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Biomedical subjects

M K Hamdy

Publications and source records attributed to M K Hamdy.

At least 19 recordsLinked to original sources
PubMed2003

Combined effects of ionizing-irradiation and different environments on Clostridium botulinum type E spores.

We examined the combined effects of gamma-radiation (24 degrees C) on spores of Clostridium botulinum-type Eklund strain suspended in different gas-saturated Na-phosphate buffer in absence or presence of protectors or sensitizers. Response surface methodology (RSM) was also used to ascertain the effects of radiation on the recovery of spores using a medium containing various levels of NaCl or Na-thioglycollate. The former (< 0.5%) decreased viable spore counts, but the latter (0.15%) did not. Irradiation inactivation of Eklund spores was most effective in air-saturated buffers compared to N2O and N2 gas. The Na2-EDTA (0.01 M) was the most efficient radioprotector of spores due to its reactivity toward hydroxy radicals, followed by t-butanol (0.1 M) in NO2 or N(2)-saturated buffers, respectively. Catalase (10.0 mg ml(-1)) and DL-cysteine (0.1 mM) sensitized the spores during irradiated N2O or N(2)-saturated buffers, and NaCl (0.01 M) only sensitized spores in N2 environment. Spores frozen at -75 degrees C for 30 days and thawed prior to use were more sensitive to radiation damage compared to freshly prepared spores. Glycerol (15%), in Na-phosphate buffer (pH 7.0, 0.06 M), protected Eklund spores and increased the number of spores from 10(6) to 10(11) colony forming unit (CFU) ml(-1), and enhanced their radiosensitivities. Seven strains of C. botulinum type E were screened for plasmids and strain BL764 had two plasmids (15.8 and 46.8 mDa), BL4028 also had two (4.4 and 13.2 mDa), BL4850 contained only one (4.9 mDa), whereas EQA, BL211, Eklund, and Beluga had none. Gamma-Radiation (10 kGy, absorbed dose) cured the 15.8-mDa plasmid in strain BL764, but its absence yielded no changes in toxigenicity.

Clostridium botulinum↗
PubMed2001

Bacterial amelioration of bauxite residue waste of industrial alumina plants.

The high alkali content of bauxite residue deposits from alumina production plants in industrial nations poses a challenge to reestablish flora and fauna at the deposit sites. The present study demonstrated that low levels of injured bacterial cells in the bauxite residue actively grew using various added nutrients and/or hay. The organisms grew from less than 10 to more than 10(9) cells g(-1) bauxite residue and formed organic acids that lowered the pH from 13 to about 7.0. A total of 150 cultures was isolated from treated bauxite residue and included species of Bacillus, Lactobacillus, Leuconostoc, Micrococcus, Staphylococcus, Pseudomonas, Flavobacterium and Enterobacter. Scanning electron micrographs demonstrated that untreated particles (control) of the bauxite residue were clumped together, and in treated bauxite residue these particles were highly dispersed with microcolonial structures. Furthermore, the treated bauxite residue supported growth of several plants and earthworms that survived for over 300 days. In a test plot bioremediation on a residue deposit at Alcoa Point Comfort, TX, the Bermuda grass hay used was effective mulch material and encouraged water filtration, leading to establishment and growth of salt-tolerant vegetative species.

Aluminum↗
PubMed1994

Detection of Clostridium botulinum type F using the polymerase chain reaction.

The polymerase chain reaction (PCR) was used to amplify a portion of the Clostridium botulinum type F toxin gene. An 1137-bp fragment was amplified from 11 different strains of type F C. botulinum with primers derived from the published sequence of type F strain no. 202. This fragment was not amplified from the DNA of C. botulinum types A, B and E, or from other clostridial organisms examined. When used as a hybridization probe, the 1137-bp PCR-generated fragment generated from one of the type F strains (the proteolytic strain type F Langeland) hybridized to the PCR products from all other type F toxin-producing strains tested. Portions of fragments amplified from the type F Langeland strain were sequenced. The sequence of this strain was found to exhibit approximately 3% variation from the published sequence of the non-proteolytic type F strain no. 202. Primers designed to pair with the regions of maximum sequence variation between strain 202 and the Langeland strain gave amplification products only with DNA from type F strains that exhibited the same proteolytic properties as the strain from which the primer sequences were derived. These findings underscore the need to consider variations in sequence when designing oligonucleotide probes and PCR primers in order to avoid false negative results.

Animals↗
PubMed1990

Monoclonal antibody to type F Clostridium botulinum toxin.

Hybridomas synthesizing monoclonal antibodies (MAbs) against type F Clostridium botulinum toxin were developed. MAb from one stable hybridoma, hybridoma 223, consisted of kappa light chains and an immunoglobulin G subclass 2a heavy chain. This MAb was used in a double-sandwich enzyme-linked immunosorbent assay to detect type F toxin in foods, culture fluids, and purified toxin preparations. The sensitivity of the double-sandwich enzyme-linked immunosorbent assay was approximately 10 mouse lethal doses of toxin per ml of toxic fluid.

