Clinical evaluation of the addition of gentamicin to commercially prepared mycological media.

A simple procedure is presented whereby an antibiotic solution can be added to prepared agar media for conversion to a selective medium to isolate fungi. Gentamicin solution was deposited onto slants of a variety of previously prepared agar media, allowed to diffuse overnight, and then the slants were inoculated with clinical specimens. Control media without gentamicin included a cycloheximide-chloramphenicol medium (CC), Sabouraud dextrose agar (SDA), and brain heart infusion agar (BHI). Of 75 specimens originating from the respiratory tract, the fungi isolated were predominantly yeast; 35, 39, and 43 were positive on CC, SDA, and SDA with gentamicin, respectively, incubated at 25 C. At 37 C, 32, 34, and 41 positive cultures were obtained with the same media, respectively. The same specimens, inoculated onto BHI with and without gentamicin, yielded 23 and 39 positive cultures, respectively. Of 90 specimens that were either urine, cutaneous, or mucocutaneous, the predominant flora again were yeasts, although on nine occasions dermatophytes were isolated. Positive cultures, 32, 34, and 41, were obtained with CC, SDA, and SDA containing gentamicin, respectively. Bacterial contamination was significantly reduced by the gentamicin, especially on BHI incubated at 37 C. None of the specimens was positive for systemically pathogenic fungi, other than species of Candida, Torulopsis, and Aspergillus. The effectiveness of varying concentrations of gentamicin was investigated by comparing growth of recently isolated bacteria. Of the bacterial isolates, 33% grew on CC, 16% grew on SDA containing gentamicin, 50 mug/ml, and 3% grew on SDA with a gentamicin concentration at 100 mug/ml. With BHI, 3% grew in the presence of 50 mug of gentamicin/ml and less than 1% grew at 100 mug of gentamicin/ml.     

Performance characteristics of a commercially prepared biphasic blood culture bottle.

A biphasic blood culture bottle (BiPB: GIBCO Laboratories, North Andover, Mass.) with an architectural design that physically separates the agar slant from the broth was compared with a conventional vented monophasic bottle (MPB-A) for use in the routine culture of blood. Both bottles contained tryptic soy broth. Tryptic soy agar was used for the BiPB slant. A third unvented bottle (MPB-N) with Columbia broth was included as part of the blood culture set. Of 3,537 sets collected, 444 were positive; 57 of these 444 sets were positive by virtue of an exclusively positive anaerobic bottle. Both BiPB and MPB-A were positive in 235 of the remaining 387 positive sets. A total of 521 isolates was recovered during the study. Of these isolates, 252 were recovered in both the BiPB and the MPB-A from the same set; 105 isolates grew in the BIPB but not in MPB-A, 95 isolates grew only in the MPB-A but not in BiPB, and 69 grew exclusively in the MPB-N. The BiPB allowed more rapid recovery of Candida spp., J-K diphtheroids, Pseudomonas spp. Making BiPB subcultures was easy enough to permit both early and daily subculture, which provided isolated colonies sooner than could be done by using the MPB-A. Isolated colonies and, therefore, identification and susceptibility results were available at least 1 day earlier for the BiPB isolates in approximately 50% of instances when both the BiPB and the MPB-A were positive. Staphylococcus epidermidis and streptococci were recovered more frequently in the BiPB, while gram-positive anaerobes were detected at a significantly (P less than 0.025) more frequent rate in the MPB-A than in the BiPB. Either bottle, however, should be used in conjunction with an anaerobic bottle for optimal recovery of anaerobic bacteria.     

Imipenem susceptibility testing with a commercially prepared dry-format microdilution tray.

MICs of imipenem, concurrently generated in commercially prepared microdilution trays containing predried antibiotic dilutions (Sensititre), and in a standard agar dilution assay (as recommended by the National Committee for Clinical Laboratory Standards, Villanova, Pa.), were within +/- 1 twofold dilution for 94% of 226 bacterial isolates. Imipenem biological activity remained stable over 5 months of tray storage at room temperature against Pseudomonas aeruginosa ATCC 27853. Activity of imipenem was shown by microdilution testing with 890 clinical isolates to be high, with only 4% of isolates having MICs of greater than or equal to 16 micrograms/ml (in vitro resistance).     

Determinants of the ability of general practitioners to detect psychiatric illness.

