SARS-CoV-2 infections in pediatric and young adult recipients of chimeric antigen receptor T-cell therapy: an international registry report

BACKGROUND

Immunocompromised patients are at increased risk of SARS-CoV-2 infections. Patients undergoing chimeric antigen receptor (CAR) T-cell therapy for relapsed/refractory B-cell malignancies are uniquely immunosuppressed due to CAR T-mediated B-cell aplasia (BCA). While SARS-CoV-2 mortality rates of 33%-40% are reported in adult CAR T-cell recipients, outcomes in pediatric and young adult CAR T-cell recipients are limited.

METHODS

We created an international retrospective registry of CAR T recipients aged 0-30 years infected with SARS-CoV-2 within 2 months prior to or any time after CAR T infusion. SARS-CoV-2-associated illness was graded as asymptomatic, mild, moderate, or severe COVID-19, or multisystem inflammatory syndrome in children (MIS-C). To assess for risk factors associated with significant SARS-CoV-2 infections (infections requiring hospital admission for respiratory distress or supplemental oxygen), univariate and multivariable regression analyses were performed.

RESULTS

Nine centers contributed 78 infections in 75 patients. Of 70 SARS-CoV-2 infections occurring after CAR T infusion, 13 (18.6%) were classified as asymptomatic, 37 (52.9%) mild, 11 (15.7%) moderate, and 6 (8.6%) severe COVID-19. Three (4.3%) were classified as MIS-C. BCA was not significantly associated with infection severity. Prior to the emergence of the Omicron variant, of 47 infections, 19 (40.4%) resulted in hospital admission and 7 (14.9%) required intensive care, while after the emergence of the Omicron variant, of 23 infections, only 1 (4.3%) required admission and the remaining 22 (95.7%) had asymptomatic or mild COVID-19. Death occurred in 3 of 70 (4.3%); each death involved coinfection or life-threatening condition. In a multivariable model, factors associated with significant SARS-CoV-2 infection included having two or more comorbidities (OR 7.73, CI 1.05 to 74.8, p=0.048) and age ≥18 years (OR 9.51, CI 1.90 to 82.2, p=0.014). In the eight patients infected with SARS-CoV-2 before CAR T, half of these patients had their CAR T infusion delayed by 15-30 days.

CONCLUSIONS

In a large international cohort of pediatric and young adult CAR-T recipients, SARS-CoV-2 infections resulted in frequent hospital and intensive care unit admissions and were associated with mortality in 4.3%. Patients with two or more comorbidities or aged ≥18 years were more likely to experience significant illness. Suspected Omicron infections were associated with milder disease.

Development of clinical pathways to improve multidisciplinary care of high-risk pediatric oncology patients

Clinical pathways are evidence-based tools that have been integrated into many aspects of pediatric hospital medicine and have proven effective at reducing in-hospital complications from a variety of diseases. Adaptation of similar tools for specific, high-risk patient populations in pediatric oncology has been slower, in part due to patient complexities and variations in management strategies. There are few published studies of clinical pathways for pediatric oncology patients. Pediatric patients with a new diagnosis of leukemia or lymphoma often present with one or more “oncologic emergencies” that require urgent intervention and deliberate multidisciplinary care to prevent significant consequences. Here, we present two clinical pathways that have recently been developed using a multidisciplinary approach at a single institution, intended for the care of patients who present with hyperleukocytosis or an anterior mediastinal mass. These clinical care pathways have provided a critical framework for the immediate care of these patients who are often admitted to the pediatric intensive care unit for initial management. The goal of the pathways is to facilitate multidisciplinary collaborations, expedite diagnosis, and streamline timely treatment initiation. Standardizing the care of high-risk pediatric oncology patients will ultimately decrease morbidity and mortality associated with these diseases to increase the potential for excellent outcomes.

GD2-CAR T cell therapy for H3K27M-mutated diffuse midline gliomas

Diffuse intrinsic pontine glioma (DIPG) and other H3K27M-mutated diffuse midline gliomas (DMGs) are universally lethal paediatric tumours of the central nervous system¹. We have previously shown that the disialoganglioside GD2 is highly expressed on H3K27M-mutated glioma cells and have demonstrated promising preclinical efficacy of GD2-directed chimeric antigen receptor (CAR) T cells², providing the rationale for a first-in-human phase I clinical trial (NCT04196413). Because CAR T cell-induced brainstem inflammation can result in obstructive hydrocephalus, increased intracranial pressure and dangerous tissue shifts, neurocritical care precautions were incorporated. Here we present the clinical experience from the first four patients with H3K27M-mutated DIPG or spinal cord DMG treated with GD2-CAR T cells at dose level 1 (1 × 10⁶ GD2-CAR T cells per kg administered intravenously). Patients who exhibited clinical benefit were eligible for subsequent GD2-CAR T cell infusions administered intracerebroventricularly³. Toxicity was largely related to the location of the tumour and was reversible with intensive supportive care. On-target, off-tumour toxicity was not observed. Three of four patients exhibited clinical and radiographic improvement. Pro-inflammatory cytokine levels were increased in the plasma and cerebrospinal fluid. Transcriptomic analyses of 65,598 single cells from CAR T cell products and cerebrospinal fluid elucidate heterogeneity in response between participants and administration routes. These early results underscore the promise of this therapeutic approach for patients with H3K27M-mutated DIPG or spinal cord DMG.

NOT-Gated CD93 CAR T Cells Effectively Target AML with Minimized Endothelial Cross-Reactivity

CD93 CAR T cells eliminate AML in preclinical models without targeting hematopoietic progenitor cells, and a NOT-gated CAR engineering strategy mitigates on-target, off-tumor toxicity to endothelial cells.

