The impact of methicillin resistance in Staphylococcus aureus bacteremia on patient outcomes: mortality, length of stay, and hospital charges.

OBJECTIVE: To evaluate the impact of methicillin resistance in Staphylococcus aureus on mortality, length of hospitalization, and hospital charges. DESIGN: A cohort study of patients admitted to the hospital between July 1, 1997, and June 1, 2000, who had clinically significant S. aureus bloodstream infections. SETTING: A 630-bed, urban, tertiary-care teaching hospital in Boston, Massachusetts. PATIENTS: Three hundred forty-eight patients with S. aureus bacteremia were studied; 96 patients had methicillin-resistant S. aureus (MRSA). Patients with methicillin-susceptible S. aureus (MSSA) and MRSA were similar regarding gender, percentage of nosocomial acquisition, length of hospitalization, ICU admission, and surgery before S. aureus bacteremia. They differed regarding age, comorbidities, and illness severity score. RESULTS: Similar numbers of MRSA and MSSA patients died (22.9% vs 19.8%; P = .53). Both the median length of hospitalization after S. aureus bacteremia for patients who survived and the median hospital charges after S. aureus bacteremia were significantly increased in MRSA patients (7 vs 9 days, P = .045; 19,212 dollars vs 26,424 dollars, P = .008). After multivariable analysis, compared with MSSA bacteremia, MRSA bacteremia remained associated with increased length of hospitalization (1.29 fold; P = .016) and hospital charges (1.36 fold; P = .017). MRSA bacteremia had a median attributable length of stay of 2 days and a median attributable hospital charge of 6916 dollars. CONCLUSION: Methicillin resistance in S. aureus bacteremia is associated with significant increases in length of hospitalization and hospital charges.     

Clinical outcomes and costs due to Staphylococcus aureus bacteremia among patients receiving long-term hemodialysis.

OBJECTIVE: To examine the clinical outcomes and costs associated with Staphylococcus aureus bacteremia among hemodialysis-dependent patients. DESIGN: Prospectively identified cohort study. SETTING: A tertiary-care university medical center in North Carolina. PATIENTS: Two hundred ten hemodialysis-dependent adults with end-stage renal disease hospitalized with S. aureus bacteremia. RESULTS: The majority of the patients (117; 55.7%) underwent dialysis via tunneled catheters, and 29.5% (62) underwent dialysis via synthetic arteriovenous fistulas. Vascular access was the suspected source of bacteremia in 185 patients (88.1%). Complications occurred in 31.0% (65), and the overall 12-week mortality rate was 19.0% (40). The mean cost of treating S. aureus bacteremia, including readmissions and outpatient costs, was $24,034 per episode. The mean initial hospitalization cost was significantly greater for patients with complicated versus uncomplicated S. aureus bacteremia ($32,462 vs $17,011; P = .002). CONCLUSION: Interventions to decrease the rate of S. aureus bacteremia are needed in this high-risk, hemodialysis-dependent population.     

Carriage of Staphylococcus aureus and of gram-negative bacilli resistant to third-generation cephalosporins in cirrhotic patients: a prospective assessment of hospital-acquired infections.

OBJECTIVE: To study the relation between Staphylococcus aureus nasal and stool colonization, stool carriage of gram-negative bacilli resistant to third-generation cephalosporins (CephR), and subsequent infections during hospitalization. DESIGN: Prospective study. PATIENTS: 551 cirrhotic patients with 589 consecutive hospital stays. All patients were screened within 48 hours of admission; 589 nasal swabs, 417 stool specimens, and 589 urine samples were analyzed. RESULTS: Carriage rates were 18.8% for methicillin-sensitive S aureus (MSSA), 16.3% for methicillin-resistant S aureus (MRSA), and 13.7% for CephR. We observed 87 episodes of spontaneous bacterial peritonitis, 63 cases of bacteremia, and 167 urinary tract infections occurred. Only 1 case of bacteremia and 4 urinary tract infections due to CephR occurred in patients carrying the same organism in their stools. The risk of MRSA ascitic fluid infections, bacteremia, and urinary tract infections was 3.1% versus 1% (not significant), 8.3% versus 0.8% (P<.001), and 11.4% versus 0.6% (P<.001) in carriers and noncarriers, respectively. Pulsed-field gel electrophoresis (PFGE) of isolates from 16 patients infected by MSSA (3 cases) and MRSA (13 cases) demonstrated that the colonizing strains matched the invasive strains in the 3 MSSA cases and in 8 of 13 MRSA cases. CONCLUSION: Carriage of CephR strains is not associated with subsequent infection by these organisms in hospitalized cirrhotic patients. In contrast, MRSA carriage was an important risk factor for MRSA bacteremia and urinary tract infection.     

