Heart transplantation in the early phase of the COVID-19 pandemic: A single-center case series

The infectious disease coronavirus disease 2019 (COVID‐19) was declared a pandemic by the World Health Organization in March 2020. The impact of COVID‐19 on solid organ transplantations, including heart transplantation, is currently unclear. Many transplant programs have been forced to swiftly re‐evaluate and adapt their practices, leading to a marked decrease in transplants performed. This trend has been due to various factors, including increased donor COVID‐19 screening scrutiny and recipient waiting list management in anticipation of COVID‐19 critical care surge capacity planning. In the face of these unknown variables, determining when and how to proceed with transplantation in our population of patients with end‐stage cardiomyopathies is challenging. Here, we describe our center's experience with orthotopic heart transplantation (OHT) in one of the country's pandemic epicenters, where we performed eight OHTs in the first 2 months after community spread began in late February 2020.

Successful Treatment of Scedosporium Sinusitis in Two Lung Transplant Recipients: Review of the Literature and Recommendations for Management

Background

Scedosporium fungal infection is an emerging disease which is difficult to diagnose and treat. Patients undergoing lung transplant may be colonized prior to transplantation and are at risk for lethal allograft infection after transplantation.

Objectives

To identify and evaluate treatment options.

Methods

This study is a retrospective review of patients treated at a tertiary academic medical center from 2007 to 2017 with positive sinonasal cultures. A review of the literature was also performed to identify additional cases.

Results

Two lung transplant patients had a positive culture for Scedosporium. The literature search resulted in 37 citations, which yielded only 2 prior cases of Scedosporium paranasal sinus colonization or infection in lung transplant recipients. Three of the 4 patients had cystic fibrosis. Two of the patients were colonized before initial transplant, while 1 patient was colonized before subsequent transplant. Three of the 4 patients survived, and all 3 had disease isolated to their sinuses and lungs treated with sinus surgery, while the fourth had disseminated disease and did not undergo sinus surgery. All patients were treated with multiple antifungals due to resistance patterns. One surviving patient cleared both sinus and lung cultures in less than 1 month, while the other 2 surviving patients achieved negative cultures after a minimum of 6 months.

Conclusions

Surgery may be especially important in patients with fungal sinus colonization or infection before or after lung transplantation. Chronic sinusitis is an important source for persistent fungal colonization and reinfection of the allograft which could be removed with surgical debridement before causing highly morbid pulmonary disease.

Clinical phenomapping and outcomes after heart transplantation

BACKGROUND

Survival after heart transplantation (HTx) is limited by complications related to alloreactivity, immune suppression, and adverse effects of pharmacologic therapies. We hypothesize that time-dependent phenomapping of clinical and molecular data sets is a valuable approach to clinical assessments and guiding medical management to improve outcomes.

METHODS

We analyzed clinical, therapeutic, biomarker, and outcome data from 94 adult HTx patients and 1,557 clinical encounters performed between January 2010 and April 2013. Multivariate analyses were used to evaluate the association between immunosuppression therapy, biomarkers, and the combined clinical end point of death, allograft loss, retransplantation, and rejection. Data were analyzed by K-means clustering (K = 2) to identify patterns of similar combined immunosuppression management, and percentile slopes were computed to examine the changes in dosages over time. Findings were correlated with clinical parameters, human leucocyte antigen antibody titers, and peripheral blood mononuclear cell gene expression of the AlloMap (CareDx, Inc., Brisbane, CA) test genes. An intragraft, heart tissue gene coexpression network analysis was performed.

RESULTS

Unsupervised cluster analysis of immunosuppressive therapies identified 2 groups, 1 characterized by a steeper immunosuppression minimization, associated with a higher likelihood for the combined end point, and the other by a less pronounced change. A time-dependent phenomap suggested that patients in the group with higher event rates had increased human leukocyte antigen class I and II antibody titers, higher expression of the FLT3 AlloMap gene, and lower expression of the MARCH8 and WDR40A AlloMap genes. Intramyocardial biomarker-related coexpression network analysis of the FLT3 gene showed an immune system-related network underlying this biomarker.

