Relationship between spread of methicillin-resistant Staphylococcus aureus and antimicrobial use in a French university hospital

A case study on Staphylococcus aureus bacteraemia: available treatment options, antibiotic R&D and responsible antibiotic-use strategies

Objectives

This case study addresses: (i) antibiotic treatment options for Staphylococcus aureus bacteraemia (SAB), for both empirical and targeted therapy; (ii) the current status of and priorities for the antibiotic pipeline to ensure access of effective antibiotics for SAB; and (iii) strategies for responsible antibiotic use relevant to the clinical management of SAB.

Methods

Evidence to address the aims was extracted from the following information sources: (i) EUCAST and CLSI recommendations, summaries of product characteristics (SPCs), antibiotic treatment guidelines and the textbook Kucers’ The Use of Antibiotics; (ii) the www.clinicaltrial.gov database; and (iii) quality indicators for responsible antibiotic use.

Results

Current monotherapy treatment options for SAB include only three drug classes (β-lactams, glycopeptides and lipopeptides), of which two also cover MRSA bacteraemia (glycopeptides and lipopeptides). The analysis of the antibiotic pipeline and ongoing clinical trials revealed that several new antibiotics with S. aureus (including MRSA) coverage were developed in the past decade (2009–19). However, none belonged to a new antibiotic class or had superior effectiveness and their added clinical value for SAB remains to be proven. Responsible antibiotic use for the treatment of SAB was illustrated using 11 quality indicators.

Conclusions

Awareness of the problem of a limited antibiotic arsenal, together with incentives (e.g. push incentives), is needed to steer the R&D landscape towards the development of novel and effective antibiotics for treating SAB. In the meantime, responsible antibiotic use guided by quality indicators should preserve the effectiveness of currently available antibiotics for treating SAB.

Impact of colonization pressure on acquisition of extended-spectrum β-lactamase-producing Enterobacterales and meticillin-resistant Staphylococcus aureus in two intensive care units: a 19-year retrospective surveillance

BACKGROUND

Colonization pressure is a risk factor for intensive care unit (ICU)-acquired multi-drug-resistant organisms (MDROs).

AIM

To measure the long-term respective impact of colonization pressure on ICU-acquired extended-spectrum β-lactamase-producing Enterobacterales (ESBL-PE) and meticillin-resistant Staphylococcus aureus (MRSA).

METHODS

All patients admitted to two ICUs (medical and surgical) between January 1997 and December 2015 were included in this retrospective observational study. Rectal and nasal surveillance cultures were obtained at admission and weekly thereafter. Contact precautions were applied for colonized or infected patients. Colonization pressure was defined as the ratio of the number of MDRO-positive patient-days (PDs) of each MDRO to the total number of PDs. Single-level negative binomial regression models were used to evaluate the incidence of weekly MDRO acquisition.

FINDINGS

Among the 23,423 patients included, 2327 (10.0%) and 1422 (6.1%) were colonized with ESBL-PE and MRSA, respectively, including 660 (2.8%) and 351 (1.5%) acquisitions. ESBL-PE acquisition increased from 0.51/1000 patient-exposed days (PEDs) in 1997 to 6.06/1000 PEDs in 2015 (P<0.001). In contrast, MRSA acquisition decreased steadily from 3.75 to 0.08/1000 PEDs (P<0.001). Controlling for period-level covariates, colonization pressure in the previous week was associated with MDRO acquisition for ESBL-PE (P<0.001 and P=0.04 for medical and surgical ICU, respectively), but not for MRSA (P=0.34 and P=0.37 for medical and surgical ICU, respectively). The increase in colonization pressure was significant above 100/1000 PDs for ESBL-PE.

CONCLUSION

Colonization pressure contributed to the increasing incidence of ESBL-PE but not MRSA. This study suggests that preventive control measures should be customized to MDROs.

What antibiotics for what pathogens? The sensitivity spectrum of isolated strains in an intensive care unit

Antibiotic sensitivity spectrum of isolated strains differs according to hospital departments, the hospitals themselves, and countries. Discrepancies also exist in terms of antibiotic use and dosage. The aim of the present study is to compare the antibacterial agents, the types of infections, the number and type of pathogens, and the sensitivity to antibiotics used in the Intensive Care Unit (ICU) of the Emergency Clinical County Hospital of Oradea, Romania. Over a one-year period, data were gathered from the pharmacy computer system and medical records of inpatients. WHO Anatomical Therapeutic Chemical (ATC)/defined daily doses (DDD) methodology was used to assess drug administration data, and antibiotic use was expressed as DDD/1000 PD (patient days). The antibiotic susceptibility of isolated strains was expressed through the cumulative antibiogram. The overall consumption of antimicrobial agents was 1247.47 DDD/1000 PD. The most common drugs used were cephalosporins and fluoroquinolones (52.97% of the total). Ceftriaxone was the most commonly used, followed by levofloxacin. Infections of the respiratory and urinary tract were the most frequently diagnosed infections. The most commonly isolated bacteria type was Acinetobacter baumannii (22.12% overall), isolated especially from the respiratory tract and resistant to all the β-lactam antibiotics including carbapenems. Antimicrobials intake at the ICU is much higher compared to medical and surgical wards. After we tested the existence of a possible connection between antibiotic consumption and antibiotic resistance of bacteria, it was revealed that on our sample exists a poor positive association.

Estimating Factors Related to Fluoroquinolone Resistance Based on One Health Perspective: Static and Dynamic Panel Data Analyses From Europe

Objectives: Antimicrobial resistance (AMR) has become a One Health problem in which fluoroquinolone resistance has caused great concern. The aim of this study is to estimate factors related to fluoroquinolone resistance involving the professionals and antimicrobial consumption (AMC) in human and animal fields. Methods: A country-level panel data set in Europe from 2005 to 2016 was constructed. The dependent variables were measured by Escherichia coli ( E. coli ) and Pseudomonasaeruginosa ( P. aeruginosa ) resistance rates to fluoroquinolones. Both the static and dynamic panel data models were employed to estimate the above factors associated with the resistance rates. Results: The 10% increase in the number of medical staff and veterinary professionals per 100,000 population were significantly correlated with the 32.44% decrease of P. aeruginosa and 0.57% decrease of E. coli resistance rates to fluoroquinolones (Coef. = -3.244, -0.057; p = 0.000, 0.030, respectively). The 10% increase in the human AMC was correlated with 10.06% and 8.04% increase of P. aeruginosa resistance rates to fluoroquinolones in static and dynamic models (Coef. = 1.006, 0.804; p = 0.006, 0.001, respectively). The 10% increase in veterinary AMC was related to a 1.65% decrease of P. aeruginosa resistance rates to fluoroquinolones (Coef. = -0.165, p = 0.019). Conclusions: The increases in medical and veterinary professionals are respectively associated with the decrease of P. aeruginosa and E. coli resistance rates to fluoroquinolones. The increase in human AMC is also associated with increase of P. aeruginosa resistance rates, while the increase in veterinary AMC was found to be associated with a decrease in resistance rate for P. aeruginosa.

Impact of respiratory virus molecular testing on antibiotic utilization in community-acquired pneumonia

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Viral pathogens account for approximately 30% of community-acquired pneumonia (CAP) cases.

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Polymerase chain reaction respiratory virus panels can identify specific viral pathogens in CAP.

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Study patients with viral CAP had only a minor decrease in antibiotic utilization.

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Additional interventions are needed to reduce antibiotic use in viral CAP.

We compared the clinical characteristics and antibiotic therapy of community-acquired pneumonia patients who were positive on a respiratory virus molecular test (polymerase chain reaction) with those who were negative. We found that respiratory virus molecular polymerase chain reaction testing has a minimal impact on reducing antibiotic utilization among viral pneumonia patients.

