Gentamicin combinations

C. Isolation and purification of XK-62-2 100 g of the white powder obtained in the above step B are placed to form a thin, uniform layer on the upper part of a 5 cm0X 150 cm column packed with about 3 kg of silica gel advancely suspended in a solvent of chloroform, isopropanol and 17% aqueous ammonia (2 1 1 by volume). Thereafter, elution is carried out with the same solvent at a flow rate of about 250 ml/hour. The eluate is separated in 100 ml portions. The active fraction is subjected to paper chromatography to examine the components eluted. XK-62-2 is eluted in fraction Nos. 53-75 and gentamicin Cja is eluted in fraction Nos. 85-120. The fraction Nos. 53-75 are combined and concentrated under reduced pressure to sufficiently remove the solvent. The concentrate Is then dissolved in a small amount of water. After freeze-drying the solution, about 38 g of a purified preparate of XK-62-2 (free base) is obtained. The preparate has an activity of 950 units/mg. Likewise, fraction Nos. 85-120 are combined and concentrated under reduced pressure to sufficiently remove the solvent. The concentrate is then dissolved in a small amount of water. After freeze-drying the solution, about 50 g of a purified preparate of gentamicin Cja (free base) is obtained. 

Listeriosis may he treated with a combination ofampicillin and gentamicin. 

Patients with PVE caused by penicillin-susceptible strains of viridans streptococci require treatment for 6 weeks with penicillin G or ceftriaxone with or without gentamicin during the initial 2 weeks of therapy. However, if the organism demonstrates less susceptibility to penicillin (MIC greater than 0.12 mcg/mL), a combination therapy with penicillin G or ceftriaxone plus gentamicin should be given for the entire 6 weeks. Vancomycin remains the primary alternative if the patient is allergic to (l-lactams (e.g., penicillins, cephalosporins, etc.). 

It is important to determine (1) whether the isolate is methicillin-susceptible or methicillin-resistant and (2) whether the patient has a prosthetic valve. For patients with no prosthetic material, methicillin-susceptible staphylococci treatment should consist of a penicillinase-resistant penicillin (e.g., nafcillin or oxacillin) with or without gentamicin, and for methicillin-resistant strains, therapy should consist of vancomycin (see Table 71-4). Combination therapy with aminoglycosides, when used in these patients, typically is given only during the first 3 to 5 days of therapy. In the absence of prosthetic material, some treatment guidelines do not recommend combination therapy against MRSA. However, many clinicians may combine either gentamicin or rifampin with vancomycin if the patient is unresponsive to monotherapy. 

Clindamycin and metronidazole appear to be equivalent in efficacy when combined with agents effective against aerobic gram-negative bacilli (e.g., gentamicin or aztreonam). 

Recommended therapy in the uncomplicated case caused by fully susceptible strains is 4 weeks of either high-dose penicillin G or ceftriaxone, or 2 weeks of combined therapy with high-dose penicillin G plus gentamicin (Table 37-3). 

The recommended therapy for patients with left-sided IE caused by methicillin-sensitive S. aureus (MSSA) is 4 to 6 weeks of nafcillin or oxacillin, often combined with a short course of gentamicin (Table 37-6). 

In addition to isolates with high-level aminoglycoside resistance, /3-lacta-mase-producing enterococci (especially Enterococcus faecium) are increasingly reported. If these organisms are discovered, use of vancomycin or ampicillin-sulbactam in combination with gentamicin should be considered. 

Docusate sodium is a preparation used for softening ear wax before removal. Hydrocortisone is a corticosteroid, whereas gentamicin, neomycin and clioquinol are antibacterial agents. Otitis externa may be managed by the use of antibacterial preparations used alone or in combination with topical corticosteroids. 

Blepharitis is a topical inflammation of the eyelid margins that should be treated using topical antibacterial agents. Gentamicin eye ointment is preferred to the fusidic acid drops since the ointment is a better formulation to be used where the condition involves the eyelid margins. Chloramphenicol eye drops is the third option since it is an antibiotic with a wider spectrum of activity. A combination of corticosteroid and antibiotic is not recommended because of the side-effects associated with the steroid. The use of oral tablets is not usually recommended since blepharitis can easily be managed with topical drops. The use of dexamethasone eye drops, monotherapy steroid, could clear the inflammation but mask persistence of infection. 

Empiric treatment for subacute endocarditis likely to be caused by penicillin-sensitive streptococci consists of high dose penicillin G (6 x 3 million units i.v. daily) plus gentamicin (1x3 mg/kg). In acute endocarditis a staphylococcal etiology is more likely and, therefore, gentamicin is combined with (flu)cloxacillin (6 x 2 g i.v. daily). 

Acute salpingitis (pelvic inflammatory disease) due to Neisseria gonorrhoeae. Chlamydia trachomatis, or both is often complicated by superinfection with gramnegative bacilli and anaerobes. A combination of gentamicin, clindamycin, and doxycycline has been shown to be an effective treatment for this polymicrobial infection. 

Vancomycin is also an effective alternative therapy for the treatment of staphylococcal enterocolitis and endocarditis. The combination of vancomycin and either streptomycin or gentamicin acts synergisticaUy against enterococci and is used effectively for the treatment or... 

The aminoglycosides include streptomycin, neomycin, kanamycin, amikacin, gentamicin, tobramycin, sisomicin, netilmicin, and others. They are used most widely against gram-negative enteric bacteria, especially in bacteremia and sepsis, in combination with vancomycin or a penicillin for endocarditis, and for treatment of tuberculosis. 

Neomycin is available in numerous topical formulations, both alone and in combination with polymyxin, bacitracin, and other antibiotics. It is also available as a sterile powder for topical use. Gentamicin is available as an ointment or cream. 

Lincomydn is an antibiotic produced by Streptomyces lincolnensis. It is used in monopreparations or in combination with other antibiotics such as spectinomycin, sulfamethazine, and gentamicin, for the initial treatment of mild to moderate staphylococcal infections in a variety of animal species. It can be administered orally to poultry at dosages equivalent to up to 50 mg/kg hw/day for up to 7 days, and to swine at dosages equivalent to up to 10 mg/kg bw/day for up to 21 days. In calves, sheep, goats, and swine, it can be administered intramuscularly at dosages of up to 15 mg/kg bw/day for up to 4-7 days. It is also added in feeds for growth-promoting purposes. 

Electrochemical detection has also been suggested for determination of underivatized aminoglycosides in edible animal products (3, 19), while laser-based polarimetric detection has also been used in the analysis of underivatized gentamicin in milk (9). Liquid chromatography combined with mass spectrometry... 

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