Fatal panresistant Lomentospora prolificans fungemia in a patient with aplastic anemia: First report from Türkiye

Lomentospora prolificans is an opportunistic pathogen that can cause invasive lomentosporiosis in immunocompromised patients. Patients with hematological malignancies and those who have undergone stem cell or solid organ transplantations are in the highest risk group. In addition to the limitations and delays in diagnostic possibilities, L. prolificans has a high mortality due to its resistance to all available antifungal drugs. In a patient diagnosed with aplastic anemia, we described the first case of L. prolificans in Türkiye. L. prolificans was identified in the blood culture, and despite the initiation of antifungal treatments, the fungemia resulted in mortality on the 7th day of intensive care hospitalization. This case highlights the importance of early recognition and prompt initiation of appropriate antifungal therapy to improve the outcome of patients with rare mold infections.     

Voriconazole plus terbinafine combination antifungal therapy for invasive Lomentospora prolificans infections: analysis of 41 patients from the FungiScope® registry 2008–2019

ObjectivesLomentospora prolificans is an emerging cause of serious invasive fungal infections. Optimal treatment of these infections is unknown, although voriconazole-containing treatment regimens are considered the treatment of choice. The objective of this study was to evaluate the role of combination antifungal therapy for L. prolificans infections.MethodsWe performed a retrospective review of medical records of patients with invasive L. prolificans infection diagnosed between 1 January 2008 and 9 September 2019 that were documented in the FungiScope® registry of rare invasive fungal infections. We compared clinical outcomes between antifungal treatment strategies.ResultsOver the study period, 41 individuals with invasive L. prolificans infection from eight different countries were documented in the FungiScope® registry. Overall, 17/40 (43%) had treatment response/stable disease and 21/40 (53%) had a fatal outcome attributed to invasive fungal infection. Combination antifungal therapy was associated with increased 28-day survival (15/24 survived versus 4/16 receiving monotherapy; p 0.027) and the combination voriconazole plus terbinafine trended to be associated with higher rates of treatment success (10/16, 63%, 95% CI 35%–85%) compared with other antifungal treatment regimens (7/24, 29%, 95% CI 13%–51%, p 0.053). In Kaplan–Meier survival analysis there was a higher survival probability in individuals receiving the voriconazole/terbinafine combination compared with other antifungal regimens (median survival 150 days versus 17 days).ConclusionsWhile overall mortality was high, combination antifungal treatment, and in particular combination therapy with voriconazole plus terbinafine may be associated with improved treatment outcomes compared with other antifungal regimens for the treatment of invasive L. prolificans infections.     

Successful Control of Disseminated <Emphasis Type="Italic">Scedosporium prolificans</Emphasis> Infection with a Combination of Voriconazole and Terbinafine

Disseminated Scedosporium prolificans infections are almost uniformly fatal because of their resistance to antifungal agents. Recently, synergy between triazoles and terbinafine has been demonstrated against Scedosporium prolificans in vitro. Reported here is a patient who developed disseminated Scedosporium prolificans infection following bone marrow transplantation and who was successfully treated with a combination of voriconazole and terbinafine in addition to aggressive surgical debridement. Antifungal synergy testing and combination therapy should be considered in cases of disseminated infection with Scedosporium prolificans. Electronic Publication     

Prognostic factors in 264 adults with invasive Scedosporium spp. and Lomentospora prolificans infection reported in the literature and FungiScope®

