Risk profile of Enterobacter sakazakii, an emergent pathogen associated with infant milk formula

Impact of kdpE gene deletion on virulence and environmental resilience in Cronobacter sakazakii

Cronobacter sakazakii is a Gram-negative, foodborne pathogen associated with severe infections, particularly in infants and immunocompromised individuals. Given its significant public health implications and its remarkable resilience in powdered infant formula, understanding the genetic factors that contribute to its virulence and environmental tolerance is crucial. This study focuses on the kdpE gene in Cronobacter sakazakii, part of a two-component regulatory system known for its role in adaptation to environmental stress. A kdpE knockout mutant of Cronobacter sakazakii was constructed to evaluate its effects on bacterial growth, virulence, biofilm formation, and desiccation tolerance. The results revealed that kdpE deletion reduced bacterial growth and virulence, as evidenced by higher survival rates in rats infected with the ΔkdpE mutant compared to the wild-type strain. Notably, the ΔkdpE mutant showed significant downregulation of proteins involved in carbon metabolism and respiratory activity, while proteomic analysis revealed increased deamidation of proteins related to glycolysis. Furthermore, biofilm formation was significantly impaired in the mutant, although its desiccation tolerance was enhanced, attributed to the upregulation of the molecular chaperone GrpE. These findings suggest that kdpE plays a crucial role in regulating the virulence and environmental adaptability of Cronobacter sakazakii, with implications for understanding its pathogenic mechanisms and developing preventive measures.

Disruption of the rpfB Gene Impairs Growth and Virulence in Cronobacter sakazakii through Downregulation of the Shikimate Pathway

The rpfB gene, encoding long-chain acyl-CoA synthetase, plays an essential role in the fatty acid metabolism of Cronobacter sakazakii, a pathogenic bacterium known to cause neonatal infections. Here, we investigate the functional consequences of rpfB gene knockout and its effect on bacterial growth and virulence. Our findings demonstrate that rpfB deletion leads to significantly reduced bacterial growth and virulence in a murine infection model. Proteomic analysis revealed that the disruption of rpfB markedly downregulates key enzymes in the shikimate pathway, including aroA and aroK, which are essential for the biosynthesis of aromatic amino acids. Supplementation with aromatic amino acids restored the growth defect, highlighting the critical link between fatty acid metabolism and the shikimate pathway. These results uncover a novel regulatory role for rpfB in coordinating metabolic networks that control bacterial growth and virulence. This study provides a new understanding of the metabolic mechanisms underlying C. sakazakii pathogenicity and identifies possible metabolic targets for antimicrobial development.

Structural and Functional Characterization of a Putative Type VI Secretion System Protein in Cronobacter sakazakii as a Potential Therapeutic Target: A Computational Study

Background

Cronobacter sakazakii, a foodborne pathogen with a fatality rate of 33%, is a rod-shaped, Gram-negative, non-spore-forming bacterium responsible for causing meningitis, bacteremia, and necrotizing enterocolitis. Despite many unknown functions of hypothetical proteins in bacterial genomes, bioinformatic techniques have successfully annotated their roles in various pathogens.

Objectives

The aim of this investigation is to identify and annotate the structural and functional properties of a hypothetical protein (HP) from Cronobacter sakazakii 7G strain (accession no. WP_004386962.1, 277 residues) using computational tools.

Methods

Multiple bioinformatic tools were used to identify the homologous protein and to construct and validate its 3D structure. A 3D model was generated using SWISS-MODEL and validated using tools, developing a reliable 3D structure. The STRING and CASTp servers provided information on protein-protein interactions and active sites, identifying functional partners.

Results

The putative protein was soluble, stable, and localized in the cytoplasmic membranes, indicating its biological activity. Functional annotation identified TagJ (HsiE1) within the protein, a member of the ImpE superfamily involved in the transport of toxins and a part of the bacterial type VI secretion system (T6SS). The 3-dimensional structure of this protein was validated through molecular docking involving 6 different compounds. Among these, ceforanide demonstrated the strongest binding scores, -7.5 kcal/mol for the hypothetical protein and -7.2 kcal/mol for its main template protein (PDB ID: 4UQX.1).

Conclusion

Comparative genomics study suggests that the protein found in C. sakazakii may be a viable therapeutic target because it seems distinctive and different from human proteins. The results of multiple sequence alignment (MSA) and molecular docking supported HP's potential involvement as a T6SS. These in silico results represent that the examined HP could be valuable for studying C. sakazakii infections and creating medicines to treat C. sakazakii-mediated disorders.

Prevalence of Cronobacter spp. in Tropical Seafood From Mumbai, India: Comparative Study of Isolation Media and PCR Detection

BACKGROUND

Cronobacter species are opportunistic emerging pathogens associated with diverse foods of plant and animal origin. Considering the diversity of the Cronobacter group of bacteria and their co-existence with closely related Enterobacterales in the aquatic environment, their isolation from fish and shellfish is a challenge.

OBJECTIVE

This study aimed to investigate the incidence of Cronobacter in finfish, shellfish, and dried fish, and to compare nine combinations of enrichment broth-selective isolation media for efficient isolation of Cronobacter spp.

METHODS

Seventy-five seafood samples collected from five different retail markets were subjected to multiple selective-enrichment methods to isolate Cronobacter, which were presumptively identified by biochemical tests followed by confirmation with genus- and species-specific PCRs.

RESULTS

Of 75 seafood samples analyzed, 24 (32%) were positive for Cronobacter spp. The highest incidence was in dried fish (21 samples, 47.72%), followed by 19 (43.18%) fresh finfish and four (9.09%) shellfish samples. Forty-four isolates from these samples were identified as Cronobacter spp. by PCR. Species-specific PCR further categorized these as C. sakazakii (25), C. malonaticus (16), and C. turicensis (1), while two isolates remained unidentified at species level. Enrichment in Cronobacter screening broth or Rappaport Vassiliadis (RV) medium, followed by isolation on chromogenic Cronobacter sakazakii agar was found to be the most effective combination for the isolation of Cronobacter spp. from seafood.

CONCLUSIONS

Dried fish is an important reservoir of C. sakazakii owing to its desiccation tolerance and absence of competing microbiota in dried fish. Although C. sakazakii is the only known pathogen among Cronobacter spp., improved and specific methods to identify diverse members of this genus are needed.

HIGHLIGHTS

Cronobacter sakazakii and C. malonaticus are predominant in tropical seafood. RV with chromogenic CS agar is the most efficient isolation medium for Cronobacter. Specificity of existing PCRs is limited to C. sakazakii and C. malonaticus only. Genus- and species-specific PCRs enhance Cronobacter identification.

