Gastroscope processing in washer-disinfectors at three different temperatures

Endoscopes are processed chemo-thermally at approximately 56 degrees C in washer-disinfectors in Germany. In this study we investigated the processing of gastroscopes by an endoscope washer-disinfector at different temperatures. A total of 87 gastroscopes were tested hygienically and microbiologically before manual cleaning (after patient use), as well as after manual cleaning and after endoscope washer-disinfector processing at running temperatures of 43, 51 and 56 degrees C. In all tests the suction/biopsy channels of the gastroscopes were flushed with 50 mL sterile solution throughout their full length, from the proximal to the distal ends. The rinse solutions were plated on to various culture media. Also, in order to detect low bacterial counts, 3x10 mL rinse solution was membrane filtrated. The German guideline level for total bacterial counts, applicable since 2002, was exceeded at all temperatures tested (159 cfu/mL at 43 degrees C, <60 cfu/mL at 51 degrees C, and 8 cfu/mL at 56 degrees C). A temperature increase from 43 to 51 degrees C resulted in a highly significant reduction of the residual contamination by aerobic bacteria (P<0.001, Mann-Whitney U Test), Gram-negative bacilli (P<0.001), and pseudomonads (P=0.002). A further temperature increase from 51 to 56 degrees C resulted in a further highly significant drop in residual contamination by aerobic bacteria (P=0.021) and pseudomonads (P=0.036). The aim of the user-minimizing material damage to endoscopes or prolonging their product life-cannot be achieved through lowering the processing temperature without putting patients at risk. In order to ensure adequate processing, endoscope washer-disinfectors should meet the requirements of current draft standards.

Voltage-activated calcium signals in myotubes loaded with high concentrations of EGTA

In the present study we describe the analysis of optically recorded whole cell Ca(2+) transients elicited by depolarization in cultured skeletal myotubes. Myotubes were obtained from the mouse muscle-derived cell line C2C12 and from mouse satellite cells. The cells were voltage-clamped and perfused with an artificial intracellular solution containing 15 mM EGTA to ensure that the bulk of the Ca(2+) mobilized by depolarization is bound to this extrinsic buffer. The apparent on- and off-rate constants of EGTA and the dissociation rate constant of fura-2 in the cell were estimated by investigating the Ca(2+)-dependence of kinetic components of the fluorescence decay after repolarization. These parameters were used to calculate the time course of the total voltage-controlled flux of Ca(2+) to the myoplasmic space (Ca(2+) input flux). The validity of the procedure was confirmed by model simulations using artificial Ca(2+) input fluxes. Both C2C12 and primary-cultured myotubes showed a very similar phasic-tonic time course of the Ca(2+) input flux. In most measurements, the input flux was considerably larger and showed a different time course than the estimated Ca(2+) flux carried by the L-type Ca(2+) channels, indicating that it consists mainly of voltage-controlled Ca(2+) release from the sarcoplasmic reticulum. In cells with extremely small fluorescence transients, the calculated input fluxes matched the kinetic characteristics of the Ca(2+) inward current, indicating that Ca(2+) release was absent. These measurements served as a control for the fidelity of the fluorimetric flux analysis. The procedures promise a deeper insight into alterations of Ca(2+) release gating in studies employing myotube expression systems for mutant or chimeric protein components of excitation-contraction coupling.

Survival of MRSA on sterile goods packaging

For many years, MRSA (methicillin-resistant Staphylococcus aureus) has been a world-wide problem. Stringent infection control regimens need to be followed to prevent spread. One such measure is the disposal of unused, MRSA-contaminated single-use items, which is quite expensive. An alternative, less costly measure is to store these items temporarily, re-using them once the organism is non-viable. To establish survival times of MRSA on sterile goods packaging, paper and foil samples were contaminated with MRSA (approximately 10(8)-10(9) cfu/sample). The number of pathogens recoverable from the samples was measured at defined times. MRSA was demonstrated to survive on sterile goods packaging for more than 38 weeks. No MRSA was recoverable after 50 weeks. Temporary storage of MRSA-contaminated single-use items for such a long period of time is not an appropriate or reliable means of decontamination, but many be considered for items that would be costly to replace.

