Removing bacteria from hospital surfaces: a laboratory comparison of ultramicrofibre and standard cloths.

We compared the ability of ultramicrofibre-woven cloths with conventional cloths moistened with water only, for their ability to remove several types of organisms relevant to hospital-acquired infections from a variety of surfaces in hospitals. We showed that ultramicrofibre cloths consistently outperformed conventional cloths in their decontamination ability, across all surfaces, and irrespective of whether the bacteria were coated on to the surfaces with phosphate-buffered saline (PBS) or PBS containing horse serum to simulate real-life soiling. The ability of the cloths to remove bacteria from surfaces was assessed by contact plating and colony formation, and by swabbing and measurement of ATP bioluminescence. The results suggest potential for use of ultramicrofibre in healthcare environments. Further studies are required, however, to define accurately how these cloths, which are designed to be used without detergent or biocides, might be capable of safe and effective deployment and recycling in the healthcare environment.

The efficacy of the inorganic copper-based biocide CuWB50 is compromised by hard water.

AIMS: We sought to explain the unexpected failure of the inorganic copper-based biocide CuWB50 to effectively decontaminate microfibre cleaning cloths that became contaminated with Acinetobacter lwoffii. METHODS AND RESULTS: CuWB50 was diluted using distilled water or tap water obtained from two different ICUs. Microtitre plate assays were used to determine the minimum inhibitory concentration (MIC) for the implicated A. lwoffii. pH and oxidation-reduction potential (ORP) tests were performed and representative water samples were chemically analysed. When diluted in distilled water, the CuWB50 MIC for A. lwoffii was 9 mg l(-1) but in tap water from each ICU it was 37 and 75 mg l(-1) at hardness levels of 246 and 296 mg CaCO(3) l(-1) respectively. CuWB50-distilled water solutions consistently had a lower pH and higher ORP than CuWB50-tap water solutions. CONCLUSIONS: Hard water adversely affects the biocidal efficacy of CuWB50. SIGNIFICANCE AND IMPACT OF THE STUDY: Unintentional environmental contamination is a risk when using wet microfibre cloths. This occurred when cloths were stored in CuWB50 overnight combined with the unintentional but erroneous use of tap water. This study emphasizes the need for clearly documented cleaning protocols embedded within a culture of adequate training and constant supervision of cleaning staff.

'Sample-in, answer-out'? Evaluation and comprehensive analysis of the Unyvero P50 pneumonia assay.

This study aimed to evaluate the performance of the Unyvero P50 pneumonia assay, the first 'sample-in, answer-out' system for rapid identification of pathogens and antibiotic resistance markers directly from clinical specimens. Overall, Unyvero P50 displayed very good sensitivity (>95%); however, specificity was low (33%) mainly because 40% of the specimens were reported as normal flora. Specifically, one or more pathogens were identified in 28 of them. From a detailed analysis of 42 specimens selected at random, 76% of the additionally reported pathogens were confirmed present in primary specimens. Detection of selected resistance markers was compared to routine phenotypic susceptibility testing, supplemented with Checkpoints microarray system, PCR and sequencing. Concordance was mixed, primarily due to issues with panel's choice of markers and detection of some intrinsic beta-lactamases. Finally, we offer a critical analysis of the assay's microbial panel and resistance markers and provide suggestions for improvement.

Mitochondrial K(ATP) channel opening protects a human atrial-derived cell line by a mechanism involving free radical generation.

