Endocarditis is a rare but serious manifestation of Listeria monocytogenes (LM). However, the optimal treatment strategy for LM endocarditis has yet to be established. Current antibiotic strategies for listeriosis include penicillin G or ampicillin (AMP) monotherapy, or AMP + gentamicin combination therapy which is often favored for endocarditis. The primary objective of our investigation was to assess the utility of AMP + ceftriaxone (CRO) and AMP + daptomycin (DAP) against LM, modeling less nephrotoxic antibiotic combinations traditionally used to manage resistant enterococcal endocarditis. Here we report a case of LM endocarditis, review the world literature, and evaluate alternative treatment strategies for listeriosis utilizing in vitro and ex vivo studies. The combination of AMP + CRO and AMP + DAP were each noted to have synergistic activity against a LM endocarditis isolate. Additionally, co-incubation of the isolate with sub-lethal concentrations of antibiotics (AMP, CRO, DAP, AMP + CRO or AMP + DAP) sensitized the bacterium to whole blood killing while pretreatment with CRO and DAP (at 1/4 MIC) sensitized the bacterium to neutrophil killing. However, these effects did not reflect potentiation of antibiotic activity to human cathelicidin peptide LL-37, which is abundant in neutrophils and highly active against LM. Interestingly, AMP pretreatment of the LM endocarditis isolate resulted in increased DAP binding to the bacterium when assessed by fluorescence microscopy. These in vitro and ex vivo studies suggest further investigation of combination therapy using AMP + CRO or AMP + DAP as an alternative treatment for LM infection is warranted.

46Microbial colonization of bone is an important mechanism of post-mortem skeletal degradation. 47However, the types and distributions of bone and tooth colonizing microbes are not well characterized. It 48 is unknown if microbial communities vary in abundance or composition between bone element types, 49which could help explain patterns of human DNA preservation. The goals of the present study were to (1) 50identify the types of microbes capable of colonizing different human bone types and (2) relate microbial 51 abundances, diversity, and community composition to bone type and human DNA preservation. DNA 52 extracts from 165 bone and tooth samples from three skeletonized individuals were assessed for bacterial 53 loading and microbial community composition and structure. Random forest models were applied to 54 predict operational taxonomic units (OTUs) associated with human DNA concentration. Dominant 55 bacterial bone colonizers were from the phyla Proteobacteria (36%), Actinobacteria (23%), Firmicutes 56 (13%), Bacteroidetes (12%), and Planctomycetes (4.4%). Eukaryotic bone colonizers were from 57Ascomycota (40%), Apicomplexa (21%), Annelida (19%), Basidiomycota (17%), and Ciliophora (14%). 58Bacterial loading was not a significant predictor of human DNA concentration in two out of three 59individuals. Random forest models were minimally successful in identifying microbes related to patterns 60 of DNA preservation, complicated by high variability in community structure between individuals and 61 body regions. This work expands on our understanding of the types of microbes capable of colonizing 62human bone and contributing to human skeletal DNA degradation. 63 64

We evaluated the ability of a novel lithium niobate (LN) thickness-mode device to atomize disinfectants and reduce microbial burden on model surface materials. A small-scale plastic model housed the LN thickness-mode device and circular coupon surface materials including polycarbonate, polyethylene terephthalate, stainless steel, borosilicate glass, and natural rubber. Coupon surfaces were coated with methicillin-resistant Staphylococcus aureus (MRSA) or multidrug-resistant (MDR) strains of Gram-negative bacterial pathogens (Klebsiella pneumoniae, Escherichia coli, and Acinetobacter baumannii), atomized with disinfectant solutions of varying viscosity (including 10% bleach, 70% ethanol (EtOH), or 25% triethylene glycol (TEG)) using the LN thickness-mode device, and assessed for surviving bacteria. The LN thickness-mode device effectively atomized disinfectants ranging from low viscosity 10% bleach solution or 70% EtOH to highly viscous 25% TEG. Coupons harboring MDR bacteria and atomized with 10% bleach solution or 70% EtOH were effectively decontaminated with ~ 100% bacterial elimination. Atomized 25% TEG effectively eliminated 100% of K. pneumoniae (CRE) from contaminated coupon surfaces but not MRSA. The enclosed small-scale plastic model established proof-of-principle that the LN thickness-mode device could atomize disinfectants of varying viscosities and decontaminate coupon surface materials harboring MDR organisms. Future studies evaluating scaled devices for patient rooms are warranted to determine their utility in hospital environmental decontamination.

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