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BACKGROUND AND OBJECTIVES: The effect of mogamulizumab in cutaneous T-cell lymphoma (CTCL) on T cells (TC) in the peripheral blood and its potential role to navigate treatment intervals are explored. METHODS: We investigated within a retrospective monocentric analysis the effect of mogamulizumab on the CD3+ TC and the aberrant T cell population (TCP), i.e., the CD4+ /CD7- and the CD4+ /CD26- TC, analyzed by flow cytometry. RESULTS: Thirteen patients with CTCL were included. After four cycles there was a mean reduction of 57% in CD3+ TC, 72% in the CD4+ /CD7- and 75% in the CD4+ /CD26- TCP compared to the individual baseline of each patient. The reduction in CD4+ /CD7+ and CD4+ /CD26+ TC was lower, averaging 54% and 41%. A significant decrease in aberrant TCP was already evident after the first administration. A median plateau of TCP already occurred during the IP. Progressive disease occurred in 5/13 patients without a clear correlation to aberrant TCP. CONCLUSIONS: Already after one dose of mogamulizumab, aberrant TCP and, to a lesser extent, normal TC decrease. We did not observe a clear correlation between TCP and the efficacy of mogamulizumab, but further studies with larger numbers of patients are needed.
Assuntos
Linfoma Cutâneo de Células T , Micose Fungoide , Síndrome de Sézary , Neoplasias Cutâneas , Humanos , Linfócitos T/metabolismo , Dipeptidil Peptidase 4/análise , Dipeptidil Peptidase 4/metabolismo , Dipeptidil Peptidase 4/uso terapêutico , Micose Fungoide/patologia , Neoplasias Cutâneas/tratamento farmacológico , Neoplasias Cutâneas/patologia , Estudos RetrospectivosRESUMO
BACKGROUND: BC-3781 is an investigational semi-synthetic pleuromutilin antibiotic, which recently finished a clinical Phase 2 trial in acute bacterial skin and skin structure infections. BC-3781 binds to the 50S ribosomal subunit and cross-resistance with other antimicrobial classes is uncommon. We evaluated the activity of BC-3781 against organisms responsible for community-acquired respiratory tract infections (CARTIs). METHODS: BC-3781 and comparator agents were susceptibility tested against Streptococcus pneumoniae (157 isolates; 33% penicillin resistant), Haemophilus influenzae (102; 50% ß-lactamase producers), Moraxella catarrhalis (50) and Legionella pneumophila (30) by broth microdilution and the agar dilution method. Mycoplasma pneumoniae (50 strains) was tested by broth microdilution, while Chlamydophila pneumoniae (50 strains) MIC values were determined using HEp-2 cells. RESULTS: Against S. pneumoniae (MIC(50/90) 0.12/0.25 mg/L) BC-3781 was 16- and 8-fold more active than azithromycin (MIC(50/90) 2/>16 mg/L) and levofloxacin (MIC(50/90) 1/1 mg/L), respectively, and its activity was not adversely affected by resistance to penicillin. S. pneumoniae showed high resistance rates to azithromycin (50.3%) and clindamycin (31.2%), all being inhibited by BC-3781 at concentrations ≤0.5 mg/L. H. influenzae and M. catarrhalis exhibited low BC-3781 MIC values independent of ß-lactamase production. BC-3781 activity against L. pneumophila (MIC(50/90) 0.06/0.5 mg/L) was similar to that of erythromycin, but lower than that of azithromycin. BC-3781 also showed potent activity against M. pneumoniae and C. pneumoniae, with MIC(50/90) of 0.006/0.006 and 0.02/0.04 mg/L, respectively. CONCLUSIONS: BC-3781 was very active against organisms commonly associated with CARTIs and its activity was not negatively influenced by resistance to other antimicrobials.
