Does a microwave oven disinfect food?
Microwave ovens can indeed kill bacteria in food by heating them to high temperatures. For example, this article found that microwave heating could kill all of the Salmonella bacteria in a chicken thigh sample:


  The effect of microwave heating on Salmonella Enteritidis inoculated
  on fresh chicken was investigated using a microwave oven (800 w) to
  determine the destruction of Salmonella Enteritidis isolated from
  chicken carcasses, in relation to the time of heating at two power
  settings: high (power level 10) and medium (power level 6); The
  relationship between heating time and temperature was also been
  studied. The destruction was 6.4 log cycles at time 95 sec for the
  high power level, and 5 log cycles at time 140 sec for medium power
  setting. After 110 sec for higher power level, no survival of
  Salmonella Enteritidis was detected in samples (100g), but at 140 sec
  for medium power level, these food pathogens were still present.


However, the main issue is balancing the amount of microwave exposure. Heating the food for too long will result in the food becoming dehydrated or burned, and heating it for too short a period of time will result in food poisoning. 

This paper shows that insufficient microwave exposure can and will lead to food poisoning if there is a large amount of bacteria inside the food:


  Leftover samples of a savoury rice dish consumed by all six ill
  persons contained 6×103/gm Salmonella enteritidis PT4. The rice salad
  comprised boiled rice, raw carrots, eggs, cheese and curry powder. The
  curry powder and remainder of the pack of six eggs were negative on
  microbiological analysis. The rice dish had been prepared by heating
  in a 500 W microwave oven with a rotating turntable on full power for
  5 min.