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Introduction: Many historic dermatology departments keep and preserve valuable collections of dermatological moulages. Aim: The aim of the present research was to find out whether the specimens collected in the Museum of the Department of Dermatology, Venereology, and Allergology of Wroclaw Medical University are colonized by microorganisms, and whether these organisms can pose a risk of damage to this heritage or a health risk to visitors. Material and methods: In the study 32 historic moulages and their environment (museum) were subjected to microbiological evaluation. Results: Swabs from moulages turned to be positive in 28% of cases. Micrococcus luteus was mainly isolated. The flora isolated from the air and the external surfaces of the museum display cases was much richer. Environmental bacteria and fungi were determined, as well as organisms probably associated with the hospital flora: Pseudosomonas spp., Paebacillus sp., Acinetobacter sp. Conclusions: The close proximity of clinical wards probably influences the composition of the museum environment. The surprisingly low contamination of the moulages may be due to the antiseptic properties of the bee wax from which they were made. Conservation work on the moulages as well as people visiting the museum do not pose significant health risks. However, the small number of studies devoted to this topic limits the conclusions. Further research on medical collections is needed to provide 'evidence-based care' for this heritage.
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Proper protection of vascular access after haemodialysis is one of the key measures for the prevention of catheter-related infections. Various substances with bactericidal and anticoagulant properties are used to fill catheters, but due to the unsatisfactory clinical effects and occurrence of adverse reactions, the search for new substances is still ongoing. In the present paper, we compared the in vitro antimicrobial activity of solutions used for tunnelled catheter locking (taurolidine, trisodium citrate) and solutions of substances that could potentially be used for this purpose (sodium bicarbonate, polyhexanide-betaine). The studies have been conducted on bacteria that most commonly cause catheter-related infections. The values of both minimum inhibitory concentration and minimum biofilm eradication concentration of the substances were determined. The ability of the tested substances to eradicate biofilm from the dialysis catheter surface was also evaluated. The results showed that polyhexanide-betaine inhibited the growth of all microbes comparably to taurolidine, even after ≥ 32-fold dilution. The activity of trisodium citrate and sodium bicarbonate was significantly lower. Polyhexanide exhibited the highest activity in the eradication of bacterial biofilm on polystyrene plates. The biofilm formed on a polyurethane dialysis catheter was resistant to complete eradication by the test substances. Polyhexanide-betaine and taurolidine showed the highest activity. Inhibition of bacterial growth regardless of species was observed not only at the highest concentration of these compounds but also after dilution 32-128x (taurolidine) and 32-1024x (polyhexanide-betaine). Therefore, it can be assumed that taurolidine application as a locking solution prevents catheter colonization and systemic infection development. Taurolidine displays high antimicrobial efficacy against Gram-positive cocci as well as Gram-negative bacilli. On the contrary, the lowest antibacterial effect displayed product contained sodium bicarbonate. The inhibitions of bacterial growth were not satisfactory to consider it as a substance for colonization prevention. Polyhexanidine-betaine possessed potent inhibitory and biofilm eradication properties comparing to all tested products. PHMB is applied as a wound irrigation solution worldwide. However, based on our results, we assume that the PHMB is a promising substance for catheter locking solutions thanks to its safety and high antimicrobial properties.
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Anti-Infecciosos Locais/farmacologia , Anti-Infecciosos/farmacologia , Bactérias/efeitos dos fármacos , Infecções Relacionadas a Cateter/prevenção & controle , Cateteres Venosos Centrais/microbiologia , Bactérias/patogenicidade , Biofilmes/efeitos dos fármacos , Infecções Relacionadas a Cateter/tratamento farmacológico , Infecções Relacionadas a Cateter/microbiologia , Cateterismo , Soluções para Hemodiálise/química , Humanos , Diálise Renal/efeitos adversos , Taurina/análogos & derivados , Taurina/farmacologia , Tiadiazinas/farmacologiaRESUMO
This study aimed to characterize the protein composition of fractionated seminal plasma (SP) by liquid chromatography mass spectrometry (LC-MS/MS) analysis and investigate its effects on survival of frozen-thaw (FT) boar spermatozoa following storage. Seminal plasma (SP) was fractionated by gel filtration chromatography to give two fractions, SP1 with more than 40 kDa (>40 kDa) and SP2 with less than 40 kDa (<40 kDa). SP1 and SP2 were subjected to LC-MS/MS and bioinformatics analysis. Following cryopreservation, FT boar semen (n = 7) was thawed in Beltsville Thawing Solution (BTS), BTS + SP1 or BTS + SP2, stored at different periods and subjected to post-thaw (PT) quality assessment. A total of 52 and 22 abundant proteins were detected in SP1 and SP2, respectively. FN1, ANGPTL1, and KIF15 proteins were more abundance in SP1, whereas a high abundance of spermadhesins (PSP-I and PSP-II) was detected in SP2. Proteins of the fractionated SP were involved in various biological processes, such as cell motility and signal transduction. The dominant pathway of SP1 proteins was the apelin signaling pathway (GNA13, MEF2D, SPHK2, and MEF2C), whereas a pathway related to lysosome (CTSH, CTSB, and NPC2) was mainly represented by SP2 proteins. In most of the boars, significantly higher motility characteristics, membrane integrity, and viability were observed in FT spermatozoa exposed to SP1 or SP2 compared with BTS. The results of our study confirm that a combination of several proteins from the fractionated SP exerted beneficial effects on the sperm membrane, resulting in improved quality characteristics following PT storage.
