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Municipal wastewater includes human waste that contains both commensal and pathogenic enteric microorganisms, and this collective community microbiome can be monitored for community diseases. In a previous study, we assessed the salmonellosis disease burden using municipal wastewater from Honolulu, Hawaii, which was monitored over a 54-week period. During that time, a strain of Salmonella enterica serovar Paratyphi B variant L(ϩ) tartrate(ϩ) (also known as Salmonella enterica serovar Paratyphi B variant Java) was identified; this strain was detected simultaneously with a clinically reported outbreak, and pulsed-field gel electrophoresis patterns were identical for clinical and municipal wastewater isolates. Months after the outbreak subsided, the same pulsotype was detected as the dominant pulsotype in municipal wastewater samples, with no corresponding clinical cases reported. Using genomic characterization (including core single-nucleotide polymorphism alignment, core genome multilocus sequence typing, and screening for virulence and antibiotic resistance genes), all S. Java municipal wastewater isolates were determined to be clonal, indicating a resurgence of the original outbreak strain. This demonstrates the feasibility and utility of municipal wastewater surveillance for determining enteric disease outbreaks that may be missed by traditional clinical surveillance methods. IMPORTANCE Underdetection of microbial infectious disease outbreaks in human communities carries enormous health costs and is an ongoing problem in public health monitoring (which relies almost exclusively on data from health clinics). Surveillance of municipal wastewater for community-level monitoring of infectious disease burdens has the potential to fill this information gap, due to its easy access to the mixed community microbiome. In the present study, the genomes of 21 S. Java isolates (collected from municipal wastewater in Honolulu) were analyzed; results showed that the same Salmonella strain that caused a known salmonellosis clinical outbreak in spring 2010 remerged as the most dominant strain in municipal wastewater in spring 2011, indicating a new outbreak that was not detected by health clinics. Our results show that wastewater monitoring holds great promise to inform the field of public health regarding outbreak status within communities.

Clinical surveillance of enteric pathogens like Salmonella is integral to track outbreaks and endemic disease trends. However, clinic-centered disease monitoring biases toward detection of severe cases and underestimates the incidence of self-limiting gastroenteritis and asymptomatic strains. Monitoring pathogen loads and diversity in municipal wastewater (MW) can provide insight into asymptomatic or subclinical infections which are not reflected in clinical cases. Subclinical infection patterns may explain the unusual observation from a year-long sampling campaign in Hawaii: Salmonella Derby was the most abundant pulsotype in MW but was detected infrequently in clinics over the sampling period. Using whole genome sequencing data of Salmonella isolates from MW and public databases, we demonstrate that the Derby serovar has lower virulence potential than other clinical serovars, particularly in genes linked with immune evasion and symptom production, suggesting its potential as a subclinical salmonellosis agent. Furthermore, MW had high abundance of a rare Derby MLST sequence type, ST-72 (rather than the more common Derby ST-40). ST-72 isolates had higher frequencies of fimbrial adherence genes than ST-40 isolates; these are key virulence factors involved in colonization and persistence of infections. However, ST-72 isolates lack the Derby-specific Salmonella Pathogenicity Island SPI-23, which invokes host immune responses. In combination, ST-72's genetic features may lead to appreciable infection rates without obvious symptom production, allowing for subclinical persistence in the community. This study demonstrates wastewater's capability to provide community infectious disease information – such as background infection rates of subclinical enteric illness – which is otherwise inaccessible through clinical approaches. IMPORTANCE Wastewater-based epidemiology (WBE) has been conventionally used to analyze community health via the detection of chemicals, such as legal and illicit drugs; however, municipal wastewater contains microbiological determinants of health and disease as well, including enteric pathogens. Here, we demonstrate that WBE can be used to examine subclinical community salmonellosis patterns. Derby was the most abundant Salmonella serovar detected in Hawaii wastewater over a year-long sampling study, with few corresponding clinical cases. Comparative genomics analyses indicate that the normally rare strain of S. Derby found in wastewater has a unique combination of genes which allow it to persist as a subclinical infection without producing symptoms of severe gastroenteritis. This study shows that WBE can be used to explore trends in community infectious disease patterns which may not be reflected in clinical monitoring, shedding light on overall enteric disease burden and rates of asymptomatic cases.

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This study assessed the impact of chemical coagulation using alum on the removal of three endocrine-disrupting compounds (EDCs; bisphenol A, clofibric acid and estriol) and nine pharmaceutically active compounds (PhACs; acetaminophen, carbamazepine, diclofenac, gemfibrozil, ketoprofen, naproxen, pentoxifylline, sulfamethoxazole and sulfachloropyridazine). The impact on natural organic matter (NOM) fractions as determined using liquid chromatography–organic carbon detection (LC–OCD; total dissolved organic carbon (DOC), hydrophobic DOC, biopolymers, humic substances, building blocks, low molecular weight neutrals and acids) was also examined. Three test surface waters were included: Lake Ontario, Grand River and Otonabee River water (Ontario, Canada). Gemfibrozil concentrations were reduced in both Otonabee and Grand River waters. Reductions were noted for carbamazepine and (inconsistently) for acetaminophen, and estrone appeared to increase in concentration in Grand River water with increasing alum doses. NOM removal was primarily attributed to the humic fraction, with small reductions in biopolymers in all of the waters studied.