Chondrocyte Invasion May Be a Mechanism for Persistent Staphylococcus Aureus Infection In Vitro

BACKGROUND

Recurrent bone and joint infection with Staphylococcus aureus is common. S. aureus can invade and persist in osteoblasts and fibroblasts, but little is known about this mechanism in chondrocytes. If S. aureus were able to invade and persist within chondrocytes, this could be a difficult compartment to treat.

QUESTION/PURPOSE

Can S. aureus infiltrate and persist intracellularly within chondrocytes in vitro?

METHODS

Cell lines were cultured in vitro and infected with S. aureus. Human chondrocytes (C20A4) were compared with positive controls of human osteoblasts (MG63) and mouse fibroblasts (NIH3T3), which have previously demonstrated S. aureus invasion and persistence (human fibroblasts were not available to us). Six replicates per cell type were followed for 6 days after infection. Cells were treated daily with antibiotic media for extracellular killing. To determine whether S. aureus can infiltrate chondrocytes, fluorescence microscopy was performed to qualitatively assess the presence of intracellular bacteria, and intracellular colony-forming units (CFU) were enumerated 2 hours after infection. To determine whether S. aureus can persist within chondrocytes, intracellular CFUs were enumerated from infected host cells each day postinfection.

RESULTS

S. aureus invaded human chondrocytes (C20A4) at a level (2.8 x 105 ± 5.5 x 104 CFUs/mL) greater than positive controls of human osteoblasts (MG63) (9.5 x 102 ± 2.5 x 102 CFUs/mL; p = 0.01) and mouse fibroblasts (NIH3T3) (9.1 x 104 ± 2.5 x 104 CFUs/mL; p = 0.02). S. aureus also persisted within human chondrocytes (C20A4) for 6 days at a level (1.4 x 103 ± 5.3 x 102 CFUs/mL) greater than that of human osteoblasts (MG63) (4.3 x 102 ± 3.5 x 101 CFUs/mL; p = 0.02) and mouse fibroblasts (NIH3T3) (0 CFUs/mL; p < 0.01). S. aureus was undetectable within mouse fibroblasts (NIH3T3) after 4 days. There were 0 CFUs yielded from cell media, confirming extracellular antibiotic treatment was effective.

CONCLUSION

S. aureus readily invaded human chondrocytes (C20A4) in vitro and persisted viably for 6 days after infection, evading extracellular antibiotics. Chondrocytes demonstrated a greater level of intracellular invasion and persistence by S. aureus than positive control human osteoblast (MG63) and mouse fibroblast (NIH3T3) cell lines.

CLINICAL RELEVANCE

Chondrocyte invasion and persistence may contribute to recurrent bone and joint infections. Additional research should assess longer periods of persistence and whether this mechanism is present in vivo.

Application of Enhanced Recovery after Surgical Treatment of the Occipitocervical Region

Objective

The concept of enhanced recovery after surgery (ERAS) has been proposed to provide guidance for the improved postoperative rehabilitation of patients with occipitocervical region disease (ORD).

Methods

This study retrospectively investigated 208 consecutive patients (116 men and 92 women) ranging in age from 22 to 76 years with ORD between July 2014 and June 2017 in our medical center, who were divided into three groups that received different preoperative, intraoperative, and postoperative management plans: traditional group (n = 73), ameliorated group (n = 70), and ERAS group (n = 65). We compiled a range of data relating to demographics and postoperative changes in hemoglobin and albumin, surgery duration, intraoperative blood loss, number of postoperative hospitalization days and expenses, readmission rates, and visual analog scale pain symptoms. Data were statistically evaluated using one‐way analysis of variance with Student–Newman–Keuls‐q post hoc tests or chi‐square tests.

Results

There were no significant differences in terms of age (P = 0.235), gender (P = 0.691), body mass index (P = 0.723), American Society of Anesthesiologists grade (0.747), lesion character (P = 0.337) and lesion site (P = 0.957) between the three groups. Within a 6 months follow‐up period, there was no significant difference between the three groups in terms of surgery duration (P = 0.225), blood loss (P = 0.172), changes in hemoglobin (P = 0.255) and albumin (P = 0.178). However, postoperative hospitalization days (P = 0.000), postoperative costs (P = 0.019) and improvement of pain symptoms (P = 0.000) in ERAS group were significantly lower or higher than those in traditional group or ameliorated group, respectively. There were 29 (39.73%), 22 (31.43%), and 13 (20.00%), recorded cases of postoperative complications in traditional group, ameliorated group and ERAS group, respectively; complications in ERAS group were significantly lower than those in other two groups (P = 0.043). Moreover, all of the complications were mitigated effectively by the infusion of fluid, analgesia, treatment of infections, or antiemetic medications. There were 2 (2.74%), 3 (4.29%) and 2 (3.08%), recorded cases of re‐admission in traditional group, ameliorated group and ERAS group, respectively, but there were no statistically significant differences when compared across the three groups (P = 0.866).

