Food Safety and Invasive Cronobacter Infections during Early Infancy, 1961-2018

Uncovering the pathogenic mechanisms of Cronobacter turicensis: A dual transcriptomics study using a zebrafish larvae model

PURPOSE

Cronobacter (C.) is an emerging opportunistic pathogen representing a significant cause of mortality in neonatal patients with bacteremia and meningitis. The pathobiology of Cronobacter mediated meningitis has primarily been investigated using in vitro models. In this study, we used zebrafish to investigate in vivo the infection strategy of the sepsis/meningitis-causing strain C. turicensis z3032 (LMG 23827T) and the immune response of zebrafish larvae after central nervous system (CNS) invasion. Global gene expression profiles of both organisms were analyzed using RNA-Seq.

METHODS

Injection of bacteria into the yolk sac resulted in proliferation of bacteria and translocation to different tissues, including the brain. Infected larval heads were obtained by microdissection and dual RNA-sequencing was performed on host and pathogen simultaneously.

RESULTS

A total of 1432 genes in C. turicensis z3032 and 80 genes in zebrafish were found to be differentially expressed. Upregulated virulence genes in C. turicensis included those encoding for denitrification and anaerobic respiration, chemotaxis, surface structures, and secretion systems. In zebrafish, transcriptional changes included inflammatory processes, cytokine mediated signaling pathways, and NF-kB signaling as the primary GO categories for upregulated genes in response to infection.

CONCLUSION

The dual transcriptomics approach provided a unique opportunity to create a comprehensive catalog of differentially expressed genes in both the pathogen and the host, offering new insights into the infection strategies of C. turicensis and zebrafish immune response.

Cronobacter Surveillance in Minnesota, United States, 2002-2024

Cronobacter sakazakii is an opportunistic pathogen associated with bloodstream infections and meningitis in neonates and infants. C. sakazakii isolated from infants under 1 year of age has been reportable in Minnesota since 2003. Invasive Cronobacter infections in infants was recently made notifiable nationally in 2024. Therefore, this summary of over 20 years of reportable surveillance for C. sakazakii from Minnesota infants will inform other jurisdictions. During 2002-2024, 23 C. sakazakii cases in infants, including 8 invasive and 15 non-invasive cases, were identified and confirmed using MALDI-TOF or conventional biochemical methods. Invasive cases were younger (median, 18 days; range, 8 days to 10 months) than non-invasive cases (median, 98 days; range, 7 days to 8 months). Cronobacter isolates from infant (21), child (4), and adult (15) cases were submitted for whole genome sequencing (WGS) to obtain a contextual understanding of potential relatedness. In addition, C. sakazakii isolated from powdered infant formula (PIF) in 2003 was sequenced for comparison. Sequence type (ST) 4 was responsible for the majority of C. sakazakii cases overall (65%) and invasive infant cases (88%). Opened and unopened PIF was cultured from 10 investigations representing both invasive and non-invasive cases. Two (25%) opened PIF samples tested positive for C. sakazakii ST 4 while one (11%) unopened PIF sample tested positive for C. sakazakii ST 4. WGS demonstrated that no clinical cases were associated with a recognized outbreak. Several cases were likely due to contamination of PIF in the home during preparation, highlighting the importance of infant caregiver education to prevent infections.

Impact of Human Body Temperature on Stress Tolerance and Transcriptome of Cronobacter sakazakii

Cronobacter sakazakii is a food-borne pathogen that can thrive in various environments, including the human body. The human body's physiological temperature exceeds that of the environment (22-30 °C), necessitating adaptations to heat stress during this transition. Managing heat stress is crucial when transitioning from the environment to the human body. In this study, we explored the effect of human body temperature on the growth of planktonic C. sakazakii, as well as its acid resistance, osmotic stress resistance, autoaggregation, and cell surface hydrophobicity. Our study demonstrated that human body temperature facilitated the growth, acid resistance, and osmotic resistance of C. sakazakii, compared to 28 °C. The relationship between human body temperature and phenotypes was studied by comparing gene expression at human and environmental temperatures (37 to 28 °C) using high-throughput sequencing. The results revealed up-regulation in the expression of 626 genes, including genes involved in arginine and proline metabolism, carbon fixation pathways, and nitrogen metabolism. Further analysis showed that human body temperature is essential for the environmental stress resistance of C. sakazakii. It boosts denitrification, betaine transport, and universal stress proteins, supporting membrane integrity and osmoprotectant transport. This study enhances our understanding of the strategies employed by C. sakazakii during its adaptation to the human body.

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.

The applicability of the SERS technique in food contamination testing - The detailed spectroscopic, chemometric, genetic, and comparative analysis of food-borne Cronobacter spp. strains

Microorganisms assigned as Cronobacter are Gram-negative, facultatively anaerobic, bacteria widely distributed in nature, home environments, and hospitals. They can also be detected in foods, milk powder, and powdered infant formula (PIF). Additionally, as an opportunistic pathogen, Cronobacter may cause serious infections, sometimes leading to the death of neonates and infants. Thus, it is essential to test food products for the presence of Cronobacter spp. The currently used standard described in ISO 22964:2017 is a laborious method that could be easily replaced by surface-enhanced Raman scattering (SERS). Here, we demonstrate that SERS allows the identification of food-borne bacteria belonging to Cronobacter spp. based on their SERS spectra. For this purpose, twenty-six Cronobacter strains from different food samples were analyzed. Additionally, it was shown that it is possible to differentiate them from other closely related pathogens such as Salmonella enterica subsp. enterica, Escherichia coli, or Enterobacter spp. The SERS results were supported by principal component analysis (PCA), as well as and sequencing of 16S rRNA, rpoB and fusA genes. Last but not least, it was demonstrated that the cells of Cronobacter sakazakii may be easily separated from PIF using an appropriate filter, microfluidic chip, and dielectrophoresis (DEP) technique.

