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PubMed2001

Methicillin resistant Staphylococcus aureus (MRSA) infection in cystic fibrosis.

BACKGROUND: Methicillin resistant Staphylococcus aureus (MRSA) infection is increasingly found in patients with cystic fibrosis (CF). AIMS: To determine whether MRSA infection has a deleterious effect on the clinical status of children with CF. METHODS: Children with MRSA in respiratory cultures during a seven year period were identified and compared with controls matched for age, sex, and respiratory function. Respiratory function tests, anthropometric data, Shwachman-Kulczycki score, Northern chest x ray score, intravenous and nebulised antibiotic therapy, and steroid therapy were compared one year before and one year after MRSA infection. RESULTS: From a clinic population of 300, 10 children had positive sputum or cough swab cultures for MRSA. Prevalence rose from 0 in 1992-1994 to 7 in 1998. Eighteen controls were identified. Children with MRSA showed significant worsening of height standard deviation scores and required twice as many courses of intravenous antibiotics as controls after one year. They had significantly worse chest x ray scores at the time of the first MRSA isolate and one year later, but showed no increase in the rate of decline in chest x ray appearance. There was a trend towards lower FEV(1) and FEF(25-75) in children with MRSA. There were no significant differences between the two groups with respect to change in weight, body mass index, or Shwachman score. There was no significant difference in prior use of steroids or nebulised antibiotics. CONCLUSION: MRSA infection in children with CF does not significantly affect respiratory function, but may have an adverse effect on growth. Children with MRSA require significantly more courses of intravenous antibiotics and have a worse chest x ray appearance than controls.

Adolescent↗

PubMed2006

Community-acquired MRSA and pig-farming.

BACKGROUND: Sporadic cases of CA-MRSA in persons without risk-factors for MRSA carriage are increasing. CASE PRESENTATION: We report a MRSA cluster among family members of a pig-farmer, his co-workers and his pigs. Initially a young mother was seen with mastitis due to MRSA. Six months later her baby daughter was admitted to the hospital with pneumococcal otitis. After staying five days in hospital, the baby was found to be MRSA positive. At that point it was decided to look for a possible source, such as other family members and house-hold animals, including pigs on the farm, since those were reported as a possible source of MRSA earlier. Swabs were taken from the throat and nares of family members and co-workers. A veterinarian obtained swabs from the nares, throat and perineum of 10 pigs. Swabs were cultured following a national protocol to detect MRSA that included the use of an enrichment broth. Animal and human strains were characterized by PFGE, spa-typing, MLST analysis, SSCmec, AGR typing, and the detection for PVL, LukM, and TSST toxin genes. Three family members, three co-workers, and 8 of the 10 pigs were MRSA positive. With the exception of the initial case (the mother) all persons were solely colonized, with no signs of clinical infections. After digestion with SmaI, none of the strains showed any bands using PFGE. All isolates belonged to spa type t108 and ST398. CONCLUSION: 1. This report clearly shows clonal spread and transmission between humans and pigs in the Netherlands. 2. MLST sequence type 398 might be of international importance as pig-MRSA, since this type was shown earlier to be present in epidemiologically unrelated French pigs and pig-farmers. 3. Research is needed to evaluate whether this is a local problem or a new source of MRSA, that puts the until now successful Search and Destroy policy of the Netherlands at risk.

Adult↗

PubMed2005

Efficacy of an alcohol/chlorhexidine hand hygiene program in a hospital with high rates of nosocomial methicillin-resistant Staphylococcus aureus (MRSA) infection.