Correlation between antibiotic consumption and resistance of bloodstream bacteria in a University Hospital in North Eastern Italy, 2008-2014

PURPOSE

The spread of multidrug-resistant bacteria is a worrisome problem worldwide. This study investigated the correlation between antibiotic consumption and antimicrobial resistance trends of the most important bacteria causing bacteremia at the University hospital of Trieste, Italy, from 2008 to 2014.

METHODS

Antibiotic consumption (Defined Daily Dose-DDD-per 100 patient/days) and antibiotic resistance (percentage of antibiotic intermediate o resistant isolates) were analyzed independently with linear correlation by year. Potential correlations between antibiotic consumption and bacteria resistance rates were investigated through the Pearson's correlation.

RESULTS

The overall consumption of antibiotic grew from 80 to 97 DDD 100 patient/days (p = 0.005) during the study period. The increased consumption of amoxicillin/clavulanate and piperacillin/tazobactam was associated with the reduction of MRSA rate from 48.5 to 25.9% (p = 0.007 and p = 0.04, respectively). The increased consumption of piperacillin/tazobactam was associated with the reduction of ESBL-positive Enterobacteriaceae rate from 28.9 to 20.9% (p = 0.01). The increased consumption of carbapenems was associated with the increased rate of carbapenem-resistant Acinetobacter baumannii from 0 to 96.4% (p = 0.03). No carbapenem-resistant Enterobacteriaceae isolates were reported. The consumption of vancomycin grew significantly (p = 0.005). A dramatic spread of vancomycin-resistant Enterococcus faecium occurred in 2014. The consumption of fluoroquinolones and extended-spectrum cephalosporins remained stable.

CONCLUSIONS

An antibiotic stewardship program targeted to limit the consumption of extended-spectrum cephalosporins and fluoroquinolones in favor of amoxicillin/clavulanate and piperacillin/tazobactam correlates with a decreasing rate of MRSA and ESBL-positive Enterobacteriaceae. The analysis of correlations between antibiotic consumption and bacterial resistance rates is a useful tool to orient antimicrobial stewardship policies at local level.

Prior antibacterial drug exposure in dogs with meticillin-resistant Staphylococcus pseudintermedius (MRSP) pyoderma

BACKGROUND

The emergence of meticillin-resistant Staphylococcus pseudintermedius (MRSP) has become a significant animal health problem. Recent studies have indicated that previous antibacterial drug exposure is a factor in acquisition of meticillin-resistant strains of staphylococci.

HYPOTHESIS/OBJECTIVES

The purpose of this study was to identify factors associated with prior antimicrobial drug use and MRSP pyoderma in dogs presented to a veterinary teaching hospital.

ANIMALS

Dogs diagnosed with pyoderma associated with MRSP (n = 53) or meticillin-sensitive S. pseudintermedius (MSSP; n = 45).

METHODS

The medical records of dogs diagnosed with pyoderma associated with isolation of S. pseudintermedius between January 2006 and November 2012 were reviewed. All cases with a complete twelve month to 3 yr drug history prior to the diagnosis were included.

RESULTS

Fifty two of 53 (98%) MRSP cases and 42 of 45 (93%) MSSP cases had received at least one course of antibacterial drug prior to diagnosis. The total number of antibacterial drug prescriptions provided to pet owners and the variety of antibacterial drug classes represented were higher for cases with MRSP than for cases with MSSP (P < 0.0001 and P = 0.009, respectively). More cases with MRSP (98%) received beta-lactam drugs than those with MSSP (82%; P = 0.007) and the proportion of MRSP cases that had received concurrent immunomodulatory therapy was higher (62% versus 42%; P = 0.048).

CONCLUSIONS AND CLINICAL IMPORTANCE

These results suggest that the total number of antibacterial drug prescriptions, exposure to multiple drug classes (beta-lactams in particular) and concurrent immunomodulatory therapy may be associated with increased risk for acquisition of MRSP.

Rapid, highly discriminatory binary genotyping to demonstrate methicillin-resistant Staphylococcus aureus transmission in a tertiary care intensive care unit

OBJECTIVES

No previous studies of methicillin-resistant Staphylococcus aureus (MRSA) epidemiology in adult intensive care units (ICUs) have assessed the utility of rapid, highly discriminatory strain typing in the investigation of transmission events.

DESIGN

Observational.

SETTING

A 22-bed medical-surgical adult ICU. Patients Those admissions MRSA-positive on initial screening and all admissions <48 hours in duration were excluded, leaving a cohort of 653 patients (median age, 61 years; APACHE-II, 19).

METHODS

We conducted this study of MRSA transmission over 1 year (August 1, 2011 to July 31, 2012) using a multiplex PCR-based reverse line blot (mPCR/RLB) assay to genotype isolates from surveillance swabs obtained at admission and twice weekly during ICU stays. MRSA prevalence and incidence rates were calculated and transmission events were identified using strain matching. Colonization pressure was calculated daily by summation of all MRSA cases.

RESULTS

Of 1,030 admissions to ICU during the study period, 349 patients were excluded. MRSA acquisition occurred during 31 of 681 (4.6%) remaining admissions; 19 of 31(61%) acquisitions were genotype-confirmed, including 7 (37%) due to the most commonly transmitted strain. Moving averages of MRSA patient numbers on the days prior to a documented event were used in a Poisson regression model. A significant association was found between transmission and colonization pressure when the average absolute colonization pressure on the previous day was ≥3 (χ2=7.41, P=0.01).

CONCLUSIONS

mPCR/RLB characterizes MRSA isolates within a clinically useful time frame for identification of single-source clusters within the ICU. High MRSA colonization pressure (≥3 MRSA-positive patients) on a given day is associated with an increased likelihood of a transmission event.

Studying the time trend of Methicillin-resistant Staphylococcus aureus (MRSA) in Norway by use of non-stationary γ-Poisson distributions

OBJECTIVES

Study the time development of methicillin-resistant Staphylococcus aureus (MRSA) and forecast future behaviour. The major question: Is the number of MRSA isolates in Norway increasing and will it continue to increase?

DESIGN

Time trend analysis using non-stationary γ-Poisson distributions.

SETTING

Two data sets were analysed. The first data set (data set I) consists of all MRSA isolates collected in Oslo County from 1997 to 2010; the study area includes the Norwegian capital of Oslo and nearby surrounding areas, covering approximately 11% of the Norwegian population. The second data set (data set II) consists of all MRSA isolates collected in Health Region East from 2002 to 2011. Health Region East consists of Oslo County and four neighbouring counties, and is the most populated area of Norway.

PARTICIPANTS

Both data sets I and II consist of all persons in the area and time period described in the Settings, from whom MRSA have been isolated.

PRIMARY AND SECONDARY OUTCOME MEASURES

MRSA infections have been mandatory notifiable in Norway since 1995, and MRSA colonisation since 2004. In the time period studied, all bacterial samples in Norway have been sent to a medical microbiological laboratory at the regional hospital for testing. In collaboration with the regional hospitals in five counties, we have collected all MRSA findings in the South-Eastern part of Norway over long time periods.

RESULTS

On an average, a linear or exponential increase in MRSA numbers was observed in the data sets. A Poisson process with increasing intensity did not capture the dispersion of the time series, but a γ-Poisson process showed good agreement and captured the overdispersion. The numerical model showed numerical internal consistency.

CONCLUSIONS

In the present study, we find that the number of MRSA isolates is increasing in the most populated area of Norway during the time period studied. We also forecast a continuous increase until the year 2017.

Antimicrobial Pharmacokinetics and Pharmacodynamics

BACKGROUND

Antimicrobial medications are beneficial when used appropriately, but adverse effects and resistance sometimes limit therapy. These effects may be more problematic with inappropriate antimicrobial use. Consideration of the pharmacokinetic and pharmacodynamic properties of these medications can help optimize drug use.

