Antimicrobial susceptibility of cinnamon and red and common thyme essential oils and their main constituent compounds against Streptococcus suis.

Streptococcus suis is an emerging zoonotic pathogen causing different diseases, in both humans and pigs. Generally, the control of this pathogen is based on antimicrobial therapy, but the development of bacterial resistance has led one to look for new options. In this sense, the essential oils (EOs) constitute a promising alternative. The activity of cinnamon, common thyme and red thyme EOs and their main active compounds (cinnamaldehyde and thymol) against S. suis isolates from pigs (n = 50) and humans (n = 6) was determined by the broth microdilution method. MIC50-90, MBC50-90 and the bactericidal index (BI) (minimal bactericidal concentration (MBC)/minimal inhibitory concentration (MIC)) were calculated. Also, the time-kill curve of each product against the S. suis P1/7 European reference strain was determined. No differences in the MIC or MBC values were observed between all the tested products, which suggest a homogeneous behaviour of S. suis, independently of their origin, organ of isolation or resistance profile. All the products showed a concentration-dependent and time-dependent killing activity and achieved the virtual eradication of S. suis at supra-inhibitory concentrations within the first 5 min of exposure, except cinnamaldehyde that showed only bacteriostatic effect. It suggests that these products could be utilized as antimicrobials in veterinary medicine for the control of this zoonotic pathogen.

Combined effect of conventional antimicrobials with essential oils and their main components against resistant Streptococcus suis strains.

Streptococcus suis is a major swine pathogen. Different strategies to reduce the antimicrobial resistance to conventional antimicrobials (AMBs) have been proposed, including the combined use with essential oils (EOs). The objective of this work was to evaluate the effectiveness of the combination of cinnamon, oregano, common thyme and red thyme EOs and their main components (cinnamaldehyde, carvacrol and thymol) with conventional AMBs (oxytetracycline, trimethoprim-sulfamethoxazole, gentamicin and penicillin) against field resistant S. suis strains. The checkerboard method was used to assess the interaction, by the fractional inhibitory concentration index (FICindex ) determination. All the AMBs showed synergistic (FICindex  ≤ 0·5) or additive (0·5 < FICindex  ≤ 1) effect with at least one of the four essential oils. In general, the combination of the AMBs with the EOs showed better results than combination the AMBs with the main components, although no antagonist effects were detected in any case. The results obtained would support the combined use of AMBs agents with EOs for the treatment of S. suis. SIGNIFICANCE AND IMPACT OF THE STUDY: Streptococcus suis is an important pig pathogen and a zoonosis. Control is based on antimicrobials; however, there is pressure to reduce the use of antimicrobials and new products or combination therapies are of considerable interest. We have evaluated the combined interaction of four essential oils or their main components with conventional antimicrobials against resistant S. suis strains. A positive interaction between gentamicin and oxytetracycline with cinnamon, oregano or thyme was observed, suggesting that a combination of conventional antimicrobials with EOs is a promising alternative for the control of S. suis infections.

FAS and ErbB2 expression in early local recurrent oral cancer.

BACKGROUND: Local failure occurs in 13.9-62.6% and it is a well known indicator of poor prognosis in patients with oral squamous cell carcinoma (OSCC), despite aggressive treatments. The purpose of this study was to investigate the value of histopathology and molecular biomarkers in predicting the development of early local recurrence. METHODS: This study included a total of 69 patients. There were 23 patients with early recurrent OSCC and 46 patients without local recurrence with the same clinical stage and tumor site, in a pair-matched study design. Their charts were retrospectively analyzed. All surgical specimens of the primary tumors were evaluated according to the system proposed by Anneroth et al. and immunohistochemical for ErbB2 and FAS were performed. RESULTS: A significant correlation of early local recurrence with grade of histological malignancy (more than 15 points) was observed (Fisher's exact test, P = 0.03). Early local recurrence was also significantly associated with weak FAS expression and strong intracytoplasmic ErbB2 staining (Mantel-Haenszal chi-square, P = 0.0038 and P = 0.0068, respectively). Histological grade of malignancy (more than 15 points) was also correlated with reduced survival (log-rank, P = 0.06). Among the histopathological parameters, keratinization, pattern of invasion and inflammation were important for overall survival (log-rank, P < 0.0001). Regarding the biomarkers, only FAS was significantly associated with overall survival (log-rank, P = 0.0002). Moreover, a positive correlation of FAS and membrane ErbB2 expression with keratinization was noticed. CONCLUSION: Histopathological characteristics and the expression of FAS and ErbB2 carry prognosis importance in local recurrence and overall survival in OSCC.