Görkem Yaman

Role of Treg in immune regulation of allergic diseases

Allergy is a Th2‐mediated disease that involves the formation of specific IgE antibodies against innocuous environmental substances. The prevalence of allergic diseases has dramatically increased over the past decades, affecting up to 30% of the population in industrialized countries. The understanding of mechanisms underlying allergic diseases as well as those operating in non‐allergic healthy responses and allergen‐specific immunotherapy has experienced exciting advances over the past 15 years. Studies in healthy non‐atopic individuals and several clinical trials of allergen‐specific immunotherapy have demonstrated that the induction of a tolerant state in peripheral T cells represent a key step in healthy immune responses to allergens. Both naturally occurring thymus‐derived CD4+CD25+FOXP3+ Treg and inducible type 1 Treg inhibit the development of allergy via several mechanisms, including suppression of other effector Th1, Th2, Th17 cells; suppression of eosinophils, mast cells and basophils; Ab isotype change from IgE to IgG4; suppression of inflammatory DC; and suppression of inflammatory cell migration to tissues. The identification of the molecules involved in these processes will contribute to the development of more efficient and safer treatment modalities.

IgG4 production is confined to human IL-10–producing regulatory B cells that suppress antigen-specific immune responses

BACKGROUND IL-10-producing regulatory B cells suppress immune responses, and lack of these cells leads to exacerbated symptoms in mouse models of chronic inflammation, transplantation, and chronic infection. IgG4 is a blocking antibody isotype with anti-inflammatory potential that is induced in human high-dose antigen tolerance models. OBJECTIVE We sought to characterize human inducible IL-10-secreting B regulatory 1 (BR1) cells and to investigate their immunoregulatory capacity through suppression of cellular immune responses and production of anti-inflammatory immunoglobulins. METHODS Highly purified IL-10-secreting B cells were phenotypically and functionally characterized by means of whole-genome expression analysis, flow cytometry, suppression assay, and antibody production. B cells specific for the major bee venom allergen phospholipase A2 (PLA) were isolated from beekeepers who displayed tolerance to bee venom antigens and allergic patients before and after specific immunotherapy. RESULTS Human IL-10+ BR1 cells expressed high surface CD25 and CD71 and low CD73 levels. Sorting of CD73-CD25+CD71+ B cells allowed enrichment of human BR1 cells, which produced high levels of IL-10 and potently suppressed antigen-specific CD4+ T-cell proliferation. IgG4 was selectively confined to human BR1 cells. B cells specific for the major bee venom allergen PLA isolated from nonallergic beekeepers show increased expression of IL-10 and IgG4. Furthermore, the frequency of IL-10+ PLA-specific B cells increased in allergic patients receiving allergen-specific immunotherapy. CONCLUSION Our data show the characterization of IL-10+ BR1 cells and in vivo evidence for 2 essential features of allergen tolerance: the suppressive B cells and IgG4-expressing B cells that are confined to IL-10+ BR1 cells in human subjects.

Evaluation of the MALDI TOF-MS method for identification of Candida strains isolated from blood cultures

Matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI TOF-MS) allows rapid and accurate identification of microorganisms. It is being used increasingly and becoming an important tool in clinical laboratories. Phenotypic identification of Candida species remains labor- and time consuming, and the results may sometimes be inconclusive. Rapid and reliable species identification of Candida is essential for antifungal treatment due to species-specific susceptibility patterns. In this study, we evaluated the performance of MALDI TOF-MS for identification of Candida strains. A total of 281 clinical Candida strains isolated from blood cultures were included in this study. Candida species were identified with conventional methods and automated VITEK 2 YST panels as well as with MALDI TOF-MS. Isolates with discrepant results were subjected to DNA sequencing of the internal transcribed spacer (ITS) region (ITS1-5.8S-ITS2). Ninety-four percent of the isolates were identified correctly by VITEK 2 and MALDI TOF-MS. Altogether, MALDI-TOF MS yielded the correct species identification for 281 (100%) clinical Candida isolates. MALDI-TOF proved to be a rapid and reliable method for identification of Candida strains in the clinical laboratory.

In vitro effects of sulbactam combinations with different antibiotic groups against clinical Acinetobacter baumannii isolates

Abstract Treatment of multidrug resistant (MDR) Acinetobacter baumannii infections causes some problems as a result of possessing various antibacterial resistance mechanisms against available antibiotics. Combination of antibiotics, acting by different mechanisms, is used for the treatment of MDR bacterial infections. It is an important factor to determine synergy or antagonism between agents in the combination for the constitution of effective therapy. The study aimed to determine in vitro interactions interpreted according to calculated fractional inhibitory concentration (FIC) index between sulbactam and ceftazidime, ceftriaxone, cefepime, ciprofloxacin, gentamicin, meropenem, tigecycline, and colistin. Ten clinical isolates of A. baumannii were tested for determination of synergistic effects of sulbactam with different antimicrobial combinations. Minimal inhibitory concentration (MIC) values of both sulbactam and combined antibiotics decreased 2- to 128-fold. Synergy and partial synergy were determined in combination of sulbactam with ceftazidime and gentamicin (FIC index: ≤0·5 or >0·5 to <1) and MIC values of both ceftazidime and gentamicin for five isolates fell down below the susceptibility break point. Similarly, MIC value of ciprofloxacin for six ciprofloxacin resistant isolates was determined as below the susceptibility break point in combination. However, all isolates were susceptible to colistin and tigecycline, MIC values of both were decreased in combination with sulbactam. Although synergistic and partial synergistic effects were observed in the combination of sulbactam and ceftriaxone, all isolates remained resistant to ceftriaxone. The effect of cefepime–sulbactam combination was synergy in five, partial synergy in one and indifferent in four isolates. Meropenem and sulbactam showed a partial synergistic effect (FIC index: >0·5 to <1) in three, an additive effect (FIC index: 1) in one and an indifferent effect (FIC index: >1–2) in six isolates. Antagonism was not determined in any combination for clinical A. baumannii isolates in the study. In conclusion, sulbactam is a good candidate for combination treatment regimes for MDR A. baumannii infections.

