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Contribution of fimbriae and flagella of Salmonella enteritidis to colonization and invasion of chicks
Isogenic mutants of Salmonella enteritidis defective for the elaboration of fimbrial types SEF14, SEF17, SEF21 and flagella were used to study the contribution these organelles made to colonization, invasion and lateral transfer in young chicks. The caecum, liver and spleen were colonized within 24 h following oral inoculation of 1-day-old chicks with 10(5) wild-type S. enteritidis strain LA5. However, for some mutants, the numbers of organisms recovered from internal organs was reduced significantly, particularly at 24 h post-inoculum, which supported the hypothesis that the organelles contribute to invasion and dissemination to internal organs. Specifically, mutations affecting SEF17, SEF21 and flagella contributed to a delay in colonization of the spleen, and those affecting SEF21 and flagella delayed colonization of the liver. Lower numbers of bacteria were recovered from the caecum with mutants deficient in elaboration of SEF21. Sentinel birds were colonized by LA5 or EAV40 (14(-), 17(-), 21(-), fla(-)) directly from the environment within 2 days, although a consistent slight delay was observed with the multiple mutant. Overall, our data suggest a collective role for SEF17, SEF21 and flagella, but not SEF14, in the early stages of colonization and invasion of young chicks by S. enteritidis, but these surface appendages appear unnecessary for colonization of birds from their immediate environment
Resistência antimicrobiana em Salmonella Enteritidis isoladas de amostras clÃnicas e ambientais de frangos de corte e matrizes pesadas Antimicrobial resistance in Salmonella Enteritidis isolated from clinical and environmental broiler chickens and breeders broiler
<abstract language="eng">The antimicrobial resistance of Salmonella Enteritidis strains isolated from clinical and environmental poultry samples in the Southern Brazil during the years of 1999, 2000 and 2001 was evaluated. Among the 79 isolated samples, 64 (81%) were resistant to at least one of the antimicrobial agents tested, showing 22 different resistance patterns. Tetracycline showed the highest percentage (64,5%) of resistance among the antimicrobial agents used. Resistance to drugs at different levels was found as the following: ampicillin (1.2%), kanamycin (1.2%), ciprofloxacin (2.5%), enrofloxacin (8.8%), gentamicin (21.5%), streptomycin (20.2%), nitrofurantoin (26.6%), and nalidixic acid (30.4%). None of the S. Enteritidis strains were resistant to chloramphenicol, norfloxacin, and polimycin B. Among the 64 S. Enteritidis strains that showed resistance, 43 (67.2%) were resistant to two or more antimicrobial agents. Twenty-one (32.8%) strains were resistant to only one of the antimicrobial agents, 14 to tetracycline, three to nalidixic acid, three to nitrofurantoin, and one to gentamycin. These antimicrobial resistance levels suggest a high occurrence of tetracycline resistant S. Enteritidis strains and resistance to two or more antimicrobial agents