Association between intensity of chlorhexidine use and micro-organisms of reduced susceptibility in a hospital environment

Supragingival dental biofilm profile and biofilm control during orthodontic treatment with fixed orthodontic appliance: A randomized controlled trial

OBJECTIVE

The effectiveness of supragingival dental biofilm control during orthodontic treatment and changes in the bacterial profile were analyzed.

DESIGN

Sixty-four participants aged 12-22 years (57% female) were included in the study. Participants underwent orthodontic treatment with fixed appliances and were randomly assigned to one of the three groups, which during a period of one month: (I) used chlorhexidine digluconate (CHX), (II) used high concentration of fluoride (F) gel and (III) performed standard oral hygiene. The plaque and gingivitis index, pH of biofilm and white spot lesions (WSL) were assessed. Changes of the bacteria in the biofilm were analyzed by the quantitative polymerase chain reaction RESULTS: Increase in the plaque index, pH of biofilm, and WSL was observed during orthodontic treatment with standard oral hygiene. Large interindividual variability was present, and the effects of one-month use of fluorides and CHX on clinical parameters were not significant. Despite standard hygiene the abundance of studied biofilm bacteria increased - the most Streptoccocus mutans (14.2x) and S. salivarius (3.3x), moderate Veillonella parvula (3x) and the least S. sobrinus (2.3x) and Agregatibacter actinomycetemcomitans (1.9x). The use of CHX reduced S. sobrinus (2.2x) and A. actinomycetemcomitans (1.9x). Fluoride use reduced A. actinomycetemcomitans (1.3x) and S. sobrinus (1.2x). Fluorides better controlled S. mutans than CHX.

CONCLUSION

Bacterial biomass in supragingival biofilm increased during treatment with metal orthodontic appliances, with greater increase in cariogenic bacteria than periopathogens. Fluoride controlled S. mutans, while CHX S. sobrinus and A. actinomycetemcomitans.

Effective elimination of bacteria on hard surfaces by the combined use of bacteriophages and chemical disinfectants

Hospital-acquired infections (HAIs) represent one of the significant causes of morbidity and mortality worldwide, and controlling pathogens in the hospital environment is of great importance. Currently, the standard disinfection method in the hospital environment is chemical disinfection. However, disinfectants are usually not used strictly according to the label, making them less effective in disinfection. Therefore, there is an emergent need to find a better approach that can be used in hospitals to control pathogenic bacteria in the clinical environment. Bacteriophages (phages) are effective in killing bacteria and have been applied in the treatment of bacterial infections but have not received enough attention regarding the control of contamination in the clinical environment. In this study, we found that various phages remain active in the presence of chemical disinfectants. Moreover, the combined use of specific phages and chemical disinfectants is more effective in removing bacterial biofilms and eliminating bacteria on hard surfaces. Thus, this proof-of-concept study indicates that adding phages directly to chemical disinfectants might be an effective and economical approach to enhance clinical environment disinfection.

IMPORTANCE

In this study, we investigated whether the combination of bacteriophages and chemical disinfectants can enhance the efficacy of reducing bacterial contamination on hard surfaces in the clinical setting. We found that specific phages are active in chemical disinfectants and that the combined use of phages and chemical disinfectants was highly effective in reducing bacterial presence on hard surfaces. As a proof-of-concept, we demonstrated that adding specific phages directly to chemical disinfectants is an effective and cost-efficient strategy for clinical environment disinfection.

Towards a Harmonized Terminology: A Glossary for Biocide Susceptibility Testing

Disinfection is a key strategy to reduce the burden of infections. The contact of bacteria to biocides-the active substances of disinfectants-has been linked to bacterial adaptation and the development of antimicrobial resistance. Currently, there is no scientific consensus on whether the excessive use of biocides contributes to the emergence and spread of multidrug resistant bacteria. The comprehensive analysis of available data remains a challenge because neither uniform test procedures nor standardized interpretive criteria nor harmonized terms are available to describe altered bacterial susceptibility to biocides. In our review, we investigated the variety of criteria and the diversity of terms applied to interpret findings in original studies performing biocide susceptibility testing (BST) of field isolates. An additional analysis of reviews summarizing the knowledge of individual studies on altered biocide susceptibility provided insights into currently available broader concepts for data interpretation. Both approaches pointed out the urgent need for standardization. We, therefore, propose that the well-established and approved concepts for interpretation of antimicrobial susceptibility testing data should serve as a role model to evaluate biocide resistance mechanisms on a single cell level. Furthermore, we emphasize the adaptations necessary to acknowledge the specific needs for the evaluation of BST data. Our approach might help to increase scientific awareness and acceptance.

A Comparison of the Adaptive Response of Staphylococcus aureus vs. Streptococcus mutans and the Development of Chlorhexidine Resistance

Antimicrobials with nonselective antibacterial efficacy such as chlorhexidine can be effective in reducing biofilm, but bear the risk of inducing resistance in specific bacteria. In clinical practice, bacteria such as Staphylococcus aureus have been found resistant to chlorhexidine, but other bacteria, including Streptococcus mutans, have largely remained susceptible to chlorhexidine despite its widespread use in oral healthcare. Here, we aim to forward a possible reason as to why S. aureus can acquire resistance against chlorhexidine, while S. mutans remains susceptible to chlorhexidine. Measurement of surface-enhanced fluorescence indicated that chlorhexidine caused gradual, but irreversible deformation to adhering green fluorescent S. aureus due to irreparable damage to the cell wall. Concurrently, the metabolic activity of adhering staphylococci was higher than of planktonic bacteria, suggesting efflux mechanisms may have been activated upon cell wall deformation, impeding the buildup of a high chlorhexidine concentration in the cytoplasm and therewith stimulating the development of chlorhexidine resistance in S. aureus. Exposure of S. mutans to chlorhexidine caused immediate, but reversible deformation in adhering streptococci, indicative of rapid self-repair of cell wall damage done by chlorhexidine. Due to cell wall self-repair, S. mutans will be unable to effectively reduce the chlorhexidine concentration in the cytoplasm causing solidification of the cytoplasm. In line, no increased metabolic activity was observed in S. mutans during exposure to chlorhexidine. Therewith, self-repair is suicidal and prevents the development of a chlorhexidine-resistant progeny in S. mutans.

Molecular epidemiology and decreased susceptibility to disinfectants in carbapenem-resistant Acinetobacter baumannii isolated from intensive care unit patients in central China

BACKGROUND

Infection with carbapenem-resistant Acinetobacter baumannii (CRAB) is an increasing problem for critically ill patients. The srains are frequently resistant to all antibiotics and disinfectants are often used to block the spread of these bacteria, playing an important role in infection control.

OBJECTIVES

The aim of this study was to investigate the antibiotic susceptibility, the clonal relationship, disinfectant resistance gene, β-lactamase genes and the disinfectant sensitivity of 82 A. baumannii isolates collected at a large hospital in Wuhan, China.

DESIGN

A retrospective basic study.

