Lysis if enterobacteria by cefoxitin, cefuroxime, and cephalothin

Relationship between the bactericidal and bacteriolytic activity of cephalosporins and changes in the cell volumes of Escherichia coli cultures

The bactericidal effect of cefoxitin and cefotaxime in relation to concentration and exposure time, as demonstrated by the killing curve diagrams of Escherichia coli cultures, was compared with the degree of bacteriolysis and the cell volume increase measured by the coulter counter-channel analyser system. Human plasma ultrafiltrate was used as the growth medium. Cefoxitin has a higher bactericidal activity than cefotaxime. With increasing concentrations the bactericidal efficacy of cefoxitin increases more rapidly in the lower range of concentrations (2-10 mg/l) than in the higher range (10-40 mg/l). In contrast, the bactericidal effect of cefotaxime in the range 0.06-1.2 mg/l is virtually constant and can only be increased by high levels (10-40 mg/l). The morphometric effect of cefoxitin on E. coli cultures, as demonstrated by volume distribution curves, is characterized by intensive and rapidly appearing bacteriolysis 20 min after exposure to the antibiotic without a preceding increase in bacterial cell volume. Higher concentrations result in an earlier onset of bacteriolysis. In contrast, the application of cefotaxime reveals a massive increase in bacterial cell volume (more than five-fold) with a delayed (greater than 2 h) onset of bacteriolysis. High cefotaxime concentrations reduce the extent of bacterial cell volume increase, associated with an earlier and more intensive onset of bacteriolysis. With both cephalosporins, the bacterial cell alterations are particularly dependent on the exposure time. There is evidently a close correlation between bactericidal and bacteriolytic activity. This is valid both for the two cephalosporins and generally for the concentration-activity relationships.

Review of the new second-generation cephalosporins: cefonicid, ceforanide, and cefuroxime

The new second-generation cephalosporins, cefonicid, ceforanide, and cefuroxime, have recently become available. These agents are generally less active against gram-positive cocci than first-generation cephalosporins and, at best, equal to cefoxitin and cefamandole against many gram-negative bacteria. Cefuroxime, however, is the most active cephalosporin for beta-lactamase-producing Haemophilus influenzae. These newer agents have superior pharmacokinetic characteristics over cefoxitin and cefamandole. Smaller doses, longer dosing intervals and, potentially, a reduction in total drug cost may be the real advantage of these agents. Open trials and a limited number of comparative studies have documented the effectiveness of cefonicid, ceforanide, and cefuroxime in the treatment of most mild-to-serious infectious diseases, although failures with cefonicid in the treatment of staphylococcal infections have been reported. Notably, cefuroxime has received approval for the treatment of common pediatric bacterial meningitis infections. Replacement of cefamandole or cefoxitin with one of these "longer-acting" agents may be cost-beneficial; however, clinicians must be on alert for the development of bacterial resistance or decreased efficacy.

Cefoxitin levels in human aqueous humor

We administered 2 g of cefoxitin to 25 patients before cataract surgery. An additional 23 patients received 500 mg of probenecid 30 minutes before the 2-g doses of cefoxitin. Average aqueous humor levels of 1.54, 3.16, 2.46, 1.22, and 0.82 microgram/ml were achieved at 30 minutes and one, two, four, and six hours, respectively, after the 2-g dose. The addition of probenecid prolonged significant aqueous humor levels. Therapeutic levels against common gram-positive pathogens were consistently achieved at two hours after injection without probenecid and from two to four hours after injection with probenecid. Therapeutic levels effective against Enterobacteriaceae were inconsistent.

Growth curves, microscopic morphology, and subcultures of beta-lactamase-positive and -negative Haemophilus influenzae under the influence of ampicillin and cefamandole

In contrast to the results obtained with ampicillin, the minimum inhibitory concentrations of cefamandole against Haemophilus influenzae were within the same range (0.5 to 1.5 mug/ml) whether or not the strains were beta-lactamase producers. The minimum bactericidal concentrations were somewhat higher for beta-lactamase-positive strains (6.4 mug/ml) than for negative strains (1.2 mug/ml). In a culture with high initial microbial density, monitored by recording optical densities, the addition of 10 mug of cefamandole per ml brought about rapid lysis of a beta-lactamase-negative strain. Observation of a beta-lactamase-positive strain revealed, in the early part of the growth curve, absence of lysis and an increase of biomass similar to that observed in a drug-free control curve. In contrast to the results obtained with ampicillin, the culture consisted uniformly of spherical forms, probably in the process of division, which were capable of generating colonies. When the microbial density exposed to cefamandole was increased still further, persistent bacillary forms were observed, and after 24 h hydrolysis had eliminated every trace of microbiologically active cefamandole.

Cefoxitin: a review of its antibacterial activity, pharmacological properties and therapeutic use

Cefoxitin is a beta-lactam antibiotic derived from cephamycin C, a naturally occurring substance produced by Streptomyces lactamdurans. Its resistance to destruction by beta-lactamases results in a broad spectrum of antibacterial activity which includes anaerobic as well as Gram-positive and Gram-negative aerobic bacteria, including many resistant to cephalothin and other cephalosporins. Given by intravenous or intramuscular injection, cefoxitin is effective against a wide variety of infections caused by Gram-positive or Gram-negative aerobes as well as by anaerobic bacteria. It is generally well tolerated, thrombophlebitis, skin rash and some degree of discomfort after intramuscular injection, being the most commonly reported side effects. Cefoxitin has not been shown to cause adverse effects on renal function.