Prevention and Control of Methicillin-Resistant Staphylococcus aureus in Acute Care Settings

Methicillin-resistant Staphylococcus aureus (MRSA) is a leading cause of health care-associated infections worldwide. Controversies with regard to the effectiveness of various MRSA control strategies have contributed to varying approaches to the control of this pathogen in different settings. However, new evidence from large-scale studies has emerged, particularly with regards to MRSA screening and decolonization strategies, which will inform future control practices. The implementation as well as outcomes of control measures in the real world is not only influenced by scientific evidence but also depends on economic, administrative, governmental, and political influences.

Staphylococcus aureus resistance to topical antimicrobials in atopic dermatitis

Background

Topical antimicrobial drugs are indicated for limited superficial pyodermitis treatment, although they are largely used as self-prescribed medication for a variety of inflammatory dermatoses, including atopic dermatitis. Monitoring bacterial susceptibility to these drugs is difficult, given the paucity of laboratory standardization.

Objective

To evaluate the prevalence of Staphylococcus aureus topical antimicrobial drug resistance in atopic dermatitis patients.

Methods

We conducted a cross-sectional study of children and adults diagnosed with atopic dermatitis and S. aureus colonization. We used miscellaneous literature reported breakpoints to define S. aureus resistance to mupirocin, fusidic acid, gentamicin, neomycin and bacitracin.

Results

A total of 91 patients were included and 100 S. aureus isolates were analyzed. All strains were methicillin-susceptible S. aureus. We found a low prevalence of mupirocin and fusidic acid resistance (1.1% and 5.9%, respectively), but high levels of neomycin and bacitracin resistance (42.6% and 100%, respectively). Fusidic acid resistance was associated with more severe atopic dermatitis, demonstrated by higher EASI scores (median 17.8 vs 5.7, p=.009). Our results also corroborate the literature on the absence of cross-resistance between the aminoglycosides neomycin and gentamicin.

Conclusions

Our data, in a southern Brazilian sample of AD patients, revealed a low prevalence of mupirocin and fusidic acid resistance of S. aureus atopic eczema colonizer strains. However, for neomycin and bacitracin, which are commonly used topical antimicrobial drugs in Brazil, high levels of resistance were identified. Further restrictions on the use of these antimicrobials seem necessary to keep resistance as low as possible.

Susceptibility of Nosocomial Staphylococcus aureus to Chlorhexidine After Implementation of a Hospital-wide Antiseptic Bathing Regimen

Hospital use of chlorhexidine (CHX) containing antiseptics to decrease nosocomial infections may promote CHX resistance among pathogenic organisms. Nosocomial bloodstream-infecting Staphylococcus aureus isolates from before and after adoption of hospital-wide CHX bathing were tested for CHX susceptibility, and no decreased susceptibility or resistance-promoting genes were discovered. Infect Control Hosp Epidemiol 2017;38:873-875.

Vaccine development to prevent Staphylococcus aureus surgical-site infections

BACKGROUND

Staphylococcus aureus surgical-site infections (SSIs) are a major cause of poor health outcomes, including mortality, across surgical specialties. Despite current advances as a result of preventive interventions, the disease burden of S. aureus SSI remains high, and increasing antibiotic resistance continues to be a concern. Prophylactic S. aureus vaccines may represent an opportunity to prevent SSI.

METHODS

A review of SSI pathophysiology was undertaken in the context of evaluating new approaches to developing a prophylactic vaccine to prevent S. aureus SSI.

RESULTS

A prophylactic vaccine ideally would provide protective immunity at the time of the surgical incision to prevent initiation and progression of infection. Although the pathogenicity of S. aureus is attributed to many virulence factors, previous attempts to develop S. aureus vaccines targeted only a single virulence mechanism. The field has now moved towards multiple-antigen vaccine strategies, and promising results have been observed in early-phase clinical studies that supported the recent initiation of an efficacy trial to prevent SSI.

CONCLUSION

There is an unmet medical need for novel S. aureus SSI prevention measures. Advances in understanding of S. aureus SSI pathophysiology could lead to the development of effective and safe prophylactic multiple-antigen vaccines to prevent S. aureus SSI.

Decolonization of Staphylococcus aureus carriage

Staphylococcus aureus nasal colonization is a well-known independent risk factor for infection caused by this bacterium. Screening and decolonization of carriers have been proven effective in reducing S. aureus infections in some populations. However, a gap remains between what has been proven effective and what is currently done. We aimed to summarize recommendations and current knowledge of S. aureus decolonization to answer the following questions: Why? For whom? How? When? And what are the perspectives?

Decolonization in Prevention of Health Care-Associated Infections

Colonization with health care-associated pathogens such as Staphylococcus aureus, enterococci, Gram-negative organisms, and Clostridium difficile is associated with increased risk of infection. Decolonization is an evidence-based intervention that can be used to prevent health care-associated infections (HAIs). This review evaluates agents used for nasal topical decolonization, topical (e.g., skin) decolonization, oral decolonization, and selective digestive or oropharyngeal decontamination. Although the majority of studies performed to date have focused on S. aureus decolonization, there is increasing interest in how to apply decolonization strategies to reduce infections due to Gram-negative organisms, especially those that are multidrug resistant. Nasal topical decolonization agents reviewed include mupirocin, bacitracin, retapamulin, povidone-iodine, alcohol-based nasal antiseptic, tea tree oil, photodynamic therapy, omiganan pentahydrochloride, and lysostaphin. Mupirocin is still the gold standard agent for S. aureus nasal decolonization, but there is concern about mupirocin resistance, and alternative agents are needed. Of the other nasal decolonization agents, large clinical trials are still needed to evaluate the effectiveness of retapamulin, povidone-iodine, alcohol-based nasal antiseptic, tea tree oil, omiganan pentahydrochloride, and lysostaphin. Given inferior outcomes and increased risk of allergic dermatitis, the use of bacitracin-containing compounds cannot be recommended as a decolonization strategy. Topical decolonization agents reviewed included chlorhexidine gluconate (CHG), hexachlorophane, povidone-iodine, triclosan, and sodium hypochlorite. Of these, CHG is the skin decolonization agent that has the strongest evidence base, and sodium hypochlorite can also be recommended. CHG is associated with prevention of infections due to Gram-positive and Gram-negative organisms as well as Candida. Conversely, triclosan use is discouraged, and topical decolonization with hexachlorophane and povidone-iodine cannot be recommended at this time. There is also evidence to support use of selective digestive decontamination and selective oropharyngeal decontamination, but additional studies are needed to assess resistance to these agents, especially selection for resistance among Gram-negative organisms. The strongest evidence for decolonization is for use among surgical patients as a strategy to prevent surgical site infections.

