Manufacturing Process
Germination Stage: A lyophilized culture of M. purpurea is added to a 300 ml
shake flask containing 100 ml of the following sterile medium: 3 grams bactobeef extract; 5 grams tryptose; 1 gram dextrose; 24 grams starch (soluble);
5 grams yeast extract; and 1,000 ml tap water. The flask and its contents are
incubated for 5 days at 37°C on a rotary shaker (280 rpm, 2 inch stroke).
Inoculum Preparation Stage: Two batches of inoculum of about 50 gallons
each are prepared by the following method: A 25 ml inoculum (from the
germination stage) is transferred to each of four 2-liter flasks, each containing
500 ml of the sterile medium utilized for germination. The flasks and contents
are incubated for 5 days at 28°C on a rotary shaker (280 rpm, 2 inch stroke).
The contents of the flasks are pooled, a 25 ml inoculum (taken from the pool)
is added to each of twenty 2-liter flasks, each containing 500 ml of the
following sterile medium: 30 grams soybean meal; 40 grams dextrose
(cerelose); 1 gram calcium carbonate; 1,000 milliliters tap water. The flasks
and their contents are incubated for 3 to 5 days at 28°C on a rotary shaker
(280 rpm, 2 inch stroke). The broth is pooled and aseptically transferred into
a sterile inoculum flask having a side arm (total volume, about 10 liters).
The 10 liters of inoculum is aseptically transferred to a 65-gallon fermenter
containing 50 gallons of the following sterile medium: 600 grams bacto-beef
extract; 1,000 grams bacto-tryptose; 200 grams dextrose (cerelose); 4,800
grams starch (soluble); 1,000 grams yeast extract; 100 ml antifoamer GE 60
(General Electric Co. brand of silicone defoamer), or other defoamer; and tap
water, qs to 50 gallons.
The pH is adjusted to 6.9 to 7.0 before sterilization and aerobic fermentation
is effected for 24 hours (until the packed cell volume is about 10 to 15%) under the following conditions: temperature, 37°C; sterile air input, 54
ft3/min; pressure, 7 psi; and agitation, 180 rpm.
Fermentation Stage: One 50-gallon batch of inoculum is aseptically
transferred to a 675-gallon fermenter (fermenter A) containing the following
medium: 54.0 kg soybean meal; 72.0 kg cerelose; 9.0 kg calcium carbonate;
300 ml antifoamer GE 60; and 450 gallons soft water. The other 50-gallon
batch of inoculum is aseptically transferred to a similar fermenter (fermenter
B) containing the same medium as fermenter A with the addition of 200 mg of
CoCl2 · 6H2O. Fermentation is effected in each fermenter at 35°C while
agitating at 120 rpm with air input at 7 psi and 15 ft3/min. At various times,
samples of the fermented broth are withdrawn and assayed for antibiotic
production by the disc assay method. The following table shows the increase
in yield effected by the presence of cobalt, (as described in US Patent
3,136,704).
The conversion of the broth to gentamicin sulfate is described in US Patent
3,091,572.
Clinical Use
Gentamycin Sulphate (Garamycin) was isolated in 1958 and reported in 1963 by Weinstein et al. to belong to the streptomycinoid(aminocyclitol) group of antibiotics. It is obtained commerciallyfrom Micromonospora purpurea. Like the other membersof its group, it has a broad spectrum of activity againstmany common pathogens, both Gram-positive and Gramnegative. Of particular interest is its strong activity against P. aeruginosa and other Gram-negative enteric bacilli.
Gentamycin Sulphate is effective in the treatment of various skin infectionsfor which a topical cream or ointment may be used.Because it offers no real advantage over topical neomycin inthe treatment of all but pseudomonal infections, however, itis recommended that topical gentamicin be reserved for usein such infections and in the treatment of burns complicatedby pseudomonemia. An injectable solution containing 40 mgof gentamicin sulfate per milliliter may be used for serioussystemic and genitourinary tract infections caused by Gramnegativebacteria, particularly Pseudomonas, Enterobacter,and Serratia spp. Because of the development of strains ofthese bacterial species resistant to previously effective broadspectrumantibiotics, gentamicin has been used for the treatmentof hospital-acquired infections caused by such organisms.
Veterinary Drugs and Treatments
The inherent toxicity of the aminoglycosides limit their systemic
(parenteral) use to the treatment of serious gram-negative infections
when there is either a documented lack of susceptibility
to
other less toxic antibiotics or when the clinical situation dictates
immediate treatment of a presumed
gram-negative infection before
culture and susceptibility results are reported.
Various gentamicin products are approved for parenteral use
in dogs, cats, chickens, turkeys, and swine, although the injectable
small animal products appear to be no longer marketed. Although
routinely used parenterally in horses, gentamicin is only approved
for intrauterine infusion
in this species. Oral products are approved
for gastrointestinal infections in swine and turkeys. For more information,
refer to the Dosage section below.
