Governance for planetary health equity-the Planetary Health Equity Hothouse project

BACKGROUND

Planetary health equity (PHE) is defined here as equitable good health in a stable Earth system. PHE is arguably in crisis. Human-made climate change is damaging global populations through hotter temperatures, wildfires, and more severe and frequent storms, flooding, and landslides. A tsunami of health inequities will result from this, as pre-existing health conditions and inequities in living and working conditions ensure that socially disadvantaged groups and people in low-income and middle-income countries are disproportionately affected by climate change. Despite evidence of these massive challenges and multiple calls to action, why has there been so little effective remedial action? And more importantly, how can we overcome this failure? To answer these questions, this panel discusses new research for understanding the conditions that enable coherent governance to improve planetary health equity outcomes.

METHODS

The panel draws on emerging research from the Planetary Health Equity Hothouse. With perspectives from political economy, public health, policy studies, and systems science, we present new conceptual thinking and empirics around the complexities, dynamics, and trajectories of the global consumptogenic system in the 21st century, with a focus on the intersections between climate change and social and health inequities. The research examines mechanisms via which the global political economy creates planetary health inequities; identifies policy that optimises the climate, social, and health equity outcomes of mitigation actions; and discusses how governance for planetary health equity must evolve into the future, focusing on the structural, institutional, and ideational factors that advance action to promote PHE outcomes.

FINDINGS

The global consumptogenic system of institutions, actors, norms, policies, and commercial activities that incentivise excessive production and consumption of fossil fuel-reliant goods and services with negative environmental, social, and health effects lies at the heart of the PHE crisis. Using network analysis, we show that the global PHE governance architecture is highly centralised and dominated by economic governance organisations. We also discuss a new Planetary Health Equity Impact Assessment tool to assess the PHE effects of existing policy and business practices within the consumptogenic system. An initial assessment of the mitigation sections of national governments' Nationally Determined Contribution reports to the UN Framework Convention on Climate Change shows a dominance of economic language and issues. This highlights a missed opportunity for mitigation policy to be inclusive of social and health matters. Finally, we present new conceptual understandings of multilevel governance coherence and relevant strategies to advance PHE focused action.

INTERPRETATION

The major contribution from research on governance for planetary health equity lies in detailing the what, who, and how of effective governance that advances health, social equity, and the environment in an interconnected way, helping to shift institutional norms and behaviours towards principles of fairness, sustainability, and human wellbeing. Crucially, it provides strategies for socially oriented actors, including governments, civil society, and international organisations to change the consumptogenic system and advance action for PHE.

FUNDING

Australian Research Council.

Towards practice change: a qualitative study examining the impact of a Child Psychiatric Access Program (Project TEACH) on Primary Care Provider practices in New York State during pandemic times

BACKGROUND

This study aims to explore the perceived impact of Project TEACH (Training and Education for the Advancement of Children's Health), a New York State Office of Mental Health funded Child Psychiatric Access Program (CPAP), on pediatric Primary Care Providers (PCPs) and their practice. Practice change over time was assessed in the context of rising mental health needs and in the context of COVID19 pandemic.

METHODS

Focus groups utilizing a semi-structured format were conducted with pediatric PCPs who have been high utilizers of Project TEACH over the past 5-10 years and PCPs in similar regions who have been low or non-utilizers of the program. The semi-structured interview focused on practice change, asking about pediatric mental health, practice setting and flow, professional development, and changes over time in the context of COVID-19 pandemic and Project TEACH.

RESULTS

Themes identified include increasing confidence of PCPs, particularly those who are high utilizers of the phone consultation line, increased routine use of screening and comfort bridging pediatric patients with mental health needs. Challenges include rising mental health needs, inadequate mental health services, difficulties with family follow through and high emotional burden on PCPs caring for these patients. In this context, participants noted that collaboration with Project TEACH provided needed emotional support.

CONCLUSIONS

Integrated care and CPAPs such as Project TEACH are vital to helping PCPs handle rising mental health needs particularly in current crisis times. Ongoing systemic challenges accessing care remain and contribute to emotional burden placed on pediatric PCPs.

"I can guess the month … but beyond that, I can't tell" an exploratory qualitative study of health care provider perspectives on gestational age estimation in Rajasthan, India

BACKGROUND

Accurately estimating gestational age is essential to the provision of time-sensitive maternal and neonatal interventions, including lifesaving measures for imminent preterm birth and trimester-specific health messaging.

METHODS

We explored healthcare provider perspectives on gestational age estimation in the state of Rajasthan, India, including the methods they use (last menstrual period [LMP] dating, ultrasound, or fundal height measurement); barriers to making accurate estimates; how gestational age estimates are documented and used for clinical decision-making; and what could help improve the accuracy and use of these estimates. We interviewed 20 frontline healthcare providers and 10 key informants. Thematic network analysis guided our coding and synthesis of findings.

RESULTS

Health care providers reported that they determined gestational age using some combination of LMP, fundal height, and ultrasound. Their description of their practices showed a lack of standard protocol, varying levels of confidence in their capacity to make accurate estimates, and differing strategies for managing inconsistencies between estimates derived from different methods. Many frontline healthcare providers valued gestational age estimation more to help women prepare for childbirth than as a tool for clinical decision making. Feedback on accuracy was rare. The providers sampled could not offer ultrasound directly, and instead could only refer women to ultrasound at higher level facilities, and usually only in the second or third trimesters because of late antenatal care-seeking. Low recall among pregnant women limited the accuracy of LMP. Fundal height was heavily relied upon, despite its lack of precision.

CONCLUSION

The accuracy of gestational age estimates is influenced by factors at four levels: 1. health system (protocols to guide frontline workers, interventions that make use of gestational age, work environment, and equipment); 2. healthcare provider (technical understanding of and capacity to apply the gestational age estimation methods, communication and rapport with clients, and value assessment of gestational age); 3. client (time of first antenatal care, migration status, language, education, cognitive approach to recalling dates, and experience with biomedical services); and, 4. the inherent limitations and ease of application of the methods themselves.

