Isolation and Molecular Typing ofCronobacterspp. in Commercial Powdered Infant Formula and Follow-Up Formula

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

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

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.

Cronobacter spp. in Commercial Powdered Infant Formula Collected From Nine Provinces in China: Prevalence, Genotype, Biofilm Formation, and Antibiotic Susceptibility

The purpose of this study was to investigate the prevalence of Cronobacter spp. in commercial powdered infant formula (PIF) from nine provinces in China from March 2018 to September 2020, and to reveal the genotype, biofilm-forming ability, and antibiotic susceptibility of these isolates. A total of 27 Cronobacter strains, consisting of 22 Cronobacter sakazakii strains, 3 Cronobacter malonaticus strains, 1 Cronobacter turicensis strain, and 1 Cronobacter dublinensis strain, were isolated from 3,600 commercial PIF samples with a prevalence rate of 0.75%. Compared with the other 8 provinces, PIF from Shaanxi province had a higher prevalence rate (1.25%) of Cronobacter spp. These isolates were divided into 14 sequence types (STs), and 6 Cronobacter serotypes. The main Cronobacter STs were ST4, ST1, and ST64, and the dominant Cronobacter serotype was C. sakazakii serotype O2. Approximately 88.89% of Cronobacter isolates had a strong ability (OD₅₉₅ > 1) to form biofilms on tinplate, among which the strains with ST4 were more dominant. All isolates were susceptible to ampicillin-sulbactam, ceftriaxone, cefotaxime, sulfadiazine, sulfadoxine, trimethoprim-sulfamethoxazole, gentamicin, tetracycline, ciprofloxacin, and colistin, while 55.56 and 96.30% isolates were resistant to cephalothin and vancomycin, respectively. Taken together, our findings highlighted the contamination status and characterization of Cronobacter spp. in commercial PIF from nine provinces of China, and provided guidance for the effective prevention and control of this pathogen in the production of PIF.

Occurrence, Molecular Characterization, and Antibiotic Resistance of Cronobacter sakazakii in Goat Milk-Based Infant Formula from Shaanxi Province, China

This study aimed to investigate the prevalence of Cronobacter sakazakii in goat milk-based infant formula (GIF) collected from Shaanxi Province, China, and reveal the molecular characterization and antibiotic resistance profile of these isolates. A total of 750 GIF samples were collected from the retail markets in 5 cities in Shaanxi Province from February 2019 to February 2021. Molecular characterization was investigated using multilocus sequence typing and O-antigen serotyping. Antibiotic resistance of C. sakazakii isolates was assessed using antimicrobial susceptibility testing. Thirty-two strains of C. sakazakii were isolated from GIF samples with a prevalence rate of 4.27% and were divided into 16 sequence types (STs); among them, ST4 (6/32, 18.75%) and ST21 (5/32, 15.63%) were dominant. Five C. sakazakii serotypes (O2, O1, O7, O4, and O3) were detected, and C. sakazakii serotype O2 (15/32, 46.88%) was the main. Of the 21 antimicrobials, isolates showed higher resistance against cephalothin (87.5%), amoxicillin (25%), azithromycin (18.75%), oxytetracycline (18.75%), ampicillin (12.5%), and streptomycin (12.5%). In addition, three isolates were found to be resistant to three antimicrobials. These findings revealed the potential epidemiological risk and characterization of C. sakazakii in GIF from Shaanxi Province, China, and provided reference data for the effective prevention and control of C. sakazakii in powdered infant formula.

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.

Advances in our understanding and distribution of the Cronobacter genus in China

This review considers how research in China has progressed our understanding and subsequent improved control of Cronobacter. This emergent bacterial pathogen is associated with neonatal infections through the ingestion of contaminated prepared feed. The review includes large-scale surveys of various sources of the organism, including infant formula production facilities. The analysis of over 20,000 samples is presented. Over 10,000 being from powdered infant formula and other infant foods as well as environmental sampling of production facilities, the remaining being from food, food ingredients, and human carriage. A major advance in China was adopting DNA-sequence-based methods (that is, multilocus sequence typing, clustered regularly interspaced short palindromic repeats-cas array profiling, and single-nucleotide polymorphism analysis) for the identification and genotyping of the organism. These methods have considerably advanced our understanding of the taxonomy, ecology, and virulence of this organism. In turn, this has improved source tracking of the organism both in infant formula production facilities and epidemiological investigations. Furthermore, whole-genome sequencing has revealed a range of virulence and persistence mechanisms as well as plasmid-borne multidrug resistance traits. China now has reliable and robust methods for accurate microbial source tracking of Cronobacter for use both in the food production environment and epidemiological analysis.

