml(-1) respectively. These results suggest that the macrolide phosphotransferase encoded by mph(G) is essential for macrolide resistance, while the efflux pump encoded by mef(C) is required for high-level macrolide resistance. The tandem-pair arrangements of the mef(C) and mph(G) genes were conserved on plasmids ranging in size from 240 to 350 kb of the 22 erythromycin-resistant strains belonging to Vibrio and Photobacterium obtained from the fish farm. Sixteen of 22 plasmids ranged in size from 300 to 350 kb. This is the first report of novel macrolide resistance genes originating from a marine bacterium. SIGNIFICANCE AND IMPACT OF THE STUDY: In this study, mef(C) and mph(G) were found to be novel macrolide-resistance genes, and this is the first report of macrolide-resistance genes originating from a marine bacterium. These genes may be responsible for previously reported cases of the emergence of erythromycin-resistant bacteria in aquaculture sites by an unknown mechanism. The introduction of the tandem arrangement of the mef(C) and mph(G) genes in Escherichia coli increased the MICs to erythromycin, clarithromycin and azithromycin, suggesting a novel mechanism conferring high-level macrolide resistance via combined expression of the efflux pump and macrolide phosphotransferase.201525765542
5997140.9997Resistance of potential probiotic lactic acid bacteria and bifidobacteria of African and European origin to antimicrobials: determination and transferability of the resistance genes to other bacteria. Probiotic bacteria and starter cultures of Lactobacillus, Weissella and Bifidobacterium of African and European origins were studied and compared for their susceptibility to antimicrobials. The study included, for all isolates, determination of MICs (Minimal Inhibitory Concentration) for 24 antimicrobials, detection of resistance genes by PCR reactions using specific primers and sequencing of positive amplicons. The ability of Lb. reuteri from Africa to transfer the erythromycin resistance gene erm(B) to closely related bacteria was investigated by conjugation. Variations were observed and high levels of intrinsic resistance were found among the tested species. Positive amplicons were obtained for resistance genes encoding aminoglycoside (aph(3')-III, aadA, aadE) and tetracycline (tet(S)) from isolates from Europe and macrolide (erm(B)) from an isolate from Africa. However, only the erm(B) gene found in Lb. reuteri L4: 12002 from Africa contained a homologous sequence to previously published sequences. This gene could be transferred in vitro to enterococci. Higher prevalence of phenotypic resistance for aminoglycoside was found in isolates from Europe.200818063151
5992150.9997Emergence of Enterococcus gallinarum carrying vanA gene cluster displaying atypical phenotypes. Motile enterococci such as Enterococcus gallinarum has the ability to acquire and transfer antibiotic resistance genes to other enterococci. Even though infections caused by E. gallinarum are rare, the discovery of this bacteria in food sources and in clinical environments is disturbing. Here, we report the isolation and identification of E. gallinarum from the wound of a hospital in-patient. The isolate was identified using 16S rDNA sequencing. Isolate 146 harboured the vanA and vanC1 gene clusters, was vancomycin-susceptible, and displayed resistance to ampicillin, penicillin, erythromycin and teicoplanin. This isolate also showed intermediate resistance to linezolid and sequencing of the 23S rRNA peptidyl transferase region did not unveil any known mutations associated to the conferment of linezolid resistance. The presence of vanA did not confer resistance to vancomycin. Structural analyses into the Tn1546 transposon carrying the vanA gene revealed distinct genetic variations in the vanS, vanY and vanS-vanH intergenic region that could be associated to the atypical antibiotic resistance phenotypes of isolate 146. Finding from this study are suggestive of the occurrence of interspecies horizontal gene transfer and that similarities in genotypic characteristic may not necessarily correlate with actual antibiotic resistance pattern of E. gallinarum.201633579083
5999160.9996Food isolate Listeria monocytogenes harboring tetM gene plasmid-mediated exchangeable to Enterococcus faecalis on the surface of processed cheese. The genetic basis of tetracycline resistance in a food isolate Listeria monocytogenes (Lm16) was evaluated. Resistance to tetracycline was associated with the presence of the tetM gene in plasmid DNA. The sequence of tetM showed 100% of similarity with the Enterococcus faecalis sequences found in the EMBL database, suggesting that Lm16 received this gene from E. faecalis. Various size bands were detected in the DNA plasmid analysis, the largest being approximately 54.38 kb. Transferability of the tetM gene was achieved in vitro by agar matings between Lm16 and E. faecalis JH2-2, proving the potential for the spread of tetM by horizontal gene transfer. Furthermore, the conjugation experiments were performed on the surface of processed cheese, confirming the transferability in a food matrix. PCR assays were used to confirm the identity of E. faecalis and to detect the tetM gene in transconjugant bacteria. Additionally, the minimal inhibitory concentration for tetracycline and rifampicin and plasmid profiling were performed. This is the first report of a food isolate L. monocytogenes carrying the tetM gene in plasmid DNA, and it highlights the potential risk of spreading antimicrobial resistance genes between different bacteria.201829580513
