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Population-based studies of Staphylococcus aureus contribute to understanding the epidemiology of S. aureus infection. We enrolled surgical inpatients admitted to an African tertiary-care hospital in order to prospectively analyze the nosocomial impact of S. aureus. Data collection included an active sampling of the anterior nares and infectious foci within 48 h after admission and subsequently when clinically indicated. All S. aureus isolates were spa and agr genotyped. Possession of Panton-Valentine leukocidin (PVL) and other toxin genes was determined. We analyzed antibiotic susceptibility profiles by VITEK 2 systems and verified methicillin-resistant S. aureus (MRSA) by mecA/C PCR. Among 325 patients, 15.4% carried methicillin-susceptible S. aureus (MSSA) at admission, while 3.7% carried MRSA. The incidence densities of nosocomial infections due to MSSA and MRSA were 35.4 and 6.2 infections per 10,000 patient-days, respectively. Among all 47 nosocomial infections, skin and soft-tissue (40.4%) and bones or joints’ (25.5%) infections predominated. Six (12.7%) infection-related S. aureus isolates harbored PVL genes including two (4.2%) MRSA: overall, seventeen (36.2%) isolates carried pyrogenic toxin superantigens or other toxin genes. This study illustrates the considerable nosocomial impact of S. aureus in a Nigerian University hospital. Furthermore, they indicate a need for effective approaches to curtail nosocomial acquisition of multidrug-resistant S. aureus.
Methicillin-Resistant Staphylococci and Macrococci at the Interface of Human and Animal Health
(2021)
Background: For years, coagulase-negative staphylococci (CoNS) were not considered a cause of bloodstream infections (BSIs) and were often regarded as contamination. However, the association of CoNS with nosocomial infections is increasingly recognized. The identification of more than 40 different CoNS species has been driven by the introduction of matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry. Yet, treatment guidelines consider CoNS as a whole group, despite increasing antibiotic resistance (ABR) in CoNS. This retrospective study provides an in-depth data analysis of CoNS isolates found in human blood culture isolates between 2013 and 2019 in the entire region of the Northern Netherlands. Methods: In total, 10,796 patients were included that were hospitalized in one of the 15 hospitals in the region, leading to 14,992 CoNS isolates for (ABR) data analysis. CoNS accounted for 27.6% of all available 71,632 blood culture isolates. EUCAST Expert rules were applied to correct for errors in antibiotic test results. Results: A total of 27 different CoNS species were found. Major differences were observed in occurrence and ABR profiles. The top five species covered 97.1% of all included isolates: S. epidermidis, S. hominis, S. capitis, S. haemolyticus, and S. warneri. Regarding ABR, methicillin resistance was most frequently detected in S. haemolyticus (72%), S. cohnii (65%), and S. epidermidis (62%). S. epidermidis and S. haemolyticus showed 50–80% resistance to teicoplanin and macrolides while resistance to these agents remained lower than 10% in most other CoNS species. Conclusion: These differences are often neglected in national guideline development, prompting a focus on ‘ABR-safe’ agents such as glycopeptides. In conclusion, this multi-year, full-region approach to extensively assess the trends in both the occurrence and phenotypic resistance of CoNS species could be used for evaluating treatment policies and understanding more about these important but still too often neglected pathogens.
