Clustering analysis of antibiotic resistance in multidrug-resistant bacteria from spoiled vegetables

Antibiotic resistance in foodborne bacteria is a growing public health concern, particularly in fresh produce. This study evaluates multidrug-resistant bacteria (MDRB) isolated from spoiled zucchini, cucumber, and potato collected from Sabia, Abu Arish, and Samta in the Jazan region. Bacterial isolates were cultured on MacConkey and Mannitol salt agar, followed by Gram staining to identify three Gram-negative (KMcS, CMcA, PMcSa) and three Gram-positive (KMS, CMA, PMSa) isolates. Antibiotic susceptibility testing was performed against Penicillin (P), Streptomycin (S), Cefotaxime (CTX), Chloramphenicol (C), Ofloxacin (OF), and Erythromycin (E). The inhibition zones varied across antibiotics, with Ofloxacin exhibiting the largest inhibition zones (40-50 mm) and Cefotaxime and Erythromycin showing the weakest inhibition (≤14 mm). The Resistance Index (RI), which represents the proportion of antibiotics with no inhibition, ranged from 0.2 (moderate resistance) to 0.6 (high resistance in the PMcSa isolate). ANOVA (p ≈ 6.95e-08) confirmed significant differences in inhibition zones across antibiotics, while Tukey's HSD test showed that Ofloxacin was significantly more effective than both Cefotaxime (p = 0.0005) and Erythromycin (p = 0.0035). Correlation analysis revealed strong positive associations between resistance to Chloramphenicol, Streptomycin, and Ofloxacin (r > 0.7), suggesting potential cross-resistance mechanisms. Hierarchical clustering and KMeans analysis (K = 3) grouped bacterial isolates based on their resistance patterns, while PCA visualization distinguished Ofloxacin-sensitive and multidrug-resistant isolates. The findings highlight an urgent need for targeted antibiotic stewardship programs, especially in agricultural practices, to limit the overuse of antibiotics. Additionally, enhanced sanitation measures during food handling and real-time monitoring of bacterial contamination in the food supply chain could significantly reduce the spread of antibiotic-resistant bacteria from farm to table.