Essential oils from Lebanese plants could be used to selectively control foodborne pathogens, including fungi and bacteria. These essential oils could represents an alternative to conventional anti microbials as they did not affect benefiacial food‐related bacteria.
In recent years, popularity of raw milk has increased in many industrialised countries.
This study (i) enumerated total viable counts (TVC) and Escherichia coli counts, (ii) assessed prevalence of Staphylococcus (S.) aureus, Salmonella spp. and STEC, (iii) screened for methicillin resistant S. aureus (MRSA) and extended-spectrum β-lactamases (ESBL)-producing Enterobacteriaceae in sheep and goat tank milk samples collected throughout Switzerland and (iv) provided further strain characteristics on isolated pathogens and MRSA. One hundred and twenty-three tank milk samples from 116 farms were analysed. The median TVC was 3.8 log cfu mL-1. E. coli was detected in 16 (13.0%) and S. aureus in 18 (14.6%) samples. Polymerase chain reaction for stx genes was positive in 14 (11.4%) samples. MRSA were isolated from 4 (3.3%) samples. Salmonella spp. and ESBL-producing Enterobacteriaceae were not isolated.
Abstract
Milk is a substantial source of nutrients needed by all humans across lifespan development. Given its nutritional composition, milk is considered a vehicle for various microbes including beneficial and pathogenic bacteria. In this study, 270 milk samples comprising raw cow and buffalo milk and pasteurized milk with different shelf-life durations were tested along with pasteurized organic milk for the presence of Staphylococcus aureus and Escherichia coli. Collectively, 21 E. coli and 14 S. aureus isolates were cultivated and identified from total milk samples. All E. coli and S. aureus isolates exhibited resistance to erythromycin and penicillin, respectively. Serogroups O26, O128, and O111 were the most frequently identified amongst E. coli isolates, whereas staphylococcal enterotoxins (SEs) were inconsistently produced across S. aureus isolates. The molecular profile showed clustering of 6 isolates of E. coli by harboring stx1, stx2, eaeA genes, and 5 isolates of S. aureus by mecA gene. Findings revealed the bacteriological quality of popularly consumed milk in Egypt, including raw and pasteurized milk with preference to pasteurized organic milk and 7-day shelf life (7DSL) pasteurized milk. However, raw milk and 3MSL pasteurized milk were the major sources of E. coli and S. aureus, posing a serious public health issue.
Bacteriocins are antimicrobial peptides, produced by Gram-positive bacteria such as lactococci and staphylococci, that have limited bactericidal action against Gram-negative bacteria. The aim of this paper was to study the sensitivity of three strains of Escherichia coli to bacteriocins: nisin (as Nisaplin®) and two staphylococcal peptides (warnerin and hominin) during sucrose-induced osmotic stress. We found that all peptides in a 0.3 g·mL−1 sucrose solution significantly reduced the number of viable E. coli. The most pronounced antibacterial effect was achieved by nisin against E. coli K-12 (3 log reduction). Slightly less bactericidal effects were observed with warnerin (1 mg·mL−1) and hominin (1 mg·mL−1) in sucrose solution. The lytic activity of staphylococcal peptides was detected by decreased optical density and viable cell counts. Moreover, it was confirmed by the increased amount of DNA and protein in the medium and the morphological changes detected by atomic force microscopy after 20 h of treatment. Zymographic analysis revealed the release of lytic enzymes from E. coli cells after treatment with staphylococcal peptides and sucrose. These results indicated that the antimicrobial action of peptides can be extended to Gram-negative bacteria via combination with high concentrations of sucrose.
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Previous studies have shown the efficacy of high concentrations of salt as the main preservative against vegetative bacteria present on natural sausage casings. These studies were limited in the number of variables and the interactions between these variables that were assessed. To remedy this situation, a MicroCasing high-throughput model was developed and validated to study the inactivation kinetics of various combinations of parameters (salt concentration, pH, and temperature) on eight bacterial isolates of Salmonella enterica, Staphylococcus aureus, Escherichia coli, and Listeria monocytogenes over a prolonged period. A Weibullian power model was the best fit to show the trends in sensitivity of each bacterial isolate to salt, pH, and temperature over time. The inactivation kinetics generated with this novel approach could serve as a predictive model for the required salting period for casings. The actual bacterial contamination of the product can vary with the respective production step during processing from animal intestine into sausage casings (initial level, ∼105 CFU/g; level after salting, <102 CFU/g). Subsequent selection and grading of these casings will require complete removal of all salt, and upon completion of this production step, the casings will be resalted. By determining the actual contamination level before the salting process, the minimum storage period in salt can be calculated and potentially optimized by adjusting the pH and temperature. As a result, a standard holding period of at least 30 days may no longer be necessary to produce salted natural casings in accordance with validated quality and food safety criteria.
