The adhesion of Saccharomyces cerevisiae to hydrophilic alumina (Al2O3) particles and its removal by caustic alkali cleaning were studied. The surface charge properties of S. cerevisiae cells and Al2O3 particles were determined by potentiometric titration as a function of pH. The cells could adhere spontaneously to Al2O3 surfaces even though they had the same type of net charge as that of Al2O3. The maximum adhesion of 44.0mg dry cell/m2 was observed for the adhesion of negatively charged cells to positively charged Al2O3 in the pH range of 4.2 to 6.6. Approximately 43% of S. cerevisiae cells adhering to Al2O3 were desorbed rapidly by rinsing alone and the remainder was removed by subsequent caustic alkali cleaning. The rate of desorption of S. cerevisiae cells during caustic alkali cleaning depended both on the pH and on temperature, and was analyzed by evaluating the first-order desorption rate constant as a measure of cleaning efficiency. After caustic alkali cleaning, whole S. cerevisiae cells were completely removed, but polymeric substances presumably originating from alkali cell lysis remained on the Al2O3 surface.
The detergency effect of trisodium phosphate (Na3PO4) on the removal of irreversibly adsorbed bovine serum albumin (BSA) from alumina (Al2O3) particles during cleaning with 0.05 M NaOH solution was kinetically studied. The desorption curve of BSA, obtained by plotting the logarithm of the amount of residual BSA against cleaning time, during cleaning with the NaOH solution with and without Na3PO4 could be apparently reduced to the sum of two straight lines with different slopes. This fact suggested that two species of BSA, i.e., a fasterdesorbing species (BSAf) and a slower-desorbing species (BSAs), were present on Al2O3 surfaces and desorbed according to a first-order process. The first-order desorption rate constant (ks) of BSAs obtained from cleaning with the NaOH solution alone was approximately 56-fold lower than that (Kf) of BSAf. The addition of Na3PO4 to the NaOH solution had no influence on the desorption of BSAf, whereas it accelerated the desorption of BSAs, with an approximately 7-fold increase in the ks. Potentiometric titration showed that phosphate ions were adsorbed on Al2O3 surfaces after cleaning with the NaOH solution containing Na3PO4. The results indicated that hydroxide ion and phosphate ions could displace the slower-desorbing BSAs species at Al2O3-water interfaces in a synergistic manner.
We developed the resistance of Pseudomonas aeruginosa ATCC 10145 to N-dodecylpyridinium iodide (P-12), a quaternary ammonium compound (QAC), by using a standard broth dilution method and compared its characteristics with those of the sensitive strain. The minimum inhibitory concentration (MIC) against the resistant strain was 8 times higher than that against the sensitive strain and the adapted resistance to P-12 was stable. Population analysis showed that there were some variations in the extent of the resistance of P. aeruginosa to P-12. The cell surface of the resistant strain was more hydrophilic than that of the sensitive strain. In order to investigate the relationship between the resistance to P-12 and the biofilm formation of P. aeruginosa, alginic acid was isolated and its concentration was determined. The results revealed that the alginic acid was produced only in the resistant strain. Moreover, the observation by scanning electron microscope (SEM) of both strains showed that many clusters of bacteria were seen only in the resistant strain. These results suggested that not only the hydrophilic change of cell surface but also the biofilm formation is involved in the resistance of P. aeruginosa to P-12.
To examine the antibacterial effectiveness of handwashing with electrolyzed water (EW) when everyday nursing procedures are performed, the cleansing effectiveness of washing for 10s or 30s with EW, washing with 7.5O (w/v) povidone-iodineliquid (PI-washing), washing with medicated liquid soap (mls-washing), and washing with non-antiseptic, plain liquid soap (Is-washing) was compared. When the bacterial counts from hands after nursing procedures were 103cfu/hand or greater, it was suggested that washing for 10s or 30s with EW could be expected to have the same level of washing effectiveness asthat for mis-washing or Iswashing. Compared to PI-washing, however, the survival ratios were higher. When the bacterial counts from hands were less than 103cfu/hand after nursing procedures, washing for 10s or 30s with EW was more effective than Is-washing. Furthermore, EW could keep the bacterial counts from hands as low as those after PI-washing. Based on the above results, washing with EW was as effective as mls-washing, and though slightly less effective than PI-washing, it was considered that the same level of effectiveness seen with PI-washing could be expected for relatively lightly contaminated hands after daily nursing procedures.
