Showing papers on "Typing published in 1994"

Comparison of traditional and molecular methods of typing isolates of Staphylococcus aureus.

Abstract: Fifty-nine Staphylococcus aureus isolates and 1 isolate of Staphylococcus intermedius were typed by investigators at eight institutions by using either antibiograms, bacteriophage typing, biotyping, immunoblotting, insertion sequence typing with IS257/431, multilocus enzyme electrophoresis, restriction analysis of plasmid DNA, pulsed-field or field inversion gel electrophoresis, restriction analysis of PCR-amplified coagulase gene sequences, restriction fragment length polymorphism typing by using four staphylococcal genes as probes, or ribotyping. Isolates from four well-characterized outbreaks (n = 29) and a collection of organisms from two nursing homes were mixed with epidemiologically unrelated stock strains from the Centers for Disease Control and Prevention. Several isolates were included multiple times either within or between the sets of isolates to analyze the reproducibilities of the typing systems. Overall, the DNA-based techniques and immunoblotting were most effective in grouping outbreak-related strains, recognizing 27 to 29 of the 29 outbreak-related strains; however, they also tended to include 3 to 8 epidemiologically unrelated isolates in the same strain type. Restriction fragment length polymorphism methods with mec gene-associated loci were less useful than other techniques for typing oxacillin-susceptible isolates. Phage typing, plasmid DNA restriction analysis, and antibiogram analysis, the techniques most readily available to clinical laboratories, identified 23 to 26 of 29 outbreak-related isolates and assigned 0 to 6 unrelated isolates to outbreak strain types. No single technique was clearly superior to the others; however, biotyping, because it produced so many subtypes, did not effectively group outbreak-related strains of S. aureus.

PCR for capsular typing of Haemophilus influenzae.

Abstract: A PCR method for the unequivocal assignment of Haemophilus influenzae capsular type (types a to f) was developed. PCR primers were designed from capsule type-specific DNA sequences cloned from the capsular gene cluster of each of the six capsular types. PCR product was amplified only from the capsular type for which the primers were designed. Product was confirmed by using either an internal oligonucleotide or restriction endonuclease digestion. A total of 172 H. influenzae strains of known capsular type (determined genetically) comprising all capsular types and noncapsulate strains were tested by PCR capsular typing. In all cases the PCR capsular type corresponded to the capsular genotype determined by restriction fragment length polymorphism analysis of the cap region. When used in conjunction with PCR primers derived from the capsular gene bexA, capsulate, noncapsulate, and capsule-deficient type b mutant strains could be differentiated. PCR capsular typing overcomes the problems of cross-reaction and autoagglutination associated with the serotyping of H. influenzae strains. The rapid and unequivocal capsular typing method that is described will be particularly important for typing invasive H. influenzae strains isolated from recipients of H. influenzae type b vaccine.

Laboratory investigation of a multistate food-borne outbreak of Escherichia coli O157:H7 by using pulsed-field gel electrophoresis and phage typing.

Abstract: Two hundred thirty-three isolates of Escherichia coli O157:H7 were analyzed by both pulsed-field gel electrophoresis (PFGE) and bacteriophage typing All 26 isolates from persons whose illness was associated with a recent multistate outbreak of E coli O157:H7 infections linked to the consumption of undercooked hamburgers and all 27 isolates from incriminated lots of hamburger meat had the same phage type and the same PFGE pattern Twenty-five of 74 E coli O157:H7 isolates from Washington State and 10 of 27 isolates from other states obtained during the 6 months before the outbreak had the same phage type as the outbreak strain, but only 1 isolate had the same PFGE pattern PFGE thus appeared to be a more sensitive method than bacteriophage typing for distinguishing outbreak and non-outbreak-related strains The PFGE patterns of seven preoutbreak sporadic isolates and five sporadic isolates from the outbreak period differed from that of the outbreak strain by a single band, making it difficult to identify these isolates as outbreak or non-outbreak related Phage typing and PFGE with additional enzymes were helpful in resolving this problem While not as sensitive as PFGE, phage typing was helpful in interpreting PFGE data and could have been used as a simple, rapid screen to eliminate the need for performing PFGE on unrelated isolates

Rapid DNA typing for HLA‐C using sequence‐specific primers (PCR‐SSP): Identification of serological and non‐serologically defined HLA‐C alleles including several new alleles

