Occurrence of Cronobacter spp. in retail foods

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.

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.

Antibiotic Resistant Enterobacteriaceae in Milk Alternatives

The consumption of non-dairy milk is on the rise due to health benefits. Although there is increasing inclination towards milk alternatives (MA), there is limited data on antibiotic resistant bacteria in these substitutes. The aim of this study was to investigate antimicrobial resistance of bacteria isolated from MA. A total of 138 extracts from almonds (n = 63), cashew nuts (n = 36), and soybeans (n = 39) were analyzed for Enterobacteriaceae. The identification of the bacteria was based on biochemical and PCR methods. Antibiotic sensitivity was determined by using the Kirby-Bauer disk diffusion technique. Overall, 31% (43 of 138) of extracts were positive for Enterobacteriaceae. Ten bacterial species were identified, of which Enterobacter cloacae (42.7%) and Enterobacter cancerogenus (35.4%) were the most predominant species (p < 0.05). Antibiotic resistance was exhibited to vancomycin (88.3%), novobiocin (83.8%), erythromycin (81.1%), which was significantly higher (p < 0.05) than in tetracycline (59.5%), cefpodoxime (30.6%), and nalidixic acid (6.3%). There was no resistance displayed to kanamycin and imipenem. ERY-NOV-VAN-TET and ERY-NOV-CEP-VAN-TET were the most common resistant patterns displayed by Enterobacter cloacae. The findings of this study suggest that MAs, though considered healthy, may be a reservoir of multidrug resistant opportunist pathogens.

Microbiological Quality of Nuts, Dried and Candied Fruits, Including the Prevalence of Cronobacter spp

Cronobacter genus bacteria are food-borne pathogens. Foods contaminated with Cronobacter spp. may pose a risk to infants or immunocompromised adults. The aim of this study was to determine the microbiological quality of nuts, seeds and dried fruits with special emphasis on the occurrence of Cronobacter spp. Analyses were carried out on 64 samples of commercial nuts (20 samples), dried fruits (24), candied fruits (8), seeds (4), and mixes of seeds, dried fruits and nuts (8). The samples were tested for the total plate count of bacteria (TPC), counts of yeasts and molds, and the occurrence of Cronobacter spp. Cronobacter isolates were identified and differentiated by PCR-RFLP (Polymerase Chain Reaction - Restriction Fragments Length Polymorphism) and RAPD-PCR (Random Amplified Polymorphic DNA by PCR) analysis. TPC, and yeasts and molds were not detected in 0.1 g of 23.4%, 89.1%, and 32.8% of the analyzed samples. In the remaining samples, TPC were in the range of 1.2–5.3 log CFU g⁻¹. The presence/absence of Cronobacter species was detected in 12 (18.8%) samples of: nuts (10 samples), and mixes (2 samples). The 12 strains of Cronobacter spp. included: C. sakazakii (3 strains), C. malonaticus (5), and C. turicensis (4). The results of this study contribute to the determination of the presence and species identification of Cronobacter spp. in products of plant origin intended for direct consumption.

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.

Examining the Presence of Cronobacter spp. in Ready-to-eat Edible Insects

Edible insects present a potential solution to increasing global food insecurity. However, there is limited research on the microbial hazards they may pose. These include opportunistic pathogens like Cronobacter spp. (formerly Enterobacter sakazakii). In this study, nine types of ready-to-eat edible insect products purchased in the UK were examined for their microbial load (total aerobic count, total Enterobacteriaceae count), and screened for the presence of Cronobacter sakazakii(C. sakazakii) by selective enrichment and plating on chromogenic agar. While microbial load was generally low, presumptive Cronobacter spp. were detected in five of the edible insect products. Four of the isolates were identified as C. sakazakii, using the Remel RapID ONE biochemical test kit. Genotypic characterisation of the isolates by ITS-PCR, however, demonstrated that the isolates may be other species of Cronobacter instead. Further studies into understanding microbial hazards linked to edible insects for human consumption are required.

