Selection of Dieldrin-Resistant Strains of Lucilia cuprina (Diptera: Calliphoridae) After Ethyl Methanesulfonate Mutagenesis of a Susceptible Strain

1992 ◽  
Vol 85 (2) ◽  
pp. 352-358 ◽  
Author(s):  
Kerrie-Ann Smyth ◽  
Anthony G. Parker ◽  
Janet L. Yen ◽  
John A. McKenzie
Keyword(s):  
Susceptible Strain ◽  
Ethyl Methanesulfonate ◽  
Lucilia Cuprina ◽  
Resistant Strains ◽  
Selection Of ◽  
Ethyl Methanesulfonate Mutagenesis

Development of a changed response in Lucilia cuprina (Wied.) to organophosphorus insecticides in New South Wales

1966 ◽  
Vol 57 (1) ◽  
pp. 93-100 ◽  
Author(s):  
G. J. Shanahan
Keyword(s):  
New South ◽  
New South Wales ◽  
Susceptible Strain ◽  
Lucilia Cuprina ◽  
Organophosphorus Insecticides ◽  
Field Surveys ◽  
South Wales ◽  
Sensitivity Tests ◽  
Resistant Strains ◽  
Continued Use

Since 1956, samples of Lucilia cuprina (Wied.) from many parts of New South Wales have been tested annually for signs of resistance to organophosphours insecticides, which are used there to prevent fly-strike in sheep. For tests, 0.1 μg. diazinon per fly was applied topically; this discriminating dose was twice that required to kill 100 per cent. of susceptible flies. In 1965, some of the flies in a sample from Dubbo, in central-western N.S.W., survived the discriminating dose. Sensitivity tests of the progeny of the survivors (DB strain) and of a normal susceptible strain revealed that the LC50 of the DB strain was about three times that of the normal one. Further tests established that a roughly similar change in sensitivity had ocurred to other diethoxy (dichlofenthion, fenthion-ethyl, bromophos-ethyl, parathion) and to dimethoxy (fenchlorphos, parathion-menthyl, bromophos) organophosphors compounds. The change was therefore non-specific and, since it was also small, is regarded as an example of tolerance rather than of resistance.Subsequent field surveys in 1965–66 showed that tolerance of L. cuprina to diazinon was widespread in N.S.W. The possibility that resistant strains will be selected out by continued use of organophosphorus insecticides is discussed.

Microencapsulation: A Prospective to Protect Probiotics

2020 ◽  
Vol 16 (6) ◽  
pp. 891-899 ◽  
Author(s):  
Wissam Zam
Keyword(s):  
Gastrointestinal Tract ◽  
Food Industry ◽  
Health Benefits ◽  
Probiotic Bacteria ◽  
Bacterial Cells ◽  
Beneficial Effects ◽  
Host Health ◽  
Resistant Strains ◽  
Selection Of

Probiotics are viable microorganisms widely used for their claimed beneficial effects on the host health. A wide number of researchers proved that the intake of probiotic bacteria has numerous health benefits which created a big market of probiotic foods worldwide. The biggest challenge in the development of these products is to maintain the viability of bacterial cells during the storage of the product as well as throughout the gastrointestinal tract transit after consumption, so that the claimed health benefits can be delivered to the consumer. Different approaches have been proposed for increasing the resistance of these sensitive microorganisms, including the selection of resistant strains, incorporation of micronutrients, and most recently the use of microencapsulation techniques. Microencapsulation has resulted in enhancing the viability of these microorganisms which allows its wide use in the food industry. In this review, the most common techniques used for microencapsulation of probiotics will be presented, as well as the most usual microcapsule shell materials.

scholarly journals Polygenic and single gene responses to selection for resistance to diazinon in Lucilia cuprina.