Abstract: Detection of HLA-C antigens by complement mediated cytotoxicity using human alloantisera is often difficult. Between 20 to 40% of individuals in every race have undetectable HLA-C locus antigens and 9 out of the 29 sequenced HLA-C alleles so far published encode serologically undetected antigens. In addition, HLA-C molecules are expressed at the cell surface at about 10% of the levels of HLA-A and HLA-B. Recently, amplification of DNA using sequence-specific primers (PCR-SSP) has proved a reliable and rapid method for typing HLA-DR, HLA-DQA and HLA-DQB genes. PCR-SSP takes two hours to perform and is therefore suitable for the genotyping of cadaveric donors. We have designed a set of primers which will positively identify the HLA-C alleles corresponding to the serologically defined series HLA-Cw1, Cw2, Cw3, Cw4, Cw5, Cw6, Cw7 and Cw8. The serologically undetectable alleles have also been detected in groups according to sequence homology. In addition, three new unsequenced variants have been identified. DNA samples from 56 International Histocompatibility Workshop reference cell lines and 103 control individuals have been typed by the HLA-C PCR-SSP technique. 4/56 cell line types and 11/103 normal control individuals types were discrepant with the reported serological types. All combinations of serologically detectable and most of the serologically blank HLA-C antigens can be readily identified. DNA typing for HLA-Cw by PCR-SSP can take as little as 130 minutes from start to finish, including DNA preparation.

VP4 typing of bovine and porcine group A rotaviruses by PCR.

Abstract: A PCR typing assay was developed to identify rotavirus P types (VP4 specificity) of bovine NCDV, UK, and B223 strains and porcine OSU and Gottfried strains. Thirty-nine human and animal strains representing all known, and some undefined, rotavirus P types were used to develop and evaluate the specificity of the method. No cross-amplification was observed. The PCR results agreed with previous characterizations by monoclonal antibodies, sequence analysis, and hybridization assays, except for the Gottfried strain, which showed a P type distinct from the human asymptomatic strains. Analysis of a small number of field specimens suggested a high level of VP4 polymorphism among porcine strains. The assay should be of value in typing field isolates and tracing interspecies infections.

PCR-based restriction fragment length polymorphism typing of Helicobacter pylori.

Abstract: We applied a molecular typing approach for Helicobacter pylori that uses restriction fragment length polymorphism (RFLP) analyses of an 820-bp PCR-amplified portion of the ureC gene in H. pylori. The PCR products were digested with restriction enzyme HhaI, MboI, or MseI, and the fragments generated were analyzed by agarose electrophoresis. Among 25 independent clinical isolates, each showed a different pattern when a combination of the three RFLP patterns was used. Using this method, we studied isolates from the antrum or the body of the stomach of 14 patients before and after antibiotic therapy. Before treatment, successful isolation of H. pylori from the two sites of the stomach was possible for 12 of the 14 patients. For 10 of these 12 patients, each pair of isolates had identical RFLP profiles. For the other two patients (16.7%), however, isolates from the antrum and the body of the stomach had different RFLP profiles. Treatment was successful for 6 of the 14 patients; of the 8 patients with treatment failures, 5 had identical isolate pairs. In each case, the isolates found posttreatment were the same as the pretreatment isolates. For one of the patients who was colonized with two different isolates pretreatment, one of the isolates was identified at both sites after unsuccessful treatment. We also studied six long-term follow-up patients who had sequential biopsies at intervals of up to 5 months. Each follow-up isolate from each patient had the same RFLP profile as the initial isolate. This typing method provides a reliable and reproducible typing scheme for the study of H. pylori infections and indicates that infection with more than one H. pylori isolate is not rare. Images

Genotyping of hepatitis C virus isolates by a modified polymerase chain reaction assay using type specific primers: epidemiological applications

