Introduction: According to the Turkish Food Codex Regulation on Microbiological Criteria, Cronobacter sakazakii is regarded as risky only in infant formula and not evaluated in terms of this microorganism in other dairy products. In this... more
Introduction: According to the Turkish Food Codex Regulation on Microbiological Criteria, Cronobacter sakazakii is regarded as risky only in infant formula and not evaluated in terms of this microorganism in other dairy products. In this study, enumeration of Enterobacteriaceae, detection of C. sakazakii, Salmonella spp. and Listeria monocytogenes were found of vanilla (n = 30), chocolate (n = 30), mixed fruit (n = 30) in 90 ice cream samples.
This study investigated the synergistic effects of combined ultrasound (US; 37 kHz, 380 W for 10 e60 min) and peroxyacetic acid (PAA; 50e200 ppm) on reducing Cronobacter sakazakii biofilms on cucumbers. US was not sufficient to eliminate... more
This study investigated the synergistic effects of combined ultrasound (US; 37 kHz, 380 W for 10 e60 min) and peroxyacetic acid (PAA; 50e200 ppm) on reducing Cronobacter sakazakii biofilms on cucumbers. US was not sufficient to eliminate C. sakazakii biofilms (0.04e0.60 log-reduction), whereas PAA (200 ppm) significantly (p < 0.05) reduced biofilm formation on cucumber (0.89e1.88 log reduction). Furthermore, the combination of 60 min US and 200 ppm PAA resulted in an additional 1.63 log-reduction of C. sakazakii biofilms (3.51 log-reduction ¼ 1.88 þ 1.63 log). Synergistic reduction of C. sakazakii biofilms was observed in most combined treatment, although the most synergistic reduction values were <1.0 log 10 CFU/cm 2. The highest synergistic value of reduction in cucumber was 1.03e1.08 log 10 CFU/cm 2 when treated with a combination of 60 min US and 150e200 ppm PAA. In addition, the Hunter color(" L " , " a " , and " b "), moisture contents(%), and texture(hardness and chewiness) after combined treatment with 60 min US and 200 ppm PAA did not differ significantly from those of cucumbers exposed to a single treatment. These results indicate that combined treatment with 60 min US and 150 e200 ppm PAA could be a useful approach to reduce C. sakazakii biofilms on fresh-produce and could help enhance their shelf-life during transportation and storage.
Enterobacter sakazakii is considered an opportunistic pathogen and has been implicated in food-associated cases of meningitis or enteritis, especially in neonates and infants. The organism has been detected in various types of food and in... more
Enterobacter sakazakii is considered an opportunistic pathogen and has been implicated in food-associated cases of meningitis or enteritis, especially in neonates and infants. The organism has been detected in various types of food and in food production units, but so far only powdered infant formula has been linked to outbreaks of disease. Survival and persistence in such environments requires the ability to adapt to high osmotic potentials and/or dry conditions. Fifty-six E. sakazakii strains were evaluated for several features important for persistence and survival: (i) biofilm formation and the putative production of cellulose as one of the components of the extracellular matrix, (ii) adherence to hydrophilic and hydrophobic surfaces, (iii) the production of extracellular polysaccharides, and (iv) the ability of E. sakazakii to produce cell-to-cell signaling molecules. Pellicle and flock formation was observed in 21 of the strains grown in Luria-Bertani broth and in 44 of the st...
The objective of this research was to characterize the resistance of Cronobacter sakazakii to ultrasonic waves under pressure (manosonication, MS). The DMS value (decimal reduction time value) of C. sakazakii in standard conditions (35°C,... more
The objective of this research was to characterize the resistance of Cronobacter sakazakii to ultrasonic waves under pressure (manosonication, MS). The DMS value (decimal reduction time value) of C. sakazakii in standard conditions (35°C, 117μm, 200kPa, citrate–phosphate buffer pH 7.0) was 0.41min. This value was higher than that of Yersinia enterocolitica (DMS=0.19min) and lower than those of Salmonella enterica serovar
In 2010, two infants became ill at a hospital in Mexico. Subsequently, a range of clinical, environmental, and powdered and rehydrated infant formula isolates were identified by using a combination of phenotyping and PCR probes. The... more
In 2010, two infants became ill at a hospital in Mexico. Subsequently, a range of clinical, environmental, and powdered and rehydrated infant formula isolates were identified by using a combination of phenotyping and PCR probes. The strains were clustered according to pulsed-field gel electrophoresis. The causative agent was reported as Cronobacter sakazakii, with powdered infant formula (PIF) identified as the likely source of the infections. This new study further characterized the isolates from this outbreak by using multilocus sequence typing and whole genome sequencing of selected strains. Though four PIF isolates and one hospital environmental isolate were identified as C. sakazakii sequence type 297 by multilocus sequence typing, they were isolated 6 months prior to the outbreak. Genotypic analyses of patient isolates identified them as Enterobacter hormaechei and Enterobacter spp. The pulsed-field gel electrophoresis profile of the Enterobacter spp. isolates matched those of...
