Identification of genes involved in serum tolerance in the clinical strain Cronobacter sakazakii ES5

BMC Microbiology

Angelika Lehner¹  Roger Stephan¹  Katrin Zurfluh¹  Taurai Tasara¹  Sarah Schwizer¹ 

[1] Institute for Food Safety and Hygiene, Vetsuisse Faculty, University of Zurich, Zurich, Switzerland

关键词: Expression analysis;    Complementation;    PCR;    Identification;    Tn5-mutagenesis;    Serum tolerance;    Clinical isolate;    Cronobacter sakazakii ES5;   

Others  :  1144418
DOI  :  10.1186/1471-2180-13-38

 received in 2012-10-26, accepted in 2013-02-14,  发布年份 2013

【 摘 要 】

Background

Cronobacter spp. are opportunistic pathogens that can cause septicemia and infections of the central nervous system primarily in premature, low-birth weight and/or immune-compromised neonates. Serum resistance is a crucial virulence factor for the development of systemic infections, including bacteremia. It was the aim of the current study to identify genes involved in serum tolerance in a selected Cronobacter sakazakii strain of clinical origin.

Results

Screening of 2749 random transposon knock out mutants of a C. sakazakii ES 5 library for modified serum tolerance (compared to wild type) revealed 10 mutants showing significantly increased/reduced resistance to serum killing. Identification of the affected sites in mutants displaying reduced serum resistance revealed genes encoding for surface and membrane proteins as well as regulatory elements or chaperones. By this approach, the involvement of the yet undescribed Wzy_C superfamily domain containing coding region in serum tolerance was observed and experimentally confirmed. Additionally, knock out mutants with enhanced serum tolerance were observed. Examination of respective transposon insertion loci revealed regulatory (repressor) elements, coding regions for chaperones and efflux systems as well as the coding region for the protein YbaJ. Real time expression analysis experiments revealed, that knock out of the gene for this protein negatively affects the expression of the fimA gene, which is a key structural component of the formation of fimbriae. Fimbriae are structures of high immunogenic potential and it is likely that absence/truncation of the ybaJ gene resulted in a non-fimbriated phenotype accounting for the enhanced survival of this mutant in human serum.

Conclusion

By using a transposon knock out approach we were able to identify genes involved in both increased and reduced serum tolerance in Cronobacter sakazakii ES5. This study reveals first insights in the complex nature of serum tolerance of Cronobacter spp.

【 授权许可】

   
2013 Schwizer et al.; licensee BioMed Central Ltd.

【 图 表 】

Figure 1.

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