The role of surveillance cultures in the prediction of susceptibility patterns of Gram-negative bacilli in the intensive care unit

Surveillance cultures may detect colonisation with drug-resistant Gram-negative bacteria and can be hypothesised to guide appropriate initial antibiotic treatment for intensive care unit (ICU) patients. We investigated the microbiological data of 228 episodes of nosocomial bloodstream infection (BSI) due to Gram-negative bacteria in an ICU in which piperacillin/tazobactam or meropenem was used empirically for serious infections, to evaluate the contribution of surveillance cultures to an appropriate choice of initial antibiotic therapy. Surveillance cultures were taken in advance of BSI in 218 (95.6%) of 228 episodes. Concordant organisms with identical identification and susceptibilities were found in prior surveillance cultures and subsequent blood cultures in 65 (29.8%) of 218 episodes. Surveillance cultures predicted resistance in 52.9% and 51.4% of BSIs caused by resistant pathogens to piperacillin/tazobactam and meropenem, respectively. The negative predictive value of surveillance cultures negative for a resistant organism also exceeded 90% for piperacillin/tazobactam and meropenem. Given that the overall resistant rates of BSI pathogens of our study were 11.3% to piperacillin/tazobactam and 16.4% to meropenem, surveillance cultures in our setting may provide important information on the probability of drug resistance of the causative pathogens and some utility in aiding empiric antibiotic therapy for ICU patients who subsequently develop BSI.

MRSA as an occupational disease: a case series

OBJECTIVES

Occupationally acquired infection with methicillin-resistant Staphylococcus aureus (MRSA) is an issue of increasing concern. However, the number of cases of occupational disease (OD) due to MRSA in healthcare workers (HCWs) and the characteristics of such cases have not been reported for Germany.

METHODS

Cases of OD due to MRSA were identified from the database of a compensation board (BGW) for the years 2006 and 2007 and the individual files analyzed. The variables extracted from these data were occupation, workplace, workplace exposure, and the reasons for recognizing a claim as an OD. Seven cases were selected due to the specific characteristics of their medical history and described in more detail.

RESULTS

Over a 2-year period, a total of 389 MRSA-related claims were reported to the BGW, of which 17 cases with infections were recognized as an OD. The reasons for not recognizing claims as an OD were either a lack of symptomatic infection or lack of a work-related MRSA exposure. The recognized cases were predominantly among staff in hospitals and nursing homes. The most frequent infection sites were ears, nose, and throat, followed by skin infections. Three cases exhibited secondary infection of the joints, associated with skin damage primarily caused by trauma. There was only one case in which a genetic link between an MRSA-infected index patient and MRSA in a HCW was documented. MRSA infections were recognized as an OD due to known contact with MRSA-positive patients or because workplace conditions were presumed to involve increased exposure to MRSA. Long-term incapacity resulted in four cases.

CONCLUSION

MRSA infection can cause severe health problems in HCWs that may lead to long-term incapacity. As recognition of HCW claims often depends on workplace characteristics, improved surveillance of MRSA infections in HCWs would facilitate the recognition of MRSA infections as an OD.

Universal MRSA nasal surveillance: characterization of outcomes at a tertiary care center and implications for infection control

BACKGROUND

Recognition of methicillin-resistant Staphylococcus aureus (MRSA) nasal carriage by active surveillance cultures has been widely debated. Our institution implemented universal nasal screening by polymerase chain reaction (PCR) for MRSA and isolation of screen positive patients in December 2007. Here we present data about the correlation between screen positivity and subsequent development of infection and the impact of isolation on surgical site infection rates.

METHODS

This was a retrospective, observational study from January 1, 2008, through June 30, 2008, on all inpatient admissions with a nasal MRSA PCR screen. Genotype of 15 MRSA blood isolates was determined utilizing the Diversilab® (bioMérieux, Hazelwood, MO) system. A phenotypic rule was deduced and utilized for analyzing all MRSA clinical isolates.

RESULTS

5375 patients were screened at ≤48 hours following admission. 581 MRSA positive nasal carriers (10.80%) were identified. 496 (85.3%) were asymptomatic MRSA nasal carriers. There were a total of 158 MRSA clinical infections. 85 (14.6%) MRSA nasal carriers had clinical infection. Of the 4794 (89.1%) non-nasally colonized patients, 73 (1.5%) had MRSA clinical infection. MRSA surgical site infection rate remained unchanged during the intervention period. Phenotypic predictive rule inferred 59.8% community-acquired MRSA (CA-MRSA) infections and 40% hospital-acquired MRSA (HA-MRSA) infections.