Repeated Transplantation of Microencapsulated Hepatocytes for Sustained Correction of Hyperbilirubinemia in Gunn Rats

In previous studies we demonstrated that transplantation of microencapsulated hepatocytes could correct congenital hyperbilirubinemia in Gunn rats for 4 to 6 wks. Reduction in hyperbilirubinemia followed a single transplantation of isolated encapsulated hepatocytes (IEH). After 4 to 6 wks of transplantation IEH gradually lose their functionality. To sustain long-term supplementation of liver function we have investigated the efficacy of monthly IEH transplantations for 6 mo. Hepatocytes, isolated from young Wistar rats, were microencapsulated with a collagen matrix within an alginate-poly L-lysine composite membrane. We transplanted IEH intraperitoneally into homozygous Gunn rats at monthly (4-wk) intervals for 6 mo. Control Gunn rats received intraperitoneal transplantations of empty microcapsules. Total serum bilirubin was measured in the IEH-transplanted and control Gunn rats at weekly intervals for the duration of the 6-month study. A significant (p < 0.01) and sustained decrease (by nearly 50%) in total serum bilirubin levels was observed following monthly IEH transplantations in Gunn rats for the duration of the study. No such decrease in total serum bilirubin levels was seen in the controls. The Gunn rats exhibited good tolerance for the multiple IEH transplantations. Thus, repeated IEH transplantations may be one strategy for providing long-term supplementation of liver function in congenital metabolic liver disease.

Hepatocyte Immobilization on Phema Microcarriers and its Biologically Modified Forms

Polyhydroxyethylmethacrylate (PHEMA) based microcarriers with different bulk structures were prepared by a phase inversion polymerization technique. PHEMA surfaces were further modified chemically by glow-discharge treatment, and biologically by covalent attachment of fibrinogen and collagen. Hepatocytes were isolated from young male Wistar rats using an in situ portal vein collagenase perfusion technique. Freshly isolated hepatocytes were seeded at 6 × 105 cells/mL and microcarrier concentration was 10 g/L. Stationary microcarrier cultures were carried out in standard (nontissue culture) polystyrene petri dishes in a humidified 5% CO2 incubator at 37 ± 0.5°C. Cell attachment was followed by light microscopy by taking samples from the culture medium every 30 min. Urea and protein syntheses by microcarrier-attached hepatocytes were determined by standard techniques. Nonswellable (highly cross-linked) hydrophilic PHEMA microcarriers did not support cell attachment and viability. However, swellable (low cross-linked) PHEMA microcarriers (pretreated in FBS) allowed high attachment and cell spreading. PHEMA microcarriers treated in dimethylaminoethylmethacrylate (DMAEMA) glow-discharge plasma also improved the cell attachment characteristics of the PHEMA microcarriers. The highest attachment efficiencies (immobilization yields) were observed with the biologically modified PHEMA microcarriers, especially modified with fibronectin. Metabolic activity, as estimated by urea and protein syntheses, was also higher in these microcarriers.

In vitro activity of cefoxitin and imipenem against Mycobacterium abscessus complex

The in vitro activity of cefoxitin and imipenem was compared for 43 strains of the Mycobacterium abscessus complex, mostly isolated from cystic fibrosis patients. The MICs of imipenem were lower than those of cefoxitin, although the number of imipenem-resistant strains was higher according to the CLSI breakpoints. Strain comparisons indicated that the MICs of cefoxitin were significantly higher for Mycobacterium bolletii than for M. abscessus. The MICs of both β-lactams were higher for the rough morphotype than for the smooth morphotype. The clinical impact of the in vitro difference between the activity of imipenem and that of cefoxitin remains to be determined.

Backbone and side-chain 1H, 15N and 13C assignment of apo- and imipenem-acylated L,D-transpeptidase from Bacillus subtilis

The D,D-transpeptidase activity of Penicillin Binding Proteins (PBPs) is essential to maintain cell wall integrity. PBPs catalyze the final step of the peptidoglycan synthesis by forming 4 → 3 cross-links between two peptide stems. Recently, a novel β-lactam resistance mechanism involving L,D-transpeptidases has been identified in Enterococcus faecium and Mycobacterium tuberculosis. In this resistance pathway, the classical 4 → 3 cross-links are replaced by 3 → 3 cross-links, whose formation are catalyzed by the L,D-transpeptidases. To date, only one class of the entire β-lactam family, the carbapenems, is able to inhibit the L,D-transpeptidase activity. Nevertheless, the specificity of this inactivation is still not understood. Hence, the study of this new transpeptidase family is of considerable interest in order to understand the mechanism of the L,D-transpeptidases inhibition by carbapenems. In this context, we present herein the backbone and side-chain (1)H, (15)N and (13)C NMR assignment of the L,D-transpeptidase from Bacillus subtilis (Ldt(Bs)) in the apo and in the acylated form with a carbapenem, the imipenem.

Pilot evaluation of a biopsychosocial integrated standardized patient examination in a family medicine clerkship

OBJECTIVE

A new biopsychosocial Integrated Standardized Patient Examination (ISPE) was implemented to assess communication skills for medical students participating in a family medicine clerkship.

METHOD

Mixed method, multi-level evaluation.

RESULTS

Pilot ISPE scores were significantly higher than previous Objective Structured Clinical Examination (OSCE) (p < .01). Family Physician and Social/Behavioral Scientist rater scores were correlated (p < .001), and Cronbach's alpha statistics were acceptable (FM: alpha = .837; BH: alpha = .768). Preceptor scores on "relations with professionals" (beta = .694, p = .008) significantly predicted ISPE scores, but other clerkship assignment grades were inversely associated with ISPE. Qualitative focus group themes included lack of readiness, divergence in beliefs on scope of physician practice, and focus on grade.

CONCLUSIONS

This pilot project describes the process and demonstrates the possibility of implementing a complex standardized patient case to assess students' management of complicated primary care patients with medical, psychological, and social issues.