CONCLUSIONS

Time-dependent precision phenotyping is a mechanistically insightful, data-driven approach to characterize patterns of clinical care and identify ways to improve clinical management and outcomes.

The Role of TGF-β in the Association Between Primary Graft Dysfunction and Bronchiolitis Obliterans Syndrome

Primary graft dysfunction (PGD) is a possible risk factor for bronchiolitis obliterans syndrome (BOS) following lung transplantation; however, the mechanism for any such association is poorly understood. Based on the association of TGF-β with acute and chronic inflammatory disorders, we hypothesized that it might play a role in the continuum between PGD and BOS. Thus, the association between PGD and BOS was assessed in a single-center cohort of lung transplant recipients. Bronchoalveolar lavage fluid concentrations of TGF-β and procollagen collected within 24 h of transplantation were compared across the spectrum of PGD, and incorporated into Cox models of BOS. Immunohistochemistry localized expression of TGF-β and its receptor in early lung biopsies posttransplant. We found an association between PGD and BOS in both bilateral and single lung recipients with a hazard ratio of 3.07 (95% CI 1.76-5.38) for the most severe form of PGD. TGF-β and procollagen concentrations were elevated during PGD (p < 0.01), and associated with increased rates of BOS. Expression of TGF-β and its receptor localized to allograft infiltrating mononuclear and stromal cells, and the airway epithelium. These findings validate the association between PGD and the subsequent development of BOS, and suggest that this association may be mediated by receptor/TGF-β biology.

Interaction between Pseudomonas and CXC chemokines increases risk of bronchiolitis obliterans syndrome and death in lung transplantation

RATIONALE

Pseudomonas aeruginosa is the most commonly isolated gram-negative bacterium after lung transplantation and has been shown to up-regulate glutamic acid-leucine-arginine-positive (ELR(+)) CXC chemokines associated with bronchiolitis obliterans syndrome (BOS), but the effect of pseudomonas on BOS and death has not been well defined.

OBJECTIVES

To determine if the influence of pseudomonas isolation and ELR(+) CXC chemokines on the subsequent development of BOS and the occurrence of death is time dependent.

METHODS

A three-state model was developed to assess the likelihood of transitioning from lung transplant (state 1) to BOS (state 2), from transplant (state 1) to death (state 3), and from BOS (state 2) to death (state 3). This Cox semi-Markovian approach determines state survival rates and cause-specific hazards for movement from one state to another.

MEASUREMENTS AND MAIN RESULTS

The likelihood of transition from transplant to BOS was increased by acute rejection, CXCL5, and the interaction between pseudomonas and CXCL1. The pseudomonas effect in this transition was due to infection rather than colonization. Movement from transplant to death was facilitated by pseudomonas infection and single lung transplant. Transition from BOS to death was affected by the length of time in state 1 and by the interactions between any pseudomonas isolation and CXCL5 and aspergillus, either independently or in combination.

CONCLUSIONS

Our model demonstrates that common post-transplantation events drive movement from one post-transplantation state to another and influence outcomes differently depending upon when after transplantation they occur. Pseudomonas and the ELR(+) CXC chemokines may interact to negatively influence lung transplant outcomes.

Usefulness of immune monitoring in lung transplantation using adenosine triphosphate production in activated lymphocytes

BACKGROUND

The ImmuKnow (Cylex Inc, Columbia, MD) assay measures the amount of adenosine triphosphate (ATP) produced by helper CD4(+) cells after stimulation with a T-cell mitogen. We hypothesized that this assay can be used to assess the immune function of lung transplant recipients and identify those at risk of developing acute cellular rejection and respiratory infection.

METHODS

Lung transplant recipients at University of California Los Angeles between January 1, 2006 and December 31, 2009 received a bronchoscopy with broncheoalveolar lavage, transbronchial biopsy and ImmuKnow values drawn at regular intervals as well as during episodes of clinical deterioration. The recipient's clinical condition at each time-point was classified as healthy, acute cellular rejection, or respiratory infection. Mixed-effects models were used to compare the ATP levels among these groups, and odds ratios for rejection and infection were calculated.

