Viable Campylobacter jejuni on Eggshells and Its Potential to Cross-contaminate Egg White and Yolk When Using a Manual Separation Technique, Determined by Culture and Propidium Monoazide (PMA) qPCR

Manual separation of egg yolk from egg white using the eggshell is common practice in private households. For this, the egg is cracked and both components are separated by passing the egg yolk back and forth between the two halves of the eggshell, allowing the egg white to drip down while the egg yolk remains in the shell. During this process, the egg content naturally gets in contact with the outside of the eggshell, which might lead to a cross-contamination with its microorganisms, thus was correspondingly assessed in this study. Campylobacter jejuni is one of the most important zoonotic pathogens that can be found on eggshells. Therefore, this bacterium was used to artificially contaminate the eggshells (n = 22) with concentrations of 3.1 ± 0.6 log10 cfu/g. After separating the egg yolk from the egg white, cross-contamination was determined using culture and qPCR. Altogether, cross-contaminations with C. jejuni were found in 15 egg white (68%) and in three egg yolk (14%) samples. Afterward, 90 eggs from 30 egg packs from different producers in and around Munich (Germany) were obtained for field study purposes. To address the problem of culturing due to a possible viable but nonculturable (VBNC) status of C. jejuni, a method to differentiate viable and dead C. jejuni on eggshell using 10 µM propidium monoazide (PMA) and qPCR was developed. As a result, seven egg packs (23%) were positive for C. jejuni. Of these, only one (3%) was contaminated with viable cells, but still in a concentration of 3.3 log10 cells/g shell. According to these results and considering that eggshells might also be naturally contaminated with other pathogens, the authors recommend avoiding the manual separation technique of egg white and yolk by the eggshell. Especially if raw egg white or yolk is used for preparation of not sufficiently heated foods, where contaminating pathogens are not inactivated during processing, this technique might be a safety hazard for the consumer.

Investigation of Meat from Ostriches Raised and Slaughtered in Bavaria, Germany: Microbiological Quality and Antimicrobial Resistance

Simple Summary

The rapid increase in the world population might lead to the need for new food resources. Ostrich meat remains an exotic food product, although it is characterized by high nutritional value. However, to secure food safety, good monitoring and control programs have to be implemented. Furthermore, standard data concerning the general microbiological status of meat, its evolution in time, and aspects influencing the different parameters have to be assessed in order to provide current information. Thus, production, slaughter, and processing procedures may be improved. For this purpose, the microbiological status, prevalence of zoonotic pathogens, and presence of antimicrobial-resistant microorganisms were assessed. The results will provide baseline data that can be used for future official specific hygiene control procedures and monitoring programs for producing ostrich meat.

Abstract

Ostrich meat is characterized by high nutritional value; however, it remains an exotic product in most countries worldwide. In Europe, only few data are available regarding its microbial contamination, prevalence of antimicrobial-resistant bacteria, and safety. Therefore, this study aimed to investigate the microbiological quality and safety of ostrich meat samples (n = 55), each from one animal, produced in Bavaria, Germany. The provided microbiological status of ostrich meat included mesophilic aerobic bacteria, Enterobacteria, and mesophilic yeast and molds. In terms of food safety, all meat samples were negative for Salmonella spp. and Trichinella spp. Additionally, meat samples and a further 30 stool samples from 30 individuals were investigated for Shiga toxin-producing Escherichia coli genes, with two meat samples that were qPCR-positive. Antimicrobial-resistant Enterobacteriaceae, Enterococcus faecalis, and Enterococcus faecium strains were from meat and stool samples also analyzed; 13 potentially resistant Enterobacteriaceae (meat samples) and 4 Enterococcus faecium (stool samples) were isolated, and their susceptibility against 29 and 14 antimicrobials, respectively, was characterized. The results of this study provide an overview of microbial loads and food safety aspects that may be used as baseline data for the ostrich meat industry to improve their hygienic quality. However, the implementation of monitoring programs is recommended, and microbiological standards for ostrich meat production should be established.

