Genetic diversity of three classes of integrons in antibiotic-resistant bacteria isolated from Jiulong River in southern China

Abstract

We identified antibiotic-resistant bacterial isolates from the surface waters of Jiulong River basin in southern China and determined their extent of resistance, as well as the prevalence and characterization of three classes of integrons. A phylogenetic analysis of 16S ribosomal DNA (rDNA) sequences showed that 20 genera were sampled from a total of 191 strains and the most common genus was Acinetobacter. Antimicrobial susceptibility testing revealed that the 191 isolates were all multiresistant and there were high levels of resistance to 19 antimicrobials that were tested, particularly the β-lactam, sulfonamide, amphenicol, macrolide, and rifamycin classes. Moreover, class 1 integrons were ubiquitous while only five out of 191 strains harbored class 2 integrons and no class 3 integrons were detected. The variable region of the class 1 integrons contained 30 different gene cassette arrays. Nine novel arrays were found in 65 strains, and seven strains had empty integrons. Among these 30 arrays, there were 34 different gene cassettes that included 25 resistance genes, six genes with unknown functions, two mutant transposase genes, and a new gene. The unique array dfrA1-sat2-aadA1 was detected in all five isolates carrying the class 2 integron. We found that antibiotic-resistant bacterial isolates from Jiulong River were diverse and antibiotic resistance genes associated with integrons were widespread.

Markers Specific to Bacteroides fragilis Group Bacteria as Indicators of Anthropogenic Pollution of Surface Waters

“…The present results corroborate the findings of other authors who reported on the dominance of the int I1 gene among integrase-encoding genes in environmental samples [ 67 ]. Integrons are ubiquitous in TWW [ 25 , 32 , 68 , 69 ] and in rivers such as the Vistula, Warta, and Łyna [ 29 , 60 , 70 , 71 ]. These genetic structures promote rapid bacterial evolution by enabling bacteria to accumulate, express, and transfer coding sequences such as ARGs [ 67 , 72 ].…”

Comparative genomics analysis of the multidrug-resistant Aeromonas hydrophila MX16A providing insights into antibiotic resistance genes

“…A. hydrophila strain MX16A was isolated from Jiulong River, Fujian, China ( Lin et al., 2015 ), and cultured with Luria-Bertani broth (Hopebio, Qingdao, China) at 30 °C in a shaking incubator for 24 h. In previous experiments, MX16A was found to be insensitive to a variety of antibiotics, and contain various resistance genes and virulence genes detected by PCR.The toxicity tests showed that the median lethal concentration (LD50) of A. hydrophila MX16A to zebrafish was 1.6×10 6 CFU/fish, indicating that MX16A had pathogenicity to aquatic animals. Antimicrobial susceptibility testing was performed using the Kirby-Bauer disk diffusion method (OXOID, UK).…”