Corneal subepithelial nodular scarring treated with phototherapeutic keratectomy in a child with Rothmund-Thomson syndrome.

PURPOSE: To report the use of excimer laser phototherapeutic keratectomy (PTK) in the treatment of corneal subepithelial nodular scarring in a child with Rothmund-Thomson syndrome (RTS), a form of ectodermal dysplasia. METHODS: A case report and review of the literature. RESULTS: Excimer laser PTK successfully treated the recurrent anterior stromal fibrosis and irregular astigmatism, facilitating visual development. The use of excimer laser PTK prevented the development of dense amblyopia in this child. CONCLUSION: This case demonstrates an indication for excimer laser PTK in the pediatric population.

Dextromethorphan- and pseudoephedrine-induced agitated psychosis and ataxia: case report.

Pseudoephedrine and dextromethorphan are therapeutic constituents of numerous commonly used, over-the-counter cough and cold preparations. Although this drug combination is generally considered quite safe if utilized in recommended doses, overmedication or overdose can result in serious neurologic and cardiovascular abnormalities that occasionally can be life-threatening. We present a case of a 2-year-old child who developed hyperirritability, psychosis, and ataxia after being overmedicated with a pseudoephedrine/dextromethorphan combination cough preparation, and discuss probable mechanisms of toxicity and risk factors for adverse events.

Photorefractive keratectomy versus laser in situ keratomileusis for moderate to high myopia. A randomized prospective study.

OBJECTIVE: This report presents the results of a randomized clinical trial of photorefractive keratectomy (PRK) and laser-assisted in situ keratomileusis (LASIK). DESIGN: A randomized, prospective multicenter clinical trial. PARTICIPANTS: A total of 220 eyes of 220 patients entered the study cohort: 105 randomized to PRK and 115 to LASIK. The mean preoperative manifest refraction spherical equivalent was -9.23 diopters (D) in the PRK group and -9.30 D in the LASIK group. INTERVENTION: All patients received a one-pass, multizone excimer laser ablation as part of either a PRK or LASIK procedure using the Summit Apex excimer laser. Attempted corrections ranged from 6.00 to 15.00 D. MAIN OUTCOME MEASURES: Data on uncorrected and spectacle-corrected visual acuity, predictability,and stability of refraction, corneal haze, and flap complications were analyzed. Patients were observed for up to 6 months. RESULTS: One day after surgery, 0 (0.0%) and 3 (4.5%) eyes in the PRK group saw 20/20 and 20/40 or better uncorrected, respectively, while 7 (10%) and 48 (68.6%) eyes in the LASIK group saw 20/20 and 20/40 or better, respectively. At 6 months after PRK, 13 (19.1%) and 45 (66.2%) eyes saw 20/20 and 20/40 or better, respectively, while after LASIK, 16 (26.2%) and 34 (55.7%) eyes saw 20/20 and 20/40 or better, respectively (odds ratio = 0.56 for likelihood of uncorrected visual acuity < 20/40 for PRK vs. LASIK, 95% confidence interval [CI] = 0.31-1.19). After PRK, 39 eyes (57.4%) were within 1.0 D of attempted correction compared with 24 eyes (40.7%) in the LASIK group (odds ratio = 0.50 for likelihood fo undercorrection 1.0 D for PRK vs. LASIK, 95% CI = 0.24-1.04); however, the standard deviation of the predictability was similar between groups: 1.01 D for PRK and 1.22 D for LASIK. From months 1 to 6, there was an average regression of 0.89 D in the PRK group and 0.55 D in the LASIK group. After PRK, eight eyes (11.8%) had a decrease in spectacle-corrected visual acuity of two Snellen lines or more; after LASIK, two eyes (3.2%) had a decrease of two lines or more (odds ratio = 3.89 for risk of loss of spectacle-corrected visual acuity for PRK vs. LASIK, 95% CI = 0.71-21.30). Only two eyes had postoperative spectacle-corrected visual acuity less than 20/32, however. CONCLUSIONS: Although improvement in uncorrected visual acuity is more rapid in LASIK than in PRK, efficacy outcomes in the longer term generally are similar between the two procedures. There is a greater tendency toward undercorrection in LASIK eyes using the specific laser and nomogram in this study, but the scatter in achieved versus attempted correction is similar, suggesting little difference in the accuracy of the two procedures. A suggestion of decreased propensity for loss of spectacle-corrected visual acuity in LASIK eyes requires further investigation.

Corneal endothelial changes after divide and conquer versus chip and flip phacoemulsification.

