scholarly journals Phenotypic characterization of R-factor tetracycline resistance determinants

1974 ◽  
Vol 24 (3) ◽  
pp. 333-343 ◽  
Author(s):  
T. J. Foster ◽  
Áine Walsh
Keyword(s):  
Tetracycline Resistance ◽  
Phenotypic Characterization ◽  
Resistance Determinants ◽  
R Factor ◽  
Moderate Resistance ◽  
High Level ◽  
R Factors ◽  
Phenotypic Groups ◽  
Level Resistance

SUMMARYThe tetracycline-resistance determinants of R-factors from different compatibility groups have been tested inEscherichia coliK12 and phenotypically classified into two major classes. Class I determinants confer high-level resistance to tetracycline (> 100 μg/ml) and moderate resistance to minocycline (5–25 μg/ml) while those of Class II gave moderate resistance to tetracycline (50–70 μg/ml) and low resistance to minocycline. Each class was subdivided because of variation in resistance profiles and in the abilities of tetracycline and minocycline to induce increased resistance. Strains carrying two compatible TetrR-factors of the same or different phenotypic groups did not show increased tetracycline resistance.

scholarly journals Evidence that there are two types of determinant for tetracycline resistance among R-factors

1978 ◽  
Vol 31 (1) ◽  
pp. 75-84 ◽  
Author(s):  
E. C. R. Reeve
Keyword(s):  
Growth Rate ◽  
Host Cell ◽  
Resistance Gene ◽  
Tetracycline Resistance ◽  
Repressor Gene ◽  
Homologous Group ◽  
R Factor ◽  
High Level ◽  
R Factors ◽  
Level Resistance

SUMMARYA series of derepressed mutants of the tetracycline resistance (T) determinant in R-factor R57 have been found to be repressor-negative and recessive to the T determinant in R6. It is shown that these (Tdr) mutants are dominant to the inducible T determinant in RPl, indicating that the T determinants in R57 and RP1 code for different repressors of the resistance gene. The same Tdr determinants are unstable in cells carrying both the R57 mutant and RP1, probably due to selection against the dominant Tdr gene because it depresses the growth rate of the host cell compared with its T+homologue. It is suggested that the T determinants giving high-level resistance in R57, R6 and R100 form one homologous group, probably disseminated by the transposon TnlO, while T determinants giving a much lower level of resistance, such as that in RP1, form a separate group, which may include those in R46, and R199. It is proposed that the gene responsible for tetracycline resistance should be designatedtetAand the repressor genetetI. The R57 Tdr mutants then have the genotypetetI−tetA+.

scholarly journals Analysis of the resistance mediated by several R-factors to Tetracycline and Minocycline

1972 ◽  
Vol 20 (2) ◽  
pp. 239-252 ◽  
Author(s):  
J. M. Robertson ◽  
E. C. R. Reeve
Keyword(s):  
Tetracycline Resistance ◽  
Klebsiella Aerogenes ◽  
R Factor ◽  
Before And After ◽  
Challenge Tests ◽  
Simple Growth ◽  
High Level ◽  
K 12 ◽  
R Factors ◽  
Level Group

SUMMARYThe resistance levels conferred by the T-determinants in four R-factors to Tetracycline and Minocycline in cells ofEscherichia coliK 12, before and after induction of maximum resistance by treatment with sub-inhibitory concentrations of the drugs, are measured by simple growth-and-challenge tests. The effect of a plasmid TKwhich confers tetracycline resistance on its hostKlebsiella aerogenesis tested in the same way. The five T-determinants fall into a high-level and a low-level group for resistance, the former giving 3- to 4-fold higher resistance in both induced and uninduced cells than the latter. The T-determinants all confer much lower resistance to Minocycline (a tetracycline molecule modified at the C-6 and C-7 positions) than to Tetracycline. The main cause of this difference is that cells carrying a T-determinant exclude Minocycline much less efficiently than Tetracycline, but in addition Minocycline is less effective than Tetracycline in inducing increased resistance. These results are discussed in the light of a model put forward to explain the inducible nature of R-factor resistance to the tetracyclines.

scholarly journals Phenotypic Characterization of Two Ancylostoma caninum Isolates with Different Susceptibilities to the Anthelmintic Pyrantel