Chimeric antigen receptor (CAR) T cells hold promise for the treatment of acute myeloid leukemia (AML), but optimal targets remain to be defined. We demonstrate that CD93 CAR T cells engineered from a novel humanized CD93-specific binder potently kill AML in vitro and in vivo but spare hematopoietic stem and progenitor cells (HSPC). No toxicity is seen in murine models, but CD93 is expressed on human endothelial cells, and CD93 CAR T cells recognize and kill endothelial cell lines. We identify other AML CAR T-cell targets with overlapping expression on endothelial cells, especially in the context of proinflammatory cytokines. To address the challenge of endothelial-specific cross-reactivity, we provide proof of concept for NOT-gated CD93 CAR T cells that circumvent endothelial cell toxicity in a relevant model system. We also identify candidates for combinatorial targeting by profiling the transcriptome of AML and endothelial cells at baseline and after exposure to proinflammatory cytokines.

Tuning the Antigen Density Requirement for CAR T-cell Activity

Insufficient reactivity against cells with low antigen density has emerged as an important cause of chimeric antigen receptor (CAR) T-cell resistance. Little is known about factors that modulate the threshold for antigen recognition. We demonstrate that CD19 CAR activity is dependent upon antigen density and that the CAR construct in axicabtagene ciloleucel (CD19-CD28ζ) outperforms that in tisagenlecleucel (CD19-4-1BBζ) against antigen-low tumors. Enhancing signal strength by including additional immunoreceptor tyrosine-based activation motifs (ITAM) in the CAR enables recognition of low-antigen-density cells, whereas ITAM deletions blunt signal and increase the antigen density threshold. Furthermore, replacement of the CD8 hinge-transmembrane (H/T) region of a 4-1BBζ CAR with a CD28-H/T lowers the threshold for CAR reactivity despite identical signaling molecules. CARs incorporating a CD28-H/T demonstrate a more stable and efficient immunologic synapse. Precise design of CARs can tune the threshold for antigen recognition and endow 4-1BBζ-CARs with enhanced capacity to recognize antigen-low targets while retaining a superior capacity for persistence. SIGNIFICANCE: Optimal CAR T-cell activity is dependent on antigen density, which is variable in many cancers, including lymphoma and solid tumors. CD28ζ-CARs outperform 4-1BBζ-CARs when antigen density is low. However, 4-1BBζ-CARs can be reengineered to enhance activity against low-antigen-density tumors while maintaining their unique capacity for persistence.This article is highlighted in the In This Issue feature, p. 627.

CAR T Cell Therapy for Neuroblastoma

Patients with high risk neuroblastoma have a poor prognosis and survivors are often left with debilitating long term sequelae from treatment. Even after integration of anti-GD2 monoclonal antibody therapy into standard, upftont protocols, 5-year overall survival rates are only about 50%. The success of anti-GD2 therapy has proven that immunotherapy can be effective in neuroblastoma. Adoptive transfer of chimeric antigen receptor (CAR) T cells has the potential to build on this success. In early phase clinical trials, CAR T cell therapy for neuroblastoma has proven safe and feasible, but significant barriers to efficacy remain. These include lack of T cell persistence and potency, difficulty in target identification, and an immunosuppressive tumor microenvironment. With recent advances in CAR T cell engineering, many of these issues are being addressed in the laboratory. In this review, we summarize the clinical trials that have been completed or are underway for CAR T cell therapy in neuroblastoma, discuss the conclusions and open questions derived from these trials, and consider potential strategies to improve CAR T cell therapy for patients with neuroblastoma.

Cleavage of the papillomavirus minor capsid protein, L2, at a furin consensus site is necessary for infection

Papillomaviruses (PV) comprise a large family of nonenveloped DNA viruses that include the oncogenic PV types that are the causative agents of human cervical cancer. As is true of many animal DNA viruses, PV are taken into the cell by endocytosis and must escape from the endosomal compartment to the cytoplasm to initiate infection. Here we show that this step depends on the site-specific enzymatic cleavage of the PV minor virion protein L2 at a consensus furin recognition site. Cleavage by furin, a cell-encoded proprotein convertase, is known to be required for endosome escape by many bacterial toxins. However, to our knowledge, furin has not been previously implicated in the viral entry process. This step is potentially a target for PV inhibition.

Vancomycin resistance reversal in enterococci by flavonoids

The development of clinical vancomycin-resistant strains of enterococci (VRE) is a major cause for concern. Here we show that a combination of galangin or 3,7-dihydroxyflavone with vancomycin may be used to sensitize resistant strains of Enterococcus faecalis and Enterococcus faecium to the level of vancomycin-sensitive strains. Minimum inhibitory concentrations (MICs) and viable counts were determined in Iso-sensitest broth using a microtitre method. MICs of vancomycin against 67% of resistant clinical isolates and a type strain of enterococci were lowered from > 250 microg mL(-1) to < 4 microg mL(-1) in the presence of galangin (12.5 microg mL(-1)) or 3,7-dihydroxyflavone (6.25 microg mL(-1)). Viable counts for type culture E. faecalis ATCC 51299 showed the flavonoids alone significantly lowered numbers of colony forming units (CFUs). CFUs were maintained at low levels (< 10(3) CFU mL(-1)) for 24 h by vancomycin/flavone combinations. This combinational action in reversing vancomycin resistance of enterococci highlights novel drug targets and has importance in the design of new therapeutic regimes against resistant pathogens.

Baicalin synergy with beta-lactam antibiotics against methicillin-resistant Staphylococcus aureus and other beta-lactam-resistant strains of S. aureus

Bacterial resistance to antibiotics is a serious global problem and includes strains of beta-lactam-resistant Staphylococcus aureus and methicillin-resistant S. aureus (MRSA). Novel antimicrobials and/or new approaches to combat the problem are urgently needed. The Chinese herb Xi-nan Huangqin (Scutellaria amoena C.H. Wright) has been used in traditional Chinese medicine to treat a wide range of infectious diseases. In this study we have examined the antibacterial action of baicalin, a flavone isolated from the herb. When combined with 16 microg mL(-1) baicalin, minimum inhibitory concentrations (MICs) of benzylpenicillin against MRSA and penicillin-resistant S. aureus were reduced from 125 and 250 microg mL(-1) to 4 and 16 microg mL(-1), respectively. This activity of baicalin was dose-dependent. Viable counts showed that the killing of MRSA and beta-lactam-resistant S. aureus cells by 10 to 50 microg mL(-1) ampicillin, amoxycillin, benzylpenicillin, methicillin and cefotaxime was potentiated by 25 microg mL(-1) baicalin. From the study it was concluded that baicalin has the potential to restore the effectiveness of beta-lactam antibiotics against MRSA and other strains of beta-lactam-resistant S. aureus. In view of its limited toxicity baicalin offers potential for the development of a valuable adjunct to beta-lactam treatments against otherwise resistant strains of microorganisms.

