Dose considerations for alcohol-based hand rubs.

BACKGROUND: Manufacturers' recommended dosages for alcohol-based hand rubs are typically determined by measuring product efficacy using a model protocol such as EN 1500; however, anecdotal reports and informal observation suggests that in many cases users self-titrate to much lower doses in real-world application. AIM: To examine the interdependence of alcohol-based hand-rub volume on in-vivo efficacy using the EN 1500 standard test method, on drying time on users' hands, and on their perceptions of acceptability. METHODS: Three formulations were studied using EN 1500 and a modification of this method. The modification used volumes ranging from 0.5 to 3.0 mL and 30 s application. Drying times were recorded and user acceptability was established using a three-point scale (too long, OK, or too short). Dying times were analysed in relation to hand surface area. FINDINGS: The drying time for all three products increased as a function of volume. The drying time displayed a positive association with volume and a negative association with hand surface area. The optimum volume for user acceptability was between 1.5 and 2 mL, yielding a drying time of between 20 and 30 s. CONCLUSION: Whereas EN 1500 is appropriate for establishing the efficacy of a hygienic hand-rub formulation compared to a benchmark, it does not reflect actual in-use conditions or the likely clinical effectiveness of the product. In particular, it fails to address the need to optimize the volume of application and user acceptability of the product.

Development of a sporicidal test method for Clostridium difficile.

BACKGROUND: Disinfectants with claimed activity against Clostridium difficile must be evaluated to ensure efficacy against the spores that comprise an environmental source of patient infection. Unfortunately there is, at present, no generally accepted method for evaluating these disinfectants. In the absence of such a method, laboratories have to adapt protocols that were not designed for products used in medical environments and consequently may use inappropriate test organisms, exposure times, and pass criteria. AIM: To develop and evaluate a method for testing the activity of disinfectants against C. difficile spores using exposure times and pass criteria which are relevant to clinical application. METHODS: A Joint Working Party of the Healthcare Infection Society (HIS) and the Advisory Committee on Antimicrobial Resistance and Healthcare Associated Infections (ARHAI) of the Department of Health in England was assembled. The Working Party adapted a previously described enzyme-based method for spore purification (the Clospore method) using an exposure time of 5 min and a 5 log10 kill as a pass criterion. FINDINGS: Evaluation of the method by three laboratories demonstrated that the method is simple to follow and that the results are repeatable and reproducible. CONCLUSION: The method described by the Working Party produces a clean suspension with a high titre of spores. It is recommended that, for a disinfectant used in the environment, the product should demonstrate a 5 log10 reduction in 5 min under clean or dirty conditions to fulfil the requirements of the test.

Genome sequencing and characterization of an extensively drug-resistant sequence type 111 serotype O12 hospital outbreak strain of Pseudomonas aeruginosa.

A series of extensively drug-resistant isolates of Pseudomonas aeruginosa from two outbreaks in UK hospitals were characterized by whole genome sequencing (WGS). Although these isolates were resistant to antibiotics other than colistin, we confirmed that they are still sensitive to disinfectants. The sequencing confirmed that isolates in the larger outbreak were serotype O12, and also revealed that they belonged to sequence type ST111, which is a major epidemic strain of P. aeruginosa throughout Europe. As this is the first reported sequence of an ST111 strain, the genome was examined in depth, focusing particularly on antibiotic resistance and potential virulence genes, and on the reported regions of genome plasticity. High degrees of sequence similarity were discovered between outbreak isolates collected from recently infected patients, isolates from sinks, an isolate from the sewer, and a historical isolate, suggesting that the ST111 strain has been endemic in the hospital for many years. The ability to translate easily from outbreak investigation to detailed genome biology by use of the same data demonstrates the flexibility of WGS application in a clinical setting.

The antibacterial activity and stability of acetic acid.

Acetic acid has been shown to have good antibacterial activity against micro-organisms such as Pseudomonas aeruginosa. This study examined the activity against a range of bacterial pathogens and also assessed any reduction in antibacterial activity due to evaporation or inactivation by organic material in dressings. Acetic acid was active at dilutions as low as 0.166% and the activity was not reduced by evaporation nor by inactivation by cotton swabs. Burn injuries are a major problem in countries with limited resources. Acetic acid is an ideal candidate for use in patients who are treated in those parts of the world.

Sporicides for Clostridium difficile: the devil is in the detail.

A taskforce has now been formed with representatives from the Department of Health's Advisory Committee on Antimicrobial Resistance and Healthcare Associated Infection (ARHAI), the Hospital Infection Society (HIS), the Department of Health (England) and the Health Protection Agency. The aims of the ARHAI/HIS Taskforce on Sporicidal Disinfectants are: to develop an accepted standard for laboratory testing of disinfectants which claim to have activity against C. difficile spores; to develop a network of laboratories with capability to perform in vitro assays of sporicidal activity of disinfectants; and to explore the creation of a national quality assessment scheme for laboratories which perform in vitro assays of sporicidal activity of disinfectants.

Currently available sporicides for use in healthcare, and their limitations.

