A UNIQUE BACTERIUM PATHOGENIC FOR WARM-BLOODED 

 AND COLD-BLOODED ANIMALS 



By PHILIP J. GRIFFIN' and STANISLAS F. SNIESXKO,'' Bacteriolosists 



The vast majority of bacterial fish diseases are 

 caused by motile or noimaotile Gram-negative 

 bacteria. Some of these, such as Bacterium sal- 

 monicida, have stable characteristics and represent 

 bacterial species with well-defined properties. 

 There are, however, many inadequately described 

 motile Gram-negative bacteria which have been 

 isolated from diseased warm- and cold-water 

 fishes, amphibians, and reptiles from all over the 

 world. Many of these bacteria belong to the genus 

 Pseudomonas. Some bacteria, pathogenic to am- 

 phibians and reptiles (Hinshaw and McNeil 1946, 

 1946a, 1947), have been recently described and 

 classified as paracolons. 



The microorganism described in this report has 

 a peculiar taxonomic position, because some of 

 its characteristics indicate that it should be classi- 

 fied as a pseudomonad, while its physiological 

 and antigenic properties suggest relationship with 

 the paracolons. 



Paracolon organisms isolated from outbreaks of 

 gastrointestinal diseases in man have been de- 

 scribed as a group of aberrant coliform organisms 

 comprising a distinct biological group (Stuart et 

 al. 1943). Borman, Stuart, and Wheeler (1944) 

 referred coliform-like bacteria that slowly fer- 

 mented lactose to a separate genus, Paracolobac- 

 trum. Those organisms which produced acetyl- 

 methylcarbinol were termed Paracolobadrum aero- 

 genoides. 



This report is believed to be the first description 

 of organisms conforming largely to the description 

 of Paracolobadrum aerogenoides and pathogenic for 

 fish. Microorganisms were isolated from the body 

 cavities of four aquarium fish belonging to several 

 species (Corydoras aeneus, Xiphophorus hellerii, 

 Platypoecilus maculatus, Lebistes reticulatus) all 

 of which had died suddenly within a period of a 



' Department of Microbiology, Yale University, New Haven, Conn. 

 » Microbiological Laboratory, U. S. Fish and Wildlife Service, Kearaeys- 

 vlUe, W. Va. 



956468°— 61 



week. One strain (1) was obtained from a living, 

 infected Corydoras aeneus. 



We are indebted to Dr. E. K. Borman, Bureau 

 of Laboratories, Connecticut State Department 

 of Health, Hartford, for preliminary antigenic 

 typing and for his advice and comments, and to 

 Dr. S. H. Hutner, Haskins Laboratories, New 

 York, and to Dr. R. W. Hinshaw, Camp Detrick, 

 Md., for advice and reading of the manuscript. 



DESCRIPTION 



In all cases observed, lesions developed on one 

 side of the body as small areas of greenish discol- 

 oration just under the skin between the pectoral 

 and ventral fins. Upon incision, a fetid and 

 purulent material was exuded. A Gram stain of 

 the discharge revealed numerous Gram-negative 

 rods, 1.3 to 2 microns long and 0.7 micron ^v^de, 

 with romided ends, and exhibiting bipolar staining. 



In broth and on agar, the bacteria were arranged 

 singly, in pairs, and occasionally in filaments. 

 The rods were encapsulated, as determined by 

 Anthony's method, and did not form endospores. 

 Active motOity was observed and single polar 

 flagella were demonstrated by Novel's method 

 (1939). The organisms were facultatively an- 

 aerobic but grew best with unrestricted access to 

 air. In nutrient broth, the optimum growth 

 temperature was 37° C, the ma.ximum 43° C, 

 and the minimum 5° C. The pH range for growth 

 was from 5.0 to 9.5 with the optimum range be- 

 tween 6.5 and 7.5; best growth occurred at pH 7. 

 Cultures maintained for almost 8 months in the 

 refrigerator stUl contained viable organisms. 



On nutrient agar, colonies averaged 2 mm. in 

 diameter in 24 hours. They were circular, smooth, 

 entire, slightly convex, and opaque. On blood 

 agar, strains 1 and 2 exhibited a beta hemolytic 

 zone averaging 7 mm. in diameter in 24 hours. 

 After 48 hours the colonics were surrounded by a 

 16-mm. hemolytic zone with a greenish-bro\vn 



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