Inhibitory Effect of Xoconostle (Opuntia matudae) on the Growth of Salmonella and Escherichia coli O157:H7

Introduction: Antimicrobial agents, including natural and chemical preservatives, have been used to inhibit foodborne pathogens and extend the shelf life of processed food. Plants, herbs, and spices are rich in naturally occurring compounds that have many health benefits and could have strong inhibitory effect on the growth of foodborne pathogens. Xoconostle (Opuntia matudae) has demonstrated strong anticancer and antioxidant characteristics and may contribute to inhibitory effect.

Purpose: This study focuses the inhibitory effect of xoconostle pears against the growth of Salmonella and Escherichia coli O157:H7 in culture medium BHI.

Methods: Seven strains of Salmonella and four strains of E. coli O157:H7 were individually tested with xoconostle extract. Growth over time assay and agar well diffusion assay were used to determine the inhibitory effect of xoconostle extract. 

Results: Results showed that bacterial population in control for Salmonella and E. coli O157:H7 reached an average of 9.73 ± 0.153 and 8.96 ± 0.315 logs CFU/ml respectively, while the addition of 10% xoconostle extract caused the bacterial population to remain within 2.82 ± 0.115 and 3.48 ± 0.317 logs CFU/ml respectively. The minimum inhibitory volumes (MIV), the lowest concentration that has significant inhibitory effect after 10 – 12 h of incubation at 37 °C, for Salmonella and E. coli O157:H7 were 200 and 275 µl/ml (V/V) respectively and the minimum lethal inhibitory volumes (MLV), the lowest concentration that has significant inhibitory effect after three days of incubation at 37 °C, for Salmonella and E. coli were 450 and 550 µl/ml (V/V), respectively.  

Significance: These results indicated that xoconostle has potential inhibitory effect against the growth Salmonella and E. coli. Xoconostle could provide a natural means of controlling pathogenic contamination, thereby mitigating food safety risks.