A critical analysis of microbiota associated with the production of shellfish in Saldanha bay, South Africa

Abstract

Aquaculture is part of the blue economy and is entrusted to fulfil some of the United Nations’ sustainable development goals. The aquaculture industry in South Africa is steadily growing, which comes with added responsibility to ensure sustainable aquaculture. There is an increasing concern globally about food accessibility and security for a growing population. It is estimated that global population growth will reach 9 billion by 2050. The development of sustainable marine aquaculture farming is attributed as the solution to food security. Marine bivalve molluscs such as mussels, oysters and cockle are harvested commercially from various parts of the world for human consumption as part of aquaculture. They are grown in freshwater ecosystems, brackish or coastal waters, and their cultivation areas must be approved by relevant authorities to ensure food safety requirements are adhered to. Bivalve molluscs are filter feeders by nature. They bioaccumulate and retain contaminants available in their growing waters and, therefore, are regarded as a major contributor to foodborne outbreaks worldwide, as they are eaten raw or partially cooked. Bivalve mollusc production areas are often exposed to various types of pollutants, including the disposal of treated and untreated sewage. Sewage contains a wide diversity and concentration of microorganisms. The primary concern is the contamination of bivalve molluscs produced by pathogenic microorganisms (bacteria, viruses, and protozoa), creating a public health threat. A critical analysis of microbiota associated with the primary production of shellfish in Saldanha Bay in South Africa was investigated. The aims of this study were to investigate the sources of potential contaminations and microbiota during the primary production of mussels and oysters and to develop practical ways to eliminate or reduce risks related to sources of contamination and associated hazards to acceptable limits. The methodology used involved sample collection and analysis of mussels, oysters, and seawater samples using conventional culture methods to isolate Salmonella, Vibrio species in mussels, oysters and seawater samples. Serotyping of microorganisms detected was done using the Vitek compact 2 instrument. The following microorganisms were identified: Enterobacter cloacae complex; Citrobacter freundii; Klebsiella pneumoniae; Aeromonas sobria; Vibrio alginolyticus; and Sphingomonas paucimobilis. Most Probable Number analysis technique was used for detection and enumeration of faecal coliforms and Escherichia coli. The findings from this study included the need for consistency in the microbiological monitoring programme as well as the development of a microbiota database for the identification of possible pathogenic bacteria which were excluded from the commonly known foodborne disease-causing bacteria. Regulatory gaps, where some gaps included duplication of regulations by various departments and lack of a centralised Competent Authority for aquaculture activities. In conclusion, it was recommended that further studies need to be conducted on the bacterial species identified and the application of One Health approach to prevent the occurrence of public health threats due to contaminated shellfish by pathogenic bacteria.