OBJECTIVES: The mechanism by which the mitochondrial K(ATP) channel openers confer protection against ischemia/reperfusion injury is debated. Evidence suggests that rather than solely being an end effector, opening of these channels may act by a trigger mechanism. We examined the effects of the mitochondrial K(ATP) channel opener, diazoxide on parameters of mitochondrial function with specific reference to reactive oxygen species (ROS) generation in a human atrial derived cell line model of simulated ischemia/reperfusion (LSI/R). METHODS AND RESULTS: Propidium iodide (PI) exclusion was used to assess survival. Diazoxide treatment conferred protection against LSI/R (13.9+/-0.9% vs. 36.9+/-4.5% controls) that was abolished by pre-treatment with the mitoK(ATP) channel blocker, 5-hydroxydecanoate (5-HD) (33.3+/-3.6%) and with the free radical scavenger, 2-mercaptopropionylglycine (MPG) (29+/-4.0%). Diazoxide caused increased oxidation of the ROS probe, reduced mitotracker orange (1.3 vs. 1.0 arbitrary units for control; P<0.01 vs. control) that was abrogated by either 5-HD or MPG (1.07 and 1.07 arbitrary units, respectively). At the same time there was no change in orange fluorescent signal from the membrane potential sensitive probe, JC-1 indicating no change in mitochondrial membrane potential. Changes in light scattering, reflecting changes in mitochondrial volume, occurred during treatment with diazoxide. CONCLUSION: These results demonstrate for the first time that the mitoK(ATP) channel opener diazoxide can act as a trigger of preconditioning by a mechanism involving mitochondrial swelling and the generation of ROS.

A new method for measuring clustering in suspension between accessory cells and T lymphocytes.

Specifying the molecular basis and clinical significance of cluster formation between antigen-presenting cells and T lymphocytes will be important in many areas of immunology. In this paper we describe a novel and reproducible technique for measuring cluster formation in suspension between purified human blood monocytes and purified autologous T lymphocytes, and its application to determining the effects of recall antigens and mitogen. Blood monocytes and T lymphocytes from eight normal subjects were separately prelabelled with two different carbocyanine dyes prior to co-culture in suspension with or without antigen (PPD, SKSD) or mitogen (PHA). At 24 h the co-cultures were examined for cluster formation by ultraviolet microscopy and flow cytometry. Control experiments showed that the carbocyanine dyes were non-toxic in vitro, that cell labelling was stable for culture periods up to 120 h, and that the two dyes did not leak from cell to cell. By this technique we measured the proportion of monocytes clustering one or more T lymphocytes in the presence and absence of recall antigen or PHA. There was a close correlation between visual and flow cytometric measurement of monocyte: T lymphocyte clustering (p < 0.001) as well as a close relationship between the ability of the two recall antigens to increase the extent of clustering above baseline (p < 0.001). Antigen-increased cluster formation did not correlate with baseline clustering, unlike PHA-increased clustering, which was related to baseline levels (p = 0.02), suggesting the operation of distinct mechanisms. The method is applicable to measuring cell-cell associations in suspension during extended periods of culture, as well as for the study of agents which might modify intercellular adhesion processes.

Flow cytometric analysis of chlorhexidine action.

The mechanism by which chlorhexidine kills bacteria is still ill defined. We have investigated the action of chlorhexidine on Escherichia coli JM101/psb311 using a combination of flow cytometry and traditional methods. Chlorhexidine-induced uptake by E. coli cells of bis-(1,3-dibutylbarturic acid) trimethine oxonol and propidium iodide, which monitor membrane potential and membrane integrity respectively, was shown to be concentration dependent for the range 0.003-0.3 mmol-1. In addition, cells in log phase growth were more susceptible to 0.03 mmol-1 chlorhexidine than those in stationary phase. There was, however, no direct correlation between dye uptake and decline in colony forming units.

The application of flow cytometry to the study of bacterial responses to antibiotics.

Experiments were performed to determine whether a modern flow cytometer could be used to study bacterial populations in suspension, with particular reference to their morphological characteristics and their responses to antibiotics. The FACScan, a commercial benchtop flow cytometer fitted with an air-cooled laser, designed primarily for the study of eukaryotic peripheral blood mononuclear cells, yielded reproducible data relating to bacterial shape and internal architecture. It was sensitive enough to detect changes in bacterial morphology on entry into the growth cycle and after exposure to antibiotics. Antibiotic-induced morphological changes affecting subpopulations of bacteria were sufficiently specific to allow differentiation between antibiotics with different cell-wall enzyme targets. Simultaneously, the effect of such antibiotics on the integrity of the outer cell membrane of Escherichia coli was assessed by measurement of the association of the nucleic acid-binding dye propidium iodide with the bacteria. These experiments demonstrated complex patterns of probable cell-wall leakage, related to the modes of action of the antibiotics. The FACScan is a useful and sensitive tool for the study of the morphology and physiology of bacterial populations in suspension, and is especially applicable to the study of antibiotic action.

