Morphological and biochemical properties of the strain:
The red gel has been harvested with a swab and dispersed on solid and liquid medium. Both aerobic and
anaerobic growth occured. On 5% blood agar, Mueller-Hinton and Mac Conkey agar presented S-type, medium
size, red pigmented colonies after 24 hours of incubation. Pigment production was very low when incubated at 37
ºC and much more intense at room temperature (20 ºC). Also, more pigment produced on blood agar than on
Mueller-Hinton medium. In liquid medium, after 24h of incubation, an uniform turbidity presented; without deposit.
Gram staining show small Gram-negative rods.
Non-haemolytic, catalase positive and oxidase negative. Glucose fermented with gas production, Indole negative,
Urea negative, H2S negative, Citrate positive (weak), Motility weak / doubtful.
Biochemical results on API 20 E strip:
Positive results for ONPG, citrate utilization, Voges-Proskauer test, gelatin hydrolysis, nitrate reduction, acid
production from: glucose, mannitol, inositol, saccharose, melibiose, amygdalin and arabinose.
Negative results for arginine dihydrolase, lysine decarboxylase, ornithine decarboxylase, H2S production, urea
hydrolysis, tryptophane deaminase, indole production, acid production from sorbitol and rhamnose.
API identified the strain as Serratia rubidaea 92%. With ABIS 6 software (using some tests used by API identification
and more biochemical tests not taken in consideration by API) resulted Serratia rubidaea 89%
|Serratia rubidaea contaminated coconut after
opening and slicing
|Serratia isolation from coconut
- short communication -
DVM Costin Stoica
Two bacteria have been suspected for contamination: Erwinia and
Serratia. Lab tests have been performed for identification. Results
concluded in Serratia rubidaea contamination.
Source of contamination could not been established (coconut disease or
most probably from the opening tools). Although it may be concluded
that Serratia rubidaea grows easily on coconut marrow.
One coconut has been opened and sliced then left at room temperature. After 24 hours a sticky red coloured gel
appeared on the surface of all slices.
When stored at 4ºC for 3 days, colour intensified.
(c) Costin Stoica