Clostridium difficile has been recognised for some time as a pathogen which can contaminate the environment and which is associated with secondary spread via this route. Unfortunately many of the disinfectants currently used in healthcare environments are inactive against this organism. For example, alcohol-containing hand rubs do not have sporicidal activity and some quaternary ammonium compounds and detergents may even encourage sporulation. European standards have been developed to allow a standardised methodology for testing the efficacy of disinfectants, but no European standard exists for testing products against C. difficile in medical environments. Most laboratories use an adapted version of EN 13704 which was designed for food, domestic and industrial applications. It is important when testing a disinfectant that it is tested under dirty as well as clean conditions and that the disinfectant is adequately neutralised. Some of the currently available biocides have good activity against C. difficile although relatively long contact times are sometimes required and this may not accurately reflect in-use practises. Other agents have very little activity against C. difficile even after a contact time of 1h. It has to be recognised that testing activity against C. difficile is technically very challenging and therefore there can be large interlaboratory variations in results. When interpreting data, it is essential to scrutinise the methodology used in detail.

A prevalence screen of MRSA nasal colonisation amongst UK doctors in a non-clinical environment.

Screening for methicillin-resistant Staphylococcus aureus (MRSA) carriage in healthcare workers (HCWs) is both contentious and confounded by a lack of knowledge of background prevalence rates. This study examines prevalence of nasal MRSA carriage amongst a spectrum of medical professionals in a non-clinical environment. Medical conference attendees volunteered for screening for nasal MRSA carriage, and anonymised demographic data and attitudes towards screening were recorded. Two hundred sixty volunteers participated. One hundred seventy-three participants (67%) were from the British Medical Association's Annual Representatives Meeting, and 87 participants (33%) were attending the Association of Surgeons in Training conference. Six (2%) participants were positive for MRSA nasal carriage (BMA = 1%, ASIT = 5%; p = 0.099). Participants from a surgical specialty (4.8%) were more likely to be MRSA positive (p = 0.039). All positive samples came from male participants (p = 0.182). However, there was no significant association with gender, seniority or country of employment and MRSA status. Routine screening for MRSA was supported by 63% of participants in HCWs; 36% had previously undergone such screening. MRSA nasal carriage rates within this cross-sectional study are lower than studies reporting carriage rates in HCWs within the clinical environment. Further research is required to examine the relationship between MRSA nasal colonisation status of a HCW and subsequent MRSA infection in patients.

Concentrations in plasma, epithelial lining fluid, alveolar macrophages and bronchial mucosa after a single intravenous dose of 1.6 mg/kg of iclaprim (AR-100) in healthy men.

OBJECTIVES: A validated microbiological assay was used to measure concentrations of iclaprim (AR-100) in plasma, bronchial mucosa (BM), alveolar macrophages (AM) and epithelial lining fluid (ELF) after a single 1.6 mg/kg intravenous 60 min iv infusion of iclaprim. METHODS: Male volunteers were randomly allocated to three nominal sampling time intervals 1-2 h (Group A), 3-4 h (Group B) and 5.5-7.0 h (Group C) after the start of the drug infusion. RESULTS: Mean iclaprim concentrations in plasma, BM, AM and ELF, respectively, were for Group A 0.59 mg/L (SD 0.18), 0.51 mg/kg (SD 0.17), 24.51 mg/L (SD 21.22) and 12.61 mg/L (SD 7.33); Group B 0.24 mg/L (SD 0.05), 0.35 mg/kg (SD 0.17), 7.16 mg/L (SD 1.91) and 6.38 mg/L (SD 5.17); and Group C 0.14 mg/L (SD 0.05), no detectable level in BM, 5.28 mg/L (SD 2.30) and 2.66 mg/L (SD 2.08). CONCLUSIONS: Iclaprim concentrations in ELF and AM exceeded the MIC(90) for penicillin-susceptible Streptococcus pneumoniae (MIC90 0.06 mg/L), penicillin-intermediate S. pneumoniae (MIC90 2 mg/L), penicillin-resistant S. pneumoniae (MIC90 4 mg/L) for 7, 7 and 4 h, respectively, and Chlamydia pneumoniae (MIC90 0.5 mg/L) for 7 h. Mean iclaprim concentrations in ELF exceeded the MIC90 for Haemophilus influenzae (MIC90 4 mg/L) and Moraxella catarrhalis (MIC90 8 mg/L) for up to 4 and 2 h, respectively; in AM the MIC90 was exceeded for up to 7 h. Furthermore, the MIC90 for methicillin-resistant Staphylococcus aureus of 0.12 mg/L was exceeded at all sites for up to 7 h. These data suggest that iclaprim reaches lung concentrations that should be effective in the treatment of community-acquired pneumonia.

An outbreak of Serratia marcescens on the neonatal unit: a tale of two clones.