CONCLUSIONS

Our study showed a positive correlation between having a nasal screen positivity and subsequent development of infection. Isolation of MRSA screen positive patients alone as an intervention did not reduce the surgical site infection rates. Since most of our isolates are CA-MRSA, our institution is implementing several new interventions to further reduce the incidence of HA-MRSA conditions.

Prevention of healthcare-associated infections in children: new strategies and success stories

PURPOSE OF REVIEW

Attention to patient safety has made hospital infection prevention and control strategies a subject of increasing focus from healthcare personnel, patients and families, accrediting organizations, and government. This review highlights recent literature and new successes in the prevention of healthcare-associated infections in children.

RECENT FINDINGS

Emerging evidence about risk factors for various healthcare-associated infections in children will help target available adjunctive preventive interventions. Multicenter pediatric collaborative efforts to emphasize best practices have resulted in decreases in infection rates, particularly for central line-associated bloodstream infections. A low prevalence of colonization or infection with multidrug-resistant organisms in hospitalized children, combined with a lack of compelling evidence of effectiveness for active surveillance and decolonization, have made decisions about routine screening challenging.

SUMMARY

A renewed interest in infection prevention by multiple stakeholders has energized our field and contributed to impressive successes in reducing rates of healthcare-associated infections. Nevertheless, important knowledge gaps remain and an emphasis on funding of high-quality, rigorous studies to answer unresolved questions will be critical to our efforts to further prevent infections for hospitalized children.

Hospital methicillin-resistant Staphylococcus aureus active surveillance practices in Los Angeles County: Implications of legislation-based infection control, 2008

Pending California legislation prompted an on-line survey of methicillin-resistant Staphylococcus aureus (MRSA) active surveillance practices administered to infection preventionists of all 102 acute care licensed hospitals in Los Angeles County. We describe reported surveillance methods. Ninety-six hospitals responded with 41% performing MRSA active surveillance. Comments indicated resistance to implementation of active surveillance because its benefits remain controversial.

Epidemiology of methicillin-resistant Staphylococcus aureus (MRSA) nasal colonization among patients and healthcare workers in a Portuguese hospital: a pre-intervention study toward the control of MRSA

This two-year study investigated the epidemiology of nasal colonization with methicillin-resistant Staphylococcus aureus (MRSA) among patients and healthcare workers (HCWs) in two wards with a high frequency of MRSA isolation, at Hospital Geral de Santo António (HGSA), Portugal. Three point-prevalence surveys per year were carried out. A case-control approach was used to identify potential risk factors associated with MRSA carriage among patients. Incidence rates and risk factors of MRSA carriage among HCWs who were negative at the baseline observation were estimated. Prevalence of MRSA carriage among 276 patients screened was 5.1%. Admission to HGSA or attendance to the Diabetic Foot Outpatient Unit (DFOU) of HGSA within the past 12 months, and previous MRSA isolation were significant risk factors for MRSA carriage. Among HCWs (n = 126), the prevalence of MRSA carriage was 4.8% and the incidence rate was 61/1000 person-years. Nurses and nurse aids were the HCW categories with the highest risk of becoming colonized with MRSA over time (p = 0.01). One HCW chronically colonized was detected. Molecular typing revealed a clonal identity for isolates recovered from patients and HCWs of the same wards, with 88.6% of isolates belonging to the EMRSA-15 (ST22-MRSA-IV) clone.

Universal methicillin-resistant Staphylococcus aureus (MRSA) surveillance for adults at hospital admission: an economic model and analysis

BACKGROUND

Methicillin-resistant Staphylococcus aureus (MRSA) transmission and infections are a continuing problem in hospitals. Although some have recommended universal surveillance for MRSA at hospital admission to identify and to isolate MRSA-colonized patients, there is a need for formal economic studies to determine the cost-effectiveness of such a strategy.

METHODS

We developed a stochastic computer simulation model to determine the potential economic impact of performing MRSA surveillance (ie, single culture of an anterior nares specimen) for all hospital admissions at different MRSA prevalences and basic reproductive rate thresholds from the societal and third party-payor perspectives. Patients with positive surveillance culture results were placed under isolation precautions to prevent transmission by way of respiratory droplets. MRSA-colonized patients who were not isolated could transmit MRSA to other hospital patients.

RESULTS

The performance of universal MRSA surveillance was cost-effective (defined as an incremental cost-effectiveness ratio of less than $50,000 per quality-adjusted life-year) when the basic reproductive rate was 0.25 or greater and the prevalence was 1% or greater. In fact, surveillance was the dominant strategy when the basic reproductive rate was 1.5 or greater and the prevalence was 15% or greater, the basic reproductive rate was 2.0 or greater and the prevalence was 10% or greater, and the basic reproductive rate was 2.5 or greater and the prevalence was 5% or greater.

