Risk Factors For Methicillin-resistant Staphylococcus Aureus Acquisition Research Articles

SCC mec typing among the clinical isolates of Methicillin Resistant Staphylococcus aureus (MRSA) from a Tertiary Care Hospital, Puducherry

Introduction: Methicillin resistance is exhibiteddue to presence of mecA gene and is commonly referred as SCCmec types in MRSA. SCCmec typing helps and acts a way to characterize MRSA infections and gain knowledge in its epidemiology. Our study aims to characterize mecA gene responsible in methicillin resistance by SCCmec typing and emphasize the use of SCCmec typing in routine diagnosis for the classification of MRSA. Methods: A total of 191 clinical isolates were included for the study.Documentation like clinical details and associated risk factors for MRSA acquisition were done. SCCmec typing (type I-V) was done by using M-PCR as per Boyeet al., 2007 protocol. Results: In our study, five different SCCmec types namely SCCmec type I, type II, type III, type IV and type V were detected among the clinical isolates of MRSA. Sccmec type V (53%) was found to be the most predominant type followed by SCCmec type III (47%) and SCCmec type IV (37.6%). Among the 191 MRSA isolates, 7 clinical isolates were SCCmec non-typeable isolates. Conclusion: Our study reports existence of multiple SCCmec types among the MRSA clinical isolates. SCCmec typing is helpful in determining the contribution of the isolates in understanding their association being CA-MRSA or HA-MRSA which in turn helps in designing effective surveillance and control strategies in the management of MRSA infections.

Existence of multiple SCCmec elements in clinical isolates of methicillin-resistant Staphylococcus aureus.

Methicillin-resistant Staphylococcus aureus (MRSA) can be classified into hospital-acquired MRSA (HA-MRSA) and community-associated MRSA (CA-MRSA), based on the associated epidemiological risk factors and their SCCmec types. We therefore studied the diversity and distribution of SCCmec elements among MRSA isolates in our region and also evaluated SCCmec typing as a tool for the classification of MRSA. Two hundred isolates of MRSA obtained from various clinical specimens were included. The clinical and demographic details of the patients and the epidemiological risk factors for MRSA acquisition were documented. Multiplex PCR was optimized for all the major SCCmec types (I to V). Subtyping of SCCmec type IV (IVb, IVc, IVd, IVh) was carried out by simplex PCR. Based on epidemiological criteria, CA-MRSA constituted 57 % (114/200) of the the test isolates and HA-MRSA made up 43 % (86/200). The predominant SCCmec type found in our study was type III (62%), followed by type V (52.5%) and type I (47.5%), while type II was carried by a single isolate. Of the 200 isolates, 118 carried multiple SCCmec types and 3 were non-typable. The existence of multiple SCCmec types in individual MRSA isolates resulted in our inability to categorize many of these isolates as either CA-MRSA or HA-MRSA as defined by the SCCmec type criterion. The major limitation of the study was that the SCC mec element of MRSA isolates exhibiting multiple types was not sequenced and hence this finding could not be confirmed.

Nasal carriage of sequence type 22 MRSA and livestock-associated ST398 clones in Tangier, Morocco.

This study aimed to provide data of Staphylococcus aureus and methicillin-resistant Staphylococcus aureus (MRSA) nasal carriage as well as to determine the genetic lineages of this circulating MRSA in the Tangier community. Between 2012 and 2013 two subpopulations consisting of randomly chosen healthy volunteers and outpatients in 11 healthcare facilities were screened. The antibiotic resistance phenotype was determined by disk diffusion. Toxin Panton-Valentin Leukocidin (PVL), toxic shock syndrome toxin-1 gene (tst), and mecA were detected by polymerase chain reaction (PCR). Nasal swabs were obtained from persons with no identified risk factors for MRSA acquisition. MRSA molecular typing was performed by pulsed-field gel electrophoresis (PFGE), staphylococcal chromosomal cassette mec, and Staphylococcus protein A (spa) typing. A total of400 subjects (33.3%) were nasally colonized with S. aureus, and 17 (1.4%) were nasal carriers of MRSA. The analysis did not identify age, gender, and the two subpopulations as predictors for MRSA colonization. MRSA were more likely to harbor the tst gene (p < 0.05). This work highlighted a low prevalence of nasal MRSA carriage, with 52.94% belonging to sequence type (ST) ST22. The remaining isolates were distributed as singletons (ST8, ST1, and ST398), whereas approximately one-third of MRSA was not identified, including three novel spa-types (t13247, t13248, and t13249). Although we highlighted the current clones present in the Tangier community, they are limited in space and time. Therefore, further studies would be required to obtain a comprehensive picture of the dissemination of MRSA in the community, hospital, and livestock.

