Molecular Epidemiology of Salmonellosis in Florida, USA, 2017-2018.

The state of Florida reports a high burden of non-typhoidal Salmonella enterica with approximately two times higher than the national incidence. We retrospectively analyzed the population structure and molecular epidemiology of 1,709 clinical isolates from 2017 and 2018. We found 115 different serotypes. Rarefaction suggested that the serotype richness did not differ between children under 2 years of age and older children and adults and, there are ~22 well-characterized dominant serotypes. There were distinct differences in dominant serotypes between Florida and the USA as a whole, even though S. Enteritidis and S. Newport were the dominant serotypes in Florida and nationally. S. Javiana, S. Sandiego, and S. IV 50:z4, z23:- occurred more frequently in Florida than nationally. Legacy Multi Locus Sequence Typing (MLST) was of limited use for differentiating clinical Salmonella isolates beyond the serotype level. We utilized core genome MLST (cgMLST) hierarchical clusters (HC) to identify potential outbreaks and compared them to outbreaks detected by Pulse Field Gel Electrophoresis (PFGE) surveillance for five dominant serotypes (Enteritidis, Newport, Javiana, Typhimurium, and Bareilly). Single nucleotide polymorphism (SNP) phylogenetic-analysis of cgMLST HC at allelic distance 5 or less (HC5) corroborated PFGE detected outbreaks and generated well-segregated SNP distance-based clades for all studied serotypes. We propose "combination approach" comprising "HC5 clustering," as efficient tool to trigger Salmonella outbreak investigations, and "SNP-based analysis," for higher resolution phylogeny to confirm an outbreak. We also applied this approach to identify case clusters, more distant in time and place than traditional outbreaks but may have been infected from a common source, comparing 176 Florida clinical isolates and 1,341 non-clinical isolates across USA, of most prevalent serotype Enteritidis collected during 2017-2018. Several clusters of closely related isolates (0-4 SNP apart) within HC5 clusters were detected and some included isolates from poultry from different states in the US, spanning time periods over 1 year. Two SNP-clusters within the same HC5 cluster included isolates with the same multidrug-resistant profile from both humans and poultry, supporting the epidemiological link. These clusters likely reflect the vertical transmission of Salmonella clones from higher levels in the breeding pyramid to production flocks.

Spatial Epidemiology of Salmonellosis in Florida, 2009-2018.

Non-typhoidal Salmonella enterica infections cause a high disease burden in the United States with an estimated 1.2 million illnesses annually. The state of Florida consistently has a relatively high incidence compared to other states in the United States. Nevertheless, studies regarding the epidemiology of nontyphoidal salmonellosis and its spatial and temporal patterns in Florida were rarely reported. We examined the spatial and temporal patterns of 62,947 salmonellosis cases reported to FL Health Charts between 2009 and 2018. Dominant serotypes circulating in Florida were also explored using whole genome sequencing (WGS) based serotype-prediction for 2,507 Salmonella isolates sequenced by the Florida Department of Health during 2017 and 2018. The representativeness of laboratory-sequenced isolates for reported cases was determined by regression modeling. The annual incidence rate of salmonellosis decreased from 36.0 per 100,000 population in 2009 to 27.8 per 100,000 in 2016, and gradually increased in 2017 and 2018. Increased use of culture-independent testing did not fully explain this increase. The highest incidence rate was observed in children, contributing 40.9% of total reported cases during this period. A seasonal pattern was observed with the incidence peaking in September and October, later than the national average pattern. Over these 10 years, the Northeast and Northwest regions of the state had higher reported incidence rates, while reported rates in the Southeast and South were gradually increasing over time. Serotypes were predicted based on WGS data in the EnteroBase platform. The top-five most prevalent serotypes in Florida during 2017-2018 were Enteritidis, Newport, Javiana, Sandiego and Braenderup. The highest percentage of isolates was from children under 5 years of age (41.4%), and stool (84.7%) was the major source of samples. A zero-inflated negative binomial regression model showed that the reported case number was a strong predictor for the number of lab-sequenced isolates in individual counties, and the geospatial distribution of sequenced isolates was not biased by other factors such as age group. The spatial and temporal patterns identified in this study along with the prevalence of different serotypes will be helpful for the development of efficient prevention and control strategies for salmonellosis in Florida.

Characterization of the grappa gene, the Drosophila histone H3 lysine 79 methyltransferase.

We have identified a novel gene named grappa (gpp) that is the Drosophila ortholog of the Saccharomyces cerevisiae gene Dot1, a histone methyltransferase that modifies the lysine (K)79 residue of histone H3. gpp is an essential gene identified in a genetic screen for dominant suppressors of pairing-dependent silencing, a Polycomb-group (Pc-G)-mediated silencing mechanism necessary for the maintenance phase of Bithorax complex (BX-C) expression. Surprisingly, gpp mutants not only exhibit Pc-G phenotypes, but also display phenotypes characteristic of trithorax-group mutants. Mutations in gpp also disrupt telomeric silencing but do not affect centric heterochromatin. These apparent contradictory phenotypes may result from loss of gpp activity in mutants at sites of both active and inactive chromatin domains. Unlike the early histone H3 K4 and K9 methylation patterns, the appearance of methylated K79 during embryogenesis coincides with the maintenance phase of BX-C expression, suggesting that there is a unique role for this chromatin modification in development.

Global changes in the expression patterns of RNA isolated from the hippocampus and cortex of VX exposed mice.

One of the established activities of the nerve agent VX is inhibition of the enzyme acetylcholinesterase (AChE). This inhibition affects the cholinergic nervous system by decreasing the activity of the neurotransmitter-hydrolyzing enzyme cholinesterase (ChE). In an effort to gain a more comprehensive understanding of the molecular pathways affected by low-level exposure to VX, an expression profiling approach was used to identify genes with altered RNA expression patterns after exposure.Specifically, mice were exposed to 0.1, 0.2, 0.4, and 0.6 LD50 VX for a period of 2 weeks. At 2 h, 72 h, and 2 weeks after the final exposure, RNA was isolated from both the hippocampus and the cortex. Changes in gene expression levels were assessed by DNA microarray technology and grouped according to their expression patterns. Data presented here demonstrate that 2 weeks postexposure all up-regulated gene expression has returned to pre-exposure levels, including genes related to the central nervous system. Additionally, this investigation has revealed non-AChE pathway genes involved in other neuronal functions that display altered expression profiles after VX exposure.