Prevalence and transmission of antimicrobial resistance among Aeromonas populations from a duckweed aquaculture based hospital sewage water recycling system in Bangladesh

Abstract

In order to investigate the influence of a duckweed aquaculture based hospital sewage water recycling plant on the prevalence and dissemination of antibiotic resistance, we made use of an existing collection of 1,315 Aeromonas isolates that were previously typed by the biochemical fingerprinting PhP-AE system. In these treatment plant, hospital raw sewage water is first collected in a settlement pond (referred to as sewage water in this study) and is then transferred to a lagoon, where the duckweed (Lemnaceae) is grown (referred to as lagoon). The duckweed is harvested and used as feed for the fish in a separate pond (referred to as fish pond). From this collection, representatives of 288 PhP types were subjected to antibiotic susceptibility testing for eight antimicrobials by broth microdilution method. The overall resistance rates among Aeromonas isolates from the treatment plant were highest for ampicillin (87%) and erythromycin (79%) followed by cephalothin (58%), nalidixic acid (52%), streptomycin (51%), tetracycline (31%), chloramphenicol (13%) and gentamicin (8%). A significantly lower prevalence of antibiotic resistance was found in Aeromonas from environmental control water, patient stool samples, duckweed and fish compared to sewage water isolates. The prevalence of resistance in the sewage water was not significantly reduced compared to the lagoon water and fish pond. Throughout the treatment system, the frequencies of resistant strains were found to diminish during the sewage water purification process, i.e. in the lagoon where sewage water is used to grow the duckweed. However, the frequency of resistant strains again increased in the fish pond where sewage grown duckweed is used for aquaculture. Among the selected isolates, two multiresistant clonal groups of Aeromonas caviae HG4 were identified that exhibited indistinguishable PhP and amplified fragment length polymorphism fingerprints and shared a common plasmid of approximately 5 kb. Representatives of both groups were recovered from almost every part of the sewage treatment plant but not in the control ponds nor in human samples, which suggests that specific multiresistant Aeromonas clones are able to persist and spread throughout the entire purification process.

Antibiotic Resistant Bacteria in the Environment as Bio-Indicators of Pollution

“…For example, an important part of sewage water purification in the future will be monitoring the influence of the process on the antimicrobial susceptibility profiles of bacterial indicators that could spread to the environment and to humans [33].…”

“…First, it is well documented that it allows antibiotic resistance determinants to spread from one species of bacteria to another [30 -32]. For example, there is good evidence for horizontal transfer of resistance genes between bacteria that cause infections in animals and those that cause infection in humans [33]. Second, resistance determinants for multiple antibiotics can potentially be transmitted at the same time.…”

Antibiotic resistant bacteria in terrestrial and aquatic environments: A review

“…This sort of transfer apparently occurs quite commonly within environmental reservoirs where resistance genes are generated by mutation, where bacteria and antimicrobial agents coexist, and where the bacterial population is high. There is strong evidence for horizontal transfer of resistance genes between bacteria that cause infections in animals and those that cause infection in humans [28]. It was reported that environmental isolates of MARB could transfer resistance to previously susceptible normal flora Escherichia coli [29].…”

Survival and Growth of Bacteria in Treated Wastewater and Water Distribution Systems and their Implication in Human Health: A review

“…Some new technologies that have potential for more efficient waste treatment are essential. Note that an important part of sewage water purification in the future will be monitoring the influence of the process on the antimicrobial susceptibility profiles of bacterial indicators that could spread to the environment and to humans [59].…”