A neuropsychological profile of off-diet adults with phenylketonuria

The metabolic disorder phenylketonuria (PKU) is treated early by a low-phenylalanine diet. While this prevents global cognitive impairment, some patients still experience cognitive and neurophysiological abnormalities. Neuropsychological testing of early treated, currently off-diet, PKU patients attending an adult PKU clinic showed a reduction in the Perceptual Organization Index (POI), Processing Speed Index (PSI) from the Wechsler Adult Intelligence Scale Third Edition (WAIS-III), and Part A of the Trail Making Test for the PKU group relative to controls. Taken together, these results supported a profile of reduced information-processing speed.

Meta-Analysis of Neuropsychological Symptoms of Adolescents and Adults with PKU

Phenylketonuria (PKU; OMIM 261600) is an autosomal recessive inborn error of phenylanaline metabolism. PKU is characterized by deficient or defective phenylalanine hydroxylase activity and persistantly increased levels of the essential amino acid phenylalanine in the circulation. The present article examines current understanding of the etiology of PKU, along with a meta-analysis examining neuropsychological and intellectual presentations in continuously treated adolescents and adults. Patients with PKU differed significantly from controls on Full-Scale IQ, processing speed, attention, inhibition, and motor control. Future research utilizing an integrative approach and detailed analysis of specific cognitive domains will assist both the scientist and clinician, and ultimately the patient.

Event-related potentials elicited during a visual Go-Nogo task in adults with phenylketonuria

OBJECTIVE

The aim of the present study was to examine the nature of previously reported deficits in sustained attention and response inhibition in adults with the developmental disorder, phenylketonuria (PKU).

METHODS

This study used event-related potentials (ERPs) to examine the performance of PKU adults (n=9) and a matched control group (n=9) on a visual Go-Nogo task.

RESULTS

Comparison of behavioural measures between the PKU and control groups failed to reach statistical significance, yet analysis of the ERPs showed statistically significant amplitude reductions in the P1 and N1 components elicited following presentation of stimuli, and a reduction in the amplitude of the N2 component elicited following presentation of Nogo stimuli.

CONCLUSIONS

These results suggest that adults with PKU, despite being continuously treated from birth, manifest subtle impairments in distinct aspects of information processing including early sensory processing of visually presented information, as well as impairments in inhibitory functions.

SIGNIFICANCE

The results contribute to an understanding of the neurophysiological mechanisms that are implicated in PKU and highlight the sensitivity of ERP techniques for the identification of the loci of information processing deficits in clinical groups.

Derivation of a clinical decision rule to guide the interhospital transfer of patients with blunt traumatic brain injury

OBJECTIVE

To derive a clinical decision rule for people with traumatic brain injury (TBI) that enables early identification of patients requiring specialised trauma care.

METHODS

We collected data from 1999 through 2003 on a retrospective cohort of consecutive people aged 18-65 years with a serious head injury (AIS > or =3), transported directly from the scene of injury, and evaluated in the ED. Information on 22 demographical, physiological, radiographic, and lab variables was collected. Resource based "high therapeutic intensity" measures occurring within 72 hours of ED arrival (the outcome measure) were identified a priori and included: neurosurgical intervention, exploratory laparotomy, intensive care interventions, or death. We used classification and regression tree analysis to derive and cross validate the decision rule.

RESULTS

504 consecutive trauma patients were identified as having a serious head injury: 246 (49%) required at least one of the HTI measures. Five ED variables (GCS, respiratory rate, age, temperature, and pulse rate) identified subjects requiring at least one of the HTI measures with 94% sensitivity (95% CI 91 to 97%) and 63% specificity (95% CI 57 to 69%) in the derivation sample, and 90% sensitivity and 55% specificity using cross validation.

CONCLUSIONS

This decision rule identified among a cohort of head injured patients evaluated in the ED the majority of those who urgently required specialised trauma care. The rule will require prospective validation in injured people presenting to non-tertiary care hospitals before implementation can be recommended.

Role of penicillin-binding protein 5 in expression of ampicillin resistance and peptidoglycan structure in Enterococcus faecium

The contribution of penicillin-binding protein 5 (PBP 5) to intrinsic and acquired beta-lactam resistance was investigated by constructing isogenic strains of Enterococcus faecium producing different PBP 5. The pbp5 genes from three E. faecium clinical isolates (BM4107, D344, and H80721) were cloned into the shuttle vector pAT392 and introduced into E. faecium D344S, a spontaneous derivative of E. faecium D344 highly susceptible to ampicillin due to deletion of pbp5 (MIC, 0.03 microg/ml). Immunodetection of PBP5 indicated that cloning of the pbp5 genes into pAT392 resulted in moderate overproduction of PBP 5 in comparison to wild-type strains. This difference may be attributed to a difference in gene copy number. Expression of the pbp5 genes from BM4107 (MIC, 2 microg/ml), D344 (MIC, 24 microg/ml), and H80721 (MIC, 512 microg/ml) in D344S conferred relatively low levels of resistance to ampicillin (MICs, 6, 12, and 20 microg/ml, respectively). A methionine-to-alanine substitution was introduced at position 485 of the BM4107 PBP 5 by site-directed mutagenesis. In contrast to previous hypotheses based on comparison of nonisogenic strains, this substitution resulted in only a 2.5-fold increase in the ampicillin MIC. The reversed-phase high-performance liquid chromatography muropeptide profiles of D344 and D344S were similar, indicating that deletion of pbp5 was not associated with a detectable defect in cell wall synthesis. These results indicate that pbp5 is a nonessential gene responsible for intrinsic resistance to moderate levels of ampicillin and by itself cannot confer high-level resistance.

Identification of the UDP-MurNAc-pentapeptide:L-alanine ligase for synthesis of branched peptidoglycan precursors in Enterococcus faecalis

Many species of gram-positive bacteria produce branched peptidoglycan precursors resulting from the transfer of various L-amino acids or glycine from amino acyl-tRNA to the epsilon-amino group of L-lysine. The UDP-MurNAc-pentapeptide:L-alanine ligase and alanyl-tRNA synthetase genes from Enterococcus faecalis were identified, cloned, and overexpressed in Escherichia coli. The purified enzymes were necessary and sufficient for tRNA-dependent addition of L-alanine to UDP-MurNAc-pentapeptide in vitro. The ligase belonged to the Fem family of proteins, which were initially identified genetically as factors essential for methicillin resistance in Staphylococcus aureus.

