engleski

Multi-drug resistant Aeromonas, pathogenic and spoilage bacteria detected in fish from karst river environment

Although karst aquifers supply around 25% of population with drinking water (Ford & Williams, 1989), there is a shortage of microbiological studies concentrated on pathogenic and antibiotic resistant bacteria in karst aquatic environment. Karst rivers are particularly vulnerable aquatic environments due to poor filtering of any potential contamination through permeable karst rocks. Especially genus Aeromonas, ubiquitous in aquatic environments, have been recommend as a good indicator of antibiotic pollution in aquatic environments on the basis of their adaptability in both polluted and pristine environments and increasing number of resistant strains (Figueroa et al., 2011 ; Odeyemi & Ahmad, 2015 ; Usui et al., 2016 ; Varela et al., 2016 ; Baron et al., 2017). Investigation was conducted in September 2016 on 3 karst rivers (Kupa, Mrežnica and Dobra), located at the south-west edge of Black Sea basin in Croatian karst. Study sites are within fishing area of significance for commercial fisheries, aquaculture and sports fisheries. Physico-chemical parameters and microbiological quality of river water were analysed. River water quality varied between I. and II. class for all sampling sites, while microbiological quality varied in number of total coliforms, enterococci and heterotrophic bacteria. Swab samples from fish organs (gills, spleen, liver and kidneys) were cultured and 94 isolates were identified by MALDI-TOF MS. Genus Aeromonas was dominant in fish microbiota and tested for antibiotic sensitivity by disc diffusion method. Aeromonas isolates known as most pathogenic were selected (A. veronii, A. veronii biovar sobria, A. sobria, A. caviae) and tested for ampicillin, chloramphenicol, enrofloxacin, erythromycin, florfenicol, flumequine, nitrofurantoin, norfloxacin, novobiocin, ofloxacin, oxytetracycline, penicillin, piperacillin, tetracycline and trimethoprim resistance. Half of isolates demonstrated resistance to three or more antibiotic categories. Even though 42.5% isolates were identified as genus Aeromonas, the highest number of identified genera belonged to family Enterobacteriaceae (Butiauxella, Citrobacter, Serratia, Plesiomonas, Pantoea, Hafnia, Edwardsiella etc.), with majority of them known as pathogenic bacteria for humans and animals, and spoilage bacteria for fish. Hence, this investigation provides new insights in the health of the investigated karst rivers, which may reflect on animals and human health.

Karst rivers ; fish ; Aeromonas ; multi-drug resistance ; pathogenic bacteria ; spoilage bacteria

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