In Vivo Effect of Quaternized Chitosan-Loaded Polymethylmethacrylate Bone Cement on Methicillin-Resistant Staphylococcus epidermidis Infection of the Tibial Metaphysis in a Rabbit Model

Abstract

bInfection of open tibial fractures with contamination remains a challenge for orthopedic surgeons. Local use of antibiotic-impregnated polymethylmethacrylate (PMMA) beads and blocks is a widely used procedure to reduce the risk of infection. However, the development of antibiotic-resistant organisms make the management of infection more difficult. Our in vitro study demonstrated that quaternized chitosan (hydroxypropyltrimethyl ammonium chloride chitosan [HACC])-loaded PMMA bone cement exhibits strong antibacterial activity toward antibiotic-resistant bacteria. Therefore, the present study aimed to investigate the in vivo antibacterial activity of quaternized chitosan-loaded PMMA. Twenty-four adult female New Zealand White rabbits were used in this study. The right proximal tibial metaphyseal cavity was prepared, 10 7 CFU of methicillin-resistant Staphylococcus epidermidis was inoculated, and PMMA-only, gentamicin-loaded PMMA (PMMA-G), chitosan-loaded PMMA (PMMA-C), or HACC-loaded PMMA (PMMA-H) bone cement cylinders were inserted. During the follow-up period, the infections were evaluated using X rays on days 21 and 42 and histopathological and microbiological analyses on day 42 after surgery. Radiographic indications of bone infections, including bone lysis, periosteal reactions, cyst formation, and sequestral bone formation, were evident in the PMMA, PMMA-G, and PMMA-C groups but not in the PMMA-H group. The radiographic scores and gross bone pathological and histopathological scores were significantly lower in the PMMA-H group than in the PMMA, PMMA-G, and PMMA-C groups (P < 0.05). Explant cultures also indicated significantly less bacterial growth in the PMMA-H group than in the PMMA, PMMA-G, and PMMA-C groups (P < 0.01). We concluded that PMMA-H bone cement can inhibit the development of bone infections in this animal model inoculated with antibiotic-resistant bacteria, thereby demonstrating its potential application for treatment of local infections in open fractures.

In vivo evaluation of the anti-infection potential of gentamicin-loaded nanotubes on titania implants

“…The validity of this bone infection model was confirmed by the X-ray images at 3 weeks and 6 weeks postsurgery, which were consistent with previous research. 36,39 Subsequently, physical examination, radiographic evaluation, gross bone pathology, microbiological evaluation, and histological assessment were used for the comparison of efficacy between the NT-G, Ti, and NT groups in the treatment of intramedullary implant-related infections. Our in vivo observations demonstrated that, in all animals, body weights increased gradually and temperatures did not fluctuate; these observations indicated that the infections were localized around the femurs.…”

“…Body temperature and weight were selected as general index observations and evaluated from all the nine animals in each group. 36 Weight was measured on a precision scale (TCS, Shanghai, People's Republic of China), and body temperature was determined by a veterinary digital infrared thermometer (HRQ-S60; Zhengzhou, People's Republic of China). Local clinical signs of infection included knee joint swelling, skin exudation, and other inflammatory signs.…”

“…Radiographic manifestations were assessed on the basis of a modified scoring system, 36,37 as follows: 1, periosteal reaction; 2, osteolysis; 3, soft tissue swelling; 4, deformity; 5, general impression; 6, spontaneous fracture; and 7, sequestrum formation. Parameters 1-5 were scored as follows: 0, absent; 1, mild; 2, moderate; and 3, severe.…”

“…Femurs from each group were then cut sagittally for gross pathological observation, and those samples were subsequently used for histopathological evaluation. The gross bone pathology scores were assessed using a grading system: 36,38 0, absence of abscess, sequestrum, active bone formation, and erythema; 1, minimal erythema without abscess or evidence of new bone formation; …”

“…Following implant removal, the three femurs of each group were weighed, chilled with liquid nitrogen, crushed into fragments, and pulverized in a sterile bone mill. 36 The bone powder was homogeneously vortexed in 5 mL PBS for 2 minutes. After centrifuging at 10,000 rpm for 20 seconds, 50 μL of the supernatant was drawn and serially diluted tenfold.…”