Changing epidemiology of community-onset methicillin-resistant Staphylococcus aureus bacteremia.

OBJECTIVES: To review cases of community-onset Staphylococcus aureus bacteremia and to evaluate whether the risk factors and epidemiology of methicillin-resistant S. aureus (MRSA) bacteremia have changed from early reports. DESIGN: Retrospective case-comparison study of community-onset MRSA (n = 26) and methicillin-susceptible S. aureus (MSSA) (n = 26) bacteremias at our institution. SETTING: A 600-bed urban academic medical center. PATIENTS: Twenty-six patients with community-onset MRSA bacteremia were compared with 26 patients with community-onset MSSA bacteremia. Molecular analysis was performed on S. aureus isolates from the 26 MRSA cases as well as from 13 cases of community-onset S. aureus bacteremia from 1980 and 9 cases of nosocomial S. aureus bacteremia from 2001. RESULTS: The two groups were similar except that patients with MRSA bacteremia were more likely to have presented from a long-term-care facility (26.9% vs 4%; P = .05) and to have had multiple admissions within the preceding year (46% vs 15%; P = .03). Clamped homogeneous electric fields analysis of MRSA isolates from 1982 revealed predominantly that one clone was the epidemic strain, whereas there were 14 unique strains among current community-onset isolates. Among current nosocomial isolates, 3 patterns were identified, all of which were present in the community-onset cases. CONCLUSIONS: Previously described risk factors for MRSA acquisition may not be helpful in predicting disease due to the polyclonal spread of MRSA in the community. Unlike early outbreaks of MRSA in patients presenting from the community, current acquisition appears to be polyclonal and is usually related to contact with the healthcare system.     

住院患儿MSSA与MRSA的分布特点及耐药性

目的比较住院患儿甲氧西林敏感金黄色葡萄球菌(MSSA)与耐甲氧西林金黄色葡萄球菌(MRSA)的分布及耐药特点,为临床经验治疗提供依据。方法回顾性分析2011—2015年某院住院患儿分离的金黄色葡萄球菌及其临床资料,比较MSSA与MRSA的分布及耐药特点。结果共分离金黄色葡萄球菌919株,其中MSSA632株(68.77%),MRSA 287株(31.23%)。MSSA与MRSA感染患儿中29d~1岁婴儿组所占比率最高,分别为65.03%、64.11%。MSSA和MRSA标本主要来自痰(80.38%、79.09%)。MSSA和MRSA主要分布科室均为儿童呼吸科(50.73%、45.89%)和儿童神经内科(22.98%、26.84%)。MSSA对除青霉素和红霉素外的抗菌药物耐药率均20.00%;MRSA对青霉素、苯唑西林、红霉素及克林霉素的耐药率均40.00%;MRSA对四环素、红霉素、克林霉素、左氧氟沙星、环丙沙星、莫西沙星、呋喃妥因及利福平的耐药率均高于MSSA。结论住院患儿分离的金黄色葡萄球菌以MSSA为主,1岁以内婴儿为主要分离人群;呼吸道标本来源的MSSA和MRSA主要分布科室相似,MRSA的耐药率普遍高于MSSA。     

Epidemiology and clonality of methicillin-resistant and methicillin-susceptible Staphylococcus aureus causing bacteremia in a tertiary-care hospital in Spain.

