Development of resistance to streptomycin by Bact. lactis aerogenes (Aerobacter aerogenes ) II. A comparison of mutants of different origins

1961 ◽  
Vol 154 (957) ◽  
pp. 571-578 ◽  
Keyword(s):  
Ultra Violet ◽  
Direct Selection ◽  
Replica Plating ◽  
Negative Results ◽  
Development Of Resistance ◽  
Low Concentrations ◽  
Resistant Strains ◽  
Induction Of Resistance ◽  
Different Origins ◽  
Basic Similarity

Streptomycin-resistant strains of Bact . lactis aerogenes have been obtained by ( a ) direct selection in a minimal salt-glucose medium containing 1 unit/ml. streptomycin (strain R s 1 ). ( b ) indirect selection in the absence of streptomycin with the replica plating technique (strain R rp ). ( c ) irradiation with ultra-violet light (strain R uv ). The rate at which colonies develop when these three strains respectively are inoculated on to minimal agar plates containing 1000 u/ml. streptomycin has been subjected to statistical comparison. The results suggest that a basic similarity exists between the strains. Experiments designed to investigate the possible specific induction of resistance by low concentrations of streptomycin in phosphate buffer suspensions of the organism yielded negative results.

Development of resistance to streptomycin by Bact . lactis aerogenes ( Aerobacter aerogenes ) I. The role of mutation and of physiological adaptation

1961 ◽  
Vol 154 (957) ◽  
pp. 449-462 ◽  
Keyword(s):  
Ultra Violet ◽  
Inhibitory Effect ◽  
Progressive Increase ◽  
Mean Value ◽  
Physiological Adaptation ◽  
Replica Plating ◽  
Development Of Resistance ◽  
Drug Concentrations ◽  
High Concentrations ◽  
Average Size

Streptomycin at a concentration below 0.1 unit/ml. has no detectable inhibitory effect on cultures of Bact . lactis aerogenes in a salt-glucose medium. At higher concentrations of the drug only resistant mutants, occurring in a proportion of about 1 in 4 x 10 8 survive. These ‘first-stage’ mutants have been isolated directly by the selective action of 1 unit/ml. streptomycin and indirectly by replica plating (1 unit (u) ≡ 1 μg streptomycin base). Mutation to resistance has also been induced by suitable irradiation with ultra-violet light. The mutants give no lag in streptomycin media but at high concentrations grow at a greatly retarded rate which can be progressively improved by subculture in the presence of the drug. It has been demonstrated that at this stage the majority of cells undergo adaptation and that further selection at the high drug concentrations does not occur. Examination of colony diameter histograms for successive subcultures on streptomycin plates reveals a progressive increase in the average size reached in a standard time, although the width of the distribution about the mean value remains essentially constant. Reconstruction experiments with mixtures of untrained cells and those trained to 1000 u/ml. streptomycin have provided further evidence of an adaptive response. It is concluded that full resistance to higher concentrations of streptomycin results from a combination of first-stage mutation and physiological adaptation of these mutants.

Treatment of Trace Organic Compounds by Membrane Processes: At the Lake Arrowhead Water Reuse Pilot Plant

1999 ◽  
Vol 40 (4-5) ◽  
pp. 293-301 ◽  
Author(s):  
Bruno B. Levine ◽  
Kapal Madireddi ◽  
Valentina Lazarova ◽  
Michael K. Stenstrom ◽  
Mel Suffet
Keyword(s):  
Pilot Plant ◽  
Water Reuse ◽  
Ultra Violet ◽  
Treatment Efficiency ◽  
Small Molecular Weight ◽  
Potable Reuse ◽  
Low Concentrations ◽  
Neutral Compounds ◽  
Indirect Potable Reuse ◽  
Trace Organic

Organic and trace organic performance data for ultrafiltration (UF), nanofiltration (NF) and reverse osmosis (RO) at the Lake Arrowhead water reclamation pilot plant are analyzed to determine the treatment efficiency of these processes in an indirect potable reuse design. Four organic parameters were studied: dissolved organic carbon (DOC), ultra-violet absorbance at 254 nm (UV-254), SUVA and base neutral analysis (BNA). UF and NF removed the larger compounds from the influent, but had no significant impact on the base neutral fraction with the exception of sterols. The RO process removed DOC and UV-absorbance compounds from the effluent to their respective detection limits. Base neutral compounds were significantly removed by RO, leaving at extremely low concentrations small molecular weight compounds, indicating indirect potable reuse is technically feasible.