Influence of trauma system implementation on process of care delivered to seriously injured patients in rural trauma centers

BACKGROUND

Statewide trauma systems are implemented by health care policy makers whose intent is to improve the process of care delivered to seriously injured patients. In Oregon, Advanced Trauma Life Support (ATLS) training was mandated for all physicians employed in the emergency department of trauma centers. The purpose of this study was to test the hypothesis that mandatory ATLS training favorably influenced processes of care.

METHODS

Seriously injured patients treated at 9 rural Level 3 and Level 4 hospitals were studied before (PRE) and after (POST) implementation of Oregon's trauma system. The processes of care evaluated on the basis of chart review were 20 diagnostic and therapeutic interventions advocated in the ATLS course. A cumulative process score (CPS) between 0 and 1 was assigned on the basis of the processes of care delivered. A CPS of 1 indicated optimal process of care.

RESULTS

Mean CPS for 506 PRE period patients (0.44 +/- 0.27) was significantly lower than the mean CPS for 512 POST period patients (0.57 +/- 0.27) with an unpaired t test (P <.001). For the subgroup with injury severity score of 16 to 34, the mean CPS of survivors (0.67 +/- 0.19) was significantly higher than the mean CPS of decedents (0.57 +/- 0.25).

CONCLUSIONS

Process of care for seriously injured patients improved after categorization of rural trauma centers in Oregon. Evidence shows improved process of care may have benefitted patients with serious but survivable injuries. Measurement of process of care is an alternative to mortality analysis as an indication of the quality of care.

Mortality among seriously injured patients treated in remote rural trauma centers before and after implementation of a statewide trauma system

BACKGROUND

Injury mortality in rural regions remains high with little evidence that trauma system implementation has benefited rural populations.

OBJECTIVE

To evaluate risk-adjusted mortality in remote regions of Oregon before and after implementation of a statewide trauma system.

RESEARCH DESIGN

A retrospective cohort study assessing injury mortality through 30 days after hospital discharge.

SETTING

Nine rural Oregon hospitals serving counties with populations <18 persons per square mile.

SUBJECTS

Severely injured patients presenting to four level-3 and five level-4 trauma hospitals 3 years before and 3 years after trauma system implementation.

MEASURES

Interhospital transfer, hospital death, and demise within 30 days following hospital discharge.

RESULTS

A total of 940 patients were analyzed. After trauma system implementation, patients presenting to level-4 hospitals were more likely transferred to level-2 facilities (P <0.001). Interhospital transfer times from level-3 hospitals lengthened significantly after system implementation (P <0.001). Overall mortality rates were higher in the postsystem period (8.3%) than the presystem period (6.7%), but not significantly. Controlling for covariates, no additional benefit to risk-adjusted mortality was associated with trauma system implementation. Additional deaths, occurring after trauma system implementation, included head-injured patients transferred from rural hospitals to nonlevel-1 trauma center hospitals.

CONCLUSIONS

Increased injury survival after Oregon trauma system implementation, demonstrated in urban and statewide analyses, was not confirmed in remote regions of the state. Efforts to improve trauma systems in rural areas should focus on the processes of care for head-injured patients transferred to higher designation trauma centers.

Bactericidal activity of gentamicin against Enterococcus faecalis in vitro and in vivo

The activity of gentamicin at various concentrations against two strains of Enterococcus faecalis was investigated in vitro and in a rabbit model of aortic endocarditis. In vitro, gentamicin at 0.5 to 4 times the MIC failed to reduce the number of bacteria at 24 h. Rabbit or human serum dramatically increased gentamicin activity, leading to a >/=3-log(10) CFU/ml decrease in bacterial counts when the drug concentration exceeded the MIC. Susceptibility testing in the presence of serum was predictive of in vivo activity, since gentamicin alone significantly reduced the number of surviving bacteria in the vegetations if the peak-to-MIC ratio was greater than 1. However, gentamicin selected resistant mutants in rabbits. The intrinsic activity of gentamicin should be taken into account in evaluation of combinations of gentamicin and cell wall-active agents against enterococci.

Novel mechanism of beta-lactam resistance due to bypass of DD-transpeptidation in Enterococcus faecium

The peptidoglycan structure of in vitro selected ampicillin-resistant mutant Enterococcus faecium D344M512 and of the susceptible parental strain D344S was determined by reverse phase high performance liquid chromatography and mass spectrometry. The muropeptide monomers were almost identical in the two strains. The substantial majority (99.3%) of the oligomers from the susceptible strain D344S contained the usual d-alanyl --> d-asparaginyl (or d-aspartyl)-l-lysyl cross-link (d-Ala --> d-Asx-l-Lys) generated by beta-lactam-sensitive DD-transpeptidation. The remaining oligomers (0.7%) were produced by beta-lactam-insensitive LD-transpeptidation, because they contained l-Lys --> d-Asx-l-Lys cross-links. The muropeptide oligomers of the ampicillin-resistant mutant D344M512 contained only these l-Lys --> d-Asx-l-Lys cross-links indicating that resistance was due to the bypass of the beta-lactam-sensitive DD-transpeptidation reaction. The discovery of this novel resistance mechanism indicates that DD-transpeptidases cannot be considered anymore as the sole essential transpeptidase enzymes.