The purpose of this study is the determination of the presence of Cronobacter sakazakii, Listeria monocytogenes, Salmonella spp. and Enterobactericeae count in ice creams and infant formulas, and present its importance with regard to... more
The purpose of this study is the determination of the presence of Cronobacter sakazakii, Listeria monocytogenes, Salmonella spp. and Enterobactericeae count in ice creams and infant formulas, and present its importance with regard to hygienic quality in dairy products. For this purpose, 25 unpackaged and 65 packaged ice cream samples, and 90 packaged infant formulas have been analysed. Among the unpackaged ice cream samples 9 was determined to have C. sakazakii and four was determined to have L. monocytogenes, and one packaged ice cream was determined to have C. sakazakii. Enterobacter cloacae was determined in 13 infant formulas. None of the ice cream and infant formulas samples were determined to have Salmonella spp.. It was concluded that the detection of C. sakazakii and E. cloacae in ice creams bears importance for public health.
Bicarinalin is a linear and C-terminus amidated cationic peptide characterized from the Tetramorium bicarinatum ant venom. In the present study, the antibacterial activity of bicarinalin against four representative strains of Enterobacter... more
Bicarinalin is a linear and C-terminus amidated cationic peptide characterized from the Tetramorium bicarinatum ant venom. In the present study, the antibacterial activity of bicarinalin against four representative strains of Enterobacter genus and Cronobacter sakazakii, emerging opportunistic pathogens in foods, was evaluated in laboratory conditions. The lowest minimal inhibitory and minimal bactericidal concentrations were obtained on C. sakazakii, while the highest values were found on Enterobacter cloacae. Whatever the microorganism, bicarinalin was more potent than melittin, ampicillin and tetra-cycline. SYTOX green nucleic acid staining was used to assess the effect of bicarinalin on bacterial membrane integrity. In all strains, permeabilization of the membrane was observed for sub-MIC values, indicating that bicarinalin efficiently disrupted the plasma membrane leading to the bacterial death. Collectively, these data suggest that this natural peptide could be used for enhancing the microbial safety of food and prevent the microbial spoilage of diverse biological matrices by Enterobacteriaceae.
We present the results of a study using high-throughput whole-transcriptome sequencing (RNA-seq) and vibrational spectroscopy to characterize and fingerprint pathogenic-bacterium injury under conditions of unfavorable stress. Two... more
We present the results of a study using high-throughput whole-transcriptome sequencing (RNA-seq) and vibrational spectroscopy to characterize and fingerprint pathogenic-bacterium injury under conditions of unfavorable stress. Two garlic-derived organosulfur compounds were found to be highly effective antimicrobial compounds against Cronobacter sakazakii, a leading pathogen associated with invasive infection of infants and causing meningitis, necrotizing entercolitis, and bacteremia. RNA-seq shows changes in gene expression patterns and transcriptomic response, while confocal micro-Raman spectroscopy characterizes macromolecular changes in the bacterial cell resulting from this chemical stress. RNA-seq analyses showed that the bacterial response to ajoene differed from the response to diallyl sulfide. Specifically, ajoene caused downregulation of motility-related genes, while diallyl sulfide treatment caused an increased expression of cell wall synthesis genes. Confocal micro-Raman spectroscopy revealed that the two compounds appear to have the same phase I antimicrobial mechanism of binding to thiol-containing proteins/enzymes in bacterial cells generating a disulfide stretching band but different phase II antimicrobial mechanisms, showing alterations in the secondary structures of proteins in two different ways. Diallyl sulfide primarily altered the α-helix and β-sheet, as reflected in changes in amide I, while ajoene altered the structures containing phenylalanine and tyrosine. Bayesian probability analysis validated the ability of principal component analysis to differentiate treated and control C. sakazakii cells. Scanning electron microscopy confirmed cell injury, showing significant morphological variations in cells following treatments by these two compounds. Findings from this study aid in the development of effective intervention strategies to reduce the risk of C. sakazakii contamination in the food production environment and on food contact surfaces, reducing the risks to susceptible consumers.
The present study investigated the synergistic effects of combined ultrasound (37 kHz, 380 W for 5 e100 min) and sodium hypochlorite (NaOCl) (50e200 ppm) on reducing Cronobacter sakazakii KCTC 2949 in head lettuce. Ultrasound was not... more
The present study investigated the synergistic effects of combined ultrasound (37 kHz, 380 W for 5 e100 min) and sodium hypochlorite (NaOCl) (50e200 ppm) on reducing Cronobacter sakazakii KCTC 2949 in head lettuce. Ultrasound was not enough to inactivate C. sakazakii (0.01e0.58 log-reduction), whereas NaOCl significantly (P < 0.05) reduced C. sakazakii (0.58e2.77 log-reduction). Despite the significant reduction in C. sakazakii with NaOCl treatment (200 ppm), the combination of 100 min ultrasound and 200 ppm NaOCl resulted in an additional 1.67 log-reduction of C. sakazakii (4.44 logreduction ¼ 2.77 þ 1.67 log). Synergistic reductions on C. sakazakii were observed in most combined treatments, although the most synergistic reduction values were <1.0 log10 CFU/g. The highest synergistic value of reduction in head lettuce was 1.08 log10 CFU/g when treated with a combination of 100 min ultrasound and 200 ppm NaOCl. Moreover, the pH and Brix after combined treatment with 5 e100 min ultrasound and 50e200 ppm NaOCl did not significantly differ from any single treated lettuce. These results indicate that combined treatment with 100 min ultrasound and 200 ppm NaOCl could be a potential approach to reduce C. sakazakii on post-harvest leaf vegetable during processing and enhance the shelf-life during distribution and storage.