Are cases of Methicillin-resistant Staphylococcus aureus clonal complex (CC) 398 among humans still livestock-associated?

Methicillin-resistant Staphylococcus aureus (MRSA) of clonal complex (CC) 398 are widespread among pigs, cattle and poultry as well as among humans who have contact to these livestock animals. However, there is limited data on livestock-independent dissemination of MRSA CC398 in the general population. MethodsIn this case–control study MRSA isolates derived (between July 2013 and June 2014) from patients of four hospitals located in a livestock-dense region were S. aureus protein A (spa) typed and risk factors for MRSA acquisition were assessed from patients colonized or infected with MRSA CC398 vs. other MRSA molecular types (MRSA non-CC398). ResultsOf 384 patients, 21% were colonized with MRSA CC398. Contact with livestock (Odds Ratio (OR) 46.03) and residence directly on a pig farm (OR 12.82) were associated with MRSA CC398. Of 55 patients with MRSA CC398, 21 (38%) did not report direct livestock contact. Among the latter we identified several risk factors that could have facilitated indirect transmission, such as living on farms (without being farmer), private contact with known MRSA carriers or previous hospitalization. DiscussionThis study suggests that MRSA CC398 is still mostly disseminated via direct contact to livestock. However, a substantial proportion of patients seem to acquire MRSA CC398 via other pathways.

Fluoroquinolone use is a risk factor for methicillin-resistant Staphylococcus aureus acquisition in long-term care facilities: a nested case-case-control study.

Methicillin-resistant Staphylococcus aureus (MRSA) nasal colonization is a well-established risk factor for subsequent infection and a key event in interindividual transmission. Some studies have showed an association between fluoroquinolones and MRSA colonization or infection. The present study was performed to identify specific risk factors for MRSA acquisition in long-term care facilities (LTCFs). A prospective cohort of patients naive for S. aureus colonization was established and followed (January 2008 through October 2010) in 4 French LTCFs. Nasal colonization status and potential risk factors were assessed weekly for 13 weeks after inclusion. Variables associated with S. aureus acquisition were identified in a nested-matched case-case-control study using conditional logistic regression models. Cases were patients who acquired MRSA (or methicillin-sensitive S. aureus [MSSA]). Patients whose nasal swab samples were always negative served as controls. Matching criteria were center, date of first nasal swab sample, and exposure time. Among 451 included patients, 76 MRSA cases were matched to 207 controls and 112 MSSA cases to 208 controls. Multivariable analysis retained fluoroquinolones (odds ratio, 2.17; 95% confidence interval, 1.01-4.67), male sex (2.09; 1.10-3.98), and more intensive care at admission (3.24; 1.74-6.04) as significantly associated with MRSA acquisition, and body-washing assistance (2.85; 1.27-6.42) and use of a urination device (1.79; 1.01-3.18) as significantly associated with MSSA acquisition. Our results suggest that fluoroquinolones are a risk factor for MRSA acquisition. Control measures to limit MRSA spread in LTCFs should also be based on optimization of fluoroquinolone use.

Staphylococcus, not MRSA? A Final Report of Carriage and Conversion Rates in Nursing Students

