Objective To establish rabbit models of mixture-infectious endophthalmitis induced by exogenous Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli). Methods A total of 84 eyes of 42 New Zealand white albino rabbits were randomly divided into 4 groups. There were 21 eyes in each group. Rabbit eyes in group 1, 2, 3 and 4 received an intravitreal injection of 0.1 ml of mix bacterium (2times;104 CFU/ ml, including 103 S. aureus and 103 E. coli), S. aureus (104 CFU/ ml), E. coli (104 CFU/ml), and sterilized saline respectively. The eyes were examined by slit-lamp microscopy, ophthalmoscopy, A/B scan, electroretinography (ERG) and bacterial culture of vitreous humors at the timepoints of 6, 12, 24, 48 and 72 hours, and 4, 7, 10, 14 days after intravitreal injection. All eyeballs were then enucleated for histopathological examination. Results Various degrees of inflammatory reactions were presented in the 3 experimental groups after the injection, and the development trend of the disease was nearly the same. In group 1 active intraocular inflammation like anterior chamber exudates, started at 12 hours after injection (which was early than that in group 2 and 3), aggravated between 48 and 72 hours, alleviated slowly from 4 to 7 days, and was obviously better after 10 to 14 days while the corneal neovascularization and vitreous gray opacity begun to form. The bacterial culture was positive in group 1 (100％, 6 hours to 14 days after injection), group 2 (100%, 6 hours to 3 days after injection) and group 3 (100% from 6 hours to 7 days, and 67.67% at 14 days after injection). It was negative for group 2 (7 to 14 days after injection) and group 4 (6 hours to 14 days after injection). The amplitude of ERG b wave dissapeard in group 1 to 3, and decreased less than 30% in group 4 from the 48th hour after injection. Histopathological examination revealed that all intraocular structures infiltrated with inflammatory cells. Conclusion Complicated endophthalmitis rabbit models can be successfully established by intravitreal injection with S. aureus and E. coli.
Objective To evaluate the toxic effects of staphylococcus aureus exotoxins and neutrophils on retinal pigment epithelium (RPE) cells (RPEC). Methods An in-vitro model of bacteroidal endophthalmitis was established by co-culturing of human RPE cell line D407 and human peripheral blood neutrophils in the present of staphylococcus aureus exotoxins ATCC29213. The level of lactate dehydrogenase hydroxide（LDH）in the cuture supernant was measured, and the viability of RPE was evlauated by flow cytometry and Hoechst 33342/Propidium Iodide（PI）staining. Results When RPE cells were cultured with the exotoxin ATCC29213, the LDH level and necrotic RPE cells were positive proportional to the dosage of exotoxin, but only 250mu;l or 500mu;l of ATCC29213 had a statistical significant effect. When RPE cells were co-cultured with neutrophils in the present of ATCC29213 for 6 hours, 100mu;l of ATCC29213 already had a statistical significant effect on LDH level and necrotic RPEC, and the effect was proportional to the amount of neutrophils in the culture. Conclusion Both staphylococcus aureus exotoxins and neutrophils can damage the RPEC by inducing necrosis, and their function had synergetic effect.