Intermediate species possessing bent DNA are present along the pathway to formation of a final TBP-TATA complex

Binding of the TATA-binding protein (TBP) to the "TATA" sequences present in the promoters of eukaryotic class II genes is the first step in the sequential assembly of transcription pre-initiation complexes. Myriad structural changes, including severe bending of the DNA, accompany TBP-TATA complex formation. A detailed kinetic study has been conducted to elucidate the mechanistic details of TBP binding and DNA bending. The binding of Saccharomyces cerevisiae TBP to the adenovirus major late promoter (AdMLP) was followed in real-time through a range of temperatures and TBP concentrations using fluorescence resonance energy transfer (FRET) and stopped-flow mixing. The results of association and relaxation kinetics and equilibrium binding experiments were analyzed globally to obtain the complete kinetic and energetic profile of the reaction. This analysis reveals a complex mechanism with two intermediate species, with the DNA in the intermediates apparently bent similarly to the DNA in the final complex. TBP binding and DNA bending occur simultaneously through the multiple steps of the reaction. The first and third steps in this sequential process show nearly identical large increases in both enthalpy and entropy, whereas the middle step is highly exothermic and proceeds with a large decrease in entropy. The first intermediate is significantly populated at equilibrium and resembles the final complex both structurally and energetically. It is postulated that both this intermediate and the final complex bind transcription factor IIB in the second step of pol II pre-initiation complex assembly. A consequence of such a reactive intermediate is that the rate of assembly of transcriptionally competent pre-initiation complexes from bi-directionally bound TBP is greatly increased.

In-vitro investigation of the antibacterial activity of agents which may be used for the oral treatment of lung infections in CF patients

The effect of triple therapy with ciprofloxacin, trimethoprim and either sulphadiazine or sulphamethoxazole on the MICs and development of resistance of three strains of Pseudomonas aeruginosa, two strains of Staphylococcus aureus and one of Burkholderia cepacia was compared with that of single or dual therapy with these agents using an agar dilution method. Ciprofloxacin MICs were 0.2-0.8 mg/L for the P. aeruginosa and S. aureus strains. For trimethoprim the MIC ranges were 64-128 and 0.25-1 mg/L for P. aeruginosa and S. aureus, respectively. For the sulphonamides the ranges were 64-2500 and 20-39 mg/L for P. aeruginosa and S. aureus, respectively. All combinations of agents were effective at lower concentrations than the single agents. The combination of ciprofloxacin, sulphonamide and trimethoprim showed enhanced activity against all test organisms. The highest ciprofloxacin concentration was one-tenth of the normally attainable serum concentration of 2.5 mg/L. Thus peak plasma concentrations of > or =8 x MIC for ciprofloxacin against P. aeruginosa and S. aureus are theoretically achievable in the presence of clinically acceptable concentrations of trimethoprim and a sulphonamide, making the development of resistance less likely. The development of resistance, as shown by the proportional increase in MICs, was repressed by the triple regimen as compared with the development of resistance to agents used singly or in pairs. Killing curve determinations also demonstrated the advantage of the triple-agent therapy against all organisms tested: the combination of ciprofloxacin 0.5 mg/L, trimethoprim 1 mg/L and sulphadiazine 20 mg/L had an initial bactericidal effect against log-phase inocula of 10(6) cfu/mL of two clinical strains of P. aeruginosa and one clinical strain of S. aureus. The pseudomonas strains were reduced by 2-4 log cycles. Both recovered over 24 h but did not exceed the initial inoculum. The S. aureus was reduced to 10(2) cfu/mL in 4 h and did not recover over 24 h. A repeat dose of the triple therapy against the more resistant of the P. aeruginosa strains after 12 h also had a bactericidal effect. These data suggest the possibility of an effective exclusively oral therapy for the treatment of lung infections in cystic fibrosis patients.

Is the ultrastructural damage caused by subinhibitory concentrations of trimethoprim and sulphadiazine part of their normal mechanism of action?

The test organism was Escherichia coli 1810 which was highly resistant to trimethoprim (TMP). Electron microscopy (EM) of cells grown in the presence of subinhibitory concentrations of 300 micrograms/ml sulphadiazine (SD) and/or 300 micrograms/ml TMP indicated marked structural damage. No effect on the outer membrane (OM) or ultrastructure of E. coli 1810 was observed with 7.68 micrograms/ml TMP and/or 16.9 micrograms/ml SD. Concentrations of antibacterials affecting the ultrastructure of the bacterial cells of resistant and sensitive E. coli as determined by EM, were shown by a permeability probe (Triton X-100) to alter the OM permeability and to partially inhibit growth of E. coli 1810 cultures. It was concluded that, since the action of SD and TMP, singly and in combination, on the cell structure of E. coli 1810 took place only at concentrations approaching the respective MICs, then this was a part of their normal mechanisms of antibacterial action.

Drug-related problems in elderly patients admitted to Tayside hospitals, methods for prevention and subsequent reassessment

INTRODUCTION

although drug-related problems (DRPs) are known to be prevalent in elderly patients, the literature on prevention of iatrogenic disease is sparse. The present study addresses this requirement.

OBJECTIVES

to assess the incidence of DRPs in elderly patients admitted to Tayside hospitals before (phase I) and after (phase II) implementation of preventive strategies.

