Systemic Absorption of Gentamicin Irrigation in Joint Replacement Surgery: A cause of concern

Thriving Under Stress: Pseudomonas aeruginosa Outcompetes the Background Polymicrobial Community Under Treatment Conditions in a Novel Chronic Wound Model

In vitro infection models are important for studying the effects of antimicrobials on microbial growth and metabolism. However, many models lack important biological components that resemble the polymicrobial nature of chronic wounds or infections. In this study, we developed a perfused meat model that supports the growth of the human pathogen Pseudomonas aeruginosa in a native meat microbial background to investigate the impact of antibiotics and hydrogen peroxide on polymicrobial community growth and metabolism. P. aeruginosa plays an important role as an etiological agent involved in chronic infections and is a common opportunistic pathogen. Chemical stressors in the form of hydrogen peroxide, carbenicillin, and gentamicin were perfused through the meat with polymicrobial growth on the surface. The relative abundances of P. aeruginosa and the background microbial community were analyzed by cell viability assays, and metabolic changes of the entire community in response to different antimicrobial treatments were characterized by GC-MS analysis of volatile organic compounds. The meat background community was characterized by amplicon sequencing. Relative densities of P. aeruginosa and background microbiota were similar under control conditions. Antimicrobial stressors, even at sub-inhibitory, physiologically relevant concentrations, spurred P. aeruginosa dominance of the meat surface community. Volatile metabolite ion intensity levels showed that antibacterial treatments drive changes in microbial metabolism. The abundance of the P. aeruginosa-derived metabolite, acetophenone, remained stable with treatment, whereas the relative abundances of 2-butanone, 2-nonanone, and 2-aminoacetophenone changed in response to treatment, suggesting these could serve as biomarkers of infection. Our model recapitulates some of the physiological conditions of chronic wounds and facilitates high throughput experiments without the high cost of in vivo models. Expanded use of this perfusion model will contribute to the understanding of polymicrobial growth and metabolism in the context of chronic wounds and infections.

Locally Used Antibiotics for Spinal Infection Prophylaxis and Their Effects on Epidural Fibrosis: an Experimental Laminectomy Study in Rats Using Rifamycin and Gentamycin

The study aims to assess the effects of antibiotics (ABs), which are typically used in spinal infection prophylaxis, on the formation of epidural fibrosis (EF). Specifically, we investigated the effect of rifamycin and gentamycin on EF formation in laminectomized rats. Thirty-two rats were randomly and equally divided into four groups as follows: laminectomy and physiological saline (0.9% NaCl) solution (control); laminectomy and rifamycin; laminectomy and gentamicin; and laminectomy and a mixture of rifamycin and gentamicin. Laminectomy was performed on L1 and L2 vertebrae in all rats. One month after spinal surgery, spinal tissue samples surrounding the laminectomy were cut with a microtome and stained with hematoxylin-eosin and Masson's trichrome. The histopathological analysis included examining the extent of EF, fibroblast cell density, and cartilage and bone regeneration. Statistical analysis was performed using the IBM SPSS Statistics 22 program (SPSS IBM, Turkey). A value of p < 0.05 was considered statistically significant. EF value differences between the AB treatment groups and the control group were statistically significant (p = 0.030). Specifically, binary comparisons indicated that the EF value was significantly higher in the rifamycin group than that in the control group (p = 0.003; p < 0.05). Our study suggests that locally applied ABs, especially rifamycin, should be diluted before administration to the epidural space.