Salmonellosis, one of the most common food and water-borne diseases, has a major global health and economic impact. Salmonella cells present high infection rates, persistence over inauspicious conditions and the potential to preserve virulence in dormant states when cells are viable but non-culturable (VBNC). These facts are challenging for current detection methods. Culture methods lack the capacity to detect VBNC cells, while biomolecular methods (e.g. DNA- or protein-based) hardly distinguish between dead innocuous cells and their viable lethal counterparts. This work presents and validates a novel bacteriophage (phage)-based microbial detection tool to detect and assess Salmonella viability. Salmonella Enteritidis cells in a VBNC physiological state were evaluated by cell culture, flow-cytometry and epifluorescence microscopy, and further assayed with a biosensor platform. Free PVP-SE1 phages in solution showed the ability to recognize VBNC cells, with no lysis induction, in contrast to the minor recognition of heat-killed cells. This ability was confirmed for immobilized phages on gold surfaces, where the phage detection signal follows the same trend of the concentration of viable plus VBNC cells in the sample. The phage probe was then tested in a magnetoresistive biosensor platform allowing the quantitative detection and discrimination of viable and VBNC cells from dead cells, with high sensitivity. Signals arising from 3 to 4 cells per sensor were recorded. In comparison to a polyclonal antibody that does not distinguish viable from dead cells, the phage selectivity in cell recognition minimizes false-negative and false-positive results often associated with most detection methods.

The in vitro susceptibilities of 703 clinical isolates of Salmonella to ciprofloxacin (CIP) and pefloxacin (PEF) were compared with those to trimethoprim-sulfamethoxazole (TMP-SMZ), chloramphenicol (CO) and ampicillin (AP). All isolates were susceptible to CIP, while PEF inhibited 90.7% of the strains. In contrast, resistance rates of 40, 29.2 and 27% were detected for AP, TMP-SMZ and CO, respectively. PEF resistance was detected in S.panama (1), S. typhi (3) and S. typhimurium (17), the latter representing the most frequently serovar isolated in our country. None of the S. typhi isolates was resistant to CO. Combined resistance was most frequently found among S. typhimurium isolates, with the patterns PEF-TMP-SMZ-AP (10) and PEF-TMP-SMZ-CO-AP (5) predominating.

From 154 food samples, including vegetables (lettuce), milk and meals served at school it was possible to isolate and identify 400 Gram negative bacilli distributed among 339 enteric bacteria (Escherichia, Shigella, Citrobacter, Klebsiella, Enterobacter, Serratia and Proteus) and other 61 non enteric bacilli (Acinetobacter, Flavobacterium, Aeromonas and Pseudomonas). Submitting this cultures to the drugs sulfadiazine (Su), streptomycin (Sm), tetracycline (Tc), chloramphenicol (Cm), kanamycin (Km), ampicillin (Ap), nalidixic acid (Nal) and gentamycin (Gm) it was observed only six stocks susceptible to all drugs and total sensibility to Gm. Among enteric bacteria the profiles Su (27,6%) and Su-Ap (39,6%) predominated, while for the non enteric bacilli percentages of 18.0 for Ap and 9.8 for Su-Ap were detected. Aiming to better characterization of resistance, experiments of conjugation were made with standard strains of Escherichia coli K 12. Great concern was raised by the recognition of these cultures due to the elevated R+ taxes for the enteric bacilli that were close to 90% (milk and food at school) and about 70% in relation to lettuce.

Análise bacteriológica de ordem qualitativa foi desenvolvida em duas estações de tratamento de esgoto da cidade do Rio de Janeiro no período de 1984 a 1985. A pesquisa considerou o isolamento e a identificação de 540 culturas de Escherichia coli, advindas de afluentes e efluentes. Estudou-se a resistência a oito antimicrobianos (sulfadiazina, estreptomicina, tetraciclina, cloranfenicol, canamicina, ampicilina, ácido nalidíxico e gentamicina) e a três metais pesados (sulfato de cobre, cloreto de mercúrio e sulfato de zinco), além da colicinogenia. Foi possivel a detecção de percentuais até 95 para culturas isoladas dos efluentes com marcadores genéticos, contrapondo-se com taxas ao redor de 70% para aquelas provindas dos afluentes.

The object of the investigation was the evaluation of the susceptibility to antibiotic and chemotherapeutic agents of 240 strains of Salmonella agona isolated from different sources (human, food and environment) obtained from five Brazilian states (Minas Gerais, São Paulo, Rio de Janeiro, Pernambuco and Rio Grande do Sul). The presence of R factors in 26 representative strains of the sample was also determined.

The transference of the genetic markers and the presence of DNA plasmidial in 240 cultures of Escherichia coli was investigated. The strains were originated from Waste Treatment Plant (inffluent and effluents) located in Ilha do Governador, Rio de Janeiro. By conjugation analysis, E. coli K 12 allowed the isolation of the transconjugants resistant to antibiotics Su, Sm, Tc, Cm, Ap; heavy metals (Cu, Hg and Zn) and colicinogenic factors (Ia, Ib and V) mainly in coliforms isolated Cm and Ap from the terminals of the treatment plant. The percentual distribution of the plasmids was prevalent in the cultures of E. coli originated from material collected in the effluents and reached a rate higher than 65%.