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Abstract
One hundred samples of Clarias lazera, Tilapia nilotica, Bagrus bayad and Mugil cephalus (25 of each) were collected randomly from different fish markets in Cairo governorate. All collected samples were examined bacteriologically for isolation and identification of the members of Enterobacteriaceae contaminating such examined fish samples.
The obtained results indicated that the mean values of total
Enterobacteriaceae and total coliform counts in the examined
samples of fresh water fishes were 1.38 x ± 0.26 x & 2.52 x
1 0 ± 0.61 x 1 O3cfu/g for Clarias lazera, 5.17 x 1 ± 1.09 x 1 0 &
1.07 x 10 ± 0.24 x lO3cfu/g for Tilapia nilotica, 2.65 x i03 ± 0.78 x
& 6.10 x 102 ± 1.18 x 102 cfu/g for Bagrus bayad and 8.04 x 102
± 2.13 x 102 & 2.35 x 102 ± 0.55 x lO2cfu/g for Mugil cephalus,
respectively. Accordingly, the examined samples of Clarias lazera
were more contaminated either with Enterobacteriaceae or coliforms
as compared with those of Tilapia nilotica, Bagrus bcIyad and Mugil
cephalus.
The differences between the examined fresh water fish samples as a result of total enterobacteriaceae or total coliform counts were significant (P < 0.05).
Citrobacter diversus, Citrobacter freundii, Enterobacter aero genes, Enterob agglomerans, Enterobacter cloacae, Enterobacter hafniae, Kiebsiella ozaenae, Kiebsiella pneumon iae,
Proteus mira bills, Proteus rettgerii, Proteus vulgaris, Serratia liquefaciens and Serratia marcescens were isolated from the examined samples of Clarias lazera, Tilapia nilotica, Bagrus bayad and Mugil cephalus with varying percentages.
Furthermore, Enteropathogenic E.coli was isolated from 32%,
20%, 16% and 8% of the examined samples of Clarias lazera,
Tilapia nilotica, Bagrus bayad and Mugil cephalus, respectively.
Out of 8 strains of E.coli isolated from Clarias lazera, 3 strains were
serologically identified as 0124 : K72 (B17), 2 identified as 026 : K
(B6), 2 were 0128 : K67 (B12) and the last strain was 086 : K(B7).
However, K58 (B9), 026 : K6o (B6), 0124 : K72 (B17) and 0128
K67 (B12) strains were identified from Tilapia niloticus. Moreover,
026: K60(B6), °m : K58 (B9) and 0128 : K67(B12) were recovered from
8%, 4% and 4% of Bagrus bayad samples, respectively. Concerning
Mugil cephalus, out of 2 strains of E.coli, one could be identified as
086 : K (B7) and the other strain was 0124 : K72(B17).
On the other hand, 20%, 12% and 8% of the examined samples of Clarias lazera, Tilapia nilotica and Bagrus bayad were contaminated with Salmonella organisms, respectively. While, all examined samples of Mugil cephalus were free from such organism. Serotyping of the isolated Salmonellae indicated that S. enteritidis (8%, 4% & 4%) and S. lyphimurium (8%, 8% & 4%) were serologically identified from the examined samples of Clarias lazera, Tilapia nilotica and Bagrus bayad, respectively. In contrast,
only one strain (4%) isolated from Clarias lazera was serologically identified as S. hafa.
Therefore, Vibrio parahaemolyticus was detected in 28%, 16% and 4% of the examined Clarias lazera, Tilapia nilotica and Bagrus bayad, respectively. However, such organisms could not be isolated from the examined samples of Mugil cephalus.
In regard to Yersinia enterocolitica, 20% and 4% of the examined samples of Clarias lazera and Tilapia nilotica were contaminated with this pathogen, respectively. All examined samples of Bagrus bayad and Mugil cephalus were free from Yersinia enterocolitica.
Consequently, Clarias lazera was the most contaminated with all members of Enterobacteriaceae followed by Tilapia nilotica, Bagrus bayad and Mugil cephalus.
The public health significance of isolated Enterobacteriaceae and the possible sources of contamination of fresh water fishes with these organisms as well as suggestive hygienic measures to improve the quality of such fishes were discussed.