Emergence of Cronobacter sakazakii in Cases of Neonatal Sepsis in Upper Egypt: First Report in North Africa

BACKGROUND AND AIM

Cronobacter sakazakii (C. sakazakii) has attracted considerable attention as an emerging neonatal pathogen and has been associated with outbreaks of life-threatening septicemia, necrotizing enterocolitis, and meningitis in neonates and infants globally. No data about the role of C. sakazakii as a cause of neonatal sepsis in North Africa is availale. Herein, we aimed to study the incidence of C. sakazakii in cases of neonatal sepsis, its distribution in different food samples in Egypt, antimicrobial profile, and the ability of the strains to form biofilms.

METHODS

A total of 100 positive blood cultures from cases of neonatal sepsis admitted to the neonatal ICU at Assiut University Children's Hospital, Egypt, were analyzed. In addition, 1,100 food samples, including 400 powdered infant formula (PIF), 500 herbs, and 200 water samples were screened for the presence of C. sakazakii. We evaluated the antimicrobial profile and the ability of the strains to form biofilms.

RESULTS

Cronobacter sakazakii was detected in 12 out of 100 cases of neonatal sepsis. The organism was also isolated from PIF, herbs, and water in percentages of 17.5, 9.2, and 7.5%, respectively. Regarding the antimicrobial sensitivity, all strains were resistant to ampicillin, amoxicillin, ampicillin/sulbactam, clindamycin, cephalothin, and cephalexin. In addition, C. sakazakii strains showed the ability to form biofilms, but with variable degrees of cell density.

CONCLUSION

We reported, for the first time, cases of neonatal sepsis caused by the emerging life-threatening pathogen C. sakazakii in Egypt. The organism was also detected in contaminated PIF, herbs, and water, which may be sources of infection for neonates, especially in countries where natural herbs are widely used as an alternative medicine. Finally, collective efforts by the parents, manufacturers of PIF, and healthcare personnel are essential to prevent serious infections caused by C. sakazakii, particularly in infants.

Prevalence, genetic analysis and CRISPR typing of Cronobacter spp. isolated from meat and meat products in China

Cronobacter spp. are important foodborne pathogens that infections occur in all age groups, especially cause serious life-threatening diseases in infants. This study aimed to acquire data on Cronobacter spp. contamination of meat and meat products (n = 588) in China during 2011 to 2016, and investigated the use of CRISPR typing technology as an approach for characterizing the genetics of Cronobacter spp. The overall contamination rate for Cronobacter spp. was determined to be 9.18% (54/588). Of the positive samples, 90.74% (49/54) had <10 MPN/g, with duck samples had a relatively high contamination rate (15.69%, 8/51) and highest contamination level (28.90 MPN/g). Four species and nine serotypes were identified among 69 isolates, of which C. sakazakii was the major species (n = 50) and C. sakazakii serogroup O1 and O2 (n = 17) were the primary serotypes. The majority of Cronobacter spp. strains were found to be susceptible to most antibiotics except exhibited high resistance to cephalothin (76.81%, 53/69), and total two multi-drug resistant C. sakazakii strains were isolated from duck. The genetic diversity of Cronobacter spp. was remarkably high, as evidenced by the identification of 40 sequence types (STs) and 60 CRISPR types (CTs). C. sakazakii ST64 (n = 7) was the predominant genotype and was further divided into two sub-lineages based on CRISPR diversity, showing different antibiotic resistance profile. These results demonstrate that CRISPR typing results have a good correspondence with bacterial phenotypes, and it will be a tremendously useful approach for elucidating inter-subtyping during molecular epidemiological investigations while interpreting the divergent evolution of Cronobacter. The presence of Cronobacter spp. in meat and meat product is a potential threat to human public health.