2008 ◽  
Vol 52 (11) ◽  
pp. 3980-3986 ◽  
Author(s):  
Steven R. Kopp ◽  
Glen T. Coleman ◽  
James S. McCarthy ◽  
Andrew C. Kotze
Keyword(s):  
Nicotinic Acetylcholine Receptors ◽  
Acetylcholine Receptors ◽  
Resistance Mechanism ◽  
Fold Increase ◽  
Phenotypic Characterization ◽  
Gastrointestinal Helminths ◽  
Ancylostoma Caninum ◽  
High Level ◽  
Level Resistance

ABSTRACT The anthelmintic pyrantel plays an important role in the control of gastrointestinal helminths of humans and domestic animals. Despite the demonstration of pyrantel resistance in several helminth species over the last 20 years, the resistance mechanism remains unclear. It has been hypothesized that resistance may arise as a consequence of changes to the relative proportions of subpopulations of nicotinic acetylcholine receptors (nAchRs). To test this hypothesis, we examined the responses of two isolates of the canine hookworm Ancylostoma caninum with low-level resistance (isolate NT) and high-level resistance (isolate PR) to pyrantel to nicotinic agonist drugs reported to be selective for three nAchR subtypes. We used larval motility and conformation assays and force transduction experiments with adult worms. Pyrantel and levamisole were less potent against larvae of isolate PR than larvae of isolate NT (up to an 18-fold increase in the 50% inhibitory concentration); on the other hand, bephenium was more potent against larvae of isolate PR than larvae of isolate NT (twofold) and nicotine had the same potency against larvae of both isolates. In adults, pyrantel, levamisole, and nicotine were less potent against isolate PR than isolate NT (two- to threefold), but the potency of bephenium against the two isolates was equivalent. Our data indicate a complex pattern of nAchRs in this species and suggest that the two isolates differ in their relative sensitivities to agonists targeting different nAchRs.

scholarly journals High level resistance to Erythromycin and Tetracycline and dissemination of resistance determinants among clinical enterococci in Kerman-Iran

2021 ◽  
Author(s):  
Nikta Ahmadpoor ◽  
Roya Ahmadrajabi ◽  
Sarvenaz Esfahani ◽  
Zoya Hojabri ◽  
Mohammad Hassan Moshafi ◽  
...  
Keyword(s):  
Minimum Inhibitory Concentration ◽  
Inhibitory Concentration ◽  
Tetracycline Resistance ◽  
Resistance Mechanisms ◽  
Resistance Determinants ◽  
High Prevalence ◽  
Genes Encoding ◽  
High Level ◽  
O 31 ◽  
Level Resistance

Objectives: The purpose of this study was to investigate the distribution pattern of genes responsible for erythromycin and tetracycline resistance and their association with resistance phenotype in enterococci isolates. Materials and Methods: Eighty six Enterococcus faecalis and 26 E. faecium isolates were collected from two hospitals in Kerman-Iran. Minimum inhibitory concentration of erythromycin and tetracycline were determined and then, genes encoding resistance to erythromycin; erm (A-C), mef and msr -and tetracycline; tet (M), tet (O), tet (S), tet (K) and tet (L) – were investigated. Results: In all resistant isolates (n= 72, 64%), high level resistance to both tested antibiotics was found. The most prevalent erm gene was erm (B) (77.7%), followed by erm (A) (15.2%) and erm (C) (8.3%). Genes mediating erythromycin efflux, were detected in 70.8 % (mef) and 9.7% (msr) of resistant isolates. Regarding tetracycline, tet (M) was detected at the highest rate (50%), followed by tet (O) (31%) and tet (S) (11%). Export of tetracycline was found in 31% (tet (K)) and 12% (tet (L)) of isolates. Conclusion: High prevalence of high level resistance to both erythromycin and tetracycline was documented. The alteration at ribosomal level, had bigger role in erythromycin and tetracycline resistance than efflux systems. Concurrent resistance mechanisms were more involved in resistance to erythromycin than tetracycline.

scholarly journals A Combination of sbmA and tolC Mutations in Escherichia coli K-12 Tn10-Carrying Strains Results in Hypersusceptibility to Tetracycline

2007 ◽  
Vol 190 (4) ◽  
pp. 1491-1494 ◽  
Author(s):  
Ricardo E. de Cristóbal ◽  
Paula A. Vincent ◽  
Raúl A. Salomón
Keyword(s):  
Escherichia Coli ◽  
Double Mutant ◽  
Phenotypic Expression ◽  
Tetracycline Resistance ◽  
Additive Effect ◽  
Complete Suppression ◽  
High Level ◽  
K 12 ◽  
Level Resistance

