Prevalence of and risk factors for colonization with methicillin-resistant Staphylococcus aureus at the time of hospital admission.

OBJECTIVES: To determine the prevalence of methicillin-resistant Staphylococcus aureus (MRSA) colonization among patients presenting for hospital admission and to identify risk factors for MRSA colonization. DESIGN: Surveillance cultures were performed at the time of hospital admission to identify patients colonized with S. aureus. A case-control study was performed to identify risk factors for MRSA colonization. SETTING: A tertiary-care academic medical center. PATIENTS: Adults presenting for hospital admission (N = 974). RESULTS: S. aureus was isolated from 205 (21%) of the patients for whom cultures were performed. Methicillin-sensitive S. aureus was isolated from 179 (18.4%) of the patients, and MRSA was isolated from 26 (2.7%) of the patients. All 26 MRSA-colonized patients had been admitted to a healthcare facility in the preceding year, had at least one chronic illness, or both. In multivariate analyses comparing MRSA-colonized patients with control-patients, admission to a nursing home (odds ratio [OR], 16.5; 95% confidence interval [CI95], 1.4 to 192.1; P = .025) or a hospitalization of 5 days or longer during the preceding year (OR, 3.91; CI95, 1.1 to 13.9; P = .035) were independent predictors of MRSA colonization. CONCLUSIONS: Patients colonized with MRSA admitted to this hospital likely acquired the organism during previous encounters with healthcare facilities. There was no evidence that MRSA colonization occurs commonly among low-risk individuals in this community. These data suggest that evaluation of recent healthcare exposures is essential if true community acquisition of MRSA is to be confirmed.     

Prevalence of and risk factors for methicillin-resistant Staphylococcus aureus carriage at hospital admission.

To determine the prevalence of and risk factors for methicillin-resistant Staphylococcus aureus (MRSA) carriage at the time of admission to our hospital, we screened the medical records of 1,128 patients for demographic and clinical data. The antimicrobial resistance pattern and genotype of MRSA isolates were studied. The prevalence of MRSA carriage at hospital admission was 1.4%. Older patients and patients previously admitted to healthcare centers were the most likely to have MRSA carriage at admission.     

Estimation of methicillin-resistant Staphylococcus aureus transmission by considering colonization pressure at the time of hospital admission

Our objective was to evaluate the accuracy of a methicillin-resistant Staphylococcus aureus (MRSA) rate using the imported MRSA reservoir identified at the time of hospital admission. Two indicators were used: the number of imported MRSA patient-days/total number of patient-days [representing colonization pressure (CP) at the time of admission] and the incidence of hospital-acquired MRSA isolated from clinical samples expressed as density/100 patient-days for carriers identified at the time of admission [representing the incidence taking CP into account (ICP)]. The variations of these indicators were analysed and compared with two more common indicators: percentage of MRSA acquired in our hospital and the incidence of hospital-acquired MRSA isolated from clinical samples expressed as density/1000 patient-days within three four-month periods during 2002. Common indicators varied similarly, with marked decline during the third period; first-period CP was twice that of other periods (P<10(-6)) and the highest (>two-fold) ICP was seen in the summer (second) period (P<0.001) when the personnel/patient ratio was the lowest. Thus, comparison of different indicators within four-month periods underlines important differences between common and novel indicators. Despite several limitations, ICP should be helpful in the interpretation of MRSA surveillance data, particularly for estimating the extent of MRSA transmission.     

Epidemiology of methicillin-resistant Staphylococcus aureus colonization in a surgical intensive care unit.

