The ever-changing microenvironment of Staphylococcus aureus in cutaneous infections

Background:Staphylococcus aureus is responsible for the majority of skin and soft tissue infections,which are often diagnosed at a late stage,thereby impacting treatment efficacy.Our study was designed to reveal the physiological changes at different stages of infection by S.aureus through the combined analysis of variations in the skin microenvironment,providing insights for the diagnosis and treatment of S.aureus infections.Methods:We established a murine model of skin and soft tissue infection with S.aureus as the infectious agent to investigate the differences in the microenvironment at different stages of infection.By combining analysis of the host immune status and histological observations,we elucidate the progression of S.aureus infection in mice.Results:The results indicate that the infection process in mice can be divided into at least two stages:early infection(1–3 days post-i nfection)and late infection(5–7 days post-i nfection).During the early stage of infection,notable symptoms such as erythema and abundant exudate at the infection site were observed.Histological examination revealed infiltration of numerous neutrophils and bacterial clusters,accompanied by elevated levels of cytokines(IL-6,IL-10).There was a decrease in microbial alpha diversity within the microenvironment(Shannon,Faith's PD,Chao1,Observed species,Simpson,Pielou's E).In contrast,during the late stage of infection,a reduction or even absence of exudate was observed at the infected site,accompanied by the formation of scabs.Additionally,there was evidence of fibroblast proliferation and neovascularization.The levels of cytokines and microbial composition gradually returned to a healthy state.Conclusion:This study reveals synchrony between microbial composition and histological/immunological changes during S.aureus-i nduced SSTIs.

Healthcare-associated Staphylococcus aureus infections in children in Turkey:A six-year retrospective,single-center study

Objective:To describe clinical and epidemiological characteristics,antimicrobial susceptibility and mortality-associated factors of healthcare-associated infections(HCAIs)caused by Staphylococcus(S.)aureus in children.Methods:We conducted a retrospective,single-centre study of pediatric HCAIs caused by S.aureus from a tertiary care hospital in Turkey between February 2014 and December 2019.The clinical and epidemiological characteristics and antimicrobial susceptibility of the methicillin-susceptible and methicillin-resistant S.aureus(MSSA and MRSA)isolates was evaluated.Results:A total of 310 pediatric patients were examined.Overall,225(72.6%)isolates were MSSA and 85(27.4%)were MRSA.All S.aureus isolates were susceptible to teicoplanin,vancomycin,linezolid,tigecycline,mupirocin,and daptomycin.Penicillin resistance rates were high(89.0%),while fosfomycin,gentamicin,and clindamycin resistance rates were low(1.3%,1.0%,and 2.3%,respectively).Except susceptibility to fosfomycin,which was significantly lower in 2014 compared to 2018 and 2019,no significant difference was found in the antimicrobial susceptibility of S.aureus isolates between the years.Baseline characteristics and mortality rate were similar comparing MRSA and MSSA causing HCAIs.The mortality rate of HCAIs caused by S.aureus was 6.5%(20 patients).Malignancy was an independent risk factor associated with mortality in the multivariate analysis(OR 5.446,95%CI 1.573-18.849).Conclusions:Our findings demonstrate that MSSA remained the most causative agent of HCAIs caused by S.aureus.The mortality rate was 6.5%,the antibiotic resistance rate was quite high for penicillin and diagnosis of malignancy was the main risk factor for increasing mortality in children.These findings could help improve the management of HCAIs caused by S.aureus in children.

Discovery of Kaempferol,a Novel ADAM10 Inhibitor,as a Potential Treatment for Staphylococcus aureus Infection

Host-directed therapy(HDT)is an emerging novel approach for treating multidrug-resistant Staphylococcus aureus(S.aureus)infection.Functioning as the indispensable specific cellular receptor for a-toxin(Hla),a-disintegrin and metalloproteinase 10(ADAM10)is exploited to accelerate S.aureus infection through diverse mechanisms.The extraordinary contribution of ADAM10 to S.aureus pathogenesis renders it an attractive HDT target for combating S.aureus infection.Our study is the first to demonstrate the indispensable role of ADAM10 in S.aureus-induced necroptosis,and it enhances our knowledge of the role of ADAM10 in S.aureus infection.Using a fluorogenic substrate assay,we further identified kaempferol as a potent ADAM10 inhibitor that effectively protected mice from S.aureus infection by suppressing Hla-mediated barrier disruption and necroptosis.Collectively,our work presents a novel hostdirected therapeutic strategy for using the promising candidate kaempferol to treat S.aureus infection and other diseases relevant to the disordered upregulation of ADAM10.