Influence of a 5-year serial infection control and antibiotic stewardship intervention on cardiac surgical site infections

BACKGROUND

Surgical site infections (SSIs) complicate surgery, resulting in higher morbidity and mortality. Infection control bundles and antibiotic stewardship can be effective at reducing SSIs. The influence of long-term serial interventions is unclear.

OBJECTIVE

The goal of this retrospective quasiexperimental study was to assess the influence of a 5-year serial infection control and antibiotic stewardship intervention on SSIs.

METHODS

The multidisciplinary program actively implemented pre-, intra-, and postoperative strategies over a 5-year period from 2009-2014 for all patients undergoing coronary artery bypass graft (CABG), valve replacement, or both at a tertiary care public institution. Outcomes are compared with a 2-year preinterventions period (2007-2009) and 1-year postinterventions period (2014-2015).

RESULTS

A total of 6,518 procedures were included. After interventions, the overall combined infection rate for CABG, CABG and valve, and valve procedures decreased by 66.3%, from 11.9%-4.0% (odds ratio, 0.34; 95% confidence interval, 0.23-0.49; P < .001). A significant decrease of >50% (P < .001) relative rate was observed in overall, sternum, leg, CABG, and combined CABG and valve infection rates when comparing pre- and postinterventions groups. The antibiotic stewardship intervention increased overall conformity to the internal surgical prophylaxis protocol by 46.8%, from 39.8%-86.6% (95% confidence interval, 41.0-52.4; P < .001).

CONCLUSION

Long-term, serial comprehensive infection control and antibiotic stewardship interventions decrease overall SSIs in patients undergoing CABG and valve replacement procedures.

Chlorhexidine and Mupirocin Susceptibility of Methicillin-Resistant Staphylococcus aureus Isolates in the REDUCE-MRSA Trial

Whether targeted or universal decolonization strategies for the control of methicillin-resistant Staphylococcus aureus (MRSA) select for resistance to decolonizing agents is unresolved. The REDUCE-MRSA trial (ClinicalTrials registration no. NCT00980980) provided an opportunity to investigate this question. REDUCE-MRSA was a 3-arm, cluster-randomized trial of either screening and isolation without decolonization, targeted decolonization with chlorhexidine and mupirocin, or universal decolonization without screening to prevent MRSA infection in intensive-care unit (ICU) patients. Isolates from the baseline and intervention periods were collected and tested for susceptibility to chlorhexidine gluconate (CHG) by microtiter dilution; mupirocin susceptibility was tested by Etest. The presence of the qacA or qacB gene was determined by PCR and DNA sequence analysis. A total of 3,173 isolates were analyzed; 2 were nonsusceptible to CHG (MICs, 8 μg/ml), and 5/814 (0.6%) carried qacA or qacB At baseline, 7.1% of MRSA isolates expressed low-level mupirocin resistance, and 7.5% expressed high-level mupirocin resistance. In a mixed-effects generalized logistic regression model, the odds of mupirocin resistance among clinical MRSA isolates or MRSA isolates acquired in an ICU in intervention versus baseline periods did not differ across arms, although estimates were imprecise due to small numbers. Reduced susceptibility to chlorhexidine and carriage of qacA or qacB were rare among MRSA isolates in the REDUCE-MRSA trial. The odds of mupirocin resistance were no different in the intervention versus baseline periods across arms, but the confidence limits were broad, and the results should be interpreted with caution.

Distribution of high-level mupirocin resistance among clinical MRSA

Mupirocin is a topical antibiotic for methicillin-resistant Staphylococcus aureus (MRSA) decolonization in hospital settings and nursing homes and is used as a highly effective antibiotic against MRSA. In this study, we aimed to evaluate the frequency of high-level mupirocin-resistant (HLMR) strains among the MRSA subtypes. A total of 188 clinical MRSA isolates were collected from 2011 to 2014, and their susceptibility to antimicrobial agents and vancomycin resistance was evaluated using disc diffusion method and micro-dilution method, respectively. Furthermore, the presence of mecA, SSCmec, mupA and mupB was assessed by PCR. All isolates were multi-drug resistant (MDR) but 2 strains (1.06%) were resistant to mupirocin. Minimum inhibitory concentration (MIC) of vancomycin for 8 strains (4.7%) was higher than 2 μg/ml. Of 188 isolates, 188 (100%), 64 (34.04%), 8 (4.3%), 150 (79.8%), 26 (13.8%), 2 (1.06) and 2 (1.06%) isolates possessed mecA, SCCmec types I, II, III, IV, mupA and mupB genes, respectively. Our data showed that despite infection control policy enforced by health care committee, the rate of mupirocin resistance among MRSA strains is continuously rising.

Prevention of Recurrent Staphylococcal Skin Infections

Staphylococcus aureus infections pose a significant health burden. The emergence of community-associated methicillin-resistant S aureus has resulted in an epidemic of skin and soft tissue infections (SSTI), and many patients experience recurrent SSTI. As S aureus colonization is associated with subsequent infection, decolonization is recommended for patients with recurrent SSTI or in settings of ongoing transmission. S aureus infections often cluster within households, and asymptomatic carriers serve as reservoirs for transmission; therefore, a household approach to decolonization is more effective than measures performed by individuals alone. Novel strategies for the prevention of recurrent SSTI are needed.

Staphylococcus aureus: the current state of disease, pathophysiology and strategies for prevention

Staphylococcus aureus is both a commensal organism and also an important opportunistic human pathogen, causing a variety of community and hospital-associated pathologies, such as bacteremia-sepsis, endocarditis, pneumonia, osteomyelitis, arthritis and skin diseases. The resurgence of S. aureus during the last decade in many settings has been facilitated not only by bacterial antibiotic resistance mechanisms but also by the emergence of new S. aureus clonal types with increased expression of virulence factors and the capacity to neutralize the host immune response. Prevention of the spread of S. aureus infection relies on the use of contact precautions and adequate procedures for infection control that so far have not been fully effective. Prevention using a prophylactic vaccine would complement these processes, having the potential to bring additional, significant progress toward decreasing invasive disease due to S. aureus.

Catheter-related bloodstream infection in end-stage kidney disease: a Canadian narrative review

Purpose of the review

Patients with end-stage renal disease (ESRD) are at a high risk of bacterial infection. We reviewed publications on risk factors, prevention, and treatment paradigms, as well as outcomes associated with bacterial infection in end-stage kidney disease. We focused in particular on studies conducted in Canada where rates of haemodialysis catheter use are high.

Sources of information

We included original research articles in English text identified from MEDLINE using search terms ‘chronic kidney failure’, ‘renal dialysis’, or ‘chronic renal insufficiency’, and ‘bacterial infection’. We focused on articles with Canadian study populations and included comparisons to international standards and outcomes where possible.

