الفهرس 
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Abstract
A total of 512 samples were collected from cows
with mastitis in closed herd, during the period of
investigation (18 month). Out of these samples, 127
samples were found tobe repeated cases for 2 times or more and were considered as recurrent mastitic cases.
The mean monthly incidence of recurrent mastitic cases in relation to the actual number of clinic mastitic cases was ranged between 5.5% to 11.2% with a total mean of 8.3% .
The repeatation of the recurrent mastitic cases was studied during the investigated period. Out of the recurrent mastitic cases, 32, 12, 4, 1 and 1 cases were found repeated for 2, 3, 4, 5 and 6 times respec-tively.
bacteriological studies
were conducted for the
recurrent mastitic cases. Results revealed that 9 different types of bacteria could be isolated.
Isolated strains were identified using different sugar fermentation tests and different biochemical reaction. Also specific media and tests were applied
for confirmation.
Stash aureus and Strept agalactia were the most common contagious bacterial cause of recurrent mas-
titis. These two types of bacteria were isolated for
65 and 41 times respectively. Thus it was concluded
that these 2 types play an important role in producing
recurrent mastitis. Escherichia coli strains were isolated for 27 times either alone or in mixed infection with an incidence of 16.1Y. This organism belongs to the environmental type of bacteria which differs from the contagious bacteria in that E.coli exists in cows environment mainly by faecal contamination. Thus it is difficult to eleminate it from the cow environment. The previously mentioned 3 types of bacteria showed to be the most prevalent bacterial microorganisms in-volved in recurrent mastitis in cows. The rest types of isolated bacteria were categorized as ” uncommon mastitic pathogens which were divided into two groups. Pseudomonas guro_gi.nosa and Coryne pyoqenes were isolated 5 and 2 times from the recurrent mas-titic samples in an incidence of 3.07. and 1.27. respec-tively, they were considered as the major pathogen group of bacteria which commonly inhibit the bovine udder but rarely produce mastitis. Also other bacteria were identified such as Staph citrus, B.anthracoid, Proteus mirabilis and 5A_Aph albus.
Antibiotic sensitivity testing was carried out by the disc diffusion method. Results showed that the isolated Staph aureus was highly sensitive to Nitrof-urantoin and Oxytetracycline. Strept aqalactia was found to be highly sensitive to Nitrofurantoin and
Gentamycin.
Nitrofurantoin and Neomycin were effective on E.coli isolation, while Streptomycin and Gentamycin were effective on Ps.auraginosa.