This study of psychiatric illness among 4098 patients attending 91 general practitioners compares 2 methods of case identification: 'conspicuous morbidity' by the doctor's own assessments, and 'probable prevalence' by the patients' responses to the General Health Questionnaire (GHQ). In general, the latter gives somewhat higher estimates than the former, but there are wide variations in morbidity between practices. The ability of each general practitioner to detect psychiatric illness was measured by computing Spearman's correlation coefficient between his assessments and the GHQ scores of his patients. The mean correlation coefficient was + 0.36, but the range was very wide (0.09-0.60). The first part of the study deals with various demographic characteristics of the patients themselves which are associated with an increased likelihood of the doctor detecting a psychiatric illness; such factors include unemployment, female sex, and marriages which have ended by separation, divorce or death. The second part of the study examines characteristics of the doctors themselves in an attempt to account for the wide variation between them in their ability to detect psychiatric illness. A research psychiatrist made detailed observations on 2098 interviews carried out by 55 general practitioners. Each doctor's verbal and non-verbal styles were recorded minutely, and in addition various global ratings were made. The doctors completed personality inventories and supplied details of training and professional background. It was possible to account for 67% of the variance of correlation coefficient mainly in terms of 2 dimensions: 'interest and concern' and 'conservatism'. The way in which the doctor interviews his patients is shown to be important, but there are interactions between interview style and the doctor's personality.     

Failure of an automated blood culture system to detect nonfermentative gram-negative bacteria

During a 1-year study we observed that both aerobic and anaerobic blood culture bottles from patients were negative by the BacT/Alert system during a 7-day incubation period. However, upon subcultivation of negative bottles, growth of Pseudomonas aeruginosa was detectable. In an attempt to explain this observation, aerobic BacT/Alert Fan bottles were seeded with a defined inoculum (0.5 McFarland standard; 1 ml) of Escherichia coli, Klebsiella pneumoniae, Serratia marcescens, P. aeruginosa, Stenotrophomonas maltophilia, or Acinetobacter baumannii. Half of the inoculated bottles were loaded into the BacT/Alert system immediately, and the remainder were preincubated for 4, 8, 16, and 24 h at 36 degrees C. With preincubation all bottles seeded with the Enterobacteriaceae signaled positive during the next 1.5 h. Organisms in bottles seeded with the nonfermentative species P. aeruginosa and A. baumannii remained undetected by the BacT/Alert system for 7 days. S. maltophilia was detected if the preincubation time was equal or less than 8 h. Without preincubation all bottles seeded with the Enterobacteriaceae or nonfermentative species signaled positive. Since nonfermentative species seem to enter a state of bacteriostasis within the preincubation period, we reasoned that an unknown factor is consumed. Accordingly, a smaller inoculum should allow the detection of nonfermentative species, even after preincubation, and serial dilutions of P. aeruginosa were detected in preincubated bottles. In this case preincubated bottles signaled positive faster than bottles without preincubation. We conclude that all bottles from clinical settings should be subcultured prior to loading to avoid false negatives. An alternative may be preincubation at room temperature.     

Application of a forced-choice memory procedure designed to detect experimental malingering.

The detection of dissimulated cognitive deficits is an important issue in many clinical assessment situations. Specific procedures designed to aid in this detection can be useful additions to standard assessment protocols. The present study investigates the potential utility of a modification of the forced-choice, symptom validity paradigm to the assessment of memory deficits. Previous research indicated that the procedure could discriminate between college students instructed to malinger memory impairment and college students instructed to perform at their best ability. The present study administered a forced-choice memory assessment instrument to 60 psychiatric patients, 60 normal community volunteers, and 60 neuropsychological patients. Thirty psychiatric patients and 30 community volunteers were given instructions to malinger. Discriminant function analyses yielded an overall correct group classification rate of 90.6%, with 5% of the nonmalingering subjects and 18.3% of the experimental malingerers incorrectly classified.     

Development of the ability to detect visual motion in infant macaque monkeys.

A preferential looking technique was used to measure detection of visual motion by 12 infant macaque monkeys (10 Macaca fuscata and 2 Macaca mulatta at ages between 1 and 100 days). A 0.25 cycles/deg square-wave grating was presented at speeds from 40 to 0.4 deg/s. The threshold was determined by a two-alternative forced-choice preferential looking method, in conjunction with a staircase procedure. The threshold for detection of visual motion decreased exponentially with age over the first 100 days of life. At each age there was substantial variability among the individual infants tested, but each monkey's ability to detect visual motion improved with age.     

Use of commercially available rapid chloramphenicol acetyltransferase test to detect resistance in Salmonella species.