Assuntos
Antibacterianos/farmacologia , Bactérias/efeitos dos fármacos , Infecções Bacterianas/microbiologia , Infecções Comunitárias Adquiridas/microbiologia , Infecções Respiratórias/microbiologia , Bactérias/isolamento & purificação , Diterpenos/farmacologia , Humanos , Testes de Sensibilidade Microbiana , Compostos Policíclicos , PleuromutilinasRESUMO
Systematic SARS-CoV-2 testing is a valuable tool for infection control and surveillance. However, broad application of high sensitive RT-qPCR testing in children is often hampered due to unpleasant sample collection, limited RT-qPCR capacities and high costs. Here, we developed a high-throughput approach ('Lolli-Method') for SARS-CoV-2 detection in children, combining non-invasive sample collection with an RT-qPCR-pool testing strategy. SARS-CoV-2 infections were diagnosed with sensitivities of 100% and 93.9% when viral loads were >106 copies/ml and >103 copies/ml in corresponding Naso-/Oropharyngeal-swabs, respectively. For effective application of the Lolli-Method in schools and daycare facilities, SEIR-modeling indicated a preferred frequency of two tests per week. The developed test strategy was implemented in 3,700 schools and 698 daycare facilities in Germany, screening over 800,000 individuals twice per week. In a period of 3 months, 6,364 pool-RT-qPCRs tested positive (0.64%), ranging from 0.05% to 2.61% per week. Notably, infections correlated with local SARS-CoV-2 incidences and with a school social deprivation index. Moreover, in comparison with the alpha variant, statistical modeling revealed a 36.8% increase for multiple (≥2 children) infections per class following infections with the delta variant. We conclude that the Lolli-Method is a powerful tool for SARS-CoV-2 surveillance and can support infection control in schools and daycare facilities.
Assuntos
COVID-19 , COVID-19/diagnóstico , COVID-19/epidemiologia , Teste para COVID-19 , Criança , Técnicas de Laboratório Clínico/métodos , Humanos , SARS-CoV-2/genética , Sensibilidade e EspecificidadeRESUMO
A collaborative study, International Evaluation Measurement Programme-25a, was conducted in accordance with international protocols to determine the performance characteristics of an analytical method for the determination of dissolved bromate in drinking water. The method should fulfill the analytical requirements of Council Directive 98/83/EC (referred to in this work as the Drinking Water Directive; DWD). The new draft standard method under investigation is based on ion chromatography followed by post-column reaction and UV detection. The collaborating laboratories used the Draft International Organization for Standardization (ISO)/Draft International Standard (DIS) 11206 document. The existing standard method (ISO 15061:2001) is based on ion chromatography using suppressed conductivity detection, in which a preconcentration step may be required for the determination of bromate concentrations as low as 3 to 5 microg/L. The new method includes a dilution step that reduces the matrix effects, thus allowing the determination of bromate concentrations down to 0.5 microg/L. Furthermore, the method aims to minimize any potential interference of chlorite ions. The collaborative study investigated different types of drinking water, such as soft, hard, and mineral water. Other types of water, such as raw water (untreated), swimming pool water, a blank (named river water), and a bromate standard solution, were included as test samples. All test matrixes except the swimming pool water were spiked with high-purity potassium bromate to obtain bromate concentrations ranging from 1.67 to 10.0 microg/L. Swimming pool water was not spiked, as this water was incurred with bromate. Test samples were dispatched to 17 laboratories from nine different countries. Sixteen participants reported results. The repeatability RSD (RSD(r)) ranged from 1.2 to 4.1%, while the reproducibility RSD (RSDR) ranged from 2.3 to 5.9%. These precision characteristics compare favorably with those of ISO 15601. A thorough comparison of the performance characteristics is presented in this report. All method performance characteristics obtained in the frame of this collaborative study indicate that the draft ISO/DIS 11206 standard method meets the requirements set down by the DWD. It can, therefore, be considered to fit its intended analytical purpose.
Assuntos
Bromatos/análise , Abastecimento de Água/análise , Algoritmos , Cromatografia Líquida de Alta Pressão , Cromatografia por Troca Iônica , Indicadores e Reagentes , Espectrometria de Massas , Padrões de Referência , Reprodutibilidade dos Testes , Espectrofotometria UltravioletaRESUMO
This is the seventh chapter of the guideline "Calculated initial parenteral treatment of bacterial infections in adults - update 2018" in the 2nd updated version. The German guideline by the Paul-Ehrlich-Gesellschaft für Chemotherapie e.V. (PEG) has been translated to address an international audience. The chapter deals with the empirical and targeted antimicrobial therapy of complicated intra-abdominal infections. It includes recommendations for antibacterial and antifungal treatment.
