Giants Hiding in Small Places: A Case of New Onset Heart Failure, Atrioventricular Block, and Ventricular Arrhythmias

Woman with new-onset heart failure, atrioventricular block, and ventricular tachycardia found to have giant cell myocarditis.

Spontaneous remission of acute lymphoblastic leukemia: A series of nine cases and a review of literature

AIMS

To report a series of acute lymphoblastic leukemia (ALL) cases with spontaneous remission and provide presenting clinical and pathologic information and details of clinical course to raise awareness among oncologists and patients.

METHODS

We identified and analyzed nine patients with ALL and spontaneous remission. Review of literature reveals an additional nine previously reported cases with similar clinical course.

RESULTS

All of these patients, ranging in age from 2 to 12 years of age, presented with inciting signs and symptoms of viral or bacterial infection. All of the patients showed varying percentages of lymphoblasts (.2% to 90%) in diagnostic bone marrow biopsy. All B-ALL cases shared a similar blast phenotype on flow cytometry with coexpression of CD19, CD10 and TdT and variable CD20 expression. All nine patients achieved spontaneous remission of their leukemia as confirmed by flow cytometry and/or bone marrow biopsy without chemotherapeutic intervention. Time to remission from presentation ranged from 1 to 8 weeks. After remission, all patients redeveloped ALL, and time from remission to reemergence ranged from 2 to 24 weeks.

CONCLUSION

Our series of cases and cases identified in literature show that ALL diagnosed with modern methods of flow cytometry and molecular analysis will recur within weeks to months from disappearance, usually with cytopenias, which provides a template for oncologic follow-up and testing in these patients.

Cohort profile: the ESC EURObservational Research Programme Non-ST-segment elevation myocardial infraction (NSTEMI) Registry

AIMS

The European Society of Cardiology (ESC) EURObservational Research Programme (EORP) Non-ST-segment elevation myocardial infarction (NSTEMI) Registry aims to identify international patterns in NSTEMI management in clinical practice and outcomes against the 2015 ESC Guidelines for the management of acute coronary syndromes in patients presenting without ST-segment-elevation.

METHODS AND RESULTS

Consecutively hospitalised adult NSTEMI patients (n = 3620) were enrolled between 11 March 2019 and 6 March 2021, and individual patient data prospectively collected at 287 centres in 59 participating countries during a two-week enrolment period per centre. The registry collected data relating to baseline characteristics, major outcomes (in-hospital death, acute heart failure, cardiogenic shock, bleeding, stroke/transient ischaemic attack, and 30-day mortality) and guideline-recommended NSTEMI care interventions: electrocardiogram pre- or in-hospital, pre-hospitalization receipt of aspirin, echocardiography, coronary angiography, referral to cardiac rehabilitation, smoking cessation advice, dietary advice, and prescription on discharge of aspirin, P2Y12 inhibition, angiotensin converting enzyme inhibitor (ACEi)/angiotensin receptor blocker (ARB), beta-blocker, and statin.

CONCLUSION

The EORP NSTEMI Registry is an international, prospective registry of care and outcomes of patients treated for NSTEMI, which will provide unique insights into the contemporary management of hospitalised NSTEMI patients, compliance with ESC 2015 NSTEMI Guidelines, and identify potential barriers to optimal management of this common clinical presentation associated with significant morbidity and mortality.

A Case of Acute Disseminated Histoplasmosis of the Liver in a Patient Receiving Amphotericin-B Therapy

Introduction/Objective

Acute disseminated histoplasmosis (DH), caused by Histoplasma Capsulatum (HC), occurs primarily in immunocompromised hosts. It is characterized by an abrupt onset of symptoms (fever, malaise, hepatosplenomegaly, lymphadenopathy, anemia, leucopenia and thrombocytopenia) and a lack of granulomatous inflammatory response. If left untreated, death occurs within three months of the disease. The treatment of choice is a two-week course of Amphotericin-B (AmpB-Tx). Studies show a drop in fungal load in 85% of blood cultures and a drop of 1.6 U and 2.1 U in serum and urine antigen levels of histoplasmosis respectively, within 14 days of treatment thereby making it unlikely to see liver failure secondary to acute DH in a patient receiving AmpB-Tx.