Temporal influence of different antibiotics onto the inhibition of Escherichia coli bacterium grown in different media

Escherichia coli (E. coli) is a Gram-negative bacterium commonly found in the lower intestine of warm-blooded organisms, including humans. Although the majority of the strains are considerably harmless, some serotypes are pathogenic, frequently causing diarrhea and other illnesses outside the intestinal tract. The standard antidote against bacteria is the use of antibiotics. Depending on their type, the antibiotics have various mechanisms of action on bacteria. Moreover, in case of in-vitro cultivation of bacteria, the used growth media plays a crucial role, since it influences bacterial inhibition as well. In the present study, we emphasize the importance of cultivability in bacterial inhibition under the treatment with five different antibiotics belonging to different classes. Consequently, E. coli was cultivated in three different growth media: trypcase soy broth (TSB), Mueller Hinton (MH), and minimal salts (M9) enriched with glucose, respectively. MALDI-TOF MS (matrix-assisted laser desorption ionization time-of-flight mass spectrometry) analyses, that were used for fast characterization of changes that occur in ribosomal protein profiles, revealed differentiation and similarities between investigated cases, while flow cytometry (FCM) tests better explained the given changes that occurred in the analyzed samples after 3, 24 and 48 h of experimental campaign.

Evaluation of Methods for Inoculating Dry Powder Foods with Salmonella enterica, Enterococcus faecium, or Cronobacter sakazakii

Salmonella and Cronobacter are two bacteria of concern in powdered food ingredients with low water activity, due to their ability to remain viable for long periods of time. There is great interest in studying the survival of these bacteria in powdered foods, but discrepancies have been reported between broth-grown and lawn-grown bacterial cells and their thermal resistance and desiccation tolerance once inoculated onto powdered foods. The purpose of this study was to evaluate three different powdered food inoculation methods, two broth-grown and one lawn-grown. To evaluate these methods on three types of powdered food matrices, Salmonella enterica serovar Typhimurium LT2 (ATCC 700720), Salmonella surrogate Enterococcus faecium (NRRL B-2354), and Cronobacter sakazakii (ATCC 29544) were inoculated onto nonfat dry milk powder, organic soy flour, and all-purpose flour using one of the three previously developed inoculation methods. In the first broth-grown method, labeled broth-grown pelletized inoculation, a bacterial cell pellet was added to powdered foods directly and mixed with a sterile wooden stick. The second broth-grown method, labeled broth-grown spray inoculation, used a chromatography reagent sprayer to spray the bacterial cell suspension onto the powdered foods. The third inoculation method, lawn-grown liquid inoculation, made use of a spot inoculation and a stomacher to incorporate each bacterium into the powdered foods. Results indicated that the method of inoculation of each powder impacted repeatability and bacteria survivability postequilibration (4 to 6 days). Broth-grown spray inoculation, regardless of the powder and bacterium, resulted in the highest log reduction, with an average ∼1-log CFU/g reduction following equilibration. Broth-grown pelletized inoculation resulted in the second-highest log reduction (∼0.79 log CFU/g), and finally, lawn-grown liquid inoculation was the most stable inoculation method of the three, with ∼0.52-log CFU/g reduction. Overall, the results from this inoculation study demonstrate that inoculation methodologies impact the desiccation tolerance and homogeneity of C. sakazakii, E. faecium, and Salmonella Typhimurium LT2.

Occurrence of virulence factors in Cronobacter sakazakii and Cronobacter malonaticus originated from clinical samples

BACKGROUND

Cronobacter spp. are Gram-negative, facultative-anaerobic, non-spore forming, enteric coliform bacteria, which belongs to the Enterobacteriaceae family. Cronobacter spp. are opportunistic pathogens that have brought rare but life-threatening infections such as meningitis, necrotizing enterocolitis and bloodstream infections in neonates and infants. Information on the diversity, pathogenicity and virulence of Cronobacter species obtained from various sources is still relatively scarce and fragmentary. The aim of this study was to examine and analyse different pathogenicity and virulence factors among C. sakazakii and C. malonaticus strains isolated from clinical samples.

METHODS

The thirty-six clinical Cronobacter strains have been used in this study. This bacterial collection consists of 25 strains of C. sakazakii and 11 strains of C. malonaticus, isolated from different clinical materials. Seven genes (ompA, inv, sip, aut, hly, fliC, cpa) were amplified by PCR. Moreover, the motility and the ability of these strains to adhere and invade human colorectal adenocarcinoma (HT-29) and mouse neuroblastoma (N1E-115) cell lines were investigated.

RESULTS

Our results showed that all tested strains were able to adhere to both used cell lines, HT-29 and N1E-115 cells. The invasion assay showed that 66.7% (24/36) of isolates were able to invade N1-E115 cells while 83% (30/36) of isolates were able to invade HT-29 cells. On the average, 68% of the C. sakazakii strains exhibited seven virulence factors and only 18% in C. malonaticus. All strains amplified ompA and fliC genes. The other genes were detected as follow: sip 97% (35/36), hlyA 92% (33/36), aut 94% (34/36), cpa 67% (24/36), and inv 69% (25/36).