Invasive Scedosporium spp. and Lomentospora prolificans infections are an emerging threat in immunocompromised and occasionally in healthy hosts. Scedosporium spp. is intrinsically resistant to most, L. prolificans to all the antifungal drugs currently approved, raising concerns about appropriate treatment decisions. High mortality rates of up to 90% underline the need for comprehensive diagnostic workup and even more for new, effective antifungal drugs to improve patient outcome. For a comprehensive analysis, we identified cases of severe Scedosporium spp. and L. prolificans infections from the literature diagnosed in 2000 or later and the FungiScope^® registry. For 208 Scedosporium spp. infections solid organ transplantation (n?=?58, 27.9%) and for 56?L. prolificans infection underlying malignancy (n?=?28, 50.0%) were the most prevalent risk factors. L. prolificans infections frequently presented as fungemia (n?=?26, 46.4% versus n?=?12, 5.8% for Scedosporium spp.). Malignancy, fungemia, CNS and lung involvement predicted worse outcome for scedosporiosis and lomentosporiosis. Patients treated with voriconazole had a better overall outcome in both groups compared to treatment with amphotericin B formulations. This review discusses the epidemiology, prognostic factors, pathogen susceptibility to approved and investigational antifungals, and treatment strategies of severe infections caused by Scedosporium spp. and L. prolificans.     

Unique histological characteristics of Scedosporium that could aid in its identification

Scedosporium prolificans has been increasingly recognized as an etiological agent of disseminated mycelial infections in profoundly immunocompromised patients. Reported herein is a case of disseminated S. prolificans infection in a patient undergoing anti‐neoplastic chemotherapy for acute myeloid leukemia. Antemortem blood culture yielded S. prolificans, which was confirmed on conventional morphological examination and polymerase chain reaction‐based DNA sequencing targeting internally transcribed spacer regions. Histopathology of autopsy specimens indicated fungal infection in the heart, lungs, liver, kidneys, spleen, pancreas and gastrointestinal tract, with the development of hemorrhagic and ischemic necrosis. The infecting fungus had developing septate hyphae and was identified as belonging to the genus Scedosporium, on in situ hybridization of tissue. The combination of haphazardly branching hyphae and lemon‐shaped conidia appeared to be the most useful distinguishing features to allow differentiation of this fungus from other filamentous fungi in tissue. Three other unique histopathological characteristics of the fungus were noted: (i) parallel hyphae bridged at right angles to produce letter‐H patterns; (ii) intravascular conidiation; and (iii) purple conidia in tissue, though these are usually described as brown in most text books. Precise histopathology, in addition to other techniques such as in situ hybridization, can aid in the identification of etiological fungi.     

Emerging infectious endocarditis due to <Emphasis Type="Italic">Scedosporium prolificans</Emphasis>: a model of therapeutic complexity

Scedosporium prolificans is an emerging agent for severe infections. Although among the dematiaceous fungi Scedosporium is the most frequently isolated in blood cultures, Scedosporium endocarditis is rarely reported. We show herein a patient with acute leukaemia who developed S. prolificans endocarditis. Twelve cases were found in an extensive review of the English literature. In six cases (46%), there was predisposing heart conditions such as a prosthetic valve or an intracavitary device. Only 4 patients (31%) were immunocompromised hosts with haematologic neoplasia, solid-organ transplantation or acquired immunodeficiency syndrome (AIDS). Exposure to Scedosporium was observed in immunocompetent patients who developed infection while in the community. Scedosporium endocarditis occurred on both sides of the heart. Systemic and pulmonary emboli and other metastatic complications were seen in all of these patients. The overall mortality was 77% and, specifically, all of the immunocompromised hosts and 6 out of 7 patients with mitral or aortic valve endocarditis died. Patients with right-sided endocarditis associated with a removable intracardiac device exhibited a better prognosis. Scedosporium endocarditis, although still rare, is an emerging infection with an ominous prognosis. At the present time, valve replacement or the removal of cardiac devices plus combined antifungal treatment may offer the best possibility of cure.     