The bacterial counts (log cfu/hand) on hands after conducting daily nursing procedures on a long-term hospitalized patient were quantitatively examined by using the wiping method. Since measures such as wearing gloves were taken when heavy contamination was expected in certain nursing procedures, most of the bacterial counts on the hands after various nursing procedures were 2-5, and the mean was 3.12±0.80. The post - procedure hand bacterial counts, however, were different depending on the type of procedure. The hand bacterial counts were from highest to lowest in the following order: after bed bath (4.19±0.41); after oral care (3.60±1.31); after diapering (3.48±0.71); after genital wash (3.20±0.72); after changing positions (2.82±0.51); and after endotracheal aspiration (2.34±0.57). The hand bacterial counts after bed baths, diapering, and genital wash differed depending on the condition of the diaper of the patient, with higher hand bacterial counts on the days with patient defecation, compared to the days without defecation. Based on the above results, it was suggested that the hand bacterial counts after nursing procedures were highest after procedures involving direct contact with the patient's skin (or saliva), lower for procedures in which the patient's clothing, etc., was touched, and lowest for procedures involving no direct contact with the patient.
We examined the antibacterial effectiveness of handwashing with electrolyzed water (EW) depending on the type of nursing procedure and differences in the degree of bacterial contamination on hands after the procedure. With respect to the bacteria on the hands after diapering (relatively heavy contamination), changing positions (relatively light contamination), and endotracheal aspiration (light contamination), handwashing for 10s and 30s with EW lowered the hand bacterial counts after handwashing to the same level as or lower than that before the procedures. Washing with EW was as effective as washing with medicated liquid soap and 7.5% (w/v) povidone-iodine liquid. Based on these results, we considered that handwashing for 10s with EW could be applied to any of the procedures that require direct contact with the patient's skin (diapering) or clothing (changing positions), as well as the procedures involving no direct contact with the patient (endotracheal aspiration). Furthermore, effective washing could be expected in a short period of time, with no rising of resident bacteria to the surface of the hand.
This study was to establish a method using DNA-DNA hybridization to identify species of lactic acid bacteria isolated from various types of salted vegetables. Enough chromosomal DNA could be obtained from lactic acid bacteria by lysing with N-acetylmuramidase in combination with lysozome in order to carry out DNA-DNA hybridization. A total of 35 strains of lactic acid bacteria isolated from salted vegetables were of the Lactobacillus, Lactococcus, Leuconostoc and Pediococcus species, and these bacteria were identified by DNA-DNA hybridization using the microdilution plate method. The present DNA-DNA hybridization method could identify 29 of 35 strains of lactic acid bacteria isolated from salted vegetables.
Hinokitiol, citral and allylisothiocyanate, which are chemicals of plant extracts, were investigated for their effectiveness as antifungal agents against the genera Saprolegnia, Aphanomyces and Achlya. The minimum inhibitory concentrations (MICs) of these chemicals were 12.5μg/ml of hinokitiol against all fungal isolates, and 100.0-200.0μg/ml of citral and 50.0-100.0μg/ml of allylisothiocyanate were appeared to inhibit the growth of Saprolegnia and Aphanomyces, but not Achlya. Among these chemicals, 100.0μg/ml of hinokitiol was the most effective agent to inhibit the hyphal growth of S. parasitica ATCC 90213 and Aphanomyces spp. but not of S. diclina ATCC 90215 and Achlya. Hinokitiol also inhibited at 100.0μg/ml the zoospore germination of Saprolegnia spp., whereas 12.5-25.0μg/ml of hinokitiol inhibited the zoospore germination of Aphanomyces spp.(but not Achlya). Treatment with a higher concentration of citral (800.0μg/ml) had an effectiveness of inhibiting the hyphal growth of all fungal isolates but the zoospores of all isolated strains showed higher sensitivity to citral (200.0-400.0μg/ml) than their vegetative stages did. The treatment with 100.0-400.0μg/ml of allylisothiocyanate was found to inhibit the vegetative growth of all fungal isolates except Achlya. On the other hand, the zoospores of all isolates showed higher sensitivity to allylisothiocyanate (200.0-400.0μg/ml) than their vegetative stages did.
The effects of temperature and water activity (Aw) were studied on the growth activity of Cladosporium sphaerospermum and C. cladosporioides. High growth was noted in C. sphaerospermum at high temperatures and in C. cladosporioides at low temperatures, but the growth activity of both C. sphaerospermum and C. cladosporioides was similar at 23-30°C. With regard to Aw, growth of C. cladosporioides was greater than that of C. sphaerospermum at 10-23°C. At 32-36°C, higher activities were shown in C. sphaerospermum. C. sphaerospermum and C. cladosporioides showed morphological changes such as dark brown hyphae with thick and cigar shaped cells, .and irregulary swollen cells at low Aw. C. sphaerospermum showed a broader range of growth temperature and Aw than C. cladosporioides.
We investigated the resistance of shell eggs stored under various conditions of temperature and storage periods in summer, autumn and winter in Japan to the growth of Salmonella Enteritidis (SE). SE (5-20 cells/egg) was inoculated at a point in the egg white near the egg yolk. In autumn and winter, stored shell eggs were more resistant to the growth of inoculated SE. Shell eggs inoculated with SE on d 0 of storage in these three seasons showed slight growth of SE at a high frequency. These results showed the necessity of controlling shell egg temperature and storage period in all seasons.