Seasonal and spatial patterns differ between intracellular and extracellular antibiotic resistance genes in urban stormwater runoff

Abstract

Antibiotic resistance is a public health threat that is exacerbated by the dispersion of antibiotic resistance genes (ARGs) into aquatic environments. Urban stormwater runoff has been recognized as a source...

Antibiotic resistance in urban stormwater: a review of the dissemination of resistance elements, their impact, and management opportunities

“…70 intI1 in urban stormwater supports this idea as it has been found to be significantly correlated with the ARGs sul1, bla TEM , and tetC as well as indicators of human sewage. 48,50,61 Correlation analysis, while effective to show probable relationships, does not prove mobility. Future research should remain focused on identifying the hosts of ARGs in urban runoff particularly as it relates to pathogenic bacteria and MGEs, but more rigorous analyses need to be established to confirm colocation and implications for the threat associated with ARGs hosts.…”

“…[48][49][50] Primarily, previous research has sought to describe the resistance elements in stormwater runoff by sampling at stormwater outfalls, where runoff from a larger urban area is piped and discharged into a water body (e.g., lake, river, reservoir) at one central point (Table 1). [48][49][50][51][52][53][54][55][56][57][58][59][60][61] The stormwater disseminated from outfalls is mostly runoff collected via overland flow, but stormwater can include sewage inputs as it travels through a storm sewer system. 56 The presence of sewage in stormwater can significantly alter the ARGs present and their concentration at an outfall.…”

“…The range in reported ARG concentration values is very large. sul1, a sulfonamide resistance gene, is the most frequently reported ARG in stormwater runoff with its concentration ranging from 1.66 × 10 3 to 4.68 × 10 9 gene copies per L. 48,55 tetA is a tetracycline resistance gene that has also been reported multiple times, with its concentration ranging from 3.80 × 10 3 to 1.36 × 10 7 gene copies per L. 52,61 Interestingly in a study that sampled from 12 outfall sites, the most of any study included in Table 1, they were able to conclude that sul1 and tetA were highly prevalent in stormwater as they were detectable in >95% of samples. 52 However, in one of the few studies that sampled stormwater directly from the ground, sul1 or tetA was not detected in any stormwater sample.…”

“…This research gap was recently addressed, in which it was found that stormwater runoff contributes to an increase in extracellular resistance elements in urban water bodies. 48 Moreover, eARGs displayed different seasonal and temporal dynamics from that of iARGs, highlighting the importance of including eARGs in comprehensively characterizing the dynamics influencing the resistome of urban runoff. 48 Beyond this one study, the fate and transport of eARGs in urban runoff and the impact of stormwater properties on the occurrence of eARGs and their rate of transformation remain unknown.…”

“…55 In addition to watershed dynamics, hydrologic factors such as the antecedent dry weather period, rainfall intensity, and rainfall duration are important concerns for the profile of resistance elements observed at stormwater outfalls. Specifically, long antecedent dry weather periods enable the buildup of contaminants on impervious surfaces that are able to be picked up and transported by stormwater, 48 while short, intense storms are able to mobilize a higher concentration of ARGs. 55,58 Such research exemplifies the dynamic nature of ARGs in runoff collected from urban environments, in addition to highlighting the number of factors that must be considered when designing a study for sampling stormwater.…”