Characterization of tetracycline-resistant bacteria in an urbanizing subtropical watershed

Abstract

Aims: The objective of this study was to determine whether varying levels of urbanization influence the dominant bacterial species of mildly resistant (0Á03 mmol l À1 tetracycline) and highly resistant (0Á06 mmol l À1 tetracycline) bacteria in sediment and water. Also, the level of urbanization was further evaluated to determine whether the diversity of tetracycline resistance genes present in the isolates and the capability of transferring their resistance were influenced. Methods and Results: Sediment and water samples collected from five sampling sites were plated in triplicate on nutrient agar plates with a mild dose (0Á03 mmol l À1 ) and a high dose (0Á06 mmol l À1 ) of tetracycline. Five colonies from each plate plus an additional five from each triplicate group were randomly selected and isolated on nutrient agar containing 0Á03 mmol l À1 tetracycline (400 isolates). The isolates were identified by 16S rRNA gene sequencing and comparison to GenBank using BLAST. The isolates were also screened for 15 tetracycline resistance genes using a multiplex PCR assay and their ability to transfer resistance through conjugation experiments using a kanamycin-resistant Escherichia. coli K-12 strain labelled with a green fluorescent protein gene. Results from this study indicate that the dominant resistant organisms in this watershed are Acinetobacter spp., Chryseobacterium spp., Serratia spp., Pseudomonas spp., Aeromonas spp. and E. coli. All of these organisms are Gram negative and are closely related to pathogenic species. A majority of the isolates (66%) were capable of transferring their resistance, and there was a greater incidence of tet resistance transfer with increasing urbanization. Also, it was determined that the dominant resistance genes in the watershed are tet(W) and tet(A). Conclusion: Urbanization significantly affected dominant tetracycline-resistant bacteria species, but did not affect dominant resistance genes. There was correlation between increased urbanization with an increase in the ability to transfer tetracycline resistance. This indicates that urban areas may select for bacterial species that are capable of transferring resistance. Significance and Impact of Study: These results indicate that urbanization influences the occurrence of tetracycline-resistant bacteria and the potential for transfer of resistance genes.

Origins and environmental mobility of antibiotic resistance genes, virulence factors and bacteria in a tidal creek's watershed

“…Since TRG incidence frequency was more than two‐fold higher in Hog Hammock's, this village was most likely the main contributor to TRGs in the watershed, however, free ranging cattle, high densities of whitetail deer and a large stork and egret rookery may have also contributed. Impact of land use on the occurrence of antibiotic resistance genes in densely populated watersheds (Sullivan and Karthikeyan ), and correlation between antibiotic resistance of animal‐associated E. coli and the density of human populations in animals' vicinities (Skurnik et al . ) have been previously suggested.…”

Removal of tetracycline by aerobic granular sludge and its bacterial community dynamics in SBR

“…The Chryseobacterium is highly resistant to several antimicrobial drugs, such as the third generation cephalosporins, aminoglycoside, carbapenemases and tetracycline. [32][33][34] Its drugresistance mechanism is due to the production of b-lactamase induced by chromosomes, except outside the permeable barrier of the bacterial membrane. The Actinotignum was enriched in R1 reactor with the relative abundance increasing from 0.73% to 19.97%, which was probably because the Actinotignum adapted to the operational conditions of the AGSBR technology with time.…”

“…The Actinotignum became the most dominant genus of AGS in R1-6 and R2-6. The study showed that the bacterial genus could take tetracycline as the carbon source, [32][33][34] which was helpful for removing tetracycline. The Actinotignum is more common than implied by routine cultivation.…”

Examination of the Aerobic Microflora of Swine Feces and Stored Swine Manure

“…Interestingly, the use of Nutrient Broth agar for plating resulted in at least a 10-fold reduction in recovery of strains for both feces and manure. Nutrient agar has been previously used in recovering tetracycline-resistant bacteria from soil and water environments (Sullivan and Karthikeyan, 2011;Sullivan et al, 2013), so it is important to note the improved recovery of isolates using BHI or T-Soy media versus Nutrient Broth agar. The use of habitat-simulating medium for manure samples resulted in recovery of strains similar to that of BHI and T-Soy.…”