Prevalence of antiseptic-resistance genes in Staphylococcus aureus and coagulase-negative staphylococci colonising nurses and the general population in Hong Kong

Sustainable reduction of nasal colonization and hand contamination with Staphylococcus aureus in food handlers, 2002-2011

A longitudinal study of nasal colonization and hand contamination of food handlers with Staphylococcus aureus commenced in 2002 prior to the outbreak of severe acute respiratory syndrome. In the follow-up in 2003 when hygiene measures were strictly implemented, significant reductions in carriage were observed. To investigate if this change was sustained, nasal and hand carriage rates were compared between the earlier studies and a further sampling in 2011. The initial nasal carriage rate was 35% and hand contamination 41·2%, decreasing to 23·5% and 11·6%, respectively in 2003 (P < 0·001). In 2011, nasal carriage was similar to 2003 (22·9%), while hand contamination dropped further to 3·7% (P < 0·001). Spa-typing revealed 39 types in 2002 and 42 in 2011. This study reveals that the marked reduction in colonization had been sustained. This may be attributed to reduced opportunities for spread due to enhanced hygiene and reinforces its importance for control of disease.

Novel insight into antimicrobial resistance and sensitivity phenotypes associated to qac and norA genotypes in Staphylococcus aureus

Staphylococcus aureus strains harboring QacA, QacB, QacC, QacG transporters and norA promoter up-regulating mutations were characterized by phenotype microarray (PM), standard methods for susceptibility testing, and ethidium bromide efflux assays, in order to increase knowledge on phenotypes associated to efflux pumps and their substrates. PM data and standard susceptibility testing lead to the identification of new potential efflux targets, such as guanidine hydrochloride or 8-hydroxyquinoline for QacA and QacC pumps, respectively. The identification of compounds to which the presence of efflux pumps induced increased susceptibility opens new perspectives for potential adjunct anti-resistance treatment (i.e. strains bearing QacB transporters showed increased susceptibility to thioridazine, amitriptyline and orphenadrine). Although the tested isolates were characterized by high degree of heterogeneity, a hallmark of clinical isolates, direct ethidium bromide efflux assays were effective in highlighting differences in efflux efficiency among strains. These data add to characterization of substrate specificity in the different classes of staphylococcal multidrug efflux systems conferring specific substrate profiles and efflux features to each of them.

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.

Effect of multipurpose solutions against Acinetobacter carrying QAC genes

PURPOSE

Acinetobacter has low virulence but causes infections in subjects with reduced immunity. It has been reported in ocular infections including those of patients using contact lenses. Treatment is difficult because Acinetobacter is frequently multidrug resistant. Antibiotic-resistant strains frequently also harbor genes for antiseptic resistance (quaternary ammonium compound [QAC]) genes. Because Acinetobacter is part of the normal flora, it may contaminate contact lens and accessories. This study aims to investigate carriage rates of QAC genes in household and clinical isolates of Acinetobacter and to determine the effectiveness of two multipurpose solutions (MPSs) for soft lenses against organisms carrying QAC genes.

METHODS

DNA was extracted from 11 bathroom isolates and 15 clinical isolates and amplified by polymerase chain reaction to determine the presence of qacEΔ1. Gene-positive and gene-negative control strains were used to challenge the two MPSs, and minimum inhibitory concentrations (MICs) of these organisms to benzalkonium chloride and chlorhexidine gluconate were determined.

RESULTS

More than 90% of isolates carried qacEΔ1. The MICs of clinical isolates were higher than those of isolates of bathrooms. Both MPSs were able to produce a 3-log reduction in the numbers of all isolates.

CONCLUSIONS

Although most isolates carried qacEΔ1 and elevated MICs to benzalkonium chloride and chlorhexidine gluconate were observed, all were susceptible to both MPSs tested. However, if there were to be poor compliance with care procedures, it is probable that such organisms could survive in the presence of diluted or expired solutions.

Relationship between the resistance genes to quaternary ammonium compounds and antibiotic resistance in staphylococci isolated from surgical site infections

BACKGROUND

We aimed to investigate the prevalence of disinfectant resistance genes (qacA/qacB,qacC) and the aminoglycosides resistance genes [(aac(6')aph(2''),aph(3')-IIIa,ant(4')-Ia)] in both S. aureus and coagulase-negative staphylococcal strains (CoNS) isolated from surgical site infections.

