Strategies for the identification and tracking of cronobacter species: an opportunistic pathogen of concern to neonatal health

A Probiotic Amylase Blend Positively Impacts Gut Microbiota Modulation in a Randomized, Placebo-Controlled, Double-Blind Study

The present study was performed to determine if ingesting a blend of probiotics plus amylase would alter the abundance and diversity of gut microbiota in subjects consuming the blend over a 6-week period. 16S and ITS ribosomal RNA (rRNA) sequencing was performed on fecal samples provided by subjects who participated in a clinical study where they consumed either a probiotic amylase blend (Bifidobacterium breve 19bx, Lactobacillus acidophilus 16axg, Lacticaseibacillus rhamnosus 18fx, and Saccharomyces boulardii 16mxg, alpha amylase (500 SKB (Alpha-amylase-Dextrinizing Units)) or a placebo consisting of rice oligodextrin. The abundance and diversity of both bacterial and fungal organisms was assessed at baseline and following 6 weeks of probiotic amylase blend or placebo consumption. In the subjects consuming the probiotic blend, the abundance of Saccharomyces cerevisiae increased 200-fold, and its prevalence increased (~20% to ~60%) (p ≤ 0.05), whereas the potential pathogens Bacillus thuringiensis and Macrococcus caseolyticus decreased more than 150- and 175-fold, respectively, after probiotic-amylase blend consumption. We also evaluated the correlation between change in microbiota and clinical features reported following probiotic amylase consumption. Nine (9) species (seven bacterial and two fungal) were significantly (negatively or positively) associated with the change in 32 clinical features that were originally evaluated in the clinical study. Oral supplementation with the probiotic-amylase blend caused a marked increase in abundance of the beneficial yeast S. cerevisiae and concomitant modulation of gut-dwelling commensal bacterial organisms, providing the proof of concept that a beneficial commensal organism can re-align the gut microbiota.

Antibacterial action of slightly acidic electrolytic water against Cronobacter sakazakii and its application as a disinfectant on high-risk contact surfaces

Powdered infant formula (PIF) is prone to Cronobacter sakazakii (C. sakazakii) contamination, which can result in infections that endanger the lives of newborns and infants. Slightly acidic electrolytic water (SAEW) has shown antibacterial effects on a variety of foodborne pathogens and has a wide applicability in the food industry. Here, the antibacterial activity of SAEW against C. sakazakii and its use as a disinfectant on contact surfaces with high infection transmission risk were investigated. The inactivation of SAEW on C. sakazakii was positively correlated to the SAEW concentration and treatment time. The antibacterial effect of SAEW was achieved by decreasing the intracellular adenosine triphosphate (ATP), K+, protein, and DNA contents of C. sakazakii, reducing the intracellular pH (pHin) and destroying the cell morphology, which led to inactivation of C. sakazakii ultimately. To test the applicability of this study, the results showed that approximately 103 CFU/cm2 of C. sakazakii were successfully inactivated on stainless steel and rubber surfaces after a 30 mg/L SAEW treatment for 20 s. These results indicate the antibacterial mechanism and potential application of SAEW against C. sakazakii, as well as a new strategy for the prevention and control of C. sakazakii on stainless steel and rubber surfaces.

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.

[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.

Outbreak of Cronobacter turicensis in European brown hares (Lepus europaeus)

This is the first report of acute deaths in five European brown hares (Lepus europaeus) attributed to mucoid and necrotizing typhlocolitis caused by genetically different Cronobacter (C.) turicensis strains in northeastern Austria. As this opportunistic pathogen is mainly known for causing disease in immunocompromised humans and neonates, this previously unrecognized potential for a spillover from a wildlife reservoir to humans warrants further attention.

In silico species identification and serotyping for Cronobacter isolates by use of whole-genome sequencing data

Cronobacter spp. are foodborne pathogens that can cause severe infections in neonates through contaminated powdered infant formula. Accurate and rapid pathogen identification and serotyping are crucial to limit the detrimental effects of bacterial infections, and to prevent outbreaks and sporadic infections. Conventional serotyping is tedious, laborious, and time-consuming; however, with whole-genome sequencing (WGS) becoming faster and cheaper, WGS has vast potential in routine typing and surveillance. Hence, in this study, we developed a publicly available tool, CroTrait (CronobacterTraits), for in silico species identification and O serotyping of Cronobacter isolates based on WGS data. CroTrait showed excellent performance in species identification and O serotyping when 810 genomes with known species identities and 276 genomes with known O serotype were tested. Moreover, CroTrait allows rapid prediction of new potential O serotypes. We identified 11 novel potential O serotypes of Cronobacter using CroTrait. Therefore, CroTrait is a convenient and promising tool for species identification and O serotyping of Cronobacter isolates.

