Chloramphenicol acetyltransferase may confer resistance to fusidic acid by sequestering the drug.

Enterobacterial chloramphenicol acetyltransferase bound fusidic acid with high affinity, but did not acetylate the drug at an experimentally detectable rate. The enzyme may therefore confer resistance to fusidic acid by sequestering the drug and thereby preventing the drug from binding to translational elongation factor G.     

Analysis of drug resistance in the archaebacterium Methanococcus voltae with respect to potential use in genetic engineering

The sensitivity of the methanogenic archaebacterium Methanococcus voltae to 12 inhibitors was tested in liquid medium. Four compounds appeared to be inhibitors of growth. Their MICs were as follows: pseudomonic acid, 0.1 micrograms/ml (0.19 microM); puromycin, 2 micrograms/ml (3.6 microM); methionine sulfoximine, 30 micrograms/ml (170 microM); and fusidic acid, 100 micrograms/ml (170 microM). On solid medium, the MICs were similar and the frequency of spontaneous resistance was found to be 5 X 10(-5) (methionine sulfoximine), 10(-7) (pseudomonic acid), and less than 10(-7) (puromycin and fusidic acid). Pseudomonic acid was found to inhibit isoleucyl-tRNA synthetase activity as measured by the in vitro aminoacylation of M. voltae tRNA with L-[U-14C]isoleucine. Fusidic acid and puromycin were shown to inhibit poly(U)-dependent polyphenylalanine synthesis in S30 extracts. Acetylpuromycin was inhibitory at much higher concentrations both in vivo and in vitro for M. voltae. Thus, the pac gene of Streptomyces alboniger, which is responsible for acetylation of puromycin and which conferred resistance to puromycin when introduced in eubacteria and eucaryotes, is a potential selective marker in gene transfer experiments with M. voltae. The latter was recently shown to be transformable. The same would be true for the cat gene of Tn9, which encodes resistance to fusidic acid in eubacteria in addition to resistance to chloramphenicol.     

Analysis of drug resistance in the archaebacterium Methanococcus voltae with respect to potential use in genetic engineering.

The sensitivity of the methanogenic archaebacterium Methanococcus voltae to 12 inhibitors was tested in liquid medium. Four compounds appeared to be inhibitors of growth. Their MICs were as follows: pseudomonic acid, 0.1 micrograms/ml (0.19 microM); puromycin, 2 micrograms/ml (3.6 microM); methionine sulfoximine, 30 micrograms/ml (170 microM); and fusidic acid, 100 micrograms/ml (170 microM). On solid medium, the MICs were similar and the frequency of spontaneous resistance was found to be 5 X 10(-5) (methionine sulfoximine), 10(-7) (pseudomonic acid), and less than 10(-7) (puromycin and fusidic acid). Pseudomonic acid was found to inhibit isoleucyl-tRNA synthetase activity as measured by the in vitro aminoacylation of M. voltae tRNA with L-[U-14C]isoleucine. Fusidic acid and puromycin were shown to inhibit poly(U)-dependent polyphenylalanine synthesis in S30 extracts. Acetylpuromycin was inhibitory at much higher concentrations both in vivo and in vitro for M. voltae. Thus, the pac gene of Streptomyces alboniger, which is responsible for acetylation of puromycin and which conferred resistance to puromycin when introduced in eubacteria and eucaryotes, is a potential selective marker in gene transfer experiments with M. voltae. The latter was recently shown to be transformable. The same would be true for the cat gene of Tn9, which encodes resistance to fusidic acid in eubacteria in addition to resistance to chloramphenicol.     

