Sporicidal action of alkaline glutaraldehyde: factors influencing activity and a comparison with other aldehydes

The sporicidal efficacy of glutaraldehyde (2% w/v) was investigated under various conditions. Numerous factors influenced its activity: method of spore production, inherent spore resistance characteristics, alkalination, storage time and storage temperature. The sporicidal action of 2% alkaline glutaraldehyde at room temperature was compared with that of other aldehydes and commercially available formulations. Cidex (glutaraldehyde) and Sporicidin (glutaraldehyde + phenol full strength) were the most effective, followed by 8% (w/v) formaldehyde and 10% (v/v) Gigasept, a formaldehyde-containing product. Five per cent (v/v) Gigasept and 10% (w/v) glyoxal also had good sporicidal activity, though that of Sporicidin (1:16) was poor. No activity was observed with 10% (w/v) butyraldehyde.     

Bactericidal activity of alkaline glutaraldehyde solution against a number of atypical mycobacterial species

The mycobactericidal activity of 2% alkaline glutaraldehyde solution was determined using standardized suspensions of 10 species of atypical mycobacteria and compared with that for virulent Mycobacterium tuberculosis. Suspensions of M. avium, M. intracellulare and M. gordonae were more resistant to disinfection by the glutaraldehyde than were virulent tubercle bacilli while M. kansasii, M. scrofulaceum and M. szulgae were somewhat more susceptible. Mycobacterium marinum, M. smegmatis and M. fortuitum were highly sensitive to the disinfectant action of the alkaline glutaraldehyde solution. This variation in sensitivity shown by apparently closely related strains of mycobacteria to this disinfectant has important practical implications.     

Bactericidal activity of alkaline glutaraldehyde solution against a number of atypical mycobacterial species

The mycobactericidal activity of 2% alkaline glutaraldehyde solution was determined using standardized suspensions of 10 species of atypical mycobacteria and compared with that for virulent Mycobacterium tuberculosis. Suspensions of M. avium, M. intracellulare and M. gordonae were more resistant to disinfection by the glutaraldehyde than were virulent tubercle bacilli while M. kansasii, M. scrofulaceum and M. szulgae were somewhat more susceptible. Mycobacterium marinum, M. smegmatis and M. fortuitum were highly sensitive to the disinfectant action of the alkaline glutaraldehyde solution. This variation in sensitivity shown by apparently closely related strains of mycobacteria to this disinfectant has important practical implications.     

Use of membrane filters for measurement of mycobactericidal activity of alkaline glutaraldehyde solution

Bactericidal assays of 2% alkaline glutaraldehyde solution were carried out using Millipore membranes, and the rate of kill was compared with that of mycobacteria in suspension and on Penicylinder surfaces when using the methods recommended for the official tuberculocidal test. The rate of inactivation observed on the membrane filter surface was similar to that achieved using Penicylinders. The absence of visible colonies on the treated membranes provided a direct demonstration of sterility. The use of filter membranes in tuberculocidal tests provides a simple quantitative assay.     

Lactase and other enzymes bound to chitin with glutaraldehyde

Acid tolerant lactase (I), α-chymotrypsin (II), and acid phosphatase (III) were immobilized on chitin with glutaraldehyde. Pretreatments of the chit in with acid, alkali, ammonia, and pronase were compared with respect to release of titratable amino groups and ability to retain lactase activity. Shrimp chitin appeared to be more sensitive to pretreatment conditions and so effort was concentrated on crab. An acid-alkali pretreatment was selected as most practical and economical, and the properties of enzymes fixed on crab chitin were studied intensively. The pH optima of the fixed enzymes were shifted about one pH unit; the shift for I was toward more acid pH, for II was toward alkaline pH, and for III was toward acid pH. The retained activity of immobilized I was approximately 60% that of the native enzyme. A column in continuous operation with I on chitin-glutaraldehyde gave an apparent activity half-life of 27 days.     

Use of membrane filters for measurement of mycobactericidal activity of alkaline glutaraldehyde solution.

Bactericidal assays of 2% alkaline glutaraldehyde solution were carried out using Millipore membranes, and the rate of kill was compared with that of mycobacteria in suspension and on Penicylinder surfaces when using the methods recommended for the official tuberculocidal test. The rate of inactivation observed on the membrane filter surface was similar to that achieved using Penicylinders. The absence of visible colonies on the treated membranes provided a direct demonstration of sterility. The use of filter membranes in tuberculocidal tests provides a simple quantitative assay.     