Findings

Bacterial infections in this setting are most commonly due to Gram-positive skin flora, particularly Staphylococcus, with methicillin-resistant Staphylococcus aureus (MRSA) carrying a poorer prognosis. Interventions that may decrease mortality from sepsis include a collaborative care model that includes a nephrology team, an infectious disease specialist, and use of standardized care bundles that adhere to proven quality-of-care indicators. Decreased infectious mortality may be achieved by ensuring appropriate antibiotic selection and dosing as well as avoiding catheter salvage attempts. Reduction in bloodstream infection (BSI) incidence has been observed with the use of tPA catheter-locking solutions and the use of mupirocin or polysporin as a topical agent at the catheter exit site, as well as implementing standarized hygiene protocols during catheter use.

Limitations

There has been a paucity of randomized controlled trials of prevention and treatment strategies for catheter-related BSIs in haemodialysis. Some past trials have been limited by lack of blinding and short duration of follow-up. Microbiological epidemiology, although well characterized, may vary by region and treatment centre.

Implications

With the high prevalence of catheter use in Canadian haemodialysis units, further studies on long-term treatment and preventative strategies for BSI are warranted.

The effect of targeted decolonization on methicillin-resistant Staphylococcus aureus colonization or infection in a surgical intensive care unit

BACKGROUND

The effect of decolonization on the control of methicillin-resistant Staphylococcus aureus (MRSA) may differ depending on intensive care unit (ICU) settings and the prevalence of antiseptic resistance in MRSA.

METHODS

This study was conducted in a 14-bed surgical ICU over a 40-month period. The baseline period featured active surveillance for MRSA and institution of contact precautions. MRSA decolonization via chlorhexidine baths and intranasal mupirocin was implemented during a subsequent 20-month intervention period. Pre-post and interrupted time series analysis were used to evaluate changes in the clinical incidence of hospital-acquired MRSA colonization or infection. MRSA isolates were tested for the presence of qacA/B genes and mupirocin resistance.

RESULTS

In pre-post analysis, the clinical incidence of MRSA significantly decreased by 61.6% after implementation of decolonization (P < .001). Meanwhile, interrupted time series analysis showed decreases in both the level (β = -0.686; P = .210) and trend (β = -0.011; P = .819) of clinical MRSA incidence, but these changes were not statistically significant. Of 169 MRSA isolates, 64 (37.8%) carried the qacA/B genes, and 22 (13.0%) showed either low- (n = 20) or high-level (n = 2) resistance to mupirocin. Low-level mupirocin resistance significantly increased from 0%-19.4% during the study period.

CONCLUSION

Although decolonization using antiseptic agents was helpful to decrease hospital-acquired MRSA rates, the emergence of antiseptic resistance should be monitored.

Prevalence of qacA/B Genes and Mupirocin Resistance Among Methicillin-Resistant Staphylococcus aureus (MRSA) Isolates in the Setting of Chlorhexidine Bathing Without Mupirocin

OBJECTIVE

We aimed to determine the frequency of qacA/B chlorhexidine tolerance genes and high-level mupirocin resistance among MRSA isolates before and after the introduction of a chlorhexidine (CHG) daily bathing intervention in a surgical intensive care unit (SICU).

DESIGN

Retrospective cohort study (2005-2012) SETTING: A large tertiary-care center

PATIENTS

Patients admitted to SICU who had MRSA surveillance cultures of the anterior nares

METHODS

A random sample of banked MRSA anterior nares isolates recovered during (2005) and after (2006-2012) implementation of a daily CHG bathing protocol was examined for qacA/B genes and high-level mupirocin resistance. Staphylococcal cassette chromosome mec (SCCmec) typing was also performed.

RESULTS

Of the 504 randomly selected isolates (63 per year), 36 (7.1%) were qacA/B positive (+) and 35 (6.9%) were mupirocin resistant. Of these, 184 (36.5%) isolates were SCCmec type IV. There was a significant trend for increasing qacA/B (P=.02; highest prevalence, 16.9% in 2009 and 2010) and SCCmec type IV (P<.001; highest prevalence, 52.4% in 2012) during the study period. qacA/B(+) MRSA isolates were more likely to be mupirocin resistant (9 of 36 [25%] qacA/B(+) vs 26 of 468 [5.6%] qacA/B(-); P=.003).

CONCLUSIONS

A long-term, daily CHG bathing protocol was associated with a change in the frequency of qacA/B genes in MRSA isolates recovered from the anterior nares over an 8-year period. This change in the frequency of qacA/B genes is most likely due to patients in those years being exposed in prior admissions. Future studies need to further evaluate the implications of universal CHG daily bathing on MRSA qacA/B genes among hospitalized patients.

Current Molecular Epidemiology of Methicillin-Resistant Staphylococcus aureus in Elderly French People: Troublesome Clones on the Horizon

Objective: In 2015, we conducted at 44 healthcare facilities (HCFs) and 21 nursing homes (NHs) a 3-month bloodstream infection (BSI) survey, and a 1-day prevalence study to determine the rate of carriage of methicillin-resistant Staphylococcus aureus (MRSA) in 891 patients and 470 residents. We investigated the molecular characteristics of the BSI-associated and colonizing MRSA isolates, and assessed cross-transmission using double-locus sequence typing and pulsed-field gel electrophoresis protocol.

Results: The incidence of MRSA-BSI was 0.040/1000 patient-days (19 cases). The prevalence of MRSA carriage was 4.2% in patients (n = 39) and 8.7% in residents (n = 41) (p < 0.001). BSI-associated and colonizing isolates were similar: none were PVL-positive; 86.9% belonged to clonal complexes 5 and 8; 93.9% were resistant to fluoroquinolones. The qacA/B gene was carried by 15.8% of the BSI-associated isolates [3/3 BSI cases in intensive care units (ICUs)], and 7.7% of the colonizing isolates in HCFs. Probable resident-to-resident transmission was identified in four NHs.

Conclusion: Despite generally reassuring results, we identified two key concerns. First, a worryingly high prevalence of the qacA/B gene in MRSA isolates. Antisepsis measures being crucial to prevent healthcare-associated infections, our findings raise questions about the potential risk associated with chlorhexidine use in qacA/B⁺ MRSA carriers, particularly in ICUs. Second, NHs are a weak link in MRSA control. MRSA spread was not controlled at several NHs; because of their frequent contact with the community, conditions are favorable for these NHs to serve as reservoirs of USA300 clone for local HCFs.