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A new model system was developed for analysis of bacterial inactivation kinetics in foods.
The novel model allows determination of product-specific bacterial inactivation over time.
Effects of time, temperature, pH, and salt on casing preservation can be clarified with the model.
Prediction of inactivation parameters allows casing production to meet HACCP criteria.
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High hydrostatic pressure processing (HPP) is a mild preservation technique, and its use for processing foods has been widely documented in the literature. However, very few quantitative synthesis studies have been conducted to gather and analyze bacterial inactivation data to identify the mechanisms of HPP-induced bacterial inactivation. The purpose of this study was to conduct a quantitative analysis of three-decimal reduction times (t3δ) from a large set of existing studies to determine the main influencing factors of HPP-induced inactivation of three foodborne pathogens (Listeria monocytogenes, Staphylococcus aureus, and Salmonella enterica) in various foods. Inactivation kinetics data sets from 1995 to 2017 were selected, and t3δ values were first estimated by using the nonlinear Weibull model. Bayesian inference was then used within a metaregression analysis to build and test several models and submodels. The best model (lowest error and most parsimonious) was a hierarchical mixed-effects model including pressure intensity, temperature, study, pH, species, and strain as explicative variables and significant factors. Values for t3δ and ZP associated with inactivation under HPP were estimated for each bacterial pathogen, with their associated variability. Interstudy variability explained most of the variability in t3δ values. Strain variability was also important and exceeded interstudy variability for S. aureus, which prevented the development of an overall model for this pathogen. Meta-analysis is not often used in food microbiology but was a valuable quantitative tool for modeling inactivation of L. monocytogenes and Salmonella in response to HPP treatment. Results of this study could be useful for refining quantitative assessment of the effects of HPP on vegetative foodborne pathogens or for more precisely designing costly and labor-intensive experiments with foodborne pathogens.
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A meta-analysis was performed to identify factors influencing HPP inactivation of pathogens.
Three-decimal reduction times following HPP were estimated from existing data.
Staphylococcus aureus is the most piezoresistant of the three pathogens studied.
These three foodborne pathogens are less HPP resistant in acidic products.
Abstract
This work was aimed at determining the occurrence and antibiogram of Staphylococcus aureusisolated from fresh and fermented milk samples in parts of Nasarawa State, Nigeria. A total of 180 samples comprising of fresh raw milk, bulk milk, nono, and kindirmo were collected over a period of 6 months (May to October, 2017). Standard microbiological procedures were employed in the isolation, identification, characterisation, and determination of the antibiogram of S. aureus from the milk samples. Characterisation of the S. aureus isolates was by morphological, biochemical characteristics using conventional methods, Microgen® STAPH-ID kits. Confirmed isolates were tested for susceptibility or resistance to a panel of 11 commonly used antibiotics using the agar disc diffusion technique. Out of the 180 milk samples examined, 9 S. aureus were isolated giving a prevalence of 5.0%. The occurrence of S. aureus was higher in nono (12.1%) and kindirmo (10.6%) than in fresh raw milk (5.9%). The high occurrence of S. aureus in nono disproved the assertion that fermented foods are not good media for the survival and growth of S. aureus. The antibiotic susceptibility profile of the S. aureus isolates indicated all of the nine isolates were completely resistant to cefoxitin, ampicillin, and amoxicillin/clavulanic acid. The isolates were moderately resistant to erythromycin (22.2%), sulphamethoxazole/trimethoprim (22.2%), and tetracycline (44.4%). Five antibiotic resistance patterns were recorded among the isolates. All of the isolates had a multiple antibiotics resistance (MAR) index of 0.3 and above, an indication of possible antibiotic misuse in the areas studied.