CONCLUSIONS

Universal MRSA surveillance of adults at hospital admission appears to be cost-effective at a wide range of prevalence and basic reproductive rate values. Individual hospitals and healthcare systems could compare their prevailing conditions (eg, the prevalence of MRSA colonization and MRSA transmission dynamics) with the benchmarks in our model to help determine their optimal local strategies.

Active surveillance testing and decontamination strategies in intensive care units to reduce methicillin-resistant Staphylococcus aureus infections

BACKGROUND

Active surveillance testing (AST) and decontamination strategies (DS) using a topical methicillin-resistant Staphylococcus aureus (MRSA) cleansing agent was introduced in July 2007 in a medical intensive care unit (MICU) and a surgical ICU (SICU) of a tertiary care hospital to reduce the incidence of MRSA infection.

METHODS

Data on ICU admissions between July 1, 2007, and June 30, 2008, was analyzed. All subjects, excluding known MRSA status, had an ICU length of stay (LOS) of more than 24 hours and nasal swabs performed on ICU admission, every 7 days during the ICU stay, and on discharge. MICU and SICU specimens were sent for culture and in-house real-time polymerase chain reaction, respectively. MRSA-colonized (MRSAc) patients were subjected to contact isolation precautions and DS for 5 days or until ICU discharge. Data recorded included demographics, LOS, and antibiotic use. Results were analyzed using SPSS. Control charts were used to determine special cause variation.

RESULTS

Of 653 eligible patients admitted to the ICU, 85 (13%) were determined to be MRSAc on ICU admission. A further 15% (52 of 351) were determined to be MRSAc during the ICU stay or at discharge. Thus, AST detected MRSA in at least 137 of the 653 patients (21.0%). In contrast, clinical cultures for MRSA were positive in only 12 patients (1.8%). Compared with noncolonized patients, MRSAc patients at any screening point had a longer pre-ICU LOS (P =.001), received more antibiotics (P = .004), and had a longer ICU LOS (P = .003). Compared with the preintervention period of July 2006 to June 2007, there was no significant reduction in mean MRSA infection incidence rate in both ICUs (3.8 to 3.0 per 1000 patient-days [P = .057] in the SICU and 1.4 to 1.7 per 1000 patient-days in the MICU) following intervention.

CONCLUSIONS

In ICUs, AST detected 11 times more MRSA than clinical cultures. The lack of reduction in MRSA infection rates in the ICUs does not negate the roles of AST and DS, but does argue for better study design and outcome measures like MRSA transmission incidence, which perhaps would have demonstrated a true benefit of AST and DS.

To screen or not to screen for methicillin-resistant Staphylococcus aureus

There are few more compelling questions in clinical microbiology today than the issue of whether or not to screen for the presence of methicillin-resistant Staphylococcus aureus (MRSA), with the results being used to institute infection control interventions aimed at preventing transmission of MRSA in health care environments. Numerous different matters must be addressed when considering a screening program. Who is to be screened, what method is to be employed to detect MRSA, and what sites should be sampled? When and how often should the screening be performed? Who is going to pay for the screening, and, finally and perhaps most importantly, how are screening results to be communicated to health care providers and what kind of interventions are best undertaken based on the results? Numerous governmental agencies have mandated MRSA screening programs, and yet several authorities in infection control organizations have questioned the appropriateness of mandated screening. In this Point-Counterpoint feature, Dr. Lance Peterson of Evanston Hospital (Evanston, IL) offers his perspective on why screening for MRSA is to be encouraged. Dr. Daniel Diekema of the University of Iowa Carver College of Medicine (Iowa City, IA) offers an opposing view.

Controlling antimicrobial resistance in the hospital

Most evidence-based methods to control the spread of antimicrobial resistance have been developed and applied to the hospital setting. Strategies to control the emergence and spread of antimicrobial resistance in hospitals can be categorized as either infection control or antibiotic stewardship strategies. Infection control is the discipline focused on preventing the spread of infections within the health care setting; antibiotic stewardship can help minimize the emergence of multidrug-resistant organisms by promoting prudent use of antibiotics. This article describes different infection control and antibiotic management strategies that can be used to control antimicrobial resistance in hospital settings.

Nasopharyngeal colonization with methicillin-resistant staphylococcus aureus and mortality among patients in an intensive care unit

Nasopharyngeal colonization with Methicillin-resistant Staphylococcus aureus (MRSA) is common in critically ill patients, but its effect on patient prognosis is not fully elucidated. A retrospective cohort study was carried out enrolling 122 patients from an intensive care unit who were screened weekly for nasopharyngeal colonization with MRSA. The outcomes of interest were: general mortality and mortality by infection. Several exposure variables (severity of illness, procedures, intercurrences and MRSA nasopharyngeal colonization) were analyzed through univariate and multivariable models. Factors significantly associated with mortality in general or due to infection were: APACHE II and lung disease. The performance of surgery predicted favorable outcomes. MRSA colonization did not predict mortality in general (OR=1.02; 95%CI=0.35-3.00; p=0.97) or by infectious causes (OR=0.96; 95%CI=0.33-2.89; p=0.96). The results suggest that, in the absence of severity of illness factors, colonization with MRSA is not associated with unfavorable outcomes.

