Depression: an individual-level early warning indicator of virologic failure in HIV patients in South Africa.

OBJECTIVE: To identify individual-level early warning indicators of virologic failure in HIV patients receiving antiretroviral therapy (ART) in South Africa. DESIGN: A matched case-control study of individuals with and without virologic failure (VF) (>5 months on ART and HIV-1 plasma viral load >1,000 copies/mL) was conducted between June 2014 and June 2018. Of the 1,000 participants enrolled in the parent cohort, 96 experienced VF, and 199 additional controls were identified from the parent cohort and matched 1:2 (some matched 1:3) for sex, age, ART duration, and site. Participants were interviewed while clinical, pharmacy refill, laboratory, and objective pharmacological data were obtained. Multivariate conditional logistic regression models were constructed using model selection to identify factors associated with VF. Significant determinants of VF were identified using an alpha level of 0.05. RESULTS: In a full conditional model, higher cumulative ART adherence, quantified using tenofovir-diphosphate concentrations in dried blood spots (OR 0.26) and medication possession ratio (OR 0.98) were protective against VF, whereas an increase in total depression score (OR 1.20) was predictive of VF. CONCLUSION: This analysis demonstrates the importance of depression as a key individual-level early warning indicator of VF. Efforts to address mental health concerns among patients with people living with HIV could improve virologic suppression.

OBJECTIF: Identifier les indicateurs d'alerte précoce au niveau individuel de l'échec virologique chez les patients séropositifs recevant un traitement antirétroviral (TAR) en Afrique du Sud. MÉTHODE: Une étude cas-témoins appariée de personnes avec et sans échec virologique (FV, pour l'anglais « virologic failure ¼) (>5 mois sous ART et charge virale plasmatique du VIH-1 >1 000 copies/ml) a été menée entre juin 2014 et juin 2018. Sur les 1 000 participants inscrits dans la cohorte parente, 96 ont présenté une FV et 199 témoins supplémentaires ont été identifiés dans la cohorte parentale et appariés 1:2 (certains appariés 1:3) pour le sexe, l'âge, la durée du TAR et le site. Les participants ont été interrogés pendant que des données cliniques, de renouvellement de pharmacie, de laboratoire et pharmacologiques objectives ont été obtenues. Des modèles de régression logistique conditionnelle multivariée ont été construits à l'aide d'une sélection de modèles pour identifier les facteurs associés à la FV. Les déterminants significatifs de la FV ont été identifiés à l'aide d'un niveau alpha de 0,05. RÉSULTATS: Dans un modèle conditionnel complet, une observance cumulative plus élevée du TAR, quantifiée à l'aide des concentrations de ténofovir-diphosphate dans les gouttes de sang séché (OR 0,26) et du ratio de possession de médicaments (OR 0,98) protégeait contre la FV, tandis qu'une augmentation du score de dépression totale (OR 1,20) était prédictive de la FV. CONCLUSION: Cette analyse démontre l'importance de la dépression en tant qu'indicateur précoce clé au niveau individuel de la FV. Les efforts visant à résoudre les problèmes de santé mentale chez les personnes vivant avec le VIH pourraient améliorer la suppression virologique.

Energetic, structural, and antimicrobial analyses of beta-lactam side chain recognition by beta-lactamases.

BACKGROUND: Penicillins and cephalosporins are among the most widely used and successful antibiotics. The emergence of resistance to these beta-lactams, most often through bacterial expression of beta-lactamases, threatens public health. To understand how beta-lactamases recognize their substrates, it would be helpful to know their binding energies. Unfortunately, these have been difficult to measure because beta-lactams form covalent adducts with beta-lactamases. This has complicated functional analyses and inhibitor design. RESULTS: To investigate the contribution to interaction energy of the key amide (R1) side chain of beta-lactam antibiotics, eight acylglycineboronic acids that bear the side chains of characteristic penicillins and cephalosporins, as well as four other analogs, were synthesized. These transition-state analogs form reversible adducts with serine beta-lactamases. Therefore, binding energies can be calculated directly from K(i) values. The K(i) values measured span four orders of magnitude against the Group I beta-lactamase AmpC and three orders of magnitude against the Group II beta-lactamase TEM-1. The acylglycineboronic acids have K(i) values as low as 20 nM against AmpC and as low as 390 nM against TEM-1. The inhibitors showed little activity against serine proteases, such as chymotrypsin. R1 side chains characteristic of beta-lactam inhibitors did not have better affinity for AmpC than did side chains characteristic of beta-lactam substrates. Two of the inhibitors reversed the resistance of pathogenic bacteria to beta-lactams in cell culture. Structures of two inhibitors in their complexes with AmpC were determined by X-ray crystallography to 1.90 A and 1.75 A resolution; these structures suggest interactions that are important to the affinity of the inhibitors. CONCLUSIONS: Acylglycineboronic acids allow us to begin to dissect interaction energies between beta-lactam side chains and beta-lactamases. Surprisingly, there is little correlation between the affinity contributed by R1 side chains and their occurrence in beta-lactam inhibitors or beta-lactam substrates of serine beta-lactamases. Nevertheless, presented in acylglycineboronic acids, these side chains can lead to inhibitors with high affinities and specificities. The structures of their complexes with AmpC give a molecular context to their affinities and may guide the design of anti-resistance compounds in this series.