Prevalence, Antibiotic Susceptibility, and Molecular Characterization of Cronobacter spp. Isolated From Edible Mushrooms in China

Cronobacter spp. are foodborne pathogens that can infect and cause life-threatening diseases in all age groups, particularly in infants and immunocompromised elderly. This study aimed to investigate the prevalence, antibiotic susceptibility, and molecular characteristics of Cronobacter spp. isolates in edible mushrooms collected from 44 cities in China. In total, 668 edible mushrooms were collected from traditional retail markets and supermarkets and were analyzed by quantitative methods, PCR-based serotyping, multilocus sequence typing (MLST), and antibiotic susceptibility testing. Among the 668 samples tested, 89 (13.32%) were positive for Cronobacter spp., and the contamination levels exceeded the 110 most probable number (MPN)/g in 13.48% (12/89) of the samples. Flammulina velutipes samples had the highest contamination rate of 17.54% (37/211), whereas Hypsizygus marmoreus samples had the lowest contamination rate of 3.28% (2/61). Ten serotypes were identified among 115 isolates, of which the C. sakazakii serogroup O1 (n = 32) was the primary serotype. MLST indicated that there was quite high genetic diversity in Cronobacter spp. and 72 sequence types were identified, 17 of which were new. Notably, C. sakazakii ST148 (n = 10) was the most prevalent, followed by C. malonaticus ST7 (n = 5). Antibiotic susceptibility testing revealed that the majority of Cronobacter spp. strains were susceptible to the 16 antibiotics tested. However, a portion of isolates exhibited relatively high resistance to cephalothin, with resistance and intermediate rates of 93.91 and 6.09%, respectively. One isolate (cro300A) was multidrug-resistant, with resistance to five antibiotics. Overall, this large-scale study revealed the relatively high prevalence and high genetic diversity of Cronobacter spp. on edible mushrooms in China, indicating a potential public health concern. To our knowledge, this is the first large-scale and systematic study on the prevalence of Cronobacter spp. on edible mushrooms in China, and the findings can provide valuable information that can guide the establishment of effective measures for the control and precaution of Cronobacter spp on edible mushrooms during production processes.

Contamination of Cronobacter spp. in Chinese Retail Spices

Crononbacter spp. is an opportunistic foodborne pathogen that causes infections in neonates, infants, and immunocompromised adults. Although the contamination of spices with Cronobacter has been previously reported in some countries, there have been no studies on Cronobacter contamination in China. Therefore, this study aimed to investigate the prevalence of Cronobacter spp. in Chinese retail spices. Fifty-six packaged Chinese spices were collected from different markets, and 32 of these were found to be contaminated with Cronobacter. Five species were identified from the 54 isolates of the 32 positive samples: Cronobacter sakazakii (n = 35), Cronobacter muytjensii (n = 8), Cronobacter malonaticus (n = 6), Cronobacter turicensis (n = 3), and Cronobacter dublinensis (n = 2). Pulsed-field gel electrophoresis demonstrated high genetic diversity, as 53 PFGE profiles were revealed for the 54 isolates. Multilocus sequence typing analysis revealed 46 sequence types, and of these, 26 were newly identified. Most of the isolates were sensitive to antibiotics (n = 15), with the exception of cefazolin. This study revealed that the contamination of Chinese retail spices by Cronobacter spp. poses a potential risk to the consumer.

Cronobacter Species in Powdered Infant Formula and Their Detection Methods

Cronobacter species have been associated with disease outbreaks and sporadic infections, particularly in premature and immunocompromised infants. Cronobacter species can cause foodborne infections such as neonatal meningitis, septicaemia and necrotising enterocolitis. Accordingly, there is an urgent need to control and monitor the Cronobacter species in food, especially in powdered infant formula (PIF) and other baby foods. Therefore, in this review, the isolation and prevalence of Cronobacter species in infant food including PIF and the recent advance of detection methods are discussed for the better understanding on the current research status of Cronobacter species.