To evaluate and characterize staphylococcal carriage, possibly including methicillin-resistant Staphylococcus aureus (MRSA), and conversion rates in nursing students across clinical semester rotations and to describe risk factors. A prospective longitudinal cohort design with six times of measurement. Data collected August 2010 to May 2012. Institutional Review Board approval (2010F5693). Texas State University, San Marcos, TX. Eighty-seven nursing students. A positive MRSA swab was considered an end point for participation. Intervention offered was bactroban (mupirocin) for nasal decolonization and an oral antibiotic, doxycycline; follow-up post treatment collection sample was done to verify decolonization prior to next clinical rotation. Screening for Staphylococcus aureus and MRSA identification; confirmation and antibiotic susceptibility by Vitek 2; self-administered questionnaires delineating demographics and risk factors; panel logistic regression models by Stata version 13. MRSA colonization did not increase. S. aureus incidence was 17.7 - 26.4%. Staphylococcal species incidence other than S. aureus increased (9.2 - 82.3%). The following odds ratio (OR) associations were found to be statistically significant: boil or skin infections with S. aureus (OR = 2.94, p < .01), working or volunteering in a healthcare facility odds with species other than S. aureus (OR = 4.41, p < .01) and gym and sports facilities odds with S. other (OR 2.45, p < .01). The most frequently occurring species at Wave 5 was S. hominis (21 isolates) while the most frequently occurring species at Wave 6 was S. epidermidis (25 isolates). MRSA colonization did not increase during longitudinal study. S. aureus colonization remained fairly stable throughout the study (17 - 26%). Species colonization with non S. aureus species (e.g. S. hominis, S. epidermis, S. haemolyticus) increased significantly (9.2 - 82.3%) during clinical rotations. Knowledge of infection control and compliance may have contributed to an absence of MRSA colonization; however, the colonization by other staphylococci has been shown to be a risk factor for MRSA acquisition.

First Outbreak with MRSA in a Danish Neonatal Intensive Care Unit: Risk Factors and Control Procedures

IntroductionThe purpose of the study was to describe demographic and clinical characteristics and outbreak handling of a large methicillin-resistant Staphylococcus aureus (MRSA) outbreak in a neonatal intensive care unit (NICU) in Denmark June 25th–August 8th 2008, and to identify risk factors for MRSA transmission.MethodsData were collected retrospectively from medical records and the Danish Neobase database. All MRSA isolates obtained from neonates, relatives and NICU health care workers (HCW) as well as environmental cultures were typed.ResultsDuring the 46 day outbreak period, 102 neonates were admitted to the two neonatal wards. Ninety-nine neonates were subsequently sampled, and 32 neonates (32%) from 25 families were colonized with MRSA (spa-type t127, SCCmec V, PVL negative). Thirteen family members from 11 of those families (44%) and two of 161 HCWs (1%) were colonized with the same MRSA. No one was infected. Five environmental cultures were MRSA positive. In a multiple logistic regression analysis, nasal Continuous Positive Airway Pressure (nCPAP) treatment (p = 0.006) and Caesarean section (p = 0.016) were independent risk factors for MRSA acquisition, whereas days of exposure to MRSA was a risk factors in the unadjusted analysis (p = 0.04).ConclusionsMRSA transmission occurs with high frequency in the NICU during hospitalization with unidentified MRSA neonates. Caesarean section and nCPAP treatment were identified as risk factors for MRSA colonization. The MRSA outbreak was controlled through infection control procedures.

Methicillin-Resistant Staphylococcus aureus (MRSA) Nasal Carriage in Residents of Veterans Affairs Long-Term Care Facilities: Role of Antimicrobial Exposure and MRSA Acquisition

To identify risk factors associated with methicillin-resistant Staphylococcus aureus (MRSA) acquisition in long-term care facility (LTCF) residents. Multicenter, prospective cohort followed over 6 months. Three Veterans Affairs (VA) LTCFs. All current and new residents except those with short stay (<2 weeks). MRSA carriage was assessed by serial nares cultures and classified into 3 groups: persistent (all cultures positive), intermittent (at least 1 but not all cultures positive), and noncarrier (no cultures positive). MRSA acquisition was defined by an initial negative culture followed by more than 2 positive cultures with no subsequent negative cultures. Epidemiologic data were collected to identify risk factors, and MRSA isolates were typed by pulsed-field gel electrophoresis (PFGE). Among 412 residents at 3 LTCFs, overall MRSA prevalence was 58%, with similar distributions of carriage at all 3 facilities: 20% persistent, 39% intermittent, 41% noncarriers. Of 254 residents with an initial negative swab, 25 (10%) acquired MRSA over the 6 months; rates were similar at all 3 LTCFs, with no clusters evident. Multivariable analysis demonstrated that receipt of systemic antimicrobials during the study was the only significant risk factor for MRSA acquisition (odds ratio, 7.8 [95% confidence interval, 2.1-28.6]; P = .002). MRSA strains from acquisitions were related by PFGE to those from a roommate in 9/25 (36%) cases; 6 of these 9 roommate sources were persistent carriers. MRSA colonization prevalence was high at 3 separate VA LTCFs. MRSA acquisition was strongly associated with antimicrobial exposure. Roommate sources were often persistent carriers, but transmission from roommates accounted for only approximately one-third of MRSA acquisitions.