Abstract: A polymerase chain reaction (PCR)-based assay using primers against the hepatitis C core gene has been described [Okamoto et al. (1992a): Journal of General Virology 73:673-679]. Within the two major HCV genotypes 1 and 2, the Okamoto system identifies two subtypes each (1a, 1b and 2a, 2b, respectively). Typing is achieved by a primary PCR with consensus primers followed by a nested PCR with type specific primers. The original assay was modified by addition of a parallel second PCR identifying the recently described major genotype 3. The assay also identifies in duplicate subtype 1b (type II by Okamoto), suggested to respond poorly to interferon. Reaction conditions were reviewed and melting temperatures of all typing primers equalised to increase strigency. The modified system functioned well and typing results were supported by partial core sequencing. The following distribution of genotypes was found in 53 hepatitis C virus (HCV) infected Swedish blood donors: genotype 1a (57%), 3 (19%), 1b (13%), and 2b (11%). In six recipients of HCV infected blood identified in a retrospective study, the recipient HCV genotype was identical to donor HCV genotype. Furthermore, in HCV positive couples identical genotype was observed when only one partner had an external risk factor; whereas genotypes were often diverse if both sex partners had parenteral risk factors. Finally, a cluster of hepatitis C cases in a haemodialysis unit was evaluated retrospectively. Eight patients had genotype 1b, two had mixed 1a and 1b, and one had type 1a. The modified HCV genotyping assay was of value in examining different epidemiological situations and can be expanded presumably to include future genotypes.

Polymorphism of bovine mhc class ii genes. joint report of the fifth international bovine lymphocyte antigen (bola) workshop, interlaken, switzerland, 1 august 1992

Abstract: SUMMARY Polymorphism of the bovine DRB, DQA, DQB, DYA, DOB and DIB genes was investigated using restriction fragment length polymorphism (RFLP) analysis, isoelectric focusing (IEF), class II serology and polymerase chain reaction (PCR) based typing techniques. The simultaneous application of multiple typing techniques and the characterization of multiple genes resulted in a greatly enhanced picture of the bovine class II regions. Thirty-eight class IIa (DR-DQ) and 5 class lib (DYA-DOB-DIB) haplotypes were defined. It was found that IEF types were associated with DRB3 polymorphism defined by DRB3 PCR-RFLP and DRB3 microsatellite PCR. Serologically defined polymorphism was associated with distinct molecular/IEF motifs and, therefore, DR and DQ specificities could be tentatively distinguished. Although the DR and DQ genes are tightly linked, neither DR nor DQ typing defined all of the class IIa region polymorphism. Furthermore, even the most powerful DRB3 typing technique, DRB3 PCR-RFLP, failed to detect all expressed DRB3 polymorphism. All detected DRB3 polymorphism could, however, be distinguished with a combination of two molecular techniques: DRB3 PCR-RFLP and DRB3 microsatellite PCR. RFLP typing with transmembrane probes detected significantly less polymorphism than typing with cDNA or exon probes. However, the transmembrane probes were useful because they were locus specific. The presence of only 5 of 12 possible class lib haplotypes was unexpected and indicates that the DYA, DOB and DIB genes are tightly linked.

Typing of Pneumocystis carinii strains that infect humans based on nucleotide sequence variations of internal transcribed spacers of rRNA genes.

Abstract: Small portions of the 18S and the 26S rRNA genes, the entire 5.8S rRNA gene, and internal transcribed spacers ITS1 and ITS2 (located between the 18S and 5.8S rRNA genes and between the 5.8S and 26S rRNA genes, respectively) of Pneumocystis carinii that infect humans were cloned and sequenced. The nucleotide sequences of the 18S, 5.8S, and 26S rRNA genes determined in the study were approximately 90% homologous to those of P. carinii that infect rats, while the sequences of ITS1 and ITS2 of P. carinii from the two different hosts were only 60% homologous. The 18S, 5.8S, and 26S rRNA gene sequences of P. carinii from 15 patient specimens were determined and were found to be identical to each other, whereas the ITS sequences were found to be variable. With the observed sequence variation, it was possible to classify the ITS1 sequences into two types and the ITS2 sequences into three types. P. carinii strains that had the same type of ITS1 sequence could have a different type of ITS2 sequence. On the basis of the sequence types of the two ITS regions, P. carinii from the 15 patients were classified into four groups. P. carinii from three patient specimens were found to contain two different ITS sequence patterns. More surprisingly, one additional specimen was found to have one ITS sequence typical of P. carinii isolates that infect humans and another typical of P. carinii isolates that infect rats. The studies indicate that it is possible to type P. carinii strains on the basis from one patient, suggesting that coinfection with more than one strain of P. carinii may occur in the same patient.

Genetic variation in Staphylococcus aureus coagulase genes: potential and limits for use as epidemiological marker.

