Тобрамицин

Описание

Tobramycin is one component (factor 6) of a mixture produced by fermentation of Streptomyces tenebrari us. Lacking the C-3′ hydroxyl group, it is not a substrate for APH(3′)-1 and APH(3′)-II and so has an intrinsically broader spectrum than kanamycin. It is a substrate, however, for adenylation at C-2′ by ANT (2′) and acetylation at C-3 by AAC(3)-I and AAC(3)-II and at C-2′ by AAC(2′).

Химические свойства

White or almost white powder.

Использование

Tobramycin is an aminoglycoside antibiotic.

Определение

ChEBI: A amino cyclitol glycoside that is kanamycin B lacking the 3-hydroxy substituent from the 2,6-diaminoglucose ring.

Показания

Tobramycin is highly active with respect to Gram-negative microorganisms (blue-pus bacillus and gastric bacilli, rabbit fever, serratia, providencia, enterobacteria, proteus, salmonella, shigella), as well as Gram-positive microorganisms (staphylococci, including those resistant to penicillin and some cephalosporins), and a few strains of streptococci.
It is used for severe bacterial infections: peritonitis, sepsis, meningitis, osteomyelitis, endocarditis, pneumonia, pleural empyema, pulmonary abscess, purulent skin infections and soft tissue infections, and infections of the urinary tract caused by microorganisms that are sensitive to the drug. Synonyms of this drug are nebicine, obracine, and others.

Антимикробная активность

In-vitro activity against Ps. aeruginosa is usually somewhat greater than that of gentamicin; against other organisms activity is similar or a little lower. Other Pseudomonas species are generally resistant, as are streptococci and most anaerobic bacteria. Other organisms usually susceptible in vitro include Acinetobacter, Legionella and Yersinia spp. Alkaligenes, Flavobacterium spp. and Mycobacterium spp. are resistant. It exhibits bactericidal activity at concentrations close to the MIC and bactericidal synergy typical of aminoglycosides in combination with penicillins or cephalosporins.

Приобретенная устойчивость

It is inactivated by many aminoglycoside-modifying enzymes that inactivate gentamicin. However, AAC(3′)-I does not confer tobramycin resistance and AAC(3′)-II confers a lower degree of tobramycin resistance than of gentamicin resistance. Conversely, ANT(4′) confers tobramycin but not gentamicin resistance, as do some types of AAC(6′). Overproduction of APH(3′), conferring a low degree of resistance to tobramycin (MIC 8 mg/L), but not gentamicin (MIC 2 mg/L), was ascribed to ‘trapping’ rather than phosphorylation.
Resistance rates are generally similar to those of gentamicin, although they may vary locally because of the prevalence of particular enzyme types.

Биологическая активность

Pharmacologically, tobramycin is quite similar to gentamicin. The drug is somewhat more active against Ps. aeruginosa than gentamicin. Tobramycin also acts synergistically with penicillin, but to a lesser degree than gentamicin.

Клиническое использование

Severe infections caused by susceptible micro-organisms Ps. aeruginosa infections, including chronic pulmonary infections in cystic fibrosis (administration by injection or nebulizer)
For practical purposes use is identical to that of gentamicin, except possibly for Pseudomonas infection, where it has somewhat greater activity against gentamicin-susceptible and some gentamicin-resistant strains. Its value as a substitute for gentamicin in the speculative treatment of severe undiagnosed infection is offset by its lower activity against other organisms that may be implicated.
It has been used extensively to treat Ps. aeruginosa infections in patients with cystic fibrosis.