ENZYMATIC ACTIVITIES OF STREPTOMYCIN-DEPENDENT ESCHERICHIA COLI IN RELATION TO VALINE FORMATION

Bragg, P. D. (University of British Columbia, Vancouver, B.C., Canada), and W. J. Polglase. Enzymatic activities of streptomycin-dependent Escherichia coli in relation to valine formation. J. Bacteriol. 88:1399-1402. 1964.-The activities of several enzymes were compared in antibiotic-depleted and antibiotic-supplemented streptomycin-dependent Escherichia coli. Depleted cells were somewhat lower than supplemented cells in several oxidase activities. Isocitric dehydrogenase was very much lower in depleted cells than in supplemented cells. The lactic dehydrogenase activity of depleted and supplemented cells was similar. The balance of enzymatic activities in depleted and supplemented cells was thus found to correlate well with the observed extracellular products. Thus, depleted cells excreted lactic acid and were deficient in oxidase activity (although normal in lactic dehydrogenase activity), whereas supplemented cells excreted valine and were rich in the reduced nicotinamide adenine dinucleotide phosphate-producing enzyme, isocitric dehydrogenase. Since antibiotic-depleted cells were not deficient in lactic dehydrogenase, it appeared probable that the failure of depleted cells to metabolize lactate was related to a deficiency in the electron-transport system.

SOME PHYSIOLOGICAL CHARACTERISTICS OF NEOMYCIN AND KANAMYCIN-RESISTANT STRAINS OF STAPHYLOCOCCUS AUREUS

Five hundred and fifty-two strains of Staphylococcus aureus of hospital origin were resistant to penicillin, streptomycin, and tetracycline. Of these, 298 were also resistant to neomycin and kanamycin, and this resistance was related to pigment production on glycerol monoacetate agar, the production of beta-lysin, the absence of fibrinolytic and proteolytic activity, and to phage susceptibility. The use of physiological markers, the inadequacy of phage typing, and the possible reasons for the emergence of neomycin-resistant staphylococci are discussed.

A REPORT OF THREE STRAINS OF PASTEURELLA SEPTICA ISOLATED IN HONG KONG

Three strains of Past. septica were isolated in Hong Kong. The clinical histories and the detailed bacteriological and serological studies are presented.

ACTIVITY OF AMPICILLIN IN VITRO COMPARED WITH OTHER ANTIBIOTICS

Comparative tests in vitro for antibacterial activity were carried out with ampicillin, tetracycline, and chloramphenicol using 673 clinical isolates of Gram-negative bacilli and Streptococcus faecalis. Further comparative tests were also carried out with ampicillin, chloramphenicol, colistin sulphate, colistin methane sulphonate, cycloserine, kanamycin, nitrofurantoin, polymyxin, streptomycin, and tetracycline, using groups of 20 strains of each of the main species selected at random from the total number of isolates. Of the total number of isolates a higher percentage was inhibited by ampicillin than by tetracycline or chloramphenicol. Ampicillin showed particularly high activity against certain species of bacteria and displayed an antibacterial spectrum not shown by any of the other antibiotics tested.

GENETIC RECOMBINATION BETWEEN THE RESISTANCE TRANSFER FACTOR AND THE CHROMOSOME OF ESCHIERICHIA COLI

Ginoza, Herbert S. (National Aeronautics and Space Administration, Moffett Field, Calif.), and Robert B. Painter. Genetic recombination between the resistance transfer factor and the chromosome of Escherichia coli. J. Bacteriol. 87:1339-1345. 1964.-Genetic instability for high-level streptomycin and chloramphenicol resistance was observed in several strains of Escherichia coli infected with the resistance transfer factor (RTF) episome. The altered site was always found on the chromosome, and the resistance characteristics were similar to, if not identical with, the corresponding determinant found on the episome. The high-level drug resistance phenotype was ascribed to two separate loci acting cooperatively within the host. The instability phenomenon had been attributed to a genetic exchange mechanism in which the chromosome copies the drug-resistance information from the episome, thus giving rise to a diploid homogenote for this segment. In a reciprocal exchange system, the tetracycline-resistance marker on the chromosome was shown to recombine with the RTF episome lacking this information.

RESISTANCE OF THE MOUSE'S INTESTINAL TRACT TO EXPERIMENTAL SALMONELLA INFECTION. II. FACTORS RESPONSIBLE FOR ITS LOSS FOLLOWING STREPTOMYCIN TREATMENT

Determinations of pH, Eh, and concentrations of acetic, butyric and lactic acids were made on the content of cecum and transverse colon of groups of mice killed 1, 3, and 5 days after oral administration of 50 mg streptomycin. Control observations on untreated mice are reported in the preceding communication. Heat-killed supenatants of suspensions of bowel content were tested in vitro for their ability to inhibit multiplication of our standard streptomycin-resistant strain of Salmonella enteritidis during aerobic and anaerobic incubation. Also tested in like fashion were series of cultures in broth buffered at various pH levels and containing acetic, butyric, and lactic acids in varying concentrations. In colon content of mice on the 1st day after streptomycin treatment, the pH had risen and the concentrations of the fatty acids fallen, a combination of effects which adequately accounts for its inability to inhibit multiplication of Salmonella in vitro and in vivo. By the 3rd day after streptomycin treatment, pH and fatty acid concentrations had returned to normal levels. The susceptibility of mice to oral challenge on the 3rd day was explained by the finding that lactic acid had accumulated in colon content to levels which, in broth, effectively counteracted the activity of inhibitory concentrations of the fatty acids. Other cocarboxylic acids also antagonized the inhibitory activity of the fatty acids; glucose did not.

CHLORAMPHENICOL IN BLOOD: SIMPLE CHEMICAL ESTIMATIONS IN PATIENTS RECEIVING MULTIPLE ANTIBIOTICS

A simple method is described which obviates the difficulties of estimating the concentration of chloramphenicol in the blood in the presence of other antibiotics. This is of importance in avoiding hematologic depression from chloramphenicol toxicity.