Determination of glutaraldehyde residues on flexible endoscopes after chemothermal treatment in an endoscope washer-disinfector

BACKGROUND AND STUDY AIMS

Although there are several cases of glutaraldehyde-induced colitis following colonoscopy there is only one study on residues after disinfecting. Our report describes the determination of water-soluble glutaraldehyde residues after processing endoscopes with a glutaraldehyde-containing disinfectant.

MATERIALS AND METHODS

A gastroscope and a colonoscope were processed in a washer-disinfector and then immersed in 201 of NaCl solution. Glutaraldehyde was determined by high performance liquid chromatography in 84 samples. Samples were taken after immersing the endoscopes for 5 h and 24 h with and without rinsing the channels.

RESULTS

After 5 h and with the channels having been rinsed, the median for colonoscopes was only 0.409 mg/l. The highest level of glutaraldehyde was 0.846 mg/l.

CONCLUSIONS

After endoscopes have been processed in the washer-disinfector there is no risk of a glutaraldehyde-induced colitis, proctitis or diarrhoea.

Excitation-contraction coupling in skeletal muscle of a mouse lacking the dihydropyridine receptor subunit gamma1

1. In skeletal muscle, dihydropyridine (DHP) receptors control both Ca(2+) entry (L-type current) and internal Ca(2+) release in a voltage-dependent manner. Here we investigated the question of whether elimination of the skeletal muscle-specific DHP receptor subunit gamma1 affects excitation-contraction (E-C) coupling. We studied intracellular Ca(2+) release and force production in muscle preparations of a mouse deficient in the gamma1 subunit (gamma-/-). 2. The rate of internal Ca(2+) release at large depolarization (+20 mV) was determined in voltage-clamped primary-cultured myotubes derived from satellite cells of adult mice by analysing fura-2 fluorescence signals and estimating the concentration of free and bound Ca(2+). On average, gamma-/- cells showed an increase in release of about one-third of the control value and no alterations in the time course. 3. Voltage of half-maximal activation (V(1/2)) and voltage sensitivity (k) were not significantly different in gamma-/- myotubes, either for internal Ca(2+) release activation or for the simultaneously measured L-type Ca(2+) conductance. The same was true for maximal Ca(2+) inward current and conductance. 4. Contractions evoked by electrical stimuli were recorded in isolated extensor digitorum longus (EDL; fast, glycolytic) and soleus (slow, oxidative) muscles under normal conditions and during fatigue induced by repetitive tetanic stimulation. Neither time course nor amplitudes of twitches and tetani nor force-frequency relations showed significant alterations in the gamma1-deficient muscles. 5. In conclusion, the overall results show that the gamma1 subunit is not essential for voltage-controlled Ca(2+) release and force production.

Freely accessible endoscope channels improve efficacy of cleaning

BACKGROUND AND STUDY AIMS

Inadequate cleaning and disinfection of medical devices, including flexible endoscopes, can result in the transmission of micro-organisms to patients. The aim of this study was to investigate the influence of the design of medical devices on the efficacy of manual cleaning of endoscope channels.

MATERIALS AND METHODS

The investigation was carried out using four endoscopes (two duodenoscopes and two gastroscopes). The air/water channels of one duodenoscope and one gastroscope were freely accessible and could be brushed. The instrumentation and the air/water channels were contaminated with blood containing Enterococcus faecium as a test organism. After manual cleaning of the channels by flushing and, where possible, brushing, the recovery rates for the test organism were studied.

RESULTS

The comparable rates for recovery of the test organism after cleaning of the instrumentation channels proved that the method used was reproducible. With regard to the air/water channels, the rate of micro-organisms in the cleaning solution recovered after flushing alone was a maximum of 3 % relative to the rate detected after brushing and flushing.