Chloramphenicol resistance among Salmonella spp. has important public health and clinical implications, especially in areas of the world where these strains are endemic. The availability of rapid and sensitive screening methods for detection of antibiotic resistance is important. Therefore, we tested 33 strains of Salmonella for chloramphenicol acetyltransferase (CAT) activity using two rapid techniques. Evaluation of a 1-h tube method and a 30-min commercial disk procedure demonstrated that they are as accurate as standardized susceptibility techniques. Both the 1-h tube and 30-min disk methods detected CAT enzymatic activity produced by one CAT gene copy per cell.     

Porous hydroxyapatite ceramics and their ability to be fixed by commercially available screws.

We developed porous hydroxyapatite ceramics (HAP) which are screw fixable and evaluated the fixing abilities of commercially available screws using pull-out tests with the HAP implants. The fixing abilities were higher in the following order: Leibinger micro PLUS titanium screw > Osteomed M3 titanium screw > Leibinger standard mini screw > Martin-drill free screw. In preliminary examinations, the fixing ability of each of the screws differed according to the hole diameter and depth of insertion but if inserted under optimum conditions, all were deemed to have adequate fixing ability for clinical applications. Therefore, screw systems are superior for fixing HAP implants to surrounding bone than the use of thread or wire. Specifically, Leibinger's micro PLUS titanium screws system seems to be a good option currently. The fact that effective fixation was achieved should result in a further increase in the clinical use of synthetic porous HAP implants whose porosity and pore size are completely controlled for those purposes.     

Link between the ability to detect and manage emotional disorders: a study of general practitioner trainees.

Independent ratings were made of videotaped consultations involving six general practice vocational trainees, of whom three were poor identifiers and three were able identifiers of emotional illness. Taped consultations were selected so that each trainee was rated interviewing five patients with low general health questionnaire scores, and five patients with high scores. It was found that able identifiers of emotional illness were more likely than poor identifiers to offer patients information, advice and treatment relevant to their illness, and that they did so in a manner likely to maximize patient satisfaction and cooperation. This was true for both distressed and non-distressed patients. It is argued that both the ability to identify emotional disturbances and the ability to manage emotional illness are characteristics of a generally superior interview style. This may reflect a common variable: the possession of good communication skills.     

Behaviour of commercially prepared I-125 fibrinogen in metabolic studies.

In-vivo studies of fibrinogen metabolism were carried out using an I-120 labelled preparation of fibrinogen supplied commercially by the Radiochemical Centre, Amerhsham for use in the diagnosis of deep venous thrombosis. These studies show that the material is suitable for obtaining the main metabolic parameters of clinical interest, though degradation products may be present initially or appear during storage. If suitable corrections are applied the results agree well with those of other authors.     

The ability of the mouse lymphoma TK assay to detect aneugens

There is some evidence that the mouse lymphoma TK assay (MLA) can detect aneugens, and this is accepted in the current International Conference on Harmonisation guidance for testing pharmaceuticals. However, whether or not it can be used as a reliable screen for aneugenicity has been the subject of debate. Consequently, aneugens with diverse mechanisms of action were tested in the MLA using 24-h exposure. No evidence of increased mutant frequency was seen with noscapine, diazepam or colchicine and increases were seen with taxol, carbendazim, econazole and chloral hydrate only at high levels of toxicity (for all but one taxol concentration survival reduced to ≤10% of control). None of these agents would be unequivocally classified as positive using currently accepted criteria. The largest increases in mutant number were seen with taxol and carbendazim; therefore, trifluorothymidine (TFT)-resistant clones resulting from treatment with them were cultured and analysed for chromosome 11 copy number using fluorescent in situ hybridisation (FISH) and loss of heterozygosity (LOH). High concentrations of these aneugens induced LOH at all loci examined indicating only one chromosome 11 was present but, perhaps surprisingly, all were found to have two copies of chromosome 11 using FISH. This would be consistent with loss of the tk(+) chromosome 11b with concomitant duplication of chromosome 11a, which has been proposed as a likely mechanism for induction of TFT-resistant clones. However, it was also surprising that analysis of centromere size showed that almost all the clones had both small and large centromeres, i.e. suggesting the presence of both chromosomes 11a and 11b. In conclusion, it appears that the TFT-resistant mutants resulting from treatment with toxic concentrations of some aneugens such as taxol and carbendazim have undergone complex genetic changes. However, these data show that the MLA cannot be used as a routine screen to detect aneugens.     

A comparison of the ability of beta-galactosidase and horseradish peroxidase enzyme-antibody conjugates to detect specific antibodies.