Methods/Case Report

We present a case of a 41-year-old male, newly diagnosed with HIV (CD4=44; viral load=5,350,000) and DH on AmpB-Tx. At presentation, his liver function tests (LFT’s) were mildly elevated (Bilirubin =2.7mg/dL; ALP=259U/L; AST=271U/L; ALT=71U/L). On Day-9 of AmpB-Tx, he became somnolent and jaundiced with hepatosplenomegaly and ascites. His LFTs were markedly raised, showing an obstructive pattern (Bilirubin=16mg/dL; ALP=1578U/L; AST=261U/L; ALT=213U/L). On Day-11 of treatment, we received a liver biopsy for HIV cholangiopathy versus drug induced hepatotoxicity. The clinicians considered DH to be a less likely cause since the patient was already on AmpB-Tx. The liver biopsy showed hepatocytes with cholestasis, minimal acute portal inflammation and numerous portal tract and parenchymal macrophages laden with fungal organisms. Gomori-Methenamine-Silver stain confirmed the fungal organisms as being HC. This diagnosis prompted the continuation of AmpB-Tx past 14 days. The patient’s LFT’s reached maximum values of Bilirubin=18mg/dL; ALP=1680U/L; AST=355U/L; ALT=324U/L. After 25 days of AmpB-Tx, his LFT’s trended downwards with a resolution of his hepatic encephalopathy and jaundice. While a 14 day course was initially intended, AmpB-Tx was continued for a total of 28 days until a resolution of symptoms was achieved.

Results (if a Case Study enter NA)

NA.

Conclusion

Our case identifies a patient with progressive hepatic histoplasmosis in spite of AmpB-Tx. Keeping in mind and identifying such cases on pathology can alter the course of treatment for patients.

The Accidental Discovery of a Rare and Diagnostically Challenging Antibody, Anti Diegoa

Introduction/Objective

Anti Diegoa antibody (DiA) is a rare antibody, associated with severe hemolytic disease of the newborn. It is seen in American Indians and Asians of Mongoloid descent. Only 2.6% of Hispanics and <0.01% of Caucasians and African Americans have this antibody, making it challenging to diagnose. We present a case of a DiA discovered accidentally.

Methods/Case Report

A 31-year-old G4P3 Hispanic female at 35 weeks 5 days of gestation presented with limited prenatal care and gestation complicated by chronic deep vein thrombosis, on enoxaparin. Her gestational history was significant for Anti-E Antibody (Anti-E) with a gel titer of 1:8 during her second gestation. During her current pregnancy her Anti-E Ab gel titer was 1:32 and an Anti-c Antibody (Anti-c) was also detected. R1R1 panel was used to detect further antibodies since the patient was Anti-E and Anti-c. The initial gel panel could not rule out Duffy Antibody (FyA) and Kidd Antibody (JkB). Two R1R1 panels had already been cross matched and both were compatible. A second gel panel showed Kell antigen (KpA), FyA and JkB, all with a +2 positivity in a R1R1 cell panel (Cell X). Antigen typing labelled the patient as JkB+ and FyA-. One compatible unit was FyB- making FyA- unlikely. One of the cross matched compatible units was FyA+. An additional homozygous R1R1 cell was negative for FyA. Therefore FyA- was ruled out. The positivity on Cell X was then thought to be KpA. A solid phase panel (Cell Y) was conducted and was positive, supporting KpA as the causative factor. A decision was made to repeat our test using the initial patient sample plus a CBC tube. This demonstrated KpA negativity, negating KpA as the causative factor. However the Cell Y positivity in the solid phase panel was still questionable. DiA, a low frequency antibody is also found on this cell. This led to further testing. Another R1R1 cell showed +3 positivity for DiA. Antibody identification confirmed this as DiA with a titer of 2. The patient underwent induction of labor and delivered a healthy neonate.