Towards European urinalysis guidelines. Introduction of a project under European Confederation of Laboratory Medicine.

Improved standardized performance is needed because urinalysis continues to be one of the most frequently requested laboratory tests. Since 1997, the European Confederation of Laboratory Medicine (ECLM) has been supporting an interdisciplinary project aiming to produce European urinalysis guidelines. More than seventy clinical chemists, microbiologists and ward-based clinicians, as well as representatives of manufacturers are taking part. These guidelines aim to improve the quality and consistency of chemical urinalysis, particle counting and bacterial culture by suggesting optimal investigative processes that could be applied in Europe. The approach is based on medical needs for urinalysis. The importance of the pre-analytical stage for total quality is stressed by detailed illustrative advice for specimen collection. Attention is also given to emerging automated technology. For cost containment reasons, both optimum (ideal) procedures and minimum analytical approaches are suggested. Since urinalysis mostly lacks genuine reference methods (primary reference measurement procedures; Level 4), a novel classification of the methods is proposed: comparison measurement procedures (Level 3), quantitative routine procedures (Level 2), and ordinal scale examinations (Level 1). Stepwise strategies are suggested to save costs, applying different rules for general and specific patient populations. New analytical quality specifications have been created. After a consultation period, the final written text will be published in full as a separate document.

Performance of ultramicrofibre cleaning technology with or without addition of a novel copper-based biocide.

This study compared the bacterial removal performance of ultramicrofibre cloths and mops (UMF) moistened with water (UMF+water), with those moistened with a novel copper-based biocide (UMF+CuWB50, 300ppm) in several working hospital environments, specifically accident and emergency (A&E) and three other wards. A total of 13 defined sampling sites (10 sites per ward) were sampled in order to retrieve, culture, and enumerate total viable (bacterial) counts (TVC) for each site. We sampled 1h before, and 1 and 4h after, cleaning three times per week. The trial ran for 7 weeks. Two wards were cleaned with UMF+water for 3 weeks, and UMF+CuWB50 for 4 weeks. The reverse applied to the other two wards in a cross-over design fashion, to eliminate ward- and time-specific bias. Multivariate statistical analyses were used to establish extent and significance of any perceived differences, and to eliminate the effects of potential confounders. Cleaning with UMF+water reduced TVC on the test surfaces by 30%, whereas cleaning with TVC+CuWB50 reduced TVC by 56%. CuWB50 had two separate effects; a direct antibacterial effect (evident shortly after cleaning), and a residual antibacterial effect that lasted approximately 2 weeks. The residual effect requires regular application of CuWB50 if it is to persist. This 'real life' hospital implementation study demonstrates encouraging microbiological cleaning performance for UMF, which is further enhanced with CuWB50.

Human bronchoalveolar macrophage heterogeneity demonstrated by histochemistry, surface markers and phagocytosis.

Human alveolar macrophages (AM) were obtained by bronchoalveolar lavage from 18 patients with a variety of conditions. For each patient the percentages of AM showing the following properties were determined: (1) staining for the enzymes non-specific esterase (NSE) and acid phosphatase (ACP); (2) in vitro phagocytosis of Candida guillermondii; (3) expression of cell surface markers detected by two monoclonal antibodies (MoAb) (1B5 and DA2) and two anti-monocyte/macrophage MoAb (UCHMI and RFD2); and (4) simultaneous phagocytosis of C. guillermondii and staining with the MoAb. In all patients the majority of AM were found to be Ia positive (90 +/- 10%) ACP positive (100%) and NSE positive (97 +/- 4%). In contrast a smaller proportion were UCHM1 and RFD2 positive (77 +/- 11%, 68 +/- 12%) and less were phagocytic (37 +/- 17%). Whilst the total percentage of cells staining with the MoAb was unaltered by phagocytosis, the proportion of UCHM1 or RFD2 positive cells was significantly higher in the phagocytic population than in the non-phagocytic population (90% and 85%, as opposed to 65% and 55%, P less than 0.001). Thus only a proportion of Ia positive AM expressed monocyte/macrophage antigens and were phagocytic. Such heterogeneity may reflect different stages of macrophage maturation or the existence of macrophage subpopulations with functionally distinct roles in airways immunity.

