Is ciprofloxacin active against clinically important anaerobes?

The comparative activity of ciprofloxacin against 272 clinical isolates and reference strains of anaerobes was determined by an agar dilution method. The majority of strains of Bacteroides fragilis and clostridia were resistant (MIC greater than 2 mg/l). The effect of pH, inoculum size and medium composition was also studied; the activity of ciprofloxacin was decreased at acid pH and by increasing inoculum size but was unaffected by the composition of the test media. Ciprofloxacin should not be used for the treatment of anaerobic infections because of its limited in-vitro activity against these organisms.

The comparative in-vitro activity of cefotetan against anaerobic bacteria.

The in-vitro activity of cefotetan, a new cephamycin, was assessed against a total of 336 strains of anaerobic bacteria by means of an agar dilution procedure and compared with that of cefoxitin, mezlocillin, piperacillin, clindamycin and metronidazole. Overall clindamycin and metronidazole were the most active of the test compounds. Cefotetan showed good activity against anaerobic cocci and clostridia, except for Clostridium difficile (MIC90 = 16 mg/l), although it was comparatively less active than the other beta-lactams against anaerobic cocci. In the case of the Gram-negative anaerobes, cefotetan showed moderate activity comparable to that of cefoxitin; against the 120 test strains of Bacteroides fragilis both cefotetan and cefoxitin were markedly more active than the penicillins. In studies with antibiotic combinations, cefotetan + cefsulodin showed marked synergy (FIC index less than 0.3) against the majority of strains of Bact. fragilis tested.

Effect of the growth of anaerobic bacteria on the surface pH of solid media.

Changes in surface pH occurring after varying periods of anaerobic incubation were measured for a total of 23 test solid media. There was little change in the surface pH of uninoculated plates, but plates inoculated with Bacteriodes fragilis showed a striking fall in pH, to pH 5 in the case of some of the test media. The problems of controlling the surface pH of solid media are discussed and possible methods of control are considered.

The in-vitro activity of bicozamycin against anaerobic bacteria of clinical interest.

The in-vitro activity of bicozamycin (bicyclomycin, CGP 3543E; FR 1881), an oral antidiarrhoeal agent, was assessed against 389 clinical isolates and reference strains of anaerobic bacteria. The compound inhibited the majority of Gram-negative anaerobes at concentrations of 256 mg/l or less, but all of the test anaerobic cocci and 40 out of 43 strains of clostridia were resistant to this concentration, with MIC values usually in excess of 1024 mg/l. MBC values for bicozamycin against strains of Bacteroides fragilis were generally greatly in excess of MIC values.

Effects of erythromycin and gentamicin in experimental peritonitis.

Erythromycin and gentamicin were used to analyse the concept of bacterial synergy in an experimental model of acute appendicitis. Erythromycin given orally suppressed the aerobic flora other than the Enterobacteriaceae. When given by injection, a notable reduction in the counts of bacteroides and other anaerobic Gram-negative bacteria was also achieved. The addition of gentamicin, itself inactive against bacteroides, resulted in their total suppression. The implications of these findings are discussed.