Genetics ◽  
1992 ◽  
Vol 130 (3) ◽  
pp. 613-620 ◽  
Author(s):  
J A McKenzie ◽  
A G Parker ◽  
J L Yen
Keyword(s):  
Resistant Strain ◽  
Single Gene ◽  
Natural Populations ◽  
Susceptible Strain ◽  
Selection Line ◽  
Base Population ◽  
Gene Response ◽  
Biochemical Profiles ◽  
Resistant Strains ◽  
Selection For

Abstract Following mutagenesis with ethyl methanesulfonate, selection in a susceptible strain with a concentration of the insecticide diazinon (0.0004%, w/v) above that required to kill 100% of the susceptible strain, the LC100 of that strain, resulted in a single gene response. The resultant four mutant resistant strains have equivalent physiological, genetical and biochemical profiles to a diazinon-resistant strain derived from a natural population and homozygous for the Rop-1 allele. Modification of the microsomal esterase E3 is responsible for resistance in each case. The Rop-1 locus maps approximately 4.4 map units proximal to bu on chromosome IV. Selection within the susceptible distribution, at a concentration of diazinon [0.0001% (w/v)] less than the LC100, resulted in a similar phenotypic response irrespective of whether the base population had been mutagenized. The responses were polygenically based, unique to each selection line and independent of Rop-1. The relevance of the results to selection for insecticide resistance in laboratory and natural populations is discussed.

scholarly journals Comparative study of once-weekly azithromycin and once-daily amoxicillin treatments in prevention of recurrent acute otitis media in children.

1996 ◽  
Vol 40 (12) ◽  
pp. 2732-2736 ◽  
Author(s):  
P Marchisio ◽  
N Principi ◽  
E Sala ◽  
L Lanzoni ◽  
S Sorella ◽  
...  
Keyword(s):  
Otitis Media ◽  
Randomized Study ◽  
Acute Otitis Media ◽  
Occurrence Rate ◽  
Once Daily ◽  
Recurrent Acute Otitis Media ◽  
Periodic Administration ◽  
Resistant Strains ◽  
Selection Of

Continuous chemoprophylaxis is effective in the prevention of new episodes of acute otitis media (AOM) in otitis-prone children, but compliance can be a problem and thus efficacy can be decreased. Intermittent chemoprophylaxis has so far shown conflicting results. Azithromycin, which has a peculiar pharmacokinetics, resulting, even after a single dose, in persistently elevated concentrations in respiratory tissues, could permit a periodic administration with higher compliance. We compared a 6-month course of once-weekly azithromycin (5 or 10 mg/kg of body weight) with that of once-daily amoxicillin (20 mg/kg) in a single-blind, randomized study of prophylaxis for recurrent AOM in 159 children aged 6 months to 5 years with at least three episodes of AOM in the preceding 6 months. In the amoxicillin group, 23 (31.1%) of 74 children developed 29 episodes of AOM, while in the 10-mg/kg azithromycin group, 11 (14.9%) of 74 children experienced 15 episodes. The 5-mg/kg/week azithromycin trial was prematurely interrupted after nine cases, due to the high occurrence rate of AOM (55.5%). During the 6-month prophylaxis period, the proportion of children with middle ear effusion declined similarly in both groups. No substantial modification of the nasopharyngeal flora was noted at the end of prophylaxis in both antimicrobial groups. In the 6-month-postprophylaxis follow-up period, about 40% of children in both groups again developed AOM. Azithromycin at 10 mg/kg once weekly can be regarded as a valid alternative to once-daily low-dose amoxicillin for the prophylaxis of AOM. Although in the present study no microbiological drawback was noted, accurate selection of children eligible for prophylaxis is mandatory to avoid the risk of emergence of resistant strains.

scholarly journals In vitro anti-mycobacterial activity of (E)-N´-(monosubstituted-benzylidene) isonicotinohydrazide derivatives against isoniazid-resistant strains

2012 ◽  
Vol 4 (1) ◽  
pp. 13 ◽  
Author(s):  
Tatiane S. Coelho ◽  
Jessica B. Cantos ◽  
Marcelle L.F. Bispo ◽  
Raoni S.B. Gonçalves ◽  
Camilo H.S. Lima ◽  
...  
Keyword(s):  
Antibacterial Activity ◽  
Resistant Strain ◽  
Mechanisms Of Action ◽  
Susceptible Strain ◽  
Clinical Isolates ◽  
Coding Region ◽  
Resistant Strains

