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

Optimization of Haskap Extract and Tannic Acid Combined with Mild Heat Treatment: A Predictive Study on the Inhibition of Cronobacter sakazakii

Cronobacter sakazakii is an opportunistic food-borne pathogen that causes severe infections with high morbidity and mortality rates in neonates, the elderly, and immunocompromised individuals. The plant extracts containing natural antibacterial compounds are currently under consideration as alternatives to synthetic artificial preservatives for the control of C. sakazakii. There has been increasing interest in using plant-derived antimicrobials in combination with mild heat to control pathogens in preservative-free foods. In this study, the individual and combined effects of four independent variables, i.e., polyphenol-rich haskap extract (HE) concentration (2-10%), tannic acid (TA) concentration (0.1-0.5), temperature (35-55 °C), and time (1-5 min), on C. sakazakii inactivation were investigated by response surface methodology (RSM) with a five-level four factor central composite design (CCD) and an optimal combination for maximum inhibition was determined. The statistic metrics of R2, R2adjusted, R2predicted, coefficient of variation (CV), Predicted Residual Error Sum of Squares (PRESSs), adequate precision, and lack-of-fit were used to reveal the prediction performance. The results revealed that all the independent variables, except time, influenced C. sakazakii inactivation. Among the independent variables, the temperature was the most effective variable (p < 0.0001) as regards inactivation. The synergistic effects of HE with TA and temperature were observed. Many possible optimum conditions of mild heat treatment that maximized the inhibition of C. sakazakii were obtained. The findings indicated that two distinct combinations were identified as the most effective inhibition of C. sakazakii: high concentration at low temperature and high temperature at low concentration. It can be concluded that haskap polyphenol extract, alone or in combination with tannic acid, has the potential to be used as a natural preservative to reduce the risk of C. sakazakii.

Distribution characteristics and seasonal variation of microbial communities in powdered infant formula processing environment

The powdered infant formula (PIF) processing environment, as an industrial production site, provides a habitat conducive to microbial aggregation and colonization. However, the distribution and dynamics of microbial communities within this environment remain inadequately characterized. In this study, microbial community analysis was conducted using high-throughput sequencing on samples collected from the full production chain of 8 PIF factories. The sampling encompassed various types (raw milk, staff, air, equipment, wall and ground, and others) during two different seasons (summer and winter). The microbial diversity, composition, and dominant species varied across different groups. Potential source tracking analysis revealed close interactions between staff, air, and surface samples, indicating a potential risk of microbial transfer between staff and the processing environment. The β-nearest taxon index based null model showed that stochastic processes predominantly governed microbial community assembly across all groups. Positive interspecies interactions within the network structure, observed across different seasons and sample types, played a vital role in stabilizing and assembling microbial communities. Notably, the microbiota association networks of summer were more complex but demonstrated higher susceptibility to external disturbances. Conversely, the network structure of surface samples was more robust than that of other types of samples. These findings have improved our understanding of the microbial community distribution patterns in PIF processing environments, facilitating the prospective prediction and assessment of potential microbial sources and contamination risks in the processing chain, which in turn guides the implementation of refined control measures.

Clinical Profile and Antibiotic Susceptibility Patterns of Cronobacter sakazakii in the Northern Region of Oman

Background

Cronobacter sakazakii is an opportunistic pathogen that mostly affects neonates, infants, and elderly people with weakened immune systems. No study has reported the frequency and antibiotic susceptibility patterns of C. sakazakii from Oman, and thus this study was conducted to fill this gap in the literature.

Materials and Methods

This single-center retrospective study included C. sakazakii isolates identified from different clinical samples of patients treated at Sohar Hospital, Oman, between January 2017 and December 2023. Bacterial identification and antibiotic susceptibility testing were done using the VITEK II automated microbiological system in accordance with the Clinical Laboratory Standards Institute (CLSI) guidelines.

Results

A total of 185 C. sakazakii isolates were included, most commonly from patients aged >60 years (42.7%) and <1 year (11.4%). C. sakazakii strains had high susceptibility (>80%) to most of the tested antibiotics; however, for beta-lactam antibiotics, it ranged from 0% to 50%. Approximately 26.5% of the strains were multidrug resistant. Independent risk factors for increased frequency of multidrug-resistant strains were urinary catheterization (P = 0.002), surgery (P = 0.021), previous antibiotic therapy (P = 0.047), and critical care unit admission (P = 0.048). About one-fifth of the patients experienced life-threatening C. sakazakii infections such as septicemia (15%) and pneumonia (4.7%). All deaths due to septicemia occurred in the >60 years (n = 12) and <1 year (n = 4) age groups.

Conclusions

Cronobacter sakazakii isolates from the North Batinah region of Oman were most frequently isolated from elderly and infant patients and had high antibiotic susceptibility; however, the significant resistance against beta-lactams suggests their low effectiveness. The high number of multidrug-resistant strains coupled with the independent risk factors suggests the need for following stricter antibiotic stewardship protocols and infection control practices.

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.