The ability of two different enzyme-antibody conjugates to detect specific antibodies has been compared. beta-Galactosidase was conjugated to antibodies raised against rabbit Fc fragments using m-maleimidobenzoyl-N-hydroxysuccinimide ester (MBS). Horseradish peroxidase (HRP) was conjugated to part of the same batch of antibodies using the periodate method. The beta-galactosidase and HRP labels enabled detection of approximately 8 fmoles and 4 fmoles respectively of human growth hormone (HGH) antibodies, when their enzyme activities were measured spectrophotometrically. The detection limit of the beta-galactosidase label was increased 4-fold when a fluorimetric detection system was employed.     

Chromogenic cephalosporin spot test to detect beta-lactamase in clinically significant bacteria.

lactamase production. Reacteroides melaniongenicus, 14     

Monoclonal antibodies to detect human tumours: an experimental approach.

The use of monoclonal antibodies which can be raised to antigens of choice offers a selective and specific approach for the detection of tumours both in vivo and at a cellular level in biopsy specimens. We demonstrate that a monoclonal antibody raised to human teratoma will localise in a teratoma, growing as a xenograft in immune-suppressed mice.     

Effects of bovine serum albumin on the ability of Barbour-Stoenner-Kelly medium to detect Borrelia burgdorferi.

The ability of decreasing inocula of Borrelia burgdorferi to grow in otherwise identical Barbour-Stoenner-Kelly (BSK) media containing different lots of bovine serum albumin (fraction V) was determined. These media differed significantly in ability to detect B. burgdorferi. Some BSK media required inocula of 2 x 10(5) organisms per ml for detection, while other media could stimulate growth after inoculation with less than 2 organisms per ml. In addition, organisms from the less sensitive BSK media were thinner, longer, and less tightly coiled. The endpoint dilutions of indirect fluorescent-antibody titers, especially immunoglobulin M, exhibited up to 16-fold decreases, and both immunoglobulin G and M titers were more difficult to interpret with diagnostic slides prepared from some longer, thinner B. burgdorferi. These results demonstrate that, when performing laboratory investigations which rely on B. burgdorferi, it is essential that the quality of the BSK medium be determined.     

Concurrent comparability of automated systems and commercially prepared microdilution trays for susceptibility testing.

Susceptibility test results from 100 clinical isolates, using the AMS, MS-2, Autobac MTS, Micro-Media system, and Sensititre, were compared with results from the proposed National Committee for Clinical Laboratory Standards reference microdilution method for minimum inhibitory concentrations and with Bauer-Kirby results. Isolates were tested concurrently by each method on consecutive days to obtain duplicate results. The data were computer analyzed, using National Committee for Clinical Laboratory Standards guidelines for break point interpretation. Analysis was centered on drug-organism combinations and not on overall percent correlation. Data were analyzed for comparability to the reference methods and for reproducibility within each system. Commercial system results were very reproducible. Results from 4- to 8-h tests (AMS, MS-2, MTS) gave more very major discrepancies when compared with either reference method than did results from 15- to 18-h systems (Micro-Media, Sensititre).     

Use of the spiral Salmonella assay to detect the mutagenicity of complex environmental mixtures

The success demonstrated by the spiral Salmonella assay in a recent study of 20 pure prompted us to examine the effectiveness of this automated bacterial mutagenicity assay for testing complex environmental mixtures. Three sets of combustion emissions were selected for evaluation: automotive diesel exhaust, woodsmoke, and a coal combustion emission. Each sample was tested in the Salmonella mutagenicity assay according to standard protocol (plate incorporation) and spiral assay techniques. In the spiral assay, a specialized plating instrument dispenses the bacteria, test agent, and S9 mix in a spiral pattern onto a minimal agar plate supplemented with histidine and biotin. The components of the assay are administered in such a way that a uniform density of bacteria is exposed to a concentration gradient of the test agent on a single plate. When results are analyzed, a dose-response curve comprised of 13 data points is generated. A comparison of results from the two assays demonstrated the following: 1) Diesel exhaust was generally the most mutagenically potent sample in both assays, followed closely by the coal combustion emission. The woodsmoke sample was only weakly mutagenic in the standard assay but demonstrated higher mutagenic activity in the spiral assay. 2) Samples were more mutagenic on rev/microgram basis in the spiral assay, especially when metabolic activation was added. This disparity presumably was due to differences in the relative amounts of S9 administered across the dose range. 3) The spiral assay required 1/20 the sample mass of the standard assay to test equivalent doses; in addition, for some samples, 50 times more sample mass was required by the standard assay to generate a comparable dose response. 4) Dichloromethane extracts of the complex mixtures could be tested for mutagenicity in the spiral assay, thereby precluding solvent exchange (to dimethylsulfoxide) required by the standard assay for sample/bioassay compatibility.