Antimicrobial susceptibility, phage types, and pulsetypes of Salmonella Typhimurium, in São Paulo, Brazil

A total of 283 Salmonella Typhimurium strains isolated from cases of human infections and non human sources, were examined for antimicrobial susceptibilityand the incidence of resistance was 38% and multiple resistance (to three or more antimicrobials) was 15%. All 43 multidrug-resistant strains (MDR) and 13 susceptible ones were characterized by phage typing and pulsed- field gel electrophoresis (PFGE). The strains encompassed 14 definitive phage types (DT), three were untypable (UT), and 18 atypicals or reaction does not conform (RDNC), which belonged to 21 PFGE patterns, A1-A21. The predominant phage types were DT49, DT193, and RDNC and two strains belonging to DT 104 and 104b were also identified. The most commum PFGE patterns were A1 and A8. Analysis by PFGE and phage typing demonstrated that the most of the MDR were multiclonal and association among multiresistance, phage typing, and PFGE patterns was not so significant

In vitro characterization and in vivo properties of Salmonellae lytic bacteriophages isolated from free-range layers

Occurrence of food poisoning related to Salmonella-contaminated eggs and chicken meat has been frequent in humans. Salmonella Enteritidis (SE) and Salmonella Typhimurium (ST) are included among the most important paratyphoid salmonellae associated with chicken meat and eggs. Elimination of Salmonella at the pre-harvest stage can play a significant role in preventing the introduction of this pathogen into the food chain and consequently in the reduction of food poisoning in humans. Bactericidal bacteriophages may provide a natural, nontoxic, feasible and non-expensive component of the multi-factorial approach for a pre-harvest control of Salmonella in poultry. Five bacteriophages lytic for SE PT4 and ST were obtained from 107 samples of feces of free-range layers in Brazil. All bacteriophages were characterized in vitro and in vivo, showing head and tail morphology and dsDNA as nucleic acids. Results of "in vivo" studies suggested that bacteriophages do not remain in Salmonella-free birds longer than one day, whereas they multiply in Salmonella-infected birds for longer periods. Besides, selection for phage-resistant SE PT4 did not seem to occur in the short term. Isolated bacteriophages will be investigated for their potential for pre-harvest biocontrol of SE PT4 in poultry

Comparação de Meios de Enriquecimento e de Plaqueamento Utilizados na Pesquisa de Salmonella em Carcaças de Frango e Fezes de Aves Comparison of Different Enrichment Broth and Plating Media Used to Isolating Salmonella from Chicken Carcasses and Poultry Faeces Samples

Este trabalho foi desenvolvido para avaliar, comparativamente, os caldos de enriquecimento Rapapport-novobiocina (RVN), selenito-cistinanovobiocina (SCN) e tetrationato-novobiocina (TN) e os meios para plaqueamento ágar Hektoen (HE), ágar MacConkey (MC), ágar Salmonella-Shigella (SS), ágar verde brilhante (VB) e ágar xilose lisina desoxicolato (XLD), utilizados no isolamento de Salmonella em carcaças de frango e fezes de aves. O procedimento bacteriológico consistiu das etapas de pré-enriquecimento, enriquecimento em caldos seletivos, plaqueamento, testes bioquímicos presuntivos e confirmação sorológica com soros polivalentes anti antígenos somáticos e flagelares de Salmonella.. As fezes foram experimentalmente contaminadas com 8 sorotipos de Salmonella (Agona, Anatum, Enteritidis, Havana, Infantis, Owakam, Schwazengrund e Typhimurium) e a concentração final foi aproximadamente de 1,2 x 10² ufc/g. As fezes foram inoculadas nos caldos enriquecedores e a partir daí, seguiu-se o mesmo procedimento utilizado para as carcaças. Os resultados referentes às carcaças de frango não foram estatisticamente diferentes (p>0,01) para os caldos e as placas. Todavia, verificou-se superioridade numérica em relação aos caldos SCN e TN sobre o caldo RVN, e em relação ao ágar XLD sobre os demais. Verificou-se também que com o emprego de dois caldos de enriquecimento e de dois meios para plaqueamento pode-se obter maior positividade. Quanto ao exame das fezes, o caldo TN mostrou-se superior aos demais (p>0,01), não havendo diferença (p>0,01) de resultados para os meios de plaqueamento. Os resultados sugerem que a utilização de mais de um meio de enriquecimento e de plaqueamento poderia aumentar as chances de isolamento de Salmonella.<br>This study was undertaken to compare selenite-cystine-novobiocin (SCN) broth, tetrationate-novobiocin (TN) broth and Rappaport-Vassiliadisnovobiocin (RVN) broth as enrichment and MacConkey (MC) agar, brilliant green (BG) agar, Hektoen (HE) agar, Salmonella-Shigella (SS) agar and xylose Iysine desoxycholate (XLD) agar as plating media for isolating Salmonella from broiler carcasses and chicken feces. The carcasses were washed with 300mL of Buffer Peptone Water 0.1% (BPW). The BPW solation was incubated 6h at ambient temperature and up to 24 h/43ºC. From this, 2 mL were inoculate in 20 mL of enrichment broth, incubated at 43ºC/24h. The enrichment broth was plated on the five tested selective agars, also incubated at 43ºC/24h. Up to five colonies from each plate were inoculated in TSI agar and LIA agar, incubated at 37ºC/24h. The genus of Salmonella was confirmed by slide agglutination test using poly serum anti-somatic Salmonella antigens (O) and poly serum anti-fiagellar (H) Salmonella antigens. The feces were experimentally contaminated with eight Salmonella serotypos (Agona, Anatum, Enteritidis, Havana, Intantis, Owakam, Schwazengrundand Typhimurium). Each serotype was tested five times. Salmonella serotypes were added in the sample of feces individually so that the final concentration of the bacterium was 1,2 x iO³ ufclg. Two grams of each sample were inoculated in 20 mL of the enrichment broth. The proceduring from this point wes the same adopted to carcasses examination. To broiler carcasses there was no statistic difference (p>0, 001) among the enrichment broth and among plating media. However the use of two enrichment broth (SCN and TN) and two agars between XLD agar, SS agar and HE agar gave the bost results. The assay done with feces showed that the TN broth was much better than the others and, in this case it can be plated either HE agar, or VB agar or SS agar The results from the broiler carcasses examination and the feces examination showed that it is not easy to determine the better bacteriologic routine to search for Salmonella and suggest that the association of two eorichments broth and two plating media may improve the test