PURPOSE: To evaluate changes in central corneal endothelial cells and corneal thickness after divide and conquer phacoemulsification and chip and flip phacoemulsification. SETTING: Houston Eye Clinic, Houston, Texas, USA. METHODS: Forty-four eyes were randomly assigned to one of two groups to have divide and conquer (D/C Group) or chip and flip (C/F Group) phacoemulsification with implantation of a posterior chamber, foldable, silicone intraocular lens performed by one surgeon. Of these, 41 eyes of 37 patients (22 D/C Group, 19 C/F Group) met the inclusion criteria. All surgeries were uneventful. A complete eye examination including specular microscopy and pachymetry was performed preoperatively and 1 week and 1 and 3 months postoperatively. RESULTS: There were no significant between-group differences in any of the following means: sex; age; time at 70% phaco power; total phacoemulsification time. No correlation was found between ultrasound time and increased corneal thickness except for a significant increase in percentage of hexagonal cells in the C/F Group at 1 month. The only statistically significant between-group differences were greater endothelial cell loss in the C/F Group at 1 month and the percentage change in hexagonal cells at 1 week (1.1% increase, D/C Group; 10.7% decrease, C/F Group). CONCLUSION: The divide and conquer technique led to less endothelial loss and hexagonal cell change than the chip and flip technique, although at 3 months the differences were not significant.

Pyrolysis mass spectrometry studies on Bacillus anthracis, Bacillus cereus and their close relatives.

Pyrolysis mass spectrometry was used to examine strains of B. anthracis, of B. cereus, of B.cereus either proven to cause emetic illness or connected with outbreaks of emetic food poisoning and of B.thuringiensis. Analysis of the data-set for all strains allowed differentiation between B.anthracis, the emetic B.cereus and B.thuringiensis but B.cereus strains could not be clearly discriminated. Removal of data for the B.thuringiensis and the emetic B.cereus strains, followed by re-analysis, allowed clear separation of the B. anthracis and B. cereus groups. Furthermore, PyMS was found to be capable of discriminating between some strains of B.anthracis, and demonstrating sub-groupings of others. This work provides further evidence of the ability of PyMS to distinguish rapidly between very closely related organisms and indicates its potential in epidemiology.

A polyphasic reassessment of the genus Paenibacillus, reclassification of Bacillus lautus (Nakamura 1984) as Paenibacillus lautus comb. nov. and of Bacillus peoriae (Montefusco et al. 1993) as Paenibacillus peoriae comb. nov., and emended descriptions of P. lautus and of P. peoriae.

Seventy-seven strains representing 10 species in the Paenibacillus polymyxa 16S rRNA group and 3 other species that exhibit phenetic relatedness to members of this group, Bacillus lautus, "Bacillus longisporus," and Bacillus peoriae, were characterized genotypically and phenotypically by performing an amplified ribosomal DNA restriction analysis, a randomly amplified polymorphic DNA analysis, a fatty acid methyl ester analysis, sodium dodecyl sulfate-polyacrylamide gel electrophoresis of whole-cell proteins, pyrolysis mass spectrometry, and API and other routine phenotypic tests. These analyses revealed distinct clusters representing Paenibacillus alvei, Paenibacillus amylolyticus, Paenibacillus azotofixans, Paenibacillus durum, Paenibacillus larvae subsp. larvae, Paenibacillus larvae subsp. pulvifaciens, B. lautus, Paenibacillus macerans, Paenibacillus macquariensis, B. peoriae, P. polymyxa, and Paenibacillus validus, which confirmed the distinctness of these species, but appreciable within-species heterogeneity was observed in P. alvei, B. lautus, P. macerans, P. polymyxa, and P. validus. The type strain of Paenibacillus pabuli did not cluster with other strains of this species, and in several analyses a relationship between strains of P. pabuli and "B. longisporus" was observed. As the analyses showed that B. lautus and B. peoriae are closely related to the genus Paenibacillus, these species are reclassified as members of this genus.

Reclassification of Paenibacillus (formerly Bacillus) pulvifaciens (Nakamura 1984) Ash et al. 1994, a later subjective synonym of Paenibacillus (formerly Bacillus) larvae (White 1906) Ash et al. 1994, as a subspecies of P. larvae, with emended descriptions of P. larvae as P. larvae subsp. larvae and P. larvae subsp. pulvifaciens.

A polyphasic taxonomic study of four strains of Paenibacillus larvae and four strains of Paenibacillus pulvifaciens (including duplicates of both type strains) supported the reclassification of both former Bacillus species into one species, P. larvae. Our conclusions were based on morphological and Analytab Products (API) tests, sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) of whole-cell proteins, gas chromatography of methylated fatty acids, pyrolysis mass spectrometry, DNA-DNA binding, and the following genomic fingerprinting methods: amplified ribosomal DNA restriction analysis, random amplified polymorphic DNA analysis, and AFLP analysis. The last method is a novel high-resolution DNA fingerprinting technique based on the selective amplification of restriction fragments. Despite more than 90% DNA relatedness between the strains studied, SDS-PAGE of whole-cell proteins, biochemical tests, and DNA fingerprinting (AFLP) distinguished between the P. larvae and P. pulvifaciens strains at the subspecies level. Taking this evidence along with differences in pathogenicity, we propose to reclassify the honeybee pathogens P. larvae and P. pulvifaciens as P. larvae subsp. larvae and P. larvae subsp. pulvifaciens. An emended description of the species and descriptions of the subspecies are given. The type strains are P. larvae subsp. larvae ATCC 9545 (LMG 9820) and P. larvae subsp. pulvifaciens NRRL B-3685 (LMG 6911 and ATCC 13537).

