Sialic acid utilization by Cronobacter sakazakii

Background: The Cronobacter genus is composed of seven species, and can cause infections in all age groups. Of particular concern is C. sakazakii, as this species is strongly associated with severe and often fatal cases of necrotizing enterocolitis and meningitis in neonates and infants. Whole genome sequencing has revealed that the nanAKT gene cluster required for the utilisation of exogenous sialic acid is unique to the C. sakazakii species (ESA_03609-13). Sialic acid is found in breast milk, infant formula, intestinal mucin, and gangliosides in the brain, hence its metabolism by C. sakazakii is of particular interest. Therefore its metabolism could be an important virulence factor. To date, no laboratory studies demonstrating the growth of C. sakazakii on sialic acid have been published nor have there been reports of sialidase activity. The phylogenetic analysis of the nan genes is of interest to determine whether the genes have been acquired by horizontal gene transfer

Genotypic and phenotypic characteristics of Cronobacter species, with particular attention to the newly reclassified species C. helveticus, C. pulveris, and C. zurichensis [forthcoming]

In 2013, Enterobacter helveticus, E. pulveris and E. turicensis, were reclassified as Cronobacter helveticus, C. pulveris and C. 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 BIGSdb 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

Genomic dissection of the 1994 Cronobacter sakazakii outbreak in a French neonatal intensive care unit

Background: Cronobacter sakazakii is a member of the genus Cronobacter that has frequently been isolated from powdered infant formula (PIF) and linked with rare but fatal neonatal infections such as meningitis and necrotising enterocolitis. The Cronobacter MLST scheme has reported over 400 sequence types and 42 clonal complexes; however C. sakazakii clonal complex 4 (CC4) has been linked strongly with neonatal infections, especially meningitis. There have been a number of reported Cronobacter outbreaks over the last three decades. The largest outbreak of C. sakazakii was in a neonatal intensive care unit (NICU) in France (1994) that lasted over 3 months and claimed the lives of three neonates. The present study used whole genome sequencing data of 26 isolates obtained from this outbreak to reveal their relatedness. This study is first of its kind to use whole genome sequencing data to analyse a Cronobacter outbreak. Methods: Whole genome sequencing data was generated for 26 C. sakazakii isolates on the Illumina MiSeq platform. The whole genome phylogeny was determined using Mugsy and RaxML. SNP calls were determined using SMALT and SAMtools, and filtered using VCFtools. Results: The whole genome phylogeny suggested 3 distant clusters of C. sakazakii isolates were associated with the outbreak. SNP typing and phylogeny indicate the source of the C. sakazakii could have been from extrinsic contamination of reconstituted infant formula from the NICU environment and personnel. This pool of strains would have contributed to the prolonged duration of the outbreak, which was up to 3 months. Furthermore 3 neonates were co-infected with C. sakazakii from two different genotype clusters. Conclusion: The genomic investigation revealed the outbreak consisted of an heterogeneous population of C. sakazakii isolates. The source of the outbreak was not identified, but probably was due to environmental and personnel reservoirs resulting in extrinsic contamination of the neonatal feeds. It also indicated that C. sakazakii isolates from different genotype clusters have the ability to co-infect neonates

Draft genome sequence of "Candidatus Cronobacter colletis" NCTC 14934T, a new species in the genus Cronobacter

Members of the Cronobacter genus are associated with serious infections in neonates. This is the first report of the draft genome sequence for the newly proposed species Cronobacter colletis

Draft genome sequences of three newly identified species in the genus Cronobacter, C. helveticus LMG23732T, C. pulveris LMG24059, and C. zurichensis LMG23730T

Cronobacter helveticus, Cronobacter pulveris, and Cronobacter zurichensis are newly described species in the Cronobacter genus, which is associated with serious infections of neonates. This is the first report of draft genome sequences for these species

Draft genome sequence of the earliest Cronobacter sakazakii sequence type 4 strain, NCIMB 8272

The Cronobacter sakazakii clonal lineage defined as sequence type 4 (ST4) is associated with severe cases of neonatal meningitis and persistence in powdered infant formula. For genome sequencing of the earliest deposited culture collection strain of Cronobacter sakazakii ST4, we used the strain NCIMB 8272, originally isolated from milk powder in 1950

The Nexus of Ethical Leadership, Job Performance, and Turnover Intention: The Mediating Role of Job Satisfaction

