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ABSTRACT Vibrio spp. and phytoplankton are naturally abundant in marine environments. Recent studies have suggested that the co-occurrence of phytoplankton and the pathogenic bacterium Vibrio parahaemolyticus is due to shared ecological factors, such as nutrient requirements. We compared these communities at two locations in the Delaware Inland Bays, representing a site with high anthropogenic inputs (Torquay Canal) and a less developed area (Sloan Cove). In 2017 to 2018, using light microscopy, we were able to identify the presence of many bloom-forming algal species, such as Karlodinium veneficum , Dinophysis acuminata , Heterosigma akashiwo , and Chattonella subsalsa . Dinoflagellate biomass was higher at Torquay Canal than that at Sloan Cove. D. acuminata and Chloromorum toxicum were found only at Torquay Canal and were not observed in Sloan Cove. Most probable number real-time PCR revealed V. parahaemolyticus and Vibrio vulnificus in environmental samples. The abundance of vibrios and their virulence genes varied between sites, with a significant association between total dissolved nitrogen (TDN), PO 4 − , total dissolved phosphorus (TDP), and pathogenic markers. A generalized linear model revealed that principal component 1 of environmental factors (temperature, dissolved oxygen, salinity, TDN, PO 4 − , TDP, NO 3 :NO 2 , NO 2 − , and NH 4 + ) was the best at detecting total ( tlh+ ) V. parahaemolyticus , suggesting that they are the prime drivers for the growth and distribution of pathogenic Vibrio spp. IMPORTANCE Vibrio-associated illnesses have been expanding globally over the past several decades (A. Newton, M. Kendall, D. J. Vugia, O. L. Henao, and B. E. Mahon, Clin Infect Dis 54:S391–S395, 2012, https://doi.org/10.1093/cid/cis243 ). Many studies have linked this expansion with an increase in global temperature (J. Martinez-Urtaza, B. C. John, J. Trinanes, and A. DePaola, Food Res Int 43:10, 2010, https://doi.org/10.1016/j.foodres.2010.04.001 ; L. Vezzulli, R. R. Colwell, and C. Pruzzo, Microb Ecol 65:817–825, 2013, https://doi.org/10.1007/s00248-012-0163-2 ; R. N. Paranjpye, W. B. Nilsson, M. Liermann, and E. D. Hilborn, FEMS Microbiol Ecol 91:fiv121, 2015, https://doi.org/10.1093/femsec/fiv121 ). Temperature and salinity are the two major factors affecting the distribution of Vibrio spp. (D. Ceccarelli and R. R. Colwell, Front Microbiol 5:256, 2014, https://doi.org/10.3389/fmicb.2014.00256 ). However, Vibrio sp. abundance can also be affected by nutrient load and marine plankton blooms (V. J. McKenzie and A. R. Townsend, EcoHealth 4:384–396, 2007; L. Vezzulli, C. Pruzzo, A. Huq, and R. R. Colwell, Environ Microbiol Rep 2:27–33, 2010, https://doi.org/10.1111/j.1758-2229.2009.00128.x ; S. Liu, Z. Jiang, Y. Deng, Y. Wu, J. Zhang, et al. Microbiologyopen 7:e00600, 2018, https://doi.org/10.1002/mbo3.600 ). The expansion of Vibrio spp. in marine environments calls for a deeper understanding of the biotic and abiotic factors that play a role in their abundance. We observed that pathogenic Vibrio spp. were most abundant in areas that favor the proliferation of harmful algal bloom (HAB) species. These results can inform managers, researchers, and oyster growers on factors that can influence the growth and distribution of pathogenic Vibrio spp. in the Delaware Inland Bays. 

ABSTRACT Gram-positive methicillin-resistant Staphylococcus aureus (MRSA) is an emerging cause of hospital-associated urinary tract infections (UTI), especially in catheterized individuals. Despite being rare, MRSA UTI are prone to potentially life-threatening exacerbations such as bacteremia that can be refractory to routine antibiotic therapy. To delineate the molecular mechanisms governing MRSA urinary pathogenesis, we exposed three S. aureus clinical isolates, including two MRSA strains, to human urine for 2 h and analyzed virulence characteristics and changes in gene expression. The in vitro virulence assays showed that human urine rapidly alters adherence to human bladder epithelial cells and fibronectin, hemolysis of sheep red blood cells (RBCs), and surface hydrophobicity in a staphylococcal strain-specific manner. In addition, transcriptome sequencing (RNA-Seq) analysis of uropathogenic strain MRSA-1369 revealed that 2-h-long exposure to human urine alters MRSA transcriptome by modifying expression of genes encoding enzymes catalyzing metabolic pathways, virulence factors, and transcriptional regulators. In summary, our results provide important insights into how human urine specifically and rapidly alters MRSA physiology and facilitates MRSA survival in the nutrient-limiting and hostile urinary microenvironment. IMPORTANCE Methicillin-resistant Staphylococcus aureus (MRSA) is an uncommon cause of urinary tract infections (UTI) in the general population. However, it is important to understand MRSA pathophysiology in the urinary tract because isolation of MRSA in urine samples often precedes potentially life-threatening MRSA bacteremia. In this report, we describe how exposure to human urine alters MRSA global gene expression and virulence. We hypothesize that these alterations may aid MRSA in acclimating to the nutrient-limiting, immunologically hostile conditions within the urinary tract leading to MRSA UTI.