Phenotypic and Genetic Comparison of a Plant-Internalized and an Animal-Isolated Salmonella Choleraesuis Strain

Contamination of fresh produce with human pathogens poses an important risk for consumers, especially after raw consumption. Moreover, if microorganisms are internalized, no removal by means of further hygienic measures would be possible. Human pathogenic bacteria identified in these food items are mostly of human or animal origin and an adaptation to this new niche and particularly for internalization would be presumed. This study compares a plant-internalized and an animal-borne Salmonella enterica subsp. enterica serovar Choleraesuis aiming at the identification of adaptation of the plant-internalized strain to its original environment. For this purpose, a phenotypical characterization by means of growth curves under conditions resembling the indigenous environment from the plant-internalized strain and further analyses using Pulsed-field gel electrophoresis and Matrix-assisted laser desorption ionization time of flight spectrometry were assessed. Furthermore, comparative genomic analyses by means of single nucleotide polymorphisms and identification of present/absent genes were performed. Although some phenotypical and genetic differences could be found, no signs of a specific adaptation for colonization and internalization in plants could be clearly identified. This could suggest that any Salmonella strain could directly settle in this niche without any evolutionary process being necessary. Further comparative analysis including internalized strains would be necessary to assess this question. However, these kinds of strains are not easily available.

Antimicrobial resistance of Enterobacter cloacae complex isolates from the surface of muskmelons

The increasing antimicrobial resistance (AMR) among pathogenic and opportunistic pathogenic microorganisms is one of the main global public health problems. The consumption of food contaminated with such bacteria (ARB), especially of raw products, might result in the direct acquisition of ARB and in a spread of resistant bacteria along the food chain. The aim of the study was to characterize the antimicrobial susceptibility of potentially extended spectrum β-lactamase (ESBL) producing or AmpC resistant Enterobacteriaceae isolated from the surface of 147 muskmelons from wholesale and retail. A phenotypic analysis was carried out by using minimum inhibitory concentration (MIC) test strips for ESBL detection and MIC susceptibility plates against 14 antimicrobials. Furthermore, ESBL genes, sul-genes and plasmid-mediated AmpC resistance were analyzed by real-time PCR. Additionally, a further insight in the AmpC resistance of isolates of the Enterobacter cloacae complex (ECC) was obtained by analyzing the sequence of the ampC regulatory region (n = 15). A total of 73 potentially resistant Enterobacteriaceae were isolated from 56 muskmelons. Of these, 15 isolates of the ECC were suspicious for ESBL/AmpC resistance, and eleven thereof were positive for the AmpC family EBC. Phenotypic analysis showed diminished susceptibility against "critically" and "highly important" antimicrobials, according to the WHO classification. Furthermore, divergence in the ampC regulatory region was detected between the 15 isolates. These findings highlight the important role that raw produce might play in the transmission of antimicrobial resistances along the food chain.

Endogenous microbial contamination of melons (Cucumis melo) from international trade: an underestimated risk for the consumer?

BACKGROUND

Fruits and vegetables have increasingly been related to foodborne outbreaks. Besides surface contamination, a possible internalization of microorganisms into edible parts of plants during growth has already been observed. To examine an actual risk for the consumer, microbial contamination of the rind and pulp of 147 muskmelons from international trade was assessed using cultural and biochemical methods, polymerase chain reaction and matrix-assisted laser desorption/ionization-time of flight mass spectrometry.

RESULTS

One hundred percent of the rind samples [3.69-8.92 log colony forming units (CFU) g^-1 ] and 89.8% of the pulp samples (maximum load 3.66 log CFU g^-1 ) were microbiologically contaminated. Among the 432 pulp isolates, opportunistic and potentially pathogenic bacteria were identified, mainly Staphylococcus spp. (48.9%), Clostridium spp. (42.9%) and Enterobacteriaceae (27.9%). Salmonella spp., Escherichia coli and isolates of the Bacillus cereus group were found on the rind (1.4%, 0.7% and 42.9%, respectively) and in the pulp (0.7%, 1.4% and 4.7%). Clostridium perfringens was isolated from the rind of seven melons.

CONCLUSION

The present study revealed a regularly occurring internal contamination of melons. Possible health risks for consumers because of an occurrence of microorganisms in melon pulp should be considered in future food safety assessments. © 2018 Society of Chemical Industry.