Production of penicillinases by certain penicillin-resistant bacteria. (C) factors affecting the activities of penicillinases produced by Staphylococcus aureus, S9.

The activities of penicillinases produced by Staphylococcus aureus, S9 were found to be affected by pH, temperature, substrate concentration and type of penicillin derivative used as a substrate. The optimal activities of penicillinases produced by S. aureus, S9 were obtained at pH 6, at 37 degrees C, 0.5-10 mu/ml penicillin G concentration, and by increasing the enzyme concentration.

Lipases production by Bacillus circulans under mesophilic and osmophilic conditions. Factors affecting lipases production.

A facultative osmophilic bacterium able to produce lipases (isolated from bee honey) was identified as Bacillus circulans. Factors affecting lipases production by such isolate were studied. Dox's liquid medium supplied with 2 and/or 30% sucrose was used as a basal medium, under static culture condition, for such a purpose. Results have showed that the optimal sucrose concentration at which the isolate produced its maximal yield of lipases was 30% after an incubation period of 24 hours at 40 degrees C, and this was corresponding to an incubation period of 48 hours at 40 degrees C in presence of 2% sucrose. The optimal pH value was 7 in the first case while, 6.5 in the second. Furthermore production of extracellular lipases by such isolate was achieved in presence and absence of tributyrin as a carbon source instead of sucrose when supplied to Dox's liquid medium. Also the production of extracellular lipases by such isolate was not enhanced in presence of tributyrin as a supplement to Dox's liquid medium when supplied with 2 and/or 30% sucrose as carbon sources. This might suggest that the extracellular lipases of such isolate is constitutive in nature.

Interaction of Salmonella paratyphi A and Schistosoma mansoni in hamsters.

It has previously been shown that Salmonella paratyphi A associates with adult Schistosoma mansoni worms in animal models and in patients with schistosomiasis, resulting in Salmonella infections that are difficult to manage unless the helminthic parasite is eliminated. In the present study, characteristics of this association were explored. In vitro, fresh serum, but not heat-inactivated (56 degree C, 30 minutes) serum, from normal hamsters (NH) and schistosome-infected hamsters (SIH) equally inhibited bacterial growth. When either group of animals was given S. paratyphi A intracardially, there was a decline in recoverable bacteria in the blood for 3 days, but after the third day, the number of bacteria increased in SIH whereas NH blood became sterile. Co-cultivation of S. paratyphi A in Earle's medium with live worms yielded more bacterial growth than occurred in the medium without worms, suggesting that nutritional factors are involved in the relationship. An intimate association in vivo of bacteria and trematodes was confirmed by culturing Salmonella from both worm surfaces and homogenized worms, with more bacteria being recovered from female worms. Although the bacterial infection induced a significant hepatic shift of adult worms in SIH, oogram analyses were normal and no lethal effect of bacteria on worms was noted.

Salmonella paratyphi A in hamsters concurrently infected with Schistosoma mansoni.

The present work deals with the development of an improved animal model to study the association of salmonellosis and schistosomiasis. The animal chosen was the hamster, Mesocricetus auratus, which can be readily infected with Schistosoma mansoni. Normal hamsters and schistosome-infected hamsters (SIH) were given approximately 2.0 x 10(7) Salmonella paratyphi A intracardially. It was found that S. mansoni infections enhanced and prolonged the growth of S. paratyphi A in hamsters. Animals with dual infections had increased mortality in comparison with those infected with just bacteria or parasite during the 50 days post-bacterial challenge. Further studies showed that in SIH, S. paratyphi A persisted in various organs for up to 8 weeks post infection. In contrast, concurrent Leishmania donovani infections have no effect on S. paratyphi A infections. Significant numbers of bacteria were cultured from well-washed schistosome worms recovered from SIH 6--8 weeks post-bacterial challenge. These findings suggest that a direct physical relationship between the bacteria and worms facilitates the establishment and growth of S. paratyphi A in vivo, and that a deficit in host immune response is not a major factor involved in the enhanced growth of S. paratyphi A.

Bacillus stearothermophilus from Saudi Arabian Soils.

Ten thermophilic Gram-positive bacteria were isolated from various soils of Saudi Arabia. The strains are spore-forming rods belonging to the species Bacillus stearothermophilus. The cells are motile, strictly aerobic, catalase and oxidase positive. The sporangia appear to be swollen and their position varies from terminal in some to sub-terminal in others. The thermal stability of some enzymes of these bacteria was investigated; extracellular alpha-amylase appears to be very sensitive to pH and temperature. The ultrastructure of these bacteria shows specific changes in the cell wall when grown at the maximum, minimum and optimum growth temperatures, respectively.

Lipase productivity of a lipolytic strain of Thermoactinomyces vulgaris.

An attempt was made to evaluate the lipase productivity by Thermoactinomyces vulgaris with various nutritional and environmental factors. Results suggest optimum conditions for production, viz. age of inoculum 18 hours, 55 degrees C, pH 6.8, 0.2% yeast extract, specific substrates, and shaken cultures incubated for 24--36 hours. Lipases are induced by corn oil in presence of yeast extract or of certain substitutes; starch could replace these at 55 degrees C. A suggestion is given of a regulatory system of lipase synthesis, involving the supply of starch to initiate growth, allowing induction of lipase by the inductive substrate.

Identity and lipase activity of an isolate of Thermoactinomyces vulgaris.

An actinomycete with thermophilic nature and strong lipolytic activity was isolated by enrichment from an Egyptian soil. It proved to be Thermoactinomyces vulgaris. Variabilities justifying Adansonian systematics were reported and discussed. The potential relation of an occasional drop in successfully resumed activity to an auto-inhibition phenomenon has been notified. Optimum conditions for the activity of the extracellular lipase(s), including stability, suggest the practical importance of the enzyme(s) in the growth filtrates.

Relation of lipids to the action of streptomycin on Bacillus subtilis and Escherichia coli and griseofulvin and fungizone on Aspergillus niger.

An attempt was made to reveal the relation between the lipid content and components of B. subtilis and E. coli and the action of streptomycin, and those of A. niger and the action of griseofulvin and fungizone (Amphotericin B). Total lipids were extracted in CO2 atmosphere, dried, and weighed. Lipid components were analyzed by thin-layer chromatography. Complements to the growth medium of A. niger with extracted total lipids and phospholipids were made to verify the obtained results. It has been found that the action of streptomycin and griseofulvin was not correlated with lipids. On the other hand, fungizone action was manifested by the decrease in total lipids, free sterols, sterol esters, and triglycerides. Supplementation studies gave evidence of the role of total lipids and phospholipids in protecting A. niger cells against fungizone. Supplementation of 1 g of phospholipid per litre medium raised the M.I.D. of fungizone from 2.5 up to 25 microgram/ml. It was suggested to keep the fat level controlled at a minimum if it is required to increase fungizone activity.