METHODS

Here we investigated 82 A. baumannii isolates from intensive care unit patients in a major teaching hospital in China for the distribution of resistance-associated genes and susceptibility to chlorine disinfectant (CLR), benzalkonium bromide (BB) and Chlorhexidine gluconate(CHG). Multi-locus sequence typing (MLST) was applied to explore their genetic evolution relationships.

RESULTS

qacE (30.48%, 25/82) and qac△E1 (76.82%, 63/82) genes were detected in our study, while none were positive for qacA/B, qacC/D or qacG. The MIC values of CLR were 250mg/L; The MIC values ranged from 32 to 128μg/mL for BB; The MIC values ranged from 0.0019% to 0.0078% for CHG. The presence or absence of qacE gene has a significant impact(p＜0.05) on MICs of BB or CHG. All isolates harboured bla_OXA-51/23 genes, and 98.78% of isolates contained the ISaba1 insertion sequence. All isolates were classified into 8 sequence types(STs) within clonal complex 92(CC92).

CONCLUSIONS

The predominant CRAB strains in our intensive care unit are bla_OXA-23-containing A. baumannii of CC92. The high prevalence of qac genes and reduced susceptibility to disinfectants confirm the need for continued vigilance against nosocomial infections.

Risks and benefits of using chlorhexidine gluconate in handwashing: A systematic literature review

BACKGROUND

Antimicrobial soaps containing chlorhexidine gluconate (CHG) are indicated for hand hygiene (HH) in specific situations. This study aimed to identify whether the continuous use of CHG for HH affects the reduction of healthcare-associated infections (HAI), the selection of microorganisms resistant to CHG, or hands skin damage.

METHODS

Systematic review was performed using the protocol of the Joanna Briggs Institute, including clinical trials and observational comparative studies. Search was conducted via PubMed, Medline, CINAHL, LILACS, Embase, Cochrane Library, Scopus, Web of Science, ProQuest, Google Scholar, and gray literature. To evaluate outcomes, 3 independent reviews were conducted: HAI rates, presence of resistance genes or higher minimum inhibitory or bactericidal concentration, and damage to skin integrity.

RESULTS

Studies showed no significant difference in HAI rates when using CHG for HH. Among 13 studies, 10 suggested an association with use of and tolerance to CHG. The use of CHG was associated with skin reaction events.

CONCLUSIONS

Strong evidence regarding the risks and benefits of CHG for HH is still lacking. Due to potential risk of selecting mutants carrying genes for cross-resistance to CHG and antibiotics, it is advisable to reserve the use of CHG for purposes other than HH.

A Novel, Widespread qacA Allele Results in Reduced Chlorhexidine Susceptibility in Staphylococcus epidermidis

Chlorhexidine gluconate (CHG) is a topical antiseptic widely used in health care settings. In Staphylococcus spp., the pump QacA effluxes CHG, while the closely related QacB cannot due to a single amino acid substitution. We characterized 1,050 cutaneous Staphylococcus isolates obtained from 173 pediatric oncology patients enrolled in a multicenter CHG bathing trial. CHG susceptibility testing revealed that 63 (6%) of these isolates had elevated CHG MICs (≥4 μg/ml). Screening of all 1,050 isolates for the qacA/B gene (the same qac gene with A or B allele) by restriction fragment length polymorphism (RFLP) yielded 56 isolates with a novel qacA/B RFLP pattern, qacA/B₂₇₃ The CHG MIC was significantly higher for qacA/B₂₇₃ -positive isolates (MIC₅₀, 4 μg/ml; MIC range, 0.5 to 4 μg/ml) than for other qac groups: qacA-positive isolates (n = 559; MIC₅₀, 1 μg/ml; MIC range, 0.5 to 4 μg/ml), qacB-positive isolates (n = 17; MIC₅₀, 1 μg/ml; MIC range, 0.25 to 2 μg/ml), and qacA/B-negative isolates (n = 418, MIC₅₀, 1 μg/ml; MIC range, 0.125 to 2 μg/ml) (P = 0.001). A high proportion of the qacA/B₂₇₃ -positive isolates also displayed methicillin resistance (96.4%) compared to the other qac groups (24.9 to 61.7%) (P = 0.001). Whole-genome sequencing revealed that qacA/B₂₇₃ -positive isolates encoded a variant of QacA with 2 amino acid substitutions. This new allele, named qacA4, was carried on the novel plasmid pAQZ1. The qacA4-carrying isolates belonged to the highly resistant Staphylococcus epidermidis sequence type 2 clone. By searching available sequence data sets, we identified 39 additional qacA4-carrying S. epidermidis strains from 5 countries. Curing an isolate of qacA4 resulted in a 4-fold decrease in the CHG MIC, confirming the role of qacA4 in the elevated CHG MIC. Our results highlight the importance of further studying qacA4 and its functional role in clinical staphylococci.

Genetic resistance determinants to fusidic acid and chlorhexidine in variably susceptible staphylococci from dogs

BACKGROUND

Concern exists that frequent use of topically-applied fusidic acid (FA) and chlorhexidine (CHX) for canine pyoderma is driving clinically relevant resistance, despite rare description of FA and CHX genetic resistance determinants in canine-derived staphylococci. This study aimed to determine minimum inhibitory concentrations (MICs) and investigate presence of putative resistance determinants for FA and CHX in canine-derived methicillin-resistant (MR) and -susceptible (MS) staphylococci. Plasmid-mediated resistance genes (fusB, fusC, fusD, qacA/B, smr; PCR) and MICs (agar dilution) of FA and CHX were investigated in 578 staphylococci (50 MR S. aureus [SA], 50 MSSA, 259 MR S. pseudintermedius [SP], 219 MSSP) from Finland, U.S.A., North (NUK) and South-East U.K. (SEUK) and Germany. In all isolates with FA MIC ≥64 mg/L (n = 27) fusA and fusE were amplified and sequenced.

RESULTS

FA resistance determinants (fusA mutations n = 24, fusB n = 2, fusC n = 36) were found in isolates from all countries bar U.S.A. and correlated with higher MICs (≥1 mg/L), although 4 SP isolates had MICs of 0.06 mg/L despite carrying fusC. CHX MICs did not correlate with qacA/B (n = 2) and smr (n = 5), which were found in SEUK SA, and SP from NUK and U.S.A.

CONCLUSIONS

Increased FA MICs were frequently associated with fusA mutations and fusC, and this is the first account of fusB in SP. Despite novel description of qacA/B in SP, gene presence did not correlate with CHX MIC. Selection pressure from clinical use might increase prevalence of these genetic determinants, but clinical significance remains uncertain in relation to high skin concentrations achieved by topical therapy.

Resistance Toward Chlorhexidine in Oral Bacteria - Is There Cause for Concern?