Teicoplanin combined with conventional vancomycin therapy for the treatment of pulmonary methicillin-resistant Staphylococcus aureus and Staphylococcus epidermidis infections

BACKGROUND Vancomycin and teicoplanin are both antibiotics that have significant antimicrobial effects on Gram-positive cocci.AIM To explore the value of teicoplanin combined with conventional(vancomycin only)anti-infective therapy for the treatment of methicillin-resistant Staphylococcus aureus and Staphylococcus epidermidis pulmonary infections.METHODS A total of 86 patients with methicillin-resistant Staphylococcus aureus or methicillin-resistant Staphylococcus epidermidis pulmonary infections,treated in our hospital between January 2018 and February 2020,were assigned to the study and control groups using a random number table method,with 43 patients in each group.The control group received conventional treatment(vancomycin),and the study group received both teicoplanin and conventional treatment.The following indicators were assessed in both groups:the time required for symptom relief,treatment effectiveness,serum levels of inflammatory factors(procalcitonin,interleukin-1β,tumor necrosis factor-α,C-reactive protein),clinical pulmonary infection scores before and after treatment,and the incidence of adverse reactions.RESULTS Patients in the study group were observed to have faster cough and expectoration resolution,white blood cell count normalization,body temperature normalization,and rales disappearance than patients in the control group(all P<0.05);the total rate of effectiveness was 93.02%in the study group,higher than the 76.74%in the control group(P<0.05).The pre-treatment serum levels of procalcitonin,interleukin-1β,tumor necrosis factor-α,and C-reactive protein as well as the clinical pulmonary infection scores were similar among the patients in both groups.However,the post-treatment serum levels of procalcitonin,interleukin-1β,tumor necrosis factor-α,and C-reactive protein as well as the clinical pulmonary infection scores were significantly lower in the study group than in the control group(P<0.05).There was no significant difference in the incidence of adverse reactions between the groups.CONCLUSION Compared with conventional(vancomycin only)therapy,teicoplanin and vancomycin combination therapy for patients with pulmonary methicillinresistant Staphylococcus aureus and methicillin-resistant Staphylococcus epidermidis infections can improve patient clinical symptoms,modulate serum inflammatory factor levels,and improve treatment efficacy,without increasing the risk of adverse reactions.

The Prevalence of Methicillin-Resistant Staphylococcus aureus Colonization in Patients with Complicated Skin and Skin Structure Infections after Treatment with Linezolid or Vancomycin

Background: Complicated skin and skin structure infections (cSSSIs) due to Staphylococcus aureus, including methicillin-resistant S. aureus (MRSA), are associated with significant morbidity. Re-ducing MRSA carriage has been a focus of infection control interventions. The prevalence of MRSA colonization after successful treatment of a MRSA cSSSI is unknown. Methods: Secondary analysis of a randomized controlled trial comparing linezolid and vancomycin for the treatment of MRSA cSSSI. Adult patients that had a colonization culture, confirmed MRSA cSSSI, received at least one dose of study treatment, and had an outcome recorded at end of study. Patient, clinical characteristics and prevalence of colonization were compared by treatment regimens. A multivariate regression model identified predictors of MRSA colonization at EOS. Results: There were 456 patients evaluated. The prevalence of MRSA colonization was higher for vancomycin treated patients compared to linezolid treated patients at end of treatment (EOT) (28% vs. 5%, p < 0.001) and EOS (34% vs. 22%, p < 0.01). Independent predictors of colonization at EOS after treatment for a MRSA cSSSI included diagnosis, primarily driven by abscess, black race, treatment with vancomycin, MRSA mixed infection and male gender. Conclusion: Patients treated with linezolid for a cSSSI had less MRSA colonization at EOT and EOS compared to those treated with vancomycin. Multiple independent predictors of MRSA colonization were identified. Additional studies evaluating the relationship of MRSA colonization after treatment of cSSSI are needed.