METHODS

Review of the pertinent English-language literature.

RESULTS

The pharmacokinetic principles of absorption, distribution, metabolism, and elimination determine whether an appropriate dose of medication reaches the intended pathogen. The pharmacodynamic properties of antimicrobial medications define the relation between the drug concentration and its observed effect on the target pathogen. Improvements in clinical outcomes have been observed when antimicrobial agents are dosed optimally according to these properties. In surgical patients, substantial changes in the volume of distribution and elimination necessitate a clear understanding of these principles. Additionally, less adverse drug effects and antimicrobial resistance may occur with optimal use of these drugs.

CONCLUSION

Selecting and dosing antimicrobial medications with consideration of pharmacokinetics and pharmacodynamics may improve patient outcomes and avoid adverse effects.

Acquisition of Methicillin-Resistant Staphylococcus aureus in the Acute Care Setting: Incidence and Risk Factors

Our objective was to assess the incidence of and risk factors for methicillin-resistant Staphylococcus aureus (MRSA) acquisition among patients in acute care wards. For 5 months, patients were screened for MRSA colonization at admission and at discharge. At admission, 6.6% of patients had cultures positive for MRSA, and 3.1% of patients who had tested negative for MRSA on admission had cultures positive for MRSA at discharge. Only the presence of chronic skin breaks at admission was independently associated with MRSA acquisition.

Antibiotic use and emerging resistance: how can resource-limited countries turn the tide?

Antibiotic resistance is a global crisis driven by appropriate and inappropriate antibiotic use to treat human illness and promote animal growth. The antimicrobial resistance epidemic continues to spread due to the triple threat of unfettered access, minimal product regulation and oversight of antibiotic prescription, and lack of clinical diagnostic tools to support antibiotic de-escalation in low-resource settings. In high-resource settings, evidence-based strategies have improved the appropriateness of antibiotic use, limiting the spread of drug-resistant organisms and reducing hospital-associated infections, strategies which may also be effective to stop the spread of resistance in resource-poor countries. Current research and surveillance efforts on antimicrobial resistance and hospital-associated infections in low-resource settings are extremely limited and largely focused on intensive care units. Many challenges exist to improving antibiotic use and infection control in resource-limited settings, and turning the tide requires intensifying research and surveillance, antimicrobial stewardship, and developing new bedside diagnostic tools for bacterial infections and antimicrobial susceptibility.

Molecular epidemiology and antimicrobial susceptibility of clinical Staphylococcus aureus from healthcare institutions in Ghana

The objective of this study was to determine the antimicrobial susceptibility patterns and clonal diversity of clinical Staphylococcus aureus isolates from Ghana. A total of 308 S. aureus isolates from six healthcare institutions located across Northern, Central and Southern Ghana were characterized by antibiotyping, spa typing and PCR detection of Panton Valentine leukocin (PVL) genes. Methicillin-resistant S. aureus (MRSA) were confirmed by PCR detection of mecA gene and further characterized by SCCmec and multi-locus sequence typing (MLST). The prevalence of antimicrobial resistance was below 5% for all agents tested except for penicillin (97%), tetracycline (42%) and erythromycin (6%). Ninety-one spa types were found, with t355 (ST152, 19%), t084 (ST15, 12%) and t314 (ST121, 6%) being the most frequent types. Based on established associations between spa and MLST types, isolates were assigned to 16 clonal complexes (CCs): CC152 (n = 78), CC15 (n = 57), CC121 (n = 39), CC8 (n = 36), CC5 (n = 33), CC1 (n = 29), CC45 (n = 9), CC88 (n = 8), CC30 (n = 4), CC9 (n = 3), CC25 (n = 2), CC97 (n = 2) CC20 (n = 2), CC707 (n = 2), CC7 (n = 3) and CC522 (n = 1). Most isolates (60%) were PVL-positive, especially those belonging to ST152, ST121, ST5, ST15, ST1, ST8, and ST88. Nine (3%) isolates were MRSA belonging to seven distinct clones: ST88-IV (n = 2), ST250-I (n = 2), ST8-IV (n = 1), ST72-V (n = 1), ST789-IV (n = 1), ST2021-V (n = 1), and ST239-III (n = 1). The study confirmed a high frequency of PVL-positive S. aureus in Africa, low prevalence of antimicrobial resistance and high diversity of MRSA lineages in Ghana compared to developed countries and other African countries. The detection of known pandemic MRSA clones in the absence of routine MRSA identification in most Ghanaian clinical microbiology laboratories calls for capacity building to strengthen surveillance and prevent spread of these clones.

Correlation between antimicrobial consumption and incidence of health-care-associated infections due to methicillin-resistant Staphylococcus aureus and vancomycin-resistant enterococci at a university hospital in Taiwan from 2000 to 2010

Objectives

This study was conducted to investigate the correlation between antibiotic consumption and the incidence of health-care-associated infections (HCAIs) caused by methicillin-resistant Staphylococcus aureus (MRSA) (HCAI-MRSA) and vancomycin-resistant enterococci (VREs) (HCAI-VREs) at a university hospital in Taiwan during the period from 2000 to 2010.

Methods

Data on annual patient-days and annual consumption (defined daily dose/1000 patient-days) of glycopeptides (vancomycin and teicoplanin), linezolid, fusidic acid, tigecycline, and daptomycin were analyzed. Yearly aggregated data on the number of nonduplicate clinical MRSA and VRE isolates causing HCAI were collected.

Results

Overall, the consumption of teicoplanin and linezolid significantly increased during the study period. A significant decrease in the incidence of HCAI-MRSA and a significant increase in the incidence of HCAI-VRE were found during the study period. A significant correlation was found between the increased use of teicoplanin and linezolid and the decreased incidence of HCAI-MRSA. By contrast, positive correlations were found between the consumption of teicoplanin and tigecycline and the incidence of HCAI-VRE.

Conclusion

This study identified various correlations between the consumption of antibiotics and the incidence of HCAI-MRSA and HCAI-VRE. Strict implementation of infection-control guidelines and reinforcement of administering appropriate antibiotic agents would be helpful in decreasing the incidence of MRSA and VRE in hospitals.

Methicillin-resistant Staphylococcus aureus (MRSA) is increasing in Norway: a time series analysis of reported MRSA and methicillin-sensitive S. aureus cases, 1997-2010

BACKGROUND

Accurate estimates of the incidence and prevalence of methicillin-resistant Staphylococcus aureus (MRSA) infections are needed to inform public health policies. In Norway, where both MRSA infection and carriage are notifiable conditions, the reported incidence of MRSA is slowly increasing. However, the proportion of MRSA in relation to all S. aureus isolates is unknown, making it difficult to determine if the rising incidence is real or an artifact of an increasing number of tests performed.

AIM

To characterize recent trends in MRSA infections and obtain a more complete understanding of the MRSA level in Norway.

METHODS

All reported cases of MRSA and methicillin-sensitive S. aureus (MSSA) from Oslo County (1997-2010) and Health Region East (2008-2008), representing approximately 11% and 36% of the Norwegian population, respectively, were analyzed using a stochastic time series analysis to characterize trends.

RESULTS

In Oslo County, the proportion of methicillin-resistant cases increased from 0.73% to 3.78% during the study period and was well modeled by an exponential growth with a doubling constant of 5.7 years (95% CI 4.5-7.4 years). In Health Region East, the proportion of MRSA cases increased from 0.4% to 2.1% from 2002 to 2008, with a best-fitting linear increase of 0.26% (95% CI 0.21-0.30%) per year. In both cases, the choice of a linear or exponential model for the time trend produced only marginally different model fits. We found no significant changes due to revised national MRSA guidelines published in June 2009. Significant variations in the increasing time trend were observed in the five hospitals within the region. The yearly reported incidence of MSSA was relatively stable in both study areas although we found seasonal patterns with peaks in August.