Abstract: To perform coagulase gene typing, the repeated units encoding hypervariable regions of the Staphylococcus aureus coagulase gene were amplified by the PCR technique; this was followed by AluI restriction enzyme digestion and analysis of restriction fragment length polymorphism (RFLP) patterns. In order to assess the discriminatory power of this typing method, 30 epidemiologically unrelated S. aureus strains which differed by their pulsed-field gel electrophoresis patterns were examined. Although 18 of the 30 strains had unique and unshared AluI RFLP patterns, there were only four observed patterns in the remaining 12 strains. This finding indicated that unrelated strains may share identical AluI RFLP patterns. To elucidate the degree of genetic variation in the C-terminus-encoding loci within the coagulase genes, the PCR products of these 12 strains were subjected to Taq polymerase-mediated sequencing. Sequence analysis confirmed the AluI recognition sites in each of the four RFLP groups and demonstrated that AluI appears to yield the highest RFLP in restriction enzyme analysis. By their DNA sequences the majority of strains sharing common AluI groups could be clearly differentiated from each other and revealed between 93.2 and 98.5% homology. When we determined the nucleotide sequences of two strains after six subcultivations no significant alterations were observed. Because the discriminatory power of the current coagulase gene typing method is not great enough to be used as the sole method to type S. aureus, additional techniques are necessary. Sequence analysis of the repeated unit-encoding region for the typing of S. aureus may be potentially useful as an alternative to other current molecular typing techniques. Images

Monitoring spread of Malassezia infections in a neonatal intensive care unit by PCR-mediated genetic typing.

Abstract: Malassezia furfur and Malassezia pachydermatis were isolated from newborn children and incubators in a neonatal intensive care unit To assess whether persistence or frequent import of the organisms was the cause of the elevated incidence, genetic typing of the strains was performed by PCR-mediated DNA fingerprinting By using PCR primers aimed at repeat consensus motifs, six different genotypes could be detected in a collection of six M furfur reference strains In the case of 10 M pachydermatis reference strains, nine different genotypes were detected by three different PCR assays None of these assays could document genetic differences among the clinical isolates of either M furfur or M pachydermatis On the basis of these results it is concluded that within the neonatal intensive care unit the longitudinal persistence of both an M furfur and an M pachydermatis strain has occurred and that Malassezia species can persist on incubator surfaces for prolonged periods of time It can be concluded that PCR fingerprinting is a Malassezia typing procedure that is to be preferred over the analysis of chromosomal polymorphisms by pulsed-field gel electrophoresis in this genus Images

Comparison of four different methods for epidemiologic typing of Acinetobacter baumannii.

Abstract: A set of 103 epidemiologically well-defined Acinetobacter baumannii isolates obtained from nine hospital outbreaks and 21 unrelated strains were characterized by pulsed-field gel electrophoresis (PFGE) of total genomic DNA digested with ApaI. Among outbreak strains, eight different patterns and five possible variants were identified by PFGE. Results were compared with those from traditional typing methods such as plasmid profile analysis, antimicrobial susceptibility, and biotyping. Plasmid analysis revealed six different and two related patterns; one outbreak strain lacked plasmids. A total of 16 of the 21 unrelated strains harbored plasmids and exhibited unique patterns. Epidemiologically unrelated strains were placed into only two biotypes and had similar antimicrobial susceptibility patterns but were clearly distinguished by PFGE. PFGE of A. baumannii chromosomal DNA yielded reproducible and easily readable results and showed excellent discriminatory power. However, plasmid profile analysis may provide a cost-effective first step in epidemiological typing of A. baumannii isolates obtained from well-defined hospital outbreaks.

RAPD typing for distinguishing species and strains in the genus Listeria

Abstract: The randomly amplified polymorphic DNA (RAPD) technique was employed in the development of a typing protocol for Listeria isolates, particularly Listeria monocytogenes strains. A single strain of L. monocytogenes was used and 200 random decamer primers were screened for their discriminatory abilities by visualizing the amplification products electrophoretically. Three candidate primers displaying potentially useful banding patterns were selected and tested against 52 L. monocytogenes strains, encompassing 11 serotypes, and 12 other strains representing five other Listeria spp. Thirty-four banding profiles were obtained with one particular primer. RAPD analysis allowed differentiation between Listeria spp. and was found to further subdivide strains of the same serotype. Where only one primer was used strains from different serotypes were occasionally found to produce identical banding profiles. RAPD analysis, which in our hands proved to be reproducible, shows much promise as a molecular alternative to traditional L. monocytogenes typing protocols.