Transcriptomics analysis of the role of SdiA in desiccation tolerance of Cronobacter sakazakii in powdered infant formula

The quorum-sensing receptor SdiA is vital for regulating the desiccation tolerance of C. sakazakii, yet the specific mechanism remains elusive. Herein, transcriptomics and phenotypic analysis were employed to explore the response of C. sakazakii wild type (WT) and sdiA knockout strain (ΔsdiA) under drying conditions. Following 20 days of drying in powdered infant formula (PIF), WT exhibited 4 log CFU/g higher survival rates compared to ΔsdiA. Transcriptome revealed similar expression patterns between csrA and sdiA, their interaction was confirmed both by protein-protein interaction analysis and yeast two-hybrid assays. Notably, genes associated with flagellar assembly and chemotaxis (flg, fli, che, mot regulon) showed significantly higher expression levels in WT than in ΔsdiA, indicating a reduced capacity for flagellar synthesis in ΔsdiA, which was consistent with cellular morphology observations. Similarly, genes involved in trehalose biosynthesis (ostAB, treYZS) and uptake (thuEFGK) exhibited similar expression patterns to sdiA, with higher levels of trehalose accumulation observed in WT under desiccation conditions compared to ΔsdiA. Furthermore, WT demonstrated enhanced protein and DNA synthesis capabilities under desiccation stress. Higher expression levels of genes related to oxidative phosphorylation were also noted in WT, ensuring efficient cellular ATP synthesis. This study offers valuable insights into how SdiA influences the desiccation tolerance of C. sakazakii, paving the way for targeted strategies to inhibit and control this bacterium.

Nanopore Sequencing Allows Recovery of High-Quality Completely Closed Genomes of All Cronobacter Species from Powdered Infant Formula Overnight Enrichments

Precision metagenomic approaches using Oxford Nanopore Technology (ONT) sequencing has been shown to allow recovery of complete genomes of foodborne bacteria from overnight enrichments of agricultural waters. This study tests the applicability of a similar approach for Cronobacter genome recovery from powdered infant formula (PIF) overnight enrichments, where Cronobacter typically dominates the overall microbiome (>90%). This study aimed to test whether using ONT sequencing of overnight PIF enrichments could recover a completely closed Cronobacter genome for further genomic characterization. Ten PIF samples, each inoculated with different Cronobacter strains, covering Cronobacter sakazakii, C. muytjensii, C. dublinensis, C. turicensis, and C. universalis, were processed according to the Bacteriological Analytical Manual (BAM) protocol. Real-time quantitative PCR (qPCR) was used for initial screening (detection and quantification) of the overnight enrichments and confirmed that the inoculated PIF samples after the overnight enrichment had high levels of Cronobacter (107 to 109 CFU/mL). DNA from overnight PIF enrichments was extracted from the enrichment broth and sequenced using ONT. Results showed that ONT sequencing could accurately identify, characterize, and close the genomes of Cronobacter strains from overnight PIF enrichments in 3 days, much faster than the nearly 2 weeks required by the current BAM method. Complete genome recovery and species differentiation were achieved. This suggests that combining qPCR with ONT sequencing provides a rapid, cost-effective alternative for detecting and characterizing Cronobacter in PIF, enabling timely corrective actions during outbreaks.

Neonatal Bacterial Meningitis: What Have We Learned From the Last Decade?

Bacterial meningitis is a devastating disease with significant morbidity and mortality, especially in neonates and young infants. The overall incidence of meningitis has decreased with focused screening, public health interventions, and vaccination, but the disease remains a significant concern in high-risk groups. In this review, we provide an update on bacterial meningitis in children younger than age 60 days, including epidemiology, clinical presentation, diagnostic approaches, treatment, and prognosis. [Pediatr Ann. 2024;53(11):e425-e432.].

Cronobacter sakazakii lysozyme inhibitor LprI mediated by HmsP and c-di-GMP is essential for biofilm formation and virulence

Cronobacter sakazakii poses a significant threat, particularly to neonates and infants. Despite its strong pathogenicity, understanding of C. sakazakii biofilms and their role in infections remains limited. This study investigates the roles of HmsP and c-di-GMP in biofilm formation and identifies key genetic and proteomic elements involved. Gene knockout experiments reveal that HmsP and c-di-GMP are linked to biofilm formation in C. sakazakii. Comparative proteomic profiling identifies the lysozyme inhibitor protein LprI, which is downregulated in hmsP knockouts and upregulated in c-di-GMP knockouts, as a potential biofilm formation factor. Further investigation of the lprI knockout strain shows significantly reduced biofilm formation and decreased virulence in a rat infection model. Additionally, LprI is demonstrated to bind extracellular DNA, suggesting a role in anchoring C. sakazakii within the biofilm matrix. These findings enhance our understanding of the molecular mechanisms underlying biofilm formation and virulence in C. sakazakii, offering potential targets for therapeutic intervention and food production settings.IMPORTANCECronobacter sakazakii is a bacterium that poses a severe threat to neonates and infants. This research elucidates the role of the lysozyme inhibitor LprI, modulated by HmsP and c-di-GMP, and uncovers a key factor in biofilm formation and virulence. The findings offer crucial insights into the molecular interactions that enable C. sakazakii to form resilient biofilms and persist in hostile environments, such as those found in food production facilities. These insights not only enhance our understanding of C. sakazakii pathogenesis but also identify potential targets for novel therapeutic interventions to prevent or mitigate infections. This work is particularly relevant to public health and the food industry, where controlling C. sakazakii contamination in powdered infant formula is vital for safeguarding vulnerable populations.

