Effect of frequency and amplitude of vibration on void formation in dies poured from polyvinyl siloxane impressions

To determine the susceptibility of Escherichia coli O157:H7 to freezing and thawing in apple cider, methods that recover injured cells are needed for accurate enumeration. This study compared the ISO-GRID hydrophobic grid membrane filter (HGMF) SD-39 agar method to two other methods: a reference most probable number (MPN) method, and plating on sorbitol MacConkey agar (SMA). To determine numbers of injured cells, SMA spread plating was also compared to Trypticase soy agar (TSA) spread plating. Two strains of E. coli O157:H7 QA 326 and ATCC 43895, were inoculated into presterilized apple cider (10 ml) which was then frozen (-20 degrees C for 24 h). Samples were thawed at 4 degrees C for 4 h, or at 23 degrees C for 1.5 h, or in a microwave oven (700 W for 10 s). Substantial cell death (0.69- to 6.33 log10 CFU/ml decreases) and injury (0.70- to 2.38-log10 CFU/ml decreases) occurred during freezing and thawing. The extent of death and injury varied with strain and thawing method. The TSA spread plating method recovered the most cells while the HGMF method always recovered more viable cells than the reference MPN method and also either recovered significantly more (P < 0.05) cells or a not significantly different number of cells than SMA spread plating. Some injured cells of both strains were not counted by the HGMF method. Significant numbers of cells injured by freezing and thawing at 4 degrees C in apple cider were enumerated in the cider was diluted 1:2 Trypticase soy broth immediately before plating. Two epifluorescent microscopic methods showed that injury was not associated with loss of cell membrane integrity.     

Relative value of selective group A streptococcal agar incubated under different atmospheres

A commercially available selective group A streptococcal agar (ssA) was evaluated for the recovery of group A streptococci (GAS) in comparison with recovery from simultaneous cultures on conventional sheep blood agar (SBA). Both sets of plates were incubated in air, 5% CO2, and anaerobically for 48 h, with a first reading taken at 24 h. A total of 402 (67.0%) GAS were isolated from the 600 specimens that were submitted. Recovery of GAS was significantly greater after 48 h of incubation than after 24 h of incubation for each medium-atmosphere combination. After 48 h of incubation, the sensitivities of GAS detection obtained by each culture technique were as follows: ssA-anaerobic atmosphere, 98.5%; SBA-anaerobic atmosphere, 89.5%; ssA-CO2 atmosphere, 88.0%; SBA-air, 86.5%; SBA-CO2 atmosphere, 82.0%; and ssA-air, 74.6%. There were no cultures positive in air or CO2 which were not positive anaerobically on either medium. The increased sensitivity of detecting positive GAS cultures when incubation was done in an ssA-anaerobic atmosphere for 48 h uncovered patients truly infected with the organisms.     

Rural palliative care volunteer education and support program

Autogenous hip marrow is an excellent source of pluripotential cells for regenerative procedures. However, before this treatment modality can be employed a method to attenuate osteoclast activity must be developed. The shock of cold storage (4 degrees C) is thought to abate osteoclast activity through the downregulation of osteolytic cytokines produced by osteoblasts. The objective of this study was to evaluate the effects of cold storage (4 degrees C) and endotoxin challenge on bone cell culture viability and interleukin-6 (IL-6) production. These cells (osteoblasts) were primarily harvested from murine calvaria utilizing sequential digestions, separated by density gradient and combined. Twelve-well cell culture plates were inoculated with 2 x 10(4) cells/ml and placed in cold storage for 1-14 d. After cold storage the cultures were then incubated at 37 degrees C for 1-20 d. A set of replicate plates was also challenged with 10 ng/ml endotoxin upon incubation at 37 degrees C for 4 consecutive days. Cells were evaluated daily for alkaline phosphatase activity. Cell culture supernatants were also collected daily and batch assayed for IL-6 production. Cell cultures did not survive more than 48 h of cold storage. There was a decrease in IL-6 secretion in all refrigerated cultures and a significant decrease in those cells refrigerated for 48 h versus control cultures (p < 0.05). Replicate cultures treated with endotoxin secreted significantly increased amounts of IL-6 in both the control cultures and the cultures exposed to 24 h of cold storage versus non-endotoxin-treated control cultures (p < 0.05). These observations suggest that after 48 h of cold storage autogenous marrow may be safe to use because of the dramatic decrease in IL-6 production by osteoblasts.     

