scholarly journals An Unexpected Effect of Tetracycline Concentration: Growth Phase-Associated Excision of the Bacteroides Mobilizable Transposon NBU1

2008 ◽  
Vol 191 (3) ◽  
pp. 1078-1082 ◽  
Author(s):  
Bo Song ◽  
Gui-Rong Wang ◽  
Nadja B. Shoemaker ◽  
Abigail A. Salyers
Keyword(s):  
Growth Phase ◽  
Inhibitory Concentration ◽  
Regulatory System ◽  
Tetracycline Resistance ◽  
Inducible Promoter ◽  
Mutant Form ◽  
Phase Effect ◽  
Late Exponential Phase ◽  
Tetracycline Resistance Gene ◽  
Low Concentrations

ABSTRACT Early studies of the Bacteroides mobilizable transposon NBU1 established that excision, the first step in NBU1 transfer, requires exposure of the cells to tetracycline. More recently, we found that excision is also associated with growth phase; even after exposure to tetracycline, excision is detectable only after the cells enter late exponential phase. The tetracycline effect is mediated by a two-component regulatory system, RteA and RteB, which is provided in trans by an integrated self-transmissible element, CTnDOT. The rteA and rteB genes are part of a three-gene operon that also contains the tetracycline resistance gene tetQ. We report here that neither transcription nor translation of the tetQ-rteA-rteB operon is affected by growth phase. Moreover, RteA is not required for the growth phase effect, because a mutant form of RteB that does not require phosphorylation by RteA did not make excision independent of growth phase. Two conditions made NBU1 excision independent of growth phase. One was reducing the tetracycline concentration from an inhibitory concentration (1 μg/ml) to a subinhibitory level (0.05 μg/ml). Independence of growth phase also occurred when rteA and rteB were placed under the control of a heterologous maltose-inducible promoter, P susA . Our results suggest that at low concentrations of tetracycline, ribosomes are capable of translating enough RteA and RteB for excision to occur. At higher tetracycline concentrations, however, TetQ is needed to protect enough ribosomes to allow the translation of excision genes, and this protection takes time to develop. Thus, subinhibitory concentrations of tetracycline may increase the probability of gene transfer because, in contrast to inhibitory concentrations, excision can occur at all phases of growth.

scholarly journals New Trimethoprim-Like Molecules: Bacteriological Evaluation and Insights into Their Action

Antibiotics ◽  
2021 ◽  
Vol 10 (6) ◽  
pp. 709
Author(s):  
Marta Jorba ◽  
Marina Pedrola ◽  
Ouldouz Ghashghaei ◽  
Rocío Herráez ◽  
Lluis Campos-Vicens ◽  
...  
Keyword(s):  
Inhibitory Concentration ◽  
Efflux Pump ◽  
Synergistic Effects ◽  
Nicotinamide Adenine Dinucleotide Phosphate ◽  
Detailed Characterization ◽  
Low Concentrations ◽  
Pump Activity ◽  
Bacteriological Evaluation ◽  
Kinetics Of

This work reports a detailed characterization of the antimicrobial profile of two trimethoprim-like molecules (compounds 1a and 1b) identified in previous studies. Both molecules displayed remarkable antimicrobial activity, particularly when combined with sulfamethoxazole. In disk diffusion assays on Petri dishes, compounds 1a and 1b showed synergistic effects with colistin. Specifically, in combinations with low concentrations of colistin, very large increases in the activities of compounds 1a and 1b were determined, as demonstrated by alterations in the kinetics of bacterial growth despite only slight changes in the fractional inhibitory concentration index. The effect of colistin may be to increase the rate of antibiotic entry while reducing efflux pump activity. Compounds 1a and 1b were susceptible to extrusion by efflux pumps, whereas the inhibitor phenylalanine arginyl β-naphthylamide (PAβN) exerted effects similar to those of colistin. The interactions between the target enzyme (dihydrofolate reductase), the coenzyme nicotinamide adenine dinucleotide phosphate (NADPH), and the studied molecules were explored using enzymology tools and computational chemistry. A model based on docking results is reported.

