Evidence of Increased Antibiotic Resistance in Phylogenetically-Diverse Aeromonas Isolates from Semi-Intensive Fish Ponds Treated with Antibiotics

Abstract

The genus Aeromonas is ubiquitous in aquatic environments encompassing a broad range of fish and human pathogens. Aeromonas strains are known for their enhanced capacity to acquire and exchange antibiotic resistance genes and therefore, are frequently targeted as indicator bacteria for monitoring antimicrobial resistance in aquatic environments. This study evaluated temporal trends in Aeromonas diversity and antibiotic resistance in two adjacent semi-intensive aquaculture facilities to ascertain the effects of antibiotic treatment on antimicrobial resistance. In the first facility, sulfadiazine-trimethoprim was added prophylactically to fingerling stocks and water column-associated Aeromonas were monitored periodically over an 11-month fish fattening cycle to assess temporal dynamics in taxonomy and antibiotic resistance. In the second facility, Aeromonas were isolated from fish skin ulcers sampled over a 3-year period and from pond water samples to assess associations between pathogenic strains to those in the water column. A total of 1200 Aeromonas isolates were initially screened for sulfadiazine resistance and further screened against five additional antimicrobials. In both facilities, strong correlations were observed between sulfadiazine resistance and trimethoprim and tetracycline resistances, whereas correlations between sulfadiazine resistance and ceftriaxone, gentamicin, and chloramphenicol resistances were low. Multidrug resistant strains as well as sul1, tetA, and intI1 gene-harboring strains were significantly higher in profiles sampled during the fish cycle than those isolated prior to stocking and these genes were extremely abundant in the pathogenic strains. Five phylogenetically distinct Aeromonas clusters were identified using partial rpoD gene sequence analysis. Interestingly, prior to fingerling stocking the diversity of water column strains was high, and representatives from all five clusters were identified, including an A. salmonicida cluster that harbored all characterized fish skin ulcer samples. Subsequent to stocking, diversity was much lower and most water column isolates in both facilities segregated into an A. veronii-associated cluster. This study demonstrated a strong correlation between aquaculture, Aeromonas diversity and antibiotic resistance. It provides strong evidence for linkage between prophylactic and systemic use of antibiotics in aquaculture and the propagation of antibiotic resistance.

Biofilm and Sediment are Major Reservoirs of Virulent Aeromonas hydrophila (vAh) in Catfish Production Ponds

“…; Patil et al. ). Many studies have tried to identify the environmental factors that affect abundance and distribution of A. hydrophila , primarily due to its potential as a human pathogen (Pettibone ; Lee et al.…”

Abundance and antibiotic resistance of Aeromonas isolated from the water of three carp ponds

“…Intensive fish farming in recent years has resulted in growing problems of bacterial diseases, which led to a widespread antibiotic use for their treatment (Guz and Kozinska 2004;Daood 2012). Wide use of antibiotics to prevent and treat bacterial diseases and the application of subtherapeutic dose of antibiotics have inducted a global increase in the levels of antibiotic resistance among pathogenic bacteria in fish farming (Patil et al 2016;Mulyani et al 2018). As a result, the development of antibiotic resistance among aquatic bacterial pathogens will ultimately reduce the efficiency of antimicrobial agents used for treating and can favour the development of resistant bacteria in native fish species (Belèm-Costa and Cyrino 2006).…”

Antibiotic resistance and virulence factors in mesophilic Aeromonas spp. from Czech carp fisheries

“…Aeromonads isolated from fresh fish were found to frequently carry resistance to oxytetracycline (Nawaz et al 2006;Cizek et al 2010) or quinolones (Alcaide et al 2010;Dobiasova et al 2014). Because of their higher ability to transfer resistance genes via mobile genetic elements, they are able to ensure a broad expansion of the genes within bacterial populations (Janda and Abbott 2010;Patil et al 2016). Aeromonads also carry several virulence factors, such as adhesins, haemolysins, cytotoxins, enterotoxins, lipases, proteases, the type II secretion system, the type III secretion system (T3SS), the type VI secretion system and genes for biofilm production, enabling them to overcome the secure system of the host and to infect various tissues (Rasmussen-Ivey et al 2016).…”