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The objective of this study was to compare the inactivation efficacy of saturated steam (SS) and superheated steam (SHS) on Staphylococcus aureus biofilms on food contact surfaces, including type 304 stainless steel coupons with No. 4 finish (STS No. 4), type 304 stainless steel coupons with 2B finish (STS 2B), high-density polyethylene (HDPE), and polypropylene (PP). In addition, the effects of the surface characteristics on the inactivation efficacy were evaluated. Biofilms were formed on each food contact coupon surface using a three-strain cocktail of S. aureus. Five-day-old biofilms on STS No. 4, STS 2B, HDPE, and PP coupons were treated with SS at 100°C and SHS at 125 and 150°C for 2, 4, 7, 10, 15, and 20 s. Among all coupon types, SHS was more effective than SS in inactivating the S. aureus biofilms. S. aureus biofilms on steel coupons were more susceptible to most SS and SHS treatments than the biofilms on plastic coupons. S. aureus biofilms on HDPE and PP coupons were reduced by 4.00 and 5.22 log CFU per coupon, respectively, after SS treatment (100°C) for 20 s. SS treatment for 20 s reduced the amount of S. aureus biofilm on STS No. 4 and STS 2B coupons to below the detection limit. With SHS treatment (150°C), S. aureus biofilms on HDPE and PP needed 15 s to be inactivated to below the detection limit, while steel coupons only needed 10 s. The results of this study suggest that SHS treatment has potential as a biofilm control intervention for the food industry.
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SHS was more effective than SS for inactivating biofilm cells of S. aureus.
Biofilms on steel coupons were more susceptible than those on plastic coupons.
The thermal conductivity of the coupon was an important factor in SHS treatment.
Biofilm; Saturated steam; Staphylococcus aureus; Superheated steam
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Bacterial biofilms constitute a major source of sanitary problems and economic losses in the food industry. Indeed, biofilm removal may require intense mechanical cleaning procedures or very high concentrations of disinfectants or both, which can be damaging to the environment and human health. This study assessed the efficacy of a technique based on spectroscopy in the visible, near-infrared, and short-wavelength infrared range for the quick detection of biofilms formed on polystyrene by the pathogenic bacterium Staphylococcus aureus. To do that, biofilms corresponding to three S. aureus strains, which differed in biofilm-forming ability and composition of the extracellular matrix, were allowed to develop for 5 or 24 h, representing an active formation stage and mature biofilms, respectively. Spectral analysis of the samples, corresponding to three biological replicates of each condition, was then performed by using a portable device. The results of these experiments showed that partial least-squares discriminant analysis of the spectral profile could discriminate between surfaces containing attached bacterial biomass and noninoculated ones. In this model, the two first principal components accounted for 39 and 19% of the variance and the estimated error rate stabilized after four components. Cross-validation accuracy of this assessment was 100%. This work lays the foundation for subsequent development of a spectroscopy-based protocol that allows biofilm detection on food industrial surfaces.
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A biofilm detection spectroscopy–based technique with a portable device was tested.
Staphylococcus aureus biofilms of different strengths were scanned with the device.
Spectral data showed correlation with crystal violet staining quantification results.
Data from spectral analysis was suitable for prediction of biofilm contamination.
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Because of increased susceptibility, older adults have an increased risk of foodborne infection, and data suggest elevated incidence; therefore, food hygiene is essential to reduce the risk. Research suggests older adults’ inadequate knowledge and negative attitudes toward food hygiene may increase implementation of unsafe food practices. Data on microbiological contamination of domestic kitchens of older adults are lacking. Therefore, this study aimed to determine microbiological contamination of domestic kitchens of older adults. Food contact surfaces and equipment (n = 1,292) in domestic kitchens (n = 100) of older adults (≥60 years) were analyzed to isolate aerobic bacteria, Enterobacteriaceae, Staphylococcus aureus, and Listeria spp.; self-reported hygiene practices were also recorded. Highest contamination levels were determined on in-use cleaning equipment (dish brushes, dishcloths, sponges) with aerobic bacteria <9.3 log CFU per item, Enterobacteriaceae <8.8 log CFU per item, and S. aureus <7.0 log CFU per item. Reported usage length of dish brushes was significantly correlated (P< 0.05) with Enterobacteriaceae contamination. Significant correlations (P < 0.05) were determined between contamination and reported cleaning frequency of refrigerators. Contamination of hand towels in single-occupant households was significantly greater (P < 0.05) than in multioccupant households. The study facilitates novel comparison between reported hygiene practices with microbial contamination, suggesting older adults fail to implement adequate and regular hygiene practices that may increase the possibility of cross-contamination in the domestic kitchen and the associated risk of foodborne illness. Data from this study have determined a need for older adults to improve food hygiene practices in the domestic kitchen.
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In-use dish brushes and dishcloths were most commonly contaminated with high counts of bacteria.
Correlations existed between dishcloth contamination and multiple kitchen sites.
Reported dish brush usage length was significantly correlated with contamination level.
Reported time since cleaning of refrigerators was positively correlated with contamination levels.
Inadequate and irregular hygiene practices may increase foodborne illness risk to older adults.
FoodWorld 