Survival of Yersinia enterocolitica and mesophilic aerobic bacteria on eggshell after washing with hypochlorite and organic acid solutions

Effectiveness of Quaternary Ammonium in Reducing Microbial Load on Eggs

Table eggs are an affordable yet nutritious protein source for humans. Unfortunately, eggs are a vector for bacteria that could cause foodborne illness. This study aimed to investigate the effectiveness of a quaternary ammonium compound (quat) sanitizer against aerobic mesophilic bacteria, yeast, and mold load on the eggshell surface of free-range and commercial farms and the post-treatment effect on microbial load during storage. Total aerobic mesophilic bacteria, yeast, and molds were enumerated using plate count techniques. The efficacy of the quaternary ammonium sanitizer (quat) was tested using two levels: full factorial with two replicates for corner points, factor A (maximum: 200 ppm, minimum: 100 ppm) and factor B (maximum: 15 min, minimum: 5 min). Quat sanitizer significantly (p < 0.05) reduced approximately 4 log10 CFU/cm² of the aerobic mesophilic bacteria, 1.5 to 2.5 log10 CFU/cm² of the mold population, and 1.5 to 2 log10 CFU/cm² of the yeast population. However, there was no significant (p ≥ 0.05) response observed between individual factor levels (maximum and minimum), and two-way interaction terms were also not statistically significant (p ≥ 0.05). A low (<1 log10 CFU/cm²) aerobic mesophilic bacteria trend was observed when shell eggs were stored in a cold environment up to the production expiry date. No internal microbial load was observed; thus, it was postulated that washing with quat sanitizer discreetly (without physically damaging the eggshell) does not facilitate microbial penetration during storage at either room temperature or cold storage. Current study findings demonstrated that the quat sanitizer effectively reduced the microbial population on eggshells without promoting internal microbial growth.

Response to environmental stress as a global phenomenon in biology: the example of microorganisms

Any modification of the environment that leads to a physiological, genetic, or epigenetic adaptive response in microorganisms may be considered as a stress. Historically, forms of stresses affecting biological structures were classified either as non-thermal, such as osmotic, oxidative, or acid stress or as thermal stress, hot or cold. Currently, the classification in biology is as abiotic, including physical and chemical stress, or biotic. The aim of this mini-review is to show, through the example of microorganisms, that the response to stress can be considered, in biology, as a global phenomenon, which can be extended to anthropogenic pressure.

Bacterial shell contamination in the egg collection chains of different housing systems for laying hens

The bacterial eggshell contamination of eating eggs in different commercial housing systems; two conventional cages, one organic aviary system and one barn production, were compared. The total counts of aerobic bacteria and the total counts of Gram-negative bacteria on the shell were used to detect key points where contamination occurred and to study the progress of contamination in the egg collection and transportation chains. The key points in the chain were those where eggs accumulated on a short conveyor belt, initial shell contamination in the alternative housing systems and extra nest-boxes placed on the ground. The high bacterial load of floor eggs (>6.3 log CFU total aerobic flora/eggshell) explains why they cannot be used for eating. On average higher initial shell contamination with total counts of aerobic bacteria was found for eggs from the alternative housing systems compared to the conventional systems; respectively 5.46 compared to 5.08 log CFU/eggshell. However, initial contamination with total counts of Gram-negative bacteria on the shells was less in the alternative systems: 3.31 compared to 3.85 log CFU/shell. Initial bacterial shell contamination tended to correlate positively with the concentration of bacteria in the air of the poultry houses. Storing shell eggs, whether temporarily refrigerated or not, for 9 d or more, resulted in a decrease in bacterial eggshell contamination for both bacterial variables.