The study included 50 isolates of Neisseria meningitidis isolated from patients with generalized forms of meningococcal infection and 48 isolates, which were isolated from carriers. The isolates were identified by MALDI-TOF mass spectrometry using a Microflex LT mass spectrometer (Bruker Daltonics, Germany). Minimum inhibitory concentrations (MICs) of benzylpenicillin, ampicillin, ceftriaxone, meropenem, ciprofloxacin, azithromycin, rifampicin, and chloramphenicol were assessed by the method of serial agar dilution with interpretation of the results according to EUCAST 2021 criteria. Clinical resistance to penicillin was detected in 7% of isolates. However, all isolates with MIC >0.064 µg/ml (n=26) had mutations in the penA gene. Decreased sensitivity to rifampicin was found in four isolates isolated from patients and four isolated from carriers. Seven out of eight isolates with reduced sensitivity to rifampicin had mutations in the rpoB gene. Resistance to ceftriaxone, meropenem, ciprofloxacin was not detected.
Prevalence and therapy of infections due to MRSA remain one of the most serious problems in the world. Therefore, correct laboratory identification of the MRSA phenotype based on the use of the marker antibiotic cefoxitine, as a more susceptibile one vs. oxacillin, is of great importance. There is lately being observed a tendency towards emergence of strains with lower susceptibility to the last reserve drugs protecting from MRSA, i. e. vancomycin and daptomycin. Susceptibility of MSRA to these drugs was not investigated in Russia and there are no data on the prevalence of the VISA and hVISA phenotypes. The results of our study on estimation of susceptibility of 316 MRSA isolates from several regions of Russia to oxacillin, cefoxitine, vancomycin and daptomycin are presented herein. It was shown that the ranges of the oxacillin MIC were extremely wide, i. e. 0.5 to 512 mcg/ml, while 2.2 +/- 1% of the isolates was susceptible by the phenotype to oxacillin, in spite of the mecA gene presence. As for cefoxitine, the MRSA isolates were rather resistant to it at the MIC > 16 mcg/ml. The tests with serial microdilutions revealed that 30.7 +/- 7% of the isolates had a critical level of susceptibility to vancomycin at the MIC 2 mcg/ml. The E-tests revealed 1.3 +/- 1% of the isolates which were susceptible at the MIC 2-4 mcg/ml. The MRSA isolates were highly susceptible to daptomycin, while high levels of the MIC (2 mcg/ml) were characteristic of 2.8 +/- 1% of the isolates. Cross reduction of the susceptibility to vancomycin and daptomycin was observed.
Aim: demonstration of basic molecular biological, metabolic and immunological effects of fecal microbiota transplantation (FMT), on the example of a rare case of acute graft-versus-host disease (GVHD) with intestinal damage in a patient after allogeneic hematopoietic stem cell transplantation (allo-HSCT). Materials and methods. To monitor the basic effects of FMT, we performed targeted DNA sequencing of 16S rRNA gene (V3–V4) using MiSeq platform as well as multiplex real-time PCR, MS/gas chromatography technique, immunophenotyping of blood lymphocytes, histological and immunohistochemical techniques. Clinical case. A 40-year-old female patient diagnosed with myelodysplastic syndrome, with a history of two unsuccessful allo-HSCTs due to graft failure, underwent the third haploidentical HSCT (haplo-HSCT) from her father as ‘salvage’ therapy. Due to early viral/bacterial colitis post-transplant associated with a multidrug-resistant strain of K. pneumoniae and herpes virus type 6, FMT was performed on days 46 and 47 after allo-HSCT. Complete resolution of the enteropathy symptoms was noted following FMT. However, immunosuppressive therapy was canceled on D+106 after haplo-HSCT due to the detection of minimal residual disease causing development of the ‘overlap’-type GVHD with damage skin lesions grade 4, and intestinal mucous membranes grade 3. This complication required resumption and subsequent intensification of immunosuppressive therapy with complete resolution of GVHD symptoms. Following FMT treatment, the patient showed complete resolution of clinical colitis symptoms. According to results of 16S rRNA sequencing, the species-specific diversity of fecal microbiota increased significantly, along with decreased relative contents of opportunistic bacteria ( Klebsiella, Enterococcus, Streptococcus genera). A significant growth was revealed for commensal Bacteroidota , and re-emergence of Faecalibacterium, Blautia, Roseburia . Acute gastrointestinal GVHD promoted by tacrolimus withdrawal was associated with repeated depletion of intestinal microbiota. Upon resolution of GVHD and resumed immunosuppression, increased microbiota diversity (Shannon index) was again recorded, and the parameters of patient’s fecal microbiota reached the donor values. The microbiota shifts at all clinical stages (before and after FMT, at the peak of acute intestinal GVHD and intensive immunosuppressive therapy) showed some relations with metabolism of bile and fatty acids in blood plasma and immune parameters. Conclusions. FMT may be a component of complex therapy aimed at early reconstitution of immune system and organic acid metabolism in patients after allo-HSCT. The composition of fecal microbiota, metabolic profile and spectrum of lymphocyte subpopulations may be markers for monitoring complex rehabilitation after allo-HSCT.