The inducible alkaline phosphatase of rat heart. Some properties of the enzyme and factors influencing its activity

Subcutaneous injection of isoprenaline into rats produces a rapid rise in alkaline phosphatase activity which is largely confined to the right atrium of the heart. The phosphatase activity of extracts of atrial tissue from treated animals is on average four times that of controls. The rise in activity is largely suppressed by previously treating the animals with cycloheximide or actinomycin D. Comparison of the properties of the alkaline phosphatase in extracts of atria from isoprenaline-treated rats with control preparations shows the stimulated enzyme activity to be similar to that present in the resting state. In a number of respects, including substrate specificity, response to activators and inhibitors, rate of loss of activity on heating and electrophoretic mobility of the native and modified enzyme, the atrial phosphatase resembles alkaline phosphatases from other mammalian non-intestinal and non-placental tissues. These results suggest that the effect of isoprenaline is to increase the rate of synthesis of atrial alkaline phosphatase, and the ability of the tissues of the right atrium to respond in this way may be related to the rich sympathetic innervation of this part of the heart.     

Environmental and other factors influencing fertility in Sri Lanka

The study utilizes the complete tabulations from the 1971 census and data from the Registrar General's and Meteorological departments for the same year. It applies a multiple regression analysis of the total fertility rate for each district for 1971 on a series of environmental variables. These include the proportion of the rural population by district to the all-island rural population; the district mean annual rainfall and the proportion of the district population employed in the major rural occupations to the total employed. To these 3 environmental variables were added 2 socioeconomic variables: the proportion of the population aged 10+ years and who are literate, and infant mortality. Results indicate that the 5 independent variables are clearly intercorrelated. The multiple regression analysis shows that the 5 variables together account for 76.4% of the total variation in district total fertility rate. It is argued that this and other studies undertaken previously provide useful pointers to the type of variable to be considered in any policy aimed at population control and indicate where major efforts should be directed.     

Antimicrobial activity of pefloxacin in comparison with other quinolones]

The antibiotic sensitivity of 338 microbial cultures isolated from patients with inflammatory renal and urinary diseases was studied. 66.3 per cent of the isolates proved to be poly-resistant which corresponded to rurological patient specificity. It was shown that abactal (pefloxacin, LEK, Yugoslavia) had a higher antimicrobial activity than the nonfluorinated quinolones especially against Staphylococci and a lower antimicrobial activity than the fluorinated quinolones in vitro. The abactal sensitivity to Pseudomonas aeruginosa amounted only to 23 per cent which was likely to be due to development of cross-resistance to ofloxacin. 1/3 of the polyresistant isolates were sensitive to abactal. The activity of abactal weakly depended on the medium pH. The MBC was generally no more than 2 MICs.     

Sporicidal action of peracetic acid and protective effects of transition metal ions

Although peracetic acid (PAA) is used widely for cold sterilization and disinfection, its mechanisms of sporicidal action are poorly understood. PAA at high concentrations (5–10%) can cause major loss of optical absorbance and microscopically-visible damage to bacterial spores. Spores killed by lower levels of PAA (0.02–0.05%) showed no visible damage and remained refractile. Treatment of spores ofBacillus megaterium ATCC 19213 with PAA at concentrations close to the lethal level sensitized the cells to subsequent heat killing. In addition, PAA was found to act in concert with hypochlorite and iodine to kill spores. Antioxidant sulfhydryl compounds or ascorbate protected spores against PAA killing. Trolox, a water-soluble form of -tocopherol, was somewhat protective, while other antioxidants, including -tocopherol, urate, bilirubin, ampicillin and ethanol were not protective. Chelators, including dipicolinate, were not protective, but transition metal ions, especially the reduced forms (Co²⁺, Cu⁺ and Fe²⁺) were highly protective. The net conclusions are that organic radicals formed from PAA are sporicidal and that they may act as reducing agents for spores that are normally in a highly oxidized state, in addition to their well known actions as oxidizing agents in causing damage to vegetative cells.     

