556 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE 



Sulfonamides were administered at the rate of For the inoculation of the solid media, 24-hour- 

 200 milligrams per kilogram of trout per day, or old cultures in nutrient broth were used. These 

 9gramsper 100 pounds of fish. Chloramphenicol^ were streaked with cotton swabs on 10-cm.- 

 was given at the rate of 75 milligrams of pure diameter petri plates, each containing 20 ml. of 

 antibiotic activity per kilogram of fish per day, medium, and the disks were placed in position. 

 or 3.4 grams per 100 pounds of fish. Treatment The quantitative sensitivity tests were run in 

 was continued to the end of the observations liquid media. In order to select the most satis- 

 recorded in tables 1 to 3. Drugs were mixed factory substrate, the following media were tested: 

 with the quantities of food calculated from the Leetown standard furunculosis medium with- 

 Cortland Hatchery feeding charts (Deuel et al., out agar. 



1952). A daily record of mortality was kept and Vitamin-free casamino acids (Difco), 1 per- 



most of the dead trout were examined bacteriologi- cent, 



pally. Tryptic digest of casein, 1 percent. 



Nutrient broth (Difco). 



Drug sensitivity tests in vitro Nutrient broth (Difco) buffered with 0.5 



The drug sensitivity tests were performed with percent of secondary sodium phosphate 



84 cultures isolated from the experiment on j^^j adjusted to desired pH. 



therapy here described or procured during the Proteose peptone No. 3 (Difco), 1 percent, 



past years from other experiments or received N-Z-Case (Sheffield Chemical Co.), 1 percent, 



from other trout hatcheries (table 4). The rou- Nutrient broth buft'ered with sodium phosphate 



tine qualitative sulfonamide and antibiotic sensi- .^^^s selected as most promising for our purposes, 



tivity tests were run with commercial multiple Because most of the sulfonamides are only 



sensitivity paper disks ^ on solid bacteriological slightly soluble in water, stock solutions of sodium 



media. Sensitivity to sulfonamides has also been g^itg were prepared by dissolving a known quan- 



determined in a quantitative manner by prepara- jity of sulfonamide in diluted sodium hydroxide, 



tion of serial dilutions of these drugs in liquid Excess alkali over that needed for keeping sulfo- 



bacteriological media. namides in solution was neutralized with hydro- 



The following solid bacteriological media were chloric acid. Stock solutions were sterilized by 



used with the paper disks: filtration, stored under refrigeration, and used 



1. Leetown standard furunculosis medium within a week. Serial dilutions of 1:25 or 1:50 



having the following composition: stock solutions were carried out in 5 ml. of media. 



Tryptic digest of casein 10 grams. The first tube contained double-strength medium. 



Yeast e.xtract 5 grams. and after the serial dilutions were made 5 ml. 



Sodium chloride 2.5 grams. were discarded from the last tube. Inocula con- 



Agar 15.0 grams. gjg^p^j ^f q^ j^j of ^ 24-hour-old culture diluted 



• 1 : 5 with sterile water. All cultures were mcubated 



prl D.o— /.U. - , 



at 20° C. and results were read as soon as abundant 



lA. The same, but buffered with 0.5 percent ^^.^^^j,^ developed, usuallv within 24 to 48 liours. 

 of secondary sodium phosphate and 



adjusted to pH 8.0. RESULTS 



2. Sensitivity Test medium C (Case I^abora- Treatment with sulfonamides and chloramphenicol 



*°"''^''' The response to treatment with sulfonamides 



2A. The same, but buffered aiul adjusted as ^nd chloramphenicol of experimental furunculosis 



^o- 2. in two strains of brook trout and one strain of 



3. Mueller Hinton medium (Bacto). brown trout is presented in tables 1 to 3. Sul- 



4. Trypticase Soy agar (Baltimore Biological fonamide treatment of experimental fiuunculosis 



Laboratory). in the Erwin brook trout failed completely (table 

 1). Losses were high because the trout were 



' Racemic Chloromycetin, Parke. Davi.sA Co.. was used at a cloiibli. rate SUSCCptible tO furunculosis and tlu' Strain of ^1. 



because the manufacturer advise.l that it ha.s about .10 percent the thera- .■.almonicida USed tO produce the disease developed 



peutic value of the d-rotatory i.somer .  t i • 



> Muiiidisits, Case Laboratories, Chicago, 111. rcsistaucc to Sulfonamides. When tlic experuueiit 



