Nile tilapia is a cornerstone of fish farming in Egypt, which is the largest aquaculture producer in Africa. With 900,000 tons of tilapia harvested annually, the country has risen to become the seventh aquaculture producer in the world (Feidi, 2018). The progress of this fast-growing industry is impeded by many challenges such as poor water quality and associated bacterial infections (El-Gohary et al., 2020). As a result, the use of antibiotics in the aquafeeds to mitigate infectious diseases or to boost growth performance is commonly practised. The prophylactic use of antibiotics and chemotherapies, however, has been scrutinized which eventually led to their ban in aquaculture by law in many countries (Dawood et al., 2018). In the context of the banning and restrictions of antibiotic use, the need to establish new ways of potentiation of immune reaction in fish is clear. Immunostimulants are considered as an alternative for antibiotics, which will boost the immune system of the cultured organism, thus effectively countering the assault of pathogens. The use of medicinal plants/natural ingredients (whole plant, roots and leaves) and/or their extracts has been proposed as valuable feed additives to boost fish immunity and an eco-friendly approach for the control of pathogens (

An extracellular toxic protease, KB76 from Brevibacterium otitidis was successfully purified to 31.3-fold by anion-exchange and gel filtration chromatography. The molecular mass was determined to be 47 kDa using SDS-PAGE. The optimum temperature and pH of the protease were 7.4 and 40• C, respectively. Ethylenediaminetetraacetic acid and phenylmethylsulfonyl fluoride inhibited the activity of the enzyme but soybean trypsin inhibitor and aprotinin had no obvious inhibition, which suggested the presence of both metal and hydrosulfuryl at or near the active site. Additionally, the isoelectric point of this protein was 5.5 ± 0.2. Its apparent Km and Vmax for the synthetic substrate N-succinyl-Lphenylalanine p-nitroanilide were 2.41 mM and 21.74 µM/min, respectively. Further, studying the lethality of the protease on mice by intraperitoneal injection, it exhibited 48-h LD50 value of 9.6 mg/kg body weight. Gross and electron microscopic study in mice revealed that purified protease was capable of eliciting a variety of tissue responses resulted in liver necrosis. In conclusion, this protease produced by B. otitidis represents a potential toxic agent.

The nine most frequent bacterial strains out of 127 were isolated form ten drinking water samples collected from tap water and bottled water in sharqia governorate. The nine isolates were purified and examined for their resistance to increasing concentrations of two heavy metal ions, lead (Pb +2) and iron (Fe +3). Four stains out of the nine isolates encoded I, II, IV, and VIII showed the highest efficiency of both Pb +2 and Fe +3 uptake from nutrient broth media containing 100 ppm of the heavy metal ions. The four bacteria were preliminary identified and then confirmed by the Biolog examination as Corynebacterium jeikeium, Pseudomonas putida biotype A, Acinetobacter calcoaceticus and Acidovorax delafieldii. The increased concentrations of Pb +2 ions (from 100 to 500 ppm) in nutrient broth media had deleterious effect on the process of heavy metal uptake (biosorption) by all the four selected isolates. Whereas percentage of Pb +2 uptake decreased from 42.9 to 24%; from 72.6 to 42%, from 78.9 to 37% and from 68.8 to 45%, for the four selected isolates, respectively. Meanwhile there was slight decrease change in Fe +3 uptakes percentage accompanying the increase in heavy metal ion concentration. Optimization of the cultural conditions releaved maximum uptake op pb +2 and Fe +3 by the four tested strains in presence of 100 ppm heavy metal concentration when incubated at 25 o C except for Acinetobacter calcoaceticus at 35 o C in case of Pb +2 uptake, when pH, was adjusted at 5 under static conditions. Upon addition of 50 ppm Cu +2 ions to broth media supplemented with 100 ppm Pb +2 ions, the percentage of metal biosorption by the four tested isolated decreased between 41.11% and 48.45% according to type of strain. Similarly presence of Cu +2 ions caused decrease in Fe +2 uptake by the four isolates ranging between 29.14-45.1%. Percentage of Pb +2 ions uptake by the tested bacteria sharply decreased when a sterile tap water sample was used as natural medium for cell-metal contact. The percentage of uptake inhibition of Pb +2 ranged between 57-65.23% and between 75.1-84.27% for Fe +3 ions. Cell hydrolysate of three tested bacteria appeared to be free from plasmid DNA proving that the genetic character of heavy metal resistance is plasmidless and related to chromosmal DNA in

This study was carried out to evaluate the microbial infections in natural way and reduce the antibiotic resistance. One hundred bacterial isolates were collected from clinical specimens of patients suffering from bacterial infection (55 females and 45 males). The bacterial isolates were obtained from 8 different specimens with the following percentage representations: urine (30.58 %), blood (20%), abscess (20%), wound (9.41%), throat and tube swab (5.88%), ear discharges (5.88%), vaginal swabs (5.88%) and eye swab (2.35%).The results showed that (29.41%) Escherichia coli, (23.53%) Klebsiella pneumoniae, (17.65%) Staphylococcus aureus, (15.29%) Pseudomonas aeruginosa, (8.24%) Proteus vulgaris, (5.88%) Acinetobacter baumannii. Among 17 antibiotics tested, meropenem, a carbapenem antibiotic, was the most effective drug against most of the gram-negative and gram-positive bacteria. Detection of biofilm by two different methods show that most of isolates were multidrug resistant. Three species of lactic acid bacteria namely L.acidophilus (DSM20079), L.plantarum (DSM20174) and L.salivarus (DSM20555) were used for reducing the microbial infections. Bacteriocins were isolated from MRS broth culture of these lactic acid bacteria through the precipitation method using 1N HCL and were tested against different pathogenic bacteria. Antibacterial activity of bacteriocins extracted from L. acidophilus (DSM20079) showed maximum activity against most isolated bacteria as compare to others. Also, L.salivarus (DSM20555) have the highest activity against Methicillin-resistant Staph aureus. The present study has showed the antibacterial role of bacteriocin isolated from lactic acid bacteria can be used for treatment variety of human diseases.

Surgical site infection (SSI) remains an important cause of morbidity and mortality among hospitalized patients. A total of 254 bacterial isolates were collected from 303 surgical specimens which were isolated from 92 males (53.2%) and 81 females (46.8%), their mean ages were 39.616.05 years (ranged from 1 month to 74 years). These isolates were identified as Staphylococcus aureus, Escherichia coli, Klebsiella pneumoniae, Proteus vulgaris, Pseudomonas aeruginosa and commensal Gram+ve and Gram-ve bacteria. The most effective antibiotics were imipenem while ampicillin and penicillin G (First and second generation of -Lactam) showed much lower activity against all types of bacterial strains. The minimum inhibitory concentrations (MIC) of imipenem determined by E-test were 0.047-0.064 , 0.125, 0.19, 0.25 and 0.75g/ml against Staphylococcus aureus, Escherichia coli, Proteus vulgaris, Klebsiella pneumoniae and Pseudomonas aeruginosa respectively.