Results (if a Case Study enter NA)

N/A

Conclusion

Since DiA is located in the same panel as KpA, the positive result was presumed to be secondary to KpA. However repeat testing demonstrated KpA negativity and thereby unmasked DiA as the culprit.

The feasibility of solar-powered small-scale brackish water desalination units in a coastal aquifer prone to saltwater intrusion: A comparison between electrodialysis reversal and reverse osmosis

In the face of increasing water shortages worldwide, water desalination has the potential to expand the available freshwater supply options in many water stressed regions. This paper assesses the feasibility of adopting photovoltaic powered small-scale brackish water desalination units in a coastal aquifer facing saltwater intrusion and chronic water shortages. Moreover, a detailed cost comparison, which incorporates the associated environmental costs, is conducted between the Electrodialysis Reversal (EDR) technique and Reverse Osmosis (RO). The results showed that PV-powered small-scale desalination units were more economically viable as compared to grid-powered units, when the electricity tariffs reflected non-subsidized electricity prices and environmental costs were internalized. EDR-PV proved to be more economically feasible and with a lower environmental footprint as compared to RO-PV, up until the salinity of the aquifer was below 5000 ppm (EDR: 0.57-1.18 $/m³; RO = 1.19-1.59 $/m³). Beyond that salinity, the RO-PV was found to be the more economically viable option, with costs reaching as high as 2.65 $/m³ at a salinity of 25,000 ppm. Overall, the environmental costs between the two technologies varied significantly, largely due to differences in the generated brine volume, with EDR having better efficiencies at lower salinity levels. Finally, the study highlighted the risk of accelerating saltwater intrusion as a result of the increased market penetration of solar-powered desalination units along vulnerable coastal aquifers.

POS1166 UNDERSTANDING PRESCRIPTION BEHAVIOR ACROSS HEALTHCARE PROFESSIONALS IN TREATING KNEE OSTEOARTHRITIS BEFORE AND DURING THE 2020 COVID-19 PANDEMIC

Background:

Knee Osteoarthritis (OA) treatment aims to provide symptom relief, easing joint pain and enabling mobility. The COVID-19 pandemic affected healthcare systems globally, including ways OA patients were treated.

Objectives:

This study is to understand how treatment management of knee OA patients and prescribing behavior across US healthcare professionals (HCPs) was affected when COVID-19 impacted healthcare systems and regimes globally

Methods:

A multi-center online medical chart review study of patients with OA was conducted between May – July 2019 & 2020 among US rheumatologists (rheums), orthopedic surgeons (orthos), primary care physicians with a focus in sports medicine (SM PCPs), and pain specialists, practicing across hospital and private practices. Recruited from a large access panel, physicians were screened for duration of practice in their specialty (3-50 years) and caseload (35 or more knee OA patients personally managed, at least 10 of which must be classified as moderate-severe). Patient charts were recorded for the next 5 eligible patients seen during the screening period. Respondents abstracted patient demographics and treatment regimes used. Descriptive statistics were used to analyse the data

Results:

275 physicians were recruited and collectively reported 1375 patients between May-Jul 2019; 260 physicians were recruited and collectively reported 1300 patients between May-Jul 2020.

Looking at treatments patients were receiving at time of reporting, oral medications, particularly NSAIDs, were widely used, regardless of the physician specialty. A directional increase of 6% in the proportion of reported patients deriving from sampled primary care SM PCPs from pre-COVID (Q219) to during COVID (Q220), whilst the same is not true for rheums, orthos, and pain specialists.

Figure 1.