OBJECTIVE: To assess the effect of a multifaceted hand hygiene culture-change program on health care worker behaviour, and to reduce the burden of nosocomial methicillin-resistant Staphylococcus aureus (MRSA) infections. DESIGN AND SETTING: Timetabled introduction of interventions (alcohol/chlorhexidine hand hygiene solution [ACHRS], improved cleaning of shared ward equipment, targeted patient decolonisation, comprehensive "culture change" package) to five clinical areas of a large university teaching hospital that had high levels of MRSA. MAIN OUTCOME MEASURES: Health care worker hand hygiene compliance; volume of ACHRS used; prevalence of patient and health care worker MRSA colonisation; environmental MRSA contamination; rates of clinical MRSA infection; and rates of laboratory detection of ESBL-producing Escherichia coli and Klebsiella spp. RESULTS: In study wards, health care worker hand hygiene compliance improved from a pre-intervention mean of 21% (95% CI, 20.3%-22.9%) to 42% (95% CI, 40.2%-43.8%) 12 months post-intervention (P < 0.001). ACHRS use increased from 5.7 to 28.6 L/1000 bed-days. No change was observed in patient MRSA colonisation or environmental colonisation/contamination, and, except in the intensive care unit, colonisation of health care workers was unchanged. Thirty-six months post-intervention, there had been significant reductions in hospital-wide rates of total clinical MRSA isolates (40% reduction; P < 0.001), patient-episodes of MRSA bacteraemia (57% reduction; P = 0.01), and clinical isolates of ESBL-producing E. coli and Klebsiella spp (90% reduction; P < 0.001). CONCLUSIONS: Introduction of ACHRS and a detailed culture-change program was effective in improving hand hygiene compliance and reducing nosocomial MRSA infections, despite high-level MRSA endemicity.

Anti-Infective Agents, Local↗

PubMed2002

Investigation of prevalence of MRSA in referrals to neurosurgery: implications for antibiotic prophylaxis.

In order to establish the appropriateness of our current prophylactic antibiotic regimen we analysed the prevalence of MRSA in emergency referrals to our unit. MRSA screening records for all emergency admissions for a 3-month period were analysed. One-hundred-and-seventy-five patients were admitted as transfers from another hospital. Evidence of screening was found in 61% (107 patients). Of the screened patients, 15% (16) were MRSA positive. Source of referral or length of inpatient stay after referral to the time of transfer were not predictive for MRSA status. Gentamicin is active against more than 95% of MRSA strains cultured in our hospital and against 87% of MRSA strains cultured in the neurosurgery unit. A number-needed-to-treat (NNT) analysis showed that, with MRSA prevalence at 15%, cefuroxime plus gentamicin at induction could prevent one MRSA infection per 421 treated patients compared with cefuroxime alone. Vancomycin had minimal additional benefit over cefuroxime plus gentamicin (NNT: 1684). We conclude that MRSA carriage is common in patients referred as emergencies from other hospitals. Cefuroxime plus gentamicin can be used as antibiotic prophylaxis in this group. Vancomycin can be reserved for patients known to be colonized with MRSA (NNT: 51).

Adult↗

PubMed2006

Cutaneous infections with community-acquired MRSA in aviators.

Methicillin-resistant Staphylococcus aureus (MRSA) is a pathogen of growing concern among community-based practices in medicine, particularly those in the military. The risk of colonization and infection by community-acquired MRSA (CA-MRSA) is significantly higher among military members than that of the general population. The unique environment of the deployed, military aviator (impaired hygiene practices, close contact in warm, space-limited cockpits, and shared life support equipment) may increase risks of colonization, infection, and transmission of CA-MRSA and hence warrants the clinical attention of the flight surgeon. Studies of molecular genetics indicate that isolates of CA-MRSA contain a unique mobile genetic element (SCCmec type IV), indicating that CA-MRSA evolved separately from nosocomially acquired MRSA. Skin infections involving CA-MRSA are unlike their nosocomial counterparts in that CA-MRSA infections are susceptible to multiple classes of antibiotics and, on average, are clinically more aggressive. Awareness of this pathogen and appropriate clinical intervention can lead to prompt resolution of the infection and reduce rates of CA-MRSA colonization.

Aerospace Medicine↗

PubMed2006

[Positive screening for MRSA--clinical consequences?].

BACKGROUND: The worldwide rise of MRSA is equivalent to an increase of nasal colonization with MRSA. The objectives of this study were to investigate the rate of occult nasal MRSA colonization in trauma patients, to elucidate the role of MRSA carriers for endogenous infection (nose --> wound) and to check the efficiency of mupirocin therapy. PATIENTS AND METHODS: A total of 643 consecutive trauma patients underwent MRSA screening (nasal swabs) on admission. At the same time all MRSA wound infections were registered and all isolates were analysed with PFGE (pulsed-field gel electrophoresis) to detect cross-infection between individuals. RESULTS: In 13 patients (2.0%) we found MRSA in the nose and limited isolation as well as therapy with mupirocin were performed. No endogenous transmission of MRSA from the nose to the wound could be seen, and no cross-infection to other patients could be detected. CONCLUSION: Our findings suggest that in our patients with nasal colonization the risk of intra- and interindividual transmission of MRSA is very small. Therefore, in trauma patients screening on admission does not seem to be absolutely necessary either for clinical or for epidemiological reasons.