Alveolar macrophages from patients with bronchogenic carcinoma and sarcoidosis similarly express monocyte antigens.

It has been shown that bronchoalveolar lavages (BALs) from patients with sarcoidosis and other interstitial lung diseases contain abnormally increased numbers of alveolar macrophages (AM) expressing antigens found on monocytes. The aim of this study was to compare the phenotype of AM from patients with sarcoidosis with those from patients with non-interstitial lung disease, namely carcinoma. Using a panel of monoclonal antibodies against cells of the mononuclear phagocytic series and immunohistochemical staining, we have compared the expression of antigens on AM recovered at BAL and peripheral blood monocytes from patients with sarcoidosis, with similar cell preparations from bronchogenic carcinoma patients and normal volunteers. We have shown that CD14, CR1 (CD35) and CR3 (CD11b, CD18) are expressed on the majority of monocytes from all subjects, but on only a minority of normal AM. In both patients with sarcoidosis and patients with bronchogenic carcinoma increased proportions of AM expressed these monocyte-associated antigens. Since BALs from the carcinoma patients were derived from lung lobes which were radiologically free of tumour, the accumulation of AM expressing monocytic antigens is not a local response to the tumour. We conclude that infiltration of the lung with monocytes is a more general response to lung disease than has hitherto been reported.

Flow cytometric monitoring of antibiotic-induced injury in Escherichia coli using cell-impermeant fluorescent probes.

Three fluorescent nucleic acid binding dyes-propidium iodide, TO-PRO-1, and SYTOX green-were evaluated, and their abilities to distinguish between bacterial cells with and without an intact cytoplasmic membrane were compared. Each dye was readily able to discriminate between healthy and permeabilized cells of Escherichia coli, although SYTOX green showed a greater enhancement in fluorescence intensity on staining-compromised, as opposed to healthy, cells in log-phase growth, than either PI or TO-PRO-1. Flow cytometric analysis of E. coli stained with these dyes after exposing them to several antimicrobial agents showed that all three dyes were able to detect antimicrobial action. Notably, however, the intensity of the cell-associated fluorescence was related to the mechanism of action of the antimicrobial agent. Large changes in fluorescence intensity were observed for all the dyes subsequent to beta-lactam antibiotic action, but smaller changes (or no change) were seen subsequent to exposure to antimicrobials acting directly or indirectly on nucleic acid synthesis. Furthermore, cell-associated fluorescence did not relate to loss of viability as determined by plate counts. Despite offering much insight into antimicrobial mechanisms of action, these fundamental problems become relevant to the development of rapid antimicrobial susceptibility tests if colony formation is used as the standard.

Antibiotic susceptibility testing by flow cytometry.

Flow cytometry can provide a rapid indication of antibiotic susceptibility. This unit describes a number of fluorescent dyes that allow the cytometer to distinguish the heterogeneic nature of populations exposed to antibiotics. No single method can be used for multiple organisms, since it is the interference with the organisms growth and structural integrity that signals the impact of the antibiotic so rapidly. This unit discusses membrane structural changes as well as alterations in nucleic acid and the probes that can be successfully used with flow cytometry.

Antimicrobial action of rabbit leukocyte CAP18(106-137).

