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1.  Prevalence of Hemolysin Genes and Comparison of ehxA Subtype Patterns in Shiga Toxin-Producing Escherichia coli (STEC) and Non-STEC Strains from Clinical, Food, and Animal Sources 
Applied and Environmental Microbiology  2013;79(20):6301-6311.
Shiga toxin-producing Escherichia coli (STEC) belonging to certain serogroups (e.g., O157 and O26) can cause serious conditions like hemolytic-uremic syndrome (HUS), but other strains might be equally pathogenic. While virulence factors, like stx and eae, have been well studied, little is known about the prevalence of the E. coli hemolysin genes (hlyA, ehxA, e-hlyA, and sheA) in association with these factors. Hemolysins are potential virulence factors, and ehxA and hlyA have been associated with human illness, but the significance of sheA is unknown. Hence, 435 E. coli strains belonging to 62 different O serogroups were characterized to investigate gene presence and phenotypic expression of hemolysis. We further investigated ehxA subtype patterns in E. coli isolates from clinical, animal, and food sources. While sheA and ehxA were widely distributed, e-hlyA and hlyA were rarely found. Most strains (86.7%) were hemolytic, and significantly more hemolytic (95%) than nonhemolytic strains (49%) carried stx and/or eae (P < 0.0001). ehxA subtyping, as performed by using PCR in combination with restriction fragment length polymorphism analysis, resulted in six closely related subtypes (>94.2%), with subtypes A/D being eae-negative STECs and subtypes B, C, E, and F eae positive. Unexpectedly, ehxA subtype patterns differed significantly between isolates collected from different sources (P < 0.0001), suggesting that simple linear models of exposure and transmission need modification; animal isolates carried mostly subtypes A/C (39.3%/42.9%), food isolates carried mainly subtype A (81.9%), and clinical isolates carried mainly subtype C (66.4%). Certain O serogroups correlated with particular ehxA subtypes: subtype A with O104, O113, and O8; B exclusively with O157; C with O26, O111, and O121.
doi:10.1128/AEM.02200-13
PMCID: PMC3811216  PMID: 23934487
3.  Characterization of microflora in Latin-style cheeses by next-generation sequencing technology 
BMC Microbiology  2012;12:254.
Background
Cheese contamination can occur at numerous stages in the manufacturing process including the use of improperly pasteurized or raw milk. Of concern is the potential contamination by Listeria monocytogenes and other pathogenic bacteria that find the high moisture levels and moderate pH of popular Latin-style cheeses like queso fresco a hospitable environment. In the investigation of a foodborne outbreak, samples typically undergo enrichment in broth for 24 hours followed by selective agar plating to isolate bacterial colonies for confirmatory testing. The broth enrichment step may also enable background microflora to proliferate, which can confound subsequent analysis if not inhibited by effective broth or agar additives. We used 16S rRNA gene sequencing to provide a preliminary survey of bacterial species associated with three brands of Latin-style cheeses after 24-hour broth enrichment.
Results
Brand A showed a greater diversity than the other two cheese brands (Brands B and C) at nearly every taxonomic level except phylum. Brand B showed the least diversity and was dominated by a single bacterial taxon, Exiguobacterium, not previously reported in cheese. This genus was also found in Brand C, although Lactococcus was prominent, an expected finding since this bacteria belongs to the group of lactic acid bacteria (LAB) commonly found in fermented foods.
Conclusions
The contrasting diversity observed in Latin-style cheese was surprising, demonstrating that despite similarity of cheese type, raw materials and cheese making conditions appear to play a critical role in the microflora composition of the final product. The high bacterial diversity associated with Brand A suggests it may have been prepared with raw materials of high bacterial diversity or influenced by the ecology of the processing environment. Additionally, the presence of Exiguobacterium in high proportions (96%) in Brand B and, to a lesser extent, Brand C (46%), may have been influenced by the enrichment process. This study is the first to define Latin-style cheese microflora using Next-Generation Sequencing. These valuable preliminary data will direct selective tailoring of agar formulations to improve culture-based detection of pathogens in Latin-style cheese.
doi:10.1186/1471-2180-12-254
PMCID: PMC3503605  PMID: 23134566
Latin-style cheese; Next Generation Sequencing; Microflora; Bacteria; Exiguobacterium
4.  Genetic Characterization of Escherichia coli O104 Isolates from Different Sources in the United States 
Escherichia coli O104 isolates collected from different sources in the United States were examined for virulence genes typical of enterohemorrhagic E. coli and those identified in the O104:H4 isolate associated with the 2011 German outbreak. The unexpected presence of virulence markers in these isolates highlights the importance of screening unusual and potentially pathogenic Shiga toxin-producing E. coli serotypes.
doi:10.1128/AEM.07533-11
PMCID: PMC3294489  PMID: 22210209
5.  Evaluation of Liquid- and Fog-Based Application of Sterilox Hypochlorous Acid Solution for Surface Inactivation of Human Norovirus▿  
Applied and Environmental Microbiology  2007;73(14):4463-4468.
Noroviruses (NVs) are the most frequent cause of outbreaks of gastroenteritis in common settings, with surface-mediated transfer via contact with fecally contaminated surfaces implicated in exposure. NVs are environmentally stable and persistent and have a low infectious dose. Several disinfectants have been evaluated for efficacy to control viruses on surfaces, but the toxicity and potential damage to treated materials limits their applicability. Sterilox hypochlorous acid (HOCl) solution (HAS) has shown broad-spectrum antimicrobial activity while being suitable for general use. The objectives of this study were to evaluate the efficacy of HAS to reduce NV both in aqueous suspensions and on inanimate carriers. HOCl was further tested as a fog to decontaminate large spaces. HOCl effectiveness was evaluated using nonculturable human NV measured by reverse transcriptase PCR (RT-PCR) and two surrogate viruses, coliphage MS2 and murine NV, that were detected by both infectivity and RT-PCR. Exposing virus-contaminated carriers of ceramic tile (porous) and stainless steel (nonporous) to 20 to 200 ppm of HOCl solution resulted in ≥99.9% (≥3 log10) reductions of both infectivity and RNA titers of tested viruses within 10 min of exposure time. HOCl fogged in a confined space reduced the infectivity and RNA titers of NV, murine NV, and MS2 on these carriers by at least 99.9% (3 log10), regardless of carrier location and orientation. We conclude that HOCl solution as a liquid or fog is likely to be effective in disinfecting common settings to reduce NV exposures and thereby control virus spread via fomites.
doi:10.1128/AEM.02839-06
PMCID: PMC1932820  PMID: 17483283

Results 1-5 (5)