Abstract
Salmonellosis is one of the most common and widely distributed foodborne diseases. The emergence of Salmonella strains that are resistant to a variety of antimicrobials is a serious global public health concern. Salmonella enterica serovar Typhimurium definitive phage type 104 (DT104) is one of these emerging epidemic multidrug resistant strains. Here we collate information from the diverse and comprehensive range of experiments on Salmonella proteomes that have been published. We then present a new study of the proteome of the quinolone-resistant Se20 strain (phage type DT104B), recovered after ciprofloxacin treatment and compared it to the proteome of reference strain SL1344. A total of 186 and 219 protein spots were recovered from Se20 and SL1344 protein extracts, respectively, after two-dimensional gel electrophoresis. The signatures of 94% of the protein spots were successfully identified through matrix-assisted laser desorption/ionization mass spectrometry (MALDI-TOF MS). Three antimicrobial resistance related proteins, whose genes were previously detected by polymerase chain reaction (PCR), were identified in the clinical strain. The presence of these proteins, dihydropteroate synthase type-2 (sul2 gene), aminoglycoside resistance protein A (strA gene) and aminoglycoside 6'-N-acetyltransferase type Ib-cr4 (aac(6')-Ib-cr4 gene), was confirmed in the DT104B clinical strain. The aac(6')-Ib-cr4 gene is responsible for plasmid-mediated aminoglycoside and quinolone resistance. This is a preliminary analysis of the proteome of these two S. Typhimurium strains and further work is being developed to better understand how antimicrobial resistance is developing in this pathogen.
Highlights
Non-typhoid Salmonella is a common and widely distributed cause of food poisoning [1]
Typhimurium definitive phage type 104 (DT104) that results from the integration of antimicrobial resistance genes into virulence plasmids involved in systemic infection [9]
In vivo selection of quinolone and aminoglycoside resistance was observed post-treatment [18]. This strain was resistant to nalidixic acid, to all of the fluoroquinolones tested and to the aminoglycosides amikacin, tobramycin, kanamycin and streptomycin
Summary
Non-typhoid Salmonella is a common and widely distributed cause of food poisoning [1]. S. Typhimurium SL1344 is among the most extensively studied pathogenic strains and is frequently used as a reference organism to investigate Salmonella pathogenicity [6]. Typhimurium DT104 that results from the integration of antimicrobial resistance genes into virulence plasmids involved in systemic infection [9]. These hybrid plasmids provide an adaptive advantage that enhances the epidemic potential of these strains. Antimicrobial resistance and virulence are determinant in the clinical outcome of severe Salmonella infections, so it is important to understand how the associated genetic mechanisms are regulated [10]. Total bacterial proteomes from different strains can be compared to identify proteins that correlate with different antimicrobial resistance profiles [17]. To elucidate biocide tolerance mechanisms by comparing 2-D DIGE protein profiles of a triclosan sensitive strain and the isogenic tolerant mutant in the presence and absence of triclosan
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