Assessing bacteriological quality of fresh black soldier fly larvae.
Date
2023
Authors
Laiser, Ester
Journal Title
Journal ISSN
Volume Title
Publisher
The University of Zambia
Abstract
Black Soldier fly larvae (BSFL) is an insect larva that is used as a source of proteins for animals, including pigs, poultry, and fish. It is also used to decompose organic matter. This study aimed to assess the bacteriological quality of fresh BSFL and investigate the occurrence of antimicrobial resistance using Escherichia coli and Staphylococcus as potential model pathogens. A total of 17 BSFL samples were collected from a dumpsite in May 2022. Then washed, disinfected with 70% ethanol before rinsed twice with distilled water, 1g weighed and
homogenized then inoculated to MacConkey and Blood agar media and incubated at 37 °C for 24 hours. Bacteria isolated from BSFL were identified using colony morphology, Gram staining, Catalase test, Mannitol Salt Agar for Staphylococcus and Eosin Methylene Blue for E. coli, and the isolates obtained were selected based on their characteristics. E. coli and Staphylococcus were subjected to Antimicrobial Susceptibility Test (AST) using
the Kirby-Bauer disk diffusion method. Antibiotics-resistant isolates were further assessed for extended-spectrum beta-lactamase-encoding genes using Polymerase Chain Reaction. From 17 samples the process of culturing yielded 79 isolates based on colony morphology. Out of 79 isolates, only 20 (25%) were Gram-negative, while the remaining 59 (75%) were Gram-positive. Among the 20 Gram-negative strains, 95% (19/20) were E. coli, while Gram-positive isolates were dominated by Staphylococcus at 47.5% (28/59). All 19 E. coli isolates were resistant to three or more antibiotics classes (multidrug-resistant), exhibiting resistance to gentamicin, tetracycline, chloramphenicol, nalidixic acid, cefotaxime, cotrimoxazole, ciprofloxacin, streptomycin, and ampicillin. Furthermore, three out of 19 (3/19, 16%) E. coli isolates tested positive for blaTEM and blaCTX-M drug resistance genes that encode class A extended spectrum β-lactamases (ESBLs) and can be responsible for therapeutic problems due to the resistant conferred. While all Staphylococcus isolates showed resistance to cloxacillin, none of them was
positive for the mecA gene. The study revealed that fresh BSFL harbour bacteria of zoonotic significance.
Description
Thesis of Master of Science in Tropical Infectious Diseases and Zoonosis (TDZ).