Investigation of an epidemic of invasive aspergillosis: utility of molecular typing with the use of random amplified polymorphic DNA probes.

Abstract: When seven immunocompromised patients developed invasive aspergillosis during construction at a hospital, new methods were performed to compare fungal isolates and a case-control study was conducted to determine risks for infection. Typing of Aspergillus flavus with the use of restriction endonuclease analysis and restriction fragment length polymorphism using random amplified polymorphic DNA reactions to generate DNA probes revealed different patterns between isolates from two patients and a similar pattern among those from one patient, a health care worker, and an environmental source. Case patients were more likely than controls to have longer periods of hospitalization (median, 83 vs. 24 days ; P < 0.01), neutropenia (median, 33 vs. 6 days ; P < 0.05), and exposure to broad spectrum antimicrobials (median, 56 vs. 15 days ; P = 0.08). No patients restricted to protected areas developed aspergillosis. Risk of exposure of immunocompromised patients to opportunistic organisms stirred up by construction activity may be decreased by admitting these patients to protected areas away from construction activity and by restricting traffic from construction sites to these areas. Although typing of A. flavus isolates did not reveal a single type or source of organism responsible for infection, this method may facilitate epidemiologic investigation of possible nosocomial sources and transmission in similar settings.

SSOP typing of the Tenth International Histocompatibility Workshop reference cell lines for HLA‐C alleles

Abstract: HLA-C gene products are the most poorly understood of the HLA class I molecules because they express at low level on the cell surface compared to HLA-A and -B. However, recent evidence shows that HLA-C molecules are functionally competent in eliciting T-cell responses and in controlling NK-cell recognition. Approximately 20 to 50% of HLA-C alleles type "blank" in most populations. To provide a better definition of the HLA-C alleles, we analyzed 98 extensively characterized B-cell lines from the 10th International Histocompatibility Workshop. Selective HLA-C-specific DNA amplification of exons 2 and 3 from DNA prepared from the cell panel was achieved with the use of two sets of locus-specific primers. We used 64 sequence-specific oligonucleotide probes (SSOPs) complementary to variable sites in exons 2 and 3 to generate hybridization patterns. Twenty-five alleles were found among these patterns, including seven new alleles in the homozygous cell lines and seven potential new alleles in heterozygous cell lines. Differences between the new alleles and known alleles were generally small. Five major groups were identified in the Cw "blank" cells by the SSOP patterns. In addition, linkage between HLA-B specificities and HLA-C alleles was similar to previous observations. The present study demonstrated that SSOP typing was effective in identifying new alleles in homozygous typing cells but not in the heterozygous cells. Also, DNA typing can facilitate the identification of all HLA-C alleles, including those that serologically type as blanks. The HLA-C locus may be more polymorphic than was previously recognized.

Pseudomonas aeruginosa serotype O12 outbreak studied by arbitrary primer PCR.

Abstract: A total of 16 colonizing and infecting ofloxacin-resistant Pseudomonas aeruginosa strains and two strains isolated from ventilation equipment fluids, all with similar colonial morphologies and with minor but distinct susceptibility differences, were suspected of belonging to a single outbreak and were studied by arbitrary primer (AP) PCR. Thirteen nonrelated strains were included to evaluate the discriminatory capacity of the technique. AP PCR fingerprinting was compared with serotyping, phage typing, and antibiotic susceptibility testing. AP PCR was performed independently with three different primers. The different AP PCR typing systems yielded almost identical patterns for the epidemic strains and enabled us to differentiate most of the nonrelated strains from each other and from the outbreak strains. The combination of AP PCR typing and the phenotyping techniques that we used enabled us to conclude that an outbreak was occurring. In general, the typeability of AP PCR was greater than those of phage typing and serotyping, while the discriminatory powers of the three methods were comparable.

Typing of Staphylococcus aureus by amplification of the 16S-23S rRNA intergenic spacer sequences.