CONCLUSION

The level of MRSA is increasing in Norway, and the proportion of methicillin resistance in all S. aureus isolates are higher than the reported proportion of MRSA in invasive infections.

Surveillance on secular trends of incidence and mortality for device-associated infection in the intensive care unit setting at a tertiary medical center in Taiwan, 2000-2008: a retrospective observational study

Background

Device–associated infection (DAI) plays an important part in nosocomial infection. Active surveillance and infection control are needed to disclose the specific situation in each hospital and to cope with this problem effectively. We examined the rates of DAI by antimicrobial-resistant pathogens, and 30–day and in–hospital mortality in the intensive care unit (ICU).

Methods

Prospective surveillance was conducted in a mixed medical and surgical ICU at a major teaching hospital from 2000 through 2008. Trend analysis was performed and logistic regression was used to assess prognostic factors of mortality.

Results

The overall rate of DAIs was 3.03 episodes per 1000 device–days. The most common DAI type was catheter–associated urinary tract infection (3.76 per 1000 urinary catheter–days). There was a decrease in DAI rates in 2005 and rates of ventilator–associated pneumonia (VAP, 3.18 per 1000 ventilator–days) have remained low since then (p < 0.001). The crude rates of 30–day (33.6%) and in–hospital (52.3%) mortality, as well as infection by antibiotic-resistant VAP pathogens also decreased. The most common antimicrobial-resistant pathogens were methicillin–resistant Staphylococcus aureus (94.9%) and imipenem–resistant Acinetobacter baumannii (p < 0.001), which also increased at the most rapid rate. The rate of antimicrobial resistance among Enterobacteriaceae also increased significantly (p < 0.05). After controlling for potentially confounding factors, the DAI was an independent prognostic factor for both 30–day mortality (OR 2.51, 95% confidence interval [CI] 1.99–3.17, p = 0.001) and in–hospital mortality (OR 3.61, 95% CI 2.10–3.25, p < 0.001).

Conclusions

The decrease in the rate of DAI and infection by resistant bacteria on the impact of severe acute respiratory syndrome can be attributed to active infection control and improved adherence after 2003.

Rates and appropriateness of antimicrobial prescribing at an academic children's hospital, 2007-2010

OBJECTIVE AND DESIGN

Antimicrobial use in hospitalized children has not been well described. To identify targets for antimicrobial stewardship interventions, we retrospectively examined pediatric utilization rates for 48 antimicrobials from 2007 to 2010 as well as appropriateness of vancomycin and cefepime use in 2010.

PATIENTS AND SETTING

All children hospitalized between 2007 and 2010 at the Mayo Clinic Children's Hospital, a 120-bed facility within a larger adult hospital in Rochester, Minnesota.

METHODS

We calculated antimicrobial utilization rates in days of therapy per 1,000 patient-days. Details of vancomycin and cefepime use in 2010 were abstracted by chart review. Two pediatric infectious disease physicians independently assessed appropriateness of antibiotic use.

RESULTS

From 2007 to 2010, 9,880 of 17,242 (57%) hospitalized children received 1 or more antimicrobials. Antimicrobials (days of therapy per 1,000 patient-days) used most frequently in 2010 were cefazolin (97.8), vancomycin (97.1), fluconazole (76.4), piperacillin-tazobactam (70.7), and cefepime (67.6). Utilization rates increased significantly from 2007 to 2010 for 10 antimicrobials, including vancomycin, fluconazole, piperacillin-tazobactam, cefepime, trimethoprim-sulfamethoxazole, caspofungin, and cefotaxime. In 2010, inappropriate use of vancomycin and cefepime was greater in the pediatric intensive care unit than ward (vancomycin: 17.8% vs 6.4%, P = .001; cefepime: 9.2% vs 3.9%, P = .142) and on surgical versus medical services (vancomycin: 20.5% vs 8.0%, P = .001; cefepime: 19.4% vs 3.4%, P ≤ .001). The most common reason for inappropriate antibiotic use was failure to discontinue or de-escalate therapy.

CONCLUSIONS

In our children's hospital, use of 10 antimicrobials increased during the study period. Inappropriate use of vancomycin and cefepime was greatest on the critical care and surgical services, largely as a result of failure to de-escalate therapy, suggesting targets for future antimicrobial stewardship interventions.

Correlation between levofloxacin consumption and the incidence of nosocomial infections due to fluoroquinolone-resistant Escherichia coli

BACKGROUND/PURPOSE

The relationship between fluoroquinolone resistance in Escherichia coli isolates causing nosocomial infection and hospital antibiotic consumption were investigated. Restriction of levofloxacin use was implemented to control the incidence of fluoroquinolone-resistant E coli in the hospital.

METHODS

The study was conducted from January 2004 to December 2010. Antimicrobial agent consumption was obtained from the pharmacy computer system and presented as the defined daily doses per 1000 patient-days every 6 months. The incidence of fluoroquinolone-resistant E coli isolates causing nosocomial infections was obtained from the Department of Infection Control every 6 months. An antimicrobial stewardship program, restricting levofloxacain use, was implemented in July 2007.

RESULTS

The incidence of fluoroquinolone-resistant E coli causing nosocomial infections was significantly correlated with fluoroquinolone usage (p = 0.005), but not with the use of third- or fourth-generation cephalosporins, piperacillin-tazobactam, or carbapenems. Parenteral (p = 0.002), oral (p = 0.018), and total levofloxacin (p = 0.001) use were significantly correlated with the extent of fluoroquinolone resistance. With a reduction of levofloxacin use, a decrease of the incidence of fluoroquinolone resistance in E coli isolates was observed.

CONCLUSION

There is a significant correlation between levofloxacin use and the incidence of nosocomial fluoroquinolone-resistant E coli isolates. The incidence of fluoroquinolone-resistant E coli could be reduced by limiting levofloxacin consumption.

Reduction of fluoroquinolone use is associated with a decrease in methicillin-resistant Staphylococcus aureus and fluoroquinolone-resistant Pseudomonas aeruginosa isolation rates: a 10 year study

OBJECTIVES

High rates of methicillin-resistant Staphylococcus aureus (MRSA) and fluoroquinolone-resistant Pseudomonas aeruginosa may be related, in part, to the overuse of fluoroquinolones. The objective was to analyse and correlate long-term surveillance data on MRSA and fluoroquinolone-resistant P. aeruginosa rates and antibiotic consumption after implementation of an institution-wide programme to reduce fluoroquinolone use.

METHODS

An interrupted time series/quasi-experimental study of monthly fluoroquinolone use and MRSA and fluoroquinolone-resistant P. aeruginosa isolation rates was carried out in a tertiary hospital during three periods: pre-intervention (January 2000-August 2005), intervention (September 2005-March 2006), and post-intervention (March 2006-March 2010). The effect of the intervention on the consumption of fluoroquinolones and bacterial resistance was assessed using segmented regression analyses.

RESULTS

Mean monthly fluoroquinolone consumption dropped by 29.1 defined daily doses per 1000 patient-days (DDD/1000 PD) (95% CI 13.1-45.9; P = 0.0005) from a mean of 148.2 to 119.1 DDD/1000 PD during the intervention period. A sustained and significant decrease in fluoroquinolone consumption of -0.95 DDD/1000 PD/month was also observed during the post-intervention period (P = 0.0002). During the post-intervention period the rate of fluoroquinolone-resistant P. aeruginosa continuously decreased, from a mean of 42% to 26%, with a constant relative change rate of -13%/year (95% CI -19 to -5, P = 0.001). A decrease in the MRSA rate was observed during the intervention period, from a mean resistance rate of 27% to 21% (P < 0.0001).