Molecular lipophilicity potential by CLIP, a reliable tool for the description of the 3D distribution of lipophilicity: application to 3-phenyloxazolidin-2-one, a prototype series of reversible MAOA inhibitors

Six methods were compared for detection of three strains of Escherichia coli O157:H7 in enrichments of inoculated apple juice. Juice was inoculated at levels varying from 0.1 to 100 CFU/ml and centrifuged after overnight storage at 4 degrees C, and pellets were incubated at 37 degrees C in nonselective enrichment broth. At hourly intervals between 5 and 10 h and at 24 h, the enrichments were tested for E. coli O157:H7 by direct fluorescent antibody (DFA), antibody-direct epifluorescent filter technique (Ab-DEFT), direct selective plating on sorbitol MacConkey agar (SMA), immunomagnetic separation coupled to either selective plating (IMS-SMA) or the polymerase chain reaction (IMS-PCR), and flow cytometry (FC). The most consistent detection of 0.1 CFU/ml of the slowest growing strain of the pathogen was provided by the IMS-SMA and IMS-PCR after 8 h of enrichment. The time required for detection at the level of 0.1 CFU/ml for each assay was Ab-DEFT, 11 h; IMS-PCR, 16 h; FC, 24 h; IMS-SMA, 32 h; and SMA, 48 h. Absolute detection limits (without enrichment) were: IMS-PCR, 10(3) CFU/ml; Ab-DEFT and IMS-SMA, 10(4) CFU/ml; SMA, 10(5) CFU/ml; and DFA, 10(6) CFU/ml. Recovery of the pathogen (10 CFU/ml) in apple juice after 28 days of 4 degrees C storage was possible by means of an 8-h enrichment and Ab-DEFT, IMS-PCR, or IMS-SMA.     

Enumeration of intestinal enterococci and interfering organisms with Slanetz-Bartley agar, KF streptococcus agar and the MUST method

The recovery of intestinal species of enterococci and streptococci and potentially interfering nonfaecal species was measured on KF streptococcus agar, Slanetz-Bartley agar and in a medium based on 4-methylumbelliferyl-beta-D-glucoside (MUST method) using pure cultures. Both of the solid media yielded high recoveries of the target species. Their selectivity was better at elevated incubation temperature but nonfaecal Enterococcus and Staphylococcus species were not eliminated even at the elevated temperature. The MUST method tended to give slightly lower recoveries than the agar cultivation methods with some target species at 44 degrees C but recoveries were better at 41 degrees C.     

New antiepileptic drugs

Survival of Escherichia coli O157:H7 strains QA 326, and ATCC 43889, 43894, and 43895 after freezing (-20 degrees C, 24 h) and thawing (4 degrees C for 12 h, 23 degrees C for 3 h, or microwave heating of 700 W for 120 s) in ground beef patties was determined by reference most probable number (MPN), hydrophobic grid membrane filter SD-39 agar, and sorbitol MacConkey agar (SMA) spread-plating methods. Populations decreased from 0.62 to 2.52 log10 CFU/g, with the extent varying significantly by strain. Strain QA 326 populations almost always decreased the most, up to 1.87 log10 CFU/g more than the least sensitive strain. Microwave heating was the most lethal thawing treatment for strain QA 326, and 4 degrees C thawing was the most lethal treatment for strain ATCC 43894. Thawing treatments varied in relative lethality for the other two strains. For strain QA 326 (4 degrees C and microwave thaw treatments) and strain ATCC 43889 (4 and 23 degrees C thawing), the enumeration method significantly affected a population decrease. The SD-39 agar method best recovered strain QA 326 while the SD-39 agar method and the reference MPN method best recovered strain ATCC 43889 after 4 and 23 degrees C thawing, respectively. The greatest difference in population decrease measured by any two methods was 0.58 log10 CFU/g. Results showed (i) a wide range in freeze-thaw sensitivity among E. coli O157:H7 strains, (ii) no thawing method had consistently and significantly greater lethality, and (iii) the reference MPN, SD-39 agar, and SMA methods differed little in ability to enumerate E. coli O157:H7.     

