Assessing the Occurrence of Carbapenemase Producers Using Marine Animals as Sentinel Species

Abstract

Carbapenemase-producing (CP) strains represent a substantial global threat, deactivating carbapenems and conferring resistance to β-lactam antibiotics. They can spread across various environments, yet data on their presence in marine animals are sparse. This study aimed to assess the occurrence of carbapenemase-producing strains in wild marine animals and to analyse their antimicrobial resistance (AMR) profiles to crucial antimicrobials and heavy metals frequently encountered in the marine environment due to anthropogenicactivity. A total of 28 samples were obtained from a fish auction in the Centre Region of Portugal. Non-fermenting bacilli (NFB) was isolated from the visceral content of wild marine animals. Identification of isolates was achieved through PCR-based amplification of the 16S rRNA gene, followed by sequencing. Antimicrobial susceptibility testing was conducted according to EUCAST guidelines, covering nine antimicrobials. Research of carbapenemases and metal tolerance genes was conducted by PCR, and statistical analysis utilized the Fisher’s exact test. Pseudomonas spp. and Aeromonas spp., among other isolates were identified (n=47/9/7, respectively). Susceptibility profiles showed 100% resistance or intermediate resistance to ticarcillin, piperacillin, piperacillin-tazobactam, ceftazidime, ciprofloxacin, and imipenem (n=63/63), while 27% were resistant to meropenem (n=17/63) and 13% to tobramycin (n=8/63). All of them exhibited susceptibility to amikacin and carried multidrug resistance (MDR) profiles, including heavy metal genes (merA and silA). None harboured the carbapenemase genes searched (blaKPC, blaGES, blaIMP, blaNDM or/and blaVIM). In this study, MDR profiles to clinically important antimicrobials were observed, including to carbapenems. However, no carbapenemase-producing strains were identified, suggesting the presence of other genes or alternative mechanisms of resistance. These findings underscore the importance of monitoring AMR in marine ecosystems, particularly given its close ties to the food chain.