MATERIAL AND METHODS

Totally, 130 staphylococcal strains isolated from surgical site infections between January 2012 and February 2013 were included in the study. The PCR technique was employed to verify any presence of methicillin resistance gene (mecA), aminoglycoside resistance genes [(aac(6')/aph (2''), aph(3)-III a ant (4')-1a)], and disinfectant resistance genes (qacA/qacB,qacC) in staphylococci.

RESULTS

MecA gene was determined in 58 (44.6%) of 130 staphylococcal isolates. A total of 28 (73.7%) of 38 S. aureus isolates were found to be positive for the mecA gene, and 4 (12.9%) of 31 isolates sensitive to amikacin were sensitive to methicillin. Eighteen (47.4%) of 38 amikacin-resistant S. aureus isolates were found to be positive for qacA/qacB genes and 11 (8.9%) of them were positive for qacC gene. Both mecA and qacA/qacB genes were found to be positive at the same time in 19 amikacin-resistant S. aureus strains. Seven (18.4%) S. aureus isolates were determined to be positive for qacA/qacB and qacC genes. Frequency of qacA/B genes was found to be 47.4% among amikacin-resistant S. aureus strains, while qacC gene was found to be 28.9% (p<0.05). The ratio of qacA/B and qacC genes in CoNS was found to be 37.9% and 20.7%, respectively (p<0.05).

CONCLUSIONS

Quaternary ammonium resistance genes were found to be positive at a remarkable ratio in the staphylococcal isolates from surgical wounds. Especially, the high rates of aminoglycosides and methicillin-resistance gene was remarkable in S. aureus isolates. Quaternary ammonium resistance genes were found to be positive.

Implementation of a novel in vitro model of infection of reconstituted human epithelium for expression of virulence genes in methicillin-resistant Staphylococcus aureus strains isolated from catheter-related infections in Mexico

Background

Methicillin-resistant Staphylococcus aureus (MRSA) are clinically relevant pathogens that cause severe catheter-related nosocomial infections driven by several virulence factors.

Methods

We implemented a novel model of infection in vitro of reconstituted human epithelium (RHE) to analyze the expression patterns of virulence genes in 21 MRSA strains isolated from catheter-related infections in Mexican patients undergoing haemodialysis. We also determined the phenotypic and genotypic co-occurrence of antibiotic- and disinfectant-resistance traits in the S. aureus strains, which were also analysed by pulsed-field-gel electrophoresis (PFGE).

Results

In this study, MRSA strains isolated from haemodialysis catheter-related infections expressed virulence markers that mediate adhesion to, and invasion of, RHE. The most frequent pattern of expression (present in 47.6% of the strains) was as follows: fnbA, fnbB, spa, clfA, clfB, cna, bbp, ebps, eap, sdrC, sdrD, sdrE, efb, icaA, and agr. Seventy-one percent of the strains harboured the antibiotic- and disinfectant-resistance genes ermA, ermB, tet(M), tet(K), blaZ, qacA, qacB, and qacC. PFGE of the isolated MRSA revealed three identical strains and two pairs of identical strains. The strains with identical PFGE patterns showed the same phenotypes and genotypes, including the same spa type (t895), suggesting hospital personnel manipulating the haemodialysis equipment could be the source of catheter contamination.

Conclusion

These findings help define the prevalence of MRSA virulence factors in catheter-related infections. Some of the products of the expressed genes that we detected in this work may serve as potential antigens for inclusion in a vaccine for the prevention of MRSA-catheter-related infections.

Basic rules of hygiene protect health care and lab workers from nasal colonization by Staphylococcus aureus: an international cross-sectional study