Aged↗

PubMed2006

Case-control study of the relationship between MRSA bacteremia with a vancomycin MIC of 2 microg/mL and risk factors, costs, and outcomes in inpatients undergoing hemodialysis.

BACKGROUND: An increased prevalence of bacteremia caused by methicillin-resistant Staphylococcus aureus (MRSA) with a vancomycin hydrochloride MIC of 2 microg/mL was noted in a population of inpatients undergoing hemodialysis at Baptist Memorial Health Care, Memphis, Tennessee. OBJECTIVES: The aims of this study were to determine risk factors for infection with MRSA and to assess the differences in clinical and economic outcomes in patients undergoing hemodialysis with MRSA bacteremia with vancomycin MIC 2 microg/mL versus those with MRSA bacteremia with vancomycin MIC < or =0.5 microg/mL and uninfected controls. METHODS: This retrospective case-control study was conducted at Baptist Memorial Health Care. The study population (inpatients undergoing hemodialysis for MRSA bacteremia with vancomycin MIC 2 microg/mL [high-MIC group], MIC < or = 0.5 microg/mL [low-MIC group], and uninfected controls) was identified. Risk factors and clinical and economic outcomes (costs of hospitalization, nursing, and pharmacy) were determined and compared using univariate and multivariate statistics. RESULTS: Fifty patients with MRSA bacteremia undergoing hemodialysis were identified during the study period (high-MIC group, 17 [11 women, 6 men; mean (SD) age, 60 (17) years]; low-MIC group, 33 [23 women, 10 men; mean (SD) age, 62 (14) years]) and matched with 100 uninfected controls (57 men, 43 women; mean [SD] age, 63 [15] years). Risk factors for MRSA bacteremia found to be associated with high MIC included female sex, higher body mass index (1-point increments), recent surgery, and a history of cardiovascular disease (P < 0.05, P < 0.046, P = 0.04, and P = 0.028, respectively) (multivariate analysis). In the outcomes analysis, mortality was significantly higher in the high-MIC group compared with those in the low-MIC and control groups (35% vs 24% and 15%, respectively; P = 0.022). Total mean (SD) hospitalization costs were significantly higher in the high-MIC group compared with those in the low-MIC group and controls (US $47,624 [$80,534] vs $26,792 [$25,167] and $13,185 [$15,568], respectively; P < 0.001). Nursing costs were almost 6-fold higher in both infected groups compared with those in controls. Pharmacy costs in the low- and high-MIC groups were 3- to 6-fold higher, respectively, compared with those in controls. CONCLUSIONS: Surgery within the previous 6 months and intensive care unit admission were identified as significant risk factors for patients with MRSA bacteremia with a vancomycin MIC 2 microg/mL undergoing hemodialysis. These patients experienced a longer mean hospital length of stay and increased hospital costs compared with patients with MRSA bacteremia with a vancomycin MIC < or =0.5 microg/mL and uninfected controls.

Adult↗

PubMed2004

Frequency and diversity of molecular epidemiology of methicillin-resistant Staphylococcus aureus (MRSA) isolates from patients of a South West German teaching hospital.

We have determined the frequency and the genetic diversity of methicillin-resistant Staphylococcus aureus (MRSA) strains isolated from inpatients of a South West German teaching hospital. The frequency of primary MRSA isolates remained constant over the two-year surveillance period: 108 of the total number of 1450 S. aureus isolates (7.5%) were MRSA in 2001 and the corresponding figures were 110 MRSA out of 1412 S. aureus isolates (7.8%) in 2002. Six clusters of nosocomial MRSA infection were observed during 2001 and 2002. Cluster infections involved 65 patients on four different wards. Molecular typing of the 65 cluster isolates demonstrated that 51 (79%) belonged to a single predominant clone. The remaining 14 isolates represented seven genetically unrelated MRSA clones. Molecular typing of 50 additional non-cluster, sporadic isolates demonstrated 37 different pulsed-field gel electrophoresis (PFGE) banding patterns. Our results demonstrate that primary MRSA strains from hospitalized patients show a high degree of genetic heterogeneity. In contrast, however, MRSA isolates from nosocomial clusters were mostly derived from a single predominant clone, thus indicating a significant intra-ward and intra-hospital distribution. Molecular typing methods may lead to an improved understanding of MRSA epidemiology and thus allow the establishment of effective preventive measures.