RESULTS

The mean ATP level was 431 ± 189 ng/ml for the rejection group vs 377 ± 187 ng/ml for the healthy group (p = 0.10). A recipient with an ATP level > 525 ng/ml was 2.1 times more likely to have acute cellular rejection (95% confidence interval [CI] 1.1-3.8). Similarly, the mean ATP level was 323 ± 169 ng/ml for the infection group vs 377 ± 187 ng/ml for the healthy group (p = 0.03). A recipient with an ATP level < 225 ng/ml was 1.9 times more likely to have respiratory infection (95% CI, 1.1-3.3). However, the test was associated with poor performance characteristics. It had low sensitivity, specificity with an area under the receiver operating characteristic curve of only 0.61 to diagnose rejection and 0.59 to diagnose infection.

CONCLUSIONS

The ImmuKnow assay appears to have some ability to assess the overall immune function of lung transplant recipients. However, this study does not support its use as a reliable predictor of episodes of acute cellular rejection or respiratory infection.

CXCR3 chemokine ligands during respiratory viral infections predict lung allograft dysfunction

Community-acquired respiratory viruses (CARV) can accelerate the development of lung allograft dysfunction, but the immunologic mechanisms are poorly understood. The chemokine receptor CXCR3 and its chemokine ligands, CXCL9, CXCL10 and CXCL11 have roles in the immune response to viruses and in the pathogenesis of bronchiolitis obliterans syndrome, the predominant manifestation of chronic lung allograft rejection. We explored the impact of CARV infection on CXCR3/ligand biology and explored the use of CXCR3 chemokines as biomarkers for subsequent lung allograft dysfunction. Seventeen lung transplant recipients with CARV infection had bronchoalveolar lavage fluid (BALF) available for analysis. For comparison, we included 34 BALF specimens (2 for each CARV case) that were negative for infection and collected at a duration posttransplant similar to a CARV case. The concentration of each CXCR3 chemokine was increased during CARV infection. Among CARV infected patients, a high BALF concentration of either CXCL10 or CXCL11 was predictive of a greater decline in forced expiratory volume in 1 s, 6 months later. CXCR3 chemokine concentrations provide prognostic information and this may have important implications for the development of novel treatment strategies to modify outcomes after CARV infection.

Benefit of immune monitoring in heart transplant patients using ATP production in activated lymphocytes

BACKGROUND

Balancing immunosuppression to prevent rejection while minimizing infection or drug toxicity risk is a major challenge in heart transplantation. Therapeutic drug monitoring alone is inadequate to measure the immune response. An immune monitoring (IM) assay (ImmuKnow; Cylex, Columbia, MD) performed on peripheral blood measures adenosine triphosphatase (ATP) release from activated lymphocytes and may predict the immune state. Therefore, we sought to determine the utility of IM in heart transplant recipients.

METHODS

Between November 2005 and July 2008, 296 heart transplant recipients had a total of 864 IM assays performed at 2 weeks to 10 years post-transplant and were correlated with infection and rejection events that occurred within 1 month after IM testing. All patients received standard triple-drug immunosuppressive therapy with tacrolimus, mycophenolate mofetil and corticosteroids, without induction therapy.

RESULTS

There were 38 infectious episodes and 8 rejection episodes. The average IM score was significantly lower during infection than steady state (187 vs 280 ng ATP/ml, p < 0.001). The average IM score was not significantly different during rejection when compared with steady state (327 vs 280 ng ATP/ml, p = 0.35). Interestingly, 3 of 8 rejection episodes were antibody-mediated rejections and had hemodynamic compromise and, for these, the mean IM score was significantly higher than for steady-state patients (491 vs 280 ng ATP/ml, p < 0.001).

CONCLUSIONS

The non-invasive IM test appears to predict infectious risk in heart transplant patients. The association between high IM scores and rejection risk is inconclusive due to the small number of rejection episodes. Further studies with larger sample sizes for rejection episodes are required.

Diagnosis of coccidioidomycosis with use of the Coccidioides antigen enzyme immunoassay

BACKGROUND

We have previously shown antigenuria in patients with coccidioidomycosis through use of the Histoplasma antigen enzyme immunoassay (EIA), and now we have developed a specific Coccidioides antigen EIA.