OBJECTIVES: To describe the relative proportions of nosocomial and community-onset Staphylococcus aureus bacteremia at our institution and the epidemiologic characteristics and clonal diversity of S. aureus isolates, as determined by pulsed-field gel electrophoresis (PFGE) and antimicrobial resistance patterns. DESIGN: Retrospective cohort study of all cases of S. aureus bacteremia between October 2001 and October 2002. SETTING: A 1300-bed, tertiary-care hospital. RESULTS: One hundred sixty-two unique episodes of S. aureus bacteremia were identified. Forty-three cases (26.5%) were caused by methicillin-resistant S. aureus (MRSA). Most cases of S. aureus bacteremia, whether MRSA or methicillin susceptible (MSSA), were nosocomial in origin (77.2%) or were otherwise associated with the healthcare system (16%). Only 11 (6.8%) of the cases (all MSSA) were strictly community acquired. Thirty-five unique macrorestriction patterns were identified among the 154 isolates that were typed by PFGE. Four major genotypes were defined among the isolates of MRSA, with 36 (85.7%) represented by a single PFGE type. Of the isolates within this major clone, all (100%) were ciprofloxacin resistant and 77.8% were erythromycin resistant. In contrast, the 112 isolates of MSSA comprised 31 different PFGE types, 3 of which represented 42.9% of all MSSA isolates and were associated with both nosocomial and community-onset bacteremia. CONCLUSIONS: Most cases of S. aureus bacteremia in our healthcare region are nosocomial in origin or are acquired through contact with the healthcare system and are thus potentially preventable. To preclude dissemination of pathogenic clones, it is therefore necessary to redouble preventive measures in both the hospital and the community.     

Nosocomial methicillin-resistant and methicillin-susceptible Staphylococcus aureus primary bacteremia: at what costs?

OBJECTIVE: To determine the attributable hospital stay and costs for nosocomial methicillin-sensitive Staphylococcus aureus (MSSA) and methicillin-resistant S. aureus (MRSA) primary bloodstream infections (BSIs). DESIGN: Pairwise-matched (1:1) nested case-control study. SETTING: University-based tertiary-care medical center. PATIENTS: Patients admitted between December 1993 and March 1995 were eligible. Cases were defined as patients with a primary nosocomial S. aureus BSI; controls were selected according to a priori matching criteria. MEASUREMENTS: Length of hospital stay and total and variable direct costs of hospitalization. RESULTS: The median hospital stay attributable to primary nosocomial MSSA BSI was 4 days, compared with 12 days for MRSA (P=.023). Attributable median total cost for MSSA primary nosocomial BSIs was $9,661 versus $27,083 for MRSA nosocomial infections (P=.043). CONCLUSION: Nosocomial primary BSI due to S. aureus significantly prolongs the hospital stay. Primary nosocomial BSIs due to MRSA result in an approximate threefold increase in direct cost, compared with those due to MSSA.     

Risk factors and costs associated with methicillin-resistant Staphylococcus aureus bloodstream infections.

OBJECTIVES: To compare the cost of hospitalization of patients with methicillin-resistant Staphylococcus aureus (MRSA) bloodstream infection (BSI) versus patients with methicillin-sensitive S. aureus (MSSA) BSI, controlling for severity of underlying illness; and to identify risk factors associated with MRSA BSI. DESIGN: Retrospective case-control study based on medical chart review. SETTING: A 640-bed, tertiary-care hospital in Seattle, Washington. PATIENTS: All patients admitted to the hospital between January 1, 1997, and December 31, 1999, with S. aureus BSI confirmed by culture. RESULTS: Twenty patients with MRSA BSI were compared with 40 patients with MSSA BSI. Univariate analysis identified 5 risk factors associated with MRSA BSI. Recent hospital admission (P = .006) and assisted living (P = .004) remained significant in a multivariate model. Costs were significantly higher per patient-day of hospitalization for MRSA BSI than for MSSA BSI (dollar 5,878 vs dollar 2,073; P = .003). When patients were stratified according to severity of illness as measured by the case mix index, a difference of dollar 5,302 per patient-day was found between the two groups for all patients with a case mix index greater than 2 (P < .001). CONCLUSION: These observations suggest that MRSA BSI significantly increases hospitalization costs compared with MSSA BSI, even when controlling for the severity of the patient's underlying illness. As MRSA BSI was also found to be significantly associated with a group of patients who have repeated hospitalizations, such infections contribute substantially to the increasing cost of medical care.     