Comparison of MRSASelect Agar, CHROMagar Methicillin-Resistant Staphylococcus aureus (MRSA) Medium, and Xpert MRSA PCR for detection of MRSA in Nares: diagnostic accuracy for surveillance samples with various bacterial densities

Rapid laboratory methods provide optimal support for active surveillance efforts to screen for methicillin-resistant Staphylococcus aureus (MRSA). Most laboratories struggle to determine the optimal use of resources, considering options to balance cost, speed, and diagnostic accuracy. To assess the performance of common methods, the first comparison of MRSASelect agar (MS) and CHROMagar MRSA (CA), with and without broth enrichment followed by a 24-h subculture to MS, was performed. Results were compared to those of the Xpert MRSA assay. For direct culture methods, the agreement between MS and CA was 98.8%. At 18 h, direct MS identified 93% of all positive samples from direct culture and 84% of those identified by the Xpert MRSA. For Trypticase soy broth-enriched MS culture, incubated overnight and then subcultured for an additional 24 h, the agreement with Xpert MRSA was 96%. The agreement between direct MS and Xpert MRSA was 100% when semiquantitative culture revealed a bacterial density of 2+ or greater; however, discrepancies between culture and Xpert MRSA arose for MRSA bacterial densities of 1+ or less, indicating low density as a common cause of false-negative culture results. Since 1+ or less was established as the most common MRSA carrier state, broth enrichment or PCR may be critical for the identification of all MRSA carriers who may be reservoirs for transmission. In this active-surveillance convenience sample, the use of broth enrichment followed by subculture to MS offered a low-cost but sensitive method for MRSA screening, with performance similar to that of Xpert MRSA PCR.

Isolation precautions for antibiotic-resistant bacteria in healthcare settings

PURPOSE OF REVIEW

Emergence of drug-resistant bacteria and new or changing infectious pathogens is an important public health problem. Transmission of these pathogens in an acute care setting may occur frequently if proper precautions are not taken. Despite several guidelines and an abundance of literature on the prevention of transmission of epidemiologically important organisms in the healthcare setting, substantial controversy exists. This review focuses on recent data regarding the use of infection control and isolation precautions.

RECENT FINDINGS

New data are available, but the conflict surrounding the use of active surveillance of methicillin-resistant Staphylococcus aureus (MRSA) has not been resolved. The emergence of multidrug-resistant Gram-negative bacteria has prompted a greater interest in infection control strategies for prevention of their spread. Outbreaks of Clostridium difficile have responded to broad infection control initiatives, but further research is required to determine whether the best infection control precautions are being utilized.

SUMMARY

Effective prevention of the transmission of pathogens within the healthcare system requires a multifaceted approach. Existing guidelines should be used to create institutional policies specific to individual patient populations, problem pathogens and the ability to practically implement various infection control procedures. Despite ongoing study, the use of active surveillance to prevent transmission of MRSA continues to be a complex, controversial and challenging issue.

Screening and isolation for infection control

Control measures aimed to reduce the prevalence of healthcare-associated infections include active surveillance cultures (ASCs), contact isolation of patients colonised with epidemiologically significant pathogens, and pre-emptive isolation of high risk patients. However, the benefits of these measures are questionable. A systematic review of isolation policies demonstrated that intensive concerted interventions including isolation can substantially reduce nosocomial meticillin-resistant Staphylococcus aureus (MRSA) infection. Monitoring of interventions is fundamental. Surveillance data should be presented and fed back appropriately. International guidelines suggest that only intensive care units should apply extensive ASCs. However, legislation for mandatory screening at hospital admission has been advocated in many countries. Targeted screening could be used to limit the potential for dissemination of antibiotic-resistant pathogens from otherwise unsuspected carriers from the start of patients' hospitalisation, as opposed to other strategies, in which screening programmes target patients already hospitalised. Although the influx of antibiotic-resistant pathogens into the hospital would not change, early detection would reduce the time colonised patients might have to disseminate pathogens. Recently, rapid methods for molecular detection of MRSA have been developed. Data on the impact of these tests on the MRSA acquisition rate are extremely heterogeneous. Published studies differ according to the settings in which they have been evaluated, the choice of patient population to be screened, other infection control measures employed and, most importantly, study design and baseline prevalence of MRSA. Based on these studies, definitive recommendations cannot be made.