Resistance delaying development

Trimethoprim-sulfamethoxazole (TMP-SMX) was introduced as a fixed dose combination in 1968. Trimethoprim was added to sulfamethoxazole to synergisti-cally and sequentially inhibit bacterial synthesis of tetrahydrofolic acid. The combination was also designed to delay development of bacterial resistance. Sulfamethoxazole was selected in part because it is a congener of the frequently used sulhsoxazole but exhibits slower enteric absorption and urinary excretion. Sulfamethoxazole has a half-life similar to that of trimethoprim. 

However, each new resistance that develops will produce a different genetic situation. The solutions found by weeds to escape herbicide selection pressures may be varied. Due to the high selective value conferred by the resistance genes in herbicide treated areas, mutation events at very low frequencies have high probability to lead to the appearance of resistant plants. In addition, weeds will certainly display after a short delay the bacterial genes transferred to crops for herbicide resistance, and some wild plants could be expected to become new weeds because of resistant genes. 

Resistance to older biocides used as pesticides Resistance to third- and fourth-generation pesticides How to delay development of resisfance 9.4.1 Refuge strategy... 

Many species of small-bodied pests experience classical responses to host resistance phenomena during an encounter with foliage of 5. berthaultii. These include host avoidance and restlessness, reduced feeding, delayed development, reduced adult weight and reproductive performance, increased mortality, and diminished longevity. In several cases, these responses are associated with entrapment or immobilization by trichome exudate. 

To achieve the lowest possible delay a bipolar switching transistor developed by IBM minimizes parasitic resistances and capacitances. It consists of self-aligned emitter and base contacts, a thin intrinsic base with an optimized collector doping profile, and deep-trench isolation (36). Devices must be isolated from each other to prevent unwanted interactions in integrated circuits. While p—n junctions can be used for isolation, IBM s approach etches deep trenches in the siUcon wafer which are filled with Si02 to provide electrical insulation. 

Temperature can destroy the piezoelectric properties of the probe, although techniques for cooling probes (delay blocks), and development of temperature-resistant piezoelectric materials, are extending the temperature range. Differences of up to 5% in thickness can occur between hot and cold readings. 

The rapid growth in the use of OPs and the proliferation of new active ingredients and formulations was not without its problems. Some OPs proved to be too hazardous to operators because of very high acute toxicity. A few were found to cause delayed neurotoxicity, a condition not caused by ChE inhibition (e.g., mipafox, lepto-phos). There was also the problem of the development of resistance, for example, by... 

The answer is c. (Hardman, pp 1161-1162.) An important problem in the chemotherapy of TB is bacterial drug resistance For this reason, concurrent administration of two or more drugs should be employed to delay the development of drug resistance. Isoniazid is often combined with ethambutol for this purpose. Streptomycin or rifampin may also be added to the regimen to delay even further the development of drug resistance. 

Problems with other normal mucosal defense mechanisms may also contribute to the development of GERD, including prolonged acid clearance time from the esophagus, delayed gastric emptying, and reduced mucosal resistance. 

Four nurses who were sterilizing endoscopes with glutaraldehyde developed symptoms of asthma and rhinitis temporally related to exposures to glutaraldehyde. Three of the four nurses, however, had a prior history of mild seasonal asthma." On specific provocation testing, one patient had an increase in nasal airway resistance, with a dual immediate and late response pattern. Another patient had a delayed 22% decline in FEVi 80 minutes after the final exposure to glutaraldehyde. The occurrence of late reactions suggested that the underlying mechanism involved sensitization rather than an irritant effect." ... 

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