Abstract
Hurricane-caused stormwater runoffs transport diverse terrestrial pollutants, adversely impact microbiological water quality, and introduce fecal and other pathogens to coastal water environments. This study investigated the genotypic diversity, phylogenetic composition, antibiotic resistance patterns, and virulence gene repertoire of the Enterococcus population in the Hilo Bay coastal water after the immediate impact of Hurricane Lane. DNA fingerprinting of Enterococcus isolates exhibited large genotypic diversity, while 16S rRNA gene sequencing identified four major species, including E. faecalis (34.7%), E. faecium (22.4%), E. hirae (22.4%), and E. durans (18.4%). Four common enterococcal virulence genes (cylA, esp, asa1, and gelE) were detected in the Enterococcus population, with significant portions of E. durans (33.3%), E. faecalis (41.2%), E. faecium (36.4%), and E. hirae (27.3%) isolates possessing two or more virulence genes. Considerable antibiotic resistance to rifampin, erythromycin, tetracycline, and nitrofurantoin was detected in the Enterococcus population, with one E. durans isolate showing vancomycin resistance. The results indicate considerable health implications associated with Enterococcus spp. in the hurricane-impacted tropical coastal water, illustrating the needs for more comprehensive understanding of the microbiological risks associated with storm-impacted coastal water.
Highlights
Hilo town area (Hawaii island, Hawaii), which has a tropical rainforest climate (NOAA 2021), is populated with dense sewer networks and a large number of on-site wastewater treatment systems (e.g. 8,700 cesspools; Silvius et al 2005) and is located next to the mouth of the Wailuku River
Diversity of Enterococcus in hurricane-impacted coastal water Forty unique genotypes out of a total 49 Enterococcus isolates were identified based on the similarities of the BOX A2R fingerprinting patterns, which were grouped into four major clusters (Figure 1)
Eleven genotypes comprised of E. faecium (n 1⁄4 8), E. durans (n 1⁄4 7), and E. faecalis (n 1⁄4 1) were grouped in cluster C, where one strain of E. durans which was resistant to vancomycin and one strain of E. faecium which was resistant to ampicillin were grouped together in this cluster
Summary
Hilo town area (Hawaii island, Hawaii), which has a tropical rainforest climate (NOAA 2021), is populated with dense sewer networks and a large number of on-site wastewater treatment systems (e.g. 8,700 cesspools; Silvius et al 2005) and is located next to the mouth of the Wailuku River. Hurricane Lane, a category five hurricane that affected the area during August 15–29, 2018, caused heavy rainfall over the Hilo town area and resulted in its wettest 3-day period on record in precipitation (80.9 cm) (Beven II & Wroe 2019). This unprecedented rainfall resulted in significant stormwater runoff and flooding, and sanitary sewer overflows due to rainfall-derived infiltration and inflow into the aging sewer infrastructures in the area. Pathogenicity of enterococci is contributed by several common virulence factors encoded by the asa, cylA, gelE, esp, and hyl genes ( Jett et al 1994). The hyl gene encodes hyaluronidase that is linked to increased gastrointestinal colonization in mouse models (Rice et al 2003)
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