CAP18 is a cationic antimicrobial protein originally isolated from rabbit neutrophils, of which a 32-mer sequence from its C-terminal and (CAP18(106-137)) has been found to be the most active. The bactericidal action of this peptide has been characterized by conventional culture techniques and flow cytometry. Cultures of Escherichia coli NCTC10418 were exposed to the MBC (12 microM) of the peptide for up to 60 min and stained with a fluorochrome sensitive to changes in either membrane potential (bis-(1,3-dibutylbarbituric acid)trimethine oxonol [DiBAC4(3)), or membrane integrity (propidium iodide [PI]) before flow cytometric analysis. Addition of CAP18(106-137) to E. coli in broth culture resulted in immediate collapse of membrane potential [as determined by uptake of DiBAC4(3)] and loss of membrane integrity (as indicated by uptake of PI), with a corresponding 6- to 8-log decrease in viable counts as determined by colony formation on solid media. In identical experiments, the presence of Mg2+ (1 to 10 mM), K+ (50 to 250 mM), or EDTA (5 mM) or incubation in nutrient-free buffer or at 4 degrees C had no effect on peptide-induced dye uptake. In contrast, addition of Ca2+ (1 to 10 mM) or the respiratory chain poison carbonyl cyanide m-chlorophenylhydrazone (CCCP) (50 microM) inhibited the uptake of both dyes. These findings, however, did not relate to bacterial recovery on solid media, where (unless in the presence of K+ 150 to 250 mM) CAP18(106-137) at 12 microM fulfilled the MBC criteria (99.9% killing). We conclude that CAP18(106-137) exerts a rapid and profound action on E. coli cytoplasmic membranes and viability as measured by colony formation. The results suggest, however, that CAP18(106-137) may exert its action at sites additional to the cell membrane and that its activity profile is unique among cationic antimicrobial proteins.

A fluorescent Gram stain for flow cytometry and epifluorescence microscopy.

The fluorescent nucleic acid binding dyes hexidium iodide (HI) and SYTO 13 were used in combination as a Gram stain for unfixed organisms in suspension. HI penetrated gram-positive but not gram-negative organisms, whereas SYTO 13 penetrated both. When the dyes were used together, gram-negative organisms were rendered green fluorescent by SYTO 13; conversely, gram-positive organisms were rendered red-orange fluorescent by HI, which simultaneously quenched SYTO 13 green fluorescence. The technique correctly predicted the Gram status of 45 strains of clinically relevant organisms, including several known to be gram variable. In addition, representative strains of gram-positive anaerobic organisms, normally decolorized during the traditional Gram stain procedure, were classified correctly by this method.

Normal and sarcoid alveolar macrophages differ in their ability to present antigen and to cluster with autologous lymphocytes.

Human bronchoalveolar macrophages from normal individuals function poorly as accessory cells for the presentation of common recall antigens. In sarcoidosis, alveolar macrophages (AM) are reported to be effective accessory cells for the presentation of such antigens. In this study normal and sarcoid AM were compared with blood monocytes for their ability to act as accessory cells in presenting tuberculin purified protein derivative (PPD) and streptokinase-streptodornase (SKSD) to autologous T lymphocytes, or to form spontaneous, antigen- or mitogen-induced clusters with the T cells. When compared to autologous monocytes, normal AM failed to present the two recall antigens effectively. Likewise normal AM formed very few clusters with T lymphocytes when compared to monocytes, even in the presence of antigens or the mitogen phytohaemagglutinin (PHA). In contrast, sarcoid AM presented both antigens as effectively, and were equally effective as monocytes in forming clusters with T lymphocytes, spontaneously and in further response to antigen or mitogen. The results suggest that in sarcoidosis enhanced accessory cell function and enhanced cluster formation may be related features of bronchoalveolar macrophage populations.

A novel leucocyte-depleting filter for use in continuous venovenous haemofiltration: preliminary in vitro studies.

Multiple organ failure (MOF) secondary to circulatory shock, sepsis, or trauma was first described over 20 years ago. Despite much research effort and clinical trials of biological response modifiers, MOF continues to be the leading cause of death in both medical and surgical intensive care units (ICU). MOF is associated with widespread cellular and humoral systemic inflammatory responses which, in turn, are linked with inadequate tissue perfusion to vital organs and the inappropriate accumulation of activated neutrophils, resulting in microcirculatory injury. Much evidence suggests that such activated neutrophils cause vascular damage by adhering to the endothelium and releasing a variety of highly reactive and toxic moieties; these may subsequently produce endothelial injury and compromised organ function. We reasoned that a clinical device designed to remove such cells in a controlled fashion from the circulation of patients with MOF by means of using a continuous venovenous circuit might be beneficial. We report the leucocyte depletion performance of a novel filter medium as a first step towards the production of a clinical device, and show specific depletion of phagocytes relative to other formed elements in the blood.