BACKGROUND: Methicillin-resistant Staphylococcus aureus (MRSA) is a cause of healthcare-associated infections among surgical intensive care unit (ICU) patients, though transmission dynamics are unclear. OBJECTIVE: To determine the prevalence of MRSA nasal colonization at ICU admission, to identify associated independent risk factors, to determine the value of these factors in active surveillance, and to determine the incidence of and risk factors associated with MRSA acquisition. DESIGN: Prospective cohort study. SETTING: Surgical ICU at a teaching hospital. PATIENTS: All patients admitted to the surgical ICU. RESULTS: Active surveillance for MRSA by nasal culture was performed at ICU admission during a 15-month period. Patients who stayed in the ICU for more than 48 hours had nasal cultures performed weekly and at discharge from the ICU, and clinical data were collected prospectively. Of 1,469 patients, 122 (8%) were colonized with MRSA at admission; 75 (61%) were identified by surveillance alone. Among 775 patients who stayed in the ICU for more than 48 hours, risk factors for MRSA colonization at admission included the following: hospital admission in the past year (1-2 admissions: adjusted odds ratio [aOR], 2.60 [95% confidence interval {CI}, 1.47-4.60]; more than 2 admissions: aOR, 3.56 [95% CI, 1.72-7.40]), a hospital stay of 5 days or more prior to ICU admission (aOR, 2.54 [95% CI, 1.49-4.32]), chronic obstructive pulmonary disease (aOR, 2.16 [95% CI, 1.17-3.96]), diabetes mellitus (aOR, 1.87 [95% CI, 1.10-3.19]), and isolation of MRSA in the past 6 months (aOR, 8.18 [95% CI, 3.38-19.79]). Sixty-nine (10%) of 670 initially MRSA-negative patients acquired MRSA in the ICU (corresponding to 10.7 cases per 1,000 ICU-days at risk). Risk factors for MRSA acquisition included tracheostomy in the ICU (aOR, 2.18 [95% CI, 1.13-4.20]); decubitus ulcer (aOR, 1.72 [95% CI, 0.97-3.06]), and receipt of enteral nutrition via nasoenteric tube (aOR, 3.73 [95% CI, 1.86-7.51]), percutaneous tube (aOR, 2.35 [95% CI, 0.74-7.49]), or both (aOR, 3.33 [95% CI, 1.13-9.77]). CONCLUSIONS: Active surveillance detected a sizable proportion of MRSA-colonized patients not identified by clinical culture. MRSA colonization on admission was associated with recent healthcare contact and underlying disease. Acquisition was associated with potentially modifiable processes of care.     

Prevalence of nasal colonization with methicillin-resistant Staphylococcus aureus in selected patient populations.

Methicillin-resistant Staphylococcus aureus nasal colonization was investigated in patients arriving for elective cardiovascular surgery, renal patients admitted for arteriovenous graft surgery, and patients transferred to our hospital from other institutions. Renal patients were significantly more likely to be colonized and represent a potential source of MRSA to our institution.     

Prevalence of community-acquired methicillin-resistant Staphylococcus aureus colonization in a random sample of healthy individuals.

BACKGROUND: Concern has recently arisen that the prevalence of methicillin-resistant Staphylococcus aureus (MRSA) colonization among populations at low risk for acquiring this pathogen has been increasing. Although previous studies have reported on the prevalence of MRSA colonization, most of these studies have been performed in healthcare settings, with few studies performed in the community among healthy individuals in non-healthcare locations. OBJECTIVES: To determine the prevalence of community-acquired (CA) MRSA colonization in a random sample of healthy individuals in 4 non-healthcare locations and to compare the genetic similarity between these CA isolates and nosocomial MRSA isolates. DESIGN: Prospective, observational study conducted from October 2004 through February 2005. SETTING: Two colleges, 1 church, and 1 restaurant in Newark and Wilmington, Delaware. PARTICIPANTS: A total of 295 healthy volunteers. RESULTS: The rate of S. aureus colonization was 26.8%. Of the 79 S. aureus isolates analyzed, 3 (4%) were resistant to methicillin. Ribotyping of the 3 MRSA isolates showed that they were genetically distinct from each other. Each of the 3 CA isolates were genetically indistinguishable from 3 different nondominant clusters of MRSA isolates found in the medical and surgical intensive care units of Christiana Care Health System (Newark) and Wilmington Hospital (Wilmington). CONCLUSION: The overall prevalence of CA-MRSA colonization in a random sample of healthy individuals in 4 non-healthcare locations in Newark and Wilmington was 1.0%. Despite concerns that the prevalence of MRSA colonization is increasing, it still remains relatively low in our community, perhaps because CA-MRSA colonization tends to occur in clusters.     