Abstract: The possibility of using polymorphisms in the spacer regions between 16S and 23S rRNA genes in order to type Staphylococcus aureus has been evaluated. To this purpose, DNA extracted from 74 independent isolates was amplified making use of a pair of primers complementary to conserved regions in the 16S and 23S genes. We have demonstrated that the method provides a good discrimination between unrelated isolates, giving better results when methicillin-sensitive strains are considered. Moreover, the amplification profiles were reproducible and all strains were typable. Given these results, and the technical simplicity of the process, we propose PCR-ribotyping to be taken into consideration as a method for typing S. aureus.

Typing of group A streptococci by random amplified polymorphic DNA analysis.

Abstract: Random amplified polymorphic DNA (RAPD) analysis was evaluated in comparison with restriction endonuclease analysis (REA) of genomic DNA and serotyping in the typing of 160 epidemiologically unrelated group A streptococci (GAS). Amplification of genomic DNA of GAS was performed with a single primer with an arbitrarily selected nucleotide sequence of 12 nucleotides. In total, 31 RAPD patterns and 15 REA patterns were observed among the isolates studied. The results of RAPD analysis were in accordance with the results of REA for 86% of the isolates, as both methods identified 15 different strains among 138 isolates. However, RAPD analysis differentiated 16 additional strains among 22 isolates. RAPD analysis was somewhat better than REA for differentiation of isolates of the same and different serotypes. However, not all of the serotypes were differentiated by RAPD analysis either. In conclusion, RAPD analysis provides a practical alternative for genomic typing of GAS. It can be recommended for the typing of GAS, especially if used in parallel with serotyping. Images

Comparative evaluation of molecular typing of strains from a national epidemic due to Salmonella brandenburg by rRNA gene and IS200 probes and pulsed-field gel electrophoresis.

Abstract: In Switzerland in 1992 there was a prolonged series of outbreaks of human salmonellosis caused by a previously rare serotype, Salmonella brandenburg. In order to examine the genotypic basis of the epidemic, molecular typing was applied to representative strains of this serovar isolated between 1983 and 1992. These included sporadic human isolates up to 1985, isolates from unrelated geographical areas, and Swiss isolates from humans, animals, and meat products isolated after 1991. Plasmid profiling was not found to be applicable to S. brandenburg, but chromosomal typing was accomplished by analyzing restriction fragment length polymorphisms with DNA probes for three marker loci; the 16S and 23S rRNA genes and sites of insertion of the mobile DNA element IS200. The macrorestriction profiles of the whole genome were examined by pulsed-field gel electrophoresis, which proved to be the most discriminatory of the typing methods. The study demonstrated the comparative value and complementary relationship between these typing methods for epidemiological purposes. All approaches concurred in identifying the 1992 isolates as a single genotypic clone, which was present in multiple (food) vehicles of infection. They were distinct from sporadic isolates of this serovar and from strains of S. brandenburg isolated in other countries.