Methicillin-resistant Staphylococcus aureus nasal colonization among adult patients visiting emergency department in a medical center in Taiwan.

BackgroundWithin the past 10 years, methicillin-resistant Staphylococcus aureus (MRSA) has not only been a hospital pathogen but also a community pathogen. To understand the carriage rate of methicillin-resistant Staphylococcus aureus (MRSA) among the adult patients visiting emergency department (ED), we conducted this study.Methodology/Principal FindingsFrom May 21 to August 12, 2009, a total of 502 adult patients visiting emergency department (ED) of a tertiary care hospital in northern Taiwan were recruited in this study and surveyed for nasal carriage of MRSA. A questionnaire regarding the risk factors for MRSA acquisition was also obtained.The overall prevalence of MRSA nasal carriage among the patients was 3.8%. The carriage rate was significantly higher in patients with risk factors for MRSA acquisition (5.94%) than those without risk factors (2.12%). Patients with urinary complaints, diabetes mellitus, chronic kidney disease and current percutaneous tube usage were significantly associated with MRSA colonization. By multiple logistic regression analysis, only current usage of catheters or tubes was the independent predictor for MRSA nasal colonization. Of the 19 MRSA, most isolates belonged to one of two linages, characterized as sequence type (ST) 239 (32%) and ST 59 (58%). The latter linage, accounting for 83% of 6 isolates from patients without risk factors, is a community-associated (CA) clone in Taiwan, while the former linage is among healthcare-associated clones.Conclusion/SignificanceA substantial proportion of patients visiting ED, particularly with current usage of percutaneous catheter or tubes, in northern Taiwan carried MRSA, mostly community strains, in nares.

Comparison of the Methicillin-Resistant Staphylococcus aureus Acquisition among Rehabilitation and Nursing Home Residents

Objective.To assess risk factors for methicillin-resistantStaphylococcus aureus(MRSA) acquisition among extended care residents focusing on level of care (residential vs rehabilitation) and room placement with an MRSA-positive resident.Design.Prospective cohort study.Setting.Extended care units at 2 healthcare systems in Maryland.Participants.Four hundred forty-three residents with no history of MRSA and negative MRSA surveillance cultures of the anterior nares and areas of skin breakdown at enrollment.Methods.Follow-up cultures were collected every 4 weeks and/or at discharge for a period of 12 weeks. Study data were collected by a research nurse from the medical staff and the electronic medical records. Cox proportional hazards modeling was used to calculate adjusted hazards ratios (aHRs) and 95% confidence intervals (CIs).Results.Residents in rehabilitation care had 4-fold higher risk of MRSA acquisition compared with residents in residential care (hazard ratio [HR], 4. [95% CI, 2.2-8.8]). Being bedbound was significantly associated with MRSA acquisition in both populations (residential care, aHR, 4.3 [95% CI, 1.5-12.2]; rehabilitation care, aHR, 4.8 [95% CI, 1.2-18.7]). Having an MRSA-positive roommate was not significantly associated with acquisition in either population (residential care, aHR, 1.4 [95% CI, 0.5-3.9]; rehabilitation care, aHR, 0.5 [95% CI, 0.1-2.2]); based on concordantspatyping, only 2 of 8 residents who acquired MRSA and had room placement with an MRSA-positive resident acquired their MRSA isolate from their roommate.Conclusion.Residents in rehabilitation care appear at higher risk and have different risk factors for MRSA acquisition compared to those in residential care.