Multiplex tandem PCR: a novel platform for rapid detection and identification of fungal pathogens from blood culture specimens

We describe the first development and evaluation of a rapid multiplex tandem PCR (MT-PCR) assay for the detection and identification of fungi directly from blood culture specimens that have been flagged as positive. The assay uses a short-cycle multiplex amplification, followed by 12 simultaneous PCRs which target the fungal internal transcribed spacer 1 (ITS1) and ITS2 region, elongation factor 1-α (EF1-α), and β-tubulin genes to identify 11 fungal pathogens: Candida albicans, Candida dubliniensis, Candida glabrata, Candida guilliermondii, Candida krusei, Candida parapsilosis complex, Candida tropicalis, Cryptococcus neoformans complex, Fusarium solani, Fusarium species, and Scedosporium prolificans. The presence or absence of a fungal target was confirmed by melting curve analysis. Identification by MT-PCR correlated with culture-based identification for 44 (100%) patients. No cross-reactivity was detected in 200 blood culture specimens that contained bacteria or in 30 blood cultures without microorganisms. Fungi were correctly identified in five specimens with bacterial coinfection and in blood culture samples that were seeded with a mixture of yeast cells. The MT-PCR assay was able to provide rapid (<2 h), sensitive, and specific simultaneous detection and identification of fungal pathogens directly from blood culture specimens.     

FatalScedosporium prolificans infection in a leukemic patient

The case is described of a 42-year-old patient with acute myeloid leukemia who received two courses of chemotherapy complicated by prolonged bone marrow depression. He was admitted to hospital with fever, hepatosplenomegaly and bilateral nodular pulmonary infiltrates. After admission diffuse cutaneous skin nodules, and hypodense lesions in the hemispheres and cerebellum developed. Cultures of cerebrospinal fluid, bronchoalveolar lavage fluid, skin biopsy specimens and blood revealedScedosporium prolificans, indicative of disseminated mycosis. Treatment with amphotericin B and fluconazole was unsuccessful and the patient died within five days after admission. Features that may enhance early recognition ofScedosporium prolificans infection by both clinicians and microbiologists, as well as options in the treatment of infection with this fungal agent are discussed.     

Matrix-assisted laser desorption ionization-time of flight mass spectrometry for fast and accurate identification of Pseudallescheria/ Scedosporium species

An increasing number of infections due to Pseudallescheria/Scedosporium species has been reported during the past decades, both in immunocompromised and immunocompetent patients. Additionally, these fungi are now recognized worldwide as common agents of fungal colonization of the airways in cystic fibrosis patients, which represents a risk factor for disseminated infections after lung transplantation. Currently six species are described within the Pseudallescheria/Scedosporium genus, including Scedosporium prolificans and species of the Pseudallescheria/Scedosporium apiospermum complex (i.e. S. apiospermum sensu stricto, Pseudallescheria boydii, Scedosporium aurantiacum, Pseudallescheria minutispora and Scedosporium dehoogii). Precise identification of clinical isolates at the species level is required because these species differ in their antifungal drug susceptibility patterns. Matrix-assisted laser desorption ionization (MALDI)-time of flight (TOF)/mass spectrometry (MS) is a powerful tool to rapidly identify moulds at the species level. We investigated the potential of this technology to discriminate Pseudallescheria/Scedosporium species. Forty-seven reference strains were used to build a reference database library. Profiles from 3-, 5- and 7-day-old cultures of each reference strain were analysed to identify species-specific discriminating profiles. The database was tested for accuracy using a set of 64 clinical or environmental isolates previously identified by multilocus sequencing. All isolates were unequivocally identified at the species level by MALDI-TOF/MS. Our results, obtained using a simple protocol, without prior protein extraction or standardization of the culture, demonstrate that MALDI-TOF/MS is a powerful tool for rapid identification of Pseudallescheria/Scedosporium species that cannot be currently identified by morphological examination in the clinical setting.     