CONCLUSIONS

C. sakazakii and C malonaticus strains demonstrate the diversity of the virulence factors present among these pathogens. It is necessary to permanently monitor the hospital environment to appropriately treat and resolve cases associated with disease. Furthermore, in-depth knowledge is needed about the source and transmission vehicles of pathogens in hospitals to adopt pertinent prevention measures.

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.

The Effects of Temperature on the Growth and Heat Resistance of Cronobacter spp

　The growth and survival of Cronobacter isolates were examined under incubation at different temperatures, and their thermal death behavior was investigated at high temperature conditions of above 50℃. Seventy three strains isolated from fresh vegetables, dried foods and soil were tested: 28 of Cronobacter sakazakii, 5 of C. dublienensis, 27 of C. malonaticus and 13 of C. turicensis. All Cronobacter strains grew and multiplied predominantly at 35 and 44℃ until 16 hours of incubation, but showed poor growth at 15℃, and no growth at 5℃. At 48℃, the bacteria grew slightly during 6 to 8 h-incubation but decreased or were inactivated after 16 h-incubation. The heat resistance of Cronobacter spp. was measured under the conditions of 50, 55, 60, 65 and 70℃. Cronobacter strains survived almost without decrement for 30 min at 50℃, but decreased suddenly and perished completely within 10 to 20 min at 55℃ and within 2 - 5 min at above 60℃. Some food materials should be stored below 5℃ until the preparation, and dried food including powdered infant milk formula should be utilized immediately after reconstitution and preparation.

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.

Updates on the Cronobacter Genus

There has been considerable concern related to Cronobacter spp. in foods, especially due to their highlighted association with neonatal infections through the ingestion of reconstituted powdered infant formula (PIF). This concern resulted in improved microbiological criteria recommendations by the Codex Alimentarius Commission and revised WHO advice on the preparation of infant feeds. In recent years, the diversity of the genus has been well described, and various detection and typing methods have been developed. This review considers our current knowledge of the genus and how DNA-sequence-based methods have contributed considerably to research into improved detection methods and more reliable identification procedures, genotyping schemes, and genomic analysis. The broader occurrence of Cronobacter in food ingredients, finished products, and food manufacturing environments is covered. This review also highlights the significance of clonal lineages in microbial source tracking and the use of CRISPR-cas array profiling.

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.

Mass spectrometric techniques for the analysis of volatile organic compounds emitted from bacteria

Bacteria are the main cause of many human diseases. Typical bacterial identification methods, for example culture-based, serological and genetic methods, are time-consuming, delaying the potential for an early and accurate diagnosis and the appropriate subsequent treatment. Nevertheless, there is a stringent need for in situ tests that are rapid, noninvasive and sensitive, which will greatly facilitate timely treatment of the patients. This review article presents volatile organic metabolites emitted from various micro-organism strains responsible for common bacterial infections in humans. Additionally, the manuscript shows the application of different analytical techniques for fast bacterial identification. Details of these techniques are given, which focuses on their advantages and drawbacks in using for volatile organic components analysis.

Foodborne pathogens

Foodborne pathogens are causing a great number of diseases with significant effects on human health and economy. The characteristics of the most common pathogenic bacteria (Bacillus cereus, Campylobacter jejuni, Clostridium botulinum, Clostridium perfringens, Cronobacter sakazakii, Esherichia coli, Listeria monocytogenes, Salmonella spp., Shigella spp., Staphylococccus aureus, Vibrio spp. and Yersinia enterocolitica), viruses (Hepatitis A and Noroviruses) and parasites (Cyclospora cayetanensis, Toxoplasma gondii and Trichinella spiralis), together with some important outbreaks, are reviewed. Food safety management systems based on to classical hazard-based approach has been proved to be inefficient, and risk-based food safety approach is now suggested from leading researchers and organizations. In this context, a food safety management system should be designed in a way to estimate the risks to human health from food consumption and to identify, select and implement mitigation strategies in order to control and reduce these risks. In addition, the application of suitable food safety education programs for all involved people in the production and consumption of foods is suggested.

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.