Medication usage in reported knee OA patients across all sampled specialties - Q2 2019 vs Q2 2020

With regards to the usage of injectable therapy, the opposite pattern is seen - higher proportions of reported patients deriving from sampled rheums, orthos & pain specialists receiving injectables vs those deriving from sampled SM PCPs. While focusing on orthos, the proportion of reported patients deriving from them who receive injectables grew by 5% in Q220 (during COVID) vs Q219 (pre-COVID) – directionally more so than other specialties. This is possibly due to limited elective surgeries during the pandemic.

Looking deeper into injectable usage amongst reported patients deriving from sampled rheums and orthos, the proportion of the total reported patient set receiving this treatment type is relatively similar across both specialties, prior to, and during the COVID-19 pandemic. However, among reported patients who received surgery, a directionally higher proportion of this reported patient cohort deriving from orthos are noted to receive injectables vs those from rheums – this is true both pre- and during the pandemic.

Conclusion:

From the sample surveyed, it appears that primary care SM PCPs adopted their treatment adjustment during COVID-19 pandemic differently, by prescribing more orals, while other secondary care physicians (rheums, orthos, pain specialists) focused on injection treatment for longer pain relief. Considering movement restrictions and limited elective surgeries during the pandemic, the lack of targeted treatment options for knee OA has been made more apparent. With a burgeoning pipeline, many of which are targeted therapies, it is hopeful that knee OA treaters will be less reliant on symptom remedies and can readily offer patients’ longer-acting pain relief or disease modifying options to combat joint deterioration

References:

[1]Ipsos Osteoarthritis Therapy Monitor (May – July 2019, 275 specialists reporting on 1375 OA patients seen in consultation; May – July 2020, 260 specialists reporting on 1300 OA patients seen in consultation, data collected online. Participating physicians were primary treaters and saw a minimum number of 35 knee OA patients). Data © Ipsos 2021, all rights reserved.

Disclosure of Interests:

None declared.

Academic Performance of University Students: A Case in a Higher Learning Institution

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Synthesis and characterization of fibrous silica ZSM-5 for cumene hydrocracking

Fibrous silica ZSM-5 (FZSM-5) with a novel dendrimeric morphology was synthesized using a CTAB-based microemulsion system. The dendrimers increased the active site accessibility and enhanced the catalytic activity for large molecule hydrocracking and ethylbenzene dehydrogenation.

[Dermoid cyst of the floor of the mouth. A case report]

This is the case of a young woman, 16-year-old, calling to our Department because of the appearance, in the floor of the mouth, of a mass progressively growing until about 5 cm diameter. Through fine needle biopsy was diagnosed of epidermoid cyst. Despite its size and infrahyoid site was removed successfully. Perusal review of last years bibliography and its variants.

Genotypic, phenotypic, and modeling studies of a deletion in the beta3-beta4 region of the human immunodeficiency virus type 1 reverse transcriptase gene that is associated with resistance to nucleoside reverse transcriptase inhibitors

Point mutations and inserts in the beta3-beta4 region of human immunodeficiency virus type 1 (HIV-1) reverse transcriptase (RT) are associated with resistance to nucleoside analog inhibitors. This report describes HIV-1 strains from seven patients that were found to have a 3-bp deletion in the beta3-beta4 region of the RT gene. These patient strains also had a mean of 6.2 drug resistance-associated mutations in their RT genes (range, 3 to 10 mutations). The deletion was most frequently found in strains with the Q151M mutation. Nonnucleoside RT inhibitor mutations were found in six of seven strains. Culture-based drug sensitivity assays showed that deletion-containing isolates had reduced susceptibility to four to eight RT inhibitors. Site-directed mutagenesis experiments showed that the deletion alone conferred reduced susceptibility to nucleoside analogs. Changes in the three-dimensional models of the RT deletion mutants were consistently observed at the beta3-beta4 loop and at helices C and E in both the presence and the absence of dTTP. Loss of hydrogen bonds between the RT and dTTP were also observed in the RT deletion mutant. These results suggest that the deletion in the RT gene contributes to resistance to several nucleoside analogs through a complex interaction with other mutations in the RT gene.