CONCLUSIONS

We showed the sustained impact of a fluoroquinolone control programme on the reduction of fluoroquinolone use with a significant decrease in fluoroquinolone-resistant P. aeruginosa and MRSA rates over 4 years.

Economic implications of the dynamic relationship between antibiotic use and hospital-acquired infections

OBJECTIVES

The emergence and spread of antimicrobial resistance is still an unresolved problem worldwide. Recent evidence shows correlations between the volume of broad-spectrum antibiotics used in the hospital setting and the incidence of multidrug-resistant bacteria. According to this dynamic relationship, loss of antibiotic activity can be modeled as a negative externality of antibiotic consumption.

METHODS

The present study proposes to present an economic model describing the probability of antibiotic treatment failure as a function of antimicrobial use and alcohol-based hand-rub use. Furthermore, the results of recently conducted time-series analyses and cost-of-illness studies are applied to the model to determine the externalities of antibiotic consumption and alcohol-based hand-rub use with respect to the costs of hospital-acquired infections.

RESULTS

According to our calculations, the consumption of third-generation cephalosporins and fluoroquinolones is associated with the highest negative externalities (€143 and €101, respectively) because their use has been shown to be associated with most types of hospital-acquired infections. In contrast, the use of alcohol-based hand-rub solution for hand disinfection is associated with a positive externality of 41 cents per single disinfection of the hands.

CONCLUSIONS

The externalities presented in this work represent a possible application of cost-of-illness data to quantify the impact of antibiotic use on antimicrobial resistance. In addition, the results indicate that most economic research on the topic is biased in assuming the overall use of antibiotics to be responsible for the spread of antimicrobial resistance.

Colonization, pathogenicity, host susceptibility, and therapeutics for Staphylococcus aureus: what is the clinical relevance?

Staphylococcus aureus is a human commensal that can also cause a broad spectrum of clinical disease. Factors associated with clinical disease are myriad and dynamic and include pathogen virulence, antimicrobial resistance, and host susceptibility. Additionally, infection control measures aimed at the environmental niches of S. aureus and therapeutic advances continue to impact upon the incidence and outcomes of staphylococcal infections. This review article focuses on the clinical relevance of advances in our understanding of staphylococcal colonization, virulence, host susceptibility, and therapeutics. Over the past decade key developments have arisen. First, rates of nosocomial methicillin-resistant S. aureus (MRSA) infections have significantly declined in many countries. Second, we have made great strides in our understanding of the molecular pathogenesis of S. aureus in general and community-associated MRSA in particular. Third, host risk factors for invasive staphylococcal infections, such as advancing age, increasing numbers of invasive medical interventions, and a growing proportion of patients with healthcare contact, remain dynamic. Finally, several new antimicrobial agents active against MRSA have become available for clinical use. Humans and S. aureus co-exist, and the dynamic interface between host, pathogen, and our attempts to influence these interactions will continue to rapidly change. Although progress has been made in the past decade, we are likely to face further surprises such as the recent waves of community-associated MRSA.

MRSA prevention strategies and current guidelines

We review prevention strategies to minimise the risk of MRSA soft tissue and bone infections, which can be devastating for the patient and costly for the healthcare provider. Department of Health (England) policy is that screening for emergency admissions will be mandatory from 2011, in addition to existent elective admission screening. Rapid screening technology has not been shown to be cost-effective, meaning that there will be a lag time between admission and the patient's MRSA status being known. Thus, standard infection control policies regarding isolation of high-risk patients will remain, with a continuing focus on MRSA decolonisation, aimed at minimising the risks of auto-infection and transmission to other patients. Antimicrobial prescribing policies should be designed to take into account the local burden of resistant organisms, but also minimise unnecessary antibiotic use. There is an increasing realisation that reducing the use of fluoroquinolones and third-generation cephalosporins (which have been associated with increased carriage of MRSA) in patient populations where MRSA is prevalent can be a useful control measure. Prevention of orthopaedic infections clearly involves general operating theatre protocols, such as suitable antiseptic skin preparation, and additional measures including the use of laminar airflow. Antibiotic prophylaxis is adjusted in patients known to have MRSA to include a glycopeptide, and local guidelines may adopt such regimens for all patients due to the burden of MRSA in the local patient population. A future development that may have an effect on practice is the development of a Staphylococcus aureus vaccine, which has been shown to be cost-effective in a computer-modelled evaluation.

Predictors of agr dysfunction in methicillin-resistant Staphylococcus aureus (MRSA) isolates among patients with MRSA bloodstream infections

Despite emerging evidence that dysfunction in the accessory gene regulator (agr) locus is associated with deleterious outcomes among patients treated with vancomycin for methicillin-resistant Staphylococcus aureus (MRSA) infections, factors predictive of agr dysfunction have not been evaluated. This study describes the epidemiology of agr dysfunction, identifies predictors of agr dysfunction in MRSA isolates among those with MRSA bloodstream infections, and describes the relationship between agr dysfunction and other microbiologic phenotypes. A cross-sectional study of patients with MRSA bloodstream infections at two institutions in upstate New York was performed. Clinical data on demographics, comorbidities, disease severity, hospitalization history, and antibiotic history were collected. Microbiologic phenotypes, including agr dysfunction, MIC values by broth microdilution (BMD) and Etest, and vancomycin heteroresistance (hVISA) were tested. Multivariable analyses were performed to identify factors predictive of agr dysfunction. Among 200 patients with an MRSA bloodstream infection, the proportion of strains with agr dysfunction was 31.5%. The distribution of MICs determined by both BMD and Etest were equivalent across agr groups, and there was no association between agr dysfunction and the presence of hVISA. Severity of illness, comorbidities, and hospitalization history were comparable between agr groups. In the multivariate analysis, prior antibiotic exposure was the only factor of variables studied found to be predictive of agr dysfunction. This relationship was predominantly driven by prior beta-lactam and fluoroquinolone administration in the bivariate analysis. Identifying these institution-specific risk factors can be used to develop a process to assess the risk of agr dysfunction and guide empirical antibiotic therapy decisions.

Systematic review of measurement and adjustment for colonization pressure in studies of methicillin-resistant Staphylococcus aureus, vancomycin-resistant enterococci, and clostridium difficile acquisition

OBJECTIVE

Colonization pressure is an important infection control metric. The aim of this study was to describe the definition and measurement of and adjustment for colonization pressure in nosocomial-acquisition risk factor studies of methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-resistant enterococci (VRE), and Clostridium difficile.

METHODS

We performed a computerized search of studies of nosocomial MRSA, VRE, and C. difficile acquisition published before July 1, 2009, through MEDLINE. Studies were included if a study outcome was MRSA, VRE, or C. difficile acquisition; the authors identified risk factors associated with MRSA, VRE, or C. difficile acquisition; and the study measured colonization pressure.

RESULTS

The initial MEDLINE search yielded 505 articles. Sixty-six of these were identified as studies of nosocomial MRSA, VRE, or C. difficile acquisition; of these, 18 (27%) measured colonization pressure and were included in the final review. The definition of colonization pressure varied considerably between studies: the proportion of MRSA- or VRE-positive patients (5 studies), the proportion of MRSA- or VRE-positive patient-days (6 studies), or the total or mean number of MRSA-, VRE-, or C. difficile-positive patients or patient-days (7 studies) in the unit over periods of varying length. In 10 of 13 studies, colonization pressure was independently associated with MRSA, VRE, or C. difficile acquisition.

CONCLUSION

There is a need for a simple and consistent method to quantify colonization pressure in both research and routine clinical care to accurately assess the effect of colonization pressure on cross-transmission of antibiotic-resistant bacteria.