A case of methicillin-resistant Staphylococcus aureus infection following bile duct stenting

AIM: To present a case of methicillin-resistant Staphylococcus aureus (MRSA) infection following bile duct stenting in a patient with malignant biliary obstruction.METHODS: A 78-year-old male patient was admitted to a community hospital with progredient painless jaundice lasting over two weeks, weight loss and sweating at night.Whether a stent should be implanted pre-operatively in jaundiced patients or whether these patients should directly undergo surgical resection, was discussed.RESULTS: ERC and a biopsy from the papilla of Vater revealed an adenocarcinoma. In addition, a 7-Ch plastic stent was placed into the common bile duct. Persistent abdominal pain, increasing jaundice, weakness and indigestion led to the transfer of the patient to our hospital.A pylorus-preserving pancreatoduodenectomy wasperformed. Intraoperatively, bile leaked out of the transected choledochus andthe stent was found to be dislocated in the duodenum. A smear of the bile revealed an infection with MRSA, leading to post-operative isolation of the patient.CONCLUSION:As biliary stents can cause severe infection of the bile, the need for pre-operative placement of biliary stents should be carefully evaluated in each individual case.

Characterization of <i>Staphylococcus aureus</i>infections among children in an outpatient clinic, China

Objective: We aimed to investigate the epidemiology and identify antibiotic resistance patterns of isolates from children with skin and soft tissue infections attending an outpatient clinic in Southern China. Method: An observational study of outpatient pediatric patients was conducted in a rural area of Guangxi. Infections were characterized in 230 patients and staphylococcal isolates tested for susceptibility to a range of antibiotics. Results: Among the 307 patients, 38.5% were infants. Culture yielded Staphylococcus aureus (S. aureus) in 230 patients, of which 24 (10.4%) were methicillin-resistant S. aureus (MRSA). Staphylococcal strains were most isolated from hand, foot and umbilicus. The 1-12 mon group had the highest staphylococcal infection rate (86%), followed by the 6-12 year group, but MRSA was more common in the older children (19.5% of S. aureus). MRSA had significantly more resistance than MSSA to chloromycin (46% vs 11%), clindamycin (67% vs 19%), gentamicin (33% vs 2%), rifampicin (25% vs 2.9%), and sulphamthoxazole-trimethoprim (17% vs 3%). Conclusion: S. aureus remains a leading cause of pediatric skin and soft tissue infections. Over 10% of isolates were methicillin-resistant with high rates of resistance to non-beta lactam antibiotics, reducing options for therapy and limiting choices for empirical treatment.

Anti-viral activity of Staphylococcus aureus lysates against herpes simplex virus type-Ⅰinfection:an in vitro and in vivo study

AIM:To investigate the effect of Staphylococcus aureus(S.aures)lysates(SALs)on herpes simplex virus type-Ⅰ(HSV1)infection in human corneal epithelial(HCE)cells and in a mouse model of HSV1 keratitis.METHODS:HCE,Vero,HeLa,and BV2 cells were infected with HSV1[HSV1f strain,HSV1f;HSV-1-H129 with green fluorescent protein(GFP)knock-in,HSV1g].Pre-or post-infection,SAL at various concentrations was added to the culture medium for 24 h.GFP fluorescence in HSV1g or plaque formation by HSV1f were examined.The effects of heat-treated SAL,precooled acetone-precipitated SAL,and SAL subjected to ultrafiltration(100 kDa)were evaluated.The effects of other bacterial components and lysates on HSV1 infection were also tested,including lipoteichoic acid(LTA),peptidoglycan(PGN),staphylococcal protein A(SPA),andα-hemolysin from S.aureus(α-toxin)as well as lysates from a wild-type S.aureus strain,S.epidermidis,and Escherichia coli(W-SAL,SEL,and ECL,respectively).In addition,SAL eye drops were applied topically to BALB/c mice with HSV1 keratitis,followed by in vivo observations.RESULTS:The cytopathic effect,plaque formation(HSV1f),and GFP expression(HSV1g)in infected cells were inhibited by SAL in a dose-dependent manner.The active component of SAL(≥100 kDa)was heat-sensitive and retained activity after acetone precipitation.In HSV1ginfected cells,treatment with LTA-sa,α-toxin,PGN-sa,or SPA did not inhibit GFP expression.SAL,W-SAL,and SEL(but not ECL)decreased GFP expression.In mice with HSV1 keratitis,SAL reduced corneal lesions by 71%.CONCLUSION:The results of this study demonstrate that SAL can be used to inhibit HSV1 infection,particularly keratitis.Further studies are needed to determine the active components and mechanism underlying the effects of SAL.

