Detection of mecA-mediated resistance using reference and commercial testing methods in a collection of Staphylococcus aureus expressing borderline oxacillin MICs

Phenotypic methods for detecting mecA-mediated resistance in Staphylococcus aureus include both oxacillin and cefoxitin susceptibility tests; many laboratories perform multiple tests. Conflicting oxacillin and cefoxitin susceptibility results are most likely to occur for isolates that either have reduced susceptibility to oxacillin by a non-mecA-mediated mechanism or are mecA positive but are very heteroresistant. To understand the performance of oxacillin and cefoxitin tests for such isolates, we tested 135 S. aureus isolates using either cefoxitin or oxacillin and compared the results with mecA polymerase chain reaction. These strains either expressed borderline oxacillin MICs (1-4 microg/mL) and had undetermined mecA status or were mecA positive but were not detected by oxacillin broth microdilution (BMD) or disk diffusion (DD) in original testing. For 24-h readings, performance of cefoxitin tests (sensitivity/specificity) were DD (99/100), Etest using < or =6 microg/mL as susceptible (99/98), and Phoenix MIC using < or =4 microg/mL as susceptible (98/100). Using 6 microg/mL of cefoxitin as a screen test in both BMD and agar dilution also worked well (98/98-100). Sensitivity/specificity of oxacillin methods were oxacillin agar screen (BBL: 80/86; Remel, Lenexa, KS: 85/50), DD (91/59), BMD (85/88), MicroScan (89/96), VITEK Legacy (82/93), VITEK 2 (91/73), and Phoenix, (67/96). These results suggest that a cefoxitin test can be used alone to predict mecA-mediated resistance in S. aureus.     

Urinary clearance of albumin is critically determined by its tertiary structure

The excretion of serum albumin in the urine is considered the net result of renal glomerular filtration and tubular uptake. During routine experiments, we observed that a batch of tritium-labeled albumin yielded anomalous results, being excreted in the urine of isolated perfused kidneys at 10 times the rate of normal tritiated albumin. This anomalous albumin, when simultaneously studied with normal carbon 14-labeled albumin, exhibited 10 times greater excretion than normal [(14)C]albumin. Anomalous albumin could not be reversed to normal albumin by means of conditioning with blood. In vivo clearances of anomalous albumin could not be quantitated because anomalous albumin is degraded during circulation. Anomalous albumin appeared to have the same molecular size (as determined with sodium dodecyl sulfate-polyacrylamide gel electrophoresis, capillary electrophoresis, and gel chromatography) and isoelectric-point profile (2-dimensional electrophresis) as normal albumin. Normal albumin could be transformed to anomalous albumin with alkali/heat treatment. Reverse-phase high-pressure liquid chromatography analysis of fragments from tryptic digests of anomalous albumin, alkali/heat-treated albumin, and normal albumin suggest that anomalous albumin and alkali/heat-treated albumin have altered tertiary structure, possibly as a result of denaturation and disulfide exchange. These studies show that the tertiary structure of albumin, beyond simple size and charge, is a critical determinant for albumin processing by the kidney and suggest that a specific albumin-recognition event by the kidneys is critical to normal renal handling of albumin.     

An Introduction to Low-Molecular-Weight Heparins and Their Use in the Treatment of Deep Venous Thrombosis

Low-molecular-weight heparins (LMWHs) are fractions of standard heparin (SH) with an average molecular weight of 4000--5000 daltons. They have the ability to inhibit the activity of factor Xa in the coagulation cascade but are unable to significantly change the activity of thrombin (factor IIa). Therefore, LMWHs have antithrombotic properties, but they do not prolong the activated partial thromboplastin time (APTT). In contrast to SH, the pharmacokinetic profiles of LMWHs are different. LMWHs exhibit minimal binding with plasma proteins, endothelial cells and platelet factor IV, a longer half-life, and linear elimination. Due to these properties, the clinical response is more predictable than that seen with SH. In addition, monitoring of clotting factors and subsequent dosage adjustment are not necessary to ensure efficacy when using a LMWH. These agents may have a decreased risk of thrombocytopenia and bleeding. LMWHs have been used in the initial treatment of deep venous thrombosis (DVT) and have been found to be safe and efficacious. When compared to SH, the LMWHs studied have been more effective in improving venographic scores and short-term treatment, but further evaluation is needed to determine if a benefit exists in preventing recurrent DVT.     

ANALYSIS OF GRAFT-VERSUS-HOST DISEASE IN SYRIAN HAMSTERS : IV. THE REFRACTORY STATE AND IMMUNOLOGIC COMPETENCE

The so-called refractory state, one sequela of acute graft-versus-host disease, has been studied in adult (CB x MHA)F₁ hybrid Syrian hamsters inoculated with sublethal numbers of MHA-anti-CB lymphoid cells. Intracutaneous challenge of these animals with 200 million MHA-anti-CB lymphoid cells after the acute syndrome subsided failed to evoke epidermal necrolysis, whereas a similar challenge administered to normal F₁ recipients invariably resulted in lethal epidermolysis. Moreover, the gradual attrition of lymphatic tissues in these hosts and their fading capacity to display adequately immune lymphocyte transfer reactions in the skin coincided with increasing evidence of host refractoriness, suggesting a causal interrelationship. It was possible to circumvent refractoriness by challenging these animals intracutaneously with MHA-anti-CB cells if: (a) the hosts had been lethally irradiated and reconstituted with F₁ hematopoietic cells, or (b) the intracutaneous inocula contained admixed F₁ lymphoid cells. This evidence provides additional support for the hypothesis that in GVH disease donor lymphocytes attack primarily host lymphoid cells bearing offending homologous antigens. The GVH process can continue so long as these lymphocyte-bound antigens persist within the host, and will abate only as the aggregate host lymphatic mass is effectively destroyed (hamsters) or its antigenic determinants are masked by isoantibodies (rats, mice, man?). At this point, insufficient target tissues remain for rechallenge to incite significant recrudescence of the disease.     