Occurrence of Cronobacter spp. in Dried Foods, Fresh Vegetables and Soil

　The present study surveyed the occurrence of Cronobacter spp. in dried foods including milk powder, spices and herbs and others, and fresh vegetables commercially available in markets, and ground soil materials for the agriculture. Cronobacter spp. were isolated from 15% of 33 spice and herb samples and 3% of 36 taste foods, and these were C. turicensis, C. malonaticus, C. sakazakii and C. dubliensis. Cronobacter spp. from fresh vegetables were detected in 12% of field vegetables and 13% of hydroponic vegetables. C. turicensis was prevalent in field vegetables, and C. malonaticus was in hydroponic ones. And, Cronobacter spp. in shredded vegetables were detected from 44% of 9 samples, and these were C. dubliensis, C. turicensis and C. sakazakii. Also, Cronobacter spp. in soil from rice field, vegetable field and sandpits were predominantly C. sakazakii and C. malonaticus.

Antibiotic and Desiccation Resistance of Cronobacter sakazakii and C. malonaticus Isolates from Powdered Infant Formula and Processing Environments

This study evaluated the antimicrobial and desiccation resistance of Cronobacter sakazakii and Cronobacter malonaticus isolates from powdered infant formula and processing environments. The antimicrobial susceptibility tests showed that the 70 Cronobacter strains, representing 19 sequence types, were susceptible to the most of the antibiotics except for amoxicillin-clavulanate, ampicillin, and cefazolin. Furthermore, the growth of six C. sakazakii and two C. malonaticus strains from different sequence types (STs) in hyperosmotic media was measured. The growth of the two C. sakazakii strains (CE1 and CE13) from the neonatal pathovars ST4 and ST8, were significantly higher (p < 0.05) than that of other strains. C. malonaticus strain CM35 (ST201) was the slowest grower in all strains, and most could not grow in more than 8% NaCl solution. Also the survival of these strains under desiccation conditions was followed for 1 year. The viable count of Cronobacter spp. under desiccation conditions was reduced on average by 3.02 log cycles during 1 year, with CE13 (ST8) being the most desiccation resistant strain. These results will improve our understanding of the persistence of the two closely related species C. sakazakii and C. malonaticus which are of concern for neonatal and adult health.

Opioid Dependent Malingerer with Self-Induced Sepsis

A 21-year-old woman was admitted to the emergency department (ED) with severe sepsis. Both the mechanism of infection and organisms discovered were unusual.

Microbiological Quality of Raw Dried Pasta from the German Market, with Special Emphasis on Cronobacter Species

The microbiological quality of 132 dried pasta products available on the German market, originating from 11 different countries, was studied. Sample materials included soft or durum wheat products, some of which produced with other ingredients such as eggs, spices, or vegetables. Parameters included hygiene indicators (aerobic plate count, mold count, the presence of Enterobacteriaceae) and pathogenic/toxinogenic bacterial species (Salmonella spp., Staphylococcus aureus, presumptive Bacillus cereus, and Cronobacter spp.). The overall results of hygiene parameters indicated a satisfactory quality. Salmonella was not found in any sample. Three samples were positive for S. aureus (10(2) to 10(4) colony forming unit (CFU)/g). Presumptive B. cereus at levels of 10(3) to 10(4) CFU/g were detected in 3 samples. Cronobacter spp. were isolated from 14 (10.6%) products. Of these, 9 isolates were identified as C. sakazakii, 2 each as C. turicensis and C. malonaticus, and 1 as C. muytjensii. The isolates were assigned to 9 multilocus sequence typing (MLST) sequence types and to 14 different PFGE profiles. Although pasta products are typically cooked before consumption, some consumers, and children in particular, may also eat raw pasta as nibbles. Raw pasta seems to be a relevant source of exposure to dietary Cronobacter spp., although health risks are probably restricted to vulnerable consumers. High numbers of presumptive B. cereus as found in some samples may be a risk after improper storage of cooked pasta products because toxinogenic strains are frequently found within this species.

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.

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.

Genotypic and phenotypic characteristics of Cronobacter species, with particular attention to the newly reclassified species Cronobacter helveticus, Cronobacter pulveris, and Cronobacter zurichensis

In 2013, Enterobacter helveticus, Enterobacter pulveris and Enterobacter turicensis, were reclassified as Cronobacter helveticus, Cronobacter pulveris and Cronobacter zurichensis, respectively. Previously these species had been used as negative controls for some Cronobacter detection assays. This study examined cultural, biochemical and molecular Cronobacter detection and identification assays, with emphasis on the new species. Additionally, 32 Cronobacter genomes were examined for the presence of PCR target genes using the BLAST function of the online Cronobacter PubMLST facility. The results of the cultural methods varied and no single medium was able to correctly detect all Cronobacter spp. Since the supporting databases have not been updated to include the Cronobacter genus, Enterobacter sakazakii was returned for four strains of the newly reclassified species with ID32E and none with API 20E. PCR probes targeting rpoB and ompA could not correctly identify the new Cronobacter spp., due to primer specificity or absent target genes. As neonates have been identified as a high-risk group for infection, international standards require the absence of all Cronobacter species in powdered infant formula. However, many conventional detection methods cannot correctly identify the newly recognized species. Conversely, DNA sequence-based methods can adapt to taxonomic revisions and will likely become more common.

