Alteration or spoilage flora seem to be bacteria which form on surfaces. I think spoilage flora is the more common term.

HERE ARE A FEW EXAMPLES:

The manufacture of acidified food requires that the finished product not present to the consumer a health hazard. The product must have a pH of 4. 6 of lower, which must be reached within a time period of the approved schedule process. “Acidified food shall be heat processed to destroy vegetative cells of microorganisms of public health significance” and spoilage flora that could shorten shelf life under normal handling and retailing.

http://www.umaine.edu/foodinfo/Micro_Bob_Quality_Safety_web....

Staphylococcus aureus is a part of the normal flora of poultry, and
even adherence to good processing practices cannot totally prevent
carcass contamination. However, staphylococci do not compete well with
normal spoilage flora of poultry and are not likely to multiply on chilled
carcasses. They become a problem only if cooked poultry is contaminated
and subsequently subjected to time-temperature abuse.
http://www.icmsf.iit.edu/pdf/icmsf2.pdf

In the beef study conducted by Foegeding et al. (1983), Pseudomonas had maintained 104 CFU/g from day 0 to day 6 in beef samples. Enterobacteriaceae had also been reported as the spoilage flora of fresh meat that undergo aerobic refrigerated storage (Eribo and Jay, 1985; Gamage et al., 1997). Giannuzzi et al. (1998) checked microbial flora at temperature of 0, 4, 7, 9, and 10oC and the results of Enterobacteriaceae was 102 CFU/g to 103-5 CFU/g, LAB was 103 CFU/g to 104-6 CFU/g and Pseudomonas was 102 to 103 CFU/g to 104 to 107 CFU/g from day 0 to day 7 by using gas permeable packaging. In the study of Palumbo et al. (1997), they used ground beef with background bacteria of 103 CFU/g and 106 CFU/g and E. coli with 103 CFU/g.
http://ohioline.osu.edu/sc183/sc183_9a.html

AND IN FRENCH FOR Enterobacteriaceae (AS MENTIONED ABOVE)

2. Les bactéries de la flore d’altération :

Une grande variété de micro-organismes peut contaminer les aliments entraînant des effets indésirables tels que des modifications des caractéristiques organoleptiques (odeur : acide, alcool, ammoniac, goût : acide, alcool, « beurre »).

La flore d’altération est présente dans les ateliers de fabrication, notamment dans l’embosseur et sur la table à découper.



Exemples de bactéries de la flore d’altération :


Enterobacteriaceae spp : responsables d’altérations

Bien que rares dans le saucisson sec fermier, leur présence représente une perte économique pour les fabricants. Généralement, elles proviennent de l’atelier et non de la viande.

http://www.enitac.fr/cerpat/saucissons/pagesweb/fermentation...