This study aims to examine the impact of ethical leadership on employees’ job satisfaction, performance, and turnover intention. A conceptual framework is developed which clearly integrates job satisfaction as a mediating mechanism in explaining the nexus among ethical leadership, job performance, and turnover intention. This framework is then analysed employing data from a sample (n = 114) of tourist companies in Lahore, Pakistan. The results reveal that ethical leadership has positive effect on employees’ job satisfaction, performance and has negative effect on their turnover intentions. Further, job satisfaction positively mediates the effect of ethical leadership on employees’ job performance and turnover intentions. The findings recommend that the demonstration of ethical leadership behaviours by managers at workplace enhances employees’ job satisfaction and performance, and decreases the intention of employees to leave the job. The main narrative of this study encompasses the imperative role of ethical leadership in the workplace where it serves as a factor that enhances employees’ job satisfaction, performance, and decreases turnover intention. This research explicitly demonstrates that in Pakistani tourism sector, ethical leadership plays a vital role to achieve performance goals. Future research could analyse the said nexus in different sectors and cultures, and may also consider other measures of individual performance. The consideration of job satisfaction as mediating variable in probing the linkages among ethical leadership, job performance, and turnover intention in the context of the workplace in Pakistan and the analysing of this linkage is novel

Draft genome sequence of a meningitic isolate of Cronobacter sakazakii clonal complex 4, strain 8399

The Cronobacter sakazakii clonal lineage defined as clonal complex 4 (CC4), composed of nine sequence types, is associated with severe cases of neonatal meningitis. To date, only closely related C. sakazakii sequence type 4 (ST4) strains have been sequenced. C. sakazakii strain 8399, isolated from a case of neonatal meningitis, was sequenced as the first non-ST4 C. sakazakii strain

Genomic profiling of the neonatal meningitic Cronobacter sakazakll clonal complex 4

The Cronobacter sakazakii clonal complex 4 (CC4) represents a dominant lineage of the genus Cronobacter in Cronobacter PubMLST. A strong association of C. sakazakii CC4 with neonatal infections especially neonatal meningitis has been established. The composition of C. sakazakii CC4 isolates in Cronobacter PubMLST indicates that at least 70% of these isolates were obtained either from clinical sources or infant formula. The dominant association of the C. sakazakii CC4 with neonatal infections especially meningitis and its predominant isolation from the infant formula and environment was intriguing which drove the rationale for the in-depth genomic analysis presented in the current PhD study. The whole genome phylogeny revealed that despite their geographical and temporal spread, the CC4 isolates cluster tightly with each other representing a clonal and a stable lineage within the Cronobacter genus. An exhaustive search of the sequenced genomes to identify virulence or environmental fitness associated traits indicated no significant difference between the virulence potential of C. sakazakii CC4 and C. sakazakii non-CC4. The interesting observation was the presence of two hypothetical proteins predominant in CC4 isolates, one of which was the homologue of an inner membrane protein. In addition, an hypothetical protein was noted to be largely absent from the C. sakazakii CC4 genomes. The O:2 was found to be the dominant serotype of CC4, however not exclusive to CC4. A giant adhesion associated gene was also noted predominantly in the C. sakazakii CC4 genomes. Single nucleotide polymorphism indicated low degree of sequence diversity within CC4 with average distance of 300-400 SNPs against the reference isolate. The subdivision of the low invasive CC4 isolates was intriguing, however no unique invasion associated traits were determined in a highly invasive CC4 isolate whereas one low invasive isolate indicated the presence of heavy metal resistance associated traits. The metal resistance assays could not differentiate the high and low invasive CC4 isolates. The case study of the 1994 French outbreak using genome sequenced data suggested powdered infant formula (PIF) to be the dominant, yet not the exclusive source of outbreak for the C. sakazakii isolates. The current PhD study was the first to explore the genomes of C. sakazakii CC4 revealing some interesting variations. Future studies are warranted to characterise hypothetical proteins predominant in CC4 to elucidate their significance in this clonal lineage. Furthermore, transcriptomics studies are warranted to find out any unique genes differentially expressed in the CC4 genomes under different stressful conditions

Guided Waves for the Inspection of Titanium Diffusion Bonds

The aggressive environment encountered by the high speed civil transport (supersonic) aircraft (HSCT) places severe requirements on the types of materials used in its construction. The state-of- the-art materials available to the commercial aerospace industry will not meet these severe environmental requirements. New materials have been evaluated that will meet these severe environmental requirements. One such material is the super plastic formed/diffusion bonded (SPF/DB) titanium. Structures with this material have been fabricated to be used on the HSCT aircraft. Because the HSCT is a commercial program, the FAA requires that nondestructive evaluation techniques must be developed for the inspection of these structures