Aerobic resistance of Trichomonas vaginalis to metronidazole induced in vitro

Parasitology ◽  
1993 ◽  
Vol 106 (1) ◽  
pp. 31-37 ◽  
Author(s):  
J. Tachezy ◽  
J. Kulda ◽  
E. Tomková
Keyword(s):  
Parent Strain ◽  
Trichomonas Vaginalis ◽  
Drug Resistant ◽  
Ferredoxin Oxidoreductase ◽  
Low Concentrations ◽  
Percent Concentration ◽  
Resistant Strains ◽  
Pyruvate Ferredoxin Oxidoreductase

SUMMARYAerobic resistance of Trichomonas vaginalis to metronidazole was induced in vitro by anaerobic cultivation of drug-susceptible trichomonads with low concentrations of the drug (2–3 μg/ml) for 50 days. Minimal lethal concentrations (MLC) for metronidazole of the resistant derivatives were high in aerobic susceptibility assays (MLC = 216–261.5 μg/ml) but low in anaerobic assays (MLC = 4.2–6.3 μg/ml), surpassing MLC values of their parent strain approximately 50-fold and 3-fold under aerobiosis and anaerobiosis, respectively. Sensitivity to metronidazole under anaerobic conditions and activity of the hydrogenosomal enzyme pyruvate: ferredoxin oxidoreductase indicated that the resistance was of the aerobic type. Dependence of the resistance manifestation on O2 was further confirmed by susceptibility assays in vitro performed in defined gas mixtures of different oxygen content (1–20%). Five percent concentration of O2 proved to be the threshold required for resistance demonstration and the MLC values further increased with increasing O2 concentrations. The in vitro-induced resistance was also demonstrated in vivo by subcutaneous mouse assay. The dose of metronidazole needed to cure 50% of infected mice (DC50) was 223 mg/kg × 3 for resistant derivative MR-3a but 6.6 mg/kg × 3 only for its drug-susceptible parent strain. The metronidazole – resistant strains developed in this study correspond by their properties to drug-resistant T. vaginalis strains isolated from patients refractory to treatment, and promise to be a useful tool in the study of 5-nitroimidazole aerobic resistance.

scholarly journals THE USE OF AGENTS BASED ON THE BACTERIUM BACILLUS THURINGIENSIS VAR. ISRAELENSIS FOR MOSQUITO CONTROL

2019 ◽  
Vol 98 (8) ◽  
pp. 893-896
Author(s):  
Svetlana A. Roslavtseva
Keyword(s):  
Bacillus Thuringiensis ◽  
Aedes Aegypti ◽  
Synergistic Effect ◽  
Mosquito Control ◽  
Mosquito Species ◽  
Bacillus Sphaericus ◽  
Development Of Resistance ◽  
Blood Sucking ◽  
Low Concentrations ◽  
Bacterium Bacillus

Mosquito control is necessary to improve the epidemic and, consequently, the sanitary and hygienic situation in human settlements. At the same time, the safest and more environmentally friendly way of controlling is not the fight against adult mosquitoes, but the treatment of reservoirs with microbiological larvicides based on entomopathogenic, aerobic, spore-forming, saprophytic bacteria Bacillus thuringiensis (de Barjac) (Bti). A new serotype of the bacterium B. thuringiensis was found in Israel in the Negev desert. This serotype being more active against larvae of blood-sucking and non-blood-sucking mosquitoes and midges than previously known serotypes, was named israelensis. Bti endotoxin is a typical insecticide with intestinal type of action for different mosquito species. For example, Bti H14 is highly insecticidal to the larvae of Aedes aegypti and Ae. albopictus at very low concentrations. The parasporal body (endotoxin crystal), a crystalline protein consisted of four main polypeptides and two minor polypeptides, possesses of a larvicidal action. Larvicidal activity is associated with a synergistic effect in a combination of four polypeptides. The possibility of development of resistance to products based on Bti and Bacillus sphaericus in populations of mosquitoes (Culicidae) was investigated. The use of domestic microbiological formulations based on Bti («Baktitsid», «Larviol-pasta», and «Antinat») was shown an eradication the larvae of bloodsucking mosquitoes and midges to be possible and rational, since they are not generated resistant populations of mosquitoes. This is confirmed by more than 30 years of the use of such formulations.

scholarly journals The Central Role of Multiple P450 Genes and Their Co-factor CPR in the Development of Permethrin Resistance in the Mosquito Culex quinquefasciatus

2022 ◽  
Vol 12 ◽  
Author(s):  
Youhui Gong ◽  
Ting Li ◽  
Qi Li ◽  
Shikai Liu ◽  
Nannan Liu
Keyword(s):  
Culex Quinquefasciatus ◽  
Resistance Mechanism ◽  
Gene Overexpression ◽  
Degradation Pathways ◽  
Cytochrome P450 Reductase ◽  
Major Threat ◽  
Development Of Resistance ◽  
Toxic Product ◽  
Resistant Strains