Antibiotic survey ofLactococcus lactisstrains to six antibiotics by Etest, and establishment of new susceptibility-resistance cut-off values

2007 ◽  
Vol 74 (3) ◽  
pp. 262-268 ◽  
Author(s):  
Ana Belén Flórez ◽  
Morten Danielsen ◽  
Jenni Korhonen ◽  
Joanna Zycka ◽  
Atte von Wright ◽  
...  
Keyword(s):  
Antibiotic Resistance ◽  
Inhibitory Concentration ◽  
Tetracycline Resistance ◽  
Large Collection ◽  
Bacterial Strains ◽  
Resistance Determinants ◽  
Resistant Strains ◽  
Geographical Locations ◽  
S Genes ◽  
Acquired Antibiotic Resistance

In order to establish cut-off values forLactococcus lactisto six antibiotics to distinguish susceptible and intrinsically resistant strains from those having acquired resistances, the minimum inhibitory concentration (MIC) of tetracycline, erythromycin, clindamycin, streptomycin, chloramphenicol and vancomycin was determined in 93 differentLc. lactisstrains using the Etest. These bacterial strains were originally isolated from dairy and animal sources in widely separated geographical locations. Cut-offs were defined on the basis of the distribution of the MICs frequency of the studied antibiotics, which in the absence of acquired determinants should approach to a normal statistical distribution. In general, the new cut-off values proposed in this study are higher than previously defined (European Commission, 2005. The EFSA Journal 223, 1–12). Based on these new values, all the strains tested were susceptible to erythromycin, chloramphenicol and vancomycin, and 79 susceptible to all six antibiotics. However, 11 strains (around 12%) were considered resistant to tetracycline (six of which had been identified after screening of a large collection of lactococci strains for tetracycline resistance) and five (5·4%) resistant to streptomycin. Of these, two fish isolates proved to be resistance to both tetracycline and streptomycin. From the tetracycline resistant strains,tet(M) and mosaictet(L/S) genes were amplified by PCR, demonstrating they harboured acquired antibiotic resistance determinants.

scholarly journals Novel Tetracycline Resistance Determinant from the Oral Metagenome

2003 ◽  
Vol 47 (4) ◽  
pp. 1430-1432 ◽  
Author(s):  
M. L. Diaz-Torres ◽  
R. McNab ◽  
D. A. Spratt ◽  
A. Villedieu ◽  
N. Hunt ◽  
...  
Keyword(s):  
Resistance Gene ◽  
Tetracycline Resistance ◽  
Resistance Determinant ◽  
Tetracycline Resistance Gene ◽  
Major Drawback

ABSTRACT A major drawback of most studies on how bacteria become resistant to antibiotics is that they concentrate mainly on bacteria that can be cultivated in the laboratory. In the present study, we cloned part of the oral metagenome and isolated a novel tetracycline resistance gene, tet(37), which inactivates tetracycline.

scholarly journals Occurrence of the New Tetracycline Resistance Gene tet(W) in Bacteria from the Human Gut

2000 ◽  
Vol 44 (3) ◽  
pp. 775-777 ◽  
Author(s):  
Karen P. Scott ◽  
Claire M. Melville ◽  
Teresa M. Barbosa ◽  
Harry J. Flint
Keyword(s):  
Resistance Gene ◽  
Bifidobacterium Longum ◽  
Tetracycline Resistance ◽  
Human Feces ◽  
Human Gut ◽  
Tetracycline Resistance Gene ◽  
Butyrivibrio Fibrisolvens

ABSTRACT Members of our group recently identified a new tetracycline resistance gene, tet(W), in three genera of rumen obligate anaerobes. Here, we show that tet(W) is also present in bacteria isolated from human feces. The tet(W) genes found in human Fusobacterium prausnitzii andBifidobacterium longum isolates were more than 99.9% identical to those from a rumen isolate of Butyrivibrio fibrisolvens.

scholarly journals Analysis of a Growth-Phase-Regulated Two-Component Regulatory System in the Periodontal Pathogen Treponema denticola