Comparison of the Methicillin-Resistant Staphylococcus aureus Acquisition among Rehabilitation and Nursing Home Residents

To assess risk factors for methicillin-resistant Staphylococcus aureus (MRSA) acquisition among extended care residents focusing on level of care (residential vs rehabilitation) and room placement with an MRSA-positive resident. Prospective cohort study. Extended care units at 2 healthcare systems in Maryland. Four hundred forty-three residents with no history of MRSA and negative MRSA surveillance cultures of the anterior nares and areas of skin breakdown at enrollment. Follow-up cultures were collected every 4 weeks and/or at discharge for a period of 12 weeks. Study data were collected by a research nurse from the medical staff and the electronic medical records. Cox proportional hazards modeling was used to calculate adjusted hazards ratios (aHRs) and 95% confidence intervals (CIs). Residents in rehabilitation care had 4-fold higher risk of MRSA acquisition compared with residents in residential care (hazard ratio [HR], 4. [95% CI, 2.2-8.8]). Being bedbound was significantly associated with MRSA acquisition in both populations (residential care, aHR, 4.3 [95% CI, 1.5-12.2]; rehabilitation care, aHR, 4.8 [95% CI, 1.2-18.7]). Having an MRSA-positive roommate was not significantly associated with acquisition in either population (residential care, aHR, 1.4 [95% CI, 0.5-3.9]; rehabilitation care, aHR, 0.5 [95% CI, 0.1-2.2]); based on concordant spa typing, only 2 of 8 residents who acquired MRSA and had room placement with an MRSA-positive resident acquired their MRSA isolate from their roommate. Residents in rehabilitation care appear at higher risk and have different risk factors for MRSA acquisition compared to those in residential care.

MRSA in a large German University Hospital: Male gender is a significant risk factor for MRSA acquisition.

Background: The continually rising number of hospital acquired infections and particularly MRSA (Methicillin-resistant Staphylococcus aureus) colonization poses a major challenge from both clinical and epidemiological perspectives. The assessment of risk factors is vital in determining the best prevention, diagnosis and treatment strategies. Materials and methods: We analyzed 798 cases of MRSA in a large German University Hospital over a 7-year period. Data was collected retro- and prospectively including patient age, sex, type of ward and duration of inpatient stay. In addition we analyzed all cases on ICU with regards to cross infection and MRSA genotyping via DNA MicroArray Technology. The years 2004 to 2007 were analyzed with a specific focus on gender.Results: Male gender is significantly correlated with increased risk of MRSA acquisition (p<0.001), the predominant setting for MRSA is on ICU. 75% of the MRSA positive patients are over 50 years of age (average age 59.8 years). The inpatient time was 4.15 times higher in MRSA carriers compared with non-MRSA cases, however this was not significant. MRSA genotyping on ICU showed mainly the subtypes ST 5, ST 22, ST 228, however cross contamination with identical genotypes was only detected in a minority of cases (5 out of 22).Conclusion: Unlike previous studies which show no or inconclusive evidence of gender as a risk factor, our data confirm that male gender is a significant risk factor for MRSA carrier status. Further research will be required to investigate the aetiology of these findings.

Transmission of Methicillin-Resistant Staphylococcus aureus to Household Contacts

ABSTRACT The frequency of and risk factors for methicillin-resistant Staphylococcus aureus (MRSA) transmission from a MRSA index person to household contacts were assessed in this prospective study. Between January 2005 and December 2007, 62 newly diagnosed MRSA index persons (46 patients and 16 health care workers) and their 160 household contacts were included in the study analysis. Transmission of MRSA from an index person to household contacts occurred in nearly half of the cases (47%; n = 29). These 29 index persons together had 84 household contacts, of which two-thirds (67%; n = 56) became MRSA positive. Prolonged exposure time to MRSA at home was a significant risk factor for MRSA transmission to household contacts. In addition, MRSA colonization at least in the throat, younger age, and eczema in index persons were significantly associated with MRSA transmission; the presence of wounds was negatively associated with MRSA transmission. Furthermore, an increased number of household contacts and being the partner of a MRSA index person were household-related risk factors for MRSA acquisition from the index person. No predominant pulsed-field gel electrophoresis (PFGE) type was observed to be transmitted more frequently than other PFGE types. To date, screening household contacts and providing MRSA eradication therapy to those found positive simultaneously with the index person is not included in the “search-and-destroy” policy. We suggest including both in MRSA prevention guidelines, as this may reduce further spread of MRSA.