Genetic Variation↗

PubMed2006

Reduction in MRSA environmental contamination with a portable HEPA-filtration unit.

There is renewed interest in the hospital environment as a potentially important factor for cross-infection with methicillin-resistant Staphylococcus aureus (MRSA) and other nosocomial pathogens. The aim of this study was to evaluate the effectiveness of a portable high-efficiency particulate air (HEPA)-filtration unit (IQAir Cleanroom H13, Incen AG, Goldach, Switzerland) at reducing MRSA environmental surface contamination within a clinical setting. The MRSA contamination rate on horizontal surfaces was assessed with agar settle plates in ward side-rooms of three patients who were heavy MRSA dispersers. Contamination rates were measured at different air filtration rates (60-235 m(3)/h) and compared with no air filtration using Poisson regression. Without air filtration, between 80% and 100% of settle plates were positive for MRSA, with the mean number of MRSA colony-forming units (cfu)/10-h exposure/plate ranging from 4.1 to 27.7. Air filtration at a rate of 140 m(3)/h (one patient) and 235 m(3)/h (two patients), resulted in a highly significant decrease in contamination rates compared with no air filtration (adjusted rate ratios 0.037, 0.099 and 0.248, respectively; P < 0.001 for each). A strong association was demonstrated between the rate of air filtration and the mean number of MRSA cfu/10-h exposure/plate (P for trend < 0.001). In conclusion, this portable HEPA-filtration unit can significantly reduce MRSA environmental contamination within patient isolation rooms, and this may prove to be a useful addition to existing MRSA infection control measures.

Adult↗

PubMed2004

Role of macrophages in a mouse model of postoperative MRSA enteritis.

BACKGROUND: We have established a mouse model for fatal postoperative enteritis due to Staphylococcus aureus to analyze mechanisms of bacterial translocation and determine reasons for the lethality of this infection. In the present study the role of macrophages was ascertained in protection against S. aureus induced enteritis. MATERIALS AND METHODS: Mice were pretreated with cyclophosphamide (CY), an immunosuppressant, and then infected directly into the jejunum with methicillin-resistant S. aureus (MRSA) isolated from a patient. In other groups of mice liposome-encapsulated dichloromethylene diphosphate (Cl2MDP) was administered to deplete macrophages in vivo. Other experimental groups received lipoteichoic acid (LTA), which was used to inhibit the ability of macrophages to bind MRSA, and additionally, to analyze dependence of bacterial clearance on the macrophage scavenger receptor. The ability of macrophages to bind MRSA was compared with survival rates in this mouse model of fatal postoperative enteritis. RESULTS: Injection of liposome-encapsulated Cl2MDP decreased survival rate of mice infected intraintestinally with MRSA in a dose-dependent manner. Cyclophosphamide also decreased survival rate of MRSA-infected mice and was found to correlate with its ability to decrease the number of macrophages in the spleen. Intravenous LTA administration did not affect total splenocyte numbers or the number of splenic macrophages but decreased the ability of macrophages to bind MRSA and adversely affected survival of mice infected with MRSA. CONCLUSIONS: Macrophages play a critical role in protection against MRSA administered directly into the jejunum. LTA recognition sites (probably type A scavenger receptors) on macrophages are required for binding and phagocytosing MRSA.

Animals↗

PubMedDate not supplied

Isolation of patients in single rooms or cohorts to reduce spread of MRSA in intensive-care units: prospective two-centre study.