Conclusions

ERAS can provide benefits when it applied to patients undergoing ORD surgery mainly in terms of reducing postoperative complications, however, ERAS does not increase the economic burden of patients or decrease the risk of readmission.

Intracellular Staphylococcus aureus in bone and joint infections: A mechanism of disease recurrence, inflammation, and bone and cartilage destruction

Bone and joint infections are devastating afflictions. Although medical interventions and advents have improved their care, bone and joint infections still portend dismal outcomes. Indeed, bone and joint infections are associated with extremely high mortality and morbidity rates and, generally, occur secondary to the aggressive pathogen Staphylococcus aureus. The consequences of bone and joint infections are further compounded by the fact that although they are aggressively treated, they frequently recur and result in massive bone and articular cartilage loss. Here, we review the literature and chronicle the fact that the fundamental cellular components of the musculoskeletal system can be internally infected with Staphylococcus aureus, which explains the ready recurrence of bone and joint infections even after extensive administration of antibiotic therapy and debridement and offer potential treatment solutions for further study. Moreover, we review the ramifications of intracellular infection and expound that the massive bone and articular cartilage loss is caused by the sustained proinflammatory state induced by infection and offer potential combination therapies for further study to protect bone and cartilage.

Republished: Intracranial vessel occlusion preceding the development of mycotic aneurysms in patients with endocarditis

Mycotic aneurysms (MA) are an uncommon complication of infectious endocarditis. Septic emboli are thought to be the precipitating event in their development, but the evidence for this is sparse. We present three cases in which septic embolic occlusion preceded MA development at the occlusion site, suggesting that documented angiographic emboli in patients with infectious endocarditis and bacteremia constitute a risk factor for MA formation. Two adult patients with a history of intravenous drug use and one child with congenital heart disease are described. They were all diagnosed with infectious endocarditis and developed neurological symptoms during their hospital course. Initial catheter-based cerebral angiograms demonstrated vascular occlusions, which were followed by the development of MA at the same sites within 1 month. Septic emboli, documented on cerebral angiogram, in patients with infectious endocarditis may precede the appearance of MA. Patients with angiographic occlusions in the setting of endocarditis warrant close follow-up.

Intracranial vessel occlusion preceding the development of mycotic aneurysms in patients with endocarditis

Mycotic aneurysms (MA) are an uncommon complication of infectious endocarditis. Septic emboli are thought to be the precipitating event in their development, but the evidence for this is sparse. We present three cases in which septic embolic occlusion preceded MA development at the occlusion site, suggesting that documented angiographic emboli in patients with infectious endocarditis and bacteremia constitute a risk factor for MA formation. Two adult patients with a history of intravenous drug use and one child with congenital heart disease are described. They were all diagnosed with infectious endocarditis and developed neurological symptoms during their hospital course. Initial catheter-based cerebral angiograms demonstrated vascular occlusions, which were followed by the development of MA at the same sites within 1 month. Septic emboli, documented on cerebral angiogram, in patients with infectious endocarditis may precede the appearance of MA. Patients with angiographic occlusions in the setting of endocarditis warrant close follow-up.

Inflammation by activated macrophage-like THP-1 cells increases human dura mater cell adhesion with alteration of integrin α2 β1 and matrix metalloproteinase

This study was designed to investigate (i) extracellular matrix to specify adhesive substrates to human dura mater cell (hDMC); (ii) the alteration on adhesion-related molecules in hDMC; and (iii) secreted matrix metalloproteinases (MMPs) linked with extracellular matrix remodeling after exposure to inflammation. The hDMC was cultured from human dura mater tissue, and the studies were performed with hDMC after co-culturing with macrophage like THP-1 cells (Mϕ). The adhesion of co-cultured hDMC through collagen I increased 6.4-fold and through collagen IV increased 5.0-fold compared with the adhesion of naïve cells (p < 0.001). Integrin subtype α₂ β₁ expression was increased 6.3-fold (p < 0.001) and α₁ expression was decreased 2.0-fold (p < 0.001) in the co-cultured cells compared with the naïve cells. Co-culturing induced significant increases in MMP-1 (13.9-fold, p < 0.01), MMP-3 (7.6-fold, p < 0.01), and VEGF (VEGF: 3.8-fold, p < 0.05) expression and decreases in MMP-9 (0.1-fold, p < 0.01) compared with the sum of naïve hDMC and Mϕ values. Increased hDMC adhesion under inflammatory conditions is caused by an increased cellular affinity for collagen I and IV mediated by increased hDMC levels of integrin subtype α₂ β₁ and environmental MMP-1, -3 and decreased MMP-9. Selective integrin subtype α₂ β₁ inhibition assay showed 37.8% and 35.7% reduction in adhesion of co-cultured hDMC to collagen I (p < 0.001) and IV (p = 0.057), respectively. The present study provides insight into the pathological conditions related to dura mater adhesion in inflammation. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 9999:1-11, 2019.