Modeling transmission of methicillin-resistant Staphylococcus aureus among patients admitted to a hospital.

OBJECTIVE: To determine the impact of the screening test, nursing workload, handwashing rates, and dependence of handwashing on risk level of patient visit on methicillin-resistant Staphylococcus aureus (MRSA) transmission among hospitalized patients. SETTING: General medical ward. METHODS: Monte Carlo simulation was used to model MRSA transmission (median rate per 1,000 patient-days). Visits by healthcare workers (HCWs) to patients were simulated, and MRSA was assumed to be transmitted among patients via HCWs. RESULTS: The transmission rate was reduced from 0.89 to 0.56 by the combination of increasing the sensitivity of the screening test from 80% to 99% and being able to report results in 1 day instead of 4 days. Reducing the patient-to-nurse ratio from 4.3 in the day and 6.8 at night to 3.8 and 5.7, respectively, reduced the number of nosocomial infections from 0.89 to 0.85; reducing the ratio to 1 and 1, respectively, further reduced the number of nosocomial infections to 0.32. Increases in handwashing rates by 0%, 10%, and 20% for high-risk visits yielded reductions in nosocomial infections similar to those yielded by increases in handwashing rates for all visits (0.89, 0.36, and 0.24, respectively). Screening all patients for MRSA at admission reduced the transmission rate to 0.81 per 1,000 patient-days from 1.37 if no patients were screened. CONCLUSION: Within the ranges of parameters studied, the most effective strategies for reducing the rate of MRSA transmission were increasing the handwashing rates for visits involving contact with skin or bodily fluid and screening patients for MRSA at admission.     

Prevalence of nasal colonization among patients with community-associated methicillin-resistant Staphylococcus aureus infection and their household contacts.

OBJECTIVE: To evaluate the prevalence of colonization among patients with community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) infection and their household contacts. DESIGN: Prospective, observational laboratory study of nasal colonization among patients and their household members from September 15, 2004, to February 20, 2006. SETTING: A 600-bed, urban, academic medical center. PATIENTS: Fifty-one patients who presented with CA-MRSA infections and 49 household members had cultures of nasal swab specimens performed. RESULTS: Skin and soft-tissue infections were seen in 50 patients (98%) and 2 household members. Twenty-one (41%) of 51 patients and 10 (20%) of 49 household members were colonized with MRSA. An additional 5 patients (10%) and 12 household members (24%) were colonized with methicillin-susceptible Staphylococcus aureus. Most MRSA isolates (95%; infective and colonizing) carried the staphylococcal cassette chromosome mec type IV complex, and 67% represented a single clone, identical to USA 300. Of the colonized household members, 5 had isolates related to the patients' infective isolate. CONCLUSIONS: The frequency of CA-MRSA colonization among household members of patients with CA-MRSA infections is higher than rates reported among the general population. Among colonized household members, only half of the MRSA strains were related to the patients' infective isolate. Within the same household, multiple strains of CA-MRSA may be present.     

National hospital infection surveillance on methicillin-resistant Staphylococcus aureus

Surveillance of methicillin-resistant Staphylococcus aureus (MRSA) infections in Japan was performed in 1995 and 1996. Hospital infection rates of MRSA appear to have remained stable in recent years, and this study was undertaken to test this hypothesis. In national surveillance, the incidence of MRSA hospital infections per 100 admissions remained stable at between 0.7 and 0.8 from 1999 to 2003, with a tendency towards a slight decline. This study shows that precautions against MRSA infection in Japan may prove to be an effective preventive measure.     

