Frank Kristi L, Vergidis Paschalis, Brinkman Cassandra L, Greenwood Quaintance Kerryl E, Barnes Aaron M T, Mandrekar Jayawant N, Schlievert Patrick M, Dunny Gary M, Patel Robin
Department of Microbiology, University of Minnesota, Minneapolis, Minnesota, United States of America.
Division of Clinical Microbiology, Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, Minnesota, United States of America.
PLoS One. 2015 Jun 15;10(6):e0130187. doi: 10.1371/journal.pone.0130187. eCollection 2015.
Enterococcus faecalis can cause healthcare-associated biofilm infections, including those of orthopedic devices. Treatment of enterococcal prosthetic joint infection is difficult, in part, due to biofilm-associated antimicrobial resistance. We previously showed that the E. faecalis OG1RF genes ahrC and eep are in vitro biofilm determinants and virulence factors in animal models of endocarditis and catheter-associated urinary tract infection. In this study, we evaluated the role of these genes in a rat acute foreign body osteomyelitis model and in in vitro biofilm-associated antimicrobial resistance. Osteomyelitis was established for one week following the implantation of stainless steel orthopedic wires inoculated with E. faecalis strains OG1RF, ΩahrC, and ∆eep into the proximal tibiae of rats. The median bacterial loads recovered from bones and wires did not differ significantly between the strains at multiple inoculum concentrations. We hypothesize that factors present at the infection site that affect biofilm formation, such as the presence or absence of shear force, may account for the differences in attenuation in the various animal models we have used to study the ΩahrC and ∆eep strains. No differences among the three strains were observed in the planktonic and biofilm antimicrobial susceptibilities to ampicillin, vancomycin, daptomycin, linezolid, and tetracycline. These findings suggest that neither ahrC nor eep directly contribute to E. faecalis biofilm-associated antimicrobial resistance. Notably, the experimental evidence that the biofilm attachment mutant ΩahrC displays biofilm-associated antimicrobial resistance suggests that surface colonization alone is sufficient for E. faecalis cells to acquire the biofilm antimicrobial resistance phenotype.
粪肠球菌可引起医疗保健相关的生物膜感染，包括骨科器械相关感染。粪肠球菌假体关节感染的治疗很困难，部分原因是生物膜相关的抗菌耐药性。我们之前表明，粪肠球菌OG1RF基因ahrC和eep是心内膜炎和导管相关尿路感染动物模型中的体外生物膜决定因素和毒力因子。在本研究中，我们评估了这些基因在大鼠急性异物性骨髓炎模型以及体外生物膜相关抗菌耐药性中的作用。将接种了粪肠球菌菌株OG1RF、ΩahrC和∆eep的不锈钢骨科钢丝植入大鼠胫骨近端，建立骨髓炎模型一周。在多个接种浓度下，从骨骼和钢丝中回收的细菌载量中位数在各菌株之间没有显著差异。我们推测，感染部位存在的影响生物膜形成的因素，如剪切力的有无，可能是我们用于研究ΩahrC和∆eep菌株的各种动物模型中衰减差异的原因。在浮游菌和生物膜对氨苄西林、万古霉素、达托霉素、利奈唑胺和四环素的抗菌敏感性方面，未观察到这三种菌株之间存在差异。这些发现表明，ahrC和eep均未直接导致粪肠球菌生物膜相关的抗菌耐药性增强。值得注意的是，生物膜附着突变体ΩahrC表现出生物膜相关抗菌耐药性的实验证据表明，仅表面定植就足以使粪肠球菌细胞获得生物膜抗菌耐药表型。
