Veterinary Research Forum

Abstract The purpose of this study was to elucidate some factors affecting the growth of Salmonella typhimurium. These factors included Carum copticum essential oil (0%, 0.015%, 0.03% and 0.06%), temperature (25 ˚C and 35 ˚C), pH (5, 6 and 7) and inoculum size (10³ and 10⁵
 CFU mL^-1). Brain heart infusion broth was used as the growth medium. There were 48 treatment combinations and the experiment was carried out in triplicate. Growth was monitored by visible turbidity over a 30 days period. A parametric survival model based on the log-normal distribution was used to estimate the most influential factors on the time to detection of Salmonella growth. According to our results, the selected factors significantly affected the growth of Salmonella typhimurium. Furthermore, the final graph demonstrated good agreement between the values predicted by predictive model and the results which were observed in this study. So that a parametric survival model can be a useful and practical tool to predict how the parameters will influence the bacterial growth.

Abstract Clostridium perfringens is an important cause of bacterial food poisoning worldwide. The disease is caused by C. perfringens enterotoxin (CPE) encoded by cpe gene. The aim of this research was to identify the different types of C. perfringens and the presence of cpe gene in isolated bacteria from broilers’ meat marketed in retail meat shops of Mashhad city in Northeastern of Iran. After isolation of C. perfringens using conventional culture method and confirmation by specific 16S rDNA gene, a multiplex polymerase chain reaction assay with specific primers, were performed for toxin typing of isolates. Clostridium perfringens was isolated from 31 broilers’ meat samples (15.50%) out of 200 samples and for toxin typing the results showed 9 isolates as type A (29.03%) and 22 isolates as type C (70.96%). In this study, cpe-positive C. perfringens were detected in eight isolates of type C (25.00%). Our results indicated that C. perfringens type C is the most common type in broiler chicken carcasses.

Abstract Listeria monocytogenes can be found throughout the environment and in many foods. It is associated primarily with meat and animal products. Listeria monocytogenes has become increasingly important as a food-borne pathogen. The aim of this study was to evaluate the effect of microwave (MW) treatment of chicken meat samples which were inoculated with L. monocytogenes. Drumettes of broiler carcasses were soaked in fully growth of L. monocytogenes in Brain-Heart Infusion broth. The swab samples were taken from the inoculated samples, after various times of radiation (10, 20, 30, 40, 50, 60, 70 and 80 sec), using a domestic MW oven at full power. Following exposures, viable counts and surface temperaturemeasurements were performed. The bacterial counts were performed on Oxford agar. The results indicated that equal or longer than 60 sec exposures of chicken portions to MW heating which enhances the median surface temperature more than 74 ˚C could eliminate the superficial contamination of chicken meat with L. monocytogenes. Statistical analysis showed samples with equal or longer than 60 sec exposures to MW heating had significant decrease in population of inoculated bacteria compared with positive control group(p < 0.05). Pearson correlation showed a significant correlation between the bacterial population and temperature of samples due to MW exposure (p < 0.001, r = – 0.879 and r² = 0.773).  

Abstract Black zira (Bunium persicum) is a medicinal plant and spice, naturally grows in Iran. The aim of this study was to investigate the combined effects of different concentrations of Bunium persicum essential oil (EO; including 0, 0.08, 0.16 and 0.24%), three incubation temperatures (15, 25 and 35˚C), three levels of pH (5, 6 and 7 adjusted by hydrochloric acid), and three inoculum size (10², 10³ and 10⁴ CFU mL^-1) on the growth of Staphylococcus aureus in the brain heart infusion broth. Black zira EO was extracted and its component was identified using gas chromatography-mass spectrometry (GC-MS) analyses. The experiment was carried out in triplicate. Growth was monitored by visible turbidity during a 30-day period. To evaluate effects of explanatory variable on time to detection (TTD) of bacterial growth, parametric survival models based on Log-normal distribution was used. All explanatory variables had significant association with time to detection (p < 0.05). The final model accurately predicted the growth initiation and inhibition of S. aureus.