Acquisition of nasal Staphylococcus aureus (S. aureus) colonization by contaminated hands is likely an important determinant of its nasal carriage rate in health care and lab setting. The objective of our cross-sectional study was to assess the prevalence of nasal methicillin-sensitive (MSSA) or -resistant Staphylococcus aureus (MRSA) carriage among health care professionals (HCPs) attending an international symposium and to study the association between compliance with hygiene rules, individual-related parameters, and medical conditions with nasal S. aureus carriage in this population. After obtaining consent, two nasal swabs were collected. Nasal MSSA and MRSA carriage was measured by the: i) molecular approach targeting spa, mecA and mecA-orfX junction sequences, and ii) culture on selective S. aureus media combined with mecA molecular detection of isolated strains. Information on compliance with hygiene rules, demographic variables, sector of activity and long-term medication was collected by anonymous questionnaire. The participation rate was 32.3%. In total, 176 subjects from 34 countries were included in the analysis. S. aureus was isolated from the nasal swabs of 57 (32.4%) subjects, of whom 3 (5.3%) harbored MRSA strains. Overall, 123 subjects reported working in microbiology laboratories with direct manipulation of S. aureus, and 29 acknowledged regular contacts with patients. In this exposed population, hydro-alcoholic solutions appeared to have a significant protective effect against nasal S. aureus carriage (OR = 0.36; 95% CI: 0.15-0.85). Hospital work was associated with increased risk of nasal S. aureus carriage (OR = 2.38; 95% CI: 1.07-5.29). The results of this study showed that compliance with basic rules of hygiene, such as the use of hydro-alcoholic solutions, could reduce the risk of nasal S. aureus colonization. Hydro-alcoholic solution could interrupt auto-transmission of the pathogen, consequently decreasing the overall nasal carriage rate, specifically in transient carriers.

Occupational exposure to raw meat: a newly-recognized risk factor for Staphylococcus aureus nasal colonization amongst food handlers

Staphylococcus aureus contaminating raw meat may increase nasal colonization risk for occupationally-exposed food handlers. Food handlers from six catering establishments were nasally sampled for S. aureus and completed a questionnaire on carriage risk factors. Isolates were characterized for antibiotic susceptibility, spa type and, for methicillin-resistant strains, SCCmec type. Of 434 food handlers, 99 (22.8%) were colonized with S. aureus. Five isolates were methicillin-resistant belonging to SCCmec IV (2) and V (3). Resistance to tetracycline (20%), and erythromycin (16%) was high, but <10% to other antibiotics. Spa typing revealed 17% of isolates as t189, with 8% each t127 and t1081. Food handlers ever handling raw meat had a significantly higher colonization risk (OR=2.7; 95% CI: 1.7-4.5), increasing to 3.7 (95% CI: 2.0-6.8) for those always exposed. This is the first report of increased colonization risk in food handlers exposed to raw meat. This occupational hazard may increase infection risk, so improved compliance with workplace hygiene may be required.

Recently introduced qacA/B genes in Staphylococcus epidermidis do not increase chlorhexidine MIC/MBC

OBJECTIVES

Chlorhexidine is used as a disinfectant to prevent surgical infections. Recently, studies have indicated that chlorhexidine usage has selected methicillin-resistant Staphylococcus aureus strains that are tolerant to chlorhexidine and that this may be related to the presence of the qacA/B-encoded efflux pumps. Here, we evaluated if high-level exposure to chlorhexidine selects for tolerant colonizing Staphylococcus epidermidis and we addressed the consequences of long-term exposure to chlorhexidine.

METHODS

Chlorhexidine susceptibility and carriage of qacA/B was determined for colonizing S. epidermidis isolated from scrub nurses heavily exposed to chlorhexidine and were compared with isolates from non-users of chlorhexidine hand rubs. S. epidermidis blood isolates from the 1960s, before the wider introduction of chlorhexidine to the market, were also tested and compared with recently collected S. epidermidis blood isolates.

RESULTS

There was no correlation between the use of chlorhexidine in scrub nurses and the presence of qacA/B genes in S. epidermidis isolates or increased MICs/MBCs of chlorhexidine for S. epidermidis isolates. While 55% of current blood isolates harboured the qacA/B genes, none of the 33 historical S. epidermidis isolates did, although their MICs and MBCs of chlorhexidine were comparable to those for current isolates.

CONCLUSIONS

Chlorhexidine used as a hand rub does not select for S. epidermidis isolates with increased MICs or MBCs of chlorhexidine. However, the absence of qacA/B genes in S. epidermidis isolates obtained in the 1960s suggests that long-term use of biocides like chlorhexidine or related compounds may select for the presence of qacA/B genes.

