The prevalence of antibiotic-resistant bacteria (ARB) in waters of the Lower Ballona Creek Watershed, Los Angeles County, California.

Screening for the prevalence of antibiotic-resistant bacteria (ARB) was done at the Ballona Creek and Wetlands, an urban-impacted wetland system in Los Angeles, California. The goals were (1) to assess the overall prevalence of ARB, and (2) compare differences in ARB abundance and the types of antibiotic resistance (AR) among the following sample types: lagoon water from Del Rey Lagoon, urban runoff from Ballona Creek, and water from the Ballona Wetlands (tidal water flooding in from the adjacent estuary, and ebbing out from the salt marsh). Antibiotic resistance distributions were analyzed using the Kolmogorov-Smirnov test to develop the cumulative frequency of bacteria having resistance of up to eight antibiotics. Distributions from the environmental water samples were compared to unchlorinated secondary effluent from the Hyperion Water Reclamation Plant that was used as comparator samples likely to have an abundance of ARB. As expected, densities of total and ARB were highest in secondary effluent, followed by urban runoff. Samples of water flooding into the wetlands showed similar results to urban runoff; however, a reduction in densities of total and ARB occurred in water ebbing out of the wetlands. During preliminary work to identify ARB species, several bacterial species of relevance to human illness (e.g., Staphylococcus aureus, Enterococcus hirae, Pseudomonas aeruginosa, Aeromonas veronii, Enterobacter cancerogenus, Serratia marcescens, Pseudomonas stutzeri, and Staphylococcus intermedius) were isolated from sampled waters. If wetlands are a sink for ARB, construction and restoration of wetlands can help in the mediation of this human and environmental health concern.