DESIGN

all elderly people admitted to hospital were screened by a pharmacist; individual case reviews were prepared for all those with a potential DRP and reviewed by a three-member panel which made a final decision on the presence of a DRP and its contribution to admission.

SETTING

all hospital wards admitting elderly patients in the Tayside region of Scotland.

SUBJECTS

1011 elderly patient admissions over a 9-month period (phase I); 857 elderly patient admissions over an 8-month period (phase II).

MAIN OUTCOME MEASURES

incidence of DRPs before and after targeted intervention strategies (information bulletin for general practitioners, patient information leaflet, oral presentation to trainee general practitioners).

RESULTS

in phase I, the incidence of DRPs was 144/1011 (14.2%), with 54/1011 (5.3%) of the admissions identified as being definitely or probably drug-related. Non-steroidal anti-inflammatory drugs (NSAIDs) were the main drug group involved, being responsible for 15/54 (28%) of admissions primarily due to a DRP. Over 66% of admissions due to adverse effects of NSAIDs were considered to be definitely preventable. In phase II, after targeted intervention strategies, there was no significant reduction in total incidence of DRPs or incidence of DRPs related to NSAIDs. However, there appeared to be an improvement in the first 4 months, and a significant drop in NSAID prescribing in Tayside compared with the rest of Scotland was observed.

CONCLUSION

DRPs remain a significant problem in elderly patients and NSAIDs are the major contributor. The intervention strategies used in the study were not demonstrably effective, but a continuous programme of education may be necessary to limit NSAID use.

Sensitive high-performance liquid chromatographic assay for aminoglycosides in biological matrices enables the direct estimation of bacterial drug uptake

Following the development of a sensitive high-performance liquid chromatographic (HPLC) assay for gentamicin in biological matrices, the utility of this assay for the determination of other clinically important aminoglycosides (neomycin, netilmicin and sisomicin) in bacterial culture media or plasma is demonstrated. The high sensitivity of the assay enables direct measurement of the aminoglycoside content of bacterial cells cultured in the presence of unlabelled drug.

Detection of stroke during cardiac operations with somatosensory evoked responses

OBJECTIVES

The objectives of this study were to determine if monitoring of intraoperative somatosensory evoked potentials could be used to detect stroke during cardiac operations and to establish indicators of cerebral ischemia based on changes in these potentials.

METHODS

Twenty-five patients undergoing cardiac operations underwent preoperative and postoperative neurologic examinations as well as intraoperative recording of somatosensory evoked potentials. Detailed analysis of the waveforms of these potentials was performed.

RESULTS

Two of the 25 patients had intraoperative strokes. These patients and only these patients had changes in their somatosensory evoked potentials during the operation suggesting cerebral ischemia. The unilateral disappearance of the cortical somatosensory evoked potential waves correlated significantly with the clinical outcome of stroke (p < 0.004). Ischemic changes were detected in real time and were related to the removal of the aortic crossclamp in one patient and to the initiation of cardiopulmonary bypass in the other.

CONCLUSIONS

Somatosensory evoked potentials can detect intraoperative stroke during cardiac operations. Acute, unilateral decreases in amplitude of the cortical potential are more useful than changes in latency in detecting intraoperative stroke.

Mechanism for synergism between sulphonamides and trimethoprim clarified

Pseudomonas aeruginosa, Escherichia coli, Pseudomonas cepacia and Moraxella catarrhalis were selected for their markedly different resistance patterns to sulphonamides and trimethoprim. In addition, strains of E. coli and P. cepacia were selected having different resistance profiles to the inhibition of dihydropteroate synthetase and dihydrofolate reductase. All inhibitors of dihydropteroate synthetase combined in any combination with inhibitors of dihydrofolate reductase resulted in mutual enhancement of bacterial uptakes of the inhibitors and corresponding increased antibacterial activity of the combinations. High concentrations of sulphonamides or p-aminobenzoic acid plus trimethoprim caused a decrease in overall activity of the combination and indicated that both sulphonamides and p-aminobenzoic acid at high concentrations can interact with dihydrofolate reductase. The antibacterial activity of p-aminobenzoic acid at high concentrations is considered to be a blocking effect on dihydrofolate reductase even though p-aminobenzoic acid at low concentrations is an essential part of the synthesis of dihydrofolic acid. These findings support an alternative hypothesis for the mechanism of antibacterial action of individual antifolates and their mechanism of synergism in combination.

Determination of peptidoglycan-associated protein in Escherichia coli NCIB 8545 by capillary zone electrophoresis

An efficient reliable and sensitive capillary zone electrophoresis assay for the six major bacterial peptidoglycan-associated proteins of Escherichia coli NCIB 8545 is described. The method provides the facility to determine quantitatively the effect of antibacterials on bacterial peptidoglycan-associated protein synthesis and thus to further elucidate the mechanism of antibacterial action of such drugs as the antifolates which recently have been shown to adversely affect peptidoglycan synthesis.

Excipient interaction with cetylpyridinium chloride activity in tablet based lozenges

PURPOSE

The purpose of the investigation was to determine the effect of tablet excipients on the activity of cetylpyridinium chloride (CPC) and the relative interaction between excipients and CPC.

METHODS

An analytical assay was developed to evaluate the interaction between CPC and the excipients. In vivo activity was investigated using six volunteers by determining the reduction in colony forming units recoverable from the oropharynx after sucking each proprietary lozenge separately on different days. In vitro determinations investigated the relative antimicrobial activity of aqueous solutions of the lozenges and, the effect of pH and tablet base excipients on that activity against Staphylococcus aureus, Streptococcus pyogenes and Candida albicans.

RESULTS

Both in vivo and in vitro results showed that the tablet based lozenges had markedly reduced antimicrobial activities compared with previous results with a candy based lozenge (in vivo and in vitro) or the same concentration of aqueous CPC (in vitro). Magnesium stearate suspensions in CPC 250 micrograms/ml indicated that magnesium stearate adsorbed CPC and at 0.4% lozenge weight and above significantly reduced the antimicrobial activity of CPC 250 micrograms/ml.