METHODS

The Coccidioides EIA uses antibodies to Coccidioides galactomannan. The sensitivity of the Coccidioides and Histoplasma EIAs was evaluated in patients with more-severe coccidioidomycosis, and the specificity of these EIAs was evaluated in patients with nonfungal infections, in patients with other endemic mycoses, and in healthy individuals.

RESULTS

Among patients in the present study, antigenuria was detected in 70.8% of patients with coccidioidomycosis with use of the Coccidioides EIA and in 58.3% of patients with use of the Histoplasma EIA. Antigenuria was absent in 99.4% of healthy individuals, patients with nonfungal infections, and patients with noninfectious conditions. Cross-reactions with other endemic mycoses were observed in 10.7% of patients.

CONCLUSIONS

The Coccidioides EIA has potential to be useful in the rapid diagnosis of more-severe forms of coccidioidomycosis.

Diagnosis of coccidioidomycosis by antigen detection using cross-reaction with a Histoplasma antigen

BACKGROUND

In 2005, patients with coccidioidomycosis were observed to have positive Histoplasma antigen test results.

METHODS

We performed a review of the records of patients with coccidioidomycosis who were under our care who underwent testing for Histoplasma antigen to determine the value of this test in the diagnosis of coccidioidomycosis. Many of the patients were immunosuppressed and critically ill.

RESULTS

The Histoplasma antigen test had positive results when urine samples from 11 (58%) of 19 patients who had acute or chronic coccidioidomycosis were tested. The sensitivity was highest for patients who had acute coccidioidomycosis, and antigenuria was detected in 11 (79%) of 14 patients. One patient who had chronic coccidioidomycosis but who had a negative result when a urine sample was tested had antigen detected in bronchoalveolar lavage fluid.

CONCLUSIONS

Physicians should be alerted that infections with Coccidioides species may cause positive Histoplasma antigen test results. There is potential for the use of this test in the diagnosis of coccidioidomycosis by taking advantage of this observed cross-reactivity. The greatest benefit appears to be in the population of seriously ill patients with acute pneumonia who live in areas that are endemic for Coccidioides infection.

Transmission of mycobacterium tuberculosis via lung transplantation

Organ donors are not routinely screened for tuberculosis (TB) in the United States. We investigated a case of pulmonary TB in a double-lung transplant recipient. We reviewed the donor's and recipient's records, and used molecular methods to compare the lung recipient's isolate with others from three sources: her hospital, the California state health department's genotyping database, and the donor's resident-nation of Guatemala. A respiratory specimen obtained from the lung recipient 1 day after transplantation grew Mycobacterium tuberculosis. Donor chest radiograph had a previously unnoticed pulmonary opacity that was present on post-transplant recipient chest radiographs and computed tomographs. The recipient's isolate was molecularly distinct from others at her hospital and in the state database, but was identical to two isolates from Guatemala. Tuberculosis was transmitted from lung donor to recipient. As organ transplantation becomes more common worldwide, similar cases could occur. Screening for TB in potential organ donors should be considered.

Clinical cases in transplantation

A series of cases are presented to illustrate the complexity of the care of immunocompromised patients with established invasive fungal infections. These discussions by an expert panel serve to identify areas of controversy and for future research in the care of transplant recipients.

Fungal infection in lung transplantation

Fungal infection remains a significant cause of postoperative morbidity and mortality in lung transplant recipients. The lung recipient remains the only solid-organ allograft continuously open to the environment and to the myriad of fungal spores and pathogens. Many factors may predispose to fungal infection in these patients, including: preoperative chronic lung diseases and inherent palliative immunosuppression, intraoperative complications such as abnormalities in the bronchial anastomosis or lung injury, and postoperative complications such as enhanced immunosuppression for early rejection, graft dysfunction, concurrent viral and bacterial infections, and bronchiolitis obliterans syndrome. The risk factors and time course for fungal infection in lung transplant recipients parallel the observations in other solid-organ transplant recipients. Early fungal infections are related to surgical complications, while the period of 1-6 months reflect opportunistic, relapsed, or residual infections; fungal infections greater than 6 months and thereafter are usually associated with treatments for chronic rejection or bronchial airway mechanical abnormalities. The majority of fungal infections in lung transplant recipients involve Aspergillus species, followed by Candida, Pneumocystis, Cryptococcus, geographically-restricted agents, and newly emerging fungal pathogens. The identification of at-risk patients (preoperatively and postoperatively) is essential in implementing prophylaxis or preemptive management. Some anti-fungal strategies and future options for clinical research are discussed.

