New options for nitrocefin-based beta-lactamase testing.
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Bacteria↗
Biomedical subjects
L F Strenkoski
Publications and source records attributed to L F Strenkoski.
A novel, convenient, multiple test system for detection of bacteriuria.
A novel, convenient, multiple test system for the detection of bacteriuria is described and evaluated. The system consists of a small plastic strip with three dry reagent areas. One rapidly detects the presence of nitrite in urine and the remaining two quantitate total and gram-negative bacterial urine population after 18 to 24 hours of incubation. Quantitative accuracy was evaluated in two blind studies. In the first, known concentrations of 18 different organisms were compared and in the second, unknown concentrations of 218 randomly collected urine specimens were quantitated by both the calibrated loop streak method the new system. Overall correlation was 96 per cent for growth reagent areas. The nitrite area detected 84 per cent of the urines positive for bacteriuria. The advantages of the system over conventional bacteriuria detection systems are described.
Bacteriuria↗
pH-conditional, ammonia assimilation-deficient mutants of Hydrogenomonas eutropha: isolation and growth characteristics.
Two mutants of the facultative autotroph Hydrogenomonas eutropha were isolated by using a modified penicillin selection method. The mutation involved was unusual in that its effect on cellular growth was conditional with regard to extracellular pH and the type of substrate employed. Growth of both mutants was abnormal under autotrophic conditions and during heterotrophic cultivation in the presence of organic substrates which lacked an amino group. Abnormal growth was characterized by linear growth rates which were low at pH 6.0 and moderate at pH 7.2. In contrast, growth of the mutants was normal on most amino acids. Those substrates yielding abnormal growth were oxidized at normal rates by the mutants, indicating the mutation did not impair their uptake or metabolism. The data suggest that the mutants are defective in their ability to assimilate inorganic nitrogen into organic forms, and this defect is strongly influenced by pH.
Alanine↗
pH-conditional, ammonia assimilation-deficient mutants of Hydrogenomonas eutropha: evidence for the nature of the mutation.
Two amination-deficient mutants of Hydrogenomonas eutropha, characterized by pH-dependent linear growth on non-amino acid substrates, were investigated to determine the exact nature of the mutation. Glutamate dehydrogenase, the only aminating enzyme found in wild-type cells, was present at similar levels in mutant cells. Phenylalanine and aspartate, which allowed normal growth of the mutants, could transaminate 2-oxoglutarate to glutamate, whereas alanine, which does not support normal growth, could not transfer its amino nitrogen to form glutamate. In H. eutropha, l-alanine is apparently synthesized by beta-decarboxylation of aspartate. Studies with NH(4) (+) ions as the sole nitrogen source demonstrated that growth rates of the mutant strains were dependent on both extracellular pH and NH(4) (+) ion concentration. Comparison of these results revealed that the growth rate of mutant cultures was proportional to the concentration of extracellular NH(3). Wild-type cultures were not dependent on extracellular NH(3) since exponential growth rates did not vary with pH or NH(4) (+) ion concentration. The results suggest that the mutant strains lack an NH(4) (+) ion transport system and consequently are dependent on NH(3) diffusion which does not support optimal amination rates. The significance of the findings for the amino acid metabolism of H. eutropha is discussed.
Alanine↗