Isolation of Pathogenic Cronobacter Species as Bacteriological Risks Indicator in Powdered Infant Formula Available to Deprived Infants in Lagos Metropolis, Nigeria

Powdered infant formula (PIF) is rich in nutrients that support the survival and growth of bacteria that trigger food safety disorders in deprived infants through life-threatening illnesses. The study aims to examine and identify the incidence of pathogenic bacteria of concern in PIF upon reconstitution in lukewarm water. A total of 172 samples consisting of 38 brands of PIF available in the Lagos metropolis were sampled, suspended in water (10 g in 100 mL), and bacteria strains were isolated using combinational enrichment and selective culture techniques. Pure bacterial strains were characterized and identified based on their physiology and 16S rRNA gene sequence homology. While 85 bacterial strains were isolated from the enriched culture system, 20 strains were selectively isolated based on tolerance to sodium deoxycholate. Approximately 13% of the selected bacteria were identified as Cronobacter spp., exhibiting virulence traits including extracellular protease production, coagulation and proteolysis of casein, haem-agglutination, and β-haemolysis of human blood. Approximately 82% of the Cronobacter strains tolerated NaCl (10%) and bile salt; and exhibited resistance to cefotaxime, ceftriaxone, gentamicin, and Amoxicillin-clavulanic acid antibiotics. The presence of Cronobacter spp. in 13% of the PIF brands available to infants calls for concern about the safety of deprived infants that might be fed with such PIF. Consequently, PIF safety alerts need to be activate while further studies on critical points at which the pathogens get introduced to the PIFs need to be identified.

Emergent methods for inactivation of Cronobacter sakazakii in foods: A systematic review and meta-analysis

Cronobacter sakazakii is a potentially pathogenic bacterium that is resistant to osmotic stress and low aw, and capable of persisting in a desiccated state in powdered infant milks. It is widespread in the environment and present in various products. Despite the low incidence of cases, its high mortality rates of 40 to 80 % amongst neonates make it a microorganism of public health interest. This current study performed a comparative assessment between current reduction methods applied for C. sakazakii in various food matrices, indicating tendencies and relevant parameters for process optimization. A systematic review and meta-analysis were conducted, qualitatively identifying the main methods of inactivation and control, and quantitatively evaluating the effect of treatment factors on the reduction response. Hierarchical clustering dendrograms led to conclusions on the efficiency of each treatment. Review of recent research trend identified a focus on the potential use of alternative treatments, with most studies related to non-thermal methods and dairy products. Using random-effects meta-analysis, a summary effect-size of 4-log was estimated; however, thermal methods and treatments on dairy matrices displayed wider dispersions - of τ2 = 8.1, compared with τ2 = 4.5 for vegetal matrices and τ2 = 4.0 for biofilms. Meta-analytical models indicated that factors such as chemical concentration, energy applied, and treatment time had a more significant impact on reduction than the increase in temperature. Non-thermal treatments, synergically associated with heat, and treatments on dairy matrices were found to be the most efficient.

Genomic Analysis of Cronobacter condimenti s37: Identification of Resistance and Virulence Genes and Comparison with Other Cronobacter and Closely Related Species

Cronobacter condimenti are environmental commensals that have not been associated with any clinical infections. To date, they are the least understood and described Cronobacter species within the genus. The objective of this study was to use a draft genome sequence (DGS) of the Cronobacter condimenti strain s37 to screen for genes encoding for antibiotic resistance, virulence, response to environmental stress, and biofilm formation. The strain was isolated in Poland from commercial small radish sprouts. This is the second genome of this species available in the GenBank database. The comparative genome analysis (cgMLST) of C. condimenti s37 with other Cronobacter spp. including the pathogenic species C. sakazakii and the plant-associated closely related genera Franconibacter and Siccibacter was also performed. The assembled and annotated genome of the C. condimenti s37 genome was 4,590,991 bp in length, with a total gene number of 4384, and a GC content of 55.7%. The s 37 genome encoded for genes associated with resistance to stressful environmental conditions (metal resistance genes: zinc, copper, osmotic regulation, and desiccation stress), 17 antimicrobial resistance genes encoding resistance to various classes of antibiotics and 50 genes encoding for the virulence factors. The latter were mainly genes associated with adhesion, chemotaxis, hemolysis, and biofilm formation. Cg-MLST analysis (3991 genes) revealed a greater similarity of C. condimenti s37 to S. turicensis, F. pulveris, and C. dublinensis than to other species of the genus Cronobacter. Studies on the diversity, pathogenicity, and virulence of Cronobacter species isolated from different sources are still insufficient and should certainly be continued. Especially the analysis of rare strains such as s37 is very important because it provides new information on the evolution of these bacteria. Comparative cgMLST analysis of s37 with other Cronobacter species, as well as closely related genera Franconibacter and Siccibacter, complements the knowledge on their adaptability to specific environments such as desiccation.

Integrating Recombinase Polymerase Amplification and Photosensitization Colorimetric Detection in One Tube for Fast Screening of C. sakazakii in Formula Milk Powder

Cronobacter sakazakii (C. sakazakii) is a widely existing opportunistic pathogen and thus threatens people with low immunity, especially infants. To prevent the outbreak, a rapid and accurate on-site testing method is required. The current standard culture-based method is time-consuming (3-4 days), while the nucleic acid amplification (PCR)-based detection is mostly carried out in central laboratories. Herein, isothermal recombinase polymerase amplification (RPA) coupled with a photosensitization colorimetric assay (PCA) was adopted for the on-site detection of C. sakazakii in powdered infant formulas (PIFs). The lowest visual detection concentration of C. sakazakii is 800 cfu/mL and 2 cfu/g after 8 h bacteria pre-enrichment. Furthermore, to avoid typical cap opening-resulted aerosol pollution, the PCA reagents were lyophilized onto the cap of the RPA tube (containing lyophilized RPA reagents). After amplification, the tube was subjected to simple shaking to mix the PCA reagents with the amplification products for light-driven color development. Such a one-tube assay offered a lowest concentration of 1000 copies of genomic DNA of C. sakazakii within 1 h. After 8 h of bacterial enrichment, the lowest detecting concentration could be pushed down to 5 cfu/g bacteria in PIF. To facilitate on-site monitoring, a portable, battery-powered PCA device was designed to mount the typical RPA 8-tube strip, and a color analysis cellphone APP was further employed for facile readout.