住院患者耐甲氧西林金黄色葡萄球菌定植与感染相关研究

目的调查住院患者耐甲氧西林金黄色葡萄球菌（MRSA）定植及感染的状况，分析MRSA定植与感染的关系。方法对某大医院神经内科住院患者在入院48h内及以后每周一、三、五采集鼻前庭标本，同时收集该期间住院患者送检临床标本中分离的MRSA菌株。以低频限制性位点聚合酶链反应（IRS—PCR）基因分型法对患者鼻前庭标本和临床标本分离的MRSA菌株进行同源性分析。结果共调查265例患者，MRSA定植者14例（5．28％），其中7例为入院前定植，7例为入院后定植；MRSA感染者10例（3．77％），其中8例的鼻前庭标本和临床标本均分离出MRSA，另2例仅临床标本分离出MRSA。IRS—PCR基因分型显示MRSA感染患者临床标本和鼻前庭标本分离出的MRSA具有很高的同源性。结论住院患者定植MRSA是发生MRSA医院感染的一个重要危险因素。     

Prevalence of methicillin-resistant Staphylococcus aureus carriage at the time of admission in two acute geriatric wards

Studies on methicillin-resistant Staphylococcus aureus (MRSA) in the elderly have been concerned with patients hospitalized in nursing homes or long-term care facilities. Our objective was to estimate the prevalence of MRSA at the time of admission in two acute geriatric wards with high endemic MRSA incidence in a French teaching hospital. A prospective screening of MRSA carriers was conducted by swabbing nares and wounds during five weeks for all patients on the day of admission. For each patient demographic, administrative, clinical and therapeutic data were recorded. Their associations with MRSA carriage were studied by logistic regression analysis. On the day of admission, 35 patients (14.6%) were MRSA carriers. Variables independently associated with carriage were hospitalization within the six last months (OR = 4.64; P < 0.001) and the existence of wounds or bedsores (OR = 2.864; P = 0.02). The high prevalence of MRSA carriage at the time of admission could explain in part the high incidence of MRSA in these wards. A systematic selective screening targeted on patients with high risk of carriage should be helpful to implement barrier precautions and reduce cross-transmission.     

Evaluation of a strategy of screening multiple anatomical sites for methicillin-resistant Staphylococcus aureus at admission to a teaching hospital.

We compared the sensitivity of screening with nasal culture alone with that of a multiple-site screening method for the identification of carriers of methicillin-resistant Staphylococcus aureus at hospital admission. If nasal cultures alone had been used during the 1-year study, 27.0% of carriers of methicillin-resistant S. aureus would have been missed, which corresponds to 560 theoretical isolation days. If rectal screening had not been used, 431 theoretical isolation days would have been missed, and, if axillary screening had not been used, 99 theoretical isolation days would have been missed.     

耐甲氧西林金黄色葡萄球菌感染与定植危险因素分析

目的通过对耐甲氧西林金黄色葡萄球菌(MRSA)感染与定植病例的调查,探讨医院MRSA感染与定植的危险因素及防治策略。方法选取MRSA感染与定植病例80例患者临床资料,采用流行病学研究方法,根据综述、专家咨询以及实际工作经验,最终确定变量进行危险因素分析;通过EPIDATA3.02软件进行数据录入;使用SPSS16.0软件对数据进行统计分析,应用χ2检验对定性资料进行单因素分析,应用非条件logistic回归分析进行多因素分析。结果纳入单因素分析的变量共12个,经过统计分析,筛选出8个变量进入多因素logistic回归模型;调整了年龄、性别、基础疾病的影响后,抗菌药物使用时间≥14d、抗菌药物使用种类≥3种、住院天数≥30d是独立的危险因素;抗菌药物使用≥14d与<14d的感染或定植率分别为89.3%和28.8%、抗菌药物使用种类≥3种与<3种的感染或定植率分别91.3%和33.3%、住院天数≥30d与<30d的感染或定植率分别为50.8%和47.6%;3种危险因素的OR值(95%CI)分别为28.887(19.103～33.237)、21.194(18.156～29.993)、18.142(13.782～27.104)。结论抗菌药物长期使用、联合使用、长期住院是MRSA感染与定植的危险因素,应根据患者病情特点,积极采取预防控制措施,防止耐药菌的产生和传播。     

Prevalence of Staphylococcus aureus and methicillin-resistant Staphylococcus aureus (MRSA) on retail meat in Iowa