The effect of redeepening incisions on radial keratotomy outcome.

BACKGROUND: Patients scheduled to undergo radial keratotomy in both eyes received redeepening incisions in one eye and single pass incisions in the other. Eye and order of surgery were assigned randomly and surgical parameters were otherwise identical in the two eyes. METHODS: This study was designed to measured the improvements in myopia obtained by radial keratotomy, with and without redeepening incisions. RESULTS: There was a greater decrease in spherical equivalent manifest refraction in the redeepening group than in the control group at 1 week (0.41 D) and 1 month (0.36 D) after surgery, as measured by keratometry. The difference in change between groups was 0.41 D at one week, 0.36 D at 1 month, and 0.26 D at 3 months. Change in spherical equivalent was significantly more in the redeepened group at 3 months after surgery (0.37 D); however, the improvement constituted only 8.8 percent of the decrease in myopia achieved by radial keratotomy without redeepening (3.87 D). CONCLUSIONS: Although redeepening yields an incremental effect in the correction of myopia, the technical difficulties of redeepening and the increased chance of perforation of the cornea with redeepening outweigh the benefits of the procedure.

Paenibacillus (formerly Bacillus) gordonae (Pichinoty et al. 1986) Ash et al. 1994 is a later subjective synonym of Paenibacillus (formerly Bacillus) validus (Nakamura 1984) Ash et al. 1994: emended description of P. validus.

A polyphasic study in which we performed an amplified ribosomal DNA restriction analysis, sodium dodecyl sulfate-polyacrylamide gel electrophoresis of whole-cell proteins, a gas chromatographic analysis of methylated fatty acids, pyrolysis mass spectrometry, a random amplified polymorphic DNA analysis, a phenotypic analysis, and an analysis of the levels of DNA binding of Paenibacillus gordonae and Paenibacillus validus strains (including both type strains) showed that these organisms form a homogeneous group and that the names P. gordonae and P. validus are therefore synonyms. P. validus has nomenclatural priority, and an emended description of this species is given; the type strain is strain LMG 11161 (= ATCC 43897).

Effect of incision direction on radial keratotomy outcome.

The goal of maximizing radial keratotomy results by using optical-zone-directed (centrally directed) incisions rather than limbus-directed (peripherally directed) incisions is evaluated in this prospective study. Five patients had bilateral radial keratotomy, with optical-zone-directed incisions in one eye and limbus-directed incisions in the other. The order of surgery and eye was randomly assigned. Patients were evaluated preoperatively, at one week, and at one month. There were no significant differences preoperatively between the two groups of eyes in spherical equivalent or keratometry. At one week postoperatively, however, there were significant group differences in spherical equivalent changes (P less than .010). Eyes with limbus-directed incisions were -2.2 diopters (D) myopic, on average, while eyes with optical-zone-directed incisions were near emmetropic, with a mean spherical equivalent of 0.10 D. Because of these results, we stopped randomizing cases at this point. The difference in surgical effect was still significant at three months (P less than .01); eyes with limbus-directed incisions had an average of 3.5 D less surgical effect than eyes with optical-zone-directed incisions.

Characterization of exopolymers of aquatic bacteria by pyrolysis-mass spectrometry.

Exopolymers from a diverse collection of marine and freshwater bacteria were characterized by pyrolysis-mass spectrometry (Py-MS). Py-MS provides spectra of pyrolysis fragments that are characteristic of the original material. Analysis of the spectra by multivariate statistical techniques (principal component and canonical variate analysis) separated these exopolymers into distinct groups. Py-MS clearly distinguished characteristic fragments, which may be derived from components responsible for functional differences between polymers. The importance of these distinctions and the relevance of pyrolysis information to exopolysaccharide function in aquatic bacteria is discussed.

Detection of small genotypic changes in Escherichia coli by pyrolysis mass spectrometry.

Pyrolysis mass spectrometry (Py-MS) has been used to discriminate between four very closely related strains of Escherichia coli; a parent strain UB5021 and three derivatives each containing one of the antibiotic resistance plasmids, pBR322, pACYC184 or R388.

Reproducibility of pyrolysis mass spectrometry: effect of growth medium and instrument stability on the differentiation of selected Bacillus species.