vanC Gene-Related Intrinsic Teicoplanin Resistance Detected in Enterococcus casseliflavus and E. gallinarum Strains by the BD Phoenix Automated Microbiology System

Enterococcus members are becoming increasingly important agents of human disease, largely because of their resistance to antimicrobial agents. Because of their resistance to penicillins and cephalosporins of several activity ranges, the acquisition of high-level resistance to aminoglycosides, and now the emergence of vancomycin resistance, these bacteria are often involved in serious superinfections among patients receiving broad-spectrum antimicrobial chemotherapy (2). Acquired glycopeptide resistance in Enterococcus species corresponds to five different phenotypes, with VanA and VanB phenotypes being the most prevalent and important clinically. Strains with the vanA genotype characteristically display inducible, transposon-mediated, high-level resistance to both vancomycin (MIC, 64 to 1,000 μg/ml) and teicoplanin (MIC, 16 to 512 μg/ml). Strains with the vanB genotype have acquired inducible resistance to various concentrations of vancomycin (MIC, 4 to 1,000 μg/ml) but remain susceptible to teicoplanin (MIC, 0.5 to 1 μg/ml), although rare vanB strains may also be resistant to the latter antibiotic. Isolates that have the vanC genotype display intrinsic, constitutive, low-level resistance to vancomycin (MIC, 2 to 32 μg/ml) and are susceptible to teicoplanin (MIC, 0.5 to 1 μg/ml). The vanC genotype corresponds to the intrinsic glycopeptide resistance seen in Enterococcus gallinarum, E. casseliflavus, and E. flavescens (2). The antibacterial activities of teicoplanin against gram-positive bacteria, including those expressing resistance to unrelated compounds, are similar to that of vancomycin, but with increased potency, particularly against Streptococcus spp. and Enterococcus spp. Teicoplanin is active against vancomycin resistance caused by VanB and VanC but is not active against VanA resistant strains. Despite the increasing importance of glycopeptide resistance, teicoplanin has proved its clinical worth and continues to have important potential in the treatment of life-threatening gram-positive sepsis (1a). Automated microbiology systems are routinely used for identification and antimicrobial susceptibility testing of a wide spectrum bacteria, including those of the Enterococcus genus. The Phoenix Automated Microbiology System (Becton Dickinson) is one of these systems used in our microbiology laboratory at Yuzuncu Yil University Medical Faculty Hospital. Recently, E. casseliflavus and E. gallinarum strains were isolated from two different urine samples from a patient, and teicoplanin was reported as resistant, although the MIC was ≤1. Upon examination of the preliminary reports, a change from sensitive to resistant for teicoplanin by the automated BDXpert system in accordance with rule 1099 of that system was observed (1). Rule 1099 under the expert trigger rules states that “E. casseliflavus or E. gallinarum is intrinsically low-level resistant to vancomycin and teicoplanin (VanC),” and because of the identified bacteria, the exchange for teicoplanin from sensitive to resistant was made following this rule. Resistance to teicoplanin in Enterococcus species is often seen in E. faecalis and E. faecium strains due to the vanA gene. Identification and antibiotic susceptibility tests for both of the two isolated strains were repeated in order to prevent any misidentifications, but there was not any change in the results. Antimicrobial testing of teicoplanin by use of the Kirby-Bauer disc diffusion method was performed on both of the isolated strains, and they were both detected as sensitive to teicoplanin. E. casseliflavus and E. gallinarum strains have the chromosomal nontransferable vanC gene, and they are intrinsically low-level resistant to vancomycin; however, they are sensitive to teicoplanin. Researchers in clinical microbiology laboratories using automated systems for antimicrobial susceptibility tests should be aware of this situation, and the result needs to be verified using a reference method before reporting the isolate as resistant to teicoplanin.

The Isolation of Candida Species from the Samples That Come From the Patients at Intensive Care Unit and Antifungal Susceptibility

Bu makale 14. Türk Klinik Mikrobiyoloji ve İnfeksiyon Hastalıkları Kongresinde poster olarak sunulmuştur. Poster no.15-04 (25-29 Mart 2009, Antalya) *Sorumlu Yazar: Dr. Aytekin Çıkman, Yüzüncü Yıl Üniversitesi Tıp Fakültesi, Tıbbi Mikrobiyoloji Anabilim Dalı, 65100 VAN, Tel: 0 (432) 216 47 11, GSM: 0 (505) 691 82 00, E-mail: draytekin65@hotmail.com Geliş Tarihi: 03.08.2011, Kabul Tarihi: 24.12.2015 KLİNİK ÇALIŞMA / CLINICAL RESEARCH