A series of twenty-three <em>N-acylhydrazones</em> derived from isoniazid (INH 1-23) have been evaluated for their <em>in vitro</em> antibacterial activity against INH- susceptible strain of <em>M. tuberculosis</em> (RG500) and three INH-resistant clinical isolates (RG102, RG103 and RG113). In general, derivatives 4, 14, 15 and 16 (MIC=1.92, 1.96, 1.96 and 1.86 mM, respectively) showed relevant activities against RG500 strain, while the derivative 13 (MIC=0.98 mM) was more active than INH (MIC=1.14 mM). However, these derivatives were inactive against RGH102, which displays a mutation in the coding region of <em>inhA</em>. These results suggest that the activities of these compounds depend on the inhibition of this enzyme. However, the possibility of other mechanisms of action cannot be excluded, since compounds 2, 4, 6, 7, 12-17, 19, 21 and 23 showed good activities against <em>katG</em>-resistant strain RGH103, being more than 10-fold more active than INH.

scholarly journals Antipneumococcal Activities of Two Novel Macrolides, GW 773546 and GW 708408, Compared with Those of Erythromycin, Azithromycin, Clarithromycin, Clindamycin, and Telithromycin

2004 ◽  
Vol 48 (11) ◽  
pp. 4103-4112 ◽  
Author(s):  
Vlatka Matic ◽  
Klaudia Kosowska ◽  
Bulent Bozdogan ◽  
Linda M. Kelly ◽  
Kathy Smith ◽  
...  
Keyword(s):  
Ribosomal Protein ◽  
Protein Sequence ◽  
Single Step ◽  
23S Rrna ◽  
Susceptible Parent ◽  
Rrna Sequence ◽  
Resistant Strains ◽  
Resistant Mutants ◽  
Rrna Sequences ◽  
Selection Of

ABSTRACT The MICs of GW 773546, GW 708408, and telithromycin for 164 macrolide-susceptible and 161 macrolide-resistant pneumococci were low. The MICs of GW 773546, GW 708408, and telithromycin for macrolide-resistant strains were similar, irrespective of the resistance genotypes of the strains. Clindamycin was active against all macrolide-resistant strains except those with erm(B) and one strain with a 23S rRNA mutation. GW 773546, GW 708408, and telithromycin at two times their MICs were bactericidal after 24 h for 7 to 8 of 12 strains. Serial passages of 12 strains in the presence of sub-MICs yielded 54 mutants, 29 of which had changes in the L4 or L22 protein or the 23S rRNA sequence. Among the macrolide-susceptible strains, resistant mutants developed most rapidly after passage in the presence of clindamycin, GW 773546, erythromycin, azithromycin, and clarithromycin and slowest after passage in the presence of GW 708408 and telithromycin. Selection of strains for which MICs were ≥0.5 μg/ml from susceptible parents occurred only with erythromycin, azithromycin, clarithromycin, and clindamycin; 36 resistant clones from susceptible parent strains had changes in the sequences of the L4 or L22 protein or 23S rRNA. No mef(E) strains yielded resistant clones after passage in the presence of erythromycin and azithromycin. Selection with GW 773546, GW 708408, telithromycin, and clindamycin in two mef(E) strains did not raise the erythromycin, azithromycin, and clarithromycin MICs more than twofold. There were no change in the ribosomal protein (L4 or L22) or 23S rRNA sequences for 15 of 18 mutants selected for macrolide resistance; 3 mutants had changes in the L22-protein sequence. GW 773546, GW 708408, and telithromycin selected clones for which MICs were 0.03 to >2.0 μg/ml. Single-step studies showed mutation frequencies <5.0 × 10−10 to 3.5 × 10−7 for GW 773546, GW 708408, and telithromycin for macrolide-susceptible strains and 1.1 × 10−7 to >4.3 × 10−3 for resistant strains. The postantibiotic effects of GW 773546, GW 708408, and telithromycin were 2.4 to 9.8 h.

scholarly journals Synergy of Linezolid with Several Antimicrobial Agents against Linezolid-Methicillin-Resistant Staphylococcal Strains

