A. Eley

Factors influencing the activity of the trometamol salt of fosfomycin

The antibacterial activity of trometamol fosfomycin and its potentiation by glucose-6-phosphate were found to vary considerably in different culture media, although not all bacteria tested were equally affected. In general, the lowest MICs were obtained in the presence of glucose-6-phosphate in nutrient broth and Eugonbroth. The influence of inoculum size, pH and potentiation by glucose-6-phosphate were investigated by agar incorporation MIC titrations on nutrient agar. The activity of trometamol fosfomycin against many strains increased as the pH was lowered from 7.9 to 5.5. Only 9% of the strains showed an inoculum effect when tested at pH 5.5 in the presence of glucose-6-phosphate compared with 37% of the strains tested at pH 7.1 and 22% of the strains tested at pH 7.9. In the absence of glucose-6-phosphate, about 10% of the strains showed an inoculum effect at all three pH levels. The addition of glucose-6-phosphate to culture media seems reasonable for the testing of fosfomycin susceptibility.

Relationship of beta-lactamase production to growth phase inBacteroides species

1. Kunin, C. M., Brandt, D.: Comparative studies ofampicillin, cephalothin and a new cephalosporin derivative,cephaloglycin. American Journal of the Medical Sciences 1968, 255 : 196-201. 2. Yourassowsky, E., Van der Linden, M. P., Lismont, M. J., Crokaert, F.: Growth curve patterns and regrowth in post antibiotic period of Escherichia coli exposed to ampicillin and amoxicillin. Journal of Antimicrobial Chemotherapy 1983, 11: 333-338. 3. Goodell, E. W., Lopez, IL, Thomasz, A.: Suppression of lytic effect of beta-lactams on Escherichia coli and other bacteria. Proceedings of the National Academy of Sciences of the United States of America 1976, 73: 3293-3297. 4. Lopez, R., Ronda-Lain, C., Tapia, A., Waks, S. B., Thomasz, A.: Suppression of the lyric and bactericidal effects of cell wall-inhibitory antibiotics. Anrimicrobial Agents of Chemotherapy 1976, 10: 697-706. 5. Tallgren, L. G., Von Bonsdoref, C. H.: The effect of varying the pH level upon the sensitivity of urinary bacteria to antibiotics. Acta Medica Scandinavica 1965, 178: 543-551.

Newer Antibiotics Active Against Bacteroides Fragilis: Comparison with Older Agents

The activity of eleven antibiotics against a high inoculum (ca 108 cfu./ml) of Bacteroides fragilis was examined in an anaerobic turbidimeter which allowed the removal of samples during the course of the experiment for the parallel investigation of bactericidal activity and morphological effects. When comparative bacteriostatic and bactericidal activities were related to achievable blood levels, imipenem, clindamycin and the combination of benzylpenicillin with clavulanic acid exhibited the highest activity. Surprisingly, fusidic acid also showed good activity. Although metronidazole displayed only moderate bacteriostatic and bactericidal activity in relation to achievable blood levels it was the only agent found to be bactericidal to cultures in the stationary phase of growth, and this may help to explain its excellent activity in vivo.