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Virulence of Salmonella typhimurium 1,4,[5],12:i:- : the new emergent strain
Publication . Seixas, Rui Emanuel Antunes de; Oliveira, Maria Manuela Castilho Monteiro de; Bernardo, Fernando Manuel d’Almeida
Salmonella serovar 1,4,[5],12:i:- is presently considered one of the major serovars
responsible for human salmonellosis worldwide. A multidisciplinary approach, including the
fields of epidemiology, spatial statistics, clinical and applied microbiology was used to
perform an extensive characterization of Salmonella 1,4,[5],12:i:- isolates obtained by the
National Health Institute Dr. Ricardo Jorge, which was lacking due to the recent emergence.
It was observed that cases are reported in most districts, being more frequent in the
Portuguese coastland. Spatial statistical analysis showed a significant geographic clustering,
pointing out for the importance of evaluating these areas to identify risk factors, in order to
establish adequate prevention programs.
The most relevant antimicrobial profile in this serovar is the tetra-resistance pattern (R-type
ASSuT), displaying resistance to ampicillin, streptomycin, sulphonamides and tetracyclines.
A high occurrence of R-type ASSuT isolates was observed in the isolates under study, with
the majority harboring the resistance genes frequently associated with the European clone,
namely blaTEM, sul2, straA-straB, tetB. Additionally, resistance to quinolones and 3rd
generation cephalosporin was also detected.
In Portugal, the rapid spread of Salmonella 1,4,[5],12:i:- R-type ASSuT might be related with
the diversity of pulsotypes and also the presence of a core of virulence factors, including
biofilm production. Biofilm-forming ability varied between sample locations and collection
year, and can be one of the virulence features related with the rise of this serovar.
Furthermore, biofilm formation was evaluated in vitro using a simulated human intestinal
environment. In such conditions was observed an impairment of biofilm production, revealing
that conditions mimicking the human intestinal tract can influence the biofilm-forming ability
of the isolates under study.
This research highlight the critical importance of close surveillance of Salmonella
1,4,[5],12:i:- in Portugal, including R-type ASSuT isolates. Information gathered may unravel
Salmonella 1,4,[5],12:i:- features, prevent the dissemination to other regions and also benefit
the medical community in order to rationalize salmonellosis antimicrobial therapeutics.
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Fundação para a Ciência e a Tecnologia
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SFRH
Número da atribuição
SFRH/BD/75836/2011