Cronobacter spp.--opportunistic food-borne pathogens. A review of their virulence and environmental-adaptive traits

The genus Cronobacter consists of a diverse group of Gram-negative bacilli and comprises seven species: Cronobacter sakazakii, Cronobacter malonaticus, Cronobacter muytjensii, Cronobacter turicensis, Cronobacter dublinensis, Cronobacter universalis and Cronobacter condimenti. Cronobacter are regarded as opportunistic pathogens, and have been implicated in newborn and infant infections, causing meningitis, necrotizing enterocolitis and bacteraemia or sepsis. Cronobacter virulence is believed to be due to multiple factors. Some strains were found to produce diarrhoea or cause significant fluid accumulation in suckling mice. Two iron acquisition systems (eitCBAD and iucABCD/iutA), Cronobacter plasminogen activator gene (cpa), a 17 kb type VI secretion system (T6SS), and a 27 kb filamentous haemagglutinin gene (fhaBC) and associated putative adhesins locus are harboured on a family of RepFIB-related plasmids (pESA3 and pCTU1), suggesting that these are common virulence plasmids; 98% of 229 tested Cronobacter strains possessed these plasmids. Even though pESA3 and pCTU1 share a common backbone composed of the repA gene and eitCBAD and iucABCD/iutA gene clusters, the presence of cpa, T6SS and FHA loci depended on species, demonstrating a strong correlation with the presence of virulence traits, plasmid type and species. Other factors were observed, in that Cronobacter form biofilms, and show unusual resistance to heat, dry and acid stress growth conditions. The outer-membrane protein A is probably one of the best-characterized virulence markers of Cronobacter. Furthermore, it was reported that Cronobacter employ phosphatidylinositide 3-kinase/Akt signalling, which activates protein kinase C-α and impairs the host cell's mitogen-activated protein kinase pathway, in order to invade cells. Cronobacter can also use immature dendritic cells and macrophages to escape the immune response. This review addresses the various virulence and environmental-adaptive characteristics possessed by members of the genus Cronobacter.

Isolation of Cronobacter spp. (Enterobacter Sakazakii) from Artisanal Mozzarella

Cronobacter spp. (Enterobacter sakazakii) is an opportunistic bacterial pathogen capable of causing disease and even fatalities in newborn infants within the first weeks of life if consumed as part of the diet. Premature and immunocompromised newborn infants are at particular risk. The microorganism has been isolated from a variety of foods including contaminated infant milk formula powder and milk powder substitute. The study aimed to evaluate the level of microbiological contamination in 47 samples of mozzarella cheese made with cow's milk collected from artisan cheese producers in Southern Italy. Samples were collected from commercial sales points and underwent qualitative and quantitative microbiological analyses to test for the bacterial contaminants most commonly found in milk and cheese products. The 47 samples underwent qualitative and quantitative microbiological tests according to ISO UNI EN standards. Analyses focused on Staphylococcus aures, Salmonella spp., Listeria monocytogenes, Pseudomonas spp., E. coli, Yersinia spp., total coliforms and Cronobacter sakazakii. The ISO/TS 22964:2006 method was used to investigate possible contamination by C. sakazakii. Biochemical identification was carried out using an automated system for identification and susceptibility tests. None of the samples examined resulted positive for Salmonella spp. or Listeria spp. Only one sample resulted positive for Staphylococcus aureus. Pseudomonas spp. was isolated in 10 (21%) of 47 samples. High levels of total coliforms were found in 10 of 47 samples. Cronobacter spp. (Enterobacter sakazakii) was isolated in one sample. This is the first study to confirm isolation of C. sakazakii in artisan mozzarella cheese made from cow's milk. The presence of C. sakazakii could be related to external contamination during the phases of production or to the use of contaminated milk. Since mozzarella is recommended in the diet of children and adults of all ages, this present study helps define it as a potential vehicle for C. sakazakii in subjects at particular risk.