Relevance of genetic causes and environmental adaptation of Cronobacter spp. isolated from infant and follow-up formula production factories and retailed products in China: A 7-year period of continuous surveillance based on genome-wide analysis

The possible contamination routes, environmental adaptation, and genetic basis of Cronobacter spp. in infant and follow-up formula production factories and retailed products in mainland China have been determined by laboratory studies and whole-genome comparative analysis in a 7-year nationwide continuous surveillance spanning from 2012 to 2018. The 2-year continuous multicenter surveillance of the production process (conducted in 2013 and 2014) revealed that the source of Cronobacter spp. in the dry-blending process was the raw dry ingredients and manufacturing environment (particularly in the vibro sieve and vacuum cleaner), while in the combined process, the main contamination source was identified as the packing room. It is important to note that, according to the contamination control knowledge obtained from the production process surveillance, the contamination rate of retail powdered infant formula (PIF) and follow-up formula (FUF) products in China decreased significantly from 2016 onward, after improving the hygiene management practices in factories. The prevalence of Cronobacter spp. in retailed PIF and FUF in China in 2018 was dramatically reduced from 1.55 % (61/3925, in 2012) to an average as low as 0.17 % (13/7655 in 2018). Phenotype determination and genomic analysis were performed on a total of 90 Cronobacter spp. isolates obtained from the surveillance. Of the 90 isolates, only two showed resistance to either cefazolin or cefoxitin. The multilocus sequence typing results revealed that C. sakazakii sequence type 1 (ST1), ST37, and C. malonaticus ST7 were the dominant sequence types (STs) collected from the production factories, while C. sakazakii ST1, ST4, ST64, and ST8 were the main STs detected in the retailed PIF and FUF nationwide. One C. sakazakii ST4 isolate (1.1 %, 1/90) had strong biofilm-forming ability and 13 isolates (14.4 %, 13/90) had weak biofilm-forming ability. Genomic analysis revealed that Cronobacter spp. have a relatively stable core-genome and an increasing pan-genome size. Plasmid IncFIB (pCTU3) was prevalent in this genus and some contained 14 antibacterial biocide- and metal-resistance genes (BMRGs) including copper, silver, and arsenic resistant genes. Plasmid IncN_1 was predicted to contain 6 ARGs. This is the first time that a multi-drug resistance IncN_1 type plasmid has been reported in Cronobacter spp. Genomic variations with respect to BMRGs, virulence genes, antimicrobial resistance genes (ARGs), and genes involved in biofilm formation were observed among strains of this genus. There were apparent differences in copies of bcsG and flgJ between the biofilm-forming group and non-biofilm-forming group, indicating that these two genes play key roles in biofilm formation. The findings of this study have improved our understanding of the contamination characteristics and genetic basis of Cronobacter spp. in PIF and FUF and their production environment in China and provide important guidance to reduce contamination with this pathogen during the production of PIF and FUF.

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.

Microbiological survey and genomic analysis of Cronobacter sakazakii strains isolated from US households and retail foods

Cronobacter species are opportunistic pathogens that are capable of causing morbidity and mortality, particularly in infants. Although the transmission dynamics involved in Cronobacter infections remain largely unknown, contaminated powdered infant formula (PIF) has been linked to 30% of Cronobacter sakazakii cases involving invasive illness in infants. As several lines of evidence have implicated the domestic environment in PIF contamination, we undertook a microbiological survey of homes (N = 263) across the US. Cronobacter spp. and C. sakazakii were isolated from 36.1% and 24.7% of US homes, respectively, with higher recovery rates observed for floor and kitchen surfaces. Multi-locus sequence typing indicated that the dominant strain was C. sakazakii ST4, the sequence type most commonly associated with neonatal meningitis. For comparison purposes, retail foods (N = 4,009) were also surveyed, with the highest contamination frequencies (10.1%-26.3%) seen for nut products, seeds, and grains/baked goods/flours. The sequence type profile of isolates recovered from homes mirrored that of isolates recovered from retail foods, with increased representation of ST1, ST4, ST13, ST17, and ST40. Analysis of 386 whole genomic sequences revealed significant diversity. Redundancies were only observed for isolates recovered from within the same domicile, and there were no identical matches with sequences archived at the NCBI pathogen database. Genes coding for putative virulence and antibiotic resistance factors did not segregate with clinically significant sequence types. Collectively, these findings support the possibility that contamination events occurring within the home should not be overlooked as a contributor to community-onset Cronobacter infections.

IMPORTANCE

Cronobacter sakazakii is an opportunistic pathogen that can cause significant morbidity and mortality in neonates. Its transmission dynamics are poorly understood, though powered infant formula (PIF) is thought to be the major transmission vehicle. How the PIF becomes contaminated remains unknown. Our survey shows that roughly 1/4 of US homes are contaminated with Cronobacter sakazakii, particularly in the kitchen setting. Our analyses suggest that the domestic environment may contribute to contamination of PIF and provides insights into mitigating the risk of transmission.

Survival and Expression of rpoS and grxB of Cronobacter sakazakii in Powdered Infant Formula Under Simulated Gastric Conditions of Newborns

Cronobacter sakazakii can cause severe illnesses in infants, predominantly in preterm newborns, with consumption of contaminated powdered infant formula (PIF) being the major vehicle of infection. Using a dynamic human gastrointestinal simulator called the SHIME, this study examined the effects of gastric acidity and gastric digestion time of newborns on the survival and expression of stress genes of C. sakazakii. Individual strains, inoculated at 7 log CFU/mL into reconstituted PIF, were exposed to gastric pH values of 4.00, 5.00 and 6.00 for 4 h with gradual acidification. The survival results showed that C. sakazakii grew in the stomach portion of the SHIME during a 4-h exposure to pH 4.00, 5.00 and 6.00 by 0.96-1.05, 1.02-1.28 and 1.11-1.73 log CFU/mL, respectively. The expression of two stress genes, rpoS and grxB, throughout gastric digestion was evaluated using reverse transcription qPCR. The upregulation of rpoS and grxB during the 4-h exposure to simulated gastric fluid at pH 4.00 showed that C. sakazakii strains may be experiencing the most stress in the pH 4.00 treatment. The gene expression results also suggest that C. sakazakii strains appeared to develop an acid adaptation response during the 4-h exposure that may facilitate their survival. Altogether, this study highlights that a combination of low gastric acidity, long digestion time in the presence of reconstituted PIF, created a favorable environment for the adaptation and survival of C. sakazakii in the simulation of a newborn's stomach. This study gives directions for future research to further advance our understanding of the behavior of C. sakazakii in the GI tract of newborns.