Global and regional prevalence of Cronobacter sakazakii in powdered milk and flour

Cronobacter sakazakii (Cz) infections linked with powdered milk/flour (PMF) are on the increase in recent times. The current study aimed at assessing worldwide and regional prevalence of Cz in PMF. Cz-PMF-directed data were conscientiously mined in four mega-databases via topic-field driven PRISMA protocol without any restriction. Bivariate analysis of datasets was conducted and then fitted to random-intercept logistic mixed-effects regressions with leave-one-study-out-cross-validation (LOSOCV). Small-study effects were assayed via Egger's regression tests. Contributing factors to Cz contamination/detection in PMF were determined using 1000-permutation-bootstrapped meta-regressions. A total of 3761 records were found out of which 68 studies were included. Sample-size showed considerable correlation with Cz positivity (r = 0.75, p = 2.5e-17), Milkprod2020 (r = 0.33, p = 1.820e-03), and SuDI (r = - 0.30, p = 4.11e-03). The global prevalence of Cz in PMF was 8.39% (95%CI 6.06-11.51, PI: 0.46-64.35) with LOSOCV value of 7.66% (6.39-9.15; PI: 3.10-17.70). Cz prevalence in PMF varies significantly (p < 0.05) with detection methods, DNA extraction method, across continents, WHO regions, and world bank regions. Nation, detection method, world bank region, WHO region, and sample size explained 53.88%, 19.62%, 19.03%, 15.63%, and 9.22% of the true differences in the Cz prevalence in PMF, respectively. In conclusion, the results indicated that national will power in the monitoring and surveillance of Cz in PMF matched with adequate sample size and appropriate detection methods will go a long way in preventing Cz contamination and infections.

Environmental risk factors associated with the survival, persistence, and thermal tolerance of Cronobacter sakazakii during the manufacture of powdered infant formula

Cronobacter sakazakii is an opportunistic foodborne pathogen of concern for foods having low water activity such as powdered infant formula (PIF). Its survival under desiccated stress can be attributed to its ability to adapt effectively to many different environmental stresses. Due to the high risk to neonates and its sporadic outbreaks in PIF, C. sakazakii received great attention among the scientific community, food industry and health care providers. There are many extrinsic and intrinsic factors that affect C. sakazakii survival in low-moisture foods. Moreover, short- or long-term pre-exposure to sub-lethal physiological stresses which are commonly encountered in food processing environments are reported to affect the thermal resistance of C. sakazakii. Additionally, acclimation to these stresses may render C. sakazakii resistance to antibiotics and other antimicrobial agents. This article reviews the factors and the strategies responsible for the survival and persistence of C. sakazakii in PIF. Particularly, studies focused on the influence of various factors on thermal resistance, antibiotic or antimicrobial resistance, virulence potential and stress-associated gene expression are reviewed.

Cronobacter spp. Isolated from Quick-Frozen Foods in China: Incidence, Genetic Characteristics, and Antibiotic Resistance

Cronobacter spp. are emerging foodborne pathogens that cause severe diseases. However, information on Cronobacter contamination in quick-frozen foods in China is limited. Therefore, we studied the prevalence, molecular characterization, and antimicrobial susceptibility of Cronobacter in 576 quick-frozen food samples collected from 39 cities in China. Cronobacter spp. were found in 18.75% (108/576) of the samples, and the contamination degree of the total positive samples was 5.82 MPN/g. The contamination level of frozen flour product samples was high (44.34%). Among 154 isolates, 109 were C. sakazakii, and the main serotype was C. sakazakii O1 (44/154). Additionally, 11 serotypes existed among four species. Eighty-five sequence types (STs), including 22 novel ones, were assigned, indicating a relatively high genetic diversity of the Cronobacter in this food type. Pathogenic ST148, ST7, and ST1 were the main STs in this study. ST4, epidemiologically related to neonatal meningitis, was also identified. All strains were sensitive to cefepime, tobramycin, ciprofloxacin, and imipenem, in which the resistance to cephalothin was the highest (64.94%).Two isolates exhibited multidrug resistance to five and seven antimicrobial agents, respectively. In conclusion, these findings suggest that the comparatively high contamination level of Cronobacter spp. in quick-frozen foods is a potential risk warranting public attention.

"Multidimensional correlation analysis of temperature and contact time on eradication of biofilms of Cronobacter sakazakii on abiotic surfaces by combination of hypochlorite and malic acid"

AIM

In the present study, malic acid in combination with sodium hypochlorite is evaluated for eradication of biofilms formed by Cronobacter sakazakii strains individually and in a cocktail on different abiotic surfaces.

METHOD AND RESULTS

The biofilm formation by five strains of C. sakazakii and their cocktail culture on different substrates was studied in Tryptone Soy Broth (TSB) and reconstituted Powdered Infant Formula (PIF). Further, the effect of temperature (4, 27, 37 and 50°C) and contact time (10, 20, 30, 40, 50 and 60 min) on antibiofilm potential of test solution (0.0625 mol l-1 malic acid and 0.00004 mol l-1 sodium hypochlorite) against biofilm formed by C. sakazakii cocktail culture was investigated on these surfaces. The effect was evaluated in terms of viable cell count and biofilm texture using scanning electron microscopy (SEM). Principal Component Analysis (PCA) revealed that the maximum biofilm reduction was observed for stainless steel at 4°C after 60 min of contact whereas at 25, 37 and 50°C, maximum biofilm reduction was observed for polycarbonate. For glass and polyurethane, maximum log reductions were observed at 50°C. The SEM images revealed cell surface deformation and disruption in biofilms after treatment with the test solution.

CONCLUSIONS

The antibiofilm potential was observed to be greatly affected by contact time and temperature. These results indicated that the combination of malic acid NaOCl can effectively kill and remove C. sakazakii biofilms from food contact surfaces and enteral feeding tubes.

Factors Influencing Biofilm Formation by Salmonella enterica sv. Typhimurium, E. cloacae, E. hormaechei, Pantoea spp., and Bacillus spp. Isolated from Human Milk Determined by PCA Analysis

Bacteria enter milk during poor hygiene practices and can form a biofilm on surfaces that come into contact with human milk. The presence of a biofilm increases the risk of infections among newborns as bacteria protected by biofilm are resistant to washing and disinfection processes. The formation of the biofilm depends on the microbial species, environmental conditions, and the specific materials colonized. The aim of this study is to analyze the effects of factors such as temperature, incubation time, and initial cell concentration on biofilm formation by pathogenic bacteria isolated from human milk on model hydrophobic polystyrene surfaces. Model studies confirm that pathogenic bacteria appearing in human milk as a result of cross-contamination tend to form a biofilm. The majority of isolates formed biofilm at both 25 and 37 °C after 12 h at 1 × 10³ CFU/mL inoculum count. Multivariate principal component analysis (PCA) showed that at lower temperatures, biofilm formation by bacterial isolates was the main determinant of biofilm formation, other factors were less important; however, at 37 °C, time was a factor in biofilm formation. The model research performed underlines the importance of maintaining the proper hygiene of rooms, surfaces, and devices for expressing, storing, and preparing mothers' milk and powdered infant formula (PIF) in facilities responsible for feeding newborns and premature babies.

Virulence, antimicrobial susceptibility, and phylogenetic analysis of Cronobacter sakazakii isolates of food origins from Jordan

AIMS

to characterize a collection of Cronobacter sakazakii isolates collected from various origins in Jordan.