OBJECTIVE: To investigate the ability of repairing bone defect with the compound of coralline hydroxyapatite porous (CHAP), fibrin sealant(FS) and staphylococcus aureus injection (SAI), and the feasibility to use the compounds as bone substitute material. METHODS: The animal model of bone defect was made on the bilateral radius of 54 New Zealand white rabbits, which were randomly divided into the experimental group(the defect was repaired with CHAP-FS-SAI), control group(with autograft) and blank control group(the defect was left unrepaired) with 18 rabbits in each group. The ability of bone defect repair was evaluated by gross observation, histopathological study, X-ray and biomechanical analysis 2, 4, 8 and 12 weeks after repair. RESULTS: (1) In the 2nd week, tight fibro-connection could be found between the implant and fracture site and there were many fibroblasts and capillary proliferation with many chondrocytes around CHAP in the experimental group, while only a few callus formed, and chondrocytes, osteoblast and osteoclast existed in the control group. (2) In experimental group and control group, a large quantity of callus was found 4 and 8 weeks; ossification of chondrocytes with weave bone formation were found 4 weeks and many osteocytes and weave bones and laminar bones were found 8 weeks. (3) In the 12th week, the complete ossification of implant with well bone remodeling, a large number of mature osteocytes and laminar were found in experimental group and control group, and CHAP still existed in the experimental group; the defect area filled with fibro-scar tissue and only many fibroblasts could be seen in blank control group. (4) X-ray findings were the following: In experimental and control groups, callus formation could be seen 2 weeks postoperatively, more callus formed 4 weeks, the bone defect area disappeared and CHAP scattered in the callus 8 weeks; the fracture line disappeared and medullary cavity became united (in control group); and in the 12th week, the cortex became continuous, the medullary cavity became united, and remodeling completed, while bone defect was not still united in blank control group. The maximal torque and torsional stiffness in the experimental group is higher than those in the control group 2 weeks (P lt; 0.05), but there was no significant difference (P gt; 0.05) between the two groups 4, 8, 12 weeks after repair. CONCLUSION: The compound of CHAP-FS-SAI has good biological compatibility, and it can be used for one kind of bone substitute material to repair the bone defect.
Objective To investigate the genetic polymorphism of methicillin resistant Staphylococcus aureus ( MRSA) isolated from hospital acquired pneumonia. Methods Seventy-four hospitalized patients were diagnosed as noscomial MRSA pneumonia from January 2007 to January 2008 in Xinhua Hospital, Shanghai Jiaotong Univesity. The genes of MRSA were amplified by random amplified polymorphic DNA typing ( RAPD) assay in 82 clinical isolates from these patients. Results Two to 15 amplified DNA fragments were observed in agarose gel and they were classified into 11 genotypes. Genotypes Ⅲ, Ⅵ and Ⅶ ( 32. 56% , 30. 23% and 13. 95% , respectively) were mainly isolated from the ICU. Both independent genotypes and overlapping genotpyes with those from ICU were identified in isolates from the departments of geriatrics, emergency and respiratory medicine. Outbreak or cluster cases ( 48. 65% ) were found in 36 of the 74 patients while all outbreak cases occurred in the ICU. Conclusions Noscomial MRSA pneumonia is easy to disseminate and small-scale outbreak may occur especially in ICU. RAPD is valuable for identification and prevention of the spread of MRSA in hospital.
Objective To validate the advantage of repairing bone defect by staphylococcus aureus injection carried in collagen membrane. Methods Twentyfour adult New Zealand rabbits were divided into two groups randomly. After the experimental model of standard bone defect had been made by operation, collagen membrane/staphylococcus aureus injection and staphylococcus aureus injection with the same quantity were transplanted in bone defect areas of the two groups respectively. The reconstructed tissues were observed by general method, X-ray, histology, and immunohistochemistry at 2nd、4th、6th、8th week respectively. Results The experimental group showed that new bone proliferated distinctly in bone defect areaand the proliferation lasted long, and no excessive connective tissue in defectarea. X-ray observation showed that there was continual callus growth in transplantation area in early stage and the distribution of new bones was even in the group. Histological observation showed that there were many new bone growth centers in bone defect area, trabecular bones were sequentially distributed, and mature bone replacement was complete. Immunohistochemical examination showed that bone morphogenetic protein (BMP) could be seen for a long time and BMP took up a large part in the new bone tissues. Conclusion Collagen membrane could prevent parenchyma from penetrating into bone defect area and provide room for new bone growth. As the carrier of staphylococcus, collagen membrane could reduce the overflow of staphylococcus and improve its curative effect as well.