Production of enterotoxins by Bacteroids fragilis strains--effect of clindamycin

Four B. fragilis strains were examined: one nonenterotoxigenic (NTBF) and three producing enterotoxin (ETBF). The growth of cultures was determined and enterotoxin, which is released to the culture medium during growth of strains, was detected. BHI broth and BHI broth with addition of subinhibitory doses (sub-MIC) of clindamycin were applied. Bacterial cultures were incubated at 37 degrees C for 48 hours. After 4, 8, 16, 24, 48 hours of cultivation, samples of bacterial cultures were collected and the optical density was measured. Then the samples were centrifuged, supernatants were filtered through 0.45 micron filters and concentrated three times with 5000 D ultrafilters. Prepared samples were kept frozen at -70 degrees C until used. The titre of enterotoxin in samples was determined on human colon adenocarcinoma cell line HT 29/C1. Neutralization assay was performed with culture filtrates, which were enterotoxin-positive and with rabbit anti-enterotoxin serum. The results of the experiments indicate that enterotoxin is detected after 16 hours of incubation of ETBF strains. Clindamycin at subinhibitory concentrations (sub-MIC) inhibits the growth of B. fragilis cultures. The antibiotic causes also delay and decrease in enterotoxin production by ETBF strains.     

Comparison of NNA agar culture and selective broth culture for detection of group B streptococcal colonization in women

In 1996, the Centers for Disease Control and Prevention recommended the use of a selective broth culture for the improved detection of genital tract or anorectal carriage of group B streptococci (GBS) in pregnant women. In order to verify this recommendation in our laboratory, we compared the sensitivity of Todd-Hewitt medium with gentamicin and nalidixic acid (SBM) with our current method of direct plating on blood agar medium containing neomycin and nalidixic acid (NNA). Five hundred consecutive cervicovaginal and anorectal specimens submitted for GBS culture were included in the study. Swabs were plated onto NNA and the swabs were immersed in SBM, followed by overnight incubation at 35 degrees C. On the following day, the NNA plates were examined for colonies typical of GBS and the organisms were identified by the CAMP test or by latex agglutination. SBM cultures were subcultured onto blood agar and CNA agar plates, and the plates were reincubated for 24 h. Negative specimens from either medium were incubated for an additional 24 h and were examined again before finalization of the results. GBS were recovered from 78 specimens by both methods; from SBM only for 17 specimens (sensitivity, 86%) and from NNA only for 16 specimens (sensitivity, 85%). A moderate to heavy growth of Enterococcus faecalis was observed on plates containing NNA-positive, SBM-negative specimens. Competitive growth studies suggested that E. faecalis suppressed the growth potential of GBS in SBM. Our study suggests that direct plating on NNA, as a single method, is equivalent in sensitivity to SBM for the recovery of GBS, and the results are often available 24 h sooner. However, it appears that both direct plating and selective broth amplification techniques are required for the maximum level of identification of colonization with GBS in pregnant women.     

The influence of post-mortem conditions on contractile and relaxant responsiveness of guinea-pig isolated tracheal smooth muscle

Responsiveness to various contractile and relaxant agonists was assessed in tracheal preparations from guinea-pigs that had been incubated in situ at 4-37 degrees C for 0-168 h post-mortem. The potencies of histamine and acetylcholine were increased up to 168 h at 4 degrees C post-mortem and up to 24 h post-mortem at 22 degrees C. Histamine potency also increased with increasing post-mortem time at 37 degrees C. After 48 h at 22 degrees C and 8 h at 37 degrees C, responses to all spasmogens were abolished. Increases in histamine and acetylcholine potencies were similarly observed in tracheal tissue that had been removed at death and then incubated at 4 degrees C in oxygenated Krebs-bicarbonate solution for 0-168 h. The increased potency of these drugs may be explained by epithelial damage and/or loss of an epithelium-derived inhibitory factor (EpDIF). Both basal and spasmogen-stimulated increases in intracellular phosphoinositides fell with increasing time and ambient temperature post-mortem, despite the fact that contraction in response to these agonists could still be evoked. This suggests the selective failure of this signal transduction pathway and the maintenance of responsiveness via other mechanisms. The potencies and maximum effects of relaxant agonists remained unaltered in tracheal tissue with increasing time post-mortem, suggesting little change in the function of the appropriate receptor-signal transduction processes. This study has therefore demonstrated that at 4 degrees C. contractile and relaxant responses were preserved for up to 168 h post-mortem, although the modulatory influence of the epithelium on histamine and acetylcholine responses was rapidly lost.     

