Cronobacter Species in the Built Food Production Environment: A Review on Persistence, Pathogenicity, Regulation and Detection Methods

Chitosan oligosaccharide efficiently inhibits Cronobacter sakazakii biofilm by interacting with out membrane protein A for regulating CpxRA-mediated cellulose production pathway

Chitosan oligosaccharide (COS) can efficiently inhibit Cronobacter sakazakii (C. sakazakii) biofilm independent on antibacterial activity. However, the mechanism is still unclear. In this study, the role of out membrane protein A (OmpA) and its downstream CpxRA-mediated cellulose production pathway in COS's inhibition on C. sakazakii biofilm were explored. The spectroscopic results were shown that COS could interact with OmpA, and this changed OmpA's second structure and spatial conformation as well as cell membrane permeability and COS uptake. C. sakazakii ΔOmpA strain under COS treatment had a lower cell membrane permeability and COS uptake rate. The interaction between OmpA and COS could further initiate CpxRA system. The regulon cpxP expression level was therefore up-regulated. The deletion of the response regulator cpxR gene reduced inhibitory effect of COS on biofilm. CpxRA system inhibited expression of csgD and adrA, which coded diguanylate cyclase to generate cyclic diguanosine monophosphate (c-di-GMP). The expression of bcsAB was then down-regulated by c-di-GMP, and the cellulose production as well as biofilm were reduced. The addition of exogenous c-di-GMP could mitigate the inhibition of COS on C. sakazakii biofilm. These results not only help to elucidate biofilm inhibition mechanism of COS, but also provided a basis for developing anti-biofilm agents targeted OmpA.

Whole-transcriptome analysis after the acquisition of antibiotic resistance of Cronobacter sakazakii: Mechanisms of antibiotic resistance and virulence changes

The emergence of antibiotic-resistant bacteria led to the misuse of antibiotics, resulting in the emergence of more resistant bacteria and continuous improvement in their resistance ability. Cronobacter sakazakii (C. sakazakii) has been considered a pathogen that harms infants. Incidents of C. sakazakii contamination have continued globally, several studies have indicated that C. sakazakii is increasingly resistant to antibiotics. A few studies have explored the mechanism of antibiotic resistance in C. sakazakii, and some have examined the antibiotic resistance and changes in virulence levels. We aimed to investigate the antibiotic resistance mechanism and virulence differences in C. sakazakii. The level of virulence factors of C. sakazakii was modified after induction by antibiotics compared with the antibiotic-sensitive strains, and the XS001-Ofl group had the strongest capacity to produce enterotoxin (85.18 pg/mL) and hemolysin (1.47 ng/mL). The biofilm formation capacity after induction significantly improved. The number of bases and mapped reads in all groups accounted for more than 55 % and 70 %, as detected by transcriptomic analysis. The resistance mechanism of different antibiotics was more common in efflux pumps, cationic antimicrobial peptides, and biofilm formation pathways. The level of antibiotic resistance mainly affected the expression of virulence genes associated with flagella assembly and synthesis.

Characterization of Cronobacter sakazakii and Cronobacter malonaticus Strains Isolated from Powdered Dairy Products Intended for Consumption by Adults and Older Adults

The objective of this study was to characterize Cronobacter spp. and related organisms isolated from powder dairy products intended for consumption by adults and older adults using whole-genome sequencing (WGS), and to identify genes and traits that encode antibiotic resistance and virulence. Virulence (VGs) and antibiotic resistance genes (ARGs) were detected with the Comprehensive Antibiotic Resistance Database (CARD) platform, ResFinder, and MOB-suite tools. Susceptibility testing was performed using disk diffusion. Five presumptive strains of Cronobacter spp. were identified by MALDI-TOF MS and ribosomal MLST. Three C. sakazakii strains were of the clinical pathovar ST1, one was ST31, and the remaining isolate was C. malonaticus ST60. In addition, Franconibacter helveticus ST345 was identified. The C. sakazakii ST1 strains were further distinguished using core genome MLST based on 2831 loci. Moreover, 100% of the strains were resistant to cefalotin, 75% to ampicillin, and 50% to amikacin. The C. sakazakii ST1 strains were multiresistant (MDR) to four antibiotics. Additionally, all the strains adhered to the N1E-115 cell line, and two invaded it. Eighteen ARGs mainly involved in antibiotic target alteration and antibiotic efflux were detected. Thirty VGs were detected and clustered as flagellar proteins, outer membrane proteins, chemotaxis, hemolysins, and genes involved in metabolism and stress. The pESA3, pSP291-1, and pCMA1 plasmids were detected, and the prevalent mobile genetic elements (MGEs) were ISEsa1, ISEc52, and IS26. The isolates of C. sakazakii and C. malonaticus exhibited multiresistance to antibiotics, harbored genes encoding various antibiotic resistance proteins, and various virulence factors. Consequently, these contaminated powdered dairy products pose a risk to the health of hypersensitive adults.