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.

Electricity-free amplification and visual detection of Cronobacter species in powdered infant formula

Due to the lack of electricity and thermostatic instruments in certain settings for convenient detection of Cronobacter species in powdered infant formula (PIF), a novel investigation was conducted to establish an electricity-free visual detection system for rapid detection of Cronobacter species in PIF. This system included a portable electricity-free heater that could use the exothermic reaction of calcium oxide and water and 3 kinds of phase change materials to supply 3 constant temperatures for immunomagnetic separation, DNA extraction, and loop-mediated isothermal amplification assay. Meanwhile, the amplified reaction combined with hydroxynaphthol blue could achieve rapid visual detection. Primers designed based on the 16S-23S ribosomal RNA internal transcribed spacer were used in loop-mediated isothermal amplification to specifically monitor Cronobacter species, and the detection limit can reach 4.2 × 10² cfu/g in PIF by an electricity-free heater in 2 h 30 min. Moreover, 2 h of pre-enrichment was necessary when the level of the PIF samples with Cronobacter spp. was 10⁰ cfu/g. The stability of the system was evaluated in ambient temperature at 4°C, 25°C, and 37°C. The results suggested that the electricity-free heater can maintain 3 constant temperatures to support different processes. Therefore, this amplification and visual system is applicable for use in many fields for rapid and specific detection of Cronobacter species in PIF.

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.

Occurrence of Cronobacter Spp. in Ready-to-Eat Vegetable Products, Frozen Vegetables, and Sprouts Examined Using Cultivation and Real-Time PCR Methods

Environmental matrices and food products are hypothesized to be sources of Cronobacter spp. The severity of neonatal infections, increasing number of cases in elderly and immunocompromised individuals, as well as isolation of Cronobacter spp. from clinical materials demands that more attention should be paid to Cronobacter spp. detection and occurrence of the bacteria in food products. Here, a total of 175 samples of ready-to-eat vegetables, frozen vegetables, and sprouted seeds were collected during a period of 1 year and examined for the presence of Cronobacter spp. using a cultivation method with two different sample preparations and real-time polymerase chain reaction (qPCR). In total, Cronobacter spp. were detected in 22.3% of tested samples using cultivation. In comparison, direct qPCR detected Cronobacter spp. in 37.7% of these samples (p < 0.01; Fisher's exact test) and the numbers of genome equivalents per gram reached 10⁸ in some samples of sprouts. Cronobacter spp. were isolated from 51.4%, 37.2%, and 5.2% samples of sprouts, frozen vegetables, and cut green leaves/salads, respectively. Using qPCR, the most frequently contaminated sample types were sprouts (91.4%) and frozen vegetables (60.5%), whereas the rate of positivity for cut green leaves/salads was, in comparison, only 8.2% (p < 0.01; χ² -test for independence). PRACTICAL APPLICATION: This study provided valuable information on the occurrence of Cronobacter spp. in ready-to-eat vegetables using cultivation and qPCR. Cronobacter spp. are emerging opportunistic pathogens that can be present in food of plant origin. Cronobacter spp. were isolated from sprouts, frozen vegetables, and cut green leaves/salads, and the numbers of genome equivalents per gram reached 10⁸ in some samples of sprouts.