Gut microbiota composition in patients with Crohn's disease in Saudi Arabia

Crohn's disease (CD) entails intricate interactions with gut microbiome diversity, richness, and composition. The relationship between CD and gut microbiome is not clearly understood and has not been previously characterized in Saudi Arabia. We performed statistical analysis about various factors influencing CD activity and microbiota dysbiosis, including diagnosis, treatment, and its impact on their quality of life as well as high-throughput metagenomic V3-V4 16S rRNA encoding gene hypervariable region of a total of eighty patients with CD, both in its active and inactive state with healthy controls. The results were correlated with the demographic and lifestyle information, which the participants provided via a questionnaire. α-diversity measures indicated lower bacterial diversity and richness in the active and inactive CD groups compared to the control group. Greater dysbiosis was observed in the active CD patients compared to the inactive form of the disease, showed by a reduction in microbial diversity. Specific pathogenic bacteria such as Filifactor, Peptoniphilus, and Sellimonas were identified as characteristic of CD groups. In contrast, anti-inflammatory bacteria like Defluviitalea, Papillibacter, and Petroclostridium were associated with the control group. Among the various factors influencing disease activity and microbiota dysbiosis, smoking emerged as the most significant, with reduced α-diversity and richness for the smokers in all groups, and proinflammatory Fusobacteria was more present (p<0.05). Opposite to the control group, microbial diversity and richness were lower in CD participants of older age compared to younger ones, and male CD participants showed less diversity compared to women participants from the same groups. Our results describe the first report on the relationship between microbiota and Crohn's disease progress in Saudi Arabia, which may provide a theoretical basis for the application of therapeutic methods to regulate gut microbes in CD.

Microbiological hazards in infant and toddler food in China: A comprehensive study between 2004 and 2022

Infant and toddler food (ITF), including powdered infant and follow-up formula (PIFF) and complementary food (CF), provides the majority of early-life nutrients for young children. As infants and toddlers are more vulnerable to foodborne diseases, the safety concern of ITF is the ultimate priority. However, nationwide surveillance for the presence of hazards, specifically microbiological hazards, in the Chinese ITF is partially known, posing a significant knowledge gap for risk ranking. Most importantly, the related regional surveys were largely published in Chinese, making the data unavailable for global sharing. To bridge these gaps, we screened 5,306 publications and conducted a comprehensive meta-analysis for microbiological hazards using 129 qualified studies. The four most reported microbiological hazards in ITF were Bacillus cereus (13.4 %), Cronobacter (4.8 %), Staphylococcus aureus (1.3 %), and Salmonella (1.1 %). B. cereus is a risk factor in ITF, specifically in PIFF, cereals, and ready-to-eat food. The prevalence of B. cereus was high in Northern and Southern China, while the prevalence of Cronobacter was high in Central China. Cronobacter is a microbiological hazard, specifically in PIFF, with a prevalence of 3.0 %. Interestingly, the prevalence dynamics of Cronobacter and B. cereus in ITF were rising and stable, respectively, whereas the prevalence of S. aureus and Salmonella decreased over time. Together, our analysis will promote the global sharing of these critical findings and may guide future policy making.

CpxAR two-component system contributes to virulence properties of Cronobacter sakazakii

Cronobacter sakazakii (C. sakazakii) is a foodborne pathogen which threaten susceptible hosts including infants. CpxA/CpxR, a regulatory two-component system (TSC), contributes to stress response and virulence in various Gram-negative pathogens, but its role in C. sakazakii has not been thoroughly studied. In this study, we constructed CpxA, CpxR, CpxAR deletion and complementation strains. The mutants showed weakened bacterial adhesion to and invasion of HBMEC and Caco-2, reduced intracellular survival and replication of C. sakazakii within RAW264.7 macrophages, and decreased translocation of HBMEC and Caco-2 monolayers. Mutants demonstrated lower levels of tight junction proteins disruption and reduced apoptosis and cytotoxicity in Caco-2 monolayer compared to wild type strain. CpxAR TCS deletion mutants demonstrate attenuated virulence in newborn mice, which was evidenced by fewer bacterial cells loads in tissues and organs, lower levels of intestinal epithelial barrier dysfuction and milder damages in intestinal tissues. All these phenotypes were recovered in complemented strains. In addition, qRT-PCR results showed that CpxAR TCS of C. sakazakii played roles in regulating the expression of several genes associated with bacterial virulence and cellular invasion. These findings indicate that CpxAR TCS is an important regulatory mechanism for virulence of C. sakazakii, which enrich our understanding of genetic determinants of pathogenicity of the pathogen.

Maltodextrin-binding protein as a key factor in Cronobacter sakazakii survival under desiccation stress

Cronobacter sakazakii (C. sakazakii) is a notorious pathogen responsible for infections in infants and newborns, often transmitted through contaminated infant formula. Despite the use of traditional pasteurization methods, which can reduce microbial contamination, there remains a significant risk of pathogenic C. sakazakii surviving due to its exceptional stress tolerance. In our study, we employed a comparative proteomic approach by comparing wild-type strains with gene knockout strains to identify the essential genes crucial for the successful survival of C. sakazakii during desiccation. Our investigation revealed the significance of envZ-ompR, recA, and flhD gene cassettes in contributing to desiccation tolerance in C. sakazakii. Furthermore, through our comparative proteomic profiling, we identified the maltodextrin-binding protein encoded by ESA_03421 as a potential factor influencing dry tolerance. This protein is regulated by EnvZ-OmpR, RecA, and FlhD. Notably, the knockout of ESA_03421 resulted in a 150% greater reduction in Log CFU compared to the wild-type C. sakazakii. Overall, our findings offer valuable insights into the mechanisms underlying C. sakazakii desiccation tolerance and provide potential targets for the development of new antimicrobial strategies aimed at reducing the risk of infections in infants and newborns.