Ophthalmic methicillin-resistant <i>Staphylococcus aureus</i>infections: Sensitivity and resistance profiles of 65 isolates in central California

Purpose: To capture the sensitivity and resistance trends of ophthalmic Methicillin-resistant Staphylococcus aureus (MRSA) in a heterogenous demographic. Methods: Between 1/1/2004-12/31/2011, ophthalmic MRSA infections were searched in the electronic medical record system ofCommunityRegionalMedicalCenterinFresno,California. We reviewed whether the infection was community-acquired or hospital-acquired, culture site, and sensitivity/resistance profiles. Results: The ophthalmic MRSA isolates tested for vancomycin, sulfamethoxazole-trimethoprim, and gentamycin were 100% sensitive to these to these antibiotics. Tetracycline and rifampin had the next highest sensitivity to resistance ratio, followed by clindamycin. More cases were community-acquired than hospital acquired. Almost half of the hospital-acquired cases were in newborns. Most hospital acquired infections were post-ophthalmic surgery. Conclusion: There is an increasing trend of community- acquired ophthalmic MRSA infection with eyelid involvement being the most common manifestation. Hospital-acquired cases are common in newborns and post-ophthalmic surgery. Have a high index of suspicion for MRSA infection with suspected “insect bites”. Vancomycin, sulfamethoxazole-trimethoprim, gentamycin, tetracycline, and rifampin are good choices to treat ophthalmic MRSA infection. There may be emerging resistance to clindamycin, at least in theCentral Californiaregion. If MRSA infection is suspected, erythromycin and fluoroquinolones should be avoided.

Phenotypic Characterization and Risk Factors of Nosocomial <i>Staphylococcus aureus</i>from Health Care Centers

Multidrug resistant Staphylococcus aureus (MDRS) is a serious threat to hospitalized patients globally and now represents a challenge for public health, as community-acquired infections appear to be on the increase in both adults and children. S. aureus colonization has been shown to be a risk factor for community-acquired and nosocomial infections. A total of 130 subjects from the community and 100 subjects from health care-related facilities were evaluated for the prevalence of Staphylococcus aureus colonization and to identify risk factors associated with methicillin-resistant S. aureus (MRSA) and vancomycin resistant S. aureus (VRSA) colonization. Among the community subjects, 35.38% had MRSA and 1.53% VRSA colonization. Subjects from health care-related facilities had a lower MRSA colonization rate (17%) than community subjects and the colonization VRSA has not been found. Age was a risk factor for S. aureus colonization, with subjects under age 20 years or between 60 and 80 years showing higher rates of colonization. In conclusion, a high prevalence of MRSA colonization was observed among people with relationship to the hospital setting. The high level of multiple-drug resistance among community MRSA strains in association with the previously reported excessive use of antibiotics highlights the importance of the problem of antibiotic selective pressure. Our results indicate that the spread of both MRSA and VRSA and the transmission of hospital isolates contribute to the high MRSA/VRSA burden in the community.

Susceptibility of <i>Staphylococcus aureus</i>Isolates Causing Bloodstream Infection to the Antimicrobial Peptide LL-37

Both bacterial and host factors contribute to complicated bloodstream infection (BSI) caused by Staphylococcus aureus including methicillin-resistant S. aureus (MRSA). One bacterial factor that may affect the persistence of S. aureus in complicated BSI is reduced susceptibility to the innate immune defence peptide LL-37. LL-37 susceptibility among S. aureus isolates causing uncomplicated and complicated BSI was investigated. Following incubation with 2.5 μg/ml LL-37 for 1 h, the mean percentage survival was 67.6% and 74.9% for isolates causing uncomplicated and complicated BSI, respectively. Reduced LL-37 susceptibility may contribute to the persistence of S. aureus in complicated BSI.

