Sisomicin Versus Netilmicin: In Vitro Susceptibility Testing

Netilmicin (SCH 20569), a new broad-spectrum aminoglycoside derived from sisomicin, was compared with gentamicin in the therapy of experimental Escherichia coli meningitis in rabbits. Meningitis was produced in 48 animals by the intracisternal inoculation of 105 E. coli colony-forming units. The minimum bactericidal concentration was 2 ,tg/ml against the test strain for both gentamicin and netilmicin. The two aminoglycosides demonstrated comparable penetration into the cerebrospinal fluid (CSF). The mean percent penetration [(CSF concentration/serum concentration) x 100%] was 22.5 ± 6.0 and 20.6 ± 7.2 for netilmicin and gentamicin, respectively (P = 0.18). However, netilmicin achieved bactericidal activity irn the CSF at lower levels than did gentamicin. When mean CSF concentrations ranged from 4 to 8 ,ug/ml, mean CSF bacterial titers decreased 2.98 logs in rabbits treated with netilmicin but only 0.16 log in rabbits treated with gentamicin. A 2-log decrease in CSF bacterial counts was produced by a mean CSF concentration of 1.4 ,ug of netilmicin per ml as compared to 14.1

Section: Resultsmentioning

confidence: 99%

Comparison of Netilmicin with Gentamicin in the Therapy of Experimental Escherichia coli Meningitis

Scheld

Brown

Sande

1978

“…It has been shown to have in vitro activity similar to that of sisomicin and gentamicin against gram-negative pathogens (4,5,7,8) and also to be active against some gentamicinresistant strains of gram-negative bacteria (6)(7)(8). Netilmicin also has been shown to have a pharmacokinetic profile similar to that of gentamicin (8).…”

mentioning

confidence: 96%

“…The Netilmicin (Sch 20569) is a new, semisynthetic aminoglycoside derived by ethylation of the 1-N position of the deoxystreptamine ring of sisomicin (9). It has been shown to have in vitro activity similar to that of sisomicin and gentamicin against gram-negative pathogens (4,5,7,8) and also to be active against some gentamicinresistant strains of gram-negative bacteria (6-8). Netilmicin also has been shown to have a pharmacokinetic profile similar to that of gentamicin (8).…”

mentioning

confidence: 99%

In Vitro Susceptibility Studies with Netilmicin: Comparison of a 10-μg Netilmicin Disk with a Standardized 10-μg Gentamicin Disk

Habwe

Shadomy

1978

Netilmicin is a new, semisynthetic aminoglycoside antibiotic active against some gentamicin-resistant gram-negative bacteria. In this study we compared a 10-,ig netilmicin disk with the standardized 10-jig gentamicin disk in terms of their abilities to predict probable clinical susceptibility to netilmicin. The Netilmicin (Sch 20569) is a new, semisynthetic aminoglycoside derived by ethylation of the 1-N position of the deoxystreptamine ring of sisomicin (9). It has been shown to have in vitro activity similar to that of sisomicin and gentamicin against gram-negative pathogens (4,5,7,8) and also to be active against some gentamicinresistant strains of gram-negative bacteria (6-8). Netilmicin also has been shown to have a pharmacokinetic profile similar to that of gentamicin (8). This in vitro study compared a 10-,ug netilmicin disk with the standardized 10-,Ig gentamicin disk in terms of their abilities to predict probable clinical susceptibility or resistance to netilmicin.One hundred eighteen clinical isolates of gram-negative bacilli were studied. These included 25

“…Netilmicin has been reported to have considerable activity against gram-negative clinical isolates (2,3,5,6,(8)(9)(10) and to be effective against some gentamicin-resistant strains (3,(7)(8)(9). This in vitro study evaluates the correlation between netilmicin agar dilution minimal inhibitory concentrations (MICs) and disk diffusion zone diameters.…”

mentioning

confidence: 99%

Correlation of Netilmicin Agar Dilution and Disk Diffusion Susceptibilities

Goldmann

Syriopoulou²,

Semple³

1977

A study of 283 isolates of gram-negative bacilli revealed a good correlation (r = -0.74) between disk diffusion zones of inhibition and agar dilution minimal inhibitory concentrations. Regression analysis suggested that strains with zone sizes 11 mm should be considered resistant, but 34 of 45 strains resistant by minimal inhibitory concentration (including 27 strains ofPseudomonas aeruginosa) would have been called susceptible using this break point.Netilmicin (Sch 20569), the 1-N-ethyl derivative of sisomycin, is a new aminoglycoside with a pharmacokinetic profile similar to that of gentamicin (8). Netilmicin has been reported to have considerable activity against gram-negative clinical isolates (2,3,5,6,(8)(9)(10) and to be effective against some gentamicin-resistant strains (3,(7)(8)(9). This in vitro study evaluates the correlation between netilmicin agar dilution minimal inhibitory concentrations (MICs) and disk diffusion zone diameters.Two hundred eighty-three clinical isolates of gram-negative bacilli were studied: 69 strains of Pseudomonas aeruginosa, 6 strains ofPseudomonas sp., 20 strains of indole-positive Proteus, 28 strains of Enterobacter, 64 strains of Klebsiella, 10 strains of Serratia, 10 strains of Citrobacter, and 76 strains of Escherichia coli. MICs were performed by the agar dilution method as recommended by the International Collaborative Study of the World Health Organization (4). Bacteria were grown overnight in Mueller-Hinton broth (BBL). Serial twofold dilutions of the antibiotics to be tested were prepared in Mueller-Hinton agar (BBL). The Mueller-Hinton agar plates were inoculated with approximately 104 organisms using a Steers replicator. Plates were read after 24 h of incubation at 37C. Gentamicin resistance was defined as an MIC 58 ,ug/ml. Disk diffusion susceptibility testing was performed according to the method of Bauer et al.(1) using a 10-,.g netilmicin disk. Correlation between netilmicin zone diameters and MICs was examined by linear regression analysis. Netilmicin sulfate and netilmicin sulfate disks were supplied by the Schering Corp. There was good correlation between log2 MICs for netilmicin obtained by the agar dilution technique and zone diameters obtained by the Bauer-Kirby method. The linear regression curve for all 283 strains is shown in Fig. 1