Activity of gentamicin against Pseudomonas and hospital Staphylococci.

Peripheral inactivation of gentamicin

“…There seems to be a twofold increase in MIC from pH 7-4-70 (Barber & Waterworth, 1966;Paisley & Washington, 1979). From pH 7'4-65 the increase in MIC may be as low as two-fold for some strains (Sabath & Toftegaard, 1974) fourfold for other strains (Barber & Waterworth, 1966;Sabath & Toftegaard, 1974), or occasionally 8-fold and 16-fold for individual strains (Young & Hewitt, 1973;Strausbaugh & Sande, 1978) (Table). In this context, it should be recalled that pH estimates inside purulent exudates may vary widely from 72-62 (Hays & Mandell, 1974).…”

“…Unfortunately, such reduction cannot be quantified with accuracy, because changes in MIC and MBC are neither sensitive, nor accurate parameters. Changes in MIC and MBC with changes in pH vary widely according to different investigators (Barber & Waterworth, 1966;Sabath & Toftegaard, 1974;Strausbaugh & Sande, 1978;Paisley & Washington, 1979), possibly because of differences in assay systems and in the species of the bacteria tested. There seems to be a twofold increase in MIC from pH 7-4-70 (Barber & Waterworth, 1966;Paisley & Washington, 1979).…”

“…Changes in MIC and MBC with changes in pH vary widely according to different investigators (Barber & Waterworth, 1966;Sabath & Toftegaard, 1974;Strausbaugh & Sande, 1978;Paisley & Washington, 1979), possibly because of differences in assay systems and in the species of the bacteria tested. There seems to be a twofold increase in MIC from pH 7-4-70 (Barber & Waterworth, 1966;Paisley & Washington, 1979). From pH 7'4-65 the increase in MIC may be as low as two-fold for some strains (Sabath & Toftegaard, 1974) fourfold for other strains (Barber & Waterworth, 1966;Sabath & Toftegaard, 1974), or occasionally 8-fold and 16-fold for individual strains (Young & Hewitt, 1973;Strausbaugh & Sande, 1978) (Table).…”

Gentamicin Inactivation in Purulent Exudates: Role of Cell Lysis

“…Binding of aminoglycosides was substantially higher in a study by Bryant and Hammond than in ours, probably as a result of laboratory manipulations such as homogenization and resuspension in hypotonic medium [4]; these factors influenced dramatically the degree of binding of native, purulent exudates, as shown in table 4. Nevertheless, a 10%-30% inactivation of aminoglycosides by a native, purulent exudate could have important consequences in association with other factors present in inflammatory exudates such as low pH and low Po 2 , both of which are known to affect adversely the antibacterial effect of aminoglycosides [17,18]. Experiments performed on an animal model may help to clarify these aspects.…”

Pseudomonas Aeruginosa AmpR Transcriptional Regulatory Network

“…This phenomenon is termed 'adaptive resistance'. Though the phenomenon was observed in the 1960s (81), it has not been studied in detail. The four main defining features of adaptive resistance are (i) it is transient, (ii) not heritable, (iii) generally reverts upon removal of the inducing signal and (iv) is dependent on the environment (35).…”