The threat of antibiotic resistance has attracted strong interest during the last two decades, thus stimulating stewardship programs and research on alternative antimicrobial therapies. Conversely, much less attention has been given to the directly related problem of resistance toward antiseptics and biocides. While bacterial resistances toward triclosan or quaternary ammonium compounds have been considered in this context, the bis-biguanide chlorhexidine (CHX) has been put into focus only very recently when its use was associated with emergence of stable resistance to the last-resort antibiotic colistin. The antimicrobial effect of CHX is based on damaging the bacterial cytoplasmic membrane and subsequent leakage of cytoplasmic material. Consequently, mechanisms conferring resistance toward CHX include multidrug efflux pumps and cell membrane changes. For instance, in staphylococci it has been shown that plasmid-borne qac ("quaternary ammonium compound") genes encode Qac efflux proteins that recognize cationic antiseptics as substrates. In Pseudomonas stutzeri, changes in the outer membrane protein and lipopolysaccharide profiles have been implicated in CHX resistance. However, little is known about the risk of resistance toward CHX in oral bacteria and potential mechanisms conferring this resistance or even cross-resistances toward antibiotics. Interestingly, there is also little awareness about the risk of CHX resistance in the dental community even though CHX has been widely used in dental practice as the gold-standard antiseptic for more than 40 years and is also included in a wide range of oral care consumer products. This review provides an overview of general resistance mechanisms toward CHX and the evidence for CHX resistance in oral bacteria. Furthermore, this work aims to raise awareness among the dental community about the risk of resistance toward CHX and accompanying cross-resistance to antibiotics. We propose new research directions related to the effects of CHX on bacteria in oral biofilms.

Adaptive bacterial response to low level chlorhexidine exposure and its implications for hand hygiene

Chlorhexidine digluconate (CHG) is commonly used in healthcare, e.g. in skin antiseptics, antimicrobial soaps, alcohol-based hand rubs and oral or wound antiseptics. Aim of the literature review was to evaluate the potential of bacteria to adapt to low level CHG exposure. A maximum 4fold MIC increase to CHG was found after low level exposure in most of the 71 evaluated bacterial species. A strong adaptive mostly stable MIC change was described in strains or isolates of the healthcare-associated species E. coli, S. marcescens and P. aeruginosa (up to 500fold, 128fold or 32fold, respectively). The highest MIC values after adaptation were 2,048 mg/l (S. marcescens) and 1,024 mg/l (P. aeruginosa). A new resistance to tetracycline, gentamicin, meropeneme or triclosan was found in some adapted isolates. In E. coli horizontal gene transfer was induced (sulfonamide resistance by conjugation), pointing out an additional risk of sublethal CHG. The use of CHG in patient care - but also all other settings such as consumer products and households - should therefore be critically assessed and restricted to indications with a proven health benefit or justifiable public health benefits. Additional CHG has no health benefit when used in alcohol-based hand rubs and is not recommended by the WHO. For routine hand washing of soiled hands the use of plain soap is sufficient, CHG in soaps has no health benefit. In surgical hand antisepsis alcohol-based hand rubs should be preferred to CHG soaps. Implementation of these principles will help to reduce avoidable selection pressure.

Chlorhexidine and octenidine use, carriage of qac genes, and reduced antiseptic susceptibility in methicillin-resistant Staphylococcus aureus isolates from a healthcare network

OBJECTIVES

With the widespread use of antiseptics in healthcare facilities for the prevention of methicillin-resistant Staphylococcus aureus (MRSA) transmission, there are concerns for antiseptic tolerance and resistance. We sought to understand the use of chlorhexidine and octenidine, carriage of qac genes, and reduced antiseptic susceptibilities.

METHODS

A serial cross-sectional study was conducted in an acute care hospital and three extended-care facilities of a healthcare network in June-July, 2014-2016. Two of the extended-care facilities were exposed to intranasal octenidine and universal daily chlorhexidine/octenidine bathing. The minimum inhibitory concentration (MIC) levels and qac genes were determined by broth microdilution tests and whole genome sequencing respectively. Multivariable logistic regression was used to assess for the independent associations between antiseptic exposures, qac genes, and reduced antiseptic susceptibilities.

RESULTS

A total of 878 MRSA isolates were obtained. There were associations between qacA/B carriage and chlorhexidine (adjusted odds ratio (aOR) 7.80; 95% confidence interval (CI) 3.25-18.71) and octenidine (aOR 11.79; 95% CI 5.14-27.04) exposures. Chlorhexidine exposure was associated with reduced chlorhexidine susceptibility (MIC ≥4 mg/L) (aOR 3.15; 95% CI 1.14-8.74). Carriage of qacA/B (aOR 10.65; 95% CI 4.14-27.40) or qacC (aOR 2.55; 95% CI 1.22-5.32) had an association with reduced chlorhexidine susceptibility; while MRSA sequence type modified the association. However, we found no direct association between (i) antiseptics use and qacC carriage, (ii) octenidine exposure and reduced susceptibility, and (iii) reduced octenidine susceptibility and qacA/B or qacC carriage.

CONCLUSIONS

Antiseptic exposures were associated with carriage of qac genes. Chlorhexidine exposure was associated with reduced chlorhexidine susceptibility, requiring continued surveillance for the emergence of resistance.

Efficacy and safety of a novel skin cleansing formulation versus chlorhexidine gluconate

BACKGROUND

This study evaluated whether a multi-ingredient surfactant colloidal silver technology was noninferior to a 4% chlorhexidine gluconate (CHG) antiseptic on immediate and persistent antimicrobial activity.

METHODS

The inguinal regions of 81 healthy adults were demarcated into 4 quadrants, and 3 were used for testing each product at baseline, 10 minutes, and 6 hours postapplication. The log of the number of colony forming units was obtained using a cylinder sampling technique. The 95% confidence interval of the test product to the control product with a margin of 0.65 was established as the upper limit of noninferiority.

RESULTS

A total of 81 individuals were enrolled. The colloidal silver product was found to be noninferior to 4% CHG at both 10 minutes and 6 hours postapplication.

CONCLUSIONS

The colloidal silver-based product was noninferior to the 4% CHG product at 10 minutes and 6 hours postapplication.

Distribution of biocide resistant genes and biocides susceptibility in multidrug-resistant Klebsiella pneumoniae, Pseudomonas aeruginosa and Acinetobacter baumannii - A first report from the Kingdom of Saudi Arabia

PURPOSES

The aim of this study was to determine the frequency of biocide resistant genes, qacA, qacE and cepA in multidrug resistant (MDR) bacteria: Klebsiella pneumoniae, Pseudomonas aeruginosa and Acinetobacter baumannii and to correlate the presence or absence of resistant genes with biocides susceptibility.

MATERIALS AND METHODS

The study included 44 MDR K. pneumoniae, P. aeruginosa and A. baumannii microorganisms. The bacteria were screened for the presence of biocide resistant genes by the polymerase chain reaction (PCR) method. The test organisms were isolated from various clinical specimens in the Qassim region, Saudi Arabia. The in vitro susceptibility tests of the three biocides (benzalkonium chloride, cetrimide and chlorhexidine gluconate) were studied against the test isolates by broth microdilution method following Clinical and Laboratory Standards Institute guidelines.

