Null mutation in sspA of Cronobacter sakazakii influences its tolerance to environmental stress

Abstract

Cronobacter sakazakii is a known foodborne opportunistic pathogen that can affect the intestinal health of infants. Despite undergoing complex manufacturing processes and low water concentration in the finished product, infant formula has been associated with Cronobacter infections, suggesting that the pathogenicity of C. sakazakii may be related to its tolerance to stress. In this study, the effect of the stringent starvation protein A (SspA), which plays an important role in E. coli cellular survival under environmental stress, on the stress tolerance of C. sakazakii BAA894 was investigated by creating a sspA-knockout mutant. The effects of this mutation on acid, desiccation, and drug tolerance were assessed, and the results showed that acid tolerance decreased, while desiccation tolerance increased in LB and decreased in M9. Moreover, the minimum inhibitory concentrations of 10 antibiotics in LB medium and 8 antibiotics in M9 medium were determined and compared between the wild type and ΔsspA strains. Transcriptome analysis showed that 27.21% or 37.78% of the genes in ΔsspA were significantly differentially expressed in LB or M9 media, the genes relevant to microbial metabolism in diverse environments, and bacterial chemotaxis were analyzed in detail. The current study contributes to an improved understanding of the role of SspA in C. sakazakii BAA894 stress tolerance.