Fighting antibiotic resistance in the intensive care unit using antibiotics

Antibiotic resistance is a global and increasing problem that is not counterbalanced by the development of new therapeutic agents. The prevalence of antibiotic resistance is especially high in intensive care units with frequently reported outbreaks of multidrug-resistant organisms. In addition to classical infection prevention protocols and surveillance programs, counterintuitive interventions, such as selective decontamination with antibiotics and antibiotic rotation have been applied and investigated to control the emergence of antibiotic resistance. This review provides an overview of selective oropharyngeal and digestive tract decontamination, decolonization of methicillin-resistant Staphylococcus aureus and antibiotic rotation as strategies to modulate antibiotic resistance in the intensive care unit.

Chlorhexidine and mupirocin susceptibilities in methicillin-resistant Staphylococcus aureus isolates from bacteraemia and nasal colonisation

Chlorhexidine and mupirocin have been increasingly used in healthcare facilities to eradicate methicillin-resistant Staphylococcus aureus (MRSA) carriage. The aim of this study was to determine the prevalence and mechanisms of chlorhexidine and mupirocin resistance in MRSA from invasive infections and colonisation. MRSA isolates obtained from blood and nasal samples between 2012 and 2014 were analysed. Susceptibility to mupirocin was determined by disk diffusion and Etest and susceptibility to chlorhexidine by broth microdilution. The presence of mupA and qac (A/B and C) genes was investigated by PCR. Molecular typing was performed in high-level mupirocin-resistant (HLMR) isolates. Mupirocin resistance was identified in 15.6% of blood isolates (10.9% HLMR) and 15.1% of nasal isolates (12.0% HLMR). Presence of the mupA gene was confirmed in all HLMR isolates. For blood isolates, chlorhexidine minimum inhibitory concentrations (MICs) ranged from ≤0.125 to 4mg/L and minimum bactericidal concentrations (MBCs) from ≤0.125 to 8mg/L. In nasal isolates, chlorhexidine MICs and MBCs ranged from ≤0.125 to 2mg/L. The qacA/B gene was detected in 2.2% of MRSA isolates (chlorhexidine MIC range 0.25-2mg/L) and the qacC gene in 8.2% (chlorhexidine MIC range ≤0.125-1mg/L). The prevalence of qacC was 18.9% in HLMR isolates and 3.6% in mupirocin-susceptible isolates (P=0.009). Most of the HLMR isolates (97.1%) belonged to ST125 clone. These results suggest that chlorhexidine has a higher potential to prevent infections caused by MRSA. In contrast, mupirocin treatment should be used cautiously to avoid the spread of HLMR MRSA.

Prevention of Surgical Site Infections: Decontamination With Mupirocin Based on Preoperative Screening for Staphylococcus aureus Carriers or Universal Decontamination?

Perioperative decolonization of Staphylococcus aureus nasal carriers with mupirocin together with chlorhexidine body washing reduces the incidence of S. aureus surgical site infection. A targeted strategy, applied in S. aureus carriers only, is costly, and implementation may reduce effectiveness. Universal decolonization is more cost-effective but increases exposure of noncarriers to mupirocin and the risk of resistance to mupirocin in staphylococci. High-level mupirocin resistance in S. aureus can emerge through horizontal gene transfer originating from coagulase-negative staphylococci (CoNS) and through clonal transmission. The current evidence on the occurrence of high-level mupirocin resistance in S. aureus and CoNS, in combination with the results of mathematical modeling, strongly suggests that the increased selection of high-level mupirocin resistance in CoNS does not constitute an important risk for high-level mupirocin resistance in S. aureus. Compared with a targeted strategy, universal decolonization seems associated with an equally low risk of mupirocin resistance in S. aureus.

Randomized, placebo-controlled, double-blind clinical trial to evaluate the efficacy of polyhexanide for topical decolonization of MRSA carriers

OBJECTIVES

The objective of this study was to evaluate the efficacy of polyhexanide (Prontoderm(®)) in eliminating MRSA carriage.

METHODS

In a 1900 bed teaching hospital, MRSA-colonized patients were randomized into a double-blind, placebo-controlled superiority trial between January 2011 and July 2014. Patients were treated with either polyhexanide or placebo applied to the anterior nares (thrice daily) and skin (once daily) for 10 days. The primary outcome was MRSA decolonization at day 28 (D28) after the end of treatment assessed by ITT responder and PP analyses (microbiological follow-up ± 7 days and topical treatment ≥ 5 days). Secondary outcomes included safety, emergence of resistance and MRSA genotype changes. Registered trial number ISRCTN02288276.

RESULTS

Of 2590 patients screened, 146 (polyhexanide group, 71; placebo group, 75) were included. ITT analysis showed that 24/71 (33.8%) patients in the polyhexanide group versus 22/75 (29.3%) in the placebo group were MRSA-free at D28 (risk difference, 4.5%; 95% CI, -10.6% to 19.5%; P = 0.56). PP analysis confirmed the results with 19/53 (35.8%) decolonized polyhexanide-treated patients versus 17/56 (30.4%) in the placebo arm (risk difference, 5.5%; 95% CI, -12.2% to 23%; P = 0.54). Nine serious adverse events occurred in the polyhexanide group versus 12 in the placebo group; none was attributable to study medication. Emergence of polyhexanide resistance or cross-resistance between polyhexanide and chlorhexidine was not observed. No case of exogenous recolonization by a genotypically different MRSA strain was documented.

CONCLUSIONS

This study suggests that under real-life conditions, a single polyhexanide decolonization course is not effective in eradicating MRSA carriage.

Screening for methicillin-resistant Staphylococcus aureus … all doors closed?

PURPOSE OF REVIEW

To describe the latest evidence for methicillin-resistant Staphylococcus aureus (MRSA) infection control strategies, with particular emphasis on active surveillance cultures with contact precautions and targeted decolonization, and their impact.

RECENT FINDINGS

Several major trials published last year questioned the effectiveness of universal screening and contact precautions in controlling MRSA. These trials generally recommend universal decolonization as part of bundles to control MRSA, especially in ICUs, with some even concluding that universal decolonization should replace active screening and contact precautions. However, emerging resistance to agents used for decolonization, such as mupirocin and chlorhexidine, is a major concern. Several other studies confirmed a combination of hand hygiene enhancement, screening, contact precaution and targeted decolonization as a more viable MRSA infection control strategy for specific population groups.

SUMMARY

Universal decolonization is an acceptable MRSA control strategy for intensive care units; however, close monitoring of chlorhexidine and mupirocin resistance is warranted. As a strategy, screening and contact precautions are suitable for hospital-wide MRSA control. Targeted decolonization is a proven measure for patients undergoing clean surgery. Enhancement of hand hygiene is a core measure regardless of the strategy.