RESULTS

With the distribution of biocide resistant genes in K. pneumoniae, all 9 isolates (100%) possessed cepA; 4 (44.4%) and 1 (11.1%) isolate contained qacA and qacE genes respectively. Among 24 isolates of A. baumannii tested, cepA, qacA and qacE genes were found in 54.2%, 16.7% and 33.3% of isolates respectively. Among 11 P. aeruginosa isolates, 63.6% contained cepA gene, 18.2% contained qacE genes, and none of the isolates harboured qacA gene. There was no significant correlation between presence or absence of biocide resistant genes and high MIC values of the test isolates (p≥0.2).

CONCLUSION

Our observations imply that there was no significant correlation between presence or absence of biocide resistant genes and MICs observed in MDR K. pneumoniae, P. aeruginosa and A. baumannii. Further studies are required to find to confirm the trend of reduced susceptibility to biocides of problematic nosocomial pathogens.

Phenotypic chlorhexidine and triclosan susceptibility in clinical Staphylococcus aureus isolates in Australia

Antiseptics such as chlorhexidine gluconate and triclosan are widely used in healthcare settings for both skin antisepsis and decolonisation of Staphylococcus aureus. We determined the minimum inhibitory concentration (MIC) of 198 methicillin susceptible and resistant Staphylococcus aureus clinical isolates to both chlorhexidine and triclosan using an agar dilution method. Of these, 10% (19/198) showed a raised MIC to chlorhexidine and 3% (6/198) showed an elevated MIC to triclosan. The multilocus sequence type (MLST) of each isolate was predicted using a binary method, and although ST93-MRSA-IV was the most common, ST22-MRSA-IV was shown to have statistically higher chlorhexidine MIC values compared with non ST22-MRSA-IV isolates (z = -8.7, p < 0.01). Additionally, isolates from patients known to have failed decolonisation were included and did not demonstrate elevated MIC to the decolonisation antiseptic. Monitoring for non-susceptibility of clinical isolates to biocides is important to determine trends, and may have clinical implications in terms of sub-lethal concentration in residues and concomitant antibiotic resistance.

Comparison of Topical Chlorhexidine and Mupirocin for the Prevention of Exit-Site Infection in Incident Peritoneal Dialysis Patients

♦ OBJECTIVE: Prevention of exit-site infection (ESI) is of paramount importance to peritoneal dialysis (PD) patients. The aim of this study was to evaluate the effectiveness of chlorhexidine in the prevention of ESI in incident PD patients compared with mupirocin. ♦ METHODS: This retrospective, pre-test/post-test observational study included all incident PD patients at Singapore General Hospital from 2012 to 2015. Patients received daily topical exit-site application of either mupirocin (2012 - 2013) or chlorhexidine (2014 - 2015) in addition to routine exit-site cleaning with 10% povidone-iodine. The primary outcome was ESI rate during the 2 time periods. Secondary outcomes were peritonitis rate, times to first ESI and peritonitis, hospitalization rate, and infection-related catheter removal. Event rates were analyzed using Poisson regression, and infection-free survival was estimated using Kaplan-Meier and Cox regression survival analyses. ♦ RESULTS: The study included 162 patients in the mupirocin period (follow-up 141.5 patient-years) and 175 patients in the chlorhexidine period (follow-up 136.9 patient-years). Compared with mupirocin-treated patients, chlorhexidine-treated patients experienced more frequent ESIs (0.22 vs 0.12 episodes/patient-year, p = 0.048), although this was no longer statistically significant following multivariable analysis (incidence rate ratio [IRR] 1.78, 95% confidence interval [CI] 0.98 - 3.26, p = 0.06). No significant differences were observed between the 2 groups with respect to time to first ESI (p = 0.10), peritonitis rate (p = 0.95), time to first peritonitis (p = 0.60), hospitalization rate (p = 0.21) or catheter removal rate (0.03 vs 0.04/patient-year, p = 0.56). ♦ CONCLUSIONS: Topical exit-site application of chlorhexidine cream was associated with a borderline significant, higher rate of ESI in incident PD patients compared with mupirocin cream.

Reduction in chlorhexidine efficacy against multi-drug-resistant Acinetobacter baumannii international clone II

BACKGROUND

Nosocomial infections caused by Acinetobacter baumannii international clone II (IC II) can cause severe clinical outcomes.

AIM

Differential evaluation of bactericidal efficacy of chlorhexidine gluconate (CHX) and benzethonium chloride (BZT) disinfectants against IC II and non-IC II isolates.

METHODS

Minimum inhibitory concentrations (MICs) of CHX and BZT were determined for 137 A. baumannii IC II, 99 non-IC II and 69 non-baumannii isolates, further classified according to MIC values into disinfectant-reduced susceptible (DRS) and disinfectant-susceptible (DS) groups. Time-kill curves and minimum bactericidal concentrations (MBCs) were evaluated for representative isolates in each group.

RESULTS

CHX and BZT MIC₉₀s for IC II isolates were 100 and 175mg/L, respectively, but those for non-IC II and non-baumannii isolates were <100mg/L. Nevertheless, time-kill curves indicated that CHX and BZT reduced live bacterial cell number by 5 log₁₀ for IC II and non-IC II isolates within 30s when used at 1000mg/L, comparable to practical use concentrations. CHX MBC at 30s was 1000mg/L for IC II and non-IC II isolates, and was not influenced by addition of 3% bovine serum albumin (BSA); BZT MBC at 30s was 100mg/L without BSA and increased up to 500mg/L upon addition of BSA. No significant differences in BSA were found between DRS and DS isolates.

CONCLUSION

CHX and BZT were effective against Acinetobacter spp. including IC II at a concentration of 1000mg/L and exposure for at least 30s, but their concentrations should be considered carefully to ensure sufficient effects in both clinical and healthcare settings.

Effect of Hand Antisepsis Agent Selection and Population Characteristics on Surgical Site Infection Pathogens

BACKGROUND

Selection of a pre-operative hand antisepsis agent has not been studied in relation to surgical site infection (SSI) culture data. In our hospital, we introduced an alcohol-based hand rub (ABR) in 2012 as an alternative to traditional aqueous surgical scrubs (TSS). It was the goal of this study to review any effect of this implementation on SSI pathogen characteristics. In addition, we sought to compare our SSI culture data with available National Healthcare Safety Network (NHSN) data. We hypothesized that SSI pathogens and resistant isolates are affected by surgical hand antisepsis technique.

METHODS

Data collected prospectively between 2007 and 2014 were retrospectively analyzed for two time periods at the Veterans Affairs Boston Healthcare System (VABHS): Before ABR implementation (TSS group) and after (ABR group). Pathogen distribution and pathogenic isolate resistance profiles were compared for TSS and ABR, and similar comparisons, along with procedure-associated SSI comparisons, were made between VABHS and NHSN. All VABHS data were interpreted and categorized according to NHSN definitions.