Occurrence and characterization of Cronobacter spp. in powdered formula from Chinese retail markets

Cronobacter spp. (formerly known as Enterobacter sakazakii) are foodborne pathogens that cause rare but life-threatening diseases in neonates and infants through consumption of contaminated powdered infant formula. This study was conducted to investigate the occurrence of Cronobacter spp. in powdered formula in China and to further characterize Cronobacter isolates. Isolates were identified to the species level based on the fusA gene sequence, and strains of C. sakazakii were further subtyped by applying the polymerase chain reaction (PCR)-based serotyping method. A total of 23 strains of Cronobacter spp. isolated from 530 powdered formula samples were identified using conventional biochemical methods and duplex PCR. Cronobacter spp. were detected in 6.25%, 1.82%, 3.64%, 5.45%, and 2.50% of the general formula, infant formula (age <6 months), follow-up formula (6-12 months of age), growing-up formula (1-3 years of age), and children's formula (3-6 years of age), respectively. The individual species were identified as C. sakazakii (22 isolates) and C. malonaticus (1 isolate). Among 22 C. sakazakii isolates, representatives of all but two O-antigen serotypes (serotypes O5 and O6) were recognized.

Food Safety: Emerging Pathogens

This article presents information related to emerging pathogens that are foodborne or have the potential to be foodborne including bacteria, viruses, and parasites. The phenotypic characteristics of these pathogens, their epidemiology, prevalence in foods, and transmission routes to humans as well as means for their control are also discussed.

Lack of continuity between Cronobacter biotypes and species as determined using multilocus sequence typing

The accuracy of the Cronobacter biotyping scheme was compared with the 7-loci multilocus sequence typing scheme. Biotyping did not reliably assign species level identification, as only half (17/31) of the biotype variants were unique to any of the seven Cronobacter species and the remaining biotypes were shared across the genus.

The potential of matrix-assisted laser desorption/ionization time-of-flight mass spectrometry for the identification of biogroups of Cronobacter sakazakii

RATIONALE

The bacterial genus Cronobacter was established quite recently, in 2008. Therefore, its systematic classification is still in progress as well as the risk assessment of Cronobacter strains. The possibility of rapid identification within the biogroup level has an essential epidemiological significance. We examined the potential of mass spectrometry to accomplish this task on species Cronobacter sakazakii comprising eight different biogroups.

METHODS

Members of all Cronobacter sakazakii biogroups were characterized by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) using intact cells. Analyses were performed on a Biflex IV MALDI-TOF mass spectrometer in the range of 2000 to 20 000 Da in linear mode with an accelerated voltage of 19 kV.

RESULTS

Optimal conditions for a proper identification of biogroups, such as suitable cultivation media or growth time of bacteria, were investigated. The biomarker patterns characterizing each of the Cronobacter sakazakii biogroups were obtained. The established identification protocol was applied to ten previously non-identified strains and their biogroups were successfully determined.

CONCLUSIONS

The presented work is the first report of successful and rapid bacterial biogroup taxonomy classification using MALDI-TOF-MS that could substitute demanding biochemical testing.

Prevalence and relative risk of Cronobacter spp., Salmonella spp., and Listeria monocytogenes associated with the body surfaces and guts of individual filth flies

Although flies are important vectors of food-borne pathogens, there is little information to accurately assess the food-related health risk of the presence of individual flies, especially in urban areas. This study quantifies the prevalence and the relative risk of food-borne pathogens associated with the body surfaces and guts of individual wild flies. One hundred flies were collected from the dumpsters of 10 randomly selected urban restaurants. Flies were identified using taxonomic keys before being individually dissected. Cronobacter spp., Salmonella spp., and Listeria monocytogenes were detected using the PCR-based BAX system Q7. Positive samples were confirmed by culture on specific media and through PCR amplification and sequencing or ribotyping. Among collected flies were the housefly, Musca domestica (47%), the blowflies, Lucilia cuprina (33%) and Lucilia sericata (14%), and others (6%). Cronobacter species were detected in 14% of flies, including C. sakazakii, C. turicensis, and C. universalis, leading to the proposal of flies as a natural reservoir of this food-borne pathogen. Six percent of flies carried Salmonella enterica, including the serovars Poona, Hadar, Schwarzengrund, Senftenberg, and Brackenridge. L. monocytogenes was detected in 3% of flies. Overall, the prevalence of food-borne pathogens was three times greater in the guts than on the body surfaces of the flies. The relative risk of flies carrying any of the three pathogens was associated with the type of pathogen, the body part of the fly, and the ambient temperature. These data enhance the ability to predict the microbiological risk associated with the presence of individual flies in food and food facilities.