Moderate-level resistance to glycopeptide LY333328 mediated by genes of the vanA and vanB clusters in enterococci

Three of five natural plasmids carrying a wild-type vanA gene cluster did not confer LY333328 glycopeptide resistance on Enterococcus faecalis JH2-2 (MIC = 2 microg/ml). The two remaining plasmids conferred resistance to the drug (MIC, 8 microg/ml). The vanB gene cluster did not confer resistance to LY333328, since this antibiotic was not an inducer. Mutations in the vanS(B) sensor gene that allowed induction by teicoplanin or constitutive expression of the vanB cluster led to LY333328 resistance (MIC, 8 to 16 microg/ml). Overproduction of the VanH, VanA, and VanX proteins for D-alanyl-D-lactate (D-Ala-D-Lac) synthesis and D-Ala-D-Ala hydrolysis was sufficient for resistance to LY333328 (MIC, 16 microg/ml). Mutations in the host D-Ala:D-Ala ligase contributed to LY333328 resistance in certain VanA- and VanB-type strains, but the MICs of the antibiotic did not exceed 16 microg/ml. Addition of D-2-hydroxybutyrate in the culture medium of mutants that did not produce the VanH D-lactate dehydrogenase led to incorporation of this D-2-hydroxy acid at the C-terminal ends of the peptidoglycan precursors and to LY333328 resistance (MIC, 64 microg/ml). The vanZ gene of the vanA cluster conferred resistance to LY333328 (MIC, 8 microg/ml) by an unknown mechanism. These data indicate that VanA- and VanB-type enterococci may acquire moderate-level resistance to LY333328 (MIC </= 16 microg/ml) in a single step by various mechanisms.

Single-cell analysis of glycopeptide resistance gene expression in teicoplanin-resistant mutants of a VanB-type Enterococcus faecalis

The vanB gene cluster confers resistance to vancomycin but not to the related antibiotic teicoplanin, as the VanRB SB two-component regulatory system triggers expression of the glycopeptide resistance genes only in response to vancomycin. The VanRB regulator activates promoters PRB and PYB for transcription of the regulatory (vanRB SB) and resistance (vanYB WHB BXB) genes respectively. The gfpmut1 gene encoding a green fluorescent protein was fused to PYB to analyse promoter activation in single cells by fluorescence microscopy and flow cytometry. Characterization of 17 teicoplanin-resistant mutants indicated that amino acid substitutions on either side of the VanSB autophosphorylation site led to a constitutive phenotype. Substitutions in the membrane-associated domain resulted in a gain of function, as they allowed induction by teicoplanin. A vanSB null mutant expressed gfpmut1 at various levels under non-inducing conditions, and the majority of the bacteria were not fluorescent. Bacteria grown in the presence of vancomycin or teicoplanin were homogeneously fluorescent. The increase in the number of fluorescent bacteria resulted from induction in negative cells rather than from selection of a resistant subpopulation, indicating that VanRB was activated by cross-talk. Transglycosylase inhibition was probably the stimulus for the heterologous kinase, as moenomycin was also an inducer.

Two-step acquisition of resistance to the teicoplanin-gentamicin combination by VanB-type Enterococcus faecalis in vitro and in experimental endocarditis

The activity of vancomycin and teicoplanin combined with gentamicin was investigated in vitro against strains of Enterococcus faecalis resistant to vancomycin and susceptible to teicoplanin (VanB type) and against mutants that had acquired resistance to teicoplanin by three different mechanisms. In vitro, gentamicin selected mutants with two- to sixfold increases in the level of resistance to this antibiotic at frequencies of 10(-6) to 10(-7). Teicoplanin selected teicoplanin-resistant mutants at similar frequencies. Both mutations were required to abolish the activity of the gentamicin-teicoplanin combination. As expected, simultaneous acquisition of the two types of mutations was not observed. In therapy with gentamicin or teicoplanin alone, each selected mutants in three of seven rabbits with aortic endocarditis due to VanB-type E. faecalis BM4275. The vancomycin-gentamicin combination selected mutants that were resistant to gentamicin and to the combination. In contrast, the teicoplanin-gentamicin regimen prevented the emergence of mutants resistant to one or both components of the combination. These results suggest that two mutations are also required to suppress the in vivo activity of the teicoplanin-gentamicin combination.

Characterization and modelling of VanT: a novel, membrane-bound, serine racemase from vancomycin-resistant Enterococcus gallinarum BM4174

Sequence determination of a region downstream from the vanXYc gene in Enterococcus gallinarum BM4174 revealed an open reading frame, designated vanT, that encodes a 698-amino-acid polypeptide with an amino-terminal domain containing 10 predicted transmembrane segments. The protein contained a highly conserved pyridoxal phosphate attachment site in the C-terminal domain, typical of alanine racemases. The protein was overexpressed in Escherichia coli, and serine racemase activity was detected in the membrane but not in the cytoplasmic fraction after centrifugation of sonicated cells, whereas alanine racemase activity was located almost exclusively in the cytoplasm. When the protein was overexpressed as a polypeptide lacking the predicted transmembrane domain, serine racemase activity was detected in the cytoplasm. The serine racemase activity was partially (64%) inhibited by D-cycloserine, whereas host alanine racemase activity was almost totally inhibited (97%). Serine racemase activity was also detected in membrane preparations of constitutively vancomycin-resistant E. gallinarum BM4174 but not in BM4175, in which insertional inactivation of the vanC-1 D-Ala:D-Ser ligase gene probably had a polar effect on expression of the vanXYc and vanT genes. Comparative modelling of the deduced C-terminal domain was based on the alignment of VanT with the Air alanine racemase from Bacillus stearothermophilus. The model revealed that almost all critical amino acids in the active site of Air were conserved in VanT, indicating that the C-terminal domain of VanT is likely to adopt a three-dimensional structure similar to that of Air and that the protein could exist as a dimer. These results indicate that the source of D-serine for peptidoglycan synthesis in vancomycin-resistant enterococci expressing the VanC phenotype involves racemization of L- to D-serine by a membrane-bound serine racemase.

