Motile Aeromonas septicemia is a common bacterial disease that affects Oreochromis niloticus and causes tremendous economic losses globally. In order to investigate the prevalence, molecular typing, antibiogram and the biodiversity of Aeromonas hydrophila complex, a total of 250 tilapia (Oreochromis niloticus) were collected randomly from 10 private tilapia farms (25 fish/farm) at El-Sharkia Governorate, Egypt. The collected fish were subjected to clinical and bacteriological examinations. The majority of infected fish displayed ulcerative necrosis, exophthalmia, and internal signs of hemorrhagic septicemia. The prevalence of A. hydrophia complex was 13.2%, where the liver was the most predominant affected organ (54.1%). Polymerase chain reaction (PCR) was used to verify the identification of A. hydrophila complex using one set of primers targeting gyrB as well as the detection of virulent genes (aerA, alt, and ahp). All isolates were positive for the gyrB-conserved gene and harbored aerA and alt virulence genes. However, none of those isolates were positive for the ahp gene. The antimicrobial sensitivity was carried out, where the recovered strains were completely sensitive to ciprofloxacin and highly resistant to amoxicillin. All retrieved strains showed the same phenotypic characteristics and were identical based on the restriction fragment length polymorphism (RFLP). Experimentally challenged fish presented a high mortality rate (76.67%) and showed typical signs as in naturally infected ones. In conclusion, the synergism of phenotypic and genotypic characterization is a valuable epidemiological tool for the diagnosis of A. hydrophila complex. RFLP is a fundamental tool for monitoring the biodiversity among all retrieved strains of A. hydrophia.

This study aimed to evaluate the prevalence, multidrug-resistance traits, PCR-detection of virulence, and antibiotic-resistance genes of E. coli isolated from secondary infections following FMD-outbreak in cattle. A total of 160 random samples were gathered from private dairy farms in Damietta Province, Egypt. The specimens were subjected to bacteriological examination, serotyping, congo-red binding assay, antibiogram-testing, and PCR-monitoring of virulence-determinant genes (tsh, phoA, hly, eaeA, sta, and lt) as well as the antibiotic-resistance genes (blaTEM, blaKPC, and blaCTX). The prevalence of E. coli was 30% (n = 48) distributed in 8 serogroups (40/48, 83.3%), while 8 isolates (8/48, 16.6%) were untypable. Besides, 83.3% of the examined isolates were positive for CR-binding. The tested strains harbored the virulence genes phoA, hly, tsh, eaeA, sta, and lt with a prevalence of 100% and 50%, 45.8%, 25%, 8.4%, and 6.2%, respectively. Furthermore, 50% of the recovered strains were multidrug-resistant (MDR) to penicillins, cephalosporins, and carbapenems, and are harboring the blaTEM, blaCTX, and blaKPC genes. Moreover, 25% of the examined strains are resistant to penicillins, and cephalosporins, and are harboring the blaTEM and blaCTX genes. To the best of our knowledge, this is the first report concerning the E. coli secondary bacterial infections following the FMD-outbreak. The emergence of MDR strains is considered a public health threat and indicates complicated treatment and bad prognosis of infections caused by such strains. Colistin sulfate and levofloxacin have a promising in vitro activity against MDR-E. coli.

This study was undertaken to investigate the effect of sea-cucumber (Holothuriaatra) population density on sea bottom sediment; redox potential, Total organic matter (TOM) assimilation, ammonification and nitrification activity. In protected aquaculture ponds at National Institute of Oceanography and Fisheries (NIOF), Four treatments of high population density (108 individuals/HPDP of 30m 2), mediumpopulation density (54 individuals/MPDP of 30m 2), low population density (18 individuals/LPDP of 30m 2) and reference (RP; Empty ofH.atra). Intestinal (Foregut and hindgut) of H. atra and ambient sediment samples were used. The data showed that presence of Holothuriaatra increase the Redox Potential of sediment and kept its characteristics in the oxidized form which enhanced the biological activities.The TOM decreased by16.04% (22.32% to 6.28%); 5.34% (10.54% to 5.2%); 3.02 % (8.02% to 5.0%) and 3.61% (8.35% to 4.74%) in HPDP, MPDP, LPDP and reference pond respectively. The maximum monthly mean of ammonia was 6.93µgg-1 in HPDP and the lowest mean was 0.09µg g-1 in recorded in LPDP. Ammonia and nitrate concentrations in the ponds of H. atrawereslightly reduced compared with the RP while nitrite concentration followed different pattern. The highest count of ammonifying,ammonium oxidizing and nitrite oxidizing bacteria were 1100 MPN/g, 460 MPN/g and64 MPN/g recorded in foregut contents.Meanwhile the lowest count was31.5 MPN/g, 20 MPN/g and 6.75 in RP, hindgut contents and LPDP respectively.The highest Ammonification and nitrification activity were36.69 µg/g/h and 1.19 µg/g/hrecorded in HPDP meanwhile, the lowest values were 7.38 µg/g/h and0.07 µg/g/h in RP. Ammonification rate and nitrification rate in foregut were higher than in hindgut contents and the ambient sediment. Data analysis showed ammonia-N; nitrate-N and nitrite-N concentration varied non significantly with H. atra population density (p˃0.05) while a highly significant effect recorded with oxidation reduction potential (Eh) and Nitrification activity (p<0.01) and significant effect on TOM matter and Ammonification rate (p<0.05). This study emphasizes the ecological role of the most dominant holothurians species, H. atra, especially in relation to organic matter assimilation, through its associated bacteria that enhance ammonification and nitrification processes in sediment.