Effects of copper-bearing montmorillonite on Salmonella spp. in vitro study

Clay is an important material available in nature. Montmorillonite is considered viable for producing enhanced performance in a variety of materials and products. Farmed animals such as pigs and poultry receive additional Zn and Cu in their diets as supplements in their compound feed and these elements are also used for medical remedies. This study aimed to observe the bactericidal activity of copper-bearing montmorillonite (Cu-MMT) against Salmonella spp. in vitro. The experiments were divided into two methods that effect Salmonella spp.. First, Cu-MMT was used to precipitate the Cu2+ ion supernatant mixed with bacteria. The second, Cu-MMT was directly mixed with the bacteria. The results indicate that the optimal bactericidal concentration of the Cu2+ ion supernatant precipitated by Cu-MMT was 0.1 mg/mL for 24 hours, and the optimal sterilisation concentration of Cu-MMT was directly mixed with Salmonella spp. at 0.05 mg/mL for 24 hours. When Salmonella spp. was mixed with Cu2+ ion or Cu-MMT, the effects on the cell types could be clearly discerned with an electron microscope. Scanning electron microscope (SEM) or Transmission electron microscope (TEM) showed that many bacteria were adsorbed by Cu-MMT. The appearance of the bacteria exhibited an uneven morphology, the cell wall was ruptured, the cell membrane was broken, the cells appeared as bubbles and the osmotic pressure of the Cu2+ ion liquid caused the cell wall to separate from the cytoplasm. Here was an important reason for the antibacterial effect and bactericidal ability of Cu-MMT.