Calf diarrhea is one of the considerable infectious diseases in calves, which results in tremendous economic losses globally. To determine the prevalence of Shiga-toxigenic E. coli (STEC) and Enterotoxigenic E. coli (ETEC) incriminated in calf diarrhea, with special reference to Shiga- toxins genes (stx1 and stx2) and enterotoxins genes (lt and sta) that govern their pathogenesis, as well as the virulence genes; eaeA (intimin) and f41(fimbrial adhesion), and the screening of their antibiogram and antimicrobial resistance genes; aadB, sul1, and bla-TEM, a total of 274 fecal samples were collected (April 2018–Feb 2019) from diarrheic calves at different farms in El-Sharqia Governorate, Egypt. The bacteriological examination revealed that the prevalence of E. coli in diarrheic calves was 28.8%. The serotyping of the isolated E. coli revealed 7 serogroups; O26, O128, O111, O125, O45, O119 and O91. Furthermore, the Congo red binding test was carried out, where 89.8% of the examined strains (n = 71) were positive. The antibiogram of the isolated strains was investigated; the majority of E. coli serotypes exhibit multidrug resistance (MDR) to four antimicrobial agents; neomycin, gentamycin, streptomycin, and amikacin. Polymerase chain reaction (PCR) was used to detect the prevalence of the virulence genes; stx1, stx2 lt, sta, f41 and eaeA, as well as the antimicrobial resistance genes; aadB, sul1, and bla-TEM. The prevalence of STEC was 20.2% (n = 16), while the prevalence of ETEC was 30.4% (n = 24). Briefly, the Shiga toxins genes; stx1 and stx2, are the most prevalent virulence genes associated with STEC, which are responsible for the pathogenesis of the disease and helped by the intimin gene (eaeA). In addition, the lt gene is the most prevalent enterotoxin gene accompanied by the ETEC strains, either alone or in combination with sta and/or f41 genes. The majority of pathogenic E. coli incriminated in calf diarrhea possesses the aadB resistance gene, followed by the sul1 gene. Enrofloxacin, florfenicol, amoxicillin-clavulanic acid, and ampicillin-sulbactam, are the most effective antimicrobial agents against the isolated STEC and ETEC strains.

Dairy production is threatened by antibiotic resistant pathogens worldwide, and alternative solutions to treat mastitis are not available. The prevalence of antibiotic resistant strains is not well known in less developed countries. The prevalence of pathogenic bacteria and their resistance to 21 commercial antibiotics were studied in milk samples taken from 122 dairy cows suffering from the symptoms of mastitis in Egypt. The bacterial species were identified with molecular methods, and antibiotic resistance was studied with disc diffusion method. The prevalence of Streptococcus aureus, Escherichia coli and Pseudomonas aeruginosa were 30%, 17% and 3.5%, respectively. Most (90%) of the S. aureus strains showed resistance to penicillin whereas only 10% of the strains were resistant to oxacillin. Nearly half (40%) of E. coli strains showed resistance to streptomycin. Six P. aeruginosa strains showed resistance to several antibiotics, including ceftriaxone, enrofloxacin and levofloxacin. This points out that despite P. aeruginosa was not common, it should be followed up carefully. Potential biocontrol agents against antibiotic resistant mastitis bacteria were searched among 30 endophytic actinobacterial strains derived from wild medicinal plants. Three plants, namely Mentha longifolia, Malva parviflora and Pulicaria undulata were chosen for a more detailed study; their endophytic actinobacteria were used to prepare metabolic extracts. The crude metabolites of the actinobacteria were extracted with ethyl acetate. All metabolic extracts inhibited the growth of S. aureus, methicillin-resistant Staphylococcus aureus (MRSA), E. coli and P. aeruginosa in vitro. The 16S rRNA sequence analysis revealed that the most efficient actinobacterial strains were two Micromonospora sp. and one Actinobacteria bacterium. We conclude that the combination of the metabolites of several endophytic actinobacteria derived from several medicinal plants would be the most efficient against pathogens. Different metabolite cocktails should be studied further in order to develop novel biocontrol agents to treat antibiotic resistant mastitis bacteria in dairy cows.

This study was planned to throw the light on the incidence of S. aureus in 485 random samples of meat, milk and their products, The bacteriological examination of 200 meat and meat products revealed that the prevalence of S. aureus was 19 isolates (9.5%), The bacteriological examination of 285 milk and milk product revealed that the prevalence of S. aureus was16 isolates (18.8%). The prevalence of S. aureus in examined milk collected from (farms, dairy shops and street vendors) were (16%, 16% and 22.8%) respectively, While milk products showed that, the prevalence of S. aureus was 8 isolates (4%). All isolated strains were identified as S. aureus by using specific culture media and biochemical tests. Detection of enterotoxin in S. aureus isolates proved that, 27out of 43 of them were entrotoxignic , 15 isolates out of 27 were enterotoxin A producer,7 isolates were enterotoxin C producer and 5 isolates were harbored the type (A and C). PCR used for confirmation of S. aureus isolates, revealed that S. aureus had four DNA fragments patterns of 410, 740, 910 and 970 b.p. with primer (1) meanwhile with primer (2), the pattern of S. aureus had two bands of 562 and 928 b.p. Studying the antibiotic sensitivity test of S. aureus for 15 different types of antibiotics in lab, the result revealed that most strains which isolated from meat, milk and their products were show highly degree of resistant to Methicillin followed by Oxacillin, Chloramphenicol, Amoxiciilin, Cephranin, Cephalothin, Amikacin, Gentamycin, Ciprofloxacin, doxycycline while they were sensitive to Cefaclor, Streptomycin, Norfloxacin, Erythromycin and trimethoprim-sulphamethoxazole. PCR also, confirmed the presence of mec A gene in 4 isolates (methicillin resistant S. aureus).

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ARTICLE INFO Staphylococcus aureus is a common cause of food-borne disease worldwide and food poisoning. This study reports the effect of nisin (0, 10 and 12.5 ppm) against Staphylococcus aureus in manufactured kareish cheese. Nisin was effective in reducing S. aureus count in cheese; a reduction of S. aureus count was observed from the 2nd day of storage period. S. aureus in kareish cheese decreased gradually from 4x10 8 to (8×10 7 , 6.5×10 7 , 5.8×10 7 CFU/gm.) in the 1 st week till reached at the end of storage period of the 4 th week to (4 ×10 4 , 1.1×10 3 , 1×10 2 CFU/gm.) for cheese containing (0, 10 and 12.5 ppm) of nisin, respectively during manufacture and storage for a month in the refrigerator at 4 ˚C. The data obtained in this study suggested that the use of nisin-containing cheese can be an effective method of controlling the growth and multiplication of S. aureus in cheese.