Requirement of the VanY and VanX D,D-peptidases for glycopeptide resistance in enterococci

Transposon Tn 1546 confers resistance to glycopeptide antibiotics in enterococci and encodes two D,D-peptidases (VanX and VanY) in addition to the enzymes for the synthesis of D-alanyl-D-lactate (D-Ala-D-Lac). VanY was produced in the baculovirus expression system and purified as a proteolytic fragment that lacked the putative N-terminal membrane anchor of the protein. The enzyme was a Zn2+-dependent D,D-carboxypeptidase that cleaved the C-terminal residue of peptidoglycan precursors ending in R-D-Ala-D-Ala or R-D-Ala-D-Lac but not the dipeptide D-Ala-D-Ala. The specificity constants kcat/Km were 17- to 67-fold higher for substrates ending in the R-D-Ala-D-Ala target of glycopeptides. In Enterococcus faecalis, VanY was present in membrane and cytoplasmic fractions, produced UDP-MurNAc-tetrapeptide from cytoplasmic peptidoglycan precursors and was required for high-level glycopeptide resistance in a medium supplemented with D-Ala. The enzyme could not replace the VanX D,D-dipeptidase for the expression of glycopeptide resistance but a G237D substitution in the host D-Ala:D-Ala ligase restored resistance in a vanX null mutant. Deletion of the membrane anchor of VanY led to an active D,D-carboxypeptidase exclusively located in the cytoplasmic fraction that did not contribute to glycopeptide resistance in a D-Ala-containing medium. Thus, VanX and VanY had non-overlapping functions involving the hydrolysis of D-Ala-D-Ala and the removal of D-Ala from membrane-bound lipid intermediates respectively.

Mutations leading to increased levels of resistance to glycopeptide antibiotics in VanB-type enterococci

The vanB gene cluster mediates glycopeptide resistance by production of peptidoglycan precursors ending in the depsipeptide D-alanyl-D-lactate (D-Ala-D-Lac) instead of D-Ala-D-Ala found in susceptible enterococci. Synthesis of D-Ala-D-Lac and hydrolysis of D-Ala-D-Ala is controlled by the VanR(B)S(B) two-component regulatory system that activates transcription of the resistance genes in response to vancomycin but not to teicoplanin. Two substitutions (A3C-->G or D168-->Y) in the VanS(B) sensor kinase resulted in induction by teicoplanin, indicating that the N-terminal domain of the protein was involved in glycopeptide sensing. A substitution (T237-->K) located in the vicinity of the putative autophosphorylation site of VanS(B) (H233) was associated with a constitutive phenotype and affected a conserved residue known to be critical for the phosphatase activity of related kinases. A mutant producing an impaired host D-Ala:D-Ala ligase required vancomycin for growth, since D-Ala-D-Lac was only produced under inducing conditions. The ddl and vanS(B) mutations, alone or in combination, resulted in various resistance phenotypes that were determined by the amount of D-Ala-D-Ala and D-Ala-D-Lac incorporated into peptidoglycan precursors under different inducing conditions.

Selection of glycopeptide-resistant mutants of VanB-type Enterococcus faecalis BM4281 in vitro and in experimental endocarditis

Enterococcus faecalis BM4281 is resistant to vancomycin, susceptible to teicoplanin (VanB phenotype), and intrinsically resistant to low levels of gentamicin. The efficacy of glycopeptides against BM4281 was investigated in a rabbit model of experimental endocarditis for reduction of bacterial counts in cardiac vegetations and selection of mutants with increased resistance to glycopeptides. Teicoplanin led to a 100-fold reduction of bacteria in the vegetations, whereas vancomycin had no effect. Monotherapy with either antibiotic selected mutants with homogeneous or heterogeneous resistance to high levels of both glycopeptides. Vancomycin also selected mutants that required the antibiotic for growth. The combination of gentamicin plus teicoplanin was bactericidal, prevented the emergence of mutants, and allowed sterilization of the vegetations in 25% of the rabbits, indicating that the combination may be an alternative if penicillin cannot be used against VanB-type enterococci.

The VanS sensor negatively controls VanR-mediated transcriptional activation of glycopeptide resistance genes of Tn1546 and related elements in the absence of induction

Transposon Tn1546 from Enterococcus faecium BM4147 encodes a histidine protein kinase (VanS) and a response regulator (VanR) that regulate transcription of the vanHAX operon encoding a dehydrogenase (VanH), a ligase (VanA), and a D,D-dipeptidase (VanX). These last three enzymes confer resistance to glycopeptide antibiotics by production of peptidoglycan precursors ending in the depsipeptide D-alanyl-D-lactate. Transcription of vanS and the role of VanS in the regulation of the vanHAX operon were analyzed by inserting a cat reporter gene into vanS. Transcription of cat and vanX was inducible by glycopeptides in partial diploids harboring vanS and vanS(omega)cat but was constitutive in strains containing only vanS(omega)cat. Promoters P(R) and P(H), located upstream from vanR and vanH, respectively, were cloned into a promoter probing vector to study transactivation by chromosomally encoded VanR and VanS. The promoters were inactive in the absence of vanR and vanS, inducible by glycopeptides in the presence of both genes, and constitutively activated by VanR in the absence of VanS. Thus, induction of the vanHAX operon involves an amplification loop resulting from binding of phospho-VanR to the P(R) promoter and increased transcription of the vanR and vanS genes. Full activation of P(R) and P(H) by VanR was observed in the absence of VanS, indicating that the sensor negatively controls VanR in the absence of glycopeptides, presumably by dephosphorylation. Activation of the VanR response regulator in the absence of VanS may involve autophosphorylation of VanR with acetyl phosphate or phosphorylation by a heterologous histidine protein kinase.

Optimizing the cell efficacy of synthetic ribozymes. Site selection and chemical modifications of ribozymes targeting the proto-oncogene c-myb

Expression of the proto-oncogene c-myb is necessary for proliferation of vascular smooth muscle cells. We have developed synthetic hammerhead ribozymes that recognize and cleave c-myb RNA, thereby inhibiting cell proliferation. Herein, we describe a method for the selection of hammerhead ribozyme cleavage sites and optimization of chemical modifications that maximize cell efficacy. In vitro assays were used to determine the relative accessibility of the ribozyme target sites for binding and cleavage. Several ribozymes thus identified showed efficacy in inhibiting smooth muscle cell proliferation relative to catalytically inactive controls. A combination of modifications including several phosphorothioate linkages at the 5'-end of the ribozyme and an extensively modified catalytic core resulted in substantially increased cell efficacy. A variety of different 2'-modifications at positions U4 and U7 that confer nuclease resistance gave comparable levels of cell efficacy. The lengths of the ribozyme binding arms were varied; optimal cell efficacy was observed with relatively short sequences (13-15 total nucleotides). These synthetic ribozymes have potential as therapeutics for hyperproliferative disorders such as restenosis and cancer. The chemical motifs that give optimal ribozyme activity in smooth muscle cell assays may be applicable to other cell types and other molecular targets.