Mosquitoes’ increasing resistance to insecticides is becoming a major threat for control efforts worldwide. Multiple P450 genes that are up-regulated in permethrin resistant strains of Culex quinquefasciatus have been linked to the development of resistance. In the current study, we characterized the function of six P450 genes, CYP6P14, CYP6BZ2, CYP9J33, CYP9J34, CYP9J40, and CYP9J45, that are overexpressed in the permethrin resistant Culex mosquitoes and showed their capability in metabolism of permethrin. These six P450 genes can convert 3-phenoxybenzoic alcohol (PBCHO) to a less toxic product, 3-phenoxybenzoic acid (PBCOOH), indicating that these P450s play an important role in permethrin degradation pathways. Although we know multiple P450 genes are over-expressed in permethrin resistant Culex mosquitoes, it remains to be seen whether cytochrome P450-reductase (CPR) gene that are co-overexpressed with P450 genes in permethrin resistant mosquitoes do indeed serve as a resistance mechanism. An in-depth investigation of the expression of CPR gene in resistant mosquitoes was conducted in permethrin resistant mosquitoes. The finding of CPR gene overexpression in permethrin resistant mosquitoes suggested the importance of co-overexpression of multiple P450 genes with their obligatory electron donor CPR in the complex detoxification system, boosting the metabolism of permethrin and hence the development of permethrin resistance in Cx. quinquefasciatus.

scholarly journals Antibacterial Peptides Resistance in Staphylococcus aureus: Various Mechanisms and the Association with Pathogenicity

Genes ◽  
2021 ◽  
Vol 12 (10) ◽  
pp. 1527
Author(s):  
Miki Kawada-Matsuo ◽  
Mi Nguyen-Tra Le ◽  
Hitoshi Komatsuzawa
Keyword(s):  
Staphylococcus Aureus ◽  
Antimicrobial Peptides ◽  
Antibacterial Peptides ◽  
Low Concentrations ◽  
Component Systems ◽  
Two Component Systems ◽  
Resistant Strains ◽  
Resistant Mutants ◽  
High Concentrations

Staphylococcus aureus is a bacterium that mainly colonizes the nasal cavity and skin. To colonize the host, it is necessary for S. aureus to resist many antibacterial factors derived from human and commensal bacteria. Among them are the bacteria-derived antimicrobial peptides (AMPs) called bacteriocins. It was reported that some two-component systems (TCSs), which are signal transduction systems specific to bacteria, are involved in the resistance to several bacteriocins in S. aureus. However, the TCS-mediated resistance is limited to relatively low concentrations of bacteriocins, while high concentrations of bacteriocins still exhibit antibacterial activity against S. aureus. To determine whether we could obtain highly bacteriocin-resistant mutants, we tried to isolate highly nisin A-resistant mutants by exposing the cells to sub-minimum inhibitory concentrations (MICs) of nisin A. Nisin A is one of the bacteriocins produced by Lactococcus lactis and is utilized as a food preservative worldwide. Finally, we obtained highly nisin A-resistant mutants with mutations in one TCS, BraRS, and in PmtR, which is involved in the expression of pmtABCD. Notably, some highly resistant strains also showed increased pathogenicity. Based on our findings, this review provides up-to-date information on the role of TCSs in the susceptibility to antibacterial peptides. Additionally, the mechanism for high antimicrobial peptides resistance and its association with pathogenicity in S. aureus is elucidated.

scholarly journals Low concentrations of commercial alcohol hand rubs facilitate growth of and secretion of extracellular proteins by multidrug-resistant strains of Acinetobacter baumannii

2007 ◽  
Vol 56 (12) ◽  
pp. 1595-1599 ◽  
Author(s):  
Justin Edwards ◽  
Geeta Patel ◽  
David W. Wareham
Keyword(s):  
Acinetobacter Baumannii ◽  
Culture Supernatant ◽  
Multidrug Resistant ◽  
Extracellular Proteins ◽  
Nosocomial Pathogen ◽  
Emulsifying Activity ◽  
Health Care Settings ◽  
Low Concentrations ◽  
Resistant Strains ◽  
Minimal Media

Acinetobacter baumannii is increasingly recognized as an important multidrug-resistant nosocomial pathogen. Recent work has highlighted enhanced growth and heightened virulence in the presence of ethyl alcohols. As alcohol-based hand rubs (ABHRs) are extensively used in health care settings, the authors set out to determine whether the hand rubs could also influence the growth of prevalent multidrug-resistant strains circulating in UK hospitals. A significant increase in growth was observed when minimal media were supplemented with concentrations of 1 % and lower of four commercially available hand rubs. In addition, growth in ABHR-supplemented media resulted in secretion of proteins into the culture supernatant. One of these was identified as OmpA, which is recognized as having emulsifying activity, which could potentially confer enhanced pathogenicity to A. baumannii.

