Klebsiella pneumoniae as a Spoilage Organism in Mozzarella Cheese

Mozzarella cheese is a soft, plastic cheese typical of Italy and of notable economic relevance because of the steady rise in its production and consumption.It is a particularly perishable cheese, having a brief commercial shelf-life (20 to 30 d) that is dependent on the extent and degree of refrigerated storage.Other authors have described diverse cases of spoilage: extremely soft consistency (13), appearance of anomalous pigmented spots on the surface (11, 17), development of bitter taste (5), production of slime, and surface flaking (26).Although yeasts, colifonns, heterofennentative lactic acid bacteria, clostridia, and Bacillus spp.have often been associated with gas pro-ABSTRACT A high concentration of total and fecal colifonns (5 x lOS and 3 x 10 7 cfu/g, respectively) was observed in samples representative of two production lots of Mozzarella cheese from a local dairy.Contamination was manifested by the swelling of plastic pouches and the fonnation of gas holes in Mozzarella cheese.Aerobic and anaerobic sporefonners, heterofennentative lactic acid bacteria, propionibacteria, and yeasts were absent.Of the 41 isolates identified, there were 37 Klebsiella pneumoniae, 2 Klebsiella oxytoca, 1 Enterobacter aerogenes, and 1 Escherichia coli.Exposure at 63"C for 15 min caused the death of all total and fecal colifonns.