Isolation and Characterization of a Second Isolate of Streptococcus iniae

Abstract

A second strain of Streptococcus iniae has been recovered from an Amazon freshwater dolphin (Inia geoffrensis). This isolate differs from the first-described isolate in its ability to produce acid from lactose but not salicin and its inability to hydrolyze esculin. The two isolates share a common cell wall antigen that appears to represent the C polysaccharide grouping antigen of this species. In addition, there are strain-specific antigens associated with each isolate. The second strain has been designated strain BU (= ATCC 29177).We previously (3) characterized a single strain of a new isolate of beta-hemolytic streptococcus obtained from dermal lesions on an Amazon freshwater dolphin, Inia geoffrensis, housed in the Steinhart Aquarium in San Francisco, Calif. Subsequently, a second isolate of beta-hemolytic streptococcus was obtained from a swab of the interior wall of a dermal lesion on another specimen of I. geoffrensis housed at the Niagara Falls Aquarium in New York. This second strain, designated BU, was found to have numerous similarities to the first isolate, the most important being a serologically identical cell wall antigen that appears to represent the C polysaccharide of this species. Differences were noted, however, in some sugar fermentation patterns and biochemical reactions as well as in antigens. The characters of the second isolate of Streptococcus iniae are presented as further evidence that these two organisms represent a new species and serogroup of Streptococcus. MATERIALS AND METHODSBacterial strains. Strain PW, the previously described type strain of S. iniae (3), was compared with the second isolate of this species, strain BU.Methods. Maintenance and growth of cultures, morphological and physiological studies, antibiotic susceptibility testing, determination of deoxyribonucleic acid (DNA) base composition, preparation of antisera and seroassays, and animal studies were all performed as previously described for strain -PW (3). Corroboration of new serogroup status was carried out by R. R. Facklam, Center for Disease Control, Atlanta, Ga., and R. L. Wood, National Animal Disease Laboratory, Ames, Iowa.Hemolysis testing. Heart infusion agar with 5% defibrinated blood from either guinea pigs, rabbits, humans, or a freshwater dolphin was used to test for hemolysis.Antigen preparation. Seven extraction procedures were used to prepare antigens from freeze-dried whole bacteria. Four procedures, designated HC1, lytic enzyme, autoclave, and formamide extraction, were previously described (3). The three additional extraction procedures were: (i) 2% trypsin in 0.05 M tris(hydroxymethy1)aminomethane (Tris) with 0.0115 M calcium chloride (pH 8); (ii) 2% pepsin in 0.1 M sodium acetate (pH 4); and (iii) 10% trichloroacetic acid. The proteolytic enzyme extractions were performed at 37°C for 24 h, and the trichloroacetic acid extraction was performed at 4°C for 24 h. Cells were removed by centrifugation and the supernatants were brought to pH 7.4.Chemical analysis. The protein contents of the antigen e...

Streptococcus iniae, a bacterial infection in barramundi Lates calcarifer

“…The causative agent of disease was reported as a Streptococcus sp., but variations in the isolates obtained from moribund fish with regards to biochemical tests and serology indicate that more than one species was involved in the outbreak. The isolates obtained from the Chinese barramundi displayed vague similarity in biochemical responses to that of the 2nd isolate of S. iniae that was described by Pier et al (1978) from another captive Amazon freshwater dolphin. Whether or not this isolate is indeed S. iniae is uncertain.…”

Invasive Infections Due to a Fish Pathogen,Streptococcus iniae

“…1,2,16 The characteristics used to identify streptococcal species as S. iniae were that they had a b -hemolytic reaction on trypticase soy agar with 5 percent sheep's blood; that they were not groupable with Lancefield groups A through V antiserum; that they were susceptible to vancomycin, not gas-producing, nonmotile, and positive for pyrolidonyl arylamidase and leucine aminopeptidase; and that they produced negative results on bile-esculin, Voges-Proskauer, and hippurate tests. Most strains grew at 10°C but not at 45°C, and most did not grow in 6.5 percent sodium chloride.…”

“…TREPTOCOCCUS iniae was first reported in 1976 to cause subcutaneous abscesses in Amazon freshwater dolphins ( Inia geoffrensis ) at aquariums in San Francisco and New York. 1,2 Since the early 1980s, epizootic meningoencephalitis caused by streptococci has been recognized as an important cause of morbidity and mortality in cultured fishponds. [3][4][5][6][7][8] Outbreaks in Japan, Taiwan, Israel, and the United States have affected tilapia (oreochromis species), yellowtail ( Seriola quinqueradiata ), rainbow trout, and coho salmon.…”

Pathological changes in cultured channel catfish Ictalurus punctatus spontaneously infected with Streptococcus iniae

“…It can cause different diseases, depending on the host species infected. Previous studies have shown that S. iniae infection can cause multifocal subcutaneous abscesses in dolphins Inia geoffrensis (Pier & Madin 1976, Pier et al 1978, Bonar & Wagner 2003, and skin lesions and necrotizing myositis in red drum Sciaenops ocellatus (Eldar et al 1999). In barramundi Lates calcarifer, S. iniae infection induces systemic and necrotizing inflammation (Creeper & Buller 2006) and, in tilapia, meningoencephalitis and pa noph thalmitis (Eldar et al 1995).…”