Short communicationMicrobial diversity on commercial eggs as affected by the production system. A first approach using PGM

- An approach to analyse eggshell microbiota by PGM was developed for first time.
- PGM allowed to obtain an exhaustive analysis of eggshell microbiota.
- Eighteen phyla not previously linked to eggs were identified.
- Egg production system effect (cage/free range) on microbial diversity was discussed.
- Samples from both systems had a similar microbiota but different relative abundances.

A novel DNA-based technique (PGM) has been employed for first time to analyse commercial eggs with the advantage of allowing an exhaustive identification of the microbiota present. Eggs from two different production systems, i.e. a free range system and a cage system, were analysed. Twenty-one and twenty-two phyla were identified on the surface of cage system and free range system eggs, respectively. In both cases, Firmicutes was the dominant phylum (representing around 50% of total phyla), being found families frequently reported to be present in the intestinal microbiota of chickens or hens, such as Clostridiaceae, Ruminococcaceae and Lachnospiraceae. Additionally, other phyla and families not previously described in association with eggshells could also be identified in this work. Most of the potential pathogenic genera associated with eggs (Salmonella, Clostridium, Helicobacter, Pseudomonas and Staphylococcus) showed higher incidence in eggs coming from cage systems than in eggs coming from free range systems, although the abundance of these genera were very low in both cases (< 5% of total bacteria).