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Aspartic acid racemization dating of Holocene brachiopods and bivalves from the southern Brazilian shelf, South Atlantic
- Susan L. Barbour Wood, Richard A. Krause, Jr., Michał Kowalewski, John Wehmiller, Marcello G. Simões
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- Journal:
- Quaternary Research / Volume 66 / Issue 2 / September 2006
- Published online by Cambridge University Press:
- 20 January 2017, pp. 323-331
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The extent of racemization of aspartic acid (Asp) has been used to estimate the ages of 9 shells of the epifaunal calcitic brachiopod Bouchardia rosea and 9 shells of the infaunal aragonitic bivalve Semele casali. Both taxa were collected concurrently from the same sites at depths of 10 m and 30 m off the coast of Brazil. Asp D/L values show an excellent correlation with radiocarbon age at both sites and for both taxa (r2Site 9 B. rosea = 0.97, r2Site 1 B. rosea = 0.997, r2Site 9 S. casali = 0.9998, r2Site 1 S. casali = 0.93). The Asp ratios plotted against reservoir-corrected AMS radiocarbon ages over the time span of multiple millennia can thus be used to develop reliable and precise geochronologies not only for aragonitic mollusks (widely used for dating previously), but also for calcitic brachiopods. At each collection site, Bouchardia specimens display consistently higher D/L values than specimens of Semele. Thermal differences between sites are also notable and in agreement with theoretical expectations, as extents of racemization for both taxa are greater at the warmer, shallower site than at the cooler, deeper one. In late Holocene marine settings, concurrent time series of aragonitic and calcitic shells can be assembled using Asp racemization dating, and parallel multi-centennial to multi-millennial records can be developed simultaneously for multiple biomineral systems.
A continuous multi-millennial record of surficial bivalve mollusk shells from the São Paulo Bight, Brazilian shelf
- Troy A. Dexter, Darrell S. Kaufman, Richard A. Krause, Jr., Susan L. Barbour Wood, Marcello G. Simões, John Warren Huntley, Yurena Yanes, Christopher S. Romanek, Michał Kowalewski
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- Journal:
- Quaternary Research / Volume 81 / Issue 2 / March 2014
- Published online by Cambridge University Press:
- 20 January 2017, pp. 274-283
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To evaluate the potential of using surficial shell accumulations for paleoenvironmental studies, an extensive time series of individually dated specimens of the marine infaunal bivalve mollusk Semele casali was assembled using amino acid racemization (AAR) ratios (n = 270) calibrated against radiocarbon ages (n = 32). The shells were collected from surface sediments at multiple sites across a sediment-starved shelf in the shallow sub-tropical São Paulo Bight (São Paulo State, Brazil). The resulting 14C-calibrated AAR time series, one of the largest AAR datasets compiled to date, ranges from modern to 10,307 cal yr BP, is right skewed, and represents a remarkably complete time series: the completeness of the Holocene record is 66% at 250-yr binning resolution and 81% at 500-yr binning resolution. Extensive time-averaging is observed for all sites across the sampled bathymetric range indicating long water depth-invariant survival of carbonate shells at the sediment surface with low net sedimentation rates. Benthic organisms collected from active depositional surfaces can provide multi-millennial time series of biomineral records and serve as a source of geochemical proxy data for reconstructing environmental and climatic trends throughout the Holocene at centennial resolution. Surface sediments can contain time-rich shell accumulations that record the entire Holocene, not just the present.
Quantitative comparisons and models of time-averaging in bivalve and brachiopod shell accumulations
- Richard A. Krause, Jr., Susan L. Barbour, Michał Kowalewski, Darrell S. Kaufman, Christopher S. Romanek, Marcello G. Simões, John F. Wehmiller
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- Journal:
- Paleobiology / Volume 36 / Issue 3 / Summer 2010
- Published online by Cambridge University Press:
- 08 April 2016, pp. 428-452
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The variation in time-averaging between different types of marine skeletal accumulations within a depositional system is not well understood. Here we provide quantitative data on the magnitude of time-averaging and the age structure of the sub-fossil record of two species with divergent physical and ecological characteristics, the brachiopod Bouchardia rosea and the bivalve Semele casali. Material was collected from two sites on a mixed carbonate-siliciclastic shelf off the coast of Brazil where both species are dominant components of the local fauna.