CONCLUSIONS

The reduced activity of CPC in tablet based lozenges resulted from a decreased availability of CPC in solution due to an adsorption of CPC on magnesium stearate. To avoid this reduction in activity tablet based lozenges containing CPC 250 micrograms/ml, or similar concentrations, plus magnesium stearate should contain not more than 0.3% w/w lozenge weight of the lubricant.

Brodimoprim synergy against Enterococcus faecalis evaluated in vitro

Combinations of either brodimoprim or trimethoprim plus either carbenicillin, gentamicin, ciprofloxacin or rifampicin showed synergy at sub-inhibitory concentrations against both Enterococcus faecalis NCTC 5957 and 775. Brodimoprim alone and in combination showed greater antibacterial activity against both strains of E. faecalis than trimethoprim. MBCs of brodimoprim and trimethoprim were 14.4 and 25.6 mg/L for E. faecalis NCTC 5957 and 7.2 and 12.8 mg/L for E. faecalis NCTC 775. Combinations of either brodimoprim or trimethoprim plus the other antibacterial agents, except gentamicin and dibromopropamidine isethionate, were bactericidal at achievable plasma concentrations. Viable count determinations of cultures of both test organisms in the presence of 3/4 of the MIC of each of the four antibiotics and the two antifolates alone and combinations of each antibiotic with either brodimoprim or trimethoprim indicated that only the combinations prevented recovery and regrowth of the cultures over 24 h. The ATP released from cultures of both strains of E. faecalis treated with brodimoprim and trimethoprim at the same concentrations was approximately 1.5 times greater with brodimoprim than with trimethoprim. Combinations of 3/4 of the MIC of each of the antibiotics in combination with 3/4 of the MIC of brodimoprim against cultures of both strains of E. faecalis resulted in greater release of ATP than occurred with equivalent trimethoprim combinations. It is postulated that the increased activities observed with the brodimoprim combinations resulted from an effect of brodimoprim on the bacterial cell permeability control. These results indicate that both brodimoprim and trimethoprim offer potential benefits for use with either carbenicillin, gentamicin, ciprofloxacin or rifampicin for the treatment of E. faecalis infections.

The effect of formulation on the antimicrobial activity of cetylpyridinium chloride in candy based lozenges

PURPOSE

The purpose of this investigation was to determine the influence on the antimicrobial activity of cetylpyridinium chloride of the various components of the formulation of each of six candy based lozenges.

METHODS

In vivo activity was investigated using six volunteers by determining the reduction in colony forming units recoverable from the oropharynx after sucking each lozenge separately on different days. In vitro determinations investigated the relative activity of aqueous solutions of the lozenges, the effect on activity of additional active ingredients, pH and lozenge base ingredients against separate inocula of each of the test organisms Staphylococcus aureus, Streptococcus pyogenes and Candida albicans.

RESULTS

Both in vivo and in vitro results showed that the pH of the dissolved lozenge solution was the single most influential readily adjustable formulation parameter which significantly influenced the activity of cetylpyridinium chloride activity in candy based lozenges.

CONCLUSIONS

Lozenges containing cetylpyridinium chloride as the active ingredient should be formulated at a pH greater than 5.5.

Sensitive fluorimetric determination of gentamicin sulfate in biological matrices using solid-phase extraction, pre-column derivatization with 9-fluorenylmethyl chloroformate and reversed-phase high-performance liquid chromatography

A high-performance liquid chromatographic method is described for the determination of gentamicin in bacterial culture medium or plasma with increased sensitivity and improved separation of the C1 component. Gentamicin was extracted from the biological matrix with high efficiency using carboxypropyl (CBA)-bonded silica. Derivatization with 9-fluorenylmethyl chloroformate (FMOC-Cl) followed by C18 reversed-phase chromatography allowed the fluorimetric detection of gentamicins C1, C1a and C2. A fourth component, considered to be gentamicin C2a, was partially resolved from the C2 peak. Optimal conditions for the extraction and derivatization of gentamicin are described. The detection limit was below 50 micrograms/l, the assay was linear to 5 mg/l and showed good reproducibility. It is concluded that pre-column derivatization with FMOC-Cl substantially improves the analysis of gentamicin compared with present methods based on reaction with o-phthaldialdehyde.

Mechanism of sulphadiazine enhancement of trimethoprim activity against sulphadiazine-resistant Enterococcus faecalis

Sulphadiazine had little or no antibacterial effect against three strains of Enterococcus faecalis (MICs of above 3600 mg/L) but it caused approximately six-fold increases in bacterial uptake of trimethoprim, increased release of bacterial ATP and produced ultrastructural damage to both the trimethoprim resistant E. faecalis 463 and the trimethoprim sensitive NCTC 5957. MICs of trimethoprim were 0.6, 0.8 and 76.8 mg/L for E. faecalis NCTC 775, NCTC 5957 and 463 respectively. When log phase E. faecalis 463 and NCTC 5957 were grown for 4 h in trimethoprim 56 and 0.6 mg/L plus sulphadiazine 320 and 100 mg/L respectively there was an approximate ten-fold and nine-fold increase in uptake of sulphadiazine and a two-fold increase in leakage of ATP. Trimethoprim caused more damage to the cell wall and cytoplasmic membrane than sulphadiazine but the combination of sulphadiazine plus trimethoprim caused the most cell damage. The increased activity observed with the combination seems very likely to have resulted from the increased uptakes of the antibacterials, which in turn had resulted from the cell wall damage and consequent increased cell permeability caused by each antibacterial. It is proposed that a markedly subinhibitory concentration of sulphadiazine enhanced the antibacterial activity of trimethoprim against all three strains of E. faecalis by this mechanism.