Infections of the Central Nervous System after Unrelated Donor Umbilical Cord Blood Transplantation or Human Leukocyte Antigen–Matched Sibling Transplantation

We analyzed the incidence, clinical characteristics, prognostic factors, and outcome of central nervous system (CNS) infections in consecutive patients with receiving umbilical cord blood transplantation (UCBT) (n?=?343) or HLA-matched sibling donor stem cell transplantation (MST) (n?=?366). Thirty-four CNS infections were documented at a median time of 116 days after transplantation (range, 7 to 1161). The cumulative incidence (CI) risk of developing a CNS infection was .6% at day +30, 2.3% at day +90, and 4.9% at 5 years. The 5-year CI of CNS infection was 8.2% after UCBT and 1.7% after MST (P?<?.001). The causative micro-organisms of CNS infections were fungi (35%), virus (32%), Toxoplasma spp. (12%), and bacteria (12%). Fungal infections occurred in 11 patients after UCBT and 1 after MST and were due to Aspergillus spp. (n = 8), Cryptococcus neoformans (n = 2), Scedosporium prolificans (n = 1), and Mucor (n = 1). Except for 1 patient, all died from CNS fungal infection. Viral infections occurred in 9 patients after UCBT and 1 after MST and were due to human herpes virus 6 (n = 7), cytomegalovirus (n = 2), and varicella zoster virus (n = 1). CNS toxoplasmosis was diagnosed in 3 patients after UCBT and 1 after MST. Other pathogens were Staphylococcus spp, Nocardia spp, Streptococcus pneumoniae, and Mycobacterium tuberculosis. Twenty of the 34 patients (59%) died from the CNS infection. In multivariable analysis, UCBT and disease stage beyond first complete remission were independently associated with the risk of developing CNS infections. The 5-year overall survival was 19% in patients who developed a CNS and 39% for those who did not (P?=?.006). In conclusion, our study showed that CNS infections are a significant clinical problem after stem cell transplantation associated with poor survival. They were more frequent after UCBT compared to MST.     

Comparison of In Vitro Activities of the New Triazole SCH56592 and the Echinocandins MK-0991 (L-743,872) and LY303366 against Opportunistic Filamentous and Dimorphic Fungi and Yeasts

The in vitro antifungal activities of SCH56592, MK-0991, and LY303366 against 83 isolates of Acremonium strictum, Aspergillus flavus, Aspergillus fumigatus, Aspergillus terreus, Bipolaris spp., Blastomyces dermatitidis, Cladophialophora bantiana, Fusarium oxysporum, Fusarium solani, Histoplasma capsulatum, Phialophora spp., Pseudallescheria boydii, Rhizopus arrhizus, Scedosporium prolificans, and Sporothrix schenckii were compared. The in vitro activities of these agents against 104 isolates of yeast pathogens of Candida spp., Cryptococcus neoformans, and Trichosporon beigelii were also compared. MICs were determined by following a procedure under evaluation by the National Committee for Clinical Laboratory Standards (NCCLS) for broth microdilution testing of the filamentous fungi (visual MICs) and the NCCLS M27-A broth microdilution method for yeasts (both visual and turbidimetric MICs). The in vitro fungicidal activity of SCH56592 was superior (minimum fungicidal concentrations [MFCs], 0.25 to 4 μg/ml for 7 of 18 species tested) to those of MK-0991 and LY303366 (MFCs, 8 to >16 μg/ml for all species tested) for the molds tested, but the echinocandins had a broader spectrum of fungicidal activity (MFCs at which 90% of strains are inhibited [MFC₉₀s], 0.5 to 4 μg/ml for 6 of 9 species tested) than SCH56592 (MFC₉₀s, 0.25 to 8 μg/ml for 4 of 9 species tested) against most of the yeasts tested. Neither echinocandin had in vitro activity (MICs, >16 μg/ml) against C. neoformans and T. beigelii, while the SCH56592 MICs ranged from 0.12 to 1.0 μg/ml for these two species. The MICs of the three agents for the other species ranged from <0.03 to 4 μg/ml. These results suggest that these new agents have broad-spectrum activities in vitro; their effectiveness in the treatment of human mycoses is to be determined.     

