الفهرس 
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Abstract
The present investigation was designed to study the quality of 200 samples comprised four species of imported fish namely Sardine, Mullus spp., Basa (Bangasius hypophanmus) and Herring (50 of each) which were collected from different markets at Alexandria province.
Sensory assessment as a mean of determining quality showed that 176 out of 200 examined samples (88%) were accepted. Only two of each Sardine, Mullus spp., Basa and Herring was unacceptable. The accepted Sardine had 3 total score, Mullus spp. had 12 total score, Basa had 10 total score and Herring had 10 total score from 15 total score.
Two chemical parameters namely pH and total volatile nitrogen (TVN) were used for determining fish quality. The mean pH values of the examined Sardine, Mullus spp., Basa and Herring was 6.4 ± 0.4, 6.3 ± 0.3, 6.6 ± 0.3 and 6.8 ± 0.5, respectively whereas the mean TVBN contents was 12.32 ± 1.6, 1.12 ± 1.1, 15.6 ± 2.1 and 9.3 ± 1.2 mg/100g muscle of the examined fishes, respectively. A significant difference was noticed in the pH values and TVBN contents between the four examined fish species.
Regarding the microbiological status of the examined imported fish, the mean values of total bacterial counts of Sardine, Mullus spp., Basa and Herring was 8.2 x 104 ± 2.1 x 104, 7.6 x 104 ± 1.2 x 104, 6.3 x 104 ± 0.8 x 104 and 1.4 x 105 ± 9.6 x 104 cfu/g respectively.
Also, the mean values of total Enterobacteriaceae and total coliforms count in the examined samples of imported fishes was 1.1 x 103 ± 6.2 x 102 and 0.9 x 103 ± 6.5 x 10 cfu/g for Sardine, 6.7 x 103 ± 1.1 x 103 and 1.1 x 103 ± 2.6 x 102 cfu/g for Mullus spp., 2.8 x 103 ± 0.9 x 103 and 2.4 x 103 ± 1.6 x 102 cfu/g for Basa and 1.48 x 104 ± 6.7 x 103 and 6.4 x 103 ± 7.1 x 102 cfu/g for Herring, respectively. Accordingly, the examined samples of Herring were more contaminated either with Enterobacteria or coliforms as compared with those of Sardine, Mullus spp. and Basa.
The differences between the examined imported fish samples as a result of total Enterobacteriacaea or total coliforms count were significant (P<0.05).
Citrobacter diverus, Citrobacter freundii, Enterobacter aerogenes, Enterobacter agglomerans, Enterobacter cloacae, Enterobacter hafniae, Klebsiella ozanae, Klebsiella pneumonae, Proteus mirabilis, Proteus rettgeri, Proteus vulgaris, Serratia liquefaciens and Serratia marcescens were isolated from the examined samples of Sardine, Mullus spp., Basa and Herring with varying percentages.
Furthermore, Enteropathogenic E. coli was isolated from 8%, 20%, 16% and 32% of the examined samples of Sardine, Mullus spp., Basa and Herring, respectively. Out of 8 strains of E. coli isolated from Herring, 3 strains were serologically identified as O124: K72 (B17), 2 identified as O26: K60 (B6), 2 were O128: K67 (B12) and the last strain was O86: K61 (B7). However, O111: K58 (B9), O26: K60 (B6), O124: K72 (B17) and O128: K67 (B12) strains were identified from Mullus spp. Moreover, O26: K60 (B6), O111: K58 (B9) and O128: K67 (B12) were recovered from 8%, 4% and 4% of Basa samples, respectively. Concerning Sardine, out of 2 strains of E. coli, one could be identified as O86: K61 (B7) and the other strain was O124: K72 (B17).
On the other hand, 8%, 12% and 20% of the examined samples of Mullus spp., Basa and Herring were contaminated with Salmonella organisms, respectively. While all examined samples of Sardine were free from such organism. Serotyping of the isolated Salmonella indicated that Sal. enteritidis (4%, 4% and 8%) and Sal. typhimurium (8%, 4% and 8%) were serologically identified from the examined samples of Mullus spp., Basa and Herring, respectively. In contrast, only one strain (4%) isolated from Herring was serologically identified as S. haifa.
Therefore, Vibrio parahaemolyticus was detected in 16%, 4% and 28% of the examined, Mullus spp., Basa and Herring respectively. However, such organisms could not be isolated from the examined samples of Sardine.
In regard to Yersinia enterocolitica, 4% and 20% of the examined samples of Mullus spp. and Herring were contaminated with this pathogen, respectively. All examined samples of Sardine and Basa were free from Yersinia enterocolitica.
Consequently, Herring was the most contaminated with all members of Enterobacteriaceae followed by Mullus spp., Basa and Sardine.
Regarding to the Staphylococcus count of the examined imported fishes revealed that the mean values of the Staphylococcus count was 1.1 x 103 ± 6.7 x 102, 1.2 x 103 ± 5.4 x 102, 1.9 x 103 ± 4.6 x 102 and 8.2 x 103 ± 1.2 x 102 cfu/g for Sardine, Mullus spp., Basa and Herring respectively.
Regarding to mycological status of the examined imported fishes (Sardine, Mullus spp., Basa and Herring) the mean total mould counts was 8.2 x 102 ± 1.1 x 102, 9.4 x 102 ± 1.3 x 102, 8.9 x 102 ± 1.2 x 102 and 8.2 x 103 ± 2.1 x 102 cfu/g respectively. Also the mean values of total yeast counts was 1.3 x 103 ± 9.2 x 102, 1.3 x 103 ± 8.4 x 102, 2.3 x 103 ± 7.6 x 102, and 9.2 x 103 ± 2.2 x 103 cfu/g respectively.
The public health significance of contaminants and the possible sources of contamination of imported fishes with these organisms as well as suggestive hygienic measures to improve the quality of such fishes were discussed.