RESULTS

Compared with TSS (n = 4,051), ABR (n = 2,293) had a greater rate of Staphylococcus aureus (42.6% vs. 38.0%), Escherichia coli (12.8% vs. 9.9%), Pseudomonas aeruginosa (8.5% vs. 2.8%), and Enterobacter spp. (10.6% vs. 2.8%), and a lower rate of Klebsiella pneumoniae/K. oxytoca (4.3% vs. 8.5%) cultured from superficial and deep SSIs (p < 0.05). Of the S. aureus isolates, 35.0% and 44.4% were resistant to oxacillin/methicillin (MRSA) in ABR and TSS, respectively (p = 0.06). Looking at all SSIs, coagulase-negative staphylococci and K. pneumoniae/K. oxytoca at VABHS (4.0% and 10.4%, respectively) accounted for the biggest difference from NHSN (11.7% and 4.0%, respectively). Aside from MRSA, where there was no difference between VABHS and NHSN (42.9% vs. 43.7%, respectively; p = 0.87), statistically significant (p < 0.05) differences were observed among multi-drug-resistant K. pneumoniae/K. oxytoca (0% vs. 6.8%, respectively) and Escherichia coli (10.0% vs. 1.6%, respectively), as well as among extended-spectrum cephalosporin-resistant K. pneumoniae/K. oxytoca (4.8% vs. 13.2%, respectively) and Enterobacter (58.3% vs. 27.7%, respectively). VABHS had a greater proportion of SSIs in abdominal and vascular cases than did NHSN (48.6% vs. 22.5% and 13.2% vs. 1.5%, respectively). Overall, these differences were significant (p < 0.05).

CONCLUSIONS

The TSS and ABR groups differed in the distribution of pathogens recovered. Those differences, along with SSI pathogen distribution, pathogenic isolate resistance profiles, and procedure-associated SSIs between VABHS and NHSN, warrant further investigation.

Dental plaque bacteria with reduced susceptibility to chlorhexidine are multidrug resistant

BACKGROUND

Chlorhexidine (CHX) is used in oral care products to help control dental plaque. In this study dental plaque bacteria were grown on media containing 2 μg/ml chlorhexidine gluconate to screen for bacteria with reduced CHX susceptibility. The isolates were characterized by 16S rRNA gene sequencing and antibiotic resistance profiles were determined using the disc diffusion method.

RESULTS

The isolates were variably resistant to multiple drugs including ampicillin, kanamycin, gentamicin and tetracycline. Two species, Chryseobacterium culicis and Chryseobacterium indologenes were able to grow planktonically and form biofilms in the presence of 32 μg/ml CHX. In the CHX and multidrug resistant C. indologenes we demonstrated a 19-fold up-regulation of expression of the HlyD-like periplasmic adaptor protein of a tripartite efflux pump upon exposure to 16 μg/ml CHX suggesting that multidrug resistance may be mediated by this system. Exposure of biofilms of these resistant species to undiluted commercial CHX mouthwash for intervals from 5 to 60 s indicated that the mouthwash was unlikely to eliminate them from dental plaque in vivo.

CONCLUSIONS

The study highlights the requirement for increased vigilance of the presence of multidrug resistant bacteria in dental plaque and raises a potential risk of long-term use of oral care products containing antimicrobial agents for the control of dental plaque.

The role of the healthcare environment in the spread of multidrug-resistant organisms: update on current best practices for containment

The role of the environment in harboring and transmitting multidrug-resistant organisms has become clearer due to a series of publications linking environmental contamination with increased risk of hospital-associated infections. The incidence of antimicrobial resistance is also increasing, leading to higher morbidity and mortality associated with hospital-associated infections. The purpose of this review is to evaluate the evidence supporting the existing methods of environmental control of organisms: environmental disinfection, contact precautions, and hand hygiene. These methods have been routinely employed, but transmission of multidrug-resistant organisms continues to occur in healthcare facilities throughout the country and worldwide. Several new technologies have entered the healthcare market that have the potential to close this gap and enhance the containment of multidrug-resistant organisms: improved chemical disinfection, environmental monitoring, molecular epidemiology, self-cleaning surfaces, and automated disinfection systems. A review of the existing literature regarding these interventions is provided. Overall, the role of the environment is still underestimated and new techniques may be required to mitigate the role that environmental transmission plays in acquisition of multidrug-resistant organisms.

Photodynamic antimicrobial polymers for infection control

Hospital-acquired infections pose both a major risk to patient wellbeing and an economic burden on global healthcare systems, with the problem compounded by the emergence of multidrug resistant and biocide tolerant bacterial pathogens. Many inanimate surfaces can act as a reservoir for infection, and adequate disinfection is difficult to achieve and requires direct intervention. In this study we demonstrate the preparation and performance of materials with inherent photodynamic, surface-active, persistent antimicrobial properties through the incorporation of photosensitizers into high density poly(ethylene) (HDPE) using hot-melt extrusion, which require no external intervention except a source of visible light. Our aim is to prevent bacterial adherence to these surfaces and eliminate them as reservoirs of nosocomial pathogens, thus presenting a valuable advance in infection control. A two-layer system with one layer comprising photosensitizer-incorporated HDPE, and one layer comprising HDPE alone is also described to demonstrate the versatility of our approach. The photosensitizer-incorporated materials are capable of reducing the adherence of viable bacteria by up to 3.62 Log colony forming units (CFU) per square centimeter of material surface for methicillin resistant Staphylococcus aureus (MRSA), and by up to 1.51 Log CFU/cm² for Escherichia coli. Potential applications for the technology are in antimicrobial coatings for, or materials comprising objects, such as tubing, collection bags, handrails, finger-plates on hospital doors, or medical equipment found in the healthcare setting.

Comparative analysis of Salmonella susceptibility and tolerance to the biocide chlorhexidine identifies a complex cellular defense network

Chlorhexidine is one of the most widely used biocides in health and agricultural settings as well as in the modern food industry. It is a cationic biocide of the biguanide class. Details of its mechanism of action are largely unknown. The frequent use of chlorhexidine has been questioned recently, amidst concerns that an overuse of this compound may select for bacteria displaying an altered susceptibility to antimicrobials, including clinically important anti-bacterial agents. We generated a Salmonella enterica serovar Typhimurium isolate (ST24(CHX)) that exhibited a high-level tolerant phenotype to chlorhexidine, following several rounds of in vitro selection, using sub-lethal concentrations of the biocide. This mutant showed altered suceptibility to a panel of clinically important antimicrobial compounds. Here we describe a genomic, transcriptomic, proteomic, and phenotypic analysis of the chlorhexidine tolerant S. Typhimurium compared with its isogenic sensitive progenitor. Results from this study describe a chlorhexidine defense network that functions in both the reference chlorhexidine sensitive isolate and the tolerant mutant. The defense network involved multiple cell targets including those associated with the synthesis and modification of the cell wall, the SOS response, virulence, and a shift in cellular metabolism toward anoxic pathways, some of which were regulated by CreB and Fur. In addition, results indicated that chlorhexidine tolerance was associated with more extensive modifications of the same cellular processes involved in this proposed network, as well as a divergent defense response involving the up-regulation of additional targets such as the flagellar apparatus and an altered cellular phosphate metabolism. These data show that sub-lethal concentrations of chlorhexidine induce distinct changes in exposed Salmonella, and our findings provide insights into the mechanisms of action and tolerance to this biocidal agent.