BACKGROUND: Hospital-acquired infection due to meticillin-resistant Staphylococcus aureus (MRSA) is common within intensive-care units. Single room or cohort isolation of infected or colonised patients is used to reduce spread, but its benefit over and above other contact precautions is not known. We aimed to assess the effectiveness of moving versus not moving infected or colonised patients in intensive-care units to prevent transmission of MRSA. METHODS: We undertook a prospective 1-year study in the intensive-care units of two teaching hospitals. Admission and weekly screens were used to ascertain the incidence of MRSA colonisation. In the middle 6 months, MRSA-positive patients were not moved to a single room or cohort nursed unless they were carrying other multiresistant or notifiable pathogens. Standard precautions were practised throughout. Hand hygiene was encouraged and compliance audited. FINDINGS: Patients' characteristics and MRSA acquisition rates were similar in the periods when patients were moved and not moved. The crude (unadjusted) Cox proportional-hazards model showed no evidence of increased transmission during the non-move phase (0.73 [95% CI 0.49-1.10], p=0.94 one-sided). There were no changes in transmission of any particular strain of MRSA nor in handwashing frequency between management phases. INTERPRETATION: Moving MRSA-positive patients into single rooms or cohorted bays does not reduce crossinfection. Because transfer and isolation of critically ill patients in single rooms carries potential risks, our findings suggest that re-evaluation of isolation policies is required in intensive-care units where MRSA is endemic, and that more effective means of preventing spread of MRSA in such settings need to be found.

Adult↗

PubMed1998

A control programme for MRSA (methicillin-resistant Staphylococcus aureus) containment in a paediatric intensive care unit: evaluation and impact on infections caused by other micro-organisms.

Methicillin-resistant Staphylococcus aureus (MRSA) is increasingly reported as a hospital-acquired pathogen in intensive care units (ICUs). The inconsistent application of hygiene measures by healthcare workers accounts largely for the epidemic dissemination of such resistant strains. The efficacy of a control programme to prevent spread of MRSA was assessed in our paediatric ICU (PICU) from April 1992 to December 1995. Patients initially had weekly MRSA cultures taken from samples of anterior nares and perineum, but from January 1994, cultures were also obtained upon admission. Immediately after notification, all MRSA carriers were isolated. Education of hospital staff was an essential component of our programme. Nosocomial infection rates were recorded retrospectively in 1992 and 1993, and prospectively in 1994 and 1995. Incidence rates between 'pre-programme' and 'programme' periods were compared. The rate of MRSA infection decreased from 5.9-0.8/1000 Patient-Days (PD), (P < 10(-7). MRSA carriage also decreased from 34-2% (P < 10(-9) and the ratio of MRSA to all S. aureus fell from 71-11% (P < 10(-4). The decrease in the global incidence of infection from 20.1-13.9/1000 PD (P = 0.002) was due only to the decrease in MRSA infection. However, between 1994 and 1995, there was a significant increase in the number of transplant patients despite a constant patient/nurse ratio. The nosocomial infection rates caused by other micro-organisms decreased among the transplant patients from 64.8-33.2/1000 transplanted PD (P = 0.009) between 1994 and 1995. At the same time, we observed a slight increase of infections in non-transplanted patients, which may have been due to the effect of increased overall workload on those patients who were supposed to have fewer nosocomial risk factors. We conclude that implementation of infection control measures directed towards limiting person-to-person spread was effective in controlling high MRSA infection rates in a PICU, but it is important to allow enough time for staff to carry out hygiene practices thoroughly.

Child↗

PubMed1996

Frequency, clonal heterogeneity and antibiotic resistance of methicillin-resistant Staphylococcus aureus (MRSA) isolated in 1992-1994.

Since 1992, the proportion of methicillin-resistant Staphylococcus aureus (MRSA) isolated from patients of the University Hospital of Frankfurt/Main and six community hospitals increased to a level of 11% and has remained constant during the following two years. MRSA and methicillin-sensitive Staphylococcus aureus (MSSA) were distributed equally among almost all specimens except blood. There was evidence of a diminished potency of MRSA to cause bacteremia. All MRSA strains were susceptible to glycopeptides and mupirocin. Resistance rates to other non-beta-lactam antibiotics were low for fusidic acid (7.1%), fosfocin (8.3%), amikacin (11.4%) and cotrimoxazole (18.3%) and high for gentamicin (90.7%), ofloxacin (94.3%) and erythromycin (95.5%). Among 378 MRSA strains originating from 180 individuals, macrorestriction analysis of chromosomal DNA revealed 39 different genotypes. These could be divided into 14 epidemic strains isolated from 155 patients and 25 sporadic strains isolated from single patients. As most of the sporadic strains emerged in close local proximity to epidemic strains, we suppose a horizontal genetic transfer from MRSA to MSSA leading to the appearance of novel MRSA genotypes. Upon repeated isolation of MRSA strains from the same individuals, resistance rates and genotypes remained stable. Resistance patterns of the non-beta-lactams correlated poorly with macrorestriction analysis, whereas several MRSA genotypes could be distinguished by particular MICs of methicillin.