Tracking the Emerging Human Pathogen Pseudallescheria boydii by Using Highly Specific Monoclonal Antibodies

Pseudallescheria boydii has long been known to cause white grain mycetoma in immunocompetent humans, but it has recently emerged as an opportunistic pathogen of humans, causing potentially fatal invasive infections in immunocompromised individuals and evacuees of natural disasters, such as tsunamis and hurricanes. The diagnosis of P. boydii is problematic since it exhibits morphological characteristics similar to those of other hyaline fungi that cause infectious diseases, such as Aspergillus fumigatus and Scedosporium prolificans. This paper describes the development of immunoglobulin M (IgM) and IgG1 κ-light chain monoclonal antibodies (MAbs) specific to P. boydii and certain closely related fungi. The MAbs bind to an immunodominant carbohydrate epitope on an extracellular 120-kDa antigen present in the spore and hyphal cell walls of P. boydii and Scedosporium apiospermum. The MAbs do not react with S. prolificans, Scedosporium dehoogii, or a large number of clinically relevant fungi, including A. fumigatus, Candida albicans, Cryptococcus neoformans, Fusarium solani, and Rhizopus oryzae. The MAbs were used in immunofluorescence and double-antibody sandwich enzyme-linked immunosorbent assays (DAS-ELISAs) to accurately differentiate P. boydii from other infectious fungi and to track the pathogen in environmental samples. Specificity of the DAS-ELISA was confirmed by sequencing of the internally transcribed spacer 1 (ITS1)-5.8S-ITS2 rRNA-encoding regions of environmental isolates.Pseudallescheria boydii is an infectious fungal pathogen of humans (7, 16, 40, 58, 59). It is the etiologic agent of white grain mycetoma in immunocompetent humans (7) and has emerged over recent years as the cause of fatal disseminated infections in individuals with neutropenia, AIDS, diabetes, renal failure, bone marrow or solid organ transplants, systemic lupus erythematous, and Crohn''s disease; in those undergoing corticosteroid treatment; and in leukemia and lymphoma patients (1, 2, 3, 18, 27, 31, 32, 34, 36, 37, 38, 47, 49, 52). The fungus is the most prevalent species after Aspergillus fumigatus in the lungs of cystic fibrosis patients (8), where it causes allergic bronchopulmonary disease (5) and chronic lung lesions simulating aspergillosis (24). Near-drowning incidents and recent natural disasters, such as the Indonesian tsunami in 2004, have shown P. boydii and the related species Scedosporium apiospermum and Scedosporium aurantiacum to be the causes of fatal central nervous system infections and pneumonia in immunocompetent victims who have aspirated polluted water (4, 11, 12, 21, 22, 25, 30, 33, 57). Its significance as a potential pathogen of disaster evacuees has led to its recent inclusion in the Centers for Disease Control and Prevention list of infectious etiologies in persons with altered mental statuses, central nervous system syndromes, or respiratory illness.P. boydii is thought to be an underdiagnosed fungus (60), and misidentification is one of the reasons that the mortality rate due to invasive pseudallescheriasis is high. Detection of invasive P. boydii infections, based on cytopathology and histopathology, is problematic since it can occur in tissue and bronchoalveolar and bronchial washing specimens with other hyaline septated fungi, such as Aspergillus and Fusarium spp. (7, 23, 53, 60), which exhibit similar morphological characteristics upon microscopic examination (2, 23, 24, 28, 37, 44, 53, 60). Early diagnosis of infection by P. boydii and differentiation from other agents of hyalohyphomycosis is imperative, since it is refractory to antifungal compounds, such as amphotericin B, that are commonly administered for the control of fungal infections (10, 39, 58).The immunological diagnosis of Pseudallescheria infections has focused on the detection of antigens by counterimmunoelectrophoresis, and by immunohistological techniques using polyclonal fluorescent antibodies, but cross-reactions with antigens from other fungi, such as Aspergillus species, occurs (7, 19, 23). Pinto and coworkers (41, 42) isolated a peptidorhamnomannan from hyphae of P. boydii and proposed the antigen as a diagnostic marker for the pathogen. Cross-reactivity with Sporothrix schenckii and with Aspergillus have, however, been noted (23, 41). Furthermore, it is uncertain whether a similar antigen is present in the related pathogenic species S. prolificans, an important consideration in patient groups susceptible to mixed Scedosporium infections (6, 18).Hybridoma technology allows the production of highly specific MAbs that are able to differentiate between closely related species of fungi (54, 55, 56). The purpose of this paper is to report the development of MAbs specific to P. boydii and certain closely related species and their use to accurately discriminate among P. boydii, A. fumigatus, and other human pathogenic fungi by using immunofluorescence and double-antibody sandwich enzyme-linked immunosorbent assays (DAS-ELISAs).Currently, the natural environmental habitat of P. boydii is unknown, but nutrient-rich, brackish waters, such as estuaries, have been suggested (9, 17). In combination with a semiselective isolation procedure, I show how the DAS-ELISA can be used to rapidly and accurately track the pathogen in naturally infested estuarine muds, and in doing so illustrate the potential of the DAS-ELISA as a diagnostic platform for detection of P. boydii and related species within the Pseudallescheria complex.     

