Enterobacteriaceae contamination in locally packaged roasted cashew kernels from the Coast and Morogoro regions, Tanzania

Abstract

The increased sales of locally packaged roasted cashew kernels (RCK) in Tanzania reflect growing consumer demand for healthy, convenient snacks. Despite this popularity and frequently reported cases of gastrointestinal illness, the microbial safety of these plastic-bagged products is not well-documented, posing a potential public health concern. To address this, a study was performed to evaluate packaging hygiene, package integrity, and microbial contamination of randomly selected packages of RCK (small: n=99; medium: n=87; large: n=118) from vendors in Coast and Morogoro regions, Tanzania. Package integrity was assessed using a vacuum decay leak tester while microbial contamination on surfaces including RCK, packers' hands, and unused packaging bags was determined by a culture-based method, with presumptive isolates biochemically confirmed. While no Enterobacteriaceae were detected on the unused packaging bags, RCK samples contained them at levels ranging from 1 to 192 cfu/g. Out of 304 samples, 14.8% (45) were inadequately sealed and had significantly higher concentrations of Enterobacteriaceae compared to well-sealed samples (P < 0.05). Bacterial pathogens isolated from the RCK included Klebsiella pneumonia (65.2%), Escherichia coli (11.6%), Proteus vulgaris (11.6%), Enterobacter aerogenes (4.95%), Salmonella typhi (3.31%), Enterobacter cloacae (1.65%), Salmonella typhimurium (0.83%), and Salmonella enteritidis (0.83%). These findings indicate that RCK may be an emerging vehicle for the transmission of human pathogens. Furthermore, Enterobacteriaceae counts in the RCK strongly correlated (r = 0.67, P < 0.05) with the concentration found on the hands of RCK packers, suggesting that the packaging process contributed to the contamination. This study highlights inadequate hand hygiene during packaging and insufficient sealing as major factors compromising the microbiological quality and safety of locally packaged RCK by small-scale industries in Tanzania's Coast and Morogoro regions. We recommend using these data to establish a quantitative risk assessment for human pathogens associated with RCK consumption and to devise effective interventions for managing these microbial risks.