ObjectiveTo summarize the clinical features and experience of Methicillin-resistant Staphylococcus aureus (MRSA)-associated enteritis. MethodsClinical data of 21 patients with MRSA-associated enteritis who were treated in our hospital from Jan. 2003 to May. 2015 were analyzed retrospectively. ResultsAfter diagnosed or suspected of MRSA-associated enteritis, the 21 patients received a drug therapy with vancomycin instead of other antibiotic, 3 patients (14.3%) who failed to get satisfactory symptom relief received a plus therapy with biapenem; 13 patients (61.9%) received treatment which plus drugs such as Bacillus licheniformis capsules or combining Bifidobacterium to regulate intestinal microflora. Severe complications, such as intestinal fistula (8 patients, 38.1%）, toxic shock (16 patients, 76.2%）, organ system failure (14 patients, 66.7%) occurred in 17 patients (80.9%) of the 21 patients when 2-7 days (mean of 4.7 days) after diarrhea. Among 21 patients received therapy, 7 patients (33.3%) were cured and 2 patients (9.5%) were improved, whereas 11 patients died, with a total mortality of 52.4%, another 1 patient was lost to follow up (4.8%). There were 8 patients who were followed-up for 1-12 months (the median time was 3.1-month). During the followed-up period, 2 of them died and others stayed alive without occurrence. ConclusionAlthough uncommon, MRSA-associated enteritis progressed rapidly, with many complications and high mortality rate. Early diagnosis and timely targeted treatment restoring the balance of gastrointestinal microecology are the key to decrease its mortality.
Objective To observe the inhibitory characteristics of silver nanoparticles (AgNP) on bacterial biofilms and investigate their inhibitory effect on biofilm formation on three common orthopedic biomaterials. Methods The minimal inhibitory concentration (MIC) and minimal biofilm inhibitory concentration (MBIC) of AgNP were determined by microplate dilution assay. Biofilms of Staphylococcus aureus (ATCC 25923) were cultured on three orthopedic biomaterials (titanium alloy, titanium oxide, and stainless steel) and intervened with AgNP at concentrations of 32, 16, 8, 4, 2 and 0 μg/mL to determine the MBICs on the three materials. The effects of AgNP on biofilm formation were analyzed by scanning electron microscopy and measuring optical density. Results The MIC and MBIC of AgNP in the microplate assay were both 16 μg/mL. The MBICs of AgNP on biofilm formation in titanium oxide, titanium alloy, and stainless steel were 16 μg/mL, 32 μg/mL, and 32 μg/mL, respectively. Among the three materials, the lowest optical density was observed on titanium oxide, while the highest was on titanium alloy. Conclusions AgNP has strong antibacterial biofilm characteristics and can prevent the formation of Staphylococcus aureus biofilm in vitro. Biofilm formation is most pronounced on titanium alloy, least on titanium oxide, and intermediate on stainless steel.
ObjectiveTo explore drug resistance, resistant mechanisms and resistant phenotypes of staphylococcus aureus (SA) isolated from wound secretion to macrolides-lincosamides-streptogramins (MLS). MethodsA retrospective design was used to collect clinical data and antimicrobial resistance profiles of SA in the First Affiliated Hospital and the Second Affiliated Hospital of Fujian Medical University and Anxi County Hospital from June, 2008 to October, 2015. SPSS 19.0 software was used for data analysis. ResultsA total of 127 isolates were included. The distribution of four resistant phenotypes of SA to MLS were all susceptibility(S) type (n=48, 37.8%), ML type (n=41, 32.3%), M/iCR+ type (n=22, 17.3%) and MLS type (n=16, 12.6%), respectively; There were three kinds of phenotypes caused by target changing including ML type, M/iCR+ type and MLS type, respectively. Moreover, no moxicaxin, linezolid or tigecyline resistant strain was detected, while quinolons and tetracyclines showed low-level resistant. ConclusionCompared with the different samples, the resistant phenotypes of SA isolated from wound secretion to MLS are few, and the total resistance ratio is low.