ABSTRACT Previously, we demonstrated that Escherichia coli tolC mutations reduce the high-level resistance to tetracycline afforded by the transposon Tn10-encoded TetA pump from resistance at 200 μg/ml to resistance at 40 μg/ml. In this study, we found that the addition of an sbmA mutation to a tolC::Tn10 mutant exacerbates this phenotype: the double mutant did not form colonies, even in the presence of tetracycline at a concentration as low as 5 μg/ml. Inactivation of sbmA alone partially inhibited high-level tetracycline resistance, from resistance at 200 μg/ml to resistance at 120 μg/ml. There thus appears to be an additive effect of the mutations, resulting in almost complete suppression of the phenotypic expression of Tn10 tetracycline resistance.

Characterization of staphylococci contaminating automated teller machines in Hong Kong

2011 ◽  
Vol 140 (8) ◽  
pp. 1366-1371 ◽  
Author(s):  
M. ZHANG ◽  
M. O'DONONGHUE ◽  
M. V. BOOST
Keyword(s):  
Staphylococcus Aureus ◽  
Antibiotic Resistance ◽  
Resistance Genes ◽  
Benzalkonium Chloride ◽  
Tetracycline Resistance ◽  
Chlorhexidine Digluconate ◽  
Coagulase Negative Staphylococci ◽  
Automated Teller Machines ◽  
Resistance Determinants

SUMMARYEnvironmental staphylococcal contamination was investigated by culture of 400 automated teller machines (ATMs). Isolates were characterized for antibiotic and antiseptic susceptibility, carriage of antiseptic resistance genes (QAC genes), and spa types. MRSA, which was similar to local clinical isolates, was present on two (0·5%) of the 62 (15·5%) ATMs that yielded Staphylococcus aureus. QAC genes were more common in coagulase-negative staphylococci (qacA/B 26·0%, smr 14%) than S. aureus (11·3% qacA/B, 1·6% smr). QAC-positive isolates had significantly higher minimum inhibitory concentrations/minimum bactericidal concentrations to benzalkonium chloride and chlorhexidine digluconate. QAC gene presence was significantly associated with methicillin and tetracycline resistance. Survival of staphylococci, including MRSA, on common access sites may be facilitated by low disinfectant concentrations, which select for disinfectant-tolerant strains, while co-selecting for antibiotic-resistance determinants. Disinfection procedures should be performed correctly to help prevent spread of resistant pathogens from reservoirs in the community.

scholarly journals Genetic Characterization of Fluoroquinolone-Resistant Streptococcus pneumoniae Strains Isolated during Ciprofloxacin Therapy from a Patient with Bronchiectasis

2003 ◽  
Vol 47 (4) ◽  
pp. 1419-1422 ◽  
Author(s):  
Adela G. de la Campa ◽  
María-José Ferrandiz ◽  
Fe Tubau ◽  
Román Pallarés ◽  
Federico Manresa ◽  
...  
Keyword(s):  
Streptococcus Pneumoniae ◽  
Genetic Characterization ◽  
Susceptible Strain ◽  
Low Level ◽  
Resistant Strains ◽  
Resistant Mutants ◽  
High Level ◽  
Level Resistance

ABSTRACT Five Spain9V-3 Streptococcus pneumoniae strains were isolated from a patient with bronchiectasis who had received long-term ciprofloxacin therapy. One ciprofloxacin-susceptible strain was isolated before treatment, and four ciprofloxacin-resistant strains were isolated during treatment. The resistant strains were derived from the susceptible strain either by a parC mutation (low-level resistance) or by parC and gyrA mutations (high-level resistance). This study shows that ciprofloxacin therapy in a patient colonized by susceptible S. pneumoniae may select fluoroquinolone-resistant mutants.

scholarly journals Comparative Genomic Analysis and Phenotypic Characterization of Bronchoscope-Associated Klebsiella aerogenes