Individual shells (n = 178) were dated using amino acid racemization (aspartic acid) calibrated with 24 AMS radiocarbon dates. Shell ages range from modern to 8118 years b.p. for brachiopods, and modern to 4437 years for bivalves. Significant differences in the shape and central tendency of age-frequency distributions are apparent between each sample. Such differences in time-averaging magnitude confirm the assumption that taphonomic processes are subject to stochastic variation at all spatial and temporal scales. Despite these differences, each sample is temporally incomplete at centennial resolution and three of the four samples have similar right-skewed age-frequency distributions. Simulations of temporal completeness indicate that samples of both species from the shallow site are consistent with a more strongly right-skewed and less-complete age-frequency distribution than those from the deep site.
We conclude that intrinsic characteristics of each species exert less control on the time-averaging signature of these samples than do extrinsic factors such as variation in rates of sedimentation and taphonomic destruction. This suggests that brachiopod-dominated and bivalve-dominated shell accumulations may be more similar in temporal resolution than previously thought, and that the temporal resolution of multi-taxic shell accumulations may depend more on site-to-site differences than on the intrinsic properties of the constituent organisms.
Quality Standard for the Treatment of Bacteremia
- Peter A. Gross, Trisha L. Barrett, E. Patchen Dellinger, Peter J. Krause, William J. Martone, John E. McGowan, Jr, Richard L. Sweet, Richard P. Wenzel
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- Journal:
- Infection Control & Hospital Epidemiology / Volume 15 / Issue 3 / March 1994
- Published online by Cambridge University Press:
- 02 January 2015, pp. 189-192
- Print publication:
- March 1994
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Objective:
The objective of this quality standard is to optimize the treatment of bacteremia in hospitalized patients by ensuring that the antibiotic given is appropriate in terms of the blood culture susceptibility of the pathogen. Although this standard may appear to be minimal in scope, it is needed because appropriate antimicrobial treatment is not given in 5% to 17% of cases. To implement the standard, physicians, pharmacists, and microbiologists will need to devise a coordinated strategy.
Options:We considered criteria for appropriate dosing, most cost-effective selection, proper antibiotic levels in serum, least toxicity, narrowest spectrum, specific clinical indications, and optimal duration of treatment. All these criteria were rejected as the basis for the standard because they were too controversial and too difficult to be applied by a nonphysician chart reviewer. In contrast, the selection of an antibiotic to which the pathogen is sensitive is a non-controversial criterion and easy for a chart reviewer to apply.
Outcomes:The standard is designed to reduce the incidence of adverse outcomes of septicemia such as renal failure, prolonged hos-pitalization, and death.
Evidence:Several well-designed clinical trials without randomization as well as case-controlled studies have confirmed the benefit of using an antibiotic that is appropriate in light of the susceptibility of the isolate in blood culture. Prospective, randomized, placebo-controlled trials are not available.
Values:Our premise is that the presence of bacteremia is a risk factor for serious adverse outcomes. We also believe that the administration of antibiotics must always be guided by the susceptibility report for the pathogen(s) obtained from blood cultures. This concern is more critical for pathogens from the blood than for those from most other body sites. We had evidence that susceptibility reports for pathogens from positive blood cultures were not always used properly. We used group discussion to reach a consensus among the members of the Quality Standards Subcommittee.
Benefits, Harms, and Costs:Through the implementation of this standard, at least 5% of bacteremias could be treated more appropriately. An unknown number of deaths would likely be prevented, and mortality from bacteremia treated inappropriately would probably be reduced. The primary undesirable feature of the standard is an increased workload of pharmacists and microbiologists.
Recommendations:Treatment of bacteremia with an antibiotic that is appropriate in terms of the pathogen's blood-culture susceptibility is a minimal standard of care for all patients.