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Proteínas/genética , Motilidade dos Espermatozoides/genética , Espermatozoides/citologia , Sus scrofa/genética , Animais , Cromatografia Líquida , Criopreservação , Congelamento , Masculino , Sêmen/citologia , Sêmen/metabolismo , Análise do Sêmen/métodos , Preservação do Sêmen , Espermatozoides/crescimento & desenvolvimento , Sus scrofa/crescimento & desenvolvimento , Suínos/genética , Espectrometria de Massas em TandemRESUMO
PURPOSE: Two Demodex species (eyelash mites)-D. folliculorum and D brevis-are believed to be associated with human skin and eye diseases. However, the clinical significance of infection with Demodex species remains controversial. STUDY DESIGN: The aim of this study was to estimate the prevalence of ocular demodicosis in patients with blepharitis as compared with the prevalence in the healthy population in Poland. METHODS: This case-control prospective study was carried out from 2007 to 2016. The enrolled patients (668) were divided into 2 groups: the study group, comprising 553 patients with blepharitis (349 women and 204 men, aged 17-88 years), and the control group, comprising 115 healthy volunteers without a history of ocular pathologies (78 women and 37 men, aged 17-88 years). A sample of 10 eyelashes was taken aseptically from each eye of the examined person and later studied under a light microscope. RESULTS: Demodex species were found in 62.4% (345/544) of the patients in the study group and in 24.3% (28/100) of the controls (P = .001, OR = 0.006). The overall prevalence was 55.8% (373/668) in all the examined participants. The presence of Demodex infection increased with age in both groups. No association of Demodex infection with gender was found (119/204 vs 226/349; P > .05, OR 1.086). A high mean number of mites was present more frequently in patients aged older than 50 years and in those who complained especially about itching (P < .05). CONCLUSION: The prevalence of ocular demodicosis is significantly correlated with blepharitis and increases with age.
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Blefarite/epidemiologia , Infecções Oculares Parasitárias/epidemiologia , Pestanas/parasitologia , Previsões , Infestações por Ácaros/epidemiologia , Ácaros , Adolescente , Adulto , Idoso , Idoso de 80 Anos ou mais , Animais , Blefarite/parasitologia , Infecções Oculares Parasitárias/parasitologia , Feminino , Seguimentos , Humanos , Incidência , Masculino , Pessoa de Meia-Idade , Polônia/epidemiologia , Prevalência , Estudos Prospectivos , Adulto JovemRESUMO
BACKGROUND: Infections in pediatric patients with oncohematological diseases pose a huge therapeutic and diagnostic problem. OBJECTIVES: The aim of the study was to investigate the etiology of bacteremia and the antibiotic susceptibility of pathogenic and colonizing bacterial strains in pediatric oncohematological patients. MATERIAL AND METHODS: In the period 2011-2014, 17,209 positive test results, including 1,129 positive blood cultures, were subjected to a detailed analysis. The assessment of drug susceptibility was conducted in accordance with the CLSI (American), EUCAST (European), and KORLD (Polish) recommendations. RESULTS: A high percentage (86-91%) of negative blood culture results was demonstrated. A predominance of Gram-positive bacteria was seen in all years (60-70%) in contrast to Gram-negative strains (30-40%). Coagulase-negative staphylococci (CNS) were the strains most frequently isolated from blood (41-47%) among all bacterial strains. Susceptibility to linezolid and vancomycin was 96-100%, and to teicoplanin 82-96%. Methicyllin-resistant coagulase-negative Staphylococcus (MRCNS) were isolated in 77-86%. All Staphylococcus aureus (S. aureus) strains were susceptible to glycopeptides and linezolid, while Enterococcus spp. was susceptible to linezolid. Apart from the year 2014, no methicillin-resistant S. aureus (MRSA) were isolated. Enterobacteriaceae (EN) were the most susceptible to imipenem and meropenem (91-100%) as well as to amikacin (77-93%). From 2013 to 2014, non-fermentative rods (NF) isolated from blood were less susceptible to imipenem and meropenem (71% and 67-71%, respectively) than to other antibiotics. It has been shown that strains isolated from blood have a statistically significantly different susceptibility to antibiotics (CNS and EN are less and NF is more susceptible) than those existing as colonizing flora. CONCLUSIONS: Our results show that choosing appropriate antibiotics for treating infection in children with oncohematological diseases based on antibiograms for colonizing flora may be difficult because they may not take into account the more resistant strains. According to the antibiotic susceptibility of the strains isolated from blood in our center, the most viable active empirical and carbapenem-saving therapy could be conducted with piperacillin/tazobactam or cefepime.