Glycopeptide resistance in enterococci

Glycopeptide resistance in enterococci results from the production of peptidoglycan precursors with low affinity for these antibiotics. The mobility of the resistance genes by transposition and conjugation and the ability of the resistance proteins to interfere with synthesis of normal precursors in different hosts indicate that dissemination into other bacterial species should be anticipated.

Specificity of induction of glycopeptide resistance genes in Enterococcus faecalis

Regulation of VanA- and VanB-type glycopeptide resistance in enterococci is mediated by related two-component regulatory systems (VanR-VanS and VanRB-VanSB). The transglycosylase inhibitors vancomycin, teicoplanin, and moenomycin induced synthesis of the VanX D,D-dipeptidase in a VanA-type Enterococcus faecalis harboring transposon Tn1546. Inhibitors of reactions immediately preceding (ramoplanin) or following (penicillin G and bacitracin) transglycosylation were not inducers. These results identify accumulation of membrane-bound lipid intermediate II as a potential signal for induction of VanA-type resistance. In E.faecalis BM4281 harboring a wild vanB genetic element, D,D-dipeptidase synthesis was only inducible by vancomycin. Induction of the production of the VanB ligase by vancomycin was required for growth of a vancomycin-dependent derivative of BM4281, since introduction of a plasmid coding for constitutive synthesis of the VanA ligase eliminated the requirement of glycopeptide for growth. Both vancomycin and teicoplanin were able to induce D,D-dipeptidase synthesis in BM4281 derivatives that were vancomycin and teicoplanin resistant or vancomycin and teicoplanin dependent. Acquisition of teicoplanin resistance in the latter types of strains was due to alteration in induction specificity associated with an increase in the sensitivity of the regulatory system to vancomycin. Thus, the wild VanRB-VanSB system is unable or not sensitive enough to sense teicoplanin, although mutations can lead to recognition of this antibiotic.

Quantitative analysis of the metabolism of soluble cytoplasmic peptidoglycan precursors of glycopeptide-resistant enterococci

Transposon Tn1546 from Enterococcus faecium BM4147 mediates high-level resistance to the glycopeptide antibiotics vancomycin and teicoplanin. Tn 1546 encodes a dehydrogenase (VanH) and a ligase (VanA) that synthesize D-alanyl-D-lactate (D-Ala-D-Lac), a D,D-dipeptidase (VanX) that hydrolyses D-Ala-D-Ala and a two-component regulatory system (VanR-VanS) that controls transcription of the vanHAX operon. Strains of Enterococcus faecalis harbouring various copy numbers of the vanRSHAX cluster were tested to determine if there was a correlation between the levels of resistance to glycopeptides, the levels of expression of the corresponding resistance genes and the relative proportions of the different cytoplasmic peptidoglycan precursors. Increased transcription of the vanHAX operon was associated with increased incorporation of D-Ala-D-Lac into peptidoglycan precursors to the detriment of D-Ala-D-Ala, and with a gradual increase in the vancomycin-resistance levels. More complete elimination of D-Ala-D-Ala-containing precursors was required for teicoplanin resistance. The VanY and VanZ proteins also encoded by Tn1546 were not effectors of the regulation of the vanHAX operon but contributed to vancomycin and teicoplanin resistance, respectively. Differences at the regulatory level accounted for phenotypic diversity in acquired glycopeptide resistance by production of D-lac-ending precursors.

Mechanisms of glycopeptide resistance in enterococci

Inducible resistance to high levels of glycopeptide antibiotics in clinical isolates of enterococci is mediated by Tn1546 or related transposons. Tn1546 encodes the VanH dehydrogenase which reduces pyruvate to D-lactate (D-Lac) and the VanA ligase which catalyses synthesis of the depsipeptide D-alanyl-D-lactate (D-Ala-D-Lac). The depsipeptide replaces the dipeptide D-Ala-D-Ala leading to production of peptidoglycan precursors which bind glycopeptides with reduced affinity. In addition, Tn1546 encodes the VanX dipeptidase and the VanY D,D-carboxypeptidase that hydrolyse the dipeptide D-Ala-D-Ala and the C-terminal D-Ala residue of the cytoplasmic precursor UDP-MurNAC-L-Ala-gamma-D- Glu-L-Lys-D-Ala-D-Ala, respectively. These two proteins act in series to eliminate D-Ala-D-Ala-containing precursors. VanX is required for resistance whereas VanY only slightly increases the level of resistance mediated by VanH, VanA and VanX.

The vanZ gene of Tn1546 from Enterococcus faecium BM4147 confers resistance to teicoplanin

A five-gene cluster from Tn1546 confers resistance to the glycopeptide antibiotics vancomycin (Vm) and teicoplanin (Te) by synthesis of pentadepsipeptide peptidoglycan precursors terminating in D-lactate, which replaces D-alanine in the same position of precursors utilized by susceptible enterococci. Cloning and nucleotide sequencing indicated that Tn1546 contains an additional gene, designated vanZ, which confers low-level Te resistance, in the absence of the genes required for pentadepsipeptide synthesis. Analysis of cytoplasmic peptidoglycan precursors, accumulated in the presence of ramoplanin, showed that VanZ-mediated Te resistance does not involve incorporation of a substituent of D-alanine into the precursors.

Collagen and fibronectin immobilization on PHEMA microcarriers for hepatocyte attachment

Polyhydroxyethylmethacrylate (PHEMA) microcarriers in a size range of 150-250 microns were prepared by a suspension polymerization in an aqueous phase containing magnesium oxide. The hydroxyl groups on the PHEMA microcarriers were activated by cyanogen bromide. In order to improve cell attachment, cell-adhesive proteins, namely, collagen and fibronectin were immobilized onto PHEMA microcarriers. The nonspecific adsorption values for collagen and fibronectin were 0.10 mg collagen/g PHEMA and 0.044 mg fibronectin/g PHEMA, respectively. Collagen and fibronectin immobilization on PHEMA microcarriers were studied at different pH by using single protein solutions containing different amounts of proteins, at a constant temperature of 20 degrees C. The maximum immobilizations were 0.85 mg collagen/g PHEMA (at pH: 9.5) and 0.52 mg fibronectin/g PHEMA (at pH: 7.4). Hepatocyte attachment onto these biologically modified PHEMA microcarriers was studied. Hydrophilic PHEMA microcarriers did not support cell attachment. High hepatocyte attachment yields (up to 75% surface coverage) were observed on collagen and fibronectin immobilized PHEMA microcarriers.