Detection of Occult Scedosporium Species in Respiratory Tract Specimens from Patients with Cystic Fibrosis by Use of Selective Media

Respiratory samples from cystic fibrosis outpatients were cultured on Sabouraud''s dextrose agar (SABD) containing antibiotics, Mycosel, and Scedosporium-selective medium (SceSel+). Thirty-two (14.7%) of 218 specimens from 11/69 (15.9%) patients yielded a Scedosporium sp., most frequently Scedosporium aurantiacum (17/218). Scedosporium was recovered on SceSel+, Mycosel, and SABD from 90.6%, 50.0%, and 46.9% of the specimens tested, respectively.Opportunistic molds are increasingly isolated in respiratory specimens from children and adults with cystic fibrosis (CF) (17). Scedosporium species are the second most frequently recovered fungi, after Aspergillus fumigatus (4). Although invasive scedosporiosis is reportedly rare in CF prior to lung transplantation (11), colonization may be a risk factor for invasive disease posttransplantation, with associated high mortality (14, 19, 21-23). The impact of airway colonization by Scedosporium spp. on respiratory function has not been studied; nevertheless, as Scedosporium spp. are resistant to many antifungal agents, colonization may be a relative contraindication to transplantation (18).Isolation of multiple fungi from respiratory specimens is frequent (19). The prevalence of non-Aspergillus molds may be underestimated due to overgrowth of Aspergillus spp. on routine media (4). A medium (SceSel+) containing the selective antifungal agents dichloran and benomyl has been described for the recovery of Scedosporium from environmental samples (16, 20), but its utility in detecting Scedosporium spp. in clinical specimens has not been determined. No commercial preparation is available. Scedosporium spp. have been identified previously in respiratory specimens from 8.6 to 10% of CF patients (4, 24). These data were published prior to recent taxonomic reassignments of Scedosporium spp. (9, 10), and selective media were not used. We therefore compared the performance of two general media and one selective medium for the isolation of Scedosporium spp. from respiratory specimens and prospectively investigated the frequency and species distribution of Scedosporium in CF patients.Expectorated sputa were collected from consecutive patients at the Westmead Hospital Adult CF Unit (April 2008 to March 2009). Sputa were inoculated onto (i) Sabouraud dextrose agar (SABD; Difco, Becton Dickinson, Franklin Lakes, NJ) containing chloramphenicol (250 mg/liter) and gentamicin (26 mg/liter), (ii) Mycosel (BBL, Becton Dickinson), and (iii) SceSel+ medium (20). Plates were incubated at 30°C in air and examined twice weekly for 28 days. Suspicious colonies were identified to the species level (Aspergillus and Scedosporium spp.) or the genus level (other molds) by standard morphological/phenotypic methods (7, 9, 10). Scedosporium strains were identified as Scedosporium prolificans, S. aurantiacum, or S. apiospermum by restriction fragment length analysis of the internal transcribed spacer (ITS) region (8). ITS sequence analysis was performed on all S. apiospermum isolates and selected S. aurantiacum isolates (8).Samples (n = 218) were received from 69 patients. Filamentous fungi were detected in 142 samples (65.1%) from 56 patients (81.2%; Table ​Table1).1). The majority of the fungi (83.9%) were recovered following 6 days of incubation, and 95.1% were recovered following 10 days. Aspergillus spp. were the most frequently recovered, with A. fumigatus isolated in 45.4% of the samples. Scedosporium species were isolated on one or more media from 32 samples (14.7%) from 11 patients (15.9%; Table ​Table1).1). No sample had multiple Scedosporium spp. identified, although 60 (27.5%) sputa contained two or more fungi. Aspergillus spp. were more often present in sputa that contained Scedosporium spp. (25/32; 78.1%) than in sputa that contained Penicillium spp. (6/18; 33.3%), other hyaline hyphomycetes (5/14; 35.7%), or dematiaceous fungi (4/14; 28.6%) (all P values were <0.01).