Heat resistance of Listeria monocytogenes by two recovery media used with and without cold preincubation

Three strains of Listeria monocytogenes were heat-treated at three temperatures in physiological saline by a capillary tube method. Recovery of heat-treated bacteria was performed on blood agar and on tryptose phosphate agar with ferric citrate and aesculin (TPA-FE). Both media were used in two ways: (1) incubation at 37 degrees C for 7 d, and (2) preincubation at 4 degrees C for 5 d in order to obtain repair of heat-injured bacteria, followed by incubation at 37 degrees C for 7 d. D and z values were determined. In both incubation procedures, better average recovery was obtained on blood agar than on TPA-FE. Thus, higher D values were recorded when blood agar was used. In most cases the differences were statistically significant. Repair at 4 degrees C of heat-injured bacteria occurred on both media but the proportions of repaired bacteria were higher on blood agar. The repair on this medium was generally reflected in higher D values for preincubated samples. Some significant differences in heat resistance were noted between the strains.     

A comparison of brain heart infusion blood agar sterilized by filtration and heat on the growth of Neisseria gonorrhoeae

The growth of Neisseria gonorrhoeae on brain heart infusion blood agar in which the base was sterilized by filtration has been compared with growth on the same medium sterilized by heat. Colonies were larger on the unheated medium, and autoclaving at 115 degrees C of 121 degrees C for 15 minutes was accompanied by a progressive decrease in colony size. Viable counts on the three media showed no difference in end points. Colonies on the unheated medium were usually large enough to be easily recognizable after overnight incubation.     

Trafficking of newly synthesized surfactant protein A in isolated rat alveolar type II cells

We examined the synthesis, transport, and localization of surfactant protein A (SP-A) in primary cultures of alveolar type II cells. In type II cells maintained in culture for 6 h, 39% of the SP-A pool detected with an enzyme-linked immunosorbent assay (ELISA) was found in lamellar bodies (LBs). After 24 h in culture, 53% of the cellular SP-A pool was found in LBs. The absolute amount of SP-A in the LB compartment was almost identical at 6 and 24 h of culture. In contrast to the results obtained with ELISA, 35S labeling of newly synthesized SP-A revealed that less than 7% of the cellular SP-A pool was in LBs at either 6 or 24 h of culture. In the 6-h cultures, 17% of the total (i.e., cells and media) [35S]SP-A pool was extracellular. In the 24-h cultures, 70% of the [35S]SP-A pool was extracellular. The secretion of [35S]SP-A was blocked by brefeldin A at all times. When medium containing newly secreted [35S]SP-A was incubated with alveolar type II cells maintained in culture for 24 h, the protein was taken up and incorporated into the LB fraction. More than 80% of the internalized SP-A was associated with the LB compartment after a 6 h incubation. The uptake of [35S]SP-A was blocked at 4 degrees C and was promoted by addition of unlabeled SP-A at 37 degrees C. These findings support a pathway of extracellular routing of SP-A prior to its accumulation in LBs in cultured type II cells.     

The dual coated pit pathway hypothesis: vertebrate cells have both ancient and modern coated pit pathways for receptor mediated endocytosis

The SimPlate Total Plate Count (TPC) test, developed by IDEXX Laboratories, Inc., detects and quantitates total bacterial concentration in food after 24 h of incubation. The performance of SimPlate TPC was compared with that of the plate count agar (PCA) method for enumerating total bacterial concentration of 255 food samples representing 15 different food matrixes. Total bacterial counts on SimPlate TPC were measured after 24 h of incubation and plotted against values obtained from PCA after 48 h. Simple regression analysis of the data showed strong correlation between the methods (r = 0.95); the sensitivity of SimPlate TPC for foodborne bacteria was 96% relative to PCA (slope = 0.96). It was concluded that SimPlate TPC is a suitable alternative for the detection and quantitation of foodborne bacteria. The method has been granted Performance Tested Certification by the AOAC Research Institute.     