CONCLUSIONS

The data collected in the study show that only flushing channels that are not freely accessible resulted in significantly lower (P<0.001) recovery rates for the test organism. In practice, this means that contamination may remain in the channels, and it shows that the design of a medical device has an important influence on the reprocessing of reusable instruments such as flexible endoscopes.

Malignant hyperthermia and excitation-contraction coupling

Malignant hyperthermia (MH) is a state of elevated skeletal muscle metabolism that may occur during general anaesthesia in genetically pre-disposed individuals. Malignant hyperthermia results from altered control of sarcoplasmic reticulum (SR) Ca2+ release. Mutations have been identified in MH-susceptible (MHS) individuals in two key proteins of excitation-contraction (EC) coupling, the Ca2+ release channel of the SR, ryanodine receptor type 1 (RyR1) and the alpha1-subunit of the dihydropyridine receptor (DHPR, L-type Ca2+ channel). During EC coupling, the DHPR senses the plasma membrane depolarization and transmits the information to the ryanodine receptor (RyR). As a consequence, Ca2+ is released from the terminal cisternae of the SR. One of the human MH-mutations of RyR1 (Arg614Cys) is also found at the homologous location in the RyR of swine (Arg615Cys). This animal model permits the investigation of physiological consequences of the homozygously expressed mutant release channel. Of particular interest is the question of whether voltage-controlled release of Ca2+ is altered by MH-mutations in the absence of MH-triggering substances. This question has recently been addressed in this laboratory by studying Ca2+ release under voltage clamp conditions in both isolated human skeletal muscle fibres and porcine myotubes.

Malignant hyperthermia mutation Arg615Cys in the porcine ryanodine receptor alters voltage dependence of Ca2+ release

Ca2+ inward current and fura-2 Ca2+ transients were simultaneously recorded in porcine myotubes. Myotubes from normal pigs and cells from specimens homozygous for the Arg615Cys (malignant hyperthermia) mutation of the skeletal muscle ryanodine receptor RyR1 were investigated. We addressed the question whether this mutation alters the voltage dependence of Ca2+ release from the sarcoplasmic reticulum. The time course of the total flux of Ca2+ into the myoplasm was estimated. Analysis showed that the largest input Ca2+ flux occurred immediately after depolarization. Amplitude and time course of the Ca2+ flux at large depolarizations were not significantly different in the Arg615Cys myotubes. Ca2+ release from the sarcoplasmic reticulum was activated at more negative potentials than the L-type Ca2+ conductance. In the controls, the potentials for half-maximal activation V 1/2 were -9.0mV and 16.5 mV, respectively. In myotubes expressing the Arg615Cys mutation, Ca2+ release was activated at significantly lower depolarizing potentials (V = -23.5 mV) than in control myotubes. In contrast, V of conductance activation (13.5 mV) was not significantly different from controls. The specific shift in the voltage dependence of Ca2+ release caused by this mutation can be well described by altering a voltage-independent reaction of the ryanodine receptor that is coupled to the voltage-dependent transitions of the L-type Ca2+ channel.

Voltage-controlled Ca2+ release in normal and ryanodine receptor type 3 (RyR3)-deficient mouse myotubes