TABLE 1.

Frequency of filamentous fungi isolated in specimens from CF patients

Recombinant Aeromonas hydrophila outer membrane protein 48 (Omp48) induces a protective immune response against Aeromonas hydrophila and Edwardsiella tarda

The gene coding for an outer membrane protein Omp48 of Aeromonas hydrophila isolated from an infected fish was cloned and sequenced. Analysis of nucleotide sequence showed the omp48 gene to be an adhesin encoding a protein of 426 amino acids with high identity to the omp48 gene of Aeromonas veronii, another fish pathogen. The gene belonged to the maltoporin group of porins and had high similarity to LamB porins of A. hydrophila, Aeromonas salmonicida and Vibrio parahaemolyticus. The expressed purified recombinant protein had an estimated molecular weight of 48 kDa. Further, rabbit hyperimmune sera against the recombinant protein reacted with A. hydrophila, Aeromonas sobria and A. veronii whole cell proteins at the region of 48 kDa, in western blotting. The recombinant protein was immunogenic in the fish Labeo rohita Hamilton. Fish immunized with recombinant protein, when challenged with virulent A. hydrophila and another bacterial fish pathogen, Edwardsiella tarda, showed relative percent survivals of 69 and 60, respectively. Our results suggest that Omp48 of A. hydrophila could be used as a potential vaccine candidate for protection not only against A. hydrophila infection, but also against the fish pathogen E. tarda.     

A bi-directional immune network mechanism: Simultaneous induction of idiotype and anti-anti-idiotype in rabbits immunized with antibody to a common idiotypic specificity of anti-VHa2-allotype antibodies