Risk of methicillin-resistant Staphylococcus aureus prosthetic joint infection in elective total hip and knee arthroplasty following eradication therapy

Re-screening following methicillin-resistant Staphylococcus aureus(MRSA) decolonization will be helpful to minimize the development of prosthetic joint infection among MRSA colonizers.

Staphylococcus aureus bacteremia and infective endocarditis in a patient with epidermolytic hyperkeratosis:A case report

BACKGROUND Staphylococcus aureus bacteraemia(SAB)is among the leading causes of bacteraemia and infectious endocarditis.The frequency of infectious endocarditis(IE)among SAB patients ranges from 5%to 10%-12%.In adults,the characteristics of epidermolytic hyperkeratosis(EHK)include hyperkeratosis,erosions,and blisters.Patients with inflammatory skin diseases and some diseases involving the epidermis tend to exhibit a disturbed skin barrier and tend to have poor cellmediated immunity.CASE SUMMARY We describe a case of SAB and infective endocarditis in a 43-year-old male who presented with fever of unknown origin and skin diseases.After genetic tests,the skin disease was diagnosed as EHK.CONCLUSION A breached skin barrier secondary to EHK,coupled with inadequate sanitation,likely provided the opportunity for bacterial seeding,leading to IE and deepseated abscess or organ abscess.EHK may be associated with skin infection and multiple risk factors for extracutaneous infections.Patients with EHK should be treated early to minimize their consequences.If patients with EHK present with prolonged fever of unknown origin,IE and organ abscesses should be ruled out,including metastatic spreads.

Establishment and evaluation of diabetic ulcer model in rats infected with Staphylococcus aureus and Escherichia coli

Objective:To establish a rat model of diabetic ulcer infected by Staphylococcus aureus and Escherichia coli, and provide a suitable animal model for experimental research of diabetic ulcer. Methods: Forty male SD rats were randomly divided into five groups: general ulcer group, diabetic ulcer group, diabetic ulcer treatment group, model group, and model treatment group. After modeling, take local skin tissue for HE staining.Detection of high-sensitivity C-reactive protein, fibroblast growth factor, tumor necrosis factor-α, advanced glycosylation products, interleukin-1β, interleukin-6, and nitric oxide in rat serum by enzyme-linked immunosorbent Level, and record the wound healing time, and evaluate the stability and practicability of the model. Results:The healing time of ulcer in the model group was significantly delayed compared with other groups (p <0.001). The serum H-CRP levels in the model group and the model treatment group were higher than those in the common ulcer group, the diabetic ulcer group, and the diabetic ulcer treatment group (p <0.05). After healing, the levels of H-CRP, bFGF, AGEs, TNF-α, IL-1β, IL-6, and NO in the serum of the diabetic ulcer group were higher than those in the common ulcer group (all p <0.05);The levels of TNF-α, IL-1β, IL-6, and NO were higher than those in other groups (all p <0.05);HCRP, AGEs, TNF-α, IL-1β, IL-6, and NO levels in the serum of the model treatment group They were all higher than those in diabetic ulcer treatment group (all p <0.05). Conclusion: This model is in line with the local environment of infectious diabetic ulcers and provides a reliable tool for the study of diabetic infections.

Nitric oxide mediated Staphylococcus aureus pathogenesis and protective role of nanoconjugated vancomycin

Objective:To investigate the relation between fruit seeds,plants residuals and appendicitis. Methods:Among cases that underwent appendectomy,the appendicitis cases having fruit seeds and undigested plant residuals in their etiology were examined retrospectively.Also, histopathological features,age,sex,and parameters of morbidity and mortality were used. Results:Fruit seed was found in one case(0.05%) with presence of pus in appendix lumen, undigested plant residuals in 7 cases(0.35%).It was determined that there were appendix inflammation in 2 of the plant residuals cases,while there were obstruction and lymphoid hyperplasia in the appendix lumen of 5 cases.No mortality was observed.Conclusions:The ratio of acute appendicitis caused by plants is minimal among all appendectomised patients, but avoidence of eating undigested fruit seeds and chewing plants well may help to prevent appendicitis.

