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 investigate the effect of aureolysin （Aur） on staphylococcus aureus biofilm formation of dacron biomaterial surfaces under different Aur concentration. Methods Ninety dacron biomaterials were divided into 3 groups （group A, group IA, control group） with random number table （30 piece in each group）. Dacron biomaterials were put into vials contained staphylococcus aureus （105 CFU/ml） respectively; then Aur was added to make the concentration at 400ng/ml in group A, and group B at 80ng/ml. The thickness and number of staphylococcus aureus biofilm on the surfaces of dacron biomaterials of each group were evaluated by confocal laser microscopy and scanning electron microscopy after incubating 6h, 16h, 24h, 30h, and 48h. Results The thickness and number of staphylococcus aureus biofilm on dacron biomaterials surfaces increased significantly with time dependence in control group. The thickness and number of staphylococcus aureus biofilm in group A were less than those in group B and control group at each time points （P〈0. 05）. The thickness and number in group B were significantly decreased than those in control group （P 〈 0. 05）. Conclusion The study shows that Aur can effectively inhibit the formation of staphylococcus aureus biofilm on dacron biomaterials surfaces with dose dependence.
Objective Mesh infection may occur after incisional hernia repair using prosthetic mesh. Preparation of antibiotics-bonded meshes to prevent infection is one of the solutions. To evaluate the anti-infection effect of polypropylene mesh bonded norvancomycin slow-release microsphere by preparing the rat model of incisional hernia repair contaminatedwith Staphylococcus aureus. Methods The norvancomycin slow-release microspheres were prepared by emulsion and solvent evaporation method and they were bonded to polypropylene mesh (50 mg/mesh). The appearance of the microspheres was observed using scanning electronic microscope (SEM). The content of norvancomycin in microspheres and the release rate of the norvancomycin in norvancomycin-bonded polypropylene mesh were detected using high performance l iquid chromatography method. The rat models of incisional hernia were developed in 40 healthy Sprague Dawley rats, aged 10-11 weeks and weighing 200-250 g. The rats were divided randomly into the experimental group (norvancomycin-bonded polypropylene mesh repair, n=20) and the control group (polypropylene mesh repair, n=20). And then the mesh was contaminated with Staphylococcus aureus. The wound heal ing was observed after operation. At 3 weeks after operation, the mesh and the tissue around the mesh were harvested to perform histological observation and to classify the inflammatory reaction degree. Results The norvancomycin microsphere had integrated appearance and smooth surface with uniform particle diameter, 64% of particlediameter at 60 to 100 μm, and the loading-capacity of norvancomycin was 19.79%. The norvancomycin-bonded polypropylene patch had well-distributed surface and the loading-capacity of norvancomycin was (7.90 ± 0.85) mg/cm2. The release time of norvancomycin in vitro could last above 28 days and the accumulative release rate was 72.6%. The rats of 2 groups all survived to experiment completion. Wound infection occurred in 2 rats of the experimental group (10%) and 20 rats of the control group (100%), showing significant difference (χ2=32.727 3, P=0.000 0). The inflammatory reaction in experimental group was not obvious, grade I in 16 rats and grade II in 4 rats, and numerous inflammatory cell infiltration occurred in the control group, grade II in 3 rats and grade III in 17 rats, showing significant difference (Z=32.314, P=0.000). Conclusion The polypropylene mesh bonded norvancomycin slow-release microsphere has definite anti-infection effect in rat model of incisional hernia repair contaminated by Staphylococcus aureus.
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.
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 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 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.
ObjectiveTo analyze the pathogenic bacteria distribution, structure and characteristics of drug resistance in patients with acute stroke complicated with pulmonary infection, in order to provide reference for the prevention of hospital infection and rational use of antimicrobial agents. MethodsA total of 864 clinical specimens of acute stroke complicated with pulmonary infection were chosen for study between January 2012 and December 2014. Separation and cultivation were done in accordance with the operation procedures regulated by the Ministry of Health. Drug sensitivity examination was done by Kirby-Bauer (k-b). Super-extensive spectrum β lactamase (ESBL) and methicillin resistant staphylococcus aureus (MRSA) were detected to analyze the bacterial species and resistance transition. ResultsA total of 864 samples were cultivated, in which G-bacteria accounted for 61.2%. The main pathogenic bacteria was Klebsiella pneumoniae bacteria, Escherichia coli, Pseudomonas aeruginosa, Acinetobacter baumanmii and Staphylococcus aureus. Imipenem had high antimicrobial activity to G-bacilli, especially to Escherichia coli and Klebsiella pneumoniae bacteria. Linezolid, vancomycin and teicoplanin had high antibacterial activity to staphylococcus aureus. Vancomycin resistant Staphylococcus aureus was not found. Ciprofloxacin had high antibacterial activity to Pseudomonas aeruginosa, while imipenem had low antibacterial activity to Pseudomonas aeruginosa. Amikacin had high antibacterial activity to acinetobacter. ConclusionG-bacilli are predominant in acute stroke complicated with pulmonary infection. ESBLs and MRSA detection rate is high, and we should pay attention to the rational use of antibiotics to reduce drug resistance.
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.
ObjectiveTo analyze the clinical distribution and changes of antimicrobial resistance profiles of Staphylococcus aureus (SA), as well as to provide the basis for the prevention and treatment of infection. MethodsThe clinical data and the antimicrobial resistance profiles of SA were collected from Jan, 2008 to Dec, 2014 in West China Hospital of Sichuan University. The WHONET 5.5 software was used to analyze the resistance data. ResultsA total of 5 698 SA isolates were included within 7 years. Of all strains, 2 721 (47.8%) were isolated from secretion, 1 638 (28.75%) were from respiratory tract specimens, 451 (7.9%) were from pus, and 362 (6.4%) were from blood. 811 (49.5%) SA isolates from respiratory tract specimens were Methicillin-resistant Staphylococcus aureus (MRSA), which was higher than those from secretion, pus and blood. 1052 (18.5%) SA strains were isolated from the dermatological department, 604 (10.6%) were from the orthopedics department, 472 (8.3%) were from the intensive care unit (ICU), 471 (8.3%) were from the department of burn, and the detection rate of MRSA from ICU (341, 72.2%) was the highest. During last 7 years, the total separation rate of SA was 8.2%, among them 1 858 (32.6%) MRSA were isolated, and the detection rate was 32.6%. The resistant rate of SA to erythromycin, clindamycin, tetracycline, gentamicin, rifampin, ciprofloxacin, levofloxacin and moxifloxacin had a statistically significant decrease from 2008 to 2014, while the resistant rate of SA to trimethoprim/sulfamethoxazole had increased. No vancomycin, linezolid, teicoplanin or tigecycline resistant strain was detected. The resistance rates of MRSA to common antibiotics such as penicillin G, erythromycin, clindamycin, tetracycline, gentamicin, rifampin and fluoroquinolones were higher than those of MSSA, while the resistance rate of MRSA to trimethoprim/sulfamethoxazole was lower than MSSA. ConclusionCompared with the monitoring data in China, the drug resistance of SA in West China Hospital is well controlled. However, experience-directed antibiotic treatment of MRSA infection is still limited. MRSA infection remains a serious problem in critically ill patients. The rational use of antibiotics and application of effective infection control measures are important to decrease the MRSA infection.