Susceptibility to and resistance determinants of fusidic acid in Staphylococcus aureus isolated from Chinese children with skin and soft tissue infections

This study aims to determine the resistance rates and determinants of fusidic acid among Staphylococcus aureus isolates collected from Chinese pediatric patients with skin and soft tissue infections (SSTIs). Between 2008 and 2009, a total of 186 clinical S. aureus isolates were collected from the pediatric patients with SSTIs, abscess (44.6%) was the most common SSTI in children 0-16 years old. Four clinical isolates (4/186, 2.2%) were resistant to fusidic acid. Two of these isolates were methicillin-resistant S. aureus (MRSA) that carry the fusC gene. The other two isolates were methicillin-sensitive S. aureus (MSSA) that carry the fusB gene. In the two fusB-positive clinical isolates, the fusB gene was located in a transposon-like element that has 99% identity with a pUB101 fragment from S. aureus. The four fusidic acid-resistant clinical isolates were ST1-MRSA-SCCmecV-t127, ST93-MRSA-SCCmecIII-t202, ST680-MSSA-t5415, and ST680-MSSA-t377. The fusidic acid resistance rate of S. aureus isolated from Chinese pediatric patients with SSTIs was low, and the genes fusB and fusC were the main resistance determinants. The transposon-like element that contains the fusB gene might participate in the transmission of fusidic acid resistance genes. This is the first report regarding the emergence of fusidic acid-resistant clinical S. aureus isolates in mainland China.     

Molecular analysis of fusidic acid resistance in Staphylococcus aureus

Fusidic acid is a potent antibiotic against severe Gram-positive infections that interferes with the function of elongation factor G (EF-G), thereby leading to the inhibition of bacterial protein synthesis. In this study, we demonstrate that fusidic acid resistance in Staphylococcus aureus results from point mutations within the chromosomal fusA gene encoding EF-G. Sequence analysis of fusA revealed mutational changes that cause amino acid substitutions in 10 fusidic acid-resistant clinical S. aureus strains as well as in 10 fusidic acid-resistant S. aureus mutants isolated under fusidic acid selective pressure in vitro. Fourteen different amino acid exchanges were identified that were restricted to 13 amino acid residues within EF-G. To confirm the importance of observed amino acid exchanges in EF-G for the generation of fusidic acid resistance in S. aureus, three mutant fusA alleles encoding EF-G derivatives with the exchanges P406L, H457Y and L461K were constructed by site-directed mutagenesis. In each case, introduction of the mutant fusA alleles on plasmids into the fusidic acid-susceptible S. aureus strain RN4220 caused a fusidic acid-resistant phenotype. The elevated minimal inhibitory concentrations of fusidic acid determined for the recombinant bacteria were analogous to those observed for the fusidic acid-resistant clinical S. aureus isolates and the in vitro mutants containing the same chromosomal mutations. Thus, the data presented provide evidence for the crucial importance of individual amino acid exchanges within EF-G for the generation of fusidic acid resistance in S. aureus.     

Mutations in the G-domain of elongation factor G from Thermus thermophilus affect both its interaction with GTP and fusidic acid

Two hypersensitive and two resistant variants of elongation factor-G (EF-G) toward fusidic acid are studied in comparison with the wild type factor. All mutated proteins are active in a cell-free translation system and ribosome-dependent GTP hydrolysis. The EF-G variants with the Thr-84-->Ala or Asp-109-->Lys mutations bring about a strong resistance of EF-G to the antibiotic, whereas the EF-Gs with substitutions Gly-16-->Val or Glu-119-->Lys are the first examples of fusidic acid-hypersensitive factors. A correlation between fusidic acid resistance of EF-G mutants and their affinity to GTP are revealed in this study, although their interactions with GDP are not changed. Thus, fusidic acid-hypersensitive mutants have the high affinity to an uncleavable GTP analog, but the association of resistant mutants with GTP is decreased. The effects of either fusidic acid-sensitive or resistant mutations can be explained by the conformational changes in the EF-G molecule, which influence its GTP-binding center. The results presented in this paper indicate that fusidic acid-sensitive mutant factors have a conformation favorable for GTP binding and subsequent interaction with the ribosomes.     

