Microbiological quality aspects of ready-to-eat foods with focus on antibiotic resistance and biofilm formation abilities of foodborne bacteria

In this study, microbiological quality of 93 ready-to-eat food products was determined by enumeration of total aerobic bacteria and members of Enterobacteriaceae. Presence of Staphylococcus aureus and Listeria monocytogenes in the products were also investigated. Aerobic colony counts were between 1.9 x 10(2)-3.4 x 10(8) CFU g(-1) for 84.9% and Enterobacteriaceae counts were between 2 x 10(2) and 6.7 x 10(6) CFU g(-1) for 43% of the samples. S. aureus was detected in 7.5% of the samples, but L. monocytogenes was not detected in any sample. 72.9% of the Enterobacteriaceae isolates showed resistance to at least one antibiotic tested, and 5 among the S. aureus isolates were found to be resistant to penicillin G and 2 against methicillin. Four S. aureus isolates produced only Staphylococcal enterotoxin A and 1 isolate produced both Staphylococcal enterotoxin A and B. Biofilm experiments revealed biofilm formation on polystyrene for 95.8%, 87.5%, and 91.6% of Enterobacteriaceae isolates at 4 degrees C, 22 degrees C, and 37 degrees C, respectively, whereas all S. aureus isolates formed biofilm at all temperatures.