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Antibacterianos/uso terapêutico , Neoplasias Hematológicas/complicações , Staphylococcus aureus Resistente à Meticilina/efeitos dos fármacos , Staphylococcus aureus Resistente à Meticilina/isolamento & purificação , Criança , Bactérias Gram-Positivas , Humanos , Testes de Sensibilidade Microbiana , Infecções Estafilocócicas/diagnóstico , Infecções Estafilocócicas/tratamento farmacológico , Staphylococcus aureus/efeitos dos fármacosRESUMO
Haematological malignancies are a frequently diagnosed group of neoplasms and a significant cause of cancer deaths. The successful treatment of these diseases relies on early and accurate detection. Specific small molecular compounds released by malignant cells and the simultaneous response by the organism towards the pathological state may serve as diagnostic/prognostic biomarkers or as a tool with relevance for cancer therapy management. To identify the most important metabolites required for differentiation, an 1H NMR metabolomics approach was applied to selected haematological malignancies. This study utilized 116 methanol serum extract samples from AML (n= 38), nHL (n= 26), CLL (n= 21) and HC (n= 31). Multivariate and univariate data analyses were performed to identify the most abundant changes among the studied groups. Complex and detailed VIP-PLS-DA models were calculated to highlight possible changes in terms of biochemical pathways and discrimination ability. Chemometric model prediction properties were validated by receiver operating characteristic (ROC) curves and statistical analysis. Two sets of eight important metabolites in HC/AML/CLL/nHL comparisons and five in AML/CLL/nHL comparisons were selected to form complex models to represent the most significant changes that occurred.
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Essential oils are substances of plant origin used to produce cosmetics, to preserve and aromatize food. Recently, they have become more popular among scientists and doctors due to their germicidal, antifungal, antiviral and anti-parasitic properties. As a consequence, essential oils are regarded as the source of new therapeutic substances. Numerous publications have been written regarding their effect on microorganisms in vitro. There have also been reports regarding their use in therapy as an additive to the traditional medical treatment. Essential oils may have other properties with positive effect on health because they may have an influence on the central nervous system and human mental state. It should be, however, kept in mind that compounds of essential oils might also have side effects and lead, like antibiotics, to the selection of resistant pathogens. It is necessary to develop quality standards of obtaining and using these plant preparations, so that they may provide safe and effective assistance in the fight against human pathogens.
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Anti-Infecciosos/farmacologia , Anti-Infecciosos/toxicidade , Bactérias/efeitos dos fármacos , Fungos/efeitos dos fármacos , Óleos Voláteis/toxicidade , Vírus/efeitos dos fármacos , Humanos , Testes de Sensibilidade MicrobianaRESUMO
AIM: The aim of the study was to determine the effects of regular hydrokinezytherapy on the prevention of obesity in elderly women. MATERIALS AND METHODS: The study was carried out among the Third Age University students, participating in hydrokinezytherapy classes. The group consisted of 31 women aged 63-70 years. Body Mass Index (BMI) was calculated. The values obtained were compared with the average for the population using the assessment criteria for adults according to Ostrowska-Nawarycz. To identify the obesity type waist hip ratio (WHR) was used. The results were subjected to statistical analysis. The T-Student test was carried out. RESULTS: The results of the study showed that after a year of training the number of women with the correct, while there was no change in the WHR values before and after the training. CONCLUSIONS: The results of the research and literature data indicate that regular physical activity effectively prevents weight gain, reduces overweight and obesity.
