ST2249-MRSA-III: a second major recombinant methicillin-resistant Staphylococcus aureus clone causing healthcare infection in the 1970s.

Typing of healthcare-associated methicillin-resistant Staphylococcus aureus (MRSA) from Australia in the 1970s revealed a novel clone, ST2249-MRSA-III (CC45), present from 1973 to 1979. This clone was present before the Australian epidemic caused by the recombinant clone, ST239-MRSA-III. This study aimed to characterize the genome of ST2249-MRSA-III to establish its relationship to other MRSA clones. DNA microarray analysis was conducted and a draft genome sequence of ST2249 was obtained. The recombinant structure of the ST2249 genome was revealed by comparisons to publicly available ST239 and ST45 genomes. Microarray analysis of genomic DNA of 13 ST2249 isolates showed gross similarities with the ST239 chromosome in a segment around the origin of replication and with ST45 for the remainder of the chromosome. Recombination breakpoints were precisely determined by the changing pattern of nucleotide polymorphisms in the genome sequence of ST2249 isolate SK1585 compared with ST239 and ST45. One breakpoint was identified to the right of oriC, between sites 1014 and 1065 of the gene D484_00045. Another was identified to the left of oriC, between sites 1185 and 1248 of D484_01632. These results indicate that ST2249 inherited approximately 35.3% of its chromosome from an ST239-like parent and 64.7% from an ST45-like parent. ST2249-MRSA-III resulted from a major recombination between parents that resemble ST239 and ST45. Although only limited Australian archival material is available, the oldest extant isolate of ST2249 predates the oldest Australian isolate of ST239 by 3 years. It is therefore plausible that these two recombinant clones were introduced into Australia separately.

Carriage of an ACME II variant may have contributed to methicillin-resistant Staphylococcus aureus sequence type 239-like strain replacement in Liverpool Hospital, Sydney, Australia.

Approximately 39% of methicillin-resistant Staphylococcus aureus (MRSA) sequence type 239 (ST239)-like bloodstream isolates from Liverpool Hospital (obtained between 1997 and 2008) carry an arginine catabolic mobile element (ACME). Whole-genome sequencing revealed that an ACME II variant is located between orfX and SCCmec III, and based on pulsed-field gel electrophoresis patterns and temporal relationships of all ST239-like isolates (n = 360), ACME carriage may have contributed to subpulsotype strain replacement.

Tracheal tube forces on the posterior larynx: index of laryngeal loading.

Most tracheal tubes sold today are arcuate in shape while the human airway is S-shaped. In situ, the tubes exert different forces on the posterior larynx, depending on their stiffness. Laryngeal damage after prolonged intubation is recognized as the result of these forces. The authors tested 8 types of size 8.0 tracheal tubes to determine the magnitude of laryngeal loading in a model approximating the geometry of the human airway. The force each tube exerted on the posterior larynx was measured in conditions simulating both, immediately after intubation and after prolonged intubation of 24 h. The force was converted into an integer number, an index of laryngeal loading, that can be used to compare various types of tracheal tubes. The airway model and test procedure can be utilized by manufactures, designers, and others to provide valuable information on tracheal tube performance and to develop improved tracheal tubes in the future. The results indicate that the polyvinylchloride tubes (PVC) and the silicone rubber tubes had the lowest index of laryngeal loading after long-term conditioning and would be preferable for prolonged intubation. The red rubber tube had the highest index of laryngeal loading after long-term conditioning, yet its stiffness would facilitate intubation.

The levels of serum enzymes, plasma proteins and lipids in normal infants and small children.

A group of 291 children aged 3 weeks to 6 1/2 years was examined at a public maternal and child health center and 260 of them - who were considered to be healthy - were included in the present study. By venipuncture, serum was obtained for the analysis of 6 enzymes, and plasma for the estimation of 9 proteins and for lipid analyses. In different age groups, high levels were found for alkaline phosphatase, lactate dehydrogenase, aspartate aminotransferase, alanine aminotransferase, creatine kinase and gamma-glutamyl transferase. Haptoglobin, alpha 1-antitrypsin, prealbumin and transferrin were present at low concentrations during the first months of life. Transferrin rose later in childhood to above adult levels. Only immunoglobulin M showed a sex difference, with higher values for girls. Breast-fed infants had higher (non-fasting) concentrations of cholesterol and triglycerides than formula-fed babies, and they also had higher levels of aspartate aminotransferase and alanine aminotransferase.

