Biomedical subjects

J R Lobry

Publications and source records attributed to J R Lobry.

21 records · Page 2Linked to original sources

PubMed1993

An unexpected correlation between cardinal temperatures of microbial growth highlighted by a new model.

A new model for the prediction of microbial-specific growth rate as a function of temperature is presented. The four parameters of this model are the three cardinal temperatures (Tmax, Tmin and Topt) and the specific growth rate at the optimum temperature (mu opt). A comparison with three other models was made on the basis of several criteria (simplicity and biological significance of parameters, applicability, quality of fit, minimum structural correlations and ease of determination of parameters). A detailed comparison of a 217-point data set, and an extensive comparison of 47 different data sets show that the new model is better than its competitors. The three cardinal temperatures were found to be independent of mu opt. A very strong and unexpected linear correlation between the cardinal temperatures was observed. The consequences of this biological result are discussed, even though causes remain unknown.

Bacteria↗

PubMed1992

Maintenance requirements of Escherichia coli ATCC 25922 in the presence of sub-inhibitory concentrations of various antibiotics.

Escherichia coli ATCC 25922 was grown in minimal medium M63, with glucose 0.1 gL as limiting energy substrate, in the presence of sub-inhibitory concentrations of netilmicin, habekacin, tobramycin, dibekacin, amikacin, kanamycin, amoxycillin, ampicillin, cephalothin, cefoxitin and nalidixic acid. Maintenance requirements were determined with a simple relationship derived from batch growth curves. The apparent relationship between maintenance requirements and antibiotic concentration is an exponential increase, log m(c) = log mo + k.c, where m is maintenance, c antibiotics concentration, mo maintenance without antibiotics, and k a constant. Values for k were found to be in the range 0.5-2.0 mg-1.L.

Amikacin↗

PubMed1991

Biphasic kinetics of bacterial killing by quinolones.

The early phases of the bactericidal dynamics of three quinolones against two Escherichia coli strains were studied. Four concentrations of nalidixic acid, pefloxacin and ofloxacin were tested against each strain. In each case biphasic killing of bacteria was observed after a lag phase, and a biexponential model of microbial death could be fitted to the data. A direct relationship existed between the length of the lag phase and the drug concentration. The other parameters of the model appeared to be either strain-dependent, drug-dependent or both, and were characterised by narrow fluctuations. The degree of killing was always higher for ofloxacin. A paradoxical effect seemed to exist for nalidixic acid and pefloxacin in that survival was greater in the presence of 5 x MIC than in the presence of 3 x MIC. It was clear that ofloxacin did not act in the same way as nalidixic acid and pefloxacin. The study illustrated the relevance of mathematical modelling to investigations of the bactericidal effects of antibiotics.

Colony Count, Microbial↗