Validation:We consulted more than 50 experts in infectious diseases from the fields of medicine, surgery, pediatrics, obstetrics and gynecology, nursing, epidemiology, pharmacology, and government. In addition, the methods for its implementation were reviewed by the American Society of Hospital Pharmacists and were tested by one of the members of the Quality Standards Subcommittee.
Sponsors:The Quality Standards Subcommittee of the Clinical Affairs Committee of the Infectious Diseases Society of America (IDSA) developed the standard. The subcommittee was composed of representatives of the IDSA (Drs. Gross and McGowan), the Society for Hospital Epidemiology of America (Dr. Wenzel), the Surgical Infection Society (Dr. Dellinger), the Pediatric Infectious Diseases Society (Dr. Krause), the Centers for Disease Control and Prevention (Dr. Martone), the Obstetrics and Gynecology Infectious Diseases Society (Dr. Sweet), and the Association of Practitioners of Infection Control (Ms. Barrett). Funding was provided by the IDSA and the other cooperating organizations. This standard is endorsed by the IDSA.
Consensus Development of Quality Standards
- Peter A. Gross, Trisha L. Barrett, E. Patchen Dellinger, Peter J. Krause, William J. Martone, John E. McGowan, Jr, Richard L. Sweet, Richard P. Wenzel
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- Journal:
- Infection Control & Hospital Epidemiology / Volume 15 / Issue 3 / March 1994
- Published online by Cambridge University Press:
- 02 January 2015, pp. 180-181
- Print publication:
- March 1994
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Quality Standard for Antimicrobial Prophylaxis in Surgical Procedures
- E. Patchen Dellinger, Peter A. Gross, Trisha L. Barrett, Peter J. Krause, William J. Martone, John E. McGowan, Jr, Richard L. Sweet, Richard P. Wenzel
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- Journal:
- Infection Control & Hospital Epidemiology / Volume 15 / Issue 3 / March 1994
- Published online by Cambridge University Press:
- 02 January 2015, pp. 182-188
- Print publication:
- March 1994
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Objective:
The objectives of this quality standard are 1) to provide an implementation mechanism that will facilitate the reliable administration of prophylactic antimicrobial agents to patients undergoing operative procedures in which such a practice is judged to be beneficial and 2) to provide a guideline that will help local hospital committees formulate policies and set up mechanisms for their implementation. Although standards in the medical literature spell out recommendations for specific procedures, agents, schedules, and doses, other reports document that these standards frequently are not followed in practice.
Options:We have specified the procedures in which the administration of prophylactic antimicrobial agents has been shown to be beneficial, those in which this practice is widely thought to be beneficial but in which compelling evidence is lacking, and those in which this practice is controversial. We have examined the evidence regarding the optimal timing of drug administration, the optimal dose, and the optimal duration of prophylaxis.
Outcomes:The intended outcome is more uniform and reliable administration of prophylactic antibiotics in those circumstances where their value has been demonstrated or their use has been judged by the local practicing medical community to be desirable. The result should be a reduction in rates of postoperative wound infection with a limitation on the quantities of antimicrobial agents used in circumstances where they are not likely to help.
Evidence:Many prospective, randomized, controlled trials comparing placebo with antibiotic and comparing one antibiotic with another have been conducted. In addition, some trials have compared the efficacy of different doses or methods of administration. Other papers have reported on the apparent efficacy of administration at different times and on actual practice in specific communities. Only a small group of relevant articles found through 1993 are cited herein. When authoritative reviews are available, these-rather than an exhaustive list of original references-are cited.
Values:We assumed that reducing rates of postoperative infection was valuable but that reducing the total amount of antimicrobial agents employed was also worthwhile. The cost of and morbidity attributable to postoperative wound infections should be weighed against the cost and potential morbidity associated with excessive use of antimicrobial agents.
Benefits, Harms, and Costs:More reliable administration of antimicrobial agents according to recognized guidelines should prevent some postoperative wound infections while lowering the total quantity of these drugs used. No harms are anticipated. The costs involved are those of the efforts needed on a local basis to design and implement the mechanism that supports uniform and reliable administration of prophylactic antibiotics.