Glycopeptide resistance mediated by enterococcal transposon Tn1546 requires production of VanX for hydrolysis of D-alanyl-D-alanine

Cloning and nucleotide sequencing indicated that transposon Tn1546 from Enterococcus faecium BM4147 encodes a 23,365 Da protein, VanX, required for glycopeptide resistance. The vanX gene was located downstream from genes encoding the VanA ligase and the VanH dehydrogenase which synthesize the depsipeptide D-alanyl-D-lactate (D-Ala-D-Lac). In the presence of ramoplanin, an Enterococcus faecalis JH2-2 derivative producing VanH, VanA and VanX accumulated mainly UDP-MurNAc-L-Ala-gamma-D-Glu-L-Lys-D-Ala-D-Lac (pentadepsipeptide) and small amounts of UDP-MurNAc-L-Ala-gamma-D-Glu-L-Lys-D-Ala-D-Ala (pentapeptide) in the ratio 49:1. Insertional inactivation of vanX led to increased synthesis of pentapeptide with a resulting change in the ratio of pentadepsipeptide: pentapeptide to less than 1:1. Expression of vanX in E. faecalis and Escherichia coli resulted in production of a D,D-dipeptidase that hydrolysed D-Ala-D-Ala. Pentadepsipeptide, pentapeptide and D-Ala-D-Lac were not substrates for the enzyme. These results establish that VanX is required for production of a D,D-dipeptidase that hydrolyses D-Ala-D-Ala, thereby preventing pentapeptide synthesis and subsequent binding of glycopeptides to D-Ala-D-Ala-containing peptidoglycan precursors at the cell surface.

Contribution of VanY D,D-carboxypeptidase to glycopeptide resistance in Enterococcus faecalis by hydrolysis of peptidoglycan precursors

The vanR, vanS, vanH, vanA, and vanX genes of enterococcal transposon Tn1546 were introduced into the chromosome of Enterococcus faecalis JH2-2. Complementation of this portion of the van gene cluster by a plasmid encoding VanY D,D-carboxypeptidase led to a fourfold increase in the vancomycin MIC (from 16 to 64 micrograms/ml). Multicopy plasmids pAT80 (vanR vanS vanH vanA vanX) and pAT382 (vanR vanS vanH vanA vanX vanY) conferred similar levels of vancomycin resistance to JH2-2. The addition of D-alanine (100 mM) to the culture medium restored the vancomycin susceptibility of E. faecalis JH2-2/pAT80. The pentapeptide UDP-MurNAc-L-Ala-gamma-D-Glu-L-Lys-D-Ala-D-Ala partially replaced pentadepsipeptide UDP-MurNAc-L-Ala-gamma-D-Glu-L-Lys-D-Ala-D-Lac when the strain was grown in the presence of D-alanine. In contrast, resistance mediated by pAT382 was almost unaffected by the addition of the amino acid. Expression of the vanY gene of pAT382 resulted in the formation of the tetrapeptide UDP-MurNAc-L-Ala-gamma-D-Glu-L-Lys-D-Ala, indicating that a portion of the cytoplasmic precursors had been hydrolyzed. These results show that VanY contributes to glycopeptide resistance in conditions in which pentapeptide is present in the cytoplasm above a threshold concentration. However, the contribution of the enzyme to high-level resistance mediated by Tn1546 appears to be moderate, probably because hydrolysis of D-alanyl-D-alanine by VanX efficiently prevents synthesis of the pentapeptide.

An evaluation of the repeatability and reproducibility of a surface test for the activity of disinfectants

A collaborative study was carried out to determine the precision of a disinfectant surface test method which is currently under consideration for development as a harmonized European standard surface test. Results indicate that significant variation in microbicidal effect occurs both within and between test laboratories despite careful standardization of test conditions, but that the variability may be less than that associated with suspension tests. Indications are that much of this variability derives from random variations in the resistance of the test strains from day to day and, most particularly, from test period to test period both within as well as between laboratories. It is concluded that although the test may be sufficiently reliable to be used as a standard method, adequate replication must be specified to distinguish borderline pass from borderline fail concentrations.

Cryopreserved microencapsulated hepatocytes--transplantation studies in Gunn rats

Hepatocyte transplantation has been shown to provide significant metabolic support in several animal models of liver diseases. However, for it to be a viable alternative for supplementation of liver function in disease, large quantities of isolated hepatocytes would be necessary. At the present time there are no inexpensive routine methods for cryopreservation of hepatocytes. Existing procedures are cumbersome and require expensive programmable freezers. Hepatocyte cultures are sensitive and easily damaged in handling. By utilizing techniques of microencapsulation and cryopreservation we have attempted to overcome these problems. We have developed a simple, convenient, and inexpensive technique for the long-term storage of hepatocytes. Biological activity of the nonfrozen isolated encapsulated hepatocytes (IEH) and cryopreserved IEH (cIEH) was assessed both in tissue culture and by transplantation in Gunn rats. Significant urea and protein syntheses were detectable during the 10-day culture period even in the 30-day cIEH. Additionally, transplanted IEH and cIEH significantly reduced hyperbilirubinemia in Gunn rats for up to 30 days posttransplantation. Control (empty) microcapsules did not lower serum bilirubin levels. Thus we conclude: (1) cryopreservation of IEH is a convenient and cost-effective method for preserving and storing hepatocytes; (2) cryopreserved IEH function as well as nonfrozen IEH both in vitro and in vivo; (3) microencapsulation may protect hepatocytes from the adverse effects of cryopreservation.