Gentamicin Inactivation in Purulent Exudates: Role of Cell Lysis

Peripheral inactivation of gentamicin

“…Pus has often been described as being a zone of intense cellular destruction and necrosis. In a recent study, however, we showed that polymorphs from abscesses or pleural empyemas contained in some instances more than lOVml identifiable polymorphs with more than 60% of them excluding trypan blue (Vaudaux & Waldvogel, 1980;Waldvogel et al, in press). Some of these viable cells were even shown to have significant phagocytic bactericidal activity, when incubated with properly opsonized bacteria in a standard in-vitro phagocytic bactericidal assay (Waldvogel et al, in press).…”

“…When this observation was transposed to purulent exudates consisting of intact as well as lysed polymorphs in various proportions, a correlation was found between the concentration of trypan blue positive polymorphs and the in-vitro gentamicin binding of the material. When the proportion of trypan blue positive cells was increased to >99% by either freeze-thawing of the purulent exudates or by suspension of purulent leucocytes in distilled water, increased lysis could account for the increased [ l4 C]gentamicin binding previously mentioned (Vaudaux & Waldvogel, 1980). From these findings, it can be stated that the extent of cell lysis, as well as the total polymorph concentration within purulent exudates, determines to a large extent the degree of gentamicin binding recorded in vitro.…”

“…The effect of homogenizing the purulent material on the extent of gentamicin binding can be illustrated by our own data (Vaudaux & Waldvogel, 1980), which shows a more than two-fold increase in ['<C]gentamicin binding after freezethawing of the material (Vaudaux & Waldvogel, 1980). It is therefore possible that gentamicin and neomycin binding data were artificially enhanced in some previous studies, which used either purulent material lyophilized and suspended in distilled water (Potter et al, 1965), purulent sputum sonicated and autoclaved (Davis & Brans, 1978), or purulent exudates homogenized, frozen and diluted in water (Bryant & Hammond, 1974).…”

Recombinant human DNase I reduces the viscosity of cystic fibrosis sputum.

“…Experiments in the 1950s and 1960s revealed that DNA is present in very large amounts (3-14 mg/ml) in purulent, but not in uninfected, lung secretions (9)(10)(11). DNA, an extremely viscous polyanion, may contribute both to the increased viscosity of lung secretions and to the reduced effectiveness of aminoglycoside antibiotics (12)(13)(14). In fact, lung secretions incubated in vitro with partially purified bovine pancreatic DNase I (contaminated with proteases) show a large reduction in viscosity (15,16).…”

Alternative Strategies for Proof-of-Principle Studies of Antibacterial Agents

“…Antibacterials may also bind to cell membranes, intracellular proteins and structures, cell debris, pus, DNA, etc., leading to a reduction of the drug effect (110)(111)(112). Therefore, the advantage of measuring reductions in viable counts of pathogens, of the resident microflora or colonizers, or of applied bacteria is that such reductions represent the net effect of an antibacterial agent having been distributed and eliminated, metabolized, and bound, etc., so that the resident flora of human volunteers mirrors all of these complex interactions of the investigational agent with the host and the bacterium.…”