Daqu Fermentation Selects for Heat-Resistant Enterobacteriaceae and Bacilli

Daqu is a spontaneous solid-state cereal fermentation used as saccharification and starter culture in Chinese vinegar and liquor production. The evolution of microbiota in this spontaneous fermentation is controlled by the temperature profile, which reaches temperatures from 50 to 65°C for several days. Despite these high temperatures, mesophilic Enterobacteriaceae (including Cronobacter) and bacilli are present throughout Daqu fermentation. This study aimed to determine whether Daqu spontaneous solid-state fermentation selects for heat-resistant variants of these organisms. Heat resistance in Enterobacteriaceae is mediated by the locus of heat resistance (LHR). One LHR-positive strain of Kosakonia cowanii was identified in Daqu, and it exhibited higher heat resistance than the LHR-negative K. cowanii isolated from malted oats. Heat resistance in Bacillus endospores is mediated by the spoVA ^2mob operon. Out of 10 Daqu isolates of the species Bacillus licheniformis, Brevibacillus parabrevis, Bacillus subtilis, Bacillus amyloliquefaciens, and Bacillus velezensis, 5 did not contain spoVA ^2mob, 3 contained one copy, and 2 contained two copies. The presence and copy number of the spoVA ^2mob operon increased the resistance of spores to treatment with 110°C. To confirm the selection of LHR- and spoVA ^2mob-positive strains during Daqu fermentation, the copy numbers of these genetic elements in Daqu samples were quantified by quantitative PCR (qPCR). The abundance of LHR and the spoVA ^2mob operon in community DNA relative to that of total bacterial 16S rRNA genes increased 3-fold and 5-fold, respectively, during processing. In conclusion, culture-dependent and culture-independent analyses suggest that Daqu fermentation selects for heat-resistant Enterobacteriaceae and bacilli.IMPORTANCE Daqu fermentations select for mobile genetic elements conferring heat resistance in Enterobacteriaceae and bacilli. The locus of heat resistance (LHR), a genomic island conferring heat resistance in Enterobacteriaceae, and the spoVA ^2mob operon, conferring heat resistance on bacterial endospores, were enriched 3- to 5-fold during Daqu fermentation and maturation. It is therefore remarkable that the LHR and the spoVA ^2mob operon are accumulated in the same food fermentation. The presence of heat-resistant Kosakonia spp. and Bacillus spp. in Daqu is not of concern for food safety; however, both genomic islands are mobile and transferable to pathogenic bacteria or toxin-producing bacteria by horizontal gene transfer. The identification of the LHR and the spoVA ^2mob operon as indicators of fitness of Enterobacteriaceae and bacilli in Daqu fermentation provides insights into environmental sources of heat-resistant organisms that may contaminate the food supply.

Probe-free label system for rapid detection of Cronobacter genus in powdered infant formula

Cronobacter species previously known as Enterobacter sakazakii poses high risks to neonates and infants. In this work a rapid detection method was developed which combined loop-mediated isothermal amplification with lateral flow assay for detection of Cronobacter species in powdered infant formula. The fast amplification reaction without betaine was established and capable of performing DNA replication within 25 min. Based on the novel probe-free labeling methods, we established a lateral flow assay to capture the specific loop-mediated isothermal amplification amplicons which were labeled with fluorescein isothiocyanate and biotin. And the final detection time of this system was within 40 min. The false positive results of the lateral flow assay induced by primer dimer tagged with fluorescein isothiocyanate and biotin were eliminated by Taq single strand DNA binding protein (4 ng/μL). Simultaneously, the efficiency of the fast loop-mediated isothermal amplification assay was achieved. By injection of Taq SSB into the amplification assay as a replacement for betaine, the novel probe-free method could detect Cronobacter species with high specificity and sensitivity at the detection limit in PIF of 10¹ cfu/g. Our overall strategy has excellent potential in the rapid diagnosis of Cronobacter species label-free by integrating loop-mediated isothermal amplification and lateral flow assay.

Multiplexed Lateral Flow Test for Detection and Differentiation of Cronobacter sakazakii Serotypes O1 and O2

The ubiquitous and opportunistic pathogen Cronobacter sakazakii is responsible for severe meningitis, sepsis, and necrotizing enterocolitis in neonates and infants associated with ingestion of contaminated powdered infant formula (PIF). The current ISO method for isolation and detection of Cronobacter spp. is laborious, time-consuming and expensive. In this study, a multiplexed lateral flow test strip was developed to rapidly detect and simultaneously serotype O1 and O2 C. sakazakii serotypes. The assay is based on two monoclonal antibodies (MAb) that specifically bind to the lipopolysaccharides (LPS) of these pathogens. The test strip provides results very quickly; C. sakazakii could be detected in pure culture within 15 min with a sensitivity of 107 CFU/ml. After non-selective enrichment for 18 h as low as one Cronobacter cell per g PIF could be detected. Moreover, the established lateral flow assay (LFA) offers excellent specificity showing no cross-reactivity with other C. sakazakii serotypes, Cronobacter species or Enterobacteriaceae tested. These characteristics, together with several advantages such as speed, simplicity in performance, low analysis cost, and no requirement of specialized skills or sophisticated equipment make the developed multiplexed LFA suitable for reliable detection and serotyping of C. sakazakii serotypes O1 and O2.

