Microorganisms Associated With Spoilage Of Watermelon Fruit (Citrullus Lanatus) Sold In Rumuola Market, Port Harcourt, Rivers State, Nigeria

Abstract

Watermelon (Citrullus lanatus) is a highly nutritious and widely consumed fruit; however, its high moisture and sugar contents make it highly susceptible to microbial spoilage. This study investigated the microorganisms associated with the spoilage of watermelon fruits sold in Rumuola Market, Port Harcourt, Rivers State, Nigeria. A cross-sectional laboratory-based study was conducted using twenty visibly spoiled watermelon fruits randomly collected from ten fruit vendors between June and August 2025. Standard microbiological methods were employed for the enumeration, isolation, and identification of bacterial and fungal isolates. The total viable bacterial counts ranged from 4.8 × 10⁵ to 7.8 × 10⁵ CFU/g, while fungal counts ranged from 2.8 × 10⁴ to 5.1 × 10⁴ CFU/g, indicating substantial microbial deterioration of the fruits. Six bacterial species were isolated, with Staphylococcus aureus showing the highest frequency of occurrence (25.0%), followed by Bacillus subtilis (20.8%) and Pseudomonas aeruginosa (18.8%). The fungal isolates identified included Aspergillus niger (28.6%), Rhizopus stolonifer (22.9%), Penicillium spp. (17.1%), Mucor spp. (14.3%), Candida albicans (11.4%), and Aspergillus flavus (5.7%). The presence of potentially pathogenic bacteria and toxigenic fungi suggests that spoiled watermelon fruits sold in the study area may constitute a significant public health risk. The study highlights the need for improved hygiene, proper post-harvest handling practices, and routine microbiological surveillance of fruits to ensure consumer safety and reduce post-harvest losses