血流感染耐甲氧西林金黄色葡萄球菌对患者预后的影响

目的了解耐甲氧西林金黄色葡萄球菌(MRSA)感染对患者住院时间、院内死亡以及不良预后的影响。方法对2009年1月1日—2013年12月31日华西医院血培养确诊为金黄色葡萄球菌感染的357例住院患者进行回顾性调查分析。结果 357例患者,MRSA感染91例,甲氧西林敏感金黄色葡萄球菌(MSSA)感染266例。MRSA组和MSSA组住院时间比较(29 d vs 23 d),差异有统计学意义(P0.01);感染前MRSA组患者住院时间长于MSSA组(P0.01),感染后两组患者住院时间比较(17 d vs 16.5 d),差异无统计学意义(P=0.92)。MRSA组和MSSA组患者死亡率比较(13.19%vs 9.02%),差异无统计学意义(χ2=1.28,P=0.26);MRSA组不良预后发生率为29.67%,高于MSSA组的16.92%(χ2=6.85,P=0.01)。多因素分析结果显示,MRSA感染是患者预后不良的独立危险因素(P0.01)。结论 MRSA感染未增加患者住院时间,但MRSA血流感染是患者不良预后的危险因素。     

Antimicrobial use and methicillin-resistant Staphylococcus aureus in a large nursing home

INTRODUCTION: In 1997, 18% of Staphylococcus aureus clinical isolates at the Wisconsin Veterans Home were resistant to methicillin. By 2002, 51% were resistant. METHODS: We determined the antibiotic sensitivity pattern of our methicillin-resistant S. aureus (MRSA) isolates as well as changes in utilization of specific antibiotics between two time periods. We reasoned that antibiotics with activity against methicillin-sensitive S. aureus (MSSA), but not MRSA, might be driving the overgrowth of MRSA. RESULTS: In our facility, MRSA is usually resistant to quinolones; MSSA is usually sensitive. Both MSSA and MRSA are usually sensitive to TMP-sulfa. An increased percentage of S. aureus resistant to methicillin (18%) was associated with a 42% increase in quinolone use and a 37% decrease in TMP-sulfa use. CONCLUSION: Our analysis and previous reports suggest that replacement of TMP-sulfa by quinolones could be selecting MRSA in our facility. This conclusion, however, is speculative, based on association, and requires confirmation.     

Nosocomial methicillin-resistant Staphylococcus aureus bacteremia: is it any worse than nosocomial methicillin-sensitive Staphylococcus aureus bacteremia?

OBJECTIVE: To determine the comparative virulence of methicillin-resistant Staphylococcus aureus (MRSA) and methicillin-sensitive S aureus (MSSA) by consideration of predisposing factors and outcomes in patients infected with these organisms in the healthcare setting. DESIGN: Analysis of an historical cohort of 504 bacteremic patients (316 MSSA and 188 MRSA), examining factors associated with mortality. SETTING: A 916-bed, university-affiliated, tertiary referral hospital. RESULTS: Risk factors for the development of MRSA include male gender, admission due to trauma, immunosuppression, presence of a central vascular line or an indwelling urinary catheter, and a past history of MRSA infection. Overall mortality was 22%. Death due to bacteremia was significantly greater in the MRSA group (risk ratio, 1.68; P<.05), although these patients were not found to be more likely to die due to underlying disease during treatment of bacteremia. In those patients who recovered from bacteremia, no significant differences for the outcome of death could be determined between the MRSA and MSSA groups. CONCLUSIONS: There is a general consensus in the published literature that MRSA bacteremia is more likely to be associated with death, and we confirm this conclusion. However, in contrast to other studies, our MRSA cohort does not appear to be more at risk of death due to underlying disease during treatment for bacteremia. Similarly, the general consensus that MRSA patients have an increased overall mortality was not confirmed in our study. Differences in comorbidities of patients may provide some explanation of these conflicting results, while an alternate explanation is that MRSA strains are more virulent than MSSA in some centers. Perhaps the most plausible explanation is that treatment is provided earlier and in a more aggressive fashion in some centers, leading to an overall lower mortality rate in all staphylococcal bacteremias in these institutions.     