Impact of mupirocin resistance on the transmission and control of healthcare-associated MRSA

Objectives

The objectives of this study were to estimate the relative transmissibility of mupirocin-resistant (MupR) and mupirocin-susceptible (MupS) MRSA strains and evaluate the long-term impact of MupR on MRSA control policies.

Methods

Parameters describing MupR and MupS strains were estimated using Markov chain Monte Carlo methods applied to data from two London teaching hospitals. These estimates parameterized a model used to evaluate the long-term impact of MupR on three mupirocin usage policies: ‘clinical cases’, ‘screen and treat’ and ‘universal’. Strategies were assessed in terms of colonized and infected patient days and scenario and sensitivity analyses were performed.

Results

The transmission probability of a MupS strain was 2.16 (95% CI 1.38–2.94) times that of a MupR strain in the absence of mupirocin usage. The total prevalence of MupR in colonized and infected MRSA patients after 5 years of simulation was 9.1% (95% CI 8.7%–9.6%) with the ‘screen and treat’ mupirocin policy, increasing to 21.3% (95% CI 20.9%–21.7%) with ‘universal’ mupirocin use. The prevalence of MupR increased in 50%–75% of simulations with ‘universal’ usage and >10% of simulations with ‘screen and treat’ usage in scenarios where MupS had a higher transmission probability than MupR.

Conclusions

Our results provide evidence from a clinical setting of a fitness cost associated with MupR in MRSA strains. This provides a plausible explanation for the low levels of mupirocin resistance seen following ‘screen and treat’ mupirocin usage. From our simulations, even under conservative estimates of relative transmissibility, we see long-term increases in the prevalence of MupR given ‘universal’ use.

Clonal variation in high- and low-level phenotypic and genotypic mupirocin resistance of MRSA isolates in south-east London

OBJECTIVES

Both low-level mupirocin resistance (LMR) and high-level mupirocin resistance (HMR) have been identified. The aim of this study was to determine the epidemiology of LMR and HMR in MRSA isolates at five hospitals that have used mupirocin for targeted decolonization as part of successful institutional control programmes.

METHODS

All MRSA identified in three microbiology laboratories serving five central and south-east London hospitals and surrounding communities between November 2011 and February 2012 were included. HMR and LMR were determined by disc diffusion testing. WGS was used to derive multilocus sequence types (MLSTs) and the presence of HMR and LMR resistance determinants.

RESULTS

Prevalence of either HMR or LMR amongst first healthcare episode isolates from 795 identified patients was 9.69% (95% CI 7.72-11.96); LMR was 6.29% (95% CI 4.70-8.21) and HMR was 3.40% (95% CI 2.25-4.90). Mupirocin resistance was not significantly different in isolates identified from inpatients at each microbiology laboratory, but was more common in genotypically defined 'hospital' rather than 'community' isolates (OR 3.17, 95% CI 1.36-9.30, P = 0.002). LMR was associated with inpatient stay, previous history of MRSA and age ≥65 years; HMR was associated with age ≥65 years and residential postcode outside London. LMR and HMR varied by clone, with both being low in the dominant UK MRSA clone ST22 compared with ST8, ST36 and ST239/241 for LMR and with ST8 and ST36 for HMR. V588F mutation and mupA carriage had high specificity (>97%) and area under the curve (>83%) to discriminate phenotypic mupirocin resistance, but uncertainty around the sensitivity point estimate was large (95% CI 52.50%-94.44%). Mutations in or near the mupA gene were found in eight isolates that carried mupA but were not HMR.

CONCLUSIONS

Mupirocin resistance was identified in <10% of patients and varied significantly by clone, implying that changes in clonal epidemiology may have an important role in determining the prevalence of resistance in conjunction with selection due to mupirocin use.

Recurrent Methicillin-Resistant Staphylococcus aureus Cutaneous Abscesses and Selection of Reduced Chlorhexidine Susceptibility during Chlorhexidine Use

We describe the selection of reduced chlorhexidine susceptibility during chlorhexidine use in a patient with two episodes of cutaneous USA300 methicillin-resistant Staphylococcus aureus abscess. The second clinical isolate harbors a novel plasmid that encodes the QacA efflux pump. Greater use of chlorhexidine for disease prevention warrants surveillance for resistance.

Determining the resistance of carbapenem-resistant Klebsiella pneumoniae to common disinfectants and elucidating the underlying resistance mechanisms

INTRODUCTION

Carbapenem-resistant Klebsiella pneumoniae (CRKP) infection is a serious problem in hospitals worldwide, posing a particular risk to immunocompromised patients. Elimination strategies may prevent these drug-resistant bacteria from spreading within hospital environments. Here, the susceptibility of patient-derived CRKP strains to common chemical disinfectants and possible correlations between the presence of drug-resistance genes and increased resistance to disinfectants were investigated.

METHODS

The minimum inhibitory (MIC) and the minimum bactericidal concentrations (MBC) of common chemical disinfectants against each CRKP strain were determined using agar dilution; K. pneumoniae ATCC700603 served as a standard. The presence of the drug-resistance genes qacΔE, qacA, acrA and qacE was determined using PCR.

RESULTS

A total of 27 clinically isolated CRKP strains collected in our hospital from 2011 to 2013 exhibited sensitivity to the following common chemical disinfectants in decreasing order of sensitivity: 75% ethyl alcohol > 2% glutaraldehyde > "84" disinfectant > 0.2% benzalkonium bromide > 2% iodine tincture > 1% iodophor > 0.1% chlorhexidine acetate. Of the 27 strains, 59, 41, 19 and 15% contained qacΔE, qacA, acrA and qacE resistance genes; 15% carried acrA, qacΔE and qacA, and 26% carried both qacA and qacΔE. Comparative analysis indicated that drug-resistance genes were correlated with higher MIC values.

CONCLUSION

These pan-resistant pathogenic CRKP strains contained various drug-resistance genes and exhibited relatively high resistance to ethyl alcohol, chlorhexidine acetate and iodophor. Monitoring the drug-resistance rates of CRKP strains displaying disinfectant resistance may facilitate appropriate and effective sterilisation and thus preventing the spread of these pan-resistant strains.

Drug utilization review of mupirocin ointment in a Korean university-affiliated hospital

BACKGROUND/AIMS

Intranasal mupirocin and chlorhexidine bathing are candidate strategies to prevent healthcare-associated infections caused by methicillin-resistant Staphylococcus aureus (MRSA). In Korea, intranasal mupirocin is not available, and mupirocin ointment, an over-the-counter drug, has been used indiscriminately. Furthermore, because it is covered by health insurance, mupirocin is easy to prescribe within hospitals.