RESUMO
Because of their toxicity and biomagnification potential individual perfluoroalkyl and polyfluoroalkyl substances (PFAS) are regularly examined in food and environmental matrices by LC-MS/MS. The combustion ion chromatography (CIC) can be used to determine adsorbable organic fluorine (AOF) in aqueous samples. This report describes the optimization and validation of an automated, robust, cost-efficient and rapid CIC method for the determination of AOF. The analysis of 25 fluorinated organic reference substances was performed with recoveries between 16% and 121%. Water from selected surface waters (nâ¯=â¯74), municipal (nâ¯=â¯116) and industrial wastewaters (nâ¯=â¯33) as well as ground water (nâ¯=â¯93) were analyzed by means of CIC. The AOF values of surface water varied between 2.3 and 24.5⯵g/L. The concentrations of AOF in 85% of the wastewater discharges were between 2.0 and 8.5⯵g/L, while 15% of the samples were below the limit of quantitation (LOQâ¯=â¯2⯵g/L AOF). In 56% of the ground water samples the values were below the LOQ. In 44% of the surface water samples (nâ¯=â¯41) the values were between 2.0 and 6.1⯵g/L AOF. CIC analysis was performed in 22 samples from a chemical company wastewater treatment plant, and 14 individual PFAS were determined by LC-MS/MS. AOF values up to 555⯵g/L were found in these samples while the total of the individual PFAS, calculated as fluorine, was 8.8⯵g/L. This provides evidence, that CIC covers a huge range of fluoroorganic compounds that are presently not detected by LC-MS/MS. Furthermore, the CIC method allowed the determination of four halogens in 26 surface water samples. This demonstrated that the CIC technique can be used as a powerful screening test to support LC-MS/MS methods, and is also useful to detect organic chlorine, bromine and iodine compounds (AOCl, AOBr and AOI).
RESUMO
BACKGROUND: Perchlorate salts are relatively stable, soluble in water, and migrate into groundwater sources. Groundwater is an essential source for drinking water suppliers. Perchlorate bears health risks as it is identified to impair normal thyroid function by interfering with iodine uptake by the thyroid gland. The development of a sensitive analytical method for the determination of perchlorate is therefore of the highest interest or public health. Ion chromatography is a sensitive method suitable for perchlorate determinations. This manuscript describes the validation of an ion chromatographic method. Perchlorate is determined by ion chromatography (IC) with conductivity detection after suppression (CD) applying isocratic elution. RESULTS: In this study, the suitability of IC-CD was tested for synthetic samples, selected environmental water, drinking water, and swimming pool water in order to evaluate potential matrix effects on the perchlorate signal even after sample preparation. A sample injection volume of 750 µL was applied to the selected 2-mm-IC column. In untreated samples, the perchlorate peak can be interfered by neighbouring signals from matrix ions like chloride, nitrate, carbonate, and sulphate. Depending on the concentration of the matrix ions, the perchlorate peak can show asymmetric shape in particular when the perchlorate concentration is low. Recovery is reduced with increasing matrix ion concentrations. Dedicated matrix elimination was applied to minimize such effects. A reporting limit of 1.5 µg/L perchlorate and an expanded measurement uncertainty of 13.2 % were achieved. CONCLUSION: The extended method validation proves the applicability of IC based on the EPA 314.0 method for the determination of trace amounts of perchlorate in water samples of different origin. The results support the development of a respective international standard pursued by ISO. The approach evidenced its working robustness and ease of use in terms of eluent preparation, chromatographic resolution, column life time and sample preparation. Due to the simplified analytical workflow of the analytical procedure the application's integration into the collection of methods of interested laboratories should be facilitated.
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The global spread of multi-drug resistant organisms (MDRO) is a major threat to public health. Fighting MDRO spread requires a multi-faceted approach as summarized in the German Antibiotic Resistance Strategy (DART). In the hospital, this includes antibiotic stewardship concepts and strict infection control measures. Treatment of MDRO is sophisticated. Within the last years, several antibiotics with activity against MRSA were launched and facilitate an individual therapy according to site of infection and co-morbidities. In contrast, novel antibiotics against carbapenemase producing Gram-negatives are still lacking. Current studies have shown, that a colistin-based combination treatment can improve the prognosis in these patients. The following article reviews MDRO definitions, burden of disease, treatment options and general strategies against MDRO.