Secular trends in antibiotic use among neonates: 2001-2008

BACKGROUND

Few data exist on time trends of antibiotic consumption among neonates.

OBJECTIVES

To assess secular trends in antibiotic consumption in the context of an antibiotic policy and the effect of antibiotic use on the development of antimicrobial resistance and outcome among neonates in a single center.

METHODS

We performed a prospective cohort study between 2001 and 2008 to monitor antibiotic consumption among neonates. In parallel, we initiated a policy to shorten antibiotic therapy for clinical sepsis and for infections caused by coagulase-negative staphylococci and to discontinue preemptive treatment when blood cultures were negative. Time trend analyses for antibiotic use and mortality were performed.

RESULTS

In total, 1096 of 4075 neonates (26.7%) received 1281 courses of antibiotic treatment. Overall, days of therapy were 360 per 1000 patient-days. Days of therapy per 1000 patient-days decreased yearly by 2.8% (P < 0.001). Antibiotic-days to treat infections decreased yearly by 6.5% (P = 0.01) while antibiotic-days for preemptive treatment increased by 3.4% per year (P = 0.03). Mean treatment duration for confirmed infections decreased by 2.9% per year (P < 0.001). No significant upward trend was observed for infection-associated mortality. Of 271 detected healthcare-associated infections, 156 (57.6%) were microbiologically documented. The most frequent pathogens were coagulase-negative staphylococci (48.5%) followed by Escherichia coli (13.5%) and enterococci (9.4%). Rates for extended-spectrum beta-lactamase-producing microorganisms and methicillin-resistant Staphylococcus aureus remained low.

CONCLUSIONS

Shortening antibiotic therapy and reducing preemptive treatment resulted in a moderate reduction of antibiotic use in the neonatal intensive care unit and did not increase mortality.

The use of antimicrobial agents after diagnosis of viral respiratory tract infections in hospitalized adults: antibiotics or anxiolytics?

OBJECTIVE

Because extensive antibiotic use by inpatients has been associated with the development of multidrug-resistant organisms, we aimed to determine which variables were associated with the use of antibiotics after viral respiratory tract infection diagnosis among adult patients admitted to the hospital with respiratory symptoms.

METHODS

A retrospective cohort study was conducted at 2 affiliated urban hospitals in Pennsylvania. We identified all adult patients admitted to the hospital during the period from November 1, 2005, through August 1, 2007, with a viral assay positive for influenza A or B, parainfluenza, adenovirus, or respiratory syncytial virus. Among these patients, we identified those who received antibiotics after the diagnosis of viral RTI. Data on demographics; comorbidities; and physical examination, laboratory, and radiographic findings were ascertained to identify risk factors for antimicrobial use among these patients.

RESULTS

A total of 196 hospitalized patients with positive viral assay results were included; 125 of 131 patients administered antibiotics continued to receive them after viral RTI diagnosis. Among 52 patients with an abnormal chest radiograph, 46 continued antibiotic therapy. An abnormal chest radiograph was independently associated with continued antibiotic use (adjusted odds ratio, 4.28 [95% confidence interval, 1.71-10.77]; P = .002). However, the majority of patients (79 of 125 [63%]) who continued antibiotic therapy had normal chest imaging findings. Eight patients (6%) who continued antibiotic therapy and no patients who stopped developed C. difficile infection (95% CI, 1.5-∞; P = .05), but there was no significant difference in length of stay or mortality.

CONCLUSIONS

Antibiotics are commonly used to treat hospitalized patients with known acute viral RTIs. Continued use is strongly associated with abnormal radiograph findings at admission. However, the reasons for continuation of antibiotics in the treatment of the majority of patients with normal radiographs are unclear and may represent inappropriate use.

Two time-series analyses of the impact of antibiotic consumption and alcohol-based hand disinfection on the incidences of nosocomial methicillin-resistant Staphylococcus aureus infection and Clostridium difficile infection

OBJECTIVE

To determine the impact of antibiotic consumption and alcohol-based hand disinfection on the incidences of nosocomial methicillin-resistant Staphylococcus aureus (MRSA) infection and Clostridium difficile infection (CDI).

METHODS

Two multivariate time-series analyses were performed that used as dependent variables the monthly incidences of nosocomial MRSA infection and CDI at the Freiburg University Medical Center during the period January 2003 through October 2007. The volume of alcohol-based hand rub solution used per month was quantified in liters per 1,000 patient-days. Antibiotic consumption was calculated in terms of the number of defined daily doses per 1,000 patient-days per month.

RESULTS

The use of alcohol-based hand rub was found to have a significant impact on the incidence of nosocomial MRSA infection (P< .001). The multivariate analysis (R2=0.66) showed that a higher volume of use of alcohol-based hand rub was associated with a lower incidence of nosocomial MRSA infection. Conversely, a higher level of consumption of selected antimicrobial agents was associated with a higher incidence of nosocomial MRSA infection. This analysis showed this relationship was the same for the use of second-generation cephalosporins (P= .023), third-generation cephalosporins (P= .05), fluoroquinolones (P= .01), and lincosamides (P= .05). The multivariate analysis (R2=0.55) showed that a higher level of consumption of third-generation cephalosporins (P= .008), fluoroquinolones (P= .084), and/or macrolides (P= .007) was associated with a higher incidence of CDI. A correlation with use of alcohol-based hand rub was not detected.

CONCLUSION

In 2 multivariate time-series analyses, we were able to show the impact of hand hygiene and antibiotic use on the incidence of nosocomial MRSA infection, but we found no association between hand hygiene and incidence of CDI.

Acquisition and cross-transmission of Staphylococcus aureus in European intensive care units

OBJECTIVE

To study the acquisition and cross-transmission of Staphylococcus aureus in different intensive care units (ICUs).

METHODS

We performed a multicenter cohort study. Six ICUs in 6 countries participated. During a 3-month period at each ICU, all patients had nasal and perineal swab specimens obtained at ICU admission and during their stay. All S. aureus isolates that were collected were genotyped by spa typing and multilocus variable-number tandem-repeat analysis typing for cross-transmission analysis. A total of 629 patients were admitted to ICUs, and 224 of these patients were found to be colonized with S. aureus at least once during ICU stay (22% were found to be colonized with methicillin-resistant S. aureus [MRSA]). A total of 316 patients who had test results negative for S. aureus at ICU admission and had at least 1 follow-up swab sample obtained for culture were eligible for acquisition analysis.

RESULTS

A total of 45 patients acquired S. aureus during ICU stay (31 acquired methicillin-susceptible S. aureus [MSSA], and 14 acquired MRSA). Several factors that were believed to affect the rate of acquisition of S. aureus were analyzed in univariate and multivariate analyses, including the amount of hand disinfectant used, colonization pressure, number of beds per nurse, antibiotic use, length of stay, and ICU setting (private room versus open ICU treatment). Greater colonization pressure and a greater number of beds per nurse correlated with a higher rate of acquisition for both MSSA and MRSA. The type of ICU setting was related to MRSA acquisition only, and the amount of hand disinfectant used was related to MSSA acquisition only. In 18 (40%) of the cases of S. aureus acquisition, cross-transmission from another patient was possible.

CONCLUSIONS

Colonization pressure, the number of beds per nurse, and the treatment of all patients in private rooms correlated with the number of S. aureus acquisitions on an ICU. The amount of hand disinfectant used was correlated with the number of cases of MSSA acquisition but not with the number of cases of MRSA acquisition. The number of cases of patient-to-patient cross-transmission was comparable for MSSA and MRSA.

