Microbiological control is a regulatory requirement and one that can be defined as the continued interaction of science and applied technology with products, processes, materials, equipment, and personnel entering the manufacturing areas. In the ISO 14644-1, control of microbial contamination is addressed.
A good microbiological control program starts with understanding the risks for microbial contamination in the manufacturing process and identification of possible types of contaminants. The results obtained from such risk assessment can be used in the design of facilities and equipment as well as when establishing protocols regarding equipment and personnel. Once possible sources of contamination have been identified, control and preventative measures can be implemented and qualified/validated.
To evaluate the potential of curcumin on toxic and carcinogenic effects of Aflatoxin B1 (AFB1) in relation to AFB1 metabolism, we studied the effects of curcumin on hepatic AFB1-DNA adduct formation and glutathione S-transferase (GST) activity, and the toxic effects of AFB1 in male Fischer 344 rats. Oral administration of curcumin to 5-week-old male rats at a dose of 8 or 80 mg/kg for five consecutive days for three weeks resulted in reduction of AFB1-DNA adduct formation mediated by both liver microsomal and postmitochondrial fractions. The activity of liver GST toward a universal substrate, CDNB, was increased in curcuminadministered rats. As for the acute toxicity of AFB1, curcumin was orally administered to rats for 3 weeks and then AFB1 was given by intragastric intubation. The result showed a decrease of plasma AST and ALT activities in curcumin-treated rats compared with those which received AFB1 alone. Moreover, we have observed that curcumin also reduced glutathione S-transferase placental form positive single cells and foci caused by AFB1 treatment. These results demonstrate the potential of curcumin to reduce the toxic and carcinogenic effects of AFB1 by modulating hepatic drug metabolizing enzymes responsible for AFB1 metabolism.
Fifty strains of Campylobacter jejuni/coli were detected in 108 specimens of chicken meat and organs sampled at six supermarkets and one poultry slaughterhouse (large scale) between April and October 2013 (isolation rates: 84.8% from the slaughterhouse, 29.3% from the supermarkets). 46/50 strains were successfully recovered and subjected to the E-test to examine their susceptibility to three fluoroquinolone antibacterial agents authorized for use in poultry in Japan: enrofloxacin (ERFX), ofloxacin (OFLX), and norfloxacin (NLFX). 29 isolates (63%) were resistant to all three agents and 2 isolates (4.3%) were resistant to two agents (ERFX and OFLX). The resistance rates of strains isolated fom the supermarkets and slaughterhouse were 61.9% and 72.0%, respectively. Because the chickens processed at the slaughterhouse were raised without the use of fluoroquinolone, the results did not suggest a positive relationship between the use of these agents and the distribution of antimicrobial-resistant bacteria. Susceptibility to macrolide antibiotics (erythromycin ［EM］) was also tested in 42 strains, and one strain (2.4%), C. coli from a retailer sample, showed resistance. Previous studies have detected high rates of fluoroquinolone-resistant strains, suggesting an expanding distribution of resistant bacteria. The detection of EM-resistant bacteria downstream in the food distribution chain (i.e., closer to consumers) is a concern for human health.
The growth kinetics of Salmonella Enteritidis in raw beef has been little studied so far. Thus, this study aimed to clarify the growth kinetics of the pathogen in ground beef using a growth model. When Salmonella cells inoculated at various initial doses into ground beef were incubated at a given temperature (24℃), the maximum population (Nmax) of the microbe at the stationary phase varied with the doses. This relationship was expressed with a polynomialequation for Nmax using the initial dose. The combination of the growth model and the polynomial equation successfully predicted Salmonella growth at a given initial dose. When Salmonella cells inoculated in ground beef were incubated at various constant temperatures, the growth curves of the pathogen and natural microflora (NM) were well described with the growth model. The rate constant of growth and the Nmax values for Salmonella and NM were then analyzed kinetically. From these results, growth curves of Salmonella and NM in ground beef stored at dynamic temperatures were successfully predicted. Competition between Salmonella and NM in ground beef was also found during the storage. This study could give usable information on the growth of Salmonella and NM in ground beef at various temperatures.