The genomic content of Enterobacter sakazakii strain ATCC BAA-894 was analyzed for variable-number tandem repeats (VNTRs). In this study we report the development of a multiple-locus VNTR analysis (MLVA) strategy for the subtyping of E.... more
The genomic content of Enterobacter sakazakii strain ATCC BAA-894 was analyzed for variable-number tandem repeats (VNTRs). In this study we report the development of a multiple-locus VNTR analysis (MLVA) strategy for the subtyping of E. sakazakii. The method is based on a GeneScan analysis of four VNTR loci labeled with multiple fluorescent dyes. This approach was applied to a collection of 112 isolates representing all 16 of the currently defined E. sakazakii biogroups. MLVA successfully discriminated among these isolates and compared favorably with pulsed-field gel electrophoresis. The method was relatively fast and easy to perform. The potential value of MLVA as an epidemiological tool is discussed.
Background: Cronobacter sakazakii is associated with illness in infants from contaminated powdered infant formula (PIF) and it is frequently recovered from PIF factory environment. Limited information is available on contamination of... more
Background: Cronobacter sakazakii is associated with illness in infants from contaminated powdered infant formula (PIF) and it is frequently recovered from PIF factory environment. Limited information is available on contamination of other food such as dairy and meat products in Libya.
The aim of this study was to identify and characterize Cronobacter spp. isolated from a range of foods. A total of 71 Cronobacter strains were isolated from 602 foods in our laboratory. The highest contamination was observed in foods of... more
The aim of this study was to identify and characterize Cronobacter spp. isolated from a range of foods. A total of 71 Cronobacter strains were isolated from 602 foods in our laboratory. The highest contamination was observed in foods of plant origin, e.g. spices, teas, chocolate, nuts, pastries and vegetables. On the basis of genus and species identification performed using genus-specific PCR, 16S rRNA sequencing and AFLP genotyping, most of the strains belonged to Cronobacter sakazakii. Biochemical profiling by the tests included in API 20E, complemented with relevant additional tests, classified the strains into 13 biogroups. AFLP genotyping facilitated discrimination of six main groups at the 70% similarity level and strain grouping correlated clearly with species identification. Our results indicate that molecular typing by AFLP may be applied as a useful tool not only for direct comparison of Cronobacter isolates, providing traceability, but also for the reliable species classification. Moreover, tracing of these bacteria in a wider variety of foods should be important to enhance the knowledge of their transmission.
The aim of this study was to identify and characterize Cronobacter spp. isolated from a range of foods. A total of 71 Cronobacter strains were isolated from 602 foods in our laboratory. The highest contamination was observed in foods of... more
The aim of this study was to identify and characterize Cronobacter spp. isolated from a range of foods. A total of 71 Cronobacter strains were isolated from 602 foods in our laboratory. The highest contamination was observed in foods of plant origin, e.g. spices, teas, chocolate, nuts, pastries and vegetables. On the basis of genus and species identification performed using genus-specific PCR, 16S rRNA sequencing and AFLP genotyping, most of the strains belonged to Cronobacter sakazakii. Biochemical profiling by the tests included in API 20E, complemented with relevant additional tests, classified the strains into 13 biogroups. AFLP genotyping facilitated discrimination of six main groups at the 70% similarity level and strain grouping correlated clearly with species identification. Our results indicate that molecular typing by AFLP may be applied as a useful tool not only for direct comparison of Cronobacter isolates, providing traceability, but also for the reliable species classification. Moreover, tracing of these bacteria in a wider variety of foods should be important to enhance the knowledge of their transmission.
Enterobacter sakazakii is a foodborne pathogen that has been associated with sporadic cases and outbreaks causing meningitis, necrotizing enterocolitis and sepsis especially in neonates. The current FDA detection method includes two... more
Enterobacter sakazakii is a foodborne pathogen that has been associated with sporadic cases and outbreaks causing meningitis, necrotizing enterocolitis and sepsis especially in neonates. The current FDA detection method includes two enrichment steps, the subculturing of the second enrichment broth on a selective agar (VRBG), a further subculturing of selected grown colonies on TSA and the subsequent biochemical identification of yellow-pigmented colonies by API20E. However, there is a strong need for simplified methods for isolation and identification of E. sakazakii. In this study, two chromogenic media, which allow to indicate presumptive E. sakazakii colonies by the alpha glucosidase activity, as well as a newly developed 1,6-alpha-glucosidase based conventional PCR assay and a rRNA oligonucleotide probe based commercial test system for identification of presumptive E. sakazakii were evaluated on 98 target and non-target strains. The methods were compared with respect to specific...
