522
Correspondence Table I. Susceptibility of B. fragilis (124 strains) to antimicrobial agents Sub-species of B. fragilis
distasonis (12 strains) fragilis (61 strains) ovatus (4 strains) thetaiotaomicron (24 strains) vulgatus (23 strains)
Cumulative per cent susceptible to indicated concent (ug/ml) 0-8
1-6
31
6-2
12-5 0-8i
9
22 50
58 86 75
100 100 100
25 4
50 30
83 86
100 100
9
4
Nitrofurantoin
References Finegold, S. M., Miller, L. G., Merril, S. L. & Posnick, D. Significance of anaerobic and capnophilic bacteria isolated from the urinary tract. Progress in Pyelonephritis Kass, J. (ed.) F. A. Davis Co., Philadelphia (1965). Finegold, S. M., Harada, N. E. & Miller, L. G. Antibiotic susceptibility patterns as aids in classification and characterization of Gram negative anaerobic bacilli. Journal of Bacteriology 94: 1443-50 (1972).
4 13
31
6-2
12-5 100 or more
50 9
91 68 50
100 100 100
100 100 100
79 73
91 95
100 100
100 100 Nalidixic and oxolinic acids
Nitro-5 hidroxy-l3 quinoline
Garcia, J. A., Prieto, J., Garcia, J. E. & Gomez, A. C. Germenes anaerobios en infecciones urinarias. Ada Medica iv: 39-44 (1975). Headington, J. T. & Beyerlein B. Anaerobic bacteria in routine urine culture. Journal of Clinical Pathology 19: 573-6 (1966). Segura, J. W., Kelalis, P. P., Martin, W. J. & Smith, L. M. Anaerobic bacteria in the urinary tract. Mayo Clinical Proceedings 47: 30-3 (1972). Susceptibility of Bacteroides fragilis to fusidic acid Sir, The choice of antibacterial agents available for the treatment of systemic infection with Bacteroides fragilis is limited. In this hospital, of 122 isolates of Bacteroides spp. only 41 % were sensitive to co-trimoxazole and 47 % to tetracycline but 89 % were sensitive to fusidic acid by disc diffusion (Goodwin, 1975). The percentage of strains sensitive to fusidic acid has been reported by other workers as 42% of 19 strains (Mackenzie & Litton, 1974) 70% of 200 strains (Leigh, 1974) and 100% of 794 strains (Mitchell, 1973). Metronidazole is effective (Report, 1975) but must usually be given by mouth and its mutagenic properties may give some cause for concern. Phillips & Warren (personal communication) found the MIC of fusidic acid for B. fragilis to be 0-25 to 4 ug/ml. We determined the MIC of fusidic acid in solid medium with and without blood for 14 clinical isolates of B. fragilis (Table I). B. fragilis multiplies more rapidly at pH 6-0 than at pH 7-4 but the results for each strain were the same at both pH values. In liquid medium the results without serum were comparable but the addition of serum raised the MIC considerably although in all but one of the strains the MIC was still
Correspondence Table I. Susceptibility of B. fragilis (124 strains) to antimicrobial agents Sub-species of B. fragilis
distasonis (12 strains) fragilis (61 strains) ovatus (4 strains) thetaiotaomicron (24 strains) vulgatus (23 strains)
Cumulative per cent susceptible to indicated concent (ug/ml) 0-8
1-6
31
6-2
12-5 0-8i
9
22 50
58 86 75
100 100 100
25 4
50 30
83 86
100 100
9
4
Nitrofurantoin
References Finegold, S. M., Miller, L. G., Merril, S. L. & Posnick, D. Significance of anaerobic and capnophilic bacteria isolated from the urinary tract. Progress in Pyelonephritis Kass, J. (ed.) F. A. Davis Co., Philadelphia (1965). Finegold, S. M., Harada, N. E. & Miller, L. G. Antibiotic susceptibility patterns as aids in classification and characterization of Gram negative anaerobic bacilli. Journal of Bacteriology 94: 1443-50 (1972).
4 13
31
6-2
12-5 100 or more
50 9
91 68 50
100 100 100
100 100 100
79 73
91 95
100 100
100 100 Nalidixic and oxolinic acids
Nitro-5 hidroxy-l3 quinoline
Garcia, J. A., Prieto, J., Garcia, J. E. & Gomez, A. C. Germenes anaerobios en infecciones urinarias. Ada Medica iv: 39-44 (1975). Headington, J. T. & Beyerlein B. Anaerobic bacteria in routine urine culture. Journal of Clinical Pathology 19: 573-6 (1966). Segura, J. W., Kelalis, P. P., Martin, W. J. & Smith, L. M. Anaerobic bacteria in the urinary tract. Mayo Clinical Proceedings 47: 30-3 (1972). Susceptibility of Bacteroides fragilis to fusidic acid Sir, The choice of antibacterial agents available for the treatment of systemic infection with Bacteroides fragilis is limited. In this hospital, of 122 isolates of Bacteroides spp. only 41 % were sensitive to co-trimoxazole and 47 % to tetracycline but 89 % were sensitive to fusidic acid by disc diffusion (Goodwin, 1975). The percentage of strains sensitive to fusidic acid has been reported by other workers as 42% of 19 strains (Mackenzie & Litton, 1974) 70% of 200 strains (Leigh, 1974) and 100% of 794 strains (Mitchell, 1973). Metronidazole is effective (Report, 1975) but must usually be given by mouth and its mutagenic properties may give some cause for concern. Phillips & Warren (personal communication) found the MIC of fusidic acid for B. fragilis to be 0-25 to 4 ug/ml. We determined the MIC of fusidic acid in solid medium with and without blood for 14 clinical isolates of B. fragilis (Table I). B. fragilis multiplies more rapidly at pH 6-0 than at pH 7-4 but the results for each strain were the same at both pH values. In liquid medium the results without serum were comparable but the addition of serum raised the MIC considerably although in all but one of the strains the MIC was still