A 6-basepair insert in the reverse transcriptase gene of human immunodeficiency virus type 1 confers resistance to multiple nucleoside inhibitors

While many point mutations in the HIV-1 reverse transcriptase (RT) confer resistance to antiretroviral drugs, inserts or deletions in this gene have not been previously characterized. In this report, 14 RT inhibitor-treated patients were found to have HIV-1 strains possessing a 6-basepair insert between codons 69 and 70 of the RT gene. Known drug resistance mutations were also observed in these strains, with T215Y appearing in all strains. Genotypic analysis indicated that the inserts had substantial nucleotide variability that resulted in relatively restricted sets of amino acid sequences. Linkage of patients' treatment histories with longitudinal sequencing data showed that insert strains appeared during drug regimens containing ddI or ddC, with prior or concurrent AZT treatment. Drug susceptibility tests of recombinant patient isolates showed reduced susceptibility to nearly all nucleoside RT inhibitors. Site- directed mutagenesis studies confirmed the role of the inserts alone in conferring reduced susceptibility to most RT inhibitors. The addition of AZT-associated drug resistance mutations further increased the range and magnitude of resistance. These results establish that inserts, like point mutations, are selected in vivo during antiretroviral therapy and provide resistance to multiple nucleoside analogs.

Structure of the human Nkx2.1 gene

NKX2.1 is a member of the NK2 family of homeodomain-containing transcriptional factors which binds to and activates the promoters of thyroid and pulmonary epithelial genes. We have cloned and sequenced twelve human lung NKx2.1 cDNAs. To elucidate the origin of Nkx2.1 transcripts, we also cloned and sequenced a 12 kb human Nkx2.1 genomic clone. Alignment of cDNA sequences with the genomic clone showed that contrary to previous reports, the human Nkx2.1 gene is organized into three exons and two introns. The newly discovered exon I contains an ATG codon that falls in frame with the previously identified Nkx2.1 initiator ATG codon on one of the cDNAs, designated 5E. Northern blot analysis shows that an mRNA of approximately 2.5 kb in size, homologous to 5E, is expressed in both lung and thyroid. The deduced amino acid sequence of the longest open reading frame on 5E is identical to NKX2.1 with the exception of a 30 amino acid N-terminal extension. Coupled in vitro transcription/translation of the 5E cDNA confirms that the open reading frame is translated into a contiguous polypeptide of 44 kDa. Analysis of Nkx2.1 genomic DNA fragments suggest that at least two independent regions, one within the first intron and the other 5' of the first exon may mediate the basal promoter activity of the Nkx2.1 gene in lung epithelial cells.

Individual serum bile acids in apprentice spray painters in association with solvent exposure

The effects of exposure to solvents on serum bile acids were investigated by comparing a group of apprentice vehicle spray painters (exposed group) with one of apprentice electricians. Apprentice spray painters from the study were subdivided into high- and low-solvent-exposure groups. Concentrations of individual serum bile acids (SBA) were measured and compared with conventional liver function tests (LFTs). Total, free, glycine- and taurine-conjugated SBA were consistently found to be present at higher levels in the spray painters than in the electricians, even at the beginning of the apprenticeship. Total SBA tended to increase in spray painters with increasing years of exposure during the apprenticeship, but this was significant at only one time point. No rises were observed over the sampling period in electricians. The mean values of individual and total SBA concentrations were all found to be higher in the high-exposure group than in the low-exposure group, with some differences reaching statistical significance. None of the routine liver biochemistry parameters was different between spray painters and electricians. gamma-Glutamyl transferase (GGT) was the only enzyme found to be significantly different between the high- and low-exposure groups, but all values were within the normal range. This study suggests that occupational exposure even to low levels of solvent mixtures results in increases in SBA. The increased SBA may be indicative of a subclinical liver dysfunction. Alternatively, they may reflect solvent exposure only, with the raised levels having no pathologic implication or consequence.

