Intraspecies warfare restricts strain coexistence in human skin microbiomes.

Determining why only a fraction of encountered or applied bacterial strains engraft in a given person's microbiome is crucial for understanding and engineering these communities1. Previous work has established that metabolism can determine colonization success in vivo2-4, but relevance of bacterial warfare in preventing engraftment has been less explored. Here, we demonstrate that intraspecies warfare presents a significant barrier to strain transmission in the skin microbiome by profiling 14,884 pairwise interactions between Staphylococcus epidermidis cultured from eighteen human subjects from six families. We find that intraspecies antagonisms are abundant; these interactions are mechanistically diverse, independent of the relatedness between strains, and consistent with rapid evolution via horizontal gene transfer. Ability to antagonize more strains is associated with reaching a higher fraction of the on-person S. epidermidis community. Moreover, antagonisms are significantly depleted among strains residing on the same person relative to random assemblages. Two notable exceptions, in which bacteria evolved to become sensitive to antimicrobials found on the same host, are explained by mutations that provide phage resistance, contextualizing the importance of warfare among other lethal selective pressures. Taken together, our results emphasize that accounting for intraspecies bacterial warfare is essential to the design of long-lasting probiotic therapeutics.

Highly-resolved within-species dynamics in the human facial skin microbiome.

Human facial skin microbiomes (FSMs) on adults are dominated by just two bacterial species, Cutibacterium acnes and Staphylococcus epidermidis. Underlying this apparent simplicity, each FSM harbors multiple strains of both species whose assembly dynamics on individuals are unknown. Here, we use 4,055 isolate genomes and 360 metagenomes to trace the dynamics of strains on individuals and their transmission. Strains are shared amongst family members of all ages, but each individual harbors unique strain consortia. Strain stability changes upon formation of the adult-type FSM: S. epidermidis lineage turnover slows, and the rate of C. acnes colonization increases before stabilizing, suggesting this transitional window could facilitate engraftment of therapeutic strains. Our work reveals previously undetectable community dynamics and informs the design of therapeutic interventions.

Trophic Selective Pressures Organize the Composition of Endolithic Microbial Communities From Global Deserts.

Studies of microbial biogeography are often convoluted by extremely high diversity and differences in microenvironmental factors such as pH and nutrient availability. Desert endolithic (inside rock) communities are relatively simple ecosystems that can serve as a tractable model for investigating long-range biogeographic effects on microbial communities. We conducted a comprehensive survey of endolithic sandstones using high-throughput marker gene sequencing to characterize global patterns of diversity in endolithic microbial communities. We also tested a range of abiotic variables in order to investigate the factors that drive community assembly at various trophic levels. Macroclimate was found to be the primary driver of endolithic community composition, with the most striking difference witnessed between hot and polar deserts. This difference was largely attributable to the specialization of prokaryotic and eukaryotic primary producers to different climate conditions. On a regional scale, microclimate and properties of the rock substrate were found to influence community assembly, although to a lesser degree than global hot versus polar conditions. We found new evidence that the factors driving endolithic community assembly differ between trophic levels. While phototrophic taxa, mostly oxygenic photosynthesizers, were rigorously selected for among different sites, heterotrophic taxa were more cosmopolitan, suggesting that stochasticity plays a larger role in heterotroph assembly. This study is the first to uncover the global drivers of desert endolithic diversity using high-throughput sequencing. We demonstrate that phototrophs and heterotrophs in the endolithic community assemble under different stochastic and deterministic influences, emphasizing the need for studies of microorganisms in context of their functional niche in the community.

The Role of Liposomal Bupivacaine in Reduction of Postoperative Pain After Transforaminal Lumbar Interbody Fusion: A Clinical Study.

BACKGROUND: Postoperative pain after transforaminal lumbar interbody fusion (TLIF) is a barrier to early mobility. Intraoperative local infiltration of anesthetic agents is standard practice to alleviate postoperative pain. Liposomal formulations may prolong the action of these anesthetic agents. The purpose of this study was to investigate the role of liposomal bupivacaine in postoperative pain control in patients undergoing unilateral, single-level TLIF. METHODS: From a cohort of 74 patients, half received nonliposomal local anesthetic and half received liposomal bupivacaine (LB) (LB group) via local infiltration. Both groups received a standard postoperative analgesia regimen. Demographic information, postoperative pain scores (visual analog scale), analgesic consumption, length of stay, and complications were retrospectively collected. RESULTS: The area under the curve of cumulative pain scores was significantly lower in the LB group between 0 and 12 hours (15.0 ± 15.6 vs. 45.6 ± 21.1, P = 0.003) and between 12 and 24 hours (37.6 ± 20.6 vs. 48.4 ± 24.9, P = 0.05) after surgery. Significantly fewer narcotic equivalents were consumed in the LB group between 12 and 24 hours (16.0 ± 13.4 mg vs. 24.1 ± 19.7 mg intravenous morphine equivalents, P = 0.04). Length of stay was significantly shorter in the LB group than in the control group (3.1 ± 0.9 days vs. 4.3 ± 1.3 days, P < .001). CONCLUSIONS: LB may be a useful adjunct during unilateral TLIF for decreasing pain and narcotic consumption in the first 24 hours after surgery and may also decrease overall length of stay.

Application of Intrawound Vancomycin Powder during Spine Surgery in a Patient with Dialysis-Dependent Renal Failure.

Surgical site infections (SSIs) after spinal surgery are a serious complication that can be minimized with prophylaxis. Vancomycin is a common agent used in the prevention of SSI. Given that vancomycin is renally cleared, its use requires careful observation in dialysis-dependent patients due to toxicity at supratherapeutic levels. Since minimum inhibitory concentrations (MICs) for vancomycin have increased due to the emergence of resistant pathogens, the use of vancomycin in such patients is further complicated. Local instillation of vancomycin powder is thought to provide additional protection against SSI and have lower systemic absorption. We present a patient with end-stage renal disease that developed progressively debilitating cervical spondylotic myelopathy necessitating multilevel laminectomy and instrumented fusion. Prior to closure, 1 gram of vancomycin powder was sprinkled into the surgical incision. Postoperative serum vancomycin levels were well below those associated with nephrotoxicity and ototoxicity. Based on this experience, we reviewed the relevant guidelines that were designed to prevent postoperative infections in such dialysis-dependent patients. Intrawound application of vancomycin may be a legitimate and safe option for SSI prophylaxis in patients with renal failure on dialysis.