Lipoglycopeptide antibiotics are semi-synthetic derivatives of glycopeptides and are characterized by a pronounced bactericidal activity against gram-positive pathogens. The aim of the study was comparative assessment of the sensitivity of gram-positive clinical isolates to lipoglycopeptide antibiotics (telavancin, dalbavancin, oritavancin). The following isolates were included in the work: methicillin-resistant Staphylococcus aureus (MRSA, n=780), methicillin-resistant coagulase-negative Staphylococcus spp. (MRCoNS, n=163), and vancomycin-resistant Enterococcus faecium (VREf, n=93). Serial dilutions were used to assess sensitivity with the addition of 0.002% polysorbate 80 to the medium. Lipoglycopeptides showed more pronounced antibacterial activity against MRSA compared to vancomycin, teicoplanin, and daptomycin, and had a MIC₅₀/MIC₉₀ (µg/ml): for telavancin — 0.06 /0.125, for dalbavancin — 0.016/0.06, and for oritavancin — 0.06/0.125. A trend towards an increase in the MIC of lipoglycopeptides and daptomycin was established in MRSA with the MIC of 2 µg/ml for vancomycin, the proportion of which was 13%. For MRCoNS, MIC₅₀ and MIC₉₀ of lipoglycopeptides did not exceed 0.06 µg/ml and 0.125 µg/ml, respectively. Oritavancin showed strong activity against VREf at MIC range of 0.03 µg/ml to 0.5 µg/ml, and at MIC₉₀ of 0.25 µg/ml. Thus, lipoglycopeptide antibiotics are a plausible alternative to vancomycin and daptomycin; they are characterized by pronounced activity and can be used to treat severe forms of staphylococcal infections.
Гентамицин является одним из компонентов комбинированной терапии инфекционных эндокардитов, вызванных Staphylococcus aureus, включая метициллинорезистентные штаммы (methicillin-resistant S.aureus, MRSA). Цель исследования — анализ влияния десяти 6-часовых циклов воздействия высоких концентраций (16 мкг/мл) гентамицина in vitro на изменение фенотипа и генотипа аминогликозидочувствительных штаммов S.aureus, относящихся к четырём сиквенс-типам: ST5 (ATCC 29213), ST8, ST97 и ST22 (MRSA). Для всех штаммов, кроме ATCC 29213, после селекции отмечалось увеличение МПК гентамицина до 8–64 мкг/мл. Один штамм (SA0937) диссоциировал на три морфотипа, включая мелкоколониевый вариант (small colony variant, SCV). Вариант производного штамма SA0937 с колониями нормального размера характеризовался ассоциированной устойчивостью к даптомицину за счёт мутации P314L в MprF. Формирование устойчивости не сопровождалось изменением скорости роста, кроме морфотипа SCV. Для штамма ATCC 29213 после селекции отмечалось появление толерантности, проявляющейся в увеличении эффективного киллинга до 14 ч в 24-часовом time-killing эксперименте с концентрацией антибиотика 16 мкг/мл. У штамма ATCC 29213 выявлены мутации в пептидил т-РНК гидролазе (Pth). У трёх штаммов были обнаружены делеции в гене atpG, входящим в состав АТФ-синтазного комплекса. У остальных производных штаммов были выявлены делеции и мутации в генах метаболизма менахинона hepS, menA и трансляционном факторе элонгации G (fusA). Таким образом, использование гентамицина сопряжено с возможным быстрым формированием устойчивости и толерантности, не связанными с приобретением генов аминогликозид-модифицирующих ферментов. Выявление SCV ассоциировано с неблагоприятными клиническими исходами. При использовании комбинированной терапии необходимо учитывать, что существует возможность формирования устойчивости к даптомицину на фоне селекции гентамицином.
Dose-intensive cytostatic therapy and antibiotic treatment in allogeneic hematopoietic stem cell transplantation (allo-HSCT) cause severe abnormalities in a composition of gut microbiota as well as the emergence of antibiotic resistance. The data on the longitudinal recovery of major bacterial phyla and the expansion of genes associated with antibiotic resistance are limited. We collected regular stool samples during the first year after allo-HSCT from 12 adult patients with oncohematological disorders after allo-HSCT and performed 16SrRNA sequencing, multiplex PCR, conventional bacteriology and CHROMagar testing. We observed a decline in Shannon microbiota diversity index as early as day 0 of allo-HSCT (