A comparison between over-the-shoulder and computer-derived measurement procedures in assessing student performance in radar air traffic control.

On July 18, 1980, the air traffic control Radar Training Facility (RTF) at Oklahoma City was formally dedicated. The RTF can use the computer system in making automated measures of how well a student is moving air traffic. The purpose of this study was to compare the computer-derived automated measures with over-the-shoulder evaluation methods. Subjects were 48 recent nonradar Federal Aviation Administration (FAA) Academy air traffic control graduates who were employed at the National Aviation Facilities Experimental Center (NAFEC; renamed FAA Technical Center) in Atlantic City, NJ, on the Dynamic Simulation Facility. Two sets of measures were taken: 20 computer-derived measures and an over-the-shoulder evaluation of student performance by experts in air traffic control. The results of the study show that the automated measures predict a success criterion at least as well as an over-the-shoulder evaluation and that the automated measures are far more reliable. The study further demonstrated that the factor structures of the two sets of measures were very similar except in two areas where direct observation was necessary for evaluation.

Irreversible thermodynamics of an isometric twitch, time-dependent general formulation.

We used the phenomenological laws of irreversible thermodynamics, to derive a system of coupled differential equations describing the time course of the mechanochemical coupling underlying an isometric twitch. Our general description is concerned only with the fundamental process of energy transduction taking place within an idealized unit element of muscle and does not include the description of associated processes such as the excitation-contraction coupling and the mechanical or external coupling that, in bulk muscle, lead to or mediate the fundamental process. The values of the initial conditions and of four parameters are required to solve for the time course of the process. Two of the parameters have a clear physical interpretation and, for the specific case of muscular contraction involving hydrolysis of ATP, their values can be readily estimated from available experimental data. The interpretation of the two other parameters is more speculative, but, from their strong interdependence with the other parameters, their values can be also approximated. Solution of the coupled differential equations yields results consistent with the typical experimental time course of an isometric twitch.

Health device legislation: an overview of the law and its impact on respiratory care.

The Medical Device Amendments of 1976 were intended to protect the public from unsafe and ineffective medical devices. The Food and Drug Administration (FDA) has general authority from this law to regulate medical devices but now must establish specific regulations to do so. In this process all devices are being classified in Class I (general controls), Class II (performance standards), or Class III (premarket approval). General controls impose relatively fewer restrictions, while premarket approval can require very strict laboratory and clinical testing. Classification panels have been grouping medical devices into these three classes. The Anesthesiology Device Classification Panel and the Pulmonary Function and Respiratory Therapy Subcommittee have recommended classifications for more than 200 types of devices. After comments from the public, the FDA will publish final device classifications, probably in 1979. The Medical Device Amendments also provide for release of safety and effectiveness data to the public, for tracing of devices in the field in case of recalls or problems, and for assistance to small manufacturers in complying with the law. The Medical Device Amendments should help to improve medical devices, but official regulations cannot accomplish everything. Users must also do their part by employing preventive maintenance and applying devices knowledgeably and safely.

Myocardial contractile reserve and indices of contractility.

A close examiniation of several indices of contractility derived from the ventricular pressure was made using an isolated canine heart preparation. The repsonses to single intracoronary injections of calcium chloride as well as to increasing doses of this agent were tested. From the latter, calcium dose-transient-response curves intended to reveal the extent of myocardial/contractile reserve were constructed. Indices included various extrapolations to maximal velocity of shortening at zero load, maximal value of the quotient of the first derivative and ventricular pressure, time-tension index, energy averaged power density, and power averaged rate of generation of power density. Indices were compared over the same cardiac cycles before and after administration of calcium. Most indices showed increments from 10 to 20%, except power density functions which had increments of 40 and 70%, respectively. Calcium dose-response curves were linear for most indices, but, again, the power density functions showed the steepest slopes. After severe coronary occlusion, the curves for most indices flattened and lost linearity and, presumably, this was due to loss of myocardial contractile reserve. For milder occlusions, only the power density functions showed significant flattening. The conceptual framework of a contractile myocardial reserve appears supported by these results.