2008 ◽  
Vol 190 (18) ◽  
pp. 6162-6169 ◽  
Author(s):  
Jesse R. Frederick ◽  
Elizabeth A. Rogers ◽  
Richard T. Marconi
Keyword(s):  
Growth Phase ◽  
Regulatory Networks ◽  
Response Regulator ◽  
Regulatory System ◽  
Open Reading Frames ◽  
Periodontal Pathogen ◽  
Treponema Denticola ◽  
Rt Pcr ◽  
Two Component ◽  
Transcriptional Regulatory Mechanisms

ABSTRACT Nothing is currently known regarding the global regulatory networks of Treponema denticola and other oral spirochetes. In this report, we assess the properties and potential phosphotransfer capability of a putative two-component regulatory system (TCS) of T. denticola that is formed by the products of open reading frames tde0032 (a sensor kinase) and tde0033 (a response regulator), henceforth designated AtcS and AtcR, respectively. Using PCR and DNA sequence analyses, atcS and atcR were demonstrated to be widely distributed and conserved among T. denticola isolates. Reverse transcription-PCR (RT-PCR) analyses revealed that these genes are cotranscribed and may also be expressed as part of a larger operon that includes several flanking genes. Analyses using 5′ rapid amplification of cDNA ends identified the transcriptional start sites for these operons and provided evidence that some of these genes may be independently transcribed from internal promoters. Real-time RT-PCR and Western blot analysis revealed significant upregulation of atcRS during late-stage growth, indicating growth-phase-dependent expression. Lastly, the phosphorelay capability of the AtcRS system was assessed and demonstrated using recombinant proteins. AtcS was found to undergo autophosphorylation and to transfer phosphate to AtcR. These analyses represent the first description of a functional TCS in an oral spirochetes and provide insight into the transcriptional regulatory mechanisms of these important bacteria.

scholarly journals Prevalence of Antimicrobial Resistance and Transfer of Tetracycline Resistance Genes in Escherichia coli Isolates from Beef Cattle

2015 ◽  
Vol 81 (16) ◽  
pp. 5560-5566 ◽  
Author(s):  
Seung Won Shin ◽  
Min Kyoung Shin ◽  
Myunghwan Jung ◽  
Kuastros Mekonnen Belaynehe ◽  
Han Sang Yoo
Keyword(s):  
Escherichia Coli ◽  
South Korea ◽  
Beef Cattle ◽  
Resistance Gene ◽  
Resistance Genes ◽  
Tetracycline Resistance ◽  
Tetracycline Resistance Gene ◽  
Content Type ◽  
E Coli ◽  
Tetracycline Resistance Genes

ABSTRACTThe aim of this study was to investigate the prevalence and transferability of resistance in tetracycline-resistantEscherichia coliisolates recovered from beef cattle in South Korea. A total of 155E. coliisolates were collected from feces in South Korea, and 146 were confirmed to be resistant to tetracycline. The tetracycline resistance genetet(A) (46.5%) was the most prevalent, followed bytet(B) (45.1%) andtet(C) (5.8%). Strains carryingtet(A) plustet(B) andtet(B) plustet(C) were detected in two isolates each. In terms of phylogenetic grouping, 101 (65.2%) isolates were classified as phylogenetic group B1, followed in decreasing order by D (17.4%), A (14.2%), and B2 (3.2%). Ninety-one (62.3%) isolates were determined to be multidrug resistant by the disk diffusion method. MIC testing using the principal tetracyclines, namely, tetracycline, chlortetracycline, oxytetracycline, doxycycline, and minocycline, revealed that isolates carryingtet(B) had higher MIC values than isolates carryingtet(A). Conjugation assays showed that 121 (82.9%) isolates could transfer a tetracycline resistance gene to a recipient via the IncFIB replicon (65.1%). This study suggests that the high prevalence of tetracycline-resistantE. coliisolates in beef cattle is due to the transferability of tetracycline resistance genes betweenE. colipopulations which have survived the selective pressure caused by the use of antimicrobial agents.

Sign in / Sign up

Export Citation Format

Share Document