The importance of the role of environment in the dissemination of antimicrobial resistant bacteria is now well recognized. Thus, bacterial indicators to monitor the phenomena are required. The Aeromonas genus is autochthonous in the aquatic environment and easy to detect in any water type, such as freshwater, or wastewater. These microorganisms are also causing infections in humans and animals (including fish). Furthermore, as Aeromonas spp. is able to acquire antimicrobial resistance mechanisms, it is candidate for indicator bacteria to follow antimicrobial resistance dissemination in aquatic environments. Unfortunately, to date, interpretation criteria for Aeromonas spp. for antimicrobial susceptibility tests are scarce in the literature. No epidemiological cut-off values for Aeromonas are currently available at EUCAST to interpret Minimum Inhibitory Concentrations (MIC). The only interpretation criteria available are clinical breakpoints from CLSI that are adapted from Enterobacteriaceae. Based on the results of MIC distributions obtained for a collection of environmental isolates of Aeromonas, this study aimed at proposing tentative epidemiological cut-off values (COWT) for Aeromonas spp. assessing whether the genus is an acceptable level of definition. Thus, 233 isolates collected from 16 rivers were identified at species level using Maldi-Tof (Bruker). Eleven different species were identified, the most abundant were A. bestiarum (n = 54), A. salmonicida (n = 45), A. sobria (n = 41), and A. eucrenophila (n = 37). 96-well micro-plates containing different concentrations of 15 antimicrobials, namely cefotaxime, ceftazidime, chloramphenicol, colistin, enrofloxacin, erythromycin, florfenicol, flumequine, gentamicin, nalidixic acid, oxolinic acid, streptomycin, temocillin, tetracycline, and trimethoprim-sulfamethoxazole, were prepared. The broth micro-dilution method was used to determine the antimicrobial susceptibility of each isolate. The estimation of COWT values was satisfactory obtained at genus level for all antimicrobials except cefotaxime and erythromycin. This first step is an invitation for other research teams to increase the amount of antimicrobial resistance data collected. Then, robustness of our proposed provisional generic epidemiological cut-off values could be assessed by testing antimicrobial susceptibility of various Aeromonas collections.

Appropriate interpretation of a positive reverse transcription-PCR is an important issue for virus-related health hazard assessment because viral genomes and infectious viruses exhibit different behavior patterns in water. In this context, using Poliovirus 1 and Feline calicivirus f9 as examples of enteric viruses, first we demonstrated that the stability of infectious viruses is greatly affected by the temperature of mineral water (10, 20, and 35°C) and that, in contrast, temperature has little effect on the corresponding genomes. Second, we demonstrated that infectious particles are degraded more rapidly than viral genomes at all temperatures studied. At 35°C, Poliovirus 1 infectivity was reduced 4 logs after only 19 days, while an equivalent reduction would have taken 75 years (according to the model applied) for the viral genome. Contradictory conclusions can also be drawn concerning the sensitivity of viral serotypes depending on whether the infectious virus or the viral genome is considered. The Feline calicivirus f9 genome is more resistant than the Poliovirus 1 genome, whereas the opposite is true for the corresponding infectious viruses. Thus, we concluded that a positive test for a viral genome in mineral water must be interpreted with utmost caution because of the lack of a correlation between the presence of viral genomes and viral infectivity. Detection of viral genomes may be necessary to identify infectious risk for the human population, but it cannot be considered sufficient.

The aim of the study was to evaluate the presence of pathogenic viruses in the Moselle River and to compare the usefulness of thermotolerant coliforms and somatic coliphages as tools for river water quality assessment in terms of viral contamination. Thermotolerant coliforms and somatic coliphages were enumerated by standardized methods in 170 samples of river water drawn from five sampling sites along the Moselle River (eastern France). BGM cell culture and integrated cell culture-reverse transcription-PCR DNA enzyme immunoassay were used to determine the presence of pathogenic viral genome (Enterovirus and Norovirus genogroup II [GGII]) and infectious Enterovirus spp. in 90 1-liter samples. No infectious Enterovirus spp. were isolated, but Enterovirus and Norovirus GGII genomes were detected in 38% of the samples. Norovirus GGII genome was mostly detected in winter, whereas Enterovirus genome was mostly detected in summer and fall. Somatic coliphages appeared to be less sensitive to higher river water temperature than thermotolerant coliforms. Furthermore, the number of river water samples positive for pathogenic viral genome increased with increasing concentration of somatic coliphages, whereas coliform concentration was unrelated to viral genome contamination. Consequently somatic coliphages, which are less sensitive to environmental factors than thermotolerant coliforms in river water, would provide a promising tool for assessment of river water quality in terms of fecal and viral pollution.

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Viral inactivation and adhesion-aggregation in water are often studied as separate phenomena. When the focus is placed on viral adhesion-aggregation, inactivation is neglected because the phenomena under investigation occur over a short period measured in days. When viral inactivation is studied, adhesion-aggregation phenomena are considered to be negligible because viral survival is traced over several days or months. In the present work, we took a global approach, examining the relative contributions of each of these processes in a complex system composed of groundwater, Poliovirus 1, and a hydrophobic container (polypropylene) maintained in a dark environment at 20°C. We demonstrated that infectious viral load fell off 2.8 log 10 during the first 20 days. During this time, adhesion was far from negligible because it accounted for most of the decline, 1.5 log 10 . Adhesion was undoubtedly favored by the presence of divalent ions in the groundwater. After 20 days, aggregation may also have been the cause of 0.66 to 0.92 log 10 of viral loss. Finally, viral inactivation was quantitatively the lowest phenomena because it only explained 0.38 to 0.64 log 10 of the viral loss. This study thus clearly demonstrated that estimates of viral survival in a given system must always take into account adhesionaggregation phenomena which may be responsible for the majority of viral loss in the aqueous phase. Adhesion and aggregation are reversible processes which may lead to an underestimation of viral load in certain studies.More than 150 serotypes of enteric viruses (gastrointestinal viruses, hepatitis A and E viruses, enteroviruses) can be transmitted to humans from environmental sources. In water, the decrease of viral particles basically depends on two processes: inactivation and adhesion-aggregation. Both of these processes lead to a real (inactivation-adhesion) or apparent (aggregation) reduction in the concentration of infectious virus in the aqueous phase.Viral inactivation results from an alteration of the viral capsid or genome. The result is a reduction in the number of infectious units which requires cell culture for quantification (16,30,39). The capacity of a virus to survive depends on its serotype and on the physical (e.g., temperature), chemical (e.g., pH and salinity), and biological (e.g., microorganisms) properties of the environment (9,13,14,18,20,32,46). For example, temperature is recognized as the principal factor affecting viral survival (20,47). Studies devoted to viral survival are classically conducted in vitro using an appropriate viral model (e.g., Poliovirus 1, Adenovirus 40 and 41, hepatitis A virus), a natural (e.g., drinking water, seawater, river water) or artificial (e.g., buffer) aqueous environment, and a container (e.g., polypropylene, glass). Viral inactivation is then defined by following the time course of infectious virus in the aqueous phase. The time required for 90% of the infectious viral units to disappear (T90) is determined when the survival curve is log linear. More generall...