Investigation of In-Vitro Adaptation toward Sodium Bituminosulfonate in Staphylococcus aureus
(2020)
Ziel dieser Studie war, die Prävalenz von Borrelia burgdorferi sensu lato (s. l.) in Ixodes ricinus (I. ricinus) Zecken in Wäldern nahe Greifswald zu ermitteln und die europäischen Borrelia burgdorferi sensu lato species B. burgdorferi sensu stricto, B. afzelii, B. garinii (OspA Typen 3 bis 7), B. valaisiana und B. lusitaniae zu differenzieren. Die Zecken wurden zwischen April und Oktober 2003 in 2 Sammelgebieten (Nymphen und Adulte) und zwischen April und August 2004 in einem Sammelgebiet (nur Adulte) gefangen. Insgesamt wurden 689 Adulte (355 Weibchen, 334 Männchen) und 825 Nymphen der Spezies I. ricinus gesammelt. Adulte wurden bei DNA – Extraktion und PCR einzeln aufgearbeitet, bei den Nymphen waren je 5 Individuen zu einem Pool zusammengefasst. Es kamen verschiedene PCR Protokolle zur Anwendung, es wurde eine heminested PCR mit anschließender Restriktionsenzymanalyse, die eine Differenzierung der Genospezies erlaubte, gewählt. Im Jahr 2003 betrug die Infektionsrate adulter I. ricinus Zecken 14,9 %. Borrelien – DNA wurde in 16,8 % der Weibchen und in 12,9 % der Männchen nachgewiesen. 5,7 % der Nymphen waren positiv (Berechnung nach de Boer et al. 1993). Die mittleren Infektionsraten der zwei Sammelgebiete unterschieden sich signifikant voneinander (7,1 % bzw. 19,2 %, p= 0,005). Im Jahr 2004 unterschieden sich die Infektionsraten weiblicher und männlicher Zecken signifikant voneinander (p= 0,024): Die mittlere Infektionsrate betrug 19,9 %, wobei 25,4 % der Weibchen und 14,1 % der Männchen infiziert waren. Im Jahr 2003 war B. garinii OspA Typ 6 die häufigste Genospezies (63,9 %), gefolgt von B. afzelii (16,7 %) und B. valaisiana (11,1 %). B. garinii OspA Typ 4 und 5 und B. burgdorferi sensu stricto traten selten auf (1,4 %, 1,4 % und 5,5 %). Im Gegensatz dazu dominierte B. burgdorferi sensu stricto im Jahr 2004 (38,6 %) aufgrund der hohen Prävalenz von 65,2 % im August. 34,1 % aller Zecken waren mit B. garinii OspA Typ 6 infiziert. B. afzelii wurde in 11,4 %, B. valaisiana in 9,1 % nachgewiesen. Doppelinfektionen traten in 2,8 % (2003) und 2,3 % (2004) der Zecken auf. In Ostvorpommern wurden alle o. g. humanpathogenen Spezies und OspA – Typen außer B. lusitaniae und B. garinii OspA Typ 3 und 7 nachgewiesen. Die ermittelten Infektionsraten stimmen mit den Ergebnissen ähnlicher epidemiologischer Studien in benachbarten Regionen in Polen überein (Stanczak et al. 2000; Bukowska 2002). Am häufigsten trat B. garinii OspA Typ 6 auf, außer im August 2004, wo B. burgdorferi sensu stricto die dominante Spezies war (65,2 %). Diese hohe Infektionsrate mit B. burgdorferi sensu stricto geht einher mit den Ergebnissen einer Untersuchung durch Bukowska in Westpommern 2000 – 2001. Mischinfektionen waren selten. Nur zwei von 70 positiv getesteten Zecken im Jahr 2003 (2,8 %) waren mit zwei verschiedenen OspA – Typen der B. garinii Gruppe doppelinfiziert. Im Jahr 2004 zeigte nur eine der 43 positiv getesteten Zecken (2,3 %) eine Doppelinfektion, ebenfalls mit zwei verschiedenen B. garinii OspA – Typen. Untersuchungen zum Vorkommern von Borrelia burgdorferi sensu lato in Zecken durch Borrelien – DNA – Nachweis mittels PCR und Differenzierung der einzelnen Stämme wurden bislang vor allem im Süden Deutschlands durchgeführt. Epidemiologische Studien zur Häufigkeit und Verteilung der verschiedenen Borrelienspezies in den verschiedenen Regionen Europas ist für die prospektive Entwicklung von Vakzinen und mikrobiologischen Testsystemen von entscheidender Bedeutung.
