Hugo Sax

Universal screening for methicillin-resistant Staphylococcus aureus at hospital admission and nosocomial infection in surgical patients.

CONTEXTnExperts and policy makers have repeatedly called for universal screening at hospital admission to reduce nosocomial methicillin-resistant Staphylococcus aureus (MRSA) infection.nnnOBJECTIVEnTo determine the effect of an early MRSA detection strategy on nosocomial MRSA infection rates in surgical patients.nnnDESIGN, SETTING, AND PATIENTSnProspective, interventional cohort study conducted between July 2004 and May 2006 among 21 754 surgical patients at a Swiss teaching hospital using a crossover design to compare 2 MRSA control strategies (rapid screening on admission plus standard infection control measures vs standard infection control alone). Twelve surgical wards including different surgical specialties were enrolled according to a prespecified agenda, assigned to either the control or intervention group for a 9-month period, then switched over to the other group for a further 9 months.nnnINTERVENTIONSnDuring the rapid screening intervention periods, patients admitted to the intervention wards for more than 24 hours were screened before or on admission by rapid, multiplex polymerase chain reaction. For both intervention (n=10 844) and control (n=10 910) periods, standard infection control measures were used for patients with MRSA in all wards and consisted of contact isolation of MRSA carriers, use of dedicated material (eg, gown, gloves, mask if indicated), adjustment of perioperative antibiotic prophylaxis of MRSA carriers, computerized MRSA alert system, and topical decolonization (nasal mupirocin ointment and chlorhexidine body washing) for 5 days.nnnMAIN OUTCOME MEASURESnIncidence of nosocomial MRSA infection, MRSA surgical site infection, and rates of nosocomial acquisition of MRSA.nnnRESULTSnOverall, 10 193 of 10 844 patients (94%) were screened during the intervention periods. Screening identified 515 MRSA-positive patients (5.1%), including 337 previously unknown MRSA carriers. Median time from screening to notification of test results was 22.5 hours (interquartile range, 12.2-28.2 hours). In the intervention periods, 93 patients (1.11 per 1000 patient-days) developed nosocomial MRSA infection compared with 76 in the control periods (0.91 per 1000 patient-days; adjusted incidence rate ratio, 1.20; 95% confidence interval, 0.85-1.69; P = .29). The rate of MRSA surgical site infection and nosocomial MRSA acquisition did not change significantly. Fifty-three of 93 infected patients (57%) in the intervention wards were MRSA-free on admission and developed MRSA infection during hospitalization.nnnCONCLUSIONnA universal, rapid MRSA admission screening strategy did not reduce nosocomial MRSA infection in a surgical department with endemic MRSA prevalence but relatively low rates of MRSA infection.nnnTRIAL REGISTRATIONnisrctn.org Identifier: ISRCTN06603006.

Impact of drug resistance mutations on virologic response to salvage therapy

OBJECTIVEnTo assess the prognostic significance of drug-associated mutations in the protease and reverse transcriptase (RT) genes on virological response to salvage therapy.nnnPATIENTSnAll patients from four centres of the Swiss HIV Cohort Study who were switched, between February and October 1997, to nelfinavir plus other antiretroviral drugs following failure of highly active antiretroviral therapy (HIV-1 RNA >1000 copies/ml after > 3 months).nnnMETHODSnDirect sequencing of RT and protease genes derived from plasma RNA was performed in 62 patients before salvage therapy. Baseline predictors (drug-resistance mutations, drug exposure, clinical and biological parameters) of virological response after 4-12 weeks of therapy were assessed by linear regression analyses.nnnRESULTSnPatients had been treated with RT inhibitors and protease inhibitors for a median duration of 35.6 and 12.2 months, respectively. Baseline median CD4 cell count was 113 x 10(6)/l and HIV-1 RNA 5.16 log10 copies/ml. The median decrease of HIV-1 RNA was 0.38 log10; 32% of the patients showed > 1 log10 decrease. At baseline, 90% of the patients had RT inhibitor-resistance mutations with a median number per patient of four (range, 0-7). Primary and secondary protease inhibitor-resistance mutations were detected in 69% and 89% of the patients, respectively. The median number of total protease inhibitor-resistance mutations per patient was four (range, 0-9). In univariate analysis, virological response to salvage therapy was associated with number of RT inhibitors, primary and secondary protease inhibitor-resistance mutations, history of protease inhibitor use (duration and number), but not with clinical stage, HIV-1 RNA level or CD4 cell count. After adjustment for all variables, the number of RT inhibitor plus protease inhibitor-resistance mutations was the only independent predictor.nnnCONCLUSIONSnIn patients with advanced HIV infection, the virological response to salvage therapy containing nelfinavir is best predicted by the number of baseline RT inhibitor plus protease inhibitor-resistance mutations.

