Purpose: To investigate the presence of Aeromonas spp., gram-negative bacteria commonly found in water environments that can cause gastrointestinal disease, and bacterial fecal indicators (total coliforms (TC), Escherichia coli, Enterococcus spp.) in SNIW in Maryland.
Methods: Water samples from 2 ponds, 2 tidal rivers, 4 non-tidal rivers/creeks and 3 reclaimed wastewater treatment plants were collected in Maryland over a period of four months. Bacteria were enumerated using a standard membrane filtration method on MI (E. coli/TC) (n=49), mEI (Enterococcus) (n=49) and ADA-V (Aeromonasspp.) (n=43) agars. Water temperature, pH and turbidity were measured using a ProDSS multi-parameter meter.
Results: All samples tested (43/43) were positive for Aeromonas spp. The prevalence of E. coli, TC, Enterococcus spp. and Aeromonas spp. in water samples ranged from undetectable-4.1, 3.4-5.9, undetectable-4.6 and 2.5-5.5 log CFU/100mL of water, respectively. Mean counts were 2.9, 4.7, 3.3 and 4.3 log CFU/100ml, respectively. Non-tidal fresh water samples harbored significantly higher levels of E. coli and enterococci compared to pond and reclaimed water (p<0.05). Aeromonas counts were significantly correlated with E. coli, TC and enterococci (R2=0.42, 0.36 and 0.43; p<0.0001), respectively. Aeromonas population levels were also weakly positively correlated with water temperature (R2=0.17; P <0.01) and turbidity (R2=0.12; P <0.05).
Significance: This study is part of a two-year sampling effort to characterize the microbiological quality of surface and nontraditional water sources (CONSERVE). Results show that SNIW harbors high levels of Aeromonas spp. that correlate with bacterial fecal indicators and physical parameters of water. Risks posed by under-recognized pathogens in fresh produce need to be assessed.