الفهرس 
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Abstract
In this study a total of 310 and 240 lactating cows and buffaloes were examined for clinical mastitis. A total of 126 mastitis milk samples were examined; 87 clinically mastitic cows, 59 (67.8%) and 32 (82%) out of 39 buffaloes were confirmed to be infected with Gram-positive cocci.
Bacteriological examination of these samples resulted in the recovery of 74.6% (94/126) Staphylococcus spp. and 57.9% (73/126) Streptococcus spp.
Biochemical identification confirmed by VITEK-2-compact-SYSTEM revealed that, out of 94 Staphylococcus spp.; 26 (27.6%) isolates were confirmed as S. aureus and 68 (72.4%) isolates were coagulase-negative Staphylococci identified as S. epidermidis (22.3%), S. lentus (19.1%), S. simulans (18%) and S. hominis (12.9%). Also, out of 73 Streptococcus spp. isolates recognized; there were 34.2% (25/73) S. dysgalactiae, 20.5% (15/73) S. agalactiae, 20.5% (15/73) S. ubris, 17.8% (13/73) E. fecalis and 6.8 % (5/73%) S. lactarius respectively.
All Staphylococcus isolates were tested for in-vitro susceptibility test against 14 antimicrobial agents of 9 different antimicrobial classes of important veterinary and public health significance. The results showed that all isolates were sensitive (100%) to ceftriaxone, ciprofloxacin, ofloxacin and sulfamethoxazole-trimethoprim. On the contrary, all isolates were resistant (100%) to penicillin and streptomycin. Multidrug resistance (MDR) was detected in 21 Staphylococci isolates (22.3%).
A concerning Streptococci isolates, the highest sensitivity was recorded against Cephalosporins, Ciprofloxacin and Sulfamethoxazole-trimethoprim (100%) followed by ofloxacin, clindamycin and Apramycin. Conversely, high resistances were recorded against Penicillins, Gentamycins, Streptomycin and Doxycicllin (100%) followed by Kanamycin and Fosfomycin. MDR was identified in 26 Streptococcal isolates (35.6 %).
Biofilm (Slime) formation capacities, a very important virulence marker was assessed phenotypically in recovered isolates and revealed that, all S. aureus (26) and CNS (68) isolates were 100% curli producing Staphylococci using YESCA CR agar medium. While All examined S. agalactiae and S. dysgalactiae were biofilm producing streptococci, meanwhile, 78 %, 45.4 % and 75% of S. ubris, S. lactarius and E. fecalis were biofilm positive isolates respectively.
Using PCR for detection of 6 genes; 2 enterotoxins producing genes (sed, seb), 2 biofilm-associated genes (iCa A, fnb A) and 2 resistance genes (mec A, bla Z) among randomly selected MDR isolates; Staphylococcal isolates (n=5) revealed that sed, seb genes were the most prevalent genes found in all isolates, followed by fnb A gene which was presented in 80% of the isolates then mec A, bla Z and Ica A with 60%, 40% and 40% respectively.
Ten Streptococcal isolates showed that sed gene and seb gene were found in 20% and 80 % in order. fnb A and iCa A genes were presented in 90% and 70% respectively. mec A and bla Z genes were possessed in 90 % and 70%.
Antibacterial and anti-biofilm effect of Euycalyptus EO and Bacteriocin was studied on 18 MDR isolates of Staphylococci. Eucalyptus EO at concentration of 0.1% inhibited the growth of (83.3%) of the isolates and prevent production of biofilm in (88.8%), concentration of 0.01% repressed (50%) as antibacterial effect of Eucalyptus EO and influence the biofilm ability with (38.8)%, while concentration of 0.001% showed no antibacterial activity at all but represent weak anti-biofilm activity in (11%).
Concerning the antibacterial and antibiofilm effect of bacteriocin; the results revealed that concentration of 0.1% possessed an antibacterial and ant-biofilm effect in (33.3%) and (27.7%) respectively, while concentration of 0.2% influenced (83.3%) and (66.6%) antibacterial and ant-biofilm effect respectively.
Concerning 26 Streptococcal isolates, Eucalyptus EO at concentration of 0.1% inhibited 84.6% of isolates, meanwhile concentration of 0.01% inhibited 69.2% of isolates, while concentration of 0.001% showed antibacterial activity for 46.1%. The anti-biofilm effect at concentration of 0.1%, 0.01% and 0.001% showed 100%, 84.6% and 46.2% effect respectively.
On the other hand, bacteriocin revealed 23% and 61.5% antibacterial influence, beside 69.2% and 92.3 % anti-biofilm effect at concentrations` of 0.1% and 0.2% respectively.