Risk factors for acquisition of Methicillin-resistant Staphylococcus aureus among patients from a burn unit in Brazil

Methicillin-resistant Staphylococcus aureus (MRSA) is an important agent of colonization and infection in burn units. In order to identify risk factors for MRSA acquisition in a Brazilian burn unit, we performed two retrospective studies. In the first (“cohort” study), 175 patients who were not colonized with MRSA on admission were followed to assess risk factors for MRSA acquisition. In the second (“case–case–control” study), 143 individuals from the previous study who were negative for both MRSA and Methicillin-susceptible S. aureus (MSSA) on admission were followed. Case–control studies were performed to investigate risk factors for MRSA and MSSA acquisition. MRSA and MSSA were recovered from 75 and 23 patients, respectively. In the “cohort” study, only the number of wound excisions (Odds Ratio [OR] = 1.55, 95% Confidence Interval [CI] = 1.21–1.98, P = 0.001) was associated with MRSA acquisition. In the “case–case–control” study, burns involving head (OR = 3.43, 95%CI = 1.50–7.81, P = 0.003) and the number of wound excisions (OR = 1.83, 95%CI = 1.27–2.63, P = 0.001) were significant risk factors for MRSA. Burns involving perineum were negatively associated with MSSA acquisition (OR = 0.16, 95%CI = 0.03–0.75, P = 0.02). In conclusion, the acquisition of MRSA was related to the site of the burn and to the surgical manipulation of tissues, but not to the use of antimicrobials.

Community-Acquired Infection With Healthcare-Associated Methicillin-Resistant Staphylococcus aureus: The Role of Home Nursing Care

To better understand the role of indirect transmission in community-acquired infection with methicillin-resistant Staphylococcus aureus (MRSA). Prospective case-control study. A French teaching hospital. A total of 198 case patients and 198 control patients with MRSA or methicillin-susceptible S. aureus infection diagnosed between April 2002 and July 2003. Multivariate analysis showed a highly significant independent link between MRSA infection at admission and prior receipt of home nursing care (odds ratio [OR], 3.7; P<.001). Other independent risk factors were prior hospitalization (OR, 3.8; P<.001), transfer from another institution (OR, 2.3; P=.008), and age older than 65 years (OR, 1.6; P=.04). Prior home nursing care showed a frequency dose-response relationship. Eleven MRSA-infected patients had had home nursing procedures but no hospital stay in the previous 3 years. These patients' MRSA strains were related to the prevalent MRSA clone currently spreading in French hospitals. Home nursing care appears to be an independent risk factor for MRSA acquisition in the community. The reservoir probably consists of MRSA carriers discharged from the hospital. Community nurses seem to be a potential vector.

Five cases of bacterial endocarditis after furunculosis and the ongoing saga of community-acquired methicillin-resistant Staphylococcus aureus infections

Bacterial endocarditis secondary to Panton-Valentine leukocidin producing community-acquired methicillin-resistant Staphylococcus aureus (MRSA) infections is rare. We report 5 previously healthy patients who presented with endocarditis after developing furunculosis due to CA-MRSA. A retrospective chart review of all patients with MRSA positive blood cultures was conducted over a 12-month period. Patients with multiple positive blood cultures within 72 h of admission and who had no risk factors for MRSA acquisition were included. Modified Duke's criteria were used to define bacterial endocarditis. PCR detection of Panton-Valentine leukocidin (PVL) genes as well as SCCmec typing was performed. In addition, strain typing of MRSA isolates was performed utilizing pulsed-field gel electrophoresis. Five out of a total of 193 patients had features consistent with CA-MRSA infections and met modified Duke's criteria for bacterial endocarditis. Blood culture isolates were found to be PVL gene positive and carried the type IV SCCmec element. PFGE confirmed that skin isolate was identical to the isolate cultured from his blood. Bacterial endocarditis in patients with CA-MRSA furunculosis is an emerging entity. In areas where CA-MRSA skin infections are prevalent, inappropriate initial antibiotics remain a major problem and may result in significant morbidity.