Learning from imbalanced data in surveillance of nosocomial infection

OBJECTIVEnAn important problem that arises in hospitals is the monitoring and detection of nosocomial or hospital acquired infections (NIs). This paper describes a retrospective analysis of a prevalence survey of NIs done in the Geneva University Hospital. Our goal is to identify patients with one or more NIs on the basis of clinical and other data collected during the survey.nnnMETHODS AND MATERIALnStandard surveillance strategies are time-consuming and cannot be applied hospital-wide; alternative methods are required. In NI detection viewed as a classification task, the main difficulty resides in the significant imbalance between positive or infected (11%) and negative (89%) cases. To remedy class imbalance, we explore two distinct avenues: (1) a new re-sampling approach in which both over-sampling of rare positives and under-sampling of the noninfected majority rely on synthetic cases (prototypes) generated via class-specific sub-clustering, and (2) a support vector algorithm in which asymmetrical margins are tuned to improve recognition of rare positive cases.nnnRESULTS AND CONCLUSIONnExperiments have shown both approaches to be effective for the NI detection problem. Our novel re-sampling strategies perform remarkably better than classical random re-sampling. However, they are outperformed by asymmetrical soft margin support vector machines which attained a sensitivity rate of 92%, significantly better than the highest sensitivity (87%) obtained via prototype-based re-sampling.

Prolonged Outbreak of Mycobacterium chimaera Infection After Open-Chest Heart Surgery

BACKGROUNDnInvasive Mycobacterium chimaera infections were diagnosed in 2012 in 2 heart surgery patients on extracorporeal circulation. We launched an outbreak investigation to identify the source and extent of the potential outbreak and to implement preventive measures.nnnMETHODSnWe collected water samples from operating theaters, intensive care units, and wards, including air samples from operating theaters. Mycobacterium chimaera strains were characterized by randomly amplified polymorphic DNA polymerase chain reaction (RAPD-PCR). Case detection was performed based on archived histopathology samples and M. chimaera isolates since 2006, and the patient population at risk was prospectively surveyed.nnnRESULTSnWe identified 6 male patients aged between 49 and 64 years with prosthetic valve endocarditis or vascular graft infection due to M. chimaera, which became clinically manifest with a latency of between 1.5 and 3.6 years after surgery. Mycobacterium chimaera was isolated from cardiac tissue specimens, blood cultures, or other biopsy specimens. We were able also to culture M. chimaera from water circuits of heater-cooler units connected to the cardiopulmonary bypass, and air samples collected when the units were in use. RAPD-PCR demonstrated identical patterns among M. chimaera strains from heater-cooler unit water circuits and air samples, and strains in 2 patient clusters.nnnCONCLUSIONSnThe epidemiological and microbiological features of this prolonged outbreak provided evidence for the airborne transmission of M. chimaera from contaminated heater-cooler unit water tanks to patients during open-heart surgery.

Nursing resources: a major determinant of nosocomial infection?

Purpose of review There is growing concern that changes in nurse workforce and hospital-restructuring interventions negatively impact on patient outcomes. This review focuses on the association between understaffing and health-care-associated infections. Recent findings There is a large number of studies showing that overcrowding, understaffing or a misbalance between workload and resources are important determinants of nosocomial infections and cross-transmission of microorganisms. Importantly, not only the number of staff but also the level of their training affects outcomes. The nurse workforce is ageing, mainly due to fewer individuals engaging in a nursing career. This phenomenon, combined with cost-driven downsizing, contributes to a nursing shortage, and this tendency is not expected to revert unless important system changes are implemented. The causal pathway between understaffing and infection is complex, and factors might include lack of time to comply with infection control recommendations, job dissatisfaction, job-related burnout, absenteeism and a high staff turnover. Summary The evidence that cost-driven downsizing and changes in staffing patterns causes harm to patients cannot be ignored, and should not be considered as an inevitable outcome. More research is needed to better define the optimal patient-to-nurse ratio in various hospital settings and to estimate the economical impact of the nursing shortage. All quality-improvement interventions should carefully take into account systems and processes to be successful, as the issue of staffing is essentially a structural problem.