2021 ◽  
Vol 70 (3) ◽  
pp. 409-412
Author(s):  
FANG HUANG ◽  
SHUANG LI ◽  
LAN LOU ◽  
JUNJUN MO ◽  
HAO XU
Keyword(s):  
Antimicrobial Agents ◽  
Genomic Analysis ◽  
Phenotypic Characterization ◽  
Comparative Genomic ◽  
Klebsiella Aerogenes ◽  
Clinical Procedures ◽  
First Time ◽  
Sequence Types ◽  
Level Resistance

Bronchoscopes have been linked to outbreaks of nosocomial infections. The phenotypic and genomic profiles of bronchoscope-associated Klebsiella aerogenes isolates are largely unknown. In this work, a total of 358 isolates and 13 isolates were recovered from samples after clinical procedures and samples after decontamination procedures, respectively, over the five months. Antimicrobial susceptibility testing found seven K. aerogenes isolates exhibiting a low-level resistance to antimicrobial agents. Among seven K. aerogenes isolates, we found five sequence types (STs) clustered into three main clades. Collectively, this study described for the first time the phenotypic and genomic characteristics of bronchoscope-associated K. aerogenes.

scholarly journals DdlN from Vancomycin-Producing Amycolatopsis orientalis C329.2 Is a VanA Homologue withd-Alanyl-d-Lactate Ligase Activity

1998 ◽  
Vol 180 (21) ◽  
pp. 5792-5795 ◽  
Author(s):  
C. Gary Marshall ◽  
Gerard D. Wright
Keyword(s):  
Glycopeptide Antibiotics ◽  
Sources Of Resistance ◽  
Amycolatopsis Orientalis ◽  
Close Relationship ◽  
Key Enzyme ◽  
Vancomycin Resistant ◽  
High Level ◽  
Evaluation Of Kinetic Parameters ◽  
Level Resistance

ABSTRACT Vancomycin-resistant enterococci acquire high-level resistance to glycopeptide antibiotics through the synthesis of peptidoglycan terminating in d-alanyl-d-lactate. A key enzyme in this process is a d-alanyl-d-alanine ligase homologue, VanA or VanB, which preferentially catalyzes the synthesis of the depsipeptide d-alanyl-d-lactate. We report the overexpression, purification, and enzymatic characterization of DdlN, a VanA and VanB homologue encoded by a gene of the vancomycin-producing organism Amycolatopsis orientalisC329.2. Evaluation of kinetic parameters for the synthesis of peptides and depsipeptides revealed a close relationship between VanA and DdlN in that depsipeptide formation was kinetically preferred at physiologic pH; however, the DdlN enzyme demonstrated a narrower substrate specificity and commensurately increased affinity ford-lactate in the C-terminal position over VanA. The results of these functional experiments also reinforce the results of previous studies that demonstrated that glycopeptide resistance enzymes from glycopeptide-producing bacteria are potential sources of resistance enzymes in clinically relevant bacteria.

scholarly journals Characterization of an Enterococcus gallinarum Isolate Carrying a DualvanAandvanBCassette

2015 ◽  
Vol 53 (7) ◽  
pp. 2225-2229 ◽  
Author(s):  
Alireza Eshaghi ◽  
Dea Shahinas ◽  
Aimin Li ◽  
Ruwandi Kariyawasam ◽  
Philip Banh ◽  
...  
Keyword(s):  
Clinical Isolate ◽  
Resistance Mechanism ◽  
Vancomycin Resistance ◽  
Content Type ◽  
Enterococcal Species ◽  
Enterococcus Gallinarum ◽  
High Level ◽  
Identification And Characterization ◽  
Level Resistance

The ability of vancomycin resistance determinants to be horizontally transferred within enterococci species is a concern. Identification and characterization of vancomycin-resistant enterococci (VRE) in a clinical isolate have a significant impact on infection control practices. In this study, we describe a clinical isolate ofEnterococcus gallinarumexhibiting high-level resistance to vancomycin and teicoplanin. The genetic characterization of this isolate showed the presence ofvanAandvanBgenes in addition to the naturally carriedvanCgene.vanAwas identified on pA6981, a 35,608-bp circular plasmid with significant homology to plasmid pS177. ThevanBoperon was integrated into the bacterial chromosome and showed a high level of homology to previously reported Tn1549and Tn5382. To the best of our knowledge, this is the first report ofE. gallinarumcarrying bothvanAandvanBoperons, indicating the importance of identifying the vancomycin resistance mechanism in non-E. faeciumand non-E. faecalisenterococcal species.

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