Interaction between marihuana and altitude on a complex behavioral task in baboons.

Marihuana, or its principal active ingredient, delta-9-tetra-hydrocannabinal (delta9-THC), impairs performance on complex behavioral tasks in animals and man. Although there exists some evidence that altitude-induced hypoxia potentiates the physiological effects of marihuana, the interaction between altitude and marihuana on behavioral tasks has not been established. In the absence of evidence that use of marihuana is less frequent among members of the aviation community than among the general population, it was necessary to evaluate the effects on performance of any interaction between hypoxia and marihuana. Two baboons were trained to perform on a delayed matching-to-sample task at ground level and altitudes of 2438 and 3658 m (8000 and 12000 ft). The animals were orally administered doses of delta9-THC, ranging from 0.25 to 2.0 mg/kg, 2 h prior to experimental sessions at each altitude. No effects on accuracy of matching performance were observed for any of the drug doses or altitudes used. Amount of work output, as measured by number of trials completed and speed of responding, was not affected by delta9-THC at ground level but was markedly reduced by the higher drug doses at the 2438- and 3658-m altitudes. This interaction suggests that the behavioral impairment produced by marihuana can be potentiated by hypoxia.

Some behavioral effects of pesticides: The interaction of mevinphos and atropine in pigeons.

The interaction of the organophosphate mevinphos and atropine was examined in two pigeons performing in a variable interval schedule of reinforcement. When administered separately, both atropine and mevinphos produced a dose-related decrement in responding. The combined exposure to these drugs produced a performance decrement greater than that caused by exposure to each component drug alone. These findings suggest that prophylactic use of atropine may increase the detrimental behavioral effects of organophosphate exposure and that the atropine exposure alone may produce serious behavioral deficits.

Predictive validities of several clinical color vision tests for aviation signal light gun performance.

Scores on the American Optical Company (AOC) test (1965 edition), Dvorine test, Farnsworth Lantern test, Color Threshold Tester, Farnsworth-Munsell 100-Hue test, Farnsworth Panel D-15 test, and Schmidt-Haensch Anomaloscope were obtained from 137 men with color-defective vision and 128 men with normal color vision. The validity of each of these tests in predicting scores on the aviation signal light gun was assessed by using daytime and nighttime administrations of the light gun as the criteria. Two "best sets" of plates from the AOC and Dvorine tests were selected by calculating a multiple regression equation in a stepwise manner with the nighttime and then the daytime administration of the signal light gun test as the criteria. Based on a graphic presentation of the miss and false alarm rates for each test at various possible cut scores, suggestions were made regarding the use of each test and the selection of optimal pass/fail scores.

Spontaneous reversal of portal blood flow: the case for and against its occurrence in patients with cirrhosis of the liver.

Because of its presumed serious clinical significance, we made an analysis of the evidence for and against the occurrence of spontaneous reversal of portal flow in cirrhosis of the liver. We examined the evidence obtained from manometric studies, radioactive tracer studies, radiologic studies, and actual measurements of magnitude and direction of portal blood flow. Concerning manometric studies, we introduced a physical analysis, based on first principles, which demonstrates that the occluded portal pressures cannot be used to construct a hydraulic gradient for portal flow. Similarly, we examined the weakness of the evidence derived from radioactive tracer and radiologic studies and, in the latter, the drastically opposite results reported by different investigators. Finally, we found that actual measurements of magnitude and direction of portal flow provide impressive evidence against the occurrence of spontaneous reversal of portal flow in cirrhosis. We conclude that unless new and convincing evidence is provided, it may not serve the best interests of medicine and of our patients to continue accepting spontaneous reversal of portal flow in cirrhosis as if it were a proven phenomenon.