Effects of Halides on Plasmid-Mediated Silver Resistance in Escherichia coli

1998 ◽  
Vol 64 (12) ◽  
pp. 5042-5045 ◽  
Author(s):  
Amit Gupta ◽  
Maria Maynes ◽  
Simon Silver
Keyword(s):  
Escherichia Coli ◽  
Growth Medium ◽  
Silver Sulfadiazine ◽  
Resistance Plasmid ◽  
Low Concentrations ◽  
Resistant Strains ◽  
High Concentrations

ABSTRACT Silver resistance of sensitive Escherichia coli J53 and resistance plasmid-containing J53(pMG101) was affected by halides in the growth medium. The effects of halides on Ag+ resistance were measured with AgNO3 and silver sulfadiazine, both on agar and in liquid. Low concentrations of chloride made the differences in MICs between sensitive and resistant strains larger. High concentrations of halides increased the sensitivities of both strains to Ag+.

scholarly journals Targeting CDC7 sensitizes resistance melanoma cells to BRAFV600E-specific inhibitor by blocking the CDC7/MCM2-7 pathway

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Shaimaa A. Gad ◽  
Hamdy E. A. Ali ◽  
Rofaida Gaballa ◽  
Rania M. Abdelsalam ◽  
Mourad Zerfaoui ◽  
...  
Keyword(s):  
Drug Resistance ◽  
Metastatic Melanoma ◽  
Clinical Effect ◽  
Specific Inhibitor ◽  
Melanoma Cells ◽  
Development Of Resistance ◽  
Dual Targeting ◽  
Low Concentrations ◽  
Resistant Cells

Abstract Although the utilization of selective BRAFV600E inhibitors is associated with improved overall survival in patients with metastatic melanoma, a growing challenge of drug resistance has  emerged. CDC7 has been shown to be overexpressed and associated with poor prognosis in various cancers including melanoma. Thus, we aimed to elucidate the biological role of CDC7 in promoting Vemurafenib resistance and the anticipated benefits of dual targeting of BRAFV600E and CDC7 in melanoma cells. We performed exosomes-associated microRNA profiling and functional assays to determine the role of CDC7 in drug resistance using Vemurafenib-sensitive and resistant melanoma cells. Our results demonstrated that Vemurafenib-resistant cells exhibited a persistent expression of CDC7 in addition to prolonged activity of MCM2 compared to drug-sensitive cells. Reconstitution of miR-3613-3p in resistant cells downregulated CDC7 expression and reduced the number of colonies. Treatment of cells with low concentrations of CDC7 inhibitor TAK-931 sensitized resistant cells to Vemurafenib and reduced the number of cell colonies. Taken together, CDC7 overexpression and downregulation of miR-3613-3p were associated with Vemurafenib resistance in BRAFV600E- bearing melanoma cells. Dual targeting of CDC7 and BRAFV600E reduced the development of resistance against Vemurafenib. Further studies are warranted to investigate the clinical effect of targeting CDC7 in metastatic melanoma.

scholarly journals Mercury resistance of Staphylococcus aureus

1970 ◽  
Vol 68 (1) ◽  
pp. 121-128 ◽  
Author(s):  
Barbara M. Hall
Keyword(s):  
Staphylococcus Aureus ◽  
Nasal Carriage ◽  
Mercury Resistance ◽  
Development Of Resistance ◽  
Mercury Salts ◽  
Local Endemic ◽  
Resistant Strains ◽  
Endemic Strain ◽  
Made In

SummaryReasons for the accumulation of mercury-resistant strains of Staphylococcus aureus in hospital have been studied. A collection of paired strains, that is staphylococci similar in every respect except sensitivity to mercury salts, was made. Tests were made in an attempt to demonstrate a link between mercury resistance and some other factor which might aid survival, viz. resistance to drying and heat, production of bound coagulase, growth in the presence of sublethal amounts of tetracycline, survival in human blood at 37°C. and uptake by polymorphs at 30°0. and 37°C., development of resistance to antibiotics and competition in mixed cultures. It was not possible to demonstrate any consistent link between mercury resistance and any of these properties. Paper strips impregnated with the mercurial diuretic, Mersalyl, were shown to differentiate between mercury-resistant and -sensitive strains in vitro. Furthermore, development of resistance to mercury by passage in mercuric chloride-broth was demonstrated.It is proposed that mercury resistance has developed as a result of exposure to the mercury ion. Mercurial diuretics have been frequently used in medical and geriatric patients and it is among these that the higher carrier rates of mercury-resistant strains are found even when the local endemic strain is disregarded. In obstetric patients, where mercurials are seldom used, mercury-resistant strains are rare.Nasal carriage of factory workers exposed to mercury products showed that this group is likely to carry resistant or partially resistant strains.

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