Anti-Bacterial Agents↗

PubMed2004

MRSA in patients presenting with femoral fractures.

AIM: To assess MRSA carrier status in patients from different residences presenting with femoral fractures and to assess the incidence of MRSA deep wound infections post-operatively with regard to MRSA status on presentation. METHOD: One hundred and five patients were screened for MRSA on arrival over a 20-week period. They were then followed up post-operatively to determine the number of patients developing MRSA deep wound infection. RESULTS: One out of three patients came from an institution (nursing, residential home or hospital). Nearly one in four of these patients were MRSA carriers, compared with a carrier rate of less than 1 in 20 in patients admitted from home. Of the 11 cases presenting as MRSA carriers, two developed a MRSA deep wound infection, compared with 2 out of the 94 patients not colonised with MRSA (X2 p < 0.01).

Age Distribution↗

PubMed2003

Control and the prevention of methicillin-resistant Staphylococcus aureus in hospitals in Ireland: North/South Study of MRSA in Ireland 1999.

As part of an all-island survey of methicillin-resistant Staphylococcus aureus (MRSA) in the Republic of Ireland (the South), where there is a mixed public and private healthcare system, and Northern Ireland (the North), where the healthcare system is part of the UK National Health Service, a questionnaire was circulated to all participating hospitals on measures routinely taken to control MRSA. Response rates were 100% in the North and 89% in the South. Over 70% of hospitals screened particular groups of patients on admission to hospital. Ninety-five percent of hospitals in the North and 88% in the South attempted to eradicate MRSA from carriage sites. Most hospitals attempted to isolate or cohort positive patients. About a quarter of hospitals in both parts of Ireland screened new healthcare workers for the presence of MRSA. Terminal decontamination of the environment after the discharge of a patient positive for MRSA was the norm in over 90% of hospitals, however, 6% of hospitals in the South used inappropriate disinfectants for MRSA. All hospitals in the North, but a minority (41%) in the South, had written antibiotic prescribing policies, but only 65% of hospitals in the South had access to an infection control committee, acute hospitals having greater access than district hospitals. The prevention and control of spread of MRSA remains a major challenge in the North and in the South. Although most hospitals in the North and in the South implemented current recommended guidelines on the control of MRSA in hospitals, there was some variability that may be resource related. Policies need to be reviewed in the light of the changing epidemiology of MRSA.

Cross Infection↗

PubMed2000

[Rapid and reliable detection of multiresistent Staphylococcus aureus (MRSA) by multiplex PCR].

BACKGROUND AND OBJECTIVE: Staphylococci are widespread pathogens and are frequently associated with nosocomial infections. Many hospitals struggle with increasing amounts of methicillin-resistant Staphylococcus aureus (MRSA) which are "multiresistant" against all betalactam antibiotics. Often, applicable antibiotics for treatment are only glycopeptides like vancomycin and teicoplanin. In addition, MRSA infected patients require expensive intensive isolation measures and strict hygiene. To efficiently prevent dissemination of these pathogens rapid and reliable identification and a close collaboration between clinicians and microbiologists are required. The purpose of our study was to set up a rapid and reliable identification procedure for MRSA by the amplification of specific gene determinants by PCR in order to to efficiently support therapy and eradication of the pathogen. METHODS: 153 strains of staphylococci isolated from in-patients of the hospital of the Justus-Liebig University of Giessen were examined. The femB gene was used to differentiate between Staphylococcus aureus (S. aureus) and coagulase-negative staphylococci (CNS), a gene which allows the species-specific identification of methicillin-resistant (MRSA) and -susceptible S. aureus (MSSA). Additionally, MRSA harbor the mecA gene encoding methicillin-resistance, which is absent in MSSA strains. RESULTS: Using a multiplex PCR with femB and mecA gene-specific oligonucleotides MRSA strains were unequivocally detected within 3 hours. The femB gene was detected in all 102 strains of S. aureus but in none of the 51 CNS. The mecA determinant was detected in 12 S. aureus. Among these, 11 strains were phenotypically methicillin-resistant and one strain was susceptible. The methicillin-resistance of this particular mecA-positive/methicillin-susceptible strain (cryptic MRSA) was inducible by cultivation on agar plates supplemented with flucloxacillin. CONCLUSIONS: The described method specifically detects S. aureus and identifies phenotypical and cryptic MRSA. These cryptic MRSA are of particular relevance since they are undetectable using common phenotypically based detection methods. It is conceivable that the methicillin resistance of these strains is induced under antibiotic therapy with flucloxacillin and that the mec-encoded feature of methicillin-resistance can be transferred to previously methicillin-susceptible strains. Using the reliable detection of these strains by PCR, failure of flucloxacillin therapy is avoidable.

