الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
Mastitis is one of the most problematic diseases and continues to have major economic impact on dairy industry.So, the present work was conducted to apply bacteriological and molecular studies on some bacteria isolated from mastitis cattle. A total of 150 mastitis milk samples from cattle (50 clinical and 100 subclinical) were collected from different dairy farms at Giza governorate.The collected samples were investigated bacteriologically, where, 50 clinical mastitis milk samples are revealed 68 different bacterial isolates as following; 25 isolates of S. aureus (36.8%), 26 isolates E. coli (38.2%) and 17 isolates streptococcus spp. (25%). While Bacteriological examination of 100 subclinical mastitis milk samples are revealed 115 different bacterial isolates as following; 33 isolates of S. aureus (25.8%), 42 isolates of E. coli (32.8%), 28 isolates of streptococcus spp. (21.9%) and 25 isolates of corynebacterium spp. (19.5%) Biochemical identification of 68 clinical mastitis milk samples are revealed 53 different bacterial isolates as following; 23 isolates of S. aureus (43.4%), 18 isolates E. coli (34%) and 12 isolates streptococcus spp. (22.6%). Biochemical identification of 128 subclinical mastitis milk samples are revealed 115 different bacterial isolates as following; 31 isolates of S. aureus (26.9%), 38 isolates of E. coli (33.1%), 25 isolates of streptococcus spp. (21.7%) and 21 isolates of corynebacteria spp. (18.3%).The molecular detection of bacterial isolates by using PCR with specific primers for each genus confirmed that 20 strains of S. aureus were positive with a percent of (41.7%) from clinical mastitis milk samples and 27 strains of S. aureus were positive with a percent of (29%) from subclinical mastitis milk samples at molecular size 108 bp. Regarding to E. coli, there were 17 strains positive with a percent of (35.4%) from clinical mastitis milk samples and 32 strains positive with a percent of (36.8%) from subclinical mastitis milk samples at molecular size 585 bp. For streptococcus spp.11 strains with a percent of (22.9%) from clinical mastitis milk samples and 20 strains with a percent of (23%) from subclinical mastitis milk samples at molecular size 207 bp. For C. bovis 8 strains were detected with a percent of (9.2%) from subclinical mastitis milk samples.Multiplex PCR protocol of streptococci spp. were revealed 3 isolates (27.3%) of S. agalactiae and 8 positive isolates (72.7%) of S. dysgalactiae were detected from clinical mastitis milk samples, while subclinical mastitis isolates revealed 4 isolates (20%) of S. agalactiae and 16 positive isolates (80%) of S. dysgalactiae.Antibiotic sensitivity test were performed for 8 isolates of C. bovis isolated from milk samples of subclinical mastitis using the following antibiotic discs tetracycline (TET), 30 µg; spectinomycin (SPX), 10µg; kanamycin (KAN), 30 μg; streptomycin (STR), 10 µg; sulfamethoxazole-trimethoprim (SXT), 23.75/1.25 µg; ampicillin (AMP), 10 μg and chloramphenicol(CHL), 30 µg. The C. bovis isolates showed resistance against streptomycin (87.5%), spectinomycin (75%), tetracycline (62.5%), ampicillin (62.5%), kanamycin (37.5%), sulfamethoxazole-trimethoprim (37.5%) and chloramphenicol (25%). Class 1 integron resistance gene was found in 2 (5.7%) isolates.Further, PCR and DNA sequencing of 8 positive C. bovis fragments using primers specific to class 1 integrons revealed two isolates (25%) out of 8 C. bovis strains which have one type of class 1 integron with middle size (974 bp) and contains a single gene cassette of aadA1 (aminoglycoside adenyltransferase type A), which confers resistance to streptomycin/spectinomycin. Up to date the aadA1 gene has not been previously identified in C. bovis.