The safety of at home powdered infant formula preparation: A community science project

Formula fed infants experience gastrointestinal infections at higher rates than breastfed infants, due in part to bacteria in powdered infant formula (PIF) and bacterial contamination of infant feeding equipment. The United Kingdom National Health Service (UK NHS) has adopted the World Health Organization recommendation that water used to reconstitute PIF is ≥70°C to eliminate bacteria. We used community science methods to co-design an at home experiment and online questionnaire ('research diary') to explore the safety of PIF preparation compared to UK NHS guidelines. 200 UK-based parents of infants aged ≤12 months were recruited; 151 provided data on PIF preparation, and 143 were included in the analysis of water temperatures used to reconstitute PIF. Only 14.9% (n = 11) of 74 PIF preparation machines produced a water temperature of ≥70°C compared with 78.3% (n = 54) of 69 kettle users (p < 0.001). The mean temperature of water dispensed by PIF preparation machines was 9°C lower than kettles (Machine M = 65.78°C, Kettle M = 75.29°C). Many parents did not always fully follow NHS safer PIF preparation guidance, and parents did not appear to understand the potential risks of PIF bacterial contamination. Parents should be advised that the water dispensed by PIF preparation machines may be below 70°C, and could result in bacteria remaining in infant formula, potentially leading to gastrointestinal infections. PIF labelling should advise that water used to prepare PIF should be ≥70°C and highight the risks of not using sufficiently hot water, per WHO Europe advice. There is an urgent need for stronger consumer protections regarding PIF preparation devices.

Infant formulae - Key components, nutritional value, and new perspectives

Breastfeeding is the most effective strategy for meeting the nutritional demands of infants, whilst infant formulae are manufactured foods that mimic human milk and can be safely used to replace breastfeeding. In this paper, the compositional differences between human milk and other mammalian milk are reviewed, and thus nutritional profiles and compositions of standard bovine milk-based formulae as well as special formulae are discussed. Differences between breast milk and other mammalian milk in composition and content affect their digestion and absorption in infants. Characteristics and mimicking of breast milk have been intensively studied with the objective of narrowing the gap between human milk and infant formulae. The functions of the key nutritional components in infant formulae are examined. This review detailed recent developments in the formulation of different types of special infant formulae and efforts for their humanization, and summarized safety and quality control of infant formulae.

Human milk fortification and use of infant formulas to support growth in the neonatal intensive care unit

Newborn infants require adequate nutrition to achieve full potential growth and development. Early life nutrition and health impacts long-term outcomes through adulthood. Human milk is the optimal source of nutrition during the first 6 months of life. However, infants admitted to the neonatal intensive care unit (NICU) often have comorbidities that create more or different nutrition demands than healthy newborns. There are different strategies to meet the nutrition needs of sick newborns, including use of parenteral nutrition, human milk fortifiers (HMFs), and infant formulas. Multinutrient HMFs are frequently used to achieve the higher nutrition demands of preterm infants. They are available in various presentations, such as human milk- or cow milk-derived, liquid or powder, and acidified or nonacidified, each of which has different risks and benefits associated with its use. Infant formulas are available to meet a demand when mother's own milk or donor breast milk is not available or sufficient, and there are also specialty formulas for infants with certain diseases that present unique nutrition needs. This review is focused on the use of HMFs to support the unique nutrition requirements of preterm infants for healthy growth, as well as the indications for the use of formulas among infants in the NICU.

Ocular Bacterial Infections: A Ten-Year Survey and Review of Causative Organisms Based on the Oklahoma Experience

Ocular infections can be medical emergencies that result in permanent visual impairment or blindness and loss of quality of life. Bacteria are a major cause of ocular infections. Effective treatment of ocular infections requires knowledge of which bacteria are the likely cause of the infection. This survey of ocular bacterial isolates and review of ocular pathogens is based on a survey of a collection of isolates banked over a ten-year span at the Dean McGee Eye Institute in Oklahoma. These findings illustrate the diversity of bacteria isolated from the eye, ranging from common species to rare and unique species. At all sampled sites, staphylococci were the predominant bacteria isolated. Pseudomonads were the most common Gram-negative bacterial isolate, except in vitreous, where Serratia was the most common Gram-negative bacterial isolate. Here, we discuss the range of ocular infections that these species have been documented to cause and treatment options for these infections. Although a highly diverse spectrum of species has been isolated from the eye, the majority of infections are caused by Gram-positive species, and in most infections, empiric treatments are effective.

Cronobacter brain abscess and refractory epilepsy in a newborn: role of epilepsy surgery. Illustrative case

BACKGROUND

Neonatal meningitis due to Cronobacter is associated with powdered infant formula. Prompt recognition of this rare but aggressive infection is critical.

OBSERVATIONS

The authors report a unique case of neonatal Cronobacter meningoencephalitis complicated by brain abscess and status epilepticus, requiring surgical intervention in a preterm 4-week-old male and related to contaminated powdered infant formula. They discuss the medical and surgical management in this patient, as well as the role of epilepsy surgery in acute drug-resistant epilepsy. This is paired with a literature review examining Cronobacter infections in infants to provide a summative review of the existing literature.

LESSONS

Cronobacter contamination in powdered infant formula and breast pumps is rare but can cause life-threatening infections. When evaluating patients with Cronobacter central nervous system infections, serial neuroimaging, infection control, and prompt surgical management are essential. Future studies are needed regarding the role of epilepsy surgery in the acute infectious period.