Knowledge of standard and isolation precautions in a large teaching hospital

OBJECTIVEnTo assess the level of knowledge regarding and attitudes toward standard and isolation precautions among healthcare workers in a hospital.nnnMETHODnA confidential, self-administered questionnaire survey was conducted in a random sample of 1500 nurses and 500 physicians in a large teaching hospital.nnnRESULTSnA total of 1,241 questionnaires were returned (response rate, 62%). The median age of respondents was 39 years; 71.9% were women and 21.2% had senior staff status. One-fourth had previously participated in specific training regarding transmission precautions for pathogens conducted by the infection control team. More than half (55.9%) gave correct answers to 10 or more of the 13 knowledge-type questions. The following reasons for noncompliance with guidelines were judged as very important: lack of knowledge (47%); lack of time (42%); forgetfulness (39%); and lack of means (28%). For physicians and healthcare workers in a senior position, lack of time and lack of means were significantly less important (P < .0005). On multivariate linear regression, knowledge was independently associated with exposure to training sessions (coefficient, 0.33; 95% confidence interval, 0.08 to 0.57; P = .009) and less professional experience (coefficient per increasing professional experience, -0.024; 95% confidence interval, -0.035 to -0.012; P < .0005).nnnCONCLUSIONSnDespite a training effort targeting opinion leaders, knowledge of transmission precautions for pathogens remained insufficient. Nevertheless, specific training proved to be the major determinant of good knowledge.

Reduction of Urinary Tract Infection and Antibiotic Use after Surgery: A Controlled, Prospective, Before-After Intervention Study

BACKGROUNDnUrinary tract infection is the most frequent health care-associated complication. We hypothesized that the implementation of a multifaceted prevention strategy could decrease its incidence after surgery.nnnMETHODSnIn a controlled, prospective, before-after intervention trial with 1328 adult patients scheduled for orthopedic or abdominal surgery, nosocomial infection surveillance was conducted until hospital discharge. A multifaceted intervention including specifically tailored, locally developed guidelines for the prevention of urinary tract infection was implemented for orthopedic surgery patients, and abdominal surgery patients served as control subjects. Infectious and noninfectious complications, adherence to guidelines, and antibiotic use were monitored before and after the intervention and again 2 years later.nnnRESULTSnThe incidence of urinary tract infection decreased from 10.4 to 3.9 episodes per 100 patients in the intervention group (incidence-density ratio, 0.41; 95% CI, 0.20-0.79; P=.004). Adherence to guidelines was 82.2%. Both the frequency and the duration of urinary catheterization decreased following the intervention. Recourse to antibiotic therapy after surgery dropped in the intervention group from 17.9 to 15.6 defined daily doses per 100 patient-days (P<.005) because of a reduced need for the treatment of urinary tract infection (P<.001). Follow-up after 2 years revealed a sustained impact of the strategy and a subsequent low use of antibiotics, consistent with stable adherence to guidelines (80.8%).nnnCONCLUSIONSnA multifaceted prevention strategy can dramatically decrease postoperative urinary tract infection and contribute to the reduction of the overall use of antibiotics after surgery.

Healthcare-associated prosthetic heart valve, aortic vascular graft, and disseminated Mycobacterium chimaera infections subsequent to open heart surgery.