Comparison of mortality risk associated with bacteremia due to methicillin-resistant and methicillin-susceptible Staphylococcus aureus.

OBJECTIVE: To quantify the clinical impact of methicillin-resistance in Staphylococcus aureus causing infection complicated by bacteremia in adult patients, while controlling for the severity of patients' underlying illnesses. DESIGN: Retrospective cohort study from October 1, 1995, through December 31, 2003. PATIENTS AND SETTING: A total of 438 patients with S. aureus infection complicated by bacteremia from a single Veterans Affairs healthcare system. RESULTS: We found that 193 (44%) of the 438 patients had methicillin-resistant S. aureus (MRSA) infection and 114 (26%) died of causes attributable to S. aureus infection within 90 days after the infection was identified. Patients with MRSA infection had a higher mortality risk, compared with patients with methicillin-susceptible S. aureus (MSSA) infections (relative risk, 1.7 [95% confidence interval, 1.3-2.4]; P<.01), except for patients with pneumonia (relative risk, 0.7 [95% confidence interval, 0.4-1.3]). Patients with MRSA infections were significantly older (P<.01), had more underlying diseases (P=.02), and were more likely to have severe sepsis in response to their infection (P<.01) compared with patients with MSSA bacteremia. Patients who died within 90 days after S. aureus infection was identified were significantly older (P<.01) and more likely to have severe sepsis (P<.01) and pneumonia (P=.01), compared with patients who survived. After adjusting for age as a confounder, comorbidities, and pneumonia as an effect modifier, S. aureus infection-related mortality remained significantly higher in patients with MRSA infection than in those with MSSA infection, among those without pneumonia (hazard ratio, 1.8 [95% confidence interval, 1.2-3.0]); P<.01. CONCLUSIONS: The results of this study suggest that patients with MRSA infections other than pneumonia have a higher mortality risk than patients with MSSA infections other than pneumonia, independent of the severity of patients' underlying illnesses.     

Staphylococcus aureus bacteremia in older adults: predictors of 7-day mortality and infection with a methicillin-resistant strain.

OBJECTIVES: To determine the predictors of 7-day mortality in older adult patients with Staphylococcus aureus bacteremia after controlling for comorbidity using the Charlson weighted index of comorbidity (WIC) and to identify the risk factors associated with bacteremia due to methicillin-resistant S. aureus (MRSA). DESIGN. Retrospective cohort study from January 2003 until December 2004. SETTING. Two tertiary care, university-affiliated hospitals. METHODS. One hundred thirty-five hospitalized patients with S. aureus bacteremia were included in the study. All patients who were 60 years or older and had 1 or more blood cultures positive for S. aureus were included in the study. The primary outcome was death 7 days after the onset of S. aureus bacteremia. RESULTS. Twenty-one patients (15.6%) died within 7 days after the onset of S. aureus bacteremia. Seventy-four patients (56.1%) had MRSA bacteremia. Multivariate analysis identified 3 independent determinants of 7-day mortality: Charlson WIC score greater than 5 (odds ratio [OR], 3.6 [95% confidence interval {CI}, 1.1-11.2]; P=.03), previous hospitalization in the past 3 months (OR, 5.0 [95% CI, 1.1-25.1]; P=.04), and altered mental status at the onset of S. aureus bacteremia (OR, 13.6 [95% CI, 2.9-64.6]; P=.001). Multivariate analysis identified previous hospitalization in the past 3 months (OR, 2.6 [95% CI, 1.1-5.9]; P=.02), residence in a long-term care facility (OR, 4.5 [95% CI, 1.7-12.3]; P=.003), and altered mental status at the onset of S. aureus bacteremia (OR, 2.5 [95% CI, 1.5-5.6]; P=.02) to be independently associated with the presence of MRSA. CONCLUSIONS: The Charlson WIC is significantly associated with increased mortality of S. aureus bacteremia in older adults. Previous hospitalization in the past 3 months, residence in a long-term care facility, and altered mental status should be used as a guidance for empirical vancomycin therapy and application of infection control measures in older adults with suspected S. aureus bacteremia.     