Reducing central line infections in pediatric and neonatal patients

The stakes for the prevention of central line associated bloodstream infections (CLABSIs) have increased dramatically over the past decade. Over the past 10 years, the rate of CLABSI in the pediatric population has dropped markedly due to the significant investment in this initiative. Although there has been a substantial increase in studies on CLABSIs, difficulties in studying CLABSIs have limited the quality of the evidence produced. These difficulties include challenges in the sample size required to complete trials, pressure from external regulatory forces to reduce CLABSI rates, and challenges in defining CLABSIs. The definition of CLABSI is continuously being updated to improve the misclassification bias inherent in defining CLABSI. This is especially relevant given the stress placed on decreasing health-care-associated infections and the negative consequences associated if unsuccessful. In order to prevent CLABSIs, pediatric and neonatal intensive care units have formed bundles of basic evidenced-based strategies leading to effective reduction of CLABSIs. These basic bundles have been modified for spread to other nonintensive care areas, also yielding great results. However, additional therapies above the basic bundle have yielded mixed results, and more research is needed to understand the cost effectiveness of these therapies in the setting of decreasing CLABSI rates. As a goal, a "getting to zero" CLABSI rate should be set, but it may not be possible without significant resource allocation.

Reducing the risk of surgical site infections: does chlorhexidine gluconate provide a risk reduction benefit?

Chlorhexidine gluconate (CHG) has been available as a topical antiseptic for over 50 years, having broad clinical application throughout the health care environment. Evidence-based clinical studies have shown chlorhexidine gluconate to be a safe and effective perioperative skin-prepping agent. Renewed interest has emerged for use of the antiseptic bath/shower to reduce the microbial skin burden prior to hospital admission. Recent clinical studies have documented that multiple applications of 2% or 4% CHG using a standardized protocol results in high skin surface concentrations sufficient to inhibit/kill skin colonizing flora, including methicillin-resistant Staphylococcus aureus. A new focus for the use of CHG in surgical patients involves irrigation of the wound prior to closure with 0.05% CHG followed by saline rinse. Recent laboratory studies suggest that, following a 1-minute exposure, 0.05% CHG produces a >5-log reduction against selective health care-associated pathogens and reduces microbial adherence to the surface of implantable biomedical devices. General, orthopedic, cardiothoracic, and obstetrical surgical studies have documented the safety of selective CHG formulations in elective surgical procedures. The following discussion will address both the evidence-based literature and preliminary findings suggesting that CHG has a broad and safe range of applications when used as an adjunctive interventional strategy for reducing the risk of postoperative surgical site infections (SSI).

Multidrug Efflux Pumps in Staphylococcus aureus: an Update

The emergence of infections caused by multi- or pan-resistant bacteria in the hospital or in the community settings is an increasing health concern. Albeit there is no single resistance mechanism behind multiresistance, multidrug efflux pumps, proteins that cells use to detoxify from noxious compounds, seem to play a key role in the emergence of these multidrug resistant (MDR) bacteria. During the last decades, experimental data has established their contribution to low level resistance to antimicrobials in bacteria and their potential role in the appearance of MDR phenotypes, by the extrusion of multiple, unrelated compounds. Recent studies suggest that efflux pumps may be used by the cell as a first-line defense mechanism, avoiding the drug to reach lethal concentrations, until a stable, more efficient alteration occurs, that allows survival in the presence of that agent. In this paper we review the current knowledge on MDR efflux pumps and their intricate regulatory network in Staphylococcus aureus, a major pathogen, responsible from mild to life-threatening infections. Particular emphasis will be given to the potential role that S. aureus MDR efflux pumps, either chromosomal or plasmid-encoded, have on resistance towards different antimicrobial agents and on the selection of drug - resistant strains. We will also discuss the many questions that still remain on the role of each specific efflux pump and the need to establish appropriate methodological approaches to address all these questions.

Selection for qacA carriage in CC22, but not CC30, methicillin-resistant Staphylococcus aureus bloodstream infection isolates during a successful institutional infection control programme

OBJECTIVES

The increasing use of chlorhexidine for methicillin-resistant Staphylococcus aureus (MRSA) decolonization raises concerns about reduced susceptibility. We evaluated the carriage of chlorhexidine resistance genes and chlorhexidine susceptibility in MRSA before and after introduction of an institutional MRSA control programme incorporating chlorhexidine-based decolonization in 2004.

METHODS

MRSA bloodstream infection (BSI) isolates identified between 2001 and 2009 were tested for spa and staphylococcal cassette chromosome mec type and carriage of qacA, qacB and smr. Selected isolates were tested for chlorhexidine susceptibility. Logistic regression was used to evaluate associations between clone type, carriage of resistance genes and chlorhexidine susceptibility. Temporal trends in qacA or smr carriage were analysed using separate binomial generalized linear models.