Structure-based design and in-parallel synthesis of inhibitors of AmpC beta-lactamase.

BACKGROUND: Group I beta-lactamases are a major cause of antibiotic resistance to beta-lactams such as penicillins and cephalosporins. These enzymes are only modestly affected by classic beta-lactam-based inhibitors, such as clavulanic acid. Conversely, small arylboronic acids inhibit these enzymes at sub-micromolar concentrations. Structural studies suggest these inhibitors bind to a well-defined cleft in the group I beta-lactamase AmpC; this cleft binds the ubiquitous R1 side chain of beta-lactams. Intriguingly, much of this cleft is left unoccupied by the small arylboronic acids. RESULTS: To investigate if larger boronic acids might take advantage of this cleft, structure-guided in-parallel synthesis was used to explore new inhibitors of AmpC. Twenty-eight derivatives of the lead compound, 3-aminophenylboronic acid, led to an inhibitor with 80-fold better binding (2; K(i) 83 nM). Molecular docking suggested orientations for this compound in the R1 cleft. Based on the docking results, 12 derivatives of 2 were synthesized, leading to inhibitors with K(i) values of 60 nM and with improved solubility. Several of these inhibitors reversed the resistance of nosocomial Gram-positive bacteria, though they showed little activity against Gram-negative bacteria. The X-ray crystal structure of compound 2 in complex with AmpC was subsequently determined to 2.1 A resolution. The placement of the proximal two-thirds of the inhibitor in the experimental structure corresponds with the docked structure, but a bond rotation leads to a distinctly different placement of the distal part of the inhibitor. In the experimental structure, the inhibitor interacts with conserved residues in the R1 cleft whose role in recognition has not been previously explored. CONCLUSIONS: Combining structure-based design with in-parallel synthesis allowed for the rapid exploration of inhibitor functionality in the R1 cleft of AmpC. The resulting inhibitors differ considerably from beta-lactams but nevertheless inhibit the enzyme well. The crystal structure of 2 (K(i) 83 nM) in complex with AmpC may guide exploration of a highly conserved, largely unexplored cleft, providing a template for further design against AmpC beta-lactamase.

The complexed structure and antimicrobial activity of a non-beta-lactam inhibitor of AmpC beta-lactamase.

Beta-lactamases are the major resistance mechanism to beta-lactam antibiotics and pose a growing threat to public health. Recently, bacteria have become resistant to beta-lactamase inhibitors, making this problem pressing. In an effort to overcome this resistance, non-beta-lactam inhibitors of beta-lactamases were investigated for complementarity to the structure of AmpC beta-lactamase from Escherichia coli. This led to the discovery of an inhibitor, benzo(b)thiophene-2-boronic acid (BZBTH2B), which inhibited AmpC with a Ki of 27 nM. This inhibitor is chemically dissimilar to beta-lactams, raising the question of what specific interactions are responsible for its activity. To answer this question, the X-ray crystallographic structure of BZBTH2B in complex with AmpC was determined to 2.25 A resolution. The structure reveals several unexpected interactions. The inhibitor appears to complement the conserved, R1-amide binding region of AmpC, despite lacking an amide group. Interactions between one of the boronic acid oxygen atoms, Tyr150, and an ordered water molecule suggest a mechanism for acid/base catalysis and a direction for hydrolytic attack in the enzyme catalyzed reaction. To investigate how a non-beta-lactam inhibitor would perform against resistant bacteria, BZBTH2B was tested in antimicrobial assays. BZBTH2B significantly potentiated the activity of a third-generation cephalosporin against AmpC-producing resistant bacteria. This inhibitor was unaffected by two common resistance mechanisms that often arise against beta-lactams in conjunction with beta-lactamases. Porin channel mutations did not decrease the efficacy of BZBTH2B against cells expressing AmpC. Also, this inhibitor did not induce expression of AmpC, a problem with many beta-lactams. The structure of the BZBTH2B/AmpC complex provides a starting point for the structure-based elaboration of this class of non-beta-lactam inhibitors.

