Antibiogram, Adhesive Characteristics, and Incidence of Class 1 Integron in Aeromonas Species Isolated from Two South African Rivers

Aeromonas species are well distributed in freshwater environments, and their natural susceptibility to antimicrobials renders them interesting candidates for the survey of antimicrobial resistance in freshwater milieu. Water samples were collected from Kat and Tyume rivers in the Eastern Cape province of South Africa, and a total of 45 isolates identified as Aeromonas species were recovered from the two rivers. All Aeromonas isolates were resistant to oxacillin, penicillin, clindamycin, cephalothin, vancomycin, and rifamycin, while appreciable susceptibilities (89.3 : 94.1%, 82.1 : 94.1%, 85.7 : 88.2%, and 92.9 : 88.2%) were observed against ciprofloxacin, chloramphenicol, nitrofurantoin, and gentamicin from Kat and Tyume rivers, respectively. Multiple antibiotic resistance (MAR) indices ranged from 0.016 to 0.044 for the two rivers. Class 1 integron was detected in about 20% of the isolates, and all the isolates except one showed ability to produce biofilm in vitro as weak producers (53.33%), moderate producers (15.56%), and strong producers (28.9%). This investigation provides a baseline data on antibiotic resistance as well as the adhesive characteristics of Aeromonas isolates from Tyume and Kat rivers in the Eastern Cape province of South Africa.