Assuntos
Antibacterianos/uso terapêutico , Infecções Bacterianas/tratamento farmacológico , Infecção Hospitalar/tratamento farmacológico , Farmacorresistência Bacteriana Múltipla/efeitos dos fármacos , Infecções Bacterianas/epidemiologia , Infecções Bacterianas/prevenção & controle , Colistina/uso terapêutico , Efeitos Psicossociais da Doença , Infecção Hospitalar/epidemiologia , Infecção Hospitalar/prevenção & controle , Quimioterapia Combinada , Infecções por Bactérias Gram-Negativas/tratamento farmacológico , Infecções por Bactérias Gram-Negativas/prevenção & controle , Humanos , Staphylococcus aureus Resistente à Meticilina/efeitos dos fármacos , Infecções Estafilocócicas/tratamento farmacológicoRESUMO
Biosearch Italia and Versicor are developing dalbavancin, a novel semisynthetic derivative of the natural glycopeptide A-40926 for the potential treatment of Gram-positive infections. In May 2001, the compound entered phase II trials in the US [409929], [409932]. As of Janaury 2002, phase II trials in skin infections and bacteremia were ongoing [436430]. Both dalbavancin and MDL-63246 are dimethylaminopropyl amide derivatives of A-40926; dalbavancin differs from MDL-63246 in its acylamino sugar, which consists of glucuronic acid in dalbavancin and glucosamine in MDL-63246 [216093], [298527]. The development of MDL-63246 has been discontinued [298527]. In January 1999, Versicor gained North American market rights to BI-397 [311500]. In January 2002, UBS Warburg predicted filing of an NDA in the second half of 2003 for dalbavancin, for treatment of complicated skin and soft tissue infections [439472]. In December 2001, Lehman Brothers predicted a late 2005 launch for dalbavancin, with sales of US $7.7 million in 2005, US $65.8 million in 2006, and peak sales of US $225 million in 2008 [439469].
Assuntos
Anti-Infecciosos/uso terapêutico , Dermatite/tratamento farmacológico , Drogas em Investigação/uso terapêutico , Glicopeptídeos/uso terapêutico , Infecções por Bactérias Gram-Positivas/tratamento farmacológico , Anti-Infecciosos/farmacocinética , Anti-Infecciosos/farmacologia , Disponibilidade Biológica , Ensaios Clínicos Fase I como Assunto , Ensaios Clínicos Fase II como Assunto , Indústria Farmacêutica , Drogas em Investigação/farmacocinética , Drogas em Investigação/farmacologia , Glicopeptídeos/farmacocinética , Glicopeptídeos/farmacologia , Humanos , Testes de Sensibilidade Microbiana , Relação Estrutura-Atividade , Teicoplanina/análogos & derivados , Resultado do TratamentoRESUMO
BACKGROUND: The tested device is a new connecting tool for infusion systems that has been designed to replace conventional single-use stopcocks. Because outbreaks of bloodstream infections have been observed during the use of similar connectors in the United States, we examined the microbiological safety of the connecting device after artificial contamination in the laboratory setting and during routine clinical use. METHODS: In the first part of the study, the new device was tested in 3 types of in vitro experiments. In the second part of the study, surgical intensive care patients had their entry ports capped with novel devices (n=27) or with conventional stopcocks (n=32), and samples of infusion fluids and swabs from entry ports were taken after completion of infusion periods. RESULTS: The new device did not perpetuate bacterial contaminations in spite of high artificial inocula in the in vitro experiments. Microbial contamination rates after 96 hours of infusion therapy for the novel connecting tool versus conventional stopcock groups were as follows: swabs from 3-way ports, 6/129 versus 1/111; rest fluid from infusion lines, 0/20 versus 1/22; rest fluid from infusion bottles, 2/196 versus 2/208; rest fluid from perfusor syringes, 7/180 versus 6/142 (all differences not significant). CONCLUSION: The novel connecting device was microbiologically safe and did not increase microbial contamination rates of intravenous infusion systems.
Assuntos
Cateteres de Demora , Infecção Hospitalar/prevenção & controle , Infusões Intravenosas/instrumentação , Sepse/prevenção & controle , Contagem de Colônia Microbiana , Contaminação de Equipamentos/prevenção & controle , Desenho de Equipamento , Segurança de Equipamentos , Técnicas In VitroRESUMO
A Staphylococcus aureus strain that harbored a plasmid-borne inducibly expressed erm(C) gene was cultivated in the presence of the noninducers quinupristin, telithromycin, and ABT-773. After overnight incubation, 78 mutants that displayed combined resistance to macrolides, lincosamides, streptogramin B antibiotics, and ketolides were analyzed for the genetic basis of this altered resistance phenotype. Because this resistance phenotype is indicative for constitutively expressed erm(C) genes, the erm(C) regulatory regions of all mutants were sequenced. All 78 mutants showed sequence alterations in the erm(C) translational attenuator. Seventeen different types of sequence deletions ranging from 5 bp to 121 bp and nine different types of tandem duplications of 13-100 bp, all causing constitutive erm(C) gene expression, were detected. These sequence deletions or tandem duplications either favored the formation of mRNA secondary structures in the erm(C) translational attenuator, which did not inhibit translation of the erm(C) transcripts, or completely prevented the formation of any mRNA secondary structures in the erm(C) translational attenuator. The mean frequencies of 10-6 to 10-8 by which constitutive mutants were obtained, strongly suggest that telithromycin and ABT-773 not be recommended for the treatment of staphylococci that exhibit the inducible MLSB phenotype.