Polybrominated biphenyl (PBB) contamination of the Pine River, Gratiot, and Midland Counties, Michigan.

Michigan Chemical Corporation, St. Louis, Michigan manufactured PBB from 1970 until November 20, 1974. Studies in 1974 showed significant quantities of PBB in effluent discharged from the facility and in water, fish, ducks, and sediments from the Pine River. Fish uptake rates and bioconcentration factors were estimated. Followup surveys over the three year period since the termination of PBB production indicate a decline in PBB loadings to the river but no significant corresponding decline of PBB levels in sediments, fish and duck tissue. A Michigan Department of Public Health warning against consumption of Pine River fish from St. Louis downstream to its confluence with Chippewa River remains in effect.

Life testing of implantable batteries for a total artificial heart.

Although lithium cells may promise to be ideal as a rechargeable internal battery for a TAH, NiCd cells remain the most easily accessible off the shelf energy source. Twelve 1.2 A.hr prismatic NiCd (Sanyo, San Diego, CA) cells in series are being tested under the load condition of our TAH. The load consisted of a 1.5 A DC current with 1 A pulses of 40 msec duration at 3.33 Hz (100 bpm), a condition that can generate up to 8 L/min of cardiac output at physiologic pressures. Cells were tested at 37 degrees C. Cell voltages and temperatures were monitored. Testing was accelerated to five charge/discharge cycles per day. Discharge was terminated when any one cell dropped below 1.1 V. Charging (C/4) was continued until the battery voltage indicated a change in slope. Cell temperatures remained below 42 degrees C throughout the charge/discharge cycle. The battery pack settled to a nearly constant capacity of over 25 min after 10 cycles and has accumulated more than 1,000 cycles. Voltage differences among cells were small (SD < 25 mV), indicating consistency among cells. NiCd cells can serve as a reliable interim for TAH internal battery application.

Structures of ceftazidime and its transition-state analogue in complex with AmpC beta-lactamase: implications for resistance mutations and inhibitor design.

Third-generation cephalosporins are widely used beta-lactam antibiotics that resist hydrolysis by beta-lactamases. Recently, mutant beta-lactamases that rapidly inactivate these drugs have emerged. To investigate why third-generation cephalosporins are relatively stable to wild-type class C beta-lactamases and how mutant enzymes might overcome this, the structures of the class C beta-lactamase AmpC in complex with the third-generation cephalosporin ceftazidime and with a transition-state analogue of ceftazidime were determined by X-ray crystallography to 2.0 and 2.3 A resolution, respectively. Comparison of the acyl-enzyme structures of ceftazidime and loracarbef, a beta-lactam substrate, reveals that the conformation of ceftazidime in the active site differs from that of substrates. Comparison of the structures of the acyl-enzyme intermediate and the transition-state analogue suggests that ceftazidime blocks formation of the tetrahedral transition state, explaining why it is an inhibitor of AmpC. Ceftazidime cannot adopt a conformation competent for catalysis due to steric clashes that would occur with conserved residues Val211 and Tyr221. The X-ray crystal structure of the mutant beta-lactamase GC1, which has improved activity against third-generation cephalosporins, suggests that a tandem tripeptide insertion in the Omega loop, which contains Val211, has caused a shift of this residue and also of Tyr221 that would allow ceftazidime and other third-generation cephalosporins to adopt a more catalytically competent conformation. These structural differences may explain the extended spectrum activity of GC1 against this class of cephalosporins. In addition, the complexed structure of the transition-state analogue inhibitor (K(i) 20 nM) with AmpC reveals potential opportunities for further inhibitor design.