METHODS

We performed a mupirocin drug utilization review (DUR) within Hallym University Sacred Heart Hospital. Annual use of mupirocin was investigated between 2003 and 2013, and monthly consumption of mupirocin was assessed during the final 2-year period. The DUR focused on August 2012, the period of highest use of mupirocin. Also, we investigated trends in mupirocin resistance in MRSA between 2011 and 2013.

RESULTS

Annual consumption of mupirocin increased from 3,529 tubes in 2003 to 6,475 tubes in 2013. During August 2012, 817 tubes were prescribed to 598 patients; of these, 84.9% were prescribed to outpatients, and 77.6% at the dermatology department. The most common indication was prevention of skin infections (84.9%), and the ointment was combined with systemic antibiotics in 62.9% of cases. The average duration of systemic antibiotic administration was about 7.8 days. The rate of low-level mupirocin resistance in MRSA increased from 8.0% to 22.0%, and that of high-level mupirocin resistance increased from about 4.0% to about 7.5%.

CONCLUSIONS

Inappropriate use of mupirocin is prevalent. Considering the increase in resistance and the future application of intranasal mupirocin, prophylactic use of mupirocin in dermatology departments should be reconsidered.

Viewpoint: a response to "Screening and isolation to control methicillin-resistant Staphylococcus aureus: sense, nonsense, and evidence"

Surveillance and isolation for the prevention of methicillin-resistant Staphylococcus aureus (MRSA) has become a controversial topic, one that causes heated debate and appears to be surrounded by both politics and industrial conflicts-of-interest. There have been calls from numerous authors for a movement away from rigid mandates and toward an evidence-based medicine approach. However, much of the evidence can be viewed with an entirely different interpretation. Two major studies with negative findings have had an adverse impact on recommendations regarding active detection and isolation (ADI) for MRSA. However the negative findings in these studies can be explained by shortcomings in study implementation rather than the ineffectiveness of ADI. The use of daily chlorhexidine bathing has also been proposed as an alternative to ADI in ICU settings. There are shortcomings regarding the evidence in the literature concerning the effectiveness of daily chlorhexidine bathing. One of the major concerns with universal daily chlorhexidine bathing is the development of bacterial resistance. The use of surveillance and isolation to address epidemics and common dangerous pathogens should solely depend upon surveillance and isolation's ability to prevent further spread to and infection of other patients through indirect contact. At present, there is a preponderance of evidence in the literature to support continuing use of surveillance and isolation to prevent the spread of MRSA.

Cost-Effectiveness of Preoperative Nasal Mupirocin Treatment in Preventing Surgical Site Infection in Patients Undergoing Total Hip and Knee Arthroplasty: A Cost-Effectiveness Analysis

Objective.

To perform a cost-effectiveness analysis to evaluate preoperative use of mupirocin in patients with total joint arthroplasty (TJA).

Design.

Simple decision tree model.

Setting.

Outpatient TJA clinical setting.

Participants.

Hypothetical cohort of patients with TJA.

Interventions.

A simple decision tree model compared 3 strategies in a hypothetical cohort of patients with TJA: (1) obtaining preoperative screening cultures for all patients, followed by administration of mupirocin to patients with cultures positive for Staphylococcus aureus; (2) providing empirical preoperative treatment with mupirocin for all patients without screening; and (3) providing no preoperative treatment or screening. We assessed the costs and benefits over a 1-year period. Data inputs were obtained from a literature review and from our institution's internal data. Utilities were measured in quality-adjusted life-years, and costs were measured in 2005 US dollars.

Main Outcome Measure.

Incremental cost-effectiveness ratio.

Results.

The treat-all and screen-and-treat strategies both had lower costs and greater benefits, compared with the no-treatment strategy. Sensitivity analysis revealed that this result is stable even if the cost of mupirocin was over $100 and the cost of SSI ranged between $26,000 and $250,000. Treating all patients remains the best strategy when the prevalence of S. aureus carriers and surgical site infection is varied across plausible values as well as when the prevalence of mupirocin-resistant strains is high.

Conclusions.

Empirical treatment with mupirocin ointment or use of a screen-and-treat strategy before TJA is performed is a simple, safe, and cost-effective intervention that can reduce the risk of SSI. S. aureus decolonization with nasal mupirocin for patients undergoing TJA should be considered.

Level of Evidence.

Level II, economic and decision analysis.

Infect Control Hosp Epidemiol 2012;33(2):152-159

Acquisition of high-level mupirocin resistance in CoNS following nasal decolonization with mupirocin

OBJECTIVES

The association between mupirocin use and plasmid-based high-level resistance development mediated through mupA in CoNS has not been quantified. We determined acquisition of mupirocin resistance in Staphylococcus aureus and CoNS in surgery patients treated peri-operatively with mupirocin.

PATIENTS AND METHODS

Patients admitted for surgery were treated with nasal mupirocin ointment and chlorhexidine soap for 5 days, irrespective of S. aureus carrier status. Nasal swabs were obtained before decolonization (T1) and 4 days after surgery (T2) and were inoculated onto agars containing 8 mg/L mupirocin. Staphylococci were identified by MALDI-TOF MS and mupirocin resistance was confirmed by Etest.

RESULTS

Among 1578 surgical patients, 936 (59%) had nasal swabs obtained at T1 and T2; 192 (21%) patients carried mupirocin-resistant CoNS at T1 and 406 (43%) at T2 (P<0.001). Of 744 patients not colonized at T1, 277 acquired resistance (37%), corresponding to an acquisition rate of 7.4/100 patient days at risk. In all, 588 (97%) of 607 mupirocin-resistant CoNS had an MIC >256 mg/L (high level) and 381 of 383 (99.5%) were mupA positive. No acquisition of mupirocin resistance was observed in S. aureus.

CONCLUSIONS

Acquisition of mupirocin resistance following decolonization was widespread in CoNS and absent in S. aureus. As almost all isolates harboured the mupA gene, monitoring resistance development in S. aureus when decolonization strategies containing mupirocin are used is recommended.