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

The powdered formula market is large and growing, with sales and manufacturing increasing by 120% between 2012 and 2021. With this growing market, there must come an increasing emphasis on maintaining a high standard of hygiene to ensure a safe product. In particular, Cronobacter species pose a risk to public health through their potential to cause severe illness in susceptible infants who consume contaminated powdered infant formula (PIF). Assessment of this risk is dependent on determining prevalence in PIF-producing factories, which can be challenging to measure with the heterogeneity observed in the design of built process facilities. There is also a potential risk of bacterial growth occurring during rehydration, given the observed persistence of Cronobacter in desiccated conditions. In addition, novel detection methods are emerging to effectively track and monitor Cronobacter species across the food chain. This review will explore the different vehicles that lead to Cronobacter species' environmental persistence in the food production environment, as well as their pathogenicity, detection methods and the regulatory framework surrounding PIF manufacturing that ensures a safe product for the global consumer.

Infant burn injuries related to water heating for powdered infant formula preparation

Background

Guidance for preparing powdered infant formula (PIF) helps to ensure it meets the nutritional needs of infants and is safe to consume. Among safety concerns is Cronobacter sakazakii contamination which can lead to serious infections and death. PIF preparation guidance varies; there is a lack of consensus on whether there is a need to boil water to inactivate potential Cronobacter and for how long to let the water cool before reconstitution. We sought to quantify the burden of burn injuries among infants related to water heating for PIF preparation. Estimating this burden may help inform preparation recommendations.

Methods

Burn injuries among infants <18 months of age were identified from 2017 to 2019 National Electronic Injury Surveillance System data collected from sampled hospital emergency departments. Injuries were classified as related to PIF water heating, potentially related to PIF water heating but with undetermined causation, related to other infant feeding aspects, or unrelated to infant formula or breast milk feeding. Unweighted case counts for each injury classification were determined.

Results

Across sampled emergency departments, 7 PIF water heating injuries were seen among the 44,395 injuries reported for infants <18 months. No reported PIF water heating injuries were fatal, but 3 required hospitalization. Another 238 injuries potentially related to PIF water heating but with undetermined causation were also seen.

Conclusion

Preparation guidance should consider both the potential risk for Cronobacter infection and the potential risk for burns.

[The pathogenicity of Cronobacter in the light of bacterial genomics]

Cronobacter spp. is a genus of Gram-negative bacteria belonging to the family Enterobacteriaceae. Species of the genus Cronobacter, particularly C. sakazakii, are implicated in the development of severe disease in newborns, which occurs with necrotizing enterocolitis, sepsis and meningitis. The disease has been frequently associated with powdered infant formula (PIF) and can therefore occur in the form of outbreaks. The genus Cronobacter has undergone extensive diversification in the course of its evolution, with some species being clearly pathogenic to humans while the impact of other species on human health is uncertain or unknown. Whole genome sequencing is used both in population genetic studies to identify the limited number of genotypes associated with the disease and to detect genes associated with antibiotic resistance or virulence, ultimately allowing more precise epidemiological links to be established between pediatric disease and infant foods.

Cronobacter sakazakii Infections in Two Infants Linked to Powdered Infant Formula and Breast Pump Equipment - United States, 2021 and 2022

Cronobacter sakazakii, a species of gram-negative bacteria belonging to the Enterobacteriaceae family, is known to cause severe and often fatal meningitis and sepsis in young infants. C. sakazakii is ubiquitous in the environment, and most reported infant cases have been attributed to contaminated powdered infant formula (powdered formula) or breast milk that was expressed using contaminated breast pump equipment (1-3). Previous investigations of cases and outbreaks have identified C. sakazakii in opened powdered formula, breast pump parts, environmental surfaces in the home, and, rarely, in unopened powdered formula and formula manufacturing facilities (2,4-6). This report describes two infants with C. sakazakii meningitis reported to CDC in September 2021 and February 2022. CDC used whole genome sequencing (WGS) analysis to link one case to contaminated opened powdered formula from the patient's home and the other to contaminated breast pump equipment. These cases highlight the importance of expanding awareness about C. sakazakii infections in infants, safe preparation and storage of powdered formula, proper cleaning and sanitizing of breast pump equipment, and using WGS as a tool for C. sakazakii investigations.

Characterization and genomic analysis of JC01, a novel bacteriophage infecting Cronobacter sakazakii

The lytic bacteriophage JC01 was isolated using a strain of Cronobacter sakazakii previously isolated from powdered infant formula (PIF). The complete genome sequence of phage JC01 was determined. The double-stranded DNA genome of phage JC01 is composed of 61,736 bp with a G + C content of 58.9%, and it contains 76 putative open reading frames (ORFs) without any tRNA genes. The predicted ORFs were classified into functional groups, including DNA manipulation, transcription, phage packaging, phage structure, host lysis, and hypothetical proteins. Based on overall nucleotide sequence comparisons, calculation of phage intergenomic similarities, and phylogenetic analysis, JC01 appears to be a novel bacteriophage infecting C. sakazakii.

Identification and antibiotic resistance of Cronobacter spp. isolated from dried edible mushrooms

Cronobacter spp. is an important foodborne pathogen that can cause life-threatening diseases in infants and immunocompromised adults. The present study was carried out to understand the prevalence and characterization of Cronobacter spp. in dried edible mushrooms in Jiangsu province, China. Cronobacter isolates were identified and genotyped by multilocus sequence typing (MLST); the antimicrobial susceptibility of Cronobacter strains was determined by the disk diffusion method; the biofilm formation ability of Cronobacter spp. was assessed using the microtiter plate method. The overall prevalence of Cronobacter spp. in dried edible mushrooms was 14.8%, with the highest contamination rate of after 37.2% found in Auricularia auricular. The Cronobacter isolates were identified as C. sakazakii (n = 26), C. malonaticus (n = 2), C. dublinensis (n = 2) and C. turicensis (n = 1). The MLST scheme produced 20 sequence types (STs), two of which were newly identified. ST148 was the most prevalent ST (n = 5), followed by ST4 (n = 3), ST17 (n = 3), ST64 (n = 3), and ST540 (n = 2). One (3.2%) and 15 (48.4%) Cronobacter isolates were resistant to tetracycline and meropenem, respectively. In contrast, all of the tested isolates were susceptible to the remaining 14 antibiotics. Moreover, 20 (64.5%) Cronobacter isolates showed weak ability to produce biofilm, but no isolates showed strong or moderate biofilm-forming ability. PRACTICAL APPLICATION: Our findings revealed a high genetic diversity of Cronobacter spp. in dried edible mushrooms and provided new epidemiological evidence for the widespread existence of Cronobacter spp. in such products. The presence of Cronobacter spp. in dried edible mushrooms may pose potential risks to human health and enhancing the hygiene of such products are necessary to ensure food safety.