Recently, we identified a common idiotypic specificity (IdC) present on all of the allo and auto anti-VHa2-allotype antibodies tested. In this report, we immunized allotype-matched rabbits with anti-IdC Ab. When an a¹a¹ homozygote was immunized with anti-IdC Ab (also from an a¹a¹ rabbit), two distinct Ab populations were induced which were isolated through the use of immunoadsorbent column chromatography. One of these Ab populations, adsorbed to and eluted from an insolubilized a2 IgG column, was anti-VHa2-allotype Ab (Ab 1), which reacted with a2 Ig and inhibited the reaction between the a2 allotype and anti-VHa2-allotype Ab. The other Ab population, adsorbed to and eluted from an insolubilized immunogen anti-IdC column, was anti-anti-IdC Ab (Ab 3), which was specific for the immunogen anti-IdC Ab. In another experiment, when an a¹a¹ heterozygous rabbit was immunized with anti-IdC Ab, only the Ab 3 was induced, which appeared to be identical to the Ab 3 induced in the a¹a¹ rabbit. However, when the expression of the a2 allotype in an a¹a² heterozygous rabbit was suppressed and then this rabbit was immunized with anti-IdC Ab, both Ab 1 and Ab 3 were induced. These data indicate the occurrence of a bi-directional immune response within our immune network system. According to Jerne's network theory, Ab 3 appeared to be induced through a stimulation by the idiotope of the immunogen Ab 2, whereas Ab 1 appeared to be induced through a reverse stimulation by the paratope of the immunogen Ab 2. Furthermore, the production of Ab 1 in these rabbits exhibiting the bi-directional immune response was at least 3–5 times greater than that of Ab 3 production indicating that the response through the reverse stimulation appeared to be dominant. The importance of this bi-directional immune response is discussed in this paper.     

Detection of intrinsic blaOXA-51-like by multiplex PCR on its own is not reliable for the identification of Acinetobacter baumannii

Three clinical A. baumannii isolates Ab-508, Ab-511, and Ab-653 were recovered from South Africa, South Korea, and Turkey, respectively. Multiplex PCR to detect OXA-type carbapenemases showed atypical bla_OXA-51-like amplification products. The aim of this study was to investigate the background of changes in bla_OXA-51-like PCR products. Isolates were confirmed as A. baumannii using gyrB multiplex and rpoB sequencing and were epidemiologically unrelated by rep-PCR-based DiversiLab. Sequencing of bla_OXA-51-like revealed an insertion of ISAba15 in bla_OXA-66 (isolate Ab-511) and an insertion of the novel ISAba19 in bla_OXA-78 (isolates Ab-508 and Ab-653). Detection of the intrinsic bla_OXA-51-like by OXA-multiplex PCR should not be considered a fully reliable method for identification of A. baumannii when used without an additional independent method. Other species identification methods such as gyrB multiplex PCR and rpoB sequencing should be used to reliably identify A. baumannii.     

The involvement of PacIRA system of Stenotrophomonas maltophilia in the uptake of Pseudomonas aeruginosa pyochelin and intraspecies competition for iron acquisition

BackgroundStenotrophomonas maltophilia, a species of highly genetic diversity, has emerged as an important nosocomial pathogen. S. maltophilia and Pseudomonas aeruginosa are often co-isolated from pneumonia patients. In our previous study, we have demonstrated that the pacIRA cluster present in some but not all clinical S. maltophilia isolates. Proteins encoded by pacIRA operon are an extracytoplasmic function (ECF) sigma factor, a transmembrane anti-sigma regulator, and a TonB-dependent receptor. This study aimed to elucidate PacIRA system function and its significance to S. maltophilia.MethodsThe pacI, pacR, and pacA genes were individually or totally deleted from the chromosome of KJΔEnt, a pacIRA-positive and siderophore-null strain. Growth promotion assay was performed to examine the implication of pacIRA system in iron utilization. Gene expression was quantified by quantitative real time PCR (qRT-PCR). Growth competition assay was executed to investigate the significance of pacIRA operon to S. maltophilia.ResultsPacIRA system contributed to utilize ferri-pyochelin of P. aeruginosa as iron sources for growth in an iron-depleted condition, but hardly utilized ferric citrate, hemin, ferri-stenobactin, and ferri-pyoverdine. PacIRA was founded to belong to Fur regulon and upregulated in response to iron-depleted stress. Growth competition assay demonstrated that pacIRA-positive S. maltophilia had a superiority over pacIRA-negative S. maltophilia in iron acquisition when they were co-cultured in P. aeruginosa ferri-pyochelin-supplemented medium.ConclusionsPacIRA system of S. maltophilia is a xenosiderophore uptake implement, involving in the acquisition of pyochelin of P. aeruginosa.