Half-QWERTY: typing with one hand using your two-handed skills

Abstract: Half-QWERTY is a new one-handed typing technique, designed to facilitate the transfer of two-handed typing skill to the one-handed condition, It is performed on a standard keyboard (with modified software), or a special half keyboard (with full-sized keys). Experiments have shown [2] that it is possible for QWERTY touch-typists to achieve high one-handed typing rates (40+ wpm) in a relatively short period of time (<10 hr) using the HalfQWERTY technique. These speeds are 2-3 times the rates achievable using compact keyboards, and exceed handwriting speeds. Half-QWERTY is important in providing access to disabled users, and for the design of compact computers. KEY WO R D S: Input devices, input tasks, human performance, one-handed keyboard, QWERTY, portable computers, disabled users, skill transfer. WHAT IS IT? This Interactive Experience display demonstrates a new approach to one-handed text entry which exploits the skills already developed in two-handed typing. It is called, “HalfQWERTY,” because it uses only half of the QWERTY keyboard. The technique can be used on a standard QWERTY keyboard (using only half of the available keys, Figure 1), or with a special half keyboard (Figure 2), The former provides wide access to the technique. The latter provides a compact keyboard with full-sized keys supporting touch typing on portable computers, for example. Permission to copy without fee all or part of this materml is granted pmwded that the cop!es are not made or distributed for d!rect GwnrnerGI@ advantage, the ACM cvpyr, ght notice and the tttle of the publication and its date appear, and ncmce IS given that copy!ng is by perm{sston of the Association for Computing Machinery. To copy otherwise, or to republish, requires a fee andlor specific permission. CH194 Companion-4/94 Boston, Massachusetts USA e 1994 ACM 0-89791-651-4/94/0051 . ..$3.50 William Buxton University of Toronto& Xerox PARC c/o Computer SystemLsResearch Institute University of Toronto Toronto, Ontario, Canada M5S 1A4 (416) 978-1961 buxton@dgp.toronto.edu HOW DOES IT WORK?* A Half-QWERTY keyboard is comprised of all the keys used by one hand to type on a standard QWERTY keyboardl, with the keys of the other hand unused or absent. Keys of the typing hand are typed as before. To type characters of the missing hand, the user simply holds down the space bar and performs the finger movement previously done by the missing hand (Figure 1). Thus, using the space bar as a modifier, a typist can generate the characters of either side of a fill-sized keyboard, using only one hand. HOW WILL IT BE USED? Half-QWERTY is especially useful when performing tasks which require frequent switching between keyboard and mouse—text editing, for example. Text can be entered with one hand, and items selected and manipulated with the other. Since both hands are in “home position” for their respective task, no time is lost in moving between devices [1]. Furthermore, by implementing Half-QWERTY on a standard keyboard, one can ea~sily switch between this type of input and two-handed typing. Finally, since each side clf the keyboard is mapped onto the other side when the space bar is depressed, the user can choose which hand to use fcr one-handed typing. In effect, the user has a choice of three keyboards in one: a two-handed QWERTY keyboard, and two Half-QWERTY keyboards, one for each hand. A computer that is worn, rather than carried, has significant advantages for data collection “in the field.” By eliminating infrequently used keys (e.g., the number keys) and reducing the size of the space bar, a Ha’lf-QWERTY keyboard can be made small enough to wear on the wrist of the dominant hand (Figure 2). With an LCD screen worn on the other wrist, the resulting typing posture allows the user to type and view the display, simultaneously. lPatents pending. International Application # PCTICA90100274 published March 21, 1991, under International Publication # W091/03782.

Application of New Technology to the Detection, Identification, and Antimicrobial Susceptibility Testing of Mycobacteria

Abstract: Mycobacteria are reemerging as important causes of human disease. The increase in mycobacterial infections has prompted the development of more rapid and efficient ways of detecting and characterizing mycobacteria in the clinical microbiology laboratory. Methods currently in use or under development include more sensitive methods of direct detection, improved techniques for culture, identification, and susceptibility testing, and the use of nucleic acid probes for identification and epidemiologic typing. Broad application of rapid and sensitive methods for detection and characterization of mycobacteria are essential if we are to limit the spread of Mycobacterium tuberculosis (TB) and provide optimal care for patients infected with TB or other Mycobacterium species

Quantitative antibiogram typing using inhibition zone diameters compared with ribotyping for epidemiological typing of methicillin-resistant Staphylococcus aureus.

Abstract: Antibiogram typing of methicillin-resistant Staphylococcus aureus with selected antibiotics was evaluated as a primary epidemiological typing tool and compared with ribotyping. Antibiograms were derived with the Kirby-Bauer disk diffusion method by using erythromycin, clindamycin, cotrimoxazole, gentamicin, and ciprofloxacin. For typing, antibiogram data were analyzed by similarity analysis of disk zone diameters (quantitative antibiogram typing). One hundred seventy-two isolates were typed. Reproducibility reached 98% for the quantitative antibiogram and 100% for ribotyping. With three selected restriction enzymes (EcoRV, HindIII, and KpnI), 40 epidemiologically unrelated isolates could be classified into 21 ribotypes, whereas quantitative antibiogram typing classified these isolates into 19 groups. To evaluate the discriminatory power of the methods, we calculated an index of discrimination from data obtained with these 40 isolates. This index takes into consideration both the number of types defined by the typing method and their relative frequencies. With both ribotyping and quantitative antibiogram typing, high discrimination indices (0.972 and 0.954, respectively) were obtained. When epidemiological links between patients (ward, period of hospitalization, and contacts between staff and patients) were compared with the results of ribotyping or the quantitative antibiogram typing method, it appeared that both methods were able to discriminate epidemiological clusters, with only a few discrepancies. In conclusion, quantitative antibiogram typing, although not necessarily based on genomic markers, is a simple method which enables a reliable workup of methicillin-resistant S. aureus epidemic when sophisticated molecular typing methods are not available. Images