Microbiological Assessment of <i>Oreochromis niloticus </i>Treated with <i>Calotropis procera</i> - Silver Nanoparticles

<i>Oreochromis niloticus</i> is a highly nutritious aquatic food with limited shelf life. The mode of preservation of <i>O. niloticus </i>has raised concerns about its safety and public health due to food borne illnesses. Studies have shown that chemical preservatives are toxic and harmful to humans thereby leading to growing interest in <i>Calotropis procera</i> for its antibacterial properties, and there is limited information on the use of <i>C. procera</i> silver nanoparticles (CP-AgNPs) to preserve <I>O</I>.<i> niloticus</i>. Hence, this study aimed at evaluating its preservative effect of CP-AgNPs on <I>O</I>.<i> niloticus</i>. A total of one hundred and fifty-six samples of adult wild <I>O</I>.<i> niloticus</i> (97.41± 0.95 g) were sourced from a local river using simple random sampling. The <i>O. niloticus</i> fishes were subjected to four different treatments which included: dipping into sterile distilled water, dipping into NaCl solution, dipping into <i>Calotropis procera </i>silver nanoparticles (CP-AgNPs) solution and injecting CP-AgNPs. These were allowed to stand for 30 min, thereafter drained and held in clean basket at ambient conditions for 48 h. Samples were taken at 4 h interval for microbiological analysis according to standard methods. The isolated bacteria were identified using 16S rRNA gene sequencing. All analysis was carried out in triplicates with statistical significance set at P<0.05. The microbial count showed that CP-AgNPs exhibited antimicrobial and antifungal activities. The best treatment for preservation was the injected CP-AgNPs. Bacteria identified were <i>Pseudomonas aeruginosa</i>,<i> Streptococcus agalactiae</i>,<i> Escherichia coli</i>, <i>Enterobacter sichuanensis, Enterobacter cloacae, Staphylococcus aureus</i>,<i> Citrobacter portucalensis, Klebsiella pneumoniae</i>, <i>Klebsiella variicola</i>, <i>Proteus mirabilis</i> and <i>Aeromonas caviae</i>. This study concluded that, injecting CP-AgNPs into <i>O. niloticus</i> was the best treatment option; however, CP-AgNPs displayed antibacterial activities and preservative effect on <i>O. niloticus</i>.