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Hidroterapia , Obesidade/prevenção & controle , Idoso , Índice de Massa Corporal , Exercício Físico , Feminino , Humanos , Pessoa de Meia-Idade , PolôniaRESUMO
THE AIM: of the study was to evaluate the physical fitness in 12-13- year-old children attending randomly selected primary schools in Pabianice, and to determine which of the motor skills and abilities need to be improved in the further process of education. MATERIAL AND METHODS: The study group consisted of 236 pupils aged 12-13 years attending primary schools number 3, 5 and 17 in Pabianice. The physical fitness was evaluated using International Physical Fitness Test (IPFT). RESULTS: 12-year-olds from the studied group usually represent the medium level of physical fitness which applies to 76.7% of children. The poorest results in the girls' group refer to running speed and flexibility test, while in the boys' group to: stamina, running speed and the abdominal muscles strength test. The best results girls gained in the upper limbs strength test, while boys in the agility test.
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Aptidão Física , Adolescente , Criança , Feminino , Humanos , Masculino , Destreza Motora , Força Muscular , PolôniaRESUMO
THE AIM: of study was to estimate the body posture in children finishing primary schools. This is the last moment to make any improvement in body posture needed, because after the end of the child's growth the correction of postural defects is practically impossible. MATERIALS AND METHODS: The study was conducted on 236 pupils aged 12-13 years attending primary schools number 3, 5 and 17 in Pabianice. To evaluate body posture Kasperczyk's points method was used. It is a commonly applied method for screening purposes. RESULTS: Over 50% of studied children had poor body posture and just under 6% of pupils' posture was assessed as very good. In the study population of children finishing primary schools the occurrence of faulty posture was shown to be very high. The most common defect in body posture among pupils was an uneven alignment of shoulders and shoulder blades. CONCLUSIONS: The results obtained in this study indicate the need to undertake action reducing the occurrence of faulty posture among children in Pabianice.
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Postura , Adolescente , Criança , Feminino , Humanos , Masculino , PolôniaRESUMO
UNLABELLED: Myocardial infraction, sudden cardiac death next is one of the most serious clinical demonstrations of ischaemic heart diseases. It is characterized by an irreversible destruction (necrosis) of a part of cardiac muscle, caused by severe narrowing or blood clot (thrombosis) in the lumen of coronary arteries. The long-term, systematic and individually selected program of the physical rehabilitation has a beneficial effect to the improvement in the physical fitness at patients, after an myocardial infarction. The aim of this work was to examine the influence of the outpatient, cardiological rehabilitation on the physical fitness and the normalization of the arterial pressure at patients after STEMI, treated with methods of invasive cardiology, and determining effects of the rehabilitation. MATERIAL AND METHODS: The study included 108 patients (93 men and 15 women). An average age of patients was 53. Examined patients were divided into 2 groups: rehabilitated (55 people) and control (53 people). The program of the cardiologic rehabilitation included 24 forty-minute training sessions, for 2-3 times during the week. Every training session spread through 10 minutes of the general keep-fit exercise (warm-up), 24 minutes of the ride on cycloergometer (intervallic training) with submaximal load adjusted individually for every patient, under the constant electrocardiographic scrutiny of the action of the heart, and 6 minutes of respiratory exercises. The criterion of intensity of a physical effort was determined on the basis of a Bruce test according to on the level of the 70% of the maximum limit of the heart rate. The rehabilitation lasted about 3 months. RESULTS: Obtained findings show that the outpatient, cardiologic rehabilitation has a beneficial effect for the improvement in the physical fitness and the decrease in value of the rest arterial pressure at patients after STEMI. Examinations show the increase of the maximum load (max MET'S) and longer duration of the exercise test. CONCLUSIONS: Above findings confirm the effectiveness of the cardiological rehabilitation, although they are not spectacular. Perhaps if they increase the frequency and intensity and number of training sessions, the results would be more significant.