Several recent studies have indicated a high prevalence of methicillin-resistant Staphylococcus aureus (MRSA) in retail-available meat. However, few studies have investigated MRSA in meat in the United States. The aim of this study was to determine the presence of Staphylococcus aureus (S. aureus) on meat samples available at retail stores. Samples of fresh raw pork, chicken, beef, and turkey were purchased from 22 food stores throughout Iowa. S. aureus strains were isolated from 27 of 165 samples, giving an overall prevalence of 16.4%. Turkey, pork, chicken, and beef had individual S. aureus prevalence rates of 19.4%, 18.2%, 17.8%, and 6.9%, respectively. Two isolates of MRSA were isolated from pork, giving an overall prevalence of 1.2%. One MRSA isolate was positive for the PVL gene. Common spa types included t034, t337, t008, and t002. These results suggest that MRSA is present on low numbers of retail meat in Iowa.     

Effects of tea catechin inhalation on methicillin-resistant Staphylococcus aureus in elderly patients in a hospital ward

We investigated the effects of inhalation of tea catechin on MRSA in the 24 elderly in patients, who were known to carry MRSA in sputum. The patients in the catechin group (N=12) were administered an inhalation of tea catechin extracts (in saline/bromhexine) (3.7 g/L catechins, 43% of them are composed of epigallocatechin gallate), three times daily with hand nebulizer for four weeks. The clinical effects were compared with the control group (N=12) who were given an inhalation of saline/bromhexine alone. After a week of the course, the numbers of the patients with decreased or disappearance of MRSA in their sputum was significantly higher in the catechin group, compared with that in the control group (seven vs. no patients; P<0.05). The number of patients discharged during the study was significantly increased, and the days of hospital stay were significantly decreased in the catechin group compared with those in the control group (six vs. one patient; P<0.05, 51+/-22 vs. 85+/-50 days, mean+/-S.D.;P <0.05, respectively). No adverse effects were observed in any patients during the study. Catechin inhalation seemed to be safe, and at least temporarily effective in the reduction of MRSA and shortening of hospitalization.     

Epidemiology of methicillin-resistant Staphylococcus aureus at a children's hospital.

OBJECTIVE: To describe the relative contribution of and risk factors for both community-acquired and nosocomial methicillin-resistant Staphylococcus aureus (MRSA) infections. DESIGN: Retrospective cohort study. SETTING: 270-bed, tertiary-care children's hospital. PARTICIPANTS: All MRSA-infected children from whom MRSA was recovered between October 1, 1999, and September 30, 2001. METHODS: Demographic, clinical, and risk factor data were abstracted from medical records. Categorical variables were analyzed using the chi-square or Fisher's exact test and continuous variables were analyzed using the Mann-Whitney test. RESULTS: Of the 62 patients with new MRSA infection, 37 had community-acquired MRSA and 25 had nosocomial MRSA. Most community-acquired MRSA infections were of the skin and soft tissue, the middle ear, and the lower respiratory tract. Nosocomial MRSA infections occurred in the lower respiratory tract, the skin and soft tissue, and the blood. Risk factors for infection, including underlying medical illness, prior hospitalization, and prior surgery, were similar for patients with community-acquired MRSA and nosocomial MRSA. History of central venous catheterization and previous endotracheal intubation was more common in patients with nosocomial MRSA. Only 3 patients with community-acquired MRSA had no identifiable risk factor other than recent antibiotic use. Resistance for clindamycin, erythromycin, and levofloxacin was similar between strains of community-acquired MRSA and nosocomial MRSA. CONCLUSIONS: Similarities in patient risk factors and resistance patterns of isolates of both community-acquired and nosocomial MRSA suggest healthcare acquisition of most MRSA. Thus, classifying MRSA as either community acquired or nosocomial underestimates the amount of healthcare-associated MRSA.     

Outbreak of methicillin-resistant Staphylococcus aureus in a German tertiary-care hospital.

A biphasic outbreak of methicillin-resistant Staphylococcus aureus in intensive-care units of a German tertiary-care hospital afflicted 89 patients within 4 years. The spread of the outbreak most likely was facilitated by the contamination of mobile radiograph equipment. The outbreak was controlled by measures of hospital hygiene.