67 ± 0.67 mm, which was determined as the MIC. The largest inhibition zone (11.67 ± 0.33 mm) was observed at the highest concentration of oil applied (50%; 500 μl/ml), which was probably due to the higher concentration of active chemical components in the EO fraction. In the positive control (microwell filled with a 1000 mg/l chloramphenicol solution), an average inhibition zone of 16.67 mm was observed. In the negative control (microwell filled with DMSO without EO), no inhibition zones were observed, suggesting that there was no interference from the diluents used in the tests. The morphological cell damage of C. perfringens caused by treatment with S. montana EO at a MIC concentration are shown in the transmission

electron micrographs in Fig. 2. The micrographs selleck screening library of untreated cell culture (A and B) without exposure to EO showed continuous thin, smooth cell walls and other defined cellular structures. The C. perfringens cells treated with EO (C, D, E and F) had Selleck Everolimus adulterated morphology, where cell walls had irregularities, less smoothness, less uniformity and

degenerative changes leading to wall ruptures and subsequent cellular lysis in some cases. An unequal cytoplasm distribution caused by the clumping and agglomeration of intracellular material was observed in the treated cells (indicated by arrows). Furthermore, the cells lacked cytoplasm in certain regions due to the loss of membrane functionality, which was characteristic of the mechanism of action of the major chemical components of S. montana EO. The primary events of the sporulation process were not observed due to contact why of the EO with viable cells from the microorganism studied. The population variations of C. perfringens type A viable cells in mortadella-type sausages formulated with different concentrations of S. montana EO and levels of NaNO2 during storage at 25 °C for 30 days are shown in Table 2. In mortadella elaborated without the addition of EO and nitrite (control samples), the C. perfringens populations increased reaching 8.95 log10 CFU/g at the first day of storage. After 10 days of storage, the counts

were decreased in the control samples, showing a population of 4.83 log10 CFU/g at the end of the storage period. The samples formulated without nitrite and with 0.78% EO had populations that were not significantly different (p > 0.05) than the initial inoculum at the first day of storage. However, their growth was restricted (p ≤ 0.05) when compared to the control (bacteriostatic effect) at the first day. In the mortadella with 1.56% EO (MIC concentration) without nitrite, we observed a decrease of 1.02 log10 CFU/g on the first day of analysis showing a antimicrobial effect of the EO evaluated at concentrations higher than 1.56% added in sausages. The most drastic effect was observed in samples elaborated with 3.125% EO without NaNO2 where the bacterial population was reduced to 4.65 log10 CFU/g after 24 h of storage.