Serratia spp. are an important cause of hospital-acquired infections and outbreaks in high-risk settings. Twenty-one patients were infected or colonized over a nine-month period during 2001-2002 on a neonatal unit. Twenty-two isolates collected were examined for antibiotic susceptibility, beta-lactamase production and genotype. Random-amplified polymorphic DNA polymerase chain reaction and pulsed-field gel electrophoresis revealed that two clones were present. The first clone caused invasive clinical infection in four babies, and was subsequently replaced by a non-invasive clone that affected 14 babies. Phenotypically, the two strains also differed in their prodigiosin production; the first strain was non-pigmented whereas the second strain displayed pink-red pigmentation. Clinical features suggested a difference in their pathogenicity. No environmental source was found. The outbreak terminated following enhanced compliance with infection control measures and a change of antibiotic policy. Although S. marcescens continued to be isolated occasionally for another five months of follow-up, these were sporadic isolates with distinct molecular typing patterns.

Comparative study of the in vitro activity of a new fluoroquinolone, ABT-492.

OBJECTIVES: The in vitro activity of a new fluoroquinolone, ABT-492, was determined. METHODS: MICs were compared with those of two beta-lactams, telithromycin, ciprofloxacin and four later generation fluoroquinolones. The effects of human serum and of inoculum concentration were also investigated. RESULTS: MIC data indicate that ABT-492 has potent activity against Gram-positive organisms with enhanced anti-staphylococcal activity compared with earlier fluoroquinolones, in addition to activity against beta-haemolytic streptococci, pneumococci including penicillin- and fluoroquinolone-resistant strains and vancomycin-susceptible and -resistant Enterococcus faecalis but not Enterococcus faecium. ABT-492 was the most active agent tested against Haemophilus influenzae, Moraxella catarrhalis, Neisseria meningitidis, fluoroquinolone-susceptible Neisseria gonorrhoeae and anaerobes. Good activity was observed for ABT-492 amongst the Enterobacteriaceae and anaerobes tested, but ciprofloxacin showed superior activity for species of Proteus, Morganella and Providencia, as well as for Pseudomonas spp. In common with the other fluoroquinolones tested, organisms with reduced susceptibility to ciprofloxacin had raised MIC(90)s to ABT-492. The one isolate of H. influenzae tested with reduced fluoroquinolone susceptibility had an ABT-492 MIC close to that of the population lacking a mechanism of quinolone resistance. ABT-492 was more active than ciprofloxacin against Chlamydia spp. An inoculum effect was observed with a number of isolates of Staphylococcus aureus, Streptococcus pneumoniae, E. faecium, Klebsiella spp. and Escherichia coli, in addition to moderately raised MICs in the presence of 70% serum protein. The clinical significance of these findings is yet to be determined. CONCLUSIONS: ABT-492 is a new fluoroquinolone with excellent activity against both Gram-positive and Gram-negative organisms, with many potential clinical uses.

Triclosan resistance in methicillin-resistant Staphylococcus aureus (MRSA).

Two triclosan selected mutants showed four-fold and 16-fold increases in their minimum inhibitory concentrations (MICs) of triclosan (1 mg/L and 4 mg/L) compared with their parent strains. Four clinical isolates of MRSA were detected with the same triclosan susceptibility as the mutants. One mutant had a predicted change in the gene product on FabI (Thr 147-->His), whilst only one clinical isolate had predicted FabI amino-acid changes (Ala 198-->Gly, and Leu 208-->Phe). The lack of fabI mutations in one mutant and three of the clinical isolates showing reduced triclosan susceptibility suggest that genetic loci other than fabI may be involved in triclosan resistance.

Susceptibility of antibiotic-resistant cocci to biocides.

Biocide resistance has hitherto been a poorly studied subject, possibly due to the belief that such resistance was rare and clinically insignificant. Various recent findings, however, have underlined the importance of biocide resistance as a clinically relevant phenomenon. Outbreaks of biocide-resistant organisms in hospitals have been described and the genetic mechanism for resistance to quaternary ammonium compounds (QACs) in Staphylococcus aureus has now been elucidated. Mycobacteria resistant to commonly used endoscope disinfectants are now commonly reported and have caused numerous adverse clinical events. Cross-resistance between triclosan and antituberculous drugs has been demonstrated in other strains of mycobacteria. This is related to a common mechanism of action. The work presented here describes studies into the biocide resistance of antibiotic-resistant cocci and attempts to create biocide-resistant strains in vitro. Strains of staphylococci (including methicillin-resistant Staph. aureus (MRSA)) and enterococci (including vancomycin-resistant enterococci (VRE)) had their susceptibility to biocides assayed using broth macro dilution methods and resistant strains were selected by serial subculture on biocide-containing media. Mutants were created with relative ease; for instance, triclosan minimal bactericidal concentrations (MBCs) increased from 0.002 to 3.12 mg l(-1). Some strains of MRSA which have intermediate resistance to glycopeptides were demonstrated to have decreased susceptibility to some biocides. Biocide resistance amongst enterococci was demonstrated although there was no clear correlation between biocide and antibiotic resistance. The exact mechanisms of resistance in these strains are still being studied but it is clear that biocide resistance is an important clinical phenomenon.