Molecular Surveillance of Cronobacter spp. Isolated from a Wide Variety of Foods from 44 Different Countries by Sequence Typing of 16S rRNA, rpoB and O-Antigen Genes

Cronobacter spp. are emerging infectious bacteria that can cause acute meningitis and necrotizing enterocolitis in neonatal and immunocompromised individuals. Although this opportunistic human-pathogenic microorganism has been isolated from a wide variety of food and environmental samples, it has been primarily linked to foodborne outbreaks associated with powdered infant formula. The U.S. Food and Drug Administration use the presence of these microbes as one of the criteria to assess food adulteration and to implement regulatory actions. In this study, we have examined 195 aliquots of enrichments from the nine major categories of foods (including baby and medical food, dairy products, dried food, frozen food, pet food, produce, ready-to-eat snacks, seafood, and spices) from 44 countries using conventional microbiological and molecular techniques. The typical colonies of Cronobacter were then identified by VITEK2 and real-time PCR. Subsequently, sequence typing was performed on the 51 recovered Cronobacter isolates at the 16S rRNA, rpoB and seven O-antigen loci for species identification in order to accomplish an effective surveillance program for the control and prevention of foodborne illnesses.

Use of a Pan-Genomic DNA Microarray in Determination of the Phylogenetic Relatedness among Cronobacter spp. and Its Use as a Data Mining Tool to Understand Cronobacter Biology

Cronobacter (previously known as Enterobacter sakazakii) is a genus of Gram-negative, facultatively anaerobic, oxidase-negative, catalase-positive, rod-shaped bacteria of the family Enterobacteriaceae. These organisms cause a variety of illnesses such as meningitis, necrotizing enterocolitis, and septicemia in neonates and infants, and urinary tract, wound, abscesses or surgical site infections, septicemia, and pneumonia in adults. The total gene content of 379 strains of Cronobacter spp. and taxonomically-related isolates was determined using a recently reported DNA microarray. The Cronobacter microarray as a genotyping tool gives the global food safety community a rapid method to identify and capture the total genomic content of outbreak isolates for food safety, environmental, and clinical surveillance purposes. It was able to differentiate the seven Cronobacter species from one another and from non-Cronobacter species. The microarray was also able to cluster strains within each species into well-defined subgroups. These results also support previous studies on the phylogenic separation of species members of the genus and clearly highlight the evolutionary sequence divergence among each species of the genus compared to phylogenetically-related species. This review extends these studies and illustrates how the microarray can also be used as an investigational tool to mine genomic data sets from strains. Three case studies describing the use of the microarray are shown and include: (1) the determination of allelic differences among Cronobacter sakazakii strains possessing the virulence plasmid pESA3; (2) mining of malonate and myo-inositol alleles among subspecies of Cronobacter dublinensis strains to determine subspecies identity; and (3) lastly using the microarray to demonstrate sequence divergence and phylogenetic relatedness trends for 13 outer-membrane protein alleles among 240 Cronobacter and phylogenetically-related strains. The goal of this review is to describe microarrays as a robust tool for genomics research of this assorted and important genus, a criterion toward the development of future preventative measures to eliminate this foodborne pathogen from the global food supply.

Genetic Characterization of Cronobacter sakazakii Recovered from the Environmental Surveillance Samples During a Sporadic Case Investigation of Foodborne Illness

Cronobacter sakazakii is an opportunistic human-pathogenic bacterium known to cause acute meningitis and necrotizing enterocolitis in neonates and immunocompromised individuals. This human-pathogenic microorganism has been isolated from a variety of food and environmental samples, and has been also linked to foodborne outbreaks associated with powdered infant formula (PIF). The U.S. Food and Drug Administration have a policy of zero tolerance of these organisms in PIF. Thus, this agency utilizes the presence of these microorganisms as one of the criteria in implementing regulatory actions and assessing adulteration of food products of public health importance. In this study, we recovered two isolates of Cronobacter from the 91 environmental swab samples during an investigation of sporadic case of foodborne illness following conventional microbiological protocols. The isolated typical colonies were identified using VITEK2 and real-time PCR protocols. The recovered Cronobacter isolates were then characterized for species identification by sequencing the 16S rRNA locus. Further, multilocus sequence typing (MLST) was accomplished characterizing seven known C. sakazakii-specific MLST loci (atpD, fusA, glnS, gltB, gyrB, infB, and pps). Results of this study confirmed all of the recovered Cronobacter isolates from the environmental swab samples to be C. sakazakii. The MLST profile matched with the published profile of the complex 31 of C. sakazakii. Thus, rRNA and 7-loci MLST-based sequencing protocols are robust techniques for rapid detection and differentiation of Cronobacter species, and these molecular diagnostic tools can be used in implementing successful surveillance program and in the control and prevention of foodborne illness.

