The drop plate method as an alternative for Azospirillum spp viable cell enumeration within the consensus protocol of the REDCAI network

Abstract Quality evaluation of commercial inoculants is essential to warrant an adequate cropresponse to inoculation within a biosecurity framework. In this sense, this work is aimed at standardizing and validating the drop plate method for the enumeration of Azospirillum viable cellsas an alternative to the spread plate technique, which is currently proposed in the consensusprotocol of the REDCAI network. Between 14 and 25 private and public laboratories partici-pated in three independent trials. We obtained consistent and robust results that allowed toconfirm that both techniques are equivalent, concluding that the drop plate method is an alternative enumeration technique that is adequate to be included in the abovementioned consensusprotocol.

Resumen La evaluación de la calidad de los inoculantes comerciales es fundamental para garantizar una adecuada respuesta de los cultivos a la inoculación dentro de un marco de bioseguridad. En este sentido, el objetivo de este trabajo fue la estandarización y validación de la técnica de la microgota para la cuantificación de Azospirillum como metodología alternativa a la técnica de siembra en superficie, propuesta actualmente en el protocolo consenso de la Red de Calidad de Inoculantes, REDCAI. Entre 14 y 25 laboratorios, tanto privados como públicos, participaron de tres ensayos independientes. A partir de ellos se obtuvieron resultados reproducibles y robustos que permiten confirmar que ambas técnicas son equivalentes y concluir que la técnica de recuento por la microgota es una alternativa adecuada para ser incluida dentro del mencionado protocolo consenso.

The drop plate method as an alternative for Azospirillum spp. viable cell enumeration within the consensus protocol of the REDCAI network.

Quality evaluation of commercial inoculants is essential to warrant an adequate crop response to inoculation within a biosecurity framework. In this sense, this work is aimed at standardizing and validating the drop plate method for the enumeration of Azospirillum viable cells as an alternative to the spread plate technique, which is currently proposed in the consensus protocol of the REDCAI network. Between 14 and 25 private and public laboratories participated in three independent trials. We obtained consistent and robust results that allowed to confirm that both techniques are equivalent, concluding that the drop plate method is an alternative enumeration technique that is adequate to be included in the abovementioned consensus protocol.

Potential Zoonotic Pathovars of Diarrheagenic Escherichia coli Detected in Lambs for Human Consumption from Tierra del Fuego, Argentina.

Diarrheagenic Escherichia coli (DEC) pathovars impact childhood health. The southern region of Argentina shows the highest incidence of hemolytic uremic syndrome (HUS) in children of the country. The big island of Tierra del Fuego (TDF) in Argentina registered an incidence of five cases/100,000 inhabitants of HUS in 2019. This work aimed to establish the prevalence of STEC, EPEC, and EAEC in lambs slaughtered in abattoirs from TDF as well as to characterize the phenotypes and the genotypes of the isolated pathogens. The prevalence was 26.6% for stx+, 5.7% for eae+, and 0.27% for aagR+/aaiC+. Twelve STEC isolates were obtained and belonged to the following serotypes: O70:HNT, O81:H21, O81:HNT, O102:H6, O128ab:H2, O174:H8, and O174:HNT. Their genotypic profiles were stx1c (2), stx1c/ehxA (3), stx2b/ehxA (1), stx1c/stx2b (2), and stx1c/stx2/ehxA (4). Six EPEC isolates were obtained and corresponded to five serotypes: O2:H40, O32:H8, O56:H6, O108:H21, and O177:H25. All the EPEC isolates were bfpA- and two were ehxA+. By XbaI-PFGE of 17 isolates, two clusters were identified. By antimicrobial susceptibility tests, 8/12 STEC and 5/6 EPEC were resistant to at least one antibiotic. This work provides new data to understand the ecology of DEC in TDF and confirms that ovine are an important carrier of these pathogens in the region.

A simple method to evaluate the number of bradyrhizobia on soybean seeds and its implication on inoculant quality control.

Soybean seeds are non-sterile and their bacterial population interferes with the enumeration of beneficial bacteria, making it difficult to assess survival under different conditions. Within this context, the principal aims of this work were: (1) to improve a selective media for the enumeration of B. japonicum recovered from inoculated soybean seeds; (2) to establish the most representative mathematical function for B. japonicum mortality on soybean seeds after inoculation; (3) to evaluate if environmental or physiological conditions modify B. japonicum mortality on soybean seeds; and (4) to create a new protocol for quality control of soybean inoculants. We successfully evaluated the combination of pentachloronitrobenzene and vancomycin added to the yeast-mannitol medium to inhibit most fungi and Gram-positive soybean microbiota, thus producing reliable counts of B. japonicum from inoculated soybean seeds. Percentages of recovery and survival factors were obtained and used to construct a two-phase exponential decay non-linear regression function. High temperature and desiccation decreased these parameters, while the optimization of temperature and the use of osmoprotective compounds with inoculants increased them. The use of this protocol minimized heterogeneity between experiments and may be considered more reliable than the simple expression of direct colony count of bacteria recovered from seeds.

Streptococcus agalactiae aislados en Santa Fe, Argentina: estudio de la sensibilidad a antibióticos de uso clínico y mecanismos de resistencia a eritromicina y clindamicina / Streptococcus agalactiae isolated in Santa Fe, Argentina: antibiotic susceptibility and erythromycin-clindamycin resistance mechanisms

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Synthesis, spectroscopic and biological properties of bis(3-arylimidazolidinyl-1)methanes. A novel family of antimicrobial agents.

Synthesis, spectroscopic and biological properties of new bis(3-arylimidazolidinyl-1)methanes are described. These compounds were synthesized by condensation reaction between N-arylethylenediamines and formaldehyde. Chemical structures were confirmed by means of their (1)H- and (13)C-NMR and mass spectroscopic data. Investigation of in vitro antimicrobial activity was performed using Gram-negative and Gram-positive bacteria as well as antifungal studies against Aspergillus niger and Candida albicans. Minimal inhibitory concentrations of active compounds were determined.