RESULTS

Typing identified two dominant clones: CC22 (n = 224) and CC30 (n = 197). Annual MRSA BSI rates declined from 2004, although the rate of decline for CC22 was slower than for CC30. Carriage of qacA and smr and having a chlorhexidine MIC ≥2 mg/L did not increase overall amongst MRSA BSI isolates; however, qacA carriage increased in CC22 compared with in CC30 (OR, 7.21; 95% CI, 1.32-39.17). Furthermore, qacA+ CC22 isolates were more likely to have a chlorhexidine MIC ≥2 mg/L than qacA+ CC30 isolates (OR, 21.67; CI, 2.54-185.20).

CONCLUSIONS

A successful infection control programme was associated with the selection of qacA linked with a higher chlorhexidine MIC in one dominant endemic MRSA clone (CC22), but not another (CC30). The slower reduction in the CC22 MRSA BSI rate suggests that carriage of qacA confers a selective advantage, with implications for the sustainability of decolonization practice.

Colonization of butchers with livestock-associated methicillin-resistant Staphylococcus aureus

Reports have documented colonization of swine in Europe, North America and more recently in China with livestock-associated methicillin-resistant Staphylococcus aureus (LA-MRSA). Contamination of pig farmers, veterinarians and abattoir workers with these strains has been observed. However, although contamination levels of 10% of retail pork were reported from the Netherlands and Canada, there are limited data of contamination rates of workers handling raw meat. We investigated the rates of MRSA contamination of local butchers working in wet markets, where recently slaughtered pigs are cut up. Nasal swabs collected from 300 pork butchers at markets throughout Hong Kong were enriched in brain heart infusion broth with 5% salt and cultured on MRSASelect(®) . Isolates were confirmed as Staphylococcus aureus and susceptibility testing performed. The presence of mecA was confirmed, SCCmec and spa type determined and relatedness investigated by PFGE. Subjects completed a questionnaire on MRSA carriage risk factors. Seventeen samples (5.6%) yielded MRSA, 15 harbouring SCCmec IVb. Ten strains were t899 (CC9), previously reported from local pig carcasses. Five strains were healthcare associated: SCCmec type II, t701(CC6), colonizing two subjects at the same establishment, and single isolates of t008 (CC8), t002 (CC5) and t123 (CC45). The remaining isolates were t359 (CC97), previously reported from buffaloes, and t375 (CC5), reported from bovine milk. None of these butchers reported recent hospitalization or a healthcare worker in the family. Two had recently received antibiotics, one for a skin infection. Four reported wound infections within the last year. All were exposed to meat for >9 h per day. Carriage of MRSA was higher in butchers than in the general community. Although five strains were probably of healthcare origin, the high incidence of t899 (CC9) suggests that cross-contamination from pork occurs frequently. Washing of hands after touching raw pork is advised.

Presence of antiseptic resistance genes in porcine methicillin-resistant Staphylococcus aureus

Numerous studies have documented the presence of methicillin-resistant Staphylococcus aureus (MRSA) in meat-producing animals, which has led to concern about its spread into the community. Disinfectants play an important role in reduction of contamination in both animal husbandry and food-preparation, helping control spread of organisms from foodstuffs, including raw meat. Plasmid-borne antiseptic resistance (AR) genes increasing tolerance to several disinfectants have been reported in S. aureus of human origin (qacA/B and smr) and from bovine, equine, and caprine staphylococcal isolates (qacG, qacH, and qacJ). This study investigated the presence of AR genes in porcine MRSA isolates. Plasmid DNA from 100 MRSA ST9 strains isolated from pig carcasses was amplified for the presence of AR genes. Minimum inhibitory concentrations (MICs) and minimum bactericidal concentrations (MBCs) to benzalkonium chloride (BC) and chlorhexidine gluconate (CHX) were determined in AR gene-positive isolates. qacG was present in 45 strains, eight of which also harbored smr. No strains carried qacA/B, qacH or qacJ. Presence of smr increased MICs to both BC and CHX and MBCs of CHX, but qacG presence only resulted in elevated MBC for CHX. This is the first report of AR genes from a porcine source. AR gene positivity has previously been associated with methicillin resistance and AR gene presence in these strains may increase their ability to persist in the environment. Improved implementation of hygiene measures during transportation and pre- and post-slaughter should be considered to prevent spread in the community.