Activity of p-aminobenzoic acid compared with other organic acids against selected bacteria

The antibacterial activity of p-aminobenzoic acid against Listeria monocytogenes, Salmonella enteritidis and Escherichia coli was compared with the activity of commonly used acidulants: formic, propionic, acetic, lactic and citric acids. Viable count evaluations and MIC determinations indicated that p-aminobenzoic acid caused greater inhibitory effects than the other organic acids. The activity of p-aminobenzoic acid on the growth of the test organisms at selected pH values indicated that p-aminobenzoic acid was more active at low pH than at high pH. Uptake studies showed that the uptake of p-aminobenzoic acid by E. coli was markedly decreased as the pH values increased. Electron micrographs of E. coli cells grown in the presence of p-aminobenzoic acid indicate that p-aminobenzoic acid caused marked damage to the cell envelope. It is suggested that p-aminobenzoic acid has at least two mechanisms of action: one mechanism in common with other organic acids and the other mechanism by interfering with the synthesis of the peptidoglycan layer by an action on the dihydrofolate reductase enzyme.

Determination of thymidine, uracil and p-aminobenzoic acid in bacteriological cultures by capillary zone electrophoresis

A capillary zone electrophoresis assay has been developed which simultaneously separates and quantifies the bacterial metabolites thymidine, uracil and p-aminobenzoic acid present at bacteriologically relevant concentrations in a supplemented minimal bacteriological medium. Sulphadiazine was used as the internal standard.

A triterpene from Rubus pinfaensis

A new pentacyclic triterpene, pinfaensin, was isolated from the roots of Rubus pinfaensis and the structure elucidated by 13C NMR methods. This triterpene, a glycoside of pinfaensic acid (glucosyl 23-formyl-2 alpha,3 beta,19 alpha-trihydroxyurs-12-en-28-oate), in order to achieve purification and characterization, was hydrolysed to previously unreported pinfaensic acid which on acetylation and methylation gave methyl diacetoxypinfaensate (methyl 2 alpha,3 beta-diacetoxy-23-formyl-19 alpha-hydroxyurs-12-en-28-oate).

Study of the mutual effects of sulphadiazine and ciprofloxacin on their uptakes by Pseudomonas aeruginosa

A high-performance liquid chromatography (HPLC) assay was developed for ciprofloxacin and sulphadiazine in Isosensitest broth. Combining the HPLC assay with cell dry-weight determinations indicated that both compounds were able to enhance the uptake of the other by log phase Pseudomonas aeruginosa cultured in the presence of the compounds. It is hypothesized that the increased bacterial uptakes are the reason for the enhanced antibacterial activity previously reported for combinations of ciprofloxacin and sulphadiazine.

Capillary zone electrophoresis assay of the uridine diphosphate N-acetylmuramyl peptide precursors and the disaccharide pentapeptide derivative of bacterial cell wall peptidoglycan

Uridine diphosphate N-acetylmuramyl peptide (EDP-MurNac) precursors and disaccharide pentapeptide of bacterial cell wall peptidoglycan were extracted from Enterobacter colacae cells and examined by capillary zone electrophoresis. Five UDP-MurNac derivatives with dibromopropamidine isethionate as the internal standard, and disaccharide pentapeptide with pyrimethamine as the internal standard, were successfully and rapidly analysed by using a fused-silica capillary and sodium phosphate buffer in methanol as the organic modifier at appropriate pH. Accurate quantitation was also achieved. The method provides the potential to investigate quantitatively the effect of antibacterials on the biosynthesis of peptidoglycan and to determine the relative cellular concentrations of the murein precursors within the cell cycle.

In vitro evaluation of the antimicrobial activities of selected lozenges

The in vitro antimicrobial activities of 10 lozenges (Merothol, Merocets, Merocaine, Strepsils (two varieties), Dequacaine, Dequacets, Zensyls, Tyrozets, and Labosept) were determined by use of a microtiter counting method with Streptococcus pyogenes, Staphylococcus aureus, and Candida albicans as the test organisms. Merothol, Merocets, Merocaine, and both Strepsils formulations all reduced the counts of both S. aureus and S. pyogenes suspensions by approximately 6 log cycles within 5 and 20 min, respectively. Merothol, Merocets, and Merocaine also caused a reduction in the counts of the C. albicans suspension approximately 5 log cycles within 40 min, but no other lozenge formulation showed rapid and marked activity against C. albicans. Dequacaine and Dequacets showed marked but much slower activities against this yeast. Zensyls caused an approximately 6-log-cycle reduction in bacterial counts within 40 min, and Dequacaine, Dequacets, and Tyrozets showed marked but slower antibacterial activities. This work confirmed by a statistically sound in vitro method the in vivo antibacterial activities reported for Merothol, Merocets, and Merocaine, demonstrated equivalent antibacterial activities for Strepsils, and indicated that Merothol, Merocets, and Merocaine also showed marked activities against C. albicans.

The effects of student nurse community mental health placements on sufferers of mental health problems in the community

The effects which student nurses have on the care of clients with mental health problems in the community is an area which has seldom been studied. With the closure of large psychiatric hospitals and the rise in community placements as part of Project 2000, an increasing number of students are being placed in the community. The study gathers data from clients attending five self-help/support groups in the North Derbyshire area of England. Analysis of the data challenges assumptions generally held by community psychiatric nurses (CPNs) that the presence of a third person, e.g. student/visitor, during a CPN home visit to the client is detrimental to the therapeutic interaction between the CPN and the client. The findings are inconclusive but suggest that some client groups (possibly those with long-term mental health problems) may find the presence of a student during a CPN visit facilitative. The study raises the issue of the student nurse/patient power relationship within a support group. Findings suggest that membership of a support group is empowering to the client and illustrates that clients in the community have greater control over the involvement of student nurses in their care than patients in hospital. Groups within the sample expressed a unanimous view that student nurse placements should be long enough to allow therapeutic nurse/client relationships to develop. This is in direct contrast to the current Project 2000 Common Foundation Programme approach of short observational non-institutional placements.

