A total of 133 Listeria monocytogenes isolates were characterized by ribotyping and allelic analysis of the virulence genes hly, actA, and inlA to uncover linkages between independent phylogenetic and specific virulence markers. PCR-restriction fragment length polymorphisms revealed 8 hly, 11 inlA, and 2 actA alleles. The combination of these virulence gene alleles and ribotype patterns separated L. monocytogenes into three distinct lineages. While distinct hly and inlA alleles were generally found to cluster into these three lineages, actA alleles segregated independently. These three phylogenetic lineages were confirmed when 22 partial actA DNA sequences were analyzed. The clinical history of the L. monocytogenes strains showed evidence for differences in pathogenic potential among the three lineages. Lineage I contains all strains isolated during epidemic outbreaks of listeriosis, while no human isolates were found in lineage III. Animal isolates were found in all three lineages. We found evidence that isolates from lineages I and III have a higher plaquing efficiency than lineage II strains in a cell culture assay. Strains from lineage III also seem to form larger plaques than strains from lineage II. A distinctive ribotype fragment and unique 16S rRNA gene sequences furthermore suggest that lineage III might represent a L. monocytogenes subspecies. None of the 20 human isolates available but 11% of our animal isolates were grouped in this lineage, indicating that strains in this lineage might have reduced virulence for humans.

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Background Environmental exposures to indoor allergens are major contributors to asthma symptoms, particularly in inner cities. The effectiveness of household allergen reduction as an adjunct to National Asthma Education Prevention Program (NAEPP) guideline-based pharmacologic therapy in asthma has not been prospectively studied. Objective We studied the effect of individualized allergen reduction on ability to reduce asthma pharmacologic therapy over 40 weeks. Methods We performed a randomized, controlled trial to determine the effect of multi-faceted indoor allergen avoidance measures on ability to reduce asthma controller therapy in adults and children residing in New York City who were both sensitized and exposed to at least one indoor allergen. Asthma treatment and control were optimized in all subjects prior to randomization. Results 125 subjects were randomized to receive individualized household allergen reduction and 122 received a sham intervention. Subjects in the intervention group significantly reduced all measured allergen levels (cat, dog, dust mite in the bedroom, roach and mouse in the kitchen and bedroom); those in the control group reduced only dust mite and mouse in the bedroom and roach in the kitchen. Participants in the intervention arm reduced NAEPP based therapy from step 4.4 at randomization to 3.50 post intervention (range 0–6); participants in the control arm reduced medication from step 4.4 to 3.4 (p = 0.76). There were no differences in other measured asthma outcomes. Conclusion Targeted allergen avoidance measures do not allow for reduction in asthma pharmacologic therapy compared to usual care in patients already receiving optimal controller therapy.