METHODS AND RESULTS

the isolates were characterized using 16S rRNA sequencing, DNA microarray, multi-locus sequence typing (MLST), O-serotyping, virulence gene identification, and antibiotic susceptibility testing. The identities and phylogenetic relatedness revealed that C. sakazakii sequence type 4 (ST4) and Csak O:1 serotype was the most prevalent STs and serovars among these C. sakazakii strains. PCR screening of putative virulence genes showed that the siderophore-interacting protein gene (sip) and iron acquisition gene clusters (eitCBAD and iucABCD/iutA) were the most detected genes with noticeable variability in the type 6 secretion system (T6SS) and filamentous hemagglutinin/adhesion (FHA) gene loci. The antibiotic resistance profiles revealed that the majority of the isolates were susceptible to all antibiotics used despite harboring a class C β-lactamase resistance gene.

CONCLUSIONS

the results described in this report provide additional insights about the considerable genotypic and phenotypic heterogeneity within C. sakazakii.

SIGNIFICANCE AND IMPACT OF THE STUDY

the information reported in this study might be of great value in understanding the origins of C. sakazakii isolates, in addition to their diversity and variability, which might be helpful in preventing future outbreaks of this pathogen.

Prevalence of ESKAPE pathogens in the environment: Antibiotic resistance status, community-acquired infection and risk to human health

The ESKAPE (Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter spp.) pathogens are characterised by increased levels of resistance towards multiple classes of first line and last-resort antibiotics. Although these pathogens are frequently isolated from clinical environments and are implicated in a variety of life-threatening, hospital-associated infections; antibiotic resistant ESKAPE strains have been isolated from environmental reservoirs such as surface water, wastewater, food, and soil. Literature on the persistence and subsequent health risks posed by the ESKAPE isolates in extra-hospital settings is however, limited and the current review aims to elucidate the primary reservoirs of these pathogens in the environment, their antibiotic resistance profiles, and the link to community-acquired infections. Additionally, information on the current state of research regarding health-risk assessments linked to exposure of the ESKAPE pathogens in the natural environment, is outlined.

Characterization of Cronobacter sakazakii Strains Originating from Plant-Origin Foods Using Comparative Genomic Analyses and Zebrafish Infectivity Studies

Cronobacter sakazakii continues to be isolated from ready-to-eat fresh and frozen produce, flours, dairy powders, cereals, nuts, and spices, in addition to the conventional sources of powdered infant formulae (PIF) and PIF production environments. To understand the sequence diversity, phylogenetic relationship, and virulence of C. sakazakii originating from plant-origin foods, comparative molecular and genomic analyses, and zebrafish infection (ZI) studies were applied to 88 strains. Whole genome sequences of the strains were generated for detailed bioinformatic analysis. PCR analysis showed that all strains possessed a pESA3-like virulence plasmid similar to reference C. sakazakii clinical strain BAA-894. Core genome analysis confirmed a shared genomic backbone with other C. sakazakii strains from food, clinical and environmental strains. Emerging nucleotide diversity in these plant-origin strains was highlighted using single nucleotide polymorphic alleles in 2000 core genes. DNA hybridization analyses using a pan-genomic microarray showed that these strains clustered according to sequence types (STs) identified by multi-locus sequence typing (MLST). PHASTER analysis identified 185 intact prophage gene clusters encompassing 22 different prophages, including three intact Cronobacter prophages: ENT47670, ENT39118, and phiES15. AMRFinderPlus analysis identified the CSA family class C β-lactamase gene in all strains and a plasmid-borne mcr-9.1 gene was identified in three strains. ZI studies showed that some plant-origin C. sakazakii display virulence comparable to clinical strains. Finding virulent plant-origin C. sakazakii possessing significant genomic features of clinically relevant STs suggests that these foods can serve as potential transmission vehicles and supports widening the scope of continued surveillance for this important foodborne pathogen.

Complete genome sequences and genomic characterization of five plasmids harbored by environmentally persistent Cronobacter sakazakii strains ST83 H322 and ST64 GK1025B obtained from powdered infant formula manufacturing facilities

Background

Cronobacter sakazakii is a foodborne pathogen that causes septicemia, meningitis, and necrotizing enterocolitis in neonates and infants. The current research details the full genome sequences of two extremely persistent C. sakazakii strains (H322 and GK1025B) isolated from powdered infant formula (PIF) manufacturing settings. In addition, the genetic attributes associated with five plasmids, pH322_1, pH322_2, pGK1025B_1, pGK1025B_2, and pGK1025B_3 are described.

Materials and Methods

Using PacBio single-molecule real-time (SMRT^®) sequencing technology, whole genome sequence (WGS) assemblies of C. sakazakii H322 [Sequence type (ST)83, clonal complex [CC] 83) and GK1025B (ST64, CC64) were generated. Plasmids, also sequenced, were aligned with phylogenetically related episomes to determine, and identify conserved and missing genomic regions.

Results

A truncated ~ 13 Kbp type 6 secretion system (T6SS) gene cluster harbored on virulence plasmids pH322_2 and pGK1025B_2, and a second large deletion (~ 6 Kbp) on pH322_2, which included genes for a tyrosine-type recombinase/integrase, a hypothetical protein, and a phospholipase D was identified. Within the T6SS of pH322_2 and pGK1025B_2, an arsenic resistance operon was identified which is in common with that of plasmids pSP291_1 and pESA3. In addition, PHASTER analysis identified an intact 96.9 Kbp Salmonella SSU5 prophage gene cluster in pH322_1 and pGK1025B_1 and showed that these two plasmids were phylogenetically related to C. sakazakii plasmids: pCS1, pCsa767a, pCsaC757b, pCsaC105731a. Plasmid pGK1025B_3 was identified as a novel conjugative Cronobacter plasmid. Furthermore, WGS analysis identified a ~ 16.4 Kbp type 4 secretion system gene cluster harbored on pGK1025B_3, which contained a phospholipase D gene, a key virulence factor in several host–pathogen diseases.

Conclusion

These data provide high resolution information on C. sakazakii genomes and emphasizes the need for furthering surveillance studies to link genotype to phenotype of strains from previous investigations. These results provide baseline data necessary for future in-depth investigations of C. sakazakii that colonize PIF manufacturing facility settings and genomic analyses of these two C. sakazakii strains and five associated plasmids will contribute to a better understanding of this pathogen's survival and persistence within various “built environments” like PIF manufacturing facilities.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13099-022-00500-5.