Molecular basis of fusB-mediated resistance to fusidic acid in Staphylococcus aureus

The primary mechanism of fusidic acid resistance in clinical strains of Staphylococcus aureus involves acquisition of the fusB determinant. The genetic elements(s) responsible are incompletely defined, and the mechanism of resistance is unknown. Here we report the cloning, sequencing and overexpression of a single gene (fusB) from plasmid pUB101 capable of conferring resistance to fusidic acid in S. aureus. The fusB gene is located on a transposon-like element and encodes a small (25 kDa), cytoplasmic protein for which homologues exist in a number of clinically important and environmental Gram-positive bacterial species. Bioinformatic analysis of regions immediately upstream of fusB suggested that expression of resistance is regulated by translational attenuation, which was confirmed through use of reporter fusions. FusB was overexpressed in Escherichia coli as a polyhistidine-tagged fusion product, and the purified protein shown to protect an in vitro staphylococcal translation system from inhibition by fusidic acid in a specific and dose-dependent fashion. Purified FusB bound staphylococcal EF-G, the target of fusidic acid. The protein provided no protection from inhibition by fusidic acid when added to an in vitro E. coli translation system, consistent both with the observed failure of FusB to bind E. coli EF-G, and its inability to confer resistance in E. coli.     

Morphological stages of Bacillus subtilis sporulation and resistance to fusidic acid.

During spore development of Bacillus subtilis both protein synthesis and sporulation become resistant to the antibiotic fusidic acid. This resistance develops at the time when asymmetric prespore septa are formed. Simultaneously ribosomes lose their ability to bind fusidic acid, as demonstrated by their affinity chromatography with the immobilized drug. Mutants resistant to fusidic acid during growth are oligosporogenous; their sporulation development is blocked before septum formation. These results indicate that normal ribosomes are needed for prespore septation sporulation; only after septation can protein synthesis be maintained, throughout the development period, by fusidate resistant ribosomes.     

Fusidic-acid-resistant staphylococci

Penicillin-resistant staphylococci were examined to determine the spontaneous mutation frequency of resistance to antistaphylococcal antibiotics including fusidic acid, cephalothin and lincomycin. Fusidic-acid-resistant mutants were obtained about twenty times more frequently than cephalothin-resistant mutants and about one hundred times more frequently than lincomycin-resistant mutants. Among the fusidic-acid-resistant mutants, ninety-seven per cent were resistant to 20 g/ml and thirty percent to 100 g/ml of the drug. The fusidic-acid-resistant mutants had prolonged generation times not related to the level of drug resistance. Cross-resistance between fusidic acid and cephalothin and between lincomycin and erythromycin was detected. Preliminary evidence was presented indicating that fusidic-acid-resistant mutants inactivate fusidic acid to a greater extent than sensitive cells.     

Characterization of two malaria parasite organelle translation elongation factor G proteins: the likely targets of the anti-malarial fusidic acid

Malaria parasites harbour two organelles with bacteria-like metabolic processes that are the targets of many anti-bacterial drugs. One such drug is fusidic acid, which inhibits the translation component elongation factor G. The response of P. falciparum to fusidic acid was characterised using extended SYBR-Green based drug trials. This revealed that fusidic acid kills in vitro cultured P. falciparum parasites by immediately blocking parasite development. Two bacterial-type protein translation elongation factor G genes are identified as likely targets of fusidic acid. Sequence analysis suggests that these proteins function in the mitochondria and apicoplast and both should be sensitive to fusidic acid. Microscopic examination of protein-reporter fusions confirm the prediction that one elongation factor G is a component of parasite mitochondria whereas the second is a component of the relict plastid or apicoplast. The presence of two putative targets for a single inhibitory compound emphasizes the potential of elongation factor G as a drug target in malaria.     