The effects of daily chlorhexidine bathing on cutaneous bacterial isolates: a pilot study

Chlorhexidine gluconate (CHG) is a topical antiseptic used in a myriad of clinical settings. Recently, CHG baths have been shown to decrease multidrug-resistant organism acquisition and infections and catheter-associated bloodstream infections. The present study examined the effects of daily bathing with CHG on the recovery and antimicrobial susceptibility of cultivable cutaneous bacteria. The objectives of this study were to (1) explore the effects of clinical CHG bathing on cultivable cutaneous bacteria, (2) study the relationship between CHG minimum inhibitory concentration and antimicrobial susceptibility of coagulase-negative staphylococci, and (3) demonstrate the feasibility of the approach so a more definitive study may be performed. Significant decreases in bacterial colony counts and phenotypic diversity occurred with greater CHG exposure. The findings also suggest an inverse relationship between CHG minimum inhibitory concentration and antimicrobial susceptibility. Larger prospective studies are necessary to fully investigate the clinical impact of CHG usage.

Emergence of resistance to antibacterial agents: the role of quaternary ammonium compounds--a critical review

Quaternary ammonium compounds (QACs) are widely distributed in hospitals, industry and cosmetics. Little attention has been focused on the potential impact of QACs on the emergence of antibiotic resistance in patients and the environment. To assess this issue, we conducted a literature review on QAC chemical structure, fields of application, mechanism of action, susceptibility testing, prevalence, and co- or cross-resistance to antibiotics. Special attention was paid to the effects of QACs on microflora; in particular, the issue of the potential of QACs for applying selective pressure on multiple-antibiotic-resistant organisms was raised. It was found that there is a lack of standardised procedures for interpreting susceptibility test results. QACs have different impacts on the minimum inhibitory concentrations of antibacterials depending on the antibacterial compound investigated, the resistance genes involved, the measuring methodology and the interpretative criteria. The unmet needs for adequate detection of reduced susceptibility to QACs and antibiotics include (i) a consensus definition for resistance, (ii) epidemiological cut-off values and (iii) clinical resistance breakpoints. This review advocates the design of international guidelines for QAC use.

Back to the future: rising to the Semmelweis challenge in hand hygiene

Hand hygiene is the single most important intervention for reducing healthcare associated infections and preventing the spread of antimicrobial resistance. This sentence begins most publications regarding hand hygiene in the medical literature. But why - as we mark 150 years since the publication of Ignaz Semmelweis' landmark monograph on the subject - do we continue to repeat it? One might be tempted to regard it as a truism. However, while tremendous progress has certainly been made in this field, a significant amount of work is yet to be done in both strengthening the evidence regarding the impact of hand hygiene and maximizing its implementation. Hand hygiene cannot yet be taken for granted. This article summarizes historical perspectives, dynamics of microbial colonization and efficacy of hand cleansing methods and agents, elements and impacts of successful hand hygiene promotion, as well as scale-up and sustainability. We also explore hand hygiene myths and current challenges such as monitoring, behavior change, patient participation and research priorities.

Characterization of staphylococci contaminating automated teller machines in Hong Kong

Environmental staphylococcal contamination was investigated by culture of 400 automated teller machines (ATMs). Isolates were characterized for antibiotic and antiseptic susceptibility, carriage of antiseptic resistance genes (QAC genes), and spa types. MRSA, which was similar to local clinical isolates, was present on two (0·5%) of the 62 (15·5%) ATMs that yielded Staphylococcus aureus. QAC genes were more common in coagulase-negative staphylococci (qacA/B 26·0%, smr 14%) than S. aureus (11·3% qacA/B, 1·6% smr). QAC-positive isolates had significantly higher minimum inhibitory concentrations/minimum bactericidal concentrations to benzalkonium chloride and chlorhexidine digluconate. QAC gene presence was significantly associated with methicillin and tetracycline resistance. Survival of staphylococci, including MRSA, on common access sites may be facilitated by low disinfectant concentrations, which select for disinfectant-tolerant strains, while co-selecting for antibiotic-resistance determinants. Disinfection procedures should be performed correctly to help prevent spread of resistant pathogens from reservoirs in the community.