Animals↗
PubMed1987

Monoclonal antibody for the detection of Clostridium botulinum type A toxin.

Hybridomas producing monoclonal antibodies against type A Hall strain Clostridium botulinum toxin were generated by fusing mouse myeloma cell line P3-X63-Ag8.653 with spleen cells of Balb/c mice immunized with C. botulinum type A toxoid. The monoclonal antibody from one hybridoma, identified as No. 424, was selected from 61 others for its high antibody titre. This monoclonal antibody was used in a double-sandwich enzyme-linked immunosorbent assay (ELISA) system to detect type A toxin in culture fluids and in foods. The monoclonal antibody did not react with either C. botulinum toxin types B, C, D, E and F or with other clostridial species tested. This particular monoclonal antibody (No. 424) did not neutralize type A toxin in the mouse bioassay procedure but detected approximately 10 mouse lethal doses of type A toxin/ml culture fluid. Monoclonal antibody and rabbit antitoxin to type A C. botulinum toxin were useful in a double-sandwich ELISA for the rapid and specific detection of type A toxic fluids in culture and in food samples.

Animals↗
PubMed1985

Selective and differential medium for detecting Clostridium botulinum.

A selective and differential growth medium was developed for detection of Clostridium botulinum types A, B, and F. The medium consisted of peptone-glucose-yeast extract agar supplemented with cycloserine, 250 micrograms/ml; sulfamethoxazole, 76 micrograms/ml; and trimethoprim, 4 micrograms/ml as selective inhibitors and various types and levels of botulinal antibodies for type differentiation in the immunodiffusion reaction. Growth of proteolytic types of C. botulinum were not affected by the incorporation of the selective agents, but some nonproteolytic types were suppressed. Cross-reactions between types A and B were visually distinguishable, whereas cross-reactions between type F and Clostridium sporogenes did not occur at the optimum antibody titer. Optimum antibody titer varied with toxin type. The proposed selective differential medium should be valuable in isolating and typing of proteolytic C. botulinum types A, B, and F from samples containing mixed microbial populations.

Antitoxins↗
PubMed1981

Immunodiffusion method for detection of type A Clostridium botulinum.

A simple gel immunodiffusion agar procedure was developed for detecting toxigenic strains of Clostridium botulinum type A. The method consisted of overlaying colonies grown on thin-layer tryptone-peptone-glucose-yeast extract agar with gel diffusion agar containing desired levels of C. botulinum type A antitoxin. Concentric precipitin zones formed around colonies of C. botulinum type A. Strains of C. botulinum type A were detected by this procedure. However, C. botulinum type B reacted to a lesser degree with this system. No reaction was noted with types E, F, Langeland, F8G, Clostridium perfringens, or with strains of nontoxigenic Clostridium sporogenes. Thickness of the plating medium, incubation time and temperature, environmental growth conditions, and levels of both agar an antitoxin were important factors affecting the efficiency of the procedure, whereas the age of the culture (used as inoculum) was not critical. Thin agar medium (5 ml per plate [15 by 100 mm]) containing 1.5% agar gave consistent results, but more agar limited diffusion, and lower levels encouraged spreaders. The optimal concentration of antitoxin incorporated in to the gel diffusion agar overlay was 1.2 IU/ml gel diffusion agar. Rabbit type A antitoxin prepared with purer immunizing agent gave similar reactions. The addition of type A antitoxin in tryptone-peptone-glucose-yeast extract agar medium before inoculation with type A C. botulinum showed promising results.

Antitoxins↗
PubMed1976

Control of mercury pollution.

When a 203Ng(NO3)2 solution was kept at 25 degrees C in glass or polypropylene containers, 50 and 80% of original radioactivity was adsorbed to the containers' walls after 1 and 4 days, respectively. However, no loss in radioactivity was observed if the solution was supplemented with HgCl as carrier (100 mug Hg2+/ml) and stored in either container for 13 days. When 203Hg2+ was dissolved in glucose basal salt broth with added carrier, levels of 203Hg2+ in solution (kept in glass) decreased to 80 and 70% of original after 1 and 5 days and decreased even more if stored in polypropylene (60 and 40% of original activity after 1 and 4 days, respectively). In the absence of carrier, decreases of 203Hg2+ activities in media stored in either container were more pronounced due to chemisorption (but) not diffusion. The following factors affecting the removal of mercurials from aqueous solution stored in glass were examined: type and concentration of adsorbent (fiber glass and rubber powder); pH; pretreatment of the rubber; and the form of mercury used. Rubber was equally effective in the adsorption of organic and inorganic mercury. The pH of the aqueous 203Hg2+ solution was not a critical factor in the rate of adsorption of mercury by the rubber. In addition, the effect of soaking the rubber in water for 18 hr did not show any statistical difference when compared with nontreated rubber. It can be concluded that rubber is a very effective adsorbent of mercury and, thus, can be used as a simple method for control of mercury pollution.

Adsorption↗