Proteomic Analysis Revealed Metabolic Inhibition and Elongation Factor Tu Deamidation by p-Coumaric Acid in Cronobacter sakazakii

Screening drugs and compounds to fight against Cronobacter sakazakii (C. sakazakii), one of the most common pathogens that can cause fatal necrotizing enterocolitis, septicema and meningitis, is still needed. We found that p-coumaric acid (pCA) has an inhibitory effect on C. sakazakii in vitro and in vivo. Proteomic changes of C. sakazakii BAA-894 exposed to pCA were studied to reveal the antibacterial mechanisms involved. A total of 1,553 proteins were identified in C. sakazakii BAA-894 by label-free proteomics analysis. Fuzzy cluster analysis showed that 33 were up-regulated, and 110 were down-regulated with pCA treatment. Gene Ontology (GO) analysis concluded that pCA caused the change of metabolic state of bacteria and generally in the state of metabolic inhibition. KEGG Enrichment Analysis (KEGG) analysis showed that pCA inhibited energy metabolism and distorted the balance of amino acid metabolism. Posttranslational modification analysis showed that pCA affected the deamidation of three proteins, including Elongation factor Tu, one of the vital proteins in bacteria. Molecular docking suggested the hydrogen bond between the pCA carboxyl group and Elongation factor Tu Asn-64 might contribute to deamidation. Overall, we found that pCA interfered with cellular energy and amino acid metabolism and promoted elongation factor Tu deamidation, suggesting that pCA can be an effective natural substitute to control C. sakazakii.

Why Does Cronobacter sakazakii Survive for a Long Time in Dry Environments? Contribution of the Glass Transition of Dried Bacterial Cells

To investigate the mechanism of adaptation of Cronobacter sakazakii to desiccation stress, the present study focused on the glass transition phenomenon of dried bacterial cells, using a thermomechanical technique. The mechanical glass transition temperature (T_g) of dried C. sakazakii cells per se, prepared by different drying methods (air drying and freeze-drying) and with different water activity (a_w) levels (0.43, 0.57, 0.75, and 0.87), were determined. In addition, we investigated the survival of two strains of C. sakazakii (JCM 1233 and JCM 2127) prepared by different drying methods under different storage temperatures (4, 25, and 42°C) and a_w conditions (0.43 and 0.87). While the T_g of the air-dried C. sakazakii cells increased as the a_w decreased, the freeze-dried C. sakazakii cells showed an unclear a_w dependency of the T_g. Air-dried C. sakazakii cells showed a higher T_g than freeze-dried C. sakazakii cells at an a_w of <0.57. Freeze-dried C. sakazakii cells were more rapidly inactivated than air-dried cells regardless of the difference in a_w and temperature. The difference between the T_g and storage temperature was used as an index that took into consideration the differences in the drying methods and a_w levels. As the difference between the T_g and storage temperature increased to >20°C, the dried C. sakazakii cells survived stably regardless of the drying method. In contrast, when the difference between the T_g and storage temperature was reduced to <10°C, the viable cell numbers in dried C. sakazakii cells were quickly decreased. Thus, the T_g is a key factor affecting the desiccation tolerance of C. sakazakii.

IMPORTANCE The mechanical glass transition temperature (T_g) of dried Cronobacter sakazakii cells varied depending on differences in drying methods and water activity (a_w) levels. Because the T_g of the dried bacterial cells varied depending on the drying method and a_w, the T_g will play an important role as an operational factor in the optimization of dry food processing for controlling microbial contamination in the future. Furthermore, the differences between the T_g and storage temperature were introduced as an integrated index for survival of bacterial cells under a desiccation environment that took into consideration the differences in the drying methods and a_w levels. As the difference between the T_g and storage temperature decreased to <10°C, the dried C. sakazakii cells were inactivated quickly, regardless of the drying methods. The relationship between T_g and storage temperature will contribute to understanding the desiccation tolerance of bacterial cells.

Invited review: Stress resistance of Cronobacter spp. affecting control of its growth during food production

Members of the Cronobacter genus include food-borne pathogens that can cause infections in infants, with a mortality rate as high as 40 to 80%. The high fatality rate of Cronobacter and its isolation from numerous types of food, especially from powdered infant formula, demonstrate the serious nature of this organism. The source tracking of Cronobacter spp. and the analysis of high-frequency species from different sources are helpful for a more targeted control. Furthermore, the persistence during food processing and storage may be attributed to strong resistance of Cronobacter spp. to environment stresses such as heat, pH, and desiccation. There are many factors that support the survival of Cronobacter spp. in harsh environments, such as some genes, regulatory systems, and biofilms. Advanced detection technology is helpful for the strict monitoring of Cronobacter spp. In addition to the traditional heat treatment, many new control techniques have been developed, and the ability to control Cronobacter spp. has been demonstrated. The control of this bacteria is required not only during manufacture, but also through the selection of packaging methods to reduce postprocessing contamination. At the same time, the effect of inactivation methods on product quality and safety must be considered. This review considers the advances in our understanding of environmental stress response in Cronobacter spp. with special emphasis on its implications in food processing.

The application of bacteriophage to control Cronobacter sakazakii planktonic and biofilm growth in infant formula milk

The goal was to identify the biofilm-forming ability of Cronobacter sakazakii on surfaces of stainless steel (SS) and silicone rubber (SR) in contact with infant formula milk. Two representative bacteriophages (PBES04 and PBES19) were used to control the growth of C. sakazakii as well as its biofilm forming ability on either SS or SR surfaces. Bacterial growth was confirmed at 20 °C when PBES04 and PBES19 were used, whereas C. sakazakii was not normally detected in infant formula milk treated with both bacteriophages for 6 h. In an additional biofilm reduction experiment, the biofilm on SS or SR surfaces were reduced by 3.07 and 1.92 log CFU cm^-2, respectively after PBES04 treatment, and 3.06 and 2.14 log CFU cm^-2, respectively, after PBES19 treatment. These results demonstrate that bacteriophages can be effective in inactivating C. sakazakii in biofilms which could potentially increase food safety in commercial facilities.

Application of MALDI-TOF mass spectrometry, and DNA sequencing-based SLST and MLST analysis for the identification of Cronobacter spp. isolated from environmental surveillance samples

Cronobacter spp. are emerging infectious foodborne bacteria that can cause acute meningitis and necrotizing enterocolitis in neonates and immunocompromised individuals. Although, little is known about its reservoirs or transmission routes, it has been linked to powdered infant formula worldwide. Three Cronobacter spp. (C. sakazakii, C. malonaticus, and C. turicensis) have been described as more virulent, and isolated frequently from infant meningitis cases. The estimated mortality rates are as high as 80% in infants. Thus, surveillance and typing of Cronobacter spp. isolated from food and environmental samples is essential to prevent contamination and spread of this pathogen. In this study, we have characterized 83 Cronobacter isolates recovered from various environmental samples by conventional microbiologic protocols. Species identification was accomplished by VITEK 2 system and real-time PCR analysis. Subsequently, these isolates were analyzed using VITEK MS system. Single locus sequence typing (SLST) was achieved by characterizing the regions of 16S rRNA and rpoB genes. Multilocus sequence typing (MLST) was performed by sequence characterization of seven housekeeping genes (atpD, fusA, glnS, gltB, gyrB, infB, and pps) using ABI 3500XL Genetic Analyzer. VITEK MS system identified, the majority of isolates as Cronobacter sakazakii with a high confidence value (99.9%). MLST analysis ascertained 12 distinct clonal complexes (CC1, CC4, CC8, CC13, CC17, CC21, CC31, CC40, CC52, CC64, CC73, and CC83) for the recovered C. sakazakii isolates. The results suggest that the MALDI-TOF MS is a reliable diagnostic tool for rapid species identification whereas 7-loci MLST is a powerful technique to discriminate and differentiate Cronobacter spp. isolates.