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.

Insights into the mechanisms of Cronobacter sakazakii virulence

Cronobacter species have adapted to survive harsh conditions, particularly in the food manufacture environment, and can cause life-threatening infections in susceptible hosts. These opportunistic pathogens employ a multitude of mechanisms to aid their virulence throughout three key stages: environmental persistence, infection strategy, and systemic persistence in the human host. Environmental persistence is aided by the formation of biofilms, development of subpopulations, and high tolerance to environmental stressors. Successful infection in the human host involves several mechanisms such as protein secretion, motility, quorum sensing, colonisation, and translocation. Survival inside the host is achieved via competitive acquisition and utilization of minerals and metabolites respectively, coupled with host immune system evasion and antimicrobial resistance (AMR) mechanisms. Across the globe, Cronobacter sakazakii is associated with often fatal systemic infections in populations including neonates, infants, the elderly and the immunocompromised. By providing insight into the mechanisms of virulence utilised by this pathogen across these three stages, this review identifies current gaps in the literature. Further research into these virulence mechanisms is required to inform novel mitigation measures to improve global food safety with regards to this food-borne 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.

Processing environment monitoring in low moisture food production facilities: Are we looking for the right microorganisms?

Processing environment monitoring is gaining increasing importance in the context of food safety management plans/HACCP programs, since past outbreaks have shown the relevance of the environment as contamination pathway, therefore requiring to ensure the safety of products. However, there are still many open questions and a lack of clarity on how to set up a meaningful program, which would provide early warnings of potential product contamination. Therefore, the current paper aims to summarize and evaluate existing scientific information on outbreaks, relevant pathogens in low moisture foods, and knowledge on indicators, including their contribution to a "clean" environment capable of limiting the spread of pathogens in dry production environments. This paper also outlines the essential elements of a processing environment monitoring program thereby supporting the design and implementation of better programs focusing on the relevant microorganisms. This guidance document is intended to help industry and regulators focus and set up targeted processing environment monitoring programs depending on their purpose, and therefore provide the essential elements needed to improve food safety.

A simple and sensitive aptasensor with rolling circle amplification for viable Cronobacter sakazakii detection in powdered infant formula

Cronobacter sakazakii is a foodborne, emerging opportunistic pathogen that causes severe bacteremia, necrotizing enterocolitis, and sepsis with a mortality rate of up to 80%. In this study, we developed a simple and sensitive fluorescent turn-off aptasensor with rolling circle amplification assay for viable C. sakazakii detection in powdered infant formula. The results showed that the proposed aptasensor has good performance and specificity for detecting viable C. sakazakii in pure culture and powdered infant formula samples within 3 h. Under the optimal reaction conditions, there is a linear relationship between fluorescent intensity at 490 nm and logarithmic concentration of C. sakazakii in the range of 2.7 × 10⁵ to 2.7 × 10² cfu/mL, with a limit of detection of 2.7 × 10² cfu/mL in pure culture. The proposed aptasensor achieved a recovery of 104 to 111% in pure culture, and 96 to 107% in spiked powdered infant formula samples. The proposed aptasensor does not require complicated DNA extraction steps or antibodies, and can be performed at 37°C, making it a convenient and sensitive strategy for C. sakazakii detection.

Infection of Cronobacter sakazakii ST1 Producing SHV-12 in a Premature Infant Born from Triplet Pregnancy

Cronobacter sakazakii can cause severe life-threatening invasive infections in neonates, with a high mortality rate mostly associated with powdered infant formula consumption. The study describes a fatal C. sakazakii infection in premature infant fed only with expressed human milk. Despite the identification of etiological factor from patient's blood, the epidemiological investigation, including mother's skin, hospital surfaces, milk expressing devices, and milk samples, did not show bacterial contamination. The infection was caused by C. sakazakii ST1, being one of the leading genotypes reported in invasive infections. The phylogenetic analysis of the international collection of the ST1 organisms allowed us to identify the isolate as a member of the main cluster. The pathogenic potential of the isolate was augmented by the presence of IncFIB-like molecule representing virulence plasmids of pESA-3 family. Isolate presented ESBL phenotype associated with bla_SHV-12 gene harboured by IncX3 plasmid. The described case gave valuable information to genetics of Cronobacter, and also urges the need of wider whole-genome sequencing implementation as a part of diagnostic procedure.

Two Cases of Cronobacter Sakazakii Meningitis in Infants: The Importance Of Early Advanced Brain Imaging and Public Health Reporting

We report 2 infants hospitalized with Cronobacter sakazakii meningitis. Each infant had exposure to powdered infant formula at home. Both infants survived, but 1 infant had a subdural empyema drained and developed left sensorineural hearing loss. Early advanced brain imaging is recommended in infants with C. sakazakii meningitis. Reporting to state and federal public health officials may help identify outbreaks.

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.

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.

Meningitis and brain abscess formation caused by Cronobacter malonaticus sequence type 440 in a full-term neonate

Cronobacter spp. cause serious diseases, such as necrotizing enterocolitis, bacteremia, and meningitis in neonates and infants. Most Cronobacter-associated meningitis is reportedly due to C. sakazakii and the majority of infections caused by C. malonaticus occur in adults and are less severe. We report the case of meningitis and brain abscess caused by C. malonaticus Sequence Type (ST) 440 in a healthy full-term neonate. We should consider the possibility that full-term neonates may develop meningitis due to C. malonaticus and treat appropriately because its mortality rate is very high, and survivors are usually left with severe neurologic impairment. In addition, C. malonaticus ST440 may have virulence factors that cause neonatal meningitis akin to the previous report of meningitic ST307 strain.