Bacterial Proteins↗

PubMed2005

Prevalence and prediction of previously unknown MRSA carriage on admission to a geriatric hospital.

OBJECTIVES: to determine the prevalence and characteristics of previously unknown methicillin-resistant Staphylococcus aureus (MRSA) carriers at admission. DESIGN: two prospective case-control studies. SUBJECTS: 1,621 elderly patients were screened for MRSA carriage within 24 hours after admission to a geriatric hospital in Geneva, Switzerland. METHODS: risk factors associated with previously unknown MRSA carriage were determined in the derivation group, and the resulting risk score was evaluated in the validation cohort using logistic regression analysis. RESULTS: prevalence of MRSA carriage at admission increased from 7.3% (53/724 patients) in 2001 to 8.7% (78/897 patients) in 2003, with a corresponding prevalence of unknown MRSA carriers of 4.6 and 5.8%, respectively. Three variables were independently associated with previously unknown MRSA carriage: recent antibiotic treatment (adjusted OR (aOR) 2.3; 95% CI 1.0-5.1), intra-hospital transfer (aOR 2.5; 95% CI 1.2-5.3), and hospitalization in the past 2 years (aOR 2.7; 95% CI 1.1-6.7). In the validation cohort, the probability of MRSA carriage increased across risk scores: 0 point, 4% prevalence (6/146); 1 point, 15% (21/136); and $2 points, 31% (21/68; P<0.001). The risk score showed good discrimination and calibration in both groups. CONCLUSIONS: our risk score, which used a simple additive point system to estimate the likelihood of unknown MRSA carriage, had good accuracy and generalised well in an independent sample of patients. Once validated in a clinical trial, our risk score may be used as a tool to optimise MRSA control.

Aged, 80 and over↗

PubMed1994

The role of MRSA (methicillin-resistant Staphylococcus aureus) adherence and colonization in the upper respiratory tract of geriatric patients in nosocomial pulmonary infections.

The mechanism of nosocomial respiratory infections caused by MRSA (methicillin-resistant Staphylococcus aureus) in geriatric patients was investigated. Seriously ill patients (SIP) undergoing naso-gastric tube feeding or intravenous hyperalimentation and moderately ill patients (MIP) who were orally fed, were examined for their colonization and infection by Staphylococcus aureus (S. aureus) in the respiratory tract. Colonization of MRSA in the upper respiratory tract in SIP was from six to ten times higher than that in MIP and was associated with a high incidence of MRSA pulmonary infections. In vitro S. aureus adherence to nasal or oropharyngeal cells demonstrated that bacteria binding to nasal cells was higher, which probably can be interpreted as an elevated occurrence of S. aureus colonization in the nasal cavity than in the throat. The binding activity of MRSA was not superior to that of MSSA (methicillin-sensitive S. aureus). Though MRSA binding to the nasal cells from SIP was not higher than those from MIP, MRSA colonization in the upper respiratory tract was more frequently seen in SIP (P < 0.01). A higher incidence of total infectious episodes (P < 0.02-0.001) and more frequent use of antibiotics (P < 0.02-0.001), which were potent against MSSA might be the basis for selection of MRSA in these patients. In fact, the rate of MRSA colonization on the skin (pressure sores) was also higher in SIP (P < 0.01). A low nutritional state in SIP (P < 0.01-0.02) might also be associated with MRSA colonization.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