Isolation, molecular characterization and antimicrobial susceptibility ofAeromonasspp. obtained from Tiger Grouper (Epinephelus fuscoguttatus) and Marble Goby (Oxyeleotris marmoratus) fish in Sabah, Malaysia

Abstract

Aeromonads are ubiquitous in aquatic environments and have been implicated in fish and human infections. In this study, we isolated, studied antimicrobial susceptibility patterns and screened the existence of 15 virulence genes in aeromonads from two famously consumed fish species—seven marine Tiger Grouper (Epinephelus fuscoguttatus) and eight freshwater Marble Goby (Oxyeleotris marmoratus) from the aquaculture hatchery in Sabah, Malaysia. A total of 30 aeromonads (17 A. caviae, 9 A. rivuli, 4 A. dhakensis) were identified using PCR targeting GCAT gene, rpoD‐restriction fragment length polymorphism and multi‐locus phylogenetic analysis. All 30 strains were resistant to amoxicillin and cephalothin and five strains were multidrug‐resistant. Nine virulence genes (lip, ela, eno, fla, aerA, hylA, dam, alt and ser) present in A. dhakensis, suggesting the virulence potential of this species as a fish pathogen. This study offers as a baseline for future studies in monitoring and managing these two fish in aquaculture industry.

Resistance of Aeromonas hydrophila isolates to antimicrobials and sanitizers

“…Multidrug resistance, characterized as resistance to at least one antibiotic in three or more classes (JEONG et al, 2007), was evidenced in this study, as the A. hydrophila isolates recovered from retail fish showed resistance to at least one antibiotic in all the classes investigated. This phenomenon may be attributed to the indiscriminate use of antimicrobials in aquaculture, genetic mutations, or the horizontal dissemination of resistance genes (LAU et al, 2020).…”

“…Young colonies of A. hydrophila on TSA were suspended in sterile water and boiled for 10 min in a dry bath (thermoblock) according to the methods described by PARK et al (2021) andLAU et al (2020). Then, each suspension was centrifuged at 24,104 × g for 5 min, following which the supernatant containing total genomic DNA was collected and quantified using a NanoDrop spectrophotometer.…”

Aeromonas dhakensis: Clinical Isolates with High Carbapenem Resistance

“…Among the three carbapenems, the AST for meropenem of the 94 clinical isolates and 4 non-clinical isolates from food fish (Marble Goby) was previously reported using the Kirby–Bauer disk diffusion method [ 11 , 12 ]. However, in these studies, only one meropenem resistant clinical isolate was detected, and no resistance was observed in food fish isolates.…”

“…A total of 117 A. dhakensis isolates were retrieved from previous studies [ 7 , 8 , 9 , 10 , 11 , 12 , 22 ]. These isolates consisted of 94 clinical isolates from Malaysia and Singapore and 23 non-clinical isolates from Malaysia ( Table 4 ).…”

“…Our previous studies conducted since 2012 identified A. dhakensis as the predominant species (47/94, 50%) among clinical isolates in Malaysia by using a combination gene analysis of GCAT and rpoD genes, as well as multilocus sequence typing [ 7 , 8 ]. Following these studies, the presence of A. dhakensis was reported from aquatic sources in Malaysia, including multipurpose freshwater recreational lakes in Selangor [ 9 ], tank water of ornamental fish in Klang Valley [ 10 ], food fish in East Malaysia [ 11 ] and as clinical isolates of A. dhakensis in Singapore [ 12 ]. All aforementioned studies shed light on the clinical relevance of A. dhakensis and its ability to present/colonise various sources posing public health concerns.…”