Pin tract infection caused by Mycobacterium neoaurum in a 14-year-old child: A case report

Although rapidly growing non-tuberculosis mycobacterium can occasionally cause postoperative infections, Mycobacterium neoaurum is a rare pathogen of surgical site infection. We report a case of pin tract infection caused by M. neoaurum in a 14-year-old girl who was admitted for lengthening of her right fourth metatarsal bone. Pain, redness, and exudate were observed 18 days after external fixator insertion. Repeated exudate cultures revealed M. neoaurum, and she was diagnosed with a mycobacterial pin tract infection. She was initially administered intravenous ciprofloxacin and minocycline, and then was switched to oral trimethoprim-sulfamethoxazole and minocycline for a total of 6 months. Despite the pin tract infection, bone lengthening was completed under antibiotic treatment without removal of the pin; no other complications were noted. There are no prior reports of external fixator pin tract infection by M. neoaurum. While such cases may be rare, this case demonstrates that bone distraction may still be successfully completed using appropriate antibiotic therapy without pin removal.     

Flow cytometric analysis of expression of interleukin-2 receptor beta chain (p70-75) on various leukemic cells

We analyzed the expression of the interleukin-2 receptor (IL-2R) beta chain (p70-75) on various leukemic cells from 44 patients by flow cytometric analysis using the IL-2R beta chain-specific monoclonal antibody (MoAb), designated Mik-beta 1, which has been recently developed. Flow cytometric analysis demonstrated the expression of the IL-2R beta chain on granular lymphocytes (GLs) from all eight patients with granular lymphocyte proliferative disorders (GLPDs), on adult T-cell leukemia (ATL) cells from all three patients with ATL, and on T-cell acute lymphoblastic leukemia (T-ALL) cells from one of three patients with T-ALL. Although GLs from all the GLPD patients expressed the IL-2R beta chain alone and not the IL-2R alpha chain (Tac-antigen: p55), ATL and T-ALL cells expressing the beta chain coexpressed the alpha chain. In two of seven patients with common ALL (cALL) and in both patients with B-cell chronic lymphocytic leukemia, the leukemic cells expressed the alpha chain alone. Neither the alpha chain nor the beta chain was expressed on leukemic cells from the remaining 28 patients, including all 18 patients with acute nonlymphocytic leukemia, five of seven patients with cALL, all three patients with multiple myeloma, and two of three patients with T-ALL. These results indicate that three different forms of IL-2R chain expression exist on leukemic cells: the alpha chain alone; the beta chain alone; and both the alpha and beta chains. To examine whether the results obtained by flow cytometric analysis actually reflect functional aspects of the expressed IL-2Rs, we studied the specific binding of 125I-labeled IL-2 (125I-IL-2) to leukemic cells in 18 of the 44 patients. In addition, we performed 125I-IL-2 crosslinking studies in seven patients. The results of IL-2R expression of both 125I-IL-2 binding assay and crosslinking studies were in agreement with those obtained by flow cytometric analysis. These results indicate that flow cytometric analysis using MoAbs, anti-Tac, and Mik-beta 1 is useful for detecting the expression of the IL-2R chains.     

The rational design of a synthetic polymer nanoparticle that neutralizes a toxic peptide in vivo

Synthetic polymer nanoparticles (NPs) that bind venomous molecules and neutralize their function in vivo are of significant interest as "plastic antidotes." Recently, procedures to synthesize polymer NPs with affinity for target peptides have been reported. However, the performance of synthetic materials in vivo is a far greater challenge. Particle size, surface charge, and hydrophobicity affect not only the binding affinity and capacity to the target toxin but also the toxicity of NPs and the creation of a "corona" of proteins around NPs that can alter and or suppress the intended performance. Here, we report the design rationale of a plastic antidote for in vivo applications. Optimizing the choice and ratio of functional monomers incorporated in the NP maximized the binding affinity and capacity toward a target peptide. Biocompatibility tests of the NPs in vitro and in vivo revealed the importance of tuning surface charge and hydrophobicity to minimize NP toxicity and prevent aggregation induced by nonspecific interactions with plasma proteins. The toxin neutralization capacity of NPs in vivo showed a strong correlation with binding affinity and capacity in vitro. Furthermore, in vivo imaging experiments established the NPs accelerate clearance of the toxic peptide and eventually accumulate in macrophages in the liver. These results provide a platform to design plastic antidotes and reveal the potential and possible limitations of using synthetic polymer nanoparticles as plastic antidotes.