Characterization and detection of antibiotic resistance, virulence gene elements and biofilm formation in Aeromonas species isolated from cattle
Isoken H. Igbinosa
Department of Environmental Management and Toxicology, Faculty of Life Science University of Benin, Private Mail Bag 1154 Benin City 300283, Nigeria
This study aimed to assess the antibiogram of Aeromonas strains recovered from cattle faeces and the potential pathogenic status of the isolates.
Aeromonas species are potential food-poisoning agents; some species of Aeromonas are psychrotrophic in nature and have been associated with the spoilage of animal meat including chicken and beef. Aeromonas species produce toxins at low temperature when growth conditions become suitable.
Material and Methods:
All strains were grown on Tryptone Soya Agar for 24 - 48 h at 37oC. All strains were biochemically identified at the genus level by standard culture based methods. Molecular characterization of Aeromonas species, multiplex PCRs was performed using primer sets to detect lipase, elastase, DNA gyrase B, gyrB-veronii, gyrB-bestiarum, hydrolipase, and Veronii-16S genes and primer sets corresponding to species-specific signature regions of the 16S rRNA genes. Antimicrobial susceptibilities were determined by the agar dilution method as described by Clinical Laboratory Standard Institute guidelines.
The antibiogram of the Aeromonas isolates demonstrated total resistance to clindamycin oxacillin, trimethoprim, novobiocin and ticarcillin. However, Aeromonas strains were sensitive to cefotaxime, oxytetracycline and tobramycin. The Aeromonas strains from Fort Cox and Lovedale farms were found to possess some virulence genes. The percentage distribution was aer 71.4%, ast 35.7%, fla 60.7%, lip 35.7% and hlyA 25% for Lovedale farm and aer 63.1%, alt 10.5%, ast 55.2%, fla 78.9%, lip 21% and hlyA 35.9% for Fort Cox farm. Class 1 integron was present in 27% of Aeromonas isolates; the blaTEM gene was present in 34.8%, while the blaP1 class A β-lactamase gene was detected in 12.1% of the isolates. Approximately 86% of the isolates formed a biofilm on microtiter plates.
The presence of multiple antibiotic resistance and virulence genes in Aeromonas isolates from cattle faeces reveals the pathogenic and infectious importance of these isolates and is of great significance to public health. The possession of a biofilm-forming capability by such isolates may lead to difficulty during the management of infection related to Aeromonas species.