Activity spectrum narrow

Cefpimizole (51) appears to be less active in vitro than cefotaxime and cefoperazone and to have a somewhat narrower activity spectrum although some strains of Pseudomonas are susceptible. It is not orally active, but its performance in vivo appears superior to what would be expected from its in vitro data. Its synthesis begins by acylation of cephaloglycin (48) with the bis acid chloride of imidazole-4,5-dicarboxylic acid (49) to give amide 50. The acetyl moiety at C-3 of this intermediate is displaced with 4-pyridineethanesulfonic acid and sodium iodide to give cef-pimazole (51) [16]. 

Three subclasses Bl, B2 and B3 can be distinguished on the basis of the sequences. Bl and B3 enzymes are optimally active with 2 Zn2+ions, while the B2 enzymes are inhibited by the second Zn2+. These B2 enzymes also exhibit a very narrow activity spectrum and only hydrolyse carbapenems. The 3D structures of representative members of each subfamily have been... 

Flucytosine is a fluorinated derivative of pyrimidine. Its spectrum of activity is narrower than that of amphotericin B. However, it exhibits a synergetic effect when used in combination with amphotericin B. In sensitive fungi, flucytosine is transformed into 5-fluorouracil, which in turn is turned into 5-fluorodeoxyuracilic acid, an inhibitor of thymidylate synthetase, and correspondingly, DNA synthesis. 5-Fluorouracil triphosphate, which causes the formation of defective RNA, may also be involved in this process. The mechanism is highly selective because mammahan cells are not able to turn a large amount of flucytosine into 5-fluorouracil. 

Semisynthetic Penicillins. However useful they may be, natural penicillins have several drawbacks. They have a relatively narrow activity spectrum, primarily inhibiting Gram-positive bacteria only. They are acid- and lactamase-sensitive, and in a small percentage of patients they cause allergie side effects. All of these limitations could potentially be overcome by molecular modifications during the biosynthesis of these drugs. Unfortunately, however, the fermentation process used in penicillin production is not very flexible and does not permit the incorporation of very many amide side chains into the molecule. 

Although several chemicals, e.g. arsenicals and organophosphorus compounds, had been used with some effect to treat specific helminth infections, the introduction in 1930 of phenothiazine (1) was a revolutionary event in the control of gastrointestinal worms. Although its spectrum of activity was narrow compared to modern anthelmintics and its dose level was rather high (600-800 mg kg-1), it was the veterinary anthelmintic of choice until the 1960s. 

It should also be noted that the effective activation spectrum of photosensitizers is not necessarily exactly the same as their absorption spectrum in solution. The peak wavelengths may be shifted by several nanometers, due to binding of the photosensitizer to biomolecules (e.g. proteins). If a narrow wavelength source (e.g. laser) is used, it is important to match the wavelength to the true in vivo activation peak, so this needs to be determined, typically by studies in animal models. With broad-band sources (LEDs, lamps), this is less critical. 

Bt used in spray-on formulations is, perhaps, the most successful biopesticide. Reasons for Bt s success include ease of handling and a very high specific activity against sensitive insects. For example, a Bt insecticidal protein called CrylAc has a LCjq on Heliothis virescens neonate larvae as low as 0.07 ppm [10]. However, most individual Bt insecticidal proteins have a narrow activity spectrum. As mentioned, CrylAc is very active against H. virescens, while another Bt toxin called CrylCa is not. CrylCa is active against Spodoptera exigua, but CrylAc is not. This is perhaps... 

The penicillins can be classified on the basis of their antibacterial activity (broad spectrum, narrow spectmm), method of production (natural or semi-synthetic) and based on their stability/instability to bacterial P-lactam ases. 

Cefsulodin (60) has a sulfonic acid nx)iety on the C-7 acyl side chain. This moiety conveys antipseudomonal activity to certain penicillins, and it is interesting to note that this artifice works with cefsulodin as well. It is also interesting that, in contrast to the other so-called third-generation cephalosporins, the spectrum of cefsulodin is rather narrow and its clinical success will place a premium upon accurate diagnosis. Its synthesis begins by acylation of... 

The natural penicillins also have a fairly narrow spectrum of activity, which means that they are effective against only a few strains of bacteria Newer penicillins have been developed to combat this problem. These penicillins are a result of chemical treatment of a biologic precursor to penicillin. Because of their chemical modifications, they are more slowly excreted... 

The photochemical activity of pure Ti02 has been invesli ted extensively for decades, and it has been revealed that the primary limitation is poor solar spectrum photon absorption because of its wide band gap. Recently, it has been reported that narrowing band p,p can be achieved by doping TO2 with other elements such as nitrogen[7], sulfiir, caibon, etc. For example, fliara et al.[8] reported nitrogen doping shifts the absorption band as well as narrows the band gap. 

Chloroform (CHCI3) has a narrow spectrum of activity. It has been used extensively as a preservative in pharmaceuticals since the last century though recently has had limitations placed on its use. Marked reductions in concentration may occur through volatilization from products resulting in the possibility of microbial growth. 

It is often difficult to narrow the spectrum of activity of the antibiotic choice since the infections are usually polymicrobial. As such, patients may receive long courses of broad-spectrum antibiotics such as imipenem/cilastatin and... 

The antibiotic of choice for group B streptococcal disease is penicillin G, although ampicillin is an alternative.43 No resistance to either agent has been reported, and their narrow spectrum of activity makes them ideal choices.43 Resistance has developed with the use of alternative choices for penicillin-allergic patients. A treatment algorithm for group B Streptococcus is shown in Fig. 44—3, and dosing recommendations are shown in Table 44-5. 

Empirical selection of antimicrobial spectrum of activity should be related to the severity of the illness. Generally, acutely ill patients may require broader-spectrum antimicrobial coverage, whereas less ill patients may be managed initially with narrow-spectrum therapy. While a detailed description of antimicrobial pathogen- specific spectrum of activity is beyond the scope of this chapter, this information can be obtained readily from a number of sources.9,10... 

Oral, narrow-spectrum antibiotic therapy with activity against Staphylococcus aureus and streptococcal species. Include coverage for MRSA (HA- or CA-MRSA) according to patient history and resistance patterns in the area. 

Erythromycin is considered the optimal drug for treatment of Campylobacter infections. The rate of resistance of Campylobacter to erythromycin remains low. Other advantages of this drug include ease of administration, low cost, lack of major toxicity, and narrow spectrum of activity.14 The recommended dosage for adults is 250 mg orally four times daily or 500 mg orally twice daily for 5 to 7 days. For very ill patients, treatment with gentamicin, imipenem, cefotaxime, or chloramphenicol is indicated, but susceptibility tests should be performed. 

Spectrum of activity A qualitative term that describes the number of different bacterial species that are susceptible to an antimicrobial regimen. Generally, broad-spectrum activity refers to regimens that possess activity against many bacterial species, whereas narrow-spectrum therapy refers to activity against a few bacterial species. 

Lasers produce spatially narrow and very intense beams of radiation, and lately have become very important sources for use in the UV/VIS and IR regions of the spectrum. Dye lasers (with a fluorescent organic dye as the active substance) can be tuned over a wavelength range of, for instance, 20-50 nm. Typical solid-state lasers are the ruby laser (0.05% Cr/Al203 694.3 nm) and the Nd YAG laser (Nd3+ in an yttrium aluminium garnet host 1.06 pm). 

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