Clove essential oil in the sanitation of fertile eggs

The aim of this study was to evaluate the efficacy of sanitizing fertile eggs with clove essential oil as an alternative to paraformaldehyde; effects on the reduction in eggshell microbial count, incubation yield, and neonatal chick quality were measured. A total of 1,460 brown fertile eggs with a mean weight of 58.64 ± 0.49 g (from 37-wk-old CPK [Pesadão Vermelho] breeder hens) were collected under aseptic conditions and randomly distributed into 4 treatments (nonsanitized and sanitized with grain alcohol, clove essential oil, and paraformaldehyde) before incubation. The count of total aerobic mesophilic bacteria was significantly lower after spraying with clove essential oil (2.30 ± 0.24 log₁₀ CFU/mL) than on nonsanitized eggs (3.49 ± 0.34 log₁₀ CFU/mL) or on eggs sprayed with grain alcohol (3.09 ± 0.14 log₁₀ CFU/mL) but did not differ significantly from the count in the paraformaldehyde group (2.23 ± 0.29 log₁₀ CFU/mL). The hatchability of fertile eggs differed significantly between the studied treatments. The mean values for the eggs treated with clove essential oil (84.69 ± 1.65%) and paraformaldehyde (81.87 ± 3.92%) were statistically similar but were higher than the negative control (74.03 ± 3.58%) and grain alcohol (73.59 ± 2.87%) values. In the Pasgar© score assessment, it was determined that the clove essential oil (9.21 ± 0.89%) had a superior effect on the physical quality of the chicks compared with the effects of the other treatments. Clove essential oil is effective and safe for eggs intended for incubation. Its use as an alternative to paraformaldehyde in the sanitation of fertile eggs is strongly recommended.

Assessment of commercial companion animal kefir products for label accuracy of microbial composition and quantity

Kefir is a fermented beverage containing yeast and bacteria produced by the fermentation of water or milk with kefir grains. Lack of regulation for probiotic-containing fermented food sold for companion dogs and cats creates the potential for misreporting on viable microbial counts, taxonomy, and label claims. In this study, the microbiota of six companion animal kefir products were measured quantitatively using standard plating techniques. Microbial composition of these products was also characterized by using high-resolution, long-read amplicon sequencing of the 16S rRNA gene. Five products (83%) listed specific microorganisms, and four products (66%) guaranteed colony forming units (CFU)/g on their label. To enumerate viable lactic acid bacteria (LAB), two lots of each homogenized product were plated upon opening and following 14 d on deMan Rogosa and Sharpe (MRS) agar and incubated under anaerobic and aerobic conditions. Results from point of opening revealed that all commercial kefir products with a guaranteed CFU/g overstated the number of microorganisms present by at least 1 log, with only one product exceeding 1 × 109 CFU/g. Sequencing results demonstrated that none of the labels claiming specific bacterial genera and species on their labels were correct, and all products contained at least three additional bacterial species above the minimum detectable threshold (0.001% relative abundance) that were not disclosed by the manufacturer. In addition to the incorrect viable CFU and bacterial taxonomies, several of the product labels and websites contained a wide range of health claims, none of which are supported by the companion animal literature. Our results demonstrate a low level of accuracy in the labeling of commercial kefir products intended for use in dogs and cats. Regulatory agencies, veterinarians, pet food professionals, and pet owners must scrutinize these products and demand a higher level of accuracy and quality in the future.

A modified reinforced clostridial medium for the isolation and enumeration of Lactobacillus delbrueckii ssp. bulgaricus in a mixed culture

In this study, we modified reinforced clostridial medium (RCM) to selectively enumerate and isolate Lactobacillus delbrueckii ssp. bulgaricus, a probiotic and important starter culture in the dairy industry. The disparity in the reported carbohydrate fermentation pattern of L. delbrueckii ssp. bulgaricus was used to develop a growth medium not only selective for L. delbrueckii ssp. bulgaricus but significantly inhibitory to the growth of other lactic acid bacteria. A recently modified RCM (mRCM) was optimized for this study by the addition of 0.5% fructose, 0.5% dextrose, 1% maltose, and 0.25% sodium pyruvate while replacing lactose as a carbohydrate source. The cell recovery and bacterial counts of L. delbrueckii ssp. bulgaricus in tested products (pure L. delbrueckii ssp. bulgaricus strains, starter culture, probiotic supplements, and yogurt) using our mRCM with sodium pyruvate (mRCM-PYR) were significantly higher than in the recently modified RCM and the common de Man, Rogosa, and Sharpe (MRS) culture medium. The growth of other lactic acid bacteria (Streptococcus thermophilus, Lactobacillus acidophilus, Lactobacillus rhamnosus, and Lactobacillus reuteri) and Bifidobacteria was retarded in this modified medium compared with their growth in MRS and mRCM. This result is a significant improvement in the enumeration and differentiation of L. delbrueckii ssp. bulgaricus in mRCM-PYR compared with the results in MRS and mRCM where the high background growth of similar species interferes with the accuracy of bacterial population counts. Our results thus suggest that mRCM-PYR could be recommended as a reliable alternative growth medium for the selective enumeration and isolation of L. delbrueckii ssp. bulgaricus in a mixed culture.