Assuntos
Antibacterianos/farmacologia , Resistência Microbiana a Medicamentos/genética , Eritromicina/análogos & derivados , Eritromicina/farmacologia , Genes Bacterianos , Cetolídeos , Macrolídeos , Seleção Genética , Staphylococcus aureus/efeitos dos fármacos , Virginiamicina/análogos & derivados , Virginiamicina/farmacologia , Técnicas In Vitro , Testes de Sensibilidade Microbiana , Mutação , Biossíntese de Proteínas , Staphylococcus aureus/genéticaRESUMO
The objective of this study was to determine the activity of daptomycin, a novel lipopeptide, against European Gram-positive isolates (n = 1539). The MIC(90)-values of daptomycin against Staphylococcus aureus isolates was 0.25 mg/L, against Enterococcus faecalis 4 mg/L, against Enterococcus faecium 8 mg/L, 0.25 mg/L against Staphylococcus epidermidis, and 0.25mg/L against Streptococcus pneumoniae. Daptomycin was equally potent against antibiotic-susceptible and resistant strains within a particular species. Based on a breakpoint of 1 mg/L for S. aureus and group A streptococci, all isolates tested were susceptible to daptomycin. Based on a breakpoint of 4 mg/L for vancomcyin-susceptible E. faecalis 99.7% of these isolates were susceptible to daptomycin.
Assuntos
Daptomicina/farmacologia , Enterococcus faecalis/efeitos dos fármacos , Staphylococcus aureus/efeitos dos fármacos , Staphylococcus epidermidis/efeitos dos fármacos , Testes de Sensibilidade MicrobianaRESUMO
A multicentre surveillance study comprising 26 laboratories located in Austria, Germany, and Switzerland was carried out in November 2001. A total of 787 isolates of Staphylococcus aureus and 456 isolates of Staphylococcus epidermidis mainly recovered from hospitalised patients, were tested. MICs for mupirocin were determined using the broth microdilution procedure. Breakpoints were < or = 4 mg/l (susceptible), 8-256 mg/l (low-level resistance) and > or = 512 mg/l (high-level resistance). Rates of low- and high-level resistances were 2.9 and 0.9% in S. aureus, and 9.4 and 3.3% in S. epidermidis, respectively. Mupirocin resistance was almost exclusively observed in oxacillin-resistant isolates of S. aureus (MRSA) and S. epidermidis (MRSE). High-level mupirocin resistance was detected in 3.1 and 4.5% of MRSA and MRSE, respectively.
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Antibacterianos/farmacologia , Farmacorresistência Bacteriana , Mupirocina/farmacologia , Staphylococcus aureus/efeitos dos fármacos , Staphylococcus epidermidis/efeitos dos fármacos , Áustria , Alemanha , Humanos , Resistência a Meticilina , Testes de Sensibilidade Microbiana , Oxacilina/farmacologia , Infecções Estafilocócicas/microbiologia , Staphylococcus aureus/isolamento & purificação , Staphylococcus epidermidis/isolamento & purificação , SuíçaAssuntos
Antibacterianos/farmacologia , Farmacorresistência Bacteriana , Bactérias Gram-Negativas/efeitos dos fármacos , Bactérias Gram-Positivas/efeitos dos fármacos , Pneumonia/microbiologia , Europa (Continente) , Infecções por Bactérias Gram-Negativas/microbiologia , Infecções por Bactérias Gram-Positivas/microbiologia , Hospitalização , Humanos , Testes de Sensibilidade MicrobianaRESUMO
In many European countries, the level of pneumococcal resistance to macrolides has now passed the level of resistance to penicillin G. A total of 82 erythromycin A-resistant isolates of Streptococcus pneumoniae were collected by 11 laboratories in seven European countries. All of the isolates were tested for antimicrobial susceptibility, analyzed for clonal relatedness by multilocus sequence typing, and characterized for macrolide resistance genotypes. The prevalence of the macrolide resistance genotypes varied substantially between countries. In France (87.5% of all strains), Spain (77.3%), Switzerland (80%), and Poland (100%), strains were predominantly erm(B) positive, whereas higher levels of mef(A)-positive strains were reported from Greece (100%) and Germany (33.3%). Macrolide resistance was caused by the oligoclonal spread of some multilocus sequence types, but significant differences in clonal distribution were noted between France and Spain, countries from which high levels of macrolide resistance have been reported. Overall, sequence type 81 (Spain23F-1 clone) was by far the most widespread. The mainly erm(B)-positive serotype 14 clone (sequence type 143), first reported in Poland in the mid-1990s, is now widespread in France.