Leptospirosis, water sports, and chemoprophylaxis

Recreational activities, such as water sports and adventure travel, are emerging as an important risk factor for leptospirosis, a potentially fatal zoonosis. We report the clinical course of 2 patients who acquired leptospirosis through participation in water sports. Physicians caring for patients who participate in adventure travel involving water sports should be familiar with the risk factors for and diagnosis, prevention, and treatment of leptospirosis.

Mycobacterium haemophilum infections in heart transplant recipients: case report and review of the literature

Non-tuberculous mycobacteria are becoming increasingly important pathogens among transplant recipients. We report a case of disseminated Mycobacterium haemophilum infection in a heart transplant recipient, manifesting as cellulitis, subcutaneous nodules, septic arthritis, and pneumonitis. Our case illustrates diverse challenges in the identification and treatment of this pathogen, such as its unique culture requirements and variable antimicrobial susceptibilities. Heightened clinical suspicion is necessary to establish a timely diagnosis so that optimal treatment can be administered.

Mycobacterium abscessus empyema in a lung transplant recipient

Non-tuberculous mycobacteria (NTM) have emerged as important pathogens in organ transplant recipients. Because NTM pulmonary infections vary in their clinical and radiographic presentations, heightened clinical suspicion is necessary for accurate diagnosis. We report a case of Mycobacterium abscessus empyema in a lung transplant recipient. Repeated attempts at identifying the organism from a variety of clinical specimens led to the correct diagnosis and treatment.

Cluster of cases of invasive aspergillosis in a transplant intensive care unit: evidence of person-to-person airborne transmission

In October 1998, a patient developed deep surgical-site and organ-space infection with Aspergillus fumigatus 11 days after undergoing liver retransplantation; subsequently, 2 additional patients in the transplant intensive care unit had invasive pulmonary infection with A. fumigatus diagnosed. It was determined that debriding and dressing wounds infected with Aspergillus species may result in aerosolization of spores and airborne person-to-person transmission.

Safety and efficacy of Intralipid emulsions of amphotericin B

To evaluate the clinical role of amphotericin/20% Intralipid emulsions (ILA), we conducted a Medline search of the English literature to locate the relevant case reports and clinical studies involving the use of this formulation. Due to differences in study design and definitions, we applied a set of treatment outcome definitions to determine the clinical efficacy of this treatment modality. Only 37 patients received ILA for the treatment of documented fungal infections. Using our definitions, four were considered successfully treated, one improved, two failed, and 30 were unevaluable. While infusion-related adverse events and nephrotoxicity were reportedly reduced with ILA, use of adjunctive therapies and concomitant nephrotoxic agents, and comparisons with high infusion concentrations complicate evaluation. Furthermore, incomplete and conflicting data exist regarding the physiochemical stability of ILA. The currently available data do not support recommendations for the use of this formulation for the treatment of systemic fungal infections.

Advances in medical and antibiotic management of infective endocarditis

Infective endocarditis remains a serious medical problem despite advancements in laboratory detection, echocardiographic techniques, and newer antibiotic agents. This article summarizes the microbial agents in infective endocarditis, in addition to developments in medical and antibiotic management.

Treatment of ocular fungal infections with oral fluconazole

PURPOSE

We treated five patients who had ocular fungal infections with oral fluconazole to determine its safety and effectiveness.

METHODS

We reviewed the case histories of the five patients. One patient had coccidioidomycosis and four had endogenous Candida endophthalmitis.

RESULTS

The intraocular fungal infection resolved in all patients.

CONCLUSION

Fluconazole appears to be a safe and effective antifungal agent that can be administered orally and may be a useful agent for treating some intraocular fungal infections.

