In vitro antibacterial activity of a new fluoroquinolone, fleroxacin, against hospital bacteria and regression curve

Minimal inhibitory concentrations (MICs) of fleroxacin (FLE) were determined by agar dilution for 1261 bacterial strains isolated in 1992 in 4 university hospitals; in addition, antibiograms by agar diffusion were performed with 5 micrograms disks. Activity of FLE against nalidixic acid (NAL) susceptible (S) Enterobacteriaceae was close to that of other fluoroquinolones (FQ) (MIC 50 and 90: 0.12-0.25 micrograms/ml); like for other FQ, this activity was reduced against NAL intermediate and resistant (R) Enterobacteriaceae (4-32). MICs of FLE against P. aeruginosa were between 1 and 128 (8-128). FLE had also a good activity against NAL-S A. baumannii (0.12-0.5) but this activity is reduced against NAL-R Acinetobacter (64-128). FLE was highly active against Haemophilus (0.06-0.12), Gonococci (0.03-0.25), Meningococci (0.016-0.03) and B. catarrhalis (0.12-0.25). FLE showed activity close to the currently available FQ against methicillin susceptible Staphylococci (0.25-1); the resistant strains (32- > 128) are usually methicillin resistant. FLE is less effective against Enterococci (4-128), Streptococci (8-16) and Pneumococci (4-8). The coefficient correlation of the regression curve is 0.93; for MIC breakpoints of 1 and 4 micrograms/ml, zone diameter breakpoints should be 20 and 15 mm.     

Differential Sensitivity of Mosquito Taxa to Vegetable Tannins

The sensitivity of larval Culicidae to vegetable tannins was investigated in different taxa representative of the fauna from alpine hydrosystems (Aedes rusticus, Culex pipiens) and foreign noxious fauna (Aedes aegypti, A. albopictus). Bioassays reveal that tannic acid at concentrations of 0.1–6 mM is significantly more toxic for C. pipiens than for Aedes taxa, and A. aegypti is more sensitive than A. albopictus and A. rusticus. Comparison of the rank order of sensitivity among taxa with the associated levels of cytochrome P-450, esterase, and glutathione-S-transferase activities suggests that cytochrome P-450 and esterases may be involved in the detoxification of tannins. A possible involvement of these detoxifying enzymes is also revealed in vivo by the synergistic effects of S,S,S-tributyl phosphorotrithioate (esterase inhibitor) and piperonyl butoxide (P-450 inhibitor). The differential sensitivity to tannins among taxa is discussed in terms of ecological implications within mosquito communities from alpine hydrosystems, where the acquisition of tannins–detoxifying enzymatic systems may be considered as a key innovation.     

Comparative Capability to Detoxify Vegetable Allelochemicals by Larval Mosquitoes

In order to confirm the phytotoxicological basis for the ecological specialization of larval culicine fauna among different subalpine mosquito breeding sites, we compared the capability of six different Aedes larval taxa or populations of different ecological origin to detoxify dietary leaf litter originating from the environmental vegetation. Detoxification experiments were performed through in vitro digestion of a toxic leaf litter fraction using larval extracts as the enzymatic sources. Comparison of toxicological and detoxifying properties among the different larval samples indicates an association between their tolerance to leaf litter toxicants and their detoxification capability, which vary according to ecological origin. The fact that the detoxifying factor within the larval extracts appears to be a protein-like compound with a molecular weight bigger than 30 kDa suggests the possible involvement of detoxifying enzymes in larval tolerance to leaf litter toxicants. This is congruent with previous biochemical data that suggests the involvement of cytochrome P450 monooxygenase and esterase activities in the detoxification process.     

Fostering empowerment in online support groups

Online support groups have been used extensively, in numerous areas of distress, for 15 years. Researchers have presented conflicting findings and ideas about their effectiveness in helping people cope with respective problems. Our review of quantitative studies and our qualitative exploration of the nature of the experiences that occur in such groups show that several factors operate to potentially affect participants. Personal and interpersonal dynamics, which are central in producing effects in these groups, are induced and accelerated by the powerful online disinhibition effect. These factors, including the very impact of writing, expressions of emotions, collecting information and thereby improving understanding and knowledge, developing social relationships, and enhancing decision-making skills and consequent behavioral actions all serve as possible generators of a sense of personal empowerment for people in distress. This view may explain why empirical research has frequently found little or no specific outcomes from participating in online support groups; however, it has found much support for nonspecific personal impacts of this means of intervention. Thus, we contend that online support groups are designed to foster, and many of them actually do, well-being, a sense of control, self-confidence, feelings of more independence, social interactions, and improved feelings—all nonspecific but highly important psychological factors. As such, participating in an online support group could foster personal empowerment, which is much needed in handling specific conditions of distress. Nonetheless, this participation has potential costs, too, especially developing dependence, distancing from in-person contacts, and exposure to unpleasant experiences typical of social engagement in cyberspace.     