Control of endemic methicillin-resistant Staphylococcus aureus--recent advances and future challenges

Although the exact burden of disease caused by methicillin-resistant Staphylococcus aureus (MRSA) remains largely unknown, most experts agree that MRSA infections are an important clinical and public health problem. Thousands of reports have been published during the last four decades concerning epidemiological and microbiological aspects of MRSA, but uncertainty remains about the best approach to prevent and control this worldwide plague, especially endemic MRSA. Epidemiological methods, e.g., risk scores for targeted screening upon admission, rapid molecular tests and pre-emptive isolation of high-risk patients, new decontamination regimens and restriction of certain antibiotic classes, are all promising approaches that may decrease MRSA cross-transmission; however, further evidence is needed before these strategies can be implemented on a wide scale. Control of community MRSA is an additional challenge for the future, requiring improved surveillance and contact tracing, as well as education and treatment of both infected cases and colonised contacts. This review summarises recent advances and studies that address these issues. Overall, it seems that there is no level of MRSA prevalence for which active control measures are no longer warranted.

Modelling the impact of antibiotic use and infection control practices on the incidence of hospital-acquired methicillin-resistant Staphylococcus aureus: a time-series analysis

OBJECTIVES

Methicillin-resistant Staphylococcus aureus (MRSA) is a major nosocomial pathogen worldwide. A wide range of factors have been suggested to influence the spread of MRSA. The objective of this study was to evaluate the effect of antimicrobial drug use and infection control practices on nosocomial MRSA incidence in a 426-bed general teaching hospital in Northern Ireland.

METHODS

The present research involved the retrospective collection of monthly data on the usage of antibiotics and on infection control practices within the hospital over a 5 year period (January 2000-December 2004). A multivariate ARIMA (time-series analysis) model was built to relate MRSA incidence with antibiotic use and infection control practices.

RESULTS

Analysis of the 5 year data set showed that temporal variations in MRSA incidence followed temporal variations in the use of fluoroquinolones, third-generation cephalosporins, macrolides and amoxicillin/clavulanic acid (coefficients = 0.005, 0.03, 0.002 and 0.003, respectively, with various time lags). Temporal relationships were also observed between MRSA incidence and infection control practices, i.e. the number of patients actively screened for MRSA (coefficient = -0.007), the use of alcohol-impregnated wipes (coefficient = -0.0003) and the bulk orders of alcohol-based handrub (coefficients = -0.04 and -0.08), with increased infection control activity being associated with decreased MRSA incidence, and between MRSA incidence and the number of new patients admitted with MRSA (coefficient = 0.22). The model explained 78.4% of the variance in the monthly incidence of MRSA.

CONCLUSIONS

The results of this study confirm the value of infection control policies as well as suggest the usefulness of restricting the use of certain antimicrobial classes to control MRSA.

Relationship between rates of antimicrobial consumption and the incidence of antimicrobial resistance in Staphylococcus aureus and Pseudomonas aeruginosa isolates from 47 French hospitals

OBJECTIVE

To investigate relationships between rates of antimicrobial consumption and the incidence of antimicrobial resistance in Staphylococcus aureus and Pseudomonas aeruginosa isolates from hospitals.

METHODS

We conducted an observational study that used retrospective data from 2002 and linear regression to model relationships. Hospitals were asked to collect data on consecutive S. aureus and P. aeruginosa isolates, consumption rates for antibiotics (ie, anti-infectives for systemic use as defined by Anatomical Therapeutic Chemical class J01), and hospital characteristics, including infection control policies. Rates of methicillin resistance in S. aureus and rates of ceftazidime and ciprofloxacin resistance in P. aeruginosa were expressed as the percentage of isolates that were nonsusceptible (ie, either resistant or intermediately susceptible) and as the incidence of nonsuceptible isolates (ie, the number of nonsuceptible isolates recovered per 1,000 patient-days). The rate of antimicrobial consumption was expressed as the number of defined daily doses per 1,000 patient-days.

SETTING

Data were obtained from 47 French hospitals, and a total of 12,188 S. aureus isolates and 6,370 P. aeruginosa isolates were tested.

RESULTS

In the multivariate analysis, fewer antimicrobials showed a significant association between the consumption rate and the percentage of isolates that were resistant than an association between the consumption rate and the incidence of resistance. The overall rate of antibiotic consumption, not including the antibiotics used to treat methicillin-resistant S. aureus infection, explained 13% of the variance between hospitals in the incidence of methicillin resistance among S. aureus isolates. The incidence of methicillin resistance in S. aureus isolates increased with the use of ciprofloxacin and levofloxacin and with the percentage of the hospital's beds located in intensive care units (adjusted multivariate coefficient of determination [aR(2)], 0.30). For P. aeruginosa, the incidence of ceftazidime resistance was greater in hospitals with higher consumption rates for ceftazidime, levofloxacin, and gentamicin (aR(2), 0.37). The incidence of ciprofloxacin resistance increased with the use of fluoroquinolones and with the percentage of a hospital's beds located in intensive care ( aR(2), 0.28).

CONCLUSIONS

A statistically significant relationship existed between the rate of fluoroquinolone use and the rate of antimicrobial resistance among S. aureus and P. aeruginosa isolates. The incidence of resistant isolates showed a stronger association with the rate of antimicrobial use than did the percentage of isolates with resistance.

Bactériémies à Staphylococcus aureus résistant à la méthicilline: aspects épidémiologiques et thérapeutiques récents

PURPOSE

Staphylococcus aureus is the first agent responsible for nosocomial bacteremia in France. About 40% of the strains are resistant to methicillin (MRSA). The epidemiology of these infections has changed in the last fifteen years whereas therapeutics options have slightly progressed.

CURRENT KNOWLEDGE AND KEY POINTS

Hospital-acquired MRSA bacteremia are more and more frequent while community-acquired strains recently appeared. Factors influencing the emergence of these infections were identified thanks to numerous clinical studies, as well as patients risk factors for developing these infections and their complications. At the same time, intermediate sensitive and resistant MRSA strains to glycopeptides appeared. Conversely, the best antibiotic strategy is still unclear in absence of good clinical studies. The interest of antibiotics combinations and of glycopeptides serum-concentrations control is still a matter of debate. Finally, the number of new active molecules remains limited.

PERSPECTIVES

The frequency and severity of MRSA bacteremia are quite worrying in our country. The epidemiology of these infections must be known by every clinicians in order to prevent them. The therapeutic strategy has to be better define and need for new anti-infectious agents is critic.

Risk factors associated with methicillin-resistant Staphylococcus aureus infection in patients admitted to the ED

OBJECTIVES

The objective of our study was to define the characteristics of patients admitted to the emergency department (ED) presenting with a methicillin-resistant Staphylococcus aureus (MRSA) infection.

PATIENTS AND METHODS

The study included all patients admitted to the ED between January 2003 and December 2004 in whom a staphylococcal infection was documented. The risk factors associated with carriage of MRSA, the diagnosis made in the ED, and the treatment administered were established from the patients' medical files. The sites from which the bacteria were isolated, the spectrum of resistance of the staphylococci to different antibiotics, and the presence or absence of the gene coding for Panton-Valentin leukocidin for certain S aureus isolates were determined from the reports issued by the bacteriologic department. Two groups of patients were compared: those with an infection caused by MRSA and those with an infection due to methicillin-susceptible S aureus (MSSA).

RESULTS

A total of 238 patients were included, 93 presenting with an infection caused by MRSA and 145 an infection due to MSSA. The patients harboring MRSA had a higher median age than those carrying MSSA (74 vs 61 years, P = .0001), experienced a greater loss of autonomy (according to the Knauss index), and had more comorbidity factors. Nine patients, younger than 40 years, presented with an infection due to MRSA in the absence of any comorbidity factor or any factor associated with carriage of these bacteria. Seven patients in the MRSA group were tested for Panton-Valentine leukocidin genes, and a positive result was obtained in 2 of them. Regardless of whether the infection was caused by MRSA or by MSSA, the bacteria were most frequently isolated from a cutaneous site, in 40% and 65% of the patients, respectively. Irrespective of the group, 28% of the patients presented with bacteremia. The spectrum of resistance of these MRSA strains suggested a hospital rather than community origin. The initial antibiotic therapy was rarely appropriate in the case of an infection due to MRSA.