Evidence that serum amyloid P component binds to mannose-terminated sequences of polysaccharides and glycoproteins

Serum amyloid P component (SAP) is a normal human serum protein with pentraxin structure that has morphological and immunochemical identity to the amyloid P component found in normal tissue and amyloid deposits. In the presence of calcium, SAP binds to certain complex polysaccharides, including agarose and zymosan. While the binding of SAP to agarose involves interaction with a galactose pyruvate acetal, the ligand in zymosan has not been defined. In the present study we determined that SAP binds to ligand(s) in a soluble extract of zymosan prepared by alkaline hydrolysis, which contains the mannose oligosaccharide sequences alpha DMan1----3DMan and alpha DMan1----6DMan. SAP did not bind to the alkali-insoluble fraction of zymosan, which is predominantly a glucan polymer, and its binding to zymosan extract which had been absorbed with concanavalin A was markedly reduced, suggesting that mannose residues are involved in the binding of SAP to zymosan. We also demonstrated that SAP binds to the glycoproteins ovalbumin, thyroglobulin, beta-glucuronidase and C3bi, which contain mannose-terminated sequences, while it did not bind to native and desialized preparations of ovomucoid, alpha 1-acid glycoprotein and glycophorin, which lack terminal mannose residues. SAP did not bind to pneumococcal C polysaccharide or to N-acetylglucosamine oligosaccharides covalently linked to a protein carrier. The binding of SAP to ligand(s) in zymosan extract or ovalbumin was inhibited by the preincubation of SAP with either zymosan extract or ovalbumin glycopeptides, both of which share similar mannose oligosaccharide sequences. All of the SAP binding reactions required calcium, were maximal at approximately 1 mM calcium, and gave similar results whether purified SAP or SAP in serum was used. These findings indicate that mannose-terminated oligosaccharides of polysaccharides and glycoproteins represent a new class of ligands for SAP and suggest that SAP may function as a mannose-binding protein.

Identification of multiple forms of the P component of amyloid isolated from human serum

We examined isolated serum amyloid P component (SAP), the circulating counterpart of the amyloid P component, and established a previously unreported heterogeneity for SAP by immunological and biochemical methods. Highly purified SAP had a gel filtration Mr of 255,000, a Stokes radius of 57 A, a calculated frictional coefficient of 1.4, and 10 subunits of Mr of approximately 25,000. We present evidence suggestive of varying affinities of SAP for agarose, to which SAP is known to adsorb in the presence of calcium, by fused rocket immunoelectrophoresis. We resolved SAP subunits by isoelectric focusing into multiple species with isoelectric points of 6.08 (two forms), 6.02, and 5.95; three of these forms were delineated by high resolution two-dimensional SDS gel electrophoresis to have an Mr = 25,500, while a fourth (pI = 6.08) had an Mr = 24,500. The observed isoelectric charge heterogeneity could not be eliminated by neuraminidase treatment event though the electrophoretic migration of native desialized SAP was impeded (alpha 1 to beta) when examined by crossed immunoelectrophoresis, being consistent with the removal of anionic charges. Further, an additional neuraminidase-generated component was detected at the beta-position which could be removed by concanavalin A affinity. These data suggest SAP may exist in microheterologous or allotypic forms, the significance of which is under investigation.

Effect of divalent metal ions and pH upon the binding reactivity of human serum amyloid P component, a C-reactive protein homologue, for zymosan. Preferential reactivity in the presence of copper and acidic pH

The serum amyloid P component (SAP) has been found to associate in vitro with a variety of polysaccharide and proteinaceous ligands including the yeast cell wall polysaccharide preparation, zymosan, in the presence of calcium at neutral pH. In the present study, we have investigated the role of copper and zinc and other divalent cations and acidic pH on the binding of SAP to zymosan. We report that binding occurs not only in the presence of calcium, but in the presence of copper, zinc, and cadmium as well. No binding occurs in the absence of added metal, or in the presence of barium, cobalt, magnesium, manganese, or nickel. 125I-SAP binding in the presence of metals is inhibited by presaturating the zymosan surface with unlabeled SAP. Whereas calcium-mediated binding decreases by more than 50% as the pH is lowered to 5, copper-mediated binding increases substantially at the more acidic pH values while zinc-mediated binding is essentially unchanged. These data indicate that, in addition to calcium at neutral pH, copper (and zinc) at neutral and particularly acidic pH values mediates SAP binding to polysaccharide ligands. This suggests that SAP may well be considered a copper- as well as a calcium-dependent protein under certain conditions and that this reactivity is favored under those conditions of lowered pH which may result from metabolic processes occurring at local sites of inflammation.