Genome sequencing defines phylogeny and spread of methicillin-resistant Staphylococcus aureus in a high transmission setting

Methicillin-resistant Staphylococcus aureus (MRSA) is a major cause of nosocomial infection. Whole-genome sequencing of MRSA has been used to define phylogeny and transmission in well-resourced healthcare settings, yet the greatest burden of nosocomial infection occurs in resource-restricted settings where barriers to transmission are lower. Here, we study the flux and genetic diversity of MRSA on ward and individual patient levels in a hospital where transmission was common. We repeatedly screened all patients on two intensive care units for MRSA carriage over a 3-mo period. All MRSA belonged to multilocus sequence type 239 (ST 239). We defined the population structure and charted the spread of MRSA by sequencing 79 isolates from 46 patients and five members of staff, including the first MRSA-positive screen isolates and up to two repeat isolates where available. Phylogenetic analysis identified a flux of distinct ST 239 clades over time in each intensive care unit. In total, five main clades were identified, which varied in the carriage of plasmids encoding antiseptic and antimicrobial resistance determinants. Sequence data confirmed intra- and interwards transmission events and identified individual patients who were colonized by more than one clade. One patient on each unit was the source of numerous transmission events, and deep sampling of one of these cases demonstrated colonization with a "cloud" of related MRSA variants. The application of whole-genome sequencing and analysis provides novel insights into the transmission of MRSA in under-resourced healthcare settings and has relevance to wider global health.

Preventing the introduction of meticillin-resistant Staphylococcus aureus into hospitals

The objective of this review was to provide an up-to-date account of the interventions used to prevent the introduction of meticillin-resistant Staphylococcus aureus (MRSA) from the expanding community and livestock reservoirs into hospitals in the USA, Denmark, The Netherlands and Western Australia. A review of existing literature and local guidelines for the management of MRSA in hospitals was performed. In Denmark, The Netherlands and Western Australia, where the prevalence of MRSA is relatively low, targeted admission screening and isolation of predefined high-risk populations have been used for several decades to successfully control MRSA in the hospital. Furthermore, in Denmark and The Netherlands, all identified MRSA carriers undergo routine decolonisation, whereas only carriers of particularly transmissible or virulent MRSA clones are subjected to decolonisation in Western Australia. In the USA, which continues to be a high-prevalence MRSA country, policies vary by state and even by hospital, and whilst guidelines from professional organisations provide a framework for infection control practices, these guidelines lack the authority of a legislative mandate. In conclusion, the changing epidemiology of MRSA, exemplified by the recent emergence of MRSA in the community and in food animals, makes it increasingly difficult to accurately identify specific high-risk groups to screen for MRSA carriage. Understanding the changing epidemiology of MRSA in a local as well as global context is fundamental to prevent the introduction of MRSA into hospitals.

Mupirocin-induced mutations in ileS in various genetic backgrounds of methicillin-resistant Staphylococcus aureus

Topical mupirocin is widely used for the decolonization of methicillin-resistant Staphylococcus aureus (MRSA) carriers. We evaluated the capacity of various MRSA clonotypes to develop mutations in the ileS gene associated with low-level mupirocin resistance. Twenty-four mupirocin-sensitive MRSA isolates from a variety of genotypes (determined by a multilocus variable-number tandem-repeat assay) were selected. Mupirocin MICs were determined by Etest. The isolates were then incubated in subinhibitory concentrations of mupirocin for 7 to 14 days. Repeat MIC determinations and sequencing of the ileS gene were then performed. Doubling times of isolates exposed to mupirocin and of unexposed isolates were compared. We found that exposure to mupirocin led to rapid induction of low-level resistance (MICs of 8 to 24 μg/ml) in 11 of 24 (46%) MRSA isolates. This phenomenon was observed in strains with diverse genetic backgrounds. Various mutations were detected in 18 of 24 (75%) MRSA isolates. Acquisition of mutations appeared to be a stepwise process during prolonged incubation with the drug. Among the five isolates exhibiting low-level resistance and the highest MICs, four tested sensitive after incubation in the absence of mupirocin but there was no reversion to the susceptible wild-type primary sequence. Resistance was not associated with significant fitness cost, suggesting that MRSA strains with low-level mupirocin resistance may have a selective advantage in facilities where mupirocin is commonly used. Our findings emphasize the importance of the judicious use of this topical agent and the need to closely monitor for the emergence of resistance.

Systematic literature analysis and review of targeted preventive measures to limit healthcare-associated infections by meticillin-resistant Staphylococcus aureus

Meticillin-resistant Staphylococcus aureus (MRSA) is a major cause of healthcare-associated infections in Europe. Many examples have demonstrated that the spread of MRSA within healthcare settings can be reduced by targeted infection control measures. The aim of this systematic literature analysis and review was to summarise the evidence for the use of bacterial cultures for active surveillance the benefit of rapid screening tests, as well as the use of decolonisation therapies and different types of isolation measures. We included 83 studies published between 2000 and 2012. Although the studies reported good evidence supporting the role of active surveillance followed by decolonisation therapy, the effectiveness of single-room isolation was mostly shown in non-controlled studies, which should inspire further research regarding this issue. Overall, this review highlighted that when planning the implementation of preventive interventions, there is a need to consider the prevalence of MRSA, the incidence of infections, the competing effect of standard control measures (e.g. hand hygiene) and the likelihood of transmission in the respective settings of implementation.

Is reduced susceptibility to disinfectants and antiseptics a risk in healthcare settings? A point/counterpoint review

BACKGROUND

Given the breadth and depth of antiseptic use, it is surprising how few large-scale studies have been undertaken into the consequences of their use, particularly in clinical practice. Depending on your point of view, this may either reflect an assurance that reduced susceptibility to antiseptics, and notably whether this confers cross-resistance to systemically administered antimicrobial agents, is not an issue of concern, or relative ignorance about the potential threat.

AIM

This point/counterpoint review offers a differentiated perspective and possible answers to the question, 'Should we be worried about reduced susceptibility to disinfectants and antiseptics in healthcare settings?'.

METHODS

This topic was the subject of a debate by MHW (point) and SH (counterpoint) during the SHEA Spring Conference 2013: Advancing healthcare epidemiology and the role of the environment, held in Atlanta, GA, USA on 4(th) May 2013. This review is a general representation of the main themes presented during the debate, rather than a systematic review of the literature.

FINDINGS

There are examples of reduced susceptibility to antiseptics in clinical practice; however, to date, there is no strong evidence that reduced susceptibility to antiseptics is a major clinical problem. Given the growing number of potential indications for use of biocidal active ingredients, the potential for emergence of reduced susceptibility remains a concern.

CONCLUSIONS

Changes in the clinical use of antiseptics should be matched with surveillance studies to understand whether there are unintended microbiological or clinical consequences, including the selection of bacterial strains that can survive exposure to antiseptics.

Molecular characterization of methicillin-resistant Staphylococcus aureus clinical isolates obtained from the Rikers Island Jail System from 2009 to 2013

Inmates of Rikers Island jail potentially introduce Staphylococcus aureus into New York State prisons upon transfer. In this study, methicillin-resistant Staphylococcus aureus isolates (n = 452), collected from infected inmates (2009 to 2013), were characterized. spa type t008 was the predominant clone identified, accounting for 82.3% of the isolates, with no evidence of mupirocin or chlorhexidine resistance.