Phospholipid molecular species distribution of Porphyromonas asaccharolytica ATCC 25260T: effects of temperature, culture age and pH

The aim of this study was to determine the extent to which phospholipid molecular species profiles are affected by different environmental factors in Porphyromonas asaccharolytica ATCC 25260T. Phospholipids were analysed by Fast Atom Bombardment Mass Spectrometry (FAB-MS) in negative-ion mode. Under standard growth conditions (37 degrees C, pH 7.0, 48 h), the most intense high mass anions were m/z 653 and 662. The latter is consistent with the expected presence of PE (30:0). The only changes in profiles were quantitative. These were compared using the Pearson Coefficient of Linear Correlation. The r-values for initial pH comparisons ranged from 0.82 (pH 7.0 vs pH 6.0) to 1.00 (pH 5.0 vs pH 8.0), for incubation period, from 0.86 (48 vs 72 h) to 0.97 (96 vs 168 h), and for temperature, from 0.57 (40 vs 37 degrees C) to 0.96 (37 vs 36 degrees C). Differences were also seen when plates were incubated in anaerobe jars as opposed to an anaerobic work station (r = 0.75). It is concluded that it is essential to standardize growth parameters, and to use an anaerobe jar or an anaerobe work station, but not both.     

In vitro studies on the protoporphyrin uptake and photosensitivity of normal skin fibroblasts and fibroblasts from patients with erythropoietic protoporphyria

Fibroblasts derived from patients with erythropoietic protoporphyria (EPP) are not sensitive to violet light and do not contain an excess of protoporphyrin (PP). Fibroblasts from both normal individuals and patients with EPP can take up very low concentrations of PP from culture medium. Cells grown in PP-containing medium showed a gradually increasing but limited uptake of PP and also an increased sensitivity to light. A sensitive scanning microfluorometric method has made it possible to demonstrate that the PP is mainly localized in the perinuclear granules. After exposure to violet light, cells photosensitized by PP in a culture medium showed increased membrane permeability as well as reduced reproductive capacity. Both of these photodamage effects can be repaired during postirradiation incubation in culture medium at 37 degrees C.     

Comparison of manual and automated cell counts in EDTA preserved synovial fluids. Storage has little influence on the results

OBJECTIVE: To determine the precision and agreement of synovial fluid (SF) cell counts done manually and with automated counters, and to determine the degree of variability of the counts in SF samples, kept in the tubes used for routine white blood cell (WBC) counts--which use liquid EDTA as anticoagulant--at 24 and 48 hours at 4 degrees C, and at room temperature. METHODS: To determine precision, cell counts were repeated 10 times--both manually and by an automated counter--in a SF sample of low, medium, and high cellularity. The variances were calculated to determine the interobserver variation in two manual (M1,M2) and two automated cell counts (C1,C2). The agreement between a manual (M1) and automated counter (C1) results, was analysed by the Bland and Altman method and the difference against the mean of the two methods was plotted. Then, the mean difference between the two methods was estimated and the standard deviation of the difference. To determine the effects of storage, SF samples were kept in a refrigerator at 4 degrees C, and at room temperature; cell counts were done manually (M1) and automatically (C1) at 24 and 48 hours and the changes analysed by the Bland and Altman method. The variances were compared using an F test. RESULTS: (1) Precision. With the manual technique, the coefficients of variation were 27.9%, 14%, and 10.7% when used for counting the SF with low (270), medium (6200), and high cellularities (25,000). With the automated technique the coefficients of variation were 20%, 3.4%, and 2.9% in the same SF samples. In the fluids of medium and high cellularity, the variances of the automated cell counts were significatively lower (F test, p < 0.002) than those of the manual counts. (2) Interobserver variation. The variance between C1 and C2 (25 SF) was significatively lower (F test, p < 0.002) than that of the manual counts (41 SF). (3) Agreement between the two techniques (100 SF). For cellularities above 2000 cells/mm3, the manual method gave results between +10% to -34% of the results obtained by the coulter. For cellularities below 2000 cells/mm3, manual cell counts were between +60 to -1280 cells/mm3 of those obtained by the automated counter. (4) Influence of storage. The coulter counts of SF samples preserved at 4 degrees C showed less variance (F test, p < 0.05) than the manual counts. The worst results were obtained in manual counts of SF samples kept at room temperature; these samples at 48 hours showed a variation between -47% to 42% of the initial results. CONCLUSIONS: Automated cell count of the SF offers advantages: it gives higher precision and consumes less time. The stability of the samples preserved in the EDTA tubes used for routine WBC counts is of additional interest, because if delay cannot be avoided, the results of the WBC counts are still accurate at 24 and even at 48 hours, at least for clinical purposes.     