Costs of nosocomial pneumonia caused by meticillin-resistant Staphylococcus aureus

Nosocomial infections with meticillin-resistant Staphylococcus aureus (MRSA) lead to increased health and economic costs. The purpose of this study was to determine costs for?nosocomial MRSA pneumonia compared with meticillin-susceptible S. aureus (MSSA) pneumonia. A case-control study was conducted with patients who acquired nosocomial pneumonia?with either MRSA or MSSA between January 2005 and December 2007. Patients were matched for age, severity of underlying disease, stay on intensive care units and non-intensive care units, admission and discharge within the same year, and in-hospital stay at least as long as that of cases before MRSA pneumonia. Our analysis includes 82 patients (41 cases, 41 controls). The overall costs for patients with nosocomial MRSA pneumonia were significantly higher than for patients with MSSA pneumonia (?0,684 vs ?8,731; P=0.01). The attributable costs for MRSA pneumonia per patient were ?7,282 (P<0.001). The financial loss was higher for patients with MRSA pneumonia than for patients with MSSA pneumonia (?1,704 vs ?,662; P=0.002). More cases died than controls while in the hospital (13 vs 1 death, P<0.001). Hospital personnel should be aware of the attributable costs of MRSA pneumonia, and should implement control measures to prevent MRSA transmission.     

A comparison of clinical virulence of nosocomially acquired methicillin-resistant and methicillin-sensitive Staphylococcus aureus infections in a university hospital.

OBJECTIVES: To compare the clinical virulence of nosocomially acquired methicillin-resistant Staphylococcus aureus (MRSA) and methicillin-sensitive S aureus (MSSA) infections in 1989. DESIGN: A retrospective comparison of host factors, in-hospital exposures, sites of infections, and outcomes of patients with nosocomial MRSA and MSSA infections. SETTING: University of Illinois Hospital, Chicago, Illinois. PARTICIPANTS: Forty-four adult patients with nosocomial S aureus infections. RESULTS: The 22 MRSA-infected and 22 MSSA-infected persons were similar regarding mean age, gender, underlying diseases, and exposure to surgery. Before developing infection, MRSA-infected persons were more likely to have received antibiotics (73% compared with 27%, odds ratio = 7.1, 95% confidence interval [CI95] = 2.0-25.8 p = .003) and to have stayed in the hospital > 2 weeks (64% compared with 18%, odds ratio = 7.9, CI95 = 2.0-31.6, p = .002). Bacteremia was the most common presentation in the MRSA and MSSA groups (55% and 59%, respectively). Infectious complications and death were infrequent in both groups. CONCLUSIONS: MRSA and MSSA strains infect patients with similar demographic features and underlying diseases, but MRSA infections are significantly more common among patients with previous antibiotic therapy and a prolonged preinfection hospital stay. Clinical presentations and outcomes did not differ significantly between the 2 groups. Thus, similar to studies in the early 1980s, our findings do not suggest greater intrinsic virulence of MRSA.     

Is methicillin-resistant Staphylococcus aureus more contagious than methicillin-susceptible S. aureus in a surgical intensive care unit?