Antibiotic Susceptibility of Cronobacter spp. Isolated from Clinical Samples

Cronobacter spp. have been recognized as causative agents of various severe infections in pre-term or full-term infants as well as elderly adults suffering from serious underlying disease or malignancy. A surveillance study was designed to identify antibiotic resistance among clinical Cronobacter spp. strains, which were isolated from patients of two hospitals between May 2007 and August 2013. Altogether, 52 Cronobacter spp. isolates were analyzed. Although MALDI-TOF mass spectrometry recognized all Cronobacter sakazakii and Cronobacter malonaticus strains, it could not identify Cronobacter muytjensii strain. Nevertheless, all strains were identified as Cronobacter spp. using multilocus sequence typing (MLST). Strains were tested against 17 types of antibiotics, using the standard microdilution method according to the 2018 European Committee on Antimicrobial Susceptibility Testing criteria. Three Cronobacter species were identified as C. sakazakii (n = 33), C. malonaticus (n = 18), and C. muytjensii (n = 1); all isolates were susceptible to all tested antibiotics. All strains were PCR-negative for bla_TEM, bla_SHV, and bla_CTX-M β-lactamase genes, as well. Even though the results of this study showed that Cronobacter spp. isolates were pan-susceptible, continued antibiotic resistance surveillance is warranted.

Genetic Diversity, Antimicrobial Susceptibility, and Biofilm Formation of Cronobacter spp. Recovered from Spices and Cereals

Cronobacter species are important food-borne opportunistic pathogens which have been implicated in the cause of necrotizing enterocolitis, sepsis, and meningitis in neonates and infants. However, these bacteria are routinely found in foodstuffs, clinical specimens, and environmental samples. This study investigated the genetic diversity, antimicrobial susceptibility, and biofilm formation of Cronobacter isolates (n = 40) recovered from spices and cereals in China during 2014–2015. Based on the fusA sequencing analysis, we found that the majority (23/40, 57.5%) of Cronobacter isolates in spices and cereals were C. sakazakii, while the remaining strains were C. dublinensis (6/40, 15.0%), C. malonaticus (5/40, 12.5%), C. turicensis (4/40, 10.0%), and C. universalis (2/40, 5.0%). Multilocus sequence typing (MLST) analysis produced 30 sequence types (STs) among the 40 Cronobacter isolates, with 5 STs (ST4, ST13, ST50, ST129, and ST158) related to neonatal meningitis. The pattern of the overall ST distribution was diverse; in particular, it was revealed that ST148 was the predominant ST, presenting 12.5% within the whole population. MLST assigned 12 isolates to 7 different clonal complexes (CCs), 4, 13, 16, 17, 72, 129, and 143, respectively. The results of O-antigen serotyping indicated that C. sakazakii serotype O1 and O2 were the most two prevalent serotypes. The antimicrobial susceptibility testing showed that the 40 Cronobacter isolates were susceptible to most of the antibiotics tested except for ceftriaxone, meropenem, and aztreona. Of the 40 Cronobacter strains tested, 13 (32.5%) were assessed as weak bioflim producers, one (2.5%) was a moderate biofilm producer, one (2.5%) was strong biofilm producer, and the others (62.5%) were non-biofilm producers. MLST and O-antigen serotyping have indicated that Cronobacter strains recovered from spices and cereals were genetically diverse. Isolates of clinical origin, particularly the C. sakazakii ST4 neonatal meningitic pathovar, have been identified from spices and cereals. Moreover, antimicrobial resistance of Cronobacter strains was observed, which may imply a potential public health risk. Therefore, the surveillance of Cronobacter spp. in spices and cereals should be strengthened to improve epidemiological understandings of Cronobacter infections.