Effect of oral hygiene with 0.12% chlorhexidine gluconate on the incidence of nosocomial pneumonia in children undergoing cardiac surgery

OBJECTIVE

To evaluate the effect of oral hygiene with 0.12% chlorhexidine gluconate on the incidence of nosocomial pneumonia and ventilator-associated pneumonia (VAP) in children undergoing cardiac surgery.

DESIGN

Prospective, randomized, double-blind, placebo-controlled trial.

SETTING

Pediatric intensive care unit (PICU) at a tertiary care hospital.

PATIENTS

One hundred sixty children undergoing surgery for congenital heart disease, randomized into 2 groups: chlorhexidine (n = 87) and control (n = 73).

INTERVENTIONS

Oral hygiene with 0.12% chlorhexidine gluconate or placebo preoperatively and twice a day postoperatively until PICU discharge or death.

RESULTS

Patients in experimental and control groups had similar ages (median, 12.2 vs 10.8 months; P = .72) and risk adjustment for congenital heart surgery 1 score distribution (66% in category 1 or 2 in both groups; P = .17). The incidence of nosocomial pneumonia was 29.8% versus 24.6% (P = .46) and the incidence of VAP was 18.3% versus 15% (P = .57) in the chlorhexidine and the control group, respectively. There was no difference in intubation time (P = .34), need for reintubation (P = .37), time interval between hospitalization and nosocomial pneumonia diagnosis (P = .63), time interval between surgery and nosocomial pneumonia diagnosis (P = .10), and time on antibiotics (P = .77) and vasoactive drugs (P = .16) between groups. Median length of PICU stay (3 vs 4 days; P = .53), median length of hospital stay (12 vs 11 days; P = .67), and 28-day mortality (5.7% vs 6.8%; P = .77) were also similar in the chlorhexidine and the control group.

CONCLUSIONS

Oral hygiene with 0.12% chlorhexidine gluconate did not reduce the incidence of nosocomial pneumonia and VAP in children undergoing cardiac surgery.

TRIAL REGISTRATION

ClinicalTrials.gov identifier: NCT00829842 .

Comparison of a chlorhexidine and a benzoyl peroxide shampoo as sole treatment in canine superficial pyoderma

The clinical and antibacterial efficacy of two shampoos used as a sole antibacterial treatment in dogs with superficial pyoderma were investigated and compared. In a randomised, partially blinded study, a 3 per cent chlorhexidine gluconate shampoo (Chlorhex 3; Leo Animal Health) was compared against a 2.5 per cent benzoyl peroxide shampoo (Paxcutol; Virbac) in 22 dogs with superficial pyoderma. Dogs were washed two to three times weekly with a 10-minute contact time over 21 days. Clinical scores and bacterial counts were assessed on days 1, 8 and 22 and compared within and between treatment groups; overall response was assessed at the end of the study. Twenty dogs completed the study; 15 (68.2 per cent) showed an overall clinical improvement and the clinical signs resolved in three chlorhexidine-treated dogs. In the chlorhexidine-treated group, scores for papules/pustules (P<0.001), investigator-assessed pruritus (P=0.003), total bacterial counts (P=0.003) and counts for coagulase-positive staphylococci (P=0.003) were reduced after three weeks. Scores and bacterial counts did not vary significantly in the benzoyl peroxide-treated group.

Skin bacteria after chlorhexidine exposure-is there a difference in response to human beta-Defensin-3?

We investigated whether exposure to sub-lethal concentrations of chlorhexidine digluconate (CHG) changed the response of five Staphylococcus spp. to human beta-Defensin-3 (hBD-3). The change in response for each strain was determined in vitro with time-kill experiments in suspension by comparing the mean log(10) reduction caused by hBD-3 at 1.5 and 3 h in exposed and non-exposed bacteria. The identity of staphylococcal species was verified by DNA sequence homology in the gyrA genes in comparison with reference strains. Baseline sub-lethal concentrations allowing visible bacterial growth were between 0.0625 and 0.25 microg/ml. Sub-lethal CHG concentrations increased within 3 days in two isolates. For S. capitis 19/2, CHG-exposed cells were less susceptible to 0.5 microg/ml hBD-3 (log(10) reduction 0.78 versus 2.06 at 1.5 h; p < 0.001; t-test). For S. aureus, however, CHG-exposed cells were more susceptible to 1 microg/ml hBD-3. The observed changes between CHG-exposed and non-exposed cells did not indicate a general trend in response to hBD-3. Overall, we found no consistent evidence that 3 days of exposure to CHG changed the response of five Staphylococcus spp. to hBD-3. The use of CHG for skin antisepsis is, based on our data, unlikely to change the natural defence activity of hBD-3.

A randomized trial of chlorhexidine gluconate on oral bacterial pathogens in mechanically ventilated patients

INTRODUCTION

Dental plaque biofilms are colonized by respiratory pathogens in mechanically-ventilated intensive care unit patients. Thus, improvements in oral hygiene in these patients may prevent ventilator-associated pneumonia. The goal of this study was to determine the minimum frequency (once or twice a day) for 0.12% chlorhexidine gluconate application necessary to reduce oral colonization by pathogens in 175 intubated patients in a trauma intensive care unit.

METHODS

A randomized, double-blind, placebo-controlled clinical trial tested oral topical 0.12% chlorhexidine gluconate or placebo (vehicle alone), applied once or twice a day by staff nurses. Quantitation of colonization of the oral cavity by respiratory pathogens (teeth/denture/buccal mucosa) was measured.

RESULTS

Subjects were recruited from 1 March, 2004 until 30 November, 2007. While 175 subjects were randomized, microbiologic baseline data was available for 146 subjects, with 115 subjects having full outcome assessment after at least 48 hours. Chlorhexidine reduced the number of Staphylococcus aureus, but not the total number of enterics, Pseudomonas or Acinetobacter in the dental plaque of test subjects. A non-significant reduction in pneumonia rate was noted in groups treated with chlorhexidine compared with the placebo group (OR = 0.54, 95% CI: 0.23 to 1.25, P = 0.15). No evidence for resistance to chlorhexidine was noted, and no adverse events were observed. No differences were noted in microbiologic or clinical outcomes between treatment arms.

CONCLUSIONS

While decontamination of the oral cavity with chlorhexidine did not reduce the total number of potential respiratory pathogens, it did reduce the number of S. aureus in dental plaque of trauma intensive care patients.