Multivariate analysis of adaptive response to ferulic acid and p-coumaric acid after physiological stresses in Cronobacter sakazakii

AIM

The present study demonstrated the antimicrobial activity of ferulic acid and p-coumaric acid against unstressed and stressed (cold stressed, starved and desiccated) Cronobacter sakazakii in laboratory media (37°C) and reconstituted powdered infant formulation (PIF) with mild heat treatment (50°C).

METHODS AND RESULTS

Five phenolics, namely, quercetin, rutin, caffeic acid, ferulic acid and p-coumaric acid, were tested for antimicrobial activities against five strains of C. sakazakii either unstressed or stressed. Strain specific higher resistance to ferulic acid and p-coumaric acid was observed after stress adaptation in laboratory media. The effect of cross protection was validated using reconstituted PIF as delivery vehicle of selected compounds. Both p-coumaric acid and ferulic acid showed inhibition of C. sakazakii in a dose and time dependent manner as revealed by their viable cell counts. Principal component analysis revealed that the desiccated cells were more sensitive to phenolics in reconstituted PIF.

CONCLUSIONS

Only ferulic acid and p-coumaric acid showed marked antibacterial activity with minimum inhibitory concentration in the range of 2·5-5 mg ml^-1 for unstressed C. sakazakii cells in tryptone soy broth. The maximum inhibition was achieved with 20 mg ml^-1 of both the tested polyphenols in reconstituted PIF. Cold stress and starvation stress did not impart any protection nor increased the susceptibility of C. sakazakii, whereas desiccation resulted in increased susceptibility to phenolic compounds.

SIGNIFICANCE AND IMPACT OF THE STUDY

The results obtained in this study helps in understanding the effect of environmental stresses during processing on susceptibility of C. sakazakii to natural antimicrobial agents. Future transcriptomic studies and functional genetic studies are warranted to understand the strain specific stress responses for the development of better control methods possibly by using these natural antagonists.

First case report of acute cholangitis secondary to Cronobacter sakazakii

Introduction

Cronobacter sakazakii is an opportunistic Gram-negative, rod-shaped bacterium which may be a causative agent of meningitis in premature infants and enterocolitis and bacteremia in neonates and adults. While there have been multiple cases of C. sakazakii infections, there have been no acute cholangitis cases reported in humans.

Case presentation

An 81-year-old male with a past medical history of basal cell carcinoma, alcoholic liver cirrhosis, transjugular intrahepatic portosystemic shunt procedure, complicated by staphylococcus bacteremia, pituitary tumor, glaucoma, and hypothyroidism presented to the emergency room with the complaint of diffuse and generalized 10/10 abdominal pain of 1 day’s duration. There was a concern for pancreatitis, acute cholangitis, and possible cholecystitis, and the patient underwent a percutaneous cholecystostomy tube placement. Blood cultures from admission and biliary fluid cultures both grew C. sakazakii. The patient was treated with a carbapenem and clinically improved.

Conclusions

The case study described a patient with multiple medical comorbidities that presented with C. sakazakii bacteremia and cholangitis. While this bacterium has been implicated in other infections, we believe this is the first time the bacteria is being documented to have caused acute cholangitis.

Pyosalpinx due to Cronobacter sakazakii in an elderly woman

Background

Cronobacter sakazakii (C. sakazakii) is a bacterium known to cause severe neonatal infections in premature infants with the consumption of contaminated powdered milk formula. Adult infections are rare, and there have been no reports of pyosalpinx due to C. sakazakii to date.

Case presentation

We report a case of left pyosalpinx due to C. sakazakii in a sexually inactive postmenopausal woman. A 70-year-old woman presented to our hospital with left lower abdominal pain and fever. Abdominal computed tomography disclosed a cystic mass continuous with the left edge of the uterus. Urgent laparotomy revealed a ruptured left pyosalpinx with pus-like content. Left salpingo-oophorectomy, resection of the right tube, and washing of the abdominal cavity with saline were performed. Pathological examination of the left adnexa showed tubal tissue with acute inflammation and inflammatory exudate, which were compatible with pyosalpinx, and pus culture yielded C. sakazakii.

Conclusions

This is the first case report of pyosalpinx due to C. sakazakii. Cronobacter sakazakii infections in adult women might occur in the elderly, whose immunity has weakened. Further accumulation of cases of C. sakazakii infection is needed to clarify the etiology and behavior of C. sakazakii in adults.

Isolation and Identification of Cronobacter spp. from Fish and Shellfish Sold in Retail Markets

In this study, we investigated the incidence of Cronobacter spp. in seafood collected from retail fish markets of Mumbai, India. A total of 50 samples comprising fresh finfish (n = 32), shellfish (n = 6), dried fish (n = 9) and water (n = 3) were analyzed for Cronobacter spp. by selective enrichment, isolation and biochemical tests. Of 145 isolates presumptively identified as Cronobacter spp. by biochemical tests, 37 were confirmed as Cronobacter spp. by Polymerase Chain Reaction (PCR) specific to the internal transcribed spacer (ITS) regions. Based on the partial ITS gene sequence analysis, 35 isolates were identified as Cronobacter malonaticus and two as Cronobacter sakazakii. The highest incidence of Cronobacter spp. was in dried fish (55.6%), followed by shellfish (33.3%). The virulence gene ompA was detected in two Cronobacter sakazakii isolates. This is the first report of the incidence of Cronobacter spp. in fresh and dried seafood from India, which highlights the need to focus on this emerging pathogen in tropical seafood.