A novel method of detecting Staphylococcus aureus heterogeneously resistant to vancomycin (hetero-VRSA)

We have developed a new method of detecting clinical S. aureus strains possessing heterogeneous resistance to vancomycin (hetero-VRSA). The method exploits characteristic antagonism between vancomycin and beta-lactam antibiotics against the strain Mu3, a representative hetero-VRSA. The method comprises of the following procedures: 1) overnight culture of bacteria is streaked on brain heart infusion agar containing 4 micrograms/ml of vancomycin, 2) paper discs impregnated with any one of beta-lactam antibiotics are placed onto the plate, and 3) the plate is incubated at 37 degrees C and the cell growth was observed after 24 h and 48 h of incubation. The Mu3 cells were grown only around the beta-lactam discs due to the antagonism between vancomycin and beta-lactam against Mu3 cells. A total of 321 MRSA clinical strains isolated in 1995 and 1996 from 12 medical facilities in Japan were tested with this method. A total of 39 strains (12.1%; 24 h) and 67 strains (20.96%; 48 h) grew around the beta-lactam discs. All the 10 strains (representing 10 facilities), tested with the analysis of resistant subpopulations to vancomycin, showed similar heterogeneous patterns as observed with Mu3. The method was considered as a convenient and rapid substitute for the population analysis, the authentic method for the detection of hetero-VRSA strains.     

Growth and survival of Shigella flexneri in common Bangladeshi foods under various conditions of time and temperature

Survival and growth of Shigella flexneri were assessed in various foods, including boiled rice, lentil soup, milk, cooked beef, cooked fish, mashed potato, mashed brinjal, and raw cucumber. Growth at 25 and 37 degrees C and survival at 5 degrees C were observed by viable counts on MacConkey agar. The organism grew well in all tested foods and growth increased from 10(5) to 10(8) to 10(10) cells per ml or g within 6 to 18 h after inoculation at 25 and 37 degrees C.     

7-OH-DPAT has d-amphetamine-like discriminative stimulus properties

A fluorometric procedure has been developed for detection and estimation of laccase activity in fungal broth cultures. Laccase solution was pretreated with catalase for 1 h at 37 degrees C and pH 5. Homovanillic acid was then added and the reaction mixture incubated for a further hour at 37 degrees C. The fluorescence was then developed by addition of 0.1 M glycine buffer at pH 10. Laccase preparations from Pyricularia oryzae, Coriolus hirsutus and Pycnoporus cinnabarinus catalysed formation of a fluorescent product of HVA but the optimum pH values of enzyme activities varied. The culture fluids of several other fungi also catalysed development of fluorescence in solutions containing HVA. p-Hydroxyphenylacetic acid was a poor substrate for all laccases in vivo except that produced by Perennipora tephropora.     

Identification of mecA-related oxacillin resistance in staphylococci by the E test and the broth microdilution method

A set of 165 strains of different staphylococcal species, 67 Staphylococcus aureus, 71 novobiocin-sensitive coagulase-negative staphylococci (CNS) and 27 novobiocin-resistant CNS was used. The oxacillin and methicillin MICs were recorded after 24 and 42 h of incubation at 35 degrees C and at 30 degrees C. Significantly higher MICs were recorded at 30 degrees C compared with 35 degrees C. While a poor discrimination between mecA-positive and mecA-negative strains was obtained with methicillin, the oxacillin MICs enabled identification of resistant strains under certain conditions. The distribution of MICs differed between the three groups of species. Separation of uninduced mecA-positive (> or = 4.0 mg oxacillin/L) and mecA-negative (< or = 2.0 mg oxacillin/L) strains of S. aureus was only achieved with the E test and after 42 h of incubation. Oxacillin-induction yielded higher MICs for mecA-positive strains of S. aureus, and a separation from mecA-negative strains was achieved with the E test after 24 h and with the broth microdilution method after 42 h. Separation of mecA-positive and mecA-negative strains of novobiocin-sensitive CNS required agar supplemented with 5% blood, incubation of MIC trays and E test for 42 h, and species-specific oxacillin MIC breakpoints (S < or = 0.5 mg/L and R > or = 1.0 mg/L). The mecA-positive and mecA-negative strains of novobiocin-resistant CNS were clearly separated after 24 h of incubation by either method.