Investigation of cell envelope damage to Pseudomonas aeruginosa and Enterobacter cloacae by dibromopropamidine isethionate

Electron micrographs of log-phase Pseudomonas aeruginosa and Enterobacter cloacae cultured for 4 h in the presence of subinhibitory concentrations of dibromopropamidine isethionate indicate that this antibacterial agent can cause marked damage to the cell envelope structures of both species. This result provides an explanation of how dibromopropamidine can enhance the uptake and thus the activity of a second antibacterial agent used in combination with it.

Investigation of synergism between combinations of ciprofloxacin, polymyxin, sulphadiazine and p-aminobenzoic acid

Subinhibitory concentrations of combinations of any two of ciprofloxacin, colistin (or polymyxin B), sodium sulphadiazine and p-aminobenzoic acid were shown by checkerboard minimum inhibitory concentration determinations to have synergistic inhibitory activity against Pseudomonas aeruginosa and to have either synergistic or additive activity against Staphylococcus aureus. In addition, sulphadiazine plus either ciprofloxacin or polymyxin showed markedly enhanced killing activity against both P. aeruginosa and S. aureus. p-Aminobenzoic acid plus either ciprofloxacin or polymyxin also demonstrated enhanced killing activity against P. aeruginosa but these combinations were less effective in enhancing activity against S. aureus. Ciprofloxacin in combination with polymyxin had a marked synergistic effect against P. aeruginosa but only a slight synergistic effect against S. aureus. These findings indicate a potential usefulness for the synergistic combinations against P. aeruginosa and S. aureus in the clinical situation; that is, they indicate an extended role for sulphonamides and support a potential role for p-aminobenzoic acid as enhancers of the activity of primary antibacterial agents such as ciprofloxacin and polymyxin. We suggest that for a second antibacterial to enhance the activity of ciprofloxacin, it may be necessary for the second antibacterial to increase cell permeability so increasing bacterial uptake of ciprofloxacin.

An electronmicroscope study of the effect of sulphadiazine and trimethoprim on Enterobacter cloacae

Electronmicroscopy of thin sections of log phase cells of Enterobacter cloacae NCTC 10005 grown for 4 h in the presence of sulphadiazine 250 micrograms/ml, trimethoprim 12.5 microliters/ml or the combination of sulphadiazine 250 micrograms/ml plus trimethoprim 12.5 micrograms/ml indicated that both agents caused marked morphological damage even though the MIC of sulphadiazine for the E. cloacae strain was > 3000 micrograms/ml. The damage took the form of electron-transparent areas devoid of ribosomes in the cytoplasm and detachment of the outer membrane. The latter was most marked with trimethoprim, which also caused damage to the cytoplasmic membrane. It is postulated that the synthesis of the peptidoglycan layer was affected by the antimetabolites since the morphological effects were strikingly similar to those caused by treatment of E. cloacae with disodium edetate plus lysozyme. Viable counts of cultures undergoing the same treatments as those prepared for electronmicroscopy indicated that although sulphadiazine merely partially inhibited growth it nevertheless enhanced the bactericidal action of trimethoprim over a 5-h period.

An evaluation of the antibacterial activities of combinations of sulfonamides, trimethoprim, dibromopropamidine, and silver nitrate compared with their uptakes by selected bacteria

Modifications of antibacterial activity have been demonstrated using combinations of two antibacterials from trimethoprim, sulfonamides (sulfadiazine, sulfamerazine, and silver sulfadiazine), silver nitrate, and dibromopropamidine isethionate, either formulated in a cream base or dissolved in peptone water. The creams were evaluated using the agar cup diffusion method in isosensitest agar. The peptone water solutions provided fractional inhibitory concentrations for combinations of the antibacterial substances. The test organisms were Pseudomonas aeruginosa, Enterobacter cloacae, and Staphylococcus aureus. Bacterial uptakes of antibacterial combinations, determined by either an HPLC assay method or an atomic absorption method, combined with dry cell weight determinations, indicated that enhancement of activity of the antibacterial combinations against P. aeruginosa (two strains) and E. cloacae were related to marked increases in the bacterial uptake of the chemical agents. Decreases in activity were related to decreased uptake of either dibromopropamidine and/or silver ions. The effect of the trimethoprim and the sulfonamides was shown to depend on their effect on bacterial folate synthesis. It is suggested that partial blockade of the folate synthetic pathway leads to an effect on cell permeability which results in increased uptake of antibacterials. Dibromopropamidine isethionate also has an effect on cell permeability which produces an increased bacterial uptake of a second antibacterial present in the medium. These findings provide further explanation of how subinhibitory concentrations of trimethoprim and sulfonamide combinations are synergistic against a wide range of bacteria even when certain bacteria are resistant to either member of the combination.

Structure and activity of recombinant human interferon-gamma analogs

We have prepared interferon-gamma (IFN-gamma) analogs to study the structural role of particular amino acids in relation to their effects on antiviral activity. Three IFN-gamma analogs were prepared on the basis of predicted secondary structure. In two of the analogs, [Gln25]IFN-gamma and [Thr45]IFN-gamma, changes were made at residue 25 (Asn to Gln) and at residue 45 (Met to Thr), respectively. [Gln25Lys78]IFN-gamma had two changes, at residue 25 (Asn to Gln) and residue 78 (Asn to Lys). Another analog, [Cys-Tyr-Cys]IFN-gamma, incorporated Cys-Tyr-Cys at the amino terminus. Comparison of the structure and activity of these analogs with that of the natural sequence protein suggested that residues 25 and 78 are at the protein surface and play an important role in antiviral activity. The residue at position 45 was found to be important for maintaining the protein structure, as assessed by circular dichroism spectroscopy. The addition of Cys-Tyr-Cys resulted in a small perturbation of protein structure and a small decrease in antiviral activity.