Assuntos
Eritromicina/farmacologia , Streptococcus pneumoniae/efeitos dos fármacos , Técnicas de Tipagem Bacteriana , Farmacorresistência Bacteriana , Genótipo , Humanos , Testes de Sensibilidade Microbiana , Streptococcus pneumoniae/classificação , Streptococcus pneumoniae/genéticaRESUMO
The in vitro activities of the novel des-fluoro(6) quinolone BMS-284756, ciprofloxacin, gatifloxacin and moxifloxacin were tested against 248 genetically defined Staphylococcus aureus isolates, comprised of 116 unrelated S. aureus, seven heterogeneous vancomycin-intermediate S. aureus (hetero-VISA) strains and 125 clonally related MRSA. All strains were susceptible to BMS-284756 at an investigational breakpoint of 1 mg/L. Reserpine did not decrease the MIC of BMS-284756 in any of the strains tested. The novel des-fluoro(6) quinolone BMS-284756 showed a significantly increased anti-staphylococcal activity.
Assuntos
Anti-Infecciosos/farmacologia , Fluoroquinolonas , Indóis , Quinolonas , Staphylococcus aureus/efeitos dos fármacos , Staphylococcus aureus/genética , Avaliação Pré-Clínica de Medicamentos/métodos , Avaliação Pré-Clínica de Medicamentos/estatística & dados numéricos , Farmacorresistência Bacteriana Múltipla/genética , Humanos , Testes de Sensibilidade Microbiana/estatística & dados numéricos , Staphylococcus aureus/isolamento & purificaçãoRESUMO
Fourteen pneumococcal strains isolated in three nationwide studies were characterized for amino acid changes in the enzymes GyrA, GyrB, ParC and ParE, and for the in vitro activity of eight fluoroquinolones and the new non-fluorinated quinolone BMS 284756. Gemifloxacin and BMS 284756 exhibited the best in vitro activity against all 14 isolates tested. In nine of the 14 isolates mainly classical alterations in ParC (D83N/Y, S79Y/F), as well as rarer alterations such as S80P and D78N, contributed to the decreased susceptibility to fluoroquinolones. In two of the 14 isolates the classical alteration in GyrA (S81F) was found. In only one isolate did alterations in ParC and GyrA exist in parallel.
Assuntos
Anti-Infecciosos/farmacologia , Farmacorresistência Bacteriana/genética , Streptococcus pneumoniae/efeitos dos fármacos , Streptococcus pneumoniae/isolamento & purificação , Fluoroquinolonas , Alemanha/epidemiologia , Humanos , Testes de Sensibilidade Microbiana/estatística & dados numéricos , Streptococcus pneumoniae/genéticaRESUMO
The aim of this study was to investigate whether a Staphylococcus aureus strain that carried an inducibly expressed erm(A) gene might exhibit resistance to the non-inducers telithromycin, ABT-773, clindamycin, quinupristin, dalfopristin or the combination quinupristin-dalfopristin after incubation in the presence of inhibitory concentrations of any of these compounds. Whenever resistant mutants were obtained, these were investigated for the molecular basis of the altered resistance phenotype. Resistant mutants were not selected with dalfopristin or quinupristin-dalfopristin, but were obtained with the other four agents. Irrespective of which drug was used for selection, all mutants were cross-resistant to clindamycin, quinupristin, telithromycin and ABT-773, and exhibited structural alterations in the erm(A) translational attenuator. The structural alterations observed included deletions of 14, 83, 121, 131, 147 or 157 bp, three different tandem duplications of 23, 25 or 26 bp, two different types of point mutation, as well as the insertion of IS256. All these alterations either completely prevented the formation of mRNA secondary structures in the erm(A) regulatory region or favoured the formation of those mRNA secondary structures that allowed translation of the erm(A) transcripts. Deletions, which were observed in almost two-thirds of the mutants, might be explained by illegitimate recombination between different parts of the erm(A) regulatory region.