Epidemiology and susceptibilities of methicillin-resistant Staphylococcus aureus in Taiwan: emphasis on chlorhexidine susceptibility

Chlorhexidine is an antiseptic agent used for hand hygiene worldwide. To evaluate the susceptibility of methicillin-resistant Staphylococcus aureus (MRSA) to chlorhexidine, this study determined MICs of chlorhexidine and another 12 antimicrobial agents, carriage of the Panton-Valentine leukocidin, qacA/B, and smr genes, genetic relatedness by multilocus sequence typing (MLST), and staphylococcal cassette chromosome mec element type for 206 MRSA clinical isolates from the Taiwan Surveillance of Antimicrobial Resistance program III and IV (years 2002 and 2004) from 26 hospitals. Using MLST, we respectively identified 102 (49.5%), 68 (33.0%), 13 (6.3%), 5 (2.4%), 5 (2.4%), and 13 (6.3%) isolates as ST239, ST59, ST5, ST241, ST573, and other types. The MIC(50) and MIC(90) of chlorhexidine for all 206 isolates were 2 and 8 microg/mL, respectively. Seventy-three (35.4%) isolates carried qacA/B gene, but none carried smr. For the 72 (35.0%) MRSA isolates with chlorhexidine MIC > or =4 microg/mL, 53 were ST239 (49 of them carried qacA gene), 12 were ST5 (all carried qacB gene), 5 were ST241 (4 carried qacA gene), 1 was ST338 (and carried qacA gene), and 1 was ST573 (and carried qacA gene). Compared with other sequence-type MRSA isolates, ST239 MRSA isolates were the most resistant to both chlorhexidine and other antimicrobial agents. Methicillin-resistant S. aureus strains with disinfectant resistance qacA/B genes are common in Taiwan. High frequency of qacA/B genes among specific sequence types (ST239, ST5, and ST241) resulted in low susceptibility to chlorhexidine. Periodic surveillance of antiseptic susceptibility among MRSA isolates is important for the control of nosocomial hospital-acquired infections.

A three-year surveillance of nosocomial infections by methicillin-resistant Staphylococcus haemolyticus in newborns reveals the disinfectant as a possible reservoir

OBJECTIVE

Study of the clonality of methicillin-resistant Staphylococcus haemolyticus responsible of epidemic infections in a neonatal intensive care unit.

PATIENTS AND METHODS

Methicillin-resistant Staphylococcus haemolyticus isolates were collected during the period from March 2004 to November 2006, from newborns, the clean hands of nurses and from disinfectant bottles used in the unit. Molecular typing by pulsed-field gel electrophoresis (PFGE) was achieved for all isolates.

RESULTS

Forty-six isolates of S. haemolyticus resistant to methicillin were collected from 42 newborns, the hand of two nurses and from two disinfectant bottles used in the unit. PFGE analysis revealed five types (A, B, C, D and E) among newborns isolates. Types A and B were predominant. Nurses' isolates revealed PFGE types similar to types A and B. Disinfectant isolates were of type B. qacA/B PCR analysis revealed that the majority of type B isolates contain the disinfectant resistance gene qacA/B. No isolate of type A possessed this gene.

CONCLUSION

These results suggest that MRSH neonatal infections are caused by a limited number of clones. Clone B was able to survive in disinfectant bottles and to conserve its ability to infect newborns. We therefore conclude that the disinfectant can serve as a reservoir for MRSH and point out the need to control all disinfectants used in a neonatal intensive care unit.

Resistance to disinfectants in epidemiologically defined clinical isolates of Acinetobacter baumannii

Decreased susceptibility to biocides may contribute to epidemic spread of Acinetobacter baumannii in the hospital. This study was conducted to evaluate the susceptibility of different clinical A. baumannii strains to disinfectants. Twenty A. baumannii strains were examined, ten of which were outbreak-related and ten that were sporadic. Clinical isolates were selected on the basis of demonstrating a unique pulsed-field gel electrophoresis pattern. The in-vitro activities of propanol, combination of 1-propanol, 2-propanol and mecetronium ethylsulphate, polyvinylpyrrolidone (PVP)-iodine, triclosan and chlorhexidine were determined using a broth macrodilution method. Exposure times to the disinfectant ranged from 15 s to 2 min and concentrations ranged from undiluted to a 1:4000 dilution in order to investigate the impact of inadvertent dilution that might occur in clinical practice. Five American Type Culture Collection (ATCC) type strains (A. baumannii, Escherichia coli, Pseudomonas aeruginosa, Enterococcus faecalis and Staphylococcus aureus) were used as controls. All disinfectants inhibited growth of all isolates at concentrations and contact times recommended by the respective manufacturer. With most of the disinfectants tested, a relevant number of viable bacteria remained if contact times < 30s or diluted agents were used. No significant differences in susceptibility between outbreak-related and sporadic strains were detected, but larger studies would be required to confirm this. Resistance to currently used disinfectants is probably not a major factor in the epidemic spread of A. baumannii. However, even minor deviations from the recommended procedures leading to decreased concentrations or exposure times may play a role in nosocomial cross-transmission.

Does microbial resistance to biocides create a hazard to food hygiene?

Numerous reports are available on microbial resistance to antibiotics as well as to biocides. Instances of cross-resistance between these substance groups have been reported. Resistance, which is a genetically determined phenomenon, has to be distinguished from phenotypic adaptation processes, which are not hereditary. Adaptation can be avoided by rigorous cleaning and disinfection, avoiding concentrations of disinfectants below the microbicidal concentration. Resistance phenomena have to be divided into intrinsic and acquired resistance. Intrinsic resistance is the naturally greater resistance of certain microbial species compared to others. The term acquired resistance is used if certain strains of a microbial species differ significantly in their susceptibility to biocides compared to the average of this species. An overview of existing reports of resistance to different biocidal substances is given. In most of these reports, resistance is defined as an elevated minimum inhibitory concentration. The relevance of these data for disinfection processes, where microbicidal concentrations are applied, is discussed. Rotational use of different types of disinfectants, to avoid development of resistance, has been discussed controversially. Because of the unspecific mechanism of action of biocides, and the lack of scientific evidence for its need, rotational use of disinfectants is not recommended. In conclusion the risk of hazards in food production and processing caused by resistance to biocides is regarded as low.

Effect of gingival and dental plaque antiseptic decontamination on nosocomial infections acquired in the intensive care unit: a double-blind placebo-controlled multicenter study

OBJECTIVE

To document the effect of gingival and dental plaque antiseptic decontamination on the rate of nosocomial bacteremias and respiratory infections acquired in the intensive care unit (ICU).

DESIGN

Prospective, multicenter, double-blind, placebo-controlled efficacy study.

SETTING

Six ICUs: three in university hospitals and three in general hospitals.

PATIENTS

A total of 228 nonedentulous patients requiring endotracheal intubation and mechanical ventilation, with an anticipated length of stay > or =5 days.

INTERVENTIONS

Antiseptic decontamination of gingival and dental plaque with a 0.2% chlorhexidine gel or a placebo gel, three times a day, during the entire ICU stay.