3594170.9996Directed Recovery and Molecular Characterization of Antibiotic Resistance Plasmids from Cheese Bacteria. Resistance to antimicrobials is a growing problem of worldwide concern. Plasmids are thought to be major drivers of antibiotic resistance spread. The present work reports a simple way to recover replicative plasmids conferring antibiotic resistance from the bacteria in cheese. Purified plasmid DNA from colonies grown in the presence of tetracycline and erythromycin was introduced into plasmid-free strains of Lactococcus lactis, Lactiplantibacillus plantarum and Lacticaseibacillus casei. Following antibiotic selection, the plasmids from resistant transformants were isolated, analyzed by restriction enzyme digestion, and sequenced. Seven patterns were obtained for the tetracycline-resistant colonies, five from L. lactis, and one each from the lactobacilli strains, as well as a single digestion profile for the erythromycin-resistant transformants obtained in L. lactis. Sequence analysis respectively identified tet(S) and ermB in the tetracycline- and erythromycin-resistance plasmids from L. lactis. No dedicated resistance genes were detected in plasmids conferring tetracycline resistance to L. casei and L. plantarum. The present results highlight the usefulness of the proposed methodology for isolating functional plasmids that confer antibiotic resistance to LAB species, widen our knowledge of antibiotic resistance in the bacteria that inhabit cheese, and emphasize the leading role of plasmids in the spread of resistance genes via the food chain.202134360567
5986180.9996Transferable fluoroquinolone resistance in Enterobacteriaceae and Pseudomonas aeruginosa isolated from hemocultures. BACKGROUND: The main mechanisms causing high-level resistance to fluoroquinolones (FQ) are encoded chromosomally; that includes mutations in genes coding DNA-gyrase, but overexpression of efflux pumps contributes to increased minimum inhibitory concentration (MIC) of FQ as well. However, genes responsible for FQ-resistance may be harboured in transferable/conjugative plasmids. For some time, there was an assumption that resistance to FQ cannot be transferable in conjugation due to their synthetic origin, until 1998, when plasmid-mediated resistance transmission in Klebsiella pneumoniae was proved. We aimed to detect the occurrence of transferable FQ-resistance among Gram- negative bacteria isolated from patients in Czech and Slovak hospitals. METHODS: In this study, we tested 236 clinical isolates of Gram-negative bacteria for transferable resistance. Among relevant isolates we performed PCR detection of transferable fluoroquinolone genes (qnr). RESULTS: We have observed transfer of determinants of cephalosporin-resistance, aminoglycoside resistance as well as FQ-resistance (in 10 cases; 4.24%) not only intra-species but inter-species too. The presence of qnr gene was detected in two isolates of forty tested (5%). We have also observed that determinants of cephalosporin-resistance and aminoglycoside-resistance were linked to those of FQ-resistance and were transferred en block in conjugation. CONCLUSION: We have proved that resistance to fluoroquinolones can be transferred horizontally via conjugation among Gram-negative bacteria of different species and is associated with resistance to other antibiotics.201424844110
5499190.9996Antibiotic Resistance/Susceptibility Profiles of Staphylococcus equorum Strains from Cheese, and Genome Analysis for Antibiotic Resistance Genes. In food, bacteria carrying antibiotic resistance genes could play a prominent role in the spread of resistance. Staphylococcus equorum populations can become large in a number of fermented foods, yet the antibiotic resistance properties of this species have been little studied. In this work, the resistance/susceptibility (R/S) profile of S. equorum strains (n = 30) from cheese to 16 antibiotics was determined by broth microdilution. The minimum inhibitory concentration (MIC) for all antibiotics was low in most strains, although higher MICs compatible with acquired genes were also noted. Genome analysis of 13 strains showed the S. equorum resistome to be composed of intrinsic mechanisms, acquired mutations, and acquired genes. As such, a plasmidic cat gene providing resistance to chloramphenicol was found in one strain; this was able to provide resistance to Staphylococcus aureus after electroporation. An msr(A) polymorphic gene was identified in five strains. The Mrs(A) variants were associated with variable resistance to erythromycin. However, the genetic data did not always correlate with the phenotype. As such, all strains harbored a polymorphic fosB/fosD gene, although only one acquired copy was associated with strong resistance to fosfomycin. Similarly, a plasmid-associated blaR1-blaZI operon encoding a penicillinase system was identified in five ampicillin- and penicillin G-susceptible strains. Identified genes not associated with phenotypic resistance further included mph(C) in two strains and norA in all strains. The antibiotic R/S status and gene content of S. equorum strains intended to be employed in food systems should be carefully determined.202337511416