Contents lists available at ScienceDirect Environmental Research journal homepage: www.elsevier.com/locate/envres Analysis of potential risks from the bacterial communities associated with air-contact surfaces from tilapia (Oreochromis niloticus) fish farming ☆ Maria Jose Grande Burgos, Jose Luis Romero, Rubén Pérez Pulido, Antonio Cobo Molinos, Antonio Gálvez ⁎ , Rosario Lucas Área de Microbiología, Departamento de Ciencias de la Salud, Facultad de Ciencias Experimentales, Universidad de Jaén, 23071 Jaén, Spain ARTICLE INFO Keywords: Tilapia Aquaculture Bacterial diversity Microbiological risks ABSTRACT Tilapia farming is a promising growing sector in aquaculture. Yet, there are limited studies on microbiological risks associated to tilapia farms. The aim of the present study was to analyse the bacterial communities from solid surfaces in contact with air in a tilapia farm in order to evaluate the presence of bacteria potentially toxinogenic or pathogenic to humans or animals. Samples from a local tilapia farm (tank wall, aerator, water outlets, sink and floor) were analyzed by high throughput sequencing technology. Sequences were assigned to operational taxonomic units (OTUs). Proteobacteria was the main phylum represented in most samples (except for one). Cyanobacteria were a relevant phylum in the inner wall from the fattening tank and the wet floor by the pre-fattening tank. Bacteroidetes were the second phylum in relative abundance for samples from the larval rearing tank and the pre-fattening tank and one sample from the fattening tank. Fusobacteria showed highest relative abundances in samples from the larval rearing tank and pre-fattening tank. Other phyla (Verrucomicrobia, Actinobacteria, Firmicutes, Planktomycetes, Acidobacteria, Chloroflexi, Chlorobi, Gemmatiomonadetes or Fibrobacters) had lower relative abundances. A large fraction of the reads (ranging from 43.67% to 72.25%) were assigned to uncultured bacteria. Genus Acinetobacter (mainly A. calcoaceticus/bau- manni) was the predominant OTU in the aerator of the fattening tank and also in the nearby sink on the floor. The genera Cetobacterium and Bacteroides showed highest relative abundances in the samples from the larval rearing tank and the pre-fattening tank. Genera including fish pathogens (Fusobacterium, Aeromonas) were only detected at low relative abundances. Potential human pathogens other than Acinetobacter were either not de- tected or had very low relative abundances (< 0.01%). The results of the study suggest that the main risk factors to be monitored in tilapia farm are putative human pathogenic Acinetobacter and potential cyanotoxin-producing cyanobacteria. 1. Introduction Tilapia is an aquaculture food commodity of economic and global importance (Rafael, 2008). In 2014, the world aquacultue production of tilapia and other cichilids amounted 5308020 t (FAO, 2014). In Spain, tilapia farming is still very limited, but the sector is expected to rise in the near future (FAO, 2017). Tilapia farming generates and anthro- pogenic environment where different microbial communities develop. Deciphering the composition of bacterial communities in aquaculture ecosystems can be relevant for safety assessment of the food, evaluation of the risk of exposure to human pathogens, and adopting control measures intended to decrease the spread of possible pathogenic bac- teria. One study on bacteria associated with tilapia farming (pond water, pond sediment, fish gill and intestine) based on culture-dependent methods (Pakingking et al., 2015) revealed that Aeromonas hydrophila, Bacillus spp., Plesiomonas shigelloides, Shewanella putrefaciens, Pseudo- monas fluorescens, Staphylococcus spp. and Vibrio cholerae were the dominant bacteria identified in the gills and intestine of tilapia. These bacteria also dominated in the pond sediment and rearing water, except for the nil isolation of S. putrefaciens and V. cholerae in the water samples examined, indicating that resident bacteria in the pond water and sediment congruently typify the composition of bacterial micro- biota in the gills and intestine of tilapia which under stressful condi- tions may propel the ascendance of disease epizootics (Pakingking et al., 2015). http://dx.doi.org/10.1016/j.envres.2017.10.021 Received 27 August 2017; Received in revised form 10 October 2017; Accepted 12 October 2017 ☆ This work was supported by the University of Jaén (Research Structure AGR230). ⁎ Corresponding author. Present address: Área de Microbiología, Departamento de Ciencias de la Salud, Facultad de Ciencias Experimentales. Edif. B3, Universidad de Jaén, Campus Las Lagunillas s/n., 23071 Jaén, Spain. E-mail address: agalvez@ujaen.es (A. Gálvez). Environmental Research 160 (2018) 385–390 0013-9351/ © 2017 Elsevier Inc. All rights reserved. MARK