CONCLUSION

Infections caused by MRSA accounted for a high proportion of the staphylococcal infections diagnosed in the ED, necessitating a rational approach to the prescription of antibiotics for infections of this type.

Rapid spread of methicillin-resistant Staphylococcus aureus in a new hospital in the broad-spectrum antibiotic era

OBJECTIVES

It has been known that it takes a long time for methicillin-resistant Staphylococcus aureus (MRSA) to introduce and become endemic within a hospital. During the last decade, widespread use of broad-spectrum antibiotics might have affected the time required for MRSA to spread and become endemic in hospitals. However, there has been no report on this issue. We investigated how fast MRSA has spread and become endemic in a hospital opened in the broad-spectrum antibiotic era.

METHODS

The study was performed at a Korean hospital, which opened in 1999. We examined the change of antimicrobial susceptibility and antimicrobial use density (AUD) for 6 years since hospital opening.

RESULTS

S. aureus susceptibility to oxacillin decreased from 64% in the first month to 33% in the second month (P=.05), and then has maintained around 30%. AUD was remarkably high from the first year, in which total AUD and those of aminopenicillins, second-generation cephalosporins, fluoroquinolones, and macrolides were 4674.6, 1444.6, 1700.9, 421.3, and 520.0 DDD/1000 patient-days, respectively.

CONCLUSIONS

MRSA has spread within a few months in a hospital opened in the broad-spectrum antibiotic era. Excessively high use of broad-spectrum antibiotics seems to be responsible for rapid spread of MRSA in the hospital.

Methicillin-resistant Staphylococcus aureus infection after living-donor liver transplantation in adults

BACKGROUND

Methicillin-resistant Staphylococcus aureus (MRSA) infection frequently complicates the postoperative course in deceased-donor liver transplantation. The incidence and risk factors of MRSA infection after Living-donor Liver transplantation (LDLT), however, are unclear.

METHODS

We retrospectively reviewed the data from 242 adult patients who underwent LDLT at the University of Tokyo Hospital. The microbiologic and medical records of the patients from admission to 3 months after LDLT were reviewed. Uni- and multivariate analyses were performed to identify the independent risk factors for postoperative MRSA infection.

RESULTS

Postoperative MRSA infection occurred in 25 of 242 patients by median postoperative day 23. Preoperative MRSA colonization, preoperative use of antimicrobials, operation time (> or =16 h), and postoperative apheresis independently predicted postoperative MRSA infection.

CONCLUSION

Surveillance culture should be checked periodically after admission to identify patients at high risk for MRSA infection and to administer appropriate antimicrobials for perioperative infection. Postoperative apheresis, suggesting postoperative liver dysfunction, predisposed patients to MRSA infection.

Management of ventilator-associated pneumonia in a multidisciplinary intensive care unit: does trauma make a difference?

OBJECTIVE

Antibiotic exposure and timing of pneumonia onset influence ventilator-associated pneumonia (VAP) isolates. The first goal of this investigation was to evaluate whether trauma also influences prevalence of microorganisms.

DESIGN

A retrospective, single-center, observational cohort study.

SETTING

Multidisciplinary teaching ICU.

PATIENTS

Adult patients requiring mechanical ventilation identified as having VAP.

INTERVENTIONS

Retrospective evaluation of a prospective manual database.

MEASUREMENTS AND MAIN RESULTS

VAP isolates in a multidisciplinary ICU documented by quantitative respiratory cultures and recorded in a 42-month database were compared, based on the presence or absence of trauma. Causative microorganisms were classified in four groups, based on mechanical ventilation duration (> 5 days), and previous antibiotic exposure. One hundred eighty-three patients developed 196 episodes of VAP (98 trauma). Methicillin-sensitive Staphylococcus aureus (MSSA) was more frequent (34.5% vs. 11.5%, p < 0.01) in trauma, whereas methicillin-resistant Staphylococcus aureus (MRSA) was more frequent (2% vs. 11.5%, p < 0.01) in non-trauma. No significant differences were found between trauma and non-trauma patients regarding prevalence of other microorganisms. In trauma patients, MSSA episodes were equally distributed between early- and late-onset VAP (51% vs. 49%), but no MRSA episode occurred in the early-onset group.

CONCLUSIONS

Trauma influences the microbiology of pneumonia and it should be considered in the initial antibiotic regimen choice. Our data demonstrate that patients with trauma had a higher prevalence of MSSA, but the overall prevalence was sufficiently high to warrant S. aureus coverage for both groups. On the other hand, since no MRSA was isolated during the first 10 days of mechanical ventilation on trauma patients, MRSA coverage in these patients becomes necessary only 10 days after admission.

Clinical impact of MRSA in a stem cell transplant unit: analysis before, during and after an MRSA outbreak

Meticillin-resistant Staphylococcus aureus (MRSA) is a major nosocomial pathogen, with an increased incidence in the UK since 1993, causing serious morbidity and mortality in immunosuppressed patients. We analysed the frequency and outcome of MRSA infection in a single-centre transplant population over a 5-year period. The total number of patients infected was 41/776 (5%). The frequency in autologous, sibling and unrelated donor transplants was 3, 6 and 9%, respectively. Prior to 2004, the incidence was <4%/year; however, an outbreak in the day unit resulted in 22 patients becoming newly infected. Over 90% of infections were clinically relevant, half (49%) being bacteraemia. Three patterns were seen: known MRSA positive at any time before transplant (n=15), MRSA first detected during the neutropenia phase (n=5) and MRSA only post discharge (n=21). MRSA was implicated in a number of deaths, at all time points, in those infected. An intensive eradication policy resulted in new infections dropping to <2%. In conclusion, MRSA is likely to remain endemic in our unit, but robust early screening protocols and aggressive eradication strategies have effectively limited the spread of and morbidity due to this pathogen.

Antimicrobial drug use and infection control practices associated with the prevalence of methicillin-resistant Staphylococcus aureus in European hospitals

Major regional variations in the prevalence of methicillin-resistant Staphylococcus aureus (MRSA) are observed across Europe. This study investigated hospital MRSA prevalence in relation to patterns of antimicrobial use and infection control policies in an observational, cross-sectional study that used retrospective data from 2001 and linear regression to model relationships. MRSA prevalence (median 20.8%, n = 173 hospitals) and antimicrobial consumption (median 55.2 defined daily doses/100 bed-days, n = 140 hospitals) both varied significantly according to geographical region (p <0.001). MRSA prevalence and antimicrobial consumption data were provided by 128 hospitals, and showed a strong statistical relationship between macrolide use and MRSA prevalence. Use of (i) third-generation cephalosporins, (ii) all antimicrobial agents, and (iii) all antimicrobial agents except glycopeptides was also associated with MRSA prevalence. Up to 146 hospitals provided data on MRSA prevalence and key infection control parameters. Adjusted linear regression modelling provided strong evidence that infection control policy recommendations associated with lower MRSA prevalence rates were (i) use of alcohol-based solutions for hand hygiene (mean difference 10.3%, 99% CI 1.2-10.3), and (ii) placement of MRSA patients in single rooms (mean difference 11.2%, 99% CI 1.4-20.9). Hospitals with problems in implementing isolation policies had higher resistance levels (mean difference 12%, 99% CI 3.8-20.1). Additional recommendations showed less evidence of association with a low MRSA prevalence. Overall, this study highlighted significant associations between MRSA prevalence, antimicrobial use and various key infection control parameters, all of which showed significant individual variations according to geographical region.