Variability in Cell Response of Cronobacter sakazakii after Mild-Heat Treatments and Its Impact on Food Safety

Cronobacter spp. have been responsible for severe infections in infants associated with consumption of powdered infant formula and follow-up formulae. Despite several risk assessments described in published studies, few approaches have considered the tremendous variability in cell response that small micropopulations or single cells can have in infant formula during storage, preparation or post process/preparation before the feeding of infants. Stochastic approaches can better describe microbial single cell response than deterministic models as we prove in this study. A large variability of lag phase was observed in single cell and micropopulations of ≤50 cells. This variability increased as the heat shock increased and growth temperature decreased. Obviously, variability of growth of individual Cronobacter sakazakii cell is affected by inoculum size, growth temperature and the probability of cells able to grow at the conditions imposed by the experimental conditions should be taken into account, especially when errors in bottle-preparation practices, such as improper holding temperatures, or manipulation, may lead to growth of the pathogen to a critical cell level. The mean probability of illness from initial inoculum size of 1 cell was below 0.2 in all the cases and for inoculum size of 50 cells the mean probability of illness, in most of the cases, was above 0.7.

Simultaneous Rapid Detection and Serotyping of Cronobacter sakazakii Serotypes O1, O2, and O3 by Using Specific Monoclonal Antibodies

Cronobacter sakazakii is a foodborne pathogen associated with rare but often lethal infections in neonates. Powdered infant formula (PIF) represents the most frequent source of infection. Out of the identified serotypes (O1 to O7), O1, O2, and O3 are often isolated from clinical and PIF samples. Serotype-specific monoclonal antibodies (MAbs) suitable for application in enzyme immunoassays (EIAs) for the rapid detection of C. sakazakii have not yet been developed. In this study, we created specific MAbs with the ability to bind toC. sakazakii of serotypes O1, O2, and O3. Characterization by indirect EIAs, immunofluorescence, motility assays, and immunoblotting identified lipopolysaccharide (LPS) and exopolysaccharide (EPS) as the antigenic determinants of the MAbs. The established sandwich EIAs were highly sensitive and were able to detect between 2 × 10(3)and 9 × 10(6)CFU/ml. Inclusivity tests confirmed that 93% of serotype O1 strains, 100% of O2 strains, and 87% of O3 strains were detected at low cell counts. No cross-reactivity with >100 strains of Cronobacter spp. and other Enterobacter iaceae was observed, except for that with C. sakazakii serotype O3 and Cronobacter muytjensii serotype O1. Moreover, the sandwich EIAs detected C. sakazakii in PIF samples artificially contaminated with 1 to 10 bacterial cells per 10 g of sample after 15 h of preenrichment. The use of these serotype-specific MAbs not only allows the reliable detection of C. sakazakii strains but also enables simultaneous serotyping in a simple sandwich EIA method.

The Roles of Epidemiologists, Laboratorians, and Public Health Agencies in Preventing Invasive Cronobacter Infection

BACKGROUND

Cronobacter can cause severe, invasive infection in very young infants. These bacteria can also colonize or cause insignificant infections in immunocompromised, elderly, and/or hospitalized adults.

METHODS

This editorial review highlights key points addressed in the Frontiers Research Topic on Cronobacter, discusses the clinical presentation and epidemiology of Cronobacter infections, and examines the responses of public health agencies to this problem.

RESULTS

Cronobacter is rarely isolated from hospitalized, immunocompromised and/or elderly adults and does not cause significant disease in those patients. Certain species and strains, especially of Cronobacter sakazakii, can cause invasive illness in previously healthy infants <2 months of age. Multilocus sequence type 4 and clonal complex 4 (ST4/MLST 4) C. sakazakii are the predominant cause of Cronobacter meningitis, which occurs only in infants. These infections and this strain type are strongly linked to powdered infant formulas (PIF), which can also be contaminated with other Cronobacter strains. End-product testing is not intended to guarantee the absence of these organisms. WHO has made recommendations that can help decrease but will not eliminate the risk of this infection.

CONCLUSION

To further define the spectrum of Cronobacter-associated disease, all isolates should be genetically typed using every currently available method, typing results should be linked to the associated epidemiologic and clinical data, and these data should be analyzed in a scientifically sound manner. Based on currently available information, more can be done now to prevent cause invasive infection in young infants. This includes encouragement of exclusive breastfeeding and/or use of commercially sterile ready-to-feed formulas in the first 2 months of life.