1. Primary cultured myotubes were derived from satellite cells of the diaphragm obtained from both normal mice (RyR3+/+) and mice with a targeted mutation eliminating expression of the type 3 isoform of the ryanodine receptor (RyR3-/-). Using the whole-cell patch clamp technique, L-type Ca2+ currents were measured during step depolarizations. Simultaneously, intracellular Ca2+ transients were recorded with the fluorescent indicator dye fura-2. 2. After correction for non-instantaneous binding of Ca2+ to the indicator dye and taking into account the dynamics of Ca2+ binding to intracellular constituents, an estimate of the time course of the Ca2+ release rate from the sarcoplasmic reticulum (SR) was obtained. 3. The calculated SR Ca2+ release flux exhibited a marked peak within less than 12 ms after the onset of the voltage-clamp depolarization and fell rapidly thereafter to a five times lower, almost steady level. It declined rapidly after termination of the depolarization. 4. Signals in normal and RyR3-deficient myotubes showed no significant difference in the activation of Ca2+ conductance and in amplitude, time course and voltage dependence of the Ca2+ efflux from the SR. 5. In conclusion, the characteristics of voltage-controlled Ca2+ release reported here are similar to those of mature mammalian muscle fibres. In contrast to differences observed in the contractile properties of RyR3-deficient muscle fibres, a contribution of RyR3 to excitation-contraction coupling could not be detected in myotubes.

Microbicidal activity of a new silver-containing polymer, SPI-ARGENT II

The survival of three bacterial species and Candida albicans was studied on SPI-ARGENT II. The immediate recovery from silver-impregnated polymer and control polymer (1 cm2) was approximately 10(6) to 10(7) microorganisms. After incubation (37 degreesC) and neutralization of silver with horse serum (5%), surviving organisms were recovered. The survival of the microorganisms on the polymer was not found to be influenced by the silver implantation.

Survival of Acinetobacter baumannii on dry surfaces

Acinetobacter spp. have frequently been reported to be the causative agents of hospital outbreaks. The circumstances of some outbreaks demonstrated the long survival of Acinetobacter in a dry, inanimate environment. In laboratory experiments, we compared the abilities of five Acinetobacter baumannii strains, three Acinetobacter sp. strains from the American Type Culture Collection (ATCC), one Escherichia coli ATCC strain, and one Enterococcus faecium ATCC strain to survive under dry conditions. Bacterial solutions of the 10 strains were inoculated onto four different material samples (ceramic, polyvinyl chloride, rubber, and stainless steel) and stored under defined conditions. We investigated the bacterial counts of the material samples immediately after inoculation, after drying, and after 4 h, 1 day, and 1, 2, 4, 8, and 16 weeks of storage. A statistical model was used to distribute the 40 resulting curves among four types of survival curves. The type of survival curve was significantly associated with the bacterial strain but not with the material. The ability of the A. baumannii strains to survive under dry conditions varied greatly and correlated well with the source of the strain. Strains isolated from dry sources survived better than those isolated from wet sources. An outbreak strain that had caused hospital-acquired respiratory tract infections survived better than the strains from wet sources, but not as well as strains from dry sources. Resistance to dry conditions may promote the transmissibility of a strain, but it is not sufficient to make a strain an epidemic one. However, in the case of an outbreak, sources of Acinetobacter must be expected in the dry environment.

The 14C-aminophenazone breath test in pesticide workers

In 59 workers between the ages of 22 and 66, who had been exposed to pesticides, and 31 healthy controls between the ages of 22 and 28, the hepatic demethylation capacity was studied using the aminophenazone breath test (ABT). The ABT was carried out in two versions (version A: 111 kBq 14C-aminophenazone per 630 mg, version B: 111 kBq 14C-aminophenazone per 3 mg). The amount of 14CO2 expired per mmol CO2 per 70 kg body weight (b.w.) detected 1 h after 14C-aminophenazone intake was used to determine the demethylation capacity of the liver. The amount of expired 14CO2 depended on the ingested dose (B greater than A). The 14CO2-values measured in 13 controls did not differ from those obtained in 37 subjects who had been exposed to pesticides for 650 h per year on the average [649 vs 726 DPM/mmol X 70 kg b.w. (A)]. The 14CO2-values obtained in 22 subjects exposed to pesticides for 990 h per year on the average (B) were lower than those obtained in 18 healthy controls (736 vs 1024 DPM/mmol CO2 X 70 kg; P less than 0.05). The 14CO2-values of ABT decreased with increasing length of exposure per year (B; r = -0.51, P less than 0.05).