Antibacterial Activity of Chrysanthemum buds Crude Extract Against Cronobacter sakazakii and Its Application as a Natural Disinfectant

Cronobacter sakazakii is an opportunistic food-borne pathogen that endangers the health of neonates and infants. This study aims to elucidate the antibacterial activity and mechanism of Chrysanthemum buds crude extract (CBCE) against C. sakazakii and its application as a natural disinfectant. The antibacterial activity was evaluated by the determination of the diameter of inhibition zone (DIZ), minimum inhibitory concentration (MIC), and minimum bactericide concentration (MBC). The antibacterial mechanism was explored based on the changes of growth curve assay, intracellular ATP concentration, membrane potential, intracellular pH (pH_in), content of soluble protein and nucleic acid, and cell morphology. Finally, the inactivation effects of CBCE against C. sakazakii in biofilm on stainless steel tube, tinplate, glass, and polystyrene were evaluated. The results showed that the DIZ, MIC, and MBC of CBCE against C. sakazakii were 14.55 ± 0.44–14.84 ± 0.38 mm, 10 mg/mL, and 20 mg/mL, respectively. In the process of CBCE acting on C. sakazakii, the logarithmic growth phase of the tested bacteria disappeared, and the concentrations of intracellular ATP, pH_in, bacterial protein, and nucleic acid were reduced. Meanwhile, CBCE caused the cell membrane depolarization and leakage of cytoplasm of C. sakazakii. In addition, about 6.5 log CFU/mL of viable C. sakazakii in biofilm on stainless steel tube, tinplate, glass, and polystyrene could be inactivated after treatment with 1 MIC of CBCE for 30 min at 25°C. These findings reveal the antibacterial activity and mechanism of CBCE against C. sakazakii and provide a possibility of using a natural disinfectant to kill C. sakazakii in the production environment, packaging materials, and utensils.

Analysis of the Molecular Diversity Among Cronobacter Species Isolated From Filth Flies Using Targeted PCR, Pan Genomic DNA Microarray, and Whole Genome Sequencing Analyses

Cronobacter species are opportunistic pathogens capable of causing life-threatening infections in humans, with serious complications arising in neonates, infants, immuno-compromised individuals, and elderly adults. The genus is comprised of seven species: Cronobacter sakazakii, Cronobacter malonaticus, Cronobacter turicensis, Cronobacter muytjensii, Cronobacter dublinensis, Cronobacter universalis, and Cronobacter condimenti. Despite a multiplicity of genomic data for the genus, little is known about likely transmission vectors. Using DNA microarray analysis, in parallel with whole genome sequencing, and targeted PCR analyses, the total gene content of two C. malonaticus, three C. turicensis, and 14 C. sakazaki isolated from various filth flies was assessed. Phylogenetic relatedness among these and other strains obtained during surveillance and outbreak investigations were comparatively assessed. Specifically, microarray analysis (MA) demonstrated its utility to cluster strains according to species-specific and sequence type (ST) phylogenetic relatedness, and that the fly strains clustered among strains obtained from clinical, food and environmental sources from United States, Europe, and Southeast Asia. This combinatorial approach was useful in data mining for virulence factor genes, and phage genes and gene clusters. In addition, results of plasmidotyping were in agreement with the species identity for each strain as determined by species-specific PCR assays, MA, and whole genome sequencing. Microarray and BLAST analyses of Cronobacter fly sequence datasets were corroborative and showed that the presence and absence of virulence factors followed species and ST evolutionary lines even though such genes were orthologous. Additionally, zebrafish infectivity studies showed that these pathotypes were as virulent to zebrafish embryos as other clinical strains. In summary, these findings support a striking phylogeny amongst fly, clinical, and surveillance strains isolated during 2010–2015, suggesting that flies are capable vectors for transmission of virulent Cronobacter spp.; they continue to circulate among United States and European populations, environments, and that this “pattern of circulation” has continued over decades.

Labchip-based diagnosis system for on-site application: Sensitive and easy-to-implement detection of single recoverable Cronobacter in infant formula without post-enrichment treatment

Microfluidic labchips have achieved much advancement in the molecular diagnosis of foodborne pathogens. Whereas difficulties in the flow control during the transportation of liquid fluids can occur and should be overcome. Manipulations of reaction temperature and the complex procedures from sample pre-treatment to analysis in a single chip device are major obstacles for the on-site application. Thus, the efficient temperature control of samples without any flow of reaction fluids in microfluidic channels of plastic chip and the simplest protocol omitting post-enrichment processing steps may overcome these limitations represented by the stability and the complexity, respectively. This study aims to develop a novel type of labchip and thermocycler specialized for the gene amplification in microfluidic channels and to evaluate the detectability by sensing the minimum recoverable level of Cronobacter in powdered infant formula (PIF). We developed a thermocycling device accelerating reactions through dual heating-blocks optimized to control temperatures of samples in microfluidic-channels by direct contact with labchip sequentially and repetitively. The structural design of microfluidic channels was to eliminate interference factors associated with the optical detection of fluorescent signals (without distortion due to air bubbles in the reaction chamber). To improve the applicability, a portable device and simplified operation to allow direct loading of samples in the chip without post-enrichment procedures were also adopted. Detection performance was evaluated by a sensitivity/specificity tests using 50 isolates of Cronobacter. Cross-reactivity tests for non-Cronobacter organisms and gDNA [human, raw materials of PIF (cow, soybean)] showed that there was no interference-factor causing false-positive results. In terms of the applied research conducted by using PIF, the enrichment of samples without broth medium (distilled water) displayed outstanding performance and 12 h of incubation facilitated detecting target at concentration as low as 1 CFU/300 g PIF (as initial contamination level) without post-enrichment treatment. Validation of the operation conditions using 30 commercial PIF products was also consistent. The present study presents a novel approach of microfluidic technology with perspective to not only the performance and the practicability [easy-to-implement protocol, portable materials, cost-effectiveness (the use of a miniaturized plastic chip requires a minimum level of materials)] for on-site diagnosis.

Comparative Proteomic Analysis of Adhesion/Invasion Related Proteins in Cronobacter sakazakii Based on Data-Independent Acquisition Coupled With LC-MS/MS

Cronobacter sakazakii is foodborne pathogen that causes serious illnesses such as necrotizing enterocolitis, meningitis and septicemia in infants. However, the virulence determinants and mechanisms of pathogenicity of these species remain unclear. In this study, multilocus sequence typing (MLST) was performed on 34 C. sakazakii strains and two strains with the same sequence type (ST) but distinct adhesion/invasion capabilities were selected for identification of differentially expressed proteins using data-independent acquisition (DIA) proteomic analysis. A total of 2,203 proteins were identified and quantified. Among these proteins, 210 exhibited differential expression patterns with abundance ratios ≥3 or ≤0.33 and P values ≤0.05. Among these 210 proteins, 67 were expressed higher, and 143 were expressed lower in C. sakazakii SAKA80220 (strongly adhesive/invasive strain) compared with C. sakazakii SAKA80221 (weakly adhesive/invasive strain). Based on a detailed analysis of the differentially expressed proteins, the highly expressed genes involved in flagellar assembly, lipopolysaccharide synthesis, LuxS/AI-2, energy metabolic pathways and iron-sulfur cluster may be associated with the adhesion/invasion capability of C. sakazakii. To verify the accuracy of the proteomic results, real-time qPCR was used to analyze the expression patterns of some genes at the transcriptional level, and consistent results were observed. This study, for the first time, used DIA proteomic to investigate potential adhesion/invasion related factors as a useful reference for further studies on the pathogenic mechanism of C. sakazakii.

