Biofilm-Producing Ability and Antibiotic Resistance Pattern of Pathogenic Strains of Aeromonas hydrophila

Interconnection among bacteria and other infectious agents can transfer the genetic elements such as antibiotic resistance genes. Biofilm or such an established structure could worsen when pathogenic bacteria are in the community. The recognition of bacterial behaviors and characteristics in biofilm community or planktonic forms such as antibiotic resistance spreading is an important and essential matter.

The current study aimed at investigating the correlation between biofilm-producing ability and antibiotic resistance patterns in some pathogenic strains of Aeromonas hydrophila.

In this study, 19 strains of A. hydrophila isolated from infected carps with septicemia were identified by culture and biochemical tests. The isolated strains suspected as A. hydrophila were confirmed by duplex-PCR at both genus and species levels. The biofilm-producing ability of the confirmed isolates was evaluated by the microtiter plate crystal violet method. Antibiogram was designed for isolates by the Kirby-Bauer disc diffusion method.

All the strains were positive for biofilm production ability. Moderate and strong biofilm-producing abilities were detected in 79% and 21% of the isolates, respectively. The majority of the strains (90%) were resistant to clindamycin and vancomycin and all the strains (100%) were susceptible to ciprofloxacin and trimethoprim-sulfamethoxazole.

Strong biofilm-producing strains were resistant to 75% of the studied antibiotics but moderate biofilm-producing strains had different susceptibility rates to the studied antibiotics. An important correlation was detected between the biofilm-producing level (moderate and strong) and antibiotic resistance against tetracycline, oxytetracycline, and amoxicillin. Because of the different ways of resistance acquisition in biofilm-producing bacteria, more studies are needed for understanding the main route.