Methicillin-resistantStaphylococcus aureusNecrotizing Pneumonia

To the Editor: Methicillin-resistant Staphylococcus aureus (MRSA) strains account for >40% of all hospital-acquired S. aureus infections in Italy (1). Although cases of community-acquired MRSA (CA-MRSA) infections have been reported in recent years (2), these isolates have not been characterized for Panton-Valentine leukocidin (PVL) (3); therefore, the presence of isolates with the typical characteristics of CA-MRSA (4) in Italy remains unknown. At the beginning of April 2005, a 37-year-old woman was admitted to the University Hospital Policlinico in Rome because of fever, cough, and headache. Her medical history was unremarkable. She was a teacher in a school for foreign students in Rome, smoked 3 cigarettes per day for 15 years, and reported no recent travel abroad. Her 5-year-old daughter had influenzalike symptoms in the previous week. At hospital admission, her temperature was 39°C, heart rate was108 beats/min, respiratory rate was 32 breaths/min, and blood pressure was 105/70 mmHg. Arterial blood gas analysis showed mild hypoxemia and hypocapnia (PaO2 73 mm Hg and PaCO2 34 mm Hg on room air). Leukocyte count was 24,360 cells/μL (81% polymorphonuclear cells), and platelet count was 506,000/μL. Chest radiograph showed infiltrates in the right upper and lower lobes and left lower lobe. Empiric treatment with clarithromycin and ceftriaxone was started, but the patient's clinical conditions did not improve. Culture of sputum samples obtained at admission yielded growth of MRSA. Computed tomographic scan showed multiple lung cavitary lesions, indicating necrotizing pneumonia. On day 3 of admission, antimicrobial drug therapy was changed to linezolid (600 mg 2 times a day). Fever resolved, and the patient's condition rapidly improved. The patient was discharged after 14 days of linezolid treatment. At discharge, leukocyte count was 6,040 cell/μL (58% polymorphonuclear cells), and arterial blood gas analysis showed PaO2 of 88 mm Hg. The MRSA isolate from sputum was susceptible to all the non–β-lactam antimicrobial drugs tested, including erythromycin, clindamycin, ciprofloxacin, tetracycline, kanamycin, and fusidic acid. With established molecular methods, the isolate was found to harbor SCCmec type IV (5); lukS and lukF, the genes coding for the 2 subunits of the PVL toxin; and hlg, the γ-hemolysin gene (3). The genetic background of the isolate was determined by multilocus sequence typing (MLST) (6) and sequence typing of the tandem repeat region of protein A gene (spa typing) (7). Results showed that the isolate belonged to ST30 according to the MLST database (http://saureus.mlst.net), and spa typing, analyzed by the Ridom Staphtype software (http://www.ridom.de), indicated a novel spa type, to which type 755 was assigned. ST30, 1 of 6 clones more commonly associated with PVL-positive CA-MRSA (4), is designated also the southwest Pacific (SWP) clone, because of the area in which it circulates. Recently, the SWP clone has caused CA-MRSA infections in northern European countries (England, Scotland, the Netherlands, Sweden, and Latvia) (8,9). Molecular analysis suggests that the SWP clone has evolved from a methicillin-susceptible clone of S. aureus, termed phage type 80/81, that was pandemic in the 1950s and considered to be unusually virulent and transmissible (8). In fact, strains belonging to phage type 80/81 carry the PVL gene and appear to have subsequently acquired methicillin resistance through horizontal transfer of SCCmec type IV. The spa type of the Italian isolate comprises 7 nucleotide repeats, indicated by XJ4AKAOM in the alphabetical code. This repeat sequence differs from that of the classical SWP clone, indicated by XKAKAOMQ (8), by only 1 bp in the second repeat and loss of the last Q repeat. In spite of these differences, the spa type is in substantial agreement with the MLST result and indicates that the Italian isolate is either a descendent or a local variant of the SWP clone. The most common clone of CA-MRSA described in Europe is ST80, spa type 44. CA-MRSA belonging to ST80 tend to be more antimicrobial drug resistant than isolates belonging to other clones (4). Resistance to fusidic acid, typical of ST80, has been proposed as a marker for CA-MRSA in Europe (10). In light of our finding, we cannot rely on resistance to fusidic acid to screen for PVL-producing CA-MRSA in our country. To our knowledge, this is the first report from Italy of necrotizing pneumonia caused by PVL-positive CA-MRSA. The presentation was typically that of a severe pneumonia that occurred in a previously healthy, young adult with no risk factors for MRSA acquisition, as described in other cases (11). This is also the first report of a SWP clone isolate in southern Europe; if the strain is circulating in Italy or is occasionally imported from the SWP area, whether our patient acquired it through contact with a foreign contact remains unknown.

