Molecular identification and characterization of selected food-borne pathogens in imported dried fish sold in informal markets around Gauteng province in South Africa

MSc (Animal Health), North-West University, Mahikeng Campus

Dried fish highly contributes to the demand for nutritional protein in our daily diet. In recent years, dried fish has become more popular in informal markets, which have increased dramatically in size and become a source of income for people. It plays an important role in providing low-cost, easily accessible, and nutritious food to the urban populace. The examination of microbiological quality is therefore needed to ensure health of the general public. The purpose of this study was to assess the microbiological quality of different types of dried fish sold in Pretoria and Johannesburg, South Africa. Based on the instability of the informal markets in Pretoria and Johannesburg and the unknown number of dried fish sellers, a non-probability sampling method was used (convenience sampling).A total of 12 markets were visited, and 140 samples were collected. Three types of dried fish were obtained, which were smoked (40), sun-dried (80), salted (20). During that collection of samples, hygienic measures applied by vender were observed and recorded in a checklist and the results revealed that sellers were not adhering to the most basic hygienic practices and not using proper storage of dried fish. All the sellers did not wash hands before touching the samples, and 83.3% exposed to air outside. The mean total bacterial count, sun-dried fish recorded 2.91×107cfu/g, smoked fish 2.71×107cfu/g, and salted fish 2.13 ×107cfu/g respectively. According to the standard guideline of bacterial load in seafood, the values obtained in this study reveal that the dried fish sold in the informal markets are not suitable for human consumption as it’s above the standard guideline. The bacterial count from the three dried fish bacteria counts differs, which could be attributed to variations in the dried fish samples' preservation methods (smoking, sun, and salting).The identification of the isolated bacteria was based on conventional biochemical tests such as Gram staining, Catalase, Oxidase, Indole and Coagulase. Further the results were confirmed by the amplification of the 16S rDNA genes using the forward primer 27F (5'-AGA GTT TGA TCC TGG CTC AG-3') and the reverse 1492R (5'- ACG GCT ACC TTG TTA CGA CTT 3'). BLAST (basic local alignment search tool) from NCBI (National Center for Biotechnology Information) GenBank was used for confirmation and similarities of the isolates. The molecular identification revealed the presence of Staphylococcus spp., (11.94%), Staphylococcus sciuri (2,98%), Staphylococcus saprophyticus (2.98%), Staphylococcus aureus (4.47%), Staphylococcus lentus (5.97%), Staphylococcus xylosus (8.95%), Klebsiella pneumonia (7.46%), Klebsiella spp.,(4.47%), Clostridium spp., (14.92%), Paraclostridium bifermentaus (5.97%), Clostridium bifermentas (4.47%), Micrococcus caseolyticus subsp homonis (1.49%), Micrococcus caseolyticus (1.49%), Enterobacter spp., (1.49%), Enterobacter ludwigii (1.49%), Lysinibacillus macrolides (1.49%), Clostridium botulinum (2.98%), Enterococcus faecium (2.98%), Enterococcus faecalis (5.97%), Corynebacterium variabile (5.97%) Planococcaceace bacterium (2.98%) in the dried fish type collected. Some of these bacteria are important human pathogens responsible to for serious illness. Staphylococcus aureus, Staphylococcus sciuri, Klebsiella pneumonia are among the food-borne pathogens.The disc diffusion technique was used to test the antibiotic susceptibility of the isolated bacteria, and the results were interpreted using the Clinical Laboratory Standards Institute (CLSI). Staphylococcus aureus (100%), Staphylococcus xylosus (100%), Staphylococcus sciuri (100%), Staphylococcus saprophyticus (100%), and Staphylococcus lentus (100%) were all susceptible to Chloramphenicol, according to the findings. In addition, Enterococcus species were isolated, and the findings revealed that Enterococcus faecium and Enterococcus faecalis were completely susceptible to Amoxicillin, Chloramphenicol, and Norfloxacin.The overall results showed that the pathogens were 60.1% susceptible to the antibiotics tested and 29% were resistant; meanwhile, 10.9% of the isolates were intermediate to the tested antibiotics. 73.5% Streptomycin, 58.2% Erythromycin, and Gentamicin had the highest resistance to most pathogens isolated in this study. According to the information acquired, the informal markets continue to pose a risk of antibiotic contamination, and it is one of the major public health issues confronting Africans and the global population. The need to emphasize more caution on microbial hygiene quality of dried fish and more evaluation for public health must be taken into consideration.

Masters