Recommendations:All patients for whom prophylactic antimicrobial agents are recommended should receive them. The agents given should be appropriate in light of published guidelines. A short duration of prophylaxis (usually < 24 hours) is recommended.
Validation:More than 50 experts in infectious disease and 10 experts in surgical infectious disease and surgical subspecialties reviewed the standard. In addition, the methods for its implementation were reviewed by the American Society of Hospital Pharmacists.
Sponsors:The Quality Standards Subcommittee of the Clinical Affairs Committee of the Infectious Disease Society of America (IDSA) developed the standard. The subcommittee was composed of representatives of the IDSA (Drs. Gross and McGowan), the Society for Hospital Epidemiology of America (Dr. Wenzel), the Surgical Infection Society (Dr. Dellinger), the Pediatric Infectious Disease Society (Dr. Krause), the Centers for Disease Control and Prevention (Dr. Martone), the Obstetrics and Gynecology Infectious Diseases Society (Dr. Sweet), and the Association of Practitioners of Infection Control (Ms. Barrett). Funding was provided by the IDSA and the other cooperating organizations. The standard is endorsed by the IDSA.
Quality Standard for Assurance of Measles Immunity Among Health Care Workers
- Peter J. Krause, Peter A. Gross, Trisha L. Barrett, E. Patchen Dellinger, William J. Martone, John E. McGowan, Jr, Richard L. Sweet, Richard P. Wenzel
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- Journal:
- Infection Control & Hospital Epidemiology / Volume 15 / Issue 3 / March 1994
- Published online by Cambridge University Press:
- 02 January 2015, pp. 193-199
- Print publication:
- March 1994
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Objective:
The objective of this quality standard is to prevent nosocomial transmission of measles by assuring universal measles-mumps-rubella (MMR) vaccination of all healthcare workers who lack immunity to measles. Although the primary emphasis is on healthcare workers in hospitals, those at other sites, such as clinics, nursing homes, and schools, are also included. It will be the responsibility of designated individuals at these institutions to implement the standard.
Options:We considered advocating the use of measles vaccine rather than MMR but chose the latter because it also protects against mumps and rubella and because it is more readily available.
Outcomes:The desired outcome is a reduction in the nosocomial transmission of measles.
Evidence:Although direct comparative studies are lacking, nosocomial outbreaks of measles have been reported (as recently as 1992) in institutions where measles immunization of nonimmune healthcare workers is not universal, whereas such outbreaks have not been reported in institutions with universal immunization.
Values and Validation:We consulted more than 50 infectious-disease experts in epidemiology, government, medicine, nursing, obstetrics and gynecology pediatrics, and surgery. In light of disagreement regarding the implementation of the standard, we used group discussions to reach a consensus.
Benefits, Harms, and Cost:The consequences of the transmission of measles (and of mumps and rubella) in a healthcare institution include not only the morbidity and mortality attributable to the disease, but also the significant cost of evaluating and containing an outbreak and the serious disruption of regular hospital routines when control measures are instituted. The potential harm to healthcare workers after the implementation of the standard consists of untoward effects of MMR vaccine, although the reactions of vaccines should be minimal with adherence to recommended vaccination procedures. Implementation of the standard should entail no expense to healthcare workers; the precise cost to institutions is unknown, but the expense would be mitigated by prevention of measles outbreaks.
Recommendations:We recommend MMR vaccination of all healthcare workers who lack immunity to measles.
Sponsors:The Quality Standards Subcommittee of the Clinical Affairs Committee of the Infectious Diseases Society of America (IDSA) developed the standard. The subcommittee was composed of representatives of the IDSA (Drs. Gross and McGowan), the Society for Hospital Epidemiology of America (Dr. Wenzel), the Surgical Infection Society (Dr. Dellinger), the Pediatric Infectious Diseases Society (Dr. Krause), the Centers for Disease Control and Prevention (Dr. Martone), the Obstetrics and Gynecology Infectious Diseases Society (Dr. Sweet), and the Association of Practitioners of Infection Control (Ms. Barrett). Funding was provided by the IDSA and the other cooperating organizations. The standard is endorsed by the IDSA.