Prevalence, Molecular Characterization, and Antibiotic Susceptibility of Cronobacter sakazakii Isolates from Powdered Infant Formula Collected from Chinese Retail Markets

Cronobacter sakazakii is an opportunistic pathogen that causes severe infections in neonates and infants through contaminated powdered infant formula (PIF). Therefore, the aim of this study was a large-scale study on determine the prevalence, molecular characterization and antibiotic susceptibility of C. sakazakii isolates from PIF purchased from Chinese retail markets. Two thousand and twenty PIF samples were collected from different institutions. Fifty-six C. sakazakii strains were isolated, and identified using fusA sequencing analysis, giving a contamination rate of 2.8%. Multilocus sequence typing (MLST) was more discriminatory than other genotyping methods. The C. sakazakii isolates were divided into 14 sequence types (STs) by MLST, compared with only seven clusters by ompA and rpoB sequence analysis, and four C. sakazakii serotypes by PCR-based O-antigen serotyping. C. sakazakii ST4 (19/56, 33.9%), ST1 (12/56, 21.4%), and ST64 (11/56, 16.1%) were the dominant sequence types isolated. C. sakazakii serotype O2 (34/56, 60.7%) was the primary serotype, along with ompA6 and rpoB1 as the main allele profiles, respectively. Antibiotic susceptibility testing indicated that all C. sakazakii isolates were susceptible to ampicillin-sulbactam, cefotaxime, ciprofloxacin, meropenem, tetracycline, piperacillin-tazobactam, and trimethoprim-sulfamethoxazole. The majority of C. sakazakii strains were susceptible to chloramphenicol and gentamicin (87.5 and 92.9%, respectively). In contrast, 55.4% C. sakazakii strains were resistant to cephalothin. In conclusion, this large-scale study revealed the prevalence and characteristics of C. sakazakii from PIF in Chinese retail markets, demonstrating a potential risk for neonates and infants, and provide a guided to effective control the contamination of C. sakazakii in production process.

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.

Cronobacter spp

The Cronobacter group of pathogens, associated with severe and potentially life-threatening diseases, until recently were classified as a single species, Enterobacter sakazakii. The group was reclassified in 2007 into the genus Cronobacter as a member of the Enterobacteriaceae. This chapter outlines the history behind the epidemiology, analyzes how our understanding of these bacteria has evolved, and highlights the clinical significance the Cronobacter spp. have for neonatal and elderly patient populations and treatment of the associated infections.

Fully Closed Genome Sequences of Five Type Strains of the Genus Cronobacter and One Cronobacter sakazakii Strain

Cronobacter is associated with infant infections and the consumption of reconstituted infant formula. Here we sequenced and closed six genomes of C. condimenti^T, C. muytjensii^T, C. universalis^T, C. malonaticus^T, C. dublinensis^T, and C. sakazakii that can be used as reference genomes in single nucleotide polymorphism (SNP)-based next-generation sequencing (NGS) analysis for source tracking investigations.

Prevalence and Characterization of Cronobacter sakazakii in Retail Milk-Based Infant and Baby Foods in Shaanxi, China

Cronobacter sakazakii (formerly Enterobacter sakazakii) is an opportunistic pathogen that causes meningitis, sepsis, and necrotizing enterocolitis in neonates and infants through consumption of contaminated milk-based foods. In this study, the prevalence of C. sakazakii in 705 retail milk-based infant and baby food samples was investigated in 12 cities in Shaanxi, China, in 2010 and 2012. One hundred and nineteen samples (16.9%) were C. sakazakii positive. The isolates were further characterized for antimicrobial susceptibility to 14 antibiotics, pulsed-field gel electrophoresis profiles, and presence of the virulence genes. Samples of brand W, Y, A, and G in 2010 and 2012 were C. sakazakii positive. All isolates recovered in 2010 and 2012 were susceptible to levofloxacin and cefoperazone. In 2012, no isolate was resistant to gentamicin, cefoxitin, chloramphenicol, gatifloxacin, ciprofloxacin, and ceftriaxone. Antibiotic resistance of the isolates was most commonly found to rifampicin, amoxicillin-clavulanic acid, streptomycin, tetracycline, and ampicillin in both 2010 and 2012, except to trimethoprim/sulfamethoxazole in 2012. Pulsed-field gel electrophoresis profiles indicated that C. sakazakii isolates were genotypically diverse, although these isolates were prevalent in infant and baby foods with the same brand. A total of 34 virulence gene profiles of the C. sakazakii isolates in 2010 and 2012 were detected. Isolates that co-carried hly-ompX-eitCBAD-iucABCD/iutA genes in 2012 were significantly (p < 0.05) more prevalent than those in 2010. The results added new epidemiological evidence for the widespread occurrence of C. sakazakii in retail milk-based infant and baby foods and this should be an indicator of potential health risk for consumers.