Determining of antibiotic resistance profile in Staphylococcus aureus isolates

Objective:To determine the pattern of antibiotic resistance among Staphylococcus aureus(S. aureus) isolates from clinical specimens and to identify community-acquired methicillin-resistant Staphylococcus aureus(CA-MRSA) in specimens that have been collected from patients referring to one of the hospitals of Ahvaz.Methods:S.aureus isolates from a hospital in Ahvaz were screened for resistance to various antibiotics including methicillin.The susceptibility of the isolates was determined by Kirby-Bauer disc diffusion method.The MRSA was also treated with ethidium bromide to find the origin of resistance.Results:Among the bacterial isolates,all of 11 S.aureus were resistant to methicillin and cefixime,2 were resistant to ciprofloxacin,6 were resistant to tetracycline and the reminder were sensitive or intermediate to other antibiotics.The treated isolates were reminded resistant to methicillin and this suggested that the plasmid was not the origin of resistance in these isolates.Conclusions:These results showed that infection due to MRSA is widespread in Ahvaz and with respect to the spread of vancomycin resistance among MRSA and appearance of overwhelming infections.It is necessary to identify continuously the profile of antibiotic resistance among S.aureus isolates in other regions and finding appropriate antibiotic for infection control and eradication.

Comparative Antibiotic Sensitivity Pattern of Hospital and Community Acquired <i>Staphylococcus aureus</i>Isolates of Jessore, Bangladesh

Staphylococcus aureus has emerged over the past several decades as a leading cause of hospital acquired infections, which are more commonly termed as nosocomial infections. In recent years, strains of this bacterium which are resistant against several types of antibiotics have evolved and their prevalence is becoming a potential epidemiological threat. As there are limited data available on antibiotic resistance patterns of S. aureus that are isolated from hospital, the study was undertaken. The study was conducted by collecting swab samples from the hospital environment & volunteers and then identified them by standard methods. In case of hospital isolates, highest percentage of resistance was shown against Erythromycin (88.89%) and Ampicillin (83.33%). Significant resistance was also observed in cases of Ciprofloxacin (33.33%) and Tetracycline (33.33%). Lowest percentage of resistance was shown against Streptomycin (11.11%) and Vancomycin shows only intermediate resistant pattern (11.11%). On the other hand, community isolates were 100% sensitive against four antibiotics except Ampicillin (60% resistant) and Vancomycin (20% resistant). From the result it is easily discernable that, there are significant differences in the resistance pattern among hospital environment isolates and community acquired isolates. Samples were collected from different locations of hospital surgery room e.g. floor, wall, operating bed, trolley, sitting tool, cabinet etc. As anticipated, highest number of isolates showing resistance against these antibiotics were from the tool used for sitting.

Tuf m RNA rather than 16S r RNA is associated with culturable Staphylococcus aureus

AIM: To study the presence of various nucleic acids targets of Staphylococcus aureus(S. aureus) during bacterial growth and antibiotic induced killing in relation to viability.METHODS: S. aureus was cultured to log phase and spiked in Todd Hewitt(TH) broth and whole blood of healthy human volunteers. Viability of S. aureus after flucloxacillin treatment(0, 1, 3 and 6 d) was assessed by culture on bloodagar plates. DNA and RNA were isolated from 200 μL. c DNA synthesis was performed by using random primers. The presence of S. aureus DNA, r RNA, and m RNA were determined by real-time polymerase chain reaction of the 16 S r DNA and tuf gene(elongation factor Tu).RESULTS: S. aureus spiked in TH broth without antibiotics grew from day 0-6 and DNA(tuf and 16S), and 16 S r RNA remained detectable during this whole period. During flucloxacillin treatment S. aureus lost viability from day 3 onwards, while the 16 S r RNA-gene and its RNA transcripts remained detectable. DNA andr RNA can be detected in flucloxacillin treated S. aureus cultures that do not further contain culturable bacteria.However, tuf m RNA became undetectable from day 3onwards. Tuf m RNA can only be detected from samples with culturable bacteria. When spiking S. aureus in whole blood instead of broth no bacterial growth was seen, neither in the absence nor in the presence of flucloxacillin. Accordingly, no increase in DNA and RNA levels of both 16 S r DNA and the tuf gene were detected. CONCLUSION: Tuf m RNA expression is associated with culturable S. aureus and might be used to monitor antibiotic effects.