Antibiotics ◽  
2020 ◽  
Vol 9 (8) ◽  
pp. 496
Author(s):  
María-José Valderrama ◽  
María Alfaro ◽  
Icíar Rodríguez-Avial ◽  
Elvira Baos ◽  
Carmen Rodríguez-Avial ◽  
...  
Keyword(s):  
Antimicrobial Agents ◽  
Synergistic Effects ◽  
Ribosomal Subunit ◽  
Antagonistic Effect ◽  
Prolonged Treatment ◽  
Synergistic Activity ◽  
Methicillin Resistant ◽  
Resistant Strains ◽  
Time Kill ◽  
Selection Of

Linezolid is a synthetic oxazolydinone active against multi-resistant Gram-positive cocci that inhibits proteins synthesis by interacting with the 50S ribosomal subunit. Although linezolid-resistant strains are infrequent, several outbreaks have been recently described, associated with prolonged treatment with the antibiotic. As an alternative to monotherapy, the combination of different antibiotics is a commonly used option to prevent the selection of resistant strains. In this work, we evaluated combinations of linezolid with classic and new aminoglycosides (amikacin, gentamicin and plazomicin), carbapenems (doripenem, imipenem and meropenem) and fosfomycin on several linezolid- and methicillin-resistant strains of Staphylococcus aureus and S. epidermidis, isolated in a hospital intensive care unit in Madrid, Spain. Using checkerboard and time-kill assays, interesting synergistic effects were encountered for the combination of linezolid with imipenem in all the staphylococcal strains, and for linezolid–doripenem in S.epidermidis isolates. The combination of plazomicin seemed to also have a good synergistic or partially synergistic activity against most of the isolates. None of the combinations assayed showed an antagonistic effect.

scholarly journals Cyclic AMP Signaling Pathway Modulates Susceptibility of Candida Species and Saccharomyces cerevisiae to Antifungal Azoles and Other Sterol Biosynthesis Inhibitors

2003 ◽  
Vol 47 (10) ◽  
pp. 3195-3201 ◽  
Author(s):  
Pooja Jain ◽  
Indira Akula ◽  
Thomas Edlind
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Cyclic Amp ◽  
Adenylate Cyclase ◽  
Signaling Pathway ◽  
Sterol Biosynthesis ◽  
Fungistatic Activity ◽  
Species Analysis ◽  
Resistant Strains ◽  
Camp Levels ◽  
Selection Of

ABSTRACT Azoles are widely used antifungals; however, their efficacy is compromised by fungistatic activity and selection of resistant strains during treatment. Recent studies demonstrated roles for the protein kinase C and calcium signaling pathways in modulating azole activity. Here we explored a role for the signaling pathway mediated by cyclic AMP (cAMP), which is synthesized by the regulated action of adenylate cyclase (encoded by CDC35 in Candida albicans and CYR1 in Saccharomyces cerevisiae) and cyclase-associated protein (encoded by CAP1 and SRV2, respectively). Relative to wild-type strains, C. albicans and S. cerevisiae strains mutated in these genes were hypersusceptible to fluconazole (>4- to >16-fold-decreased 48-h MIC), itraconazole (>8- to >64-fold), or miconazole (16- to >64-fold). Similarly, they were hypersusceptible to terbinafine and fenpropimorph (2- to >16-fold), which, like azoles, inhibit sterol biosynthesis. Addition of cAMP to the medium at least partially reversed the hypersusceptibility of Ca-cdc35 and Sc-cyr1-2 mutants. An inhibitor of mammalian adenylate cyclase, MDL-12330A, was tested in combination with azoles; a synergistic effect was observed against azole-susceptible and -resistant strains of C. albicans and five of six non-C. albicans Candida species. Analysis of cAMP levels after glucose induction in the presence and absence of MDL-12330A confirmed that it acts by inhibiting cAMP synthesis in yeast. RNA analysis suggested that a defect in azole-dependent upregulation of the multidrug transporter gene CDR1 contributes to the hypersusceptibility of the Ca-cdc35 mutant. Our results implicate cAMP signaling in the yeast azole response; compounds similar to MDL-12330A may be useful adjuvants in azole therapy.

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