复方黄柏液联合夫西地酸软膏及西替利嗪 治疗面部糖皮质激素依赖性皮炎疗效观察

目的观察复方黄柏液联合夫西地酸软膏及西替利嗪治疗面部糖皮质激素依赖性皮炎（以下简称为面部激素性皮炎）的疗效。方法采用随机对照观察方法对108例面部激素性皮炎患者分成治疗组和对照组。治疗组使用复方黄柏液（湿敷）联合夫西地酸软膏（外用）,对照组用3%的硼酸溶液湿敷及维生素B6软膏外用;两组均口服西替利嗪片。2周为1个疗程,治疗2个疗程。结果治疗组有效率为80.77%;对照组有效率为56.86%。两组有效率比较差异有统计学意义（χ^2=7.16,P〈0.05）。结论复方黄柏液联合夫西地酸软膏及西替利嗪治疗面部激素性皮炎疗效好,无明显不良反应。     

Technique to Improve the Rate of Healing of Incised Abscesses

In a comparative investigation incised skin abscesses were treated by either introducing sterile fusidic acid gel into the cavity on one occasion only or applying daily superficial dressings impregnated with sodium fusidate ointment. In comparison with the dressing group, the intracavity use of fusidic acid gel reduced the mean healing time of incised abscesses by approximately one-half. When abscesses were analysed according to site and size, the reduction in mean healing time was equally striking. No hypersentisivity or irritation to fusidic acid or its sodium salt applied by either method was observed.The procedure of introducing fusidic acid gel into an incised abscess cavity is a promising alternative to superficial antibiotic dressings or wicks in the treatment of incised abscesses.     

A spectrophotometric method of analysis of fusidic acid

A spectrophotometric method for assay of fusidic acid is described. The method is based on reaction with a reagent consisting of acetic anhydride and concentrated sulfuric acid. Mathematical processing of the results of the main substance determination in fusidic acid preparations showed that the error did not exceed 2 per cent. Procedures for spectrophotometric assay of fusidic acid in control of the processes of its biosynthesis, isolation and purification were developed. The procedures provided control of the technological process of fusidic acid production.     

Confirmation of protoplast fusion-derived linkages in Staphylococcus aureus by transformation with protoplast DNA

Transformation provided definitive evidence for linkage between tyrB282::Tn551 ermB321 and omega (Chr::Tn551)34, and thus between the separate large linkage groups containing these markers, in Staphylococcus aureus NCTC 8325. Transformation also defined the chromosomal loci for the purC193::Tn551 and omega (Chr::Tn551)42 markers and the linkage of a tetracycline resistance marker (tet-3490) with a fusidic acid resistance marker (fus-149). The use of DNA isolated from protoplasts under conditions that reduced hydrodynamic shear greatly facilitated the demonstration of most of these linkages. These results provide direct evidence confirming several of the linkages predicted by a microcomputer-assisted protoplast fusion analysis in a previous study (M. L. Stahl and P. A. Pattee, J. Bacteriol. 154:395-405, 1983); those markers whose predicted linkages were not confirmed by transformation are probably separated by chromosomal distances that exceed the limits of detection by transformation, even with protoplast DNA.     

G factor mutants of Escherichia coli: map location and properties

Factor G, the translocation factor in protein synthesis, was genetically marked by fusidic acid resistance or by a temperature sensitive lesion. All the characteristic properties of the G factor were more than 97% cotransducible with streptomycin resistance, the locus near which many ribosome mutations map.     

Skin Commensal Staphylococci May Act as Reservoir for Fusidic Acid Resistance Genes

We analyzed the occurrence and mechanisms of fusidic acid resistance present in staphylococci isolated from 59 healthy volunteers. The fingers of the volunteers were screened for the presence of staphylococci, and the collected isolates were tested for resistance to fusidic acid. A total of 34 fusidic acid resistant staphylococcal strains (all were coagulase-negative) were isolated from 22 individuals (22/59, 37.3%). Examination of the resistance genes revealed that acquired fusB or fusC was present in Staphylococcus epidermidis, Staphylococcus capitis subsp. urealyticus, Staphylococcus hominis subsp. hominis, Staphylococcus warneri and Staphylococcus haemolyticus. Resistance islands (RIs) carrying fusB were found in S. epidermidis and S. capitis subsp. urealyticus, while staphylococcal chromosome cassette (SCC)-related structures harboring fusC were found in S. hominis subsp. hominis. Genotypic analysis of S. epidermidis and S. hominis subsp. hominis indicated that the fus elements were disseminated in diverse genetic strain backgrounds. The fusC elements in S. hominis subsp. hominis strains were highly homologous to SCCfusC in the epidemic sequence type (ST) 239/SCCmecIII methicillin-resistant S. aureus (MRSA) or the pseudo SCCmec in ST779 MRSA. The presence of acquired fusidic acid resistance genes and their genetic environment in commensal staphylococci suggested that the skin commensal staphylococci may act as reservoir for fusidic acid resistance genes.     