Survival of viable but nonculturable Cronobacter sakazakii in macrophages contributes to infections

Cronobacter sakazakii (C. sakazakii), a pathogen that exists in dry and low-moisture environments, such as powder infant formula (PIF), can enter a viable but nonculturable (VBNC) state under harsh conditions, which enables it to escape traditional detection methods and thus poses a potential public health risk. This study aimed at assessing the virulent nature of VBNC C. sakazakii. Our results showed that VBNC C. sakazakii induced intestinal inflammation in neonatal rats. However, the degree of inflammation was significantly lower than that of culturable bacteria due to decreasing endotoxin production, motility, adhesion, and invasion ability in the VBNC state. From the perspective of bacterial translocation, the numbers of C. sakazakii in the blood, liver, and spleen of rats treated with VBNC cells were in the same order of magnitude as those treated with its culturable counterpart and may lead to the same degree of bacteremia. According to the macrophage survival assays, the survival rate of VBNC C. sakazakii within macrophages was 4.7 times higher than that of culturable cells. Based on these findings, we hypothesize that VBNC C. sakazakii evaded the host immune defense system, penetrated the tissue barrier, and translocated to the bloodstream, liver, and spleen through macrophages. Thus, our study reveals that VBNC C. sakazakii could be a potential risk for infants' health.

Diversity of Cronobacter genus isolated between 1970 and 2019 on the American continent and genotyped using multi-locus sequence typing

This study aimed to evaluate the Cronobacter spp. strains isolated on the American continent and characterized using multi-locus sequence typing (MLST) available in the PubMLST database and current literature. From 465 Cronobacter spp. strains, the majority (n = 267, 57.4%) was from North America, mainly from USA (n = 234) and 198 (42.6%) were from South America, mainly from Brazil (n = 196). A total of 232 (49.9%) were isolated from foods, 102 (21.9%) from environmental, 87 (18.7%) from clinical, 27 (5.8%) from PIF, one from water (0.2%) and 16 (3.5%) from unknown sources. A total of five species were represented: Cronobacter sakazakii (374, 80.4%), Cronobacter malonaticus (41, 8.8%), Cronobacter dublinensis (29, 6.2%), Cronobacter turicensis (16, 3.5%) and Cronobacter muytjensii (5, 1.1%). The strains with complete MLST profile (n = 345) were assigned to 98 STs, a ratio of 3.5 strain by ST found and the calculated Simpson`s index was 0.93. The strains showed a high diversity and after eBURST analysis, 30 STs (n = 189) formed 12 single and/or double-locus variant clonal complexes (CC). A total of 38 STs (38.7%) were associated with clinical cases of infection, including well established C. sakazakii CC 1, 4, 8 and 83; C. malonaticus ST60, 307, 394 and 440; and C. sakazakii ST 12 and 494.

The Changing Face of the Family Enterobacteriaceae (Order: "Enterobacterales"): New Members, Taxonomic Issues, Geographic Expansion, and New Diseases and Disease Syndromes

The family Enterobacteriaceae has undergone significant morphogenetic changes in its more than 85-year history, particularly during the past 2 decades (2000 to 2020). The development and introduction of new and novel molecular methods coupled with innovative laboratory techniques have led to many advances. We now know that the global range of enterobacteria is much more expansive than previously recognized, as they play important roles in the environment in vegetative processes and through widespread environmental distribution through insect vectors. In humans, many new species have been described, some associated with specific disease processes. Some established species are now observed in new infectious disease settings and syndromes. The results of molecular taxonomic and phylogenetics studies suggest that the current family Enterobacteriaceae should possibly be divided into seven or more separate families. The logarithmic explosion in the number of enterobacterial species described brings into question the relevancy, need, and mechanisms to potentially identify these taxa. This review covers the progression, transformation, and morphogenesis of the family from the seminal Centers for Disease Control and Prevention publication (J. J. Farmer III, B. R. Davis, F. W. Hickman-Brenner, A. McWhorter, et al., J Clin Microbiol 21:46-76, 1985, https://doi.org/10.1128/JCM.21.1.46-76.1985) to the present.

Isolation, comparison of identification methods and antibiotic resistance of Cronobacter spp. in infant foods

Cronobacter spp. are opportunistic pathogens that cause serious infections, especially in infants, elderly, and immunocompromised people. Dehydrated infant foods are the main vehicle associated with infections caused by these bacteria. Thus, this study aims to investigate the occurrence of Cronobacter spp. in 152 commercial samples of dehydrated infant formulas (77 samples) and dehydrated infant cereals (75 samples), as well as characterize the isolates. Polymerase Chain Reaction (PCR) and Matrix-Assisted Laser Desorption/Ionization Time-of-Flight Mass Spectrometry (MALDI-TOF/MS) methods for isolate identification were used, and their results compared. Furthermore, the susceptibility to 11 antibiotics was tested, and DNA sequencing of one isolate with multi-drug resistance was analyzed. No contamination in the infant formula samples was found, whereas 17.33% (13/75) of the infant cereal samples presented contamination with Cronobacter sakazakii. The identification results by PCR and MALDI-TOF/MS were divergent for some isolates. The antimicrobial resistance results showed a high incidence of resistance to cefazolin (94.4%) besides resistance to amoxicillin (9.45%), cefpodoxime (5.55%), streptomycin (1.35%), and trimethoprim/sulfamethoxazole (1.35%). Whole genome sequencing of one multi-drug resistant isolate showed six genes associated with antimicrobial resistance and an 82% possibility of being a human pathogen based on the presence of virulence factors. The presence of Cronobacter spp. in infant foods represents a risk for the infant's health. Moreover, the presence of a pathogenic multi-drug resistant isolate in infant's food reinforces the necessity of improving food safety policies to protect young children.