Occurrence and prevalence of Cronobacter spp. in plant and animal derived food sources: a systematic review and meta-analysis

Cronobacter species are motile, non-spore forming, Gram negative emerging opportunistic pathogens mostly associated with bacteremia, meningitis, septicemia, brain abscesses and necrotizing enterocolitis in infected neonates, infants and immunocompromised adults. Members of the genus Cronobacter are previously associated with powdered infant formula although the main reservoir and routes of contamination are yet to be ascertained. This study therefore aim to summarize occurrence and prevalence of Cronobacter spp. from different food related sources. A retrospective systematic review and meta-analysis of peer reviewed primary studies reported between 2008 and 2014 for the occurrence and prevalence of Cronobacter spp. in animal and plant related sources was conducted using “Cronobacter isolation”, “Cronobacter detection” and “Cronobacter enumeration” as search terms in the following databases: Web of Science (Science Direct) and ProQuest. Data extracted from the primary studies were then analyzed with meta-analysis techniques for effect rate and fixed effects was used to explore heterogeneity between the sources. Publication bias was evaluated using funnel plot. A total of 916 articles were retrieved from the data bases of which 28 articles met inclusion criteria. Cronobacter spp. could only be isolated from 103 (5.7 %) samples of animal related food while 123 (19 %) samples of plant related food samples harbors the bacteria. The result of this study shows that occurrence of Cronobacter was more prevalent in plant related sources with overall prevalence rate of 20.1 % (95 % CI 0.168–0.238) than animal originated sources with overall prevalence rate of 8 % (95 % CI 0.066–0.096). High heterogeneity (I² = 84) was observed mostly in plant related sources such as herbs, spices and vegetables compared to animal related sources (I² = 82). It could be observed from this study that plant related sources serve as reservoir and contamination routes of Cronobacter spp.

Comparative Genotypic and Phenotypic Analysis of Cronobacter Species Cultured from Four Powdered Infant Formula Production Facilities: Indication of Pathoadaptation along the Food Chain

Cronobacter species are opportunistic pathogens commonly found in the environment. Among the seven Cronobacter species, Cronobacter sakazakii sequence type 4 (ST-4) is predominantly associated with recorded cases of infantile meningitis. This study reports on a 26-month powdered infant formula (PIF) surveillance program in four production facilities located in distinct geographic regions. The objective was to identify the ST(s) in PIF production environments and to investigate the phenotypic features that support their survival. Of all 168 Cronobacter isolates, 133 were recovered from a PIF production environment, 31 were of clinical origin, and 4 were laboratory type strains. Sequence type 1 (n = 84 isolates; 63.9%) was the dominant type in PIF production environments. The majority of these isolates clustered with an indistinguishable pulsotype and persisted for at least an 18-month period. Moreover, DNA microarray results identified two phylogenetic lineages among ST-4 strains tested. Thereafter, the ST-1 and -4 isolates were phenotypically compared. Differences were noted based on the phenotypes expressed by these isolates. The ST-1 PIF isolates produced stronger biofilms at both 28°C and 37°C, while the ST-4 clinical isolates exhibited greater swimming activity and increased binding to Congo red dye. Given the fact that PIF is a low-moisture environment and that the clinical environment provides for an interaction between the pathogen and its host, these differences may be consistent with a form of pathoadaptation. These findings help to extend our current understanding of the epidemiology and ecology of Cronobacter species in PIF production environments.

