In Vitro Activity of BL-S640 Against Gram-Negative Bacilli and Staphylococcus aureus Compared with Activity of Four Other Semisynthetic Cephalosporins

Abstract

The in vitro activity of BL-S640 (cefatrizine) was determined against 674 recent clinical isolates of Staphylococcus aureus and Enterobacteriaceae. Activity against S. aureus was less than that of cephapirin, cephalothin, and cefazolin, but greater than that of cephalexin. Activity against gram-negative isolates was variable: BL-S640 was slightly less potent than cefazolin against Escherichia coli and Klebsiella, but more active than the other compounds. As for the more resistant gram-negative genera, BL-S640 was significantly superior to the control cephalosporins. The effect of inoculum size on the antibacterial activity was moderate for most organisms except Enterobacter, Providencia stuartii, and indole-positive Proteus, the median minimal inhibitory concentrations of which were 6 to 27 times lower when determined with a 10-4-diluted culture compared with the undiluted one. The stability in aqueous solution at 37 C was remarkably high at the lower pH values, but low at the neutral point.

Use of Susceptibility Testing in Veterinary Medicine

“…However, susceptibility testing does not use cephapirin as the test antibiotic, instead, cephalothin is used because it is the recommended representative of first generation compounds . 1 This recommendation ignores the results of an in vitro study indicating one dilution difference in MIC 50 values between cephapirin and cephalothin for Staphylococcus aureus, Proteus mirabilis and Citrobacter spp, 40 and ignores general recommendations that the antibiotic to be used clinically should be tested. 5 Another example is desfuroylceftiofur, the active metabolite of ceftiofur in cattle.…”

In Vitro Activities of Five Oral Cephalosporins Against Aerobic Pathogenic Bacteria

“…Cefatrizine also is absorbed from the gastrointestinal tract of rodents and is effective orally against experimental infections in mice (7). In vitro, cefatrizine is said to be more active than cephalothin or cephalexin against clinically important gram-negative and gram-positive bacteria not including Haemophilus influenzae and Streptococcus pneumoniae (10) but is less active than cephradine, cephalothin, and cefazolin against Staphylococcus aureus (9). Cefaclor recently has been reported to be more active in vitro than either cephalexin or cephradine against a large number of gram-positive and gram-negative pathogens but less resistant to staphylococcal penicillinase (2).…”