AIMSnWe identified 10 patients with disseminated Mycobacterium chimaera infections subsequent to open-heart surgery at three European Hospitals. Infections originated from the heater-cooler unit of the heart-lung machine. Here we describe clinical aspects and treatment course of this novel clinical entity.nnnMETHODS AND RESULTSnInterdisciplinary care and follow-up of all patients was documented by the study team. Patients characteristics, clinical manifestations, microbiological findings, and therapeutic measures including surgical reinterventions were reviewed and treatment outcomes are described. The 10 patients comprise a 1-year-old child and nine adults with a median age of 61 years (range 36-76 years). The median duration from cardiac surgery to diagnosis was 21 (range 5-40) months. All patients had prosthetic material-associated infections with either prosthetic valve endocarditis, aortic graft infection, myocarditis, or infection of the prosthetic material following banding of the pulmonary artery. Extracardiac manifestations preceded cardiovascular disease in some cases. Despite targeted antimicrobial therapy, M. chimaera infection required cardiosurgical reinterventions in eight patients. Six out of 10 patients experienced breakthrough infections, of which four were fatal. Three patients are in a post-treatment monitoring period.nnnCONCLUSIONnHealthcare-associated infections due to M. chimaera occurred in patients subsequent to cardiac surgery with extracorporeal circulation and implantation of prosthetic material. Infections became clinically apparent after a time lag of months to years. Mycobacterium chimaera infections are easily missed by routine bacterial diagnostics and outcome is poor despite long-term antimycobacterial therapy, probably because biofilm formation hinders eradication of pathogens.

Nosocomial Bloodstream Infection and Clinical Sepsis

Primary bloodstream infection (BSI) is a leading, preventable infectious complication in critically ill patients and has a negative impact on patients’ outcome. Surveillance definitions for primary BSI distinguish those that are microbiologically documented from those that are not. The latter is known as clinical sepsis, but information on its epidemiologic importance is limited. We analyzed prospective on-site surveillance data of nosocomial infections in a medical intensive care unit. Of the 113 episodes of primary BSI, 33 (29%) were microbiologically documented. The overall BSI infection rate was 19.8 episodes per 1,000 central-line days (confidence interval [CI] 95%, 16.1 to 23.6); the rate fell to 5.8 (CI 3.8 to 7.8) when only microbiologically documented episodes were considered. Exposure to vascular devices was similar in patients with clinical sepsis and patients with microbiologically documented BSI. We conclude that laboratory-based surveillance alone will underestimate the incidence of primary BSI and thus jeopardize benchmarking.

Ventilator-associated pneumonia: caveats for benchmarking.

carries a low event rate of VAP in the described population. Considering that a substantial number of our patients are immunocompromised the results may be even more impressive. Whether our preventive strategies are perhaps ‘the best’ is open for discussion. Our study could have suffered from several limitations. Firstly, in our experience, most pulmonary infiltrates are not caused by pneumonia but rather by oedema or atelectasis. A low clinical likelihood of VAP encourages and reinforces a policy to withhold diagnostic procedures in patients with ‘little’ clinical evidence of infection [2]. Secondly, seasonal variation or the applied study design (3 month follow up from April to June) may have influenced the low incidence of VAP. Thirdly, although our nursing staff has specific knowledge of non-pharmacological VAP preventive measures, it is unclear whether any of our non-pharmacological measures or combination of measures really impact on outcome. Despite the low infection rate, our findings do not add anything new to the field of nosocomial infections. In fact, any given result is due to chance alone. It might well be that there is a difference in preventive measures but that this difference cannot be detected with statistical certainty. Longitudinal surveys with continuous risk estimation are often initiated to allow targeting treatments to those with the highest risk tailored to the characteristics of the individual ICU [3]. But due to methodological weakness, almost every single unit observational study on VAP is underpowered, such a study does not demonstrate the value of local measures and distinguishes associations. In our view the emphasis of quality control programs should be on structural and process indicators instead of on outcome parameters. Only prospective, randomised trials conducted to compare preventive measures with other strategies with clearly defined patient populations and disease stages can identify valuable preventive measures. Such trials should be well powered, and therefore multi-centered by design, with extreme attention and strict adherence to the protocols that would be compared, their results may help in formulating guidelines to be generally applied. In conclusion, discrepancies between ICUs may reflect: effectiveness of local VAP diagnosis and prevention strategies, the prevalence of resistant isolates, patient to staff ratio, the patient population examined, the way of reporting VAP rates, and other unknown factors. Data of local surveillance studies should be read as process indicators. Due to limited sample size most of these studies are insufficiently powered and the results do not permit a definitive conclusion. Failure to recognize these issues will lead to compromised benchmarking between units [1].