Prevalence of chlorhexidine-resistant methicillin-resistant Staphylococcus aureus following prolonged exposure

Chlorhexidine has been increasingly utilized in outpatient settings to control methicillin-resistant Staphylococcus aureus (MRSA) outbreaks and as a component of programs for MRSA decolonization and prevention of skin and soft-tissue infections (SSTIs). The objective of this study was to determine the prevalence of chlorhexidine resistance in clinical and colonizing MRSA isolates obtained in the context of a community-based cluster-randomized controlled trial for SSTI prevention, during which 10,030 soldiers were issued chlorhexidine for body washing. We obtained epidemiological data on study participants and performed molecular analysis of MRSA isolates, including PCR assays for determinants of chlorhexidine resistance and high-level mupirocin resistance and pulsed-field gel electrophoresis (PFGE). During the study period, May 2010 to January 2012, we identified 720 MRSA isolates, of which 615 (85.4%) were available for molecular analysis, i.e., 341 clinical and 274 colonizing isolates. Overall, only 10 (1.6%) of 615 isolates were chlorhexidine resistant, including three from the chlorhexidine group and seven from nonchlorhexidine groups (P > 0.99). Five (1.5%) of the 341 clinical isolates and five (1.8%) of the 274 colonizing isolates harbored chlorhexidine resistance genes, and four (40%) of the 10 possessed genetic determinants for mupirocin resistance. All chlorhexidine-resistant isolates were USA300. The overall prevalence of chlorhexidine resistance in MRSA isolates obtained from our study participants was low. We found no association between extended chlorhexidine use and the prevalence of chlorhexidine-resistant MRSA isolates; however, continued surveillance is warranted, as this agent continues to be utilized for infection control and prevention efforts.

The use of surveillance and preventative measures for methicillin-resistant staphylococcus aureus infections in surgical patients

The Agency for Healthcare Research & Quality (AHRQ) found that Methicillin-resistant Staphylococcus aureus (MRSA) is associated with up to 375,000 infections and 23,000 deaths in the United States. It is a major cause of surgical site infections, with a higher mortality and longer duration of care than Methicillin-sensitive Staphylococcus aureus. A multifactorial bundled approach is needed to control this epidemic, with single interventions unlikely to have a significant impact on attenuating MRSA infection rates. Active surveillance has been studied in a wide range of surgical patients, including surgical intensive care and non-intensive care units; cardiac, vascular, orthopedic, obstetric, head and neck cancer and gastrostomy patients. There is sufficient evidence demonstrating a beneficial effect of surveillance and eradication prior to surgery to recommend its use on an expanded basis. Studies on MRSA surveillance in surgical patients that were published over the last 10 years were reviewed. In at least five of these studies, the MRSA colonization status of patients was reported to be a factor in preoperative antibiotic selection, with the modification of treatment regiments including the switching to vancomycin or teicoplanin in MRSA positive preoperative patients. Several authors also used decolonization protocols on all preoperative patients but used surveillance to determine the duration of the decolonization. Universal decolonization of all patients, regardless of MRSA status has been advocated as an alternative prevention protocol in which surveillance is not utilized. Concern exists regarding antimicrobial stewardship. The daily and universal use of intranasal antibiotics and/or antiseptic washes may encourage the promotion of bacterial resistance and provide a competitive advantage to other more lethal organisms. Decolonization protocols which indiscriminately neutralize all bacteria may not be the best approach. If a patient's microbiome is markedly challenged with antimicrobials, rebuilding it with replacement commensal bacteria may become a future therapy. Preoperative MRSA surveillance allows the selection of appropriate prophylactic antibiotics, the use of extended decolonization protocols in positive patients, and provides needed data for epidemiological studies.

Pitfalls in evidence assessment: the case of chlorhexidine and alcohol in skin antisepsis

Chlorhexidine has attracted increasing attention for its role in skin antisepsis in recent years. It was tested in several prominent clinical trials and subsequently recommended in important guidelines for blood culture collection, vascular catheter insertion and surgical skin preparation. We noticed and subsequently reported a widespread misinterpretation of evidence surrounding chlorhexidine and its role in skin antisepsis. Multiple clinical trial reports and systematic reviews that had assessed the clinical efficacy of chlorhexidine/alcohol combinations for skin antisepsis had attributed efficacy solely to the chlorhexidine component. This misinterpretation was carried over into the tertiary literature, including evidence-based guidelines. Here we discuss some of the scientific, ethical, patient safety and infection control implications of this misinterpretation, as well as broader implications for evidence-based medicine.

Mupirocin/chlorexidine to prevent methicillin-resistant Staphylococcus aureus infections: post hoc analysis of a placebo-controlled, randomized trial using mupirocin/chlorhexidine and polymyxin/tobramycin for the prevention of acquired infections in intubated patients

PURPOSE

The reduction in acquired infections (AI) due to methicillin-resistant Staphylococcus aureus (MRSA) with the mupirocin/chlorhexidine (M/C) decontamination regimen has not been well studied in intubated patients. We performed post hoc analysis of a prior trial to assess the impact of M/C on MRSA AI and colonization.

METHODS

We conducted a multicenter, placebo-controlled, randomized, double-blind study with the primary aim to reduce all-cause AI. The two regimens used [topical polymyxin and tobramycin (P/T), nasal mupirocin with chlorhexidine body wash (M/C), or corresponding placebos for each regimen] were administered according to a 2 × 2 factorial design. Participants were intubated patients in the intensive care units of three French university hospitals. The patients enrolled in the study (n = 515) received either active P/T (n = 130), active M/C (n = 130), both active regimens (n = 129), or placebos only (n = 126) for the period of intubation and an additional 24 h. The incidence and incidence rates (per 1,000 study days) of MRSA AI were assessed. Due to the absence of a statistically significant interaction between the two regimens, analysis was performed at the margins by comparing all patient receiving M/C (n = 259) to all patients not receiving M/C (n = 256), and all patients receiving P/T (n = 259) to all patients not receiving P/T (n = 256).

RESULTS

Incidence [odds ratio (OR) 0.39, 95 % confidence interval (CI) (0.16-0.96), P = 0.04] and incidence rates [incidence rate ratio (IRR) 0.41, 95 % CI 0.17-0.97, P = 0.05] of MRSA AI were significantly lower with the use of M/C. We also observed an increase in the incidence (OR 2.50, 95 % CI 1.01-6.15, P = 0.05) and the incidence rate (IRR 2.90, 95 % CI 1.20-8.03, P = 0.03) of MRSA AI with the use of P/T.

CONCLUSION

Among our study cohort of intubated patients, the use of M/C significantly reduced MRSA AI.