Multilocus sequence typing analysis of Cronobacter spp. isolated from China

Multilocus sequence typing (MLST) has proven to be an effective approach for the subtyping isolates of the Cronobacter genus and to exhibit a high level of discrimination between isolates. In this study, 151 Cronobacter strains were isolated from different sources and provinces across China from 2010 to 2012 and analyzed by MLST. Their sequence type profiles were compared with strains from other countries which were widely geographically and temporally distributed. Out of 151 strains in this study, the majority of strains were Cronobacter sakazakii (70.9 %), C. malonaticus (15.9 %), C. dublinensis (10.6 %), C. turicensis (2.0 %), and C. muytjensii (0.7 %). The strains were divided into 85 sequence types (STs), among which only 17 had previously been reported in other countries. The 85 identified STs for the Cronobacter genus were grouped into 14 clonal complexes and 47 singletons according to eBURST algorithm. The Cronobacter isolated from China showed a high diversity when they were subtyped using the MLST method. When compared to the Cronobacter PubMLST database, some sequence types of strains cultured from food and/or water in this study were also the same with strains isolated from patients in other countries as reported previously. This result showed the potential hazard of strains contaminating water and weaning food from China.

Prevalence, molecular characterization, and antibiotic susceptibility of Cronobacter spp. in Chinese ready-to-eat foods

Cronobacter spp. are foodborne pathogens that cause rare but life-threatening diseases in neonates and infants; they can also cause disease in adults. Cronobacter spp. contamination of ready-to-eat (RTE) foods has been reported previously. However, to date, the prevalence and contamination levels of these bacteria in RTE foods in China have not yet been determined. Therefore, the aim of this study was to investigate the prevalence of Cronobacter spp. in RTE foods marketed in China. Two-hundred and eighty RTE food samples were collected from different producers and retailers and analyzed using quantitative methods. The isolates obtained were identified to the species level based on fusA sequences, and were subtyped using a PCR-based serotyping technique. Selected isolates were further characterized by multilocus sequence typing (MLST) and antimicrobial sensitivity determination. Of 280 samples tested, 52 (18.6%) were positive for Cronobacter spp. The contamination levels were less than 110 MPN/g for 78.8% (41/52) of the samples. The results of the O-antigen serotyping for 111 isolates showed that Cronobacter sakazakii serogroup O2 (28 isolates) was the most prevalent serotype. MLST analyses produced 41 sequence types (STs), including 20 novel STs. ST8 was the most prevalent ST (9 isolates) followed by ST4 (5 isolates). Antimicrobial sensitivity testing showed that 84.5% and 46.5% of the isolates were resistant to penicillin G and cephalothin, respectively; in contrast, all of the tested isolates were susceptible to cefotaxime, ciprofloxacin, tetracycline, and nalidixic acid. To the best of our knowledge, this is the first report on Cronobacter spp. prevalence in RTE foods in China, and the findings of our study nonetheless suggested that Cronobacter spp. contamination of Chinese RTE foods poses a potential risk for the consumer. Thus, the study highlights the significance of developing more effective control strategies during the manufacturing process.

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

Cronobacter species are emerging opportunistic food-borne pathogens, which consists of seven species, including C. sakazakii, C. malonaticus, C. muytjensii, C. turicensis, C. dublinensis, C. universalis, and C. condimenti. The organism can cause severe clinical infections, including necrotizing enterocolitis, septicemia, and meningitis, predominately among neonates <4 weeks of age. Cronobacter species can be isolated from various foods and their surrounding environments; however, powdered infant formula (PIF) is the most frequently implicated food source linked with Cronobacter infection. This review aims to provide a summary of laboratory-based strategies that can be used to identify and trace Cronobacter species. The identification of Cronobacter species using conventional culture method and immuno-based detection protocols were first presented. The molecular detection and identification at genus-, and species-level along with molecular-based serogroup approaches are also described, followed by the molecular sub-typing methods, in particular pulsed-field gel electrophoresis and multi-locus sequence typing. Next generation sequence approaches, including whole genome sequencing, DNA microarray, and high-throughput whole-transcriptome sequencing, are also highlighted. Appropriate application of these strategies would contribute to reduce the risk of Cronobacter contamination in PIF and production environments, thereby improving food safety and protecting public health.