Identification of strains of Citrobacter genomospecies 10 isolated from well water

Veterinarni Medicina 44, 1999, 25-28

Twenty one strains (54%) of Citrobacter genomospecies 10 were identified from 39 strains of citrobacteria isolated from well water in the region of North Moravia during one year. Two strains of genomospecies 10 isolated from raw milk and milking machines (Urbanova and Pacova, 1997) were added to the collection of 21 strains and so the total of 23 strains were studied. It is probable that the origin of the strains from milk sources is water, too. The strains were identified using the commercial kit ENTEROtest 16 (Lachema, a.s., Brno) including OXItest and ONPtest supplemented with the following rests: arginine dihydrolase, sodium acetate, melibiose, raffinose, dulcitol, alpha-methyl-D-glucoside. The current database of numerical identification system TNW (Czech Collection of Microorganisms, Masaryk University, Brno) does not contain any reference data for identification of genomospecies 10, therefore the result of identification - Citrobacter werkmanii - was incorrect (Tab. II). Both C. werkmanii and genomospecies 10 are ornithine and indolle negative, malonate positive. The two characteristics useful for their differentiation are inability of genomospecies 10 to hydrolyze urea and inability to utilize sodium citrate as a sole carbon source. Some minor differences between the biochemical results reported in Tab. I and those reported for the three strains of genomospecies 10 by Brenner et al. (1993) and O'Hara er al. (1995) are as follows: 96% (previously 67%) H2S positive, 4% (previously 0%) esculin positive, 74% (previously 100%) delayed Simmons citrate positive, 100% (previously 67%,) melibiose and cellobiose positive, 0% (previously 100%) delayed arginine dihydrolase positive. It is probable that genomospecies 10 is one of the citrobacteria most frequently isolated from well water which were previously identified as Citrobacter freundii. Four representative strains of this genomospecies were kindly reidentified by O'Hara in CDC Atlanta, U.S.A. These strains have been deposited in our Collection as Citrobacter sp. (genomospecies 10): CCM 4513 (= CDC 4562-98, milking machine), CCM 4514 (= CDC 4563-98, raw milk), CCM 4515 and CCM 4711 (= CDC 4564-98 and CDC 4565-98, well water)

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