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Terapia por Exercício , Infarto do Miocárdio/fisiopatologia , Infarto do Miocárdio/reabilitação , Aptidão Física , Eletrocardiografia , Teste de Esforço , Terapia por Exercício/métodos , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Infarto do Miocárdio/diagnóstico , Resultado do TratamentoRESUMO
It is well established that osteoblasts, the key cells involved in bone formation during development and in adult life, secrete a number of glycoproteins harboring autocrine and paracrine functions. Thus, investigating the osteoblastic secretome could yield important information for the pathophysiology of bone. In the present study, we characterized for the first time the secretome of human Hobit osteoblastic cells. We discovered that the secretome comprised 89 protein species including the powerful growth factor progranulin. Recombinant human progranulin (6nM) induced phosphorylation of mitogen-activated protein kinase in both Hobit and osteocytic cells and induced cell proliferation and survival. Notably, risedronate, a nitrogen-containing bisphosphonate widely used in the treatment of osteoporosis, induced the expression and secretion of progranulin in the Hobit secretome. In addition, our proteomic study of the Hobit secretome revealed that risedronate induced the expression of ERp57, HSP60 and HSC70, three proteins already shown to be associated with the prevention of bone loss in osteoporosis. Collectively, our findings unveil novel targets of risedronate-evoked biological effects on osteoblast-like cells and further our understanding of the mechanisms of action of this currently used compound.
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Ácido Etidrônico/análogos & derivados , Peptídeos e Proteínas de Sinalização Intercelular/metabolismo , Osteoblastos/metabolismo , Proteoma/metabolismo , Animais , Western Blotting , Linhagem Celular , Sobrevivência Celular/efeitos dos fármacos , Eletroforese em Gel de Poliacrilamida , Ácido Etidrônico/farmacologia , Humanos , Espectrometria de Massas , Camundongos , Osteoblastos/efeitos dos fármacos , Progranulinas , Reprodutibilidade dos Testes , Ácido Risedrônico , Fatores de TempoRESUMO
Hybridization between species is an important mechanism for the origin of novel lineages and adaptation to new environments. Increased allelic variation and modification of the transcriptional network are the two recognized forces currently deemed to be responsible for the phenotypic properties seen in hybrids. However, since the majority of the biological functions in a cell are carried out by protein complexes, inter-specific protein assemblies therefore represent another important source of natural variation upon which evolutionary forces can act. Here we studied the composition of six protein complexes in two different Saccharomyces "sensu stricto" hybrids, to understand whether chimeric interactions can be freely formed in the cell in spite of species-specific co-evolutionary forces, and whether the different types of complexes cause a change in hybrid fitness. The protein assemblies were isolated from the hybrids via affinity chromatography and identified via mass spectrometry. We found evidence of spontaneous chimericity for four of the six protein assemblies tested and we showed that different types of complexes can cause a variety of phenotypes in selected environments. In the case of TRP2/TRP3 complex, the effect of such chimeric formation resulted in the fitness advantage of the hybrid in an environment lacking tryptophan, while only one type of parental combination of the MBF complex allowed the hybrid to grow under respiratory conditions. These phenotypes were dependent on both genetic and environmental backgrounds. This study provides empirical evidence that chimeric protein complexes can freely assemble in cells and reveals a new mechanism to generate phenotypic novelty and plasticity in hybrids to complement the genomic innovation resulting from gene duplication. The ability to exchange orthologous members has also important implications for the adaptation and subsequent genome evolution of the hybrids in terms of pattern of gene loss.
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Antranilato Sintase/genética , Evolução Molecular , Indol-3-Glicerolfosfato Sintase/genética , Proteínas de Membrana/genética , Fragmentos de Peptídeos/genética , Proteínas Recombinantes de Fusão/genética , Proteínas de Saccharomyces cerevisiae/genética , Alelos , Genoma , Hibridização Genética , Fenótipo , Saccharomyces/genéticaRESUMO
THE AIM OF THE STUDY: Was to diagnose the body posture of physiotherapy students of the Medical University of Lodz and to determine the relationship between selected respiratory indicator and the incidence of faulty posture in the studied group. MATERIAL AND METHODS: 196 students of Medical University of Lodz were included in the study. Posture assessment was conducted using Kasperczyk's points method. In the study authors indicated selected respiratory parameters, incuding: forced vital capacity (FVC), forced expiratory volume in one second (FEV1) and maximum inspiratory and expiratory pressure measured in the mouth (MIP, MEP). RESULTS: The results of the study showed a reduction of the respiratory parameters rates (FVC, FEV1) and respiratory muscle strength (MIP, MEP) in the group of students with a poor posture compared to students with a good posture. Although the statistical analysis showed no significant correlation between the presence of the faulty posture and respiratory parameters, there was a clear tendency for those parameters to decrease in the group of students with a poor posture. CONCLUSIONS: The results of the examined indicators showed a reduction of the respiratory parameters rates (FVC, FEV1) and respiratory muscle strength (MIP, MEP) in the group of students with a poor posture compared to students with a good posture. The posture classified by Kasperczyk as good is prevailing in the studied. The results obtained in this study suggest the need to take action on the prevention and correction of faulty posture.
