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Abstract
Gram-positive bacteria cause a diseases in fishes and of a considerable importance specially in recent years.
In this investigation 1321 fishes of various species and life stages
from each Tilapia (Oreochromis species) and Nile cat fish (Cgariepinus)
which were collected from different localities in different seasons of the
year, were subjected to clinical and bacteriological examination to
determine the prevalence of some Gram-positive bacteria (Streptococcus
species, Staphylococcus spp.and Cperfringensi infection. Morphological and biochemical identification of the. isolated : bacteria (Streptococcus species, Staphylococcus spp. and Cperjringens) were applied. Beside 423 apparently healthy Oiniloticus with average ,~. body weight 50± 5 gm were used-for studying the pathogenicity of the . - isolated microorganisms, effect ·of environment (temperature and salinity) on the pathogenicity of (Streptococcus species, Staphylococcus spp. and Cperfringens) and trials of treatment of experimentally infected fish by different antibiotics according to the results of sensitivity test against the (Streptococcus species, Staphylococcus spp. and Cperfringens).
The results of survey revealed that, the percentage of Streptococcus
infection a mong examined fish was (25.5_~), (29.~1 %) in C. gariepinus
and (24.8%) in Tilapia/ The percentage of infection was highest (35.2%)
in summer, followed by (32.1 %), (25.6%) and (5.9%) in autumn, spring
and winter seasons respectively I The Staphylococcus species infection
among examined fishes were (26.9%), constituted by (32.4), (25.2%),
(24.2%), and (22.7%) in Slimmer, autumn, spring and winter seasons