The teen, Benjamin Orset, died of food poisoning Jan. 22, the day after eating two hamburgers in a Quick restaurant in Avignon in the south of France, Radio France Internationale reported Wednesday.
Prosecutors say an investigation uncovered serious lapses in hygiene standards.
Staphylococcus bacteria was found in the teenager's gastric juices and on five of the eight employees present on the day Orset ate at the restaurant, and on the tiled floor of the food wrapping stand, authorities say.
The Quick restaurant chain says it has fired the manager, who supervised three Quick outlets in the region.
Authorities ordered the Avignon restaurant closed Jan. 22. It reopened Feb. 11 but has since closed again for work on the building, authorities say.