BACKGROUND AND OBJECTIVE: In the Netherlands, the prevalence of methicillin resistance among Staphylococcus aureus isolates has been kept to less than 1% by using active screening programs and isolation. At the University Medical Center Utrecht (UMCU), an active screening program for methicillin-resistant S. aureus (MRSA) in the surgical intensive care unit (ICU) was implemented in 1986. Between 1992 and 2001, only 6 patients with MRSA were admitted to the surgical ICU. However, 4 of these 6 strains were able to spread to 23 other patients and 15 healthcare workers (HCWs). We were surprised by the epidemic behavior of these strains and wondered whether this was exceptional for S. aureus or whether methicillin-susceptible S. aureus (MSSA) was also spreading in the ICU. DESIGN: A 2-month, prospective, observational study to investigate the incidence and spread of MSSA in the surgical ICU of UMCU and historical data collected during a 10-year period regarding MRSA. SETTING: A 10-bed surgical ICU in a 1,042-bed teaching hospital. RESULTS: Weekly swabs revealed the presence of MSSA in 11 (24%) of 45 patients and 16 (22%) of 72 HCWs. Of all 4,105 patient-HCW contacts, there were only 21 episodes in which both the patient and the HCW were found to carry MSSA. With the use of pulsed-field gel electrophoresis, no identical strains could be identified. CONCLUSION: In our surgical ICU, MRSA seems to spread more easily than MSSA, probably because of selection under antibiotic pressure or a still unknown intrinsic factor within MRSA.     

新生儿病房分离金黄色葡萄球菌耐药性及耐消毒剂基因检测

目的了解新生儿病房送检标本中金黄色葡萄球菌的耐药谱及耐消毒剂基因携带情况。方法收集2013年1—12月某院新生儿病房住院新生儿送检标本分离的金黄色葡萄球菌,采用VITEK2 Compact细菌鉴定分析系统进行细菌鉴定及药敏试验,采用聚合酶链反应(PCR)检测耐消毒剂qacA/B基因。结果新生儿科送检标本中共分离225株金黄色葡萄球菌,主要来源于呼吸道(72.44%)和脐部分泌物(14.33%);耐甲氧西林金黄色葡萄球菌(MRSA)检出率为8.89%(20株);耐药监测中,MRSA的耐药率普遍高于甲氧西林敏感金黄色葡萄球菌(MSSA)。左氧氟沙星、莫西沙星、替加环素、万古霉素、利奈唑胺及呋喃妥因对所有金黄色葡萄球菌均显示出良好的抗菌活性,敏感率均为100%。携带qacA/B基因的金黄色葡萄球菌有21株,阳性率为9.33%,其中MRSA3株(15.00%),MSSA18株(8.78%)。结论新生儿病房分离的MRSA耐药严重,同时携带qacA/B基因,应引起临床重视。     

Antimicrobial susceptibility of Staphylococcus aureus isolated from hospital inpatients, 2009: report from the Australian Group on Antimicrobial Resistance

In 2009, the Australian Group on Antimicrobial Resistance (AGAR) conducted a period-prevalence survey of clinical Staphylococcus aureus isolated from hospital inpatients. Thirty medical microbiology laboratories from each state and mainland territory participated. Specimens were collected more than 48 hours post-admission. Isolates were tested by Vitek2 (AST-P579 card) and by Etest for daptomycin. Nationally, the proportion of S. aureus that were MRSA was 33.6%, ranging from 27.3% in South Australia to 41.4% in New South Wales/Australian Capital Territory. Resistance to the non-beta-lactam antimicrobials was common except for rifampicin, fusidic acid, daptomycin and high-level mupirocin. No resistance was detected for vancomycin, teicoplanin, quinupristin-dalfopristin or linezolid. Resistance in the methicillin susceptible S. aureus (MSSA) was rare apart from erythromycin (12%) and absent for vancomycin, teicoplanin, daptomycin, quinupristin-dalfopristin and linezolid. The proportion of methicillin resistant S. aureus (MRSA) has remained stable since the first AGAR inpatient survey in 2005 yet during the same time frame resistance to many antimicrobials, in particular tetracycline, trimethoprim-sulphamethoxazole and gentamicin, has significantly decreased. This suggests that non-multi-resistant community-associated MRSA (CA-MRSA) clones are becoming more common in the hospital setting and replacing the long-established multi-resistant clones such as ST239-III (Aus 2/3 EMRSA). Given hospital outbreaks of CA-MRSA are thought to be extremely rare it is most likely that patients colonised at admission with CA-MRSA have become infected with the colonising strain during their hospital stay.     