Effects of wiping copper-alloyed stainless steel surfaces with disinfectants to remove protein surface contaminants and re-establish their antibacterial activities were quantitatively studied. Disinfectants used were sodium hypochlorite aqueous solutions and ethyl alcohol aqueous solutions. Wiping with NaOCl aqueous solutions effectively removed protein surface contaminants. Ethyl alcohol aqueous solutions were also effective for cleaning, but their efficiency was less than that of NaOCl aqueous solutions. When the amount of residual surface contaminants was reduced to 0.4 ng/mm2, the surfaces of the copper-alloyed stainless steel regained antibacterial activities to the same level as those in a clean surface condition.
Vibrio vulnificus is a halophilic estuarine bacterium, but this species causes fatal septicemia in humans. V. vulnificus may encounter many kinds of stresses either in the natural environment or in the human body. One of the striking stresses is the exposure to the reactive oxygen species including nitric oxide (NO). The present study revealed that NO could participate in the regulation of the V. vulnificus community behavior. When the bacterium was cultivated in the presence of sub-lethal doses of an NO donor, the expression of the genes encoding NO-detoxifying enzymes was significantly increased. The NO donor was also found to cause significant increase in production of a metalloprotease, a putative virulence factor, by the bacterium.
Foot-and-mouth disease virus (FMDV) is an animal pathogen of great concern. It is contagious to cloven-hoofed animals and affects animals in extensive areas worldwide. In general, the primary eradication strategies for foot-and-mouth disease (FMD) in Japan are stamping out the disease and restriction of movement. It is also important to completely disinfect the infected area to prevent the spread of FMDV, including vehicles and people as well. However, there is no report on the effect of commercially available disinfectants against FMDV in a short contact time. In this study, we evaluated the virucidal effect of thirteen commercially available products, and got the following results: acidic ethanol disinfectants, alkaline cleaners and sodium hypochlorite had great effect (>3.0 log10 reduction in titer) against FMDV. On the other hand, neutral ethanol disinfectants, hand soaps, and quaternary ammonium compound sanitizers did not show great effect against FMDV. Therefore, it is presumed that acidic ethanol disinfectants are effective for human use and alkaline cleaners are effective for use in the infected environment for the control of a FMD outbreak.
Fatty acid salts are a type of surfactant known to have potent antibacterial activity. We therefore examined the antibacterial activities of fatty acid salts against Streptococcus mutans. Potassium caprylate (C10K), potassium laurate (C12K), potassium myristate (C14K), potassium oleate （C18:1K), potassium linoleate (C18:2K), and potassium linolenate (C18:3K), used at a concentration of 175 mM, resulted in a 7 log-unit reduction of S. mutans after a 10-min incubation. The minimum inhibitory concentration (MIC) of C18:2K and C18:3K was 5.5 mM. C12K also demonstrated high antibacterial activity (MIC of 21.9 mM). These results indicate that C12K, C18:2K, and C18:3K have high antibacterial activity against S. mutans, and possess great potential as antibacterial agents.
Recently we clarified the growth kinetics of Salmonella Enteritidis in raw ground beef at various temperatures with our growth model. Based on those results, this study aimed to build a new methodology to predict the growth of Salmonella in ground beef at given initial concentrations of the pathogen and temperatures. Namely, the maximum cell population of Salmonella at various combinations of its initial concentration and temperature was developed with a polynomial equation. The rate constants of Salmonella growth at various temperatures were estimated with the square root model studied in our recent study. A new system consisting of our growth model, the polynomial equation, and the square root model successfully predicted the growth of Salmonella inoculated at given concentrations in beef at constant and dynamic temperatures. The growth of natural microflora in beef at those temperature patterns were also successfully predicted with the growth model.
The thermophilic spore forming bacteria Geobacillus stearothermophilus is recognized as a major cause of spoilage in canned food. A quantitative real-time PCR assay was developed to specifically detect and quantify the species G. stearothermophilus in samples from canned food. The selected primer pairs amplified a 163-bp fragment of the 16S rRNA gene in a specific PCR assay with a detection limit of 12.5 fg of pure culture DNA, corresponding to DNA extracted from approximately 0.7 CFU/mL of G. stearothermophilus. Analysis showed that the bacterial species G. stearothermophilus was not detected in any canned food sample. Our approach presented here will be useful for tracking or quantifying species G. stearotethermophilus in canned food and ingredients.