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Postura/fisiologia , Mecânica Respiratória/fisiologia , Volume Expiratório Forçado , Humanos , Testes de Função Respiratória , Estudantes/estatística & dados numéricos , Capacidade VitalRESUMO
UNLABELLED: The aim of the study was to evaluate the influence of regularswimming activity on the respiratory system of smokers and non-smokers. MATERIAL AND METHODS: The study included 107 students, aged 19 to 24, attending weekly swimming classes. The study was composed of the following elements: measurement of selected respiratory parameters (FVC, FEV,, MIP, MEP), the percentage concentration of blood carboxyhemoglobin (%COHb) and a survey. RESULTS: After 10 months of regular swimming activity in the entire study population statistically significant increase in maximal expiratory pressure MEP (alpha < 0.02), maximal inspiratory pressure MIP (alpha < 0.03) and forced vital capacity FVC (alpha < 0.05) was observed. The value of the FEV1 was significantly reduced. CONCLUSIONS: Increased respiratory capacity and respiratory muscle strength has been noticed among non-smokers as well as among smokers. The study confirmed the importance of promoting physical activity, especially swimming, among cigarette smokers.
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Pulmão/fisiologia , Fumar/fisiopatologia , Natação/fisiologia , Adulto , Feminino , Volume Expiratório Forçado , Humanos , Masculino , Testes de Função Respiratória , Adulto JovemRESUMO
The consequence of excessive use of macrolides is a high occurrence of mechanisms responsible for resistance to these drugs. Of 97 erythromycin-resistant bacterial strains gathered in the Wroclaw area in Poland, 60% exhibited very high resistance, and those with the inducible MLS(B) (macrolide-lincosamide-streptogramin B) resistance phenotype predominated. Direct genetic investigation revealed that the erm genes coding for ribosomal methylases are the most frequently occurring erythromycin resistance-determining genes. No genetic resistance determinant was detected in 13% of the erythromycin-resistant strains. The efflux mechanism occurs in strains isolated from the nasopharyngeal cavity twice as often as in those isolated from other material, where the mechanism connected with target site modification predominates. Measurements of radiolabelled antibiotic accumulation inside bacterial cells revealed that in highly resistant strains (MIC > 1024 µg/ml), an important factor responsible for the resistance is the permeability barrier at the cell wall level. This would be a hitherto unknown mechanism of resistance to erythromycin in Staphylococcus aureus.
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Antibacterianos/farmacologia , Farmacorresistência Bacteriana/efeitos dos fármacos , Eritromicina/farmacologia , Staphylococcus aureus/isolamento & purificação , Antibacterianos/metabolismo , Radioisótopos de Carbono/química , Humanos , Testes de Sensibilidade Microbiana , Nasofaringe/microbiologia , Infecções Estafilocócicas/microbiologia , Staphylococcus aureus/genéticaRESUMO
A new generation of guanidino-labelling (GLaD) reagents were developed for quantitative proteomics using offline microcapillary liquid chromatography (LC) matrix-assisted laser desorption/ionisation mass spectrometry (MALDI-MS). In order to reduce the unwanted overlapping between the isotopic envelopes of the two differentially labelled peptide ions, a novel synthetic route was described for production of both (13)C- and (15)N-containing isotopomers of N,O-dimethylisourea. The use of these types of isotopes has no deleterious effect on the retention times of both differentially labelled peptides during offline microbore reversed-phase LC. In addition, the possibility to incorporate a mass difference of 4 Da can be exploited during post-source decay analysis to generate product ion spectra in which fragment ions containing the modifications appear as doublets in the corresponding product ion spectra, thus facilitating identification of the C-terminal fragment ions.