Antimicrobial resistance in Staphylococcus aureus at the University of Chicago Hospitals: a 15-year longitudinal assessment in a large university-based hospital.

OBJECTIVES: To describe a longitudinal profile of resistance to beta-lactam antimicrobials among isolates of Staphylococcus aureus at a large university teaching hospital and to evaluate the impact of the methicillin resistance phenotype on resistance trends for non-beta-lactam antimicrobials. DESIGN: Retrospective evaluation of antimicrobial susceptibility data for all 17,287 S. aureus isolates obtained from January 1986 through December 2000. SETTING: The University of Chicago Hospitals, a family of tertiary-care, university-affiliated hospitals in Chicago, Illinois, consisting of 547 adult and pediatric beds. RESULTS: The annual rate of resistance to methicillin increased from 13% in 1986 to 28% in 2000 (P < .001) and has not plateaued. For each non-beta-lactam antimicrobial tested, the annual rates of resistance were far higher among methicillin-resistant S. aureus (MRSA) isolates than among methicillin-susceptible S. aureus (MSSA) isolates. The annual rates of resistance to the macrolide, lincosamide, and streptogramin (MLS) antimicrobials erythromycin and clindamycin increased among MSSA isolates (P < .01), but remained lower than 20%. Resistance to the MLS antimicrobials was higher among MRSA isolates (higher than 60%), but the annual rate decreased significantly during the study (P < .01). CONCLUSION: The prevalence of methicillin resistance among S. aureus isolates has continued to increase; resistance to non-beta-lactam antimicrobials is far more common among MRSA isolates. Recent decreases in the proportion of MRSA isolates resistant to non-beta-lactam antimicrobials suggest important changes in the epidemiology of this pathogen.     

Enterotoxin and toxic shock syndrome toxin-1 production of methicillin resistant and methicillin sensitive Staphylococcus aureus strains

In this study the production of enterotoxin A-D and toxic shock syndrome toxin-1 (TSST-1) of 181 methicillin resistant (MRSA) and 100 methicillin sensitive (MSSA) Staphylococcus aureus first isolates from different patients was investigated. All the MRSA- and MSSA isolates in the study were collected in a period between 1993 and 1995 from specimens sent from 11 different acute care hospitals in the greater Düsseldorf area. As far as possible the isolates were matched according to ward and hospital. The isolates were collected in the same time period and matched for specimen from which isolated. Furthermore, only first isolates were analysed in both groups. No significant difference in the production of toxin of any type between MRSA and MSSA could be detected (51 and 40% respectively). When the individual toxins were analysed, again no significant difference between MRSA and MSSA was demonstrable (enterotoxin production by MRSA 40% and MSSA 36%, and TSST-1 16% and 8% respectively). Despite this, a slight tendency for MRSA to produce enterotoxin A and B and for MSSA to produce enterotoxin C was observed. In addition, generation of TSST-1 by both groups was independent of enterotoxin A-D production. Interestingly, no increase in the proportion of TSST-1- or enterotoxin-producing MRSA and MSSA isolates was observed in strains isolated from blood cultures from patients with a clinical diagnosis of sepsis. Genotypical pulsed-field-gel-electrophoresis (PFGE) and phenotypical (bacteriophage typing, lysotyping) characterization of the 181 MRSA isolates resulted in 28 different PFGE patterns (of which 19 were toxin producers) and 22 lysotyping groups (18 of which produced toxin). In summary, the investigated clinical S. aureus isolates showed no difference in their ability to produce toxin and this was independent of their sensitivity to methicillin.