The discrimination of a set of 53 strains, taken from four closely related Bacillus species (Bacillus subtilis, B. pumilus, B. licheniformis and B. amyloliquefaciens), was examined using pyrolysis mass spectrometry. Strains were grown on six different media to examine the effect of media variation, especially batch-to-batch variation of a single medium, on the pyrolysis mass spectra and strain discrimination achieved. Long-term reproducibility over a period of 14 months was also examined. It was shown that batch-to-batch media variation is insufficient to affect spectra and strain discrimination significantly, but different media types do affect this. It was shown that species groups could still be recovered from the data, however, with an appropriate data-handling system. It was not possible to directly compare spectra produced 14 months apart, but the strain and species discrimination achieved using each data-set were highly comparable.

Identification of Bacillus anthracis by API tests.

API and morphological tests were examined for their ability to distinguish between 37 Bacillus anthracis strains (virulent and avirulent) and 194 strains of closely related Bacillus species (B. cereus, B. mycoides and B. thuringiensis). In addition, 34 strains of B. anthracis and four of B. cereus were tested by several other methods that included capsule formation, ability to grow on a selective medium, and sensitivity to phage. It was found that virulent strains of B. anthracis were easily separated from the closely related Bacillus species by most of the test methods; but separation of slightly virulent and avirulent strains of B. anthracis from the closely related species could be done only by API and phage-sensitivity tests.

Microcomputer assisted identification of Bacillus species.

A microcomputer based system for the identification of unknown isolates of Bacillus species is described. The identification matrix includes 78 test probabilities for 38 recognised species and other groups in the genus Bacillus and it is based on the work of Logan and Berkeley (1984). Morphological characters together with the results of tests using API 20E and API 50CHB, read after 24 and 48 h incubation, are used to obtain a probabilistic identification of an unknown aerobic endospore forming rod. Any differences between the observed and expected results for any identified organism are listed. Identification can be attempted on the basis of a limited set of test results, although this is rarely if ever done with this largely API based system, and if the unknown cannot be successfully identified then a set of additional tests can be selected which should permit identification. The computer system can store and recall test results entered for any isolate. This feature allows the accumulation of data on isolates which could be used to update the identification matrix in future taxonomic studies.

Identification of Bacillus strains using the API system.

A system is described for the rapid and accurate identification of Bacillus isolates using a matrix of results from tests in the API 20E and API 50CHB strips and from supplementary tests. API System tests have been shown to be more reproducible than the classical tests. A taxonomy based upon API tests is in good agreement with those obtained by other methods. The results matrix can also be used in computer assisted identification.

Curie-point pyrolysis mass spectrometry applied to characterization and identification of selected Bacillus species.

The use of pyrolysis mass spectrometry in the characterization and identification of Bacillus species was studied. Fifty-three strains of four closely related groups, Bacillus subtilis, B. pumilus, B. licheniformis and 'B. amyloliquefaciens', were used in a study of both sporulated and nonsporulated cultures. Pyrolysis was carried out using a Pyromass 8-80, a novel pyrolysis mass spectrometer specifically designed for fingerprinting complex samples. The pyrolysis data obtained were analysed using multivariate statistical techniques. All four groups could be differentiated using data from non-sporulated cultures but the data from sporulated cultures did not separate B. subtilis from 'B. amyloliquefaciens' or B. pumilus. In contrast, B. licheniformis was more clearly differentiated from the other three species using these data. Culture maturity affected the mass spectra obtained from non-sporulated cultures.

The influence of ionic strength, pH and a protein layer on the interaction between Streptococcus mutans and glass surfaces.

The initial interaction between Streptococcus mutans and hard surfaces has been investigated using a rotating disc technique. The deposition to clean and BSA-coated glass of two strains of S. mutans, FA-1 (serotype b) and KPSK2 (serotype c), which exhibit different surface properties, was studied. Organisms were harvested from cultures grown in a chemostat at a dilution rate of 0.06 h-1 and suspended in NaCl solutions of defined ionic strengths and pH values. The deposition of both strains showed a strong dependence on electrolyte concentration, particularly at low ionic strengths, which was inversely related to the zeta potentials of the organisms. Similarly, the ionic strength at which maximum deposition was first noted (critical coagulation concentration) for the two strains correlated with their relative potentials. Deposition was insensitive to changes in pH at an electrolyte concentration of 0.05 M. The maximum observed deposition did not approach values predicted by theory, suggesting that a further barrier to deposition, other than electrostatic repulsion, might exist. Under all experimental conditions, some of the deposited bacteria were observed to be oscillating, suggesting that they were held at a distance from the collector surface. The cells did not, however, appear to be deposited in a secondary minimum predicted by DLVO theory hence it may be that long-range polymer interactions are also involved in the deposition of these organisms.