Preprint volume - SIBM

Pre-print Volume - Posters
VARIOUS TOPICS
R. FLORIS, S. MANCA, F. CHESSA, M. TRENTADUE, A. CANNAS, N. FOIS
AGRIS Sardegna, Agenzia per la Ricerca in Agricoltura. Dipartimento per la Ricerca nelle Produzioni Animali,
Servizio Risorse Ittiche, Località Bonassai S.S. 291 km 18,600 – 07040 Olmedo (SS), Italia.
rfloris@agrisricerca.it
MICROBIOLOGICAL CHARACTERIZATION OF INTESTINAL FLORA
OF GILTHEAD SEABREAMS (SPARUS AURATA L.) FROM TORTOLI
LAGOON (EASTERN SARDINIA, ITALY)
CARATTERIZZAZIONE MICROBIOLOGICA DELLA FLORA INTESTINALE
DI ORATE (SPARUS AURATA L.) PROVENIENTI DALLO STAGNO
DI TORTOLI (SARDEGNA ORIENTALE, ITALIA)
Abstract - Thirty seabreams were captured from a Sardinian lagoon (Italy) in January-February 2009 and
their intestinal tracts were analysed by conventional microbiological methods. The mean counts of aerobic
heterotrophic viable bacteria were estimated to be 1521 colony forming units (cfu/g), the mean numbers of
Enterobacteriaceae and Coliforms were 409 cfu/g and 187 cfu/g respectively. A total of 100 pure colonies
were studied by phenotipic tests. Gram negative bacteria were found to be dominant and Vibrio spp. proved
to be present in greater numbers than Pseudomonas aeruginosa sp.
Key-words: intestinal microflora, gilthead seabream, conventional microbiological methods, Sardinia.
Introduction - Sparus aurata (Linnaeus, 1758) is an euryhaline species of the Sparidae
family which is found in both marine and brackishwater environments (Moretti et al.,
1999). The study of the intestinal microflora of marine fish is important for
characterising the product, in fact, the quantity and the quality of these bacteria are a
reflection of different factors: the aqueous environment, seasonal variation, the diet and
the gastrointestinal tract anatomy (Ringo et al., 2006). The aim of this work was the
microbiological characterisation of the intestinal flora of gilthead seabreams from
lagoon in order to evaluate the quality of fish which reflects the hygienic conditions of
the aqueous environment.
Materials and methods - Thirty seabreams (mean weight 349±41g) were captured in
January-February 2009 from Tortoli lagoon (eastern Sardinia, Italy: Lat 39°56’ 854’’N,
Long 9°41’160’’E). Water average chemical-physical parameters were as follows:
temperature 12.6 (°C), salinity 30.14 (‰), dissolved oxygen 102 (%) and pH 8.2. The
intestine between the pyloric caeca and the anus of each fish was removed, weighted
off aseptically and homogenised in peptone saline solution (0.85% NaCl, 0.1 g
peptone) in plastic bags by Stomacher® 400. Serial dilutions were seeded onto
duplicate poured plates. Culture media, bacterial growth conditions and group of
microorganisms detected were as follows: Plate Count Agar (PCA) was incubated at
30°C for 48 h and Nutrient Agar (NA) at 28 °C for 72h in order to count the aerobic
heterotrophic viable bacteria, Violet Red Bile Glucose Agar (VRBGA) and Violet Red
Bile Agar Mug (VRBA-MUG) were put at 30 °C for 24 h for enumerating
Enterobacteriaceae, Coliforms and Escherichia coli respectively and de Man-Rogosa-
Sharpe (MRS) agar was put at 28 °C for 7 days for counting probiotics. A total of 100
colonies from 10 intestinal samples (10 for each fish) were isolated randomly from NA
plates, purified and stored at -80 °C in a 40% (v/v) glycerol-Nutrient broth solution.
The isolates were reactivated and observed for cell shape, motility, Gram staining and
catalase reaction. They were streaked on thiosulphate-citrate-bile salt agar (TCBS,
41 st S.I.B.M. CONGRESS Rapallo (GE), 7-11 June 2010
354