This statement is likely referring to the group of microorganisms known as mesophilic bacteria. Mesophilic bacteria are moderate-temperature loving microbes and are able to grow and reproduce within a temperature range of 20 to 45 degrees Celsius (68 to 113 degrees Fahrenheit). They are commonly found in a wide range of environments, including soil, water, and the bodies of animals and humans.
Many common spoilage and disease-causing organisms are mesophilic bacteria, such as Escherichia coli, Salmonella enterica, Listeria monocytogenes, and Staphylococcus aureus. These bacteria can cause a range of illnesses in humans and animals, including food poisoning, infections, and sepsis.
Due to their ability to grow at moderate temperatures, mesophilic bacteria can easily contaminate and spoil food products if not properly handled or stored. Therefore, they are a common target for food safety and preservation measures, such as refrigeration, pasteurization, and sterilization.