Analysis of the Clinical Characteristics and Antibiotics Resistance of Community-acquired Methicillin-resistant Staphylococcus aureus

The purpose of this investigation is to study the clinical characteristics of infections by community-acquired methicillin-resistant Staphylococcus aureus (MRSA) and the condition of antibiotics resistance of the clinical isolates in order to guide for the rational use of antibiotics. With the clinical isolates from cases of hospital-acquired MRSA at the same period as controls, the clinical characteristics of infections by community-acquired MRSA in Hangzhou area and the pattern of non-β-lactamase antibiotics resistance were determined in this study. It was found that the average age of patients with community-acquired MRSA infections was 30.89±13.3, in comparison with those of the hospital-acquired patients of 56.0±11.8, appearing to be younger than those of the latter, and the former showing no any basic illness. Both of the former and the latter were sensitive to vancomycin (100% vs 100%), and they had the same degrees of sensitivity to rifampicin, fosfomycin, and STM/TMP (86.8% vs 88.1%, P >0.05; 81.6% vs 82.9%, P >0.05; and 52.6% vs 61.9%, P >0.05, respectively). The former was more sensitive to netimycin, clindamycin, erythromycin and minocycline than those of the latter (73.7% vs 50.5%, P <0.01; 60.5% vs 45.7%, P <0.05; 28.9% vs 11.4%, P <0.01; and 81.6% vs 58.6%, P <0.01 respectively). Meanwhile, the incidence of multi-resistant strain of isolates in the former was significantly lower than that of the latter (31.6% vs 81.0%, P <0.01). In conclusion, it appears that the strains of clinical isolates isolated from patients with the community-acquired MRSA infections show different clinical characteristics and antimicrobial susceptibility in comparison with those of the hospital-acquired cases of infection, and this necessitates an alteration in the chemotherapy of infections suspected to be caused by community-acquired MRSA.

Nosocomial bloodstream infection in patients caused by Staphylococcus aureus： drug susceptibility, outcome, and risk factors for hospital mortality

Background Previous studies have different viewpoints about the clinical impact of methicillin resistance on mortality of hospital-acquired bloodstream infection （BSI） patients with Staphylococcus aureus （S.aureus）.The objective of this study was to investigate the mortality of hospital-acquired BSI with S.aureus in a military hospital and analyze the risk factors for the hospital mortality.Methods A retrospective cohort study was performed in patients admitted to the biggest military tertiary teaching hospital in China between January 2006 and May 2011.All included patients had clinically significant nosocomial BSI with S.aureus.Multivariate Logistic regression analysis was used to identify the risk factors for hospital mortality of patients with S.aureus BSI.Results One hundred and eighteen patients of more than one year old were identified as clinically and microbiologically confirmed nosocomial bacteraemia due to S.aureus,and 75 out of 118 patients were infected with methicillin-resistant S.aureus （MRSA）.The overall mortality of nosocomial S.aureus BSI was 28.0%.Methicillin resistance in S.aureus bacteremia was associated with significant increase in the length of hospitalization and high proportion of inappropriate empirical antibiotic treatment.After Logistic regression analysis,the severity of clinical manifestations （APACHE Ⅱ score） （odds ratio （OR） 1.22,95% confidence interval （CI） 1.12-1.34） and inadequacy of empirical antimicrobial therapy （OR 0.25,95% CI 0.09-0.69） remained as risk factors for hospital mortality.Conclusions Nosocomial S.aureus BSI was associated with high in-hospital mortality.Methicillin resistance in S.aureus has no significant impact on the outcome of patients with staphylococcal bacteremia.Proper empirical antimicrobial therapy is very important to the prognosis.