Undetectable interleukin (IL)-10 and persistent IL-8 expression early in hyaline membrane disease: a possible developmental basis for the predisposition to chronic lung inflammation in preterm newborns

We are interested in determining whether premature birth alters expression of counterregulatory cytokines which modulate lung inflammation. Production of proinflammatory cytokines tumor necrosis factor alpha. IL-1 beta, and IL-8 is regulated in part by the antiinflammatory cytokine IL-10. For preterm newborns with hyaline membrane disease, deficiencies in the ability of lung macrophages to express antiinflammatory cytokines may predispose to chronic lung inflammation. We compared the expression of pro- and antiinflammatory cytokines at the mRNA and protein level in the lungs of preterm and term newborns with acute respiratory failure from hyaline membrane disease or meconium aspiration syndrome. Four sequential bronchoalveolar lavage (BAL) samples were obtained during the first 96 h of life from all patients. All patients rapidly developed an influx of neutrophils and macrophages. Over time, cell populations in both groups became relatively enriched with macrophages. The expression of proinflammatory cytokine mRNA and/or protein was present in all samples from both patient groups. In contrast, IL-10 mRNA was undetectable in most of the cell samples from preterm infants and present in the majority of cell samples from term infants. IL-10 concentrations were undetectable in lavage fluid from preterm infants with higher levels in a few of the BAL samples from term infants. These studies demonstrate that 1) IL-10 mRNA and protein expression by lung inflammatory cells is related to gestational age and 2) during the first 96 h of life neutrophil cell counts and IL-8 expression decrease in BAL from term infants, but remain unchanged in BAL samples from preterm infants.

TTF-1 regulates lung epithelial morphogenesis

TTF-1 is a homeodomain transcriptional factor expressed in thyroid, lung, and parts of the brain. In vitro, TTF-1 can activate the promoter of thyroid- and pulmonary-specific genes. We postulated that TTF-1 not only is essential for the activation of tissue-specific genes, but also may directly participate in epithelial cell morphogenesis. To test this postulate, we used an antisense oligonucleotide inhibitory strategy in an in vitro model of embryonic mouse lung branching morphogenesis. This strategy suppressed TTF-1 translation and inhibited lung branching morphogenesis. The resulting abnormal phenotype was characterized by hyperplastic and unorganized proliferation of epithelial cells in the airways. The mesenchymal compartment of the lung appeared to be unaffected. These results demonstrate, for the first time, that the expression of a homeoprotein transcriptional regulator is necessary for lung epithelial morphogenesis.

Ambulatory continuous infusion ifosfamide with oral etoposide in advanced sarcomas

BACKGROUND

Chemotherapy given by continuous infusion may have different toxicity profiles and different degrees of therapeutic efficacy than when given by bolus administration. The potential therapeutic benefits of continuous infusion chemotherapy and the advantages of outpatient treatment led us to study a continuous infusion of ifosfamide with mesna and oral etoposide.

METHODS

The authors performed a Phase I-II trial in which 9 g/m2 ifosfamide was administered for 6 days and 10.5 g/m2 mesna was administered for 7 days, both by continuous infusion, in combination with 50 mg/m2/d oral etoposide for 8 days in 21 patients with sarcomas or other solid tumors. Courses were repeated every 28 days.