Successful long-term program for controlling methicillin-resistant Staphylococcus aureus in intensive care units

To evaluate the effectiveness of screening strategy and contact precautions for patients with methicillin-resistant Staphylococcus aureus (MRSA). Prospective observational cohort from 1 February 1995 to 31 December 2001 in three intensive care units (45 beds) in a French teaching hospital. 8,548 patients admitted to the three ICUs had nasal screening on ICU admission and weekly thereafter. Contact precautions were used in MRSA-positive patients. The following variables were collected: age, gender, severity score, length of stay, workload, and colonization pressure (percentage of patient-days with an MRSA to the number of patient-days in the unit). Alcohol-based handrub solution was introduced in July 2000. We compared the period before this (P1) with that thereafter (P2). Of the 8,548 admitted patients 554 (6.5%) had MRSA at ICU admission, and 456 of the 7,515 (6.1%) exposed patients acquired MRSA. Acquisition incidence decreased from 7.0% in P1 to 2.8% in P2. Independent variables associated with MRSA acquisition were: age (adjusted odds ratio 1.013), severity score (1.047), length of ICU stay (1.015), colonization pressure (1.019), medical ICU (1.58), and P2 (0.49). MRSA control in these ICUs characterized by a high prevalence of MRSA at admission was achieved via multiple factors, including screening, contact precautions, and use of alcoholic handrub solution. Our results after adjustment of risk factors for MRSA acquisition and the steady improvement in MRSA over several years strengthen these findings. MRSA spreading can be successfully controlled in ICUs with high colonization pressure.

Le staphylocoque doré résistant à la méticilline : émergence et bases moléculaires de la résistance

Methicillin-resistant Staphylococcus aureus (MRSA) is often the severe causal agent in nosocomial infections that are becoming increasingly difficult to cure because of emerging resistance to all current antibiotic classes. Geographic spread of several MRSA clones between countries and continents has been reported and proven by molecular evidence. Several strains have been isolated from patients in the community without established risk factors for MRSA acquisition. Some of them may have origins in the hospital but others appear to be community-acquired strains. Community MRSA strains have several distinguishing characteristics that may enable them to more readily colonize and infect otherwise healthy hosts. Molecular typing approaches have been used with great advantage in studying of the MRSA epidemiology. It appears that a complete characterization of MRSA requires not only identification of the genetic background of the bacteria but also identification of the structural types of Staphylococcal Cassette Chromosome mec element (SCC mec), which carries methicillin resistance determinant mecA. Rapid and precise identification of MRSA is a prerequisite for control of hospital infections. This article reviews recent publications addressing the epidemiology markers of MRSA, specially of community-acquired strains, and the genetic diversity of SCC mec for identifying MRSA. It appears that MRSA will be an increasing important pathogen in the community.

Risk factors for acquisition of methicillin-resistant Staphylococcus aureus (MRSA) by trauma patients in the intensive care unit

In a previous study in the intensive care unit (ICU) of the Alfred Hospital, Melbourne, Australia, it was demonstrated that trauma patients were at particular risk of becoming colonized by methicillin-resistant Staphylococcus aureus (MRSA). We examined risk factors for MRSA acquisition in these patients using a cohort study comparing the 31 patients who acquired MRSA with 65 who did not. Data collected included ICU length of stay (LOS), mechanism of trauma, site of injury, type of surgery, trauma severity and antibiotic usage. Odds ratios (OR) were determined and adjusted for LOS. LOS in the ICU was a significant univariate predictor of MRSA acquisition (OR 13.7). When adjusted for LOS, mechanism of trauma (OR 10.4), laparotomy (OR 6.3) and administration of ticarcillin/clavulanic acid (OR 4.5) or glycopeptides (OR 5.9) remained significant. We confirmed our previous finding that LOS was associated with MRSA acquisition. Receipt of antibiotics correlated with reported literature. Novel associations were road trauma as a mechanism and laparotomy.