DRUG RESISTA^•CE OF FURUNCULOSIS IX TROUT 



557 



was repcati'd with the same strains of trout and 

 bacteria, but witli treatment with chlorampheni- 

 eol, the response was rapid and favorable. 



A similar experiment was run concurrently with 

 a strain of brook trout from Bellefonte, Pa., tliat 

 is known to be resistant to furunculosis. The 

 fish failed to respond to sulfonamide treatment 

 and bacteria isolated from dead trout were found 

 also to be mostly resistant to sulfonamides. 

 Trout surviving the sulfonamide treatment were 

 given chloramplienicol and losses stopped within 

 the first o-day period (table 2). The overall fish 

 losses were much lower in the resistant Bellefonte 

 strain than in the susceptible Erwin strain. 



The results with brown trout (table 3) were 

 very similar to those obtained with Bellefonte 

 brook trout since they are known to be more re- 

 sistant to furunculosis than most of the strains of 

 brook trout. 



Table I. — Mortality of a strain of eastern brook trout 

 {Erwin, Tenn.), susceptible to furunculosis, foUowiny 

 treatment with sulfonamides and chloramphenicol 



A. TREATMENT WITH SULFONAMIDES ' 



tinltial weight of fish per lot (trough), 1.500 gm.; mean weight per fish. 19.8 

 gm.; mean number of fish per lot (trough), 76; fish infected orally July 29 

 and .\ug. 1. 1955. and treatment started .\ug. 8; mortality e.^pressed as 

 percent of fish at beginning of each period] 



B. TREATMENT WITH CHLORAMPHENICOL 



[Initial weight of fish per lot (trough), I.-IOO gm.: mean weight i)er fish, 30 

 gm.; mean number of fish per lot (trough), 50; fish infected orally Sept. 

 8 and 9, 1955. and treatment started Sept. 16; mortality expressed as 

 percent of fish at beginning of each period] 



Table 2. — Mortality of a strain of eastern brook trout 

 (Bellefonte, Pa.), resistant to furunculosis, following 

 treatment with sulfonamides and chloramphenicol 



A. TREATMENT WrPH SILFONAMIDES ' 



llnitiul weight of fish per lot (trough). l.iiOO gm.; mean weight per fish. 27 6 

 gm.: mean luimber of fish per lot (trough). 54; fish infecteil orally July 29 

 luid .\ug. 1. 19,5.5, and treatment started .\ug. 19: mortalitv expressed a.s 

 percent of fish at beginning of each period) 



B. TREATMENT WITH CHLORAMPHENICOL 



(Fish surviving treatment with sulfonamides (2-.\) used in thi.s experiment; 

 weight of fish per lot (trough). 2,000 gm.; mean weight per fish. 43 gm.; 

 mean number of fish per lot (trough), 46; no additional infection, with 

 treatment started Sept. 7. 1955; mortality expressed as percent of flsh at 

 beginning of each period] 



' Strains of .4. salmonicida isolated from dead fish were resistant to sulfon- 

 amides. 



Table 3. — Mortality of brown trout following treatment 

 with sulfonamides and chloramphenicol 



A. TREATMENT WITH SULFONAMIDES ' 



(Initial weight of fish per lot (trough). l.,500 gm.: mean weight per flsh, 22.0 

 gm.; mean number of flsh per lot (trough), (58: fish infected orally July 29 

 and Aug. 1, 1955. and treatment started .Aug. 12; mortality expressed as 

 percent of flsh at beginning of each period] 



' Strains otA.salmonicida isolated from dead trout were resistant to sulfona- 

 mides. 



' Oantrisin used in these studies was supplied free of cost by HolTmann 

 La Roche, Nutley, N. J. 



I strains of .4. 

 fonamides. 



salmonicida Isolated from dead flsh were resistant to sul- 



