Interaction of mezlocillin and cefoxitin against Proteus morganii in the granuloma pouch model

Ascorbate as an induction inhibitor of beta-lactamase in a strain of Enterobacter cloacae

The effect of ascorbate and anaerobiosis of beta-lactamase content (constitutive and inducible) in relation to the susceptibility of a standard strain of Enterobacter cloacae to ampicillin was studied. Enterobacter cloacae ATCC 13047 showed increasing susceptibility to ampicillin when incubated anaerobically in the presence of increasing concentrations of ascorbic acid. The inducible beta-lactamase activity in the cell-free extracts of Ent. cloacae decreased when the bacterium was grown aerobically in the presence of ascorbic acid. Under anaerobic growth conditions, however, ascorbic acid abrogated the induction of the enzyme completely. On the other hand, the constitutive enzymatic activity was markedly decreased as the bacterium was grown anaerobically. Thus under these growth conditions ascorbate-anaerobiosis, the total beta-lactamase level in the presence of ampicillin as inducer fell below the basal constitutive activity observed in the absence of ampicillin.

Correlation between pharmacokinetics, pharmacodynamics and efficacy of antibacterial agents in animal models

On the basis of a review of published literature it is demonstrated that pharmacokinetic parameters of antibacterial agents correlate well with therapeutic efficacy in animal models, provided pharmacodynamic parameters are taken into account. The time that serum levels exceed the MIC is the most significant parameter determining efficacy of beta-lactams, whereas the efficacy of aminoglycosides is dependent on serum concentrations and the area under the curve. The efficacy of quinolones tends to be correlated to the doses administered or drug levels achieved. However, specific pharmacodynamic properties contribute significantly to the therapeutic efficacy of a few quinolones only whereas other quinolones lack these specific pharmacodynamic attributes. Thus, the correlation of pharmacokinetic parameters with therapeutic efficacy provides important basic concepts for the design of preclinical and clinical studies in the course of which additional pharmacodynamic properties will become apparent.

In vitro and in vivo effect of immunoglobulin G on the integrity of bacterial membranes

The interaction between a modified 7S immunoglobulin (MISG) and bacterial membranes was studied by adopting in vitro as well as in vivo techniques. Preincubation of Escherichia coli and Pseudomonas aeruginosa with MISG resulted in a release of enzymatic markers from the periplasmic space, whereas no cytoplasmic or membrane-bound enzymes were liberated. Due to the interaction of MISG with the outer membrane of gram-negative rods, the bacteria became more susceptible to the antibacterial action of poorly penetrating penicillins because of a significantly increased rate of uptake. These in vitro effects were corroborated under in vivo conditions by adopting the granuloma pouch model. A single intravenous injection of MISG enhanced the therapeutic efficacy of mezlocillin against E. coli; similarly, the antibacterial activity of penicillin G, oxacillin, cephalothin and cefamandole against Staphylococcus aureus was augmented by MISG. These in vivo effects of MISG were not due to an increased rate of phagocytosis or complement activity. Thus, MISG sensitized bacteria to several beta-lactam antibiotics by disorganizing their outer membrane.

In vitro and in vivo effect of immunoglobulin G on the integrity of bacterial membranes

The interaction between a modified 7S immunoglobulin (MISG) and bacterial membranes was studied by adopting in vitro as well as in vivo techniques. Preincubation of Escherichia coli and Pseudomonas aeruginosa with MISG resulted in a release of enzymatic markers from the periplasmic space, whereas no cytoplasmic or membrane-bound enzymes were liberated. Due to the interaction of MISG with the outer membrane of gram-negative rods, the bacteria became more susceptible to the antibacterial action of poorly penetrating penicillins because of a significantly increased rate of uptake. These in vitro effects were corroborated under in vivo conditions by adopting the granuloma pouch model. A single intravenous injection of MISG enhanced the therapeutic efficacy of mezlocillin against E. coli; similarly, the antibacterial activity of penicillin G, oxacillin, cephalothin and cefamandole against Staphylococcus aureus was augmented by MISG. These in vivo effects of MISG were not due to an increased rate of phagocytosis or complement activity. Thus, MISG sensitized bacteria to several beta-lactam antibiotics by disorganizing their outer membrane.