Desert vines: a comparison of Australia with other areas

Aim To characterize the Australian desert vine flora and to compare it with that of deserts in other continents. Location The Stony Deserts, the Simpson Desert and the four main deserts of Western Australia. Methods The Western Australian Herbarium data base and published papers were used to develop vine checklists for each Australian desert studied. A literature search was used to classify the families and genera into phytogeographical elements and to provide data for intercontinental comparisons. Results Thirty‐seven vine species are listed for the six Australian deserts studied. They constitute from 0.8 to 2.7% of the vascular flora, which is within the normal range for arid zone floras. Comparing Australian data with those from the Sonoran and Chihuahuan deserts (North America), for non‐vine taxa, very different phylogenetic lines are present. However, for vines, three of the four most important families are the same in each case, viz. Convolvulaceae, Fabaceae and Asclepiadaceae. This reflects large pantropical and cosmopolitan families shared between all three data sets. At the generic level, in Australia pantropical taxa and taxa from the Old World tropics far outnumber endemic ones, as do pantropical and neotropical genera in North America. Herbaceous vines predominate in Australian deserts as they do in North American ones, but nevertheless, the percentage of woody vines is higher in Australia (32%) than in North America (highest value of 24%). Earlier views that Australian deserts are rich in annual vines are not supported. Main conclusions For many life‐forms, the Australian flora is composed of very different phylogenetic lines to the floras of other continents. However, for desert vines, at the level of family and even of genus, there are surprising similarities between Australia and even a continent as distant as North America, because of shared pantropical and cosmopolitan taxa.     

Household factors influencing participation in bird feeding activity: a national scale analysis

Ameliorating pressures on the ecological condition of the wider landscape outside of protected areas is a key focus of conservation initiatives in the developed world. In highly urbanized nations, domestic gardens can play a significant role in maintaining biodiversity and facilitating human-wildlife interactions, which benefit personal and societal health and well-being. The extent to which sociodemographic and socioeconomic factors are associated with engagement in wildlife gardening activities remain largely unresolved. Using two household-level survey datasets gathered from across Britain, we determine whether and how the socioeconomic background of a household influences participation in food provision for wild birds, the most popular and widespread form of human-wildlife interaction. A majority of households feed birds (64% across rural and urban areas in England, and 53% within five British study cities). House type, household size and the age of the head of the household were all important predictors of bird feeding, whereas gross annual household income, the occupation of the head of the household, and whether the house is owned or rented were not. In both surveys, the prevalence of bird feeding rose as house type became more detached and as the age of the head of the household increased. A clear, consistent pattern between households of varying size was less evident. When regularity of food provision was examined in the study cities, just 29% of households provided food at least once a week. The proportion of households regularly feeding birds was positively related to the age of the head of the household, but declined with gross annual income. As concerns grow about the lack of engagement between people and the natural environment, such findings are important if conservation organizations are successfully to promote public participation in wildlife gardening specifically and environmentally beneficial behaviour in society more generally.     

Site-directed mutagenesis of an alkaline phytase: influencing specificity, activity and stability in acidic milieu

Site-directed mutagenesis of a thermostable alkaline phytase from Bacillus sp. MD2 was performed with an aim to increase its specific activity and activity and stability in an acidic environment. The mutation sites are distributed on the catalytic surface of the enzyme (P257R, E180N, E229V and S283R) and in the active site (K77R, K179R and E227S). Selection of the residues was based on the idea that acid active phytases are more positively charged around their catalytic surfaces. Thus, a decrease in the content of negatively charged residues or an increase in the positive charges in the catalytic region of an alkaline phytase was assumed to influence the enzyme activity and stability at low pH. Moreover, widening of the substrate-binding pocket is expected to improve the hydrolysis of substrates that are not efficiently hydrolysed by wild type alkaline phytase. Analysis of the phytase variants revealed that E229V and S283R mutants increased the specific activity by about 19% and 13%, respectively. Mutation of the active site residues K77R and K179R led to severe reduction in the specific activity of the enzyme. Analysis of the phytase mutant-phytate complexes revealed increase in hydrogen bonding between the enzyme and the substrate, which might retard the release of the product, resulting in decreased activity. On the other hand, the double mutant (K77R-K179R) phytase showed higher stability at low pH (pH 2.6-3.0). The E227S variant was optimally active at pH 5.5 (in contrast to the wild type enzyme that had an optimum pH of 6) and it exhibited higher stability in acidic condition. This mutant phytase, displayed over 80% of its initial activity after 3 h incubation at pH 2.6 while the wild type phytase retained only about 40% of its original activity. Moreover, the relative activity of this mutant phytase on calcium phytate, sodium pyrophosphate and p-nitro phenyl phosphate was higher than that of the wild type phytase.