Salmonella is a type of bacterial infection. Your microwave oven is highly effective at killing bacteria when used correctly.
The CDC recommends you heat your food to 167°F (75°C) to make it safe to eat. At that temperature, most bacterial, viral and other pathogens, including salmonella, will become inactivated.
For salmonella, this study [4] shows that even 150°F is enough to destroy salmonella to undetectable levels.
These data indicate that heating perishable foods of the type studied to 150 F and holding every particle of food at this temperature for at least 12 min reduces 10 million or less salmonellae or staphylococci per gram to nondetectable levels.
The microwaves themselves (short length radio waves) do not kill bacteria directly but the can be killed by the heat produced by the microwaves.
The best course of action is to use a thermometer to check your food has reached the right temperature. Be careful to check multiple points in the food to check the heat has spread evenly. Uneven heating and cool spots are a real risk with microwaves.
If you don’t own a thermometer, aim to overheat your food in the microwave so the food is piping hot as it leaves the oven. Let it stand for 2-3 minutes for the heat to dissipate.
When you eat, there should be no cool spots, this is dangerous as the heat may be too low to kill bacteria including salmonella.
Sources:
[1] https://www.foodsafety.gov/food-safety-charts/safe-minimum-cooking-temperature
[2] https://www.fsis.usda.gov/wps/portal/fsis/topics/food-safety-education/get-answers/food-safety-fact-sheets/appliances-and-thermometers/microwave-ovens-and-food-safety/ct_index
[3] https://www.foodsafety.gov/food-safety-charts/safe-minimum-cooking-temperature
[4] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1057731/