MEASUREMENTS AND MAIN RESULTS

Demographic and clinical characteristics, organ function data (Logistic Organ Dysfunction score), severity of condition (Simplified Acute Physiologic Score), and dental plaque status were assessed at baseline and until 28 days. Bacteriologic sampling of dental plaque and saliva was done every 5 days, and blood, tracheal aspirate, and bronchoalveolar lavage cultures were performed when appropriate. The primary efficacy end point was the incidence of bacteremia, bronchitis, and ventilator-associated pneumonia, expressed as a percentage and per 1000 ICU days. All baseline characteristics were similar between the treated and the placebo groups. The incidence of nosocomial infections was 17.5% (13.2 per 1000 ICU days) in the placebo group and 18.4% (13.3 per 1000 ICU days) in the plaque antiseptic decontamination group (not significant). No difference was observed in the incidence of ventilator-associated pneumonia per ventilator or intubation days, mortality, length of stay, and care loads (secondary end points). On day 10, the number of positive dental plaque cultures was significantly lower in the treated group (29% vs. 66%; p < .05). Highly resistant Pseudomonas, Acinetobacter, and Enterobacter species identified in late-onset ventilator-associated pneumonia and previously cultured from dental plaque were not eradicated by the antiseptic decontamination. No side effect was reported.

CONCLUSIONS

Gingival and dental plaque antiseptic decontamination significantly decreased the oropharyngeal colonization by aerobic pathogens in ventilated patients. However, its efficacy was insufficient to reduce the incidence of respiratory infections due to multiresistant bacteria.

Reduction of exit-site infections of tunnelled intravascular catheters among neutropenic patients by sustained-release chlorhexidine dressings: results from a prospective randomized controlled trial

Exit-site and tunnel infections of tunnelled central intravascular catheters are a frequent source of morbidity among neutropenic patients and may necessitate catheter removal. They require antimicrobial therapy that increases healthcare costs and is associated with adverse drug reactions. A prospective randomized clinical trial was conducted among adult patients undergoing chemotherapy in a haematology unit. Tunnelled intravascular catheters were randomized to receive the control of a standard dressing regimen as recommended by the British Committee for Standards in Haematology, or to receive the intervention of a sustained-release chlorhexidine dressing. Follow-up data were available in 112 of 114 tunnelled intravascular catheters which were randomized. Exit-site or combined exit-site/tunnel infections occurred in 23 (43%) of 54 catheters in the control group, and five (9%) of 58 catheters in the intervention group [odds ratio (OR) for intervention group compared with control group =0.13, 95% confidence intervals (CI) 0.04-0.37, P<0.001]. More tunnelled intravascular catheters were prematurely removed from the control group than the intervention group for documented infections [20/54 (37%) vs 6/58 (10%), OR=0.20, 95%CI 0.53-0.07]. However, there was no difference in the numbers of tunnelled intravascular catheters removed for all proven and suspected intravascular catheter-related infections [21/54 (39%) vs 19/58 (33%)], or in the time to removal of catheters for any reason other than death or end of treatment for underlying disease. Thus chlorhexidine dressings reduced the incidence of exit-site/tunnel infections of indwelling tunnelled intravascular catheters without prolonging catheter survival in neutropenic patients, and could be considered as part of the routine management of indwelling tunnelled intravascular catheters among neutropenic patients.

Epidemiologic background of hand hygiene and evaluation of the most important agents for scrubs and rubs

The etiology of nosocomial infections, the frequency of contaminated hands with the different nosocomial pathogens, and the role of health care workers' hands during outbreaks suggest that a hand hygiene preparation should at least have activity against bacteria, yeasts, and coated viruses. The importance of efficacy in choosing the right hand hygiene product is reflected in the new Centers for Disease Control and Prevention guideline on hand hygiene (J. M. Boyce and D. Pittet, Morb. Mortal. Wkly. Rep. 51:1-45, 2002). The best antimicrobial efficacy can be achieved with ethanol (60 to 85%), isopropanol (60 to 80%), and n-propanol (60 to 80%). The activity is broad and immediate. Ethanol at high concentrations (e.g., 95%) is the most effective treatment against naked viruses, whereas n-propanol seems to be more effective against the resident bacterial flora. The combination of alcohols may have a synergistic effect. The antimicrobial efficacy of chlorhexidine (2 to 4%) and triclosan (1 to 2%) is both lower and slower. Additionally, both agents have a risk of bacterial resistance, which is higher for chlorhexidine than triclosan. Their activity is often supported by the mechanical removal of pathogens during hand washing. Taking the antimicrobial efficacy and the mechanical removal together, they are still less effective than the alcohols. Plain soap and water has the lowest efficacy of all. In the new Centers for Disease Control and Prevention guideline, promotion of alcohol-based hand rubs containing various emollients instead of irritating soaps and detergents is one strategy to reduce skin damage, dryness, and irritation. Irritant contact dermatitis is highest with preparations containing 4% chlorhexidine gluconate, less frequent with nonantimicrobial soaps and preparations containing lower concentrations of chlorhexidine gluconate, and lowest with well-formulated alcohol-based hand rubs containing emollients and other skin conditioners. Too few published data from comparative trials are available to reliably rank triclosan. Personnel should be reminded that it is neither necessary nor recommended to routinely wash hands after each application of an alcohol-based hand rub. Long-lasting improvement of compliance with hand hygiene protocols can be successful if an effective and accessible alcohol-based hand rub with a proven dermal tolerance and an excellent user acceptability is supplied, accompanied by education of health care workers and promotion of the use of the product.

Effects of quaternary-ammonium-based formulations on bacterial community dynamics and antimicrobial susceptibility

Quaternary ammonium compounds (QACs) are widely used as adjuncts to hygiene in domestic cleaning products. Current concern that the increased use of such biocides in consumer products might contribute to the emergence of antibiotic resistance has led us to examine the effects of a QAC-containing domestic cleaning fluid on the population dynamics and antimicrobial susceptibility of domestic sink drain biofilm communities. QAC susceptibilities of numerically dominant, culturable drain bacteria (15 genera, 17 species) were determined in vitro before and after repeated QAC exposure (14 passages). A fully characterized drain microcosm was then exposed to short-term (12 days) and long-term (3 months) dosing with a QAC-containing domestic detergent (QD). QAC exposure of isolated cultures caused both increases (three species) and circa twofold decreases (six species) in QAC susceptibility. The susceptibility of Ralstonia sp. was considerably decreased following 14 consecutive QAC passages. Control drain microcosm biofilms maintained dynamic stability, as evidenced by culture and denaturing gradient gel electrophoresis (DGGE) analysis. Bacterial population densities were largely unaffected during short-term exposure to use levels of QD, although 50% QD caused circa 10-fold viability reductions. DGGE analysis supported these observations; identified the major microcosm genera as Pseudomonas, Pseudoalteromonas, Erwinia, and Enterobacter, and showed that aeromonads increased in abundance under 10 to 50% QD. Long-term exposure of the microcosms to QD did not significantly alter the pattern of antimicrobial susceptibility. These data demonstrate the recalcitrance of domestic drain biofilms toward QAC and that although repeated QAC exposure of drain isolates in pure culture results in susceptibility change in some test bacteria, such changes do not necessarily occur within complex communities.