The clinical laboratory improvement amendment: how it applies to the use of urine dipsticks in the long-term care facility

The urine dipstick is one of the waived tests that is used in the long-term care facility under guidelines of the Clinical Laboratory Improvement Amendment (CLIA). Through recent surveys, the Centers for Medicare and Medicaid Services (CMS), which oversee this program, have identified significant problems in many testing sites. Because of the magnitude of the problem, the surveys will be continued. To comply with CLIA guidelines and safely and appropriately use the urine dipstick in the long-term care facility, nurses need to be aware of these guidelines. The purpose of this article is to discuss CLIA requirements regarding waived tests, specifically the urine dipstick, in the long-term care facility.     

Basis for the Design of Anticandidal Agents from Studies of Peptide Utilization in Candida albicans

The growth of Candida albicans WD 18-4, a methionine and lysine double auxotroph, on a variety of methionine- and lysine-containing peptides was determined. This yeast does not excrete extracellular peptidases. Thus, the growth response to peptides containing the required amino acid is a measure of peptide transport. A variety of methionine-containing peptides such as Met-Met, Met-Met-Met, and Met-Met-Met-Met-Met are transported. Acylation of the N-terminus of transported peptides does not affect their transport, but derivitization of the C-terminus prevents peptide uptake. In contrast, all lysine-containing peptides tested, except Lys-Gly, were not growth substrates. The inability of a peptide to substitute for the requisite amino acid was not due to the absence of cellular peptidases or to toxicity of the nonutilized peptides. Several potentially toxic amino acids were carried into Candida as a component of transported peptides. This establishes the peptide transport system as a possible tool for the design of antibiotics for Candida albicans.     

Effect of Aminoglutethimide on Blood Pressure and Steroid Secretion in Patients with Low Renin Essential Hypertension

An inhibitor of adrenal steroid biosynthesis, aminoglutethimide, was administered to seven patients with low renin essential hypertension, and the antihypertensive action of the drug was compared with its effects on adrenal steroid production. In all patients aldosterone concentrations in plasma and urine were within normal limits before the study. Mean arterial pressure was reduced from a pretreatment value of 117+/-2 (mean+/-SE) mm Hg to 108+/-3 mm Hg after 4 days of aminoglutethimide therapy and further to 99+/-3 mm Hg when drug administration was stopped (usually 21 days). Body weight was also reduced from 81.6+/-7.2 kg in the control period to 80.6+/-7.0 kg after 4 days of drug treatment and to 80.1+/-6.7 kg at the termination of therapy. Plasma renin activity was not significantly increased after 4 days of treatment but had risen to the normal range by the termination of aminoglutethimide therapy. Mean plasma concentrations of deoxycorticosterone and cortisol were unchanged during aminoglutethimide treatment whereas those of 18-hydroxydeoxycorticosterone, progesterone, 17alpha-hydroxyprogesterone, and 11-deoxycortisol were increased as compared to pretreatment values. In contrast, aminoglutethimide treatment reduced mean plasma aldosterone concentrations to about 30% of control values. Excretion rates of 16beta-hydroxydehydroepiandrosterone, 16-oxo-androstenediol, 17-hydroxycorticosteroids and 17-ketosteroids, and the secretion rate of 16beta-hydroxydehydroepiandrosterone were not significantly altered by aminoglutethimide treatment whereas the excretion rate of aldosterone was reduced from 3.62+/-0.5 (mean+/-SE) in the control period to 0.9+/-0.2 mug/24 h after 4 days and to 1.1+/-0.3 mug/24 h at the termination of aminoglutethimide treatment.The gradual lowering of blood pressure and body weight during aminoglutethimide therapy is consistent with the view that the antihypertensive effect of the drug is mediated through a reduction in the patients' extracellular fluid volume, probably secondary to the persistent decrease in aldosterone production. The observation that chronic administration of aminoglutethimide lowered blood pressure in these patients and elevated their plasma renin activity to the normal range without decreasing production of the adrenal steroids, deoxycorticosterone, 18-hydroxydeoxycorticosterone, and 16beta-hydroxydehydroepiandrosterone, makes it unlikely that these steroids are responsible either for the decreased renin or the elevated blood pressure in patients with low renin essential hypertension.     

Genome Analysis of Cytochrome in Dinotefuran-Treated Apolygus lucorum (Meyer-Dür)

Bulletin of Environmental Contamination and Toxicology - In this study, two CYP genes, CYP395G1 and CYP4EY1, were analyzed in Apolygus lucorum (Hemiptera: Miridae). The expression pattern in...