Hot extraction and characterization of a ligninlike fraction involved in larvicidal effects of decomposed leaf litter against mosquito

Hot water-extraction was performed on decomposed leaf litter in order to solubilize the toxic fraction involved in the dietary interaction against mosquito larvae in subalpine breeding sites. The toxic fraction was partially extracted by water with an optimum temperature of 60°C and recovered in an insoluble form. Phytochemical characterization was achieved through differential enzymatic hydrolyses, using the laccase mediator delignifying system, and aluminum chloride chelation monitored by standard bioassays; comparative spectrophotometric analyses in ultraviolet light after solubilization in acetyl bromide; and comparative reversed-phase high-performance liquid chromatography of the phenolic aldehydes after alkaline nitrobenzene oxidation. The results suggested the involvement of ligninlike compounds in the toxicity of the isolated fraction. Toxicity of this fraction appeared far stronger than that of the crude leaf litter. The involvement of this ligninlike fraction in the dietary toxicity of leaf litter against larval mosquito was then investigated.     

Taste sensitivity of detritivorous mosquito larvae to decomposed leaf litter

Dietary leaf litter chemistry is known to play an important ecotoxicological role in the plant–mosquito interaction in subalpine flooded areas surrounded by vegetation because of differential larvicidal effects of insoluble polyphenols formed during the leaf decaying process. This dietary interaction was investigated through comparative evaluation of the role of toxic/nontoxic leaf litter in both larval foraging and feeding behavior, by using different samples of decomposed alder leaf litter and larval Aedes aegypti as experimental references. Track analysis showed significant differences in larval foraging behavior in the absence or presence of leaf litter. Comparative alimentary preference investigations and further track analysis suggested that larvae are unable to detect leaf litter toxicity. These characteristics of the larval behavioral feeding pattern suggested that: (1) decomposed leaf litter may be involved as an important attractive food source in the habitat selection and evolutionary history of culicids, and (2) preingestive behavioral mechanisms appear to be minimally involved in the differential larval dietary adaptation to toxic leaf litter. These results may have interesting consequences for culicid biological control.     

Larvicidal Effect of a Cell-Wall Fraction Isolated from Alder Decaying Leaves

Decaying alder leaves in water from Alpine Aedes breeding sites, particularly their toxicity to larval Culicidae, were investigated and characterized with comparative toxicological and chemical methods. Bioassays that used third-instar Aedes aegypti as a reference species indicated that the larvicidal effect of crude leaf litter varied with decaying age of the litter, while no toxicity was detected from leaching water of the mosquito breeding sites. Ten-month-old leaf litter was the most toxic. Comparison of the different soluble and insoluble fractions obtained after sequential extraction of decomposed litter allowed us to localize the toxicity factor to an insoluble cell-wall fraction. The toxicity seems to be linked to phenolic activity. It is higher than that found for tannic acid solutions used as a reference to mimic the larvicidal effects of the molecules naturally occurring in decaying litter. The pattern of establishing the larvicidal effect of alder leaf litter in water of Alpine Aedes breeding sites is discussed.     

Involvement of Ligninlike Compounds in Toxicity of Dietary Alder Leaf Litter Against Mosquito Larvae

The toxicological characteristics of dietary decomposed alder leaf litter against mosquito larvae were further investigated through enzymatic and chemical purification of a phenoliclike cell-wall fraction isolated from crude litter. The toxicity of the subfractions obtained was controlled by standard bioassays on third instars of Aedes aegypti chosen as a reference target species. Enzymatic hydrolyses of the cell-wall fraction were performed with caylase, pectolyase, esterase, and -glycosidase, in order to release, respectively, cellulose material and phenolic compounds bound to lignins. These treatments did not affect the larvicidal activity and the phenolic activity of the cell-wall fraction. Chemical alkaline and acid hydrolyses were carried out to break ester and glycosidic bonds of the cell-wall fraction. Comparison of HPLC profiles of the hydrolysates from both toxic and nontoxic fractions did not reveal differences between the phenolic acids released. Aluminum chloride, known for its phenolic complexing activity, counteracted the larvicidal activity of the cell-wall fraction. Altogether, these results suggest the involvement of ligninlike compounds in the toxicity of dietary alder leaf litter against larval mosquitoes. The toxicity of this fraction, which was very sensitive to drastic and smooth oxidations, seemed to be associated with a strong oxidative potential. These results are discussed in relation to a possible mode of action of lignins in the plant–mosquito interactions.