Solubilization and electrophoretic analysis of Staphylococcus aureus membrane proteins

The protein composition of homogeneous Staphylococcus aureus 6538P cytoplasmic membranes was examined under denaturing electrophoretic conditions. A comparative analysis on the effectiveness of a variety of membrane solubilizing agents revealed the membrane protein extracts to be qualitatively similar as determined electrophoretically but different in the quantity of protein released; Zwittergent-314, sodium dodecyl sulfate, Triton X-100, Nonidet P-40, and sodium deoxycholate all proved to be effective solubilizing agents under the conditions examined. Fifty-five to sixty protein components were resolved by sodium dodecyl sulfate polyacrylamide gel electrophoresis from homogeneous late-exponential phase membranes. The profile was unaffected when phenylmethylsulfonyl fluoride was included during membrane isolation and solubilization. Analysis of the solubilized membrane proteins by two-dimensional gel electrophoresis demonstrated in excess of 100 membrane protein components in a pH gradient between 3.5 to 7.7. The profile consisted of a heterogeneous mixture of mostly acidic components with isoelectric points between pH 4 and 5 and relative molecular weights between 158,000 and 35,000. Periodic acid-Schiff staining following sodium dodecyl sulfate gel electrophoresis revealed six to ten reactive bands with two of these bands also exhibiting a reaction with concanavalin A.

Analysis of Staphylococcus aureus cytoplasmic membrane proteins by isoelectric focusing

Cytoplasmic membranes were isolated from late-exponential phase Staphylococcus aureus 6539 P and the membrane proteins examined under non-denaturing conditions by thin-layer isoelectric focusing (TLIEF) in a pH 3.5-9.5 gradient. Isolated membrane preparations retained protein integrity as judged by the demonstration of membrane bound adenosine triphosphatase (ATPase) activity in addition to four other solubilized membrane enzyme markers. Membranes were effectively solubilized with 2.5% Triton X-100 (final concentration). Examination of Triton X-100 solubilized membrane preparations established the presence of 22 membrane proteins with isoelectric points between 3.7 and 6.0. The focused proteins displayed the following enzymatic activities and isoelectric points by zymogram methods: ATPase (EC 3.6.1.3), 4.20; malate dehydrogenase (EC 1.1.1.37), 3.90; lactate dehydrogenase (EC 1.1.1.27), 3.85; two membrane proteins exhibited multiple bands upon enzymatic staining NADH dehydrogenase (EC 1.6.99.3), 4.25, 4.35; succinate dehydrogenase (EC 1.3.99.1), 4.85, 5.10, 5.35.

Staphylococcus aureus adenosine triphosphatase: inhibitor sensitivity and release from membrane

Homogeneous preparations of cytoplasmic membrane isolated from Staphylococcus aureus 6538P exhibited membrane-associated adenosine triphosphatase (ATPase) activity. Membrane ATPase activity was activated by divalent cations (4.0 mM: Mg2+ greater than Mn2+ greater than Co2+ greater than Zn2+), and ATP was hydrolyzed more readily than other nucleoside triphosphates and phosphorylated substrates. The pH optimum for the membrane ATPase was 6.5. The ATPase could not be released from the membrane by differential osmotic treatments, but detergent treatment effectively solubilized active enzyme. The nonionic detergent Triton X-100 (1%) released a protein with ATPase activity, after substrate-dependent staining in polyacrylamide gels, that differed slightly in electrophoretic migration when compared to the active enzyme solubilized with sodium dodecyl sulfate (0.1%). Membrane-associated ATPase activity was inhibited by N,N'-dicyclohexylcarbodiimide (0.001 to 1 mM) and NaF (50% inhibition at 5 mM NaF). Azide and trypsin inhibited activity, whereas ouabain had a slight inhibitory effect. Diethylstilbestrol showed appreciable activation of the membrane ATPase over the range employed (0.001 to 1 mM).