Sugar-Lectin Interactions for Direct and Selective Detection of Escherichia coli Bacteria Using QCM Biosensor

Pathogenic Escherichia coli (E. coli) remains a safety concern in the preservation and quality of green leafy vegetables. Sugar-lectin interactions provide a reliable, specific, and effective sensing platform for the detection of bacteria as compared to the tedious conventional plate counting technique. Herein, we present the synthesis of 4-(N-mannosyl) benzoic acid (4-NMBA) and 4-thiophenyl-N-mannose (4-TNM) via a two-step reductive amination for the detection of E. coli using a quartz crystal microbalance (QCM) biosensor. The 4-NMBA was synthesized with mannose and para-aminobenzoic (4-PBA), while the 4-TNM was synthesized with mannose and 4-aminophenyl disulfide (4-AHP) using water and acetic acid in a 1:1 ratio. The resultant structure of mannose derivatives (4-NMBA and 4-TNM) was characterized and confirmed using analytical tools, such as Mass Spectrometer, SEM, and FTIR. The choice of ligands (mannose derivatives) is ascribed to the specific recognition of mannose to the FimH lectin of the type 1 pilus of E. coli. Furthermore, the 4-PBA and 4-AHP conjugated to mannose increase the ligand affinity to FimH lectins. The setup of the QCM biosensor was composed of modification of the crystal surface and the covalent attachment of ligands for the detection of E. coli. The piezoelectric effect (frequency shift of the quartz) was proportional to the change in mass added to the gold crystal surface. Both the 4-NMBA- and 4-TNM-coated QCM sensors had a limit of detection of 3.7 CFU/mL and 6.6 CFU/mL with a sensitivity of 2.56 × 10³ ng/mL and 8.99 × 10^-5 ng/mL, respectively, within the dynamic range of 10³ to 10⁶ CFU/mL. This study demonstrates the application of ligand-coated QCM biosensors as a cost-effective, simple, and label-free technology for monitoring pathogenic bacteria via molecular interactions on crystal surfaces.

Dynamics of Active Fluorescent Units (AFU) and Water Activity (aw) Changes in Probiotic Products-Pilot Study

The flow cytometry method (FCM) is a widely renowned practice increasingly used to assess the microbial viability of probiotic products. Additionally, the measurement of water activity (aw) can be used to confirm the presence of viable cells in probiotic products throughout their shelf lives. The aim of this study was to investigate the correlation between changes in aw and variations in active fluorescent units (AFU), a unit commonly used in flow cytometry method, during the aging of probiotic products containing freeze-dried bacteria. We controlled the stability of probiotic products for bacterial counts (using ISO 19344 method) and aw levels in commercially available capsules containing freeze-dried bacteria such as Lactobacillus sp. or combinations of Lactobacillus sp. and Bifidobacterium sp. in standard conditions (25 ± 2 °C and 60% relative humidity) over a period of 24 months. During this time, the bacterial contents decreased by 0.12 Log10 in the single-strain product, by 0.16 Log10 in the two-strain product and by 0.26 Log10 in the multi-strain product. With the increase in aw, the number of bacteria decreased but the aw at the end point of the stability study did not exceed 0.15 in each of the three tested products. FCM combined with aw is a prospective analysis that can be used to assess the stability of probiotic products, both for its ability to detect bacterial viability and for practical (analysis time) and economic reasons.

Rapid detection of viable microbes with 5-cyano-2,3-di-(p-tolyl)tetrazolium chloride and 5(6)-carboxyfluorescein diacetate using a fibre fluorescence spectroscopy system

AIMS

To assess the efficacy of two commercially available viability dyes, 5-cyano-2,3-di-(p-tolyl)tetrazolium chloride (CTC) and 5(6)-carboxyfluorescein diacetate (CFDA), in reporting on viable cell concentration and species using an all-fibre fluorometer.

METHODS AND RESULTS

Four bacterial species (two Gram-positive and two Gram-negative) commonly associated with food poisoning or food spoilage (Escherichia coli, Salmonella enterica, Staphylococcus aureus, and Bacillus cereus) were stained with CTC or CFDA and the fibre fluorometer was used to collect full fluorescence emission spectra. A good correlation between concentration and fluorescence intensity was found for Gram-negative bacteria between 107 and 108 colony-forming units (CFU) ml-1. There was no correlation with concentration for Gram-positive bacteria; however, the information in the CTC and CFDA spectra shows the potential to distinguish Gram-negative cells from Gram-positive cells, although it may simply reflect the overall bacterial metabolic activity under staining conditions from this study.

CONCLUSIONS

The limit of detection (LoD) is too high in the dip-probe approach for analysis; however, the development of an approach measuring the fluorescence of single cells may improve this limitation. The development of new bacteria-specific fluorogenic dyes may also address this limitation. The ability to differentiate bacteria using these dyes may add value to measurements made to enumerate bacteria using CTC and CFDA.