Primary and acquired therapy resistance is a major problem in patients with BRAF-mutant melanomas being treated with BRAF and MEK inhibitors (BRAFI, MEKi). Therefore, development of alternative therapy regimes is still required. In this regard, new drug combinations targeting different pathways to induce apoptosis could offer promising alternative approaches. Here, we investigated the combination of proteasome and Kv1.3 potassium channel inhibition on chemo-resistant, BRAF inhibitor-resistant as well as sensitive human melanoma cells. Our experiments demonstrated that all analyzed melanoma cell lines were sensitive to proteasome inhibitor treatment at concentrations that are not toxic to primary human fibroblasts. To further reduce proteasome inhibitor-associated side effects, and to foster apoptosis, potassium channels, which are other targets to induce pro-apoptotic effects in cancer cells, were blocked. In support, combined exposure of melanoma cells to proteasome and Kv1.3 channel inhibitor resulted in synergistic effects and significantly reduced cell viability. On the molecular level, enhanced apoptosis correlated with an increase of intracellular Kv1.3 channels and pro-apoptotic proteins such as Noxa and Bak and a reduction of anti-apoptotic proteins. Thus, use of combined therapeutic strategies triggering different apoptotic pathways may efficiently prevent the outgrowth of drug-resistant and -sensitive BRAF-mutant melanoma cells. In addition, this could be the basis for an alternative approach to treat other tumors expressing mutated BRAF such as non-small-cell lung cancer.
Upon antigen recognition by the T cell receptor (TCR), a complex signaling network orchestrated by protein-tyrosine kinases (PTKs) and protein-tyrosine phosphatases (PTPs) regulates the transmission of the extracellular signal to the nucleus. The role of the PTPs Src-homology 2 (SH2) domain-containing phosphatase 1 (SHP1, Ptpn6) and Src-homology 2 (SH2) domain-containing phosphatase 2 (SHP2, Ptpn11) have been studied in various cell types including T cells. Whereas SHP1 acts as an essential negative regulator of the proximal steps in T cell signalling, the role of SHP2 in T cell activation is still a matter of debate. Here, we analyzed the role of the constitutively active SHP2-D61Y-mutant in T cell activation using knock-in mice expressing the mutant form Ptpn11D61Y
in T cells. We observed reduced numbers of CD8+ and increased numbers of CD4+ T cells in the bone marrow and spleen of young and aged SHP2-D61Y-mutant mice as well as in Influenza A Virus (IAV)-infected mice compared to controls. In addition, we found elevated frequencies of effector memory CD8+ T cells and an upregulation of the programmed cell death protein 1 (PD-1)-receptor on both CD4+ and CD8+ T cells. Functional analysis of SHP2-D61Y-mutated T cells revealed an induction of late apoptosis/necrosis, a reduced proliferation and altered signaling upon TCR stimulation. However, the ability of D61Y-mutant mice to clear viral infection was not affected. In conclusion, our data indicate an important regulatory role of SHP2 in T cell function, where the effect is determined by the kinetics of SHP2 phosphatase activity and differs in the presence of the permanently active and the temporally regulated phosphatase. Due to interaction of SHP2 with the PD-1-receptor targeting the protein-tyrosine phosphatase might be a valuable tool to enhance T cell activities in immunotherapy.
T cell activation plays a central role in supporting and shaping the immune response. The induction of a functional adaptive immune response requires the control of signaling processes downstream of the T cell receptor (TCR). In this regard, protein phosphorylation and dephosphorylation have been extensively studied. In the past decades, further checkpoints of activation have been identified. These are E3 ligases catalyzing the transfer of ubiquitin or ubiquitin-like proteins to protein substrates, as well as specific peptidases to counteract this reaction, such as deubiquitinating enzymes (DUBs). These posttranslational modifications can critically influence protein interactions by targeting proteins for degradation by proteasomes or mediating the complex formation required for active TCR signaling. Thus, the basic aspects of T cell development and differentiation are controlled by defining, e.g., the threshold of activation in positive and negative selection in the thymus. Furthermore, an emerging role of ubiquitination in peripheral T cell tolerance has been described. Changes in the function and abundance of certain E3 ligases or DUBs involved in T cell homeostasis are associated with the development of autoimmune diseases. This review summarizes the current knowledge of E3 enzymes and their target proteins regulating T cell signaling processes and discusses new approaches for therapeutic intervention.