Differentiation of Salmonella typhimurium from Salmonella enteritidis and other Salmonella serotypes using random amplified polymorphic DNA analysis.

Salmonella enterica ssp. enterica serovar Typhimurium and Salmonella enterica ssp. enterica serovar Enteritidis are the major dominating serotypes of Salmonella in poultry and poultry products. Infection by Salmonella Typhimurium is an important cause of morbidity and mortality in poultry. Rapid differentiation of Salmonella Typhimurium from other Salmonella serotypes including Salmonella Enteritidis can be very crutial for public health and for epidemiologists and for the poultry industry. Ten arbitrarily designed short primers (8 to 10 bases) were used in the random amplified polymorphic DNA analysis of Salmonella Typhimurium. One of the primers, primer 3 (5'-CGT GCA CGC-3'), resulted in the amplification of a band pattern that was unique to Salmonella Typhimurium. In total, 24 strains of serotype Salmonella Typhimurium were used during the study. Eighteen of them are clinical isolates, 2 of them chicken isolates (A6, A20), 2 of them from the Pasteur Institute, 1 from Refik Saydam National Culture Collection, and 1 is a type culture strain from National Culture Type Collection. Serotype Salmonella Typhimurium strains, which were collected from several different hospitals, institutes, and culture collections, have all displayed the same amplification band by primer 3. Twenty-three strains of 16 different serotypes of salmoneallae including 11 Salmonella Enteritidis strains gave only a 300-bp amplification band or no bands, whereas an additional 700-bp amplification band was observed only in samples of Salmonella Typhimurium serotype. It is concluded that random amplified polymorphic DNA analysis with primer 3 is of potential use as a serotype-specific marker for Salmonella Typhimurium.

Monovalent cations and their influence on activated sludge floc chemistry, structure, and physical characteristics.

Multivalent cations have been known to be important components of activated sludge floc structure due to their bridging ability of the negatively charged sites on the biopolymer network. Recently in batch systems it was found that excess concentration of monovalent cations led to the deterioration in settleability, dewaterability of sludges and effluent quality of the system. In this study, effect of influent monovalent cations (potassium and sodium) on activated sludge floc structure was investigated in semi-continuous reactors. Results revealed that the increase in concentration of both ions correlated to the general increase in total EPS concentration. The zeta potential values were affected by the cation type and dose in such a way that sludge from sodium reactors had always higher zeta potential values (higher negative charge) than the sludges from potassium reactors. Flocs from sodium reactors were more fragile and weak and the capillary suction time values of these sludges were higher compared to those from potassium reactors. The findings of this research conclude that the floc structure is significantly weakened with the increase of monovalent cations. Even though EPS is produced, it is unable to bind the floc components together. With this, the physical properties of sludge deteriorate for both cations.

Characterization of extracellular beta-lactamases from penicillin G-resistant cells of Streptococcus thermophilus.

In this study, biochemical properties of two extracellular beta-lactamases produced by penicillin-resistant Streptococcus thermophilus cells were investigated. Both beta-lactamases showed specificity for penicillins but not for cephaloridins. The beta-lactamases exhibited different affinities for penicillin G. The one with the higher molecular weight (FI) had a Km value of 3.44 microM and a Vmax value of 8.33 mumol/min/mg of protein, whereas the beta-lactamase with the lower molecular weight (FII) had a Km value of 4.76 microM and a Vmax value of 3.13 mumol/min/mg of protein. Both beta-lactamases were inhibited by iodine, copper sulfate, and iron sulfate but not by EDTA. The optimal pH ranged between 6 and 7, and the optimal temperatures were between 40 and 45 degrees C for both enzymes.

Effects of gamma irradiation on the survival of Listeria monocytogenes and on its growth at refrigeration temperature in poultry and red meat.

Gamma irradiation sensitivity of a strain of Listeria monocytogenes was determined in trypticase soy broth supplemented with yeast extract (TSB-YE), in a slurry of chicken breast meat and in raw ground beef. D10 values in these different media were 0.364, 0.599, and 0.699 kGy, respectively. This organism appeared most sensitive in TSB-YE, more resistant in minced fresh chicken breast meat, and most resistant in fresh minced beef. It was found that irradiation at 2.5 kGy prior to refrigeration is an efficient way for the preservation of meat products contaminated at 10(3) to 10(4) per gram initial load of L. monocytogenes for about 7 d. However, with this initial load, the injured cells might repair themselves and cause a health hazard during storage at 4 C in the presence of air after 7 d.