Antibacterial action of ciprofloxacin.

The mechanisms by which quinolones rapidly kill are ill defined. We have investigated the action of ciprofloxacin on Escherichia coli KL16 with a combination of traditional and flow cytometric methods and have analyzed cells for changes in membrane potential, membrane integrity, oxidative metabolism, morphology, and viability. Log-phase cultures were exposed to various concentrations (0.1, 1, 10, and 100 times the MIC) of ciprofloxacin and analyzed at regular intervals over 120 min. We also measured protein synthesis in the related strain PQ37 cultured under the same conditions over 300 min, using a colorimetric assay for beta-galactosidase release. Despite a 3-log order decrease in CFU after 60-min exposure to 10 and 100 times the MIC of ciprofloxacin, there was no equivalent decrease in bacterial numbers as determined by both light microscopy and flow cytometry. Furthermore, while these bacteria showed concentration-dependent morphological changes, most were capable not only of excluding the fluorescent nucleic acid-binding dye propidium iodide, but also of reducing the tetrazolium dye cyanoditodyl tetrazolium chloride. Over 90% of the bacteria maintained a membrane potential [as determined by exclusion of bis-[1,3-dibutylbarbituric acid) trimethine oxonol] when exposed to ciprofloxacin for 120 min, except at 100 times the MIC, when this figure fell to < 10%. Finally, protein synthesis was either maintained or induced at all concentrations of ciprofloxacin up to 5 h postexposure. Taken together, these results demonstrate the continuing physical and metabolic survival of ciprofloxacin-exposed bacteria; we suggest parallels with the concept of the viable nonculturable state.

Flow cytometric investigation of filamentation, membrane patency, and membrane potential in Escherichia coli following ciprofloxacin exposure.

Ninety-eight percent of the cells in a population of Escherichia coli in log-phase growth lost colony-forming ability after being exposed for 3 h to the quinolone antibiotic ciprofloxacin at four times the MIC in nutrient broth, a concentration easily reached in vivo. Flow cytometric analysis, however, demonstrated that only 68% of this bacterial population had lost membrane potential, as judged by the membrane potential-sensitive dye bis-(1,3-dibutylbarbituric acid) trimethine oxonol [DiBAC(4)(3)], and only 30% could no longer exclude the nucleic acid-binding dye propidium iodide (PI), reflecting lost membrane integrity, efflux mechanisms, or both. Subsequent removal of ciprofloxacin and resuspension in nutrient broth resulted in renewed cell division after 2 h, with a calculated postantibiotic effect (PAE) time of 57 min. The proportion of DiBAC- and PI-fluorescent cells in this recovering population remained stable for more than 4 h after antibiotic removal. Eighty percent of cells present at drug removal were filamentous. Their number subsequently decreased with time, and the increase in particle count seen at the end of the PAE resulted from the division of short cells. Exposure to ciprofloxacin in the presence of the protein synthesis inhibitor chloramphenicol increased colony-forming ability to 60% of starting population numbers. In contrast to ciprofloxacin alone, this antibiotic combination resulted in insignificant filamentation and no dye uptake. Subsequent drug removal and resuspension in nutrient broth resulted in the appearance of filaments within 1 h, with 69% of the population forming filaments at 3 h. Dye uptake was also seen, with 20% of the population fluorescing with either dye after 4 h. We were unable to relate dye uptake to the viable count. Cell division resumed 240 min after removal of both drugs, yielding a PAE calculated at 186 min. Inhibition of protein synthesis with chloramphenicol prevented ciprofloxacin-induced changes in bacterial morphology, cell membrane potential, and ability to exclude nucleic acid-binding dye. These changes persisted beyond the end of the classically defined PAE and were not a definite indicator of cell death as defined by loss of colony formation, which related at least in part to filamentation.