The Secretion of Toxins and Other Exoproteins of Cronobacter: Role in Virulence, Adaption, and Persistence

: Cronobacter species are considered an opportunistic group of foodborne pathogenic bacteria capable of causing both intestinal and systemic human disease. This review describes common virulence themes shared among the seven Cronobacter species and describes multiple exoproteins secreted by Cronobacter, many of which are bacterial toxins that may play a role in human disease. The review will particularly concentrate on the virulence factors secreted by C. sakazakii, C. malonaticus, and C. turicensis, which are the primary human pathogens of interest. It has been discovered that various species-specific virulence factors adversely affect a wide range of eukaryotic cell processes including protein synthesis, cell division, and ion secretion. Many of these factors are toxins which have been shown to also modulate the host immune response. These factors are encoded on a variety of mobile genetic elements such as plasmids and transposons; this genomic plasticity implies ongoing re-assortment of virulence factor genes which has complicated our efforts to categorize Cronobacter into sharply defined genomic pathotypes.

Antibacterial Activity of Chrysanthemum buds Crude Extract Against Cronobacter sakazakii and Its Application as a Natural Disinfectant

Cronobacter sakazakii is an opportunistic food-borne pathogen that endangers the health of neonates and infants. This study aims to elucidate the antibacterial activity and mechanism of Chrysanthemum buds crude extract (CBCE) against C. sakazakii and its application as a natural disinfectant. The antibacterial activity was evaluated by the determination of the diameter of inhibition zone (DIZ), minimum inhibitory concentration (MIC), and minimum bactericide concentration (MBC). The antibacterial mechanism was explored based on the changes of growth curve assay, intracellular ATP concentration, membrane potential, intracellular pH (pH_in), content of soluble protein and nucleic acid, and cell morphology. Finally, the inactivation effects of CBCE against C. sakazakii in biofilm on stainless steel tube, tinplate, glass, and polystyrene were evaluated. The results showed that the DIZ, MIC, and MBC of CBCE against C. sakazakii were 14.55 ± 0.44-14.84 ± 0.38 mm, 10 mg/mL, and 20 mg/mL, respectively. In the process of CBCE acting on C. sakazakii, the logarithmic growth phase of the tested bacteria disappeared, and the concentrations of intracellular ATP, pH_in, bacterial protein, and nucleic acid were reduced. Meanwhile, CBCE caused the cell membrane depolarization and leakage of cytoplasm of C. sakazakii. In addition, about 6.5 log CFU/mL of viable C. sakazakii in biofilm on stainless steel tube, tinplate, glass, and polystyrene could be inactivated after treatment with 1 MIC of CBCE for 30 min at 25°C. These findings reveal the antibacterial activity and mechanism of CBCE against C. sakazakii and provide a possibility of using a natural disinfectant to kill C. sakazakii in the production environment, packaging materials, and utensils.

Evaluation of multidrug-resistant Bacillus strains causing public health risks in powdered infant milk formulas

BACKGROUND

Antibiotic-resistant bacteria are one of the major global health issues that can affect humans, animals, and the environment. Antibiotic-resistant bacteria have emerged as opportunistic pathogenic bacteria that are frequently isolated from both clinical patients and healthy individuals. The aim of this study was to characterize the antibiotic-resistant bacteria isolated from powdered infant formulas marketed in Riyadh, Saudi Arabia.

METHODS

Infant powdered milk formulas were purchased from different pharmacies located within Riyadh, and ten products of powdered milk formulas designed for children of various ages were then transferred to the laboratory in the Department of Botany and Microbiology at King Saud University, Riyadh. Isolation and purification of Bacillus species were both performed according to standard protocols. The identification test was performed using the automated Vitek 2 system (BioMerieux, France), and antibiotic sensitivity tests were performed using the disk-diffusion method incorporating standard antibiotic disks foramikacin (30μg/disk), gentamicin (10μg/disk), imipenem (10μg/disk), moxifloxacin (5μg/disk), cefoperazone (75μg/disk), cefpodoxime (10μg/disk), ceftazidime (30μg/disk), and cefepime (30μg/disk). Statistical analysis was performed using Ward's method to obtain antibiotic resistance of the isolates.

RESULTS

The results obtained from the milk samples indicated that all isolates were sensitive to amikacin, gentamicin, and moxifloxacin. A group of isolates obtained from milk was resistant to cefoperazone by 6.49%, cefpodoxime by 25.9%, ceftazidime by 14.28%, and cefepime by 19.48%.

CONCLUSIONS

Based on these findings, we concluded that the powdered infant formula marketed in Riyadh City may act as a source of bacterial isolates that are resistant to several standard antibiotics.

Multicenter Study of Cronobacter sakazakii Infections in Humans, Europe, 2017

Cronobacter sakazakii has been documented as a cause of life-threating infections, predominantly in neonates. We conducted a multicenter study to assess the occurrence of C. sakazakii across Europe and the extent of clonality for outbreak detection. National coordinators representing 24 countries in Europe were requested to submit all human C. sakazakii isolates collected during 2017 to a study center in Austria. Testing at the center included species identification by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry, subtyping by whole-genome sequencing (WGS), and determination of antimicrobial resistance. Eleven countries sent 77 isolates, including 36 isolates from 2017 and 41 historical isolates. Fifty-nine isolates were confirmed as C. sakazakii by WGS, highlighting the challenge of correctly identifying Cronobacter spp. WGS-based typing revealed high strain diversity, indicating absence of multinational outbreaks in 2017, but identified 4 previously unpublished historical outbreaks. WGS is the recommended method for accurate identification, typing, and detection of this pathogen.

Underestimated Risks of Infantile Infectious Disease from the Caregiver's Typical Handling Practices of Infant Formula

The impact on infant caregiver as a reservoir of pathogens has not been exploited with perspective to powdered infant formula (PIF). Here we reveal novel route of pathogen transfer through hand-spoon-PIF unexpectedly occurred by even typical practices of caregivers, handling of PIF and storage of feeding-spoon in PIF container. Hand-spoon-PIF contamination route was simulated to analyze the transfer and subsequent survival of pathogens. Major pathogens associated with infantile fatal diseases (Cronobacter sakazakii, Salmonella enterica, Staphylococcus aureus) were readily transmitted to PIF from skin (3−6 log CFU/hand) via spoons following long-term survival of transferred pathogens (3 weeks; use-by date of PIF) as the excessive level of infectious dose, highlighting direct onset of diseases. Low bacterial load on skin (ca. 1 log CFU/hand) could prevent cross-contamination of PIF, however, at least 72 h survival of transferred pathogen on spoons demonstrated the probability on re-contamination of PIF. To our knowledge, this is the first study to investigate the cross-contamination of utensils in contact with powdered-foods. Bacterial load on hands is the key determinant of pathogen transfer and the extent of risk are species-dependent. These evidential results redefine risk of caregivers’ practices and facilitate incorporation of cross-contamination into risk-assessment as underestimated route of infection.