Quantification of uptake of liposomal carboxyfluorescein by professional phagocytes in-vitro. A flow microfluorimetric study on the J774 murine macrophage cell line

Unilamellar egg phosphatidylcholine/cholesterol liposomes containing carboxyfluorescein were prepared by an ether injection method. The ability of cells of the J774.2 murine macrophage cell line to incorporate the liposomal fluorophore during incubation at 37 degrees C was measured by flow microfluorimetry. Liposomes incorporating additional phosphatidylserine or phosphatidic acid were taken up much more avidly than those lacking these phospholipids and the greatest uptake of carboxyfluorescein was observed with the phosphatidylserine species. Calculation of the number of liposomes taken up, greater than or equal to 0.2% of the number given, showed that this was an inefficient process. However these uptake data support previous findings based on the intracellular bactericidal activity of liposomal antibiotics determined in an identical in-vitro system.

An in-vitro model of intracellular bacterial infection using the murine macrophage cell line J774.2

A simple model of intracellular bacterial infection based on the ability of the macrophage cell line J774.2 to phagocytose Escherichia coli in a reproducible manner is described. Viable counting of intracellular bacteria and microscopic examination of infected macrophage cultures after treatment with fluorescent E. coli antibody showed that the bacteria multiplied within the J774.2 cells. Viable intracellular bacteria may be used to study the activity of bactericidal and bacteriostatic drugs within the macrophage. The low apparent intracellular bactericidal activity of streptomycin, which was time- and concentration-dependent, accords with a low permeability of the J774.2 macrophages to this antibiotic. An exclusively intracellular infection could be achieved by inactivation of non-phagocytosed extracellular bacteria by streptomycin treatment of infected macrophage cultures. Under appropriate conditions intracellular bacterial viability was unaffected.

Enhanced activity of streptomycin and chloramphenicol against intracellular Escherichia coli in the J774 macrophage cell line mediated by liposome delivery

Streptomycin and chloramphenicol were entrapped within large neutral or anionic unilamellar vesicles of egg phosphatidylcholine prepared by an ether injection method. Both antibiotics in liposomal form were inactive against Escherichia coli in a simple tube dilution assay. A comparison was made of the activities of the free and liposomal forms of the antibiotics against E. coli located within the macrophages of the J774.2 murine cell line. The apparent intracellular antibacterial activity of both antibiotics was increased more than 10-fold by entrapment in neutral liposomes and in the case of chloramphenicol in anionic liposomes containing phosphatidylserine. Anionic liposomes containing phosphatidic acid were much less effective carriers than neutral liposomes for either antibiotic in this in vitro system. Incubation at 4 degrees C of cells with liposomes containing antibiotic or carboxyfluorescein inhibited intracellular antibacterial activity and cell-associated fluorescence. The high intracellular activity of the liposomal antibiotics is consistent with their phagocytic uptake by the macrophages followed by intracellular liposomal degradation and antibiotic release. Liposomal modification of cellular uptake and intracellular distribution of antibiotics may be used to extend the activity of existing and new agents against intracellular infection of the reticuloendothelial system.

Pseudomonas cepacia resistance to antibacterials

Reproducible growth rates of Pseudomonas cepacia were obtained. P. cepacia had a markedly different resistance pattern to single and combined antibacterials from that characteristic of Pseudomonas aeruginosa. Benzalkonium and chlorhexidine were more active against log phase P. cepacia than against log phase P. aeruginosa, but polymyxin B sulfate was inactive against log phase P. cepacia at all concentrations tested (smaller than or equal to 16 units/ml). Antagonism of antibacterial activity between edetate disodium-benzalkonium and edetate disodium-chlorhexidine combinations was marked with 16-hr P. cepacia and with 16-hr Staphylococcus aureus. Phenylethanol-benzalkonium and phenylethanolchlorhexidine combinations had no more than additive activity against log phase P. cepacia. These results have relevance to hospital disinfection and preservation of pharmaceutical solutions.

Differences in antibacterial activity of benzalkonium chloride

Benzalkonium solutions obtained from different manufacturers were shown to have different activities. This difference in activity was related to the composition of the benzalkonium chloride. The potential seriousness of this situation is emphasized, and a recommendation is made that the official monographs on benzalkonium chloride be amended appropriately, noting the apparently superior antibacterial activity of the tetradecyl (C14) homolog.

The structure of the chromatin core particle in solution

The shape and size of the nucleosomal core particle from chromatin has been examined by analysis of neutron and X-ray scattering data from dilute solutions. Calculations of scattering for many different models have been made and only one model was able to account for both the X-ray and neutron profiles. This model is an oblate structure with height about 50A and diameter 110A. The DNA is mainly confined to two annuli located at the top and bottom respectively of the core particle positioned on the outside of a compact protein core which has a height of about 40A and diameter about 73A.

Electron microscope study of effect of benzalkonium chloride and edetate disodium on cell envelope of Pseudomonas aeruginosa

Electron micrographs of Pseudomonas aeruginosa grown in nutrient broth or broth containing subinhibitory concentrations of benzalkonium chloride indicate that benzalkonium chloride at 50 and 100 mug/ml strips off the outer cell membrane. Cells grown in the presence of edetate disodium, 50-100 mug/ml had convoluted surfaces (wavy in cross section). Cells damaged by growing on nutrient agar containing benzalkonium (200 mug/ml), when subsequently grown for 16 hr in nutrient broth, produced cells with apparently normal outer lavers. Similar cells grown on nutrient agar plus benzalkonium (500 mug/ml) when grown for 16 hr in nutrient broth had normal resistance to edetate disodium lysis, but cells grown overnight in broth plus benzalkonium (500 mug/ml) showed increased sensitivity to edetate disodium lysis. Cells grown on nutrient agar in the presence of benzalkonium (800 mug/ml) grew in broth plus benzalkonium (10 mug/ml) without stripping of their external membrane, but replicate inocula into broth plus benzalkonium (10 mug/ml) and edetate disodium (50 mug/ml) produced cells with structural damage to the outer lavers of the cell envelope.