RESULTS

A total of 65 treatment cycles were given. Only six patients required hospitalization for treatment, all because of an initial poor performance status, and most carried out normal activities on an ambulatory basis. Treatment was stopped during the first course in five patients because of central nervous system toxicity, each with a poor pretreatment performance status; neurologic recovery was complete in each patient. The dose of etoposide was decreased by 20% in 11 patients and unchanged in 7 following the first treatment. Hematologic toxicity was predominantly manifested by leukopenia. An absolute neutrophil count less than 500 neutrophils/microliters occurred in 22 of 50 cycles; thrombocytopenia (platelets less than 100,000/microliters) was seen in two patients, requiring platelet transfusion in one. Neutropenic fevers occurred in 13 of 65 cycles; in 4 of these, cultures demonstrated a bacterial infection. Nausea and vomiting were mild. Objective responses occurred in 6 of 16 patients with soft tissue sarcomas (6 partial responses [PR]) (95% confidence interval, 15-65%), and 3 of 5 bone sarcomas, all of whom had been previously treated with doxorubicin and dacarbazine.

CONCLUSIONS

The authors concluded that ifosfamide and mesna given by ambulatory continuous intravenous infusion with wearable pump systems in combination with oral etoposide was well tolerated and showed substantial anti-tumor activity. This combination represents a rational therapeutic approach to patients with advanced soft tissue sarcomas and may have application to other malignancies.

Mechanism of trichloroethylene-induced elevation of individual serum bile acids. I. Correlation of trichloroethylene concentrations to bile acids in rat serum

The temporal relationship between trichloroethylene (TRI) and individual serum bile acids (SBA) has been investigated to gain insight into the mechanism of solvent-induced increases in SBA. Male Sprague-Dawley rats were treated with 1 mmol/kg TRI in corn oil, while control rats received only corn oil. Blood samples were collected from the abdominal aorta at 2, 4, 8, and 16 hr after dosing. Individual SBA were determined by high-performance liquid chromatography (HPLC). Liver and blood concentrations of TRI and one of its metabolites, trichloroethanol (TCEOH), were determined by gas chromatography. SBA levels reached their peak at 4 hr and returned to control levels by 16 hr. There was a relationship between SBA levels and TRI concentrations, which were also at their peak 4 hr after dosing. By 16 hr the levels were undetectable. However, peak blood concentrations of TCEOH were reached 8 hr after dosing, and remained high at 16 hr. Cholic acid and taurocholic acid showed the highest levels of bile acids. Some other bile acids were also elevated, including deoxycholic acid, taurodeoxycholic acid, ursodeoxycholic acid, chenodeoxycholic acid, and taurochenodeoxycholic acid. Determination of total bile acids in serum using an enzymatic/colorimetric method showed a similar pattern of response to that obtained with the HPLC analysis. The data are consistent with TRI having a rapid and specific effect on SBA levels by a mechanism other than liver cell damage.

Mumps virus meningoencephalitis complicated by subarachnoid haemorrhage

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Relative importance of fluorescent siderophores and other factors in biological control of Gaeumannomyces graminis var. tritici by Pseudomonas fluorescens 2-79 and M4-80R

Pseudomonas fluorescens 2-79 suppresses take-all, a major root disease of wheat caused by Gaeumannomyces graminis var. tritici. The bacteria produce an antibiotic, phenazine-1-carboxylic acid (PCA), and a fluorescent pyoverdin siderophore. Previous studies have established that PCA has an important role in the biological control of take-all but that antibiotic production does not account fully for the suppressiveness of the strain. To define the role of the pyoverdin siderophore more precisely, mutants deficient in production of the antibiotic, the siderophore, or both factors were constructed and compared with the parental strain for control of take-all on wheat roots. In all cases, strains that produced PCA were more suppressive than those that did not, and pyoverdin-deficient mutant derivatives controlled take-all as effectively as their respective fluorescent parental strains. Thus, the phenazine antibiotic was the dominant factor in disease suppression and the fluorescent siderophore had little or no role. The siderophore also was of minor importance in a second strain, P. fluorescens M4-80R, that does not produce PCA. Strains 2-79 and M4-80R both produced substances distinct from the pyoverdin siderophore that were responsible for fungal inhibition in vitro under iron limitation, but these substances also had, at most, a minor role in disease suppression in situ.