In Argentina, as in other countries of Latin America, cholera has occurred in an epidemic pattern. Vibrio cholerae O1 is native to the aquatic environment, and it occurs in both culturable and viable but nonculturable (VNC) forms, the latter during interepidemic periods. This is the first report of the presence of VNC V. cholerae O1 in the estuarine and marine waters of the Río de la Plata and the Argentine shelf of the Atlantic Ocean, respectively. Employing immunofluorescence and PCR methods, we were able to detect reservoirs of V. cholerae O1 carrying the virulence-associated genes ctxA and tcpA. The VNC forms of V. cholerae O1 were identified in samples of water, phytoplankton, and zooplankton; the latter organisms were mainly the copepods Acartia tonsa, Diaptomus sp., Paracalanus crassirostris, and Paracalanus parvus. We found that under favorable conditions, the VNC form of V. cholerae can revert to the pathogenic, transmissible state. We concluded that V. cholerae O1 is a resident of Argentinean waters, as has been shown to be the case in other geographic regions of the world.Cholera reemerged in Latin America in 1991 after being absent from the continent for nearly a century. In Argentina, there have been seven epidemics since 1992, all of which were caused by El Tor biotype Vibrio cholerae O1. These cholera outbreaks occurred mainly during the summer months, and, consistent with reports from other geographic regions of the world, strains of V. cholerae O1 were isolated from water samples collected from rivers during epidemic periods. However, the microorganism could not be recovered from the environment during interepidemic periods (12).V. cholerae is a natural inhabitant of aquatic environments, and it has been found to survive for extended periods in estuarine and brackish waters (12,13,15). Furthermore, in response to extreme environmental conditions, the bacteria may enter a dormant state (7, 30), which has been designated the viable but nonculturable (VNC) state, since the organism cannot be recovered by using traditional culture media. It has been hypothesized that it is in the VNC state that V. cholerae survives in the environment during interepidemic periods. Also, interaction with plankton appears to play an important role in the ecology of the microorganism and to facilitate persistence, mainly in response to low temperatures and reduced nutrient concentrations (12,13,14,19,21).In Argentina, V. cholerae non-O1 was isolated from samples collected from the Río de la Plata in previous studies (5). Several facts, such as the seasonality of the outbreaks most likely associated with temperature shifts and plankton blooms, suggested that there are environmental reservoirs of V. cholerae. Additionally, in a recent study in which the genetic diversity of V. cholerae O1 strains isolated during the seven outbreaks that occurred in this country was analyzed, most of the cholera toxin (CT)-producing strains were found to belong to a single clonal group already recognized as the Latin American epidemic stra...
The bacterioplankton diversity of coastal waters along a latitudinal gradient between Puerto Rico and Argentina was analyzed using a total of 134,197 high-quality sequences from the V6 hypervariable region of the small-subunit ribosomal RNA gene (16S rRNA) (mean length of 60 nt). Most of the OTUs were identified into Proteobacteria, Bacteriodetes, Cyanobacteria, and Actinobacteria, corresponding to approx. 80% of the total number of sequences. The number of OTUs corresponding to species varied between 937 and 1946 in the seven locations. Proteobacteria appeared at high frequency in the seven locations. An enrichment of Cyanobacteria was observed in Puerto Rico, whereas an enrichment of Bacteroidetes was detected in the Argentinian shelf and Uruguayan coastal lagoons. The highest number of sequences of Actinobacteria and Acidobacteria were obtained in the Amazon estuary mouth. The rarefaction curves and Good coverage estimator for species diversity suggested a significant coverage, with values ranging between 92 and 97% for Good coverage. Conserved taxa corresponded to aprox. 52% of all sequences. This study suggests that human-contaminated environments may influence bacterioplankton diversity.
Aims: To isolate and identify linear alkylbenzene sulfonate (LAS)‐degrading bacteria from Río de la Plata and adjacent waters, and to assay their degradation capability as a consortium and as single organisms. Methods and Results: A consortium consisting of four bacterial strains: Aeromonas caviae (two strains), Pseudomonas alcaliphila and Vibrio sp. was identified by 16S rRNA analysis. Isolates grown as a consortium produced higher biomass from LAS and CO2 release (mineralization) than individual cultures, and degraded 86% of LAS (20 mg l−1), whereas pure strains degraded between 21% and 60%. Bacterial desulfonation from LAS was evidenced in the consortium and A. caviae strains. A complete disappearance of LAS (10 mg l−1) was accomplished, and LAS levels of 50 and 100 mg l−1 led to a pronounced decrease in the biodegradation extent and inhibition of culture growth. Conclusions: A bacterial consortium capable of complete LAS degradation was isolated from the Río de la Plata and adjacent waters. This consortium was more efficient for LAS degradation than individual cultures, and was sensitive to high LAS concentrations. Significance and Impact of the Study: The autochthonous consortium with high effectiveness on LAS biodegradation is a useful tool for LAS depletion from these polluted ecosystems.
Aims: To determine the presence of Vibrio cholerae in different areas of Argentina in three sample types, to determine the composition of planktonic communities in areas at which this pathogen was detected and to characterize the virulence properties and antimicrobial resistance of the recovered environmental isolates. Methods and Results: Water and plankton samples were collected in marine, brackish and freshwater environments. Vibrio cholerae non‐O1, non‐O139 was isolated in 36·1% of the samples analysed. The micro‐organism was detected in freshwater but not in marine or brackish samples. No relationship was found between isolation of V. cholerae and presence of any species of plankton. All the isolates presented very similar virulence profiles by PCR, lacking ctxA and tcpA El Tor and containing hlyA (98·7%), rtxA (99·0%), toxR (98·7%) and stn‐sto (1·9%). Resistance to ampicillin was found in both Tucumán (21%) and Buenos Aires isolates (45%). Conclusions: We identified two geographic areas in Argentina where V. cholerae was present: freshwaters of the rivers from Tucumán and the Río de la Plata. Significance and Impact of the Study: The identification of V. cholerae strains in the environment, carrying both virulence factors and resistance to antimicrobial agents, highlight the need for a continuous and active surveillance of this pathogen.
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