Abstract
Bacterial isolates found in aquatic ecosystems often carry antibiotic resistance genes (ARGs). These ARGs are often found on plasmids and transposons, which allows them to be proliferate throughout bacterial communities via horizontal gene transfer (HGT) causing dissemination of multidrug resistance. The increase in antibiotic resistance has raised concerns about the ability to continue to use these drugs to fight infectious diseases. Novel synthetic antibiotics like ciprofloxacin that are not naturally found in the environment were developed to prevent resistances. However, ciprofloxacin resistance has occurred through chromosomal gene mutations of type 2 topoisomerases or by the acquisition of plasmid-mediated quinolone resistances (PMQR). A particular PMQR, qnr genes, encoding for pentapeptide repeat proteins that confer low levels of quinolone resistance and protect DNA gyrase and topoisomerase IV from antibacterial activity. These qnr genes have been identified globally in both clinical and environmental isolates. The aim of this study was to determine the prevalence of ciprofloxacin-resistant bacteria in aquatic environments in the Greater Toronto Area and the potential dissemination of ciprofloxacin resistance. With the selective pressure of ciprofloxacin, we hypothesize that ciprofloxacin-resistant bacteria (CipR) in the environment may carry PMQR mechanisms while the sensitive population (CipS) would not carry PMQR genes. Isolates were tested for resistance to an additional 12 different antibiotics and identified using Sanger sequencing PCR products of the 16S rRNA gene. To determine which genes are responsible for ciprofloxacin resistance, multiplex PCR of associated qnr genes, qnrA, qnrB, and qnrS, was carried out on 202 environmental isolates. Our data demonstrate a similar prevalence of qnr genes was found in CipR (19%) and CipS (14%) populations suggesting that the presence of these genes was not necessarily correlated with the phenotypic resistance to the antibiotic. Furthermore, ciprofloxacinresistant bacteria were found in all locations at similar frequencies suggesting that resistance genes are widespread and could possibly arise through HGT events. Overall, determining the underlying cause and prevalence of ciprofloxacin resistance could help re-establish the effectiveness of these antimicrobial compounds.
Highlights
IntroductionFrom bringing mankind from the dark ages and extending the average lifespan, antibiotics have been a crucial tool in modern-day medicine
1.1 Antibiotics, their Usage and MisusageFrom bringing mankind from the dark ages and extending the average lifespan, antibiotics have been a crucial tool in modern-day medicine
Ciprofloxacin resistance was observed in all sampling locations with percentages ranging from 0.12 to 1.62% of the culturable heterotrophic bacteria except at the Lake Devo site immediately after disinfection (Figure 8 and Table 2)
Summary
From bringing mankind from the dark ages and extending the average lifespan, antibiotics have been a crucial tool in modern-day medicine. The benefits of antibiotic usage for treating infectious diseases has saved millions of lives over the 90 years since their discovery. Access to these drugs has allowed better development and standards of medical practices such as organ transplants and primary care.[1,2]. In the pre-antibiotic era and most of history, bacterial infections have been the number one cause of death. Pre-antibiotic average life expectancy was 47 years in industrialized countries, illustrating the high morbidity and mortality rates worldwide of infectious diseases.[3]. The wide distribution of antibiotics has been implemented in human and veterinary medicine and agricultural practices
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