ObjectiveTo investigate the appropriate concentration of methicillin-resistant Staphylococcus aureus (MRSA) in establishing chronic femoral osteomyelitis model in rabbits.MethodsForty-eight adult New Zealand white rabbits were randomly divided into 6 groups with 8 rabbits in each group. Animals in groups B, C, D, E, and F were injected 1×109, 1×108, 1×107, 1×106, 1×105 CFU/mL MRSA on the location of 2 cm of the femoral supracondyle, respectively, and group A was injected with aseptic saline as a control. The general observation were performed at 4 weeks after operation, and the wound secretions were taken for bacteriological examination. The serum C-reactive protein content was detected at preoperation and 2 weeks and 4 weeks after operation. The X-ray, CT scan, and Norden imaging scoring were performed at 4 weeks after operation. At 4 weeks after operation, the animals were sacrificed, and the specimens were observed and evaluated by general scores; and the HE staining and histological score were also performed.ResultsFive rabbits died of severe infection in group B, 2 died in group C, and no rabbit died in groups D, E, and F. General observation showed that the incision healed without soft tissue swelling in group A; most animals had visible incision swelling and sinus formation, femoral thickening, bone destruction, and damage decreased with the decreasing of the concentration of liquid bacterial in groups B-D; the infection signs were seen in groups E and F, and the degree of infection were less than that of group D. Bacteriological examination showed that fistula formation animal in groups B, C, D, and E were cultured with positive results, and with the decrease of concentration, the number of animal fistula formation decreased gradually; and bacteriological culture did not be performed in group F because of no sinus formation. There was no significant difference in the content of C-reactive protein between groups before operation (P>0.05). The contents of C-reactive protein in groups B-F were significantly higher than those in group A at 2 and 4 weeks after operation (P<0.05). At 4 weeks after operation, the content of C-reactive protein was in the order of groups B, C, D, E, F, and A in turn from high to low, showing significant differences between groups (P<0.05). Imaging examination showed that there was no soft tissue swelling and bone destruction in group A; bone destruction, massive sequestrum formation, and soft tissue swelling were found in groups B and C; bone destruction was observed in groups D and E, and the degree of sequestrum formation was not as good as that in group C; and there was a small amount of bone infection in group F. The Norden scores in groups B-F were significantly higher than that in group A, and in groups B and C than those in groups D, E, and F, and in groups D and E than that in group F (P<0.05); there was no significant difference between groups B and C, and between groups D and E (P>0.05). The specimens general observation scores in groups B-F were significantly higher than that in group A, while in groups B and C than those in groups D, E, and F (P<0.05); there was no significant difference between groups D, E, and F (P>0.05). HE staining showed that the structure of bone trabecula in group A was clear and the structure was arranged neatly; in groups B-F, trabecular bone destruction and inflammatory cell infiltration were seen and the degree gradually decreased. The histological scores in groups B-F were significantly higher than that in group A, and in group B than those in groups C-F, in groups C and D than that in group F (P<0.05); there was no significant difference between groups C, D, and E, and between groups E and F (P>0.05).ConclusionThe optimal MRSA concentration of rabbit model of chronic osteomyelitis of femur is between 1×106 and 1×107 CFU/mL.
Methicillin-resistant Staphylococcus aureus is one of the important pathogens of healthcare-associated infections. In order to prevent and control the transmission of the drug-resistant organism in healthcare facilities, the Healthcare Infection Society and the Infection Prevention Society jointly conducted the guidelines for the prevention and control of methicillin-resistant Staphylococcus aureus in 2021. This article introduces the guide from the background, preparation process, main prevention and control measures and further studies, and compares the guidelines with the current prevention and control measures in China, so as to provide a methodological reference for preparation of the guide for domestic infection prevention and control practitioners, and provide evidence-based prevention and control strategies for clinical practice.