1272例尿液标本细菌培养结果及耐药性分析

目的调查临床送检中段尿标本菌群分布及体外抗生素耐药性,为临床合理使用抗生素提供依据。方法回顾性分析2010年1月至2012年6月住院患者送检中段尿标本中,分离的1272株细菌（剔除重复菌株）临床分布及耐药性。采用美国BDphoenix100全自动细菌鉴定药敏分析仪进行菌种鉴定及药敏试验,结合相关临床资料,应用WHONET5．6分析软件进行耐药性分析。结果从分离到的l272株细菌中,检出前5位的细菌是大肠埃希菌、肺炎克雷伯菌、屎肠球菌、粪肠球菌和铜绿假单胞菌,构成比分别为20．3％、14．4％、14．2％、9．4％和7．4％。肠杆菌对氨苄西林的耐药率最高为93．9％,耐药率较低的有亚胺培南、美洛培南、头孢哌酮／舒巴坦和多粘菌素B,它们的耐药率在10．5％～15．9％。非发酵菌对氯霉素、氨苄西林、头孢唑啉和阿莫西林／克拉维酸的耐药率最高在90．1％～100％,对多粘菌素B和头孢哌酮／舒巴坦的耐药率较低,分别为7．7％和16．9％。肠球菌对利奈唑胺、万古霉素、替考拉宁和呋西地酸的耐药率最低,分别为2．6％、7．2％、8．8％和8．8％;葡萄球菌对万古霉素的耐药率为0,对喹奴普汀-达福普汀的耐药率为0．8％,对呋哺妥因、替考拉宁、夫西地酸、利奈唑胺、利福平的耐药率在2．5％～10．7％。结论泌尿系统感染主要病原菌为肠杆菌和肠球菌,由于各病原菌均存在不同程度的耐药性,临床医师应根据尿液细菌培养结果,科学合理使用抗菌药物。     

Stable cloning of the amino terminus of the 60 kDa outer membrane protein of Chlamydia trachomatis serovar L1

Abstract Re-examination of a fusidic acid resistance mutation, fus -426 in Bacillus subtilis JH642 showed that this mutation is closely linked to temperature-sensitive (ts) sporulation in liquid medium, but not on agar plates. This defect was suppressed by a rifampicin-resistance mutation, rif -122, or by the hos -1 mutation, which affects sporulation and colony phenotype.     

Sordarin derivatives induce a novel conformation of the yeast ribosome translocation factor eEF2

The sordarins are fungal specific inhibitors of the translation factor eEF2, which catalyzes the translocation of tRNA and mRNA after peptide bond formation. We have determined the crystal structures of eEF2 in complex with two novel sordarin derivatives. In both structures, the three domains of eEF2 that form the ligand-binding pocket are oriented in a different manner relative to the rest of eEF2 compared with our previous structure of eEF2 in complex with the parent natural product sordarin. Yeast eEF2 is also shown to bind adenylic nucleotides, which can be displaced by sordarin, suggesting that ADP or ATP also bind to the three C-terminal domains of eEF2. Fusidic acid is a universal inhibitor of translation that targets EF-G or eEF2 and is widely used as an antibiotic against Gram-positive bacteria. Based on mutations conferring resistance to fusidic acid, cryo-EM reconstructions, and x-ray structures of eEF2, EF-G, and an EF-G homolog, we suggest that the conformation of EF-G stalled on the 70 S ribosome by fusidic acid is similar to that of eEF2 trapped on the 80 S ribosome by sordarin.